The main elements of a gas burner: a mixer and a burner nozzle with a stabilizing device. Depending on the purpose and operating conditions of the gas burner, its elements have a different design.
In diffusion gas burners, gas and air are supplied to the combustion chamber. The mixing of gas and air takes place in the combustion chamber. Most diffusion gas burners are mounted on the walls of a furnace or furnace. In boilers, the so-called. gas hearth burners, which are located inside the furnace, in its lower part. A gas hearth burner consists of one or more gas distribution pipes in which holes are drilled. The pipe with holes is installed on the grate or hearth of the furnace in a slotted channel lined with refractory bricks. The required amount of air enters through the refractory slotted channel. With such a device, the combustion of gas streams emerging from the holes in the pipe begins in the refractory channel and ends in the furnace volume. Bottom burners have low resistance to the passage of gas, so they can work without forced blast.
Gas diffusion burners are characterized by a more uniform temperature along the length of the flame.
However, these gas burners require an increased excess air ratio (in comparison with injection ones), and also create lower thermal stresses in the furnace volume and worse conditions for gas afterburning in the tail part of the flame, which can lead to incomplete gas combustion.
Diffusion gas burners are used in industrial furnaces and boilers, where a uniform temperature is required along the length of the torch. In some processes, gas diffusion burners are indispensable. For example, in glass, open-hearth and other furnaces, when the air going for combustion is heated to temperatures exceeding the ignition temperature of combustible gas with air. Gas diffusion burners are also successfully used in some hot water boilers.
In injection burners, combustion air is sucked in (injected) due to the energy of the gas stream and their mutual mixing occurs inside the burner body. Sometimes in gas injection burners the suction of the required amount of combustible gas, the pressure of which is close to atmospheric, is carried out by the energy of the air stream. In full-mixing burners (all the air necessary for combustion is mixed with the gas), operating on medium-pressure gas, a short flame is formed, and combustion ends in a minimum furnace volume. In partial-mixed gas injection burners, only a part (40 ÷ 60%) of the air required for combustion (the so-called primary air) is supplied, which is mixed with the gas. The rest of the air (the so-called secondary air) enters the flame from the atmosphere due to the injecting action of gas-air jets and rarefaction in the furnaces. Unlike medium pressure gas injection burners, burners low pressure a homogeneous gas-air mixture is formed with a gas content greater than the upper flammable limit; These gas burners are stable in operation and have a wide range of heat loads.
For sustainable combustion gas-air mixture In medium and high pressure gas injection burners, stabilizers are used: additional igniting torches around the main flow (burners with an annular stabilizer), ceramic tunnels, inside which the combustion of the gas-air mixture occurs, and plate stabilizers that create a vortex in the flow path.
In furnaces of significant dimensions, gas injection burners are collected in blocks of 2 or more burners.
Infrared gas injection burners (the so-called flameless burners) are widely used, in which the main amount of heat obtained during combustion is transmitted by radiation, because the gas burns out on the emitting surface in a thin layer, without a visible flame. Ceramic nozzles or metal meshes serve as the emitting surface. These burners are used to heat rooms with a high rate of air exchange (gyms, retail premises, greenhouses, etc.), to dry painted surfaces (fabrics, paper, etc.), to heat frozen soil and bulk materials, in industrial furnaces. For uniform heating of large surfaces (furnaces of oil refineries and other industrial furnaces), the so-called. panel injection radiant burners. In these burners, the gas-air mixture from the mixer enters the common box, and then the mixture is distributed through the tubes to separate tunnels, in which its combustion takes place. Panel burners have small dimensions and a wide control range, and are not sensitive to back pressure in the combustion chamber.
The use of gas turbine burners is increasing, in which air is supplied by an axial fan driven by a gas turbine. These burners were proposed at the beginning of the 20th century (Eikart's turbo burner). Under the action of the reactive force of the outflowing gas, the turbine, shaft and fan are driven in rotation in the direction opposite to the outflow of gas. The burner capacity is regulated by the pressure of the incoming gas. Gas turbine burners can be used in boiler furnaces. High-pressure gas turbine burners with self-supply of air through recuperators and air economizers are promising: gas-oil burners gas high performance, working on heated and cold air.
Burners have the following requirements:
1. The main types of burners should be manufactured at the factories in series according to technical conditions. If the burners are made according to an individual project, then upon commissioning they must undergo tests to determine the main characteristics;
2. Burners must ensure the passage of a given amount of gas and the completeness of its combustion with a minimum air flow coefficient α, with the exception of burners for special purposes (for example, for furnaces in which a reducing environment is maintained);
3. While ensuring the specified technological mode, the burners must ensure the minimum amount of harmful emissions into the atmosphere;
4. The noise level generated by the burner should not exceed 85 dB when measured with a sound level meter at a distance of 1 m from the burner and at a height of 1.5 m from the floor;
5. Burners must operate stably without separation and flame breakthrough within the design range of heat power regulation;
6. For burners with preliminary complete mixing of gas with air, the flow rate of the gas-air mixture must exceed the speed of flame propagation;
7. To reduce energy consumption for auxiliary needs when using burners with forced air supply, the resistance of the air path should be minimal;
8. To reduce operating costs, the burner design and stabilizing devices should be sufficiently easy to maintain, convenient for revision and repair;
9. If it is necessary to preserve the reserve fuel, the burners must ensure a quick transfer of the unit from one fuel to another without disrupting the technological regime;
10. Combined gas-oil burners should provide approximately the same quality of combustion of both types of fuel - gas and liquid (fuel oil).
Diffusion burners
In diffusion burners, the air necessary for gas combustion is supplied from the surrounding space to the flame front due to diffusion.
Such burners are usually used in household appliances... They can also be used when the gas flow rate is increased, if it is necessary to distribute the flame over a large surface. In all cases, the gas is supplied to the burner without admixture of primary air and is mixed with it outside the burner. Therefore, these burners are sometimes referred to as external mixing burners.
The simplest in design diffusion burners (Fig. 7.1) are a pipe with drilled holes. The distance between the holes is chosen taking into account the speed of propagation of the flame from one hole to another. These burners have low thermal outputs and are used for burning natural and low-calorific gases under small water heaters.
Rice. 7.1. Diffusion burners:
Figure 7.2. Bottom diffusion burner:
1 - air regulator; 2 - burner; 3 - viewing window; 4 - centering glass; 5 - horizontal tunnel; 6 - brick layouts; 7 - grate
Diffusion type industrial burners include bottom slot burners (fig. 7.2). Usually they are a pipe with a diameter of up to 50 mm, in which holes up to 4 mm in diameter are drilled in two rows. The channel is a slot in the bottom of the boiler, hence the name of the burners - bottom slot.
From burner 2, gas enters the furnace, where air enters from under the grate 7. Gas streams are directed at an angle to the air flow and evenly distributed over its cross section. The process of mixing gas with air is carried out in a special slot made of refractory bricks. Thanks to such a device, the process of mixing gas with air is enhanced and a stable ignition of the gas-air mixture is ensured.
The grate is laid with refractory bricks and several slots are left in which pipes with drilled holes for gas outlet are placed. Air under the grate is supplied by a fan or as a result of vacuum in the firebox. The refractory walls of the slot are combustion stabilizers, prevent flame separation and, at the same time, increase the heat transfer process in the furnace.
Injection burners.
Injection burners are called burners in which the formation of a gas-air mixture occurs due to the energy of a gas stream. The main element of an injection burner is an injector that sucks air from the surrounding space into the burners.
Depending on the amount of injected air, the burners can be completely premixed with air or with incomplete air injection.
Incomplete air injection burners . Only a part of the air necessary for combustion enters the combustion front, the rest of the air comes from the surrounding space. These burners operate at low gas pressure. They are called low pressure injection burners.
The main parts of the injection burners (fig. 7.3) are the primary air regulator, nozzle, mixer and manifold.
The primary air regulator 7 is a rotating disc or washer and regulates the amount of primary air entering the burner. Nozzle 1 serves to convert the potential energy of gas pressure into kinetic energy, i.e. to give the gas jet a speed that allows the required air to be sucked in. The burner mixer consists of three parts: injector, confuser and diffuser. Injector 2 creates a vacuum and air suction. The narrowest part of the mixer is the confuser 3, which levels the flow of the gas-air mixture. In the diffuser 4, the final mixing of the gas-air mixture and an increase in its pressure occur due to a decrease in speed.
From the diffuser, the gas-air mixture enters the manifold 5, which distributes the gas-air mixture through the holes 6. The shape of the manifold and the location of the holes depends on the type of burners and their purpose.
Low-pressure injection burners have a number of positive qualities, due to which they are widely used in household gas appliances, as well as in gas appliances for catering and other household gas consumers. The burners are also used in cast iron heating boilers.
Rice. 7.3. Injection atmospheric gas burners:
a- low pressure; b- burner for a cast iron boiler; 1 - nozzle. 2 - injector, 3 - confuser, 4 - diffuser, 5 - collector. 6 - holes, 7 - primary air regulator
The main advantages of low pressure injection burners: simplicity of design, stable operation of burners with changing loads; reliability and ease of maintenance; noiselessness of work; the possibility of complete gas combustion and operation at low gas pressures; lack of air supply under pressure.
An important characteristic of incomplete mixing injection burners is the injection ratio - the ratio of the volume of injected air to the volume of air required for complete combustion of the gas. So, if for complete combustion of 1 m 3 of gas 10 m 3 of air is needed, and the primary air is 4 m 3, then the injection ratio is 4: 10 = 0.4.
The characteristic of burners is also the rate of injection - the ratio of primary air to the gas flow rate of the burner. In this case, when 4 m 3 of air is injected into 1 m 3 of the combusted gas, the injection ratio is 4.
The advantage of injection burners: the property of their self-regulation, i.e. maintaining a constant proportion between the amount of gas supplied to the burner and the amount of injected air at a constant gas pressure.
Mixing burners. Forced air burners.
Forced air burners are widely used in various heating devices for municipal and industrial enterprises.
According to the principle of operation, these burners are divided into burners with preliminary mixing of gas (Fig. 7.4) and fuel and burners without preliminary preparation of the gas-air mixture. Burners of both types can operate on natural, coke oven, blast furnace, mixed and other low and medium pressure combustible gases. Working regulation range - 0.1 ÷ 5000 m 3 / h.
The air to the burners is supplied by low and medium pressure centrifugal or axial fans. Fans can be installed on each burner or one fan on a specific group of burners. In this case, as a rule, all the primary air is supplied by the fans, while the secondary air practically does not affect the quality of combustion and is determined only by the suction of air into the combustion chamber through leaks in the combustion fittings and hatches.
The advantages of burners with forced air supply are: the possibility of using in combustion chambers with different back pressure, a significant range of regulation of the heat output and the gas-air ratio, relatively small torch sizes, insignificant noise during operation, simplicity of design, the possibility of preheating gas or air and the use of burners large unit capacity.
Low pressure burners are used at a gas flow rate of 50 ÷ 100 m 3 / h, at a flow rate of 100 ÷ 5000 it is advisable to use medium pressure burners.
The air pressure, depending on the design of the burner and the required thermal power, is taken equal to 0.5 ÷ 5 kPa.
For better mixing of the fuel-air mixture, gas is supplied to most burners in small jets under different angle to the primary blast air flow. In order to intensify the mixture formation, the air flow is given a turbulent motion using specially installed vortex blades, tangential guides, etc.
The most common burners with forced air supply of internal mixing include burners with a gas flow rate of up to 5000 m3 / h and more. They can provide a predetermined quality of preparation of the fuel-air mixture before it is fed into the combustion chamber.
Depending on the design of the burner, the processes of mixing fuel and air can be different: the first is the preparation of the fuel-air mixture directly in the mixing chamber of the burner, when the finished gas-air mixture enters the furnace, the second is when the mixing process begins in the burner and ends in the combustion chamber. In all cases, the speed of the outflow of the gas-air mixture is different 16 ... 60 m / s. The intensification of gas and air mixture formation is achieved by jet gas supply, the use of adjustable blades, tangential air supply, etc. When gas jet supply, burners are used with a central gas supply (from the center of the burner to the periphery) and with a peripheral one.
The maximum air pressure at the burner inlet is 5 kPa. It can work with back pressure and vacuum in the combustion chamber. In these burners, in contrast to external mixing burners, the flame is less luminous and relatively small in size. Ceramic tunnels are most often used as stabilizers. However, all methods discussed above can be used.
The burner of the GNP type with forced air supply and central gas supply, designed by the specialists of the Teploproekt Institute, is intended for use in furnaces with significant thermal stresses. These burners are designed to swirl the air flow using blades. The burner kit includes two nozzles: a type A nozzle used for short-flare gas combustion with 4 ÷ 6 gas outlet holes directed perpendicularly or at an angle of 45 ° to the air flow, and a B type nozzle used to obtain an elongated flame and having one central hole directed parallel to the air flow. In the latter case, the premixing of gas and air is much worse, which leads to an elongation of the flame.
Flare stabilization is ensured by the use of a class A fireclay brick fire-resistant tunnel. Burners can operate in cold and heated air. The excess air ratio is 1.05. Burners of this type are used in steam boilers, bakery industry.
The GMG two-line gas-oil burner is designed for burning natural gas or low-sulfur liquid fuels such as diesel, household fuel, naval fuel oils F5, F12, etc. Co-firing of gas and liquid fuel is allowed.
The burner gas nozzle has two rows of holes directed at 90 ° to each other. The holes on the side surface of the nozzle allow gas to be supplied to the swirling secondary blast air stream, the holes on the end surface to the swirling primary air stream.
The process of formation of a gas-air mixture in burners with forced air supply begins directly in the burner itself, and ends already in the firebox. During the combustion process, the gas burns out with a short and non-luminous flame. The air required for gas combustion is forced into the burner by means of a fan. Gas and air are supplied through separate pipes.
This type of burner is also called two-wire or mixing burners. The most commonly used burners operate at low gas and air pressure. Also, some burner designs are used at medium pressure.
Burners are installed in boiler furnaces, heating and drying ovens, etc.
The principle of operation of a forced air burner:
The gas enters the nozzle 1 with a pressure of up to 1200 Pa and leaves it through eight holes with a diameter of 4.5 mm. These holes must be at a 30 ° angle to the burner axis. Special paddles that set rotary motion air flow are located in the burner housing 2. During operation, the gas flows in small streams into the swirling air stream, which aids in good mixing. The burner ends with a ceramic tunnel 4 with an ignition hole 5.
Rice. 7.4. Forced air burner:
1 - nozzle; 2 - case; 3 - front plate; 4 - ceramic tunnel.
Forced air burners have a number of advantages:
-high performance;
- a wide range of performance regulation;
–The ability to work on heated air.
In existing various designs burners intensification of the gas-air mixture formation process is achieved in the following ways:
–Division of gas and air flows into small flows, in which mixture formation takes place;
–Supply of gas in the form of small streams at an angle to the air flow;
- twisting the air flow with various devices built into the inside of the burners.
Combined burners.
Combined burners are burners operating simultaneously or separately on gas and fuel oil or on gas and coal dust.
They are used in case of interruptions in the gas supply, when it is urgently necessary to find another type of fuel, when the gas fuel does not provide the required temperature regime of the furnace; gas supply for this is made only at a certain time (at night) to equalize the daily irregularities in gas consumption.
The most widespread are oil-gas burners with forced air supply. The burner consists of gas, air and liquid parts. The gas part is a hollow ring with a gas inlet and eight tubes for gas atomization.
The liquid part of the burner consists of an oil head and an inner tube ending in nozzle 1 (Fig. 7.5).
The fuel oil supply to the burner is regulated by a valve. The air part of the burner consists of a body, a swirler 3, an air damper 5, with which the air supply can be regulated. The swirler serves for better mixing of the fuel oil jet with air. Air pressure 2 ÷ 3 kPa, gas pressure up to 50 kPa, and fuel oil pressure up to 0.1 MPa.
Rice. 7.5. Combined oil-gas burner:
1 - oil nozzle, 2 - air chamber, 3 - swirler, 4 - gas outlet tubes, 5 - air regulating damper.
The use of dual fuel burners gives a higher effect than the simultaneous use of gas burners and oil burners or gas pulverized coal burners.
Combined burners are necessary for the reliable and uninterrupted operation of gas-using equipment and installations of large industrial enterprises, power plants and other consumers for which an interruption in operation is unacceptable.
Consider the principle of operation of a combined dust and gas burner designed by Mosenergo (Fig.7.6)
When operating on coal dust, a mixture of primary air with coal dust is supplied to the furnace through the annular channel 3 of the central pipe, and the secondary air enters the furnace through the scroll 1.
Fuel oil is used as a reserve fuel, in this case a fuel oil nozzle is installed in the central pipe. When converting the burner to gas fuel, the oil nozzle is replaced by an annular channel through which the gas fuel is supplied.
In the central part of the channel, a pipe with a cast iron tip 2 is installed. Tip 2 has oblique slots through which the gas escapes and intersects with the swirling air flow coming out of the volute 1. In improved burner designs, instead of slots 115 holes with a diameter of 7 mm are provided in the tip. As a result, the gas exit velocity almost doubles (150 m / s).
Rice. 7.6. Combined gas and dust burner with central gas supply:
1 - a snail for twisting the air flow, 2 - a tip of gas supply pipes,
3 - an annular channel for supplying a mixture of primary air with coal dust.
New burner designs use peripheral gas flow, in which gas jets, which have a higher velocity than air ones, cross a swirling air stream moving at a speed of 30 m / s at a right angle. This interaction of gas and air flows ensures fast and complete mixing, as a result of which the gas-air mixture burns with minimal losses.
7.3. Automation of gas combustion processes.
Gas fuel properties and modern designs gas burners create favorable conditions for the automation of gas combustion processes. Automatic control of the combustion process increases the reliability and safety of operation of gas-powered units and ensures their operation in accordance with the most optimal mode.
Today, gas-powered installations use partial or complex automation systems.
Complex gas automatics consists of the following main systems:
- automatic control;
- safety automation;
- emergency signaling;
–Technical control.
The regulation and control of the combustion process is determined by the operation of gas appliances and units in a given mode and ensuring the optimal mode of gas combustion. For this, the regulation of the combustion process is intended for automatic regulation of household, municipal and industrial gas appliances and units. Thus, a constant water temperature in the tank is maintained for storage water heaters, a constant steam pressure for steam boilers.
The gas supply to the burners of gas-using installations is terminated by the safety automatics in the event of:
- extinction of the torch in the furnace;
- lowering the air pressure in front of the burners;
- increasing the steam pressure in the boiler;
- an increase in the temperature of the water in the boiler;
- lowering the vacuum in the furnace.
Deactivation of these installations is accompanied by corresponding sound and light signals. No less important is the control of the gas content of the room in which all gas appliances and units are located. For these purposes, set solenoid valves, which stop the gas supply in cases of exceeding the maximum permissible concentration in the ambient air of СН 4 and СО 2.
Achieve optimal performance in conditions technological process possible with the help of thermal control devices
The operating conditions of gas-using equipment determine the degree of its automation.
Remote control of gas-using installations is achieved by using control and signaling devices.
Single-stage, two-stage and modulating burners for heating boilers. Overview.
When choosing burners, consumers face a daunting task- which burner to choose . This choice allows them to make a small comparison of burners from different manufacturers in terms of the type of regulation and the level of automation of the burner device.
We invite you to familiarize yourself with the opinion of the specialists of our company, based on the experience of using combined, liquid fuel and gas Weishaupt burners, Elco, Cib Unigas and Baltur.
Let's define the basic requirements for burners, depending on the application. Depending on the area of application, burners can be divided into groups.
Group 1. Burners for individual heating systems (in this group we include burners with a capacity of up to 500 - 600 kW, which are installed in boiler houses of private houses, small industrial and commercial and administrative buildings).
When choosing burners for a given group of consumers, it is necessary to take into account the wishes of the buyer in the level of automation of an individual boiler room:
If you do not show increased technical requirements to the equipment to be installed and if you want to have a reliable boiler room that does not require large initial financial investments, then you can opt for burners with single-stage, two-stage modes of operation;
If as a result you want to build a heating system with a high level of automation, weather-dependent regulation, as well as low fuel and energy consumption, then you better apply modulating burners or sliding two-stage burners, which will provide the ability to program the power and a wide operating range of the burner regulation.
Group 2. Burners for heating systems of large residential complexes (in this group we include burners with a capacity of more than 600 kW for the needs of housing and communal services, central heating, as well as for heating large industrial and commercial and administrative buildings).
· Sliding two stage or modulating burners are ideal for this group. This is due to: the large capacity of boiler houses, the customer's wish to build a boiler house with a high level of automation, the desire to ensure the lowest possible fuel and electricity consumption (apply frequency regulation fan power), as well as use equipment for automatic regulation of residual oxygen in flue gases (oxygen regulation).
Group 3. Process equipment burners (this group includes burners of any capacity, depending on the capacity of the technological equipment).
For this group, it is preferable modulating burners... The choice of these burners is determined not so much by the wishes of the customer, but by the technological requirements of production. For example: in some production processes, it is required to maintain a strictly defined temperature schedule and prevent temperature drops, otherwise this can lead to disruption of the technological process, damage to products and, as a result, to significant financial losses. Step-controlled burners can also be used in process plants, but only in cases where slight temperature fluctuations are permissible and do not entail negative consequences.
Brief description of the principle of operation of burners with different types of regulation.
Single stage burners they work only in one power range, they work in a mode that is difficult for the boiler. During the operation of single-stage burners, there are frequent switching on and off of the burner, which is regulated by the boiler unit automation.
Two stage burners , as the name suggests, have two power levels. The first stage usually provides 40% of the power, and the second 100%. The transition from the first stage to the second occurs depending on the controlled parameter of the boiler (coolant temperature or steam pressure), the on / off modes depend on the boiler automation.
Sliding two stage burners allow for a smooth transition from the first stage to the second. It is a cross between a two-stage and modulating burner.
Modulating burners heat up the boiler continuously, increasing or decreasing power as necessary. The range of change of the combustion mode is from 10 to 100% of the rated power.
Modulating burners are divided into three types according to the principle of operation of modulating devices:
1.Burners with mechanical modulation system;
2. burners with pneumatic modulation system;
3. burners with electronic modulation.
Unlike burners with mechanical and pneumatic modulation, burners with electronic modulation provide the highest possible control accuracy, since mechanical errors in the operation of burner devices are eliminated.
Price advantages and disadvantages
Of course, modulating burners are more expensive than staged models, but they have a number of advantages over them. The mechanism of smooth power regulation allows to reduce the cycle of boilers on-off to a minimum, which significantly reduces mechanical stresses on the walls and in the units of the boiler, and therefore prolongs its "life". At the same time, fuel economy is at least 5%, and with proper tuning, you can achieve 15% or more... And finally, the installation of modulating burners does not require replacement of expensive boilers, if they function properly, while increasing the boiler efficiency.
Against the background of the disadvantages of staged burners, the advantages of modulating burners are obvious. The only factor compelling managers to opt for stepped models is their lower price. But these kinds of savings are deceiving: Wouldn't it be better to spend a large sum at a time on better, more economical and environmentally friendly burners? Moreover, the costs will pay off in the next few years!
Many buyers understand the benefits of using modulating burners, and now they just have to choose the models they need. Which manufacturers are better to contact? Even with a cursory study of prices for imported and domestic burners, it is clear that the difference is very significant. Some models of foreign manufacturers are more expensive than products Russian production more than doubled.
A detailed analysis of the market of burner manufacturers shows that Russian equipment is significantly inferior to imported counterparts in terms of automation. In order to achieve high level automation of Russian-made burners, it is necessary to invest a lot of money on the purchase required systems automation and works on installation and adjustment of equipment. Based on the results of all work, it turns out that the cost of retrofitted Russian-made burners is close to the cost of imported burners. But at the same time, you will not have one hundred percent guarantee that a fully equipped Russian burner will provide you with the desired result.
Conclusion of our specialists
Choosing the right burner is an important step in the construction or modernization of a boiler house. How responsibly you approached this issue depends on further work heating equipment... Stable burner operation, compliance with environmental standards, a longer service life of boilers and the ability to fully automate the operation of a thermal power plant indicate significant advantages of using modulated burners in boiler rooms. And if the benefits from their exploitation are obvious, it is simply unreasonable not to take advantage of them.
Burners Weishaupt / Germany , Elco / Germany , Cib unigas / Italy, Baltur / Italy has established itself as a reliable and high quality equipment. By choosing these burners, you gain confidence and benefit! In turn, we are ready to provide you with reasonable prices and the shortest possible delivery time for equipment.
Efficient heating management is a vital part of the efficient operation of a boiler and home heating system. The competent use of the controls will reduce the energy consumption of the unit, while creating a comfortable temperature in every room of the house, avoiding overheating of the premises. A thermostat (or programmer) controls the operation of the boiler depending on the temperature in the room.
Up to 20% of the volume of consumed energy carriers can be saved by using this kind of automation. And the prices for energy carriers are quite high and every normal person wants to reduce his expenses.
We consider a situation when the boiler is designed correctly, the necessary insulation of the premises has been completed, and the heating system is functioning normally.
There are several types of boilers: solid fuel, gas, electric and liquid fuel.
Boilers are widely used all over the world. There are domestic samples, there are boilers and imported ones. The material of manufacture is steel or cast iron. Easy to operate, economical, with the function of adjusting the temperature of the coolant. In cheaper models, this function is implemented using a special device - a thermoelement.
Structurally, a thermoelement is a metal product, the geometric dimensions of which decrease or increase under the influence of temperatures (depending on the degree of heating). And from this, in turn, the position of the special lever changes, which closes and opens the traction flap. The photo shows a sample of such a regulator:
Photo: sample thermostatThe more the damper is open, the stronger the combustion process, and vice versa. Thus, the volume of air that enters the combustion chamber closed type, is completely controlled by a thermostat, and if necessary, its supply is interrupted and the combustion process is extinguished. In more modern models, controllers are installed that, depending on the set thermal conditions, control the air flow, turning on (or off) a special fan (see photo below):
Gas boilers- the most common and cheapest units to operate. Boilers are single-circuit and double-circuit. Single-circuit boilers have one heat exchanger and are intended for heating only. The connection diagram is shown in the figure below:
Single-circuit boiler connection diagram Double-circuit boilers have two heat exchangers and are designed for heating and receiving hot water. The boiler connection diagram is presented below:
Some boilers have separate regulators for heating and hot water temperatures.
A fairly common alternative to gas and solid fuel boilers... A lot of advantages, high efficiency, but a long payback period. The connection is simple, like that of gas boilers, but without cold water supply. Provided for temperature regulation and overheating protection.
Mechanical boiler timer Using a simple mechanical timer for an electric boiler there are three options for starting the central heating system:
Mechanical timers usually have a large, round dial with a central 24-hour scale. You can turn the dial to set the desired time and then leave it that way. The boiler will turn on at the right time. The outer part consists of a set of 15-minute period tabs that are inserted for easy adjustment of operation and setting modes. An emergency reconfiguration is possible, which is carried out when the boiler is connected to the network.
Mechanical timers are easy to set up, but at the same time the boiler always turns on and off at the same time every day, and this may not satisfy the owners if the family is large, and bath procedures are carried out several times a day at different times.
By the type of functions, they can be divided into several groups:
- with one function (maintaining temperature);
- with a large number of functions (programmable).
By design, thermostats are divided into types: wireless and with wires for communication with the boiler. The thermostats are installed in a convenient place, the temperature sensor is connected, connected to the boiler control system and used.
The room thermostats need a constant supply of air for normal and correct work therefore they should not be covered with curtains or blocked by furniture. Devices adjacent to an electric thermostat can interfere with the correct operation of the device: lamps, TVs, heating devices located nearby.
The programmable electronic room thermostat allows you to select the desired and comfortable temperature at any time, it is easy to reconfigure and change the operating mode. The time timer allows you to set a different heating pattern on weekdays and weekends. Some timers allow you to set different parameters for each day of the week, this can be useful for people who work part-time or in shifts. Many Terneo and KChM models are equipped with such thermostats.
The programmable room thermostat allows you to set individual heating standards for each day in accordance with your lifestyle and maintain the temperature of the house at all times, regardless of the presence or departure of the owners.
Video: Connecting a room thermostat to a gas boiler
If a boiler with a radiator is responsible for the heating system, as a rule, only one programmable room thermostat is needed to control the entire house. Some patterns need to be adjusted in the spring and fall when the clock has moved forward and backward, or there has been a certain change in climatic conditions. We also recommend changing the temperature settings when changing day and night.
Such a climate controller has several options that expand its capabilities:
Such a thermostat is located far from your boiler and usually allows you to turn heating on or off throughout the house. Older versions are wired to the boiler, newer systems usually send signals to the command center of the device. It is with devices of a new type that rather expensive but effective devices are equipped: double-circuit boilers Ferroli, Beretta and domestic AOGV.
The most famous are room thermostats for double-circuit boiler brand Gsm and Protherm. They have a built-in dilatometric thermostat for the boiler, which, depending on the model, can work remotely; this technology is often used for an electric boiler or solid fuel units.
The room thermostat turns off the heating of the system as needed. It works by measuring the air temperature, and turning on the heating when the air temperature drops below the thermostat setting, and turning it off when set temperature will be reached.
Advice:
As a rule, the temperature of the whole house or individual rooms is based on only one climate microcontroller in the heating system. The best way its location in the living room or bedroom, which should probably be the most visited place in the house.
Room thermostats need free air flow to measure temperature, so they should not be covered with curtains or blocked by furniture. Devices adjacent to an electric thermostat may interfere with the correct operation of the device. These include lamps, televisions, neighborhood boilers through the wall, touch switches.
Thermostatic valve a simple solution to the problem of obtaining a heat carrier of a given temperature by mixing colder water with warmer one. The three-way valve is shown below:
The thermostatic radiator valve allows you to control the temperature in a room by changing the flow of hot water through the radiator. They regulate the flow of hot water through the radiator, but do not control the boiler. Such devices must be installed in order to adjust the temperature that is needed in each individual room.
This idea should be considered as a supplement to the thermoregulation installation. Also, such devices need periodic readjustment and regular performance checks (every six months during a change in operating modes).
Below is a diagram of a homemade boiler thermostat device, which is assembled on Atmega-8 and 566 series microcircuits, an LCD display, a photocell and several temperature sensors. Atmega-8 programmable microcircuit and is responsible for compliance with the specified parameters of the thermostat settings.
Strictly speaking, this circuit turns on or off the heating boiler when the outside temperature drops (increases) (U2 sensor), and also performs these actions when the room temperature changes (U1 sensor). Adjustment of the operation of two timers is provided, which allow you to adjust the time of these processes. A piece of a circuit with a photoresistor affects the process of turning on the boiler according to the time of day.
The U1 sensor is located directly in the room, and the U2 sensor is on the street. It is connected to the boiler and installed next to it. If necessary, you can add the electrical part of the circuit, which allows you to turn on and turn off high-power units:
Another thermostat circuit with one control parameter based on the K561LA7 microcircuit:
The assembled thermostat based on the K651LA7 microcircuit is distinguished by its simplicity and ease of adjustment. Our thermostat is a special thermistor that significantly reduces resistance when heated. This resistor is included in the electricity voltage divider network. Resistor R2 is also located in this circuit, with which we can set the required temperature. Based on this scheme, you can make a thermostat for any boiler: Baksi, Ariston, Evp, Don.
Another circuit for a microcontroller-based thermostat:
The device is assembled on the basis of the PIC16F84A microcontroller. The role of the sensor is performed by a digital thermometer DS18B20. A small relay controls the load. Microswitches set the temperature that is displayed on the indicators. Before assembly, you will need to program the microcontroller. First, erase everything from the chip and then reprogram, and then reassemble and use it to your health. The device is not moody and works fine.
The cost of parts is 300-400 rubles. A similar regulator model costs five times as much.
A few final tips:
A gas burner is a device for mixing oxygen with gaseous fuel in order to supply the mixture to the outlet and burn it to form a stable torch. In a gas burner, gaseous fuel supplied under pressure is mixed in a mixing device with air (air oxygen) and the resulting mixture is ignited at the outlet of the mixing device to form a stable constant flame.
Gas burners offer a wide range of benefits. The construction of a gas burner is very simple. Its start-up takes a split second and such a burner works almost without failure. Gas burners are used for heating boilers or industrial applications.
Today there are two main types of gas burners, their separation is carried out depending on the method used for the formation of a combustible mixture (consisting of fuel and air). Distinguish between atmospheric (injection) and supercharged (ventilation) devices. In most cases, the first type is part of the boiler and is included in its cost, while the second type is most often purchased separately. Forced gas burners as a combustion tool are more efficient, since they are supplied with air by a special fan (built into the burner).
Gas burners are intended for:
- supply of gas and air to the combustion front;
- mixture formation;
- stabilization of the ignition front;
- ensuring the required intensity of combustion.
Types of gas burners:
Diffusion burner - a burner in which fuel and air are mixed during combustion.
Injection burner – gas burner with premixing of gas with air, in which one of the media required for combustion is sucked into the combustion chamber of another medium (synonym - ejection burner)
Hollow premix burner - A burner in which gas is mixed with a full volume of air in front of the outlets.
A large group of burners of various designs and different performances refer to burners with incomplete premixing of gas with air. In burners of this type, the mixing process begins in the burner itself and is actively completed in the combustion chamber. As a result, the gas burns out with a short and non-luminous flame. Due to the fact that before entering the furnace, where the combustion process begins, the gas-air mixture was partially prepared, the combustion rate is determined by diffusion and kinetic factors. Consequently, these burners carry out a diffusion-kinetic method of gas combustion. Burners of the considered type consist of systems for the separate supply of gas and all the air required for combustion, as well as devices in which the mixture formation process begins. A gas-air mixture enters the furnace, which is a turbulent flow with uneven fields of concentrations of fuel and oxidizer in cross section... Getting into the zone high temperatures, the mixture is flammable. The sections of the flow, in which the concentration of gas and air is in a stoichiometric ratio, burn out in a kinetic manner, and the zones in which the process of mixture formation is not completed burn out by diffusion. The mixing process in the furnace is controlled by the mixing device of the burner, since the structure of the flow and the movement of its individual particles determine the conditions for its exit from the mixer. The mixing of gas and air in these burners occurs as a result of turbulent diffusion, which is why such burners are called turbulent mixing burners. To increase the intensity of the gas combustion process, it is necessary to intensify the mixing of gas with air as much as possible, since mixture formation is a braking link in the whole process. Intensification of the mixing process is achieved by: swirling the air flow with directing blades; tangential supply or device of snails; by supplying gas in the form of small jets at an angle to the air flow by dividing the gas and air flows into small flows in which mixture formation occurs. Turbulent mixing burners are widely used. The main positive qualities of such burners are: a) the possibility of burning a large amount of gas with a relatively small size of the burner (especially important for powerful boilers); b) a wide range of regulation of the burner performance; c) the possibility of heating gas and air to temperatures exceeding the ignition temperature, which is of great importance for some high-temperature furnaces; d) a relatively simple implementation of structures with combined combustion of fuel (gas - fuel oil, gas - coal dust). Disadvantages of the burners under consideration: forced air supply and gas combustion with a chemical incompleteness greater than with kinetic combustion... Turbulent mixing burners have different capacities from 60 kW to 60 MW. They are used to heat industrial furnaces and boilers.
Turbulent mixing burners GNP designed by Teploproekt with a capacity of 7 ... 250 m3 / h at a gas and air pressure of 0.4 ... 2 kPa are shown in Fig. 16.10. The burners are available in nine sizes with two types of gas nozzle tips. Tip A provides short flare and tip B creates an elongated flare. Gas enters the burner through the nozzle and flows out at a certain speed from the nozzle. Air is supplied to the burner under pressure; it is twisted before entering the burner spout. The mixing of gas with air begins inside the burner when the gas exits the nozzle and is intensified by the swirling air flow. With a multi-jet gas supply (with tip A), the mixture formation process proceeds faster and the gas burns out in a short flame. The burner is installed in conjunction with a ceramic tunnel that serves as a combustion stabilizer. Burners provide gas combustion in the absence of chemical incompleteness with an excess air ratio α = 1.05 ... 1.1. At a gas pressure of 4 kPa, the length of the torch for burners with a tip of type A, depending on the size of the burner, varies from 0.6 to 2.3 m. The main dimensions of the series of HNP burners are as follows: the diameter of the outlet opening varies within the range D = 25 .142 mm; the diameter of the gas holes at the type A tip is: d = 3.2 ... 15.5, and their number varies from 4 to 6; the diameter of the gas hole at the type B tip is: di = 5.5 ... 31 mm (designations are shown in Fig. 16.10). According to the results of state tests, the burners are recommended for use. Their main positive qualities are: simplicity and compactness of the design, the ability to work at low gas and air pressures, and wide range of performance regulation. Burners of this type are intended for heating forging and thermal furnaces, dryers.
Rice. 16.10. Turbulent burner, type GNP 1- body, 2- nozzle, 3- nozzle tip, type A, 4- nozzle tip, type B, 5- nozzle
Non-hollow premix burner – a burner in which the gas is not completely mixed with the air in front of the outlets. Atmospheric gas burner – injection gas burner with partial premixing of gas with air, using secondary air from the environment surrounding the flame.
An atmospheric burner designed for installation in the firebox of four- and five-section cast iron boilers (VNIISTO-Mch) is shown in Fig. 16.8. The burner head has 142 holes with a diameter of 4 mm and fits over the ejection tube. In the place where the gas-air mixture exits from the ejector, the head has no holes. If you place holes here, then the flame above them will be much higher than above other holes, since when gas outflows from these holes, dynamic pressure the flow of the gas-air mixture moving from the ejection tube to the burner head. In addition, due to an increase in the outlet speed, the flame above these holes may not be sufficiently stable. The heat load of the burner is 20 kW (0.2 m3 / h at QCK = 36 MJ / m3). The burner is designed for combustion of gas with a calorific value QCH = 25,000 ... 36,000 kJ / m3, while the diameter of the nozzle is changed depending on the value of QCH. When burning natural gas with a calorific value of 36,000 kJ / m3, the nozzle diameter is 4 mm, and the required gas pressure is 1.3 kPa. The primary air ratio of the burner can be adjusted with an air disc. The ejection tube has a flow path with low hydraulic resistance. The burner head is designed in such a way that the secondary air has an approach to each row of holes from one side. The height of the flame when the burner is operating at normal heat demand is approximately 100 mm. The burner is simple in design and reliable in operation. When operating in cast iron sectional boilers, atmospheric burners provide complete combustion of gas with a relatively low content of nitrogen oxides in combustion products. The NO X concentration usually does not exceed 0.12 g / m 3. This is due to the dispersal of the flame and staged combustion of the gas (with primary and secondary air).
Rice. 16.8. Atmospheric burner for a cast iron boiler 1- air regulator, 2- nozzle, 3- ejection tube; 4- burner head with firing holes
An atmospheric burner with one outlet is shown in fig. 16.9. The peculiarity of this burner is that its head does not have a manifold with a large number of small holes, but a conical tube with one large diameter (40 mm) hole. As a result, the burner flame is considerably lengthened. Due to the vacuum in the furnace, secondary air flows through the annular gap between the burner and a special casing to the torch root. The burner has the ability to regulate the amount of primary and secondary air. Such burners are used when converting restaurant stoves and cooking boilers to gas fuel (moreover, the stove can have one burner or a block consisting of two or three burners). The heat load of the burner is 18.6 kW, the gas pressure is 1.3 kPa. The burner is designed to burn gas with a calorific value Q with h = 36,000 kJ / m3. Depending on the heat of combustion of the gas, a nozzle of the appropriate diameter is installed in the burner.
Rice. 16.9. Atmospheric burner with one outlet 1- burner head, 2- ejection mixer, 3- regulator, 4- nozzle, 5- primary air regulator
Special burner – a burner, the principle of operation and design of which determines the type of heating unit or features of the technological process.
Recuperative burner – burner equipped with a recuperator for heating gas or air
Regenerative burner - a burner equipped with a re-generator for heating gas or air.
Automatic burner – a burner equipped with automatic devices: remote ignition, flame control, fuel and air pressure control, shut-off valves and controls, regulation and signaling.
Turbine burner – gas burner, in which the energy of the escaping gas jets is used to drive a built-in fan that blows air into the burner.
Pilot burner – auxiliary burner used to ignite the main burner.
The most applicable today are the classification of burners by the method of air supply, which are divided into:
- blow-free - air enters the furnace due to rarefaction in it;
- injection - air is sucked in due to the energy of the gas stream;
- blast - air is supplied to the burner or furnace by means of a fan.
Block ejection (injection) burners of the B and G type, developed by Promenergogaz. Burners of this type are a series of burners of different configurations and capacities, assembled from standard elements. A standard burner element consists of a set of single mixers of the same type 2 (Fig. 16.4, a), fixed in a common manifold - a gas chamber 3. A single mixer is a pipe with a diameter of 48X3 mm and a length of 290 mm. In the initial part of the pipe, which is located inside the gas manifold, there are four holes with a diameter of 1.5 mm each, the axes of which are located at an angle of about 25 ° to the axis of the burner. These holes act as peripheral nozzles through which gas flows into the ejection tube and ejects air entering through the open end of the tube. The design of the ejection part is worked out in such a way that with a vacuum in the furnace equal to 20 Pa, the gas ejects all the air necessary for combustion, with an excess coefficient a = 1.02 ... 1.05. The high velocities of the gas jets located at the periphery contribute to the creation of a velocity profile that prevents flame breakthrough. The burner blocks are lined with a refractory mass (see Fig. 16.4, b), and at their exit there is a stabilizer tunnel 100 mm deep. It prevents the flame from blowing off. The burners are completely placed within the 510 mm thick boiler lining. The nominal gas pressure in front of the burner is 80 kPa (average pressure), the coefficient of the capacity regulation depth is 3.4 ... 3.8. Depending on the layout (number of individual elements), the burner capacity varies from 10 to 240 m3 / h. BIG burners operate without chemical incompleteness of combustion with small excess air. The content of nitrogen oxides is 0.15 ... 0.18 g / m3. The burners are assembled in the form of standard sets (see Fig. 16.4, c), consisting of single ejection tubes assembled in one row of G standard sizes), in two rows of F standard sizes) and in three rows of B sizes). The burners are intended for equipping boiler units with an arrangement in the lining of the boiler walls and on the bottom instead of the grate. Boilers equipped with BIG burners have a higher efficiency (by 2%) than when equipped with ejection burners with centrally located nozzles.
Gas burners are used at various gas pressures: low - up to 5000 Pa, average - from 5000 Pa to 0.3 MPa, and high - more than 0.3 MPa. Burners are used more often.The thermal power of a gas burner is of great importance, which is maximum, minimum and nominal.
During long-term operation of the burner, where more gas is consumed without breaking off the flame, the maximum thermal power is achieved.
The minimum heat output occurs with stable operation of the burner and the lowest gas consumption without flame breakthrough.
When the burner is operating at a nominal, providing maximum efficiency with the greatest completeness of combustion, the gas flow rate is achieved by the nominal thermal power.
It is allowed to exceed the maximum thermal power over the nominal by no more than 20%. If the rated thermal power of the burner according to the passport is 10,000 kJ / h, the maximum should be 12,000 kJ / h.
One more important feature gas burners is the range of regulation of heat output.
Today, a large number of burners of various designs are used.
A burner is selected according to certain requirements, which include: stability with changes in thermal power, reliability in operation, compactness, ease of maintenance, ensuring the completeness of gas combustion.
The main parameters and characteristics of the used gas burner devices are determined by the requirements:
- thermal power, calculated as the product of the hourly gas consumption, m 3 / h, by its lowest heat of combustion, J / m 3, and being main characteristic burners;
- parameters of the combustion gas (net calorific value, density, Wobbe number);
- nominal thermal power, equal to the maximum power attainable during long-term operation of the burner with a minimum "excess air factor a and provided that the chemical underburner does not exceed the values set for this type of burner;
- nominal gas and air pressure corresponding to the nominal thermal power of the burner at atmospheric pressure in the combustion chamber;
- nominal relative torch length equal to the distance along the torch axis from the outlet section (nozzle) of the burner at nominal thermal power to the point where the carbon dioxide content at α = 1 is equal to 95% of its maximum value;
- coefficient of limiting regulation of thermal power, equal to the ratio of the maximum thermal power to the minimum;
- coefficient of operating regulation of the burner in terms of thermal power, equal to the ratio of the rated thermal power to the minimum;
- pressure (vacuum) in the combustion chamber at the rated power of the burner;
- heat engineering (luminosity, degree of blackness) and aerodynamic characteristics of the torch;
- specific metal and material consumption and specific consumption energy related to the rated heat output;
- the sound pressure level generated by the operating burner at the rated heat output.
Burner requirements
Based on the operating experience and analysis of the design of burners, the main requirements for their design can be formulated.
The burner design should be as simple as possible: without moving parts, without devices that change the cross-section for the passage of gas and air, and without complex-shaped parts located near the burner nose. Complex devices do not justify themselves during operation and quickly fail under the influence of high temperatures in the working space of the furnace.
The sections for the outlet of gas, air and gas-air mixture should be worked out during the creation of the burner. During operation, all these sections must be unchanged.
The amount of gas and air supplied to the burner should be measured with throttle devices on the supply lines.
The cross-sections for the passage of gas and air in the burner and the configuration of the internal cavities should be selected so that the resistance on the path of gas and air movement inside the burner would be minimal.
The gas and air pressure should generally provide the required speeds in the outlet sections of the burner. It is desirable that the air supply to the burner be regulated. Unorganized air supply as a result of vacuum in the working space or by partial injection of air with gas may only be allowed in special cases.
Gas supply of buildings
Gas supply of buildings- gas supply by means of a gas pipeline system, through which gas from the city will distribute, the network goes to gas appliances installed by consumers. Gas supply system includes: subscriber branches connected to the city distribution network and supplying gas to the building; in-house gas pipelines transporting gas inside the building and distributing it between individual gas appliances.
The subscriber branch consists of gas inlets to the consumer's territory, in-yard gas pipelines and gas inlets to the building. At the gas inlet to the consumer, at a distance of at least 2 m from the building line, a gate valve or a crane is made in the well. One disconnecting device is installed per group of residential buildings served by one input.
Rice. Gas supply scheme of the building: 1 - street network of low pressure gas; 2 - courtyard gas pipeline; 3- condensate trap; 4 - gas inlet; 5 - shut-off valves; 6 - distribution gas pipeline; 7 - risers; 8 - floor wiring; 9 - gas appliances; 10 carpet; 11 - valve
The inlets to the consumers' territory and the courtyard gas network, as a rule, are laid in the ground. The conditions for their laying do not differ from the conditions for laying underground city gas pipelines. Entries of gas pipelines into residential and societies, buildings can be carried out: into each staircase; directly in the kitchens of residential buildings or in the premises of societies, buildings where gas is consumed; in the basements of buildings with technical. corridors. With dry gas, it is advisable to make the inlets through the walls above the foundations. Entry device into the building through the technical corridors are allowed under the following conditions: with a corridor height of at least 1.6 m; if there are at least two entrances to the corridor from outside, not connected with other parts of the building; with natural exhaust ventilation in the corridor, providing at least one air exchange; electric lighting of the corridor must be explosion-proof; with fire-resistant ceilings. Arrangement of inlets directly into living quarters, elevator engine rooms, pump rooms, ventilation chambers, etc. is not allowed.
Intra-house gas pipelines are divided into risers that transport gas in the vertical direction, and intra-apartment gas pipelines that supply gas from the risers to individual gas appliances. Gas risers are usually installed in stairwells and kitchens. The laying of risers in living quarters is prohibited in bathrooms and toilets. To disconnect individual sections of gas pipelines, taps are made: at the inputs to the building, in apartments in front of each gas appliance.
Bronze (brass) and combined taps with tension plugs are placed in front of the meters and gas appliances. Bronze or cast iron plug tension cranes or gate valves are installed at the entrances to the building. On risers, branches to: apartments and in front of each gas appliance after the taps, counting along the gas flow, the squeegees necessary for repair work are installed.
Gas pipelines inside buildings are made of steel pipes... Pipes are connected by welding or threaded. The use of pipes made of plastics (vinyl plastic, polyethylene, etc.) is promising. Gas pipelines in buildings are laid openly at a height of at least 2.0 m from the floor to the bottom of the pipe; when supplied with wet gas - with a slope of at least 0.002 from the meter to the riser and from the meter to gas appliances. When crossing staircase ceilings and hollow or backfilled walls, gas pipelines are enclosed in steel pipe cases.
The main devices used for gas supply: stoves, water heaters, cooking kettles, ovens and boilers. Household gas stoves and water heaters are installed in the apartments. The same devices are used by public and small communal consumers. Enterprises of companies, catering are equipped with more powerful gas stoves - restaurant type, cooking boilers, ovens, boilers and water heaters. In low-rise buildings with stove heating, gas can also be used to heat stoves. Gas meters are used to measure gas consumption at consumers. Gas meters are not installed in new residential buildings.
Most gas appliances must have a drain. flue gas through chimneys into the atmosphere. In newly designed buildings, flue gases are removed from each device through a separate chimney. In existing buildings, it is allowed to connect three gas appliances to one chimney, located on the same or different floors. Combustion products are introduced into the chimney at different levels, at a distance of at least 500 mm from each other. Gas appliances They are connected to chimneys using pipes made of roofing steel, the diameter of which is determined depending on the thermal load of the device: up to 10,000 kcal! hour - from 100 to 125 mm, up to 20,000-25,000 kcal! hour - from 125 to 150 mm. The vertical section of the connecting pipes from the branch pipe of the gas appliance to the first turn of the pipe must be at least 0.5 mm. In rooms with a height of up to 2.5 m, a vertical section of 0.3 m is allowed. The total length of the horizontal pipe section is no more than 3 m, and in existing buildings no more than 6 m, and there should be no more than three turns along the entire length of the connecting pipe. Pipes are laid with a slope of at least 0.01 towards the gas appliance and only in non-residential premises. Chimneys, as a rule, are arranged in the internal walls of buildings. Chimneys should not have horizontal sections, and below the entry of the connecting pipe into the chimney, it is necessary to arrange a pocket with a depth of at least 250 mm with a hatch for cleaning it.
During normal operation of gas appliances, the vacuum value at the place where the combustion products exit from the traction breaker should be 0.4-0.7 mm of water. Art.
depending on the type of device. With a low vacuum, part of the combustion products goes into the room, and in some cases, the draft overturns. The chimney section is determined by calculation. For water heaters with a heat load of 20,000-25,000 kcal / hour, the cross-section should be no less than 150 cm2.
Liquefied petroleum gases are used for gas supply. Liquefied gas is stored in cylinders, which, depending on their size, are installed directly in the kitchen, in metal. closet outside the wall of the building or buried in the ground. In the first two cases, gas for short connecting pipes goes directly to gas appliances, and in the latter - from the tank located in the ground, there are underground gas pipelines in the yard, transporting gas to one or several buildings.
Gas pipelines are tested with air after external inspection and elimination of all visible defects. External gas pipelines - subscriber branches - are tested similarly to city gas pipelines. The internal gas network of residential and community buildings and buildings is tested for strength and density. The strength test of low pressure gas pipelines is carried out at a pressure of 1 am. Gas pipelines of residential buildings are tested for density with a pressure of 400 mm of water. Art. with an installed meter and connected gas appliances.
Gas appliances
In residential and public buildings, gas is used for cooking and hot water. The main appliances that are used to supply gas to buildings are stoves, water heaters, boilers, cooking kettles, ovens and refrigerators. The operation of gas appliances is characterized by following indicators: 1) heat load, or the amount of heat in the gas that is consumed by the device, in kW; 2) productivity, or the amount of useful heat that is transferred to the heated body, in kW; 3) Efficiency, which is the ratio of the performance to the thermal load of the device. The nominal load is considered to be the load at which the gas device operates most efficiently, i.e., with the least chemical underburning of the gas, the highest efficiency, and develops the nominal performance. At rated load of structural elements the device must not develop dangerous thermal stresses that shorten its service life. The limiting (maximum) thermal load is considered to be a load exceeding the rated load by 20%. At this load, the performance of the device should not noticeably deteriorate. Gas appliances installed in residential and public buildings operate at low pressure, they are equipped with atmospheric ejection burners. Household gas stoves are made with two, three and four burners with and without ovens. They consist of the following main parts: a body, a working oven with burner inserts, an oven, gas burners (top burners, as well as for a cabinet), a gas distribution device with taps. Parts of household stoves are made of heat-resistant, corrosion-resistant and durable materials. The surface and details of the slab (except for the back wall) are covered with white enamel. The height of the working table of household stoves is 850 mm, and the width is at least 500 mm. Distance between centers of adjacent cooking zones 230 mm. The burner burners have the following nominal loads: normal power 1.9 kW, high power 2.8 kW. The four-burner ranges can be equipped with one high power burner. The rated load of the burners must ensure uniform heating of the oven to a temperature of 285 ... 300 ° С in no more than 25 minutes. According to the current GOST, the efficiency of burner burners must be at least 56%, and the efficiency of stoves with the removal of combustion products into the chimney must be at least 40%. The content of carbon monoxide in combustion products during operation of burners at rated load should not exceed 0.05% in terms of dry flue gases and an excess of air equal to one (a = 1). Adjusted burners must operate stably, without separation and breakthrough of the flame, with a change in the calorific value of gas within ± 10% and a thermal load from the maximum to 0.2 nominal. Household gas stoves are equipped with atmospheric burners that discharge combustion products directly into the kitchen. Part of the air required for combustion (primary air) is ejected by the gas flowing out of the burner nozzles; the rest (secondary air) enters the flame directly from the environment. Air enters the oven burners through special slots and holes in the stove. The combustion products of the burner burners pass through the gap between the bottom of the cookware and the working table of the stove, rise along the walls of the cookware, heating them, and enter the surrounding atmosphere. The combustion products heat the oven and enter the kitchen through openings in the side or back of the stove. The removal of combustion products directly into the room makes high demands on the constructive qualities of burners, which must ensure complete combustion gas. The main reasons for the chemical incompleteness of gas combustion in burner burners are: a) the cooling effect of the walls of the cookware, which can lead to incomplete chemical combustion reactions, the formation of CO and soot; b) unsatisfactory mixing of gas with primary air in the flow path of the ejector; c) poor organization of the supply of secondary air and removal of combustion products. To eliminate these reasons, it is necessary to design the gas burner devices of the stove so that the following conditions are met: a) the burners must operate with the maximum coefficient of primary air, ensuring a stable flame at all capacities; b) the location of the burner in relation to the bottom of the cookware should ensure good washing with combustion products and exclude the possibility of contact of the inner flame cone with its bottom; c) the distance between the bottom of the cookware and the burner should be optimal, since with an increase in this distance, the excess of air increases and the efficiency of the burner decreases, and with a decrease, the chemical incompleteness of combustion increases. The value of the optimal distance depends on the heat load, the primary coefficient of air, the size of the burner hole and the bottom of the cookware. For burners with a heat load of 1.75 ... 1.9 kW with a burner hole diameter of 200 ... 220 mm, the optimal distance is approximately 20 mm; d) the shape of the profile of the flowing part of the ejection tube should be optimal; e) the removal of combustion products through the gap between the bottom of the cookware and the work table is ensured (the gap must be at least 8 mm). So that the stoves can operate on gaseous fuels with different heats of combustion, several replaceable nozzles with hole diameters corresponding to the heat of combustion of the gas and the nominal pressure are used. To prevent accidental opening, the taps of all burners must have latches for the closing position. The oven tap handle must be different from other handles in shape or color. The walls of the oven must have thermal insulation in the form of an air gap or a layer of insulating material so that the temperature on the surface of the stove does not exceed 120 ° C. The CCGT four-burner stove has a work table with four vertical burner burners shown in Fig. 19.3.
Rice. 19.3. Atmospheric gas burner for household stove 1 - ejection tube. 2 - cap, 3 - damper for primary air regulation, 4 - nozzle
The stove has a roasting and drying cabinet. A sight glass is mounted in the door of the oven. The oven is insulated with slag. The stove table is closed and equipped with bar hob grids. The oven is located in the middle of the stove and is heated atmospheric burner, the head of which is made in the form of an annular tube. On a vertical burner burner, the holes in the head have an outlet dimension and a pitch that prevents the flame tongues from merging. To spread the flame along the firing holes, the stamped steel cover has a flange, which is located above the torches of the burner. It provides flame ringing, which creates conditions for igniting adjacent torches and ensures combustion stability with respect to flame breakthrough. Instantaneous and storage water heaters are heat exchangers used for local hot water supply. For instantaneous water heaters, the hot water preparation mode corresponds to the consumption mode. They heat water up to 50 ... 60 ° С and give it out 1 ... 2 minutes after turning on the device. They are often referred to as fast acting. For DHW cylinders, the water preparation mode may not correspond to the water consumption mode. Water in storage tanks is heated up to 8О ... 9О ° С. Water heaters must meet the following requirements: 1) Their efficiency must be at least 82%. Water heaters should work normally at pressure tap water from 0.05 to 0.6 MPa. A constant hot water temperature must be created 1 ... 2 minutes after turning on the device. In storage tanks, the water is heated for 60 ... 70 minutes. The water heaters are equipped with draft breakers and reverse draft fuses. The temperature of the combustion products in front of the chopper must be at least 180 ° C. The outer surface of the water heater is covered with white enamel; the surface temperature during operation of the device at rated load should not exceed the ambient temperature by more than 50 ° С; 2) water heaters must be equipped with a main burner and an ignition burner. The pilot burner flame instantly ignites the gas on the main burner. Its maximum consumption through pilot burner at nominal pressure is 35 l / s. The main burner should have a steady flame. The height of the flame for instantaneous water heaters should not exceed 80 mm at rated load and 150 mm at maximum. Burners must provide steady burning gas without separation and flame breakthrough when the thermal load changes from 0.2 to 1.25 nominal. When working with the maximum load, the content of carbon monoxide CO in the combustion products should not exceed 0.1% of the volume of dry products at a theoretical air flow rate a = 1; 3) each water heater must be equipped with blocking and safety devices that allow gas to pass to the main burner only when the igniter is on and stop supplying it when the igniter goes out. Instantaneous water heaters are equipped with safety devices, thanks to which the main burner is turned off in case of stopping the drawdown of hot water or when its pressure drops below the set limit. The DHW cylinders are equipped with automatic hot water temperature control, which ensures that the main burner is turned off when the water is heated above a preset value. Instantaneous water heaters consist of the following main parts: 1) a heat exchanger, including a fire chamber, a coil and a heater; 2) a gas burner with an igniter; 3) a gas outlet device with a traction chopper and a reverse draft fuse; 4) blocking, safety and regulating devices; 5) an outer metal enamelled casing; 6) a water-folding system with taps and a shower net. Automatic flow-through water heater VPG, designed for multi-point water sampling, is shown in Fig. 19.5. Nominal
thermal load of water heaters of type VPG is 21 ... 23 kW.
A competent choice of a burner is an important stage in the construction or repair of a boiler house. The further work of the heating equipment depends on how responsibly the leaders and organizers approached this issue.
Modernization of the heating system is the most important task facing the heads of housing and communal services. The choice of a partner for the design, supply, installation and commissioning of equipment is not a problem, but the question of the efficiency of operation of boiler houses after their re-equipment remains open. A limited budget forces us to find the simplest solutions - to purchase cheap, short-lived equipment that requires constant attention. But now they exist completely automated systems, for the selection and maintenance of which it is best to turn to highly qualified specialists who have a complete understanding of how a modern boiler house should function.
When choosing burners, consumers are faced with a difficult task: what to give preference to - domestic or foreign equipment. And here the sellers of imported burners often use a clever trick: they compare sliding two-stage burners of foreign production with modulated burners of domestic production. Even with a significant difference in prices for "similar" products, they push on the German, Finnish, Italian quality, trying to persuade buyers to purchase these particular burners. However, any specialist working with boiler equipment understands that it is at least incorrect to compare different types of burners only in terms of the price component. Therefore, it is necessary to know the difference between their technical characteristics and opportunities.
The most widespread in boiler rooms are two-stage, sliding-two-stage and modulating burners. Two-stage burners, as the name suggests, have two power stages. The first stage provides 40% of the power and the second 100%. The transition from the first stage to the second occurs depending on the controlled parameter of the boiler (flow water temperature or steam pressure), the on / off modes depend on the boiler automation.
Sliding two-stage burners allow for a smooth transition from one stage to the second. It is a cross between a two-stage and modulating burner. Modulating burners heat the boiler continuously, increasing or decreasing the output as required. The range of change of the combustion mode is from 10 to 100% of the rated power.
Of course, modulating burners are more expensive than staged models, but they have a number of advantages over them. The mechanism of smooth power regulation allows to reduce the cycle of boilers on-off to a minimum, which significantly reduces mechanical stresses on the walls and in the units of the boiler, and therefore prolongs its "life". At the same time, fuel economy is at least 5%, and with proper tuning, you can achieve 15% or more... And finally, the installation of modulating burners does not require replacement of expensive boilers, if they function properly. During operation of staged burners, the boiler experiences significant loads, which over time destroy the unit.
Against the background of the disadvantages of staged burners, the advantages of modulating burners are obvious. The only factor compelling managers to opt for stepped models is their lower price. But savings of this kind are deceiving: wouldn't it be better to spend a large sum at a time on better, more economical and environmentally friendly burners, especially since these costs will pay off in the next few years?
Smart executives understand the benefits of modulating burners, and now all they have to do is select the models they need. Which manufacturers are better to contact? Even with a cursory study of prices for imported and domestic burners, it is clear that the difference is very significant. Some models of foreign manufacturers are more than twice as expensive as Russian-made products. And yet, stereotypes that quality goods come only from abroad make people pay more. However, a more detailed analysis of the burner manufacturers market shows that we also have high quality competitive products. For more than 15 years, the Starorussky Instrument-Making Plant has been producing various models of burners that are successfully installed on all types of domestic and imported boilers. Modulated block burners from this manufacturer comply with all environmental standards for fuel combustion, have a wide power control range (from 10 to 100%), while providing maximum efficiency. When looking for reliable economical burners for boiler rooms, it is simply impossible not to pay attention to them. Simple installation of equipment already gives tangible results, and if experienced specialists in setting up burners are involved in the process, then fuel savings can be more than 15%. With the use of modulated burners from Staroruspribor, managers will be able to forget for a while about one more item of expenses - boiler replacement. The transition to a "sparing" operating mode allows you to double its service life... Those who know how expensive such equipment is (prices are calculated in millions of rubles) will appreciate the possibility of a more rare replacement of these units.
A competent choice of a burner is an important stage in the construction or repair of a boiler house modernization. The further operation of the heating equipment depends on how responsibly the customers approached this issue. If, for example, we use modulated burners manufactured by JSC “Zavod“ Staroruspribor ”, then after two or three heating seasons, the costs will be more than repaid. Stable operation, compliance with environmental standards, a longer service life of boilers and the ability to fully automate the operation of a thermal power plant indicate significant advantages of using modulated burners in boiler rooms. And if the benefits from their exploitation are obvious, it is simply unreasonable not to take advantage of them.
