Methods for stabilizing flame burner in the furnace
The limits of steady operation of the burner is the separation of the flame from the burner and the flame spock inside the burner.
Flame stabilization is made using special devices and creating conditions to prevent separation or skip:
· Maintaining the speed of the DHW output during the safe limits;
· Maintaining the temperature in the combustion zone is not lower than the temperature of the DHW inflammation.
When pure gas without air flows into the burner, then the flame in this case is most stable, because Square can not be, and the separation is unlikely, because Such devices operate at low gas pressure.
In the burners in which there is a finished gas-air mixture, i.e. Gas and air, a gap and spock is possible. Flame's skill in the burner can be prevented if:
· Reduce the outlet for DHW;
· At the mouth of the burner, install a slit stabilizer with a slit size of not more than 1.2mm or a grid with a shallow cell, the size of no more than 2.5mm;
· If you cool the outlet burner.
The separation of the flame from the burner can be prevented by installing the burner constantly burning in the mouth, with the help of refractory tunnels of various designs, installation of a dissection stabilizer, installations in the firebox of a refractory cooker from refractory brick. The hill (refractory) in the furnace prevents the flame separating and maintains the temperature in the boiler firebox.
Gas-burners
A gas burner is a device that provides sustainable burning of gaseous fuel and control the combustion process.
The main functions of the burner:
· Supply gas and air to the combustion front;
· Mix formation;
· Stabilization of the Flame Front;
· Ensuring the required intensity of the gas burning process.
1. Diffusion burners.
2. Injection medium and low pressure.
3. Kinetic - with the forced air supply of low and medium pressure.
4. Combined gas-gas burners of low and medium pressure.
All burners must pass public tests in special test centers and have a "certificate of compliance with Russian standards"
(Tests:schachti, Rostov Region, Sverdlovsk Region: "Ural Test Center of Burner Devices".
Diffusion burner. Diffusion is the process of spontaneous penetration of one substance to another.
In diffusion burners, the entire air-needed air is secondary. Diffusion burners are practically nothing else. The diffusion burner is a pipe with holes for the gas outlet, the distance between the holes is determined, taking into account the spread of the flame from one hole to another. Pure gas is supplied to such a burner without air impurities. The burners are low-power, require a large volume of flue space or air supply to the fan fan.
In industry at the old factories, a sub-flow-slop diffusion burner is used, which is a pipe æ 57mm with drilled on it in 2 rows by holes.
The advantages of diffusion burners include ease of design and a steady flame.
Injection burner.The air drums due to the discharge created by the stream of expiring gas is called injection, or the air supply is carried out due to the energy of the gas jet. Injection burners are incomplete (50 ... 60%) air injection and complete injection.
In the injection burners in combustion, the air is involved primary (50 ... 60%) and secondary from the volume of the furnace. These burners are also called self-regulating (i.e., the greater the gas supply, the more air sues).
Disadvantages of these burners: need to stabilize the flame from the separation and slippath. Burning - with noise when working.
The advantages of the burners: simplicity of design, reliability in the work, the possibility of total gas burning, the possibility of working on low and medium pressures, air supply due to the energy of the gas jet, which saves electrical energy (fan).
The main parts of the injection burners are:
· Primary air regulator (1);
· Nozzle (2);
· Mixer (3).
The primary air regulator is a rotating disk, a washer or damper, with which the primary air supply is adjusted.
Nozzle is used to convert the potential gas pressure energy - in kinetic (speed), i.e. To give a gas jet of such a speed that would ensure the necessary air flow.
The burner mixer consists of 3-parts:
· Injector (4);
· Confused (5);
· Diffuser (7).
In the injector, there is a vacuum and the primary air seats are created.
The narrowest part of the burner is a confusion, in which the gas-air mixture is aligned.
The diffuser occurs the final mixing of the gas-air mixture and an increase in its pressure by reducing the speed.
Burner with forced air supply. This is a kinetic or two-wire burner. Air for combustion of gas is fed into the burner forced with a 100% fan, i.e. All air is primary. The burner is effective, high power, does not require a large flue space. It works at low and average gas pressure, needs to stabilize the flame from the separation and slippath.
The burner has an air swirl, intended for full mixing of gas with air inside the burner.
The burner has a ceramic tunnel that performs the functions of the stabilizer.
Combined gas-gas burners.These burners, in addition to the gas part there are nozzle for spraying liquid fuel. The simultaneous combustion of gas and liquid fuel is allowed briefly when switching from one type of fuel to another.
The nozzle is a type of pipe type in a pipe. A liquid fuel is supplied along the central pipe, spray air or steam is supplied along the internet space.
Electromagnetic fittings.
These are valves KG-70,40,20,10 and the SVMG valve intended for automatic shutdown and turning on the burners.
Work in the automotive and control system designed to disable gas supply to the boiler in case of deviation of any parameter of the boiler from the normal-specified one.
Electromagnetic valves KPEG-100P, KPEG-50P are also designed to work in the automatic locking system on the voltage shutdown. Turns on only manually.
Valve device.
KG valves operate on gas pipelines with a pressure of not more than 0.5 kg / cm. The valve consists of the housing, the lids, between which the membrane is shed.
On top of the membrane there is a metal disk, from below the sealing gasket that performs the valve function. Gasket and metal disk with each other with a bolt.
At the top of the cover there is a cap, under which there is a bolt-limiter of a membrane deflection.
The valve kg includes a servoclap and an electromagnet coil. The servoclap is there are two holes, in the upper part of the overhead, and the reset from the bottom, which in turns are open and closed spool connected through the rod with the core of the electromagnet coil.
In the servolapan over the spool there is a short rigid spring, which, when the voltage is disconnected, is tightly pressed towards the saddle of the spool opening.
In the absence of voltage on the electromagnet coil, the servolapan spool under the influence of the weight of the electromagnet core, the spring force overlaps the discharge hole, i.e. Sits on the saddle of a dump hole.
Through a dumping hole, closed as a spool, stops the dump of gas from the ECG abdominal cavity into the atmosphere. The bypass in the servolapan remains open. The valve subable cavity through the slots in the housing, through the open byproof hole, communicated with the above-mentioned cavity, according to the principle of reporting vessels. The pressure of the gas in the subabled and in the appreciated becomes equal. At the same time, the membrane, under the action of the weight of the disk on it and the spring forces overlaps the gas passage.
When the voltage is applied to the electromagnet coil, the core is drawn into the coil, it lifts a spool from the stem from the saddle seat, opening it and closes the overhead hole in the top of the servolapan.
The gas from the valve gauge kg through an open reset hole is reset to the atmosphere through a pulse tube. In this case, the pressure in the above-handed cavity becomes equal to atmospheric pressure.
The membrane, under the action of the input pressure of the gas under it, will join along with the sealing gasket from the bottom, and will provide a gas flow to the burner. And the reversal opening of the servolapan at the same time is closed with a spool and connection aboutdMMBRAND and SPMBLED VALUE SPACE - NO.
Faults valve kg:
1. Exactness of the adjustment of the valve to the saddle. Gas pass on the burner in the furnace.
2. Exactness of the fitting of the servolapan spool to the saddle of the discharge hole. In this case, if the reset tube is embedded in the exhaust gas pipeline, according to the passport to the manufacturer's valve, the furnace will also occur.
3. A leathed overlap of the sprinkling hole of the servolapan (the coil voltage is submitted, the valve is open). With such a leak, the valve can close due to the fact that gas from aboutthe dmmbrane cavity through the slots in the case and a leakage of the closed bypass opening will go into the valve's appreciated cavity and it will close. To eliminate leaks (the above), it is necessary to replace the sealing surfaces by showing an extraordinary imagination, because Russian enterprises zip are not supplied. To eliminate the heroes of the servolapan, you can adjust the stroke of the spool by the device in the attachment of the electromagnet core with the rod of the servolapan spool.
4. Gas leakage outward through the servocallapan sealing gasket (drawn in blue).
5. Gas leak through the bolt in the valve lid under the cap.
6. Exact assembly in the center of the valve membrane. If the leak is strong, then the pressure over the membrane and under the membrane is leveled, the valve will close and block the gas.
7. Introve the membranes. With an open valve when the voltage is filed. The pressure above and under the membrane is leveled and the valve will close. The membranes are usually torn around the perimeter, where the membrane is clamped with bolts.
8. Plastic sleeve begged at the top of the servocallapan. The tightness of the closure of the bypass hole is disturbed.
9. Gas leakage through micropores in the housing, covers.
10. The electromagnet coil burned out.
After selecting the type of fuel It is necessary to determine the power of the boiler. You need to pick up the boiler, based on the heat loss of the house. For example, for heating 10 m 2 area with ceilings 3 m and good thermal insulation requires 1 kW of power. But this is a very rough approximation. The fact is that not only the area of \u200b\u200bthe room determines the thermal losses.
To be confident in the right choice of the boiler, it is best to order in the project organization the calculation of heat losses or the project of the entire heating and water supply system.
The next step is the choice of a structural type of heating boiler.. Fortunately, many modern models of different designs allow them to use them in several power modes - this greatly simplifies the situation.
For a boiler with an open combustion chamber It is necessary for a room equipped with chimney. If there is no chimney, you can install a boiler with a closed combustion chamber.
Compact sizes of wall mounted And the floor boilers of famous manufacturers will suit any interior - whether it is a kitchen, a bathroom, an attic, a basement or comfortable niche. Outdoor gas boiler - a time-tested device for heating and hot water supply of a country house.
Gas wall boilers Sometimes called mini-boiler. Indeed, the burner and heat exchanger, and the control device, and many other components are also placed in one small case. The main advantage of wall-mounted boilers is compactness and ease of installation.
According to the water heating method Boilers are divided into single and dual-kinning.
Serves only for heating. There are no hydraulic elements of the DHW system inside it, so it is cheaper than a dual-circuit. For the supply of hot water to a single-circuit boiler, a water heat exchanger of the capacitive water heater is connected. That is, there will be a capacity of 50-1000 liters next to such a boiler, which is specifically designed for cooking and storing hot water.
Important addition to such heating systems - Capacitive water heaters. They are still typically called water-water boiler or indirect heating boilers. First, because their design does not provide for the source of energy heating water. Secondly, a tubular spiral-serpent was inserted into the tank of such a boiler, which serves hot water from the boiler, and the water in the boiler heats up from the walls of this helix.
To enjoy hot water in ordinary urban mode, the family of four people usually grabs a boiler with a volume of 250-300 liters.
Designed for heating, and for hot water supply. In such devices, the elements of the GVS system are laid in the design. They are embedded either flow water heaters or capacitive.
The advantage of a two-door boiler in front of one-contact - Complete "combat readiness". The disadvantages include limiting the power of the DHW and the boiler capacity. The wall-mounted built-in boilers does not exceed 50 liters, in the outdoor - 160 l. The gas on gas boilers fluctuate depending on the power - from 20,000 to 240,000 rubles. And the cost of the boiler is often comparable to the attendance of a single-circuit boiler.
Modern gas boilers reach CPD 93%. During the combustion of natural gas, steam is formed with thermal energy, which is lost along with gases leaving through a smoke pipe. But gas condensation equipment allows you to use this thermal energy, cooling steam in the boiler. That is, in the process of combustion, more heat is obtained - due to the additionally acquired condensate energy. Therefore, condensing boilers reach the efficiency of 109%, and also help reduce gas consumption by 30% and reduce emissions of harmful substances.
In connection with the forefront in Europe, the use of condensing units is legally encouraged. And in the UK, more recently, only condensation boilers are allowed in residential buildings.
These boilers can be Very decent power - 125 kW. This means that one such unit with its minor dimensions is able to warm up a fairly large house. If there is a special chimney, you can create cascade installations of several condensation boilers. In this case, all boilers are compact on the wall and do not require a special room.
Approximate value The wall condensation boiler can be determined by multiplying the value of its rated power by 3,000 rubles. And it is such boilers that are recommended to use as the most economical, eco-friendly, compact and comfortable.
Heat exchangers of modern floor gas boilers It is performed from gray cast iron, not subject to, in contrast to the usual cast iron, cracking due to internal stresses. In other models, high-quality stainless steel are used.
Gas-burner - This is a device for mixing oxygen with gaseous fuel in order to supply the mixture to the outlet and burning it to form a steady torch. In the gas burner, the gaseous fuel supplied under pressure is mixed in the mixing device with air (air oxygen) and the resulting mixture is set on the output from the mixing device to form a steady constant flame.
Gas burners have a wide range of advantages. The design of the gas burner is very simple. Her launch takes the share of a second and such a burner works almost reliable. Gas burners are used for heating boilers or industrial applications.
Today, there are two main types of gas burners, their separation is conducted depending on the method of formation of a combustible mixture (consisting of fuel and air). There are atmospheric (injection) and upgraded (ventilating) devices. In most cases, the first view is part of the boiler and enters its cost, the second view is most often purchased separately. The upgrade burner gas as a combustion tool is more efficient, because in them the air supply is carried out by a special fan (built-in burner).
Appointments of gas burners are:
- gas supply and air to the burning front;
- mixture formation;
- stabilization of the edge of ignition;
- ensuring the required intensity of burning.
Types of gas burners:
Diffusion burner -burner in which fuel and air
Mix the trigger.
Injection burner - Gas burner with pre-mixing gas With air, which is one of the media necessary for burning, is suited to the combustion chamber of another medium (synonymous, ejection burner)
Burner with hollow preliminary mix -the burner in which the gas is mixed with a full amount of air in front of the outlet holes.
Burner not with hollow preliminary mix– the burner in which the gas is not completely mixed with air to the outlet holes. Atmospheric gas burner– injection gas burner with partial preliminary mixing of gas with air using secondary air medium surrounding the torch.
Special purpose burner– the burner, the principle of operation and the design of which determines the type of thermal unit or the characteristics of the technological process.
Recoverable burner– burner equipped with a gas or air heating recuperator
Regenerative burner.- burner, equipped with a generator for heating gas or air.
Automatic burner– the burner equipped with automatic devices: remote ostable, flame control, fuel and air pressure control, shut-off valves and controls, control and signaling.
urban burner.– a gas burner, in which the energy of the flowing gas jets is used to drive a built-in fan that blows the air into the burner.
Putting burner– auxiliary burner, serving to ignite the main burner.
The most applies to date, the classification of burners according to the method of supplying air, which are divided into:
- conflict - air enters the furnace due to the vacuum in it;
- injection - air is sucked due to the energy of the gas jet;
- blowing - air is fed to the burner or firebox using a fan.
Gas burners are used at different gas pressures: low - up to 5000 Pa, average - from 5000 Pa to 0.3 MPa and high - more than 0.3 MPa. Especially use burners operating on medium and low gas pressure.
Of great importance is the thermal power of the gas burner, which is the maximum, minimum and nominal.
With long-term operation of the burner, where gas is consumed more without a flame breaking, maximum thermal power is achieved.
The minimum thermal power occurs during the stable operation of the burner and the smallest gas expenditures without a flame slip area.
When the burner is running with a nominal, providing maximum efficiency with the greatest completeness of burning, gas flow rate is achieved with a nominal thermal power.
It is allowed to exceed the maximum thermal power over the nominal no more than 20%. In the event that the nominal thermal power of the burner on the passport of 10,000 kJ / h, the maximum must be 12,000 kJ / h.
Another important feature of gas burners is the heat regulation range.
Today, a large number of burners of various designs are used. The burner is selected according to certain requirements, which include: Stability with changes in thermal power, reliability in operation, compactness, convenience when servicing, ensuring the completeness of the combustion of the gas.
The main parameters and characteristics of the used gas melting devices are determined by the requirements:
- thermal power calculated as a product of time consumption of gas, m 3 / h, on its low heat of combustion, J / m 3, and is the main characteristic of the burner;
- the parameters of the combined gas (lower heat of combustion, density, number of Vobbe);
- nominal thermal power equal to the maximum achieved power with long-term operation of the burner with a minimum "coefficient of an excess A air and, provided that the chemical lack does not exceed the values \u200b\u200bfor this type;
- nominal gas and air pressure corresponding to the nominal thermal power of the burner at atmospheric pressure in the heat chamber;
- nominal relative torch length equal to the distance along the torch axis from the output section (nozzle) of the burner at a rated thermal power to the point where the carbon dioxide content at α \u003d 1 is 95% of its maximum value;
- the coefficient of the limit control of thermal power equal to the ratio of the maximum thermal power to the minimum;
- coefficient of working control burner in thermal power equal to the ratio of the nominal thermal power to the minimum;
- pressure (vacuum) in the heat chamber at rated power of the burner;
- heat engineering (luminosity, degree of black) and aerodynamic characteristics of torch;
- specific metal and material intensity and specific energy consumption: nominal thermal power;
- The level of sound pressure created by the working burner at the rated thermal power.
Requirements for burners
Based on the experience and analysis of the design of burner devices, it is possible to formulate basic requirements for their design.
The burner design must be the simplest: without moving parts, without devices that change the section for the passage of gas and air and without the details of a complex shape located near the bowl of the burner. Complex devices when operating themselves do not justify themselves and quickly fail under the action of high temperatures in the workspace of the furnace.
Sections for gas, air and gas-air mixture should be operated 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 by throttle devices on the supply pipelines.
The cross sections for the passage of gas and air in the burner and the configuration of the inner cavities should be chosen in such a way that the resistance to the movement of gas and air inside the burner would be minimal.
The pressure of gas and air mainly must provide the required speeds in the weekends of the burner. It is desirable that the air supply to the burner is adjustable. The inorganized air supply due to the vacuum in the working space or by partial air injection gas can only be allowed in special cases.
The design of the burner.
The main elements of the 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 different design execution.
IN diffusion burners Gas in the combustion chamber is supplied with gas and air. Mixing gas and air occurs in the combustion chamber. Most of the diffusion burners are mounted on the walls of the furnace or furnace. The boilers were distributed by t. Gas burners, which are placed inside the furnace, in its lower part. The underground gas burner consists of one or more gas distribution pipes, in which holes are drilled. The pipe with the holes is installed on the grate grid or the firecase in the slotted channel laid out of the refractory brick. Through the refractory slot canal, the required amount of air is received. With such a device, the burning of the gas stups overlooking the holes in the pipe begins in the refractory channel and ends in the combustion volume. Pier burners create a small resistance to gas passage, so they can work without a forced blast.
Diffusion burners Gas are characterized by a more uniform temperature along the torch length.
However, these burners are required by an increased air excess coefficient (compared to injection), and also create lower thermal stresses of the coarse volume and the worst conditions for the cutting of the gas in the tail part of the torch, which can lead to incomplete combustion of the gas.
Diffusion burners Gas are used in industrial furnaces and boilers, where uniform temperature is required along the torch length. In some processes, the diffusion burners are irreplaceable. For example, in glass coarse, Martenov and other furnaces, when the air-coming air is heated to temperatures exceeding the flammable gas ignition temperature with air. Diffusion burners gas and in some water-heating boilers are successfully used.
IN injection burners The combustion air is suused (injected) due to the energy of the gas jet and their mutual mixing occurs inside the burner housing. Sometimes in the injection burners of gas suits the necessary amount of combustible gas, the pressure of which is close to the atmospheric, is carried out by the energy of the air jet. In the burners of a complete mixing (with gas, all the air-needed air), operating on the average pressure gas, is formed a short flame torch, and the burning is completed in the minimum combustion volume. In the injection burners of gas partial mixing, only part (40 ÷ 60%) required for combustion of air (so-called primary air), which is mixed with gas is received. The rest of the air (so-called secondary air) enters the torch of the flame from the atmosphere due to the injection of gas-air jets and pouring in the furnace. In contrast to the injection burners of gas average pressure, a homogeneous gas-air mixture with a gas content is formed in the low pressure burners, more than the upper limit of ignition; These gas burners are stable in operation and have a wide range of thermal load.
For sustainable combustion of gas-air mixture in injection burners of gas medium and high pressure, stabilizers are used: additional igniting torches around the main stream (burners with a ring stabilizer), ceramic tunnels, inside of which gas is combustion of gas-air mixture, and plate stabilizers that create a flux on the flow path.
In the furnaces of significant sizes, gas burners are harvested in blocks of 2 or more burners.
Injection burners Gas infrared radiation (so on. Flare burners) were obtained, in which the main amount of heat produced during burning is transmitted by radiation, because Gas burns on the radiating surface with a thin layer, without a visible torch. Ceramic nozzles or metal mesh are emitted surface. These burners are used to heat the rooms with a large multiple of air exchanging (sports halls, retail space, greenhouses, etc.), for drying painted surfaces (tissues, paper, etc.), heating the murred soil and bulk materials, in industrial furnaces. For uniform heating of large surfaces (furnaces of oil refineries, etc. industrial furnaces) are used by T.N. Panel injection emitting burners. In these burners, the gas-air mixture falls into the overall box, and then the mixture is distributed through separate tunnels, in which its combustion occurs. Panel burners have small dimensions and a wide range of regulatory, are lowly sensitive to counterpart in the heat chamber.
The use of gas turbine burners increases, in which air supply is carried out by an axial fan, which moves to the gas turbine. These burners are offered at the beginning of the 20th century (AiCarta Turbogogorod). Under the action of the reactive strength of the flowing gas, the turbine, the shaft and the fan are driven to the side opposite to the expiration of the gas. The burner performance is regulated by the pressure of the incoming gas. Gas turbine burners can be used in the fireboxes of boilers. We promising are high-pressure turbine burners gas with air self-spectacles through recuperators and air economizers: gas and fuel oil burners Gas high performance, working on heated and cold air.
The following requirements are presented to the burners:
1. The main types of burners should be manufactured at the factories of serially on specifications. If the burners are manufactured by an individual project, then when commissioning, they must pass tests to determine the main characteristics;
2. The burners must ensure the passage of a given amount of gas and the completeness of its combustion with the minimum coefficient of air flow α, with the exception of special purpose burners (for example, for furnaces in which the restorative medium is supported);
3. When providing a given technological burner, the burner must provide a minimum amount of harmful emissions into the atmosphere;
4. The noise level created by the burner should not exceed 85 dB when measured by the noiseomer at a distance of 1 m from the burner and at a height of 1.5 m from the floor;
5. The burners should be steadily operation without separation and flame slipping within the calculated temperature range of thermal power;
6. The burner with preliminary mixing of gas with air the rate of expiration of the gas-air mixture should exceed the rate of flame propagation;
7. To reduce the electricity consumption on their own needs when using burners with forced air supply, the resistance of the air tract must be minimal;
8. To reduce operating costs, the design of the burner and stabilizing devices must be quite simple in maintenance, convenient for revision and repair;
9. If it is necessary to maintain backup fuel, the burner must provide a quick transfer of an aggregate from one fuel to another without disrupting the technological regime;
10. Combined gas-gas burners should ensure approximately the same quality of burning of both types of fuel - gas and liquid (fuel oil).
Diffusion burners
In the diffusion burners, the air necessary for combustion of gas comes from the surrounding space to the front of the torch due to diffusion.
Such burners are usually used in household appliances. They can also be used with increasing gas consumption if it is necessary to distribute the flame on a large surface. In all cases, gas is fed to the burner without impurities of primary air and is mixed with it outside the burner. Therefore, sometimes these burners are called external mixing burners.
The most simple diffusion burners (Fig. 7.1) are a pipe with drilled holes. The distance between the holes is selected taking into account the rate of flame propagation from one hole to another. These burners have small thermal capacities and are used when burning natural and low-calorie gases under small water heating devices.
Fig. 7.1. Diffusion burners
Fig.7.2. Sub-line diffusion burner:
1 - air regulator; 2 - burner; 3 - viewing window; 4 - centering glass; 5 - horizontal tunnel; 6 - blasting of bricks; 7 - grate grille
The industrial burners of the diffusion type include underline coil burners (Fig. 7.2). Usually they are a pipe with a diameter of up to 50 mm, in which the holes are drilled with a diameter of up to 4 mm in two rows. The channel is a gap in the boiler, from where and the name of the burner is underground slotted.
From the burner 2, the gas goes to the furnace where the air flows from under grinding 7. Gas trickles are heading at an angle to the flow of air and is evenly distributed by its cross section. The process of mixing the gas with air is carried out in a special gap made of refractory bricks. Thanks to such a device, the process of mixing the gas with air is enhanced and a stable ignition of a gas-air mixture is ensured.
The grade grille is laid by refractory brick and several slots are left, in which pipes with drilled holes for gas output are placed. Air under the grille is supplied with a fan or as a result of discharge in the furnace. The refractory walls of the slit are burning stabilizers, prevent the flame separation and at the same time increase the heat transfer process in the furnace.
Injection burners.
Injectionaries are called burners, in which the formation of a gas-air mixture occurs due to the energy of the gas jet. The main element of the injection burner is an injector, sucking air from the surrounding space inside the burners.
Depending on the amount of air injected air, the burner can be a complete pre-mixing of the gas with air or with incomplete air injection.
Burners with incomplete air injection.On the front of the combustion comes only a part of the air required for combustion, the rest of the air comes from the surrounding space. Such 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, a nozzle, a mixer and a collector.
The primary air regulator 7 is a rotating disk or washer and adjusts the amount of primary air entering the burner. Nozzle 1 serves to convert the potential gas pressure in kinetic, i.e. To give a gas jet of such a speed, which provides sacrifice of the necessary air. The mixer of the burner consists of three parts: an injector, confuser and diffuser. Injector 2 creates a vacuum and air drum. The narrowest part of the mixer is confusion 3, leveling the gas-air mixture. In the diffuser 4, the final mixing of the gas-air mixture occurs and the increase in its pressure by reducing the speed.
From the diffuser, the gas-air mixture enters the collector 5, which distributes the gas-air mixture along the holes 6. The collector form and the location of the holes depends on the type of burners and their destination.
Low pressure injection burners have a number of positive qualities, thanks to which they are widely used in household gas devices, as well as in gas devices for public catering enterprises and other public utility consumers. Burners are also used in cast iron heating boilers.
Fig. 7.3. Injection atmospheric gas burners
but - low pressure; b. - burner for the cast-iron boiler; 1-forming. 2 - Injector, 3 - Confuzor, 4 - Diffuser, 5 - collector. 6 - Holes, 7 - Primary Air Regulator
The main advantages of low pressure injection burners: simplicity of design, stable burner operation when load changes; reliability and simplicity of service; silent work; the possibility of total gas burning and working on low gas pressures; Lack of air supply under pressure.
An important characteristic of incomplete mixing burners is injection coefficient - The ratio of the volume of injected air to the volume of air necessary for the total combustion of the gas. So, for complete combustion of 1 m 3 of gas, 10 m 3 of air is necessary, and the primary air is 4 m 3, then the injection coefficient is 4: 10 \u003d 0.4.
The burner characteristic is also multiplicity of injection - The ratio of primary air to gas flow rate burner. In this case, when 4 m 3 of air is injected at 1 m 3 of the combined gas, the injection multiplicity 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 constant gas pressure.
Mixing burners. Burners with forced air supply.
Forced air supply burners are widely used in various thermal devices of utility 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. The burners of both types can work on natural, coke, domain, mixed and other flammable gases of low and medium pressure. Operating regulation range - 0.1 ÷ 5000 m 3 / h.
Air in the burner is supplied by centrifugal or axial low and medium pressure fans. Fans can be installed on each burner or one fan to a specific burner group. At the same time, as a rule, all primary air is supplied by fans, the secondary practically does not affect the quality of the combustion and is determined only by the air drier into the flue chamber through the looser of the fiber reinforcement and the hatch.
The advantages of coercive air supply burners are: the possibility of applying in the furnace chambers with different backpressure, a significant range of thermal power regulation and gas - air ratio, relatively small torch sizes, minor noise when working, simplicity of design, the possibility of preheating gas or air and the use of burners Large single power.
Low pressure burners are used at a gas flow rate of 50 ÷ 100 m 3 / h, at consumption 100 ÷ 5000 it is advisable to use the burners of the average pressure.
The air pressure depending on the design of the burner and the necessary thermal power is taken equal to 0.5 ÷ 5kpa.
For better mixing of the fuel and air mixture to most burners, the gas is supplied by small jets at a different angle to the stream of primary blowing air. In order to intensify the mixture formation, the air flow gives turbulent movement with the help of specially installed swirl blades, tangential guides, etc.
The most common burners with the forced supply of air internal mixing are the burners with a gas flow rate of up to 5000 m3 / h or more. It is possible to provide a predetermined quality of the preparation of the fuel and air mixture until it is supplied to the bracket chamber.
Depending on the burner design, the fuel and air mixing processes may be different: the first - preparation of the fuel and air mixture directly in the burner mixing chamber when the finished gas-air mixture comes into the furnace, when the mixing process starts in the burner, and ends in the heat chamber. In all cases, the rate of expiration of the gas-air mixture is different 16 ... 60 m / s. Intensification of gas mixture and air is achieved by jet gas supply, the use of adjustable blades, tangential supply of air, etc. When the gas inkjet supply, burners are used with central gas supply (from the burner center to the periphery) and with peripheral.
The maximum air pressure at the burner is 5 kPa. It can work when tipping and rolling in the heat chamber. In these burners, in contrast to the external mixing torches, the flame is less luminous and relatively small sizes. Ceramic tunnels are most often used as stabilizers. However, all methods discussed above can be used.
The GNP type burner with forced air supply and the central gas supply, designed by the specialists of the Heat Project Institute, is intended for use in the furnace devices with significant thermal stresses. In these burners there is a twisting of the flow of air using the blades. The burner kit includes two nozzles: a nozzle of type A, used for a short-foam gas burning with 4 ÷ 6 holes for gas output, directed perpendicular or at an angle of 45 ° to the air flow, and the type used nozzle used to obtain an extended torch and having one central Hole directed parallel to the air flow. In the latter case, the preliminary mixing of the gas and air occurs significantly worse, which leads to the elongation of the torch.
Torch stabilization is provided by the use of a refractory tunnel of chamotte brick class A. Torleys can work on cold and heated air. Excess air coefficient - 1.05. The burners of this type are used in steam boilers, bakery industry.
Two-wire gas-contained burner GMG is intended for burning natural gas or small-sized models of liquid fuels of diesel, domestic, fuel fuel filling F5, F12, etc. It is allowed to combine gas and liquid fuel combustion.
The gas nozzle of the burner has two rows of holes directed at an angle of 90 ° to each other. The holes on the side surface of the nozzle allow gas to be supplied to the twisted stream of secondary blasting air, the holes on the end surface - to the twisted flow of primary air.
The process of forming a gas-air mixture in burners with a forced air supply begins directly in the burner itself, and ends already in the furnace. In the incineration process, the gas burns with a short and unhapping flame. Air required for combustion of gas is supplied to the burner forcibly with a fan. Gas and air are served in separate pipes.
This type of burner is also called two-wire or mixture burners. Most often burners operating at low gas and air pressure. Also, some burner designs are used at average pressure.
The burners are installed in the fireboxs of boilers, in heating and drying furnaces, etc.
Principle of operation of the burner with forced air supply:
Gas enters a nozzle 1 with a pressure of up to 1,200 Pa and comes out of it through eight holes with a diameter of 4.5 mm. These holes must be arranged at an angle of 30 ° to the axis of the burner. Special blades that set the rotational movement of the air flow, are located in the housing 2 burners. In the process of operation, gas in the form of fine pips enters the twisted air flow, which helps good mixing. The burner ends with a ceramic tunnel 4 having an outstanding opening 5.
Fig. 7.4. Burner with forced air supply:
1 - nozzle; 2 - body; 3 - Front plate; 4 - ceramic tunnel.
The burners with forced air supply have a number of advantages:
-high performance;
- a list of performance regulation;
- Perhaps work on heated air.
In the existing diverse designs of the burner, the intensification of the process of formation of the gas-air mixture is achieved in the following ways:
-Sbitration of gas and air flows into small streams in which mixing formation passes;
-Bid gas in the form of small pips at an angle to the stream of air;
- Covering the air flow by various devices built into the inward burners.
Combined burners.
Combined are called burners operating simultaneously or separately on gas and fuel oil or gas and coal dust.
They are used in incoming gas supply when it is necessary to urgently find another type of fuel when gas fuel does not provide the necessary temperature mode of the furnace; The gas supply to this is done only at a certain time (at night) to equalize the daily unevenness of gas consumption.
Gas-gas burners with forced air supply were obtained the greatest distribution. The burner consists of gas, air and liquid parts. A gas portion is a hollow ring having a gas supply fitting and eight gas spraying tubes.
The liquid part of the burner consists of a fuel oil head and an inner tube, an ending nozzle 1 (Fig. 7.5).
The fuel oil supply in the burner is regulated by the valve. The air part of the burner consists of a housing, a swirler 3, air damper 5, with which air supply can be adjusted. The swirl is used for better mixing jet fuel oil with air. Air pressure 2 ÷ 3 kPa, gas pressure up to 50 kPa, and fuel oil pressure up to 0.1 MPa.
Fig. 7.5. Combined gas-magazin burner:
1 - fuel oil nozzle, 2 - air chamber, 3 - swirl, 4 - gas output tubes, 5 - air adjustment valve.
The use of combined burners gives a higher effect than the simultaneous use of gas burners and fuel oil nozzles or gas dust burners.
Combined burners are necessary for the reliable and smooth operation of gas-wide equipment and installations of large industrial enterprises, power plants and other consumers, for whom the break in work is unacceptable.
Consider the principle of the combined dustgy burner of the design of Mosenergo (Fig. 7.6)
When working on coal dust in the furnace on the annular channel 3 of the central pipe, a mixture of primary air with coal dust is supplied, and the secondary air enters the furnace through the snail 1.
As a backup fuel, the fuel oil is served, in this case, a fuel oil injector is installed in the central tube. When transferring the burner on the gas fuel, the fuel inlet is replaced by the ring canal, according to which gas fuel is supplied.
In the central part of the channel, a pipe with a cast-iron tip is installed 2. The tip 2 oblique gaps through which the gas extends and intersects with the flux of twisted air coming out of the snail 1. In advanced designs of the burner in the tip instead of the slot, 115 holes with a diameter of 7 mm are provided. As a result, the gas yield rate increases almost twice (150 m / s).
Fig. 7.6. Combined dusty burner with central gas supply.
1 - Snail to twist the air flow, 2 - the tip of gas pump pipes,
3 - ring channel for feeding primary air mixture with coal dust.
In the new burner designs, the peripheral supply of gas is used, in which gas jets having a higher speed than air, crossed the twisted air flow moving at a speed of 30 m / s, at a right angle. Such interaction of gas and air flows provides fast and complete mixing, as a result of which the gas-high mixture combines with minimal losses.
7.3. Automation of gas burning processes.
The properties of gas fuel and modern designs of gas burners create favorable conditions for automating gas burning processes. Automatic control of the combustion process increases the reliability and safety of the operation of gas-grade aggregates and ensures their operation in accordance with the most optimal mode.
Today, gas-wide installations are used partial or complex automation systems.
Complex gas automation consists of the following main systems:
- automation of regulation;
- security automation;
- emergency alarm;
-Totechnical control.
Regulation and control of the combustion process is determined by the operation of gas devices and aggregates in a given mode and ensuring the optimal gas combustion mode. To do this, regulation of the combustion process is intended for automatics of regulation of household, utility and industrial gas appliances and units. Thus, the constant temperature of water in the tank is maintained in capacitive water heaters, the constant pressure of steam in steam boilers.
The gas supply to the burners of gas-wide installations is terminated by automatic security in the case of:
- resetting torch in the furnace;
- decrease in air pressure in front of the burners;
- Waste a steam pressure in the boiler;
- increase water temperature in the boiler;
- decrease in the discharge in the furnace.
Disabling these settings is accompanied by appropriate sound and light signals. Also important and control of the base of the room in which all gas devices and aggregates are located. For these purposes, electromagnetic valves are installed, which stop the supply of gas in cases of exceeding the PDC in the surrounding air of CH 4 and CO 2.
It is possible to achieve optimal regime in the technological process conditions using heat engineering instruments
The operating conditions of gas-wide equipment determine the degree of automation.
Remote control of gas-grade installations is achieved by using control and alarm instruments.
Burner calculations.
In gas-gas furnaces equipped with modern burner devices with automatic control of the combustion process, it became possible to burn natural gases and fuel oil with small excess air in virtually the absence of either the low value of the chemical incompleteness of combustion (less than 0.5%). Therefore, it is recommended that the combustion process of these fuels is recommended to maintain with a coefficient of an excess air per steamer not higher than 1.03 ÷ 1.05.
According to the method of removal of combustion products and fresh air supply, the following types of gas devices are distinguished: apparatus type A:these devices should not be connected to chimney or to extract out. Example:gas stove in the kitchen.
Apparatus type in:these devices must be connected to chimney to remove combustion products. Fresh air for the burner comes directly from the room where the device is installed.
Example:Wall boiler.
Apparatus type B1:this is a type of B type, equipped with a traction interrupter / anti-breaker in the burner chain.
Note:This machine will be the device type B2,if the fan is not installed in it.
Apparatus type B2:this apparatus type B,not equipped with a traction / anti-breaker.
Note:The device is called the apparatus type C,if he has a closed combustion chamber (the air of the room is not used).
16.6.2.2. Separate chimney for gas
Type B.
This chimney, which serves only one room. A gas boiler can be connected to such chimney. The burning of combustion products occurs due to natural traction. Such chimney can be used as an outlet for removing contaminated air from the room, provided that the upper part of the traction interrupter is located at an altitude of at least 1.80 m from the floor (see Fig. 16.42). The chimney section is determined from Table. 1 b. 2 depending:
From the height of the chimney (example: the height of the chimney is 4 to 10 m);
Availability or absence of a change in the direction of the chimney
(Fig. 16.33-16.35) (Example: direct chimney or knee);
From the diameter of the connecting pipe (the outlet of the device) and possible knees (see Types I - IV in Fig. 16.36) (Example: Type II, if the type I is with a knee of 90 °);
From the boiler power (example: boiler with a capacity of 23 or 28 kW or
more).
Example:
Direct chimney with thermal insulation:
(R≥ 0.22 m 2 ° C / W)
Connection of the boiler with a knee of 90 ° with chimney type II,
Dimmeter with chimney: 125 mm,
Chimney height: from 4 to 10m,
Muna B1 boiler: Maximum useful power 4 kW.
Find on the table:
Horizontally: mun // → Ø \u003d 125 mm -\u003e Power 41 kW.
Vertically: rising at right angles from 41 kW to 4 ≤< 10м.
We get: cross-section of chimney 200 x 200 mm.
Note: Rectangular chimneys must satisfy the condition: length / width ≤ 1.6.
Important! The boiler connected to the chimney with a natural burden cannot be installed in a room with mechanical ventilation, since the indoors can create the conditions of permanent and reverse thrust.
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Materials used for chimneys:
Cylindrical ceramic tube with solid or porous walls;
Cylindrical concrete tube with admixture of Pozzolan (if there is a technical expert opinion);
Metal tube with double walls;
Casual tube (shelter) (rigid or flexible):
18/8 stainless steel stabilized titanium,
From aluminum A5 (purity of 99.5%) with a thickness of 0.8 mm.
□Clipping pipe
The casing is called an operation that is that a separate pipe is introduced into the chimney to remove the combustion products (Fig. 16.37 - 16.39).
Double chimney with asbestos insulation. Double stainless steel walls increase the anti-corrosion properties of the chimney. This method applies when necessary:
Agree crossing the chimney with regulatory requirements and with the type of heating installation;
Provide protection against corrosion or formation of soot on its walls and the rapid removal of combustion products.
□Installation: Highlights
Ventilation from below and on top of the ring space,
Tee with a cleaning hatch at the bottom of the chimney,
Protection of the release of the chimney from the rain,
The size of the casing tube (see Table 16.2).
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□Chimney pipe height over the roof
Recommended norms are shown in Fig. 16.40 For the roof with a slope\u003e 15 °. Pipe tubes should be located at such a height so that neighboring obstacles cannot create the conditions of increased pressure at its location.
Note: when the roof is< 15° жерло трубы должно располагаться как минимум на 1,20 м выше точки выхода трубы и как минимум на / m above an alarm if the latter is at an altitude of\u003e 0.20 m.
Prescriptions
□Road volume
Gas devices with an open combustion chamber cannot be installed indoors of less than 8 m 3.
□Fishing fresh air in the firebox of the boiler
For any device with a combustion chamber, fresh air for the burner is required. Air supply and removal of combustion products directly affect the hygienic condition of the room in which the gas apparatus is located.
In each main premises of the house there is at least one input of fresh air.
The modules of the used air input are 20 and 30 m 3 / h in the main premises (living room and bedrooms).
When the combustion products is discharged due to natural ventilation, it is only required to control the sum of the air input modules depending on the power of the installed devices. At the same time distinguish two cases:
1. The room has a single gas unit, not connected to the ventilation system (for example, a gas stove). In this case, M must be\u003e 90.
2. In the room there is a gas chimney gas boiler and a gas stove without chimney. In this case, M ≥ 6.2 Ri, where RI is the sum of the beneficial capacity of the gas devices connected to the exhaust.
Example.In the Country House of T4 type in the kitchen there is a gas boiler with a capacity of 28 kW, connected to chimney with a natural burden. In 3 rooms installed air inputs with a module 30 m 3 / h -\u003e total module M \u003d 90 m 3 / h. In the dining room, 3 air inputs are installed with a module 30 m 3 / h -\u003e the total module M \u003d 90 m 3 / h. The sum of all modules is m \u003d 180 m 3 / h. The condition M≥ 6.2 RF is satisfied (6.2 x28 \u003d 173.6).
□Remove contaminated air
Each service room has several exhaust holes with a natural burden or connected to the mechanical ventilation system (Fig. 16.41 and 16.42).
→With natural traction,if there are several indoors
gas devices that are not connected to the ventilation system (on
Example, gas stove), at the top of the vertical duct
There must be an exhaust hole with a diameter of at least 100 cm 2.
→With adjustable ventilation system(RSV) Removal of contaminated
Air can be carried out:
Through the exhaust hole of the adjustable ventilation system (see Section 16.6.2.4);
Through the traction interrupter, if it is connected to the adjustable gas ventilation system (RSW-Gas), provided that the upper part of the traction interrupter is located at a distance of\u003e 1.80 m from the floor.
In all cases, if necessary, quickly removal of polluted air is required to provide a window with a minimum area of \u200b\u200b0.40 mm 2 or a light yard width of at least 2 m.
