Gas burners for boilers - classification, advantages, disadvantages and selection

Principle of operation

The principle of operation of the burners is to pre-mix the fuel with air, ensure the supply of this mixture for combustion and make sure that the combustion products go through the combustion process completely.

The work of this device is divided into three stages:

1. Preparation... At this stage, the preparation of individual elements of the future combustible mixture is carried out. At the time of the preparatory stage, air and fuel are given the necessary characteristics: direction, temperature, speed.
2. Mixing... Air and the required amount of fuel are mixed, resulting in a mixture of a combustible nature.
3. Combustion... At the final stage of the burner operation, the combustion process takes place, or rather, the oxidation reaction of the elements of the combustible action with the help of oxygen takes place. Ultimately, the mixture ignites thanks to a nozzle that is placed at the end point of the tube.

Attention, even taking into account the simple design of the burners in the event of malfunctions, in no case should you try to eliminate them yourself.

In gas burners, there are also additions that ensure the safety and automation of the device.

These include:

• Automation, independently turns off devices as a result of troubleshooting.
• Ignition, carried out thanks to a special pieza element or electricity.

Classification of gas burners

In a device called a gas burner, there is a process of mixing the supplied gas and the intake or forced air, followed by the combustion of the combustible composition in the combustion chamber. It can work in the conditions of main supply gas, as well as from a cylinder or a special tank. The process itself depends on the characteristics of the burner and the possibility of adjusting it to certain conditions.

Depending on the method of air intake, gas burners are divided into two types:

• atmospheric - the air-gas mixture is obtained by natural suction of air from the surrounding space and mixing it with the supplied gas;
• pressurized, using a fan, forcibly blowing air;
• combined.

In the first case, it is said about boilers with open combustion chambers, and in the second - with closed ones. Also, gas burners for heating boilers have a different type of power control:

• one-stage - the simplest and most affordable;
• two-stage - with two automatically switching modes of operation;
• smooth two-stage - with soft flame control between two stages;
• modulated - the most effective and reliable, with accurate and fast regulation depending on the change in the temperature regime of the coolant. Differs in high cost.

What to look for when choosing

When buying, one should take into account the operating conditions of the heating equipment, the peculiarities of its operation and the possibility of maintenance. The dimensions of the gas burner must be in accordance with the dimensions of the boiler furnace, otherwise, instead of reliability and durability, it will be possible to get a burnt combustion chamber.

Each of the burners has its own characteristics, thanks to which one or another model is chosen for each specific case.

A certain value when choosing a gas burner is:

• manufacturer;
• characteristics;
• model;
• cost;
• hardware compatibility.

It is recommended to weigh all the positive and negative sides in advance, otherwise the burner will be ineffective.

Types and functions of burners

For space heating, not only stationary heating systems are used.

There are four portable devices that are more convenient to use in some circumstances:

• Plate
• Lamp
• Heater
• Burner

Natural gas heaters are classified as air heaters.

The design of these devices is simple:

• housing,
• gas stove,
• heat exchanger,
• element capable of heating,
• balloon.

Each type of heater always has an additional possibility of connecting to a gas pipeline.

The stove works thanks to a fuel tank. With this device, cooking becomes comfortable regardless of location. This unit includes a robust housing. The body itself is made of high quality steel, which is further covered with a special enamel that protects against damage of various nature.

A lamp powered by gaseous fuel is a kind of element that emits light. The design of the lamp is similar to that of a burner.

The difference lies in the fact that its head is represented by a rod on which a special catalytic mesh is put on, which is the direct source of the glow.

For protection, a glass shade is put on over the mesh.

There are burners complete with add-ons to improve the performance of the appliances.

First of all, it is worth considering the classification of burners depending on the type of fuel used:

Gas

This type is common - natural gas refers to the fuel available to the consumer.

Gas burner devices are divided into two types in accordance with the method of supplying the oxidizer to the working area: pressurized and injection.

Pressurized burners.

They run on gaseous fuel and differ significantly in design - a built-in fan, mechanical delivery of the oxidizer (air) to the working area is provided.

With the help of the fan, the power is regulated and, in accordance with this, the operation of the device is improved, which affects the efficiency.

Additional noise is considered a disadvantage, but this is eliminated by installing special noise reduction add-ons.

Injection burners also called atmospheric. Such a device is most often included in additional standard equipment for boilers. The operation of the device consists in supplying air to the working area due to the "injection effect" - the required volume of oxidizer required for the full flow of the combustion process enters the flow of gaseous fuel using high pressure.

During manufacture, the device is set to standard settings aimed at working with natural gas.

In order for the heating system to run on liquefied gas, additional equipment will need to be installed.

The advantages of this type of burner devices are simplicity of design, absence of noise, complete safety, and long service life.

Liquid fuel

For oil burners, petroleum products are used as fuel, which go through various stages of processing. Biofuel or waste oil is also used. Those burner devices that perform work using diesel fuel are popular.

Diesel burners are not inferior to gas burners in terms of the quality of work.

At the same time, maintenance does not require large costs, the power of their work is a constant value and, which is no less important, they are able to work in conditions of negative temperatures.

Burners operating on fuel oil are considered economical, since fuel oil has a low cost, reliable in terms of a long service life of the device without preventive maintenance.

Oil burners are not used in domestic premises. The main area of ​​application is objects of industrial importance, boiler houses operating for centralized heating.

Multi-fuel or combined

For these devices, it is possible to use various types of fuel and do not require the installation of additional equipment. The cost of the device is high, but the efficiency is much lower than in other burners. Maintenance is much more complicated and therefore expensive.

Burner classification according to power:

• Low-power - ≥1500 W, used for a short time;
• Average power - from 1500 to 2500 W;
• Powerful - ≤ 2500 W.

The burners are connected to cylinders filled with gaseous fuel.

There are several types of cylinder connections, each suitable for any type of burner:

• Threaded connection - the burner is screwed onto the thread or it is done using an additional hose that is connected to the burner device.
• To perform a collet connection, a special push-type mount is used. The balloon, which is connected in this way, has a thin shell.
• The disposable connection cannot be disconnected from the burner until the fuel is completely consumed. This is due to the fact that there is no valve in the mount, and in case of untimely opening
• The valve connection is reliable, since even the slightest fuel leaks are avoided.

Some burners are equipped with additional functions that simplify the use of this device.

Power regulator... It allows you to adjust the power of the burner device, it is located on a threaded union, which is screwed to the cylinder. Since the regulator is located at a considerable distance directly from the burner, it is not always possible to keep the power under control. To eliminate this problem, two regulators are installed - on the burner device and on the fitting.

Piezo ignition... This addition greatly simplifies the initial stage of work. The ignition switch is located so that the burner start button is located under it. Therefore, the operating principle of the entire system is simple.

If the humidity is high, the device may malfunction.

Preheating... The operation of the system lies in the fact that the part of the pipe through which the fuel enters the combustion site is located not far from the burner head, therefore, in working condition, it is enveloped in a flame.

Classification of gas burners by temperature control

With the modern development of technology, new, improved methods of automatic temperature control have been developed:

• Single-stage burners are the simplest devices, the principle of which was described above. These burners operate in the same mode.

• Two-stage burners are devices that can operate in two states (40% and 100% of the total power), switching between themselves automatically.

• Sliding two-stage burners - these also operate in two states (40% and 100%), but the switching itself between modes is smoother, which significantly saves the fuel itself and improves the quality of temperature maintenance.

• Modulated gas burners with automatic controls for the boiler are the most functional devices capable of operating in a wide power range (from 10 to 100%).They can maintain a temperature regime with a deviation of only 20C from the initial value. At the same time, the efficiency of fuel combustion increases, and the temperature loads on the parts of the heater decrease.

The most effective of all is the copper heat exchanger, as it has thin walls and good thermal conductivity. BUT it does not tolerate high temperature voltages, therefore, it has a short operating period. In combination with the modulating gas burner automation, the service life of the gas burner increases.

Gas burners with the option to change the combustion level are expensive, but their efficiency quickly pays for all the costs:

- the temperature is kept in a small range;

- fuel savings up to 30%;

- the service life of the entire device is increased.

So to buy a gas burner with automatic equipment - we recommend!

Burner advantages

Positive aspects of burners operating on gaseous fuels:

• Ease of use, since the design features of this type of burners are primitive and do not require additional experience;
• There is no need for preparation before starting to use;
• Achieving high capacities;
• Flame regulation;
• Cleanliness, and this is important, since there is no need to allocate additional time for cleaning accessories;
• There is no need for additional maintenance of the burner elements, because carbon deposits do not remain after fuel combustion;
• Low cost price.

Advantages of liquid fuel devices:

• This type of fuel is consumed much more economically than gas;
• Throughout the work, the power indicator remains unchanged;
• Works at low temperatures.

Combined burners

They are produced for combined heating boilers capable of operating both on gas and on liquid fuel (fuel oil, diesel fuel). Such devices do not require replacement in the event of a transition from one combustible mixture to another. But the switching process itself is quite complicated and requires the presence of a professional.

The burners in question are fully automated, which minimizes the human factor. They have functions for controlling the flame power, combustion mode and other equally useful processes.

Combi burners have not gained popularity among homeowners due to their complex design and high price, combined with low efficiency.

Problems

Any type of burner device also has negative sides.

Disadvantages of gas powered devices:

• Under natural conditions, there is no way to replenish fuel reserves;
• Inability to transport gas cylinders on airplanes and trains by public transport;
• At a negative temperature, gaseous fuel tends to thicken, as a result of which the pressure indicator decreases and, ultimately, the burner device fails.

Negative qualities of the work of devices using liquid fuel:

• Parts of the burner structure are prone to deviations in operation, so they must be serviced often enough;
• High price;
• Possibility of fuel leakage;
• The need for additional preparation before starting work;
• Decent weight and size.

How to choose a burner

The required power of the device depends primarily on the number of consumers. With a small number of consumers, a low-power burner is sufficient. If there are 5 or 6 users, the device with the highest power is required. In the event that the number of users is much more, it is worth stocking up on several devices.

The design of the selected model depends only on personal preferences: a minimum size burner is required, or the cooking speed is important, and the device will become much larger.

For convenience, it is worth purchasing a device with piezo ignition.

Type of cylinder attachment.It is equally important to think about additional equipment. First of all, there is a need for a case for transporting the device. It is convenient when a special cookware holder is included with the burner.

The additions also include special protection against gusts of wind - blowing out the flame. Such a device significantly saves fuel. When choosing an add-on, pay attention to the design, since the presence of plastic parts in it is unacceptable.

Which is better

A multi-fuel burner is considered a good option, taking into account any conditions. Gas cylinders are not always possible to find, but liquid fuels are more common.

Multi-fuel burners have a power of 3500 watts. The fuel that suits them is both gas and gasoline.

It is desirable that the burner kit includes: a cover for transportation, tools for preventive maintenance, necessary spare parts for minor repairs (gaskets, lubricants), a pump.

Please note that the built-in piezo ignition fails rather quickly.

Exploitation

Correct use of the device guarantees a long service life. If you follow the rules for using burner devices, then there will be no difficulties even for a novice user.

Remember that these devices are highly hazardous devices, use caution.

List of rules and recommendations:

1. The device must be installed on a flat surface. If positioned incorrectly on an inclined surface, there is a likelihood of an emergency.
2. Never dry clothes or shoes with a burner.
3. If you have an additional cylinder, protect it from sunlight.
4. You cannot replenish gas cylinders with your own hands - refueling is done at specialized stations, additives are added to the gas fuel in certain proportions.
5. Do not touch the heated surface during the operation of the device - you can get burned.
6. During operation, the safety parts of the device must not be touched.
7. Use is permissible only in rooms with good ventilation and during work, the approach to flammable objects is excluded.
8. During operation, do not leave the device unattended.
9. Before starting work, it is imperative to check the correct attachment of the fuel cylinder.

Any kind of burner device requires constant maintenance. First of all, it is required to carry out internal cleaning from time to time.

If we are talking about a multi-fuel burner, then there is a thin metal cable in the inside of the fuel line. It is designed to perform two functions. First of all, it works to warm up various fuel substances. Also, the function of this device includes cleaning assistance.

When dirty, cleaning is performed with some difficulty, because it is difficult to pull out the cable.

For this, a special device is used, which is called a gripper. For these purposes, an improvised tool similar to pliers is used.

If attempts to clean up are unsuccessful, it is required to warm up the fuel line. Having taken out the cable, it is important to warm it up until it turns red and hot.

This action removes the coke that has accumulated during operation. Then the cable is inserted into the pipe and removed again. It is advisable to perform this action two or three times.

For a more thorough cleaning: it is worth unscrewing the nozzle and flushing the system with fuel, which is poured there from a cylinder under high pressure.

A specially designed needle is used to clean the nozzle. This action is performed without reaching the item to be cleaned.

General rules for the maintenance of the burner device:

• In the event that there is a choice of the type of fuel, it is worth choosing a gaseous fuel, since it minimally clogs the system.
• When using liquid fuel, it is imperative to give preference only to purified substances, which reduce the likelihood of system failure, and are distinguished by the absence of a pungent and unpleasant odor.
• Ignition of a liquid fuel appliance is undesirable in confined spaces. This is especially true for tents.
• Cleaning the burner assembly as a preventive measure is very important, even if no signs of malfunction are found.
• Assembly and disassembly of the device must be carried out carefully, preferably with the use of special tools. There is a risk of damage to the threaded fasteners.
• The pump from time to time needs to be treated with a special lubricant.

With strict adherence to the listed rules, many malfunctions and various inconveniences associated with deviations in the operation of the device are prevented.

The essence of the work of a gas burner equipped with an injector.

In this burner, the formation of a mixture of gases is carried out by injecting a combustible gas (which has a low or medium pressure) and oxygen, which is supplied from the cylinder to the burner at a pressure of 0.5-4 kgf / cm2. The process is as follows: oxygen, passing through the axial channel of the injector, is directed into the mixing chamber at a fairly high speed. As a result, a rarefaction occurs in the channel through which the combustible gas or liquid fuel vapor passes. This process forces the fuel to enter the mixing chamber as well, only it does not pass through the axial channel, but outside the injector. The mixture that forms in the chamber of the instrument is fed through the mouthpiece and ignites.

The proportions of gases in the combustible mixture, if desired, can be slightly adjusted using the burner valves. Note that for injection burners, combustible gas must be supplied from a cylinder under a pressure of at least 0.01 kgf / cm2.

Guarantee

When purchasing goods in specialized stores, a guarantee is provided.

This service applies to the performance of the device. There are also such cases when the guarantee also applies to the consumer properties of the goods.

Repair of burners at the expense of the organization is carried out if the device has a presentation, i.e. it retains seals, seals, complete safety of the case.

Therefore, before purchasing the device, make sure that it complies with the listed items, the declared characteristics and full functionality.

Most often, the warranty period is given for one year. But there are manufacturers who extend the term up to five years.

Malfunctions

The design of the device is simple, and rarely breaks down, but there are situations when the device fails. You can try to fix the device yourself, if circumstances require it.

The main causes of malfunction of devices designed to support the combustion process:

1. Clogging of the nozzle occurs during the filling of the device with fuel.
2. Splitter contamination due to accumulation of debris and dirt.
3. Melting of some parts occurs due to the use of an unacceptably large windscreen or kitchen utensils.
4. Damage to the hose.
5. Damage to gaskets resulting in fuel leakage.
6. Mechanical damage.

The quality of Chinese-made burner devices does not always meet the requirements and devices often fail. When purchasing a burner, you should pay attention to the manufacturer.

To extend the life of the burner requires careful and proper handling. Then the probability of any breakdown will be minimal.

Only contamination of the nozzles cannot be prevented.

This is inevitable anyway. The only question is time.

To independently cope with the breakdown of the device, you will need to have a set of tools:

• A set of tools for dismantling the device. This is the only way to get to the nozzle. But there are also types of devices that do not need to be disassembled.
• A special thin needle or wire of the same thickness is required to clean the nozzle. This work cannot be performed using an insufficiently thin tool, as the part can be easily damaged. After that, repairs will not be possible.

There is such a variant of a breakdown, to eliminate which it will be necessary to blow through the nozzle. It is important to know that this event should be carried out in the direction opposite to the passage of fuel.

In order not to harm the device, you should adhere to the instruction manual of the device.

Gas burners, classification and characteristics

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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 flame. 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 flawlessly. 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 the cross section. Once in a high temperature zone, the mixture ignites.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 warmis.techinfus.com/en/ 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, before entering the burner spout, it is twisted. 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. The 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 LHP 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.

Fig. 16.10. Turbulent burner type GNP 1 - body, 2 - nozzle, 3 - nozzle tip of type A, 4 - nozzle tip of type B, 5 - nozzle

Non-hollow premix burner –

a burner in which the gas does not completely mix 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 the holes are located here, then the flame above them will be much higher than above other holes, since when gas escapes from these holes, the dynamic pressure of the gas-air mixture flowing from the ejection tube to the burner head will be used. In addition, due to an increase in the output 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 gas combustion with a calorific value QCH = 25,000 ... 36,000 kJ / m3, while the nozzle diameter is changed depending on the QCH value. 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 load is approximately 100 mm. The burner is simple in design and reliable in operation. When operating in cast iron sectional boilers, atmospheric burners ensure complete combustion of gas with a relatively low content of nitrogen oxides in combustion products. The NOX concentration usually does not exceed 0.12 g / m3. This is due to the dispersal of the flame and staged combustion of the gas (with primary and secondary air).

Fig. 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 flame of the burner is significantly lengthened. Due to the vacuum in the furnace, the 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 Qsn = 36,000 kJ / m3. Depending on the heat of combustion of the gas, a nozzle of the appropriate diameter is installed in the burner.

Fig. 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 the built-in fan, which blows air into the burner.

Ignition 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 the gas flows out 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 around 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 fully positioned within the 510 mm 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 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 a greater amount of 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.

Another important feature of gas burners is the range of heat output regulation.

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, m3 / h, by its lower calorific value, J / m3, and which is the main characteristic of the burner;

- parameters of the combustion gas (net calorific value, density, Wobbe number);

- rated thermal power, equal to the maximum power attainable during long-term operation of the burner with a minimum ‘excess air ratio 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;

- content of harmful impurities in combustion products;

- heat engineering (luminosity, degree of blackness) and aerodynamic characteristics of the torch;

- specific metal and material consumption and specific energy consumption, referred to the rated thermal power;

- 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, it is possible to formulate the basic requirements for their design.

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 in such a way that the resistance on the path of gas and air movement inside the burner would be minimal.

The gas and air pressure should mainly 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 through a system of gas pipelines, 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 inlet 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.

Fig. 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 - gate 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-time 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. At the intersection of staircase ceilings, and hollow or backfilled walls, gas pipelines are enclosed in cases of steel pipes.

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 be provided with a flue gas outlet through chimneys to 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 are connected to chimneys using pipes made of roofing steel, the diameter of which is determined depending on the heat 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 section of the pipe 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 point of exit of combustion products 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 not be 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 flows through short connecting pipes directly to the 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 the following indicators: 1) heat load, or the amount of heat in the gas that is consumed by the appliance, 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, no dangerous thermal stresses should arise in the structural elements of the device, which would reduce its service life. The limiting (maximum) thermal load is considered to be a load exceeding the rated one 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 not less than 500 mm. The distance between the centers of adjacent cooking zones is 230 mm. The burner burners have the following rated 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 ° C 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 heat of combustion of the gas within ± 10% and the 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 combustion air (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 the burners, which must ensure complete combustion of the gas. The main reasons for the chemical incompleteness of gas combustion in burner burners are: a) the cooling effect of the walls of the dishes, 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 pan 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 optimum 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). In order for the stoves to be able to 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 burners shown in Fig. 19.3.

Fig. 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 by an 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 to prevent the flames 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 ° C 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 water heaters 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 operate normally at a tap water pressure of 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 flow rate through the ignition burner at a 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 ensure stable combustion of 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 drawing 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 breaker and a reverse draft safety device; 4) blocking, safety and regulating devices; 5) an outer metal enamelled casing; 6) a water-folding system with taps and a shower net. An automatic instantaneous 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.

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