Chimney of a boiler room made of bricks. Chimney for a boiler house: calculation of height and section according to technical standards

The main function that a chimney for a boiler house must perform is to remove flue gases from the boilers and scatter them in this space. There is also an additional function - to create a natural draft, resulting from the difference between the temperature in the furnace and outside.

In large boiler houses natural draft can not provide a full-fledged combustion, here it is created forcibly by means of smoke pumps. The combustion process and the discharge of its products into the atmosphere should bring as little harm to the environment and do not cause emergencies as a result of the occurrence of pressure in the combustion chamber exceeding the norm.

Structurally, the pipes for boiler houses are very different from each other both in terms of the type of the supporting structure and the material of manufacture. By the first sign, several types of pipes are distinguished.

Self-supporting boiler pipes

Such vertical structures are one- or multi-barreled. They divert combustion products from boilers and boilers. They are used regardless of the type of fuel, but subject to certain requirements:

1. The temperature of the flue gases passing through the self-supporting pipes should not exceed 350 degrees C.
2. The products of combustion must not be chemically aggressive.
3. Optimal snow load for self-supporting structures - 250 kg per kV. cm, wind power - 30 kg per kV. cm in the conditions of the II wind district.

Install a self-supporting pipe on the roof, and fix it inside the building. Its structural features provide the possibility of transportation and installation in place, because it consists of separate sections, which are 3-layer sandwich tubes. The structure is fixed to the foundation with the use of anchors.

Inside the pipe there is a layer made of strong steel that does not respond to the substances released during combustion. The outer layer protects against weathering.

Smoke pipes for large boiler houses are most often self-supporting. This building, built on an individual project and having its own infrastructure

The parameters of the smoke structures must comply with the requirements set forth in the regulatory documents. Their calculation is based on such factors as the number of boilers, power, type of fuel. Norms for emissions into the atmosphere must be taken into account. In some cases, the chimneys are completed with a platform, a ladder, a hatch for revision, a light guard.

Column Smoke Structures

The pipe of this type consists of an outer shell made of high-carbon steel and inserted in it of internal trunks of different diameters from stainless steel for the removal of gases. The design is fixed in the anchor basket filled in the foundation. They can be either 1 or several. To prevent condensation inside, heat insulation is used.

The advantage of such a constructive solution is a large operating period, the prospect of connecting several boilers. The thickness of steel and the brand is chosen, based on the temperature and aggressiveness of the combustion products.

The diameter of each barrel can reach one and a half meters, and if a common gas flue is planned to be used for several boilers, a diameter of about 3 m is required. To avoid condensation, the trunks are covered with thermal insulation.

Features of near-facade and facade chimneys

Install near-facade chimneys for boiler houses attached to the house or built-in. Attach them to the wall of the building using brackets. The components of the chimney are trunks and frame or anchorage. The barrel has 3 layers: inside stainless steel, then heat insulation and galvanized steel. Pipes are designed for boiler houses, where boilers run on gas or liquid fuels.

Most often, the facade pipes are located along the outer wall of the building. When choosing the steel grade and the wall thickness of the pipe, the chemical composition of the exhaust gases and their temperature

Around the facade and facade pipes transfer the weight load through the additional lower foundation and wind through the vibration isolating fixtures. This type of chimneys, in terms of material costs, is the most economical due to the lack of load-bearing structures and a solid foundation. The modular system used in the creation of gas-discharge barrels, provides an easy replacement of damaged parts.

Pipes of farm type

This metal structure consists of pipes fixed to a solid self-supporting column of the truss type. The farm, in turn, is fixed in an anchor basket, which is embedded in the foundation. Chimneys of truss type are suitable for use in regions with a dangerous seismological situation.

The construction of the truss type includes from 1 to 6 trunks. The column is made of tube rolled. Profile pipe   can have a square or a triangle in section. It depends on the number of trunks

To prevent corrosion, the gas outlets are covered with a primer, then stained. The barrel for evacuation of gases is made up of modules consisting of 3 layers:

• internal, contacting directly with combustion products and made of stainless steel special grades;
• thickness of 5-6 cm, performing the role of thermal insulation;
• external, protecting the heat-insulating layer from negative environmental influences.

For anticorrosion coating use paints containing a large percentage of zinc. In some constructions within a column, stairs and platforms can be provided to facilitate maintenance. The structural elements of pipes of this type are relatively light and this facilitates both their transportation and installation work.

Mast chimney pipes

The central element of the mast pipe is a supporting tower - three- or four-mast, to which chimneys are attached. All components of the structure are assembled on a base in the form of a concrete cushion, starting from the bottom and gradually moving upwards. Use a rivet connection when assembling or use self-tapping screws.

The supporting structure of the mast pipe is assembled from steel profiles, interconnected by braces and corners. The base of the column rests on the foundation, and fix it with anchor fasteners

Usually, individual elements are transported to the place of installation and assembled as a designer. It takes quite a bit of time - several hours. The height of the chimney can reach a maximum of 28.5 m. Stability of the chimney is provided by stiffeners - steel strips with a cross section of 1.6 to 2 cm. They compensate for the effect of shear forces.

Materials for the construction of boiler pipes

Smoke extraction systems are built from different materials   - brick, steel, ceramics, polymer. Chimney made of bricks is characterized by good mechanical strength, excellent heat capacity, sufficiently high degree of fire safety. The disadvantages of these structures are also quite a lot, so in modern construction completely brick chimneys   are encountered less and less. Regulations   limit the height of brick pipes 30-70 m, and the diameter of 0.6-8 m.

On the walls of the brick pipe with a lot of protrusions and depressions inside, there is always a lot of condensate, soot containing sulfur oxides. The latter, reacting with water, forms acids, actively destroying the brick. Surface irregularities, narrowing of the passage as a result of a gradual increase in the soot layer, cause a decrease in the rate of smoke passage.

Chimneys made of ceramics are more resistant to condensate and external factors, they have high fire resistance. But this system has a lot of weight, because inside there are metal rods, which give it additional strength. Hence the requirements for the mandatory installation of a separate foundation, supports, which increases the complexity and cost of installation.

Polymer chimneys are suitable in boiler houses with a maximum temperature of 250 degrees C, during installation gas columns. They are light, flexible and durable, but are relevant only for gas equipment.

A device for removing smoke from stainless steel - an assembly consisting of separate elements of the chimney, connected together by means of shaped parts: tees, nozzles, deflectors, tees, bends. Installation of such a chimney can be carried out after the construction of the building in a short time. There is a large assortment of connecting parts, so the pipe can be given any configuration.

Modular chimney can be easily dismantled and moved to another location. The advantage of the design is also its light weight, which allows you to do without foundation, resistance to moisture, a slight deposition of soot on the inner walls, high velocity of the passage of flue gases.

Sanitary norms allow to apply steel pipes   for the construction of chimneys with a height of more than 30 m, an exception is possible only when less than 5 tons of multi-ash fuel is consumed per day. The reason is that the service life of such structures is 10 years, and if high-sulfur fuel is used, it is significantly reduced.

Calculation of pipe parameters

To determine the height and diameter of the chimney for the boiler room, it is necessary to perform an aerodynamic design calculation. The diameter depends on the power of individual boilers or in the whole boiler room. The combustion of fuel and the effective removal of smoke are greatly influenced by the thrust, for the creation of which a constant supply of air to the furnace is necessary. This is provided both by natural and artificial means.

If the smoke pipe is integrated in the system, the height of the pipe is not critical. This parameter is important mainly for the calculation of harmful emissions into the atmosphere. To determine the self, you need a computation of both the height and cross section of the pipe.

Calculation of pipe height with natural draft

In order to create a normal natural traction, it is necessary to observe the condition of equality of tractive force and total resistance that occurs during the advancement of flue gases through the gas ducts of the boiler and the chimney duct. Provide this traction is possible under the condition of a small gas resistance, when the height of the pipe does not exceed 60 m.

This scheme will simplify the process of calculating the main parameters of the pipe for diverting the combustion products of any fuel in the boiler house furnaces

Normative documents regulating the location and calculation of stacks in height are SNiP41-01-2003, SP 7.13130.2009, the recommendations set out in the instructions to the boiler, in particular, the following requirements:

1. From the grate to the top of the pipe should not be less than 5 m.
2. Over a flat roof without a high fence, the pipe should rise no less than 0.5 m.
3. In relation to the height of the fence and the roof ridge, the pipe must exceed their level by 0.5 m if it is within one and a half meters of these structures.
4. When the chimney is removed from the parapet and the ridge at a distance of 1.5 to 3 m, its upper point must coincide with their height level.

If the chimney height is incorrectly calculated, many problems can arise, and the main one - air turbulence or a zone of windage. Fire in the furnace can extinguish strong gusts of wind.

When constructing a chimney, it is necessary to take into account the structure of the roof, the thickness of the roofing cake, the distance to the enclosing elements and the ridge, the rules for fire safety (+)

Compliance with fire safety rules is also a prerequisite for the design of the boiler room. It is necessary to isolate the structures adjacent to the pipe. To ensure that sparks from the ventilation openings on the pipe do not fall on the roof in the case when it is made of combustible material, the height of the structure is increased by 0.5 m. The boiler room pipe must be at least 2 m away from tall buildings and trees.

The height of the pipe is determined depending on the design of the roof. If the roof is multi-level, the height differences are taken into account, but the base in all cases is one - the height of the ridge (+)

Since the optimal thrust is due to the difference between the total density of gases leaving the chimney and the outside air column of equal height, the calculation is carried out according to the formula:

Height smoke channel   independently calculate by this formula. All values ​​can be taken from the documentation attached to the heating equipment

The calculation is rather complicated, it is better if it is performed by specialists. Parameters affecting the height of the pipe:

1. The coefficient A characterizes the meteorological situation in the region.
2. Mi is the mass of flue gases that pass through the pipe per unit time.
3. F is the rate at which the particles formed during combustion settle.
4. Сддкi and Сфi - indicators of concentration of different substances in the flue gas.
5. V is the volume of the gas.
6. T is the difference between the temperatures of the air entering and leaving the pipe.

If the boiler house is located in the annex to the house, the latter becomes a hindrance. It is necessary that in this case the pipe head is located above the zone of the wind pressure. Otherwise, normal heating equipment can not function.

To determine the size of the pipe, the highest point on the house is found, a straight forming angle of 45 degrees is made through it through the ground. The space under this line is the zone of wind propulsion, and the chimney must be located above it.

Calculation of pipe diameter

To calculate the pipe diameter, there is a formula: S = m / (ρr x w). Here, m is the fuel consumption for 1 hour, w is the velocity of the flue gases, ρr is the air density in the operating conditions, it is determined by the formula: pв = pБну х 273/273 х tо. Where to is the outside air temperature, pBu is the air density under normal conditions = 1.2932 kg / m3.

The table will help determine the value of the air density ρr in the operating conditions without performing complex calculations. The value of the density of flue gases for simplification of calculations is taken equal to the density of air (+)

Let the boiler burn 50 kg solid fuel   for an hour, then for a second it will be 50: 3600 = 0.013888 kg. The velocity of the flue gases is 2 m per second. At an air temperature of -4 degrees C, the air density is 0.6881 kg per 1 cubic meter. m. Then S = 0.013888: (0.6881 x 2) = 0.010092 sq. m. m = 92 square meters. see For the round section d = √4 x 92: 3,14 = 10,83 cm.

The diameter of the cylindrical chimney can also be calculated by another formula: d = 1000 / 1.163 x (r x Q√H), where r is the coefficient depending on the type of fuel used. For coal it is 0,03, for firewood 0,045, for gas 0,016, liquid fuels - 0,024.

Video with calculations of a chimney

The video with a visual demonstration of the process of calculating the height of the smoke channel for the arrangement of the boiler house:

  Another video to help the amateur designer:

It is not so important, on what fuel boilers work in the boiler room. In any case, do not do without a system of flue gas. The main requirements that chimneys must meet are good draft and throughput, consistent environmental standards.

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Chimney constructions of boiler plants

Chimneys are an important element of boiler plants, designed to divert and dissipate in the external environment the products of combustion of fuel. Modern boiler houses can work on gaseous, liquid and solid fuels. As a result of its combustion, reactive solid and gaseous products are formed (soot, ash, carbon dioxide, nitrogen oxides and many others). Chimney   should ensure good dispersion of toxic combustion products, i.e. observance of MPC in the ambient air. In addition, it must create a natural draft for the efficient operation of the boiler plant.

Chimney: a - single-masted, b - two-masted, four-masted, g-walled /

Principles of calculation and installation of chimneys

The height of the chimney is calculated according to three main components:

1. Fuel consumption for 1 hour of operation.
2. Ash content of fuel.
3. The sulfur content of the fuel.

In this case, the height of the pipe must not be less than 5 meters higher than the height of the roof ridge of buildings located within a radius of 25 meters from the boiler plant.

The installation of a chimney consists in the erection of a foundation, a plinth and a trunk with a chimney.

The main materials of the trunk of modern chimneys are reinforced concrete or steel. A brick self-supporting pipe is used less often, since its installation and operation involve certain difficulties. The chimney material must meet the requirements of corrosion, chemical and temperature resistance.

Designing, manufacturing and installation of a pipe of an industrial boiler plant is a complex and multi-stage process.

The project includes aerodynamic calculations, determination of the height and diameter of the pipe, calculation of the self-loading on the basis of these indicators, calculation of the strength and stability of the structure, calculation of the foundation and the mechanism of securing the trunk.

From the correct ratio of height and diameter depends the draft of the pipe and the operational properties of the entire boiler plant. This is especially important if the boilers are not equipped with smoke pumps or supercharged. Otherwise, the height of the structure is determined by the requirements of SanPiN, taking into account the degree of dispersion of harmful substances.

Depending on the number of chimneys, the pipes are single-barreled and multi-barreled. It is possible to install one flue gas ducts from several boiler units to one flue. In this case, it is necessary to calculate the total volume of exhaust gases when designing the pipe diameter, and also consider the possible variation in thrust for each unit.

Typical constructions of chimneys

• farm;

Chimneys of such pipes, as a rule, are equipped with thermal insulation, are attached to a solid self-supporting farm. The thermal insulation layer is protected from weathering by a casing of stainless steel. The supporting truss consists of metal profiled beams connected by horizontal diaphragms and a system of braces. The farm is connected to an anchor basket, which is poured into a massive reinforced concrete foundation. It is possible to fix the flue inside the grating. Installation of the truss structure is carried out on the ground with subsequent joint lifting of the sections and vertical control. For anticorrosion protection of the frame of the truss and aesthetic appearance, the metal structures are primed and painted.

• self-supporting;

The basis of this design is one or several smoke-isolating heat-insulated trunks, fixed on the shell, to which the main carrier function belongs. Gas-discharging trunks are fixed by means of an anchor basket on the foundation. The trunk of the chimney consists of three layers:

1. Internal (flue) thickness of 1 - 4 mm, made of high-quality steel, resistant to the action of chemically active combustion products.
2. Thermal insulation (mineral wool), which allows to minimize the cooling of gases and the formation of condensation of aggressive liquids.
3. The outer layer (shell) of steel 4-6 mm thick, bearing wind and static load.

• near-facade and facade;

A metal chimney with thermal insulation and a casing made of galvanized steel is fixed with clamps and brackets to the building wall or with a light frame near the wall. Installation of facade structures is possible at a sufficient height of the building. Wind load in this case is transferred to the bearing wall of the building.

• mast chimneys on stretching.

They are free-standing metal trunks fastened to the anchor basket, held in the vertical position by means of one or several straps of stretches made of metal cables. The lower part of the steel chimney for fixing to the foundation has a plinth thickness of 10-20 mm, equipped with stiffening ribs. The outer surface of the pipe is covered with refractory enamel to protect against corrosion, but it can be insulated with mineral wool and covered with a casing made of galvanized steel. Advantages of this type of pipe are low cost, no need for a massive foundation. Mounting of structures on stretch marks is possible in seismically dangerous zones.

Taking into account the peculiarities of the location and the height of the pipe, it is often necessary to equip it with additional equipment: light guards, lightning receivers, service staircases.

Modern pipes for boiler houses, as a rule, consist of several modular sections, simplifying the transportation and installation of the product. The number of sections is determined by the height of the pipe. All structural elements of the chimney must comply with the regulatory requirements for materials and production metal structures   according to GOST 23118, SP 53-101.

Chimneys of boiler houses are vertically arranged structures intended for removal to the external environment and dispersion of fuel combustion products.

In large boiler plants, instead of natural draft, an artificial one is used, carried out by smoke pumps.

General norms for chimneys

Note!

According to SanPiN ( health standards   and rules), the chimney should have a greater height, the more fuel costs per hour, its ash content and sulfur content in it.

The main elements of such structures are the foundation, the base and the trunk itself. Inside, the trunk, in most cases, is protected by a lining constructed of refractory bricks.

The height of the chimney of the boiler house must be higher, not less than 5 m of the roof ridge of the buildings, which are located within a radius of 25 meters from it.

The dimensions of industrial structures - the height, as well as the diameter of the outlet, are standardized:

• brick pipes   have a height of 30/70 m, a diameter of 0.6 / 8 m;
• reinforced concrete structures   for large industrial enterprises   can have a height, flesh up to 300 m, diameter - up to 10 m;
• smoke pipes for boilers made of sheet steel, thickness of 3/15 mm, can have a height of not more than 30/40 m and a diameter of 0.4 / 1 m.

According to the sanitary and technical standards, the construction of steel, having a height of less than 30 m, is only permissible at a daily fuel consumption of multi-ash type, not more than 5 tons. The fact is that the lifetime of such structures is 10 years and is greatly reduced when using sour fuel.

Designing a structure

Stages of calculations

Industrial chimneys of boiler-houses require multistage design.

This process includes the following items.

1. Definition of the type of structure.
2. Aerodynamic calculations of the pipe itself, as well as the gas path in the boiler room.
3. Finding the optimal height of the structure.
4. Determination of the diameter of the pipe.
5. Calculation of the speed of gases in the proposed structure, and its comparison with the permissible values.
6. The definition of the self-winding which the pipe will have.
7. Calculation of the structure for strength and stability, with the subsequent compilation of technical instructions on its foundation.
8. Thermotechnical design calculation.
9. Determination of the method and type of pipe fastening.
10. Creation of construction drawings.
11. Drawing up an estimate.

What is the calculation for?

Aerodynamic calculations are needed to determine the height and diameter that a chimney for a boiler house must have, ensuring its efficient operation.

This is the drawing up of a technical assignment for connecting gas flues of boiler equipment to it and developing its drawings.

The package of this documentation makes it possible to create a technical assignment for the foundation of the pipe, its lightning protection and earthing. If a non-standard structure is installed, then an individual passport for it is developed in parallel, as well as an operating manual.

Types of structures

At this point, the chimneys for boilers can have the following designs.

1. Smoke Column Pipe, in fact, are independent free-standing structures.
     The supporting structure of such a pipe is a shell made of high-carbon steel and fixed to an anchor basket, poured into the foundation.
2. Fermi chimneys of boiler-houses   are fixed on a solid and reliable self-supporting farm. That, in turn, is fixed to the anchor basket, poured into the foundation.
3. Facade and facade structures   Mounted on the frame to the wall of the building with the help of wall brackets. This design transmits wind loads to the facade through special vibration isolating elements. The near-facade pipe additionally has its lower foundation, transferring the weight load to it.
4. Frameless self-supporting pipe for boiler room smoke It is placed on the roof of the building and fixed inside the building.
5. Mast construction on stretching   is a free-standing structure fixed on an anchor basket, which is poured into the foundation. The pipe of such a pipe is fixed with clamps to the column.
6. In the boiler room, the chimney can be either single-barreled or multi-barrel.

Required Documentation

Design, manufacture and construction of chimneys should be carried out in accordance with the existing regulatory and technical documentation.

• Calculation of height   It is carried out on ONM # 86.
• Determination of wind loads   - according to SNIP №2.01.07-85.
• Structural strength   is calculated in accordance with SNIP No.II-23-81.
• Design of the foundation   It is carried out according to SNIP №№2.03.01-84 and 2.02.01-83.
• If a chimney is being built for gas boiler, it is necessary to use SNiP №II-35-76 "Boiler installations".
• When using an electrical analog   are guided by SNiP No. 11-01-03 "Shells, casings and casings for the installation of electrical equipment".
• When manufacturing a concrete pipe   applies SNiP №2.03.01-84 "Reinforced concrete and concrete structures."
• The construction of a steel analog requires compliance with SP No. 53-101-98 "Manufacturing and control over the quality of steel structures".
• In addition, GOST 23118-99 "Steel building structures" is used.

It should be remembered that no matter what the smoke pipe for a gas boiler is by design, only accurate calculations, competent manufacture and correct installation   will allow to use it for a long time.