Industrial chimneys

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Description

The main component of technological systems of heat power plants and industrial enterprises are special tower type structures — chimneys. The main purpose of chimneys is removal of gases from different thermal units with subsequent dispersion in the air. Chimneys are also intended for ensuring good furnace draft which depends on thickness-height ratio of the chimney channel. Natural draft in the heating structure is performed by replacement of hot layers of air with cold air.

Design of chimneys and their materials underwent big changes. New technologies of boiler systems forge ahead and that results in increase in efficiency of heating units, temperature of outgoing gases went down therefore there is no opportunity for prompt heating of the gas outlet channel. At the same time there is condensate collecting in chimneys and that leads to destruction of gas outlets made of bricks and standard steel. Application of modular systems of stainless steel gas outlets solves a problem of emergence of condensate in pipes.

Our company offers complex supply and installation of industrial chimneys or gas outlets, as well as individual performance of the services including: designing, production, installation of thermal insulation and heating, delivery, supply of processing equipment and assembly.

Designing and production of industrial chimneys and gas flues is performed according to the regulatory documents in force. Designing is performed on individual basis for every Customer.

Our specialists can help you to choose the optimal design variant for industrial chimneys and gas flues, taking into account all wishes, can offer the functional and least-cost solution meeting all requirements, regulatory documents and safety rules in force. Upon request of the Customer industrial chimneys can be produced with stairs, support frames, intermediate maintenance platforms and other auxiliary technological equipment. Taking into account further operation of chimneys they can be made of stainless steel or galvanized metal in reference to special features of further use.

In order to facilitate the product purchase process, we suggest you downloading and filling out the questionnaire in Word. Then you can send it to us using the information request form or to corporate e-mail. Thus you can quickly obtain information on equipment cost proceeding from its specification.

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Industrial chimneys

Outlet of combustion products is the main purpose of chimneys. They remove soot and smoke which obstruct passage of gases by settling down on its gas flues. The inner part of this structure is smooth in order to avoid this settlement.

There is one more purpose of chimneys: they provide draft in boiler units. The perfect variant is when combustion gases have temperature over 104 degrees at the output so that it will keep draft in a pipe.

The metal heat-insulated chimneys gradually replace brick industrial chimneys. These chimneys are often made of stainless steel or ferrous material. Such structures require maintenance from time to time otherwise performance will gradually go down because of blocking with soot and clogging. It is recommended to clean chimneys after the heating season when they are less operated. Regular inspections usually provide normal use of boiler room and prevent defects. Sometimes a mobile communication transmitter can be installed on the chimney which is over 30 meters; this will make the structure more multipurpose.

Basic fuel types for boiler rooms are liquefied hydrocarbons, natural gas, liquid fuel (oil, diesel) and solid fuel in form of turf, wood, husk, pellet of lignite charcoal and pit coal.

The draft is created due to difference of temperature of gases which are emitted when burned, and the environment. The draft is created due to combustion products which have higher temperature, than the environment and therefore they go up.

Factors to be taken into account during installation of chimney

It shall provide passage of gases through all the height of a pipe and remove combustion products to the air. For this reason the inner surface of this structure is smooth.
It is necessaty to create upward pull effect. Pipe calculations should take into account features of the equipment.
The pipe should meet environmental standards for limit concentration and emission dispersion rate.

Parameters of industrial chimneys vary from 8 to 60 m in height and have one or several gas outlet channels, from 20 cm to 1 m in diameter, and sometimes even 1,5 m. Depending on parameters of a specific chimney and requirements to its technical characteristics, the following auxilary devices can be installed on this structure:

Maintenance platforms and stairways;
Lightning rod;
Warning lights.

Rules to be taken into account during selection of the best variant of design of industrial chimney

The pipe should be arranged in the best way. Besides it is necessary to find the most effective variant of arrangement of approach of every horizontal gas exhaust duct from operating units;
The installation of one pipe with connection of gas flues from several units can be performed. In this case it is necessary to take into account the capacity of the units, operating mode, possible connection of several horizontal sections from the corresponding number of units to one gas flue. Besides it is necessary to follow safety rules (SR) and common esthetics. The main shortcoming of connection of all gas flues to only one pipe is impossibility of execution of routine maintenance as in that case it is necessary to bring all the boilers out of service.
In cases when several gas exhaust ducts are connected to one main pipe, these ducts have to be located in different planes. If they are located in one plane anyway, there can be problems with draft of one or groups of ducts. Gas exhaust ducts are connected to the common channel by means of special connecting details which should be well heat-insulated using rock wool or other nonflammable material. Besides it is necessary to make the right selection of a form of gas exhaust duct which can be square, oval or spherical. The best form of section is spherical, but in reference to each specific architectural concept the pipes of other form may be required. If rectangular section is selected, then it is necessary to choose suitable height-to-width aspect ratio. The best variant is 1:1,5 when the inner angles are rounded.
The correct determination of pipe height is also a critical moment, as correct selection of this parameter makes it possible to ensure good draft and allows following environmental requirements and standards for limit concentration and emission dispersion rate.
The correct selection of type and thickness of heat insulation is required. Heat insulation of exhaust ducts is required to prevent condensation of corrosive compounds (i.e. sulfur and nitrogen) and water vapor on their surface that often results in gradual destruction of the gas pipe.
Every gas exhaust duct should have a service opening for cleanup and diagnostics. Usually such opening is a window with lockable hatches.
Reliable fixing of chimney. This process is performed with use of the special base (so-called self-supporting). There is also an option of pipe support by means of load carrying structures which in principle withstand overload if that entails frontal pipes. Besides there are some cases when more than one gas exhaust duct is fastened to one supporting structure (that entails truss-type pipes). The chimney itself may not be a support or supporting structure for other elements of the general construction.
Only some materials can be suitable for production of chimneys. For example, the inner surface should be made of smooth, heat-resistant and corrosion-resistant materials. In turn, the external part of pipe is made of frost-resistant material.
Never use the gas pipe as an additional source of heating of indoor premises as when the product becomes cool, it isn’t removed outside so good. Therefore it is necessary to insulate safely the gas pipe.

Types of industrial chimneys

Self-supporting chimney

Self-supporting chimney is a metal single-shaft chimney of up to 30 m high to which gas pipes from one or more units are connected. During selection of this type of chimney it is necessary to consider the need of such design for your case. It is necessary to consider technical parameters and operating modes of unit which you are going to connect to the chimney. Be very attentive to this issue if you plan to connect horizontal gas exhaust duct to one chimney. The amount of removed combustion product during operation of all connected units at maximum performance should correspond to chimney capacity.

In general self-supporting chimneys include the following elements:

Ground (mounting area) which is made using sheet metal. It is fixed by means of anchor connections on the foundation.
Main gas flue. Steel pipe is used for implementation. It is designed with rigid fastening of stiffeners to the ground.
If structural reinforcement is required, the ground frame is to be reinforced using additional stiffeners. This method is combined with increase in the area of the ground. This is how conditions are established under which pipe load falls on the support plate and foundation.
If necessary, the chimney shaft is insulated with insulation layer in form of rock wool or other nonflammable material with thickness from 2,5 cm to 1 dm. The heat insulation layer is usually covered with external shell which can be made of aluminum, steel or stainless steel.
There are two types of self-supporting steel pipes: single-shaft and multi-shaft. Multi-shaft pipe is a solid structure consisting of several gas exhaust shafts and a general frame which put the system together.

The main advantage of such pipes is rather low-cost production and erection.

But self-supporting pipes have also disadvantages:

considerable metal consumption that influences the cost of the whole structure;
large weight which requires deep foundation;
rather expensive transportation because of weight of the object;
if a part of the pipe is subjected to destruction, replacement of the whole shaft is required;
if more than one horizontal gas flue is connected to the chimney, there will be a difficulty in maintenance and technical inspection — it will be necessary to put all the connected units out of service in order to perform these actions.

The self-supporting structures can be equipped with the following units if necessary:

Lightning rod;
Warning lights;
Maintenance platforms and stairways

Self-supporting truss chimney

This type of gas exhaust structure consists of supporting truss shaft and one or several heat-insulated gas flues. 1-6 gas exhaust ducts of different diameter can be installed to the supporting shaft. Such pipes can be up to 50 m high. Each gas flue can be up to 1,5 m in diameter. Each gas exhaust duct is made from modular gas flues.

The heat-insulated gas flues of modular type have three-layer structure. The layers consist of materials which are resistant to high temperature and acid environment which is created by condensate:

Inner working layer, made of AISI 304 stainless steel, which was specifically developed for operation in typical conditions for gas exhaust pipes: hostile environment and high temperatures. This material has excellent mechanical performance characteristics.
Intermediate layer which consists of rock wool, which is determined by thickness calculation. In general insulation of flues of boiler rooms is implemented by means of basalt rock wool of 5-6 cm thickness. The purpose of heat insulation is protection of pipe against fast heat loss and prevention of condensate. This layer enables to improve draft and to increase service life of the structure. During production the rock wool is used «for fire isolation».
Outer layer which is made with use of sheet steel with 0,55 mm polymer covering, or stainless steel with high strength index, excellent mechanical properties and corrosion resistance.

The truss (supporting structure) is made using rolled tubular products of various section, three- or quadrangle, that depends on quantity of gas exhaust ducts. The outer surface of the shaft is painted with high-quality and modern coating materials with increased content of zinc. There is also a possibility of arrangement of stairways and maintenance platform inside the truss.

The next advantage of such pipes is rather small weight of the whole product that simplifies transportation and erection. The total structure of the truss pipe reduces wind load to the foundation. Metal pipes under GOST 10704-91, which are connected by means of horizontal angles and bracing systems, are the supporting elements of the supporting tower.

Appearance of the tower can be adjusted, but only in a way which has no contradictions with regulatory documents and safety rules. Additional, though optional elements for such pipes are: stairways, lightning rod, warning lights, maintenance platforms, condensate extractor, explosive valves, horizontal sections and cleanout.

Columned metal chimney

Columned-type chimney is an independent self-supporting structural unit. The supporting structure of the columned-type pipe is fastened to the anchor basket in the foundation.

The structure of this chimney consists of outer supporting shell and a package of inner gas exhaust ducts. 1-5 ducts of different diameter can be installed in the shell. In general the columned self-supporting pipes are up to 34,5 dm in diameter and up to 60 m high. Inner gas exhaust ducts are made of stainless steel. Thickness and brand of stainless steel is chosen depending on corrosive power and temperature of gases. Each gas flue can be up to 1,5 m in diameter. Besides, the general gas flue can be used for more than one boiler. In that case the gas flue can be up to 3 m in diameter.
Gas exhaust ducts are covered from the outside by heat insulator which preventing condensate inside the ducts.

Thickness and brand of heat insulator is chosen depending on corrosive power and temperature of gases. In general 5-6 cm basalt rock wool is used for insulation of pipes. Insulation of exhaust pipes in co-generation plants and gas engine power plants is usually 11-12 cm thick.

The structure of ducts itself allows implementation of extraction of condensate and precipitates. Besides, it allows implementation of cleaning of their lower part. The supporting shell is made of sheet steel of different thickness. The outside surface of pipes is painted with high-quality up-to-date materials with high content of zinc. The upper third of the pipe is equipped with intertseptors — dynamic absorber — which are required in order to avoid the wind resonance. If necessary, maintenance platform, warning lights and stairways can be installed on the top of the pipe.

Esthetic appearance is provided by the features of the structure which belongs to this type of industrial pipes. Besides, a good advantage is not only the small area of the structure, but also the fact that gas exhaust ducts are inaccessible to vandals and hooligans. This type of pipes is best suitable for installation on unprotected objects and within the city.

Guyed chimney

Guyed chimney is a metal single-shaft pipe fixed by a certain quantity of guys or stays. Purpose of this structure is removal of flue gas and common smoke from different types of industrial plants.

Such gas flues with guys are widespread in the industry due to certain advantages which include: low cost, buildability and ease of erection.
This type of pipes is made by rolling of steel sheets to shells and shell stitching at the required length, the shaft of the lower part of the chimney is fastened to the mounting base. The structure is equipped with stiffeners which provide strong fastening of the gas exhaust channel. The amount of bending moments which are caused by lateral loads is reduced by means of guys which are made of rod steel with diameter of 1,6-2 cm.

Determination of height and diameter of the pipe is performed on the basis of aerodynamic, thermo-technical and even ecological calculations.
Guys should be fastened at 30 degrees to gas exhaust channel.

However this design has also disadvantages, for example, short service life. Even the most proper use of pipe won’t allow using it longer than 8-15 years. Large area is required to place buttress piers which are necessary for fastening guys. Besides it is necessary to perform great volume of ground work for arrangement of the foundation, and for this reason it is more material-intensive.

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