WO2009011670A1

WO2009011670A1 - System for cleaning fume gas exhausted from a coke oven

Info

Publication number: WO2009011670A1
Application number: PCT/UA2008/000035
Authority: WO
Inventors: Yevheniy Alekseevich Danilin; Aleksandr Aleksandrovich Lobov
Original assignee: Yevheniy Alekseevich Danilin; Aleksandr Aleksandrovich Lobov
Priority date: 2007-07-19
Filing date: 2008-06-18
Publication date: 2009-01-22
Also published as: RU2008107639A; RU2373255C1; UA85778C2

Abstract

The invention relates to systems for cleaning fume gas exhausted from a coke ovens or coke-oven plants and can be used in the coke-chemical industry. The inventive system for cleaning fume gas exhausted from a coke-oven plant (1) comprises at least one coke oven (2) connected to a smoke chimney (3) by means of a gas flue (4) provided with a flue damper (5) which is located in the area where the gas flue (4) is jointed to the smoke chimney (3). The system is also provided with a fume gas cleaning circuit (6) which comprises a waste-heat boiler (7), a smoke exhauster (8) with a guiding device (9) and a control valve (10) arranged in the output area of the circuit (6) jointed to the smoke chimney (3). The input of said fume gas cleaning circuit (6) is connected to the gas flue (4) where it is jointed to the coke oven (2). The system is also provided with a gas conduit (13) which connects the output of the fume gas cleaning circuit (6) to the gas flue (4). The input of the gas conduit (13) is coupled to said circuit (6) before the control valve (10) in the direction of the fume gas flow and the output of the gas conduit (13) is coupled to the gas flue (4) where said gas flue (4) is jointed to the smoke chimney (3) before the flue damper (5) n the direction of the fume gas flow. The gas conduit (13) is provided with a flue gas flow controller (14). Said invention makes it possible to optimise the hydraulic mode of the coke oven operation, thereby obtaining the high quality cleaning of the fume gases exhausted from the coke oven and to increase the performance of the waste-heat boiler.

Description

INSTALLATION FOR CLEANING SMOKE GASES OUT OF

COKE FURNACE

FIELD OF TECHNOLOGY

The present invention relates to plants for cleaning flue gases from coke ovens or coke oven batteries, and can be used in the coke industry.

BACKGROUND OF THE INVENTION

It is known that in coke oven plants, coke ovens account for> 60% of atmospheric emissions of pollutants contained in flue gases from coke ovens. The main pollutants contained in flue gases include nitrogen oxides (NO _x ), carbon oxides (CO _x ) and sulfur oxides (SO _x ). In addition, flue gases may contain finely dispersed carbon particles, which are also contaminants.

Currently, environmental issues in the production of coke have become particularly relevant. Environmental measures are becoming an indispensable part of the coke production technology produced by coking. Therefore, to reduce the amount of pollutants contained in the flue gas, as well as to reduce the amount of flue gas emissions into the atmosphere, various methods of cleaning flue gases from the coke ovens are used.

Traditionally, in the industrial production of coke, the coking method is used, which consists in the processing of natural fuels, mainly coal, by heating it to 950 - 1050 ⁰ C without air. In the process of coking, complex chemical reactions, physicochemical processes, and physical phenomena occur. In this case, the main products that are obtained during coking are coke and coke oven gas. When coke coals are heated to a temperature of ~ 350 ⁰ C, coke coal softens, turning into a plastic state. In this case, a complex of thermal transformations of coal occurs with the release of so-called primary products having a complex composition, and at a temperature of about 500 ⁰ C, the plastic mass hardens and a solid porous product is formed, which is called semi-coke. With further heating, the semi-coke loses residual volatile substances and undergoes shrinkage, causing its separation. At temperatures above 900 ⁰ C, semicoke completely turns into coke.

Part of the primary coking products, namely, primary gas and resinous substances, in contact with the red-hot walls and the coke oven vault, as well as with coke, undergo pyrolysis. Gaseous coking products are captured and used as raw materials for the chemical industry.

Traditionally, the coking process is carried out in a coke oven or in a coke oven battery, which includes at least one coke oven. Before loading coal into a coke oven, it is prepared, namely, it is crushed and a charge for coking is formed, which has a certain component composition, which ensures the production of conditioned commercial coke, which allows to increase the productivity of coke ovens.

In the coke oven, the coking process proceeds in layers, and the temperature of the layers gradually increases from the heated (above 1000 ⁰ C) walls of the coke oven to the middle of the load. Accordingly, the composition of the layers (starting from the walls) changes in the following sequence: coke - semi-coke - plastic state - dry charge - raw charge. Coking is considered complete when all layers of coke converge in the middle of the coke oven. Towards the end of coking, as a result of shrinkage, a so-called “coconut cake” is formed, which is divided in the middle part by a seam-gap running parallel to the heating walls of the coking chamber, and each half of the “cake” is divided into more or less large pieces by cracks. The coke obtained in the furnace is removed from it by a coke ejector and enters the quencher, where the hot coke is cooled with water or an inert gas (“wet” or “dry” method).

For compactness of the coke plant and better use of heat, coke ovens are combined into batteries, 37 to 100 coke ovens each, with heating gas supply systems, coal supply systems, raw coke oven gas removal and flue gas exhaust systems common to all furnaces.

The coke oven contains a coking chamber, heating walls located on both sides of the coking chamber, regenerators, a flue gas exhaust system, which consists of ducts located on both sides of the coke oven, while the ducts are adjacent to the hog. Loading hatches are provided in the upper part of the coking chamber; from the ends, the coking chamber is closed by removable doors. The length of coking chambers, as a rule, reaches 16 m, height 4 - 7 m, width 0.4 - 0.5 m.

Coking chambers are heated by burning in the vertical channels piers of coke, blast furnace or a mixture of various combustible gases. The heating of the coking chambers is important for the coking process of the charge, since the quality of the coke depends on the uniformity of heating along the length and height of the coking chambers, and the combustion conditions and composition of the heating gas determine the amount and composition of flue gases. ^•

The coking period of one coal charge depends on the width of the coking chamber, the temperature in the heating walls, the properties of the coal charge and is usually 13 - 18 hours. However, in some cases, the coking period can be increased to be from 18 to 30 hours. When changing the coking period the amount of heating gas for heating the coke oven changes and, accordingly, the volume of flue gases leaving the coke oven changes.

In the process of heating coking chambers by burning combustible gas in a vertical heating channel, in particular a blast furnace, coke oven or a mixture of coke oven and blast furnace gas, etc., flue gases are formed that contain nitrogen oxides, carbon oxides and sulfur oxides. Flue gases can also contain fine carbon particles. Quantity and the composition of the flue gas depends on many factors. The main ones are: the temperature level in the heating channels and the conditions for burning heating gas; the tightness of the masonry of the heating walls of the coking chambers and the coke oven heating system, the coefficient of excess air.

For the effective implementation of the coking process in coke ovens, a certain hydraulic regime is required, which provides the necessary temperature regime in each coke oven and the effective combustion of the heating gas.

So, for a coke oven, the optimum hydraulic mode is the mode that provides a small excess pressure (0.1 - 5 Pa) in the upper part of the coke oven, under the inspection hole. This mode is ensured when the thrust in the flues located on both sides of the coke oven is at the level of 200-300 Pa. Such rarefaction is supported by regulators installed in the flues, the best operating range of which is ensured when the vacuum in the hog is 400-500 Pa.

During operation of the coke oven, the hydraulic mode is constantly changing. The change in the hydraulic regime depends on many factors, in particular, on the loading of coke oven with coke coal, on the tightness of the masonry walls of the coke oven, on the type of fuel used for heating the coke oven, coking period, and ambient temperature conditions. So, for example, when choosing coke oven gas with a calorific value of -4000 kcal / m ³ , one volume of heating gas is required, and when choosing a blast furnace gas with a calorific value of ~ 900 kcal / m ^3, it is necessary to use a larger volume of heating gas compared to coke oven gas . Violation of the optimum hydraulic mode of the coke oven leads to a deterioration in the uniformity of heating and, as a consequence, to a deterioration in the quality of marketable coke, and also leads to an increase in the cost of marketable coke. In addition, a decrease in the rarefaction (draft) leads to a decrease in the productivity of the coke oven, and an increase in the vacuum leads to leaks in the heating system, an increase in the leakage of raw coke and heating gases, worsening of the conditions for burning heating gas, and, as a result, to a sharp increase in the content of pollutants in flue gases. Therefore, maintaining the optimum hydraulic mode of the coke oven at a given level is a necessary condition for its operation.

Traditionally, the flue gas is removed from the coke oven battery to the atmosphere through a chimney. Typically, a coke oven battery is connected to the chimney by a hog connecting ducts located on both sides of the coke oven battery.

The hog is a flue with a cross section from 2.5x2.5 m to 4x4 m. Usually the hog is located underground, and in the zone where the hog adjoins the chimney, a gate is installed that is designed to control the vacuum in the hog.

Also, in the area adjacent to the gas ducts to the hog, regulators are installed to regulate the vacuum in the coke ovens included in the coke oven battery.

The chimney is designed to create a natural vacuum for the removal of flue gases from the coke oven battery. The chimney consists of a foundation, a socle and a trunk. The inner surface of the chimney barrel is protected by a brick lining. The chimney should be the higher, the greater the amount of flue gases and the content of pollutants in them.

ANALOGUE

A known installation for cleaning flue gases from the coke oven (see Ukrainian patent Ne 38732, IPC C10B 45/00, F23J 15/00, publ. 05/15/2001) containing: a) a coke oven connected to the chimney by hog, b) a flue gas cleaning circuit, including a waste heat boiler and a smoke exhauster with a guide apparatus, while the input of the specified flue gas cleaning circuit is connected to a hog in the area where the hog adjoins the coke oven.

The flue gases that leave the coke oven enter the flue gas treatment circuit, including a waste heat boiler and smoke exhaust. In the waste heat boiler, the flue gas is heat treated, which results in the neutralization of the flue gas. Also in the recovery boiler, heat is removed from the cleaned flue gas. In the known installation of burs, through which the coke oven is connected to the chimney, has no means for regulating the flow of flue gases entering the chimney. Also a design feature of the known installation is that the output of the flue gas treatment loop is connected to the hog at two points. At the same time, the stream of purified flue gases that leave the waste heat boiler is divided into two flows of purified flue gases, one of which forms a countercurrent in the hog counterflow to the stream of raw flue gases leaving the coke oven, and the second stream of purified flue gases is discharged into the atmosphere through the flue the pipe.

A disadvantage of the known installation is the difficulty in maintaining the optimal hydraulic mode of operation of the coke oven, due to the fact that the vacuum in the hog is always equal to the vacuum in the chimney, since the known installation has no means to create additional resistance to the flow of flue gases and to regulate the vacuum in the hog in front of the chimney.

In the process of the known installation, the vacuum in the chimney is constantly changing, since it depends on the quantity and temperature of the flue gases, the ambient temperature, the state of the masonry of the chimney, the temperature of the chimney, etc.

An increase in ambient temperature leads to a decrease in vacuum in the chimney, and with a decrease in ambient temperature, an increase in vacuum in the chimney occurs.

At the same time, with a decrease in the temperature of the flue gases, a decrease in the vacuum in the chimney occurs. However, the temperature of the flue gases in the chimney should not be lower than the temperature at which condensation of the flue gases occurs, as a result of which water and other by-products are released, which lead to rapid wear of the chimney masonry. When using the flue gas cleaning circuit, the temperature of the flue gas is constant and is in the range 180 ⁰ C - 220 ⁰ C.

The vacuum value that the chimney creates is greater than the vacuum value required for the efficient operation of a coke oven or coke oven battery. When calculating and designing the construction of the chimney, there are criteria that are taken into account when erecting it, the main criterion being the ability of the chimney to provide the outlet all flue gases from the coke oven battery when operating at the maximum permissible coking conditions at the highest possible positive ambient temperature in the region in which the chimney will be installed. For long periods of coking, the control system of the flue gas treatment plant must provide such a negative pressure in the hog that would not interfere with the stable operation of the coke oven battery and ensure stable operation of the recovery boiler. Since the increase in vacuum and, accordingly, the draft of the chimney above the permissible value often leads, on the one hand, to an increase in leakage in the coke oven battery and a violation of its stable operation, and, on the other hand, it may lead to the separation of the torch in the waste heat boiler and its exit out of service.

Given the significant cost of building a chimney during the construction of coke plants, a chimney, in some cases, is designed to service several fuel-burning units, and is also designed to service other plants, from which it is necessary to divert other gases that were formed during the production process, for example, the removal of excess gases from the installation of dry quenching of coke. Therefore, the chimney depression is usually greater than the vacuum value necessary for the efficient operation of the coke oven battery.

An increase in vacuum in the hog to a vacuum level in the chimney leads to an additional increase in vacuum in the flue gas cleaning circuit. In order to remove flue gases from the hog to the flue gas cleaning circuit, in the latter it is necessary to create a vacuum that exceeds the vacuum in the hog, which leads to inefficient operation of the recovery boiler, because with an increase in vacuum in the recovery boiler, the efficiency of flue gas cleaning decreases, due to unorganized air suction.

PROTOTYPE

A known installation for cleaning flue gases leaving the coke oven (see "Installing thermal neutralization and heat recovery of flue gases of coke oven batteries", "Koks and chemistry" Ne 12, 2003, p. 36-39) containing: a) at least one coke oven connected to the chimney by means of a hog equipped with a gate, which is located in the area where the hog adjoins the chimney, b) a flue gas treatment circuit, including a waste heat boiler, a smoke exhauster with a guide apparatus and a control valve, located in the exit zone of the specified circuit adjacent to the chimney, while the input of the specified circuit for cleaning flue gases is connected to the hog in the zone of contact of the hog to the coke oven.

In a known installation, flue gases are discharged from the hog into a flue gas treatment loop, from which they are then diverted to the chimney. When flue gases are removed from the hog to the flue gas treatment loop, part of the cleaned flue gases is recirculated, i.e. a part of the cleaned flue gases from the chimney through the gate installed in the hog is returned to the cleaning loop along with the flue gases that are removed from the coke oven. The volume of recirculated flue gases should be minimal, not more than 2-5% of the volume of purified gases to ensure energy saving conditions. At the same time, the gate located in the area where the hog adjoins the chimney must be in a partially ajar position, that is, in a position that ensures the operation of the coke oven in case of emergency stop or breakdown of the waste heat boiler or smoke exhauster, because when the gate is closed , during an emergency stop of the recovery boiler or breakdown of the smoke exhaust, the coke oven will stop working. Partial opening of the gate ensures recirculation of flue gases in the amount of 2-5%, while the vacuum in the hog exceeds the vacuum in the chimney, which leads to a suboptimal hydraulic operation of the coke oven.

A disadvantage of the known installation is that for the implementation of recirculation of flue gases, it is necessary to maintain a vacuum level in the hog greater than the vacuum in the chimney by the amount of resistance of a part of the hog with a gate. The resistance of a part of a hog is determined by the following relationships:

ΔP = ξ (W ² / 2g) p (T / 273), (1)

W = B / F, (2) Where

ΔР - resistance of a part of a hog with a gate; ξ is the drag coefficient of part of the hog with a gate;

W is the speed of the flue gas in the hog in the area of the gate, m / s; g is the acceleration of gravity, m / s ² ; p is the density of flue gases, kg / m ³ ;

In - gas flow, m ³ / s;

F is the bore of the hog in the area of the gate, m;

T - flue gas temperature, K.

It can be seen from the above dependences that the resistance of a part of a hog with a gate depends on the amount of flue gases that pass through it.

SUMMARY OF THE INVENTION

The main objective of the invention is the creation of an installation for cleaning flue gases from the coke oven, which allows to achieve optimization of the hydraulic operating mode of the coke oven.

Another objective of the claimed invention is the development of the installation, which allows to achieve a high degree of purification of flue gases from the coke oven battery.

Another objective of the claimed invention is the development of the installation, which allows to achieve high efficiency of the waste heat boiler.

The objectives are achieved in that in the installation for the purification of gases coming from the coke oven, containing: a) at least one coke oven connected to the chimney by means of a hog equipped with a gate, which is located in the area adjacent to the chimney, b ) a flue gas cleaning circuit, including a waste heat boiler, a smoke exhauster with a guide apparatus and a control valve located in the outlet zone of the specified circuit adjacent to the chimney, while the input of the specified flue gas cleaning circuit is connected to the boro WU in the area adjacent to the coke oven, according to the claimed invention c) the installation is equipped with a gas duct that connects the outlet of the flue gas cleaning circuit to the boron, while the gas duct inlet is connected to the specified circuit in front of the control valve in the direction of the flue gas, and the gas outlet is connected to the boron in the area where the boron adjoins the chimney in front of the gate flue gas movement, while the flue is equipped with a flue gas flow regulator.

The implementation of the inventive installation of the flue, the inlet of which is connected to the flue gas purification circuit in front of the control valve in the direction of the flue gas movement, and the inlet with the hog, ensures stable and efficient operation of the coke oven or coke oven battery and eliminates the leakage of flue gases, bypassing the recovery boiler, in a chimney. This is achieved by transferring part of the flue gases from the flue gas cleaning circuit to the boron zone, which is placed in front of the gate in the direction of the flue gas, which is ensured by a control valve that regulates the flow of flue gases that directly enter the chimney from the flue cleaning circuit gases. The presence of a control valve ensures the creation of resistance to the flow of gases that move to the flue gas cleaning circuit towards the chimney with their subsequent discharge to the flue, which makes it possible to select the optimal hydraulic operating mode of the flue gas treatment plant.

The supply of flue gases to the chimney, in the area adjacent to the chimney in front of the gate, increases the amount of flue gas that passes through the chimney, in the zone of the gate, into the chimney, according to dependences (1), (2), increases the resistance of a part of the hog with gate with the appropriate degree of opening of the gate. Changing the direction of movement of the flue gases through the burs in the area of the gate and increasing the resistance in this zone leads to a decrease in the resistance in the bore to the optimum value. The decrease in vacuum in the hog also leads to a decrease in vacuum in the flue gas cleaning circuit and, as a result, to an increase in the efficiency of the waste heat boiler.

The use of a flue gas flow regulator in the flue allows you to adjust the amount of flue gases and, thus, allows stabilize and maintain vacuum at a level necessary for optimal operation of the coke oven battery.

BRIEF DESCRIPTION OF THE FIGURES

In FIG. - an installation for the purification of flue gases from a coke oven is presented.

DETAILED DESCRIPTION OF THE INVENTION

Installation for cleaning flue gases from the coke oven battery 1, contains coke ovens 2, which are connected to the chimney 3 by means of the hog 4. The hog 4 is also equipped with a gate 5, which is located in the area adjacent to the hog 4 to the chimney 3.

The flue gas cleaning circuit 6 includes a waste heat boiler 7, a smoke exhauster 8 with a guide apparatus 9 and a control valve 10.

Also, the coke oven battery 1 contains two ducts 11 ₁ and 11 ₂ , which are located on the sides of the oblique battery 1. Moreover, the ducts 111 and 11 ₂ are designed to exhaust flue gases that leave the coke oven battery 1 in the burs 4. In the area adjacent to the ducts 1 1 i and 112 to hog 4 flue gas controllers 12-ι and 12 _{2 are} installed.

The guide apparatus 9 of the smoke exhauster 8 is used to control the flow of flue gases through the recovery boiler 7. The input of the cleaning circuit 6 of the flue gas is connected to the hog 4 in the adjoining zone of the hog 4 to the coke oven 2, and the output of the cleaning circuit 6 is connected to the chimney 3 in the exit zone purification circuit 6 flue gas control valve 10 is located.

Also, the installation for cleaning flue gases leaving the coke oven is equipped with a gas duct 13, which connects the output of the cleaning circuit 6 of the flue gas with the bur 4. In this case, the inlet of the gas duct 13 is connected to the cleaning circuit 6 in front of the control valve 10 in the direction of the flue gas the gas duct 13 is connected to the hog 4 in the area of contact of the hog 4 to the chimney 3 in front of the gate 5 in the direction of the flue gas.

Also, the flue 13 is equipped with a flue gas flow regulator 14.

The installation includes a control system including a vacuum control sensor 15, which is installed in the hog 4, and a control unit 16, input which is connected to the control sensor 15, and the output of the control unit 16 is connected to the control valve 10 and the regulator 14 of the flue gas stream.

Installation for cleaning flue gases from the coke oven, operates as follows.

In the process of operation of the coke oven battery 1, flue gases are formed in the skew furnaces 2, which are discharged through the flues 11 ₁ and 11 g to the burs 4. The flue gas flow rate is controlled by the flue gas regulators 12i and 12g. In the area where the hog 4 adjoins the flue gas cleaning circuit 6, flue gases are vented to the cleaning circuit 6 using a smoke exhauster 8, which is equipped with a guiding apparatus 9. In the cleaning circuit 6, the flue gases enter the waste heat boiler 7, in which the flue gases are decontaminated . After the recovery boiler 7, one part of the cleaned flue gas is discharged into the chimney 3 through a control valve 10, and the other part of the cleaned flue gas is discharged into the gas duct 13, in which the flue gas flow regulator 14 is installed.

The amount of flue gases that pass through the gas duct 13 is determined by the dependence:

B = B-ι + B ₂ (3)

Where

In - the amount of flue gases that pass through the gas duct 13, m ³ / h;

Bi is the amount of flue gases that come from the hog 4 into the chimney 3 with an acceptable (under the condition of an emergency situation on the coke oven battery 1, in case the unit is turned off) opening degree of the gate 5, m ³ / h;

Vg - the amount of flue gases that recycle in the hog 4, m ³ / h;

From the flue 13 flue gases enter the burs 4 in front of the gate 5 in the direction of the flue gases. One part of the cleaned flue gases, which entered the burs 4 from the gas duct 13, is discharged through the gate 5 into the chimney 3, and the other part of the cleaned flue gases is counter-directed to the purification circuit 6 of the flue gases through the adjoining zone of the hog 4 to the coke ovens 2, which allows to exclude the leakage of uncontaminated flue gases into the chimney 3, bypassing the waste heat boiler 7. The change in vacuum in the hog 4 is controlled by the vacuum control sensor 15, which is installed in the hog 4. When the vacuum is increased in the hog 4, the vacuum control sensor 15 provides information to the control unit 16, which generates a control command to the control valve 10 and the regulator 14 to increase the flow of flue gases through the duct 13 and maintaining the required vacuum in the hog 4 to ensure the optimal hydraulic mode of operation of the coke oven battery 1.

Tests of the inventive installation for the purification of flue gases were carried out on a coke oven battery at ZAO ZAPOPOZHKOKC. The test results are shown in tables 1 and 2.

Table 1

From table 1 it can be seen that depending on the change in vacuum in the chimney 3 with the same amount of flue gases that leave the coke oven battery 1, in the claimed technical solution, the vacuum in the hog 4 corresponds to the optimal value necessary to ensure an effective hydraulic mode of operation of the coke oven battery 1 , while in the closest technical solution (prototype), the pressure in the hog 4 was significantly higher than the optimal value, which led to a suboptimal hydraulic mode and unstable For the full operation of the coke oven battery 1. Also, when using the proposed technical solution, the vacuum at which the waste heat boiler 7 operates, in comparison with the prototype, decreases and amounts to 500 Pa. Reducing the vacuum at which the waste heat boiler 7 works, increases the reliability of its operation, and also reduces the amount of leaks and improves the process of thermal neutralization of flue gases that leave the coke oven battery 1.

table 2

From table 2 it can be seen that, depending on the change in the amount of flue gases that leave the coke oven battery 1 at a constant vacuum in the chimney 3, the vacuum value in the hog 4, when using the claimed technical solution, was at the same level and amounted to 400 Pa, which corresponds to the optimal value of rarefaction in boron 4 for the operation of coke oven battery 1. At the same time, when using the closest technical solution, the vacuum in boron 4 was higher than the optimal value, which led to inefficient operation e coke oven battery 1.

Claims

CLAIM

1. Installation for cleaning flue gases leaving the coke oven, comprising: a) at least one coke oven connected to the chimney by means of a hog equipped with a gate, which is located in the area adjacent to the chimney, b) flue gases, including a waste heat boiler, a smoke exhauster with a guide apparatus and a control valve located in the exit zone of the specified circuit adjacent to the chimney, while the input of the specified flue gas cleaning circuit is connected to the hog in the area where the hog adjoins the cook a new furnace, characterized in that c) the installation is equipped with a gas duct that connects the outlet of the flue gas cleaning circuit to the boron, while the gas duct inlet is connected to the specified circuit in front of the control valve in the direction of the flue gas, and the gas duct outlet is connected to the boron in the boron adjoining zone to the chimney in front of the gate in the direction of the flue gas, while the flue is equipped with a flue gas flow regulator.