WO2007097734A1

WO2007097734A1 - Method for decontaminating smoke gases of fuel combusting plants

Info

Publication number: WO2007097734A1
Application number: PCT/UA2007/000011
Authority: WO
Inventors: Yevgeniy Alekseevich Danlin; Aleksandr Aleksandrovich Lobov
Original assignee: Yevgeniy Alekseevich Danlin; Aleksandr Aleksandrovich Lobov
Priority date: 2006-02-24
Filing date: 2007-02-19
Publication date: 2007-08-30
Also published as: UA81527C2; RU2006144505A; RU2363884C2

Abstract

The inventive method for decontaminating smoke gases of fuel combusting plants consists in burning fuel in the combustion chamber (1) of a fuel combusting plant in a partial combustion mode with the minimum possible air excess factor α and in afterburning fuel gases exhausted from the fuel combusting plant in a reactor (5) by supplying an additional gaseous fuel and additional air thereto. The temperature in the reactor is maintained at a level ranging from 750 to 1200o C and oxygen contained in the fuel gases is used for burning combustible components of the fuel and fuel gases. The aim of said invention is to reduce the concentration of nitrogen and carbon oxides in the fuel gases by controlling the fuel gas afterburning mode by means of the supply of the additional gaseous fuel and air by adjusting the fuel gas afterburning mode by means of the control of the additional gaseous fuel supply. The additional air supply for burning the additional gaseous fuel is adjusted according to the inventive mathematical relations.

Description

METHOD FOR DISINFECTING SMOKE GASES OF FUEL-BURNING

UNITS

FIELD OF THE INVENTION The invention relates to methods for disinfecting flue gases, and in particular, to methods for reducing the concentration of nitrogen and carbon oxides in flue gases that depart from fuel-burning units, in particular coke oven batteries, and can be used in metallurgical and other industries.

BACKGROUND OF THE INVENTION

A known method of purification of flue gases from nitrogen oxides by introducing into the flue gases at a temperature of 1100-1400 ⁰ C an aqueous suspension of aluminosilicate (see ed. Certificate of the USSR N ° 879157, M. cl. F23G 7/06, publ. 07.11.81 g .).

The disadvantages of this method are its high cost, since the use of aluminosilicate catalyst requires special devices designed to introduce this suspension into the combustion products, and the lack of efficiency of disinfection of flue gases that leave the fuel-burning units.

A known method of disinfection of flue gases of fuel-burning units, adopted as a prototype, which includes burning fuel in the fuel chamber of a fuel-burning unit in the mode of incomplete combustion of fuel with the minimum possible coefficient of excess air (θ), and the afterburning of flue gases that leave the fuel-burning unit is carried out in reactor, by introducing additional gaseous fuel and additional air into the reactor (see US Pat. N ° 47140 A, M PK F 23 G 7/00, publ. June 17, 2002).

The disadvantage of this method is the insufficient degree of purification of flue gases from oxides of nitrogen and carbon, which depart from the fuel-burning unit. The flue gas afterburning process is not optimal, namely, afterburning occurs in a static mode without controlling the amount and calorific value of the additional gaseous fuel and the amount of additional air that is supplied to the reactor. Also, the oxygen content in flue gases, which leads to unreasonable costs of additional gaseous fuel, is not taken into account. SUMMARY OF THE INVENTION

The objective of the invention is to develop a highly efficient and economical method of disinfection of flue gases of fuel-burning units, which reduces the concentration of nitrogen and carbon oxides in flue gases, both by controlling the formation of flue gases in the fuel-burning unit in the process of burning fuel, and as a result of regulating the mode of combustion of fumes gases that leave the fuel-burning units.

The problem is solved in that in the known method of disinfection of flue gases of fuel-burning units, according to which the fuel is burned in the fuel chamber of the fuel-burning unit in the mode of incomplete combustion of the fuel with the minimum possible coefficient of excess air (α), and the combustion of flue gases that leave the fuel-burning unit , carried out in the reactor, by introducing into the reactor additional gaseous fuel and additional air, according to the claimed invention, the temperature in the reactor The ore is maintained at a level of 750-1200 ⁰ C, while the oxygen contained in the flue gases is used to burn the combustible components of the fuel and flue gases, and the flue gas afterburning mode is controlled by regulating the supply of additional gaseous fuel to the reactor in accordance with the following dependence:

where: f _p - the amount of additional gaseous fuel, m ³ / h;

fdg - the amount of flue gases that were disinfected, m ³ / h; Cd _G - heat capacity of flue gases, kcal / m ^{3 o} C;

tр - flue gas temperature in the reactor, ⁰ C;

td _G - flue gas temperature at the exit of the fuel chamber of the fuel-burning unit, ⁰ C; Q out ~ the cost of heat that is released into the environment, kcal / h;

Q ps - the amount of heat that is generated as a result of burning combustible components contained in flue gases, kcal / h;

Cj p - the calorific value of the additional gaseous fuel, kcal / m ³ , while regulating the supply of additional air for burning additional gaseous fuel in accordance with the following relationship:

O ₂ tα _p φп O ₂ d _Г φдг

Ldp - - - - - - (2)

0.21 0.21

where: Ld _P - the amount of additional air, m ³ / h;

C / 2t - theoretical amount of oxygen, which is necessary for burning additional fuel, m ³ / m ³ ;

^ 2dg ~ amount of oxygen in flue gases, m ³ / m ³ ;

Qp is the coefficient of excess air in the reactor;

f _p - the amount of additional gaseous fuel, m ³ / h;

fdg ~ the amount of flue gases that have been disinfected, m ³ / h. When fuel is burned in the fuel chamber of the fuel-burning unit, such a mode of incomplete combustion of the fuel is established that provides the necessary composition of flue gases at the exit of the fuel-burning unit, namely, at the lowest possible coefficient of excess air Ct, flue gases with a low level of nitrogen oxide concentration are formed in the fuel chamber (250 -450 mg / m ³ ) and with an excessive content of carbon oxides (1000-20000 mg / m ³ ). This is achieved both by regulating the air supply to the fuel chamber of the fuel-burning unit, and by controlling the hydraulic mode of the fuel-burning unit.

The afterburning of flue gases that leave the fuel-burning unit is carried out in the reactor at a temperature that is maintained in the reactor at a level of 750-1200 ⁰ C, by introducing additional gaseous fuel into the reactor. The combustion process of the additional gaseous fuel is carried out using oxygen, which is contained in the flue gases, and additional air, which is also introduced into the reactor. The flue gas afterburning mode is controlled by adjusting the supply of additional gaseous fuel in accordance with the above dependence (1), while regulating the supply of additional air for burning additional gaseous fuel in accordance with the dependence (2).

The technical problem to which the claimed utility model is directed is to reduce the concentration of nitrogen and carbon oxides in gaseous waste (flue gases) by reducing the initial concentration of nitrogen oxides, by choosing the optimal modes of formation of flue gases in a fuel-burning unit, and their afterburning. The optimal regimes for the formation of flue gases in a fuel-burning unit are selected taking into account the initial theoretical ratio of nitrogen and carbon oxides at various coefficients of excess air (α).

As a result of the regulation of the flue gas afterburning regime in the reactor at a temperature of 750-1200 ⁰ C, the concentration of nitrogen and carbon oxides in the gaseous waste decreases to the maximum permissible values, which are the technical result achieved in claimed utility model.

BRIEF DESCRIPTION OF THE FIGURES

In FIG. depicts a fuel burning unit, which implements the inventive method of disinfection of flue gases of fuel burning units.

DETAILED DESCRIPTION OF THE INVENTION

The inventive method is carried out in a fuel-burning unit, in particular a coke oven battery (conventionally shown in Fig.), Which is used in the production of coke. It is known that a coke oven battery has from 65 to 77 coke ovens, each of which contains a separate fuel chamber. During the operation of the coke oven battery, the operating modes of each fuel chamber are significantly different from each other, which depends on the state of masonry of the coke oven heating system, and other factors associated with the peculiarities of coke production in coke oven batteries. Consider the possibility of implementing the claimed utility model on the example of a single fuel chamber of a coke oven battery.

In FIG. The fuel chamber 1 of the coke oven battery to which fuel and air was supplied is shown. In this case, the air flow rate was set in such a way as to create conditions for the combustion of fuel at the lowest possible coefficient of excess air α. The regulation of fuel and air consumption, which are supplied for combustion, was carried out using valves 2 mounted on submarine pipelines 3, 4 for supplying fuel and air to the fuel chamber 1 of the coke oven battery, respectively. Coke oven gas was used as fuel. The value of the coefficient of excess air α in the fuel chamber 1 of the coke oven battery was 1, 1-1, 3. Due to the combustion of fuel in the fuel chamber 1 at the lowest possible coefficient of excess air (0 = 1, 1-1.3), flue gases were formed with a high content of carbon monoxide with a slight formation of nitrogen oxides, which is explained by the high activity of atomic carbon, which attaches to itself atomic oxygen during combustion. As a result, the concentration of nitrogen oxides at the exit of the fuel burning unit decreased to 250-450 mg / m ³ (see Table 1). (The concentration of nitrogen oxides, which is usually formed in the fuel chambers of coke oven batteries, is at the level of 1000-1200 mg / m ³ ). The specified decrease in the concentration of nitrogen oxides in the fuel chamber 1 of the coke oven battery, when implementing the claimed technical solution, was provided both by regulating the air supply to the fuel chamber of the fuel-burning unit, and by controlling the hydraulic mode of the fuel-burning unit.

The limiting values of the increased content of carbon monoxide at the indicated indicators of the coefficient of excess air Ct were 1000-10,000 mg / m ³ in the flue gases at the exit of the fuel chamber 1.

The combustion of flue gases that leave the fuel-burning unit was carried out in the reactor 5 by introducing additional gaseous fuel into the reactor 5 at a temperature which was maintained in the reactor 5 at a level of 750-1200 ⁰ C. The process of burning the additional gaseous fuel was carried out using oxygen, which contained in flue gases, and additional air, which was also introduced into the reactor 5. Dynamic control of the flue gas afterburning mode was provided by controlling the amount of additional second gaseous fuel (f _p ) and the amount of additional air (Ldp), which were fed into the reactor 5, in accordance with the above dependencies (1), (2). At the same time, indicators such as the amount of flue gases that were disinfected (fd _G ) and the heat capacity of the flue gases were taken into account

(C _dg ), the temperature of the flue gases in the reactor 5 (t _p ), the temperature of the flue gases at the outlet of the fuel chamber 1 of the fuel _burning unit (t _dr ), the cost of heat that is released into the environment (Q _B ns). the amount of heat that is generated from the combustion of combustible components contained in flue gases (Q _P c), the calorific value of additional fuel

(Cj _n ), the amount of additional air (L _dp ), the theoretical amount of oxygen that must be supplied to burn additional fuel (Ogt), the amount of oxygen in the flue gas (Ogdg) and the coefficient of excess air in the reactor (Qp). Due to the fact that the combustion of additional gaseous fuel was carried out with significant ballasting by flue gases, the concentration of the additional content of nitrogen oxides that were formed during the combustion of additional fuel was insignificant. Thus, when flue gases were burned in the reactor 5 at a temperature of 750-1200 ⁰ C, the concentration of carbon monoxide in the flue gases at the outlet of the reactor 5 decreased to 5-150 mg / m ³ and the concentration of nitric oxide remained at the level of 200-450 mg / m ³ (see

Tab. 2). Then the flue gases that exited the reactor 5 were fed into a waste heat boiler 6, where they were cooled to a temperature of 150-190 ⁰ C, and then, using a smoke exhauster 7, they were discharged into the chimney 8.

When flue gases were burned, which left the fuel chamber 1 of the fuel-burning unit, either natural gas, or coke oven gas, or blast furnace gas, or a mixture of these gases, which were introduced into reactor 5 in a ratio of 1: 2-1, was used as additional gaseous fuel: 20 relative to the amount of flue gases, depending on the calorific value of additional fuel (Cjп) -

Examples of the method.

Tests of the proposed method were carried out on a coke oven battery Ne 1 OJSC "ZAPOPOZHKOKC". Example 1

The amount of flue gases (fdr) that were disinfected

- 120,000 m ³ / h. The composition of the flue gases that departed from the fuel chamber 1 of the coke oven battery was as follows, in mass. %: 0 ₂ = 4.8; CO ₂ = 5.8; H ₂ O = I 7.3; N ₂ = 72.1; CO = 0.2. The temperature of the flue gases at the outlet of the fuel chamber 1 of the fuel-burning unit (td _G ) was 300 ⁰ C. Moreover, the minimum yield of nitric oxide (374 mg / m ³ ) contained in the flue gases that escaped from the fuel chamber 1 was provided with a minimum possible coefficient of excess air Q = 1, 3. The output of carbon monoxide in flue gases at the outlet of the fuel chamber 1 was 2100 mg / m ³ . Then the flue gases that escaped from the fuel chamber 1 were sent to the reactor

5, where they were burned at a temperature of 910 ⁰ C and the coefficient of excess air in the reactor (CXp = I, 3). As an additional fuel used coke oven gas of the following composition, in mass. %: Cθ ₂ = 2.2; Og = 1, 1; C _m H _n = 2.2;

CO = 6.3; CH ₄ = 25.3; N ₂ = 58.0; H ₂ = 4.9. Dynamic regulation of the flue gas afterburning mode in reactor 5 was carried out by regulating the amount of additional gaseous fuel (ψ _p ) and the amount of additional air (Lд _П ), which were supplied to the reactor 5, in accordance with the above dependences (1), (2). Thus, the amount of supplemental fuel gas (Cp _n) was 6437 m ³ / h at a calorific value of the additional fuel gas (C | _p) - 4000 kcal / m ^3, and the amount of additional air (L _dn) - 14834 ^m3 / h.

The concentration of carbon monoxide in the flue gases at the outlet of the reactor 5 was 82 mg / m ³ and the concentration of nitrogen oxides decreased to 276 mg / m ³ . After that, the purified flue gases with a concentration of nitrogen oxides of 276 mg / m ³ and carbon monoxide of 82 mg / m ³ were discharged into the atmosphere. Example 2

The amount of flue gases (fdg) that were disinfected is 130,000 m ³ / h. The composition of the flue gases leaving the fuel chamber 1 of the coke oven battery was as follows, in mass. %: 0 ₂ = 4.5; Cθ2 = 5.6; HbO = I 6.4; N ₂ = 73.3; CO = O, 15; H ₂ = 0.05. The temperature of the flue gases at the outlet of the fuel chamber 1 of the fuel-burning unit (t _dg ) was 280

⁰ C. At the same time, the yield of nitrogen oxides (438 mg / m ³ ) contained in the flue gases that left the fuel chamber 1 was ensured with an excess air coefficient of Q = 1, 3. The output of carbon monoxide in flue gases at the outlet of the fuel chamber 1 was 1560 mg / m ³ . Then the flue gases leaving the fuel chamber 1 were sent to the reactor 5, where they were burned at a temperature of 1170 ⁰ C and the coefficient of excess air in the reactor (α _p = 1, 3). As additional fuel used coke oven gas of the following composition, in mass. %: CO ₂ = 2.2; O ₂ = I, 1; C _m H _n = 2.2; CO = 6.3; CH ₄ = 25.3; N ₂ = 58.0; H ₂ = 4.9. Dynamic regulation of the flue gas afterburning mode was carried out by regulating the amount of additional gaseous fuel (f _p ) and the amount of additional air (L _DP ), which was fed into the reactor 5, in accordance with the above dependencies (1), (2). Thus, the amount of supplemental fuel gas (f _n) was 10,350 m ³ / h at a calorific value of the additional fuel (Cj _n) - 4000 kcal / m ^3, and the amount of additional air (L _dn) - 35300 ^m3 / h.

The concentration of carbon monoxide in the flue gas was 12 mg / m ³ and the concentration of nitrogen oxides decreased to 367 mg / m ³ . After that, flue gases purified to a concentration of nitrogen oxides of 367 mg / m ³ and carbon monoxide of 12 mg / m ³ were vented to the atmosphere.

Table 1 shows the data regarding the concentration of nitrogen and carbon oxides in the flue gases that leave the fuel chamber 1 of the fuel-burning unit, depending on the coefficient of excess air

Q in the fuel chamber 1.

Table 1

Table 2 shows the data indicating the concentration of nitrogen and carbon oxides in the flue gases after burning the fuel-burning unit in the reactor 5, depending on the amount of additional gaseous fuel (f _p ) and the amount of additional air (L _dp ). The amount of flue gases that left the fuel chamber 1 and entered the reactor 5 was 120,000-140000 m ³ / h, at a temperature of 270-320 ⁰ C and a Q ₂ content of 4.4-4.7%. table 2

Claims

CLAIM

The method of flue gas disinfection of fuel-burning units, according to which the fuel is burned in the fuel chamber of the fuel-burning unit in the mode of incomplete combustion of the fuel with the minimum possible coefficient of excess air (α), and the afterburning of flue gases that leave the fuel-burning unit is carried out in the reactor by introducing reactor, additional gaseous fuel and secondary air, characterized in that the temperature in the reactor is maintained at 750-1200 ⁰ C for ₁ wherein the second combustion yuchih constituting the fuel and flue gas is oxygen, which is contained in the flue gases, and regulating mode flue gas afterburning is carried out by controlling the supply of additional fuel gas in accordance with the following relationship: FDH (Cg _T tp - Cg _T td _T) + Qvn _C "Qn _C

P

where: ψ _p - the amount of additional gaseous fuel, m ³ / h;

fd _G - the amount of flue gases that were disinfected, m ³ / h;

Odr is the heat capacity of flue gases, kcal / m ^{3 o} C;

Lp is the temperature of the flue gases in the reactor, ⁰ C;

td _G - flue gas temperature at the exit of the fuel chamber of the fuel-burning unit, ⁰ C;

Q out ~ the cost of heat that is released into the environment, kcal / h; Qps - the amount of heat that is generated from the combustion of combustible components contained in flue gases, kcal / h;

CJn is the calorific value of the additional gaseous fuel, kcal / m ³ , while regulating the supply of additional air for burning additional gaseous fuel in accordance with the following relationship:

OgtYaSRPp O ₂ dg ⁽ Pdg

CCP \ * -} 0.21 0.21

where: Ldp - the amount of additional air, m ³ / h;

^ 2dg ~ amount of oxygen in flue gases, m ³ / m ³ ;

Qp is the coefficient of excess air in the reactor;

fp - the amount of additional gaseous fuel, m ³ / h;

Fdg ~ the amount of flue gases that have been disinfected, m ³ / h.