CN108579360B - Coke oven regenerator waste heat utilization and SNCR/SCR coupled denitration method and device - Google Patents

Abstract

The invention relates to a method and a device for denitration by coupling waste heat utilization and SNCR/SCR of a coke oven regenerator. And selecting a proper temperature area as an ammonia spraying space in the heat storage chamber, spraying ammonia gas into the ammonia spraying space through a spray gun to perform SNCR (selective non catalytic reduction) denitration reaction, selecting a proper temperature area below the ammonia spraying space, and arranging an SCR (selective catalytic reduction) catalyst in the temperature area to perform SCR denitration reaction on the residual ammonia and the nitrogen oxides in the flue gas. The invention couples the flue gas waste heat utilization with the denitration technology, has simple process structure, is easy to disassemble and replace the checker bricks, does not need to purchase equipment such as an SCR flue gas denitration tower and the like, and reduces the energy consumption and the operation investment cost compared with the traditional SCR denitration system, thereby obviously improving the denitration efficiency.

Description

A coke oven regenerator waste heat utilization and SNCR/SCR coupling denitration method and device

technical field

The invention relates to the field of coke oven flue gas waste heat utilization and denitration, in particular to a coke oven regenerator waste heat utilization and SNCR/SCR coupling denitration method and device.

Background technique

Coking is a highly polluting industry. The pollutants discharged into the atmosphere during the production process include particulate matter, SO ₂ , NOx, CO, H ₂ S, NH ₃ , benzopyrene, phenol, etc. The harm has aroused widespread concern from all walks of life. According to statistics, in 2015, the total emission of SO ₂ in China was 18.591 million t, and the total emission of NOx was 18.518 million t. Coal coking is one of the main pollution sources in the field of industrial coal. Coke oven flue gas is the main source of exhaust gas pollution in coking enterprises, and about 60 _% of SO2 and 90% of NOx come from this. According to the data of China Coking Industry Association, as of the end of 2014, there were more than 700 coking enterprises in my country, and the total number of coke ovens was about 2,000, which could truly meet the shortcomings of the "Coking Chemical Industry Pollutant Emission Standard". One percent. Independent coking enterprises generally use COG heating, and the NOx emission is generally 800-2000 mg/m ³ ; coking plants supporting iron and steel complexes generally use BFG or MG heating, and NOx emissions are generally 350-650 mg/m ³ . The national standard "Coking Chemical Industry Pollutant Emission Standard", which was implemented on January 1, 2015, stipulates the following limits for the emission of air pollutants: _500mg /m ³ in general areas, and 150mg/m ³ in key areas. Due to the increasingly strict environmental protection requirements of national policies, the concentration of nitrogen oxides in flue gas of many existing coking plants fails to meet the national emission standards.

At present, the denitrification process commonly used in the coking industry mainly adopts the denitrification of flue gas after the furnace. The methods mainly include activated carbon adsorption method, ozone oxidation absorption method, selective non-catalytic reduction (SNCR) method and selective catalytic reduction (SCR) method. CN204073849U discloses a coke oven flue gas SCR denitration system, which solves the problem of low coke oven flue gas temperature by setting a rotary flue gas heat exchanger and a pipe burner for secondary heating. The energy consumption of the SCR denitration system increases, secondary pollution is inevitably generated during the combustion process, and the overall operating cost is increased; CN10526582B discloses a coking flue gas denitration method and a denitration system. In the SNCR reaction stage, the flue gas passes through the regenerator and reaches the flue of the first stage of the coke oven, where the SCR reaction is carried out in the flue of the first stage of the coke oven, and finally the SCR reaction is carried out in the flue of the second stage of the coke oven. If the temperature of the vertical flame is too high, the ammonia will be oxidized into nitrogen oxides, which may not achieve the denitration effect in the later stage.

The existing coke oven flue gas denitration technologies and methods are analyzed, and SCR and SNCR denitration technologies are mostly used. Compared with the flue gas of the power plant, the coke oven flue gas has a lower temperature, which cannot meet the optimum temperature of the SCR reaction, and an additional method of heating the flue gas is required, which will increase a large amount of fuel energy or the purchase cost of heat exchange equipment. . For the SNCR denitration technology used in power plant boilers, the denitration efficiency is low, and the flue gas after denitration still cannot meet the national standard requirements, which is related to the large space and complex flow field of the boiler. Ammonia is mixed with a shorter residence time.

SUMMARY OF THE INVENTION

In order to solve the above problems of high concentration of nitrogen oxides in coke oven flue gas, additional energy consumption of SCR denitration process and high investment in SCR denitration equipment operation, the present invention provides a coke oven regenerator waste heat utilization and SNCR/SCR coupling denitration method With the device, the invention can effectively reduce the concentration of nitrogen oxides to meet the national emission standard, and reduce the cost of the denitration system without adding heating equipment.

The method includes waste heat utilization and SNCR coupling denitration method, waste heat utilization and SCR coupling denitration method, and SNCR denitration and SCR denitration coupling method, wherein,

The coupling denitration method of waste heat utilization and SNCR is as follows: the coke oven flue gas enters the checkered bricks from the chute, and after the heat exchange process, the flue gas temperature is reduced to below 1100°C, and the ammonia injection space in the regenerator starts to be sprayed according to the ammonia nitrogen ratio of 1.0. -1.3 Ammonia gas is injected to carry out SNCR reaction to complete the first step of denitration process, and the denitration efficiency reaches 40% to 65%; There is enough time for the SNCR reaction.

The coupling denitration method of waste heat utilization and SCR is specifically as follows: after the coke oven flue gas undergoes the first step of waste heat utilization and SNCR coupling denitration reaction, it continues to exchange heat with the checkered bricks under the ammonia injection space, and the temperature is reduced to below 450 °C, and the coke oven flue gas continues to exchange heat with the lattice bricks under the ammonia injection space after the first step of the waste heat utilization and SNCR coupling denitration reaction. The flue gas of the furnace reaches the SCR catalyst section, and the SCR denitration reaction is carried out, and the denitration efficiency reaches 80% to 90%;

The coupling method of SNCR denitration and SCR denitration is specifically as follows: the residual ammonia gas in the waste heat utilization and SNCR coupling denitration reaction section is used in the waste heat utilization and SCR coupling denitration reaction section. The whole process only needs one injection of ammonia, and the waste heat utilization and SCR coupling denitration reaction The segment does not need to be injected with ammonia again. Compared with the existing coke oven flue gas reheating SCR denitration process, it reduces the energy consumption of flue gas preheating, and saves a lot of denitration equipment investment and space.

The shape of the checker bricks used in the waste heat utilization and SCR coupling denitration method is in the form of a square, a circle, a polygon, or a combination of a square or a circle, and the number of holes in the checker brick is 6 to 30 holes.

The ammonia injection space is set under the checkered bricks with a temperature below 1100°C, the reaction temperature range of the waste heat utilization and SNCR coupling denitration reaction is 850°C to 1100°C, and the reaction area is located in the ammonia injection space and the checker brick channel below the ammonia injection space Inside.

The SCR catalyst is built in a regenerator with a temperature range of 300°C to 450°C. The temperature in this range is consistent with the optimum temperature for the medium-temperature SCR catalytic denitration reaction. The waste heat utilization and SCR coupled denitration reaction temperature range is 300°C to 450°C. The SCR catalyst also has the function of heat storage, realizing the coupling between the utilization of flue gas waste heat and the SCR denitration of flue gas.

The device used in the coke oven regenerator waste heat utilization and SNCR/SCR coupling denitration method is divided into five sections from top to bottom: heat storage section one, heat storage and SNCR denitration coupling section, heat storage section two, heat storage and SCR coupling denitrification section and heat storage section three, including checkered brick channel, single wall of regenerator, spray gun, ammonia injection pipeline, ammonia injection space, checkered brick hole wall, SCR catalyst area and spray gun placement hole, high temperature flue gas enters checkered brick After the passage, the high-temperature flue gas and the checkered bricks undergo heat exchange, and the flue gas temperature is lower than 1100 ° C. This temperature range is the ammonia injection space. One side of the ammonia injection space is provided with a spray gun placement hole. The spray gun placement hole is used for spray guns. Ammonia, one side of the spray gun is connected with the ammonia spray pipeline, and the ammonia spray pipeline is arranged inside the single wall of the regenerator.

The beneficial effects of the above-mentioned technical solutions of the present invention are as follows:

The waste heat utilization and SCR coupling denitration method and device of the invention can be used for current coke oven flue gas denitration, and the coke oven regenerator waste heat utilization and SNCR/SCR coupling denitration method and device are more suitable for the denitration process transformation of new coke ovens. The method couples the utilization of flue gas waste heat with denitration technology, the process structure is simple, the checker bricks are relatively easy to remove and replace, and there is no need to purchase SCR flue gas denitration equipment and systems. Compared with traditional SCR denitration systems, energy consumption and operation investment costs are reduced. , so that the denitrification efficiency is significantly improved.

Description of drawings

Fig. 1 is the structural schematic diagram of the coke oven regenerator waste heat utilization and SNCR/SCR coupling denitration device of the present invention;

FIG. 2 is a schematic structural diagram of the coke oven regenerator waste heat utilization and SNCR/SCR coupling denitration structure corresponding to the lattice bricks of the present invention;

FIG. 3 is a schematic diagram of the connection structure of the hollow brick and the lattice brick of the present invention.

Among them: 1- checkered brick channel, 2- single wall of regenerator, 3- spray gun, 4- ammonia spray pipe, 5- ammonia spray space, 6- check brick hole wall, 7- SCR catalyst section, 8- spray gun placement hole .

Detailed ways

In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

The invention provides a method and a device for denitrification by coupling waste heat utilization of a coke oven regenerator and SNCR/SCR.

As shown in Figure 1, Figure 2, Figure 3, the device includes a checkered brick channel 1, a single wall of a regenerator chamber 2, a spray gun 3, an ammonia injection pipeline 4, an ammonia injection space 5, a checkered brick hole wall 6, and an SCR catalyst section 7 , the spray gun placement hole 8, wherein the checker brick channel 1, the ammonia spray space 5, and the checker brick hole wall 6 are arranged in order from top to bottom, the single wall 2 of the regenerator is located outside the checker brick channel 1, and the ammonia spray pipe 4 is located in the regenerator. In the single wall 2, a spray gun 3 is connected to the end of the ammonia spray pipeline 4, and the spray gun 3 is installed in the ammonia spray space 5 through the spray gun placement hole 8.

As shown in FIG. 1 , an ammonia injection pipeline 4 is arranged on one side of a coke oven regenerator, and the ammonia injection pipeline 4 is arranged in the single wall 2 of the regenerator.

As shown in FIG. 2 , at a certain position below the ammonia injection space 5 , the pore walls 6 of the checker bricks are made of SCR catalysts or coated with SCR catalysts, and this area is the SCR catalyst zone 7 .

Taking Figure 2 as an example, the high-temperature coke oven flue gas flows out from the ramp and enters the checkered brick channel 1 at the top of the regenerator. After the coke oven flue gas passes through the heat exchange with the checkered bricks, the flue gas enters the ammonia injection space 5. When the gas temperature is lower than 1100°C, the ammonia reducing agent entering from the ammonia injection pipeline 4 is injected into the ammonia injection space 5, the ammonia gas is mixed with the high temperature flue gas, and the ammonia gas and nitrogen oxides undergo SNCR denitration reaction. The ammonia gas that fails to complete the SNCR reaction in the ammonia injection space 5 will continue to proceed in the checkered brick channel 2 under the ammonia injection space 5 until the temperature of the checkered brick is lower than 850°C, the SNCR denitration reaction efficiency is reduced or even no longer reacts . The remaining ammonia gas continues to flow downward together with the flue gas, and reaches the checker brick temperature range of 300°C to 450°C, which is the SCR catalyst range 7 . In the SCR catalyst section 7, the remaining ammonia gas and the SCR catalyst and nitrogen oxides undergo SCR denitration reaction. The flue gas goes through the SNCR and SCR denitration reactions twice from the top to the bottom of the regenerator, and the nitrogen oxide concentration in the flue gas reaches the ultra-low emission standard when it is discharged from the bottom of the regenerator.

The above are the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (3)

1. A method for denitration by coupling waste heat utilization of a coke oven regenerator and SNCR/SCR is characterized by comprising the following steps: comprises a waste heat utilization and SNCR coupling denitration method, a waste heat utilization and SCR coupling denitration method and an SNCR denitration and SCR denitration coupling method, wherein,

the waste heat utilization and SNCR coupling denitration method specifically comprises the following steps: coke oven flue gas enters the checker bricks from the inclined flue, the temperature of the flue gas is reduced to be below 1100 ℃ through a heat exchange process, ammonia gas is sprayed into an ammonia spraying space in the heat storage chamber according to the ammonia nitrogen ratio of 1.0-1.3, SNCR reaction is carried out, the first step of denitration process is completed, and the denitration efficiency reaches 40% -65%;

the waste heat utilization and SCR coupled denitration method specifically comprises the following steps: after waste heat utilization and SNCR coupling denitration reaction of the coke oven flue gas in the first step, heat exchange with lattice bricks below an ammonia spraying space is continued, the temperature is reduced to be below 450 ℃, the coke oven flue gas reaches an SCR catalyst temperature section, SCR denitration reaction is carried out, and the denitration efficiency reaches 80-90%;

the SNCR denitration and SCR denitration coupling method specifically comprises the following steps: the residual ammonia gas in the waste heat utilization and SNCR coupling denitration reaction section is used in the waste heat utilization and SCR coupling denitration reaction section, ammonia is sprayed once in the whole process, and ammonia gas does not need to be sprayed again in the waste heat utilization and SCR coupling denitration reaction section;

the ammonia spraying space is arranged below the checker bricks with the temperature below 1100 ℃, the reaction temperature interval of the waste heat utilization and SNCR coupling denitration reaction is 850-1100 ℃, and the reaction area is positioned in the ammonia spraying space and the checker brick channels below the ammonia spraying space;

the SCR catalyst is built in a heat storage chamber with the temperature range of 300-450 ℃, the temperature of the range is consistent with the optimal temperature of the medium-temperature SCR catalytic denitration reaction, and the temperature range of the waste heat utilization and SCR coupling denitration reaction is 300-450 ℃.

2. The denitration method by coupling waste heat utilization of coke oven regenerators and SNCR/SCR as claimed in claim 1, wherein: the shape of the checker brick used in the waste heat utilization and SCR coupling denitration method is a square, circular, polygonal or square or circular combination form, and the number of the holes of the checker brick is 6-30.

3. The device for denitration by coupling SNCR/SCR of coke oven regenerator waste heat utilization according to claim 1, characterized in that: the device is divided into five sections from top to bottom in turn: the heat storage section I, heat storage and SNCR denitration coupling section, heat storage section II, heat storage and SCR coupling denitration section and heat storage section III, including checker brick passageway (1), regenerator list wall (2), spray gun (3), spout ammonia pipeline (4), spout ammonia space (5), checker brick pore wall (6), SCR catalyst interval (7) and spray gun place hole (8), high temperature flue gas gets into checker brick passageway (1), high temperature flue gas and checker brick pass through the heat exchange after, the flue gas temperature is less than 1100 ℃, be in this temperature interval for spouting ammonia space (5), one side of spouting ammonia space (5) is equipped with spray gun place hole (8), spray gun place hole (8) installation spray gun (3) are used for spouting the ammonia, one side of spray gun (3) is connected with spout ammonia pipeline (4), it sets up inside regenerator list wall (2) to spout ammonia pipeline (4).

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