Coal-fired boiler tail gas low-temperature desulfurization and denitrification purification device

Abstract

The present application relates to the technical field of flue gas treatment, particularly to a low-temperature desulfurization and denitrification purification device for tail gas of coal-fired boiler, comprising a filter screen, the left end of the filter screen is connected with an air inlet pipe, the filter screen is connected with a combustion chamber, a first reaction tank, a second reaction tank, a first oxidation tank, a second oxidation tank and a third reaction tank are sequentially connected in pipeline according to the flue gas treatment direction, the top end of the third reaction tank is connected with an exhaust pipe, the bottom end of the third reaction tank is connected with a discharge pipe, saturated calcium chloride solution is filled in the first reaction tank, saturated sodium chloride solution is filled in the second reaction tank, and saturated ammonia water is filled in the third reaction tank. The present application has the advantages of small land occupation, low cost, low operation cost and the like, and converts pollutants into chemical fertilizers for efficient utilization.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flue gas treatment technology, in particular to a low-temperature desulfurization and denitrification purification device for tail gas of coal-fired boiler. BACKGROUND

[0002] In the production process of the boiler in the coal-fired plant, a large amount of sulfur dioxide and nitrogen oxides are generated after combustion, and the emission of these pollutants into the atmosphere will cause serious environmental pollution problems, further endangering the ecological environment.

[0003] The commonly used flue gas treatment technology for coal-fired power plants on the market at present is mainly a combined process of desulfurization and denitrification. The commonly used process for desulfurization is mainly dry, semi-dry and wet method; the commonly used process for denitrification is SNCR and SCR. Although these two separate combinations can effectively solve the problem of flue gas pollution, they have problems of large occupied area and high construction cost. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a low-temperature desulfurization and denitrification purification device for tail gas of coal-fired boiler to solve the above problems.

[0005] To solve the above technical problems, the technical solution adopted by the present application is: a low-temperature desulfurization and denitrification purification device for tail gas of coal-fired boiler, comprising a filter screen, the left end of the filter screen is connected with an air inlet pipe, the filter screen is connected with a combustion chamber, and a first reaction tank, a second reaction tank, a first oxidation tank, a second oxidation tank and a third reaction tank are sequentially connected in sequence according to the flue gas treatment direction, the top end of the third reaction tank is connected with an exhaust pipe, and the bottom end of the third reaction tank is connected with a discharge pipe.

[0006] As a further solution of the present application, the first reaction tank is filled with saturated calcium chloride solution, the second reaction tank is filled with saturated sodium chloride solution, and the third reaction tank is filled with saturated ammonia water.

[0007] As a further solution of the present application, the purification steps of the purification device are as follows:

[0008] Step one, dust treatment, the coal-fired flue gas is passed into a multi-stage filter screen;

[0009] Step two, pretreatment, the clean flue gas is passed into the combustion chamber for combustion;

[0010] Step three, first-stage treatment, the combusted flue gas is passed into the first reaction tank and the second reaction tank to remove HF and HCl;

[0011] Step four, second-stage treatment, the flue gas is passed into the first oxidation tank to oxidize NO to NO2;

[0012] Step five, third stage treatment, the flue gas is passed into the second oxidation tank to catalytically oxidize SO2 and NO2 into SO3 and NO;

[0013] Step six, fourth stage treatment, the flue gas is passed into the third reaction tank to react, thereby removing SO2 and NO.

[0014] As a further scheme of the present application, the pore size of the filter screen in step one is gradually reduced, and the pore size of the last filter screen is 100 nm, and the filter screen is provided with high voltage static electricity.

[0015] As a further scheme of the present application, the filter screen is provided with high voltage static electricity.

[0016] As a further scheme of the present application, the combustible gas in step two is completely combusted, and the combustible gas is CO or CH4 or H2.

[0017] As a further scheme of the present application, the first reaction tank in step three is provided with saturated calcium chloride solution, and the second reaction tank is provided with saturated sodium chloride solution.

[0018] As a further scheme of the present application, the temperature in the first oxidation tank in step four is 0±5℃.

[0019] As a further scheme of the present application, the third reaction tank in step six is provided with saturated ammonia water.

[0020] Due to the adoption of the above technical scheme, the present application has the advantages and positive effects of:

[0021] 1. The combustible gas in the flue gas is completely combusted;

[0022] 2. HF and HCl in the flue gas are removed through the first stage treatment; SO2 is catalytically oxidized into SO3 through the second stage treatment and the third stage treatment; SO3 and NO are reacted with ammonia water to generate chemical fertilizer through the fourth stage treatment, waste is utilized, and economic benefits are improved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structural schematic view of a coal-fired boiler tail gas low-temperature desulfurization and denitrification purification device of the present application.

[0024] In the figure, 1 is an air inlet pipe, 2 is a filter screen, 3 is a combustion chamber, 4 is a first reaction tank, 5 is a second reaction tank, 6 is a first oxidation tank, 7 is a second oxidation tank, 8 is a third reaction tank, 9 is an air outlet pipe, and 10 is a discharge pipe. DETAILED DESCRIPTION

[0025] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0026] The application discloses a coal-fired boiler tail gas low-temperature desulfurization and denitrification purification device, which comprises a filter screen 2, wherein the left end of the filter screen 2 is connected with an air inlet pipe 1, the filter screen 2 is connected with a combustion chamber 3, and sequentially connected with a first reaction tank 4, a second reaction tank 5, a first oxidation tank 6, a second oxidation tank 7 and a third reaction tank 8 through pipelines according to the flue gas treatment direction, the top end of the third reaction tank 8 is connected with an air outlet pipe 9, and the bottom end of the third reaction tank 8 is connected with a discharge pipe 10. After the coal-fired boiler tail gas is filtered by the filter screen 2 to remove dust, the combustible gas is completely combusted in the combustion chamber 3, the SOx and NOx can be completely reacted through the cooperative treatment of the first reaction tank 4, the second reaction tank 5, the first oxidation tank 6, the second oxidation tank 7 and the third reaction tank 8, waste is changed into treasure, the reaction products are discharged through the discharge pipe 10, and the device is convenient, efficient and good in practicality.

[0027] Further, the first reaction tank 4 is filled with saturated calcium chloride solution, the second reaction tank 5 is filled with saturated sodium chloride solution, and the third reaction tank 8 is filled with saturated ammonia water. The saturated calcium chloride solution can react with HF, the saturated sodium chloride solution can absorb HCl, and the saturated ammonia water can react with SO3 and NO.

[0028] The treatment of the coal-fired power plant flue gas by the application comprises the following steps:

[0029] The combustible gas is completely combusted through the pretreatment of the coal-fired flue gas, and the reaction is as follows:

[0030] 2CO + O2 = 2CO2

[0031] CH4 + 2O2 = CO2 + 2H2O

[0032] 2H2 + O2 = 2H2O

[0033] The reaction of the flue gas after the first-stage treatment is as follows:

[0034] CaCl2 + 2HF = CaF2 + 2HCl

[0035] The saturated sodium chloride solution can absorb HCl, and can absorb all the HCl and precipitate NaCl crystals;

[0036] The first-stage treatment is divided into two reaction tanks, HF is treated first and then HCl is treated.

[0037] The reaction of the flue gas after the second-stage treatment is as follows:

[0038] 2NO + O2 = 2NO2

[0039] The reaction of the flue gas after the third-stage treatment is as follows:

[0040] NO2 + SO2 = NO + SO3 This is a step of preparing sulfuric acid by the lead chamber method, and will not be described in detail.

[0041] The reaction of flue gas after the fourth stage treatment is as follows:

[0042] 4NH3+6NO==5N2+6H2O

[0043] SO3+2NH3·H2O=(NH4)2SO4+H2O

[0044] From the above each stage treatment, SOx and NOx in the coal-fired flue gas can be completely reacted, and beneficial products are produced, SOx is converted into chemical fertilizer, and NOx can be converted into N2, N2 is collected, waste is changed into treasure through the treatment method of the application, the economic benefit of enterprises is improved, and the application has the advantages of small land occupation, low cost, low operation cost and the like.

[0045] Although the specific embodiments of the application are described above, those skilled in the art should understand that these are only illustrative, and various changes or modifications can be made to the embodiments without departing from the principles and essence of the application, and the protection scope of the application is only defined by the appended claims.

Claims

1. A low-temperature desulfurization and denitrification purification device for tail gas from a coal-fired boiler, comprising a filter (2), characterized in that: The left end of the filter (2) is connected to an air inlet pipe (1), the filter (2) is connected to a combustion chamber (3), and is sequentially connected to a first reaction pool (4), a second reaction pool (5), a first oxidation tank (6), a second oxidation tank (7) and a third reaction pool (8) through pipelines in accordance with the direction of flue gas treatment. The top end of the third reaction pool (8) is connected to an exhaust pipe (9), and the bottom end of the third reaction pool (8) is connected to a discharge pipe (10); The specific steps of purification of the purification device are as follows: Step 1: Dust treatment: pass the coal-fired flue gas through a multi-stage filter; Step 2: pre-treatment, passing clean flue gas into the combustion chamber for combustion; Step 3, first stage treatment, passing the burned flue gas into the first reaction tank and the second reaction tank to remove HF and HCl; Step 4, second stage treatment, passing the flue gas into the first oxidation tank to oxidize NO to NO2; Step five, the third stage of treatment, passes the flue gas into the second oxidation tank to catalytically oxidize SO2 and NO2 into SO3 and NO; Step six, the fourth stage of treatment, passes the flue gas into the third reaction tank to react, thereby achieving the purpose of removing SO2 and NO; The first reaction tank (4) is filled with a saturated calcium chloride solution, the second reaction tank (5) is filled with a saturated sodium chloride solution, and the third reaction tank (8) is filled with a saturated ammonia solution.

2. The low-temperature desulfurization and denitrification purification device for tail gas from a coal-fired boiler according to claim 1, characterized in that: In the step 1, the pore size of the filter screen decreases step by step, and the pore size of the last filter screen is 100 nm, and the filter screen is provided with high voltage static electricity.

3. The low-temperature desulfurization and denitrification purification device for tail gas from a coal-fired boiler according to claim 1, characterized in that: In the step 2, the combustible gas is completely burned, and the combustible gas is CO, CH4 or H2.

4. The low-temperature desulfurization and denitrification purification device for tail gas from a coal-fired boiler according to claim 1, characterized in that: The temperature inside the first oxidation tank in step 4 is 0±5°C.

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