Coke oven flue gas desulfurization and denitrification system and method thereof

Abstract

The invention belongs to the technical field of coke oven flue gas desulfurization and denitrification, and particularly relates to a coke oven flue gas desulfurization and denitrification system and method, which is characterized by comprising a cooling unit, a catalysis unit, a desulfurization unit and a deamination unit, the units in the system are sequentially combined into a cooling unit, a catalysis unit, a desulfurization unit, a deamination unit, a cooling unit, a desulfurization unit, a catalysis unit, a deamination unit, a cooling unit, a catalysis unit, a deamination unit, a desulfurization unit, a catalysis unit, a cooling unit, a desulfurization unit and a deamination unit; the catalytic unit, the cooling unit, the deamination unit and the desulfurization unit are arranged in sequence. The system has the beneficial effects that the desulfurization unit adopts a wet oxidation method desulfurization process or a wet absorption method desulfurization process; the deamination unit adopts a wet-type absorption deamination process to realize synchronous operation of a wet-type process, so that the aim of desulfurization and denitrification of the coke oven flue gas is fulfilled; no solid dry powder mixture is generated, and the environment-friendly effect is good; the technological process is short and operation is simple.

Description

Technical Field

[0001] The present invention belongs to the technical field of coke oven flue gas desulfurization and denitrification, and particularly relates to a coke oven flue gas desulfurization and denitrification system and a method thereof. Background Art

[0002] At present, the following three coke oven flue gas desulfurization and denitrification processes are widely adopted: 1) Medium-temperature SCR denitrification process + waste heat boiler + CFB dry desulfurization and dust removal process; 2) SDS sodium-based dry flue gas desulfurization + dust collector + medium- and low-temperature SCR denitrification process; 3) Activated coke desulfurization and denitrification process.

[0003] The advantages of the medium-temperature SCR denitrification process + waste heat boiler + CFB dry desulfurization and dust removal process are that denitrification is carried out before desulfurization, and the energy consumption of flue gas heating can be recovered by the subsequent waste heat boiler, and the operation economy is good. However, the disadvantages are that the desulfurization by-products are CaSO 4 、CaSO 3 、Ca 2 CO 3 dry powder mixture, the disposal methods are very limited, the treatment difficulty is great; the construction investment cost is high.

[0004] The advantages of the SDS sodium-based dry flue gas desulfurization + dust collector + medium- and low-temperature SCR denitrification process are that the low-temperature denitrification catalyst is placed behind the desulfurization system, the SO 2 content in the flue gas is low, it is not easy to form ammonium bisulfate on the catalyst surface, the catalyst is not easy to be poisoned, and the denitrification efficiency of the system can be guaranteed. However, the disadvantages are that the quality requirements for the desulfurizer sodium bicarbonate are high; the desulfurization by-products are NaSO 4 、Na 2 CO 3 dry powder mixture, the disposal methods are very limited, the treatment difficulty is great; the activity of the low-temperature catalyst is low, the replacement cost is high, and thermal desorption needs to be carried out regularly.

[0005] The advantages of the activated coke desulfurization and denitrification process are high desulfurization efficiency and SO 2 can be recovered and recycled. However, the disadvantages are low denitrification efficiency, large loss of activated coke and large heating energy consumption caused by heating regeneration, high operation cost; activated coke is flammable, and there are certain safety risks in the adsorption and desorption processes.

[0006] The Chinese invention patent with the application number 201710014501.9 discloses an integrated coke oven flue gas desulfurization and denitrification device, which includes a tower body, an absorption circulation pump, a concentration circulation pump, a circulating water pump, a crystallization pump, an ammonia water pump, a process water pump, a circulation tank, a crystallization tank, a circulating water tank, an ammonia water tank, a process water tank, an ozone generator, and an oxidation blower. The absorption circulation pump is connected to the tower body. The circulation tank is connected to the concentration circulation pump and is connected to the tower body through the concentration circulation pump. First, ozone is used to oxidize NO into NOx, and then an ammoniated circulating liquid is used to spray and absorb SO2 and NOx in the flue gas. Finally, ammonium sulfate and ammonium nitrate by-products are collected.

[0007] The Chinese invention with the application number 202010355260.6 discloses a desulfurization, dust removal, and denitrification device and method, which includes a Venturi jet reaction device and a desulfurization and denitrification reaction device. The top of the Venturi jet reaction device is provided with a flue gas and desulfurizing agent inlet, and the bottom is provided with a jet port. The jet port is located inside the desulfurization and denitrification reaction device. The side wall of the desulfurization and denitrification reaction device is provided with a washing water inlet, and a washing water nozzle is arranged on the washing water inlet. After the flue gas is treated, the emission is below the ultra-low emission standard. In the prior art, there is no mention of the process of using a catalyst to convert nitrogen oxides into ammonia and then participating in the desulfurization and denitrification reaction again in the wet absorption method, so the treatment efficiency is relatively low. Summary of the Invention

[0008] The purpose of the present invention is to provide a coke oven flue gas desulfurization and denitrification system and its method, which overcomes the deficiencies of the prior art. The desulfurization unit adopts a wet oxidation desulfurization process or a wet absorption desulfurization process; the ammonia removal unit adopts a wet absorption ammonia removal process, and the catalytic unit converts nitrogen oxides into ammonia, so that both sulfur dioxide and nitrogen oxides can be recycled, no solid dry mixture is generated, the environmental protection effect is good, the process flow is short, and the operation is simple.

[0009] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0010] Technical solution one: A coke oven flue gas desulfurization and denitrification system, characterized in that it includes a cooling unit, a catalytic unit, a desulfurization unit, and an ammonia removal unit. The sequential combination of each unit in the system is any one of cooling unit → catalytic unit → desulfurization unit → ammonia removal unit, cooling unit → desulfurization unit → catalytic unit → ammonia removal unit, cooling unit → catalytic unit → ammonia removal unit → desulfurization unit, catalytic unit → cooling unit → desulfurization unit → ammonia removal unit, and catalytic unit → cooling unit → ammonia removal unit → desulfurization unit.

[0011] The cooling unit is a combination of a waste heat recovery device + an indirect cooling device or a combination of a waste heat recovery device + a direct cooling device.

[0012] The desulfurization unit is a wet oxidation tower or a wet absorption tower. The ammonia removal unit is a wet absorption tower.

[0013] The catalytic unit is any one or a combination of any two or more of a photocatalytic tower, an electrocatalytic tower, and a magnetic catalytic tower.

[0014] The cooling unit consists of two parts: waste heat recovery and condensation cooling. The waste heat recovery part is arranged before the catalytic unit, and the condensation cooling part is arranged after the catalytic unit.

[0015] Technical solution two: A method for desulfurization and denitrification of coke oven flue gas, characterized in that it includes a cooling unit, a catalytic unit, a desulfurization unit, and a deammoniation unit. The process sequence of each unit in the system is any one of the combinations of cooling unit → catalytic unit → desulfurization unit → deammoniation unit, cooling unit → desulfurization unit → catalytic unit → deammoniation unit, cooling unit → catalytic unit → deammoniation unit → desulfurization unit, catalytic unit → cooling unit → desulfurization unit → deammoniation unit, and catalytic unit → cooling unit → deammoniation unit → desulfurization unit; when the wet oxidation process is used in the desulfurization unit, the desulfurizing agent is a hydrogen peroxide solution; when the wet absorption process is used, the desulfurizing agent is an ammonia water solution or an alkali metal salt solution.

[0016] The absorbent in the wet absorption tower of the deammoniation unit is a dilute sulfuric acid solution.

[0017] When the process flow with the desulfurization unit in the front and the deammoniation unit in the back is adopted, the ammonia generated in the coke oven flue gas after the catalytic unit is used as the alkali source required for the wet oxidation desulfurization process.

[0018] When the process flow with the desulfurization unit in the front and the deammoniation unit in the back is adopted, the dilute sulfuric acid / ammonium sulfate mixed solution generated by the wet oxidation desulfurization process is used as the absorbent required for the deammoniation unit.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1) The desulfurization unit adopts the wet oxidation desulfurization process or the wet absorption desulfurization process; the deammoniation unit adopts the wet absorption deammoniation process to realize the synchronous operation of the wet process, so as to achieve the goal of desulfurization and denitrification of coke oven flue gas;

[0021] 2) The catalytic unit converts nitrogen oxides into ammonia, so that both sulfur dioxide and nitrogen oxides are recycled, and no solid dry powder mixture is generated, and the environmental protection effect is good;

[0022] 3) No additional dust removal facilities need to be set in the system, and no process equipment such as thermal desorption or thermal regeneration needs to be set. The process flow is short and the operation is simple. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the process flow of Embodiment 1 of the present invention;

[0024] Figure 2 It is a schematic process flow diagram of Embodiment 2 of the present invention;

[0025] In the figure: 1 - waste heat boiler, 2 - indirect cooling tower, 3 - catalytic tower, 4 - desulfurization tower, 5 - oxidation tank, 6 - deammoniation tower, 7 - chimney, 8 - condensate circulation pump, 9 - flue gas booster, 10 - desulfurization liquid circulation pump, 11 - deammoniation liquid circulation pump, 12 - ammonium sulfate solution transfer pump, 13 - direct cooling tower, 14 - cooler. Specific embodiments

[0026] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0027] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the specific embodiments required for use in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the specific embodiments described below are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other specific embodiments can be obtained based on these specific embodiments.

[0028] Generally, the components of the embodiments of the present invention described and shown in the specific embodiments here can be arranged and designed in countless different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the specific embodiments is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention.

[0029] Embodiment 1

[0030] The flue gas from the coke oven, with a temperature of about 210°C, first enters the waste heat boiler for waste heat recovery, thereby generating low-pressure saturated steam at 0.2 MPa.

[0031] Embodiment 1 includes a cooling unit, a catalytic unit, a desulfurization unit, and a deammoniation unit. The sequential combination of each unit in the system is cooling unit → catalytic unit → desulfurization unit → deammoniation unit. The cooling unit is a combination of a waste heat recovery device + an indirect cooling device. The desulfurization unit is a wet oxidation tower. The deammoniation unit is a wet absorption tower. The catalytic unit is a photocatalytic tower.

[0032] The coke oven flue gas exiting the waste heat boiler is cooled to about 140°C and then enters the indirect cooling tower, where it is indirectly condensed and cooled to 25°C by cooling water. The top of the indirect cooling tower continuously sprays condensate to remove impurities adhering to the outer wall of the heat exchange tubes. The excess condensate is discharged to the ammonia distillation unit through liquid level adjustment.

[0033] The coke oven flue gas after leaving the intermediate cooling tower is pressurized to about 8 KPa by a flue gas booster and then enters the catalytic tower. Under the action of photocatalysis, nitrogen oxides in the flue gas react with water to generate ammonia and oxygen.

[0034] The coke oven flue gas leaving the catalytic tower enters the desulfurization tower and contacts the circulating sprayed ammonia water / ammonium sulfite solution in a countercurrent manner. Sulfur dioxide in the flue gas is absorbed by the circulating sprayed liquid and reacts with ammonia water to form ammonium sulfite. At the same time, ammonia in the flue gas is also absorbed by the circulating sprayed liquid to supplement the ammonia concentration in the circulating sprayed liquid, thereby ensuring the sulfur dioxide removal rate. In the desulfurization tower, softened water is continuously supplemented to update and supplement the circulating sprayed liquid. At the same time, the excess circulating sprayed liquid is sent to the oxidation tank through liquid level adjustment. After air oxidation and desorption, ammonium sulfite is oxidized to ammonium sulfate to obtain an ammonium sulfate solution, which is sent to the ammonia removal unit. The ammonia-containing gas at the top of the oxidation tank is sent to the flue gas pipeline in front of the flue gas booster.

[0035] The coke oven flue gas leaving the desulfurization tower enters the ammonia removal tower and contacts the circulating sprayed dilute sulfuric acid / ammonium sulfate mixed solution in a countercurrent manner. The remaining ammonia in the flue gas is absorbed by the circulating sprayed liquid and reacts with dilute sulfuric acid to form ammonium sulfate. In the ammonia removal tower, sulfuric acid and the clear liquid separated by crystallization in the ammonium sulfate unit are continuously supplemented to maintain the acidity and flow rate of the circulating sprayed liquid, ensure the ammonia removal efficiency, and the excess circulating sprayed liquid is sent to the ammonium sulfate unit through liquid level adjustment for crystallization separation to produce ammonium sulfate products.

[0036] The coke oven flue gas leaving the ammonia removal tower has achieved the goals of desulfurization and denitrification, and is sent to the chimney and discharged into the atmosphere.

[0037] Example 2:

[0038] The flue gas from the coke oven, with a temperature of about 220 °C, first enters the waste heat boiler for waste heat recovery, thereby generating low-pressure saturated steam at 0.2 MPa.

[0039] Example 2 includes a cooling unit, a catalytic unit, a desulfurization unit, and an ammonia removal unit. The sequential combination of each unit in the system is cooling unit → desulfurization unit → catalytic unit → ammonia removal unit. The cooling unit is a combination of a waste heat recovery device + a direct cooling device. The desulfurization unit is a wet absorption tower. The catalytic unit is a photocatalytic tower.

[0040] The coke oven flue gas leaving the waste heat boiler is cooled to about 140 °C and then enters the direct cooling tower, where it is directly condensed and cooled to 25 °C by the circulating sprayed liquid. The heat released by the condensation and cooling of the coke oven flue gas is removed by the cooling water through a cooler. In the direct cooling tower, the excess condensate is discharged to the ammonia distillation unit through liquid level adjustment.

[0041] The coke oven flue gas after leaving the direct cooling tower is pressurized to about 8 KPa by a flue gas booster and then enters the desulfurization tower, where it comes into countercurrent contact with the circulating hydrogen peroxide / dilute sulfuric acid mixed solution. Sulfur dioxide in the flue gas is absorbed and oxidized by the circulating spraying liquid to obtain a hydrogen peroxide / dilute sulfuric acid mixed solution. In the desulfurization tower, hydrogen peroxide is continuously replenished to maintain the concentration of hydrogen peroxide in the circulating spraying liquid, and at the same time, part of the hydrogen peroxide / dilute sulfuric acid mixed solution is continuously discharged to maintain the concentration of dilute sulfuric acid in the circulating spraying liquid, so as to ensure the desulfurization efficiency of sulfur dioxide. The discharged hydrogen peroxide / dilute sulfuric acid mixed solution is sent to the deammoniation unit as a deammoniation absorbent and replenished into the circulating spraying absorbent liquid of the deammoniation unit.

[0042] The coke oven flue gas leaving the desulfurization tower enters the catalytic tower. Under the action of photocatalysis, nitrogen oxides in the flue gas react with water to generate ammonia and oxygen.

[0043] The coke oven flue gas leaving the catalytic tower enters the deammoniation tower, where it comes into countercurrent contact with the circulating dilute sulfuric acid / ammonium sulfate mixed solution. Ammonia in the flue gas is absorbed by the circulating spraying liquid to obtain a dilute sulfuric acid / ammonium sulfate mixed solution. In the deammoniation tower, sulfuric acid and the clear liquid separated by crystallization in the ammonium sulfate unit are continuously replenished to maintain the acidity and flow rate of the circulating spraying liquid to ensure the deammoniation efficiency. The excess circulating spraying liquid is sent to the ammonium sulfate unit for crystallization separation through liquid level adjustment to produce ammonium sulfate products.

[0044] The coke oven flue gas leaving the deammoniation tower has achieved the goals of desulfurization and denitrification, and is sent to the chimney and discharged into the atmosphere.

[0045] In the above embodiments, when the wet oxidation method desulfurization process is adopted in the desulfurization unit, sulfur dioxide in the coke oven flue gas is absorbed and oxidized by the hydrogen peroxide solution to obtain a hydrogen peroxide / dilute sulfuric acid mixed solution. The hydrogen peroxide / dilute sulfuric acid mixed solution is circulated and sprayed to absorb sulfur dioxide in the coke oven flue gas, and hydrogen peroxide is continuously replenished to maintain the concentration of hydrogen peroxide in the circulating spraying liquid. At the same time, part of the hydrogen peroxide / dilute sulfuric acid mixed solution is continuously discharged to maintain the concentration of dilute sulfuric acid in the circulating spraying liquid, so as to ensure the absorption rate of SO 2 . The discharged hydrogen peroxide / dilute sulfuric acid mixed solution is sent to the deammoniation unit as a deammoniation absorbent and replenished into the circulating spraying absorbent liquid of the deammoniation unit.

[0046] When the wet absorption method desulfurization process is adopted in the desulfurization unit, sulfur dioxide in the coke oven flue gas is absorbed by the ammonia water solution to obtain an ammonia water / ammonium sulfite mixed solution. The ammonia water / ammonium sulfite mixed solution is circulated and sprayed to absorb sulfur dioxide in the coke oven flue gas. At the same time, ammonia in the flue gas is continuously absorbed (or ammonia water is replenished) to maintain the concentration of ammonia in the circulating spraying liquid, and part of the ammonia water / ammonium sulfite mixed solution is continuously discharged to maintain the concentration of ammonium sulfite in the circulating spraying liquid, so as to ensure the absorption rate of SO 2Absorption rate. The externally discharged ammonia water / ammonium sulfite mixed solution is oxidized and desorbed by air or coke oven flue gas to obtain ammonium sulfate solution, which is sent to the ammonia removal unit and supplemented to the circulating spray absorption liquid in the ammonia removal unit.

[0047] The ammonia removal unit adopts a wet absorption method for ammonia removal process, and the absorbent is dilute sulfuric acid solution. Ammonia in the coke oven flue gas is absorbed by the dilute sulfuric acid solution to obtain a mixed solution of dilute sulfuric acid / ammonium sulfate. The dilute sulfuric acid / ammonium sulfate mixed solution is circulated and sprayed to absorb ammonia in the coke oven flue gas, and sulfuric acid is continuously supplemented to maintain the concentration of dilute sulfuric acid in the circulating spray liquid. At the same time, a part of the dilute sulfuric acid / ammonium sulfate mixed solution is continuously discharged to maintain the concentration of ammonium sulfate in the circulating spray liquid and prevent blockage caused by crystallization. The externally discharged dilute sulfuric acid / ammonium sulfate is used to extract ammonium sulfate products.

[0048] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A coke oven flue gas desulfurization and denitrification system, characterized in that: The system comprises a cooling unit, a catalytic unit, a desulfurization unit and a deamination unit. The sequential combination of the units in the system is any one of cooling unit→catalytic unit→desulfurization unit→deamination unit, cooling unit→desulfurization unit→catalytic unit→deamination unit, cooling unit→catalytic unit→deamination unit→desulfurization unit, catalytic unit→cooling unit→desulfurization unit→deamination unit, catalytic unit→cooling unit→deamination unit→desulfurization unit.

2. A coke oven flue gas desulfurization and denitrification system according to claim 1, characterized in that: The cooling unit is a combination of a waste heat recovery device + an indirect cooling device or a combination of a waste heat recovery device + a direct cooling device.

3. A coke oven flue gas desulfurization and denitrification system according to claim 1, characterized in that: The desulfurization unit is a wet oxidation tower or a wet absorption tower.

4. A coke oven flue gas desulfurization and denitrification system according to claim 1, characterized in that: The deamination unit is a wet absorption tower.

5. A coke oven flue gas desulfurization and denitrification system according to claim 1, characterized in that: The catalytic unit is any one of a photocatalytic tower, an electrocatalytic tower, and a magnetic catalytic tower, or a combination of any two or more thereof.

6. A coke oven flue gas desulfurization and denitrification system according to claim 1, characterized in that: The cooling unit is composed of two parts: waste heat recovery and condensation cooling. The waste heat recovery part is arranged before the catalytic unit, and the condensation cooling part is arranged after the catalytic unit.

7. A method for desulfurization and denitrification of coke oven flue gas, characterized in that: The system comprises a cooling unit, a catalytic unit, a desulfurization unit and a deamination unit. The process sequence of the units in the system is any combination of cooling unit→catalytic unit→desulfurization unit→deamination unit, cooling unit→desulfurization unit→catalytic unit→deamination unit, cooling unit→catalytic unit→deamination unit→desulfurization unit, catalytic unit→cooling unit→desulfurization unit→deamination unit, catalytic unit→cooling unit→deamination unit→desulfurization unit; when the desulfurization unit adopts a wet oxidation process, the desulfurizer is a hydrogen peroxide solution; when the wet absorption process is adopted, the desulfurizer is an ammonia solution or an alkali metal salt solution.

8. The method for desulfurization and denitrification of coke oven flue gas according to claim 7, characterized in that: The absorbent in the wet absorption tower in the deamination unit is a dilute sulfuric acid solution.

9. The method for desulfurization and denitrification of coke oven flue gas according to claim 7, characterized in that: When the process flow is adopted with the desulfurization unit in front and the deamination unit in the back, the ammonia generated in the coke oven flue gas after the catalytic unit is used as the alkali source required for the wet oxidation desulfurization process.

10. The method for desulfurization and denitrification of coke oven flue gas according to claim 7, characterized in that: When the process flow in which the desulfurization unit is closed and the deamination unit is installed afterwards is adopted, the dilute sulfuric acid / ammonium sulfate mixed solution produced by the wet oxidation desulfurization process is used as the absorbent required by the deamination unit.

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