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(1) AS desulfurization process is the removal of cyanide in the 1980s by the German introduction of advanced desulfurization technology, is widely used in China's major coking plant, promoted the progress of China's coal gas desulfurization technology. However, due to the large investment, this technology has not been promoted on a larger scale.
(2) Compared with other related desulfurization technologies, the biggest feature of this process is that acid gas is produced in a Claus furnace, and high-purity sulfur (purity >99.0%) is formed by high temperature, catalysis and oxidation. At the same time, the secondary salt produced by the desulfurization process can be cracked into H2, N2, S, which eliminates the accumulation of the secondary salt in the desulfurization solution.
(3) There are two outstanding technical problems in the AS desulfurization and de-cyanide process. First, the desulfurization efficiency is low. After the desulfurization of the general manufacturer, the hydrogen sulfide content in the gas is above 500mg/m3, which cannot meet the requirements of energy saving and emission reduction. Second, the ammonia in the gas cannot be used as the alkali source for desulfurization, and the ammonia is decomposed. The exhaust gas is seriously corroded and cannot be returned to the gas pipeline and forced to be released to the atmosphere, polluting the environment.
1.2 Technical analysis
The waste gas of the coke oven is separated by gas and liquid and then enters the primary cooler. Here, the gas is cooled to 22-23 ° C, and then enters the desulfurization tower through the electric tar catcher. The desulfurized gas is sent to the ammonia washing tower and the benzene washing tower in turn. Finally, the gas is pumped by the blower to the gas user.
The desulfurization liquid sprayed in the desulfurization tower is formed by mixing the ammonia-rich liquid at the bottom of the ammonia scrubbing tower, the deacidified lean liquid at the bottom of the deacidification tower and the residual ammonia water, and the acid gas desorbed from the desulfurization rich liquid in the deacidification tower is sent to Claude. High-purity sulfur is produced in the furnace. Most of the deacidified lean liquid is sent to the ammonia distillation tower, and the distilled ammonia vapor is sent to the Claus furnace for ammonia decomposition. That is to say the double furnace double tower process. The tail gas of the double furnace is returned to the gas pipeline.
(2) Since ammonia is recovered by ammonia washing technology, the content of volatile ammonia in the rich liquid at the bottom of the ammonia washing tower cannot be increased (1 to 2 g/L). When the partial pressure of ammonia in the desulfurization solution is greater than the partial pressure of ammonia in the gas, the ammonia absorption will have a negative absorption effect, so that the ammonia content in the gas after the ammonia washing tower is as high as 100 mg/m3, and the amount of ammonia and nitrogen in the separated water increases. The load of the biochemical treatment device.
The desulfurization liquid is mainly used for washing ammonia rich liquid, because the volatile ammonia content in the desulfurization liquid cannot be increased (up to 2 to 3 g/L), so the desulfurization efficiency is low, and the hydrogen sulfide content in the gas after the desulfurization tower is 500 to 600 mg/m3.
Because of the Claus furnace with ammonia decomposition, most of the ammonia is decomposed, and the desulfurization alkali source is lost. The volatile ammonia content in the desulfurization solution cannot be increased, which directly affects the desulfurization efficiency.
2. Technical transformation of AS desulfurization process
In view of the above problems in the AS desulfurization process and the production experience of semi-direct recovery of ammonia, the AS desulfurization process should be appropriately modified to form new and efficient process technologies to meet environmental protection and produce high quality sulfur products. Claim. Key points of the renovation project:
(1) The ammonia washing process in the AS desulfurization process is changed to the spray type saturator to recover ammonia, and the deacidified and depleted liquid (containing 30-40 g/L of volatile ammonia) is all-matched into the circulating desulfurization liquid, which can maximize the increase. Volatile ammonia (9 ~ 10g / L) in the desulfurization solution, thereby greatly improving the desulfurization efficiency of the gas.
(2) The ammonia vapor distilled from the steaming tower is fed into the gas pipeline before desulfurization to increase the ammonia source of desulfurization, and the content of volatile ammonia in the desulfurization liquid is increased, and the ammonia in the gas is completely recovered in the spray type saturator.
(3) Retaining the treatment device of the deacidification tower and the Claus furnace desulfurization liquid in the original process to produce high-purity sulfur.
(4) The tail gas of the Claus furnace is sent to the gas pipe before the primary cooler, and the acid in the tail gas can be removed during the desulfurization to eliminate the corrosion of the gas pipeline.
After the above transformation, the desulfurization efficiency can be increased from 70% to 80% to 98% to 99%, and the hydrogen sulfide content in the clean gas after desulfurization can reach 20 mg/m3 or less. The purity of the recovered sulfur is above 99%, and no waste liquid is generated and accumulated in the desulfurization process. The Claus furnace for ammonia decomposition can be eliminated to reduce the investment cost of equipment and catalysts. The recovery rate of ammonia in the gas can reach 98% to 99%, and the ammonia content in the gas after the spray type saturator can reach 30mg/m3 or less.
3. Comparison of modified AS desulfurization process and potassium carbonate desulfurization process
(1) Process flow of desulfurization and de-cyanation by vacuum potassium carbonate method
(2) By comparing the modified AS desulfurization process with the vacuum potassium carbonate desulfurization process, it is not difficult to see that regardless of the process flow, equipment structure, or equipment parts, the investment structure is similar, and the modified AS process is replaced. The vacuum potassium carbonate desulfurization process can completely achieve the same effect.
(3) After the reformation, the AS desulfurization device is set before the deamination, and the ammonia in the gas is used as the alkali source, and the desulfurization device of the vacuum potassium carbonate desulfurization process must be set after the debenzene tower, and the alkali source potassium carbonate or sodium carbonate needs to be purchased. .
(4) The deamination unit of the modified AS desulfurization process is rationally configured (recovering ammonia by semi-direct method), which greatly improves the ammonia-sulfur ratio of the desulfurization process (the volatile ammonia content in the desulfurization solution can reach 9-10 g/L). The desulfurization efficiency can be improved by breakthrough. The hydrogen sulfide content in the gas after desulfurization can reach 10-20mg/m3, which is close to the standard of fine desulfurization.
(5) The newly desulfurization process of AS method after transformation is China's independent innovation desulfurization process, which can completely replace the vacuum potassium carbonate desulfurization process.
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