1 background and technical analysis
1.1 background
(1) AS desulfurization and cyanide removal process is the advanced desulfurization technology introduced by Germany in the 1980s. It is widely adopted by all major coke plants in our country and has promoted the progress of the gas desulfurization technology in China. However, due to large investment, this technology has not been widely promoted.
(2) Compared with other related desulfurization technologies, the most prominent feature of this process is that the acid gas is high-temperature, catalyzed and oxidized to produce high-purity sulfur (purity> 99.0%) in Claus furnace. At the same time, the secondary salt generated during desulfurization can be cracked into H2, N2, S, eliminating the accumulation of secondary salts in the desulfurization solution.
(3) AS method desulfurization cyanide process there are two prominent technical problems. First, the desulfurization efficiency is low, the average manufacturer of desulfurization gas in the hydrogen sulfide content of 500mg / m3 or more, can not meet the energy-saving emission reduction requirements; Second, the gas can not be used for all ammonia as a source of desulfurization, and ammonia decomposition Exhaust corrosion serious, can not be sent back to the gas pipeline was forced to disperse to the atmosphere, pollute the environment.
1.2 Technical Analysis
Coke oven gas shortage after the gas into the liquid cooler after the first cooler, where the gas cooled to 22 ~ 23 ℃, and then through the electric capture tar evaporator into the desulfurization tower, the desulfurization of the gas followed by ammonia wash tower and wash tower Finally, the gas is delivered by the blower to the gas user.
Desulfurization tower sprayed desulfurization solution is washed ammonia-rich liquid ammonia bottom, deacidification bottom of the deacidification lean liquid and the remaining ammonia mixed, desulfurization rich liquid deacidification tower pro-acid gas into the Claus Si furnace production of high purity sulfur. Most of the deacidification lean liquid is sent to the ammonia distillation tower, and the steamed ammonia gas is sent to the Claus furnace for ammonia decomposition. Namely, double furnace dual towers process. The exhaust from the two furnaces is returned to the gas pipeline.
(2) As ammonia is recovered by the ammonia washing process, the volatile ammonia content in the wash liquid rich in ammonia column can not be raised (1-2 g / L). When the partial pressure of ammonia in the desulfurization solution is greater than the partial pressure of ammonia in the gas, the negative absorption effect will occur when the ammonia is washed so that the ammonia content in the gas after the ammonia washing tower is as high as 100 mg / m3. The amount of ammonia and nitrogen in the separation water increases and increases The biochemical treatment device load.
Desulfurization solution is mainly washed ammonia rich solution, because the desulfurization solution in the volatile ammonia content can not be increased (up to 2 ~ 3g / L), so the desulfurization efficiency is lower, desulfurization gas after the hydrogen sulfide content of 500 ~ 600mg / m3.
Due to the ammonia decomposition with Klaus furnace, most of the ammonia is decomposed, lost the desulfurization of the alkali source, but also caused the desulfurization solution of volatile ammonia content can not be increased, directly affect the desulfurization efficiency.
Technical Transformation of 2AS Desulfurization Process
In view of the above problems existing in the desulfurization process of AS process and the practical production experience of recovery of ammonia by the semi-direct process, appropriate technological transformation of AS desulfurization process should be carried out to form new and efficient process technology to meet environmental protection and produce high quality sulfur products Claim. Key points of renovation project:
(1) The ammonia washing process in the AS desulfurization process is replaced by a spray saturator to recover the ammonia. The deacidification lean solution (containing 30 to 40 g / L of volatile ammonia) is all returned to the circulating desulfurization solution to maximize the improvement Desulfurization solution of volatile ammonia (9 ~ 10g / L), thus greatly improving the gas desulfurization efficiency.
(2) The ammonia vapor distilled from the ammonia tower is mixed with the gas pipeline before the desulfurization to increase the ammonia source for the desulfurization, and to increase the volatile ammonia content in the desulfurization solution. All the ammonia in the gas is recovered in the spray saturator.
(3) Retaining the treatment device of deacidification tower and Claus furnace desulfurization solution in the original process to produce high-purity sulfur.
(4) Klaus furnace exhaust gas into the precooler gas pipeline, the exhaust of acid in the removal of desulfurization, in order to eliminate corrosion on the gas pipeline.
After the above transformation, the desulfurization efficiency can be increased from 70% to 80% to 98% to 99%, and the desulfurization net gas content of hydrogen sulfide can reach below 20mg / m3. The purity of the recovered sulfur is over 99%, and no waste liquid is generated and accumulated in the desulfurization process. The Claus furnace for ammonia decomposition can be eliminated to reduce equipment and catalyst investment costs. The recovery rate of ammonia in the gas can reach 98% ~ 99%. The ammonia content in the gas after the spray saturator can reach below 30mg / m3.
3 After the transformation of AS desulfurization process and potassium carbonate desulfurization process comparison
(1) vacuum potassium carbonate desulfurization and cyanide process
(2) Through the comparison between the modified AS desulfurization process and the vacuum potassium carbonate desulfurization process, it is easy to see that the investment structure is similar regardless of the process flow, the structure of the equipment, Vacuum potassium carbonate desulfurization process, can achieve similar results.
(3) AS desulfurization unit after modification is located in the deamination before the ammonia gas to alkali as a source, and vacuum desulfurization process of potassium carbonate desulfurization desulfurization plant must be located in the tower, the need to outsource alkali potassium carbonate or sodium carbonate .
(4) The modified ammonia desulfurization desulfurization equipment configuration reasonable (semi-direct recovery of ammonia), greatly improving the desulfurization process ammonia ratio (desulfurization liquid ammonia content of up to 9 ~ 10g / L) Desulfurization efficiency can be a breakthrough to improve the desulfurization gas after the hydrogen sulfide content of up to 10 ~ 20mg / m3, close to the fine desulfurization standards.
(5) The new AS process after desulfurization is our independent innovation desulfurization process, can completely replace the vacuum potassium carbonate desulfurization process.
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