摘要
The sulfur recovery unit (SRU) is used to recover the clean and foul sour gas produced from other units, such as residue oil cracking unit, residue desulfurization unit and so on. During the shut-down period of SRU, the sour gas will be put into incinerator. If the incinerator abnormally smoke, the sour gas will be directed to soda scrubber. However, the current operation strategy of soda scrubber can not deal with the sour gas effectively to avoid the smoking problem. The aim of this paper is to study the strategy of soda scrubber to deal with sour gas. For the case of residue oil cracking unit with 450NM^3/hr sour gas, we got the conclusions as following： 1. The H2S contents in sour gas after treating will be less than 1,000 ppm when the pH value of absorbent is higher than 11.5. The absorbency of soda at the end of absorbing is about 70%. 2. The pH value decrease rapidly when soda absorbency exceeds 70%. 3. Under adiabatic and 70% absorbency situation, the temperature will raise 56℃, 73℃ and 95℃ with 16wt%, 20wt% and 25wt% NaOH to deal with sour gas respectively. It is suitable to use NaOH less than 16wt% to keep temperature from raising too much. 4. According the result calculated from NaHCO3 and Na2CO3 solubility data, there should not be any crystallization problem in this absorbing system. 5. The soda make-up will be 6.36 kl/hr for 16wt% concentration during continuous operation. 6. In the case of residue cracking unit, if soda scrubber deal with all the sour gas, it will take 2.63 ton 45wt% soda per hour. The total cost for one month operation will be up to 4.75 million NT$. Besides, the 150 ton/day spent caustic could be another troublesome problem. 7. The control strategy to operate the soda scrubber is to manipulate the soda make-up rate by pH value, and to control the flowrate of spent caustic by level.
並列摘要
The sulfur recovery unit (SRU) is used to recover the clean and foul sour gas produced from other units, such as residue oil cracking unit, residue desulfurization unit and so on. During the shut-down period of SRU, the sour gas will be put into incinerator. If the incinerator abnormally smoke, the sour gas will be directed to soda scrubber. However, the current operation strategy of soda scrubber can not deal with the sour gas effectively to avoid the smoking problem. The aim of this paper is to study the strategy of soda scrubber to deal with sour gas. For the case of residue oil cracking unit with 450NM^3/hr sour gas, we got the conclusions as following： 1. The H2S contents in sour gas after treating will be less than 1,000 ppm when the pH value of absorbent is higher than 11.5. The absorbency of soda at the end of absorbing is about 70%. 2. The pH value decrease rapidly when soda absorbency exceeds 70%. 3. Under adiabatic and 70% absorbency situation, the temperature will raise 56℃, 73℃ and 95℃ with 16wt%, 20wt% and 25wt% NaOH to deal with sour gas respectively. It is suitable to use NaOH less than 16wt% to keep temperature from raising too much. 4. According the result calculated from NaHCO3 and Na2CO3 solubility data, there should not be any crystallization problem in this absorbing system. 5. The soda make-up will be 6.36 kl/hr for 16wt% concentration during continuous operation. 6. In the case of residue cracking unit, if soda scrubber deal with all the sour gas, it will take 2.63 ton 45wt% soda per hour. The total cost for one month operation will be up to 4.75 million NT$. Besides, the 150 ton/day spent caustic could be another troublesome problem. 7. The control strategy to operate the soda scrubber is to manipulate the soda make-up rate by pH value, and to control the flowrate of spent caustic by level.