System startup
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On February 22nd, my 250,000-ton sulfur-based acid production system was brought online (not a initial startup). A total of 21 tons of diesel were used, over a period of 60 hours. During this operation, the temperatures in the catalyst layers were as follows: Stage 1: 430°C; Stage 2: 372°C; Stage 3: 295°C; Stage 4: 358°C. I would appreciate it if experts could advise me on whether this rate of temperature increase is too conservative, whether the amount of diesel used is excessive, whether the heating time is too long, and what other issues may exist regarding the conversion temperatures. (My company is located in a residential area; I didn’t smoke at all while driving this time.)
As you said, it seems there’s a bit too much diesel; could it be that vaporization sulfonation has occurred? But I think the temperature in those four stages is still a bit low; the fact that no smoke is visible in the exhaust does not mean there is no sulfur dioxide.
Sulfur dioxide is definitely present. In section 4, we have the pipeline valves fully open. Previously, we used valves that allowed for heating and cyclic suction to force hot gas into section 4; we were able to raise the temperature in that section to around 390 degrees. It’s more difficult to raise it any further, and perhaps opening a vent at the outlet of section 3 would help improve the situation. Thank you.
It’s really remarkable that your factory, located in a residential area, manages to keep absolutely no smoke leakage – you should share the methods you use with others. Based on what you’ve described, I think the heating time is a bit long; generally speaking, if the heating time exceeds 48 hours, it becomes less efficient. As for the conversion temperature you mentioned, if it is during the heating phase and no sulfur dioxide gas is introduced, then it’s considered normal. However, when sulfur dioxide is present, the temperatures in stages 2, 3, and 4 are extremely low; in some cases, they are not even high enough to reach the super-ignition temperature of the catalyst. Is your process one turn and one suction? These are my personal opinions; please feel free to correct me.
Nowadays, the public has a very strong awareness of environmental protection; even a slight odor or something that might harm the crops will prompt them to call Environmental Protection 110 or the media will show up. Every time we start or stop the operation, we’re in constant worry. The temperature mentioned above is the temperature at the start of gas introduction. At first, when sulfur dioxide is introduced, the system controls the gas concentration to be very low, at only 3–4%. After a certain period of conversion, although the conversion rate may not meet the standards, it’s still not extremely low. We checked in the downwind area and found basically no irritating odors. Once the temperature in stage one returns to normal, we increase the load to stages two and three, but only increase the volume of gas introduced, not its concentration. After the reaction in stage two, we gradually return to normal operating conditions.
This system features two rotations and two suction cycles; when heating up, it operates with one rotation and one suction cycle per heating stage. Based on the number of heating cycles, this system’s four stages have reached around 390 degrees at some point. It is relatively difficult to raise the temperature further in stages two and three, unless a large volume of air is used, which would result in excessive diesel consumption. Of course, it’s also possible that there is a lack of experience.
The temperatures in stages 1 and 4 can be reduced using a low-temperature catalyst; the conversion index depends on the conversion rate! Good and bad cannot be determined by the presence or absence of smoke.