Collection issue of the condenser during the switchover in the phthalic anhydride plant
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The temperature of the phthalic anhydride process gas entering the switching condenser is 140°C; the process gas contains a large amount of water, approximately 140.9479 kmol/hr. After capture by the switching condenser, phthalic anhydride deposition is captured, with the outlet temperature of the switching condenser at 60°C. During the capture process, most of the water (approximately 140.8320 kmol/hr) enters the flue gas absorption tower from the outlet of the switching condenser. In the capture mode, the condenser is cooled by heat transfer oil; in other words, the heat transfer oil is used to remove the heat from the gas and to absorb the condensation heat as anhydride changes from a gaseous state to a liquid state. However, at 60°C (gauge pressure of 0.025 MPa), the moisture should be in a liquid state ； And at such temperatures, water should be able to react with phthalic anhydride and maleic anhydride to form phthalic acid and maleic acid. I’m completely baffled by this unit operation...
I hope experts can give some advice...
The oil and gas system is outdated; the new 50,000-ton facility we’ve built uses a water and steam system
Reply to 3# wjx0624: Check the vapor pressure; no water will form if it does not reach the dew point.
Reply 1# heisejiyi: A small amount of acid is produced. You still need to distill it later.
It seems that the pretreatment of crude anhydride is aimed at addressing this issue
Reply 1# heisejiyi: As long as it exceeds the dew point temperature. A small amount of acid is produced; dehydration polymerization takes place in the pretreatment reactor, followed by distillation.
LZ, go and study physical chemistry carefully – your foundation knowledge isn’t solid enough. Moreover, the oil system is more advanced than the steam system; why then do some people think that steam is more advanced than oil? I’m completely puzzled too! ;P;P
Try raising the cold oil temperature a bit.
Using heat transfer oil is already outdated; we have been using water and steam for a long time now – as long as the temperature is above the dew point. A small amount of acid is produced; sodium carbonate is added in the pretreatment tank for dehydration polymerization, followed by distillation.
The working pressure should be around 0.008 MPa; under these conditions, no large amount of water will be generated.