Which domestic phthalic anhydride plants use mineral oil as heat transfer oil, and how many years is it typically used for?
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Many phthalic anhydride plants use German DT heat transfer oil, but DT is relatively expensive; if mineral oil is used, how many years can it last? Have you used both types of oil? Let’s discuss the advantages and disadvantages of each in terms of usage.
I’d like to ask gently, what is the operating temperature of the phthalic anhydride plant? If the price of DT is very high, it’s better to use Therminol or DOWTHERM heat transfer oils.
The operating temperature is not high; it involves only two processes: heating and cooling. The temperature rises to 175°C during heating, and then drops to 50°C during cooling. This temperature can be met by current heat transfer oils; however, since the heat transfer oil needs to be heated and cooled frequently, will this affect its service life?
It has no impact. Oxidation has a significant impact on heat transfer oil. During heating and cooling, the liquid level in the heat transfer oil expansion tank or surge tank should change significantly; if an oil seal is used, air ingress must be prevented. Nitrogen sealing is generally recommended. A manufacturer in the advertising industry posted a message on the forum saying so.
The service life of mineral oil is roughly 5-7 years; it tends to decompose when overheated. The service life of synthetic heat transfer oils is longer, as they have good thermal conductivity, help save energy and reduce consumption, and can also be recycled. TotalEnergies uses this type of synthetic heat transfer oil extensively in South China; its price is much lower than that of other imported heat transfer oils, and its service life ranges from 8-10 years, depending on the conditions of the system.