Why does the methanol raw material produced by our company have such a high wax content?
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We operate an olefin production plant using methanol, which is coal-derived methanol produced by our own company. However, the methanol contains a very high level of wax, which can easily cause blockages in the backflow systems; moreover, large amounts of red waxy material remain in the pipelines. What could be the reason for this? What methods can be used to prevent blockages?
In the methanol production process, the formation of paraffin is a complex issue; it is related to catalysts, feed gas, the internal components of the methanol synthesis tower, and the material of the tower. It is also connected to the process conditions and operating procedures of the synthesis reaction.
Methods to prevent blockage: The \"tropical\" operation method, which involves raising the temperature of the methanol cooler, melting paraffin, and carrying it into the methanol separator using synthetic recycle gas.
What is the temperature at the water-cooled outlet approximately? Because generally, there are also specified requirements for the outlet of water cooling water.
Close the inlet and outlet valves of the cooling water for the methanol cooler, and artificially increase the operating temperature of the methanol cooler for a short period of time (the specific duration depends on the fact that the inlet and outlet temperatures of the synthesis cycle compressor do not exceed the normal control temperatures). The paraffin in the methanol cooler is melted and carried into the methanol separator via the synthesis cycle gas. Due to the large volume of the methanol separator, wax formation does not pose a problem to production operations when it is not severe. After wax removal using the \"tropical\" method, the operating temperature of the methanol cooler drops significantly, while the paraffin carried into the methanol separator can be removed during shutdown for maintenance.
Thank you to the wise one for answering the questions. If this is a routine operation, it can be further optimized in terms of the process. After all, the tropical operation you mentioned is, in my opinion, an unconventional method that is not very good for the equipment
The conventional solution is to identify the cause of paraffin formation in the methanol synthesis unit as much as possible and prevent an increase in the wax content in methanol. “The “tropical” approach is merely a desperate measure to delay the blockage of equipment and pipelines as much as possible when wax-containing methanol enters downstream units, and it represents a common problem encountered in methanol downstream facilities. The key issue still lies in the upstream methanol synthesis unit.
Yes, the method of boiling wax in the methanol water cooler can only temporarily address the issue of poor cooling performance of the water cooler; it cannot solve the problem of paraffin present in the methanol. Process adjustments such as reducing the temperature of the synthesis reaction or increasing the hydrogen-to-carbon ratio of the fresh gas can help mitigate this issue. If the synthesis unit cannot resolve the problem, a methanol filter can be added later on.