What is the reason for the high COD level of 80,000 in the distillation residue?
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What is the reason for the high COD level of 80,000 in the distillation residue? In a certain company’s 200,000-ton methanol production plant, the COD level of the distillation residues was as high as 80,000. Before December 2017, the COD level of these residues was normally between 5,000 and 6,000; however, it started to rise rapidly after January 2018. 20,000 to 30,000, with the highest figure rising above 80,000.
1. Are there any deviations from the process parameters? 2. Is there any leakage in the equipment?
During the investigation process, we can list several possibilities and then proceed with a step-by-step examination.
Here are a few suggestions: 1. Check whether the temperatures at the bottom of the tower and at the second and third levels above it have deviated from their normal values. 2. Verify whether the amount of water used for extraction has decreased, which could cause the light components in the atmospheric pressure tower to move downward. 3. Conduct a comprehensive analysis of the crude methanol produced in the previous synthesis steps for reference
1. Check whether the temperatures at the bottom of the tower and at the second and third levels above it have deviated from their normal values. 2. Verify whether the amount of water used for extraction has decreased, which could cause the light components in the atmospheric pressure tower to move downward. 3. Conduct a comprehensive analysis of the crude methanol produced in the previous synthesis step. These are two aspects from which the problem can be analyzed: points 1 and 2 relate to distillation, while point 3 relates to synthesis.
Temperature of the tower bottom and the second and third points above it: that is, the temperature of the sensitivity plate
If it is a distillation issue, the levels of fusel oils and methanol in the residue will be very high； If it’s a problem with crude methanol, the wax content in it will be very high.
The reboiler in the atmospheric pressure tower is leaking; repairs are planned.