Issue of unqualified purity of formic acid
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After my precision armor system has been in use for over a month, its acidity level has become too high, even exceeding the acceptable limits. What could be the reason? The specific situation is as follows: the acidity of the samples taken from the reflux tanks of the pressurized towers and atmospheric towers analyzed every hour is below 0.0010; however, when samples are taken from the intermediate tanks, the acidity is around 0.0014. The amount of alkali used has been adjusted several times, but the results have not been satisfactory. The heat exchange equipment was checked during previous shutdowns, and no leaks were found; the issue lies solely in the high acidity level. Could someone explain why this is the case?
It’s likely a problem with the quality of the crude methanol; crude methanol contains methyl formate and ethyl acetate. At high temperatures in the reflux tank, and as the temperature drops in the methanol tank, methyl formate… Ethyl acetate decomposes into formic acid and acetic acid, resulting in a high acid value of the product
Methods for adjusting the acidity of methanol: 1. Control the operating parameters of methanol synthesis properly, avoid overheating, reduce the likelihood of side reactions, and address the acid value issue at its source； 2. Adjust the location where alkali is added, and strictly control the pH value at the bottom of the tower; the pH value should not be too high – a value of **-8.5 is sufficient ； 3. Increase the amount of potassium permanganate added appropriately to oxidize some of the organic substances, but the amount should not be too large, as this could have the opposite effect ； 4. Adjust the operations of the column: increase the temperature, raise the venting level, reduce the pressure slightly, and add more extraction water ； 5. Increase the recovery rate of fusel oils in the upper layer of the pre-condensation reflux tank.
Is NaOH being used as the base? Adjust the location where the base is added; collect more samples of fusel oils, and pay attention to controlling the parameter values of each tower.
Check whether there are any other gases or impurities that could penetrate into the intermediate tank!
I also considered the idea of using the second floor option, but adding alkali is meant to neutralize the acid and accelerate the decomposition of esters; yet esters are still being produced, which suggests that too little alkali was added Is the position where the alkali is added still incorrect? Moreover, according to what was said on the 2nd floor, if we cool the samples from the two return tanks before analyzing them, it will be the same as those from the intermediate tank?
I discussed this with the experienced technician again today, and he said he had encountered this issue before; it turned out that methanol from the crude tank had seeped into the refined tank. Generally, there are pipelines connecting the crude tank and the refined tank, which allows it to be possible to draw from the crude tank in cases where the refined methanol does not meet the standards! Your post is over a month old now; have you found out the reason? Found it, so I’m telling everyone!