Natural gas contains methanol, n-hexane, etc., which causes freezing and blockages in the liquefaction cryogenic tank

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Dear seniors, our company operates an LNG liquefaction plant. Recently, there has been severe freezing in the cryogenic tanks; we operate on three shifts around the clock, and basically each shift requires the temperature to be raised back above -90°C. During this process of warming up, discharge occurs through sight glasses and other drainage points, and white flocculent substances (which vaporize after being discharged) as well as transparent liquid can be seen. Cause analysis: 1. When gas flow increased, the upstream side injected methanol into the natural gas to prevent pipeline freezing and blockage ； 2. Recently, the content of n-hexane in the raw gas fed into the cold box for online chromatographic analysis has increased, reaching up to 2.666%; whereas during design, the content of compounds with a carbon chain length of 6 or more was specified to be less than or equal to 0.02% ； 3. The characteristics of the upstream gas supply have changed; originally, the gas source was associated gas from oil fields, but now oil extraction in those fields has stopped. The above are the factors that could have an impact as of now. The measures we have taken are to shorten the overall cycle time of the heavy hydrocarbon removal unit, while increasing the regeneration time within that cycle. These changes have been made recently, but no effects have yet been observed. Question: 1. How to remove methanol from natural gas? 2. Is it okay to make such changes to the heavy hydrocarbon removal unit? Are there any better approaches? 3. Besides the reasons mentioned above, are there any other possible causes? 4. What could the white flocculent substance and transparent liquid be? I hope the experienced experts will be kind enough to offer their guidance. I’m waiting online; it’s quite urgent.