How does ammonia get mixed into methanol in low-temperature methanol washing, and what is the amount?
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I still don’t understand low-temperature methanol washing; I hope the experts here can offer guidance and have discussions so that we can all learn from it*
Taking the Luchy process as an example, in low-temperature methanol washing, the ammonia is introduced into the system from trace amounts of ammonia coming from the upstream system via a pre-washing section in a tower; the ammonia content in the system is analyzed and monitored in the methanol reflux tank. The Linde process seems to have an ammonia scrubber, but the low-methane system still appears to contain ammonia. A small amount of ammonia in the low-temperature system is beneficial, as it helps to reduce corrosion of the equipment.
Ammonia is brought from the gasification system to the downstream system; if the ammonia scrubbing tower in the Linde methanol washing unit performs well, the process gas at its top outlet will basically be free of ammonia
Ammonia is generally provided by upstream units; for example, gasification units produce NH3, and some feed gases already contain NH3. Generally, high-pressure boiler water is used to wash the feed gas, which effectively removes NH3. As a precaution, a washing section is usually installed at the bottom of the absorption tower to absorb NH3 and other impurities.
NH3 comes from the vaporization zone; however, a small amount of NH3 remains after passing through the scrubber following the conversion process. This amount of NH3 is beneficial for equipment used in low-temperature applications, as it can be used to adjust the pH value and prevent corrosion of the equipment. The NH3 content in our plant’s low-temperature methane system is approximately 0.17%
Ammonia generally comes from the upstream gasification units; even after washing it with deionized water in a scrubber following the shift reaction, a small amount of NH3 remains. It is typically required that the ammonia level in the methanol wash step following the shift reaction be less than 50PPM.
I agree with the views of those above me; the ammonia in the low-temperature methanol washing system comes from the previous system. A small amount of ammonia in the system is beneficial for adjusting the pH value of methanol and preventing equipment corrosion! However, an excess amount will affect the absorption efficiency and can easily cause ammonium carbonate crystals to clog pipeline equipment! Therefore, a certain amount must be controlled, and our control target is 5mg/M3!
One more thing to add: ammonia exists in the form of liquid ammonia in the cold zone, but it is in gaseous form once it enters the hot zone; therefore, it is very difficult to remove ammonia during the methanol washing process!
If NH3 is used for cooling, there is also a possibility of an ammonia cooler leak! For example, we have installed a quencher at the top of the thermal regeneration tower here; a leak in this quencher could also lead to an excessive ammonia level in the system!
Ammonia generally comes from the upstream gasification units. Even after being washed in a scrubber using high-pressure boiler water and seal water (desalinated water cannot be used as the pressure is too low), a small amount of NH3 remains. It is typically required that the ammonia level in the methanol washing stage following the shift reaction be less than 50PPM. There is a pipeline to prevent ammonium carbonate crystallization between E13 and E14. It is generally discharged through the lead drain before the V6 tank pump.
It is due to the ammonia reflected in the vaporization furnace. Generally, water is used for washing before entering the purification process. However, considering the corrosion prevention of the purification equipment, it is also necessary to pass it through a methanol wash step. The amount should be determined depending on the circumstances.