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Currently, they believe that the methanol in the reflux continues to vaporize within the tower, resulting in an increased amount of vaporization there, which carries the ammonium chloride inside the tower to the condenser

Has the heat exchanger, that is, the condenser, been opened for inspection? It is confirmed to be ammonium chloride; under normal conditions, ammonium chloride enters the aqueous phase of the Reorganization components in the bottom of the tower. Is it because the temperature at the top of the tower is high, preventing ammonium chloride from condensing? Can more water phase spray be added to the top of the tower? To ensure that gaseous ammonium chloride is not carried away, would increasing the reflux rate help? What are the main components of the reflux liquid?

I’m not sure if this device is a finalized product; if it’s newly developed, it’s necessary to examine the design of each stage in order to identify any issues. For mature equipment, it is necessary to verify the specifications of the materials, the process requirements at various inspection and control points, as well as the various quality indicators of the product. Check where the problem lies. The setting of process conditions is based on the specific requirements of the materials at each stage, with a focus on verifying whether they are met. This must be specifically noted, and it cannot be considered outside the scope of applicability of the device design. For example, extremely high or low loads, and material quality exceeding the equipment’s processing capacity.

I wonder what the specific contents of ammonia, methanol, and ammonium chloride in the feed are? It’s impossible to provide analysis without a more specific description of the problem. Ammonium chloride is an ammonium salt that does not readily volatilize; it should end up in the wastewater phase at the bottom of the tower. How could it end up at the top of the tower? Adding an alkali to the liquid phase allows the ammonium chloride to react and be converted into volatile NH4OH, which is then removed from the top of the tower as ammonia gas. This prevents blockages caused by ammonium chloride crystals and also reduces the ammonia nitrogen content in the wastewater at the bottom of the tower. When the methanol content in the feed is high, it is necessary to consider installing a liquid-side stream extraction at the distillation section to remove the methanol-rich wastewater; otherwise, methanol will accumulate in the distillation section, affecting normal operation. Based on the data shown in the display, the temperature at the top of the tower is low, the ammonia recovery rate at that location is not high, ammonia in the wastewater cannot be effectively removed, and the ammonia nitrogen content in the wastewater at the bottom of the tower remains high. It mainly depends on how this wastewater from the column bottom containing recombination components will be treated subsequently.

This situation requires a thorough consideration: was it like this from the start when driving, or did it occur after driving for some time? Once all possible factors are ruled out, it becomes easier to determine what is causing the problem.

Firstly, the temperature at the top of the tower should be around the boiling point of methanol. If it is too high, it means that heavier components such as water have reached the top of the tower. Consider reducing the temperature control at the bottom of the tower. It is advisable to add temperature measurements for the gas and liquid phases in the first condenser, so as to monitor its operating condition and prevent water vapor from entering the second condenser. Since the coolant in the second condenser is at -20 degrees Celsius, ice formation is likely to occur if water is present.

Ammonium chloride is a substance that decomposes easily when heated; feeding it in the gas phase increases the tendency for its decomposition, and cooling it in a cooler results in the formation of ammonium salts, which block the condenser. If a liquid feed is used, it may alleviate the problem of ammonium salt clogging in the top condenser

I took it apart and looked; it’s a white solid, which is probably ammonium chloride. The composition levels have not been measured for the reflux; there should be a small amount of water and methanol. This is a sight glass for discharging material from the primary and secondary condensers. There are a few such sight glasses for discharging material under primary circulating water, while it’s no longer possible to see whether there is any material being discharged from the secondary condenser

If reflux should be established before starting up the distillation tower, most of the ammonium chloride in the gas-phase feed should be condensed within the distillation tower. But there is a problem: could feeding the gas phase disrupt the gas-liquid equilibrium in the distillation column, leading to an increase in the temperature at the top of the column (due to the high temperature of the gas-phase feed)?

The methanol content is not high; it’s likely less than 20%. Tests were conducted by taking samples of methanol from the reflux line, and both the temperature and pressure at the top of the tower increased as a result