Problems with ice makers and low-temperature methanol washers

7. If no water is fed into the methanol-water separation tower, it becomes difficult to control the liquid level; as a result, the tower is hard to operate and the water separation effect is poor! The water content in methanol within the process system is generally required to be 0.5%, with a limit of no more than 1%; exceeding this level not only affects the operation of the absorption tower but also causes corrosion of the equipment. 5/6. Since I’m not very familiar with your processes, I can’t say too much. Since you have a pre-washing section, it’s not necessary to have an ammonia washing tower; the pre-washing section removes the ammonia from the process gas and sends it to the water separation tower. As a result, ammonia does not end up in the process methanol, so there is no impact! 【Please let experts answer the other questions!】 】

1. Over time, the amount of oil leaking from your compressor will accumulate, resulting in a large quantity of oil. The best solution is to use an oil separator to continuously remove the oil from the ammonia liquid! Does your company use collectors? It’s hard to say something without having much experience with that stuff 2. Changes in outlet pressure certainly have an impact on low-temperature methanol washing! A low outlet pressure results in less cooling capacity. . . . . . Needless to say the opposite. 4. Insulating the ammonia pipeline is still necessary. The rest is not needed. The main components that require cooling are the liquid ammonia pipelines. 5. In the absence of an inlet separation tank, it is still necessary to pay close attention to the water content in methanol, and to adjust the load on the water separation tower accordingly. Since the process designed by Dalian University of Technology for you should not have any issues, there should be no problems. 6. Is there no interlock mechanism in place when the liquid level becomes too high? Personally, I think it has no impact on the hydrogen sulfide absorption section? It would be best to share your production process so everyone can take a look! It’s hard to say; 7 doesn’t seem to be an option! How to maintain the liquid level in the separation tower? Did the water vapor from below rise without having time to condense? Then how is the liquid level in the lower tower replenished? I still personally feel it’s completely unworkable

1. Ice machine refrigerant ammonia contains a large amount of oil; it is recommended to use an efficient oil separator to remove as much oil as possible. It is inevitable for screw compressors to have oil present, as the oil pump injects oil into the compressor chamber where it mixes with ammonia and is compressed; afterward, the oil is separated, but some oil inevitably remains in the ammonia. If oil is present for an extended period, it indicates a problem with your oil separator. It is recommended to carry out maintenance during downtime; also, take advantage of short periods of shutdown to open the drain valves on the shell sides of the ammonia coolers in order to remove the oil that has accumulated there, thereby improving the cooling efficiency of the ammonia coolers. 2. (Microcomputer-controlled explosion-proof economizer screw-type refrigeration compressor unit): A higher control setpoint for the outlet pressure of the low-pressure and high-pressure compressors provides more cooling capacity to the purification system, while a lower setpoint results in less cooling capacity. 3. Personally, I believe the oil collector should be installed as low as possible to facilitate oil drainage from various devices. 4. The gas ammonia pipelines throughout the refrigeration system need to be insulated, while the separators and oil collectors do not require insulation. 5. Your feed gas goes directly to the pre-washing section of the absorption tower without any treatment; isn’t there a feed gas heat exchanger installed before entering the pre-washing section? In that case, the temperature of the feed gas will be too high, which will affect the absorption efficiency, and a larger amount of circulation will also be required. The methanol from the pre-washing section is sent to the methanol-water separation tower, which inadvertently increases the load on this tower. It also serves a purpose of thermal regeneration (by removing hydrogen sulfide dissolved in the methanol in the pre-washing tower and releasing carbon dioxide). Meanwhile, the instability of the feed composition leads to fluctuations in the operation of the methanol-water separation tower. (My personal opinion; I’m not sure how it works in practice for you guys?) Welcome to continue the discussion! ) 6. I wonder if your pre-washing section often reaches full liquid level? What is the reason? If the full liquid level can be connected to the H2S absorption section, this may lead to an excessive water content in the system. 7. It’s essential for the methanol-water separation tower to receive water; otherwise, it won’t function properly. If only methanol is fed into the tower, its liquid level cannot be maintained, which can often lead to a dry-running condition and has a significant negative impact on the equipment’s lifespan. If there is no exhaust gas scrubber to supply water to that tower, the liquid level can be maintained by directly supplying steam! The water content in the system is generally required to be less than 1%; of course, it’s better to keep this level as low as possible. If it exceeds 1%, it not only affects the absorption efficiency but also accelerates the corrosion of the equipment!

1. What is the most appropriate way to deal with ammonia, a refrigerant used in ice machines, that contains large amounts of oil? How did the oil issue arise? How to prevent it in the future? Your compressor is a rotary vane compressor, right? If so, there should be an oil-gas separation tank at the compressor’s outlet; the oil returns to the oil tank while the gas goes into the water cooler to be cooled. 2. What impact does an increase or decrease in the outlet pressure control values of the low-pressure and high-pressure compressors in (microcomputer-controlled, explosion-proof economizer screw-type refrigeration compressor units) have on the refrigeration system? Pressure and temperature are related to each other; the principle behind the operation of a refrigeration unit is to compress gas, cool it down, and turn it into a liquid. Then, heat is absorbed during depressurized flashing. High pressure wastes energy. If the pressure is low and liquefaction cannot occur, then cooling is not possible. 4. Does the ammonia pipeline, separator, and oil collector within the entire refrigeration system all need to be insulated? For ammonia gas pipelines, the separators require insulation while the oil collectors do not. 5. The low-temperature methanol washing process used by us at Dalian University of Technology does not have an ammonia tower~ (Does our feed gas go directly to the pre-washing section of the absorption tower without any treatment?) From the pre-washing section to the methanol-water separation tower: Could someone please advise me on what impact this will have on the system? You can enter directly, but methanol spray must be available. No impact. 6. If the liquid level in the pre-washing section of the absorption tower is full, and it might be connected to the H2S absorption section, what impact will this have on the system? If the liquid level in the pre-washing section of the absorption tower reaches its maximum, it may connect to the H2S absorption section, which could lead to flooding of the tower’s air inlet and cause gas-liquid shock that damages the equipment. The pressure difference in the absorption tower is high. A high water content in the main absorption section is detrimental to absorption. 7. What impact does it have on the system if the methanol-water separation tower is not fed with water but only with feedstock? What is the typical system water content in the processes you operate? What are the high and low values? If the methanol-water separation tower is not fed with water but only with feedstock, it has little impact on the system; however, the temperature becomes difficult to control. Generally, it does not exceed 0.3%.

1. What is the most appropriate way to deal with ammonia, a refrigerant used in ice machines, that contains large amounts of oil? How did the oil issue arise? How to prevent it in the future? In screw-type ice makers, gaseous ammonia and lubricating oil enter the machine together. Generally, there is an oil separator at the outlet of the ice maker; the effectiveness of this separator varies. The oil is then cooled in an oil cooler before returning to the inlet of the oil pump for reuse. There is also a secondary oil return valve located near the upper part of the oil separator, leading back to the machine’s inlet; this valve is usually kept slightly open to help reduce the amount of oil carried by the gaseous ammonia in the upper sections of the machine. 2. What impact does an increase or decrease in the outlet pressure control values of the low-pressure and high-pressure compressors in (microcomputer-controlled, explosion-proof economizer screw-type refrigeration compressor units) have on the refrigeration system? In the interlocks of conventional screw-type ice makers, there is an oil pressure difference interlock: the oil injection pressure must be 0.15–0.3 MPa higher than the exhaust pressure; if it is lower, the machine will shut down. If the exhaust pressure is too high, the energy consumption of the unit increases, and it also becomes less safe. As long as it is possible to cool the liquid ammonia, the lower the exhaust pressure, the better – this depends on the capacity of the condenser. 3. Are there any requirements regarding the physical height of the oil collector’s installation? Agree with the opinion on floor 4; it should be installed lower. Next, pay attention to its design pressure: the design pressure of the oil collector in one factory is 0.6 MPa, the setting pressure of the safety valve is 0.37 MPa, and the outlet pressure of the ice machine is 1.5 MPa; an explosion accident occurred during the venting of oil and ammonia vapor. 4. Does the ammonia pipeline, separator, and oil collector within the entire refrigeration system all need to be insulated? For ammonia gas pipelines, the separators need to be insulated, while the oil collectors do not require insulation; although it doesn’t matter if they are insulated anyway. Our factory insulates its oil collectors.

Thank you all for your help. I was wrong in saying that the feed gas passes through no equipment at all; what I mainly want to know is what impact the absence of an ammonia tower in this process will have on the system, or whether the pre-washing section functions as a substitute for an ammonia tower

Does the pre-washing section serve the same purpose as the ammonia tower? ? Isn’t that cleaning solution made of methanol? So how is the ammonia content in methanol ensured? ? It seems we can only watch it accumulate, right? Won’t that increase the sulfur content in the process gas exiting? ? There’s no ammonia tower. Ah, does the final separation tank in your conversion unit have washing water? If not, there must be a problem with the manufacturing process~!

After the process change, there is indeed washing water; the methanol used in our pre-washing stage is sent to the methanol-water separation tower, from where it is discharged directly~