What is the reason why the outlet liquid temperature of the carbon dioxide stripping tower of the urea unit is over-temperature, and how to deal with it?

Can you explain a few parameters in more detail?

At a load of 60, your high-pressure steam reaches 1.8?? This must be too high. Do your heating steam condensate outlets have three elevations? If so: close the bottom one and the top one, open the middle one, and determine the size of the switch according to the changes in temperature and low pressure. Be careful not to accumulate a large amount of condensate, which will cause the heat exchange of the stripper to decrease and overload the low pressure!!! Also check to see if the vent in front of your tower is leaking! It will increase the liquid-to-vapor ratio of the stripping tower! Also, check if your material ratio is correct? What is the synthetic conversion rate? If your material ratio, vapor-to-liquid ratio, etc. are within the specifications, as well as the amount of heating steam, then you need to check the gas tower. It is estimated that there is a problem with part of the stripping tube! The maintenance of Jinling Petrochemical is very good.

If there is no problem with the operation, you can consider whether the heating steam is not saturated and becomes superheated steam. Increase the liquid level of the saturator appropriately and check the steam distributor in the saturator after stopping the operation. If it is suspected that the stripping holes are blocked, resulting in high outlet liquid temperature, the system can be shut down to maintain pressure, evacuate the stripping tower, introduce CO2 into the system, and backflush through the liquid outlet pipe of the synthesis tower. The system pressure can be maintained with a high-pressure system vent valve. Backflush for 30 minutes, then start feeding.

Can you tell me the specific steps for the blowback upstairs? Due to the over-temperature of 201C, our factory directly turned on a backup machine to make the CO2 entering the tower 1.5 times that of normal production. After blowing for 3 to 5 minutes, the effect was ok!

What is the specific situation of your over-temperature? Is it short-term or long-term? Are there any changes in the components?

Does the synthesis tower still need to be drained? Is there any specific operation plan?

The over-temperature situation of the stripping tower outlet liquid you mentioned has also been encountered in some factories. I mentioned part of it before. I think: 1. The load is 60%, which is definitely low. Two CO2 compressors are running. Affected by the compression ratio, the temperature of the CO2 air inlet lifter exceeds 130 degrees, and the outlet liquid temperature is obviously super high. 2. The gas outlet temperature of the stripping tower is 185 degrees, which is about 3 degrees lower than normal, indicating that the gas stripping efficiency has changed significantly. It may be that the load is too low. (How big is the equipment in your factory? ) The liquid has not flooded the gas lift hole, and there is a small amount of liquid in some gas lift tubes, causing dry burning, resulting in over-temperature. If the load of the circulation system is light, you can consider adding load to reduce the liquid outlet temperature. 3. If the air stripping holes are partially blocked, consider briefly stopping the air stripping tower to backflush it. There are many questions upstairs about how to backflush the air stripping tower. It is actually very simple.: After a short pause, the

Exit ammonia and methylammonium, put the synthetic liquid level to the outlet of the liquid outlet, exhaust the air stripping tower, exit the CO2, open the synthesis gas phase to vent, reduce the pressure to below 12MPA, fully open the synthesis tower liquid outlet butterfly valve, put a single CO2 machine into the system at full capacity, and let the CO2 pass through the synthesis tower outlet pipe and be evacuated through the scrubber. Due to the liquid sealing effect, very little methylammonium is cooled by the high-pressure methylammonium. In this way, impurities in the air stripping hole can be blown out. 4.1. 8MPA vapor pressure is definitely high. You can refer to the circulating pressure and slowly reduce it to 1. 7MPA。 5. The original grid controls the external water in the system to ensure that H/C is at 0. Within 5.

If anyone has experience in this area, you might as well share it. :victory:

1. The 60% load can only be temporary, or the load required for start-up feeding. If this load is used in normal production, it would be too uneconomical. It consumes a lot of energy, and the high-pressure working conditions are difficult to control. The stripper is prone to overtemperature and increased corrosion. 2. The steam pressure of 1.8 on the shell side of the 60% load stripper is not too high, but the outlet liquid temperature of 177 is obviously too high, about 10 degrees higher. This may be caused by the uneven distribution of liquid in the gas pipe and the high liquid level at the bottom of the stripper. 3. The pressure control of the high-pressure system is too high, which reduces the stripping efficiency. Clogged small holes in the stripping tube liquid level distributor can also cause the outlet liquid to be over-temperature. 4. The amount of water returned from the low pressure to the high-pressure system is too high. This can also be caused.

Personally, I think what the 8th floor said makes sense.

First, check the data of the last 3 months to see if the outlet liquid temperature is rising slowly. If so, you can consider it because the small hole in the stripper pipe is blocked or there is carbon formation. If you don’t find the reasons from the following places:: 1. The load of 60% is indeed too low, and the liquid distribution is uneven. 2. The 60% load high-pressure steam of 1.8MPa is relatively high. It should be observed when it drops to around 1.65--1.70. 3. If there is superheated steam, increase the drum liquid level appropriately to observe changes.

Our factory is in a similar situation. The backflush plays a certain role, but after a few cycles, it starts to overheat again. The load is about 21,000, the high pressure control is 1.95MPA, and the filter of the ammonia pump is cleaned regularly, but it is still overtemperature. What should I do? ? So anxious

How to control or alleviate the time period of small hole clogging?

The clogging of small holes is mainly caused by poor internal cleaning after the high-pressure equipment is overhauled. It is also caused by impurities brought into the high-pressure system by the ammonia pump and oil brought into the system, or oil brought by liquid ammonia, and impurities brought into the high-pressure system by the methylammonium pump in the circulation system. By following these steps, you should be able to avoid or reduce clogging of small holes. The ammonia pump brings oil into the system. As long as it does not start and stop frequently and the liquid level in the gas tower is not too low, it will not have a great impact on the small holes.

Or the spot welding between the stripper pipe and the flower plate of the stripping tower may crack, and the gas lift pipe may come out when the pressure is increased after starting the machine. This situation has just happened in our factory. Please prepare materials and stop the machine as soon as possible!

I agree with hai3. We take liquid ammonia samples at regular times every day and put them in the fume hood. After the liquid ammonia evaporates, there is sometimes oil at the bottom of the container, but most of the time, there is a lot of water in it. How can the ammonia pump prevent water from entering the system when the pump is reversed? Thank you both for your help:handshake

Liquid ammonia generally does not contain water. Water will react with liquid ammonia. The water you are talking about may be water condensed due to the volatilization of liquid ammonia. Oil removal is the key. Oil in our unit's liquid ammonia and carbon dioxide gas is very serious.

There are many reasons why the small holes of the stripper liquid distributor are blocked. If you want to solve the problem, you can only open the cover when stopping for maintenance. The reasons for the blockage are:: 1. Corrosive matter that has been corroded and fallen off of high-pressure equipment. 2. Impurities brought by the raw carbon dioxide, or catalyst powder brought by the carbon dioxide after passing through the dehydrogenation reactor. 3. Impurities in the raw ammonia, such as oil stains, catalyst powder from the ammonia synthesis tower, etc. 4. Impurities brought by the sealed water of the ammonia pump or methylamine pump.

Is the gas-liquid distributor broken? If the liquid level in the stripping tower is too high, it may also cause overtemperature!