1 problem and cause analysis
Compressor overhaul is generally based on the replacement of the second-stage inlet and outlet check valves (in most cases, the check valve leaks). Shortly after the check valve is replaced, at full load, the compressor will have a period of increase in outlet pressure and a decrease in the outlet pressure of the second stage. When the pressure of the inlet CO 2 and the temperature are basically stable, the compressor will decrease by 100 150. m 3 /h.
Due to the increase in outlet pressure, the second-stage outlet pressure dropped, and it was suspected that the two-stage check valve had a leak. The temperature of each check valve was measured by an infrared thermometer and compared with the data measured at normal time. If the temperature of a check valve rises, the valve may leak and need to be replaced.
At the beginning of the replacement of the check valve, under the full load of the compressor, the pressure and air volume of each section are normal, but the same problem will occur after more than 10 days, and it has to be stopped for maintenance.
Summarize the previous replacement of the check valve, it is found that there are always more sludge-like dirt in the valve and gas passage of the one-way valve that has been removed. There are more inlets in the first and second sections, especially in the second section. Originally thought to be the attachment of the lubricating oil after high temperature carbonization, after analysis, it was found that the residue was easily soluble in water. The analysis results of the residue components of the quality inspection center are: K +13 16%, CO 2- 3 30 58%, SO 2- 4 11 29%. It is thus determined that the main component of the residue is potassium salt, which is composed of CO 2 gas. Into. Because the temperature of the first and second inlet gases is relatively low, the potassium salt crystallizes and adheres to the one-way valve, while the gas passage on the valve plate is larger, and the gas passage on the second valve plate is smaller, so the amount of adhesion in the second section is higher. More, the impact on gas flux is more obvious.
2 no parking treatment method
Whether the compressor can clean the dirt on the check valve without stopping the compressor, after careful study, we think this scheme is feasible.
The following two treatment methods have been specifically adopted.
2 1 Method 1
Considering that the temperature of the CO 2 gas is low, the potassium salt is liable to cause crystallization, and the temperature of the second-stage inlet CO 2 gas is appropriately increased to prevent or reduce the crystallization of the potassium salt. Manually adjust the circulating water volume of the outlet cooler to increase the temperature of the second inlet gas to 50. After 12 hours of operation, the outlet pressure is only slightly decreased, and the gas volume is slightly increased, and the effect is not obvious.
2 2 Method 2
Considering that the potassium salt crystals are easily soluble in water, the low-pressure saturated steam of 0 35 MPa is added to the top of the first and second inlet buffers for purging (since the saturated steam is condensed to produce condensed water, which can dissolve the potassium salt crystals). ()). Since the outlet pressure is 250 290 kPa, the low pressure saturated steam of 0 35 MPa is used to maintain the pressure difference between the steam and the second inlet at 50 100 kPa to ensure the safety and effect of the purge.
2 3 The specific operation and precautions of Method 2
(1) Connect the rubber tube at the common point of the low pressure steam near the compression section, open the steam valve, drain the water in the rubber tube, close the steam valve, and then connect the other end of the rubber tube to the top of the second section of the buffer. , open the bottom discharge valve of the second section of the inlet buffer.
(2) Advance the appropriate amount of steam to control the opening of the bottom discharge valve of the second-stage inlet buffer to make the discharge a gas-liquid mixture, and prevent the accumulated water in the buffer from entering the cylinder to cause liquid shock.
(3) Observe the temperature of the second-stage inlet CO2 gas, and it is better to not exceed 45.
(4) After 30 40 m in, close the top discharge valve of the buffer and stop the steam. When only the gas at the bottom of the two inlet buffers is exhausted, close the discharge valve.
Follow the above procedure for the same treatment of a section of the inlet check valve.
3 effects
(1) After the steam purge was carried out on Method 29 on June 29, 2009, the outlet pressure of the first and second sections was normal, and the air volume was increased by 100 150 m 3 /h.
(2) The two-stage check valve was originally parked and replaced once every 1 month, with an average annual parking of 8 times. Now the parking is up to 2 times a year. This alone can reduce parking 6 times a year. Each parking time is 6 hours, which can reduce the parking time by about 36 hours and reduce the production loss by about 700. At the same time, it also eliminates the problem of high ammonia consumption caused by parking.
(3) Reduce the consumption of spare parts and spare parts, and save about 180,000 yuan per year.
4 Conclusion
The steam purge is used to clean the dirt on the check valve of the inlet of the CO2 compressor, which realizes the process of the system without stopping. The operation is simple, safe and reliable, and the effect is remarkable, which creates favorable conditions for high yield, stable production and low consumption of the urea system. .
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