The semi-water gas from the gas cabinet is desulfurized by the semi-water gas desulfurization system, and then enters the conversion system after being compressed by the compressor at the first, second and third stages. The converted gas is desulfurized by the shift gas desulfurization system and then enters the fourth-stage inlet of the compressor. After four stages of compression, it enters the MDEA decarbonization system. After decarburization, the gas enters the compressor's five-stage inlet after fine desulfurization. After five stages and six stages of compression, the gas enters the alcoholization system, and the alcoholized gas enters the compressor. After the stage is compressed, the gas enters the hydrocarbonization system, synthesizes the system, and synthesizes ammonia.
2 cooling water process
The cooling water of the compressor is introduced by the water supply main pipe through the branch pipe, and enters the gas cooler of the compressor, the cylinder cooling water jacket, the oil cooler and the stuffing box. After the cooling water is cooled in each equipment, it is collected into the return water main pipe, and the water is returned to the hyperbolic air cooling tower. The return water of the stuffing box is pressureless.
3 problems and solutions
(1) At the beginning of the operation of the compressor, the service life of the low-pressure gas valve is generally short. The main performance is that the valve piece and the spring are easy to break. The gas valve is shut down and replaced every shift, and the operation is extremely abnormal, which seriously affects the stability of synthetic ammonia production.
In response to this problem, the design department of the compressor manufacturer was contacted several times, and the actual production operation parameters were provided to calculate the gas valve. Through the depth of the spring hole of the lift limiter, the diameter of the spring, the material of the spring and the heat treatment method used, etc., although the service life of the valve is prolonged to some extent, but the desired target They are still far apart and cannot meet the requirements for stable production of ammonia plants. To this end, the trial of the PEEK valve valve valve, after trial and comparison, the life of the compressor valve is greatly improved.
(2) During normal operation of the compressor, the Babbitt alloy on the surface of the main bearing bush and the connecting rod head is easily damaged, and the Babbitt alloy layer is cracked and falls off. Under normal circumstances, there is basically no sign before the damage occurs. Practice shows that the temperature rise of the main bearing bush should wait until the big end of the connecting rod burns out and stop for a period of time. After the heat is transmitted through the curved neck, it will rise faster, reflecting the very lagging, basically failing to provide early warning. It has even been found that after some of the bearing pads are damaged, the temperature of the bearing pads in operation is also normal. After the big head of the connecting rod burns out, the steel back of the big head tile and the crankshaft neck are severely rubbed, the surface damage of the crankshaft neck is very serious, the repairing difficulty is high, the maintenance work is extremely large, and after the repair, the effect of use is also inferior. before.
Take measures: Add a large-flow circulating oil pump, increase the oil cooler and oil filter, increase the circulating oil pressure and oil quantity as much as possible, and then adjust the gap between the crosshead and the slideway to ensure the entry into the connecting rod. The amount of lubricating oil in the big head tile. Through a period of operation, the frequency of the connecting rods is reduced. In addition, by regularly testing the lubricating oil and periodically filtering it with a vacuum oil filter, the lubrication performance of the lubricating oil is ensured, and the operating conditions of the compressor are also improved.
(3) The compressor auxiliary machine cooler leaks. Since the composition of the circulating cooling water in the initial stage of the trial production did not fully meet the process specifications, after more than one year of use, the compressor coolers successively showed corrosion leaks, which wasteted a large amount of raw material gas and caused great safety to the compressor operation. Hidden dangers. Due to the use of pressurized return water, once the compressor is stopped and depressurized, the cooling water valve is generally closed and not easily leaked, and the circulating water will be poured into the gas system through the leak point of the cooler. When the compressor is driving, due to the presence of water in the equipment and pipes, liquid hammer is easily caused.
Take measures: regularly check the cooler of the compressor and plug it in time to minimize the impact of leakage on production. For the newly produced cooler dies, stainless steel heat exchange tubes and spiral tubes with appropriately thinned walls are used to eliminate the problem of cooler leakage caused by water quality problems.
In addition, since the filler in the cooling tower is used for a long time, it is pulverized by aging, and the debris enters the cooler with the circulating cooling water, blocks the cooling water passage, and the cooling efficiency is lowered. At the same time as parking cleaning, a pipeline filter is installed on the cooling water pipe, which relieves the clogging problem of the cooler and improves the cooling efficiency.
(4) Axial displacement of the large end of the connecting rod. When repairing a compressor, it was found that the connecting rod body could not arbitrarily stay at different positions on the crankshaft during the whole turning process. It seems that a lateral force acts on the connecting rod body to return the connecting rod body to a specific position. position. At the time of the test run, there were many cases of burning tiles in the big head tiles, and they were all unilaterally burned, and it occurred in a very short time.
Take measures: the side of the burnt surface of the big head tile is ground, and the side of the connecting rod body is also processed and removed a little. The positioning step of the inner hole of the connecting rod is also removed a certain amount to make the connecting rod big head The displacement is offset; the oil guide arc of the crosshead pin is also appropriately enlarged, and the oil guiding groove of the connecting rod small head tile is also appropriately deepened, which increases the oil supply amount of the connecting rod big head tile. Through these measures, the problem of frequent burning of tiles caused by the displacement of the large head of the connecting rod is basically solved.
(5) The problem of the four-stage cooler splitter partition is easy to damage. The four-stage cooler is a double-tube structure, the gas is taken away, and the fillet welds at both ends of the splitter plate are cracked soon after use, and the cracks extend through the fillet welds to the casing of the equipment, causing leakage and safety. Hidden dangers. In this regard, first try to increase the thickness of the split partition and improve the welding strength, but did not receive good results. After analyzing the reason: although the gas is buffered by the buffer, there are pressures and fluctuations in the flow rate. Under the pulsating impact of the gas, the splitting partition may have frequent bending, and there is a large pulse in the splitting partition. The pulling force causes cracks in the welds at both ends.
Take measures: According to the direction of the airflow, an H-shaped support is added on the split diaphragm against the direction of the gas force, which increases the rigidity of the split diaphragm and distributes the pulse force of the gas to the tube. A reinforcing plate is installed on the box cylinder and a portion in contact with the cylinder body is supported, thereby alleviating the local force of the tube box cylinder.
After more than three years of operation, there has not been a break in the weld of the split diaphragm.
(6) The service life of the six-stage and seven-stage copper piston rings is short. The piston ring reaches the replacement cycle after about 1 year, but the service life of the replacement piston ring is obviously short, which seriously affects the stability of the compressor operation. Analysis reasons: the piston ring is elliptical, the material is soft, the cylinder mirror surface is slightly worn, the amount of lubricating oil is sometimes reduced, the temperature of the seven-stage inlet gas is high and the methanol vapor is affected, which affects the piston ring to varying degrees. Service life.
Take measures: Decide to first test the piston ring made of PEEK material without changing the original structure of the piston body. After trial use, it has achieved very good results, greatly reducing the frequency of inspection and maintenance of the compressor, saving a lot of maintenance costs and achieving obvious economic benefits.
(7) In addition, the compressor conditions have been improved in the following aspects:
In view of the high operating temperature of the compressor motor bush in summer and affecting its safe operation, a thin oil station device is installed in the motor bearing housing, which increases the lubricating oil quantity and reduces the oil supply temperature and the operating temperature of the bearing bush.
For the problem that the crosshead taper pin is easy to loose and the platen bolt is easy to be broken, before the installation, the taper pin and the crosshead hole are ground to maximize the contact area of ​​the inner surface of the taper hole; the platen bolt is originally a high-strength hex head bolt Connection, but due to its short length, the amount of elastic deformation is small, and it is easy to break under the action of alternating load. Therefore, the material of the connecting bolt is changed to 35CrMoA with high strength and toughness, and the bolt length is also appropriately lengthened. Moreover, the hammer and the bolt are repeatedly hammered and bolted repeatedly for multiple times during installation, which fully ensures the contact degree between the cross pin and the taper hole. After more than a year of operation, the bolt breakage and the crosshead pin loosening did not occur.
In view of the entrainment of sulfur foam, tar and other impurities in the semi-water gas, the operating life of the low-pressure gas valve of the compressor is affected. After the desulfurization of the semi-water gas, an electrostatic de-tarder after desulfurization is added, which effectively improves the degree of gas purification and is a low pressure of the compressor. Further extension of the service life of the class valve provides conditions.
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