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Analysis and solution of molecular sieve pulverization in PSA nitrogen making unit
1. The adsorption pressure is insufficient, the switching pressure difference is large, and the molecular sieve impact powder
Troubleshooting steps:
(1) Whether the production procedure of PSA nitrogen making device is correct.
(2) Check the production records to see whether the pressure is close to the production pressure and the switching pressure difference is less than 20kPa after the PSA nitrogen production device A and B adsorbers are pressurized.
2. Equipment component damage caused by uneven distribution of air, resulting in molecular sieve powder
Troubleshooting steps:
(1) Check the switch valve of the adsorber to determine whether the valve leaks. Method: Pressurize the adsorber. When the pressure of the pipe where the valve is located is stable, apply soapy water to the valve seal to see if there are bubbles. If there are bubbles, it indicates that the valve is leaking. Depressurize the adsorber to zero on the gauge. Because there will be residual oxygen molecules between the molecular sieve pores, the valve cannot be closed immediately after pressure relief, and the pressure relief is complete until the valve is closed, the adsorber pressure no longer rises, and then the principle of pressure difference is used to check whether the valve is leaking. For example, close the inlet and outlet valve of the absorber, press the inlet valve before the valve, and maintain the pressure for 1 adsorption cycle. If the pressure gauge of the absorber does not rise, it means that the inlet valve does not leak inside.
(2) Check the pressure equalizing tube in the middle of the adsorber to determine whether the wire mesh of the distribution cylinder is damaged. Methods: Remove the interface flange of the middle pressure equalizing pipeline, and visually check whether there is molecular sieve in the distribution cylinder.
(3) Determine whether the internals such as the adsorber bed and the filter are damaged. Method: Remove the pressure relief valve pipeline interface flange, check whether there is molecular sieve powder in front of the pressure relief valve and in the pipeline. If the bed and filter are damaged, the molecular sieve will leak into the pipeline after the pressure relief.
(4) Check the dust filter. Method: Open the filter flange cover and check whether there is dust in the filter cartridge. The check result shows that there is no dust in the filter cartridge and the product gas is clean nitrogen.
3. Molecular sieve quality problems, resulting in molecular sieve powder
Troubleshooting steps:
The molecular sieve in the adsorber was sampled and compared with the unloaded molecular sieve to confirm whether the molecular sieve powder phenomenon occurred.
The sample is analyzed by the analysis station, and the national standard is compared to see if there is any unqualified situation.
4. Improper operation or operation failure caused by molecular sieve broken or damp
Troubleshooting steps:
During the operation of the PSA nitrogen production device, if the adsorber has not been alarmed, but it is found that the molecular sieve sinking of the adsorber has exceeded the alarm line during maintenance, it can be judged that the adsorber alarm device is faulty. Check that the cushioning mat has not broken into pieces. If it is, it can be judged that the molecular sieve bed is not stably and effectively pressed, and when the device is running, the molecular sieve produces fierce collision and kinetic friction, resulting in the molecular sieve crushing and even pulverizing.
Molecular sieve pulverization removes collision and kinetic friction, and another possibility is that the molecular sieve absorbs moisture, resulting in a decrease in mechanical strength resulting in pulverization.
Molecular sieve moisture absorption has the following possibilities:
① In the pressure test stage of the device, the equipment is not cleaned, there is residual water, and it is adsorbed by molecular sieve after driving. Check the device quality inspection record and acceptance report, no such phenomenon was found.
② Molecular sieve loading did not comply with the operating procedures.
Molecular sieve loading precautions:
(a) Protect the adsorbent from moisture and cannot be filled in fog or rain;
(b) The cover of the adsorbent drum should be opened only when it is ready to be filled and should be sealed properly before opening;
(c) Check whether the quality of the adsorbent is good, if there is too much dust, it should be passed through the screen, remove the dust and debris, and then loaded into the adsorption container;
(d) As far as possible, the adsorbent drum should be avoided from rolling on the ground to prevent damage to the adsorbent. Check the loading record report, no violations were found.
③ When the device is running, the micro-thermal regeneration drying system (referred to as the drying system) can not effectively remove water, resulting in wet air into the nitrogen adsorbent. When the activated alumina in the nitrogen adsorbent is saturated with water, the remaining water is adsorbed by the activated alumina molecular sieve on the upper part of the activated alumina (activated alumina is loaded in the lower part of the molecular sieve, the purpose is to remove the residual water in the process air).
④ The spare molecular sieve was improperly preserved and not sealed according to regulations, resulting in moisture exposure to the molecular sieve.
Overall solution
(1) Overhaul the adsorber alarm device. Reset the alarm line according to the instruction manual and make clear marks.
(2) Replace the brown mat with a stronger coconut mat. The practice shows that the coconut mat has stronger impact resistance than the brown mat, and can play an effective buffer role on the top molecular sieve.
(3) Replace the activated alumina in the micro-thermal regeneration dryer.
(4) Adjust the discharge cycle of the trap of the precooler to increase the number of discharge per unit time.
(5) Install dew point meter according to process requirements, and make production monitoring records.
(6) Partially replace the molecular sieve in the adsorber.
(7) The activated alumina in the adsorber is regenerated for a long period to restore its activity.
(8) The container containing the molecular sieve shall be sealed and inspected, and the molecular sieve that has been damp shall no longer be used.
(9) Retrain the production personnel of PSA nitrogen production device, strengthen professional operation knowledge, increase the execution of the operation system, and strengthen the awareness of safety precautions.
Dalian Chuangge Technology Co., Ltd
Richard Han
Doris Zhou
Headquater: 9th Floor, Century Classic Building, No.10, Xinghai Square, Shahekou District, Dalian City, Liaoning Province
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