Analysis and treatment of the three-stage pressure difference increase of chemical engineering and equipment air compressor inlet Zhang Jiangwei, Han Kunyang, Ma Qin (China Pingmei Shenma Group Nylon Chemical Co., Ltd., Pingdingshan 467013, Henan) Air compressor inlet filter adopts Three-stage filtration, the filtration efficiency is 99.9%. The third-stage pressure difference is increased, which will cause the C101 outlet flow to decrease, the airflow resistance to be large, and the service life of the third-stage filter element will be greatly reduced, and the production cost will be reduced. To cause certain harm, this paper analyzes the reasons for the increase of the third-order pressure difference and takes certain countermeasures.
The annual production capacity of a certain device is 10,500 tons of nitric acid, the product concentration is greater than 63.5%, and the annual operating cycle is 7,200 hours. The air filter required by the device can automatically update the filter cloth. The filter cloth is made of fiberglass fabric with large processing capacity and low resistance; the second level is bag type, and the third level is square box type. Second, the third stage is mounted on a fixed frame, which can filter out 0.5 micron dust. The resistance is small and the efficiency is over 99%. The basic parameters of the air filter are as follows: width 1. net height 4m, side by side 4, The air volume reaches 60000Nm3/h, the resistance is 5-35mmH20, the filtration efficiency is 45%, and the material is glass fiber fabric.
The second-stage medium-efficiency air filter has a wind volume of 60,000 Nni3/h and a resistance of 11.2-50niniH20 with a filtration efficiency of 88%.
9% of the material is plywood, fiberglass board, aluminum poise.
In the recent period, the third-stage differential pressure test shows that the third-stage differential pressure rises faster, and the replacement frequency is higher. If it is not replaced, the third-stage resistance will be large, and the gas volume will be reduced, which will affect normal production. In addition, since the third-stage filter is made of cardboard, it is easy to suck into the air compressor inlet when the resistance is large, causing the air compressor to surge. To this end, we have conducted a series of examinations and practices to find out the following reasons: 1 The filtration efficiency and accuracy of the secondary filter are low. By testing the differential pressure of the second-stage filter, it can be seen that there is almost no difference in the second-stage pressure difference. Data, we believe that the filtration accuracy of the second-stage filter is too low, the filtering effect is not good, and the third-stage pressure difference rises faster. Contact with the manufacturer to improve the filtration accuracy of the second-stage filter from the original 88% to 92. After the % data, such as the original secondary filter differential pressure data, the new installed grade speed core pressure difference data, the original two-stage filter, the three-stage differential pressure data, the new two-stage filter, the three-stage differential pressure data: “linear (original secondary filter Three-level 0221 differential pressure data) One-to-one linearity (newer second-level filter after three-stage second-stage pressure difference comparison chart third-stage pressure difference comparison chart (Note: The above is for any time before and after replacing the second-stage filter The data of 16 shifts) Zhang Jiangwei: The reason for the increase of the three-stage differential pressure of the air compressor inlet is the new secondary filter, and the measured data includes the second-stage differential pressure and the third-order differential pressure. The pressure difference comparison chart X axis is the shift, respectively, taking continuous The data measured by 16 classes, and the data measured when the second-level original filter element is measured and the data measured when the second-stage new filter element is installed.
In order to compare the effect of the replacement more intuitively from the data, we added a mean line to the data and obtained a mean line function, which can calculate the increase of each class of the second and third pressure difference from the mean line function: (1) Comparison of the second-order pressure difference: a. The average function of the pressure difference of the original secondary filter element is: y=0, so that the original secondary filter has no filtering effect, and the average increase per shift is 0kpa b. The mean value of the pressure difference of the newly installed secondary filter element is: y= +0.0129, the slope of the mean value line is k=0.0004, and the average increase of the pressure difference of the newly installed secondary filter element is 0.0004kpa. Conclusion: The filtration efficiency of the newly installed secondary filter element is obvious. Increase, the average increase of the secondary filter pressure difference from the original 0kpa to 0.0004kpa (2) third-order pressure difference comparison chart Conclusion: a. The original second-stage filter element of the third-order differential pressure mean function is: y=its slope k=0.0045, the average increase of the differential pressure of each class of the third-stage filter element is 0.0045kpa when the original secondary filter element is obtained. b. The mean value of the third-order differential pressure when the second-stage filter element is newly installed is: y=the slope k=0.0026, which results in the differential pressure of each class of the three-stage filter element when the new secondary filter element is newly installed. The average increase is 0.0026kpa. Conclusion: After changing the new secondary filter element with the filter accuracy, the average increase of the third-stage filter pressure difference from the original 0.0045kpa to the current 0.0026kpa 2 inlet air in the first stage. Short-circuit This is a human error. In the case of a primary roller blind, if you do not pay attention to the gap at the edge of the filter cloth, it is easy to cause a large gap between the filter cloth and the mounting frame, so that some air is not filtered through the primary filter cloth. Directly enter the second stage, so that the primary filtration efficiency is low, most of the impurities directly enter the secondary filter, while the secondary filtration can only filter the dust with d>=0.5um, reducing the use of the second and third filter elements. Life expectancy leads to an increase in the second and third stages of differential pressure.
3 Influence of environmental factors in the production plant area In general, the chemical plants are built in the suburbs. The ambient air quality is poor and the dust is more. This puts higher requirements on the filter precision of the filter element, and it also easily leads to short service life of the filter element. The pressure difference rises faster.
4 The quality of the first-class filter element is problematic. The filter element used in the test run in 2010 is about 5mm in Tianjin. The filtering effect is good. It can be seen from the same period of the roller blind. After the normal opening, the production thickness is 3mm. Left and right, and the texture is soft, there will be elongated and smashed in the process of rolling, and the cycle of roller blind replacement is shorter.
In view of the above analysis, we have taken the following aspects: (1) Carry out the rolling operation in strict accordance with the confirmation and confirmation tables of the roller blinds, and the precautions for the training of new employees can be carried out by experienced old workers. Moreover, the squad leader should check the gap between the filter cloth and the frame on each side of the filter after entering the filter room after the roller blind. The normal gap is between 2-3mm, and the filter cloth wound on the upper side is between 4-5mm from the wall. The shaft of the lower filter cloth should be as close as possible to the wall without leaving a gap.
(2) Contact the manufacturer to improve the filtration accuracy of the secondary bag filter. The filtration efficiency of the second-stage filter is below 88%, and the dust above 0.5 micron is removed by filtration, and we can measure the pressure difference during normal production. It can be seen that there is basically no pressure difference in the second stage, and the pressure difference is 0. As long as there is resistance, there will be a pressure difference, and there is no pressure difference, indicating that the second-stage bag filter works poorly, and passes through the primary filter. The impurities removed by the filter are not filtered in the secondary bag filter, and directly enter the third stage, resulting in a faster rise of the third stage pressure difference. On this basis, we contact the manufacturer, the second level bag The accuracy of the filter has been increased from 88% to 92%. Through the above data analysis, we can see that after the second-stage filter element with improved accuracy, the filtration efficiency is significantly improved, and the third-stage differential pressure growth rate is obviously slowed down. .
(3) Due to the poor quality of the first-stage filter cloth, we put an old filter cloth on the outside to improve the filtration efficiency. The quality of the first-stage filter cloth is not good. After discussion, we decided to be at the first level. On the basis of the filter cloth, the used old filter cloth is washed, dried, and then attached to the outside of the first-stage filter cloth, so that the larger particle size method in the air can increase the pressure difference of the three-stage filter element. Reduces, while also extending the life of the second and third-stage filter.
5 Conclusion Through the analysis of the reasons for the increase of the third-stage pressure difference at the inlet of the air compressor and the corresponding countermeasures. It not only prolongs the service life of the filter cloth, but also greatly reduces the production cost, and also promotes the safe and stable operation of the production.
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