With the development of economy and society, people's requirements for domestic water, industrial water and water environment are increasing day by day, which puts forward higher requirements for various water treatment process technologies in water supply and drainage.
The pressure swing adsorption (PSA) oxygen production process is widely used in water supply applications due to its outstanding advantages such as low oxygen production energy consumption, quick start and stop, low operation difficulty, and low equipment investment. In various practical projects of water supply and drainage, especially disinfection and sterilization and pollutant oxidation treatment, it is particularly significant.
The PSA oxygen production process has become an important technical component of various water treatment processes in water supply and drainage, and it is also an important part that cannot be ignored in the development and application research of new technologies and new processes in the field of water treatment. The relevant research on the PSA oxygen production process has become a new research direction for scientific and technological workers in the field of water supply and drainage. With the improvement and application of lithium-based zeolite molecular sieves (LiLSX) with low silicon-aluminum ratio and high oxygen-nitrogen separation coefficient, the PSA oxygen production process has become the most important production technology for producing non-high-purity oxygen (purity <95%).
The research on NEWTEK PSA oxygen production process mainly focuses on the development of oxygen production molecular sieves, the improvement of adsorber structure design and the optimization of process flow. Software simulation and research on small experimental devices have become important means for optimizing the pressure swing adsorption oxygen production process. Through process optimization, the oxygen recovery rate and purity can be improved, and the energy consumption of oxygen production can be reduced. In addition, more intelligent automatic control systems are also used in PSA oxygen production devices to reduce energy consumption.
The optimization research of PSA oxygen production process through software simulation and small experimental devices generally has a relatively short cycle, limited data obtained, and has a certain deviation from the actual operation of large-scale PSA oxygen production devices. We took the large-scale pressure swing adsorption oxygen production device in operation as the research object, obtained the process operation data of the device for more than one year through Aspen Process Data, and calculated the power consumption of producing unit volume of oxygen based on the process data. The relationship between the main influencing factors in the operation of the device and the power consumption of oxygen production was studied. It was found that when the inlet temperature of the device increased from -5℃ to 35℃, the initial oxygen production power consumption first decreased and then increased, and there was an obvious quadratic relationship between the initial oxygen production power consumption and the inlet temperature. Too high or too low intake temperature will lead to an increase in the initial oxygen production power consumption. The intake temperature with the lowest initial oxygen production power consumption is 16.2℃. For every 1℃ increase or decrease in intake temperature relative to 16.2℃, the oxygen production power consumption increases by about 7.4463*10-5kwh/Nm3. When the oxygen purity changes in a short period of time, the higher the oxygen purity, the higher the initial oxygen production power consumption. There is a linear relationship between the initial oxygen production power consumption and the oxygen purity. For every 1% increase in oxygen purity, the initial oxygen production power consumption increases by about 0.0071~0.0074kwh/Nm3. At the same time, when the oxygen purity changes by the same amplitude, the increase in initial oxygen production power consumption caused by the increase in purity during the change from low to high oxygen purity is greater than the decrease in initial oxygen production power consumption caused by the decrease in purity during the change from high to low oxygen purity. During the differential pressure change cycle of the air intake filter, the linear relationship between the initial oxygen production power consumption (i.e., corrected oxygen production power consumption) and the air intake filter differential pressure after temperature correction and purity conversion is obvious. When temperature correction and purity conversion are not performed, the relationship between the initial oxygen production power consumption and the air intake filter differential pressure is not obvious, and even appears to be contrary to the basic principle that the increase in air intake resistance leads to increased energy consumption. This further shows that the air intake temperature correction and purity conversion are reasonable and necessary, and can meet the needs of analysis and calculation. For every 1mbar increase in the differential pressure of the air intake filter, the oxygen production power consumption (i.e., corrected oxygen production power consumption) increases by about 0.0008kwh/Nm3. After determining the influence of other major influencing factors on the oxygen production power consumption during the operation of the PSA oxygen production device, Design Expert 10.0.4 was used to perform a response surface analysis on the influence of the PSA cycle process step time on the final oxygen production power consumption.
The time of the three process steps of "air blast intake", "air intake/oxygen production" and "purge provision" was used as the influencing factors, and the final oxygen production power consumption and oxygen flow rate were used as the response values to design the central combination experiment. According to the designed experimental scheme, the device was adjusted and the operation experiment was carried out to calculate the initial oxygen production power consumption under the conditions of different process step time parameters. According to the corrected relationship between the initial oxygen production power consumption and the intake temperature, oxygen purity and the corrected oxygen production power consumption and the intake filter differential pressure determined in the previous chapter, the oxygen production power consumption (i.e., the final oxygen production power consumption) under the same intake temperature, product purity, and intake filter differential pressure benchmark conditions was calculated. The model of the final oxygen production power consumption was obtained by regression. Through variance analysis, it was found that the regression model of the final oxygen production power consumption was highly significant (P≤0.0001) and statistically significant. The model lack of fit was not significant. It had sufficient discrimination accuracy within the range of the designed influencing factors. The residual distribution of the fitting model was roughly a straight line, which further showed that the model fitting effect was good and could be used to replace the real experimental points for result analysis. Through the analysis of two-dimensional contour map and three-dimensional response surface map, the influence of the three operating step time studied on the final oxygen production power consumption was determined.
The order of significance is: "air blasting" time> "purge" time> "air intake/oxygen production" time.
The optimal process time parameters that minimize the final oxygen production power consumption are solved. The optimal process step time is:
The step "air blasting" time is 7.8s, the step "air intake/oxygen production" time is 4.0s, and the step "purge" time is 3.6s. The device is actually operated with the optimal process step time parameters and the corresponding final oxygen production power consumption is calculated. The relative deviation between the model prediction value and the average value of the final oxygen production power consumption of multiple actual operations is only 3.02%, which further shows that the regression model of the final oxygen production power consumption has good accuracy and practicality. In addition to being used to analyze the influence of the process step time on the final oxygen production power consumption in the PSA oxygen production process, this model can also be used to estimate the final oxygen production power consumption under different process step times. Compared with the oxygen production power consumption of the initial design of the device, the power consumption per standard cubic meter of oxygen production after optimizing the process step time has decreased by about 5.42%. Through operation optimization, the power consumption of oxygen production can be effectively reduced to produce significant economic benefits. The method used by NEWTEK to analyze the factors affecting oxygen production power consumption and optimize the operation of the device can achieve the purpose of reducing the power consumption of oxygen production in the PSA oxygen production device, and can provide a basis and method for the energy consumption evaluation and operation optimization of the pressure swing adsorption oxygen production device. It can better provide first-class equipment for the world.
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