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Nitrogen recovery filtration system
2017-05-021388
The utility model relates to a nitrogen recovery filter device, which can be recycled to reduce the operation cost. The best process should be selected.
The flow path of the production unit using liquid nitrogen cold energy is as follows: liquid nitrogen comes from the low-temperature storage tank, the pressure in the storage tank is kept above 0.4MPa, the temperature is saturated into the production unit, and in the unit is reheated to - 30 ℃ through the liquefier, the first cooler and the second cooler, and the discharge pressure is about 0.25MPa.
The gaseous nitrogen should be further cooled and liquefied. We know that only when the temperature of gaseous substances drops below its critical temperature can they liquefy, and the critical temperature of nitrogen is far lower than the ambient temperature. To liquefy them, artificial refrigeration must be used. At present, the most common method is throttling liquefaction cycle and liquefaction cycle with expander. When compressed gas enters expander for expansion and external work, large temperature drop and cooling capacity can be obtained. Using gas output external work adiabatic expansion cycle is the most widely used flow form in gas liquefaction and separation equipment
The 0.11mpa (a) nitrogen from the reheating of the cold box enters the circulating nitrogen compressor and is compressed to 0.9mpa (a). After being pressurized at the booster end of the expander, it is divided into two parts. One part is extracted from the middle of the main heat exchanger after being cooled by the main heat exchanger and enters the expander. After being expanded, it returns to the main heat exchanger, and after being reheated, it enters the circulating nitrogen compressor to complete the cycle. The other part is liquefied into liquid nitrogen after being cooled by the main heat exchanger. The liquid nitrogen flows back to the main heat exchanger after being throttled by the valve. After being reheated, it enters the circulating nitrogen compressor to complete the circulation.
The feed nitrogen (0.35Mpa (a), - 30 ℃) is cooled by the main heat exchanger, liquefied, and then enters the liquid measuring cylinder, pressurized to 0.5MPa (a) by the low-temperature liquid nitrogen pump, and then sent to the storage tank for recycling. The liquefying circulating structure with precooling can also be used. The nitrogen extracted from the main heat exchanger enters the refrigerating unit to cool to - 28 ℃ and then enters the main heat exchanger. After Aspen simulation, although the circulating nitrogen gas volume can be reduced, a low-temperature refrigerating unit is added in investment, and the chiller also consumes part of electric energy. In general, there is no obvious advantage
This process is relatively simple and reliable, but the energy consumption is not dominant. The main thing is that two pressure pumps (one for use and one for standby) must be equipped, otherwise the liquefied nitrogen cannot enter the pressurized storage tank, so this process is not the most perfect.
Compared with the above schemes, the second scheme is the most economical and reasonable one, which is not only simple in operation and investment, but also low in operation energy consumption, wide in model selection and convenient in equipment maintenance. Compared with the other two schemes, the inlet pressure of the circulating nitrogen compressor in this process is higher, and the two-stage compression can meet the process requirements when the pressure ratio is small, the equipment investment is small and the maintenance cost is small.
The process organization of this kind of liquefaction filtration device is diversified, but its principle is the same. For the designer, a reasonable process configuration is selected through the comparison of energy consumption, operation and investment.
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