The liquid ring pump extracts the biogas from the top of the digester and recycles it to improve the mixing and reaction speed. The working liquid of the pump absorbs and compresses the heat to cool down the biogas, thus keeping the operating temperature basically constant. This has a positive impact on the service life of downstream valves, gas burners and motors, and reduces maintenance costs. At the same time, the cooling function of the working liquid can play the role of the flame cleaner and reduce the expenditure on explosion-proof. The unclean gas is cleaned in the water circle, which is similar to that in the gas scrubber, and part of the gas is dried. The gas is then oxidized and reused in the wastewater treatment process.
How to insist on three ways of vacuum tightness
(1) Reduce the leakage point of the vacuum pump, strengthen the detection method, so that the production of the vacuum pump is under strict monitoring conditions, and strive to minimize the equipment leakage point in the production process. When the air-cooled condenser is produced in the factory, the single tube of each heat exchanger is subject to 0.8MPa air tightness test, and the weld joint between the tube end of the fin tube and the tube plate is subject to penetration flaw detection. After the completion of the assembly of the whole air-cooled heat exchanger, the water pressure test shall be carried out. The air in the air-cooled pipe shall be filled with water, and the air in the pipe shall be exhausted. The pipe surface shall be dry to facilitate the inspection of the leakage point. When the wall temperature of the pipe is close to the liquid temperature, the pressure shall be slowly increased to the planned pressure of 0.15Mpa. After admitting that there is no leakage, the pressure shall be increased to the experimental pressure of 0.18mpa to ensure that it will not be changed for 30 minutes. Then when the pressure drops to 0.144mpa, it must be checked at any time. During the inspection, the pressure remains unchanged, that is to say, the water pressure test is qualified.
(2) Move the equipment quality, check the joint point for flaw detection, and try to reduce the joint point of field equipment as far as possible in planning, so as to reduce the welding amount of field equipment operation as much as possible.
(3) Reasonable selection of vacuum pump:
The amount of air entering the system is not only related to the amount of steam, but also to the tightness and quality of various equipment under vacuum. The compactness of vacuum system is generally determined by the rate of vacuum drop. Welding structure is generally used for all the joints of large-scale direct air-cooled condenser, and water seal structure is used for valves, pumps and other equipment, so that the sealing of the system moves forward greatly and the amount of air leakage is greatly reduced. For units larger than 100MW, the vacuum dropping speed shall not be greater than 0.266kpa/min. According to the rules of some projects that have been constructed in China, the partial air tightness test is carried out for the air condenser and its system, and the test pressure is 0.04MPa (0.4kgf / cm2). The test specification is: the 24-hour uniform pressure drop partial test is controlled within 0.2kpa/h (2mbar / h), and the system pressure drop is controlled within 0.4kpa/h.
Three parameters are needed to select the type of vacuum pump
(1) Air leakage
(2) Volume of vacuum system
(3) Reach the time required for vacuum