DEAR Biogas purification unit.The purpose of purging after heating the fractionator is to remove the mechanical impurities in pipes and vessels. The blowing out steps are as follows: the preparation before blowing out: close the main inlet valve of heating air and all heating valves, open the blowing out valve of oil-water separator of purifier at the same time, loosen the ejector rods of inlet and outlet valves of expander, close the on-6 valve, pull open the stem of joint-1 valve, open the blowing-1 valve, blowing-2 valve and high pressure gauge valve, and close the blowing out valve of oil-water separator of purifier;DEAR Biogas purification unit.Because krypton and xenon are very little in the air, the volume fraction of krypton is about 1 × 10-6, and the volume fraction of xenon is about 0.08 × 10 - due to the high boiling point of krypton and xenon, they are always mixed with oxygen in the air separation unit, so the oxygen product should be used as raw material (only 0.1% ~ 0.3% of krypton and xenon), and then the crude krypton (40% ~ 80% of krypton and xenon) should be prepared, and finally the krypton and xenon should be separated.
DEAR Biogas purification unit.Continue to complete the process before shutdown. If the shutdown time is long (more than 24h), the molecular sieve adsorber should be recycled for one cycle; according to the shutdown time, the cold end temperature of the main heat exchanger and the main cold liquid level, the start-up steps of the air separation unit should be determined according to the regulations.DEAR Biogas purification unit.When the air volume is reduced or the product throughput is increased, the temperature difference at the cold end will be reduced, the temperature difference at the hot end will be enlarged, and the temperature at the outlet of the circulation (or the middle extraction) will be reduced. Therefore, when increasing the air throughput or reducing the product throughput, we should pay attention to the expansion of the temperature difference between the cold end and the middle; when reducing the air throughput or increasing the product throughput, we should pay attention to the cold loss at the hot end. If necessary, it should be supplemented by circulation regulation.
DEAR Biogas purification unit.In practical operation, the temperature balance between two groups is mainly adjusted according to the temperature difference in the middle of two groups of cold accumulators or two groups of switching heat exchangers. The middle temperature difference between groups is generally controlled within 10 ℃. In addition, the actual control in the operation is often the temperature of the air at the outlet of the circulation or the middle outlet, no matter whether it is the actual middle temperature or not.The amount of rising steam in the lower tower and the amount of condensation in the condensing evaporator are reduced, which also has a certain impact on the distillation condition of the tower; after the switching of the cold accumulator (or switching heat exchanger), the backflow sewage nitrogen vaporizes the deposited liquid air due to the reduced pressure. The latent heat of vaporization should be absorbed during the evaporation of liquid air, which makes the temperature of backflow sewage nitrogen lower, which expands the temperature difference at the cold end and is not conducive to self removal;
There is a limit to the amount of water vapor that can be contained in the air. When it reaches a certain value, the content can not continue to increase, and the excess will precipitate in the state of liquid water. This maximum allowable content is called saturation content. In our daily life, we can see that in the sealed container, the water evaporates to a certain extent and will not continue to evaporate.DEAR Biogas purification unit.In order to ensure continuous gas supply, more than two adsorption towers need to be used alternately. The method of regeneration can be heating to increase temperature (TSA) or reducing pressure (PSA). This method has the advantages of simple process, convenient operation and low operation cost, but it is difficult to obtain high purity product, and the oxygen purity of the product is about 93%. Moreover, it is only suitable for separation units with small capacity (less than 4000 m3 / h).When the full low pressure oxygen generator starts up, when it comes to the stage of liquid oxygen accumulation, the surplus refrigeration capacity of the expander should be transferred to the tower as far as possible for liquid accumulation. Since all the liquid in the main cooling system of the upper tower comes from the lower tower, in order to accumulate liquid in the main cooling system, the liquefier should be used to provide as much liquid as possible.
