According to a
biogas liquid reducing treatment and a
biogas collaborative purification
system and purification method disclosed by the present invention, by adding
plant ash into the
biogas liquid,
alkalinity and pH value of the biogas liquid are increased, biogas liquid COD and
suspended matter concentration of the biogas liquid are reduced, and by film decompression concentration technology,
ammonia is recovered from the biogas liquid and biogas liquid concentration is performed, and therefore an objective of
ammonia nitrogen content control in the biogas liquid and biogas liquid reducing treatment is achieved. In the biogas liquid film decompression process,
ammonia enrichment can be further achieved, biogas can be desulfurized and decarburized at the same time by using enriched ammonia from the biogas liquid, and therefore preliminary purification of the biogas is achieved, then
ammonia gas (NH3) entrained in the biogas is washed and CO2 in the biogas is further absorbed by using concentrated biogas liquid with high pH value, and therefore the biogas is purified and
nitrogen content in the biogas liquid is controlled. The present invention can realize the biogas liquid reducing treatment, increase the
nutrient content in the biogas liquid, and ensure that the
ammonia nitrogen content is in a reasonable utilization range; and meanwhile the present invention is relied on low grade energy, and can therefore reduce costs.