| 摘要 |
PROBLEM TO BE SOLVED: To provide a biogas producing system in which circulating water can be neutralized without separately preparing a neutralizing agent.SOLUTION: The biogas producing system is provided with: a fermentation tank 3 which produces biogas 1; and a biodesulfurization tower 7 in which hydrogen sulfide in the biogas is oxidized by sulphur-oxidizing bacteria at a carrying part 8 to carry out biodesulfurization treatment. The circulating water 15 sprinkled from an upper part of the carrying part 8 includes sulfuric acid produced by contact with the sulphur-oxidizing bacteria and is discharged from a bottom part of the biodesulfurization tower 7 to a circulating liquid tank 19, and air is supplied to the circulating liquid tank 19. The circulating water 15, in which oxygen in air is dissolved, is circulated from the carrying part 8 via a circulation line 17. Further, the biogas producing system is provided with an ammonia desorption tower 11 which desorbs ammonia by supplying air to a fermentation liquid from the fermentation tank 3. Desorbed ammonia-containing air 13 is introduced from a lower part of the biodesulfurization tower 7 to the carrying part 8 via a supply line 12 to neutralize sulfuric acid. Further, oxygen is supplied from an upper part of the carrying part 8 to the circulating liquid tank 19 and moreover, oxygen from an air supply part 31 and oxygen from the desorbed ammonia-containing air 13 are supplied from a lower part of the carrying part 8. |
