Desulfurization is the most difficult par for all biogas engineering projects. Normally Chemical Scrubber costs many NaOH and additives, while Dry Type Desulfurization has to replace the filling mass regularly and cost many manpower.
CAMDA has completed more than 600 projects for Biological Desulfurization (BDS). Using microbial metabolic principle without consuming any chemicals, BDS has proofed its low operating cost and the Best Practice Technology.
CAMDA manufacturers the big PP-H tower and packing materials in China to reduce the cost. The complete system including all pumps, valves, piping, instrument and control unit are still manufactured in German workshop to ensure the quality. The experienced project management team in China have learned the knowledge of special bacterial, so are able to provide installation and start-up service smoothly in China and Southeast Asia region.
A certain amount of air is introduced into the biogas. Then the mixture of raw gas is passed through reactor for removal of H2S. Inside this reactor a big amount of packing materials (more than 10,000 pieces) are installed to provide a big growth area for bacteria. Nutrient and water solution is recycled over the package continuously. In most cases, the nutrient supply can be from natural source or man-made fertilizer i.e. :
• Digested waste water
• Liquid phase of digested sludge or manure
• Landfill leachate
• Artificial fertilizer NPK
Special aerobic bacteria (i.e. Thiothrix or Thiobacillus), start growing in the nutrient solution and also on the surface of packing material. The bacterial take up the H2S from the gas and convert it into elemental sulfur and sulfuric acid according to the following chemical reaction:
H2S + 2O2 H2SO4
2 H2S + O2 2 S + 2 H2O
S + H2O + 1.5 O2 H2SO4
The sulfuric acid is neutralized by the buffering capacity of the nutrient solution. It is then removed out of the system with PH control and water level control philosophy.
1 reactor 5 nutrients supply 9 heat exchanger 13 level control nut
2 package 6 dilution water 10 gas analysis 14 air flow contro
3 gas inlet 7 nutrient solution 11 pH control 15 spent nutrients
4 air supply 8 nutrients pump 12 temperature control 16 security flow control
The raw biogas (3) enters the reactor (1) at the bottom and passes through the package from top to bottom. Air (4) is added at the gas inlet point. The air flow is controlled via the residual oxygen concentration or via the biogas flow meter signal (10). In case of no flow or extremely low gas flow, the air supply is switched off by the security flow switch (16). The water and nutrient solution (7) is stored at the bottom of the reactor and recycled through the package continuously by pump (8). The level of the nutrient solution is controlled by the level switches (13). For best activity of the bacteria, the temperature is controlled by the heat exchanger (9) and the temperature sensor (12). The quality of the nutrient solution is controlled by the pH transmitter (11). Waste nutrient solution (15) is automatically discharged while fresh water is injected to system by adding nutrient supply NPK886 (5) and also dilution water (6).
• High efficiency :up to 99%
• High scope :up to 1.5% (15000ppm) inlet
• Low cost :the lowest operating cost ccompared with other process
• High security :multiple security devices
• Fully automatic :automatic operation
• Easy operation :easy maintenance work
• Flow range :50 - 5,000 Nm³ / h
• H2S inlet :500 - 15,000 ppm
• Removal efficiency :90% - 99%
• Inlet temperature :25 - 35 ℃
• Gas pressure :15 - 50 mbar
• Ambient temperature :-30 - + 50 ℃