A BIOTECHNOLOGICAL PROCESS FOR REMOVAL OF HYDROGEN SULPHIDE FROM BIOGAS

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A BIOTECHNOLOGICAL PROCESS FOR REMOVAL OF
HYDROGEN SULPHIDE FROM BIOGAS

• ARISCOE BIOSCRUB PROCESS
• D. R. Ranade and S. A. Dighe
• AGHARKAR RESEARCH INSTITUTE
• A. J. Apte
• SINHGAD COLLEGE OF ENGINEERING

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Biogas

• A gaseous fuel
• Produced microbiologically from organic waste in
  process called Anaerobic Digestion of Waste
• Mainly cattle dung , 3 Millions biogas plants
  (household)
• A mixture of Methane (60), carbon dioxide
  (40), traces of moisture and hydrogen sulphide
• Calorific value 50 less than LPG
• Uses Cooking gas, Lighting, Diesel engine,
• Electricity generation
• An important renewable energy source in India

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Industry, Wastewater and Biogas

• Industrial wastewater - treatment prior to safe
  disposal on land or in water course
• Biological treatment Aerobic
  Anaerobic
• Anaerobic treatment- advantageous over aerobic
• Produces biogas as one end product
• Industries -Alcohol distillery, Diary, Pulp
  Paper Mills, Starch Processing, etc - prefer
  anaerobic treatment.
• Sewage sludge if digested anaerobically produces
  biogas

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Alcohol Distillery

• 1 liter alcohol distilled ? 15 liter wastewater
  
• Anaerobic Digestion
• 1 liter wastewater ? 15 liter of biogas
• Per liter of alcohol distilled ? 225 liter
  biogas
• No. of distilleries Nearly 270, Maharashtra
  gt100.
• Total alcohol production in MS 1000 kiloliter
  /day
• Wastewater 15,000 M3 /day
• Biogas production 225,000 M3/day
• Electricity Generation 1 M3 Biogas ? 2KWh Total
  electricity 450,000 KWh

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Are distilleries producing electricity?

• NO
• Why Not?
• Presence of Hydrogen Sulphide in Biogas
• Causes corrosion in genset
• Why H2S is produced during A.D.?
• Distillery waste contains 6 to 10 g Sulphate
• per liter
• Sulphate Reducing Bacteria (SRB)
• SO--4 ? S--
• Can we inhibit SRB? NO

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Can H2S be removed from Biogas?

• Removal of H2S from Biogas is possible
• Physical Methods Absorption in water, adsorption
  in activated charcoal/peat
• Large quantity of scrubber, high cost, useful
  for low conc.
• Chemical Methods Alkali, Alkaloamine, ferric
  oxides, Zinc salts
• High cost, chemical waste generation

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Biological Methods

• Circulation of activated sludge
• Soil filter
• Photosynthetic bacteria Chromatium, Chlorobium-
  requirement for light
• Xanthomonas sp.- low specific removal rate
• Thiobacillus species

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ARISCOE BIOSCRUB Method

• Uses bacterial culture - Thiobacillus -
  specifically isolated
• A single reactor- fixed film type
• Uses specially developed packing material -
  combination of plastic/raschid rings and biomass
  derived activated carbon
• Continuous recirculation of nutrients-inorganic,
  low cost

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Laboratory Testing Completed

• Selection of strain
• Fixed film testing
• Fixed film on biomass derived activated carbon
• Gas residence time for adequate removal
• Optimum temperature and nutrients

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Results of Testing of Fixed Film on Activated
Carbon

• Lots of tests at 4 lit/hr
• Consistent removal of 95 H2S
• Best Removal of 75 removal at fraction of a
  minute Gas Residence Time at 40 lit/hr gas flow
• High level of confidence on GRT required for a
  given removal of H2S

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Economics Pay-back Period

• The capital cost of 300 M3/hr plant is expected
  to be Rs 25 lakh
• The operating cost is expected to be about 10
  paise per cubic meter of gas
• The value addition by generating electricity is
  expected to be Rs 3 / M3
• Pay-back period will be 2500,000/2.9/300 or 2900
  hours of operation about 5 months

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Environmental Aspects

• The process is eco-friendly
• The exhausted nutrient solution is the only waste
  generated and it meets the norm if mixed with
  other effluent
• (the only parameter to be adjusted is pH )
• Recovery of sulfur is possible

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Size Range of Plant

• Small semi-commercial plant sized for 400 kWe or
  200 M3/hr biogas
• Largest comfortable scale-up 500 M3/hr
• Smaller than 200 M3/hr may be expensive due to
  relative cost. But is feasible
• Smaller than 10 M3/hr not worthwhile

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Project Costs

• Setting-up of plant and machinery
• Support Facilities of Laboratory etc.
• Technology Purchase Cost
• Professional Consulting prior to erection and
  during testing
• Operating manpower for testing

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Sources of Finance

• Commercial Finance from IDBI,ICICI etc
• MNES subsidy/grant
• Technology Development Board

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Contact Dr.D.R.Ranade

• Office Address Agharkar Research
• Institute
• G.G.Agarkar Road,
• Pune 411004
• Phone No. (Off.) 020 - 5653680
• (Res.) 020 - 5443944
• Fax No. (Off.) 020 - 5651542
• E-mail drranade_at_vsnl.com

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