COPY RIGHTS : TO AVOID COPYRIGHT VIOLATIONS, ALL POSTS ARE SHOWN ALONG WITH SOURCES FROM WHERE ITS TAKEN. PLEASE CONTACT ME IN MY EMAIL SALEEMASRAF@GMAIL.COM , IF YOU ARE THE AUTHOR AND YOUR NAME IS NOT DISPLAYED IN THE ARTICLE.THE UNINTENTIONAL LAPSE ON MY PART WILL BE IMMEDIATELY CORRECTED.

I HAVE SHARED ALL MY PRACTICAL WATER TREATMENT EXPERIENCES WITH SOLVED EXAMPLE HERE SO THAT ANYBODY CAN USE IT.

SEARCH THIS BLOG BELOW FOR ENVO ,COMPACT STP,ETP,STP,FMR,MBBR,SAFF,IRON,ARSENIC,FLUORIDE,FILTER,RO,UASB,BIO GAS,AERATION TANK,SETTLING TANK,DOSING,AMC.

SEARCH THIS BLOG

Sunday, May 02, 2004

STARTING UP A BIO GAS PLANT


POST NUMBER :08   Date : 02/05/2004

BIO GAS PLANT PROCESS DESCRIPTION:

CRUSHER(less than 7mm particle size)----thermophilic primary digester(Temp 55 degree C)---Mesophilic Anaerobic Digester(37 Degree C and pH 7)---Manure Pit

Highest methane yield is observed in Mesophilic Anaerobic Reactor(37 Degree C) fed with  food waste and manure.

The segregated wet garbage (food waste) is brought to the plant site in bins and containers. It is loaded on a sorting platform and residual plastic, metal; glass and other non-biodegradable items are further segregated. The waste is loaded into a Waste Crusher along with  water, which is mounted on the platform. The food waste slurry mixed with  water is directly charged into the Primary digester from the crusher. 

This primary digester serves mainly as hydrolysis cum acidification tank for the treatment of suspended solids. For breaking slag compressed air is used for agitation of slurry. Compressed air will also help in increasing aeration since bacteria involved in this tank are aerobic in nature. Temperature at 55 degree C is maintained using heat exchanger (Hot water jacket), heater or steam from boiler.  The tank is designed in such a way that the fresh slurry entering the tank will displace equal amount of digested matter into the main anaerobic digester tank.

Main anaerobic digester tank serves as a methane fermentation tank and BOD reduction takes place here. pH is maintained at 7 with a auto dozer using lime solution . Content is mixed mechanically or by recirculation of bio gas produced. The treated overflow from this digester is connected to the manure pits. This manure can be supplied to farmers at the rate of 4-5 Rs. per Kg. Alternatively municipal gardens and local gardens can be assured of regular manure from this biogas plant. The Filtrate from manure pit is recycled back to crusher .

The biogas is collected in a dome (Gas holder) is a drum like structure, fabricated either of mild steel sheets or fiber glass reinforced plastic (FRP) or gas baloon. It fits like a cap on the mouth of digester where it is submerged in the water and rests in the ledge, constructed inside the digester for this purpose. The drum collects gas, which is produced from the slurry inside the digester as it gets decomposed and rises upward, being lighter than air. 1" GI piping will be provided up to a distance of 50 m from the Biogas plant. Biogas burners will be provided. The biogas can be used for cooking, heating and power generation purpose after proper  purification.

STARTING UP A BIO GAS PLANT:

Step One: Development of bacteria culture.  Fill up  the main anaerobic digester tank with cow dung diluted with water in 1:1 ratio fully . Add jaggery (GUR) 5% of capacity of plant ( a 100kg per day food waste plant will require around 5 kg jaggery (GUR). Left to ferment for  three days. The cow dung slurry will start forming gas after three days. 

Step Two : Checking for leaks. Wait for a three four days before feeding the system with food waste. Before that check for any leaks for bio gas.

Step Three: Food waste feeding.Feed the crusher with  water and food waste. Subsequently, food waste will be diluted with filtrate water from manure pit and used to feed the pre digester of the system. The ratio of food waste and  water or filtrate water is 1:1.
A heat exchanger (Hot Water Jacket) maintain  temperature in the pre digester at 55 degree C. The heat exchanger can be either internal or external.

DO NOT USE eggshells, Onion peels or left-over bones in this system as they will affect the efficient functioning of the system

Step Four: Initial production of gas will consist of oxygen, methane, carbon di oxide and some other gases and will not burn. These gases can be released to the atmosphere by opening the ball valve at least three / four times at a gap of three days each.

Subsequent gas will consist of about 70 to 80 percent methane and the rest carbon di oxide, which can be used in a single bio-gas burning stove or a Bunsen burner.

Either a mechanical mixer can be used, or the bio gas can be recirculated for mixing of the content of anaerobic digester.

Step Five: Digested slurry  removed from the top of the  the manure pit, which can be collected, diluted and used as organic manure.

Step Six: The  value  of    pH  of  the  anaerobic digester  should  be ideally kept  at 7 for optimum production of biogas. Make a slurry of lime by adding one kg lime with 10 liter of water and add it into the anaerobic digester chamber to make pH 7. Check with pH paper whether the pH is 7 or not regularly.


Hazards: Methane in a concentration of 6 to 15 percent with air is an explosive mixture. Since it is lighter than air, it will collect in rooftops and other enclosed areas. It is relatively odorless and detection may be difficult. Extreme caution and special safety features are necessary in the digester design and storage tank