Technical maintenance of a biogas plant consists of tasks that are necessary for its long useful life, and repair works are carried out in cases of breakage of the biogas plant.
Table 15. Daily technical maintenance [8]
Сontrol | Mistakes | Removal |
---|---|---|
gas pressure | gas pressure too high; gas pressure rises, if gas consumption is lower than the production and if the gas storage is full) |
The pressure relief valve malfunctions – it should be cleaned or renewed; |
gas pressure too low; (gas pressure falls, if the consumption (including leakage!) is higher than the production and if the gas storage is empty); |
leakage in gas conducting parts: find out the leakage and seal; |
|
substrate temperature |
temperature too high; | defective heating control system. Check control system and repair or exchange part(s) concerned; |
temperature too low; | defective heating control system. Check control system and other concerned part(s), repair or exchange; sediment layer on the heating surface: remove layer; |
|
gas production | gas production clearly under normal levels; |
biological reasons: temperature, substrate, antibiotics, change of pHvalue; leakage in digester or piping system; blocked gas pipes due to water or alien elements; identify problem and act accordingly; |
strong sludge odor | plant is overloaded or fermenting conditions are suboptimal; |
reduce substrate intake; correct pH-value with adequate means; |
Weekly/monthly (prophylactic) maintenance work• clean gas appliances;
• lubricate movable parts (slides, guiding frame of floating drum plants, taps etc.);
• servicing of biogas-driven engines within the prescribed time intervals;
• maintenance of pressure relief valves and under pressure valves;
• maintenance of slurry agitator / mixer;
• control gas appliances and fittings on tightness and function.
Table 16. Control of functions [8]
Сontrol | Mistakes | Removal |
---|---|---|
water separator | water separator is full; |
empty water separator; |
piping system | no water is collected in the water separator; gradient of the pipes is wrong; |
reinstall pipes in a way that condensation flow leads to the water separator; |
pressure | relief and under pressure valves non-functioning |
clean valves or renew them |
Annual maintenance work
• Complete check of digester and the whole plant;
• Check the plant in respect of corrosion and, if necessary, renew protective coating material;
• Check the gas pipes for gas tightness (pressure check). If necessary, search the leakage and repair the parts concerned. Minor gas leakage is usually undetected during normal operation as it is ’compensated’ by gas production
Monitoring
Monitoring presumes collection of data about operation of biogas plant for:
• determining operational problems;
• determining real economical profitability and payback period of the biogas plant;
• comparison of different substrates and operation methods for optimisation.
The following data should be gathered:
• Quantity and type of substrate, water proportion of diluting substrate.
• Temperature of substrate on different stages of digestion process. When this data is collected regularly the defects on the heating system can be easily determined and prevented.
• Biogas production: the volume of biogas produced is measured by a gas meter located between digester and gas holder and measures of biogas consumed by appliances by gas meter located between appliance and gas holder. In simple plants biogas production can be measured at the time of absence of biogas consumption. Changes in gas production and the speed of these changes allow for a more exact determination of causes of arising problems.
• Electricity and heat production in big plants.
• pH ratio (monthly).
• Daily substrate input portion.
• Hydrogen sulphide content of biogas (monthly).
• Analysis of fertilizing effect of digested sludge (yearly or seasonally) for determining optimal fertilizer quantity to be applied to soil.
• Records of breakages and their causes. Having such records allows comparison of breakages and easier determination of their causes.