Why we need biogas flow meters?

At present, the biogas market is very active and is developing very rapidly. Biogas has many uses, such as using biogas as a vehicle fuel, or using biogas to generate electricity and heat in a cogeneration plant. For biogas production equipment, we also need to monitor biogas flow rate, the fermentation temperature and digesters pressure to ensure the safety and proper operations.

Purpose of biogas metering

• In the process of biogas production and usage, the main purposes of measurement biogas flow rate are as follows:
• Provide reference data for biogas stations: The purpose of installing a flow meter at a biogas supply station is to provide basic data for the scheduling and control of biogas.
• Detecting the efficiency of the fermenter or landfill: Know the efficiency of the fermenter through the biogas flow sensor. If the flow has unexpected fluctuations, you can check the condition of the fermenter in time.
• Control the combustion efficiency of the boiler: When the biogas boiler is burning, it is necessary to understand the flow rate of the biogas to control the ventilation of the boiler. If the ventilation is too large, the furnace temperature will be lowered; if the ventilation is too low, the gas cannot be fully burned to cause waste and pollution.
• Control greenhouse gas emissions: CH4 and CO2 in biogas are greenhouse gases; CH4 is a greenhouse gas that is more harmful than CO2.
• Civil biogas metering charges: civilian users install gas flowmeters mainly for custody transfer, management departments for cost accounting.

Difficulties in biogas flow measurement

Biogas is a gas that is very difficult to measure. It has the following technical characteristics:

• (1) The pressure is extremely low: the original biogas coming out of the fermenter usually does not exceed 0.1 kg (10 kPa).
• (2) Component change: Biogas is composed of a variety of mixed gases, and the gas production materials are different, and the biogas components generated may also fluctuate greatly.
• (3) Large fluctuations in flow: With the changes in the raw materials, bacteria, temperature fluctuations, etc., the produced biogas flow will also vary greatly, so the flowmeter is required to have a larger turndown ratio.
• (4) Water vapor: Biogas is produced by biomass fermentation, and the water in the biomass is brought into the biogas, so the biogas usually contains saturated water vapor.
• (5) Corrosive: Biogas usually contains H2S. Although the content is low, H2S will form corrosive hydrogen sulphate after it encounters water vapor, which has great corrosion hazard to the metering components.

Biogas metering technology

At present, there are several biogas flow metering technologies that have been widely used in biogas, including thermal mass flow meters, turbine flowmeters, vortex flowmeters, orifice flowmeters, and ultrasonic gas flowmeters. However, due to the low biogas pressure, large changes in the flow rate of biogas components, strong corrosiveness, and viscous impurities, these flow metering techniques also have some application problems, which cause troubles for flow meter stability and routine maintenance.

• Current we often recommend Thermal mass flow meter for biogas flow measurement due to below prominent advantages
• It does not need any external temperature pressure and temperature compensation to have mass flow measurement.
• Thermal mass flow meter has large turn down ratio which can reach to 100:1; it can detect low biogas flow.
• It can measure low pressure gas.
• Gas flow sensor material is 316 stainless steel which for slightly corrosive biogas measurement.
• Digital display to show instant and total biogas flow,also for easy configurations.
• 4-20mA, pulse, RS485 and Hart Protocol is intended to different control purposes.
• Insertion type available for large pipe sizes.

Silver Automation Instruments supply good quality and economical biogas flow meters, welcome to contact us for more information.