Biogas and biomethane from methanization

SOCLEMA offers solutions for sampling biogas and biomethane from methanization: sampling probes, cyclone separators, membrane separators, regulators, traced tubing, etc.

As a specialist in industrial sampling, SOCLEMA reminds you of the guidelines for biogas and bio-methane sampling.

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The sampling equipment used for renewable gases from methanization is virtually identical to that used for natural gas. The equipment is proportioned according to pipe size (smaller) and gas flow rate (lower).

Sampling rods or probes

For liquid-free lines with temperatures well above the dew point, any type of rod is suitable. For lines where temperatures are close to the dew point, a specific rod is required to avoid problems associated with condensation and liquids entrained in the gas flow. To avoid altering the composition of the gas, liquids must be separated at source temperature and pressure.
The most basic sampling tube is a straight sampling tube. The other type of sampling tube frequently used in the gas industry is the expansion sampling tube. It is frequently used with continuous analysis systems. Expansion takes place at the end of the rod, through which the gas flow passes. The temperature drop is compensated by the thermal mass of the gas flow. We recommend installing the probe in the first third of the pipe. For pipes with a diameter of more than 30 cm, it is necessary to install the rod at least 10 cm from the wall. The sampling tube must be fitted with a suitable valve system, enabling the sampling line to be disconnected from the process line. It can be permanent or temporary.

Tubes for sampling lines

Sampling lines should be as short as possible and with the smallest possible diameter, without excessively reducing flow. The flow rate in the lines must be chosen so as to have a reduced response time.

Filters, membranes and separators

Filters and membrane separators may be necessary to obtain a clean, dry sample. It must be remembered that these systems must not alter the representativeness of the sampled composition. In general, separators are not recommended in sampling systems, but they can be used to ensure that no liquid enters the analyzer or sample cylinder. The pressure and temperature of these devices must match the pressure and temperature of the source to avoid altering the composition of the sample during the sampling process.

Safety valves

Service valves should be included at the inlet and outlet of the system; shut-off valves should be ball valves; needle valves are for flow control and regulation; relief valves should be installed to protect equipment and components. To minimize potential leakage points, the number of valves and fittings should be kept to a minimum. Elbows should be avoided; bent tubes are preferable. Valves with integral fittings are generally preferable.

Pressure regulators

In order to supply the analyzer with gas at the appropriate pressure, a pressure regulator is often required at the beginning or end of the line. Regulators are preferably made of stainless steel or PTFE. Due to the Thomson-Joule effect, the temperature drops by an average of 1°C every 2 bar, potentially creating condensation. It is usual to prevent this phenomenon by heating to compensate for the drop in temperature. The amount of heat required depends on gas composition, expansion, pressure and temperature, flow rate...

Heating units

Heating elements can be installed on the sampling probe or lines. They must be of the self-limiting type and comply with the electrical standards of the areas where they are used.