Biogas enters the gas chamber formed by the inner membrane, which rises as the stored gas volume increases. When downstream equipment draws gas, the inner membrane lowers as the stored volume decreases. An air blower supplies air to the space between the inner and outer membranes, keeping the outer membrane inflated so it maintains its shape and protects the gas chamber. The air pressure control system regulates pressure between the membranes, helping keep the biogas pressure relatively stable within the design operating range.
A freestanding gas holder typically consists of an outer membrane, an inner membrane, and a bottom membrane. The bottom membrane and the perimeter anchoring and sealing assembly form a gas-tight base. A tank-mounted gas holder is installed on top of the tank, where the inner and outer membranes are secured and sealed to the tank rim. The headspace above the liquid level communicates with the gas chamber beneath the inner membrane.
The gas holder’s operating pressure is determined by the pressure losses in the project piping and the inlet pressure requirements of downstream equipment. If a boiler, combined heat and power (CHP) unit, or biogas upgrading system requires a higher inlet pressure, a biogas booster can be added to the supply system.
A freestanding gas holder is installed on a separate foundation and connected to the anaerobic digesters, gas treatment equipment, and downstream users through the biogas piping network. This arrangement is suitable when several digesters share a common storage buffer or when an existing plant needs additional storage capacity. A separate foundation also gives plant designers flexibility to position the gas holder around site roads, piping routes, and maintenance access.
A tank-mounted gas holder can be installed directly on top of an anaerobic digester, combining digestion and gas storage in one footprint and saving the space required for a separate gas holder. When the gas holder is paired with a glass-fused-to-steel (GFS) bolted tank, Qingdao Haiyue can coordinate the tank diameter, top-rim anchoring, sealing interfaces, and nozzle locations during the design stage. For a retrofit, the tank-top connection details and structural load-bearing capacity should be verified before the installation design is finalized.
Both configurations can also be used at the same plant. Tank-mounted gas holders collect and buffer biogas at individual digesters, while freestanding gas holders provide centralized storage and help balance plant-wide supply and demand.
Gas holder sizing depends on the cumulative difference between biogas production and consumption over time. For example, if a plant generates electricity during the day and shuts down its CHP unit overnight, the biogas produced overnight must be stored for use when the unit restarts. Two plants with the same average daily biogas production may need different storage capacities if their generation schedules or gas demand profiles differ.
Qingdao Haiyue determines the required usable gas storage volume based on average daily and peak biogas production, downstream gas consumption schedules, equipment start-up and shutdown plans, and maintenance requirements. If equipment must continue operating through a specific maintenance window, the available gas supply must be checked against actual demand throughout that period. Local wind and snow loads, ambient temperature, biogas composition, and available installation space also affect the choice of membrane materials, anchoring structures, and auxiliary equipment.
Gas holder operation depends on the coordination of air blowers, pressure monitoring, stored gas volume monitoring, pressure protection devices, and downstream gas users. When the stored gas volume falls below a preset threshold, the control system can reduce downstream gas consumption or initiate an interlocked shutdown, according to the project’s control settings. If the gas holder is nearly full and downstream equipment cannot use the surplus biogas, a biogas flare can handle the excess. The design should define the conditions for normal gas use, flare activation, and pressure protection.
Depending on the feedstock and intended use of the biogas, Qingdao Haiyue can supply GFS bolted tanks, anaerobic digestion systems, double-membrane gas holders, desulfurization and dehydration equipment, biogas flares, and CHP units. Customers can purchase a single gas holder or work with Qingdao Haiyue from the tank and gas holder selection stage to coordinate piping interfaces, control signals, installation, and commissioning.
If you are planning a new biogas project or expanding storage capacity at an existing plant, send Qingdao Haiyue your estimated biogas production, gas-consuming equipment and operating schedules, tank dimensions, and project location. We can use this information to assess the suitable gas holder configuration, required usable storage volume, and scope of supply.
