What is a low-pressure wet gas holder?

Low pressure wet gas holder is the simplest and most common gas holder, which is usually used for gas storage. From the structural characteristics, the low-pressure wet cabinet belongs to variable-volume metal cabinet, which is mainly composed of water tank, bell jar, tower section and lifting guide device. At present, the supply scale of biogas is not large, and the gas storage capacity is not much. When the gas storage capacity is less than 3000m3, a single gas storage tank can be used, as shown in Figure 8-2 1.

Figure 8-2 1 Single Low Pressure Wet Gas Holder

Working principle of low-pressure wet gas holder: when biogas is input into the gas holder for storage, the bell jar and tower section placed in the water tank rise in turn (the diameter changes from small to large); When the biogas in the gas storage tank is led out, the tower section and the bell jar fall into the water tank in turn (the diameter is from large to small), and the biogas in the tank is isolated from the atmosphere by water seals between the bell jar and the tower section and between the inner tower section and the outer tower section. Therefore, with the rise and fall of the tower section, the storage capacity and pressure of biogas change. Figure 8-22 shows the working principle diagram of a single low-pressure wet gas holder.

Figure 8-22 Working Principle Diagram of Single Low-pressure Wet Gas Holder

(a) Working state of empty cabinet (b)

At present, the low-pressure wet gas holder has mature construction and use technology, simple structure, stable gas storage pressure, safe and reliable operation, convenient management, and the required pressure for transporting biogas. The following aspects should be paid attention to in the operation and management of low-pressure wet gas holder.

① Lifting position of gas holder bell jar. When calculating the maximum storage capacity of gas holder, the problem of gas expansion caused by temperature rise should be considered; When the air storage capacity is the lowest, avoid sticking the bell jar on the bottom of the sink to prevent the temperature from falling, which will cause the negative pressure in the cabinet to collapse the top of the range hood. Therefore, it is necessary to leave a safety margin for its lifting position, and the highest and lowest limits should be considered when designing and manufacturing.

② Prevent the water seal from freezing. In order to prevent the gas holder wall from freezing and the water and water seal in the gas holder from freezing, the water temperature should be kept at 5℃ in winter, and appropriate warm-keeping measures should be taken in the northern region, such as introducing boiler steam or circulating water to prevent freezing.

③ Prevent air leakage. Check the water level in the water tank and water seal regularly to prevent methane leakage due to insufficient water seal height.

(4) Prevent fire. Fences should be built outside the gas holder, and kindling is strictly prohibited in the station. A lightning rod should be installed on the gas holder, and its grounding resistance should be less than 10 ohm.

⑤ When draining the water tank, the empty valve must be opened first, so as to avoid negative pressure in the tank and cause the cabinet to collapse. In addition, the gas storage tank should be built in the area hit by typhoon, and semi-underground type should be adopted as far as possible to reduce the height of the tank.

⑥ The construction of gas holder shall be carried out by construction personnel who have received technical training. After the gas holder is put into operation, it should be managed by specialized personnel in accordance with the operating procedures.