How does cryogenic centrifugal pump perform in boil-off gas handling?

Cryogenic centrifugal pump play a vital role in handling boil-off gas (BOG) in liquefied natural gas (LNG) storage and transportation systems. BOG refers to the vaporization of a small amount of LNG that occurs due to heat leakage into the cryogenic storage tanks. Here's how cryogenic centrifugal pumps perform in BOG handling:

BOG Recirculation: Cryogenic centrifugal pumps are used to recirculate the BOG back into the storage tanks. By recirculating the BOG, the pump helps maintain the pressure and temperature within the tanks, preventing overpressure while also minimizing the loss of valuable LNG.

Re-liquefaction: The BOG is primarily composed of natural gas vapor, which can be re-liquefied and returned to the liquid state by lowering its temperature. Cryogenic centrifugal pumps transfer the BOG through a heat exchanger, where it is cooled down by heat exchange with LNG or other cooling mediums. This process re-liquefies the BOG, returning it to the storage tank as liquid.

Pressure Control: BOG handling pumps assist in controlling the pressure within the LNG storage tanks. By efficiently re-liquefying the BOG, the pumps prevent the pressure from rising to unsafe levels, ensuring the structural integrity of the tanks and minimizing the risk of ruptures or accidents.

Efficiency Improvement: The re-liquefaction of BOG through cryogenic centrifugal pumps helps to improve the overall efficiency of LNG storage and transportation systems. It reduces the energy loss associated with the vaporization of LNG and preserves the stored LNG for its intended use.

Minimizing Emissions: Handling BOG effectively using cryogenic centrifugal pumps reduces the release of natural gas emissions into the atmosphere, contributing to environmental and safety goals.

Continuous Operation: Cryogenic centrifugal pumps are designed for continuous operation, ensuring a consistent handling of BOG as it is generated. This continuous recirculation and re-liquefaction process help maintain the LNG storage system's stability and performance.

It's important to note that the design of cryogenic centrifugal pumps for BOG handling includes features to prevent heat ingress, which could lead to vaporization. These pumps are typically made from materials with low thermal conductivity and are insulated to minimize heat transfer into the pumped BOG. Additionally, they are equipped with reliable sealing mechanisms to maintain the low-temperature environment required for effective BOG re-liquefaction.

Cryogenic centrifugal pumps are essential in efficiently managing and re-liquefying boil-off gas in LNG storage and transportation systems. Their role in maintaining pressure, temperature, and the integrity of storage tanks contributes to the overall safety and efficiency of the LNG supply chain.