Centrifugal pumps play an important role during the production of liquefied gases as well as their transport, storage, and distribution. Liquefied gases offer the advantage that - unlike in the gaseous state of aggregation - they can be relatively easily transported and stored. Liquefaction is achieved by compression or cooling. In case of corresponding demand, the liquefied gas then undergoes regasification due to released pressure and can be fed to the consuming units via pumps.
A distinction is made between LPG gases (liquefied petroleum gas) and LNG gases (liquid natural gas). Agents of LPG gases are, above all, butane, propane, and their derivatives, which are used as fuel gas and fuel for heat generation and arise both during oil and gas extraction as well as in crude oil refineries. LNG gas or also liquefied natural gas, mainly methane, is also used as fuel gas.
The DIN 51622 lists all other liquefied gases. For example, ammonia (NH3) is used in refrigerating systems, or carbon dioxide (CO2) is used in the process industry and in beverage production.
EDUR offers liquefied gas pumps, which are used for production processes, transport, storage as well as for the distribution of liquefied gases. A precondition for this wide set of applications is the gas conveying capability of the centrifugal pumps guaranteed by the EDUR-design. Due to the low NPSH (Net Positive Suction Head) values, the pumps ensure an operation free of cavitation and thus full conveying capability both in suction mode and intake mode. The EDUR-liquefied gas pumps are executed according to Atex: various adjusted sealing Systems, such as double mechanical seals or hermetical magnetic couplings, ensure safe operation.
The core task of liquefied gas pumps in production processes is the gas conveyance or the enrichment of liquids with gases. In the beverage industry, for example, mineral water and soft drinks are regularly enriched with carbon dioxide (CO2). Other liquefied gases are used in water and wastewater treatment. Refrigerating plants also operate with liquefied gases.
Depending on the available technical capability, the liquefied gas is transported from the production facilities into the refineries:
The target of the transports are either large warehouses or traders and finally the end consumers. In each process, the requirements for the pump technology differ depending on the liquefied gas. With LPG, tank trucks are loaded in terminals, for instance. Liquefied gas pumps must comply with the local regulations in terms of explosion protection, which is specified by the ATEX standard in the European region. Refueling takes place using gas pendant cords so that the pumps only need to bridge the line resistance. Apart from stationary pumps with correspondingly high performances, EDUR also offers vehicle pumps equipped with hydraulic motors. The low noise emission enables to pump off the tank trucks also at night and during rest times. Characterized by high efficiency, the pumps work silently, claim only very little assembly space, and can also cope with more unfavourable conditions due to their gas conveying capability.
When pumping off tank trucks without a pendant cord, higher pump pressures are needed. EDUR-multistage centrifugal pumps fulfill this requirement and the regulation of the speed can be adjusted depending on the counter pressure in the liquefied gas tank of the final customer.
Liquefied gas storage of refineries and energy suppliers takes place in tank farms and terminals in aboveground tanks or in underground tanks. With aboveground storage, the liquefied gas pumps often have inlets from the tank and do not need to suck. The good NPSH value of EDUR-liquefied gas pumps ensures operational safety even if the inlet conditions are not ideal. Unloading of the tanks is supported by the gas conveying capability of the EDUR-pumps.
When storing liquefied gases or fuels in an underground tank, the self-priming ability of the centrifugal pump is needed in addition to the good NPSH value. Should the liquid column disrupt on the suction side, the pump generates negative pressure with the fluid remaining in the interior space. Using this negative pressure, the pump draws the liquid column up to the suction side of the pump and vents it so that conveyance will be taken up again.
Gas trading towards the final consumer is conducted either via a tank at the building or via classical gas bottles. These bottles are filled by gas traders in corresponding systems and brought into circulation by liquefied gas pumps.