New pumps benefit biodiesel leader Argent
11 Apr 2008
The WCB Universal II pumps handle glycerine-like product (GLP) and biofuel oil (BFO) - the residue of the raw fatty acid methyl esters (FAME) produced in the company's distillation process. The basic raw material used is tallow and used cooking oils and the total production cycle from intake to finished product takes 24 hours.
Argent Energy's processing of biodiesel from tallow and used cooking oils can be demanding for pumping equipment, notes Axflow. During certain stages of the production cycle the semi-processed media can prove to be problematical, while the possibility of the transfer pumps becoming clogged up is a constant threat, the equipment supplier said.
According to Argent Energy, the original pumps installed when the plant was commissioned required frequent cleaning of the rotors as they became blocked up. This was primarily because the quality, nature and solids content of the raw materials used in the process do vary considerably. There was also a problem with the rotors and seals, which being damaged by the aggressive pumped media and its temperature.
The three types of WCB pumps now used at the plant - the Universal II 45, Universal 15 and Universal 18 - operate on the circumferential-piston principle whereby arc shaped rotor wings (pistons) travel in annular shaped cylinders machined in the pump body. The resulting long sealing path reduces slippage and produces a smooth flow of product without destructive pulses or pressure peaks, and without valves or complex parts. For high viscosity fluids, the large fluid cavities of the rotors, together with the large easy entry anti-cavitation ports allow efficient pumping of slurries and liquids containing solids of the nature encountered in biodiesel processing.
With flow rates of 1000-1500l/h, the WCB U45 pumps are used on the GLP acidulation and neutralisation lines where the abrasive nature of the fluid presents a problem. Acidulation is the process used for separation and this involves the addition of a concentration of sulphuric acid into the mix to bring down the ph level. From there the fluid is transferred to a centrifuge and into a neutralisation tank where an alkaline based substance, which also has its own handling issues, is added to bring the pH level back to neutral.
The WCB U15 and U18 pumps are used on the BFO lines immediately after distillation. Argent Energy uses two distillation columns to produce BFO. The two distillation columns clean or separate the heavier phase of the fuel oils to give a lighter phase. The first column splits the heavy phase oil and the second column provides a further split to produce the desired lighter phase BFO. Giving flow rates of 800kph and 400kph respectively, the U18 is used after the first column and the U15 after the second column. Both these pumps have proved to be capable of withstanding both the temperature of heavier phase fuel oil, which can reach 120 degrees C, and its make-up. In addition, the high temperatures involved can lead to material crystallisation has not had any impact on pump performance.
Argent Energy also highlights the ability of the O-rings on the WCB Universal pumps to withstand the temperatures required for the process and the rotors to resist attack. The original pumps were constantly running at 100%, whereas the replacement WCB pumps only operate at between 30 and 40%. After 18 months operation, engineers report that maintenance has been restricted merely to O ring and seal inspection due to fair wear and tear - in contrast to the constant removal of the pump faces and clean out of the rotors required with the old pumps.
