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Down in the depths of the Peak District resides the largest battery breaking and recycling plant in the UK. HJ Enthoven & Sons recycles over 100,000 tonnes of industrial and automotive lead-acid batteries annually, and is one of the most environmentally responsible and efficient plants for lead recycling in the world. Given the toxic nature of the batteries, the Company is very much aware of its environmental responsibilities and has invested considerable resources into ensuring that the local environment is not affected by its operations.

The processes of breaking up batteries and recovering materials involve crushing the complete battery and then separating out all the individual metals, plastics and chemicals. The first stage involves crushing the batteries in a high speed hammer mill, a process that breaks the components into small parts for subsequent separation. The next stage of the process involves the crushed parts passing through primary and secondary rotating filter screens to separate acid, plastic and metallic fractions. In order to optimise the overall separation process and the removal of the lead sulphate sludges for recovery it is necessary for the internal surfaces of the screens to be continuously cleaned by internal high pressure jet-washing sprays. This can lead to the external surfaces of the screens becoming blocked and without effective high pressure washing of the external surfaces, HJ Enthoven cannot achieve the required levels of material separation required.

Historically, external screen washing was performed using a single high pressure pump to feed the spray nozzles. However, the original and subsequent pumps used were not up to the demands of the breaking process and required frequent attention and maintenance. In 2005 a major review was set up to look at these problems and Cat Pumps was requested to provide important information on spray nozzle performance curves.

 “In many respects, we took on a consultancy role,” says Cat Pumps UK general manager Brian Hubbard. “Over a period of several months, we undertook an evaluation of the pumping requirements in order to provide HJ Enthoven with a number of alternative solutions that addressed the many issues that emerged.”
 
After much consideration, HJ Enthoven elected to work with Cat Pumps as it had demonstrated a clear understanding of the importance of the spray cleaning process to the breaking plant and had shown where cost savings could be made. It was in late 2007 that the go ahead was given to design a 'ready to use' skid based package. This consisted of three individual high pressure 6811K Series triplex plunger pumps, two duty and one standby, complete with motors, control panel, header tank and pulsation dampers. The 6811K Series pumps feature 316 SSL block-style manifolds for strength and corrosion resistance and ceramic plungers which maximise seal life. To satisfy the demanding working at HJ Enthoven, the pumps were equipped with cast iron crankcases as well as incorporating special ported inlet manifolds which permit an external liquid flush.

“These pumps offered higher levels of energy-efficiency than experienced in the past, so enabling HJ Enthoven to get double the flow rate for similar electricity consumption,” reports Brian Hubbard. “We provided consultancy to help design the system and establish the pump requirements, balancing effective cleaning against water and energy consumption. The resulting pump package has the effect of doubling the output flow, enhancing the effectiveness of the process and also vastly increasing pump reliability and eliminating down-time.”

The pumps feed a single pipeline into the spray heads that wash the screens which were previously prone to blinding. Motorised valves allow the plant operators to turn these individual areas on and off as required and set sequencing cycles. Capable of providing pressures up to 4000psi and giving a flow rate of 2.6m³/hr, the pumps are required to operate 24 hours a day, handling water coming from flooded mineshafts and containing dissolved carbonates.

HJ Enthoven installed and commissioned Cat Pumps’ rig in early 2008 and after 12 months the performance had more than measured up to expectations. “We are now running the pumps 'under PLC control' incorporated into the auto start-up and shut-down sequence for the battery breaker,” comments Paul Grainger Engineering Manager, HJ Enthoven & Sons. “Cat Pumps provided a professional and friendly service, from the early design stages through commissioning and subsequent maintenance and support of the equipment.”

“Performance so far has been far better than anticipated,” he continues, “with pressure and flow satisfying our operating requirements. Overall there have not been any operational problems. We were advised by Cat Pumps in the initial stages that after 12 months continuous operation the pumps would require a routine service involving the replacement of seals and valves etc. When we inspected the pumps with Cat Pumps after more than 12 months, very little work was required, which even surprised Cat Pumps given the amount of work that they had been subjected to. We have been delighted with the performance of the equipment to date.”

Whilst the pump package meets the performance requirements in terms of pressure and flow, HJ Enthoven has been able to reduce substantially the costs incurred in pump maintenance, spare parts and downtime. In addition, the three pump set-up is far more efficient to run in terms of energy consumed.