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ABB is helping a major producer of energy from coal mine methane (CMM) to cut its pumping costs by using variable-speed drives (VSDs) to make its process more reliable. The VSDs ensure the pumps are not over stressed, allowing them to last longer.Based in the UK, Alkane Energy is an independent power generator. The company operates mid-sized 'gas to power' electricity plants providing both predictable and fast response capacity to the grid. Alkane now has a total of 81 MW of installed generating capacity and an electricity grid capacity of 100 MW.
The company uses VSDs to control the vacuum pumps on new sites but was keen to see if they could be retrofitted to existing sites. The challenge with these is that the pumps are run direct-on-line and operate at full capacity all the time. This causes extreme wear on pumps, which tend to fail after only a few months.Keith Mitchell of Alkane explains, “As we pump gas deeper from the mine, the pumps need to work even harder. A failed pump can cost around £10,000 to repair. We can also lose generation revenue, as well as the cost to remove the failed pump, so it is important we know that retrofits of drives are possible on existing sites.”Possibility of retrofitsABB authorized value provider member Inverter Drive Systems (IDS), which already supplies Alkane with VSDs for the new sites, so was asked to investigate the possibility of retrofits, with a trial to be carried out at the Old Mill Lane site in Nottinghamshire.Phil Nightingale of IDS said “The existing set up uses soft starts to slowly start the pumps. When the pump is at full speed, the soft start is bypassed with a contactor. The pressure was then controlled with a by-pass valve. The inverter installation does away with this valve and modulates the pump to keep the pressure constant and saves the wasted by-pass energy.” Mr Nightingale added, “One of the major challenges of the project was the small space available at the site. We needed to fit the drives and panel into the space previously occupied by the soft starters and added fans to cool them. We also had only one day to fit the drive panels so we did all work off-site to minimise disruption and ensure that Alkane could achieve maximum gas pumping.”The drive chosen was a 75 KW ABB industrial drive. IDS designed a bespoke door as well as a back panel to fit the existing cabinet so that the drives’ switches and connections could be accommodated. The digital edition of the magazine is distributed free of charge to readers who meet our qualifying criteria. You can apply to receive your free copy by completing this short registration form.