Finning demonstrates its skill with cooking oil20 February 2016
For a year now REG Bio-Power has been successfully producing carbon neutral power from waste cooking oil at its 18 MW Whitemoor site in the UK.
The REG Bio-Power facility located near Selby in Yorkshire is using a purpose- designed Finning power system consisting of 10 Caterpillar diesel engines to burn an unusual fuel and produce electricity for the grid under the UK government's Short Term Operating Reserve scheme.
As the first successfully built and commissioned project of its type in the UK, the new power plant is unique. It recovers used cooking oil, which is transformed into a suitable bioliquid before combustion, ultimately providing up to 18 MWe power that is rated as carbon neutral.
Finning, which is the distributor of Caterpillar engines for the UK and Ireland, took part in the planning and environmental compliance processes with REG, and provided the finance for the build stage. It has also agreed an operations and maintenance contract with REG that runs until 2022, covering the site's engines, as well as its boilers, pumps and high voltage equipment. The Whitemoor site has ten Cat 3516 BHD engines rated at 1.82 MW.
The waste cooking oil it burns is collected by REG Biopower from restaurants, food processing plants and household waste recycling centres in partnership with local councils and waste contractors.
An unusual fuel
This kind of oil is in many respects an ideal biofuel. It has a high calorific value only 7-8% lower than standard diesel oil, it can be fired in unmodified engines and, as it is a vegetable oil, it requires very little pre- combustion preparation or conditioning. That process starts when the collected oil is taken to an REG recovery facility where it is filtered in successive stages culminating in a 1 micron filter. It requires no other conditioning. The result is a proprietary biofuel called LF100. Once the fuel has been prepared it is transported to REG's Whitemoor facility.
“While the engines supplied by Finning are standard, off-the-shelf units, the fuel system is specially designed," commented Mark Radford, project manager at Finning. This is a reference to the proprietary filtering process which is retained as REG's intellectual property. "Reliability is also a major concern for REG as the Whitemoor site has been contracted to supply the UK's STOR programme, which is designed to supply the National Grid with enough power to cope with unexpected spikes in demand."
The Whitemoor site itself is unmanned most of the time, with the control system being remotely managed by Finning. When the generators need to be started up they can be run from a central control room. When a call comes in from the National Grid that power from the site is needed the Finning operators are given seven minutes notice to get on line. As the engines can be run up to full load in three minutes this leaves a safety margin of four minutes.
As well as starting on demand the engines must also go off load at a set time, again with seven minutes run-down time allowed, or REG may be subject to penalties.
Trialling the fuel
Because this was the first use of cooking oil in a Finning supplied engine, and the first of its kind in the UK, a trial run was arranged at the company's site in Slough, UK, in 2012. The engine was an off-the-shelf 12 cylinder Cat 3512 connected to a load bank, and it ran continuously for three weeks, with two short breaks, under a 2 hours on, three hours off regime.
Because the LF100 oil is vegetable rather than mineral in origin it should contains no impurities that can damage an engine, and so it proved. Other than the usual aims of such a trial, particular attention was paid to the problem of fuel solidification. In actual use at Whitemoor, the fuel system, including its two 60 000 litre fuel tanks, is kept in continuous circulation whether under firing or not, and at a temperature of 60°C to prevent any possibility that solids could precipitate. To this end a boiler is installed, providing hot water to an oil/water heat exchanger in the circuit.
The contract with National Grid includes no guarantee of minimum on-time but the facility does receive income in the form of an Availability payment under which it guarantees to be available for three specified periods during the day. These correspond to the grid's expected usual peaks but also allow for irregular events, such as an international football match or an unexpectedly hot evening in the summer, when experience suggests brief power demand surges will be experienced.
When REG receives the call it has seven minutes to come fully on line. The process of switching on is carried out automatically, triggered by a signal from the National Grid control centre at Wokingham. In a little over a year REG has made 170 STOR starts, clocking up 220 hours of operation.
Author: Staff Report
(Originally published in MPS February 2016)