Multi-stage compressor for energy recovery

As part of the potato crisp making process, potato slices (75% water) are fried in hot oil. The
low grade waste heat generated is scrubbed and discharged, resulting in a continuous vapour
plume. In a modern production facility, this leads to a loss of approximately 8 MW of energy
which is equivalent to heating requirements of 5000 average households.
The present project addresses the capture and energy recovery from this low grade waste heat.
It is proposed to compress this vapour to a higher pressure and temperature to provide useful
thermal heat for heating the fryer oil. This will reduce energy use by 43% (1.8 MW gas and
750 kW electric) and CO2 by 5 kT PA (45% reduction). This is a challenging design
requiring the development of specialised equipment as conventional technology is not
commercially viable (payback period 15 years). The process requires multiple compressor
stages with decreasing volumetric flow rates of 2-0.35 m3/s.
The proof of concept project proposed here will deliver a key enabling compressor stage for
vapour recompression that will reduce the number of stages required and hence reduce cost by
10 fold (£5m to £0.5m). The design will be a UK-based, patented, highly innovative low flow
rate compressor. The development of this compressor, TurboClaw®, reduces the payback
period to six years. Significantly this technological solution contributes to curtailing emission
pollutants and hence addresses the important issues of global warming and depletion of
natural resources.
Mechanical vapour recompression reduces the consumption of primary energy and,
consequently, the environmental load. TurboClaw® will make this technology commercially
viable. Main industries to benefit from the development of TurboClaw® technology are Food
and Beverages, Chemical, oil and gas.
Immediate sales of 145 units worldwide for the potato crisp fryer application have been
envisaged, generating a revenue of £72.5 m by 2017.