A UK-based edible oils processing plant uses activated carbon in order to clean up various contaminants contained within the oils for product quality reasons. The spent carbon is regenerated on-site in a gas fired rotary hearth furnace and the hot exhaust gases (700°C) from the furnace are a valuable high grade source of waste heat.
Due to the contaminants contained within the furnace exhaust gases, they were being cooled down to below 220°C with quench water before entering a Venturi scrubber and then sent to atmosphere. ThermTech were appointed to design a waste heat recovery system which would improve efficiencies at the plant.
Heat Recovery Solution
ThermTech have successfully harnessed this waste heat into a waste heat recovery system which generates approximately 1,500 kg per hour of steam at 13 bar g pressure, fed directly into the site’s high pressure steam main, saving ~£250,000 per year in natural gas at the boiler house, a reduction of CO2 emissions of ~1,700 tonnes/per year and a reduction of quench water evaporation of ~30 L/min.
Several factors were vital to the successful operation of the plant:
- The regeneration furnace pressure is critical and has to be maintained under all conditions
- The existing exhaust gas Venturi Scrubber, ID fan and furnace pressure control system has to remain unchanged with the waste heat recovery system either in or out of circuit
- The plant runs 24/7 and only shuts down once per year
- The furnace gases contain considerable amounts of dust, water vapour and other contaminants
- The furnace exhaust point is at the top of a 30m high building
Of the above points, the most critical is the furnace pressure control and is the heart of the project success.