In today’s economic climate, projects to produce energy from food processing waste are becoming more and more viable. In addition to the financial rewards of reduced energy and waste disposal costs, these alternative energy solutions greatly improve the carbon footprint of the organisations involved.
Any organic waste such as food processing waste, whey, distillery “spent wash” and crop waste can be Anaerobically Digested to produce methane rich biogas. The simplest use of this biogas is in a conventional boiler to produce either steam for process or hot water for heat. Boilers for this application do not differ greatly from boilers which run on Natural Gas however the combustion equipment does need to be tailored to suit the specification of biogas on that particular site.
If there is insufficient biogas on site to generate the required steam output, the biogas can be fired simultaneously with another fuel e.g. natural gas or oil within the same boiler furnace. Simultaneously firing biogas with an oil fuel will reduce NOx emission levels.
A more common use for biogas from Anaerobic Digestion, however, is in the production of electricity and heat via an internal combustion gas engine in a CHP unit. In order to increase the overall cycle efficiency and to harness the heat emitted from the exhaust, a waste heat boiler is required. These boilers are individually designed to suit the exhaust mass flow and temperature of hot gases available to produce optimum output of either steam or hot water. If this does not produce sufficient output, rather than installing another conventional boiler, Byworth Boilers of Yorkshire can design and manufacture a single boiler which comprises a waste heat boiler with a fired section. The burner can simply top up the waste heat continuously or take over if the waste heat is not in steady supply.
Phil Carr, Project Engineer in Ireland for Byworth Boilers is currently working with several Consultants on Waste to Energy projects and comments, “It is important for boiler manufacturers to be involved at the outset so that Project Engineers are aware of the latest technologies available in Waste Heat boilers. Byworth are an ideal partner as we are prepared to work on one-off designs for unique applications. Each system has specific parameters and involves bespoke design to ensure maximum fuel efficiency and minimum electrical energy consumption.”
“As with conventional boilers, we can achieve really good operating efficiency by using X-ID spirally enhanced boiler tube. This tube, exclusive to Byworth in the UK and Ireland, can increase the heat transfer in the convection tubes by over 80%. By this method the boiler exit gas temperature can be reduced to a minimum with regard to boiler water saturation temperature, thus operating at maximum efficiency. Further recovery of energy from the boiler exhaust can be achieved by installing Byworth Economisers.”
“Another area where we can help is at the beginning of the Anaerobic Digestion Process,” Phil continued, “In order to kick start the digestion process the feed stock needs to be warmed. For this we can supply temporary boilers, fully transportable in trailers, which can be hired in for the required period.”
The photograph shows a Byworth combination boiler. One of a pair currently being installed in London to produce 10,000 kgs/hour of steam each using waste heat from a CHP plant with supplementary firing facility. There are two integral flue gas economisers in each boiler, one in the waste heat section and one in the fired side.