FEATURE: BIOENERGY IN INDUSTRY Gin condenser with heat recovery and a jacket insulated infusion chamber. Bioenergy Internat ional No 79, 3-2015 9 biomass-fired boiler provides the process steam needed to heat the stills and, by using a clever heat recovery system in the distilling process, the residual heat is used to heat the buildings as well as the two greenhouses. The boiler is capable of using wood pellets but uses a mixture of locally sourced clean woodchips supplied at around 20 percent moisture content and the spent botanicals used in the gin making process. Flue gases pass a bag house capturing fly ash and other fine particulates ensuring particulate matter (PM) emissions under the 60 mg/m3 threshold. A 2 MW gasfired boiler is used for peak load and backup. In addition a 6 kW run-of-river hydro-electric turbine has been installed where the original turbine once sat as well as a photovoltaic (PV) array. – So far under normal production conditions the biomass boiler seems to manage the heat load needed though we have only been in production with it a few months. Perhaps a prolonged cold spell would require supplemental heat from the gas boiler, said Nik pointing out that, as a rectifying distillery, much less energy is needed compared to a full distillery. – A reason we choose to use a biomass boiler and pursue a heat recovery solution was that it enabled us to act upon our corporate operational efficiencies commitment. That is zero-waste to landfill by 2022, greenhouse gas (GHG) and water use reductions of 50 percent and 55 percent respectively by 2017, explained Nik adding that negotiations are underway to have a local woodchip supplier take the bottom-ash back for use as a soil improvement medium. – This closes the fuel loop and provides an incentive for both parties to keep the biomass clean and within spec, commented Nik. Vapour infusion distillation In essence gin, the name being derived from Dutch jenever or French genièvre both of which mean “juniper”, is a predominately juniperflavoured spirit with a minimum bottled strength, in the EU, of 37.5 percent alcohol by volume (ABV). Distilled gin and London (dry) gin are two additional categories. Bombay Sapphire is a London dry gin and the key differentiating feature at Laverstoke Mill distillery is the use of the so-called “vapour infusion” distillation process. – Distilled gin can be produced by either boiling botanicals together with the base spirit and then separate out the unwanted solids or by infusing directly in the spirit. Whilst both methods are quicker and thus less costly than vapour infusion, neither get anywhere close to the level of process control, predictability and repeatability. To give you some perspective it takes about six hours to produce 10,000 litres of gin by boiling botanicals whereas our vapour infusion method takes longer to produce less than half that volume, commented Fordham. The incoming base spirit, a triple distilled neutral wheat grain alcohol, is heated up in a special type of steam-jacketed still known as Dakin Carterhead vapour infusion stills. These historical pot stills of which there are only a few remaining in the world have a closed rectifying reflux column on top of the pot that originally purified lower quality spirits used to create gins before infusion. Innovative heritage Two of these refurbished Carterheads are located in the “Heritage Still House” at Laverstoke. In the “India Still House” are two new 12 000 litre modern interpretations of the classic Carterhead stills. These uniquely shaped stills are fitted with an innovative steam management system capable of applying large amounts of energy very gently as well as a reflux section that enables exceptional precision in the control of the distillation process. Furthermore all four stills have been completely insulated saving steam and eliminating the need for air-conditioning of the still houses. All the distillation equipment, the two new stills “Henry” and “Victoria”, the two refurbished Carterheads along with condensers and allied equipment were designed and fabricated by Green Engineering, an Italian engineering procurement and construction (EPC) company specialising in industrial ethanol plants for beverages, biofuels, pharmaceuticals and the chemical industry. – As the base spirit we use is already triple distilled, the original rectifying columns in the two A blend of spent botanicals from gin distillation and woodchips are used as fuel. From a small receiving hopper the material is screw-augered into a storage silo. (Below) The energy heart is a 999 kWth Uniconfort biomass boiler.
Bioenergy no 3 May 2015
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