A Volvo wheel loader works the new chip yard with storage silos and manufacturing plant in the background. Bioenergy International No 79, 3-2015 23 » mini EPC of which was contracted to Yates Construction. Prior to its installation, two existing concrete silos were demolished to make room. Chips go to one of three bins, each feeding two vertical reactors (for a total of six reactors). Once they’re filled, the capping valve is closed and steam is inserted. After a certain amount of cooking time, the pressure is reduced a little, the blow valve at the bottom is opened and the release of the steam pressure blows the material over into a blow tank cylinder. The pressures, temperatures and exact sequence is the proprietary part of the technology. A Babcock & Wilcox MEGTEC system handles the resultant vapor and sets the stage for future energy recovery. Meanwhile the dryer exhaust is treated in a new TSI wet electrostatic percipitator (ESP) and an existing regenerative thermal oxidizer (RTO). The previous plant had a scrubber and then the RTO, but Zilkha realised that if it wanted to run the dryers at top speed it needed to install a wet ESP. Material surge capacity is built into the thermal conditioning area, with material exiting the blow tank’s live bottom screw to two Andritz dry hammermills that are close-coupled to the pellet production building. The mill is running two lines of five Andritz 26LM pelletisers each. Adjacent to those lines is a “mothballed” third line of five pellet mills that the previous operation ran, but Zilkha doesn’t need them based on the existing dryer capacity. Changes in the pelleting island include new stainless steel cross conveyors and distribution conveyors and a new pellet collection conveyor. Overlooking the pellet lines is a new control room. Zilkha’s elevated control room uses the latest Allen- Bradley automation control, including FactoryTalk HMI for Ethernet network, allowing various trending analysis, recipe adjustment, machine monitors and other features through a common development environment. Zilkha also added two large 1191 tonne Scafco pellet silos, allowing the mill four days of pellet storage (at 24 hour full production days). Kesco also installed a dual truckloading station, which includes a pellet dedusting system using an adjustable counter flow air deduster, enabling less than 1 percent dust. The station includes a new pellet bucket elevator and four new 50 tonne pellet bins. The existing fire prevention and protection system required considerable refurbishment and additions. GreCon, Simplex and Clarke provided their technologies. The Selma plant is designed for 100 percent trucking to the Port of Mobile. Zilkha has left the barge loading apparatus in place but has no current plans to barge any material. For all of its pellet trucking, Zilkha is using transportation firm Billy Barnes Enterprises, based in Frisco City, Alabama. Barnes has built customised trailers and is using chip vans rather than bottom dumps in order to develop some back haul opportunities. Raw Material Zilkha contracted Forest2Market to conduct a wood basket study, focusing on inwoods residuals, first and second thinnings and otherwise pre-merchantable raw material. The results showed an enhanced wood supply since the startup of the » PELLETS The Babcock & Wilcox Megtec environmental control system deals with the exhaust vapour from the thermal conditioner and enables a future energy recovery option. (Left) The rotary dryer exhaust is treated in a new wet electrostatic percipitator (ESP) from TSI.
Bioenergy no 3 May 2015
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