Page 22

Bioenergy no 5 September 2015

22 Bioenergy International No 81, 5-2015 Internat ional Pellets NATURPELET THE PER FECT SYNERGY naturpellet is jointly owned by TAMA and Calor ERBI. The former is a sawmill and pallet manufacturing business that manages the raw material and the latter is a biomass heating installer that markets the pellets through its heating installations. The location of the pellet plant, an hour and a half from the center of Madrid, presents an excellent market opportunity. Variety of raw materials, variety of products At the TAMA plant over 200 m³ of pine logs are processed to produce about 10 000 pallets per day. – TAMA provides roughly 80 percent of the raw material needed by Naturpellet and the rest is sourced from by local sawmills, said Roberto Bravo, Manager of TAMA pallet factory and Director of Naturpellet during a guided tour of the facility. Woodchips are major by-product in the pallet production accounting for over 60 percent of residues generated, 25 percent is sawdust, 12 percent is shavings and the remainder is bark. With the exeception of bark all these materials can be used as feedstock for pellet production though other options are possible. In general, the sawdust, a part of the woodchip and the fines obtained from screening of the woodchip are used to manufacture pellets; – A portion of the chips can be processed into dry microchips and classified G30 according to market demand. And the shavings can be sold as horse bedding, a product with high added value, said Roberto. Calor ERBI consumes about 25 000 tonnes of biomass per annum to meet the heat demand of its customers, whose facilities total about 65 MW. Versatile process Two silos were built with a moving floor, one for woodchip and one for sawdust and shavings from the TAMA plant. Before entering the rotary dryer, sawdust and woodchips destined for pelletising are mixed. – If you want to get dry woodchips only, the mix is screened to separate the sawdust before drying and storing for bulk distribution. If the objective is to obtain horse bedding, the screening process removes fines before drying and finally packing into 20 kg bales, said Roberto. In search of homogeneity The heat for the rotary dryer is obtained from a 4 MW bark-fired biomass boiler supplied by Sugimat. It has a mixing chamber where the flue gases are combined with air recirculated from the dryer, which is starved of O₂ and has a temperature higher than the ambient air. This air flows through a cyclone where impurities are removed before returning to the drying chamber. This leads to optimised performance and reduces the risk of ignition in the dryer chamber. The dryer supplied by Reacalor has a throughput of up to 5 tonnes per hour in the winter, when the material is wetter and higher in summer. In the colder months the material entering the dryer has 60 percent moisture and leaves with 9–10 percent moisture. Roberto points out that it is this equipment that limits the maximum output of the plant. The rest of the pellet plant installation is sized to reach 60 000 tonnes per annum; in the future, with favourable market conditions they can add a dryer and increase the total capacity of the factory. The ”mantra” of the plant is homogeneity, the key to pellet quality at the lowest possible cost. Drying is more efficient when the material is homogeneous, although the finer particles – sawdust – leave the drier first, being lighter, and the heavier particles – microchips – stay longer, achieving equilibrium at the outlet. On leaving the dryer, 70 percent of the material is deposited by gravity, but the fines are recovered via a cyclone before the air enters the mixing chamber. The water vapour is exhausted with the hot air surplus. Without cogeneration According to Bravo seven years ago when the project was being drafted the idea included a cogeneration unit linked to a belt dryer. However the introduction of Royal Decree 1/2012 forced a rethink of the concept without electricity production. Three years ago the project took form and at the end of April 2014 the earthworks and civil works began followed by the installation of machinery in June 2014. The plant is built for 24/7 operation requiring five shifts with two staff per shift, an operator in the control room and an operator on the ground to control the machines, both trained as electromechanics. ENplus from the start The dried material is conveyed into two elevated silos with a total capacity of 1 500 m³, where the product homogenises before entering the pelleting process. From the bottom of these silos the material goes through a sieve prior to infeed conveyor for a 160 kW Rematec 8 tonne per hour hammer mill. The fines are suctioned away and conveyed directly to the pelletising section, whereas the microchips go to the mill via a conveyor. When manufacturing woodchips for sale or animal bedding, a bypass diverts the material before entering the hammer mill infeed conveyor, going instead to storage for final processing as necessary. The suctioned sawdust and ground wood material is mixed and homogenised before entering the 40 m³ silo that feeds the pelleting section supplied by Salmatec. The material passes through a conditioner which ensures that moisture is not less than 9 percent. At this stage water and additives, such as a starch binder, can be added to ensure the optimal moisture content and proper functioning of the dies. – A binder is not needed as the softwood we use here in Spain has enough lignin content, which is a natural binder, said Bravo. The octagonal blades of the maturation tank continue homogenising the mixed sawdust before entering one of the two Salmatec pellet presses each with 4 tonnes per hour nominal production capacity. – We’ve managed yields of up to 5 tonnes per hour. At the moment one press is in operation during the day, with both running at night and on weekends, to take advantage of the nighttime electricity tariff, Bravo explained. The pellet factory is already ENplus certified, code ES023, and Naturpellet carries out mandatory and discretionary quality controls, such as ash content, daily in the laboratory. After pressing the pellets are cooled and screened to remove fines and taken to the bulk shipment area or to the bagging station. Currently there is one 500 m³ storage silo, but there is space to add three more. Calor ERBI has a fleet of seven trucks, five 25 tonne solos just for bulk pellets and two pallet trucks to move bags or woodchips, if necessary. The A wood processing plant and energy services company joined forces to build one of the larger pellet plants in Spain. The 40 000 tonne per annum plant in the heart of the Tierra de Pinares region, is a perfect example of business synergy. (Left) Roberto Bravo, Manager for TAMA and Director of Naturpellet and Roberto de la Fuente, Plant Manager for Naturpellet pellet plant.


Bioenergy no 5 September 2015
To see the actual publication please follow the link above