FEATURE: RESIDUES TO RESOURCES The crude gas flows into each of the towers in turn, absorbing heat in the upward flow and releasing it in the downward flow. Complete oxidation occurs in the com- bustion chamber at a temperature of 850°C. The illustration shows the denitrification and separation process. capture heat from the excess cooling air was installed and it provides hot water for the local district heat network operated by Energie AG Oberösterreich Wärme GmbH. In the 1990’s the focus turned to noise reduction at the plant, which according to the company, has largely been achieved. Alternative fuels and raw materials On the frontend, like many cement plants, Kirchdorfer Zementverk is working to reduce its reliance on coal and fossil gas as energy sources by switching to alternative high-energy fuels. In 2011 it formed ALFUMA Gmbh, a company specialised in identifying and trading alternative fuels and materials also based in Kirchdorf. – Our focus is on rubber granulates from scrap tire recycling. This homogenous material has a high heating but low chloride value making it especially suitable as an alternative fuel, explained Anton Secklehner who is also a Director of ALFUMA. Other fuels used at the cement plant include textile lint, as well as plastic light fraction and polyurethane (PU) pellets from the recycling of refrigerators. Currently the cement plant is working with 60 to 70 percent alternative fuels. This can reduce its annual coal demand by up to 50 » Bioenergy International No 82, 6-2015 9 ability to reduce NOx using SCR, along with CO and VOC with an RTO in one device and with only one pressure drop point, said Anton Secklehner, Plant Manager, Kirchdorfer Zementverk. Process details To decompose NOx the unit uses a proven lowdust Selective Catalytic Reduction (SCR) process with ammonia (NH₃) as the reducing agent. A Regenerative Thermal Oxidiser (RTO) – controlled combustion in a combustion chamber – removes the VOCs and any odours associated with them. At its most basic setup the DeCONOx functions as a two-tower system. The crude gas flows into each of the towers in turn at one-minute intervals. The gas absorbs heat from the regenerators in the upward flow and releases it again in the downward flow. The lower regenerator heats the gas to a temperature of at least 240 °C before it flows through the catalyst. In the upper regenerator the gas is heated to the combustion chamber temperature of 850 °C enabling the complete oxidation of VOCs. – For large-scale industrial applications, plants should have three, five or more towers. In the three-tower model, for example, the third tower is flushed with clean gas to minimise the migration of pollutants into the clean gas chamber, commented Hermandinger. Environmental credibility – Environmental protection costs money and energy. The operating costs will be comparable to an SCR alone; the effect on maintenance work has yet to be seen whereas the overall energy requirements will be about eight percent higher, said Anton Secklehner commenting on seen and foreseen operating costs for the novel installation. It is not the first time the two companies have cooperated but it is a recent example of how Kirchdorfer Zementverk strives to find ways of reducing its environmental impact. – We want to actively contribute to Austria achieving its National Emissions Ceiling (NEC) target for air pollution and therefore always seek to use the best and most efficient technologies reducing emissions. I am impressed by courage when it comes to exploring new technologies. It is a partnership between two innovative companies, stated Anton Secklehner. A glance at some environmental investments made during Kirchdorfer Zementverk’s 127-year track record certainly adds credence to Secklehner’s claim. In 1958 it commissioned Austria’s first rotary kiln and ancillary equipment and shortly after installed the first electric filters reducing dust to a minimum. In 1983, a 2 MW heat recovery plant to for reducing Scheuch’s c ploring new ship betwe stated “The central idea is to use resources as sustainably as possible and to minimise the requirement for primary resources.” ANTON SECKLEHNER Plant Manager, Kirchdorfer Zementverk Anton Secklehner (left), Plant Manager, Kirchdorfer Zementverk and Alois Hermandinger, Head of Industrial Minerals, Scheuch.
Bioenergy no 6 October 2015
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