Objective
By converting a cyclone preheater belonging to a cement clinker kiln and by installing a steam boiler between two cyclone stages, steam is generated and used to produce electricity. The electricity produced can be used in the cement works itself and will significantly reduce the power drawn from the public electricity supply network. The process is extremely economical because for the first time it utilizes the excess thermal energy which inevitably occurs in the cement clinker burning process even in the most modern plants.
Energy saving is expected to be about 14 Mio. KWh/year in the cement plant.
There is minimal influence on the cement clinker kiln. The boiler start-up and shutdown procedures do not create any significant problems for operation of the kiln system. However, owing to an error in the boiler design, the quantity of heat extracted, and therefore steam and electricity production, is only half the planned level. The thickness of the deposits which form on the heating surfaces was correctly estimated, but a wrong figure was taken for the coefficient of thermal conduction. The boiler supplier has proposed a method of rectifying the defect.
It is to be expected that the existing defects (size of the heating surfaces and keeping them clean) will be successfully rectified. After that , the plant will achieve the planned output, and there will be no significant difficulties in operating the plant.
An existing five-stage cyclone preheater of a cement clinker kiln was converted so that for the first time a steam boiler could be installed between cyclone stages 2 and 3. This allows the excess thermal energy to be drawn off at such a high temperature level (between approx. 350 deg. C and approx. 600 deg. C) that relatively small boiler heating surfaces are required and a favourable steam state for power generation is produced. The steam boiler was designed so that incrustations and deposits caused by the high dust content and gaseous components of the fuel gas which impair heat transmission are kept to a minimum and the unavoidable deposits can be cleaned off by suitable systems. To increase operational reliability for the cement clinker kiln, and for inspection and maintenance purposes, the steam boiler was equipped with a by-pass with shut-off devices. The steam is used to produce electricity in a power generating plant. The total cost (including conversion of the cyclones) are about 12 Mio. DM/year. Additional cost (about 2000 t of coal) will be about 250000 DM/Year.
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DEM - Demonstration contractsCoordinator
72359 DOTTEMHAUSEN
Germany