Cement, Energy and Environment

gas after the preheater tower. If circumstances should make it necessary, the heat exchangers are designed to carry dust blowers at the relevant points. Clinker cooler (AQC) The heat exchanger in the clinker cooler air stream is loaded with about half the dust load compared to the preheater. Contrary to the preheater waste gas stream, the air after the clinker cooler is totally dry, but the dust is hard and abrasive. Therefore, at the entry of the heat exchanger, the necessary reinforcement has to be considered. Summary The ABB ORC power plant is - from the point of view of the whole cement making process - an installation of secondary importance. Therefore, the installation must not interfere negatively with the core process of cement making. This need is accommodated by installing the heat exchangers in a bypass mode. Under normal operating conditions, the waste gas and the clinker cooler air flow through the heat exchangers. If for any reason the ABB ORC Power plant should be out of operation while the kilns is under full operation, the waste gas by passes the heat exchanger and takes the conventional route through the cooling tower, and the clinker cooler air flows through the air cooler before it enters the dust precipitator. The installation of an ABB ORC power plant contributes considerably to further enhancement of energy efficiency and to a reduction of the C02 emissions caused by electricity consumption, even in highly efficient cement plants, where waste gas temperatures after the preheater are still typically between 250 and 300"C. Even in such cases, a reduction of electricity consumption of up to 20 per cent can be achieved. The installation of an ABB ORC power plant leads to considerable energy and production improvements in the cement plant. From an energy (and economic) point of view the following improvements occur: • The energy efficiency is increased by the conversion of waste heat into electricity. Thus the waste heat discharge through the stacks is reduced accordingly. • The captive electricity production leads to reduced electrical power consumption from the public grid, which is a contribution to smaller transportation losses and bigger grid stability - not to mention the reduced demand for electrical power production from (mostly fossil-fired) power plants. • The captive electricity production leads to a reduction in the respective amount of indirect C0 2 emissions. • The saving of water for cooling purposes results in a reduced amount of steam in the waste gas, which allows for either a reduction in the power consumption of the respective ID fans or an increase in clinker production by replacing the steam in the waste gas with stack gas from the kiln, i.e. by increasing the firing power of the plant. • Less water at the raw mill entry (no water evaporation in the cooling tower) enables the operators to improve the operating parameters of the cement plant (e.g. reduced temperatures for the raw mill, thus further reduction of waste gas temperature - more heat to be extracted and used in the power plant and further increases in energy efficiency). • The smaller amount of steam in the waste gas reduces the possibility of agglutination of dust in the filters, particularly if textile filters are in use. • Last but not least: water saving contributes to the sustainability of cement production by conserving the more and more important resource of (potential) drinking water. Courtesy: World Cement, March 10, Pp79-85. ENERGY-SAVING CERTIFICATES WILL BE IN MARKET BY NEXT APRIL The roll-out of the market– based mechanism that will use energy-saving certifications to spur efficiency improvements across energy-intensive industries is slated for 1April 201 1. Under the proposed PAT scheme, 714 energy-intensive industrial units across the country will be given targets for reducing their energy consumption. Those managing to better their targets will be allowed to sell energy-saving credits to those falling to achieve the required cuts, with trading slated to take place on the two operational power exchanges. BEE, which is spearheading the scheme, is currently involved in consultations with designated consumers across the country for thrashing out the modalities of the scheme. Courtesy: TERI {The Energy Resources Institute) 16-31 May 2010, P4. 32 I --"'