Cement and Energy

The feeding of combustible wastes separately into the kiln is not favoured as these will lower the name temperatu re and affect the !lame shape. It is therefore, suggested to feed these wa<.,tes in the prccalcinator as <;hown in Fig . I. PRECALCINATOR FIG 1 SCHEME FOR FEEDING OF COMBUSTIBLE WASTES TO PRECAL/NATOR Use ol cumbustib lc wa!-.te~ 111 ceme nt kiln~ ha ~ no influence on the environment. It has been found in many Cour1e1y : Nalicmal Council.fiJr Cement ami Building Malerials (NCIJ) cases that emissions from cement plants burning wastes are less than the emissions from the plants with the same production, which do not burn wastes. Some plants in india have already -; tarted fe ed ing wastes 111 the precalcina10r enab ling some !>ubst itution of coal. However. if systematic se t- up for controlled feeding is adopted by the cement industry, the results of coal substituti on wi ll be much encouraging thereby lowering the cost or energy input and fina lly the cost of cement manufacture. NC B has complete expertise and knowhow from assessment to system des ign for feed ing and fi ring or combu~t ibk vvastes for their rational utilisation as a source of energy. PILOT COGENERATION PLANT UNDER INSTALLATION S hree Cement Ltd. is installing a 2.6 MWe waste heat recovery power plant at its Beawar plant. This pilot plant has been partly financed by USAID under PACER scheme and is expected to be commi ssioned in Febru ary 1998. The plant, newly developed and patented by CALDYN Inc, New York. is ~chemati ca ll y shown in the Figure below. It recover~ the waste heat from the flue gases by mean~ of a waste heat boiler THERMOWIR in order to run a turbine/generator unit. The heat transfer tubes in th e THERMOW IR are kept du st-free constantly by generation of vortices wruch carry the dust away from the tubes. The THERMOW!R also takes out part of the dust so that the dust load in the downstream ESP is less. Mostly, fl ue gases which leave the system at 250o - 450oC, have to he cooled by atomisation and complete evaporation of water before en tering the ESP or a bag filter. This entails a wastage of approximately 20 MW thermal energy in a cement plant of !-mill ion tonne'> per annum (MTPA) capacity. 5