chapter - 1 introduction - Meghalaya State Pollution Control Board

Hills Cement Co. Limited.
Adjustable Speed Drive for Kiln Fan- Adjustable or Variable Speed
Drives (ASDs) for the kiln fan result in reduced power use and reduced
maintenance costs.
The replacement of the damper by an ASD was driven by control and
maintenance problems at the plant. The energy savings may not be typical
for all plants, as the system arrangement of the fans is different from
typical kiln arrangements.
Use of Waste-Derived Fuels- Waste fuels can be substituted for
traditional commercial fuels in the kiln. The trend towards increased waste
use will likely to increase after successful tests with different wastes. New
waste streams include carpet and plastic wastes, filter cake, paint residue
and (dewatered) sewage sludge. Cement kilns also use hazardous
wastes.
Since the early 1990’s cement kilns burn annually almost 1 million tons of
hazardous waste. The revenues from waste intake have helped to reduce
the production costs of all waste-burning cement kilns, and especially of
wet process kilns. Waste-derived fuels may replace the use of commercial
fuels, and may result in net energy savings and reduced CO 2 emissions.
The carbon dioxide emission reduction depends on the carbon content of
the waste-derived fuel, as well as the alternative use of the waste and
efficiency of use (e.g. incineration with or without heat recovery). The high
temperatures and long residence times in the kiln destroy virtually all
organic compounds, while efficient dust filters may reduce any potential
emissions to safe levels.
Conversion to Reciprocating Grate Cooler- Four main types of coolers
is used in the cooling of clinker: shaft, rotary, planetary and traveling and
reciprocating grate coolers.
The grate cooler is the modern variant and is used in almost all modern
kilns. The advantages of the grate cooler are:
• Its large capacity (allowing large kiln capacities) and efficient heat
recovery (the temperature of the clinker leaving the cooler can be as low
as 83°C, instead of 120-200°C, which is expected from planetary coolers.
• Grate coolers recover more heat than do the other types of coolers.
• For large capacity plants, grate coolers are the preferred equipment. For
plants producing less than 500 tonnes per day the grate cooler may be too
expensive.
Pollution Control Consultants (India) Pvt. Ltd. 121