Cement and Energy

.. WASTE HEAT RECOVERY FOR POWER GENERTION -CHINESE EXPERIENCE D uring the Indian Cement Industry Delegation's visit to China (22-28 December 1997) the widespread and successful adoption of waste heat recovery for power generation in Chi nese cement industry was noted wi th particul ar interest. Indeed most of thei r plants of 2000 tonnes per day capacity and above were found to have cogeneration units. This achievement owes mainly to the Tianjin Cement Industr y Design and Research Insti tute (TCDRl ), one of the 15 national institutions devoted to building materials in China. TCDRl has developed this experti se over the last 20 years and today it has a 30 - member specialists team covering turbine, boiler, pressure contai ner, power generation. in strumentation, computer, chemistry, etc. This team undertakes from design to commissioning of waste heat generation plants. To date TCDRl has to its u-edit 12 cogeneration plants commissioned, 3 under construction and an equal number under design. The cement plants to which they are adjuncts range from I00 tpd plain dry to -WOO tpd precalciner type, the lower capacity ones being simple waste heat boiler wh ile 2000 tpd and above have supplement boi ler also. Their gestation period has generally been 2-3 years. They have generall y taken 2-3 years from design to commissioning. Major tasks fulfilled by TCDRI since 1986 include: • Upgrading of parameters of a plain kiln waste heat power generati on system (steam pressure from 2.45 MPa to 3. 82 MPa, steam temperature from 400° C to 450" C), raising the quantity of power generated from 90 - 130 kWh/t c linker to 160 kWh/ t clinker. • Accomplishing of a waste heat power generation system with vertical boiler for plain kiln, raising the quantity of power generated from 160 kWh/t clinker to 190 kWh/tpd. • Carrying out experiments with Harbin Boiler Works on ash collection, blocking mechanism, regulation of heat exchange and improving heat efficiency in waste heat boiler. • Adopting computer control system for waste heat power stations. • Equipment development, design, commission ing for waste heat power station in PC and SP kiln systems, waste heat source being from 200° C at cooler exhaust and 330- 400° C at preheater exhaust. Table I summarises the technical and economic indexes of cogeneration plants TCDRI is in a position to offer. The Indian delegation visited the Conch plant at Lingdo near Nanjing. The plant, which is of 1.8 million tonnes capaci ty, has two kilns of 2000 tpd and one of 4000 tpd . The 4000 tpd li ne has recentl y been fitted with two cogeneration units with the help of the Japanese Aid Agency NEDO. These consist of one 3.25 MW generator using exhaust gases from 5- stage preheater and another similar plant using hot ai r exhausted from grate cooler. A team from TCDRl is scheduled to visit India during March/April, 1998 for exploring the use of this technology. 9