Experiences with the design of large size cement plants - Process and layout considerations in pyroprocess systems

摘要

The important task to update production process by means of latest technological developments must be accomplished by both the equipment supplier and the cement producer. The equipment supplier, being the technological partner to the industry can thus help greatly to stay competitive in the changing face of the industry. Off late due to the rapid growth rate of Indian economy there has been a thrust on the large capacity cement plants to catch up with the increasing cement demand and also take the advantage of the economies of scale. The company has the privilege of setting-up a good measure of these up-coming large plants in India of which one plant is of 10,000 tpd and three other plants are identical having 8,000 tpd rated capacity designed to produce 10,000 tpd. This paper discusses some of the major features in the selection and design of these plants and challenges to meet the layout requirements. A big challenge of the 10,000 tpd project was to accommodate the plant and machinery design to the very special location at the foot of the Himalaya mountain range in extremely hilly and environmentally protected surrounding. The topographical features of the site itself consist of several contours, hilly terrain and high altitude with a site elevation of 1370 amsl which may arguably make this plant the largest cement plant to be set-up at such a high altitude. Under normal conditions the utilized equipment is sized to produce 12,000 t of clinker per day. One of the thrust areas for equipment selection was the emphasis on equipment reliability and fulfillment of stringent pollution norms as the plant is to be operated in environmentally protected and sensitive area. After several rounds of deliberations the final technological solutions that emerged are comprising a rotary kiln with Phi 5.8 mtimes85 m length with max 4.5 rpm and 2times940 kW drive, a four-string-6-stages preheater with cyclones of 7,9 m diameter having two tertiary air ducts, two In-Line calciners wi-th separate tertiary air supply and four individual ID fans. A four string preheater system has been chosen to reduce the over-all building height below 150 m, which allows the use of cranes at this site. At the same time the four string preheater was judged more operation friendly and less pressure drop creating. Being an energy efficient and environment friendly plant, it has been incorporated with options to retrofit a combustion chamber for better adaptability to coarser alternate fuels like municipal solid waste in future. Three 8,000 tpd capacity cement plants have been ordered this year by one company to be erected at different geographical locations. The equipment will be identical for all three plants to allow the company to benefit from common operation, maintaining and spares logistics. Given the dynamic outlook for the Indian cement industry, the plant design has incorporated a lot of provisions to accommodate future requirements in terms of capacity reserves, fuel flexibility and availability safeguards. A kiln of 0 5.8 mtimes85 m length will burn meal from the first Low NO_x calciner in India. The calciner burner system will feature the unique and patented mixing chamber as well as the new splash box technology for lower temperatures and lower NO_x emissions. The clinker will be cooled in the biggest clinker cooler of the suppliers latest design yet sold with a grate area of 196 m having a roller type clinker crusher