Cement, Energy and Environment

ABSTRACT Cement manufacturing is an energy-intensive process in which the cost of thermal & electrical energy accounts for about 50% of the total energy cost. Increasing cost of fuel over the years has stimulated Cement Industry for reducing heat consumption. Apart from this, energy and process related carbon dioxide (CO2) emissions from cement manufacturing are estimated to be about 7% of global CO2 emissions. Nearly 40% of CO2 emissions are due to the combustion of fossil fuels. Hence, reducing fuel consumption which results in cutting down the Co2 emissions is top priority for majority of cement plants in India. Energy Audit studies by NCCBM in a number of cement plants reveal the fact that cement kilns are still operated with heat consumption as high as 800 kcal/kg clinker and above indicating huge potential for thermal energy reduction. In Energy Audit studies by NCCBM, various components of thermal & electrical consumption / losses are estimated based on process & electrical parameters measurements and remedial measures indicating energy saving potentials are suggested. The paper highlights case studies of energy audit indicating thermal and electrical energy losses in cement plant operation and discusses the measures to improve the performance of the system. INTRODUCTION The Indian cement industry’s estimated average specific thermal and electrical energy consumption is 762 kcal/kg clinker and 82.5 kWh/t cement respectively. However, the estimated average specific electrical energy consumption for grinding units is 35.10 kWh/t cement. Currently the best specific thermal and electrical energy consumption by the Indian cement industry is about 676 kcal/kg clinker and 66 kWh/t cement that is quite comparable to the best reported figures of 660 kcal/kg clinker and 65 kWh/t cement in a developed country such as Japan. In the Indian cement industry, there is a very wide variation in the vintage, capacity, product- mix, technology and level of technology upgradation undertaken by the plants. Hence, the actual specific energy consumption has a wide variation from plant-to- plant. General average trend of Specific Energy Consumption (SEC) is given in Table below: CASE STUDY ON THE ROLE OF ENERGY AUDIT AND RELATED BENEFITS TO CEMENT PLANT Ankur Mittal, Suresh Kr. Shaw, Ashutosh Saxena, Dr. B N Mohapatra National Council for Cement and Building Materials, Ballabgarh Process Specific Heat Specific Electrical Energy Consumption(kcal/kg cl) Consumption (kWh/t cement) Wet process 1300 115 Semi-dry 900 110 Dry process 4 stage 800 95 pre-heater with Precalciner 5 stage 750 88 pre-heater with Precalciner 6-stage 725 78 pre-heater with Precalciner Source: NCCBM Data 30