Cement Energy and Environment

,r I Upgradation/Retrofit of Existing APCEs ·To meet Proposed Point Source Emission Standards with Cost competitiveness A K Mishra, Rabindra Singh, Naga Kumar, Prateek Sharma, National Council for Cement and Building Materials 1.0 Introduction Rapid industrialization has resulted in serious environmental problem and concentration of cament plants in limestone clusters has aggravated the problem of particulate emissions besides increase in SOx and NOx levels. In Cement industry particulate emissions in air ~ollution is mainly from point source and fugitive dust. Cement plants have adopted environmentally sound technologies to control point source emissions in past two decades leading to significant reduction in dust emissions. In view of the coming up of a number of cement plants in a cluster, Ministry of Environment, Forest & Climate Change has come up with new standards on point ::ource emission for particulate matter (PM), dust ~ollution load, oxides of nitrogen and sulphur vide tJotification no. GSR 612 (E) dated 25th August ; :014 to achieve the stringent PM emissions of 30 ng/Nm 3 and dust pollution load level of 0.125 new Pollution Control Board norms of 30 mg/ Nm3, the plant decided to upgrade its cement mill venting system and NCB carried out the techno commercial feasibility study for replacement/ Upgradation of existing cement mill venting system. 2.1 Bottleneck with Existing System The major bottlenecks of the existing system are as following: • Outlet dust emission of ESP as well as bag filter is not matching with the new emission guidelines. • ESP is very old and collection efficiency which is low may further deteriorate. • ESP is also sensitive for gas characteristics changes as mill is operating at different capacity for different types of cement (OPC & PPC). • Substantial high cost of old ESP maintenance. ~.g/tonne of clinker. Thus, Plants which are • Complex operation with two de-dusting system designed for 50 mg/Nm3 and above needs to in parallel for cement mill. upgrade /retrofit or optimize their existing Air Pollution Control Equipment like bag filters, ESPsetc to achieve the new emission norms. This paper highlights the choice of technology \llith cost competitiveness to be adopted for dust Clbatement in cement plants through a case study for up-gradation of cement mill venting system. ;!.0 Case Study I The plant was operating an open circuit ball rnill of 80 tph as cement mill with ESP de-dusting ~;ystem having outlet dust emission of 250 rng/Nm 3 . Later to enhance cement mill production, rnill is converted to closed circuit system and a new bag filter system was installed to partially handle the cement mill vent gases and the balance ~ ~ases handled by existing ESP. Considering the 2.2 Basis for Proposed System Design Based on the process measurements, data collected, discussions held with plant officials, analysis of process parameters, assessment of capacity and performance of cement mill venting system was carried out to work out the most suitable option. 2.3 Dust concentration location Units Dust concentration Cement mill outlet g/Nm 3 220 Cement mill ESP stack mg/Nm 3 70-80 Cem~nt mill bag mg/Nm 3 35-40 filter stack