Cement, Energy and Environment

conditions , levels off the irregular wear of grinding bodies over the mill length, and reduces overall ball wear by 20%. During grinding in a BM, the source material size composition changes so that the amount of large particles decreases and that of small particles increases. Excessively ground particles, which are not removed in time from the bulk of material in the mill and ground further, hinder grinding of large particles and retard the entire grinding process. The smaller the particle, the less inner defects it has, the more it resists destruction, and the more energy and time is required for its grinding. Closed-cycle grinding prevents excess material grinding and increases the productivity by 20 - 25%. The main drawbacks of the closed– cycle scheme are as follows: a host of complex and unwieldy auxiliary equipment whose total power consumption exceeds 40 per cent of the BM power. Figure 8 is the structural diagram of the auxiliary equipment for a closed-cycle mill. TCM eliminates the drawbacks of the classical grinding scheme by implementing a simple closed cycle of the coal TBM type (Figure 6 and 7), using one mill fan with 20 per cent power of the TCM rating . Electric power saving for 3200 kW 4.0 x 13.5 m mills just by simplifying the auxiliary equipment process flow is over 600 kW. This is without account of cost, capital outlay, floor area, dust formation and its operation. Open circuit separators separate material less effectively than do centrifugal ones, though sufficiently well for coal mills, the coal dust residue being within required limits (6 to 7 per cent on an R 90 screen). For better quality separation of the finished product, a centrifugal open– circuit separator can be used, or a centrifugal separator can be installed after the open-circuit one in the grit recycling channel. In addition to dramatically simplifying the classical scheme of closed-cycle auxiliary equipment, this eliminates the outlet grid with the airlift together with the diaphragms in the single-chamber TCM. This increases the TCM grinding space by 11 .5%. According to (1 ), this additionally increases the productivity. A general-purpose TCM is intended for operating in the open or closed grinding cycles with both dry and moist materials in different industries. The TCM can operate with/without a variable-speed drive. Thus, the authors suggest a conceptually new mechanism and technology of grinding, which served as a basis for developing an energy-intensive TCM with a variable-speed drive. The overall TCM Efficiency exceeds 271% without accounting for the following efficiencies: variable-speed drive (up to 50%), closed-cycle grinding (20 to 25%), regular additional ball charging (13.7%), and increased TCM grinding space (11.5%). A general-purpose TCM with a variable-speed drive is comprehensive way of improving new-generation grinding plants. Its design supports easy, complete and optimal implementation of the ball operation sequence, which is line with modern grinding theory and practice. The originality and novelty of the technical solutions suggested have been confirmed and protected by many patents. Courtesy: World Cement, Oct. 2009, Pp67 -78. FEDERATION OF INDIAN MINERAL INDUSTRIES· FIMI HOUSE, B-311, Okhla Industrial Area, Phase-1, New Delhi-110020 {India) Tel: 91-11-26814596; Fax: 91-11-26814594,91-11-26814593 E-mail: fimi@ fedmin.com ; Website: www. fedmin.com FIMI'S ENVIRONMENT, SOCIAL AWARENESS AND EXCELLENCE AWARDS 2010-11 Details of these Awards along with the Application Fom1s (for the year 2010-2011) can be down-loaded from the FIMI's website (http://www.fedmin.com/html/Aw-app.pdD. It may please be noted that the last date for submission ofdully filled Application Form is 31st January 2011. 20