Cement and Energy

Emission control, quality of calcination Environmental conditions/measurements at stack and kiln outlet. Envi ronmental monitoring of NOx. S0 2 , 0 2 , CO and dust is needed to identify changes in emissions when burn ing alternative fuels and to ensure compliance with loca l statutory emission regulations. It is often necessary, in addition to the above measurements, to check from time to time NH 3 , total organic carbon, halogenated products (F, C I , Br) &' heavy metals (including Pb, Cr Ni, Hg, Va, Zn). Counesy : Wnrld Cement, Sept. 1997 • I . . C<>MPLETE GRINDING CIRCUITS AND THEIR COMPONENTS I This article examines the factors affecting grinding performance and suggests a stepwise approach to optimise and upgrade existing cement grinding facilities. I n cement manu facture, electricity is one of the biggest cost items, typicall y, 60% or more of the power is uti lised for grinding. Grinding also affects the hurnabi!ity of raw mea l, and in the case of a coal firing plant, the combustion effi ciency of the pul verised coal which has an indirect impact on the fuel consumption; wh ilt: the quality or cement is governed to some extent by the milling process and condition. Ball or tube mi lls are still the most widely installed grinding equipment to be found in cement plants. They are extensively used in the comminution of raw material and coal and al most exclusively in linished milling. The cf'li cicncy or hal l mi ll s is low. onl y 3 - 6% of the power input i ~ actuall y used for size reduction; the balance is simpl y wa:·aed as heat. wear. vibration and noise. However. hall mill s arc simple to operate and maintain and ha \'c a high availab ility of90% or more. Th e possibi lities of ortimi sing and upgrading ball mill grinding cnicicncy have received considerable attention, especially in the last decade. This has led to the development of more advanced mill linings and fl ow control diaphragms, high efficiency separators and pregrinding equipment. This article examines the factors affecting grinding performance and suggests a stepwise approach to optimise and upgrade the exi sting cement gri nding facilities. The utili sation of energy in cement grinding is limited, on the one hand , by the physical processes during comminuti on and , on the other, by the requirements for uniforml y high cement quality. The utilisation of energy in a ball mi ll therefore depends principally on the properties of the components of the material bei ng ground, especially on grindability and moisture content, and on the fineness of the cemen t being produced. Apart from this it is also strongly innuenced by the operating conditions of the grinding plant. In properly adjusted dosed-circuit grinding plants with ball mills and 10