Cement, Energy and Environment

ENERGY EFFICIENCY & CONSERVATION FLUX, VOLUME OR VISCOSITY? Dr. Micha el Clark Fluxes are of grea t importance in an indus trial cement kiln to keep down the expense of clinker formation in terms of fuel and refractory costs. In this month's Technical Forum, Dr Clark di scusses the re lative be ne fits a nd disadvantages of various flux characte ris tics. These include include the temperature of the kiln when the flux enters, its quantity and vi scosity. The article draws some interesting conclusion that seem to contradict actual cement plant practice. Courtesy: International Cement Review, Mar. 2002, Pp. 47 Email: info@CcmNet.co.uk Web: www.CemNct.com THE CASE FOR VERTICAL MILLS Don Longhurst, Krupp Plysius, US A little more than a decade ago, the firs t high pressure grinding rolls to prod uce a finished slag cement product were put into service. These systems operated at product finenesses in excess of 6000 cm 2 I gm, producing high grade slag.The high pressure grinding roll was not just a new piece of grinding equipment, it was a different grinding process, and the power savings compared to a ball mill w ere greater than expected. While the initial sys tem designs came with material handling problems, eventually these were solved, and several circuits of this type are now in operation. The last such system incorporating a high efficiency separator I shaft– dryer combination eliminated the need for bucket elevators. Modifications have increased the output and reduced opera ting costs well below that anticipated . So which system is the mos t effi cient, costs less to install and maintain, and is the least expensive and easies t to operate? Or put another way. 'which is the bes t system?' With all of the d ata collected from the va riou s sys tems, and the analytica l tools available today, it might be assumed tha t this answer would be readily ava il abl e. Unfortuna tely is it no t. Wha t is available is a realis tic examination of the various systems on a commercial scale. Commercial da ta and theories on me thods to achieve h igher efficiencies are being genera ted simultaneously. For ordin ary Portland cement grinding, comparisons of electrical energy for different grinding systems were used as a yardstick to rate them. Some of the savings were in the form of being able to produce a similar product with a coa rse r g rind , thus reduc ing en ergy consumption. For slag grinding, the ya rds tick needs to be w idened. Decreasing the grinding energy requirement in the form of electrica l power is certainly a considera tion. The heat required to dry the granula ted slag is also an energy consumer, and a major one at that. The pas t year has seen sharp changes in the cost of energy, whether it is in the form of na tural gas, oil, coal, or electrical energy. Mos t slag grinding facility do not have a source of low– grade waste hea t to d ry the slag with, therefore separa te firing systems to supply the ene rgy needed for drying are the norm for slag grinding systems. It should be expected that for d ifferent areas, the most abundant energy in the area will be the least e xpe nsive, even to the point of