New trends in weighing and dozing
With the emphasis of efficiency and quality of the cement, weighing and dosing of raw materials in the cement making process have gained high importance. Neither process engineering control of individual process stages nor comprehensive quality assurance would be conceivable nowadays without reliable metering technology. The efforts to achieve high quality standards, energy efficient systems, environmental compatibility and cost-effective production when metering bulk materials has led to a logical combination of the operations of bulk material extraction, weighing, metered feeding, discharge into the system, and data acquisition. The demands are focused not only on improved short- and long-term accuracy, large operating ranges and user-friendliness, but also on optimum integration of the bulk material metered feeding system into the automation scheme. Prospective weighing and controlling and dynamic gravimetric metering in closed metered feeding units - these are the current requirements which are fulfilled by using Rotor Weighfeeder systems.
The process of feeding material into rotary kilns is one of the key points in stabilising the process and optimising costs. The different systems available for feeding raw meal have, in the past, proven to have disadvantages and to involve difficulties: high electricity consumption for material transport, infiltration of air into the heat exchanger, and weaknesses in the electro-mechanical design which affect the process, the measuring accuracy and stability of the dosage. With the development of the Rotor Weighfeeder, which was first used to feed burners with coal dust and subsequently for feeding cement mills, the possibility arose of also using them for feeding raw meal into rotary kilns. The advantages were: advance planning in regulation of the dosage, a simple and robust construction, and reliability and accuracy in material dosage.
Cement process is highly energy consuming. Fossil fuel; primarily coal is one of the major fuel used in cement manufacturing. It is also well known that coal burning is a major source of pollution and CO2 emission. Coal also being a major cost in cement production, there has been a drive by the cement manufacturers globally to find a cheaper alternative solution. Alternative fuels from industrial waste, agricultural byproducts, sludge, municipal waste etc. have been tried in test plants in the last one and half decades. The tests have indicated that it is safe and economical to pursue the utilisation of the alternative fuels. The benefits are substantial to the cement manufacturers; helps in reduction of emission and solves the waste management of solid organic / inorganic wastes. Special feeding and dosing equipments will have to be designed to adapt to the different physical structure of the waste materials and fuels. Trials in several plants have proven that the Pfister TRW Rotor Weighfeeder is one of the most appropriate and reliable solution to this complex problem.
Volumetric feeding devices do not fulfill all the requirements of many processes because of their inefficient accuracy and they cannot be used to keep records.
Modern process therefore demand control elements which operates on a gravimetric basis and in which bulk material extraction actuating drive and direct transfer of the bulk material into the process are combined in an enclosed feeder of simple design. The world wide patented rotary gravimetric feeder system which fulfills the demand of high short term accuracy permanently gravimetric mode of operation, lag-free tracking of the process control variable and high accuracy.
Different models of rotary weigh feeder for different functions
- FRW Rotor Weighfeeder for kiln feed
- DRW Rotor Weighfeeder for pulverised coal pet-coke or lignite
- URW Rotor Weighfeeder for fly-ash as fuel additive for burners or mill feeding
- TRW-S Rotor Weighfeeder for flaky and fibrous secondary fuels like plastic, wood, paper and granulates.