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    System technology for the use ofscrap tires and other alternative fuelsfor kiln firing in the cement industry

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    Energetic utilization of scrap tires and other waste solid fuels

    The required energy input causesabout 40% of the production costsfor the manufacture of cement.Therefore apart from standardcombustibles like coal, fuel oil and

    gas the so called alternative fuelsare of considerable interest, besides a useful waste disposaltheir utilization offers importanteconomical advantages.

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    Next to waste oil, scrap tires,shredded tires, well as shreddedwood, synthetic materials,and oilsaturated mineral substances aresuitable waste or secondary fuels.

    Possible alternative fuels are available in large quantities and at a favorable price. They can be dis-posed in the high temperature pro-cess of the rotary kiln systems ofcement plants without any risk.There is neither a danger of inad-missible environmental pollution like toxic emissions nor a reductionof the quality of the cement.

    During the high temperature pro-cess all contaminants are comple-tely de stroyed at a material tempe-rature of approx. 1,450 C and gastemperatures of 2,000 C.

    Apart from their energetic utilizationalternative fuels also allow a consi-derable material contribution to thequality of the cement. Their ashesadd important mineral componentsto the cement clinker.

    Rubber is the main source of ener-gy when burning scrap tires andthe steel belt supplies ferric oxidewhich other wise would have to beadded in other forms.

    About 2/3 of the energy are usedthermically with a firing efficiency ofmore than 90 % and 1/3 of the ma-terial is totally used up.

    The production of cement is a pro-cess of material transformationconsisting of all methods neces-sary to avoid the emission ofharmful substances. The aspects of environmental friendly technology

    are particulary taken intoconsideration with regard to thestipulated maximum permissiblevalues of com bustion gas.

    Since the beginning of the eightiesa large number of installations hasbeen using alternative fuels. Longterm experience gained since thattime has proven the tremendousadvantages of this technology.

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    Alternative fuels for energy suppliers as well as raw material components

    The system technology

    BEUMER has developed a specialtechnology for the utilization of al-ternative fuels in the high tempera-ture process of rotary kilns whichhas proven its viability in a large

    Flow sheet of a conveying system for the feeding of alternative fuels to rotary kilns

    number of installations supplied tothe cement industry. Due to thecontinuous improvement of thistechnology using the important ex-perience gained a standard of high

    quality and reliability could beachieved. The enclosed flow sheetillustrates clearly the way of thecombustibles from their delivery upto the kiln inlet.

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    Economical utilization and sensible disposal of scrap tires

    and gantry cranes with polygon grippers. The size of the storagearea should correspond to the kilncapacity and fulfill a buffer functionbetween the irregular delivery ofscrap tires and their continuousconsumption. As for the construc-tion and operation of these storageareas, federal and local laws willapply. The storage area has to bedesigned in such a way that rain-water can drain and that absolutelyno toxic substances will contami-nate the soil.

    The storage area

    Because of the increase in moto-rization, more and more tires aredumped at landfill. Due to the largematerial quantities needed their outer nature and the unit weightwhich can amount to a maxium of80 kg, the energetic utilization ofscrap tires as an alternative fuel requires an automatic handling system. The manual handling ofthis task has to be excluded, thedumping of the tires in the storagearea as well as all further handlingprocesses are preferably done bymeans of bucket-wheel reclaimers

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    Scrap tires from delivery to the burning process

    The machine technology

    The handling of scrap tires requiresa special know how as well as aparticular technology.

    The difficulty is to grant a secure,controlled and automatic operationindependent of the condition of thetires as well as the weather conditi-ons. This is highly important due tothe fact that the kiln process andconsequently the quality of the cement clinker are influenced bythe supply of fuel.

    With regard to their constructionand function the single machinecomponents must be suitable forthe scrap tires of random size andquality. The special criteria are: size, form, weight and degree ofdirt content, some tires still havetheir steel rim and almost all ofthem have a considerable quantityof water in their hollow body. Therefore a corresponding prepa-ration is necessary and unsuitabletires have to be rejected by meansof a control device.

    Storage bin with filling pit and discharge bin

    Illustration showing the variable design of a fully

    automatic storage

    Supply box as an alternative to the storagearea with filling pit

    Automatically working gantry crane with polygon gripper for the storage and dis -charge of scrap tires

    Construction groups of the feeding system

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    of disturbances a single segmentcan be manually operated. Thecontrol cabinet is weatherproof andarranged in a heatable room. Anyfaults are indicated at the controlstation of the kiln to assure fasttrouble shooting.

    Additionally the kiln valve is equipped withmanually operated flaps for the emergencyoperation as well as for necessary inspec-tions. The metallic materials used are pro-tected by highly heat resistant materials.

    Steep incline conveyor to connect the pre-paration area installed at ground level withthe kiln inlet in the preheater arranged athigher level. The design, the speed and theconstructional size of the steep incline conveyor always correspond to the parti -cular requirements of each project.

    Kiln inlet valve in multiple step design withshut-off devices to avoid heat loss and inleakage of air. The opening impulses areactivated by the impact of the falling tire.

    Supply box for thedaily consumptionwith discharge bymeans of a hydrau -lically controlledmoving floor

    Control station withmeasuring devicesfor the rim detectionand profile recog -nition

    Storage and separa-ting line with rollerconveyor section incascade design

    Weighing systemwith timing function,consisting of a com-puter controlledconveyor with inte-grated pressuremeasuring cells

    Electrical control

    The electrical control is equippedwith a storage programmable elec-tronic system. All storage and sup-ply functions are controlled by means of photocells insensitive todirt. The drives are equipped with inspection switches so that in case

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    The design of the kiln inlet valveand its functional shape essentiallydepend on the type of fuel to befed. Whole tires require a specifi-cally different supply than for example shredded materials, thethroughput capacity and the rela-ted calorific value determine theopening intervals which are realizedby the process control of the kiln.

    Process of feeding the fuel into the kiln

    The valve system consists of threesteps connected in series whichcan be designed as flat slide valvesor swivel valves. The upper andcentral step open and close in forced order to protect the kilnoperation against heat loss and leakage of air. The lower step hasthe function of a shut off device incase of faults or inspections.

    Slide valve for whole tires Swivel valve for shredded combustiblesSwivel valve for whole tires

    The system is operated by meansof external compressed air cylin-ders with counterweight balanceand position control. The lowerstep can be adjusted manually foremergency operation. The metallicmaterials used are protected byhighly heat resistant materials.

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    ! Total construction of a triple flap valve.

    Combination of a swivel valve with a flat slide valve for emergency operation

    Swivel valve, interior view of the upper inlet step

    $ Swivel valve, central inlet step with direct passage into the kiln.

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    BEUMER system technology as installation concept for the thermalutilization of alternative solid fuels in the high-temperature processof rotary cement kilns

    Apart from scrap tires there is also a strongrequirement for the thermal utilization of rub-ber shreds as well as other complementarycombustibles which are mostly shreddedsuch a synthetic materials, wood or oil satu-rated substances, mineral materials from thefood industry and waste oil regeneration.

    Therefore, modern concepts aim at a flexibleuse with a quick adjustment to the differenttypes of fuels. Thus the user has the advan-tage of adjusting his energy balance with regard to the costs always to the presentmarket situation.

    The BEUMER system technolgoy is designedto meet these particular demands of con-struction and functionality. Due to the modu-lar design of all construction groups and system components, each project can be individually planned with regard to capacityrequirements.

    For more than two decades BEUMER hasgained experience in the development of systems for the burning of secondary fuelsand during this period a large number of projects has been realized. Knowledge, supplies, and engineering services are partof the support when dealing with BEUMER.

    Experience as well as the continuous development in the field of the energetic uti-liza tion of solid waste fuels have led to the demand for an exploitation of all products offered in this market