Determining equipment capacityGuide

1、the copyright for this document and all appendices are reserved by holcim group support ltd issued bymichael weihrauchrev.no./date3 / december, 2006 promap toolg1-307.1 determining equipment capacity hgrs determining equipment capacity (space for additional information or picture) hgrsdetermining eq

2、uipment capacitypage 2 of 17 5230ad0619d216c54b0bb470a1044bbf.pdfm. weihrauch3 / december, 2006 determining equipment capacity 1.introduction4 2.definition4 3.purpose4 4.influencing factors5 4.1market size and seasonal fluctuation5 4.2composition and number of cement products6 4.3process conversion

3、factors7 4.4raw materials composition and variability8 4.5feed moisture of raw materials8 4.6logistics for receipt of raw materials and fuel9 4.7downtime for preventative maintenance schedules9 5.safety factors11 6.calculation method12 6.1collect the basic information12 6.2kiln capacity12 6.3kiln fe

4、ed rate12 6.4raw meal homogenisation silo13 6.5raw mill13 6.6raw material storage capacity13 6.7clinker storage capacity15 6.8cement mill capacity15 6.9cement storage capacity16 6.10auxiliary equipment16 7.abbreviations16 hgrsdetermining equipment capacitypage 3 of 17 5230ad0619d216c54b0bb470a1044bb

5、f.pdfm. weihrauch3 / december, 2006 abstract cement manufacture is a multi-step process. each step is organized within functional departments, with the product from one department becoming the feedstock for the next. the most economical plant design occurs when all these departments work in harmony

6、and capacities are balanced to achieve the highest overall equipment utilization and plant operating efficiency. therefore, the determination of equipment capacities, with their interdependent relationship to material storage capacity, is one of the key elements in defining the overall plant concept

7、. this paper presents an overview of how these equipment and storage capacities are determined and the safety factors that should be considered. hgrsdetermining equipment capacitypage 4 of 17 5230ad0619d216c54b0bb470a1044bbf.pdfm. weihrauch3 / december, 2006 1.introduction during the conceptual and

8、preliminary engineering phase of any material handling and process industry, one of the basic and important tasks is the preparation of the massflow diagram. this diagram can only be finalized once the equipment and storage capacities are determined. the prerequisites for this determination in the c

9、ement industry are knowledge of: the market size sales volumes cement types clinker factor seasonal fluctuations in the product shipment sources and availability of raw materials the raw mix chemistry availability of alternative fuels and raw materials (afr) as well as of mineral component (mic) sla

10、g like fly ash, pozzolana etc. the constraints on logistics for receipt of the raw materials it is obvious that the size of the equipment and storage capacities have a strong influence on the investment costs. a reasonable sizing of all equipment is the basis for a successful project. 2.definition t

11、he equipment capacity determination is a calculation procedure that uses basic mathematical logic to define the criteria for equipment and storage capacities. in the course of writing this paper certain terms and abbreviations were used. a glossary of these terms and abbreviations are included in ch

12、apter 7 to assist the reader who may not be familiar with the subject. 3.purpose the purpose of this document is to guide the user through the basic steps in preparing the calculations for equipment capacity determination. the goal in defining the equipment capacities is to achieve a balance between

13、 avoiding “bottlenecks to production” and “excessive capacities”. the target is to ensure that each step within the process can achieve its requirements assuring the highest plant wide utilization and overall equipment efficiency (oee). hgrsdetermining equipment capacitypage 5 of 17 5230ad0619d216c5

14、4b0bb470a1044bbf.pdfm. weihrauch3 / december, 2006 a thorough understanding of the task and each step of the process at this early stage of the project are vital. the equipment capacity determination lays the foundation for achieving a trouble free and efficient operation with the lowest practical i

15、nvestment cost. 4.influencing factors a number of factors influence the equipment capacity determination. these include but are not limited to the following: 1. market size and seasonal fluctuation 2. composition and number of cement products 3. process conversion factors (raw meal/clinker factor, c

16、linker/cement factor) 4. raw materials composition and variability 5. feed moisture of raw materials 6. logistics for the receipt of raw materials and fuel 7. restriction on departmental hours of operation 8. downtime for preventative maintenance schedules 9. effective working time per shift period

17、the more important influencing factors will be discussed in more detail. 4.1market size and seasonal fluctuation when “greenfield” or major plant extensions are contemplated, the basis for the size of the plant is generally a market research study. the plant size is often simply stated in tons per a

18、nnum of cement. seasonal fluctuations in product demand play a major role mainly on the determination of the optimum size of cement grinding department and storage for clinker and cement. the following graph illustrates typical patterns of weekly shipments for two 1,2 mil. tpa plants. plant a is loc

19、ated in a region where freezing weather during the winter and first half of spring severely hampers construction activity. plant b is located in a subtropical region with no severe restrictions in construction activity. other reasons for seasonality might be holidays or celebrations (i.e. ramadan).

20、if the same quantity of cement were shipped each and every week of the year the plant would expect to ship the horizontal line on the graph represents this average weekly shipment. t/w 23077 521200000/ hgrsdetermining equipment capacitypage 6 of 17 5230ad0619d216c54b0bb470a1044bbf.pdfm. weihrauch3 /

21、 december, 2006 the heavy line describes the shipping pattern of plant a. the line shows that the shipments are far below the average for the first 16 weeks of the year. however, between week 22 and 46 (25 consecutive weeks) plant a ships about 762900 t. this represents an accumulation of 186000 t a

22、bove the average for shipments during this period. on the other hand, the longest consecutive duration for above average shipments from plant b is 12 weeks. in this case the cumulative shipments above this average line amounts to only 30460 t. kilns are operated most efficiently when they are produc

23、ing near their peak limit, and are expected to achieve an oee of 85% or better. it becomes quite apparent that if plant a must fulfil the requirements of yearly production, it will need significantly larger storage and grinding capacities downstream of the kiln than plant b. this may take the form o

24、f larger cement storage, larger clinker storage with corresponding larger cement grinding installation, or a balanced combination of all above. 4.2composition and number of cement products the percentage of clinker in the cement product plays a significant role in determining the equipment size. for

25、 example, a 3100 tpd kiln achieving an oee of 85 % produces about 962000 tpa clinker. if the cement were composed from 80% clinker, this clinker would be sufficient for 1,2 mil. tpa cement. if a supplemental cement additive such as blast furnace slag or pozzolana is available, the percentage of clin

26、ker might be reduced to 72%. provided the cement grinding capacity is adequate, this same quantity of clinker would support a cement production of about 1,34 mil. tpa. max. plant a 33462 t/w max. plant b 27231 t/w average plant a&b 23077 t/w 5000 10000 15000 20000 25000 30000 35000 04812162024283236

27、40444852 week no. tons hgrsdetermining equipment capacitypage 7 of 17 5230ad0619d216c54b0bb470a1044bbf.pdfm. weihrauch3 / december, 2006 the number of products and individual product types also play a major influence on the equipment capacity determination and storage. examples of this influence inc

28、lude the production of cements with dramatically different fineness. a cement mill may be rated at 120 tph when grinding an ordinary portland cement (opc) to a blaine fineness of 3300 cm/g. however, if cement with the same composition is ground to a fineness of 5500 cm/g, the production of this same

29、 mill will likely be reduced to about 58 tph. should this higher fineness cement represent 20% of the total sales, the annual cement grinding capacity is now reduced. this impact must be considered when making the capacity determination if there is seasonality in cement types. the number of products

30、 produced by a single cement mill also influences the determination of the equipment size and storage. if a single mill is assigned to produce 2 to 3 different products, the production plan should make allowances for the following. sufficient storage to ensure a product run of at least 24 hours cons

31、ideration for slightly larger overall cement storage, since it is now no longer possible to be simultaneously full of all products while maintaining active shipments. 4.3process conversion factors the following figure shows the relationship between the consumption of raw mix and the production of cl

32、inker. hgrsdetermining equipment capacitypage 8 of 17 5230ad0619d216c54b0bb470a1044bbf.pdfm. weihrauch3 / december, 2006 the exact balance is influenced to a small extent by the final clinker chemistry and the quantity of cement kiln dust that must be rejected by the process. as a general rule, if t

33、he process can be operated without wasting dust, a raw mix /clinker conversion of 1,60 is appropriate for design purposes. 4.4raw materials composition and variability one of the underlying fundamentals of a cement plant is that it is indeed a chemical factory that is expected to produce a consisten

34、t quality product while using mother natures often inhomogeneous raw materials. before making the final capacity determination, the variation of the raw materials and the effect this has on the percentage of a particular material being fed to the process must be defined. a typical example would be i

35、n the determination of a weighfeeder capacity and size of mill feed bin. if a variation in the raw materials causes the proportion of iron ore in the mix to change over a range of 0,5 to 1,3%, one must ensure that the feeder and bin capacities are large enough to support the highest feed rate. 4.5fe

36、ed moisture of raw materials one often overlooked fact is that the weight of dry material increases when it absorbs water. furthermore by virtue of the basic definition of feed moisture, 1,0 dry t with 12,0% moisture weighs 1,1361 t and not 1,120 t. raw mix proportions in the basic raw mix calculati

37、on are referenced to dry material. care must be exercised to ensure that the weight of this moisture is calculated in the determination of the actual flow of raw materials. the following table portrays the influence of moisture on the design of a 270 tph (dry basis) raw grinding system. raw material

38、 moisture % proportion dry % proportion wet % material flow dry t/h material flow wet t/h limestone 280,077,06216,0220,4 clay/shale1918,020,9748,660,0 iron ore42,01,975,45,6 total100,0 100,0270,0286,0 in this particular example the weight of the moisture (chemically unbound water) entering the mill

39、is nearly 15 t/h. if the 15 t of water were liberated as water vapour at 95 deg. c and 1,0 m asl it would occupy a volume of 27650 m3. 1 100* %12%100 0 , 1 136, 1 t t hgrsdetermining equipment capacitypage 9 of 17 5230ad0619d216c54b0bb470a1044bbf.pdfm. weihrauch3 / december, 2006 4.6logistics for re

40、ceipt of raw materials and fuel establishing the logistics for the receipt of materials is extremely important in the determination of stockpiles and the capacities of the material handling equipment. in the early stage of a project there are often numerous options available which need to be evaluat

41、ed. an example could be determining the best method of transporting coal and gypsum to the plant. the options might include unit trains (5000 t/lot) versus trucking (30 t/unit). for a 1,2 mil. tpa plant, the annual deliveries of coal and gypsum could reach 150000 t and 60000 t respectively. if we as

42、sume that there is 5,0 usd/t advantage in freight cost if a unit train delivers the coal and gypsum, the potential annual operating savings could then reach 1050000 usd. as a guideline it is generally attractive to make a capital expenditure if the costs are less than 4 to 7 times the annual savings

43、. (this number varies from one corporation to the next and should be set by the financial department at the very early stage of the project). in this example the number was set at 6. it is then a wise investment to install the unloading facility with railway connection and larger storage at the begi

44、nning of the project provided it can be accomplished for less than 6,3 mil. usd. 4.7downtime for preventative maintenance schedules an established fact regarding cement kiln operation is that it takes generally longer than a day to reach full production from a cold start. therefore the kiln operatio

45、n must: be designed to run continuously for long duration utilize robust and reliable equipment require minimum to no maintenance between major shut-downs however, other departments such as raw material and correctives preparation, raw meal preparation and cement grinding are more amenable to short

46、production stops to do preventative maintenance. the key is to provide an adequate storage to cover the scheduled duration of the maintenance stop and a production capacity sufficient to recover the inventory within a reasonable timeframe. a typical example is the design of the raw meal preparation

47、department. it is generally accepted that the raw mill should have the flexibility to shut down for one continuous 10-hour period each week. recoverable raw meal storage should be sufficient for at least a 24 hour period based on kiln feed. the following sketch illustrates the concept. the kiln feed

48、 requirement is “x” tph. the silo is designed to hold a recoverable volume of 1 day or “24 x”. hgrsdetermining equipment capacitypage 10 of 17 5230ad0619d216c54b0bb470a1044bbf.pdfm. weihrauch3 / december, 2006 starting with a full silo, the raw mill is then stopped for 10 hours. the silo level will

49、be reduced to 58%. to recover this lost inventory over the next 96 hours, the raw mill must be capable of producing at least 1,11 times the kiln feed requirement. hgrsdetermining equipment capacitypage 11 of 17 5230ad0619d216c54b0bb470a1044bbf.pdfm. weihrauch3 / december, 2006 5.safety factors with

50、any design, certain safety factors and reserves must also be included in the capacity calculation. these safety factors are needed to: compensate for the remaining uncertainty in the raw material and raw mix assumptions compensate for variations in heating value of fuels compensate for reduction in

51、efficiency as the equipment wears allow time for small unscheduled interruptions within a department deal with upset conditions the safety factors and reserves used to determine the “optimum” size for equipment and storage are based on the operating experience developed from past projects and are pa

52、rtly included in the holcim standard design criteria. hgrsdetermining equipment capacitypage 12 of 17 5230ad0619d216c54b0bb470a1044bbf.pdfm. weihrauch3 / december, 2006 6.calculation method in this chapter the reader finds the general overview and comments for the calculation of the main equipment c

53、apacity. 6.1collect the basic information the equipment capacity calculations are commenced with marketing information, which establishes the following criteria the annual sales volume forecast the different cement types to be manufactured the clinker factor a projection of the seasonal shipping pat

54、tern 6.2kiln capacity the kiln capacity is a function of the yearly cement demand and the clinker factor, defined by the cement types. the target value for the oee is set with 85%. the resulting formula is: 6.3kiln feed rate based on the kiln production capacity and the raw meal/clinker conversion f

55、actor the required kiln feed rate is determined. the raw meal/clinker conversion factor of a standard installation can range depending on the raw material between 1.5 and 1.6. higher factors might occur if kiln or bypass dust are extracted from the process. kiln feed rate (tph) 1,6 clinker rate (tph

56、) oee d/a 365 factor clinker tpaquantity cement tpdcapacity kiln hgrsdetermining equipment capacitypage 13 of 17 5230ad0619d216c54b0bb470a1044bbf.pdfm. weihrauch3 / december, 2006 6.4raw meal homogenisation silo there are two main design factors for the raw meal homogenization silo: raw mill down ti

57、me requirements on homogeneity the history of dimensioning the silo went from times when raw material and raw meal homogenization was performed mainly in the latter stage requiring relatively high storage capacities of two to three days of kiln production. the more important aspect is now to provide

58、 continuous material flow for the kiln feed during shut-down periods of the raw mill. standard capacity for the raw meal silo is 24 hours of kiln feed. this leads to the formula: in some cases the silo capacity may exceed 24 h depending on the plant operation and raw material homogeneity. 6.5raw mil

59、l the calculation of the production capacity of the raw mill is based on 4 design factors: kiln feed rate wear factor: 10% of capacity production rate index (pri) net availability index (nai) the wear factor of 10 % mainly applies to vertical roller mills, where during the lifetime of the table and

60、roller liners the capacity of the mill drops. other mills (ball mill, roller press) do show similar tendencies, but to a smaller extend than vertical roller mills. time for scheduled and unscheduled stoppages of the mill is included in the net availability index (nai) of 0.90. production fluctuation