PLANT LAYOUT - AN ACCEPTED CHALLENGE

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1 PLANT LAYOUT - AN ACCEPTED CHALLENGE Manoj Thakur ABSTRACT Cement Plants are capital intensive, in terms of plant and machinery cost as well as land cost. At the same time market competition for cement calls for reduction of production cost. Plant Layout plays a vital role in reducing costs, both at investment stage and during operation. A well designed green field project lay out takes care of the following important aspects: i. Use of available contours or topography with bare minimum earth work; ii. iii. iv. Minimization of material handling thereby minimizing pollution; Minimization of Transportation or Vehicle movement; Making economical use of floor area; v. Maintaining flexibility of arrangements and operations; vi. vii. Providing space for capacity expansion; Lowering operating cost; viii. Aesthetics ; ix. Site specific constraints of land use including Vaastu compliance. In addition to the above, the present hike in land cost leads to an additional pressure of accommodating the manufacturing process in minimum possible area. For brown field projects and for expansion projects, the lay out challenge is even more acute. It has been observed that improper lay out design has led to the failure of small up gradation projects. 1.0 Introduction Cement manufacturing is an energy-intensive process, both thermal and electrical. For consumers other than actual process equipment / machinery like crushers and grinding mills, a great deal of electrical energy is consumed for material as well asgas handling. It is now well established that like thermal energy acontinuous effort is going on throughout the globe to reduce electrical energy consumption as well to make the production process economic. Development of process equipment is helping one way reducing electrical energy consumption. At the same time, keeping specific energy consumption in mind, lot of importance is being given to the plant lay out development. The efficiency of production also depends on how well the various machines, production facilities and employee s amenities are located in a plant. Only a properly laid out plant can ensure the smooth and proper movement of material, from the raw material stage to the end product Page 1 of 8

2 stage.plant layout encompasses layout for new green field cement plant and new installation as well as improvement in the layout of existing installations. Plant layout refers to the arrangement of physical facilities such as machinery, equipment, storages etc. within the factory premises. The objective of optimum plant layout is to have smooth and leastdistance of flow of material targeting lowest cost and with the least amount of handling stages in processing from the receipt of raw material to the shipment of the finished product. It involves a judicious arrangement of production facilities so that workflow is direct. Plant layout is an important decision as it represents long-term commitment. Anideal plant layout should provide the optimum relationship among output, floor area and manufacturing process. It facilitates the production process, minimizes material handling, time and cost, and allows flexibility of operations, easyproduction flow, makes economic use of the building, promotes effectiveutilization of manpower, and provides for employee s convenience, safety,comfort at work, maximum exposure to natural light and ventilation. 2.0 Essentials of an efficient layout Apart from saving specific energy consumption an efficient plant layout is one that can be instrumental in achieving the following objectives: i. Proper and efficient utilization of available space ; ii. Ensure that construction work proceeds from one point to another point without anydelay ; iii. iv. Reduce material handling costs, investment as well as operating cost; Increase employee morale; v. Provide for operational flexibility; vi. vii. viii. ix. Provide for employee safety and health; Allow ease of maintenance; Allow high machine or equipment utilization; Improve productivity; x. Aesthetic look. Plant layout is a dynamic rather than a static concept meaning thereby if oncedone it is not permanent in nature rather improvement or revision in the existing plant layout must be made over time. Revision in plant layout may become necessary on account of the following reasons: i. Increase in the output of the existing product; ii. iii. iv. Introduction of a new product and diversification; Technological advancements in machinery; Change in raw material type or additives or production processes or fuel; v. Change in location of raw material sources; vi. vii. Change in mode of product dispatch; Deficiencies in the layout unnoticed by the layout engineer in the beginning. Page 2 of 8

3 However, any revision in layout must be made only when the savings resulting from modification exceed the costs involved in such modification. 3.0 Factors affecting the Plant Layout (Green Field) 3.1 Material Storage and Handling Material storages and Material handling are the main areas where best possibilities are seen for the layout optimization. In most cases, almost % of integrated plant is dedicated to material storage. The storage capacity requirement of individual raw materials or fuel depends on factors such as availability of infrastructure, proximity to sources, and issues relating to material inventory. Based on the storage capacity, Material stockpilescould be of longitudinal or of circular type. For example, if storage capacities are on the lower side (less than ~ ton for limestone), then a circular storage can be chosen, resulting in smaller footprint compared to longitudinal storage. Material handling and transfer involves the design of all material conveying from storage location to the process and back to intermediate or final storage. It also involves the transfer of material from mining sources to plant. Material handling, therefore, accounts for a significant portion of the total production cost, however adds no value to the product. A long distance of material handling leads to loss of time and energy. Unfortunately, the complete elimination of material handling is not possible. So the realistic approach should be made to handle material by most appropriate method and equipment at the lowest possible cost. Correct choice of material handling equipment is essential for optimum design. Both these factors play an important role in an optimized cement plant layout. In greenfield projects there is scope for incorporating these considerations in design stage itself. In addition, this can be applied to an existing plant as well to improve the efficiency of material handling. 3.2 Gas Handling Like material handling, gas handling too plays an important role. If proper care is not taken for selecting process equipment / fans location and reduction of points of turbulence, energy consumption can increase even beyond anybody s imagination. 3.3 Future expansion Nowadays almost every entrepreneur intends to keep a provision of future expansion to their current cement production units in the wake of encouraging cement demand in future. Therefore, it is important not only to decide the initial or current capacity of plant but also to have a good feel for how much the plant might be expanded in future, as well as how likely the process technology is to be modernized. The future expansion is in terms of upgrading clinker production, adding cement grinding circuits, keeping provision for additional cement storages, additional packing plants, upgrading cement dispatch methods etc. In addition to this, if not being executed at the beginning of the project,at least provisions of Waste Heat Recovery System, Alternate fuel firing system, Palletizing machines etc. should be considered for future installation. Hence, the feasibility of having interface between present system and such future buildings should be worked out and accordingly, enough space should be considered and earmarked in the plant layout. Many a times it has been found that plant up gradation could not be carried out since the layout did not have enough provisionto allow for required modifications. Elsewhere,the design of existing layout did not allow the interface between existing and new system. Sometimes plant up gradation projects have been carried out at huge costs because the initial layout was made without considering the future requirement Page 3 of 8

and to make the up-gradation feasible, longer than usual routes of ducts and material transfer routes had to be designed resulting to undue increase in specific power consumption.

4 and to make the up-gradation feasible, longer than usual routes of ducts and material transfer routes had to be designed resulting to undue increase in specific power consumption. It is always advisable to go for a relatively major up-gradation plan keeping in mind state of the art technology rather than going by in steps which has got adverse effect. 3.4 Non-Plant buildings and Temporary Installations Apart from locating the main process buildings and equipments, non-plant buildings and temporary installations too, require to be accommodated in the layout. Some non-plant buildings i.e. Store, Workshop etc. can be sized and located based on their functional requirement whereas buildings like administration, security, guest house etc. can be sized upon the staff requirement. Temporary installation i.e. fabrication yards, construction labor colony, equipment storage yards, refreshment areas etc., can be accommodated in the allocated space for future expansions or space for material storages or space for truck parking areas etc. Dedicated spaces for such facilities do not require to be given. This helps in minimizing the land requirement. 3.5 Difference in contour levels Land is never flat. There are always differences in the grade levels on the selected land for plant. It is desirable and advantageous too, if making one grade level for whole plant could be possible. It helps in making plant layout much simpler and easier; either for vehicle movement, or for material handling equipments or for building interfaces. However, doing earth work where grade level difference is high, calls for a significant investment increasing the capital cost. Hence, a good deal of effort should be put in minimizing the investment by laying out the equipment, buildings and roads using the contours as available or by doing bare minimum earth work. Upfront, it should not be assumed that it is necessary to level the site. Certain amount of study should be undertaken to find out how process can take advantages of existing topography. The difference in grade levels can always be utilized for material flow under gravity, contributing to lower power consumption. Fig-1: Example of layout taking advantage of different grade levels Fig-2: Example of layout taking advantage of different grade levels Page 4 of 8

3.6 Latest Trends and Alternatives to conventional ways Constant effort shouldbe made to remain updated with various developments and trends to get ideas which can help in optimizing the plant layout.

5 3.6 Latest Trends and Alternatives to conventional ways Constant effort shouldbe made to remain updated with various developments and trends to get ideas which can help in optimizing the plant layout. For example, cement plants equipped with railway sidings can reduce the length of rail tracks by almost half with the use of Wagon Shifter. It minimizes the land requirement and thus, minimizes the capital cost. Another example is of Intermediate Belt Conveyor discharges. A single belt conveyor can have various intermediate discharges without having a break and thus can avoid the requirement of having multiple belt conveyors. Installation and operational cost can be brought down with such options. In addition to knowledge of latest equipmenta good layout engineer should have aptitude for out of box thinking and application oriented interest. 3.7 Economical Use of Buildings and Floors Layout design is not restricted to the spread of the plant in the horizontal plane only, but it is to be applied to the vertical rise of buildings and structures as well. It is an important factor to lower the capital investment of a plant. Based on processor system requirement, floors in a process building may have comparatively less equipmentinstalled than equipments on the other floors. It is easiest for a designer to give slab for complete floor, but it is expensive due to significant investment. Hence, the requirement of slab for concrete floors and gratings/chequered plates for steel platforms should be closely analyzed and should be provided considering basic requirements like safety and maintenance. Moreover, alternative can be explored where such floors can be completely eliminated and equipment can be shifted to some other floors, not affecting the process. In order to achieve optimization, attention to such areas should be given equal importance. 3.8 Site Specific Constraints Every plant site has its own peculiar constraints, be it unavailability of certain portion of land or localized poor soil conditions which becomes evident during the course of project. It becomes quite challenging to adjust the layout to accommodate such factors especially when the project is at advance stage. Fig-3: Layout showing unavailability of certain portion of land Page 5 of 8

6 3.9 Aesthetics Aesthetics, though it barely contributes to production efficiency, is an important factor. Aesthetically designed plants, not only reflect the systems and values of an organization but also enhances the brand value of it. 4.0 Factors affecting the Plant Layout (Brown field) Following are some of the critical factors governing the layout of an up gradation project: 4.1 Space constraint One of the major factors in expansion project is the availability of sufficient space for the expansion. It has been experienced that many plants construct certain facilities unplanned way as and when need arises which subsequently becomes obstacle to major expansion projects. It becomes very challenging to lay the new facilities in and around the existing ones and make the entire system efficient and effective. 4.2 Interface with existing systems While preparing the layout, the interface of new system with the existing system has to be planned in such a way as to minimize down time of running system. It requires close study of existing operation and of proposed system to achieve the optimization. Fig-3: G.A. showing interference with existing facility Page 6 of 8

7 5.0 CASE STUDY Now a days, cement plant of 10,000 tpdcapacity of single kiln is gaining popularity not only in India but also in Gulf area. This brings a new challenge in layout engineering too. For this reason a typical example of plant layout for a 10,000 tpd plant is presented here. The layout is showing production units excluding other associated areas like residential colony, mines etc. Whole layout has been accommodated within 150 acres of land. The arrangement is made with some ideal considerations i.e. same grade level, orientation of material in coming, orientation of dispatch etc. which may have some differences with actual site conditions. Fig-3: Typical Layout of a tpd plant with provision for 2nd line of same capacity Page 7 of 8

8 Salient points of the above layout: Bunker type of hoppers to reduce the heights for same capacity Vertical transport on certain areas over inclined transport Incoming (stacker) and outgoing (reclaimer) on same side to eliminate duplicate of horizontal portion on both sides of longitudinal storages. Location of raw mill feeding hoppers in between two storages, thus, eliminating long inclined transport. All storages kept at one side of plant 6.0 CONCLUSION There is no true definition of an efficient plant layout. Every layout contributes in achieving the main goal of cement production. However, a good deal of efforts should always be put to achieve the objective of minimizing capital as well as operational cost in addition to ease of operation, aesthetic look etc. A good layout engineer should have the following important knowledge: i. Energy consumption vis a vis state of the art technology; ii. Modern / latest equipment available in market; iii. Material property and flowing behaviour; iv. Layout standard norms; v. Out of box thinking aptitude; and vi. Aesthetic sense. It is also important for a good layout engineer to visit plant site and get feedback from construction, operation and maintenance personnel to improve upon in next project. Page 8 of 8

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