After selection of equipment, the requirement of heat i.e. the steam, chilled water,i.e., refrigeration, electricity for various pumps and drives, the water and compressed air, etc. can be calculated. Most often the utilities required for each equipment are available from the equipment supplier. In certain cases, it may be calculated. Again with the help of previous example of equipment selection, we shall do estimation of steam requirement, i.e., sizing the Boiler.
Steam Requirement: Steam is most convenient source of heat in the dairy plant.The demand of heat/steam will be based on established data of product flow line diagram. Let us draw a chart indicating each operation on time scale as given below (steam load with period of operation).
Steam Load Calculation: With the help of this simple chart, we can develop Figure To do so, we take a graph paper and mark the time/period on abscissa from 0 to 24 hour basis. We may further indicate 2-hourly mark. Similarly, on ordinate side, we plot steam load by marking scale 0 to 700 kg at 100 kg mark difference. Now with the help of available information, the steam requirement is
plotted. Steam requirement starts from 6 hrs at the rate of 50 kg/h for floor cleaning; hence, X is marked in figure-1.2 at each point on chart. The 2 nd requirement is at 8 hrs for can washer and the pasteurizer. Since the three operations are at same time, the total load at 8 hrs will be 50+200+300 kg/h, i.e., 550 kg/h. This steam load will be up to 9 hrs. At 9 hrs, another operation will need 50 kg/h up to 16 hrs. At 11 hrs, the washer operation will be over, hence steam load reduction to the tune of 200 kg/h, but the cream pasteurizer will need 20 kg/h. Therefore, the drop will be 180 kg/h. The load at this point will be 420 kg/h up to 13 hr. At 13hr, the load of cream pasteurizer will be phased out and the load of 400 kg/h willcontinue till 3 p.m. From 3 p.m. steam for pasteurizer will be shut down and thereby the load will level off to 100 kg/h only up to 16 hr, further reduce to ‘O’ by 17 hrs.Similarly, the evening operation of can washing and floor cleaning will need steam from 18 hrs to 21 hrs on time scale.
Sizing of Boiler: With the above estimation, we know the maximum/peak load requirement, which is 600 kg between 9 hrs to 11 hrs. Hence, the boiler capacity must be minimum of 600 kg/h. Now the choice is to have either one boiler of minimum 600 kg./h capacities or to split load into two, of 300 kg/h each. By having one boiler, the initial capital investment will be less but we have no alternate boiler to act as standby. The standby boiler helps during sudden failure or breakdown.
Other utilities: Similarly, we should plan load requirement of refrigeration compressors with one standby, one standby tube well for water supply, one air compressor for air supply and so on. Similar provisions are made at critical points wherein we expect sudden failure.While estimating maximum load about 20% additional load as safety margin should also be added. This is done to compensate for loss in efficiency of equipment while in use. We have suggested earlier that the size of equipment will depend on its availability in the market. In this case, Boiler of 300, 500 and 1000 kg/h are available. Hence, the most appropriate decision will be to go for two Boilers of 500 kg/h capacities. This way the 2 nd Boiler will require running only during peak load.
Steam Requirement: Steam is most convenient source of heat in the dairy plant.The demand of heat/steam will be based on established data of product flow line diagram. Let us draw a chart indicating each operation on time scale as given below (steam load with period of operation).
Steam Load Calculation: With the help of this simple chart, we can develop Figure To do so, we take a graph paper and mark the time/period on abscissa from 0 to 24 hour basis. We may further indicate 2-hourly mark. Similarly, on ordinate side, we plot steam load by marking scale 0 to 700 kg at 100 kg mark difference. Now with the help of available information, the steam requirement is
plotted. Steam requirement starts from 6 hrs at the rate of 50 kg/h for floor cleaning; hence, X is marked in figure-1.2 at each point on chart. The 2 nd requirement is at 8 hrs for can washer and the pasteurizer. Since the three operations are at same time, the total load at 8 hrs will be 50+200+300 kg/h, i.e., 550 kg/h. This steam load will be up to 9 hrs. At 9 hrs, another operation will need 50 kg/h up to 16 hrs. At 11 hrs, the washer operation will be over, hence steam load reduction to the tune of 200 kg/h, but the cream pasteurizer will need 20 kg/h. Therefore, the drop will be 180 kg/h. The load at this point will be 420 kg/h up to 13 hr. At 13hr, the load of cream pasteurizer will be phased out and the load of 400 kg/h willcontinue till 3 p.m. From 3 p.m. steam for pasteurizer will be shut down and thereby the load will level off to 100 kg/h only up to 16 hr, further reduce to ‘O’ by 17 hrs.Similarly, the evening operation of can washing and floor cleaning will need steam from 18 hrs to 21 hrs on time scale.
Sizing of Boiler: With the above estimation, we know the maximum/peak load requirement, which is 600 kg between 9 hrs to 11 hrs. Hence, the boiler capacity must be minimum of 600 kg/h. Now the choice is to have either one boiler of minimum 600 kg./h capacities or to split load into two, of 300 kg/h each. By having one boiler, the initial capital investment will be less but we have no alternate boiler to act as standby. The standby boiler helps during sudden failure or breakdown.
Other utilities: Similarly, we should plan load requirement of refrigeration compressors with one standby, one standby tube well for water supply, one air compressor for air supply and so on. Similar provisions are made at critical points wherein we expect sudden failure.While estimating maximum load about 20% additional load as safety margin should also be added. This is done to compensate for loss in efficiency of equipment while in use. We have suggested earlier that the size of equipment will depend on its availability in the market. In this case, Boiler of 300, 500 and 1000 kg/h are available. Hence, the most appropriate decision will be to go for two Boilers of 500 kg/h capacities. This way the 2 nd Boiler will require running only during peak load.
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| Steam Load Diagram with Period of Operation |
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