Petroleum Conservation Research Association
Ministry of Petroleum & Natural Gas, Government of India
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Energy Audit at Dairy plant at Navsari, Gujarat.Print
A comprehensive energy conservation study of the Dairy plant at Navsari, Gujarat. was carried out by PCRA.This Dairy is engaged in the manufacture of various qualities of milk & also other milk products like buttermilk & ghee in their plant. The total milk received per day is around 2.35 Lakh litres . Annual Production of the plant Liquid milk – 88014.5 tonnes,Buttermilk - 1250 tonnes. Ghee - 149.8 tonnes.There are 2 nos. boilers-, both coal fired 2 TPH each, for generating steam for use in the plant. One boiler is in operation & the other is stand by. Annual consumption Coal consumption is 1618tonnes. The unit takes its electricity supply from the GEB .The contract demand is 850KVA. Electricity is consumed in a variety of equipment in the refrigeration plant compressors & auxiliary equipment like cooling & chilled water pumps, air compressors, water & milk pumps & lighting. Annual electricity consumption is 38.62 LakhKWH
A comprehensive energy conservation study of the plant was carried out by PCRA, The identified total annual energy saving potential is around Rs. 25.738 Lakhs on a recurring basis. The energy audit has identified several areas for energy conservation in thermal & electrical energy. The steps identified for energy conservation are given below:
- It is observed that the coal size fed to the boiler is not uniform & is around 4-5”. It is recommended that the coal size be uniformly maintained at 2.5”. This will help in complete combustion of coal & reduce unburnt % in the ash content. It is recommended that the unit procure a coal crusher such that the uniform coal size is obtained.
- It is recommended that the height of the coal bed be maintained at 8”. This is the optimum bed height for achieving good combustion with minimum excess air levels.
- The flue gas temperature for one of the boilers is in the range of 250 -260 deg c. It is recommended that the unit should install a waste heat recovery economizer to generate hot water
for boiler feed. This will result in fuel savings
- Steam line insulation was in good shape in the plant in. However, some the valves & flanges on the PRV stations are not insulated in the plant. It is recommended that the valves & flanges be insulated with box type insulation to reduce radiation losses.
- It is observed that the CIP PHE is presently bypassed & steam is being used in the CIP PHE at a pressure of 6 kg/cm2g. It is recommended that the CIP PHE be made operational & the steam utilization pressure be reduced to 3-3.5 kg/cm2g.
- It is observed that the can washer PRV is not in operation & steam is utilized at a pressure of 6 kg/cm2g. It is recommended that the PRV be made operational & the steam pressure reduced to 3 kg/cm2g. This will reduce the steam consumption in the can washers.
- It is observed that the can washer PRV station safety valve is leaking. It is recommended that the safety valve be rectified as soon as possible to reduce steam consumption.
- It is observed that the CIP PHE float traps are connected to the condensate recovery system via
same header. This results is back pressure on the steam traps & the operator thus has to keep the bypass open. It is recommended that the steam traps be connected to the condensate recovery system through separate lines. This will increase condensate recovery from the CIP PHE.
- The unit has also installed a desuperheater on the old refrigeration compressor. The unit is sending solar water into the desuperheater with the result that waste heat recovery is not optimum. It is recommended that the unit send soft water to the desuperheater. This will optimize the waste heat recovery.
- Presently, CIP hot water is drained . The quantity of CIP hot water drained is approximately 100000 litres/day. The temperature of the hot water drained is around 60 deg c. It is recommended that the unit install a waste heat recovery PHE to recover waste heat from the hot water presently drained. This will enable the unit to generate hot water at 50 deg c which can be used in the CIP tanks. Since it is contaminated water, investment for additional PHE of proper capacity V/s its feasibility is to be worked out by the unit.
- The power factor of the plant is not maintained consistently. It is observed that it fluctuates from month to month. The average power factor for the dairy is 0.992. It is recommended that the power factor be improved to unit consistently. This will result in savings in electrical bills due to increase in rebate amount.
- It is observed that the water/milk is leaking from the pump seals of the milk/water pumps. This sometimes finds it way into the motor resulting in frequent motor burnouts. This results in frequent rewinding of the pump motors , resulting in a drop in their efficiency & consequent overloading. It is recommended that the pump seals be inspected & changed on a monthly basis to reduce water/milk eakages & reduce motor burnouts. Moreover, it is recommended that motors which have been ewound more than 5 times can be considered for replacement with new high efficiency motors. This will result in savings of electricity.
- As the suction pressure of the new refrigeration plant is maintained at a higher pressure of 42-45 psi as compared to the :old refrigeration plant , it is recommended that both the prechillers & the compressors installed in the new plant be operated in series. This will reduce the overall power consumption in the refrigeration plant. The unit is conducting a trial as discharge gas line of old system & PHE system is made common between Vertical condenser outlet & Receiver inlet with diff. Dia. pipe lines.
- After operating the two new PHEs in series , the refrigeration storage capacity can be reduced. Thus the ice thickness range can be reduced from the original 1.5 “– 2” to 1.0 “– 1.5 “. This will allow an increase in the suction pressure to 35-40 psi thus leading to at least 5% power savings.
- In the old refrigeration plant cooling tower area, it is observed that the suction valves of the cooling tower pumps are throttled. It is recommended that the cooling tower pump impellers be trimmed by 15%. This will reduce the flow by 15% but will reduce the discharge pressure by 27%
to 18 meters which is more than sufficient for the cooling tower. The power consumption in the
pumps will reduce by more than 30%
- It is estimated that the air compressor operates on load for 60% of the time & on unload for 40% of the time. The unload power consumption is wasteful & can be eliminated by installing a variable frequency drive on the compressor. It is recommended that the unit establish the average running hours of the compressor on load & unload. Based on these figures, the unit can evaluate the economic viability of the VFD drive.
- Present lighting single phase voltage is 250 to 260 volts. Nowadays lighting transformers are available, which reduce the voltage to around 220 volts. The reduction in voltage also reduces
power consumption with little reduction in lumens emitted by the light source. The savings due to
installation of lighting transformer is 30% of the power consumption.
For further information, please write to:
Sanrakshan Bhawan, 10,
Bhikaji Cama Place,|
Web site: www.pcra.org