Petroleum Conservation Research Association
Ministry of Petroleum & Natural Gas, Government of India
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Energy Audit at Dairy plant at Rajkot,Gujarat.Print
A comprehensive energy conservation study of the Dairy plant at Rajkot,Gujarat. was carried out by PCRA.This Dairy is engaged in the manufacture of various qualities of milk & also other milk products like buttermilk, flavored milk & ghee in their plant. The total milk received per day is around 1.0
Lakh litres . Annual Production of the plant Liquid milk – 28023 MT,Ghee – 651.7 MT,Flavored milk – 1133.1 MT.There is one. boiler-, furnace oil fired 1.5 TPH, for generating steam for use in the plant.
Daily furnace oil consumption is 429.27 Kl .The unit takes its electricity supply from the GEB .The contract demand is 300KVA. 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 is18.19 LakhKWH
A comprehensive energy conservation study of the plant was carried out by PCRA, The identified total annual energy saving potential is around Rs. 25.857 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:
- The excess air levels in the boilers is slightly on the higher side. It is recommended that the unit procure a combustion analyzer & reduce the excess air levels such that the oxygen % in the flue gases is 3.0%. This will result in improvement in boiler efficiency.
- Furnace is stored in 2 nos. main storage tanks of capacity 30000 lts. At present there are no drain points installed on the tank. It is recommended that drain points be installed & storage tanks be drained at least once a fortnight. This will ensure that all the water is removed from furnace oil & prevent sludge formation.
- It is observed that the municipal water is directly used as boiler feed water. The municipal water has a hardness of 75-80 ppm. It is recommended that the raw water be softened to have hardness below 5 ppm before using it as boiler feed water. This will prevent scaling of boiler tubes as well as all the steam heat exchangers in the plant.
- 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. Also, some lengths of steam lines are bare near the can washer as well as in both the old & new CIP sections. It is recommended that the bare steam lines be insulated as soon as possible.
- Presently, steam is directly sent to the process section. It is observed that steam is directly injected into one section in the can washer as well as in pasteurizer hot water tanks & crate washer. It is recommended that a pressure reducing station be installed to reduce the steam pressure to 2.5 kg/cm2g before sending it to these sections.
- It is observed that the steam valve to the CIP hot water tank is continuously on. It is recommended that an auto temperature controller be installed such that the steam supply will be closed when the 8 desired hot water temperature is reached.
- The actual regeneration efficiency of the milk pasteurizer is very low at 71.8 %. It is recommended that the pasteurizer be descaled. This will reduce the steam as well as chilled water load in the pasteurizer drastically.
- Condensate is recovered from the main line steam traps. It is recommended that hot water overflow from the pasteurizer hot water tank as well as the CIP hot water trap be recovered & supplied to the boiler feed water tank.
- The power factor of the plant is not satisfactory. The average power factor for the dairy is 0.987. It is recommended that the power factor be improved to unity consistently. This will result in savings in electrical bills.
- The contract demand for the dairy is 300 KVA. It is observed that the actual maximum demand has consistently crossed 340-350 KVA. It is recommended that the contract demand be increased to 375 KVA. This will reduce the penalty payable on excess maximum demand & lead to a reduction in the electricity bills.
- Thus the efficiency of the hydroflow pump is too low. Thus it is recommended that the pump be replaced by a higher efficiency pump having efficiency of 70%. This will reduce power consumption for water pumping.
- It is observed that water pumps & milk pumps are frequently burnt out due to milk/water leakage through the seals leading to moisture in rotor /stator. It is to be noted that the efficiency of an induction motor reduces with every rewinding. It is thus recommended that motors which have been rewound frequently be replaced with high efficiency new motors. This will lead to an overall reduction in power consumption in the plant. It is also recommended that the pump seals be replaced on a monthly basis as a preventive measure to prevent leakage. This should help in reducing the number of motor burnouts in the plant.
- After milk pasteurization, the milk temperature is still on the higher side at 16 deg c. It is chilled to 1.5 – 2.0 deg c. It is recommended that the milk be chilled upto 4 deg c. This will lower the refrigeration load on the chilled water.
- As has been mentioned in section 5.7.4, the milk pasteurizer has an actual regeneration efficiency 9 of 71.8% as against a theoretical efficiency of 90%. It is recommended that the PHE be descaled so as to achieve regeneration efficiency of 90% once again. This will reduce chilled water refrigeration load significantly.
- It is observed that chilled water is used during CIP of tanks & silos using iodoform. It is recommended that chilled water be replaced by raw water . This will reduce chilled refrigeration load.
- It is recommended that the unit install an instant chiller PHE for reducing the load on the IBT. This will facilitate a 70% reduction in the refrigeration load on the IBT thus allowing reduced ice thickness on the ammonia coils. Due to reduced ice thickness, the average suction pressure can be raised to 40 psi from the present average of 30 psi. This can be taken up when the unit decides for modernization of refrigeration section.
- The unit receives 75 kl per day of corporation water . Presently around 15 kl of corporation water is used in boiler & the rest is mixed with borewell water. This is due to lack of water storing capacity. It is recommended that the unit store the clean corporation water in a separate tank & use it for cooling water make up as well as for process water use.
- It is also observed that the natural draft cooling tower is quite old. It is recommended that the unit replace it with a PHE condenser & a forced draft cooling tower. This will result in at least 10% reduction in power consumption in the refrigeration compressors.
- It is observed that the high pressure ammonia discharged from the ref compressors is at a high temperature of 100 -110 deg c. It is recommended that the unit install a de-superheater (PHE heat exchanger) to recover waste heat from the high pressure ammonia discharged from the refrigeration compressors. The waste heat can be utilized to generate hot water which can be used in CIP hot water tank as well as can washer, crate washer & for floor cleaning points.
- A walk through audit of the plant during the shut down period revealed that there were compressed air leakages in a number of locations near the pouch packing machines especially in the air regulators. It is recommended that the leakages be identified & eliminated on a weekly basis. This will reduce power consumption in the air compressors.
- Compressed air is generated at a pressure of 6.5-8.0 kg/cm2g in the diary. The pneumatic valves require a minimum pressure of 6 kg/cm2g. Thus the pressure setting of the air compressor is is on the higher side. It is recommended that the cut-off pressure be reduced to 7.5 kg/cm2g initially & 10 eventually to 7.0 kg/cm2g. This will reduce the average compressed air generation pressure to 6.75 kg/cm2g as against the present 7.5 kg/cm2g leading to power savings.
- Present lighting single phase voltage is 240 to 245 volts. Nowadays lighting transformers are available, which reduce the voltage to around 210 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 15-20% of the power consumption.
For further information, please write to:
Sanrakshan Bhawan, 10,
Bhikaji Cama Place,|
Web site: www.pcra.org