Petroleum Conservation Research Association
Ministry of Petroleum & Natural Gas, Government of India
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Energy Audit at Dairy plant at Surat, Gujarat.Print
A comprehensive energy conservation study of the Dairy plant at Surat, Gujarat. was carried out by PCRA.This Dairy is engaged in the manufacture of various qualities of milk & also other milk products like butter, ghee, paneer, buttermilk, flavored milk , masti dahi , shrikhand as well as milk powder in their plant. The average milk processed per day is around 5.52 lakh litres . Annual Production of the plant Liquid milk – 226665 MT,Ghee – 2942 MT. Table butter – 584 MT,Skim milk powder – 814 MT,Paneer – 268 MT,Butter milk – 26730 MT,Flavored milk – 1033 MT,Masti Dahi – 459.82 MT,Shrikhand – 298 MT.There are 2 nos. boilers of capacity 5 tph each for generating steam for use in the plant. The boilers use natural gas as fuel. Natural gas is also used as fuel in powder plant air heater.Annual consumptionof N.gas is 1447388 SCM. The unit takes its electricity supply from the SEC. The contract demand is 1400KVA. Electricity is consumed in a variety of equipment in the refrigeration plant compressors & auxiliary equipment like cooling & chilled water pumps, powder plant blowers, air compressors, water & milk pumps & lighting. Annual electricity consumption is 81.39 LakhKWH
A comprehensive energy conservation study of the plant was carried out by PCRA, The identified total annual energy saving potential is around Rs. 22.28 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 boiler are on the higher side on low firing. However, some fine tuning can be done such that the oxygen % in the flue gases is 2.0% & 3.0% on high & low firing respectively. This will result in improvement in boiler efficiency
- As the flue gas temperatures are quite high, it is recommended that economizer/air preheater be fitted on the boiler. This will raise the boiler water temperature from 55 deg c to 80 deg c or alternatively preheat combustion air being fed to the boiler.
- Boiler blowdown is manual for the boiler. The raw water quality has been tested & the TDS level in raw water is around 150 ppm. Condensate is recovered from the powder plant. Make up water addition is around 50% when the powder plant is in operation & 100% when the powder plant is down. Boiler water TDS is observed to be below 2000 ppm. It is recommended that the blowdown frequency be reduced such that the boiler water TDS is increased to 3500 ppm. This will reduce the heat loss in boiler blowdown & improve the efficiency of the boilers.
- It is observed that the steam generation pressure is reduced to 7.5 kg/cm2g when the powder plant is not in operation. It is to be noted that when the boiler is operated at below its rated pressure, there is an increased tendency towards foaming & consequently a reduction in dryness fraction. It is observed that the water carried over with the steam is mostly drained through steam traps & thus wasted. It is recommended that the boiler be operated at its rated pressure. This will increase its dryness fraction to 0.99.
- Steam line insulation was in good shape in the plant. However, some the valves & flanges on the PRV stations are not insulated in the plant. It is recommended that the steam valves/flanges be insulated with box type insulation. This can be removed & fitted back as & when required.
- Steam is directly injected into hot water tanks for heating milk in pasteurizers. The hot water overflow is collected in a common tank & continuously pumped to the CIP tank. It is observed that the cold make up water addition is manual . This results in hot water tank overflowing sometimes due to unnecessary addition of cold make up water. It is recommended that level controllers be fitted for make up water addition. This will minimize steam consumption in the pasteurizers.
- It is observed that steam at 5 kg/cm2g is used in paneer hot water tank. It is recommended that the steam pressure be reduced to at least 3.5 kg/cm2g.
- The steam traps in the powder plant for vibrohot & vibrocold air heating were found with their bypass open. This results in steam wastage & increased consumption of natural gas. It is recommended that after the initial cold starting period is over, the operators should be instructed to close the bypass valves to avoid steam wastage.
- Condensate is recovered from the powder plant from the first effect & pumped to an insulated overhead tank. It then flows by gravity to the boiler feed water tank. It is recommended that the condensate be taken directly into the boiler feed water . It is observed that the make up water addition is manually done It is recommended that an automatic level controller be installed which will control the operation of the make up water pump.
- It is recommended that the air heater should be tuned to reduce the excess air levels.
- It is observed that the cooling water pump discharge to the cooling towers is throttled. Thus it is recommended that the present pump impeller be trimmed by 15%. This will lower the discharge head by 27% to 18 metres while lowering the flow by 15% only. This will result in significant power savings.
- The discharge dampers of both the supply air fan & the exhaust fan are throttled by 10%. It is recommended that the unit install variable speed drives for both the supply & exhaust fans to reduce power consumption. Moreover, the exhaust fan motor can be reduced from 125 HP to 75 motor from inhouse inventory as the VFDs will also incorporate soft starter which will regulate the starting torque & current sufficiently to reduce the size of the motor.
- The volumetric efficiency of the air compressor no.1 is not satisfactory. The plant personnel have commented that the compressor is due for servicing. It is recommended that the servicing be conducted at the earliest.
- Presently the lighting load is distributed on various panels in various MCCs. It is recommended that the lighting load be segregated. This will allow the installation of the lighting transformer for reducing lighting voltage & thus reducing power consumption in lighting. The unit has already installed a voltage transformer for reducing lighting voltage in the APS section. The capacity of the transformer is quite large & can handle the entire lighting load.
For further information, please write to:
Sanrakshan Bhawan, 10,
Bhikaji Cama Place,|
Web site: www.pcra.org