Petroleum Conservation Research Association
Ministry of Petroleum & Natural Gas, Government of India
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Energy Audit at Dairy plant at Palanpur, Gujarat.Print
A comprehensive energy conservation study of the Dairy plant at Palanpur, 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, ice cream as well as milk powder in their plant. There are 2 plants – plant I – which is old & handles can reception & plant- II , which is modern & handles chilled milk reception The milk processing capacity is 3.3 & 5.3 lakh litres per day for Plant & Plant II respectively.Annual furnace oil consumption is 4555 MT for Plant-I and 3866 MT for plant- II.The unit takes its electricity supply from the GEB .The contract demand is 1400KVA & 2000 KVA for Plant I & Plant II respectively.
A comprehensive energy conservation study of the plant was carried out by PCRA, The identified total annual energy saving potential is around 169.05 lacs 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 level in all the boilers is satisfactory. However, some fine tuning can be done such that the oxygen % in the flue gases is 3.0%. This will result in improvement in boiler efficiency.
- Furnace in the main storage tank is heated by steam coils. This results in churning of the furnace oil & does not allow the moisture present in the furnace oil to settle down. It is recommended that steam heating in the main storage tank be stopped. It is also recommended that the furnace oil storage & service tanks should be drained at least once a week.
- It is observed that the steam coil in one of the furnace oil storage tanks is leaking. It is recommended that this be rectified as soon as possible.
- Furnace oil main storage tanks should be cleaned at least once a year to remove the sludge accumulated at the bottom of the tanks.
- During the audit study, it was observed that the autoblowdown valve was continuously blowing for at least 5 – 10 minutes & the TDS value of the boiler water was not coming below 3700 ppm. It is recommended that the autoblowdown TDS should be regularly cross-checked with samples tested in the laboratory. Moreover, it is recommended that a timer can be installed on the blowdown valve such that it is closed after a certain time period.
- It is recommended that heat from the blowdown from Plant I boiler be recovered by installing a blowdown heat recovery system.
- Steam line insulation was in good shape in the plant. All the valves & flanges are not insulated in the plant. Also some bare steam lines were observed. By insulating with 2" thick mineral wool with aluminium cladding, 90% of the heat loss can be minimised.
- A steam trap survey was conducted in the plant. Steam traps identified as leaking /blocked should be rectified immediately.
- Condensate should also be recovered from the 20 TPD plant & ghee plant. The unit is already thinking in this direction.
- Condensate from the 30 TPD plant is at a very high pressure. The present condensate recovery system installed does not recover the flash steam. It is recommended that flash steam recovery system be installed for recovering heat from the flash steam.
- It is recommended that the air heaters in 30 TPD plant in Plant I & 60 TPD plant in Plant II be tuned to reduce the excess air levels
- It is recommended that the supply air quantity for the 60 TPD spray dryer be reduced such that it is at design flow rate of 97000 kgs/hr. Further the supply air temperature should be raised to 185 deg C. It is to be noted that with addition of additives to the furnace oil , the flue gas temperature will not rise above 230 deg c. Thus, the supply air temperature can be raised to 185 deg c. This will result in savings of at least 10% of furnace oil in the 60 TPD air heaters. We suggest that trials be conducted on the spray dryer. Only if the trial is successful, these savings will be realized.
- Design air flow rate is not available for the 30 TPD plant. However, the present air flow of 70128 kgs/hr seems to be on the higher side. The unit is advised to reduce the air flow by 5% initially. This will result in an increase in supply air temperature & exhaust temperature. The milk flow will have to be increased to reduce the exhaust temperature to the original level of 90 deg c. It is estimated that savings of at least 5% can be achieved due to reduction in supply air flow to the air heater. This requires a detailed analysis from the unit. We suggest that trials be conducted on the spray dryer. Only if the trial is successful, these savings will be realized.
- Due to reduction in supply air flow by 10% in the 60 TPD plant, the power consumption in the Supply air fan can be brought down by 27%. Also power consumption in the exhaust fan will also come down due to reduction in air quantity. Thus it is recommended that the VFD be installed on the supply air fan to reduce its air flow & generate power savings. This is connected to the trial of reducing air flow in the 60 TPD plant. Only if the trial is successful, these savings will be realized.
- The power factor of the plant is not satisfactory. The average power factor for Plant I & Plant II is 0.986 & 0.977 respectively. It is recommended that the power factor be improved to 0.999. This will result in savings in electrical bills due to increase in rebate amount.
- The rated head of soft water & DM water pumps is quite high at 60 meters. It is recommended that the soft water & DM water pumps in the WTP section be replaced by new pumps with the same capacity & lower rated head & the throttling of the discharge valve reduced.
- It is recommended that one large pump of 200 m3/hr with a rated head of 35 meters head be installed. The chilled water flow normally required is around 200 m3/hr. Thus instead of operating 4 pumps in parallel only one large pump can be operated with its discharge valve fully open.
- The rated head of the condenser & the cooling tower pumps are high at 20 meters. Normally 2 sets of condenser pumps & 2 sets of CT pumps are in operation in the plant. Presently these pumps are operating in throttled conditioned. It is recommended that the impellers of all these pumps be trimmed by 10%. This will reduce the head delivered by these pumps by 19% & also reduce the power consumption by at least 20%.
- A few underloaded motors have been identified during the audit study. If the load on these motors is constant, the motors can be replaced by lower HP motors from the store/inventory.Alternatively, the motors should be connected permanently in star connection.
- The booster compressor in Plant I has an evaporator temperature is – 53 deg c corresponding to a suction pressure of 0.33 bar. The ice cream cold store temperature required is – 30 – 35 deg c. It is recommended that the evaporator temperature be raised to – 45 deg c. This will reduce electricity consumption in the booster compressors by at least 15 %.
- The ice cream deep freeze & the ice cream hardening room were converted from conventional cold stores. However, the insulation was not upgraded during the conversion. Thus , it is observed that the temperatures of the adjacent room to the ice cream deep freeze is as low as 11 deg c. It is recommended that the insulation be upgraded . This will reduce the cooling load on the refrigeration system drastically.
- Presently the – 10 deg c system in Plant II is operated at a suction pressure of 3.14 bar corresponding to a saturated suction temperature of -8.3 deg c. It is recommended that the – 10 deg c system be operated at -5 deg c. This will result in power savings.
- It is observed that milk is underchilled in the plant. During the audit study, we observed pasteurized milk temperatures ranging from as low as 3 deg c. This is a direct loss in terms of steam as well as of refrigeration capacity. It is recommended that the plant personnel be more vigilant & throttle the chilled water valves incase the milk flow in the pasteurizers is not as per the rated capacity of the unit.
- It is observed that the insulation of chilled water supply & return lines to Plant I is quite poor as seen from the moisture condensation on the surface of the lines. It is recommended that the insulation be upgraded at the earliest.
- It is recommended that mechanical pouch packaging machines be installed for replacing the 2nos pneumatic machines presently in operation in the pouch packing section.
- It is recommended that the compressed air requirement for powder plant pneumatic conveying system should be met by the central plant screw compressors. However, presently excess capacity is not available with the central compressors. After the pouch packing machines have been replaced by mechanical ones, excess capacity will be available .
- There are a large number of pneumatic control valves in Plant II process section. During the audit study a leakage round was taken with a leakage identification instrument. The leakages were pointed out to the plant personnel. It is recommended that these leakages be eliminated immediately. It is also recommended that the unit procure the instrument & conduct regular leakage surveys in the plant.
- 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