Saturday, April 29, 2017

Energy Audit at Dairy plant at Anand, GujaratPrint


A comprehensive energy conservation study of the Dairy plant at Anand, Gujarat was carried out by PCRA.This Dairy is engaged in the manufacture of various qualities of milk viz. standard, gold & pasteurised milk & also other milk products like butter, ghee, as well as milk powder in their plant. The milk processing capacity of the plant is 10 lakh litres per day.There are 4 nos. boilers of various capacities using natural gas as fuel for generating steam for use in the plant. The annual consumption of natural gas is 50 Lakh NM3 . Natural gas is also used as fuel in powder plant air heater .There are 3 powder plants with air heaters of various capacities The natural gas consumption of the air heater is also around 51.48 lakh Nm3.

The unit takes its electricity supply from the GEB .The contract demand is 3000KVA.The unit has also installed 2 nos. GG sets of 380 KVA operating on natural gas which generates electricity in the plant. 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.

A comprehensive energy conservation study of the plant was carried out by PCRA, The identified total annual energy saving potential is around 139.55 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 levels in the boiler was very high. It is recommended that the unit procure a combustion gas analyzer as this will help in maintaining & optimising the boiler efficiency.
  • It is recommended that an autoblowdown controller be installed on the boiler. This will optimise the boiler water TDS to 3500 ppm & thus reduce chances of water carryover along with the steam.
  • It is observed that the flue gas temperature for the 10 TPh boiler is quite high at 225 deg C on natural gas firing. It is recommended that an economiser or a preheater should be installed to preheat boiler feed water /combustion air. This will result in savings of natural gas.
  • Steam line insulation is not in good shape . 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.
  • It is recommended that the condensate should be pumped automatically from the F-60 & F-35 powder plants & also Amul 3 process. Online conductivity meters should be installed for F-60 & F-35 to check for condensate contamination. This will increase the boiler feed water temperature by at least 20 deg C.
  • Excess air levels were found to be high in F - 60 air heaters. It is recommended that the air heaters be tuned to minimise excess air.
  • There is tremendous air infiltration into the F - 35 air heaters thus increasing the excess air levels. However, as the air heaters are of single pass model, even if the air infiltration is brought down, the flue gas temperature will increase & their efficiency will remain constant at around 60%. The F - 35 plant is not in operation most of the time & thus the replacement of these air heaters is not warranted. In case, the cheese whey production starts in full swing in the F -35 plant, then it is recommended that the air heaters be replaced by new modern air heater, thereby increasing its efficiency by at least 33% resulting in savings in natural gas.
  • Presently milk is preheated from 8 - 10 deg c to 70 deg c progressively in tube bundles fitted in each calendria or a separate heat exchanger in the calendria. The milk passes from the last calendria to the first calendria picking up heat. It is proposed that the milk be preheated externally thus reducing/eliminating steam load for milk preheating.
  • A few motors in the plant were found to be under loaded. 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. This is because the efficiency of the motors when operating on low loads is better in star mode than in delta mode.
  • Chilled water is sent to the plant at 1- 2 deg c & comes back to the refrigeration section at 7 -8 deg c. It is chilled to 2-4 deg c in the PHE instant chillers- PHE+shell & then sent to the Ice building tank. Both these refrigeration loads are handled by a single - 10 deg c ammonia refrigeration system. It is recommended that the load be handled by a 2 stage system. Ammonia from the -2 deg c accumulator be used in the instant chillers & ammonia from the -5 deg c accumulator be used in the IBT & for other loads.
  • It is recommended that the air conditioning cooling loads in the plant be catered to by installing a double effect vapor absorption system based on high pressure steam.
  • It is recommended that evaporative condensers be fitted for the refrigeration systems. This will drastically reduce the power consumption in the pumping.
  • A low cost option is to replace the cooling tower pumps & the condenser pumps with lower head pumps. Presently the rated head of the pumps is 20 meters. They can be replaced with pumps of 8 meters rated head. The savings will be reduced to 40 KW. However, the investment levels will be highly reduced.
  • It is observed that the temperature in cold store /deep freezes is controlled manually. It is recommended that auto temperature control switches be installed for shutting of ammonia solenoid valves incase the cold store/deep freeze temperature has been achieved.
  • 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.
  • It is recommended to replace the existing 4 feet fluorescent tubes with Asian “E+” energy efficient tubelights. Power consumption of these tubelights is 28 Watts.

 

For further information, please write to:

Director (I/C),
PCRA,
Sanrakshan Bhawan, 10,
Bhikaji Cama Place,|
New Delhi-110066
Telephone: +91-11-26198856
Fax. +91-11-26109668
Web site: www.pcra.org