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Food & Beverage

Sector Highlights

Nepalese food sector is a very wide sector consisting of various types of industries such as sugar, flour mills, vegetable oil and ghee, noodles, biscuit, dairy, rice mills, beverage, confectionary, etc. This article considers only sugar industries as one represenatation of the food sector having huge energy saving potentials. Presently, the Sugar industries are producing white plantation sugar as main product, while baggasse and molasses are also produced in considerable quantity as valuable byproducts. Molasses is used as raw material for Spirit production and the bagasse is used by the industries as a primary energy to produce electricity as well as heat energy (GIZ/NEEP, 2012).

At present there are five large sugar mills in operation. Including around 50 small scale raw sugar producing units (so called “Khandsari) Nepal’s sugar sector provides employment to 3,432 persons and has a  value of output of NPR 3.279 Billion against the input of NPR 2.864 Billion and value addition of NPR 0.415 Billion (CBS, 2006).

Process

The major processes involved in the production of sugar are

  • Milling (Juice Extraction),
  • Evaporation,
  • Crystallization and
  • Centrifugal separation and
  • Washing of the crystallized sugar.

Process flowchart of a sugar mill

Energy Use

Sugar industries in Nepal are operational for nearly 3 to 4 months a year during the cane harvesting season (generally from December to March).

Main source of energy used in the Sugar industries in Nepal is bagasse which is a by-product of the sugar processing. Bagasse is used as fuel high pressure steam turbine to generate electricity that is mainly used for operation of different electrical drives and equipments. Electricity supply from utility company is only used for lighting and carrying out operation and maintenance work. Thermal energy is required for the operation of high pressure boilers that are also using the bagasse as fuel. All sugar mills have their own Diesel Generator set to supplement the power supply mainly for the lighting and maintenance purposes during power failure from the central grid.

Table 1: Specific energy consumption in Nepalese sugar mills (GIZ/NEEP, 2012)
Specific Energy Consumption per ton of product
Electrical Thermal
68.50 kWh/ton 128.53 MJ/ton

Heavy motors are used in sugar industries for crushing, pumps, fans, compressors and other motors. Sugar mills use old and rewound motors. The industries have not checked their motor loadings and not carried energy audit in the industries. All the mills have installed capacitor banks to improve the power factor. One of the sugar mills has surplus turbine capacity and this can be readily utilized for the supply of electricity to grid by co-generation.

Major energy consuming sections and equipment in Nepal’s Sugar mills are:

  • Cane preparation
  • Milling
  • Evaporators
  • Centrifuging
  • Boilers and Co-generation plant
  • Electrical Distribution transformer & Power systems
  • Electrical drives
  • Compressors
  • Lighting system
  • Material handling equipments.

References

  • GIZ/NEEP, 2012: Baseline Study of Selected Sector Industries to assess the Potentials for more efficient use of energy.
  • Central Bureau of Statistics (CBS), 2007: Census of Manufacturing Establishments carried out in the fiscal year 2006/07.

 

 

Saving Potential

It is estimated that sugar mill units could save around 1,900 MWh of electricity and 5,080 GJ of thermal energy. By implementing energy efficiency the sector could achieve monetary savings of about 210 Lakh Nepalese Rupees annually. In total food sector could save energy costs of around 78 Crore NPR by going efficient (GIZ/NEEP, 2012).

Table 1: Energy Saving potential in 8 Energy-intensive industrial sectors in Nepal (GIZ/NEEP, 2012)

Moreover, by implementing the concept of co-generation based on its by-product bagasse , sugar mills in Nepal could generate electricity of around 70 MW capacity. They could feed electricity into the grid during dry season and, thus, contribute to mitigate load shedding.

Experience from the past have identified many options for improving energy efficiency in sugar industries that are highly profitable, most of them with payback periods of investment of less than 1 year.

Table 2: Energy saving options for sugar mills and payback period of investment (Danida/ESPS, 2005)

Energy Saving Tips

Huge saving opportunities in sugar mills can be achieved in the following areas:

Cane Preparation & Juice Extraction

  • Install lower size pump for weighted juice pump/Install VFD for weighed juice pump
  • Install correct size pump for crusher
  • Install correct size pump for imbibition water pump
  • Install lower head pump with VFD for raw juice pump
  • Install right size pump for imbibition water pumping
  • Install Variable Frequency Drive for Imbibition Water Pump
  • Install variable frequency drive(VFD) for cane carrier drives
  • Install VFD for weighed juice pump
  • Install DC drives/hydraulic for mill drives & shredder
  • Install electronic mass flow meters for all three mills and avoid use of weighed juice transfer pump.

Juice Heating, Sulphitation, Clarification & Crystallization

  • Utilize L P steam for sugar dryer and sugar melting
  • Avoid condensate water pumps at juice heaters and evaporators
  • Commission load/unload mechanism for sulphur air compressors
  • Improve flash steam utilization for S K condensate and quad-1
  • Improve sealing of the stand-by blower, avoid damper control and reduce impeller size of the sugar drier blower
  • Install lower size pump for clarified pumping/install VFD for clarified juice pump
  • Install lower size pump for sulphite juice tank/install VFD for sulphite juice pump
  • Install right pump for filter condenser water pumping
  • Install rotary blower in place of Compressor for supplying air to syrup sulphur burner
  • Install Variable Frequency Drive for super heated wash water pump
  • Install VFD/small size pump/lower size impeller for mill IV juice transfer pump
  • Optimize operation of spray pump
  • Provide VFD for booster vacuum pump of vacuum pans (1-12)
  • Provide VFD for rotary blowers of sulphur burner
  • Segregate high vacuum and low vacuum requirements of Oliver filter
  • Segregate spray water and jet water and use cold water only for spray

Cogeneration system

  • Arrest air infiltration in boilers
  • Arrest identified steam leaks and improve the working of steam traps in identified areas
  • Improve combustion efficiency of all the boilers
  • Improve insulation in identified areas
  • Rationalize condensate collection system
  • Reduce RPM of power plant air compressor
  • Use exhaust steam for deaerator water heating
  • Convert identified MP steam users to LP steam users
  • Install a flash vessel to recover the flash from the boiler continuous blow down & HP steam header traps drain and connect to exhaust header
  • Install correct size pump for the condensate transfer pump
  • Install L P steam heater in delivery of boiler feed water pump
  • Install steam jet ejectors in place of vacuum pumps for vacuum filters
  • Install thermo compressors with 150 psi steam for compressing 8 psi and 12 psi exhaust vapors to 16 psi
  • Install variable fluid coupling for boiler ID fans
  • Install Variable Frequency Drive for Auxiliary Cooling Water (ACW) pump
  • Install Variable Frequency Drive for Condenser Water pump
  • Install Variable Frequency Drive for SA & PS fans and operate in open loop control
  • Install VFD for Boiler feed water pump
  • Optimize capacity of boiler house compressor
  • Replace identified fans with correct size high efficiency fans
  • Commission de-aerator and utilize L P steam for heating condensate water in de-aerator
  • Install heat exchanger to preheat boiler feed water

Distillery

  • Increase the temperature of fermented wash from 83 degree C to 90 Degree C by installing additional plates
  • Install additional standby PHE for fermented wash heating
  • Install lower head pump for fomenter circulation pump
  • Install steam ejector and utilize LP steam for distilleries

Electrical

  • Convert delta to permanent star connection for the identified lightly loaded motors
  • Install automatic star - delta - star converter in the identified lightly loaded motors
  • Optimize the plant operating frequency, if operating in island mode
  • Optimize the plant operating voltage
  • Improve the P.F of the Identified feeders and reduce the cable loss
  • Install automatic slip ring controller for the cane leveler
  • Install soft starter cum energy saver at the lightly loaded motors
  • Replace filament lamps installed in panel on/off indications with energy efficient led lamps
  • Replace identified faulty capacitor banks

Lighting

  • Avoid daytime lighting in identified areas
  • Increase the natural lighting by installing translucent sheets and switch off the identified light
  • Install 50 KVA step down transformer at the main lighting circuit
  • Convert the 100W incandescent lamps with 40W fluorescent lamps
  • Convert the existing 200W, 300W & 500W incandescent lamps with 160W choke less LML lamps
  • Convert the existing 40W fluorescent tubes with 36W slim tubes
  • Covert the 400 W high pressure mercury vapor lamps (HPMV) with 250 W energy efficient high pressure sodium vapor lamps (HPSV)
  • Install automatic voltage stabilizer in lighting feeder and operate at 205 -210 volts
  • Install energy efficient Copper chokes for identified fluorescent lamps

Miscellaneous

  • Install level based ON / OFF control for service water pumps
  • Install LIC for service tank/Install correct size pump for service tank
  • Install temperature cut-off switch for cooling tower fans
  • Arrest compressed air leakages at packing section
  • Convert ‘V’ belt to flat belt drive at the identified equipment
  • Install auto drain valve for instrument air compressor
  • Install correct size pumps for hot water pumping at cooling tower
  • Install FRP blades for process Cooling Tower fans
  • Install next lower size impeller for hot water process cooling tower pump
  • Install Variable Frequency Drive for Cooling Tower fans
  • Install Variable Frequency Drive for service water pump
  • Provide cooling tower for identified equipments and stop use of fresh water
  • Segregate the low vacuum and high vacuum of Oliver filter

References

  • GIZ/NEEP, 2012: Baseline Study of Selected Sector Industries to assess the Potentials for more efficient use of energy.
  • Danida/ESPS, 2005: Cleaner Production report of Sugar industry.
  • Confederation of Indian Industry: Investors manual for Energy Efficiency.
 
 

Further Resources

Energy Conservation through Co-generation in Sugar mills in India Detailed paper on energy conservation opportunities and co-generation concept for sugar mills based on experiences in India and provided by Energy Manager Training India.

Energy Manager Training India – Sugar mills Knowledge base and platform for energy auditors in India established by Bureau of Energy Efficiency India and supported by Indo-German Energy Program (IGEN). The webpage contains a database of industrial processes and respective energy saving measures as well as a directory of energy efficiency professionals and technology suppliers from India.

Energy Manager Training India – Dairy industry Knowledge base and platform for energy auditors in India established by Bureau of Energy Efficiency India and supported by Indo-German Energy Program (IGEN). The webpage contains a database of industrial processes and respective energy saving measures as well as a directory of energy efficiency professionals and technology suppliers from India.

Energy Manager Training India – Tea industry Knowledge base and platform for energy auditors in India established by Bureau of Energy Efficiency India and supported by Indo-German Energy Program (IGEN). The webpage contains a database of industrial processes and respective energy saving measures as well as a directory of energy efficiency professionals and technology suppliers from India.

Rice Knowledge Base – Rice milling The Cereal Knowledge Bank (CKB) is the world’s leading repository of extension and training materials related to cereal and cereal production. The CKB was launched in January 2008 and is managed by the International Rice Research Institute (IRRI) and International Maize and Wheat Improvement Center (CIMMYT) as a service to people working to improve the well-being of poor cereal farmers and consumers. The section rice milling contains comprehensive information on rice milling process and energy saving opportunities.