Energy Saving Potentials
Major areas for potential energy savings in Nepalese pulp and paper industries are: Improvement of combustion efficiency in the boiler, Steam distribution system including leakage control and insulation improvement, Electricity load management.
The energy cost of product value in Nepal’s pulp and paper industries is estimated to be almost 20 %. That means pulp and paper sector stands is the sector with the fourth highest energy cost per product value after Limestone-based cement, Cold storage and Fixed Chimney Brick industries.
In total Nepalese pulp and paper units could save around 919 MWh electricity annually and 136,848 GJ thermal energy (see Table). By implementing energy efficiency the sector could achieve monetary savings of about 33,663,971 Crore Nepalese Rupees (GIZ/NEEP, 2012).
Figure 1:: Monetary savings potential for Nepalese pulp and paper sector (GIZ/NEEP, 2012).
Experience from the past have identified many options for improving energy efficiency in pulp and paper industries that are highly profitable, most of them with payback periods of investment of less than 1 year. The following table shows some implemented examples option in Nepalese pulp and paper factories with the respected payback (Danida/ESPS, 2005).
Table 1: Energy saving options for Pulp & Paper section and payback period (Danida/ESPS, 2005)
Energy Saving Tips
In the following areas large energy savings can be achieved by implementation the options mentioned below:
- Avoid idle running of chippers, conveyors, etc. by installing simple interlocks.
- Ensure optimum loading of chippers
- Avoid fresh water for pulpers and beaters and use back water
- Interlock agitators with pumps at storage chests
- Providing timer control for agitators for sequential operation
- Optimize fresh water consumption in pulp mill washers e.g., alkali washer back water in chlorine washer and chlorine washer back water in brown stock washed pulp.
- Install belt conveyor for conveying wood chips instead of pneumatic conveyors.
- Install VSD for cutters and chippers
- Install two stage preheating in digesters (combination of MP steam and LP steam)
- Install water ring vacuum pumps instead of steam ejectors in evaporators, depending on the cost of steam.
- Install high capacity chippers with mechanized feeding
- Install oxygen delignification
- Installation of TDR's in place of beaters
- Install medium consistency pumping
- Replace brown stock washing with double wire press system
- Install high efficiency washing system such as, Flat belt/wire washer, Double wire press, Twin roll press
- Install VSD for primary, secondary and tertiary centri-cleaners, pumps of unbleached and bleached pulp.
- Install pressure screens in pulp mill and avoid centri-cleaners
- Install 7-effect evaporator instead of conventional triple-effect evaporator
- Installation of falling film evaporator
- Install 2-stage steam heating in black liquor pre-heater
- Install soda recovery plant in medium sized paper plants
- Install causticiser and rotary lime kiln
- Increase in TAA to get higher solids concentration in black liquor
- Installation of plate heat exchanger in evaporator section
- Optimise loading of refiners and beaters
- Interlock agitators with pumps at storage chests
- Minimise recirculation in receiving chest and machine chest
- Optimising excess capacity/ head in pump by change of impeller or trimming of impeller size
- Avoiding pump operation by utilisation of gravity head
- Optimise capacity of vacuum pumps by RPM reduction
- Install level indicating controllers for couch pit pumps
- Optimising pressure of high pressure pump used for wire cleaning and deck showers
- Stopping broke deflaker when broke refiner is in operation
- Install new correct size high efficiency pumps
- Install new high efficiency fans & blowers in boiler
- VSD for displacement pump, discharge pump, hot fill pump and warm fill pump of washing and screening plant
- Replace eddy current drive with VFD for washing and bleaching
- Install suspension type agitators to keep the pulp in suspension during pumping
- Optimising the capacity of vacuum pumps by RPM reduction or bleed-in control
- Optimise the suction line size of water ring vacuum pumps
- Install pre-separators for water ring vacuum pumps
- Install mixing type agitators to mix different types of pulp
- Introduce double dilution system
- Install double disc refiners instead of conical refiners
- Install VSD for paper machine fan pumps
- Install VSD for tanks dilution pumps
- Install VSD for mould fan pumps
- Install VSD for flat box vacuum pump to avoid bleeding or throttling
- Avoid interconnection of high and low vacuum sections
- Optimise suction pipe line size for water ring vacuum pumps
- Install pre-separators and extraction pumps for water ring vacuum pumps
- Install dual speed motors for couch pit agitator and press pit agitator
- Install VSD for MG machine/MF machine hood fans
- Replace steam ejector with water ring vacuum pump in evaporator section
- Install cascade condensate system in paper machine area
- Install flash steam recovery system for paper machines
- Reel pulper operation optimized by effective utilization of winder pulper
- Optimizing operation of hydraulic system of calender
- Automatic operation of hood and ventilation system
- Replace conical refiners with double disc refiners
- Install conical port high efficiency vacuum pumps in place of flat port vacuum pumps
- Replace centrifugal screens with pressure screen
- Segregate high-vacuum & low-vacuum sections of the paper machine and connect to dedicated systems
- Segregation of high-head and low head users in cooling towers and process areas
- Install tri-nip press section in paper machine to reduce drying load
- Install computerised automatic moisture control system for paper machines
- Install paper machine hood heat recovery system
- Convert small steam turbines in paper machine area to DC or AC drive so as to enhance cogeneration.
- Monitor excess air levels in boilers and soda recovery boilers
- Arrest air infiltration in boiler flue gas path, particularly economiser and air pre-heater section
- Plug steam leakages, however small they may be
- Always avoid steam pressure reduction through PRVs. Instead, pass the steam through turbine so as to improve cogeneration
- Insulate all steam and condensate lines
- Monitor and replace defective steam traps on a regular basis
- In case coal has higher percentage of fines, ensure wetting is done.
- Monitor boiler blow down; use Eloguard for optimising boiler blow down
- Installation of flash vessels for heat recovery from hot condensate vapours
- Monitor the blow-down quantity of water in cooling towers and the quality of water
- Install chlorine dosing and HCl dosing for circulating water.
- Install automatic combustion control system/ oxygen trim control system in steam boilers and soda recovery boilers
- Install economiser/air preheater for boilers
- Use of cheaper fuels, like bamboo dust, wood barks, pith etc.
- Install boiler air preheater based on steam to enhance cogeneration
- Install high temperature deaerator (120°C to 140°C) with suitable boiler feed water pump to enhance cogeneration
- Install heat recovery from boiler blow down
- Convert medium pressure steam users to LP steam users to increase co-generation
- Reducing moisture content of wet pith using screw presses for burning in boilers
- Install condensate recovery systems in digesters, paper machines, evaporators and air heaters
- Install automatic blow down system for boilers
- Install sonic soot blowers in place of steam operated soot blowing system
- Install VSD for SA fan, FD fan and ID fan
- Install VSD for boiler feed water pump
- Install VSD for clarified water pumps
- Install VSD for raw water/recycle water pumps
- Install VSD for roots blower (agitation purposes)
- Install VSD for final effluent discharge pumps
- Replace dyno-drives with VSD in coal feeder
- Install VSD for vibrating screen, lime feeder and mud filters in recovery boiler
- Convert chain grate/spreader stoker boilers to FBC
- Install co-generation system for medium sized paper plants
- Install vapour absorption system to utilise LP steam and enhance cogeneration
- Install cascade condensate recovery system in paper machine
- Install cascade evaporators in soda recovery plant
- Maximising solids concentration in Recovery boiler
- Rotary feeder for lime kiln feeding system
- Install steam-generating system from DG exhaust, if DG is run on a continuous basis
- Install scoop type syphons in the dryer cylinders of paper machine instead of conventional steam & condensate system with rotary joints
- Install hood recovery systems in paper machine to minimize steam consumption
- Install delta to star convertors for lightly loaded motors
- Use translucent sheets to make use of day lighting
- Install timers for automatic switching ON-OFF of lights
- Install timers for yard and outside lighting
- Grouping of lighting circuits for better control
- Operate at maximum power factor, say 0.96 and above
- Optimise TG/DG sets operating frequency and voltage
- Install maximum demand controller to optimise maximum demand
- Install capacitor banks to improve power factor
- Replace rewound motors with energy efficient motors
- Install energy efficient motors as a replacement policy
- Replace 40 Watts fluorescent lamps with 36 Watts fluorescent lamps
- Replace conventional ballast with high efficiency electronic ballasts in all discharge lamps
- Install LED lamps for panel indication instead of filament lamps
- Install CFL's for lighting in non-critical areas, such as, toilets, corridors, canteens etc.
- Optimise voltage in lighting circuit by installing servo stabilisers
- Minimising overall distribution losses, by proper cable sizing and addition of capacitor banks
- Replace V-belts with synthetic flat belts
- Ensure air compressors are loaded to a level of 90%
- Set compressor delivery pressure as low as possible
- Monitor pressure drop across suction filter and after filter
- Segregate high pressure and low pressure users
- Replace heater - purge type air dryer with heat of compression (HOC) dryer for capacities above 500 cfm
- Avoid/ minimise compressed air leakages by vigorous maintenance
- Replace old and inefficient compressors with screw or centrifugal compressors
- Use cheaper fuel for high capacity DG sets
- Increase loading on DG sets (maximum 90%)
- Increase engine jacket temperature (max. 85 o C) or as per engine specification
- Take turbocharger air inlet from outside engine room
- Installation of steam coil pre-heaters for DG set fuel in place of electrical heaters
- Replace multiple small size DG sets with bigger DG sets
- Replacement of Aluminium blades with FRP blades in cooling tower fans
- Install temperature indicator controller (TIC) for optimising cooling tower fan operation, based on ambient conditions
- Install dual speed motors/ VSD for cooling tower fans
- Install level indictor controllers to maintain chest level
- Install hour meters on all material handling equipment, such, pulpers, beaters etc.
- Floating type aerator in place of fixed aerators
- High efficiency diffuser aerators instead of conventional aerators
- Treatment of effluent through activated sludge lagoon resulting in stopping of aerators
- Solar water heating for canteen and guest house
- Replacement of Aluminium bus bars with Copper bus bars in caustic chlor unit
- Installation of DCS monitoring and targeting system for better load management
- 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 pulp and paper industry.
- Confederation of Indian Industry: Investors manual for Energy Efficiency.
- Central Bureau of Statistics (CBS), 2007: Census of Manufacturing Establishments carried out in the fiscal year 2006/07.
Supported By
