CONSERVATION OF ENERGY IN SUGAR INDUSTRIES

National Sugar Institute, Kanpur

AREAS OF HIGH POWER CONSUMPTION

•Cane preparation

•Mills

•Condensing and Cooling

•Centrifugal

AREAS OF ENERGY CONSERVATION

Area Existing plant & process

Energy efficient plant & process

Energy production Boiler/Turbine efficient operation

High pressure boiler/condensing turbine

Energy consumption Use of VFD, Helical gears, Anti friction bearings, Use of flashes etc.

DC/AC thyristor controlled motors, continuous pan, direct contact heaters etc.

ENERGY CONSERVATION POTENTIAL IN SUGAR INDUSTRY

• Indian sugar industry is highly energy-intensive

• Energy efficiency is well below that of other industrialized countries

• Energy conservation measures shall lead to reduction in cost of production

• Thus to make Indian sugar Industry more competitive globally

• The total energy conservation potential is 25% of total energy consumption

POTENTIAL FOR REDUCTION IN STEAM CONSUMPTION

• Reduction in direct steam leakages

• Insulation of bare pipes flanges and valves etc. to reduce surface temperature 55oC

• Reduction in redundant steam pipelines

• Pressure control and syrup Brix control in the evaporator section

• Adequate changes in steam and juice piping to ensure juice heating from different bodies of evaporator

• Application of continuous crystallizers for A B & C massecuites and continuous centrifugals for B & C curing, high gravity/high capacity batch centrifugals for a curing etc.

• Improved instrumentation and control for pressure and temperature of exhaust steam required for process

• Rationalization of operations of minimize fluctuations in steam demand

MAJOR ENERGY EFFICIENCY IMPROVEMENT AREAS IN SUGAR INDUSTRY

• CANE MILLING

• STEAM GENERATION

• POWER GENERATION

• SUGAR PROCESSING

• LIGHTING SYSTEM

• CO-GENERATION

CANE MILLING

• Use of antifriction bearings at head and tail shafts of cane carrier and mill transmission gears

• Use of HT motors for cane cutter and fibrizer

• Use of VFD at cane carriers, rake carriers

• Use of high efficiency planetary gear drive

• Use of hydraulic motor and AC VFD for mill drive

• Use of belt conveyor in place of chain and slat conveyor

• Optimization of imbibition percent

• Adoption of complete mill house automation

• Proper planning to decrease stoppages/reduce crushing situation due to shortage of cane

STEAM GENERATION

• By adopting high efficiency boilers, steam generation to fuel ratio can be increased

• Reduction in specific steam consumption by adopting high pressure and high temperature boilers

• Recovery of heat from flue gas by using bagasse dryer

• Use of VFD for ID and FD fans

• Use of HP/LP heater for boiler feed water to increase cycle efficiency

• Recovery of heat from blowdown

• The amount of blowdown should be minimized

• Add waste heat recovery unit to blowdown for flash steam generation

• Adoption of complete combustion

• Control on excess air supply

EFFICIENT BOILER OPERATION

• It may means to reduce the heat losses to minimum so as to increase the efficiency of boiler

• HEAT LOSSES

1. Heat loss in flue gas

2. Heat loss due to moisture in bagasse

3. Heat loss due to Hydrogen present in bagasse

4. Heat loss due to blowdown

5. Heat loss due to radiation/convection

6. Heat loss due to bad combustion of Carbon

7. Losses in unburned solids

REDUCE STACK TEMPERATURE

• Stack temperature greater than 170 deg. C indicates potential for recovery of waste heat

• Use of bagasse dryer

• 22deg.C reduction in flue gas temperature increase boiler efficiency by 1%

COMBUSTION AIR HEATING

• The rise in combustion air temperature by 20deg.C will improve thermal efficiency by 1%

INCOMPLETE COMBUSTION

IT MAY BE DUE TO FOLLOWING REASONS

• Shortage of excess air

• Excess of fuel supply

• Poor distribution of fuel

CONTROL ON EXCESS AIR

• The optimum excess air level varies with furnace design, type of fuel and process variable

• Excess air % theoretical air should not exceed to 35%

• For every 1% reduction in excess air, 0.6% rise in boiler efficiency

RADIATION AND CONVECTION HEAT LOSS

• The surfaces lose heat to the surroundings depending on surface area and the difference in temperature between the surface and surroundings

• With modern design boiler this loss may represent only 1.5% on GCV

BLOWDOWN HEAT LOSS

• This loss varies between 1% to 6% and depends on number of factors

• Total dissolved solids (TDS) allowable in boiler water

• Quality of makeup water

• Amount of uncontaminated condensate return

• Boiler load variations

• Correct checking and maintenance of feed water and boiler water quality, maximising condensate return and smoothing load swings will minimise the loss

BLOWDOWN HEAT RECOVERY

• Blowdown of boilers to reduce sludge and solids contents allows heat to go down the drain

• The amount of blowdown should be minimised by allowing a good water treatment programme

• Installation of a heat recovery unit (heat exchanger) in the blowdown line allows the waste heat to be used in preheating make up and feed water

AUTOMATIC BLOWDOWN CONTROL

• Uncontrolled continuous blowdown is very wasteful

• Automatic blowdown control can be installed that sense and respond to boiler water conductivity and pH

REDUCTION OF SCALING AND SOOT

LOSSES

• Soot build up on tubes acts as an insulator against heat transfer. Any such deposits should be removed on a regular basis. Elevated stack temperature may indicate excessive soot build up. Also same results will occur due to scaling on the water side.

• Stack temperature should be checked and recorded regularly as an indicator of soot deposits.

• Every millimeter thickness of soot coating increases the stack temperature by about 55 deg.C

• 3mm of soot thickness can cause an increase in fuel consumption by 2.5%

• A 1mm thick scale on water side could increase fuel consumption by 5 to 8%

SUGAR PROCESSING • Optimization of evaporator design to minimize exhaust steam needs and

maximize vapor bleeding

• Optimization of syrup Brix

• Stepwise recovery of flash heat from the condensate of evaporator, juice heaters and pans

• Use of first condensate for wash water heating at centrifugals.

• Recovery of waste heat from clarifier flash tank

• Selective incorporation of direct contact heater

• Use of continuous pans for massecuite boiling

• Seed sugar melting by using syrup and very low temperature vapour in place of exhaust steam and hot water

• Use of efficient heat exchanger

• Elimination of direct live steam bleeding in process

• Adoption of process automation and controls

• Discouraging production of bold grain

• Use of low temperature vapour for pan washing

• Heating of air by hot condensate at sugar dryer / hopper

• Recovery of heat from non condensable gases

USE OF PLANETARY GEAR DRIVE

• Transmission efficiency is about 90%

• Combined efficiency of conventional worm and worm wheel with enclosed worm gear box is hardly 40-50%

HELICAL GEAR DRIVE

• The efficiency of helical gear drive is approx. 96-97%

• The efficiency of worm gear box is 70-80%

LIGHTING SYSTEM

• Make maximum use of natural light (Use of translucent sheets / more windows and opening)

• Switch off when not required

• Modify lighting layout to meet the need

• Provide lighting transformer to operate at reduced Voltage

• Install energy efficient lamps, luminaries and controls

• Use of gas discharge lamps in place of incandescent lamps

• Use of Compact Fluorescent lamps (CFL)

• Use of Metal Halide lamps in place of Mercury/Sodium lamps

CO-GENERATION

• Sequential production of process heat and electricity to export with same fuel is termed as co-generation

• In sugar industry the co-generation is of TOPPING CYCLE

• TOPPING CYCLE

The steam generated is fed to the turbo generator and extracted at desired pressure for process work

BENEFIT OF CO-GENERATION

• The fuel, bagasse is renewable source of energy

• The sugar industry generates additional power with the bagasse which is used for generation of steam to meet process requirements

• Results in reduced emission levels and global warming and is therefore environment friendly

• Ensure fuel security

• Co-generation project leads to reduction in transmission losses considerably and thus helps in stabilizing the grid voltage because of their proximity to the load centres

ENERGY EFFICIENCY IMPROVEMENT

• The system upgradation in the entire sugar manufacturing process for improved energy efficiency goes for maximizing exportable power from co-generation plant

• Energy efficiency improvement and energy conservation is of great importance for making the co-generation project viable and sustainable in the long run.

• Implementing energy conservation measures in respect of both steam and electricity will reduce captive consumption and help to save additional quantity of bagasse/electricity.

TURBINE COFIGURATIONS FOR CO-GENERATION

• Pure back pressure turbine

• Single extraction back pressure turbine

• Double extraction back pressure turbine

• Pure condensing turbine

• Single extraction condensing turbine

• Double extraction condensing turbine

AREAS OF ENERGY CONSERVATIONSteam temperature at the turbine inlet, Steam pressure at the

turbine inlet, Kg/cm

40 62 63 100

440 4.25 4.00 3.90 3.86

460 4.03 3.82 3.80 3.76

470 3.98 3.79 3.70 3.60

480 3.94 3.75 3.68 3.57

490 3.90 3.72 3.60 3.50

510 3.80 3.65 3.55 3.35

RENEWABLE ENERGY

Renewable can create a significant impact in electric power generation. Indian Renewable energy programme is the largest and most extensive among the developing country. Ministry of Non-conventional energy the nodal Ministry of the Govt. is entrusted with responsibility of policy making, planning, information and co-ordination of various aspects of renewable energy. As per their draft policy set up for the goal is to be achieved till 2012 an addition of 10% share I.e. 12000 MW through renewable.

RENEWABLE ENERGY SOURCES

• Co-generation from bagasse

• Supplementary fuel such as cane trashes, wood chips, rice husk and other biomass material

• Hydro-power

• Wind power

• Sea tides

• Pelamis wave power