Update on Energy Conservation Schemes

ABSTRACT

Sugarcane is a rich source of energy and sugarcane being renewable in nature, proper utilization of energy, results in reduction of Green House Effect. Steam Consumption has always played a vital role in the economics of sugar. Modern sugar plants are now acknowledging the potential as well as the need of conserving energy through introduction of high pressure boilers, extraction-cum-condensing turbines. Heat Recovery is an essential requirement for Conservation of energy in Sugar Plants. The Conventional Sugar Plants are still working at 50+% in old plants and in new plants it is around 35% - 40%. It has been observed that there is tremendous potential in the process house itself to reduce the steam consumption to less than 35% through waste heat recovery from hot condensates and flue gas. This paper can boost up not only the confidence levels of the sugar industry but also the economic production levels through energy conservation while simultaneously producing excellent quality sugar.

Steam Conservation SCHEME DETAILS

M/s Spray Engineering Devices Limited (SED) has identified several potential areas for steam conservation which brought down the process steam requirement to 35% – 40% on cane for plantation white sugar. SED has implemented the energy economy measure covering the area of clarifier, evaporator, vacuum pans, centrifugals, melter station, molasses conditioner and boiler station for reducing the process steam consumption.

Sugarcane (Energy-Cane)
  • Sugarcane, a rich source of energy can be renamed as “Energy Cane”.
  • Energy ratio for input to output is 1.8 for Sugarcane.
  • Sugarcane being a renewable crop gives lot of renewable energy resulting in reduction of green house effect.
  • The cost of energy in real terms will be as much as Rs. 7 – Rs. 9/- kg of sugar produced i.e. Rs. 800/- per bag of sugar.
Necessity of Energy Conservation
  • Increase in demand of electric power due to rapid industrialization and increasing domestic use.
  • Limited resources of coal and fossil fuels. Bagasse is renewable.
  • Reduced steam consumption for process will result in saving which can be used for additional power generation/ bagasse saving.
  • Environment – conservation and sustainable development.
Present Scenario
  • Steam generation/ Fuel ratio in average sugar industry is +2.00%. Hardly 2% sugar industry has achieved 2.3% steam-fuel ratio.
  • Steam consumption for process used to be 50%+ on cane.
  • Gradually reduced to about 45 to 46% on cane.
  • Less number of vapour bleeding stages resulting less steam economy.
  • Lot of HP steam is also used for process viz. sulphur burner and centrifugal station.
  • Non-utilisation of the heat available in condensates, waste gases (NCG), vapours going to atmosphere and flue gas.
  • No heating of D.M. water causing poor Boiler efficiency.
  • No heating of Boiler F.D. air.
Scope for Improvement
  • Steam/ Fuel ratio can be achieved to 2.5%.
  • The steam consumption can be brought down to less than 30% on cane.
  • Already achieved less than 35% on cane in no. of factories in India.
  • Reduction/ elimination of use of HP steam for process.
  • Improved vapour bleeding system from multiple effect evaporators.
  • Use of direct contact heaters for operating the system at low approach temperatures.

Approach adopted for improvement

Process House
  • Extensive vapour bleeding system from the evaporator (i.e. vapour bleeding from later effects).
  • Change the evaporator configuration wherever possible (DEVC + Quad to Quintuple mode).
  • Introduction of vapour line juice heaters to heat raw juice thereby reduction of loss of vapour to the condenser.
  • Use of low grade vapour for pan boiling by employing Spray Continuous Pan (SCP ® ).
  • Step-wise recovery of flash heat from the condensate from various sections using FLASH CIGAR ® .
  • Selective incorporation of direct contact heaters for juice heating, syrup, filtrate and molasses conditioning.
  • Use of low temperature vapours for pan washing.
  • Seed sugar melting by using syrup and very low temperature vapours in place of exhaust steam and hot water.
  • Use of exhaust condensate to heat the hot water for a sugar washing in centrifugals.
  • Heating of air by hot condensate at sugar dryer/ hopper.
Boiler House
  • Heating the Boiler FD air by using hot condensate.
  • Heat recovery from the boiler flue gas by heating the hot condensate.
Power House
  • Heating the turbine hot well condensate and DM water by surplus hot condensate from process.
  • Water ejector in place of steam ejector for vacuum creation.
CONCLUSIONS
  • By incorporating the above measures it is very much possible to bring down the Process steam consumption to level of 31% - 32% on cane.
  • Selective application of waste heat recovery system will help in reducing the process steam consumption.
  • Continued efforts will further reduce the same to less than 28% on cane.
  • This helps in saving lot of bagasse thereby enhanced scope for Co-generation of power.
ACKNOWLEDGEMENT

The authors wish to acknowledge the tremendous efforts put by the industry technologists to bring the above measures to reality and make them successful. The authors also wish to express their gratitude to the entrepreneurs who believed in this and invested their time and money to make these concepts successful.