ENERGY SAVING IN STEAM GENERATION AND TRANSPORT IN FOOD INDUSTRY

1. ENERGY SAVING INSTEAM GENERATION AND TRANSPORT IN FOOD INDUSTRY • B. K. Kumbhar

2. Introduction • Energy – Important • Sources Exhausting at rapid rate prices increasing day by day • Energy cost 5% of total production cost • Neglected

3. HOT WATER OR STEAM? More accurate control without costly control equipments Efficient processing and high standard of hygiene with maximum fuel economy Thermal efficiency of hot water boilers is more and fuel requirement is about half Savings in water, maintenance and labour requirements, Maximum recovery is possible Lower reconstruction and capital costs Lower instrumentation costs Obviation of the use of chemicals High heat and moisture release is eliminated resulting a simple ventilation system Improvement in safety

4. Boiler Input-Output Fuel Air Water Boiler * Combustion * Heat Transfer Steam Flue gas Blowdown

6. 1. STEAM GENERATION • 1.1 Fuel • 1.2 Air • 1.3 Water • A. Treatment of water • B. Preheating of feed water • C. Use of condensate as feed water • 1.4 Flue gas • a) Temperature of flue gas • b) Quantity of flue gas • c) Condition of heat transfer surface in the boiler • 1.5 Blowdown • 1.6 Radiation and convection losses

7. 1.1 Fuel Quality of Fuel- Sulphur, Moisture content • Fuel oil Burners – Atomization - Air - Specific heat is less - Steam – Specific heat is more- twice Preheating • Coal Pulverization • Natural gas

8. 1.2 Air • Quantity Sufficient amount

9. 1.3 Water • Treatment of waterCa, Mg salts- scale formation- less heat transfer 0.79 mm – Increased fuel consumption – 7% 2.82 mm – 16% Oxygen and CO2, Low pH- Corrosion & Erosion treatment of feed water outside the boiler within the boiler (internal treatment) chemicals which remove hardness or scale forming materials that can not be removed by filtration. Oxygen and carbon dioxide - vacuum deaerators steam scrubbing deaerators

10. Water contd • Preheating of feed waterTemperature of feed water- efficiency • 6 C increase- 1% fuel saving • Economizer for preheating • Use of condensate as feed water • Reduction in use of chemicals for water softening • Preheating is prevented • Reduced water requirement • Temperature increase from 15.5 to 35 C with 100% condensate return reduced 4.2% fuel

11. 1.4 Flue gas Loss of energy> 18% • Temperature of flue gas • Temperature 70 C more than water temperature • Clean surface • Use of economizer- 10% fuel saving- payback period 1 year • Reduction of 22 C 1% increase in efficiency

12. Quantity of flue gas Proper air-fuel ratio Temperature Barometric pressure Humidity Specific gravity and viscosity of the fuel oil • Table 1 Suggested levels of excess air Fuel Burner Excess air, % Coal Spreader stoker 30‑60 Fuel oil Register type 5‑10 Multifuel type 10‑20 Natural gas Register type 5‑10 Multifuel 7‑12 •  Reduce excess air Keep CO2 level above 13% or O2 level below 3.5% 3% change in CO2 level increases 4% in efficiency 3-5% saving in automated control devices

13. Condition of heat transfer surface in the boiler • Clean surface – more heat transfer • Regular cleaning of all surfaces Standstill for few months corrosion of boiler due to residual moisture. Remove residual moisture with dryain • Residual moisture in dry air <30%

14. 1.5 Blowdown • Affects Make up water - Heat loss in blowdown Chemicals requirement • Frequency • Quantity • Heat recovery

15. Advantages of automatic Blowdown • Discharge less heat • Reduces treatment chemicals • Decrease make up water • About 20% saving from changeover

16. 1.6 Radiation and convection losses • Significant loss if not insulated • 1.5% loss in well insulated • capacity utilization. • Less- Radiation loss more • Boiler operation few hours a day • Use boiler stack damper • Close boiler house doors & windows

17. 2. STEAM TRANSPORT • 2.1 Quality steam • 2.2 Insulation • 2.3 Correct piping • 2.4 Strainers, steam traps and steam separators

18. 2.1 Quality steam • Steam Quality • Amount of water droplets present • Quality steam • Better heat transfer • Long life of the system • Dry, Clean, free from non condensable gases, right pressure and right temperature • Dirty steam • Erode and corrode value • Clogging of ports body • Leakage through valves • Non condensable – limit steam flow less heat transfer • 0254 moss film thickness – 3.3m of cu panel • Carbon di-oxide-carbonic acid- corrosion • Oxygen – accelerates corrosion

19. 2.2 Insulation • Personal protection • Condensation prevention • Process temperature control • Heat loss prevention Poor insulation – Up to 50% heat loss • To reduce loss of heat • Economic thickness – cost of fuel & insulating material installation cost, pipe size, annual hours of operation, boiler efficiency, pay back period. • Replace damaged insulation • Insulate values and flanges – uninsulated flange heat loss from 60 cm of untagged pipe.

20. 2.3 Correct piping Pipe size * Amount of steam to be transported * Pressure Oversize pipe • Pressure drop increases, • Temperature. Decreases – heat transfer reduction Length • Just sufficient • Excess length & redundant piping increases loss of heat • condensation of stem, corrosion of pipe

21. 2.4 Strainers, steam traps & steam separators • Strainers • Upstream of values and steam trafs to protect from clogging with dust & dire. • Steam traps • to remove condensate and non condensable correct size of steam trap. • Steam separator • To get drier steam – water dropter • Direction of flow path to changed • Accumulated water droplets sent to stem traps • Near a point of usage

22. 3. STEAM FOR PROCESSING • Quality steam • Efficient processes and equipment • Collecting condensate • Boiler feed water • Cleaning the equipment • Heating process streams

23. 4. WHAT CAN BE DONE? • a. Calculate the total heat, Q, present in the fuel by knowing the calorific value (cv) of the fuel and quantity of fuel (m) used. • b. Calculate the process heat requirement. This will include heat required for heating, evaporation and drying duties as the case may be. • Overall thermal efficiency of plant • Calculate total heat required in the plant • Calculate total heat available in the fuel • Boiler efficiency – 80% • Transport efficiency – 95% • Process/thermal efficiency – 80% • No. of plants – 61%

24. Boilers Large boiler – 75-85% efficiency Gas fired boilers – 92 % efficiency Efficient boiler operation and maintenance saving up to 35% Energy savings up to 20% in new boilers Efficiency • Combustion efficiency - how efficiently the boiler burns the fuel • Steady – state efficiency – under full load • Seasonal efficiency – over the entire heating season

25. Improving Efficiency • Energy saving devices - Economizer - Condensate recovery - Air preheaters - Turbulators - Oxygen trim controls - Load controls - older pneumatic control system - Analog control systems - Digital computer based distributed control systems Modern, multiple burner control and trim control – 3-5% saving

26. Selecting a new Boiler System • Replace old biter – 15 years old with a high efficiency model – save up to 35% • Older boilers oversized, inefficient • Multiple boiler systems more efficient than single boilers • Pay back period 2-4 years

27. Fire Side Maintenance • Minimize excess air – Regular monitoring (weekly) of gas oxygen or carbon dioxide content • Keep heat transfer surfaces clean - Soot build up on tubes – insulation - Elevated stack temperature Water side Maintenance • Reduce scale formation • Scale build up – loss by as much as 10-12% 1/8 inch. – 2-3% loss in boiler efficiency

28. Reduce boiler pressure – Reduction in fuel consumption and stack temperatures • Insulate Boiler and boiler piping 2.5 cm insulation – 80-90% reduction in heat loss • Optimize Boiler blowdown waters • Blowdown heat recovery - Blowdown rat4e 4-8% of total steam generated - AS high as 10% • Repair of steam leaks Steam leaks develop around valve stems pressure regulators and pipe joints Small leak represents a significant loss of energy Repair of leak have a short pay back (2-3) months.