1. ENERGY SAVING IN STEAM GENERATION AND TRANSPORT IN FOOD INDUSTRY
B. K. Kumbhar
4/1/2017

2. Introduction Energy – Important
Sources Exhausting at rapid rate prices increasing day by day
Energy cost 5% of total production cost
Neglected
4/1/2017

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
4/1/2017

5. 4/1/2017

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
4/1/2017

7. 1.1 Fuel Quality of Fuel- Sulphur, Moisture content Fuel oil Coal
Burners – Atomization
- Air - Specific heat is less
- Steam – Specific heat is more- twice
Preheating
Coal
Pulverization
Natural gas
4/1/2017

8. 1.2 Air
Quantity
Sufficient amount
4/1/2017

9. 1.3 Water
Treatment of water Ca, 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
4/1/2017

10. Preheating of feed water Temperature of feed water- efficiency
Water contd
Preheating of feed water Temperature 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
4/1/2017

11. 1.4 Flue gas Temperature of flue gas Loss of energy> 18%
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
4/1/2017

12. Table 1 Suggested levels of excess air
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
4/1/2017

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%
4/1/2017

14. 1.5 Blowdown Affects Frequency Quantity Heat recovery Make up water -
Heat loss in blowdown
Chemicals requirement
Frequency
Quantity
Heat recovery
4/1/2017

15. Advantages of automatic Blowdown
Discharge less heat
Reduces treatment chemicals
Decrease make up water
About 20% saving from changeover
4/1/2017

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
4/1/2017

17. 2. STEAM TRANSPORT 2.2 Insulation 2.3 Correct piping
2.1 Quality steam
2.2 Insulation
2.3 Correct piping
2.4 Strainers, steam traps and steam separators
4/1/2017

18. 2.1 Quality steam Steam Quality Amount of water droplets present
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
4/1/2017

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.
4/1/2017

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
4/1/2017

21. 2.4 Strainers, steam traps & steam separators
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
4/1/2017

22. 3. STEAM FOR PROCESSING Quality steam
Efficient processes and equipment
Collecting condensate
Boiler feed water
Cleaning the equipment
Heating process streams
4/1/2017

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%
4/1/2017

24. Efficiency 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
4/1/2017

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
4/1/2017

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
4/1/2017

27. Fire Side Maintenance Water 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
4/1/2017

28. Optimize Boiler blowdown waters Blowdown heat recovery
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.
4/1/2017