Energy Cost Reduction in a Rice Mill

1. Energy Cost Reduction in a Rice Mill

2. Contents • Introduction • Rice Processing • Flowchart of areas covered • Case study from Satnam Overseas Ltd.

3. Introduction • About 35000 rice mills in India • Small power requirement – less than 1 MW Steam demand – around 4TPH • Few large rice mills in North power requirement – around 1.5mw Steam demand – 10 to 15 TPH • However low eff of low cost equipments being used offers good business opportunities.

4. Rice Processing • Processed in mills to remove the husk before consumption. • Two rice processing methodologies: - • Parboiling • Partial cooking of rice grain so as to impart it desired hardness & color • Raw rice processing • .raw rice is dried & then sent for milling without any prior cooking.

5. FLOWCHART • Soaking hot water drain waste heat recovery. • Dryer blower system efficiency. • Condensate from dryer may be drained/flashing Paddy drying & storage Paddy pre-cleaning Paddy procurement Paddy pre-cleaner blower efficiency study Paddy steaming, soaking & drying From market/Govt.agencies Paddy cleaning Paddy de-stoner blower system efficiency study Paddy cleaner blower system efficiency Paddy de-stoning Powder blower silencer pr drop & efficiency study. Paddy de-husking DM/RO water as per industry standards Powder & bran removal Polishing Polisher motor load survey, blowers & compressed air requirement Compressed air system Grading & Sorting Packing & dispatch

6. Par Boiling Process

7. Why Parboiling???… • Less breakage (5-15%) during milling than raw rice processing (15-25%). • Better quality rice – hard & uniform color • Better flavor & more nutrition value. • Less paddy odour. • More bran oil can be extracted.

8. Cooking & drying cycle The complete cycle time comes to 24 hrs

9. Soaking • Average Soaking Time – 10 hrs Hot water can be used to heat ground water being heated for soaking. Investment on new PHE – Rs 4.5lacs Savings = Rs 3.5 lacs Soaking Tanks Temp – 60 to 70 oC To Drain at 58 oC Circulation Pump Hot Water Tanks Hot Water Pump

10. Dryer Operation • Most power intensive part of the rice processing as regards steam & power. • Controlled drying is must. • After soaking the moisture is 36 -38%. • Must be around 15% to avoid milling losses. • Hence drying is essential • Best drying conditions – for 1T of paddy 605m³/min of air at 60ºC.

11. Dryer Operation Average dryer operating time – 10 to 11 hrs

12. Dryer Blowers Efficiency Present eff range 62-67%. EE blowers having eff of 80% can be used. Investment per new blower = Rs. 0.9lacs Savings expected = Rs. 0.6lacs

13. Steam condensate from dryers • Steam Usage at 4 to 4.5 kg/cm2 • Steam flow is controlled manually to get desired air temp. • Steam Condensate at 4 kg/cm2 directly exhausted to atmosphere • Possibility of condensate heat recovery Heat Loss through flash steam Condensate From Radiators Condensate at 78 oC Used for paddy soaking Potential Savings for Dryer 4 and 5 – Rs 4lacs / yr Investment - Rs 3lacs

14. Study of plant blowers

15. Study methodology - 2.67 kPa (- 400 mm WC) -3.8 kPa (-570 mm WC) “Significant pressure drop across the blower suction damper. Pressure drop between machine and bag filter is significant in many cases – due to dust accumulation in the duct” Bag Filter -0.2 kPa (-30 mm WC) - 1.5 kPa (- 150 mm WC) VT 2 VT 4 VT 6

16. Potential savings achievable…

17. Areas Studied… • Electrical Distribution • Fans and Blowers of Diff. Plants • Boilers • Compressors • Par boiling and Dryers • Diesel Gen Sets

18. SUMMARY OF SAVINGS IDENTIFIED

19. Source-wise energy consumption Approx grid power drawl. (kVA)

20. Source-wise energy consumption Contract Demand 2000KVA Ave. Total demand 1250KVA Ave. Grid load 630KVA

21. Possible improvements • Increase the connected load. (not the contract demand) • Shift more load from DG to grid. • For dryer - par boiling section it will be worth evaluating separate grid connection.

22. Feasibility of increasing the connected load • Total investment required : Rs. 18.7 lacs • Present average kVA : 630 kVA • Benefits • By increasing 200 kVA avg. demand : Rs. 32.6 lacs • By increasing 400 kVA avg. demand : Rs. 65.2 lacs • By increasing 600 kVA avg. demand : Rs. 97.9 lacs (100 kW shift from DG to grid would contribute Rs. 16 lacs/yr cost reduction)

23. Boiler No.1 - Specifications • Capacity :-15TPH • Type :- Fluidized Bed Type • Pressure :- 17kg/sq.cm • Fuel :- Rice husk • Op. Load :- 12-13TPH • Stack Temp :- 209 deg. C

24. Boiler # 1 Performance Boiler # 1 Measurement Parameter F G temp : 209 Deg C O2% : 12% Furnace Eco Air Flow

25. Boiler # 1 Efficiency

26. Boiler # 1Efficiency – Impact of Oxygen

27. Plant Blowers

28. Plant –4 Observations Power : 10kW Loss due to pr drop : 71% Power lost across damper : 7.1kW MTR Blower - 393 mm WC - 115 mm WC 1 mm WC • using vfd, 95% of the lost power can be recovered. • Annual savings expected around = Rs. 2 lacs • Investment for new vfd = Rs. 1lac

29. Blower Performance Bearing Eff: 98% Bearing Loss: .17KW Impeller eff:98% Impeller loss: .17kW Motor eff: 88% Motor loss: 1.2kW Damper eff: 71% Damper loss: 7.1 kW Motor input: 100% 10kW System Requirement 1.36kW Fan input: kW System input: kW Impeller input: kW Damper loss can be brought down from 7.1 kW to a maximum of 2 kW.

30. Powder blower performance Suction Filter Silencer Cyclone separator Vane dust Blower Pressure profiling and blower efficiency have been studied.

31. Powder blower performance Plant # 3 silencer pr drop is very high. Replacement will account for Rs. 1.2 lacs per annum.

32. Powder blower performance Plant # 3 blower efficiency is low Replacement will account for Rs. 1.2 lacs per annum.

33. Other plants’ blower performance Installation of VFD or replacement of blower will result in a saving of Rs. 7.5 lacs per annum.

34. Dryer – Radiator Steam Usage • Observations – Dryer No. 5 • Average Steam Flow – 4.34 TPH • Maximum Steam Flow – 7.67 TPH • Minimum Steam Flow - Nil

35. Dryer – Radiator Steam Usage • Observations – Dryer No. 4 • Average Steam Flow – 3.00 TPH • Maximum Steam Flow – 4.10 TPH • Minimum Steam Flow - Nil

36. Compressor Performance assessment

37. Compressor Specifications • Type :- Screw • Rating :- 75kW • Pressure :- 6kg • Rated Flow(Cu ft./min) :- 408 • Operation schedule :- 1 comp acts as base load & the other caters to the press fluctuations.

38. Compressor performance Compressor loading is 52% and unloading is 48%. Power loss during unloading.

39. Compressor performance Compressor unloading power is at a higher level. Best compressor’s unloading power is 30% of the loading power.

40. Compressor performance • Options available for improvement in existing system • New Efficient compressor • Installation of VFD • Benefits • Annual savings • Replace the compressor with efficient compressor • Rs. 9.0 lacs per annum (considering 8000 hrs operation) • Installation of VFD • Rs. 3.1 lacs per annum (considering 8000 hrs operation) • Total Annual Savings : Rs. 12.1 lacs Per annum • Expected Investment : Rs. 13.6 lacs • Payback Period : 1.1 yr

41. DG Performance Assessment

42. Specific energy consumption (design) Achieved after adjustments and minor retrofits. Before adjustments and minor retrofits. Regular maintenance and monitoring the DG performance closely, to maintain 3.8 units per ltr will contribute for Rs 7.1 lacs per annum.

43. Unutilized waste heat…. • DG exhaust gas temperature is 420oC to 470oC • Existing DG efficiency is around 30% • Rest of the energy is mostly converted into heat. • High grade heat – DG exhaust gas • Low grade heat – Jacket water, lub oil and charge air cooler • Significant potential for heat recovery. • Qty of steam that can be generated : 300 – 331 kg/hr (@ 5bar pressure) per DG set • Saving potential ranges from Rs 9 – 20 lacs. • Various methods are being explored.