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Energy Cost Reduction in a Rice Mill. Contents. Introduction Rice Processing Flowchart of areas covered Case study from Satnam Overseas Ltd. Introduction. About 35000 rice mills in India Small power requirement – less than 1 MW Steam demand – around 4TPH

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contents
Contents
  • Introduction
  • Rice Processing
  • Flowchart of areas covered
  • Case study from Satnam Overseas Ltd.
introduction
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.
rice processing
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.
slide5

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

why parboiling
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.
cooking drying cycle
Cooking & drying cycle

The complete cycle time comes to 24 hrs

soaking
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

dryer operation
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.
dryer operation1
Dryer Operation

Average dryer operating time – 10 to 11 hrs

dryer blowers efficiency
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

steam condensate from dryers
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

study methodology
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

areas studied
Areas Studied…
  • Electrical Distribution
  • Fans and Blowers of Diff. Plants
  • Boilers
  • Compressors
  • Par boiling and Dryers
  • Diesel Gen Sets
source wise energy consumption
Source-wise energy consumption

Approx grid power drawl. (kVA)

source wise energy consumption1
Source-wise energy consumption

Contract Demand 2000KVA

Ave. Total demand 1250KVA

Ave. Grid load 630KVA

possible improvements
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.
feasibility of increasing the connected load
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)

boiler no 1 specifications
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
boiler 1 performance
Boiler # 1 Performance

Boiler # 1 Measurement Parameter

F G temp : 209 Deg C

O2% : 12%

Furnace

Eco

Air Flow

plant 4 observations
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
blower performance
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.

powder blower performance
Powder blower performance

Suction Filter

Silencer

Cyclone separator

Vane dust Blower

Pressure profiling and blower efficiency have been studied.

powder blower performance1
Powder blower performance

Plant # 3 silencer pr drop is very high.

Replacement will account for Rs. 1.2 lacs per annum.

powder blower performance2
Powder blower performance

Plant # 3 blower efficiency is low

Replacement will account for Rs. 1.2 lacs per annum.

other plants blower performance
Other plants’ blower performance

Installation of VFD or replacement of blower will result in a saving of

Rs. 7.5 lacs per annum.

dryer radiator steam usage
Dryer – Radiator Steam Usage
  • Observations – Dryer No. 5
  • Average Steam Flow – 4.34 TPH
  • Maximum Steam Flow – 7.67 TPH
  • Minimum Steam Flow - Nil
dryer radiator steam usage1
Dryer – Radiator Steam Usage
  • Observations – Dryer No. 4
  • Average Steam Flow – 3.00 TPH
  • Maximum Steam Flow – 4.10 TPH
  • Minimum Steam Flow - Nil
compressor specifications
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.
compressor performance
Compressor performance

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

unloading.

compressor performance1
Compressor performance

Compressor unloading power is at a higher level. Best compressor’s unloading

power is 30% of the loading power.

compressor performance2
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
specific energy consumption design
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.

unutilized waste heat
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.