The document discusses partial gasification of pre-dried pulverized coal through waste heat recovery as a future clean coal technology option. It notes that coal pulverizing is an energy intensive process dependent on coal properties. Improving pulverizer performance is limited by design and tied to drying low rank coals with high moisture content. The document proposes using waste heat from flue gases to partially dry coal prior to pulverizing, which could improve mill throughput and reduce boiler heat rate penalties from coal drying. Field studies showed this partial flue gas recirculation approach enabled higher mill capacity and steam generation compared to without waste heat recovery.

1. Partial Gasification of Pre-dried Pulverized Coal through
Waste Heat Recovery – A Future Option CCT
BIT's 3rd Annual International Symposium of
Clean Coal Technology (CCT2014)
September 16September 16--18, 2014 Venue : Taiyuan, China18, 2014 Venue : Taiyuan, China
Session 5 : Coal Gasification Technologies & Poly Generation
Date :17.9.2014
Deputy Director(Technical )Deputy Director(Technical )Deputy Director(Technical )Deputy Director(Technical ) & Associate Professor& Associate Professor& Associate Professor& Associate Professor
Time : 10.55 AM
Chittatosh Bhattacharya, PhD
National Power Training Institute,
Eastern Region – Durgapur, WB, India

2. Coal Power has
A Proven Past
A Progressive Present
& A Promising Future
To Meet Sustainable Power Demand
& A Promising Future
With the support of low cost, low to high
quality of coal resources to run at least for
another Century (if not more) to provide
affordable quality power for all with
negotiable emission.

3. Coal, 41%
OIL, 6%GAS, 21%
Nuclear, 14%
Hydro, 16%
Biomass, 1%
Wind, 1%
Solar, 0%
Power Mix -World (2008), 20183 TWh
Coal
OIL
GAS
Nuclear
Hydro
Biomass
World Energy Outlook 2010 Starting with Electric Power Energy RealitiesStarting with Electric Power Energy RealitiesStarting with Electric Power Energy RealitiesStarting with Electric Power Energy RealitiesStarting with Electric Power Energy RealitiesStarting with Electric Power Energy RealitiesStarting with Electric Power Energy RealitiesStarting with Electric Power Energy Realities
The shift from coal power is not as fast as the growth of RE over the years !!The shift from coal power is not as fast as the growth of RE over the years !!The shift from coal power is not as fast as the growth of RE over the years !!The shift from coal power is not as fast as the growth of RE over the years !!

4. IntroductionIntroduction
• “Big Five” Chinese Power Companies (Datang, Huaneng,
Guodian, Huadian, and China Power Investment) & NTPC
of India - The world’s biggest coal-fired power producers,
& among the top developers of proposed new coal-fired
plants.
• Coal Pulverising - Energy intensive physical process -• Coal Pulverising - Energy intensive physical process -
performance is dependant on physio-chemical coal
properties & responsible for complete burn out of coal.
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• Improving performance capability of pulveriser is limited
by design & supply for a specific worst / best coal quality
to be made available.

5. • Improvement in pulveriser performance is linked to Low
Rank coals(LRC) moisture drying capacity & associated
heat rate penalty.
• The existing coal moisture drying processes using
regenerative APH in boilers are energy intensive, inefficient
and inadequate for LRC particularly at higher Ambient Air
• Any deterioration of coal quality may fail to meet the PC
throughput demand for maximum steaming of boiler.
• Economics of LRC drying through waste heat recovery establishes
significant reduction in fuel consumption, emission and
improvement in overall boiler efficiency by way of reduction of
heat lost for evaporative total coal moisture from the useful heat
value of coal .
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and inadequate for LRC particularly at higher Ambient Air
Temperature (AAT) & Relative Humidity (RH).

6. Country wise Global Reserve : High Ash - Moisture LRC
9/17/2014 Burnard K; Bhattacharya, S. ; Power Gen. from Coal Ongoing Dev. Outlook, p 30; IEA 2011

7. Physical
Constituents
of Coal
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Low Rank Coal (LRC) High Rank Coal
Coal Rank as Volatile Matters

8. Common problems faced by PC fired TPS using low rank coals are:
Deteriorating heating value of the coal,
Inconsistent coal properties with adhered surface moisture,
Problems associated with Low Rank Coals used in TPP
Cost of Coal moisture may be equated to loss of coal heat
value to provide drying energy resulting equivalent boiler
Steaming Capacity loss, lowering Efficiency & adding more
Emission Penalty.
Inconsistent coal properties with adhered surface moisture,
Presence of extraneous matters,
High quantum of ash with high percentage of abrasive quartz.
Extremely high electrical resistivity in ash due to Low sulfur %
A loss of 2% of coal heat content will make a variation of
power pricing by USD 0.16 million (approx.)/year for 1000
MWe Plant. 9/17/2014

9. PC fired Boiler - Mill Performance Improvement Roadmap
• To start with measurability of coal quality impact in mill.
• Must attempt to delimit the impact of quality in performance.
• Should incorporate process modification beyond existing and
conventional options.
• Should be economically viable & implementable alternatives to• Should be economically viable & implementable alternatives to
mitigate environmental obligations for coal.
• Should be adoptable to existing declassified PC fired Boilers
irrespective of sub critical or super critical regime of operation.
• Should be adoptable as retrofit or in-process arrangement to
coal fired Carbon Capture & Sequestration system as a
sustainable Clean Coal Technology option.
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10. Carbon Hydrogen Oxygen Nitrogen Sulfur Ash Water HHV,
MJ/kg
LHV,
MJ/kg
%wt
(ar)
28.921 1.833 5.431 0.543 0.272
48 15 10.88 10.11
Ultimate Analysis of an worst variety MCL coal & its effect in Heat Loss
Coal Quality Impact Analysis in PC fired Utility & Partial Flue Gas
Recirculation (PFGR©©©©) System through Pulveriser
Experimental Investigations on fired coals of Thermal Power Plants
(ar) 48 15 10.88 10.11
%wt
(mf)
34.025 2.157 6.39 0.639 0.319 56.47 0 12.8 12.32
%wt
(amf)
78.165 4.954 14.68 1.46 0.734 0 0 29.4 28.31
wt
stack
Kg /
Kg coal
CO2 –
1.06
Evaporated
Moisture
O2 - 0 2.847 SO2 –
0.005
0.315 Wet
Stack gas
– 4.227
Dry
Stack
gas –
3.912
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11. Change Of Useful Heat Value With Varied
COAL Moisture of MCL Coal Coal Heat (%) lost in Drying MCL Coal
Coal quality impact analysis in PC power generation process & PFGR
9/17/2014
Heat (%) lost in Drying WCL Coal Coal Heat (%) lost to Dry Up ECL Coal

12. ID Fan
BOILER
ESP
FFS PFGR ©©©©
Chimney
Coal quality impact analysis in PC power generation process & PFGR
The collected flue
gas at 460-530 0
C
(60 - 100% MCR)
will improve
Mill
PA Fan
FD Fan
GR Fan
ESP
MDC
Partial Flue Gas Recirculation through Pulveriser (Scheme)
will improve
average mill inlet
PA Temp. to 315-
430 0
C .
9/17/2014

13. Study conducted for 210 MWe unit operating at 155 kg/cm2
& 535 0
C.
The design coal feeding at 100% MCR = 109 TPH @ 7% -Max. Total
Moisture, GCV -19.888MJ/Kg & 50 HGI.
Field Study Findings
Coal quality impact analysis in PC power generation process & PFGR
Change in ROM coal (AR) throughput @ 46 HGI, 15% TM & GCV
15.157 MJ/kg - 146 TPH. The Max. hot PA Temp. :3340
C (APH
O/L).Maximum drying capacity/pulverizer- 12 TPH (TM of coal)
(presuming 1% residual moisture in PC leaving mill).(presuming 1% residual moisture in PC leaving mill).
Change in coal throughput demand with experimental coal @ GCV
10.88MJ/Kg & 15% TM, 50 HGI - 200 TPH (for 100% MCR without FO
firing) presuming 88.5% ηboiler
The 100 TPH / mill coal flow - achievable by enhancing drying
capacity matching excess TM with PFGR through PA Fan intake
tapping FG from Eco. I/L at a temperature of 526 0
C & at a rate
112 TPH for a total PA flow of 119 TPH / mill ≈ 14 % of total FG
entering APH. 9 /17/2014

14. Result
Optimum Pulverizing Capacity :
Maximum experimental PC output/millMaximum experimental PC output/mill -- 100 TPH100 TPH (with PFGR)(with PFGR)
Maximum experimental PC output/millMaximum experimental PC output/mill –– 83.75 TPH83.75 TPH (W/out PFGR)
WithoutWithout PFGRPFGR steamingsteaming capacitycapacity -- 197197 MWeMWe @@ 8888..55%% ƞƞboilerboiler
WithWith PFGRPFGR steamingsteaming capacitycapacity -- 210210 MWeMWe @@ 8888..55%% ƞƞboilerboiler
..
Coal quality impact analysis in PC power generation process & PFGR ©©©©
Minimizing NOx
The additional NOx reduction with PFGR ≈ 0.07 kg/GJ approx.
with SOFA arrangement resulting 70-73% of total NOx (total
equivalent NO2 - 0.6896 kg/GJ) reduction amounting total
equivalent NO2 emission through stack reduced to 0.1888
kg/GJ. ( on the basis of evaluation through IECM© software)
9/17/2014

15. →
↑
Typical impact on flame front velocity due to VM reduction of coal
Partial VM loss is unavoidable due to hot air
drying or steam drying without proper
arrangement to capture the escaped VM in
the drying process prior coal feeding to
pulverizer.
Integrated Drying and Partial Gasification for Low Rank Coal-Power options
The Heat Value lost to dry
Typical weight loss, drying up and partial devolatilisation
for sub bituminous PC with constant rate of heating.
The Heat Value lost to dry
up the coal is significant if
the drying process is lined
up to consume useful fuel
heat value in the thermal
power generation process.
9/17/2014

16. Ash - 5 % by wt
FlameFrontVelocitym/s
Ash - 40 % by wt
Fuel Rich – devolatilisation zone
With Partial FGR through mill
Excess Air – controlled combustion
zone with oxidizing secondary air
Integrated Drying and partial gasification for low grade coal-power options
Typical Improvement in Flame
Front Velocity of PC with coal
beneficiation at constant coal
VM & devolatilisation rate.
The CO2 enrichment in dry stack
gas suggests a fuel rich coal drying
with PFGR©©©© & increasing
Flue gas - Air / PC Ratio
CO2 % in dry stack gas at various excess air
% for MCL coal.
with PFGR©©©© & increasing
opportunity to partially dry the
coal through waste heat recovery
from FG at ID fan discharge
upstream of stack resulting more
opportunity for coal heat value
saving to generate steam than to
dry the coal along partial PC
gasification at mill exit with PFGR
9/17/2014

17. PFGR© requirement /kg MCL coal at various
moisture % & available FG temperature (0C)
Moisture Removal – 40%
Moisture Removal – 15%
Moisture Removal – 30%
Integrated Drying and partial gasification for low grade coal-power options
FG waste heat
recovery drying in a
fluidized bed in ID
Fan O/L duct
improves mill drying
Moisture Removal – 15%
Moisture Removal – 10%
Moisture Removal – 6.5%
improves mill drying
capacity and provide
opportunity for
partial coal
gasification of PC
with recirculated FG
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18. Further improvement - Integrated drying & partial
coal gasification system with PFGR©
Integrated Drying and partial gasification for low grade coal-power options
9/17/2014

19. Performance Impact of Air Preheater on Overall Equipment Efficiency
FD & PA Fans
Pulverizers
Burners
Boiler Input Devices
Boiler Operation
Combustion Control
ID Fans
Environmental Emission Control DevicesBoiler Output Devices
Electrostatic Precipitators
Bag houses SCR FGD
1 4
WB/ Mill
Economizer
Evaluation of APH Leakage
1
2
Hot Flue Gas APH Bypassing
Hot Air APH Gas Side
FD FAN
+ P
PA
FAN
ID Fan
- P
2
3
2
4
Ambient Cold Air APH Gas Side
Hot Air APH Gas Side
Ambient Cold Air APH Bypassing
APH helps to dry up pulverized coal
with hot primary air, rapid
attaining of ignition temperature
and creating turbulence with more
volumetric flow of Secondary air.
3
9/17/2014

20. ・ Quantity of Air flow（ma, ）、 when (Tae) AAT
・ (Tae) AAT Humidity Ratio
Boiler (Air/Flue gas)Boiler (Air/Flue gas)
mmmmaaaa
mmmmgggg
TTTTgegegegeDPDPDPDPhhhh
Hot AirHot AirHot AirHot Air Flue GasFlue GasFlue GasFlue Gas
Effect of AAT in PerformanceEffect of AAT in Performance
Ambient air temperature (AAT) affects - mass flow rate (ma
), coefficient of heat capacity (Cpa);
density, humidity ratio (moisture content capacity of air on RH)
・ Humidity Ratio Heat loss to dry air
・ (Tae) AAT ηAPH
・ As (Tae) AAT ΔΔΔΔPh（ΔpΔpΔpΔpaaaa ::::O/L – ΔPΔPΔPΔPgggg I/L）
thus Air leakage
The result of Plant Findings speaks for it…..
FD/PA FanFD/PA Fan ESPESP
TTTTaeaeaeae TTTTglglglgl
ΔPΔPΔPΔPaaaa ΔPΔPΔPΔPgggg
mmmm
LLLL
9/17/2014

21. Reference Coal MCL Coal WCL Coal ECL Coal
Coal Rank Non-coking Gr. F Non-coking Gr. D Non-coking Gr. D
“As Recd” HHV (MJ/Kg) 10.878 19.526 20.398
Coal Price Unit Rs. (’07) Rs. (’07) RS. (’07)
Coal Price / MT 440.00 1210.00 1360.00
As Received Coal
Moisture (wt %)
15.00 19.50 1.95
Result - Coal Moisture Economics ( For 210 MWe TPP)
Coal moisture removal economics with waste heat recovery
Moisture (wt %)
Ref. Case : 2% decrease in “As Fired” coal moisture
As fired coal Moist. (wt %) 13.00 17.50 0.0
“As fired” LHV with 2%
less moisture[wt%(ar)] in
coal (MJ/Kg)
10.404 18.889 20.111
Waste heat recovery
savings in equivalent
“As Received” coal
quantity in MTPD
139.45 85.79 212.38
9/17/2014

22. Improvement in “as received” to “as fired” coal quality
with more UHV of PC is achievable with IDPCG, waste
heat recovery based coal drying, resulting least wet FG
loss through stack.
Reduced specific coal consumption / kg steam with
minimization of loss of coal heat value to dry up wet
CONCLUSIONCONCLUSION
minimization of loss of coal heat value to dry up wet
coal.
Retrofitting feasibility with near pure oxy – coal
combustion technology for enriched CO2 capture
opportunity for economic & viable emission
management through sequestration as a CCT project.
9/17/2014

23. References
Bhattacharya, C.; Sarkar, H. S.; “Economic Assessment of Utilization of Beneficiated Indian Power Coal
for Thermal Power Generation” (April 2003); National Symposium (SRP-2003) CMERI
(CSIR)/Durgapur/INDIA .(Abstracted PP: 46-47).
Bhattacharya, C.; Mitra A.K.; "Improving Pulverizer Output by Partial Flue gas Recirculation”
Proceedings of International Conference on “Advances in Energy Research”;pp 485-491 (ICAER) 12-14
Dec, 2007, IIT Mumbai, India; Macmillan India Ltd(ISBN 10:0230-63432-X).
Bhattacharya, C.; Banerjee, N; 2011; “Integrated drying and partial coal gasification for low NOx
Pulverized coal fired boiler”, Proc. of ASME 2011 Power-ICOPE Conference, Vol. I , pp. 293-300 (ISBN:Pulverized coal fired boiler”, Proc. of ASME 2011 Power-ICOPE Conference, Vol. I , pp. 293-300 (ISBN:
978-0-7918-4459-5). http://dx.doi.org./10.1115/POWER2011-55108
Bhattacharya, C.; Banerjee, N.; Sarkar, H.S.; “Economics of Removal of Coal Moisture in Thermal
Power Generation with Waste Heat Recovery, “International Journal Of Emerging Technology and
Advanced Engineering, Vol. 3, Special Issue 3:ICERTSD 2013 February 2013, pp 22-28.[ISSN 2250 -
2459] http://www.ijetae.com/files/Conference%20ICERTSD-2013/IJETAE_ICERTSD_0213_04.pdf
Bhattacharya, C.; Sengupta, B., “Effect of Ambient Air Temperature on the Performance of
Regenerative Air Preheater of Pulverised Coal Fired Boilers” Proc. of 4th Int. Conf. on Advances in
Energy Res.; ICAER 2013, pp 63-69; IIT Bombay, 10-12 Dec.’13; ISBN :978-81-928795-0-5.
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24. THANK YOU!
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chittatosh_bhattacharya@rediffmail.com