Oxy-Coal Combustion R&D Activities in China

Oxy-Coal Combustion R&D Activities in China

Prof. Ningsheng Cai

Department of Thermal Engineering, Tsinghua University, 100084, China

APP OFWG Capacity Building CourseDaejeon, KEPRI, Korea 5th and 6th February 2009

OutlineResearch Institutes of Oxyfuel

Combustion in China

Pulverized Coal Oxyfuel Combustion

Circulating Fluidized Bed OxyfuelCombustion

O2/CO2 Gases Production for Oxy-Combustion

Further Development


Combustion in China




Further Development

4 / 22

Research institutes

Tsinghua University

Huazhong University of Science & Technology

Zhejiang University

Southeast University

North China Electricity University

One-dimensional furnace system for Oxy-combustion

25kW experimental system in Tsinghua University

Parameter

Diameter: 150 mm

Height: 3.2 m

Load : 25 kW

Fuel: Gas, PC

Temperature: 1300 ℃

System introduction in Tsinghua Univ

System introduction in Huazhong

300kW experimental system in Huazhong University of Science & Technology

System introduction in Huazhong300kW experimental system in Huazhong University of Science & Technology

Area： ~200 m2

Height：12.5m

System introduction in Southeast Univ and Zhejiang Univ

烟气在线监测系统可吸入颗粒物测试系统

数据采集控制系统

底渣取样点

二

次风

一次风

气体母管

罗茨风机

气瓶

去烟囱

螺旋加料器

稀

相

区

密

相

区

风室启燃室气体预热器

布袋除尘器飞灰取样点

密封返料阀

换热器

旋风分离器烟气取样点

System introduction in Southeast Univ and Zhejiang Univ

Circulating fluidized bed oxyfuel combustion


Combustion in China




Further Development

12 / 22

Coal preparation

Combustion and heat transfer

Flue gas purify

CO2 recovery

Process operationAir separation

N2 utilization

NOx, SOx, PM, Mercury, etc

Ignition, flame stabilized and safeAsh, slag and corrosion

Research content

MeasuringInfluencing factor

Characteristic and Mechanics of Particle Formation in Oxy-CombustionConversion Mechanics of Sulfur Under Flue GasEnrichment and Migration of Trace Elements

Research Goals

Trace：Cd,PbSe,CrTh,Be

Mn

Com

ponent

Surface

Concentration

Distribution

Enrichment and Migration

Main:S,Al

Si,P,NaK,Ca

Fe，MgO2

21%，35%，45%

Research activity in Tsinghua Univ

Item Parameter Remark#1 Air Combustion#2 Oxy-coal; O2= 30%#3 Oxy-coal; O2= 35%#4 Oxy-coal; O2= 40%#5 Air Combustion

(Desulfurization)#6 Oxy-coal; O2= 35%

(Desulfurization)

（1）α=1.3；（2）coal=4.4kg/h；（3）CaCO3, Ca/S=2

Test Parameters

Research activity in Tsinghua Univ

Test Results

0

20

40

60

80

100

#1 #2 #3 #4

工况

CCO

2 (%

)

1) Air CombustionCO2=15.29%

2) Oxy-CoalCO2，max=85.63%

3) O2↑, CO2↓

4) System leakage

CO2 Concentration

Case

Test Results

0

500

1000

1500

2000

2500

#1 #2 #3 #4

工况

CNO

(ppm

v)

050

100150200250300350400

#1 #2 #3 #4

工况

MN

O(n

gNO

/J)

O2 ↑， NO↓

NO Concentration

CaseCase

0

1000

2000

3000

4000

5000

6000

#1 #2 #3 #4

工况

CSO

2 (pp

mv)

Test Results

O2 ↑， SO2↓

SO2 Concentration

0

200

400

600

800

1000

1200

1400

#1 #2 #3 #4

工况

MSO

2 （ng

SO2 /

J）

Mainly absorbed by ash in the furnace/ESP.

CaseCase

Test Results

0

1000

2000

3000

4000

5000

6000

#1 #3 #5 #6

工况

CSO2(ppmv)

0200

400600800

1000

12001400

#1 #3 #5 #6

工况

MSO

2 (ng

NO

/J)

Air

Oxy-coalAir

Oxy-coal

Desulfurization

SO2 ConcentrationAir: 1145→861ppmv; 1184→893ng/J

Oxy: 4780→2005ppmv; 846→361ng/J

CaseCase

Test Results

Mainly increase part during PM10: PM0.267;

O2 Concentration↑ , dM / dlog(Dp) ↑

dM / dlog(Dp)

Air30%Oxy35%Oxy40%OxyAir+DeSOx35%Oxy+DeSOx

Particle size distribution

AirDesulfurization

Desulfurization

Test Results

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+08

1.00E+09

0.01 0.10 1.00 10.00

Dp(μm)

dN/d

(log(

Dp)

)(1/

m3 )

#3

#6

0

2000

4000

6000

8000

10000

0.01 0.10 1.00 10.00

Dp(μm)

dM/d

(log(

Dp)

)(m

g/m

3 ) #3#5#6

PM Formation Under Desulfurization in Oxy-coal Combustion with RFG

Soot may be one reason.

Air+DeSOxOxy-coal

Oxy+DeSOx

Dp=0.083μm

Dp1=0.137μm

Dp2=3~5μm

NOx model in oxy-coal combustion

α

1 α−

Coal

Volatile-nitrogen

Char-nitrogen

HCN

NH3

NO

N2

Char reduction

Prompt NO CHi

Thermal NO

Reburing NO

CHi

O2

NO

1β

11 β−2β

21 β−

ThermalPromptFuelReburning

α=0.5

Abet= f(Fz,λ)

De Soete modelNH3/HCN=g(Fz)

NOx model in oxy-coal combustion has been developed and validated with experimental resutls.

SOx model in oxy-coal combustion

Tube Ash

Furnace

Tub

nace

Tube

Corrosion FeS

FeS

Furnace

Coal particle

α

1 α−

Coal

Volatile-sulfur

Char-sulfur

SO2

H2S

SO3

O

O21β

11 β−2β

21 β−

O2, H2

H2S will cause the high temperature corrosion of boiler. SOx(SO2, H2S, SO3) formation model in oxy-coal combustion has been developed and validated with experimental data.

Oxy-coal combustion in cement Rotary kiln

The application of low quality coalOxy-coal combustionNOx formation and reductionExperiment and simulation


Combustion in China




Further Development

Circulating Fluidized Bed Oxyfuel Combustion

Temperature distribution along bed height

Effect of limestone addition on temperature distribution

Bed temperature in O2/CO2 atmosphere is lower than that in air atmosphere. Limestone addition has little effect on the temperature distribution along bed height.


Heat loss Combustion efficiency

Heat loss (q3, q4) decrease with the increasing of O2 fraction, this is easily understood. As a result, the combustion efficiency becomehigher. While in O2/CO2 atmosphere, the combustion efficiency is lower than that of O2/N2 atmosphre.


NOx concentration increases with O2 fraction increase, this is because the flue gas volume decreases, while the NOx amount nearly keeps constant. It is obvious after converting the NOx concentration to the unit of mg-NO/g-coal.

NOx (ppm) NOx (mg-NO/g-coal)


SO2 concentration increases with O2 fraction increase, this is because the flue gas volume decreases. The sulfur removal efficiency is a little lower in O2/CO2 than that of in O2/N2 atmosphere. Limestone decomposition has been affect by CO2 concentration. CO2 concentration increasing will retards the reaction of SO2 with sorbent.

SO2 (ppm) SO2 (mg-SO2/g-coal)


Combustion in China




Further Development

slag

Recycled flue gas (CO2、H2O)

N2

O2

powercoal

Not pure O2， O2/CO2mixed gases containing 30~40%O2！

The capital of cryogenic air separation is 33% of total capital of power plant，power used for air separaton is 10~20% of total generated power！

The production of O2/CO2 gases

With recycled flue gas as purge gas

Dual fixed bed reactors

Sorbent behave as particle

With steam as purge gas，pure O2 can be obtained

x2 o o

1 O ( ) V O 2h2

g •• •+ = +

xo 2 o

1O 2h O ( ) V2

g• ••+ = +

airCO2、H2O

O2、CO2、H2ON2

boiler

waterfuel

CO2

氧存储

氧释放

perovskite-type oxides

Oxy

gen

stor

age

Oxy

gen

rele

ase


0

5

10

15

20

25

0 20 40 60 80 100

Time (min)

O2 c

once

ntra

tion

(%)

400ml/min Air100ml/min Air

240ml/min Air

O2 fraction in mixed gases

Sorption test 200mL/min

O2 can be absorbed effectively by sorbent

Air

N2

氧存储O

xyge

n st

orag

e


0

5

10

15

20

25

30

35

0 20 40 60 80 100 120Time (min)

O2 c

once

ntra

tion

(%)

100ml/min CO2

200ml/min CO2

300ml/min CO2

De-sorption tests

O2 fraction in mixed gases

With CO2 as purge gas, O2/CO2 mixed gases containing 25~35%O2 can be produced。

氧释放

CO2

O2、CO2

Oxy

gen

rele

ase


AirCO2

O2、CO2O2 depleted gases

氧存储

氧释放

Experiment of continuous O2/CO2gases production

sorbent weight： 200g×2Air flowrate： 1.2L/minCO2 flowrate： 400ml/min

switching time： 30min

Oxy

gen

stor

age

Oxy

gen

rele

ase


Experimental result of continuous O2/CO2 gases production

O2/CO2 gases stream with average ~30% O2 concentration for oxy-fuel combustion can be obtained based on chemical looping cycle in dual fixed beds



Combustion in China

Pulverised Coal Oxyfuel Combustion



Further Development

Further Development

Chinese government has paid more attention on CCS

Currently, most R&D are performed by universities

Electricity power companies like Huaneng and Datang are going to make pilot oxy-coal combustion demonstration

Not only coal fired power plant, but also cement plant, should be considered

Air separation, flue gas purification and CO2utilization etc also need to consider for cost reduction

Thank you for your attention!

Documents

Oxy-Coal Combustion R&D Activities in China