Experiment Research on Gasification Character of Pulve-rized Coal at Medium Temperature

doi:10.4236/epe.2013.54B062

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Energy and Power Engineering, 2013, 5, 315-318

doi:10.4236/epe.2013.54B062 Published Online July 2013 (http://www.scirp.org/journal/epe)

Experiment Research on Gasification Character of

Pulverized Coal at Medium Temperature

Tong Lou1, Zhon g-xiao Zhang1,2, Jun-jie Fan2, Hai-quan An2, Zhi-hao Zhou1, Pu-jie Yue1

1College of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai, China

2School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China

Email: [email protected]

Received March, 2013

ABSTRACT

In this paper, effect of gasification temperature and residence time on gasification characteristics of typical pulverized

coals under atmosphere pressure were studied on a one-dimensional electric heating drop tube furnace system to evalu-

ate gasification characteristics of pulverized coal at medium temperature. The results show that the gasification rate

increases with the raising of the gasification temperature under the temperature among 1150℃ and 1450℃, and as the

temperature is above 1350℃, the increasing rate become slower. Cold gas efficiency and carbon conversion meet the

maximum value when the temperature approaches the ash fusion point of coal. With the further rise of the temperature,

ash on the surface of the char starts to be melted, the gasification reaction rate decreases, due to the hindrance of the

effective contact between coal char and gasification agent. The gasification efficiency would become steady when the

residence time exceeds 8s.

Keywords: Gasification Characteristic; Pulverized Coal; Carbon Conversion; Cold Gas Efficiency

1. Introduction

Issues on natural resource and environment become in-

creasingly severely in China, due to the long-term use of

traditional coal combustion. Integrated gasification com-

bined cycle (IGCC) takes advantage on high efficient and

environmentally-friendly, is a new power generation

technology. Gasified is one of the key devices of IGCC

power generation system. Compared to the other gasifi-

cation technologies, entrained flow gasification technol-

ogy get rapid development for its advantages of high

gasification intensity, high carbon conversion and be

easily practiced on a large scale. Influencing factors on

gasification efficiency of entrained flow gasified are

many, effect of gasification temperature and residence

time on gasification characteristics of typical pulverized

coals were studied on a one-dimensional electric heating

drop tube furnace system under the conditions of atmos-

phere pressure and medium temperature from 1150℃ to

1450℃[1-3].

2. Experimental System and Work

Conditions

2.1. Experimental System

Figure 1 is the picture of experimental system, which is

consisted of high temperature tube electric heating fur-

nace, ash collected system and syngas cleaned and de-

tected system. The furnace is made of corundum tube(2.1

m in length, 60 mm in inner diameter), the adjust tem-

perature is up to 1550℃, the gas analysis equipment is a

infrared gas analyzer produced by Wuhan Cubic Opto-

electronics Technology Co., Ltd., which can proceed real

time measurement on CO, CO2, H2, CH4 and O2.

Figure 1. The schematic picture of the experimental process.

T. LOU ET AL.

316

2.2. Work Conditions

Datong bituminous coal, a typical bituminous coal in

China was selected for the experiment on gasification

characteristic of pulverized coal at medium temperature,

and effect of gasification temperature and residence time

were mainly considered. The average particle size of

pulverized coal is more or less than 100 µm (under 150

µm) and the feeding rate is about 0.2 kg/h. The proxi-

mate analysis and the elemental analysis of the coal is in

Table 1, the experimental operating conditions are in

Table 2.

2.3. Experimental Data Processing Methods

It’s relatively difficult to measure the syngas directly as

its high temperature. So the total amount of dry gas could

be obtained by the calculation of N2 balance, the divided

relationship between the N2 amount in the inlet and the

N2 percentage of dry gas in the outlet: 2

,in N



, the-

reinto, Q is the flow of syngas, is the flow of N2

,in N

amount in the inlet, 2



is the gas volume fraction of

N2 in the dry gas.

As the experiment proceeded in one-dimensional drop

tube furnace, residence time of pulverized coal staying in

the furnace is equal to the residence time of reactivity

gas:

Table 1. Proximate analysis and the elemental analysis of

the datong coal.

Coal Datong

Mad 1.61

Aad 26.89

Vad 28.26

Proximate analysis（%）

FCad 42.34

Cad 77.78

Had 5.39

Oad 12.79

Nad 1.09

Ultimate analysis（%）

Sad 2.69

DT 1350

ST 1370

Ash fusion temperature（℃）

FT 1400

Table 2. The Experimental operating conditions.

Pressure Temperature

（℃）

Residence time

（S）

Ratio of

O/C

1atm

1150

1250

1350

1450

1:1

288

(273 )()

inNin O

tTQ Q





thereinto, L is the length of the furnace, r is the inner

diameter of the furnace, T is the temperature of the fur-

nace; and is the flow of O2 in the inlet.

,inO

Oxygen element of the gas products is mainly from

pulverized coal and the injected O2 in the inlet, such as

CO, CO2 and H2O. Therefore, the amount of vapor in the

syngas can be calculated by the balance of O2 element,

the amount of vapor in the syngas(mol) = oxygen amount

of the injected O2 + oxygen amount of coal – the amount

of the oxygen element from carbon dioxide and carbon

monoxide in the gas, the calculation formula is

222.416 222.422.4

100%

in OCCOCO

HO in OCCOCO

QMQ Q

QQM QQ





 





 



Thereinto, α is the gas volume fraction of in the dry

gas.

Carbon conversion η is the index to calculate how

much carbon is transferred to the content in gas during

the gasification process:

()22.4

100%

COCO CH

VVV







thereinto, V is gas volume, M is the amount of coal; and



is the amount of carbon in the coal.

Cold gas efficiency ηd is the heat value proportion of

fuel and gas products, the calculation formula are:

100%

HCOCH

df coal

hhh







thereinto, h is the gas heat value, ,

coal

h is the heat value

of coal.

3. Experimental Results and Discussions

In an actually running entrained flow gasified, the con-

trollable parameter is the feeding rate of coal and O2,

residence time and the amount of steam. Commonly,

gasification temperature and the atmosphere inside the

furnace can be adjusted by changing the rate of O/C. This

adjustment would change the processes of gasification

reactivity and the content of syngas, which would defi-

nitely change the residence time of gasification agent in

the furnace. Therefore, research of gasification tempera-

ture and residence time on the gasification characteristic

of coal has a significant meaning for the design and fol-

lowing operation of the gasified [4].

3.1. Effect of Temperature and Residence Time

on the Composition of Syngas

The method of changing injecting rate of N2 to change

T. LOU ET AL. 317

the residence time of pulverized coal staying in the fur-

nace was selected in this paper, the range is from 3s to

10s. Figure 2 shows the effect of gasification tempera-

ture and residence time on the composition of syngas [5].

123456789101

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7 CO2 CO CH4 H2

Gas Volume Fraction

Residence Times(S)

(a) Temperature:1450℃

123456789101

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7 CO2 CO CH4 H2

Gas Volume Fraction

Residence Times(S)

(b) Temperature:1350℃

123456789101

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7 CO2 CO CH4 H2

Gas Volume Fraction

Residence Times(S)

112345678910

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

CO2 CO CH4 H2

Gas Volume Fracti on

Residence Times(S)

(d) Temperature:1150℃

Figure 2.The effectidence time on

e syngas

3.2. The Effect of Temperature and Residence

Figu of temperature and residence

of temperature and res

the components of synthesis gas of Datong Coal

As the figure shows that the composition of th

changes with residence time under different gasification

temperature conditions, the content of CO increases with

the increasing of residence time. When the temperature is

higher than 1300℃, the increasing rate becomes smaller

and the content of H2 slightly decreases with the increas-

ing of the residence time, while the content of CO2 gen-

erally remains steady. When the gasification temperature

is lower than 1300℃, the increasing rate of CO is rela-

tively bigger, and the fluctuation of H2 and CO2 is quite

drastic as well. The content of CO2 falls down with the

increase of residence time. With the increase of residence

time, the content of H2 would increase first and then de-

crease while the temperature is 1250℃. This is mainly

caused by the reactivity of H2O-C is higher than CO2-C.

As the residence time decreases to a certain extent, com-

bustion reactions are mainly happened in the furnace and

most of coal char would escape from the furnace directly

without reacting with H2O and CO2. So, most of H2 are

mainly produced by the paralysis of coal at this condition.

With the increase of residence time, the reacting time

between H2O-C and CO2-C would be extended corre-

spondingly. Followed by the large products of CO2 and

CO, the volume proportion of H2 in the syngas would be

decreased. Due to the reactivity of H2O-C is bigger than

CO2-C, the volume proportion of H2 in the syngas in-

creases again with the further increasing of residence

time. It can also be seen from the Figure that the volume

proportion of CH4 gets down gradually with the rise of

the temperature. When the temperature is above than

1350℃, the volume proportion of CH4 drops to 0, which

indicates that CH4 is mainly from the volatile compo-

nents, and the higher temperature of gasification reaction

is, the easier CH4 be decomposed [6,7].

Time on the Carbon Conversion and Cold

Gas Efficiency

re 3 shows the effect

time on carbon conversion and cold gas efficiency of

Datong coal. It can be seen from Figure that the carbon

conversion and cold gas efficiency increases with the

increase of residence time. When it is lower than 1350℃,

carbon conversion and cold gas efficiency increases with

the increasing of gasification temperature. When it is

higher than 1450℃, carbon conversion and cold gas effi-

ciency almost remains the same as that at 1350℃, even

slightly lower. The main reason is that the ash would be

appeared and accumulated on the surface of coal char

particles with the proceeding of gasification reactions,

when the gasification temperature is higher than the ash

fusion temperature, it would be transferred to liquid

phase. It tends to shrink as globular material on the surface

T. LOU ET AL.

318

Figure 3. Effect of Te mperature and Residence Time on the

ad to the decrease of effective surface area or separated

4. Conclusions

re is one of the most important fac-

me also has a great influence on ga-

temperature approaches to the coal ash

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