Energy and Power En gi neering, 2011, 3, 343-347
doi:10.4236/epe.2011.33043 Published Online July 2011 (
Copyright © 2011 SciRes. EPE
A New Distinguish Method of Blending Coals Slagging
Yonghua Li
North China Electric Power University, Baoding, China
Received December 27, 2010; revised February 15, 2011; accepted Marc h 2, 2011
The slagging characteristic of coal effects the safe operation of boiler unit directly, the study on coal slagging
is paid more and more attention by scholars of the world. Because of the complexity of coal characteristic,
the blending coals slagging characteristic is more complex than single coal. The study method of blending
coals characteristic is the same as the single coal method, but the simple method can’t distinguish the blend-
ing coals slagging characteristic well and truly. This paper gives the new distinguish method of blending
coals slagging characteristic based on experimentation condition, it is the rate of slag and furnace refuse. The
rate of slagging on furnace wall and the refuse on furnace bottom has utilized to distinguish the slagging
characteristic of coal. The result shows that the rate of slag and furnace refuse method has better veracity.
Keywords: Slagging, Blending Coals, Distinguish Method
1. Introduction
The slagging characteristic of coal effects the safe opera-
tion of boiler unit directly. So, scholars of the world at-
tach importance to th e study of coal slagging. At present,
the study of slagging characteristics of blending coals is
depended on the study of single coal.
The fuel character, boiler structure and operation
mode are the factors of deciding boiler slagging. The fuel
character is the basic of boiler design and operation. So,
the study on fuel slagg ing characteristic is important. The
study on distinguish slagging character is paid more and
more attention by scholars. There are many distinguish
methods and index of single coal slagging characteristics.
The most of the methods are ash melting temperature
slagging index method, ash element slagging index
method, ash viscosity slagging index method, special
type method and in tegrative distinguish method [1-3].
In USA, every slagging distinguish method are studied
in 130,300 MW and upwards units. Th e results sho w that
no method can forecast slagging trend complete accu-
rately. The resolution of the softening temperature and
silicon aluminum ratio is the highest. Harbin complete
institute distinguishes the slagging trend of 250 kinds of
Chinese coal; the resolution is 65%. Harbin boiler fac-
tory and Harbin Institute of Technology study on lignite
slagging trend, the results show th at the resolution of the
softening temperature an d silicon aluminum ratio is 74%
Some scholars adopt ash element slagging index
method and ash liquation index [5], ash melting tem-
perature [6], supporting vector machine [7], base/acid
and silica/alumina [8], to study coal slagging char acteris-
Many scholars study on blending coals slagging char-
acteristics [9,10]. They consider that the slagging char-
acter of blending coals is more complex than single coal
because of the complex of single coal slagging character.
The blending coals research method is the same as single
coal research method, but it can’t distinguish blending
coals slagging trend by single coal slagging trend. It
means that the difference of slagging character between
blending coals and singles coal is great.
This paper gives the new distinguish method of
blending coals slagging characteristic based on experi-
mentation condition, it is the rate of slag and furnace
refuse. The rate of slagging on furnace wall and the re-
fuse on furnace bottom has utilized to distinguish the
slagging characteristic of coal.
2. Test Rig and Experimental Process [11]
2.1. Coal Analysis
The single coal analysis and the rate and numbers of
blending coals are shown in Table 1 and Table 2.
Y. H. LI
Table 1. Single coal analysis.
Coal Huolinhe Yangcaogou FengguangMeihe
Mad 12.22 7.01 8.60 5.89
Aad 24.42 43.43 51.39 22.68
Vad 30.75 22.95 24.34 35.18
FCad 32.61 26.61 15.67 36.25
Cad 45.91 35.82 26.74 52.24
Had 2.70 3.21 2.42 4.04
Sad 0.50 0.35 0.18 1.65
Nad 0.73 0.53 0.73 1.38
Oad 13.52 9.65 9.94 12.12
Qnet, ar (J/g) 15919 12388 9249 19819
Table 2. The rate and number of blending coals.
The rate of single coal (%)
No. Huolinhe Meihe Fengguang Yangcaogou
1# 80 20 0 0
2# 70 30 0 0
3# 80 0 20 0
4# 70 0 30 0
5# 80 0 0 20
6# 70 0 0 30
7# 60 20 10 10
8# 70 10 10 10
9# 0 40 30 30
2.2. Test Rig
This study is conducted at Combustion Research Facility
(CRF) test rig, which is introduced from Canada. It’s
designed for a maximum coal feed rate of 20 kg/h me-
dium sulfur coal at a firing rate of 640 MJ/h (see Figure
1). Its advantages are complete equipment, advanced
control system, on-line measurement and recurring of
experimental result.
The test rig is composed of five systems, which are the
combustion system, data acquisition and control system,
compressing air and cooling system, the system of sam-
pling and analysis of flue gas and milling system. The
furnace is a refractory-lined cylindrical chamber, com-
posed of four identical modules, the bottom three with
cylindrical cooling jackets. It is 3.6 m high, and 0.3 m in
diameter. The furnace temperature is measured by plati-
num-rhodium thermocouple. The flue gas that leaving
the furnace is continuously monitored by O2, NOx, CO2,
CO and SO2 analyzers. The slag is got in the cooling
drawer at the bottom of the furnace and the fly ash is
sampled at the bottom of ESP. The coal feed rate of 20
2.3. Experimental Process
In this paper, the slag is got in the water-cooling drawer
at the bottom of the furnace, the fly ash is sampled at the
bottom of ESP. The coke adhered to furnace wall. The
coke is scratched from wall after test.
3. Test Results and Discussion
Slagging is a complex physical and chemical process. It
is not only related to the composition of coal ash, but
also influenced by the type of burners, the structure of
furnace, the temperature level in furnace, the aerody-
namic field of furnace and atmosphere in furnace. Now,
there are a few methods to predict and estimate the slag-
ging of pulverized-coal combustion, such as ash fusion,
ash composition and ash viscosity, but none of them is
accurate enough to predict correctly in practice.
According to the conditions of the test rig, this paper
got the ratio of the amount of coke attached to the wall to
the amount of slag on the bottom of the furnace. It is
presented as a discriminant parameter of slagging and
used to evaluate the extent of slagging in furnace in this
paper. The bigger the ratio is, the easier the slagging
happens. Table 3 shows the result of the ratio of coke
and slagging. On the basic of Table 3, the tendency of
Table 3. The ratio of the coke attached to furnace wall over
the slag on bottom of furnace.
Serial numberBlending Coals Coke/slag
1 9#(4M + 3F + 3Y) 2.92
2 Meihe 1.89
3 2#(7H + 3M) 1.84
4 5#(8H + 2Y) 1.44
5 Yangcaogou 1.27
6 7#(6H + 2M + 1F+1Y) 1.12
7 1#(8H + 2M) 1.17
8 6#(7H + 3Y) 1.11
9 3#(8H + 2F) 0.97
10 8#(7H + 1M + 1F + 1Y) 0.96
11 4#(7H + 3F) 0.53
Copyright © 2011 SciRes. EPE
Y. H. LI
Copyright © 2011 SciRes. EPE
19 24
18 21
113 14
15.vortex-type vacuum pump
16.vent to atmosphere
17.screw conveyor
18.pulverized coal feed hopper
19.volumetric screw feeder
21.primary air blower
8.coal puvlverizer
10.air heater
13pulse jet dust
14.explosion barrier
2.belt conveor
4.roller crusher
5.crusher coal feed hopper
6.variable sppe blow through feeder
7.feed blower
1.jig crane29.flue gas trace heater
30.electrostatic precipitator(ESP)
31.flyash hopper
33.exhaust blower
22.primary air heater
23.secondary air blower
24.secondary air heater
25.furnace chamber
27.air-cooler heat exchangers
slag sampling point
flue gas
sampling point
fly ash
sampling point
Figure 1. CRF test rig.
slagging of Meihe coal and 5#(2Y8H) coal is obvious,
while that of Huolinhe coal is weak. It fundamentally
agrees with the practice slagging tendency in boilers of
Shuangliao Power Plants on the whole. Th e ratio of coke
and slagging is a reasonable discriminant parameter of
slagging. From slagging characteristic of Meihe coal, 2#
coal, Yangcaogou coal, 1# coal, 6# coal, Huolinhe coal,
the results show that the slagging characteristic of
blending coals is between componential coals basically.
The slagging serious coal changed the slagging charac-
teristic by blended not easy slagging coal, thereby
achieved the aim that lighten slagging.
According to the Table 3, the slagging property of 9#
(4M3F3Y) coal and Meihe coal is more serious than that
of Huolinhe coal and Yangcaogou coal. This shows
when the blending of a coal of high slagging potential
with another co al with low slagging potential is u sed, the
trouble of slagging perhaps gets worse instead of getting
better. This is because the eutectic phenomenon of ash
composition makes the ash fusion of the mixed coal
lower than that of any of the coals used in the blending.
Therefore, improper blending of coals will cause serious
4. Compared with Other Methods
4.1. Slag Type Analysis
From the slag scratched from wall, the slag color of
Meihe coal, No. 9 and No. 2 blending coals is hoar and
dust color. It has alveo late hole. The intensity is high and
rigidity is great. The surface of slag is smooth. It belongs
to glaze type slag. It shows that the slagging is serious.
The slag color of Yangcaogou coal, No. 1, No. 7 and No.
5 blending coals is black, the character is relaxation. It
shows that the slagging is middling. No. 3, No. 4, No. 8,
No. 6 blending coals and Huolinhe coal slagging is
ightly. l
Y. H. LI
Copyright © 2011 SciRes. EPE
Table 4. Fusion behavior of coal ash.
Ash fusion point Tem. at oxidizing atmosphere (˚C) Ash fusion point Tem. at reducing atmosphere (˚C)
Huolinhe 1280 1395 >1450 1230 1345 >1450
Yangcaogou 1250 1410 >1450 1200 1360 >1450
Meihe 1320 1360 1430 1270 1310 1380
Fengguang >1450 - - >1450 - -
1# 1245 1340 >1450 1195 1290 >1450
2# 1220 1325 1440 1170 1275 1390
3# 1270 1365 1450 1220 1315 1400
4# 1305 1405 1450 1255 1355 1400
5# 1295 1380 1440 1245 1330 1390
6# 1235 1375 >1450 1185 1325 >1450
7# 1260 1330 1445 1210 1280 1395
8# 1220 1350 1445 1170 1300 1395
9# 1435 >1450 - 1385 >1450 -
Table 5. Distinguish result.
Method Result
The rate of slag and furnace refuse 9#, Meihe, 2#, 5#, Yangcaogou, 7#, 1#, 6#, 3#, 8#, 4#, Huolinhe
Slag type analysi s Meihe, 9#, 2#, Yangcaogou, 1#, 7#, 5#, 3#, 4#, 8#, 6 # , Huolinhe
Fusion behavior analysis Meihe, 1#, 2#, 3#, 6#, 5#, 8#, 7#, Huolinhe, Yangcaogou, 4#, 9#
4.2. Fusion Behavior Analysis
The fusion behavior of coal ash is shown in Table 4.
This paper adopts the Harbin boiler factor y an d Harbin
Institute of Technology method distinguishes the slag-
ging character. The result is that Meihe coal, No. 1, No.
2, No. 3, No. 6, No. 5, No. 8 and No. 7 blending coals
slagging middling, Huolinhe, Yangcaogou, Fengguang
coal, No. 4 and No. 9 blending coals slagging lightly.
4.3. Compare of Three Methods
Up to now, there is no method has 100% resolution. So,
the test result is most important. The compare of three
methods is shown in Table 5. The result shows that the
rate of slag and furnace refuse method has bett er veracity.
5. Conclusions
This paper gives the new distinguish method of blending
coals slagging characteristic based on experimentation
condition, it is the rate of slag and furnace refuse. The
result shows that the rate of slag and furnace refuse me-
thod has better veracity.
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