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Fuel Processing Technology 130 (2015) 282–291
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Fuel Processing Technology
j ourna l homepage: www.e lsev ie r .com/ locate / fuproc
Kinetics of steam gasification of bituminous coals in termsof their use for underground coal gasification
Stanisław Porada ⁎, Grzegorz Czerski, Tadeusz Dziok, Przemysław Grzywacz, Dorota MakowskaAGH University of Science and Technology, Faculty of Energy and Fuels, al. Mickiewicza 30, 31–464 Krakow, Poland
⁎ Corresponding author. Tel.: +48 126172601, fax: +4E-mail addresses: [email protected] (S. Porada), gcze
[email protected] (T. Dziok), [email protected]@agh.edu.pl (D. Makowska).
http://dx.doi.org/10.1016/j.fuproc.2014.10.0150378-3820/© 2014 Elsevier B.V. All rights reserved.
a b s t r a c t
a r t i c l e i n f oArticle history:Received 29 April 2014Received in revised form 3 October 2014Accepted 13 October 2014Available online xxxx
Keywords:High pressure kinetics of coal gasificationwith steamUnderground coal gasificationCoals for gasification assessment
The kinetics of steam gasification was examined for bituminous coals of a low coal rank. The examined coals canbe the raw material for underground coal gasification. Measurements were carried out under isothermal condi-tions at a high pressure of 4 MPa and temperatures of 800, 900, 950, and 1000 °C. Yields of gasification productssuch as carbonmonoxide and carbon dioxide, hydrogen andmethanewere calculated based on the kinetic curvesof formation reactions of these products. Also carbon conversion degrees are presented. Moreover, calculationswere made of the kinetic parameters of carbon monoxide and hydrogen formation reaction in the coal gasifica-tion process. The parameters obtained during the examinations enable a preliminary assessment of coal for theprocess of underground coal gasification.
© 2014 Elsevier B.V. All rights reserved.
1. Introduction
Underground coal gasification (UCG) is an alternative technicaloption for using coal without the necessity of excavating it [1]. This isan environmentally friendly way of utilizing coal [2], technically feasi-ble, and its application is also economically justifiable [3,4]. Coal conver-sion directly in the seam into a suitable fuel gas occurs with the aid ofgasification agents like air, oxygen, steam or their mixture. The mostimportant components of the gas are: carbon monoxide, hydrogen,methane, and carbon dioxide, and its calorific value ranges from 4.1 to10.7 MJ/Nm3. The shares of these components depend onmany factors,e.g. the composition of the gasification agentmixture, coal properties, aswell as geological and hydrological characteristics of the coal seam [5].The optimum operating conditions should be used in order to achievedesired conversion coal to syngas [6]. UCG is inherently an unsteadyprocess since a number of parameters, such as the growth of the cavity,inherent variation in the properties of the coal along the seam, quantityof water influx, ash layer build-up, affect the rates of the homogeneousand heterogeneous reactions occurring therein [7–9]. The gas may beused for energy production or the synthesis of chemicals, liquid fuels,or other gaseous fuels. The underground coal gasification may also besuccessfully used to produce hydrogen from coal [10].
In a coal seam, where the process of underground coal gasification isconducted, three zonesmaybedistinguished: oxidation zone, gasificationzone and pyrolysis zone. In the oxidation zone, exothermic combustion
8 [email protected] (G. Czerski),l (P. Grzywacz),
reactions occur between the oxygen contained in the gasificationmixtureand carbon contained in the coal seam (Eqs. (1)–(3)). The resulting heatcauses the warming of the seam up to a high temperature.
Cþ O2→CO2 ΔH ¼ −393;51 kJ=mol ð1Þ
Cþ 0;5O2→CO ΔH ¼ −110;53 kJ=mol ð2Þ
COþ 0;5O2→CO2 ΔH ¼ −282;98 kJ=mol ð3Þ
In the gasification zone endothermic reactions (Eqs. (4)–(5)) occurbetween steam and carbon dioxide, which results in the formation ofhydrogen and carbon monoxide.
Cþ H2O↔H2 þ CO ΔH ¼ þ131;28 kJ=mol ð4Þ
Cþ CO2↔2CO ΔH ¼ þ172;45 kJ=mol ð5Þ
Additionally, due to the catalytic influence of ash [11] and the highpressure connected with the depth at which the process occurs, apartfrom the above-mentioned reactions, the methanation reaction alsotakes place (6).
Cþ 2H2↔CH4 ΔH ¼ −74;81 kJ=mol ð6Þ
Fig. 1. The laboratory equipment for kinetic examinations of coal gasification: R — reactor;WP— steam generator; PW—water pump; CON — condenser; ZK — tar separator; MP —
rotameter; DW — coal feeder; ARP — mass flowmeter; M — pressure gauge; F — gasfilter; and RC — backpressure regulator.
Table 1Characteristics of examined coals.
Parameter Ziemowitcoal
Bobrekcoal
Bogdankacoal
Wieczorekcoal
Proximate analysis (%)Moisture — Ma 6.6 4.0 2.2 3.3Ash — Aa 5.6 2.6 4.3 13.0Volatile matter — VMdaf 40.8 37.5 41.3 38.2Higher heating value—HHV (MJ/kg) 28.3 34.6 32.8 29.6
Ultimate analysis (%)Cdaf 79.3 87.1 83.3 83.8Hdaf 5.3 5.7 5.7 5.8Stdaf 0.78 1.03 1.04 0.31Ndaf 1.2 1.3 1.5 1.4Odaf (difference) 13.4 4.9 8.5 8.7O/C ratio 0.17 0.06 0.10 0.10
Ash composition (%)Fe2O3 9.3 7.1 8.4 9.3CaO 6.5 7.1 4.8 4.9MgO 4.7 5.5 0.4 3.5Na2O 4.8 0.6 0.6 1.1K2O 0.6 2.8 0.3 1.8SiO2 28.7 43.8 32.2 39.3Al2O3 28.8 23.9 31.6 15.5Alkali index AI (−) 2.52 0.89 0.98 4.89
283S. Porada et al. / Fuel Processing Technology 130 (2015) 282–291
In the pyrolysis zone, thermal destruction of coal occurs, accompaniedby the release of such components as H2O, CO2, CO, C2H6, CH4, H2 and tar.
Also products of gasification can react especially CO according to theequation:
COþH2O↔CO2 þH2 ΔH ¼ −41;2 kJ=kmol ð7Þ
As it can be concluded from the above-mentioned reactions, themost important products, i.e. carbon monoxide (CO) and hydrogen(H2) are formed in the coal gasification zone as a result of the occur-rence of the water gas reaction (Eq. (4)) and the Boudouard reaction((Eq. (5)) there. Therefore, it is very important to learn about thisstage of the process.
The complexity of the gasification process results in the fact that it isstill the subject of numerous examinations and analyses [12]. Theimpact of particular factors on the gasification process, and, especial-ly, the carbon conversion degree as well as the yields of gaseousproducts of the process are assessed most frequently with the aidof thermovolumetric and thermogravimetric methods. In the vastmajority of cases, the examinations of gasification kinetics are conduct-ed for coal chars,with the temperature atwhich they are obtained beingvery important. The impact of temperature and pressure at which theprocess is conducted on the rate of coal and lignite gasification as wellas the yields of gaseous product still remains a valid problem [13-16].The presented examinations confirm that temperature is one of themore important factors influencing the carbon conversion degree andcoal char gasification rate. Also, the process pressure has an effect onboth, the course of the coal pyrolysis stage and coal char gasification.As far as the pyrolysis stage is concerned, pressure influences it in twoways:firstly, it affects the amount of the obtained coal char and, second-ly, its structure. The growth of pressure atwhich the pyrolysis process isconducted facilitates a reduction in the loss of coal mass, that is, theformation of greater amounts of coal char, and the most significantchanges are observed within the pressure range of 0.01–1 MPa [17].The examinations also focus on establishing the impact of the composi-tion and structure of the organic and mineral matter on the gasificationrate [18,19]. Investigations were also conducted aiming at determiningthe activation energy, during which it was found that the energy doesnot depend on grain size distribution of coal sample and it increasesalongwith the coal rank [20–22]. The results of examinations containedin the work [15] have confirmed the impact of partial pressure of steamon gasification rate. As regards gasification with steam, the H2O/C ratiois also important and according to [23], together with the increaseof this parameter, the total gas yield as well as the CO and H2 yieldsgrow, while the CO2 concentration and the carbon conversion degreedecrease. In turn, the presence of gases released during pyrolysis, aswell as hydrogen, in the course of gasification with steam results inslowing down the process [20].
Unfortunately, due to the specificity of underground coal gasifica-tion, examinations of gasification kinetics inside the coal seam are prac-tically impossible. Matching a proper coal to the gasification process isvery important [24]. At the stage of assessment of particular coals forunderground coal gasification, laboratory methods can be applied. Inthis work, examinations focused on the formation kinetics of gaseousproducts of coal gasification with steam under conditions similar tothose of the coal seam. For the purposes of the examinations, a uniquelaboratory equipment was used, which enables examining the kineticsof gasification with steam under a high pressure and for coal particlesof several millimeters. The investigations were carried out for coalswhich may be a potential raw material for underground coal gasifica-tion. A rarely used approach during gasification kinetics investigations,i.e. examining coals and not the chars obtained from them, enablesgetting practical information about phenomena occurring in a coalseam, among others, concerning the composition of gaseous productsreleased at the initial stage of the process, when the reactions of
pyrolysis dominate. The kinetic parameters of the examined coalswere determined; moreover, on the basis of the course of the kineticcurves, the yields of the most important gasification products werecalculated, i.e. hydrogen, carbon monoxide, carbon dioxide as well asmethane, and the curves of carbon conversion degree were produced.On the basis of the results of the examinations a preliminary assessmentof coals can bemade, among others, for the process of underground coalgasification [25].
0
20
40
60
80
100
120
140
160
0 10 20 30 40 50 60 70 80 90 100 110 120
dV
/dt
[cm
3 /g
* min
]
Time [min]
Ziemowit coal; 900 °C; 4 MPa
CO
CO2
H2
CH4
Fig. 2. Changes in formation rate of the tested gases during gasification of Ziemowit coal at temperature of 900 °C and pressure of 4 MPa.
284 S. Porada et al. / Fuel Processing Technology 130 (2015) 282–291
2. Material and methods
2.1. Applied equipment and methodology of examinations
The examinationswere conductedwith the use of a unique laborato-ry equipmentwhich enables examining the kinetics of gasification withsteam under a high pressure for a varying particle size distribution ofcoal samples. The equipment was thoroughly described in the works[13,26], and its diagram is shown in Fig. 1.
It is composed of three basic systems, namely: a high pressure reac-tor with a heating system, a system for feeding the reactor with steam,inert gas (argon) and coal as well as a system for collection and analysis
0
10
20
30
40
50
60
0 20 40 60 80
dV
/dt
[cm
3 /g
* min
]
Time
Ziemowit co
Fig. 3. Influence of temperature on CO formation rate duri
of the resulting gas. Inside the reactor there is a retort with the diameterof 20 mm equipped with a grate made of sintered quartz. After stabiliz-ing the parameters of the examinations, a sample of the examined coalis introduced onto the grate. For this purpose, a specially designed pistonsample feeder is used. The movement of the piston is a result of openingthe inlet valve on the pipe supplying the gas into the chamber of thefeeder. The heating of the retort with the sample is conducted bymeans of an electric oven. The pressure casing of the quartz reactor iscomposed of a heat-resistant steel blanket, the ends of which are closedwith lids equipped with pipes supplying steam and argon as well aspipes carrying away the resulting gas. Mineral wool fitted inside the cas-ing forms the insulation of the oven. The temperature of the coal sample
100 120 140 160 180
[min]
al; CO; 4 MPa
800 °C
900 °C
950 °C
1000 °C
ng gasification of Ziemowit coal at pressure of 4 MPa.
0
20
40
60
80
100
120
140
160
0 20 40 60 80 100 120 140 160 180
dV
/dt
[cm
3 /g
* min
]
Time [min]
Ziemowit coal; H2; 4 MPa
800 °C
900 °C
950 °C
1000 °C
Fig. 4. Influence of temperature on H2 formation rate during gasification of Ziemowit coal at pressure of 4 MPa.
285S. Porada et al. / Fuel Processing Technology 130 (2015) 282–291
is measured by a sensor of the thermocouple type K, which serves, at thesame time, for sending impulses to the controller–programmer main-taining the required temperature of the sample. The system for feedingsteam and argon to the reaction zone is composed of a micropump dos-ingwater, a steam generator, compressed gas cylinderswith argon and aset of pressure reducing valves, control valves as well as release valves,filters, a pressure gauge and a flow rate regulator. The resulting gasflows to the condenser, where a water and tar condensate is separatedand, subsequently, thoroughly cleared and dried on the filter. After de-compression, in the resulting gas the contents of carbon monoxide andcarbon dioxide are determined in a continuous way by means of ananalyser based on the infrared radiation adsorption. Moreover, gas sam-ples are taken in order to analyse it later in respect of the content of
0
5
10
15
20
25
30
35
40
45
50
0 20 40 60
dV
/dt
[cm
3 /g
* min
]
Time
CO; 900
Fig. 5. Changes in CO formation rate during gasification of exam
hydrogen and gaseous hydrocarbons. Two gas chromatographs are usedfor that purpose. The first one, equipped with a flame ionization detector(FID), serves for analyzing hydrocarbons, and the other one, with a ther-mal conductivity detector (TCD), is utilized to determine the hydrogencontent.
2.2. Methodology of examinations
Inside the reactor, a reaction retort is positioned and in the samplefeeder, about 1 g of coal of appropriate grain size is placed. After closingwith the lids, the reactor and the sample feeder are compressed byargon to the required pressure and then the required flow of argon isadjusted. After stabilizing the flow, the heating of the reactor and the
80 100 120 140 160
[min]
°C; 4 MPa
Ziemowit coal
Wieczorek coal
Bogdanka coal
Bobrek coal
ined coals at temperature of 900 °C and pressure of 4 MPa.
286 S. Porada et al. / Fuel Processing Technology 130 (2015) 282–291
steam generator is activated. Then, after reaching the pre-set tempera-tures, the micropump dosing water with a specific delivery is activated.After reaching the required examination parameters (pressure, thetemperature of the reactor and the steam generator as well as theflow rate of argon and water), the valve supplying compressed argonto the sample feeder is opened for several seconds, which causesthrowing the coal sample into the reactor. The resulting gas flows tothe analyser for the continuous determination of carbon monoxideand carbon dioxide contents. Moreover, its samples are taken through-out the examination period. The samples are then analyzed in respect ofthe content of hydrogen and gaseous hydrocarbons.
2.3. Methodology of calculating kinetic parameters
Based on the measurements of carbon monoxide, hydrogen, meth-ane and carbon dioxide concentrations in the resulting gas, the forma-tion rates were calculated for these products during the gasification ofthe examined samples. The obtained data enabled calculation of theyields of the examined products and formal kinetic parameters of thereaction of CO and H2 formation.
The formation rate of a given product can be expressed by theequation:
dVdt
¼ k � V∞−Vð Þ ð1Þ
where:
k constant reaction rate [1/min]V∞ maximal volume of gas product [cm3]V volume of released gas component at time t [cm3]t time [min]
After the separation of variables and integration one can obtain:
lnV∞
V∞−V¼ k � t ð2Þ
0
20
40
60
80
100
120
140
160
0 20 40 60
dV
/dt
[cm
3 /g
* min
]
Time
H2; 900
Fig. 6. Changes in H2 formation rate during gasification of exam
The graph ln[V∞/(V∞–V)] as a function of t should be a straight linewith a slope equal to k, i.e. the constant reaction rate of formation of agiven product.
While determining the constant reaction rates of formation of theexamined products for different temperatures of gasification, formalvalues of activation energy and pre-exponential factor can be calculatedby means of the Arrhenius equation.
The carbon conversion degree can be estimated on the basis of theformula:
X ¼Vco þ VCO2
þ VCH4
� ��MC
Vmol �m � Cdaf� 100 % ð3Þ
where
VCO, VCO2, VCH4
volume of released gas component [dm3/g]MC molar mass of carbon [g/mol]m sample mass [g]Cdaf dry ash free carbon content [−]Vmol volume of one mole of gas at temperature of 273 K and
pressure of 101325 Pa [dm3/mol]
2.4. Characteristics of coals and conditions of measurements
In contrast to themajority of the conducted examinations, which arecarried outwith the use of chars, themeasurementswere conducted forcoals. The kinetics of gasification of Polish bituminous coals with steamas potential rawmaterials for underground coal gasification was exam-ined. Coals from 4 mines were selected, namely: ‘Ziemowit’, ‘Bobrek’,‘Wieczorek’ and ‘Bogdanka’. The examined coals were characterized(Table 1) by means of a proximate and an ultimate analysis as well asan analysis of the ash compositionwhichmay be important for gasifica-tion kinetics.
These are bituminous coals of a relatively low coal rank with avarying ash content and composition. Additionally, the alkali index(AI) was calculated in accordance with the Eq. (4), which makes itpossible to assess the catalytic impact of the components of coalmineral
80 100 120 140 160
[min]
°C; 4 MPa
Ziemowit coal
Wieczorek coal
Bogdanka coal
Bobrek coal
ined coals at temperature of 900 °C and pressure of 4 MPa.
811
456
168
1831
994
440
209
1695
1045
325180
1771
1128
306155
1933
CO CO2 CH4 H2
Ziemowit coal800 °C 900 °C 950 °C 1000 °C
415
635
107
1229
748649
73
1399
750658
77
1445
838
634
82
1505
CO CO2 CH4 H2
Wieczorek coal800 °C 900 °C 950 °C 1000 °C
378
575
46
1091
740622
75
1524
815
565
109
1605
784
584
88
1432
CO CO2 CH4 H2
Bogdanka coal800 °C 900 °C 950 °C 1000 °C
512
631
104
1126
747
537
106
1466
741
459
133
1188
730
485
98
1279
CO CO2 CH4 H2
Bobrek coal800 °C 900 °C 950 °C 1000 °C
Fig. 7. Yields of CO, CO2, CH4 and H2 [cm3/g] in the gasification process of examined coalsfor different temperatures.
287S. Porada et al. / Fuel Processing Technology 130 (2015) 282–291
matter. Together with the growth of the Al value, the reactivity of coalsincreases [27,28].
AI ¼ Aa � Fe2O3 þ CaOþMgOþ Na2Oþ K2OSiO2 þ Al2O3
ð4Þ
where
Aa Ash content in coal sample [−]Fe2O3, CaO, MgO, Na2O, K2O, SiO2, Al2O3 content of particular oxides in
ash [%]
The examinations of gasification kinetics were conducted at a highpressure of 4MPa at the temperatures of 800, 900, 950 i 1000 °C. Duringthe examinations sampleswith the particle size of 2.5÷3.15mmand themass of 1 g were applied. The flow rate of steamwas 0.3 g/min, and thatof the inert gas — 2.5 dm3/min. Based on the conducted measurements,the yields of gaseous products of the process were calculated, and thekinetic parameters of the formation reaction of carbon monoxide andhydrogen in the process of gasification were determined. Curves ofcarbon conversion degree were also developed.
3. Results and discussion
Based on the measurements of concentrations of carbon monoxide,hydrogen, methane and carbon dioxide in the resulting gas, formationrates were calculated for particular products during the gasification ofthe examined samples. The selected examples of the changes in theformation rates of particular products during gasification under thepressure of 4 MPa and the temperature of 900 °C for the Ziemowitcoal are shown in Fig. 2.
It can be observed that, despite differences in the formation rates ofparticular products, the character of their kinetic curves is similar. In allthe cases, the initially observed high reaction rate falls, and the fall isvery big in the first phase, while later on it is much slower. The highestrates can be noticed for the formation reaction of hydrogen. Very highevolution rates of particular products in the initial phase of the processare a result of the pyrolysis reactions.
Figs. 3 and 4, using carbon monoxide and hydrogen as an example,illustrate the impact of temperature on the evolution of the gaseousproducts of gasification of the Ziemowit coal. An increase in temperatureresults in a growth of evolution rates of gaseous products and a reductionof the duration of the process.
A comparison of the formation rates of carbon monoxide and hy-drogen during the process of gasification of the examined coals atthe temperature of 900 °C is presented in Figs. 5 and 6. From an anal-ysis of the figures it can be concluded that the highest evolution rateof carbon monoxide and hydrogen is recorded for the Ziemowit coal,and, in the case of the remaining coals, the process progresses at asimilar rate.
The kinetic curves of formation reactions of the examined gasesobtained during the gasification measurements enabled the calculationof the yields of those products. The obtained values per 1 g of coal in dryand ash-free state are presented in Fig. 7. An analysis of the presenteddata leads to the conclusion that with the growth of temperature, inmost cases, the yields of carbon monoxide and hydrogen increase inthe process of gasification of the examined bituminous coals, and theyields of hydrogen are almost two times higher than those of carbonmonoxide. The recorded yields of methane are much smaller and it isformed mainly at the initial stage of the process, i.e. during pyrolysis.For the Ziemowit coal, the obtained yields of CO, H2 and CH4 are muchhigher when compared to the remaining coals. For the Wieczorek,Bogdanka and Bobrek coals, similar yields of gasification productswere obtained, as well as greater yields of CO2, when compared to theZiemowit coal.
The next stepwas the elaboration of the curves of carbon conversiondegree. Fig. 8 shows the conversion ratio for the Ziemowit coal fordifferent temperatures, and Fig. 9 represents a comparison of theconversion ratios of the examined coals at 900 °C. From an analysis ofthe presented curves, it can be seen that temperature has a significantimpact on the conversion degree. A comparison of the examined coalsshows that the highest reactivity was that of the Ziemowit coal andthe lowest one was that of the Bobrek coal, which was of the highestcoal rank, and, additionally, has the lowest alkali index. Even thoughthe Ziemowit coal was of a lower coal rank when compared tothe Bogdanka coal, it has a significantly higher alkali index and theO/C ratio.
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100 120 140 160 180
Car
bo
n c
on
vers
ion
deg
ree
[%
]
Time [min]
Ziemowit coal; 4 MPa
800 °C
900 °C
950 °C
1000 °C
Fig. 8. Changes in carbon conversion degree during gasification of Ziemowit coal at temperatures of 800, 900, 950 and 1000 °C.
288 S. Porada et al. / Fuel Processing Technology 130 (2015) 282–291
The final step of the work was the calculation of kinetic parametersof the formation reactions of CO and H2 in the process of gasificationof the examined coals with steam. To that end, using the relationshipln[V∞ / (V∞ − V)] as a function of t, the reaction rate constants k ofthe reactions in question were determined for particular temperaturesat which the measurements were conducted. Next, with the use ofthe Arrhenius equation, the activation energy and the pre-exponentialfactor were calculated. The determination of the reaction rate constantsof CO and H2 formation taking the gasification of the Ziemowit coal at950 °C as an example, are illustrated in Figs. 10 and 11. The high valuesof the coefficient of determination R2 show that the application of the
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60
Car
bo
n c
on
vers
ion
deg
ree
[%
]
Time
900 °C
Fig. 9. Comparison of carbon conversion degree during ga
first order reaction model in the process of gasification with steam forthe formation of CO and H2 was correct.
The Arrhenius plots for the reactions of CO and H2 formation duringthe gasification of the Ziemowit coal are presented in Figs. 12 and 13.From an analysis of these figures, it can be seen that, for both cases,high values of the coefficient of determination R2 were obtained. Also,for the remaining coals tested, high values of the coefficient of determina-tion R2 were obtained both, during the determination of the reaction rateconstant and for the Arrhenius plots.
The determined formal parameters of the reactions of CO and H2
formation during the gasification of the examined coals under the
80 100 120 140 160
[min]
; 4 MPa
Ziemowit coal
Wieczorek coal
Bogdanka coal
Bobrek coal
sification of examined coals at temperature of 900 °C.
y = 0.0223x + 0.0047R² = 0.9945
0.0
0.5
1.0
1.5
2.0
2.5
0 20 40 60 80 100
ln[V
∞/(V
∞-V
)]
Time [min]
Ziemowit coal; CO; 950 °C; 4 MPa
Fig. 10. Relation between ln V∞ / (V∞ − V) and t for CO formation during the Ziemowit coal gasification at temperature of 950 °C and pressure of 4 MPa.
289S. Porada et al. / Fuel Processing Technology 130 (2015) 282–291
pressure of 4 MPa are presented in Table 2. The obtained values ofactivation energy are typical for chemical reactions.
4. Conclusions
• The examinations of gasification kinetics were conducted for coals, incontrast to the experiments widely discussed in the literature, wherecoal charswere used as the rawmaterial. The presented equipment andmethodology enable conducting examinations under high pressuresand make it possible to determine a number of characteristic parame-ters of coal gasification with steam.
• Taking the examined coals as an example, the impact of temperature onthe increase in the formation rates and yields of CO, CO2, H2 and CH4
was presented, and the formal kinetic parameters of the formation
y = 0.0R²
0.0
0.5
1.0
1.5
2.0
2.5
0 20 40
Time
Ziemowit coal; H
ln[V
∞/(V
∞-V
)]
Fig. 11. Relation between ln V∞ / (V∞ − V) and t for H2 formation during the Z
reactions of CO and H2 were calculated. The carbon conversion degreewas presented; it is also possible to determine its half-time of gasifica-tion reaction.
• The highest evolution rates during gasification with steam wereobtained for hydrogen. Along with the growth of temperature,the yields of CO and H2 increased, and the conversion degree of car-bon contained in the gasified coal grew as well.
Acknowledgments
The work was conducted within the framework of the strategicProject no. SP/E/3/77008/10,financed by theNational Centre for Researchand Development.
238x - 0.0091 = 0.9875
60 80 100
[min]
2; 950 °C; 4 MPa
iemowit coal gasification at temperature of 950 °C and pressure of 4 MPa.
y = -13856x + 7.7795R² = 0.9566
-6
-5
-4
-3
-2
-1
00.00076 0.00078 0.00080 0.00082 0.00084 0.00086 0.00088 0.00090 0.00092 0.00094
ln k
1/T
Ziemowit coal; CO; 4 MPa
Fig. 12. Arrhenius plot for the reaction of CO formation during gasification of Ziemowit coal at temperatures of 800, 900, 950 and 1000 °C.
y = -10018x + 4.5702R² = 0.9834
-6
-5
-4
-3
-2
-1
00.00076 0.00078 0.00080 0.00082 0.00084 0.00086 0.00088 0.00090 0.00092 0.00094
ln k
1/T
Ziemowit coal; H2; 4 MPa
Fig. 13. Arrhenius plot for the reaction of H2 formation during gasification of Ziemowit coal at temperatures of 800, 900, 950 and 1000 °C.
Table 2Formal kinetics parameters of CO and H2 formation reaction during gasification ofexamined coals.
Kineticsparameters
Ziemowitcoal
Bobrekcoal
Bogdankacoal
Wieczorekcoal
COk0 (1/min) 2391 938 790 2187E (kJ/mol) 115 104 105 114
H2
k0 (1/min) 97 46 210 4E (kJ/mol) 83 76 93 56
290 S. Porada et al. / Fuel Processing Technology 130 (2015) 282–291
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