Oxidation Reaction of Calcium Sulfide in an Advanced PFBC Condition (I) (DONG 他) 101

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Original Paper

OxidationReaction of CalciumSulfide in an AdvancedPFBC Condition (I)

Effects of O2 concentration, type of limestone and particle size

Zhong-Bing DONG, Atsushi SATO, Masaru OKADA and Yoshihiko NINOMIYA*

Department of Industrial Chemistry, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501

(Received July 14, 1998)

The performance of chemical reaction of CaS particle under oxidizing atmosphere condition was

investigated in the temperature range of 700 to 1300•Ž by a TG-DTA apparatus. The chemical reaction

was found to be complicated process with the products of CaO, CaSO4 and the release of SO2 gas. The

weight of sample changed in the following three different ways: gain, loss, and oscillation. The whole

reaction process could be classified into three reaction steps: The reaction of CaS +2O2 CaSO4 took

place as the weight gain in the first step. The weight loss with release of SO2 gas resulted from the

reaction of CaS + 3/2O2 CaO + SO2 in the second step. The oscillation behavior in the third step can

be given explanation through the decomposition and formation of calcium sulfate. The temperature

range of the second step was strongly dependent on the O2 concentration of inlet gas. Higher bulk O2

condition led to the higher O2 concentration at the reaction front, so that the temperature of second step

shifted to higher one. The reaction rate of CaS to CaO between 950 and 1050°C at 1% O2 was expressed

as 1.1 X 1017 exp(-54847/T)

Key Words

Calcium sulfide, Oxidation reaction, Advanced PFBC

1. INTRODUCTION bent to CaS is in the range of 0.4-0.6. However, One of the principal advantages of air-blown CaS may cause difficulties with handing, disposal partial gasification and combustion or Advanced or utilization of the residues. Since the solid PFBC systems, using integrated gasification and wastes are usually intended for disposal in landfill combustion technologies is the ability to capture sites, the problem of CaS reacting with acid sulfur in-situ using low cost limestone or dolomite leachate or water and releasing H2S has been as a sorbent1) 2). Sulfur capture can be carried raised. Transformation of CaS to inert CaSO4 is out in gasifier through the sulfidation reaction. imperative to reduce treatment of the waste CaO and CaO MgO result from calcination of material. The oxidizing step is important to limestone or dolomite which is fed into the gasifi- allow safe disposal of the residual material from er with primary fuel3). Sulfur retention of 85- the char combustor of fluidized bed. 92% has been reported using limestone and For the oxidation reaction, Lynch and Elliott5) dolomite sorbents at Ca/S molar feed ratios of 1.6 gave a general description of this reaction. The to 2.04). Fractional conversion of CaO in the sor- high temperatures withlow partial pressures of *To whom correspondence should be addressed . 2 benefited the reaction: O 100 ― 「日本エネルギー学会誌」第78巻第2号(1999) ―

Table 1 CaS samples in this study

and CaSO4 with CaS content below 0.002mol.% at

(1) 940•Ž and 1% O2 condition and at 1180•Ž and above

21% condition. It was pointed out that tempera- and the low temperatures with high partial pres- ture and O2 atmosphere conditions played impor- sures of O2 should be responsible for the sulfate tant roles on the complete conversion of CaS to formation through the reaction: CaO and CaSO4 in the papers. However, the

effects of type of sorbent, initial CaS content and

particle size on oxidation reaction process and

(2) reaction scheme have not been clear. This paper

attempts to discuss the whole reaction process

Rowena6) et al yielded the reaction(1) rate con- through thermogravimetric analyzer under various stant of 8.2276 x 106exp(-20411/T) cm/s in 0.10 oxidizing conditions, deducing comprehensive atm of O2 in temperatures of 1127-1427°C in a reaction mechanism for CaS oxidation reaction. laminar flow oxidation furnace. The oxidation of The effects of limestone, initial CaS content and

CaS to CaSO4 was found by Davies7) to proceed by particle size on the reaction process, and the kinet- first-order in O2, with a rate constant of (4.5•} ics of reaction of CaS to CaO are discussed.

2.0 •~10-4 ) exp(-(5.7•}1.5)103)/T m/s between 850 and 1050°C under fluidized bed combustion condi- 2. EXPERIMENTAL METHOD tion, and they also indicated that the release of The experiment was conducted by the use of a TG-

SO2 was mainly due to the solid-solid reaction DTA apparatus (Rigaku, TG8110D). Approximately under the typical combustion condition: 25 mg CaS sample with Al2O3 as a reference was

placed in a platinum sample container (ID 8mm, height 5mm), to which a thermocouple (Pt-Pt/Rh)

(3) attached to record reacting temperature. Sample

was heated with 5,10 and 15 t per minute up to

In our previous papers8) 9), the oxidation reaction the required temperatures between 700 and 1300 t, of CaS under the fluidized bed combustion /genera- and kept for about 600 minutes at the tempera- tion conditions was investigated, suggesting that a tures. O2 concentration was varied from 1% to combustor / generator should be kept up to 950•Ž 100 %. The exit SO2 gas from TG with the inter- for CaS oxidation. CaS in the spend sorbent parti- vals of 4-minute sampling time was analyzed

le was found to be essentially converted to c CaO quantitatively by a FPD gas chromatograph, Oxidation Reaction of Calcium Sulfide in an Advanced PFBC Condition (I) (DONG 他) 101

Fig. 1 TG curves under 1 to 40% O2 atmospheres with sample K3(Kinsensan limestone,0.89mm)

which was calibrated by a mixture containing 26.9 and 46.0 cm3/mol). It is obvious that the

496.5ppm SO2 in N2 before each test. A mass fil- weight gain of CaS sample is due to reaction (2), ter analyzer with 7-second detecting time was and the reactions (1) and (3) should result in the used to get the instant reaction behavior. weight loss of CaS sample. The net result of the

CaS samples were prepared through sulfidation three reactions can simply be described as: reaction in a fluidized bed (a quartz glass tube of

I. D, 38mm and 500mm height) with 4500ppm H2S- / CaO+SO2(weight loss) 16MoXCaO 8.4%H2-N2 gas mixture as fluidized gas. Three CaS •Ë•¢m =64MOXCaSO4•|16M0XCaO types of limestones, and a dolomite produced in / CaSO4 (weight gain)64MOXCaSO4

Gifu prefecture, and a coral reef were used in this study. The average diameters of CaS samples Rewriting the above equation to have are 0.20,0.50and0.89mm. All sorbents were firstly calcined in N2 atmosphere at 900•Ž untill XCaSO4=[△m+16MOXCaO]/[64MO](4) no CO2 was detected by a TCD gas chromatograph, then the sulfurization gas was changed to Because CaO and SO2 are formed in equimolar the desired one. The sulfurization reaction fol- amounts, the conversion of CaS to CaO at any lowed with various reacting times so as to obtain reacting time t can be calculated from the samples with different CaS contents. The

CaS contents of the samples before /after oxida- (5) tion were confirmed by the methylene blue methods). The properties of sorbents and CaS where Xi is the conversion of CaS to species i, G samples are listed in Table 1. the total molar flowrate of product gas, YSO2 the

The release of SO2 is due to reactions (1) and (3), molar fraction of SO2 in the product gas, •¢m the

CaO and SO2 are formed in equimolar amounts. increase in sample's weight, MO the initial molar

There are only two kinds of solid products, CaO amount of CaS. and CaSO4, which have significant differences of By combination of equations (4) and (5), it is molar volume compared with that of CaS sample possible to calculate the composition profile of

(molar volumes of CaS, CaO and CaSO4 are 28.9, CaS sample in any reacting time assuming that 102 ― 「日本エネルギー学会誌」第78巻第2号(1999)―

Fig. 2 XRD results of original sample K3 (0.89mm diameter, 85 mol% CaS) and samples after oxidation at temperatures of1000,1120 and 1200•Ž in 21% O2 atmosphere

Fig. 3 Product profiles of sample K3 (Kinsesan limestone 0.89mm) in 1 to 21% O2 atmospheres the solid products only are CaSO4 and CaO. 3. EXPERIMENTAL RESULTS Fig. 1 shows the TG curves of white limestone

W3 (dp=0.89mm) up to 1300•Ž at the heating rate of Oxidation Reaction of Calcium Sulfide in an Advanced PFBC Condition (I) (DONG 他) 103

Table 2 Conversion of CaS to CaSO4 in 21% O2

5•Ž per minute under various oxidizing atmos- A), due to the reaction (2); and drastically

pheres. Two characteristic temperature points of decreased down with a great deal of SO2 to be

A (maximum value of weight gain) and B (beginning released because of reaction (1) and (3). From

temperature of oscillation) appeared in the all exper- the temperature of B the oscillating process fol-

iments of this study. Monotonous weight gain lowed up to 1200•Ž, after which there basically

without SO2 evolution was measured below the tem- was no CaS existing in sample. Finally, the

perature of A. In the temperature range between curves dropped down smoothly due to the decom-

A and B weight loss reaction occurred with large position reaction of sulfate. amounts of SO2 release. The temperatures of A Fig. 4 shows the effects of limestone type, parti-

and B as well as the falling gradient in weight cle size and initial CaS content on the temperatures

between them tended to rise with the increase of O2 of A and B under 1 to 100% O2. It is suggested

atmosphere. The oscillation behavior due to that type of sorbents, particle size and initial CaS

weight change and cyclic SO2 evolution was found content do not affect the temperatures of A and B between the temperature of B and approximately only if a fixed O2 concentration is given. With

1200•Ž, and above 1200•Ž the weight loss reaction the increase O2 concentration the temperatures of

took place with a large quantity of SO2. A and B shift to the higher ones. Lower O2 has

The XRD results of W3 under 21% O2 atmos- wider reaction temperature between A and B due phere are shown in Fig. 2. A gradual CaS con- to slower reaction rate of reaction (2). When an sumption as well as CaO and CaSO4 formations operating point lies in the temperature below A, was detected with the increase of temperature. there is only the reaction of CaS to CaSO4 and

At 1000•Ž, in other words, below the temperature higher O2 atmosphere results in larger conversion of A CaSO4 was primarily produced by the trans- of CaS to CaSO4. Whenever an operating point is formation of CaS to CaSO4. The formation of chosen in the range between A and B, transforma-

CaO was observed at 1120•Ž and increased with tion of CaS to CaO can be achieved at lower reac- temperature. Between temperatures of A and B , tion temperature under lower O2 concentration. CaS was basically changed into CaO, and above

1200•Ž CaS peak disappeared. 4. DISCUSSION

Fig. 3 shows that the molar fractions of CaS, 4. 1 CaSO4 formation

CaSO4 and CaO in the sample, which were calcu- The effects of particle size, initial CaS content lated by the weight change and the amount of SO2 and type of limestone on CaSO4 conversion release. CaS was converted to CaSO4 below the (XCaSO4) below the temperature of A were investi- temperature of A, and primarily oxidized to CaO gated. The results are shown in Table 2. The in the temperature range of A and B . Above the small sized CaS sample tended to have higher temperature of B, the formation and decomposi- conversion of CaS to CaSO4 with the same O2 tion of CaSO4 took place through oscillation atmosphere than the large one. The outside process. The weight of sample increased shell of sample became covered with the same smoothly to reach a maximum value, (peak point thickness of CaSO4 product layer and oxidation ― 「日本エネルギー学会誌」第78巻第2号(1999)― 104

Fig. 4 Effects of type of limestone, particle size and initial CaS content on the temperatures of A and B under various 2 atmospheres O

Fig. 5 Effect of O2 on reaction scheme Fig. 6 Effect of O2 changes on reaction process (white limestone,dp=0.50mm,50mol%CaS content) (white limestone,dp=0.50mm,50mol%CaS content)

reaction ceased due to increasing intraparticle formation. There were quite differences of diffusion resistance to the reactant gas. The ini- XCaSO4among the various types of limestone. tial CaS content seems not to affect the CaSO4 The specific area, pore size and diameter of lime- Oxidation Reaction of Calcium Sulfide in an Advanced PFBC Condition(I) (DONG 他) 105

Fig. 7 Variation of •¢(1/T)•~105/ Log(1-XCaO) with •¢Log(d•~CaO/dt)/Log(1-XCaO)

stone had large effects on intraparticle diffusion tion due to reaction (1) also goes on in the presence of resistance to the reactant gas. The larger aver- 2 and inverse reaction takes place in the presence Oof age pore diameter of Coral reef led to more CaSO4 SO2. The reaction (1) requires 1.5 mole of O2 and 1 formation than that of white limestone and Osaka mole of CaS. Therefore, the transformation of reac- limestone. The white limestone that has a big- tion (2) to (1) occurs on the actual reaction front con- ger pore size showed larger conversion of CaS to trolled by the diffusion resistance of CaSO4 produced CaSO4 than that of Osaka limestone. As for layer under low O2 and SO2 condition. dolomite, this is explained that by the presence of Two designed experiments were performed to

MgO throughout the calcined dolomite. MgO confirm the effect of O2. Fig. 5 shows W2 sample does not react with H2S, and consequently pore was heated up to 1000•Ž in 1% O2,and then the blockage is reduced and there is a better matrix bulk O2 concentration was changed to 21% with for diffusion of oxygen into the paticle10). constant temperature of 1000•Ž; and Fig. 6 shows

W2 sample was heated up to 1060•Ž in 21% O2,

4.2 Effect of 02 atmosphere and then the bulk O2 concentration was changed

The transformation of reaction (2) to reaction to 10%, keeping constant temperature of 1060•Ž.

(1) was observed at temperature of A. There are In Fig. 5, when the bulk O2 concentration was two transformation routes of CaS to CaSO4 in this changed from 1% to 21% O2 at 1000•Ž, weight condition. One is the direct transformation, increasing due to CaSO4 formation was measured reaction (2) and the other is indirect way; reac- and SO2 release dramatically decreased simultane- tion (1) and consecutive reaction: ously. The improvement of bulk O2 concentration

leads to the excess of O2 concentration in the reac-

CaO+SO2+1/2O2→CaSO4 tion front, so that reaction (2) occurs again and oxi-

△HO298=-502.18kJ/mol(6) dation is bought back to the state kept at the tem-

In order to produce CaSO4 it takes 2 moles of O2 perature below A. In Fig. 6 bulk O2 concentration and 1 mole of CaS. On the other hand, CaO forma- being changed from 21% to 10% at 1060•Ž results in 106 ― 「日本エネルギー学会誌」第78巻第2号(1999)―

centration in the reaction front, so that the temperature of A shifts to high temperature.

4.3 Kinetics of CaO formation The reaction (1) also played an important role in the oxidation reaction of CaS under the fluidized bed combustion without producing unreacted CaS in the sorbent particle. The beginning temperature of the reaction remarkably depends on the O2 concentration at reaction front. Therefore, the reaction rate should be measured at the low 2 condition. The TG data in 1% O2 atmosphereO with 5 and 15K/min. heating rate were chosen to evaluate the kinetics of CaO formation. Assuming the reaction of reaction (1) is the first order in O2, the reaction rate can be written as

dXCaO/dt=Akexp(-Ea/RT)(1-XCaO)mPO2(7) Where Ea is activation energy, m reaction order respect to CaO content. Rewriting equation (7), there is

Log(dXCaO/dt)=LogAk-Ea/2.303RT +mLog(1-Xcao)+LogPo2 (8) Fig. 8 Typical oscillation process with sample W1 (0.20mm diameter, 80 mol% CaS) at 1% O2 atmosphere For a fixed PO2, the following relationship can the O2 concentration in the reaction front being be got11). smaller than that of equilibrium for reaction (2) pro- ceeds in, so that reaction (1) leads to SO2gas release △Log(dXCaO/dt)=-Ea/2.303R△(1/T) and a great deal of weight loss. +m△Log(1-XCaO) (9) The above analysis can indicate that O2 atmos- △Log(dXCaO/dt)/△Log(1-XCaO)=-Ea/2.303R phere does determine the reaction transformation △(1/T)/△Log(1-XCaO)+m(9a) between reaction (1) and (2). Below the temperature of A O2 concentration at the reaction front Making a plot of •¢Log (dXCaO/dt) /`•¢Log(1- exists sufficiently in excess for the O2 demand of XCaO) against •¢(1/T)/Log(1-XCaO) in 1% O2 with the reaction (2). As the temperature is raised, 5 and 15K/min. heating rate, the activation ener- the reaction rate as well as the thickness of prod- gy Ea =456kJ/mol and reaction order respect to uct layer concerned in the intraparticle diffusion CaO m =0.67 were obtained from Fig. 7. The resistance to the reactant gas increases, so that different dXCaO/dt values were got under various the O2 concentration in the reaction front becomes temperatures in 1% O2 partial pressure from the low. The temperature of A is a turning point in temperature range between A and B, the calculat- 2 concentration from reaction (2) to (1). HigherO ed average value of frequency factor Ak=1.1•~1017 bulk O2 concentration leads to the higher O2 con- was given. The rate constant of the reaction

S-1 Oxidation Reaction of Calcium Sulfide in an Advanced PFBC Condition(I) (DONG 他) 107

(I) CaSO4 formation (II) Channel being closed in the channel due to formed CaSO4

(III) SO2 rushing out through (IV) Channel being reopened the narrowed channel

Fig. 9 An oscillatory reaction mechanism

Fig. 10 The comparison of the starting temperatures of oscillation and CaSO4 decomposition in oxidizing atmospheres with the addition of SO2 of CaS to CaO can be expressed as 1.1•~1017 exp for W2 in 1% O2 atmosphere. The oscillation can

(-54847/T) s-1. The rate obtained from this study is be considered a kind of behavior with instanta- the same order as that of Rowena6) at 1100•Ž. neous weight loss and gain. It is clear that each weight loss must correspond to the DTA 4. 4 Oscillation Process endothermic and SO2 releasing peaks. Weight The typical oscillation process is shown in Fig. 8 gain is in company with the heat release and the 108 ― 「日本エネルギー学会誌」第78巻第2号(1999)―

decrease of SO2. There are about 40ppm mini- consumed by the unreacted CaS through reaction mum value and 200ppm maximum value of SO2 to (1) to release SO2 like the following scheme: be detected in the product gases during the oscillation process. The oscillation behavior was also (10) observed through a microscope with heating (1) stage, where the product gases were clearly seen (3) to cyclically rush out of particle surface. The net result of reactions (10) and (1) is reaction

The enlarged picture of single cyclic weight, (3), an endothermic solid-solid reaction, which

SO2 and DTA is illustrated at the top of Fig.8, can become important at temperatures above where four characteristic locations (I) to (IV) of 850•Ž and can happen at 950•Ž even if in 21% O2- weight change are marked. They are clearly N2 atmosphere7). Our experimental data also seen that the weight gain with smooth SO2 show that reaction (3) can take place at 930•Ž in release from (I) to (II) and weight loss with great 1% SO2-N2 atmosphere. The oxygen produced

SO2 release and TDA endothermic peak from (II) by reaction (10) is quickly consumed through reac- to (IV). A possible oscillatory reaction scheme tion (1), so that reaction (10) can continue untill its for this cyclic oscillation is illustrated in Fig. 9. reaching thermodynamic equilibrium. The cal-

The formed SO2 gas by reaction (1) diffuses out culated SO2 equilibrium partial pressures of reac- through the channels, where it, together with the tion (3) are 0.55, 1.00 and 1.31 atm. at tempera- in-diffusing O2 gas reacts with CaO on the wall of tures of 1050, 1084 and 1100•Ž. The reaction (3) channel to form CaSO4 through reaction (6) there- produces 1.33 moles of SO2 per mole of CaSO4. by leading to weight gain as shown in Fig. 9(I). The total pressure of gas phase increases in the

Due to its larger molar volume, the formed sulfate channel between the sulfate layer and unreacted results in reduction of the diameters of the chan- CaS. On the other hand, the sulfation decompo- nels, finally the channels are almost closed by the sition also results in the closed channel to become formed CaSO4 to lead to the isolation of CaS core a very narrow channel. Both of above them lead from O2 atmosphere like that shown in Fig. 9(II). to the gases in the channel rushing out of the nar-

The CaS readily reacts with O2 to result in rowed channel with the greater velocity, as

reducing the O2 concentration of the isolated shown in Fig. 9(III). Of course, there also are

space between unreacted CaS core and formed the possibility that the gases in the isolated chan-

CaSO4 layer. The decrease in the O2 concentra- nel rapidly flow through the new channel being

tion leads to sulfate decomposition in the inner created by thermal crack or the other channels

channel through reaction (10), a counterreaction of narrowed by the formation of sulfate. For reac-

reaction (6). The data in Fig. 10 show that when tion (3), the other way in which CaS and CaSO4

SO2 gas exists, the decomposition temperature of interact is via a melt, both of them are completely

CaSO4 decreases if O2 concentration is lowered. ionised during the formation of a liquid phase12) 13).

CaSO4 decomposition starts at the temperatures The existence of a melt, however, could not be

of 930•Ž,950•Ž and 1120•Ž in the atmospheres of substantiated in our experiments.

pure N2, 200ppm and 1% concentration of SO2 if The decomposition of CaSO4 eventually reopens

2 concentration decreases to be zero. The data O the pores, thereby allowing more O2 to diffuse into

of 200ppm addition indicate that sulfate is possible to the unreacted core like that shown in Fig. 9(IV).

decompose at 1080•Ž even if in 1% O2 atmosphere. The O2 concentration is increased, the sulfate

The sulfate in the inner of the isolated channel decomposition turns weaker, and CaSO4 forma-

decomposes to produce oxygen, which is quickly tion becomes favored again. The consumption of Oxidation Reaction of Calcium Sulfide in an Advanced PFBC Condition (I) (DONG 他) 109 unreacted CaS and the increase of temperature m: Parameter of equation (8)[-] lead to the CaSO4formation to be more and more P02 Patial pressure of O2[-] difficulty, so that oscillation gradually declines, T: Temperature [K] and finally disappears. t: Time [s] Xi: Conversion of CaS to species i [-] 5. CONCLUSION Yso2: The molarfraction of SO2in the product gas[-] In this paper oxidation reaction of CaS was investigated under different oxidizing conditions REFERENCES by use of a thermogravimeter apparatus. The 1) Tobias Mattisson and Anders Lyngfelt, the effects of O2concentration, sample size, CaS con- 13thASME Conf on FBC, Vol.2, 819-830,USA tent and limestone type on this process were dis- 1995 cussed. The whole reaction process could be 2) Iikka T. Hippinen, Antii S. Kudjoi and Antero classified into three different steps. The yielded K. Jahkola, the 13th ASME Conf on FBC, reaction diagram can give a prediction of the oxi- Vol.2, 1021-1026,USA 1995 dization reaction of CaS. 3) Michael D. Mann, Michael L. Swanson and The smaller sized particle has better reactivity Steven L. Yagla, the 13th ASME Conf on for sulfation formation, and the structure of lime- FBC,Vol.1,333-340, USA 1995 stone is of importance to the sulfation process. 4) Arnold, M.St. J., J.J. Gale and M.K. Laughlin, The proposed reaction scheme can give a good Can.J. Chem.Eng., Vol.70, 991-997,1992 explanation of O2 effect on the shift of the reac- 5) Lyngfelt,A. and Leckner,B., ChemicalEngineering tion (2) to reaction (1). The reaction of CaO for- Journal,Vol.40,56-69,1989 mation is 0.67 order respect to CaO with the acti- 6) Rowena J. Torres-Ordonez, John P. Longwell vation energy of 456 kJ/mol. and Adel F. Sarofim, Energy& Fuel,Vol.3, 506- The weight gain before the temperature of A is 515,1989 proved to result from reaction (2),and reaction (1) 7) Davies,N. H., A.N. Hayhurst and K.M. Laughlin, leads to the great weight loss within the tempera- Proceedingsof the 25thInternational Symposium ture range of A and B. The CaSO4formation and on Combustion,Combustion Institute, 211-218, decomposition in the pores of interior particle Pittsburgh, 1994 and reaction (3) are suggested to explain the oscil- 8) Y. Ninomiya, A. Sato and A.P. Watkinson, the lation behavior. 13th ASME Conf on FBC, Vol.2 1027-1033, USA 1995 (ACKNOWLEDGEMENTS) 9) Y. Ninomiya, Z.B. Dong, A. Sato and M. Steel Industry Foundationfor the Advancementof Okada, the 14thASME Conf. on FBC, Vol.1, Environmental Protection Technology (SEPT) is 387-396,1997,Canada acknowledged for the financial support of the 10) Abbasian, J., Rehmat, A. and Banerjee. D.D., research work reported in the present paper. Ind. Eng. Chem.Res., Vol.30,1990-1994,1991 11) T. Kanbehiro and T. Ozawa, Netsubunseki, [NOMENCLATURE] Kodansha company, 1993 Ak: Frequency factor [s-1] 12) Hayhurst, A. N. and Tucker, R.F., J. Inst.Of Ea: Activation Energy [kJ/mol] Energy,Vol. 65, 166-176,1992 G: Total molar flowrateof evolutiongas [mol/s] 13) Kamphuis, B., Potma, A.W., Prins,W. and Van Am: Increase in sample's weight [kg] Swaaij, W.P. M., Chem.Eng. Sci.,Vol. 48,105- Mo: Initial molar amount of CaS [mol] 116,1993