Chlorine Removal Mechanism from Municipal Solid Waste Using

Sep 10, 2014 - For organic chlorine pyrolysis, steam temperature was changed from 463 to 573 K. For inorganic chlorine removal by steam condensation, ...
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Chlorine Removal Mechanism from Municipal Solid Waste Using Steam with Various Temperatures Tomoya Hase,† Md. Azhar Uddin,† Yoshiei Kato,*,† Masayasu Fukui,‡ and Yasuhiko Kanao‡ †

Graduate School of Environmental and Energy Science, Okayama University, 1-1 Tsushima-naka, 3-chome, Kita-ku, Okayama 700-8530, Japan ‡ Head Office, Recycling Management Japan Inc., 3-1 Benten-cho, Tsurumi-ku, Yokohama 230-0044, Japan ABSTRACT: With a goal to develop a suitable refuse derived fuel (RDF) manufacturing process, organic and inorganic chlorine removal from RDF was investigated by using steam with various temperatures. For organic chlorine pyrolysis, steam temperature was changed from 463 to 573 K. For inorganic chlorine removal by steam condensation, steam temperature was fixed at 373 K. The pyrolysis kinetics of organic chlorine increased with an increase in superheated steam temperature, whereas the chlorine emission kinetics increased with an increase in sample temperature. Part of the pyrolyzed organic chlorine changed to inorganic chlorine. Organic chlorine decreased more rapidly than a decrease in dry matter yield, but inorganic chlorine increased with a decrease in dry matter yield above 0.8, which indicated that the decreasing ratio of total chlorine was roughly as large as that of dry matter yield. Removal ratio of inorganic chlorine increased with an increase in steam condensation because inorganic chlorine was dissolved in a water droplet.

1. INTRODUCTION Refuse derived fuel (RDF) might be produced by shredding, drying in hot air, separating, and extruding municipal solid waste (MSW). During combustion of RDF, hydrogen chloride is emitted, as for example kitchen waste or plastic refuse might contain sodium chloride, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), etc. In addition, there is a risk for eroding the surface of the heat exchanger in the boiler of the electric generation plant1 and additional removal treatment of hydrogen chloride2,3 or dioxin4,5 before emission in the atmosphere is required. Therefore, low chlorination of MSW is desired in the production of RDF. Hase et al.6 investigated drying and pyrolysis of organic chlorine in MSW using superheated steam generated by home electric appliances. A simplified mathematical drying model was developed in terms of condensation heat transfer, constant drying, and decreasing drying processes, and the model was in agreement with the experimental results. It was shown that the pyrolysis behavior of organic chlorine was changed by superheated steam temperatures of 473 and 523 K. However, very little is known about the effects of sample temperature and changes in pyrolyzed organic chlorine on inorganic chlorine behavior. Several studies exist on dechlorination or drying processes of MSW or RDF by using superheated steam. For example, inorganic chlorine in carbonized RDF was reduced from 0.8 to 0.14 wt % by steam treatment with 388 K for 5 h.7 Using the combination of a hydrothermal process and water-washing, total chlorine content was reduced to 0.06 wt % after a second wash.8 Organic chlorine content in MSW was reduced from 1.0 to 0.16 wt % by a pilot-scale hydrothermal process.9 Combustion behaviors were compared by using various kinds of powder samples made by hydrothermal treatment of MSW.10 Highmoisture MSW was dried continuously by superheated steam under a steam-solid cocurrent system,11 and it was demonstrated to have the advantage of decreasing the energy consumption © 2014 American Chemical Society

compared with a conventional waste incinerator. Studies on steam as reactant were also carried out in gasification of RDF12 or MSW.13 However, the above articles on superheated steam or the hydrothermal process were insufficient to obtain the effect of material temperature on dechlorination behavior in RDF or MSW. Therefore, with a goal to develop a suitable RDF manufacturing process with low chlorine content, behaviors of organic, inorganic, and emitted chlorine were studied under various superheated steam temperatures; dry matter yield and lower heating value were also analyzed. In addition, the inorganic chlorine was removed by steam condensation on the sample using steam generation (10 kg/h) equipment.

2. EXPERIMENTAL SECTION 2.1. Sample Adjustment. From the standpoint of sample homogeneity, an RDF of 15 mm in diameter and 20−35 mm in length was produced at Hakata Clean center, Imabari, Japan, and was used for the experiment instead of MSW. Average chemical composition and components are shown in Tables 1 and 2, respectively. The RDF sample was crushed with a blender and put into a dryer at 383 K for 24 h. Total chlorine and organic and inorganic chlorine contents in the sample were 1.42, 0.92, and 0.50 wt %, respectively. The range of the organic chlorine content was between 0.77 and 1.08 wt %, whereas that of the inorganic chlorine content was between 0.48 and 0.53 wt %. 7.0 g of ion-exchanged water was added to 7.0 g of dry sample in order to have 1.0 kg-water/kg-

Table 1. Chemical Composition of RDF combustible [wt %] C 50.3

H 6.6

O 30.2

N 0.9

ash [wt %]

water [wt %]

9.8

2.2

Received: May 19, 2014 Revised: September 3, 2014 Published: September 10, 2014 6475

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Table 2. Average Composition of RDF

HL = 81(C − 3/8O) + 57 × 3/8O + 345(H − 1/16O)

paper, cloth [wt %]

plastic [wt %]

wood [wt %]

food waste [wt %]

noncombustible [wt %]

47.7

17.4

5.1

19.5

7.7

(1)

+ 25S − 54H

where C, H, and O are carbon, hydrogen, and oxygen contents (wt %), respectively. Oxygen content was estimated as

O = 100 − (C + H + N + Cl + ash)

dry sample for the organic chlorine removal trial. For the inorganic chlorine removal trial, 21.0 g of ion-exchange water was also added to 7.0 g of dry sample to obtain a final water content of 3.0 kg-water/kg-dry sample. 2.2. Experimental Procedure. Figure 1 shows the experimental apparatus composed of the boiler, steam superheater (Dai-ichi High

(2)

where N, Cl, and ash are nitrogen, chlorine, and ash contents (wt %), respectively; sulfur content was ignored because of very low content, about 0.1 wt % in the RDF. Weight of incineration ash was measured after heating about 1.0 g of sample with a dry oven at 383 K for 2 h followed by heating and incinerating with an electric furnace at 1073 K for 2 h.

3. RESULTS AND DISCUSSION 3.1. Chlorine Removal by Superheated Steam. 3.1.1. Temporal Change in Organic and Inorganic Chlorine Contents and Sample Temperature. Figure 2 shows the

Figure 1. Schematic view of experimental apparatus.

Frequency Co., Ltd., Hi-Heater 2005S), and chlorine removal chamber. Steam was generated from ion-exchanged water in the boiler and then heated to a given temperature and sent to the treatment chamber with the suspended sample. The flow rate of the superheated steam was fixed to be 10 kg/h. In addition to the superheated steam temperature just before the treatment chamber, sample and chamber temperatures were measured with K-type thermocouples. The sample was placed on the wire-woven net (0.05 m × 0.05 m × 0.01 m) in the wire-woven vessel in the form of a bowl and hung in the chamber. For the pyrolysis experiment of organic chlorine, the superheated steam temperature was varied to 463, 488, 513, and 573 K. The treatment time was changed to 30, 60, and 90 min. To avoid the temperature change in the sample caused by sampling in the middle of the treatment, the experiments of 30, 60, and 90 min were carried out independently from each other. However, there are possibilities of the experimental error due to the sample inhomogeneity as described in Section 2.1. The superheated steam temperature was kept constant during the treatment time. The sample was kept at 6 cm under the inner part of the chamber top. For the inorganic chlorine removal experiment by steam condensation, the steam temperature was fixed to 373 K and the treatment time was varied at 30, 60, 90, 120, 150, and 180 min. Both organic and inorganic chlorine contents were analyzed for each treatment time, according to the chlorine analysis method described in Section 2.3. Dry matter yield was also measured after drying with a drier at 383 K for 24 h. 2.3. Analytical Techniques. 2.3.1. Chlorine Analysis. Organic and inorganic chlorine contents were measured independently as follows. Inorganic chlorine in the sample was dissolved in heated hot water for 30 min, and organic chlorine was retained in the residue. The test liquid of organic chlorine was prepared by the Eschka method.14,15 Chlorine analysis of each test liquid was carried out by mercury(II) thiocyanate absorption spectrophotometry.16 Each measurement was repeated three times, and the mean values were used for data. The deviation from the average chlorine content was within 0.01 wt %. 2.3.2. Carbon, Hydrogen, and Nitrogen Analyses. About 5.0 mg of sample was prepared in the organic chlorine removal experiment, and the carbon, nitrogen, and hydrogen contents were measured by elemental analysis using a PerkinElmer 2400 II analyzer. 2.3.3. Lower Calorific Value. The lower calorific value, HL (kJ/kg), was calculated by substituting measured carbon, hydrogen, and nitrogen contents from the chemical composition of the RDF (Table 2) into the Steuer formula shown in eq 1.

Figure 2. Temporal change in pyrolysis of organic chlorine. (a) Data from ref 6.

temporal change in pyrolysis weight percent, Δ[wt %Cl], of organic chlorine obtained from subtracting organic chlorine weight at a given treatment time from the initial organic chlorine weight divided by the initial sample weight. It became clear that pyrolysis of organic chlorine proceeded with time and its ratio increased with an increase in superheated steam temperature, TST (K). Δ[wt %Cl] values at 30 and 60 min under a sample temperature of 488 K had a different trend from the other data as seen in Figure 2, which was supposed to be due to the sample inhomogeneity. The relation between weight fraction of organic chlorine, WCl/ WCl,init., normalized by the initial value and sample temperature is shown in Figure 3. As the sample temperature increases under the constant steam temperature, it is possible to know the treatment time of each plot in Figure 3 from the temporal change

Figure 3. Relation between normalized organic chlorine concentration and sample temperature. (a) Data from ref 6. 6476

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components in the sample. On the other hand, the WCl/WCl,init. value was attained below unity at about 570 K in the sample temperature, which meant that part of the initial inorganic chlorine was left the sample. It is estimated to be due to chemical reaction of inorganic chemical compounds such as sodium chloride with alumina or hydrated silica and continuing generation of hydrogen chloride.21−23 Chlorine emission out of the sample is equal to the difference between pyrolysis of organic chlorine and an increase in inorganic chlorine. Figure 6 shows the change in accumulated

in Figure 2. Organic chlorine in the sample decreased with an increase in sample temperature. Pyrolysis of organic chlorine proceeded remarkably above around 473 K where both polyvinyl chloride (PVC)17 and polyvinylidene chloride (PVDC)18 decomposed. The temporal change in increased weight percent, Δ[wt %Cl], of inorganic chlorine obtained from subtracting the initial inorganic chlorine weight from inorganic chlorine weight at a given treatment time divided by the initial sample weight is shown in Figure 4. The positive value of Δ[wt %Cl] means an

Figure 4. Temporal change in increased inorganic chlorine. (a) Data from ref 6.

Figure 6. Temporal chlorine emission out of the sample. (a) Data from ref 6.

increase in inorganic chlorine caused by the pyrolysis of organic chlorine, whereas the negative value indicates that inorganic chlorine, as well as organic chlorine, is emitted out of the sample. It was found that inorganic content decreased at high temperatures such as TST =573 K and the increased amount of inorganic chlorine peaked at middle temperatures such as 488 and 513 K and became small at lower temperatures like 463 and 483 K. The relation between weight fraction of inorganic chlorine, WCl/WCl,init., normalized by the initial value and sample temperature, is shown in Figure 5. As the sample temperature

chlorine emission ratio with time, calculated from the chlorine balance based on Figures 2 and 4. The negative values in Figure 6 were thought to be caused by the deviation in the initial chlorine content in the sample or measurement error. Chlorine emission increased with an increase in sample temperature caused by an increase in the superheated steam temperature. Chlorine emission was confirmed by introducing outlet gas into sodium hydroxide solution and measuring by the absorptiometric method of mercuric thiocyanate. Pyrolysis kinetics of organic chlorine and increasing ratio of inorganic chlorine for the equal TST were calculated from data in Figures 2 and 4. The relation between these kinetics and average sample temperature between the two points is shown in Figure 7.

Figure 5. Relation between normalized inorganic chlorine concentration and sample temperature. (a) Data from ref 6. Figure 7. Pyrolysis kinetics of organic chlorine and increasing kinetics of inorganic chlorine.

increases under the constant steam temperature, it is possible to know the treatment time of each plot in Figure 5 from the temporal change in Figure 4. Inorganic chlorine content peaked at around 500 K in sample temperature and became up to 1.5 times as much as the initial value. It was compatible with the data of 488 and 513 K in the superheated steam temperature shown in Figure 4. As it is known that hydrogen chloride reacts with salt such as carbonate and acetate to produce metallic chloride or metal complexed with chloride19,20 and it is fixed in the char, the increase in inorganic chlorine in Figure 4 is predicted to be due to the chemical reaction of hydrogen chloride generated by pyrolysis of organic chlorine compounds with alkaline

Data of TST = 533 K after 60 min and TST = 573 K were excluded because pyrolysis of organic chlorine had proceeded sufficiently under these conditions. Fitted curves of pyrolysis kinetics of organic chlorine and increasing kinetics of inorganic chlorine drawn in Figure 7 were given by eqs 3 and 4, respectively. d[mass%Cl]/dt = 6 × 10−25Tsample8.187 6477

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d[mass%Cl ]/dt = − 10−6Tsample 2 + 0.0009Tsample − 0.2094 (4)

where Tsample is sample temperature (K). The range between the values calculated from eqs 3 and 4 at a given Tsample indicates emission kinetics of chlorine out of the sample. The fitted curve of pyrolysis kinetics of organic chlorine was expressed as a power of sample temperature because temperature change was estimated to be shown by the Arrhenius equation. On the other hand, the rate of inorganic chlorine increased with an increase in sample temperature due to the accelerated reaction rate of hydrogen chloride generated by pyrolysis of organic chlorine with the salt in the sample until about 473 K. The further increase in the sample temperature from 473 K up to 523 K resulted in the generation of hydrogen chloride by the reaction between inorganic chlorine compounds and alumina or hydrated silica, and then, it gained ascendancy over the inorganic chloride generation above about 523 K. To express the above predicted phenomena which gave the peak value to the increasing rate of inorganic chlorine, the fitted curve was simply approximated by a two-dimensional polynomial as in eq 4. When sample temperature reached above about 523 K, inorganic chlorine as well as organic chlorine decreased. Therefore, a sample temperature above 473 K was preferable from the viewpoint of emitting organic chlorine out of the sample. 3.1.2. Lower Heating Value. Figure 8 shows the relation between lower heating values calculated from eq 1 and carbon and hydrogen weights normalized by the initial value or dry matter yield. It was found that lower heating value decreased with a decrease in carbon and hydrogen content and dry matter yield. As a decrease in dry matter yield means a decrease in carbon and hydrogen content as exothermic elements, it is desirable to practice MSW dechlorination in order to keep the dry matter yield high. 3.1.3. Dry Matter Yield and Chlorine Content after Superheated Steam Treatment. The relation between dry matter yield and sample temperature is shown in Figure 9. As shown in Table 2, the sample contained about 50% of paper and cloth made from hemicellulose and cellulose. Pyrolysis onset temperature of hemicellulose and cellulose is about 473 and 523 K,24 respectively. It was found that dry matter yield started decreasing at about 473 K which corresponded to pyrolysis onset temperature of hemicelluloses, whereas it decreased remarkably at about 523 K which was equal to that of cellulose. A slight decrease in dry matter yield below about 473 K was supposed to be due to emission of volatile matters contained in the sample. Analyzing outlet gas at TST= 473, 523, and 573 K, hydrogen and carbon dioxide were detected by GC-TCD, and methane and hydrocarbon were found by GC-FID. These gas components coincided with the pyrolysates of paper, cloth, and wood, which decrease in dry matter yield due to pyrolysis of hemicellulose and cellulose. The relation between organic or inorganic chlorine weight or sum of them normalized by the initial value and dry matter yield is shown in Figure 10. Because pyrolysis onset temperature of PVC and PVDC, about 473 K, was less than that of cellulose, about 523 K, organic chlorine decreased more rapidly than dry matter yield as seen in Figure 10a. However, as inorganic chlorine increased with a decrease in dry matter yield above 0.8 in Figure 10b, the decreasing ratio of the sum of organic and inorganic chlorine was as large as that of dry matter yield matter above about 0.8 and slightly larger than that of dry matter yield below 0.8. A decrease in dry matter yield brings about a decrease in

Figure 8. Relation between lower heating value and carbon (panel a) and hydrogen (panel b) concentration or dry matter yield (panel c). (a) Data from ref 6.

Figure 9. Relation between dry matter yield and sample temperature. (a) Data from ref 6.

lower heating value as described in Section 3.1.2, and it undermines the value of MSW as a fuel. Thus, it is a better practice to remove organic chlorine chiefly at comparatively low superheated steam temperature such as about 500 K where inorganic chlorine reaches a peak as described in Section 3.1.1 and to be followed by inorganic chlorine removal as described in Section 3.2. 3.2. Inorganic Chlorine Removal by Steam Condensation. When steam comes into contact with the sample below 373 6478

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The temporal change in the removal ratio of inorganic chlorine obtained from subtracting inorganic chlorine content at a given treatment time from the initial one is shown in Figure 12.

Figure 12. Change in removal ratio of inorganic chlorine with time.

Although removal of inorganic chlorine increased with time, its increasing ratio reduced gradually. As seen in Figure 11, the difference between steam and sample temperature became smaller with time, which decreased the increasing ratio of inorganic chlorine removal because water condensation amount on the sample decreased and the following water drops separated from the sample at a lower frequency. The removal of inorganic chlorine dissolved in water droplets from the sample following the steam condensation is similar to that of a certain amount of water addition and separation from the sample. In order to estimate a relation between removal ratio of inorganic chlorine and amount of steam condensation, water droplets were added on a 3.0 kg-water/kg-dry sample with a dropper under atmospheric conditions. The final amount of water was varied at 10, 20, 30, 40, and 50 mL. The relation between the removal ratio of inorganic chlorine and amount of water addition is shown in Figure 13. The removal ratio of inorganic chlorine increased with an increase in water addition due to the water separation from the sample with soluble inorganic chlorine in alkali salts.

Figure 10. Relation between organic (panel a), inorganic (panel b), or total chlorine (panel c) concentration and dry matter yield. (a) Data from ref 6.

K, it condensates on the sample. When water drops generated by condensation of steam grow on the sample, coalesce with each other, and fall from the sample by gravity, inorganic chlorine dissolved in the water drops is also removed from the sample.25 The larger difference between steam and sample temperatures accelerates the water condensation. When steam temperature and sample under the inner part of the chamber top are fixed to 373 K and 6 cm, respectively, the temporal change in sample temperature is as shown in Figure 11. Sample temperature approached the steam temperature and became coincident with the steam temperature in about 7 min. Figure 13. Relation between the removal ratio of inorganic chlorine and amount of water addition.

Removal ratio of inorganic chlorine in Figure 12 is estimated by using the fitting curve of Figure 13. Temporal steam condensation amount is shown in Figure 14. Steam condensation proceeded with time. Steam condensation amount was estimated to be 30 mL at 180 min of treatment time, which meant that 0.08−0.11% of steam condensed on the sample when steam flow rate was 10 kg/h.

Figure 11. Change in sample temperature with time. 6479

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(6) Hase, T.; Uddin, M. A.; Kato, Y.; Fukui, M. Drying and organic chlorine thermal decomposition behavior of municipal solid waste using superheated steam. J. Jpn. Soc. Mater. Cycles Waste Manage. 2014, 25 (1), 16−24. (7) Yamamoto, K.; Misawa, S.; Hizuka, K.; Mimura, R. Experimental study on developing uses of RDF by carbonization. J. Jpn. Soc. Mater. Cycles Waste Manage. 2000, 11 (4), 195−203. (8) Indrawan, B.; Prawisudha, P.; Yoshikawa, K. Chlorine-free solid fuel production from municipal solid waste by hydrothermal process. J. Jpn. Inst. Energy 2011, 90 (12), 1177−1182. (9) Prawisudha, P.; Namioka, T.; Yoshikawa, K. Coal alternative fuel production from municipal solid wastes employing hydrothermal treatment. Appl. Energy 2012, 90, 298−304. (10) Lu, L.; Namioka, T.; Yoshikawa, K. Effects of hydrothermal treatment on characteristics and combustion behaviors of municipal solid wastes. Appl. Energy 2011, 88 (11), 3659−3664. (11) Maruyama, N.; Tanaka, D.; Tamada, M.; Shimizu, T.; Hirota, M. Waste recycling using superheated steam and its environmental evaluation. 7th International Energy Conversion Engineering Conference, Denver, Colorado, August 2−5, 2009; American Institute of Aeronautics and Astronautics: Reston, Virginia, 2009, Paper no. AIAA 2009-4638. (12) Galvagno, S.; Casu, S.; Matino, M.; Russo, A.; Portofino, S. Steam gasification of refuse-derived fuel (RDF): Influence of process temperature on yield and product composition. Energy Fuels 2006, 20 (5), 2284−2288. (13) Onwudili, J. A.; Williams, P. T. Hydrothermal catalytic gasification of municipal solid waste. Energy Fuels 2007, 21 (6), 3676−3683. (14) JIS Z 7302-6. Densified refuse derived fuel - Part 6: Test method for total chlorine contents; Japanese Industrial Standards Committee: Tokyo, 1999. (15) Shinohara, A.; Nakamura, K.; Yamaguchi, O. Analytical method for chlorine content in refuse derived fuel. Taiheiyo Cement Kenkyu Hokoku 2000, 138, 62−72. (16) JIS A 1154. Methods of test for chloride ion content in hardened concrete; Japanese Industrial Standards Committee: Tokyo, 2011. (17) Mikata, N.; Hashimoto, S.; Takeuchi, T.; Nishiyama, H. Research in thermal decomposition characteristics of plastic waste. Shin-nittetsu Giho 1996, 360, 38−45. (18) Terakado, O.; Takahashi, Y.; Hirasawa, M. Influence of metal oxide on the fixation of chlorine in thermal decomposition of poly (vinyliden chloride co vinyl chloride). High Temp. Mater. Processes 2009, 28 (3), 133−139. (19) Hoffman, R. V.; Eiceman, G. A.; Long, Y.-T.; Collins, M. C.; Lu, M.-Q. Mechanism of chlorination of aromatic compounds absorbed on the surface of fly ash from municipal incinerators. Environ. Sci. Technol. 1990, 24 (11), 1635−1641. (20) Addink, R.; Altwicker, E. R. Formation of polychlorinated dibenzo-p-dioxins/dibenzofurans in waste combustion: Role of chlorine. Organohalogen Compd. 1996, 27, 1−4. (21) Yamamoto, H.; Tsuji, Y.; Hara, T. Mechanisms of dechlorination and fuel characteristics of char formed in the pyrolysis process of municipal solid waste (MSW). J. Jpn. Inst. Energy 2004, 83 (4), 272−280. (22) Kanters, M. J.; Nipsen, R. V.; Louw, R.; Mulder, P. Chlorine input and chlorophenol emission in the lab-scale combustion of municipal solid waste. Environ. Sci. Technol. 1996, 30 (7), 2121−2126. (23) Uchida, S.; Kamo, H. The source of HCl emission from municipal refuse incinerators. Ind. Eng. Chem. Res. 1988, 27 (11), 2188−2190. (24) Kumagai, S.; Hayashi, N.; Sasaki, T.; Nakada, M.; Shibata, M. Fractionation and saccharification of cellulose and hemicelluloses in rice hull by hot-compressed water treatment with two-step heating. J. Jpn. Inst. Energy 2004, 83 (10), 776−781. (25) Kadoma, T.; Kishimoto, T.; Tanaka, M.; Takami, S. Development of healthy cooking technology with superheated steam. Sharp Tech. J. 2005, 91 (4), 40−44.

Figure 14. Estimated amount of water condensation.

4. CONCLUSIONS Tests on organic and inorganic chlorine removal in municipal solid waste were made using various steam temperatures. The following results were obtained from the test runs. (1) Pyrolysis kinetics of organic chlorine increased with an increase in superheated steam temperature. Part of the pyrolyzed chlorine changed to inorganic chlorine, and its increased amount had a peak value at around 500 K and decreased above 500 K. Chlorine emission kinetics increased with an increase in sample temperature. (2) Organic chlorine decreased more rapidly than a decrease in dry matter yield. However, as inorganic chlorine increased with a decrease in dry matter yield above 0.8, the decreasing ratio of the sum of organic and inorganic chlorine was as large as that of dry matter yield above about 0.8 and slightly larger than that of dry matter yield below 0.8. (3) It is a suitable practice that organic chlorine is pyrolyzed at comparatively low superheated steam temperature where a decrease in dry matter yield is low and inorganic chlorine removal follows at a steam temperature of 373 K. (4) Inorganic chlorine content in the treated sample decreased due to steam condensation which made water droplets grow on the sample, coalesce with each other, and leave the sample by gravity. The removal ratio of inorganic chlorine increased with an increase in steam condensation because inorganic chlorine was dissolved in water droplets.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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REFERENCES

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