Simultaneous Removal of COS, H2S, and Dust in Industrial Exhaust

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Simultaneous Removal of COS, H2S and Dust in Industrial Exhaust Gas by DC Corona Discharge Plasma Langlang Wang, Xue Qian Wang, Ping Ning, Chen Cheng, Yixing Ma, and Ran Zhang Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b00028 • Publication Date (Web): 18 Apr 2018 Downloaded from http://pubs.acs.org on April 18, 2018

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Industrial & Engineering Chemistry Research

Simultaneous Removal of COS, H2S and Dust in Industrial Exhaust Gas by DC Corona Discharge Plasma Langlang Wang, Xueqian Wang, Ping Ning∗, Chen Cheng, Yixing Ma, and Ran Zhang (Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, Yunnan, China)1

Abstract: Simultaneous removal of COS, H2S and dust by means of DC corona discharge plasma was investigated in a plasma reactor. The results showed that the DC corona discharge was effective in removing COS, H2S and dust simultaneously. As the content of O2 increased, the conversion of COS and H2S decreased. Because O3 was produced at high O2 content, resulting in more energy was shared. Higher temperature is not conducive to the conversion of COS and H2S. Dust could react with gaseous pollutant or serve as a carrier under the electric field. The conversion of COS and H2S, as well as the yield of CO2, were slightly improved after the dust was introduced. In contrast, a significant decrease about the yield of SO2 and CO was observed. Meanwhile, the removal efficiency of dust reached 99%. In a plasma reactor, the chemical bonds of COS and H2S were broken and then further oxidized to sulfur-containing and carbon-containing products caused by free electrons, oxygen radicals and ozone. The CO and CO2 product were generated from the COS, and sulfur compounds (S, SO2, SO42-) were resulted from the oxidization of COS and H2S. Free electrons and oxidative radicals might played more significant roles in the conversion of COS and H2S. Keywords: Corona discharge plasma; Carbonyl sulfide; Hydrogen sulfide; Dust; Simultaneous removal. 1. Introduction

∗ Corresponding author E-mail: Tel./fax: +86 13708409187 [email protected] (P. Ning)

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Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The presence of carbonyl sulfide (COS) and hydrogen sulfide (H2S) in industrial exhaust gas often leads to debasing of gas quality, excessive corrosion of equipment, and deactivation and poisoning of catalysts, which limited the recovery and utilization of industrial gases. Moreover, they will cause serious adverse effects on human health and the environment when industrial gases are released without removal of COS and H2S. COS is transported into the stratosphere and subsequently oxidized to sulfur dioxide (SO2). Eventually, SO2 converts into sulfate aerosols. COS emissions originate from natural sources, such as volcanic eruption, marsh, and wetland [1]. It is also emitted from motor vehicle exhaust, burning of fossil fuels, coal gas, and other chemical and biochemical processes. Hydrogen sulfide (H2S) is an odorous sulfur compound [2], which is toxic at high concentration gas and fatal to human when concentration exceeding 200 ppm [3]. H2S exists in the naturally occurring biological processes, decomposition of organic matters, volcanic eruption, as well as a variety of industrial processes [4]. Currently, China is the largest yellow phosphorus producer in the world. During yellow phosphorus production, there are 2500-3000m3 off-gas by-products in 1 ton of yellow phosphorus. The main component of yellow phosphorus tail gas is carbon monoxide (CO), which accounts for up to 85% [5]. Other components mainly include PH3, CS2, COS, H2S, and dust. CO is the raw material of C1 chemistry with a high recycle value. It is of great practical significance to develop efficient methods for removing COS, H2S, and dust simultaneously. A number of methods have been developed to remove COS, including hydrogenation conversion, catalytic oxidation, catalytic hydrolysis, and absorption, etc [6-8]. The most widely used methods for removing H2S fall into three categories: dry desulfurization, wet desulphurization and biological method. Since these methods did not consider the simultaneous removal of COS and H2S, it is also required to remove


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dust from the gas mixture before removing COS and H2S. On the other hand, non-thermal plasma methods are attracting increasing attention from the scientific and industrial communities because of their high removal efficiencies on removing highly toxic pollutants, such as Hg0, CS2, H2S, SO2, VOCs, C2H6S, and 4-chlorophenol [9-16]. Obradovic studied removing NOx and SO2 simultaneously with a DBD (Dielectric Barrier Discharges) plasma, and compared the effects of direct oxidation and indirect oxidation on the removal efficiency [11]. Zhu reported the degradation of phenol in the mists by a non-thermal plasma reactor and investigated the decomposition efficiency of phenol, TOC removal and byproduct formation [13]. Yoshihiko Itoh also indicated that the discharging non-thermal plasma converted NO to NO2 and HC to partially oxidized HCs [17]. DC corona discharge plasma is one of the non-thermal plasma, which not only can generate a number of free electrons and radicals to remove pollutants but also can collect dust efficiently [18]. The DBD (Dielectric Barrier Discharges) plasma often serves as a method to purify gaseous pollutants, however, it cannot be applied for removing dust. Although some researchers have focused on DC corona discharge plasmas to remove gaseous pollutants, few attention have been paid to dust and reducing gases. In this study, dust-containing flue gas was used as the object of treatment. DC corona discharge plasma was investigated for the simultaneous removal of dust and gaseous pollutants in the reducing atmosphere. Moreover, the effect of oxygen concentration, reaction temperature, dust, the inlet concentration on the removal efficiency and the reaction mechanism were also investigated systemically. 2. Experimental Fig. 1 shows a sketch of the experimental setup to perform the removal of COS, H2S, and dust from the gas mixture. The experimental facility setup consists of reaction gas supply unit, reaction unit and analysis unit. In the reaction gas supply unit, the



reaction gases were taken from cylinder gas (Dalian Special Gases Co., Ltd, China), nitrogen as a carrier gas. Dust collected from electrostatic precipitator after the phosphorus furnace in phosphorus plant was mixed with reaction gas in the mixing chamber. The dust was dried at 105 °C in the oven for 72 hours and screened through mesh size of 100. The flow rate of gas was controlled as 300 mL/min by mass flow meter. The experiments were operated at 25 °C. In the reaction unit, the plasma reactor consists of the ground electrode, the discharge electrode and the heating belt unit. The discharge electrode is a stainless steel stick with a diameter of 2 mm, the effective length of the electrode is 10 cm, and the ground electrode is a stainless steel cylinder with an inner diameter of 39 mm. The heating belt unit is used to control the temperature of the reactor. The reactor employed a negative DC high-voltage power supply with adjustable output voltage. The concentrations of COS, H2S, and SO2 were determined by an HC-6 sulfur-phosphorus analyzer (Hubei Institute of Chemistry, China). The concentrations of CO and CO2 were analyzed by gas chromatography (GC-9790II, Jiangsu Fuli Analytical Instrument Co., Ltd, China). The concentration of O3 was analyzed by ozone monitor (ZX-O3). The qualitative analysis of the outlet gas was performed on an FTIR (Nicolet iS50). The chemical composition of the solid deposition collected from the electrodes of the reactor was determined by using an XRD (D/MAX-2200). The concentration of dust in gas was measured by a laser ash density meter (LD-5, Beijing Ju Dao He Sheng Technology Co., Ltd, China). According to the equations (1) and (2), the conversion efficiencies of COS and H2S were calculated. At the outlet, the yields of CO and CO2 are calculated by equations (3) and (4), respectively. The yield of SO2 was calculated by equation (5), and the total yield of S (marked as TS’ but excluding SO2) including S, SO3, SO42-, etc. was calculated by equation (6). The specific input energy (SIE, J/L) was used to express the


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power deposited into 1 L of the reaction gas, which was obtained by the equation (7).

Conv(COS）=

[COS]in - [COS]out × 100% [COS]in

(1)

Conv(H 2S）=

[H 2 S]in - [H 2 S]out × 100% [H 2S]in

(2)

YCO =

[CO]out × 100% [COS]in

(3)

YCO 2 =

[CO 2 ]out × 100% [COS]in

(4)

YSO 2 =

[SO 2 ]out × 100% [COS]in + [H 2 S]in

(5)

YTS′ =

[COS]in + [H 2S]in - [COS]out - [H 2S]out - [SO 2 ]out × 100% [COS]in + [H 2 S]in

(6)

SIE =

discharge power(W ) gas flow rate(L/S)

(7)

3. Results and discussion 3.1. Conversion of COS and H2S at different inlet concentrations The conversion of COS and H2S at various inlet concentrations (740, 2100 and 5400 ppm) was investigated to evaluate the effect of inlet concentration on the conversion efficiency. Fig. 2 shows that H2S conversion increased with the increase of SIE in all investigated inlet concentrations. When SIE was 142 J/L and H2S inlet concentration was 740 ppm, the conversion of H2S reached 82%. At the same SIE, there were only 61% and 37% conversion when H2S inlet concentrations were 2100 and 5400 ppm, respectively. Evidently, the higher concentration was, the higher SIE was required to gain the same conversion efficiency. As shown in Fig. 3, COS conversion exhibited the similar trend as that of H2S. Compared Fig. 2 with Fig. 3, the conversion of COS requires more energy than that needed for converting H2S to the same conversion



efficiency at the same inlet concentration. According to Table 1, the decomposition energy of O=CS is higher than that of the other three bonds. The results indicate that the dissociation of O=CS bonds consume more energy resulting in that COS removal efficiency was lower than that of H2S. 3.2. Simultaneous conversion of COS and H2S A simulated gas mixture containing 2100 ppm COS and 2100 ppm H2S was studied. As shown in Fig. 4, the conversion of COS in the gas mixture was lower about 10% than that under the condition of only existed COS in the 336 J/L, and then the gap became narrowed with the increase of SIE, which resulted from energy input and the properties of gas. In the case of the same input energy, the input energy is used for the decomposition of the mixed gas when the mixed gas is treated, and the energy is consumed by the different components, so the purification efficiency is lower than that of the single-component gas. As the input energy increases, the input energy is sufficient to process the gas mixture, and the gap gradually decreases. The conversion of H2S in the gas mixture is similar to the conversion patterns of COS, but the conversion had no remarkable gap, especially under high SIE. It is because COS is more difficult to be converted than H2S. It is foreseeable that a mixture gas of COS and H2S could be removed completely when the SIE was high enough. 3.3. The effect of O2 content on the simultaneous conversion of COS and H2S The Corona discharge occurred in a narrow region near the central electrode, which generates ions, free radicals and free electrons in simulated gas. O2 in the corona discharged condition would produce O· with strong oxidizing property. Theoretically, the radicals and free electrons could considerably promote the conversion of COS and H2S, and yellow phosphorous tail gas contains low O2 concentration [5]. So we investigated the conversion efficiencies of COS and H2S and the yields of their


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corresponding products at different O2 contents. A gas mixture containing 2100 ppm COS and 2100 ppm H2S was studied to explore the effect of O2 content on the COS and H2S conversion. As shown in Fig. 5, H2S conversion with different O2 contents was in the order of 0.8% > 1.5% > 3%. Overall, the effect of O2 content was approximately the same on both COS and H2S conversion. As shown in Fig. 6, O3 concentration increased with the increase of SIE and O2 content. O2 was converted to O3 under the electric field, which consumed part of the energy, so that the energy used for COS and H2S conversion would decrease correspondingly. Although O3 could react directly with COS and H2S, free electrons and oxidative radicals derived from O2 played more significant roles in the simultaneous conversion of COS and H2S. As can be seen from Fig. 7, the yield of SO2 first increased and then decreased with increasing SIE. The yield reached a maximum when the SIE was approximately 550 J/L. In contrast, the yield of TS’ continuously increased with increasing SIE. When SIE was high enough, the yield of SO2 showed a downward trend. The yield of SO2 at different O2 contents was in the order of 0.8% > 1.5% > 3%. A higher input energy could produce more oxidative radicals and promote oxidation. As the input energy increased, the amounts of oxygen radicals increased, and excess oxygen radicals further oxidized SO2. Therefore, part of SO2 was oxidized to SO3 and SO42- with the increase of O2 content. Fig. 8 shows the yields of CO and CO2 after the COS and H2S conversion at different O2 contents. The content of carbon remained constant during the conversion reaction process. Moreover, with increasing SIE, the yield of CO increased first and then decreased. With the increase of input energy, the conversion rate of COS increased, the content of CO increased, the amount of oxygen free radicals increased gradually, some of CO was oxidized to CO2 by oxygen radicals. At the input energy of 0 ~ 336 J/L, the



growth trend of oxygen free radicals was less than that of CO, so the content of CO increases with the input energy. When the input energy was more than 336 J/L, The growth trend of oxygen free radicals was greater than that of CO, causing more CO to be converted to CO2, thus resulting in a decrease in CO content. 3.4. Effect of temperature on conversion of COS and H2S Mixture gas of COS with 2100 ppm and H2S with the same concentration was studied at the different temperature. Fig. 9 presents the trend of current change with voltage under the 25 ºC, 110 ºC and 200 ºC. The current increased with the increase of voltage, and when voltage is higher than 10 kv, the current intensity was positively correlated with temperature. Meanwhile, breakdown voltage was 18, 16 and 14 kv at the temperature of 25 ºC, 110 ºC and 200 ºC, respectively. As can be seen from Fig. 10, the conversion efficiency of COS and H2S increases with increasing temperature at the same voltage. It can be inferred that the temperature affects the conversion and the breakdown voltage. The higher temperature leads to the higher conversion at the certain voltage, but it also results in the lower breakdown voltage. The increase of temperature leads to the gas density decreases and the interval between the gas molecules increases, and each electron in the electric field in the collision ionization "free travel" increases. So the electrons can obtain greater speed and kinetic energy. But when ionization effect is strengthened, the gas is easy breakdown. Therefore, the high temperature would result in low H2S and COS conversion, and the low temperature was conducive to the discharge and gas conversion. 3.5. Simultaneous removal of H2S, COS, and dust In general, efficient removal of dust, COS, and H2S is required as a prerequisite to meet applicable emission standards. Corona discharge plasma not only could produce a number of active radicals and strong oxidizing particles but also could generate a


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significant number of free electrons that can attach on the dust to prompt the collection of dust under the electric field. Dust formed by a dust generator was blended with a gas mixture at a concentration of 5600 ± 5% mg/m3. As shown in Fig. 11, the conversion of COS and H2S, as well as the yield of CO2, exhibited a slight improvement with adding dust. The promotion was more obvious in the low SIE which implied introducing dust can reduce energy consumption. It was a beloved situation that COS and H2S could be converted by corona discharge plasma when dust existed and played a weak but positive role. The highest yield of SO2 was 33% without dust. After mixed with dust, the yield of SO2 dropped to 23%, indicating some components of dust reacted with SO2 or the dust promote SO2 to be further converted to SO3 or SO42-. The CO yield decreased while the CO2 yield increased, suggesting that the addition of dust promoted the oxidation of CO to CO2. Moreover, dust could be collected by the ground electrode with a dust removal efficiency more than 99%, thus achieving simultaneous removal of COS, H2S, and dust through corona discharge plasma. Taken together, corona discharge plasma is an ideal method to remove COS, H2S and dust simultaneously. 3.6. Analysis of the products and the reaction mechanism The gas content and solid products from the reaction were analyzed for elucidating the mechanism of simultaneous removal of COS, H2S, and dust by DC corona discharge plasma. 3.6.1. FTIR analysis of outlet gasses The outlet gas was analyzed by FTIR with a gas cell. At a resolution of 4 cm−1, all spectra were collected in the 4000–400 cm−1 frequency range. Each spectrum resulted from 16 scans, corresponding to a time resolution of 19s. The results are showed in Fig. 12 and 13. Fig. 12 shows the FTIR spectra of coexisting COS and H2S under different



SIE, and Fig. 13 shows the FTIR spectra of coexisting COS and H2S with or without dust under different SIE. The absorption peak between 2071 and 2052 cm-1 was attributed to COS absorption, which showed a linear correlation with the concentration of COS [22]. Peaks between 868 and 849 cm-1 was also ascribed to the absorption of COS, as well as the peak between 2927 and 2910 cm-1. The central wavelength of the strongest absorption peak of H2S is at 80 cm-1, which requires a far-infrared spectrometer for the measurement [23]. For this reason, the absorption peak of H2S at 80 cm-1 was not observed. Absorption peaks between 2360 and 2342 cm-1 corresponded to the C=O stretching vibration of CO2 [24], as well as the peak of 669 cm-1. A broad band around 2115 cm−1 was likely due to the C≡O stretching vibration of CO [25, 26]. The absorption peak at 1373 cm−1 was likely attributed to the S=O symmetric stretching of SO2 [27]. As showed in Fig. 12, with increasing SIE, the peak intensity of COS decreased while the peak intensity of CO2 increased. The peak intensity of SO2 absorption closely correlated with the level of SIE. The peak intensity initially increased with increasing SIE. It reached a maximum around SIE of 549 J/L, and then decreased. Correspondingly, the yield of SO2 yield increased initially and then decreased with increasing SIE. Compared with the absorption peak intensities of CO at different SIE, it was evident that the peak intensity of CO increased initially and then decreased, which exhibited same variation pattern as that of SO2. In Fig. 13, compared the peak intensities with or without dust, it was found that the yield of SO2 considerably decreased with the addition of dust. 3.6.2. XRD analysis of solid products Solid products were collected from the ground electrode and discharge electrode after the reaction with the introduction of dust. Dust was obtained from electrostatic


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precipitators in a yellow phosphorus plant. Before the reaction, the dust was washed, dried, and ground. XRD patterns of products were obtained on a D/MAX-2200 X-ray diffractometer with Ni-filtered Cu Kα radiation (λ=0.15406 nm) operating at 20~60 kV and 2~50 mA. The XRD data were collected in the 2θ range with a scanning speed of 2 °/min. The XRD results are showed in Fig. 14. As shown in Fig. 14, dust was collected from electrostatic precipitator, which mainly included fluorapatite (Ca5(PO4)3F), silicon dioxide (SiO2), calcium fluoride (CaF2), KCaPO4, and aluminum phosphate (AlPO4). After reaction under the corona discharge conditions, the XRD patterns of solid that collected from electrode displayed new peaks corresponding to new chemical compositions, including calcium sulfate (CaSO4), potassium fluoride phosphate (KPO2F2), and sulfur (S), besides peaks belonging to Ca5(PO4)3F, SiO2, CaF2, and AlPO4. The possible reason is that COS and H2S decomposition products simultaneously reacted with some components of dust and generated S and sulfur oxide. The generated CaSO4 result from the reaction between CaF2 and sulfur oxide. Peaks belonging to SO3 were not observed because it reacted with other components or was not generated at all in this process. 3.6.3. Mechanism Analysis When the SIE reached a certain level, the free radicals (O·, OH·, etc.) and free electrons were generated. COS and H2S were dissociated, followed by electron transfer. The products of simultaneous conversion of COS and H2S by corona discharge plasma were CO, CO2, S, SO2, and SO42-. The content of carbon remained constant during the whole reaction process. O=CS (Bond energy = 608.4 KJ/mol) was more difficult to be cleaved than OC=S (Bond energy = 308.4 KJ/mol). On the basis of these results, it can be inferred that COS was dissociated to CO and S first by corona discharge plasma. H2S was dissociated to HS· and H· first by corona discharge plasma, then the HS· was



further dissociated into S and H·, at last the H· were combined to form hydrogen. Oxygen molecules covalent bond fracture decomposition into oxygen radicals due to the impact of electrons, and part of the O· and O2 combined to form O3. It is well established that O3 could form by corona discharge plasma. Due to the production of O· and O3, COS and H2S may be further oxidized to different kinds of products: Part of COS was oxidized by collision of oxygen radicals and form to CO2 and S, or CO and SO, and then CO and SO were further oxidized into CO2 and SO2. Part of COS was directly oxidized by O3 to CO2 and SO2. Among them, SO2 was easily oxidized to SO3 in the presence of O3 and O·. The generation of CO and CO2 is related to the conversion of COS. Part of H2S was oxidized by oxygen radicals collision and form HS· and OH·, then H2S reacts with OH· to get H2O and HS·, and the produced HS· reacts with O· to produce S and OH·. A portion of H2S reacts directly with O3 form SO2 and H2O. The formation of sulfur compounds (S, SO2, SO42-) relied on the oxidization of COS and H2S. Of all products, a small amount of elemental S may also be produced in the Claus process (H2S + SO2 = S + H2O). The generation of O3 had a negative effect on the conversion of COS and H2S since that the generation of O3 consumed part of energy and caused a low COS and H2S conversion efficiency. Although O3 could react with COS and H2S, free electrons and oxidative radicals might played more significant roles in the conversion of COS and H2S. After mixed with dust in the conversion reaction, the sulfur compounds (SO2, SO42-) reacted with some compositions of dust. What’s more, dust can react with gaseous components or act as a carrier under the electric field, which slightly improved COS and H2S conversion when dust was introduced into the reaction system as discussed in section 3.3. The proposed reaction mechanism of COS and H2S under the corona discharge plasma treatment are showed in Fig. 15.


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4. Conclusion A gas mixture of COS and H2S containing dust could be simultaneously removed under the corona discharge plasma conditions. Under investigated SIE level, the simultaneous conversion of COS and H2S were lower than the alone conversion. The products of COS and H2S simultaneous conversion contained CO, CO2, S, SO2, and SO42-. When raising the SIE, COS and H2S were easier to be converted. Moreover, it is difficult to remove COS than H2S. The simultaneous conversion of COS and H2S decreased with the increase of O2 content because more energy was consumed to form O3. Higher temperature would result in low H2S and COS conversion. When the dust was added, the conversion of COS and H2S, as well as the yield of CO2 increased, while the yield of SO2 and CO decreased under the same SIE condition. Consequently, it comes to the conclusion that the addition of dust promoted the purification of COS and H2S, and it also accelerated the oxidation of CO to CO2 in some extent. With the inlet concentration of 2100 ppm COS and 2100 ppm H2S, O2 of 0.8%, dust content of 5600 ± 5% mg/m3 and SIE of 748 J/L, COS and H2S conversion reached 90% and 98%, respectively. In the meantime, the removal efficiency of dust reached 99%. In conclusion, this study demonstrated that the simultaneous removal of COS, H2S and dust could be achieved by DC corona discharge plasma.

Acknowledgements: This work was supported by the National Natural Science Foundation of China (51568027), National Key R&D Program of China (2017YFC0210500) and Candidates of the Young and Middle Aged Academic Leaders of Yunnan Province (2015HB012).



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41, 6484–6490. [23] Spagnolo, V.; Patimisco, P.; Pennetta, R.; Sampaolo, A.; Scamarcio, G.; Vitiello, M. S.; Tittel, F. K. THz Quartz-enhanced photoacoustic sensor for H2S trace gas detection. Opt. Express 2015, 23, 7574–7582. [24] Amenomiya, Y.; Morikawa, Y.; Pleizier, G. Infrared spectroscopy of C18O2 on alumina. J. Catal. 1977, 46, 431–433. [25] Li, X. X.; Liang, X. U.; Gao, M. G.; Tong, J. J.; Liu, J. G. Fourier transform infrared greenhouse analyzer for gases and carbon isotope ratio. Optics and Precision

Engineering 2014, 22, 2359–2369. [26] Liao, L. F.; Lien, C. F.; Shieh, D. L.; Chen, M. T.; Lin, J. L. FTIR study of adsorption and photoassisted oxygen isotopic exchange of carbon monoxide, carbon dioxide, carbonate, and formate on TiO2. J. Phys. Chem. B 2002, 106, 11240–11245. [27] Zhang, J. B.; Han, F.; Wei, X. H.; Shui, L. K.; Gong, H.; Zhang, P. Y. Spectral studies of hydrogen bonding and interaction in the absorption processes of sulfur dioxidein poly (ethylene glycol) 400 + water binary System. Ind. Eng. Chem. Res. 2010,

49, 2025–2030.


Page 16 of 33

Page 17 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 1. Chemical bond energy. Chemical bond

Dissociation energy

References

O=CS→CS+O OC=S→CO+S HS-H→HS+H H-S→H+S

608.4 KJ/mol 308.4 KJ/mol 381.4 KJ/mol 353.1 KJ/mol

[19] [19] [20] [21]



Mass flow meter

Page 18 of 33

Dust device

HC-6

O2 Reactor GC-97902

N2

FT-IR Laser ash density meter

Mixing chamber

COS

ZX-O 3 DC high voltage power

H2 S

Temperature controller

Vent

Three-way valve

Fig. 1. Schematic diagram of the experimental set-up for COS, H2S and dust removal by corona discharge plasma.


Page 19 of 33

100 80 H2S Conversion (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


60 40 H2S inlet concentration of 740 ppm H2S inlet concentration of 2100 ppm

20

H2S inlet concentration of 5400 ppm 0 0

100

200

300

400

500

600

700

800

SIE (J/L)

Fig. 2. H2S conversion with different inlet concentrations under different SIE with O2 concentration of 0.8%.



100

80

COS Conversion (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 33

60

40

20 COS inlet concentration of 740 ppm COS inlet concentration of 2100 ppm COS inlet concentration of 5400 ppm

0 0

100

200

300

400

500

600

700

800

SIE (J/L)

Fig. 3. COS conversion with different inlet COS concentrations under different SIE with O2 concentration of 0.8%.


Page 21 of 33

100 80

Conversion (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


60 40

H2S alone H2S mixing

20

COS alone COS mixing

0 0

100

200

300

400

500

600

700

800

SIE (J/L)

Fig. 4. COS and H2S conversion when COS and H2S alone or simultaneous with both COS and H2S concentration of 2100 ppm under different SIE with O2 concentration of 0.8%.



100

COS and H2S Conversion (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 33

80

60

40

20

COS

0.8% O2

COS

1.5% O2

COS

3.0% O2

H2S

0.8% O2

H2S

1.5% O2

H2S

3.0% O2

0 0

100

200

300 400 SIE (J/L)

500

600

700

800

Fig. 5. COS and H2S conversion under different SIE with different inlet concentrations of O2 and both COS and H2S concentration of 2100 ppm.


Page 23 of 33

1400 0.8% O2

1200

O3 concentration (ppm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1.5% O2

1000

3.0% O2

800 600 400 200 0

0

100

200

300

400

500

600

700

800

SIE (J/L)

Fig. 6. O3 concentration under different SIE with different inlet concentrations of O2 and both COS and H2S concentration of 2100 ppm.



80

SO2 and TS' yield (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

60

SO2

0.8% O2 TS'

0.8% O2

SO2

1.5% O2 TS'

1.5% O2

SO2

3.0% O2 TS'

3.0% O2

Page 24 of 33

40

20

0 0

100

200

300 400 SIE(J/L)

500

600

700

800

Fig. 7. SO2 and TS’ yield at the outlet under different SIE with different inlet concentrations of O2 and both COS and H2S concentration of 2100 ppm.


Page 25 of 33

75 60 CO and CO2 yield (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


CO

CO2

0.8% O2

CO

CO2

1.5% O2

CO

CO2

3.0% O2

45 30 15 0 0

100

200

300 400 SIE (J/L)

500

600

700

800

Fig. 8. COS, CO, and CO2 yield at the outlet with different inlet concentration of O2 under different SIE with both COS and H2S concentration of 2100 ppm.



1200 25 °C 110 °C 200 °C

1000 800 I (µA)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 33

600 400 200 0 0

2

4

6

8

10

12

14

16

18

U (V)

Fig. 9. Volt-ampere characteristics at the different temperature with both COS and H2S concentration of 2100 ppm.


H2S conversion (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


COS conversion (%)

Page 27 of 33

60

25 °C 110 °C 200 °C

45 30 15 0 80

25 °C 110 °C 200 °C

60 40 20 0 0

4

8

12

16

U (V)

Fig. 10. H2S and COS conversion at the different temperature under different voltage with both COS and H2S concentration of 2100 ppm.


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Conversion and yield (%)


120

COS conv H2S conv

100

YSO2

Dust YSO2

YCO2

dust YCO2

Page 28 of 33

dust COS conv dust H2S conv

YCO dust YCO

80 60 40 20 0 0

100

200

300

400

500

600

700

800

SIE (J/L)

Fig. 11. CO, CO2, SO2 yield, COS and H2S conversion of coexisting COS and H2S under different SIE with both COS and H2S concentration of 2100 ppm, the O2 concentration of 0.8%, and dust of 5600 ± 5% mg/m3.


Page 29 of 33

142 J/L 336 J/L 549 J/L 2910 748 J/L 2937 Transmittance (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


4000

2342 2052 2360 2071

1373

849 669 868

2115

3500

3000

2500

2000

1500

1000

500

-1

Wavenumbers (cm )

Fig. 12. The outlet gas concentration and product yield under different SIE.



336 J/L without dust 336 J/L with dust 549 J/L without dust 2052 549 J/L with dust 2071 Transmittance (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

2910 2937

4000

3500

3000

2342 2360

1373

Page 30 of 33

849 669 868

2115

2500 2000 1500 -1 Wavenumbers (cm )

1000

500

Fig. 13. The outlet gas concentration and product yield under the SIE of 336J/L and 549J/L, with or without dust of 5600 ± 5% mg/m3.


Page 31 of 33

KCaPO 4 KPO2F2

CaF2 AlPO

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


4

Ca5(PO4)3F  CaSO4

SiO2

SiC

♦ S

Before reaction

♦

♦ 

♦ ♦

♦ ♦

After reaction 20

30

40 2θ(°)

50

60

70

Fig. 14. XRD analysis of dust before reaction and after reaction.



Fig. 15. The reaction mechanism of COS, H2S and dust were removed by DC corona discharge plasma.


Page 32 of 33

Page 33 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table of Contents Graphic

The reaction mechanism of COS, H2S and dust were removed by DC corona discharge plasma.

When the SIE reached a certain level, the free radicals (O·, OH·, etc.) and free electrons were generated. COS and H2S were dissociated, followed by electron transfer. The conversion of COS and H2S, as well as the yield of CO2, exhibited a slight improvement with adding dust. The products of simultaneous conversion of COS and H2S by corona discharge plasma were CO, CO2, S, SO2, and SO42-.


Simultaneous Removal of COS, H2S, and Dust in Industrial Exhaust

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