Novel Process of Simultaneous Removal of Nitric Oxide and Sulfur

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Novel Process on Simultaneous Removal of Nitric Oxide and Sulfur Dioxide Using Vacuum Ultraviolet (VUV)-Activated O2/H2O/H2O2 System in A Wet VUV-Spraying Reactor Yangxian Liu, Qian Wang, and Jianfeng Pan Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b02753 • Publication Date (Web): 28 Oct 2016 Downloaded from http://pubs.acs.org on November 1, 2016

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Environmental Science & Technology

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Novel Process on Simultaneous Removal of Nitric Oxide and

2

Sulfur Dioxide Using Vacuum Ultraviolet (VUV)-Activated

3

O2/H2O/H2O2 System in A Wet VUV-Spraying Reactor Yangxian Liu*, Qian Wang and Jianfeng Pan

4 5

School of Energy and Power Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013, China

6

ABSTRACT: A novel process of NO and SO2 simultaneous removal using vacuum ultraviolet (VUV, with 185nm

7

wavelength)-activated O2/H2O/H2O2 system in a wet VUV-spraying reactor was developed. The influence of

8

different process variables on NO and SO2 removal was evaluated. Active species (O3 and ·OH) and liquid

9

products (SO32-, NO2-, SO42-, NO3-) were analyzed. The chemistry and routes of NO and SO2 removal were

10

investigated. The oxidation removal system exhibits excellent simultaneous removal capacity for NO and SO2,

11

and a maximum removal of 96.8% for NO and complete SO2 removal were obtained under optimized conditions.

12

SO2 reaches 100% removal efficiency under most of test conditions. NO removal is obviously affected by several

13

process variables. Increasing VUV power, H2O2 concentration, solution pH, liquid-gas ratio and O2 concentration

14

greatly enhances NO removal. Increasing NO and SO2 concentration obviously reduces NO removal. Temperature

15

has a dual impact on NO removal, which has an optimal temperature of 318K. Sulfuric acid and nitric acid are the

16

main removal products of NO and SO2. NO removals by oxidation of O3, O· and ·OH are the primary routes. NO

17

removals by H2O2 oxidation and VUV photolysis are the complementary routes. A potential scaled-up removal

18

process was also proposed initially.

19

Keywords: Vacuum ultraviolet (VUV); O3; hydroxyl radical (·OH); SO2; NO; VUV-spraying reactor

20

*Corresponding Author: Yangxian Liu

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1. Introduction

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Tel.: +86 0511 89720178. Fax: +86 0511 89720178.

E-mail: [email protected].

Emission of NOx and SO2 from combustion of coal, fuel oils and waste has significant effects on

ACS Paragon Plus Environment


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environment and human health.1,2 Currently, both limestone-based wet flue gas desulfurization (Ca-WFGD) and

24

ammonia-based selective reduction (NH3-SCR) processes have achieved large-scale commercial application for

25

removal of SO2 and NOx from coal-fired utility boilers, but neither of them can be used for the simultaneous

26

removal of SO2 and NOx in a reactor.1-3 In China, there are a large number of small and medium-sized coal-fired

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boilers and industrial furnaces (over 800000).4 Considering the huge investment and operating costs, it is not

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feasible to simultaneously equip Ca-WFGD and NH3-SCR devices for these small and medium-sized combustion

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facilities.3 In addition, due to the limitation of the process itself, some industrial furnaces from petroleum,

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metallurgical and chemical industries can not even use high temperature NH3-SCR denitrification process.3 The

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serious situation in environmental protection prompts us to develop new SO2 and NOx simultaneous removal

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technologies which are suited for these small and medium burners.

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Simultaneous removal technology of SO2 and NOx in a reactor is considered to be a promising flue gas

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purification process, which is especially suited for small and medium-sized industrial boilers and furnaces, due to

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its simple system and small space.1,2 Currently, simultaneous removal technologies of SO2 and NOx can be

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divided into dry and wet categories. The dry removal method mainly includes catalytic oxidation, adsorption

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removal, plasma removal, photocatalytic removal, photochemical removal, microwave removal, ozonation, etc.4-11

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The wet removal method mainly includes oxidation absorption, complex absorption and reducing absorption,

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etc.1-3,12-16 These removal methods have demonstrated good prospects in certain aspects, but they also suffer from

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several form of drawbacks, mainly including high costs, low conversion efficiency, high running temperatures,

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unreliable equipments and disposal cost with several associated environmental problems.4 With the dramatic

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increase of environmental pressure, it is very desirable to develop new simultaneous removal technologies of SO2

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and NOx from flue gas, which is especially suitable for small and medium sized combustion equipments.

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Light-induced advanced oxidation processes have demonstrated good development prospects in the area of


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emission reduction of NOx and SO2 from flue gas.1,2,4,8,11,17-26 Several semiconductor-based photocatalytic

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oxidation processes have been developed for removal of NOx and SO2 from flue gas, and have exhibited good

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removal performance for NOx and SO2.11,17-20 However, some drawbacks, such as instability and low activity of

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photocatalyst, low penetration of UV-light in solids and restriction of low concentration of pollutants

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(photocatalytic oxidation processes can be only used for the treatment of pollutants with low concentration),

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hinder their industrial applications.4,20 In recent years, several photochemical oxidation processes, such as dry

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VUV radiation,8,21-24 wet UV/H2O21,4,25 and wet UV-Fenton (like) processes,2,4,26 have been developed to remove

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NOx and SO2 from flue gas. Tsuji et al.21-23 successfully used 172-nm Xe2 and 146-nm Kr2 excimer lamps as VUV

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sources to remove SO2, NO and NO2 in N2 and air without using any expensive catalysts, which shows that VUV

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is an effective light source for removals of SO2, NO and NO2. However, Tsuji’s studies21-23 did not consider the

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effect of VUV irradiation in the simultaneous presence of O2 and H2O which are the two main components of

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actual flue gases. Ye et al.24 determined for the first time the key reactive oxygen species which are generated by

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VUV radiation in simulated flue gas (N2/O2/CO2/H2O), and evaluated the key parameters which affect the yield of

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the oxidants. Subsequently, they further developed a dry removal method for simultaneous desulfurization and

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denitrification using VUV irradiation, and reached the highest simultaneous removal efficiency of 90% for SO2

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and 96% for NOx, respectively.8 However, the dry SO2 and NOx removal technology using VUV radiation is

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difficult to achieve practical application. This is because the surface of UV lamp will glue a lot of reaction

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products and impurities from the complex flue gas with the long-term continuous operation of removal

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process.4,27,28 This will make the photochemical removal device not able to maintain long-term continuous

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operation, and even finally destroy the key light sources. Hence, maintaining the surface of UV lamp long-term

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clean is the key for the application of photochemical removal technology in the area of flue gas purification.

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We recently developed wet simultaneous removal technologies of SO2 and NO using wet UV/H2O2 and wet



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UV-Fenton (like) processes in an UV-bubbling reactor, and studied the several fundamental issues.1,2,4,25,26 The

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results4 indicate that even in containing-various impurities solutions (e.g., inorganic ions, transition metal ions,

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organics, alkaline additives and particulates), the surface of the quartz tube (UV lamp) can still keep long-term

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clean. This shows that the wet photochemical removal process can maintain long-term operation, and has good

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prospect in practical application of flue gas purification. However, these techniques in our previous works still

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have some drawbacks as follows:4 (1) wet UV/H2O2 and wet UV-Fenton (like) processes, with 254nm wavelength

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UV, can not excite O2 and H2O (both of them are the free radical sources and the main components of flue gas and

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solution) to produce reactive species O3,·O and ·OH; (2) the previous studies1,2,4,25,26 were mainly carried out in

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the UV (254nm)-bubbling reactor. But our results4,25,26 indicate that the gas-liquid contact area is the key rate

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controlling step for NO removal using wet UV/H2O2 and wet UV-Fenton (like) processes in UV-bubbling reactor.

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Thus selecting a reactor with high interfacial area is the key for enhancing NO absorption. The interfacial area of

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the spraying reactor is often up to 60-120m-1, which is far greater than that of bubbling reactor (15-30m-1).23 Thus

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the spraying reactor is more suitable for UV/H2O2 and UV-Fenton (like) oxidation systems; (3) the distance of UV

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light propagation is very short in water, which hinders the industrial amplification of UV-bubbling reactor.

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Compared with the UV-bubbling reactor, the atomized solution in the UV-spraying reactor is discontinuous or

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dispersed, which will greatly increase the penetration distance of UV-light; (4) Compared with the bubbling

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reactor, the spraying reactor is the most widely used wet scrubbers in the area of flue gas purification due to its

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simple structure and small pressure drop, which has much better prospect for future application.

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Thus in the previous works,29 we developed a wet 254nm UV-spraying reactor and investigate its removal

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performance for Hg0 from flue gas. The results demonstrated that the wet UV-spraying reactor had a very good

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removal performance for Hg0 from flue gas. This inspire us to try to further study the removal of NO and SO2

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from flue gas using new vacuum ultraviolet (VUV, with 185nm wavelength)-activated O2/H2O/H2O2 oxidation


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system in the wet VUV-spraying reactor. The result will provide an important basis for achieving the final

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simultaneous removal of NO, SO2 and Hg0 from flue gas using VUV-activated O2/H2O/H2O2 oxidation system in

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the wet VUV-spraying reactor.

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Therefore, the main purpose of this article is to develop a novel process on simultaneous removal of NO and

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SO2 from flue gas using VUV-activated O2/H2O/H2O2 system in a wet VUV-spraying reactor and to study several

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key fundamental issues in removal of NOx and SO2. These fundamental issues are as follows: (1) to examine the

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feasibility of this new process about NOx and SO2 simultaneous removal in a wet VUV-spraying reactor; (2) to

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investigate the effects of several key operating parameters, including VUV power, H2O2 concentration, solution

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temperature, solution pH, liquid-gas ratio and concentrations of O2, NO, SO2, on NO and SO2 removal; (3) to

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determine and capture the key active species (e.g., O3 and ·OH) and reaction products (e.g., SO32-, NO2-, SO42-,

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NO3- and NO2); (4) to reveal the chemistry and routes of NO and SO2 removals; (5) to initially discuss and

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propose the potential removal process and equipments for this new technology. The results will provide some

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theoretical basis for the subsequent development of this technology.

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2. Experimental Section

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2.1 Experimental apparatus

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The experimental apparatus consists of a flue gas generating equipment, a wet VUV (185nm)-spraying

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reactor (60cm length and 10.0cm i.d.; Silicate Glass), a measurement and post-processing system, and a

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temperature controlling system. The flue gas generating equipment includes four flowmeters, a gas mixer and four

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cylinder gases. The measurement and post-processing system includes a flue gas analyzer and a absorption bottle.

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The wet VUV (185nm)-spraying reactor includes a cylindrical container, a quartz tube, a VUV lamp (length

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46.6cm, power 36W, wavelength, 185nm), three nozzles (spray droplet size is approximately 60-120 micrometers)

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and a pump. The temperature controlling system includes a thermometer and a thermostatic water bath. Three



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nozzles are arranged on the same horizontal plane, and maintain 120-degree angle each other. The spacing

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between the nozzles and the top of reactor is about 15cm. The experimental system is described in detail in the

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Figure 1.

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Figure 1. Schematic diagram of experimental apparatus with a wet VUV-spraying reactor 2.2 Experimental procedures and methods

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Containing-NO, SO2, O2 and N2 simulated flue gas (1.2L/min) is prepared by cylinder gases and flowmeters.

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H2O2 solution (0.4L) is prepared by commercial H2O2 reagents with mass fraction of 30% (AR, Sinopharm

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Chemical Reagent Co., Ltd.) and deionized water. Solution pH is adjusted by NaOH/HCl and measured by an

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acidometer. When solution temperature is adjusted to the desired value by constant temperature device and

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thermometer, the solution is atomized by nozzles and then encounters with the flue gas from the bottom of the wet

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VUV-spraying reactor, which will initiate a gas-liquid reaction in the reaction zone. The flue gas is analyzed via

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flue gas analyzer. Each experimental cycle is 30min. Each instantaneous concentration value is recorded every


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minute, and the average value of 30 instantaneous concentrations within 30min is used as the export concentration

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of NO or SO2 in flue gas. Concentration of SO2 or NO in flue gas was measured twice. And the average value of

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the two was used as the final concentration.

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2.3 Analytical methods

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Concentrations of SO2, NO, NO2 and O2 in flue gas were measured by flue gas analyzer (MRU-VARIO

129

PLUS, Germany). The concentrations of anions, such as NO2-, NO3-, SO32- and SO42-, in liquid phase were

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measured via ion chromatography (792 Basic IC, Metrohm in Switzerland) under the chromatographic conditions

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as follows: aluent (1.0 mmol/L Na2CO3 + 2.0 mmol/L NaHCO3 ), anion dual 2 anion column, injection volume

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(30 µl ), flow rate (1.2 mL/min), column temperature (303K), and automatic regeneration suppression system

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(H2O and 100 mmol H2SO4).

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The hydroxyl free radicals were captured by electron spin resonance (ESR) spectrometer (Bruker ESP-300)

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combining with 5,5-dimethy l-1- pyrrolidine N-oxide (DMPO) (>99%, Sigma) as the spin trapping agents under

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the setting conditions as follows: microwave power of 10mW, resonance frequency of 9.82GHz, X-band

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spectrometer, temperature of 298K, modulation frequency of 100kHz, modulation amplitude of 0.1mT, sweep

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width of 10mT, time constant of 148ms, sweep time of 180s and receiver gain of 3.0×105. The concentrations of

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O3 in the gas stream were measured by an ozone analyzer (BX-O3-Special Order Edition, Guangdong Zhenxiong

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Electronic Technology Co., Ltd., China) with the following performance parameters: measuring range: 0-500ppm,

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resolution: 1ppm, precision: ≤±2% and repeatability: ≤±1%.

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2.4 Data processing method

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The concentrations of NO and SO2, which were detected through the bypass, were used as the inlet

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concentrations of NO and SO2, respectively. The concentrations of NO and SO2, which were detected through the

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reactor outlet, were used as the outlet concentrations of NO and SO2, respectively. Removal efficiencies of NO



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and SO2 can be calculated by the following expression (1):

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Removal efficiency = (Cin − Cout ) / Cin ×100%

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where Cin is inlet concentration of NO or SO2 in flue gas; C NO is outlet concentration of NO or SO2 in flue gas.

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3. Results and discussions

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3.1 Effects of VUV power on NO and SO2 removal efficiency

(1)

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Both number of ultraviolet photons and energy consumption are closely related to the power of ultraviolet

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lamp. Thus the interrelation between VUV power and NO and SO2 removal efficiency has been investigated, and

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the results are shown in Figure 2(a). Compared with NO, SO2 has a very high solubility in water and a good

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reactivity with H2O2, thus SO2 achieves 100% removal under the test conditions. When VUV radiation is absent,

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NO removal efficiency is only 10.3%. However, when the VUV radiation is added, and as the VUV power

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increases from 0 to 72W, NO removal efficiency sharply increases from 10.3% to 95.3%. Results of the previous

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researchers1,2,4,8,24,28-30 indicate that all of O2, H2O and H2O2 can be activated and decomposed into the active

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species, O3, ·O and ·OH, according to the following equations (2)-(5).

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( λ < 200nm) O 2 + hv  → ⋅O + ⋅O

(2)

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O 2 + ⋅O → O 3

(3)

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H 2 O + hv → ⋅OH + ⋅H

(4)

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H 2 O 2 + hv → 2 ⋅ OH

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(5)

These active species, O3, ·O and ·OH, can oxidize NO and SO2 via the following equations (6)-(21).1,2,4,28-33

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NO + ⋅OH → H + + NO-2

2.0 × 1010 M −1s −1

(6)

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NO -2 + ⋅OH → NO3- + ⋅H

6.0 × 109 M −1s −1

(7)

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NO + ⋅O → NO 2

(8)

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NO + O 3 → NO 2 + O 2

(9)


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HNO 2 + H 2O 2 → HNO 3 + H 2O

(10)

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NO 2 + ⋅OH → HNO 3

(11)

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2NO 2 + H 2 O 2 → 2HNO 3

(12)

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2NO + 3H 2O 2 → 2HNO 3 + 2H 2O

(13)

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SO 2 + H 2 O ↔ HSO 3− + H +

(14)

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HSO -3 ↔ SO 32 − + H +

(15)

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HSO 3- + ⋅OH → ⋅SO3− + H 2O

4.5 × 109 M −1s −1

(16)

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SO 32- + ⋅OH → ⋅SO 3− + OH -

5.1 × 109 M −1s −1

(17)

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HSO 3- + H 2 O 2 → SO 24− + H + + H 2 O

(18)

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SO 32 - + H 2O 2 → SO 24 − + H 2O

(19)

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HSO -3 + ⋅O → SO -4 ⋅ + ⋅ H

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SO 32- + O 3 → SO 24- + O 2

(20)

8.4 × 108 M −1s −1

(21)

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According to the results of Tsuji’s studies21-23 and Ye et al.24, NO and SO2 may be also directly decomposed by

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VUV-light radiation according to following equations (22)-(25).

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NO + hv → N ⋅ + O ⋅

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SO 2 + hv → S + O 2

(23)

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SO 2 + hv → SO + O ⋅

(24)

185

SO + hv → S + O ⋅

(25)

(22)

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Based on the equations (2)-(5) and (22)-(25), it can be inferred that an increase in VUV power will increase the

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number of ultraviolet photons, which is able to increase the concentration of the active species O3, ·O and ·OH,

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and thereby can increase the removal efficiency of NO. However, it is also worth noting that when the VUV

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power exceeds 36W, with the further increase of VUV power, the growth rate of NO removal efficiency is smaller.



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This phenomenon can be explained by the following reason. For a gas-liquid heterogeneous reaction, with the

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enhancement of chemical reactions, the mass transfer process has become the controlling step of the removal

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process.4 Taking into account the energy consumption, 36W is considered to be an optimal economic value in the

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test reaction system.

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3.2 Effects of H2O2 concentration on NO and SO2 removal efficiency

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H2O2 is the most common precursor of ·OH, and its concentration often has a significant influence on the

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yield of ·OH, removal efficiency of pollutants and cost of reagent. The effects of H2O2 concentration on NO and

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SO2 removal efficiency are tested, and the results are displayed in Figure 2(b). It can be seen that SO2 achieves

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100% removal in the range of all test H2O2 concentrations. When there is no H2O2 in the reaction system, the

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removal efficiency of NO is only 20.8%. But as the H2O2 concentration increases from 0 to 1.2mol/L, the removal

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efficiency of NO greatly increases from 20.8% to 93.1%. This result illustrates that H2O2 plays a very key role in

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the oxidation reaction system. Based on the above equation (5), an increase in H2O2 concentration is conducive to

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produce more hydroxyl free radicals, thereby being able to enhance NO removal. However, the results of the

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previous researchers 1,2,34-36 also showed that adding the high concentration of H2O2 would induce the following a

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series of side reactions (Eq.s 26-28).

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H 2O 2 + ⋅ OH → HO2 ⋅ + H 2O

2.7 × 107 M −1s −1

(26)

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HO 2 ⋅ + HO 2 ⋅ → H 2O 2 + O 2

3.4 × 107 M −1s −1

(27)

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⋅ OH + HO2 ⋅ → H 2O + O 2

1.0 × 1010 M −1s −1

(28)

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These side reactions will reduce the concentrations of free radicals in the liquid phase, and accelerate the

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decomposition of H2O2, thereby hindering the removal of pollutants. From the Figure 2(b), it can be seen that

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when H2O2 concentration exceeds 0.2mol/L, the growth rate of NO removal efficiency becomes smaller, which

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keeps a good consistency with the above speculation. Thus 0.2mol/L is chosen as an optimized H2O2


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concentration in reaction system.

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214 215

Figure 2. Effects of VUV power (a), H2O2 concentration (b), solution temperature (c) and solution pH (d) on NO

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and SO2 removal efficiency. Experimental conditions: VUV power, 36W; H2O2 concentration, 0.2mol/L; solution

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temperature, 318K; Solution pH, 3.96; O2 concentration, 6%; SO2 concentration, 4000mg/m3; NO concentration,

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500mg/m3; Liquid-gas ratio, 2.5.

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3.3 Effects of solution temperature on NO and SO2 removal efficiency

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For a gas-liquid reaction, solution temperature usually affects the solubility of gas in solution and chemical

221

reaction rate. As shown in Figure 2(c), it can be observed that SO2 has a 100% removal under different solution

222

temperatures. However, there is an optimum temperature for NO removal. As the solution temperature increases

223

from 298K to 318K at first, and then further increases from 318K to 338K, the removal efficiency of NO increases

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from 80.4% to 86.7% at first, and then decreases from 86.7% to 81.7%. Related results2,4 demonstrate that the



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chemical reaction will be accelerated through increasing temperature. However, increasing temperature will cause

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the reduction of NO solubility in solution.2,4 This kind of dual influence finally leads to an optimized temperature

227

for NO removal. Besides, during the experiments, we observed that when the solution temperature exceeded 328K,

228

some very small bubbles were generated in solution in the bottom of reactor, and O2 content in exhaust slightly

229

increased (when the solution temperature reached 338K, this phenomenon became more apparent). This shows

230

that H2O2 begins to decompose due to its instability at high temperatures and under UV-light radiation. It is found

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from the Figure 2(c) that compared with the low temperatures, the removal efficiency of NO has a significant

232

decay with time at the high temperatures. This result may be caused by H2O2 decomposition. Based on the

233

previous results, the optimized temperature should be set at 318K, which is close to the traditional operating

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temperatures (313K-328K) of the common wet flue gas desulfurization systems.

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3.4 Effects of solution pH on NO and SO2 removal efficiency

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As illustrated in Figure 2(d), SO2 has a complete removal in the range of all test solution pHs. As the solution

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pH increases from 3.96 to 11.56, the removal efficiency of NO increases from 86.7% to 98.6%. Based on the

238

previous equations (6)-(13), the oxidation removal process of NO generates a large number of H + in solution.

239

Thus when OH- is added into solution, it can effectively absorb the product H+ through a acid-base neutralization

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reaction (Eq. 29),4 thereby being able to enhance oxidation-absorption of NO.

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H + + OH − → H 2O

(29)

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However, the authors argue that the acidic conditions, rather than alkaline conditions, are more suitable for this

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removal process based on two reasons. On the one hand, the ultimate goal of this removal process is to produce

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the recycling H2SO4 and HNO3 (e.g. H2SO4 and HNO3 can be converted into (NH4)2SO4 and NH4NO3 which are

245

widely used as the agricultural fertilizers in China by adding ammonia). The high solution pH will generate

246

complex salts solution, which is not conducive to the reutilization of products. On the other hand, both H2O2


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247

and ·OH are unstable under alkaline conditions, and will be needlessly consumed by the reactions (Eq.s 30-32)

248

with very high reaction rates as follows.2,4

H 2 O 2 alkaline  conditions  → HO −2 + H +

249

(30)

250

⋅ OH + HO 2− → H 2O + O -2 ⋅

7.5 × 109 M −1s −1

(31)

251

⋅ OH + OH - → H 2 O + O - ⋅

1.3 × 1010 M −1s −1

(32)

252

3.5 Effects of O2 concentration on NO and SO2 removal efficiency

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Concentrations of flue gas components will change with the changes of fuel types and combustion conditions.

254

Therefore, it is necessary to examine the effects of the concentrations of the flue gas components on NO and SO2

255

removals. The effects of O2 concentration on NO and SO2 removal efficiency were studied and the results are

256

illustrated in Figure 3(a). SO2 still has a complete removal for different O2 contents. NO removal efficiency

257

obviously increases from 66.7% to 89.8% when O2 concentration increases from 0 to 9%. Based on the above

258

equations (2),(3),(8) and (9), it can be easily inferred that an increase in O2 concentration will produce more active

259

species, thereby being able to enhance NO removal. As illustrated in the Figure 4(b), with increasing O2

260

concentration, the production rate of O3 significantly increases. The result maintains a good consistency with the

261

above speculation.

262

3.6 Effects of NO concentration on NO and SO2 removal efficiency

263

Figure 3(b) illustrates the effects of NO concentration on NO and SO2 removal efficiency. We can see that

264

with the change of NO concentration, SO2 has a complete removal. When NO concentration changes from

265

220mg/m3 to 1500mg/m3, the removal efficiency of NO greatly decreases from 91.9% to 71.8%. The effects of

266

NO concentration on removal efficiency of NO may be attributed to the following reason. Increasing NO

267

concentration will increase the amount of NO through the reactor per unit time, which will reduce the relative

268

molar ratio of oxidants to NO. Hence, an increase in NO concentration reduces NO removal efficiency.



269

3.7 Effects of SO2 concentration on NO and SO2 removal efficiency

270

The effects of SO2 concentration on NO and SO2 removal efficiency were tested, and the results are

271

displayed in Figure 3(c). It is observed that in the range of all SO2 concentrations, SO2 is removed completely.

272

However, with changing the SO2 concentrations, the removal efficiency of NO clearly changes, As the SO2

273

concentration increases from 0 to 10000mg/m3, the removal efficiency of NO decreases from 91.3% to 77.1%.

274

Based on the previous equations (14)-(21), SO2 can also consume the active species and H2O2 in the liquid phase

275

by competing with NO. Thus with increasing the SO2 concentration, the removal efficiency of NO decreases.

276

Owusu et al. also obtained a similar result30 that adding SO2 with high concentrations had an obvious inhibitory

277

for NO removal when they used ·OH produced by ultrasonic cavitation to simultaneously remove NO and SO2 by

278

wet scrubbing.

279

280 281

Figure 3. Effects of VUV power (a), H2O2 concentration (b), solution temperature (c) and solution pH (d) on NO


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282

and SO2 removal efficiency. (the experimental conditions are the same with those in Figure 2)

283

3.8 Effects of liquid-gas ratio on NO and SO2 removal efficiency

284

Liquid-gas ratio is a key process parameter for design of gas-liquid reactor and operation of wet removal

285

process. The effects of liquid-gas ratio on NO and SO2 removal efficiency are illustrated in Figure 3(d). We can

286

see that under all liquid-gas ratios, SO2 has a 100% removal. Unlike the SO2, liquid-gas ratio has a great impact

287

on NO removal. As the liquid-gas ratio increases from 1.3 to 4.2, NO removal efficiency sharply increases from

288

50.6 % to 96.8 %. The total amount of oxidizing agents through the wet VUV-spraying reactor per unit time will

289

greatly increase with increasing liquid-gas ratio, which can greatly promote NO removal. Besides, an increase in

290

liquid-gas ratio also will increase the gas-liquid mass transfer rate by strengthening the disturbance in gas-liquid

291

two-phases,37 thereby further promoting NO removal. Therefore, the increase of liquid-gas ratio can result in the

292

increase of NO removal efficiency. However, it is also noteworthy that with increasing liquid-gas ratio, the energy

293

consumption of circulating pump also will greatly increase. Therefore, an optimal value for liquid-gas ratio should

294

be selected by synthetically considering the removal efficiency and the energy consumption of circulating pump.

295

3.9 Determination of the key active species (e.g., ozone and ·OH)

296

To reveal the routes of NO and SO2 removal, the key active species, such as ·OH and O3, were measured

297

using ESR spectrometer and ozone analyzer, respectively, and the results are displayed in Figure 4 (a)-(g). It can

298

be observed from the Figure 4(a) and (b) that an increase in VUV power or O2 concentration can greatly increase

299

the yield of O3 in simulated flue gas. This result can be explained by the above equations (2) and (3). As illustrated

300

in the Figure 4(c), ESR spectrometer can not capture ·OH signals in H2O2 solution alone. However, it is observed

301

from the Figure 4(d), weak ·OH signals have been successfully captured in VUV/H2O system. A symmetrical

302

four-line peak is the typical spectrum shape of ·OH, which are measured by ESR spectrometer combining with the

303

spin trapping agent, DMPO. The constants of hyperfine splitting ( a N = 15.2 G and a N = 14.8 G ) maintain good



304

consistency with the literature data ( a N = 15.1G and a N = 14.8 G ),38 which verifies that ·OH has been

305

produced in the reaction system. This result also shows that VUV can directly excite H2O to produce ·OH in

306

liquid phase. As shown in Figure 4(e), compared with VUV/H2O, VUV/H2O/O2 system captured a stronger ·OH

307

signals, which shows that O2 plays an important role in strengthening the generation of ·OH in liquid phase.

308

It can be seen from the Figure 4(f) and (g), the addition of H2O2 greatly increase the yield of ·OH in liquid

309

phase (the intensity of ·OH signals is proportional to its concentration). The result shows that compared with H2O

310

and O2, H2O2 is the most important source of ·OH in liquid phase. Besides, as shown in the Figure 4(f) and (g), O2

311

also plays an important role in strengthening the generation of ·OH, which maintains a good consistency with the

312

phenomenon in Figure 4(d) and (e). Results of the previous studies2,4 showed that as a capture intermediate, O2

313

played an important role in restraining the combination and destruction of ·OH. Thus it is able to increase the

314

yield of ·OH in solution.

315

316


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317

318 319

Figure 4. Effects of VUV power and O2 concentration on the yield of O3 and ESR spectra of ·OH adducts.

320 321

3.10 Analysis of reaction products

322

To understand the product compositions of NO and SO2 removals in the gas-liquid two-phase, the anions in

323

solution were determined using IC, and the results are shown in Figure 5. The results demonstrate that NO3- and

324

SO42- are the major anions in solution, which suggests that NO and SO2 are mainly removed by oxidation

325

reactions. The by-products NO2- and SO32- were not found in reaction solution. Besides, according to the results of

326

Ye et al.8 and Tsuji et al.21-23 and the present results about SO2 direct photolysis (as shown in Figure 6(b)), some

327

elemental sulfur may be also produced in the reaction solution. However, it is difficult to determine its content

328

because of its very low yield in liquid phase and the complexity of the reaction solution. To avoid the gas

329

secondary contamination, the potential NO2 in exhaust was also measured by flue gas analyzer (the harm of NO2



330

for environment is far more than that of NO), but it was also not detected, which shows that this new removal

331

process will not produce new gas secondary pollution. The produced H2SO4 and HNO3 in reaction solution can be

332

easily converted into (NH4)2SO4 and (NH4)NO3, which are widely used as the important agricultural fertilizers in

333

China, by adding ammonia. The final products can be evaporated and crystallized, and then converted into solid

334

reagents, which is easy to transport and storage, through using the waste heat from coal-fired boilers.

335 336

Figure 5. The anions in solution which are determined using IC. (the experimental conditions are the same with

337

those in Figure 2)

338 339

3.11 Removal routes

340

The comparisons on NO and SO2 removal efficiency in different removal systems were conducted, and the

341

results are illustrated in Figure 6. The results illustrate that the removal efficiency of NO is only 10.3% by H2O2

342

oxidation. The results from Figure 4(a) indicate that there is no ·OH signal in H2O2 solution. This result

343

demonstrates that this part of NO removal (10.3%) should be ascribed to the oxidation of H2O2 to NO. When

344

VUV radiation alone is used only, the removal efficiency of NO is only 2.0%, which shows that although this


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345

share is very small, the route of the VUV direct decomposition for NO occurs in this removal system. The

346

removal efficiency of NO reaches 7.3% in VUV/H2O system, and at the same time, ·OH signal is also captured in

347

the same system (Figure 4(d)). This result demonstrates that NO removal by oxidation of ·OH from VUV

348

photolysis of water is one of the reaction routes.

349

When H2O2 is added into solution, NO removal efficiency respectively reaches 61.7% and 86.7% in

350

VUV/H2O2 and VUV/O2/H2O2 removal systems. As shown in the Figure 4(f) and 4(g), with the addition of H2O2,

351

the intensity of ·OH signal in liquid phase also greatly increases. This result shows that H2O2 plays a very key role

352

in the generation of ·OH, and NO removal by oxidation of ·OH from VUV photolysis of H2O2 is one of the

353

reaction routes. Besides, the important active specie, O3, has been also detected definitely, and the results in the

354

Figure 3(a) and Figure 6(a) show that adding O2 obviously promotes NO removal. Thus is can be inferred that this

355

part of NO removal by oxidations of O3/·O is also one of the reaction routes.

356

In summary, removal routes of NO mainly include five parts: (Ⅰ Ⅰ) removal of NO by oxidation of H2O2

357

(equation (13)); (Ⅱ Ⅱ) removal of NO by oxidation of ·OH from VUV photolysis of H2O2 (equations (5)-(7)); (Ⅲ Ⅲ)

358

removal of NO by oxidation of ·OH from VUV photolysis of H2O (equations (4), (6) and (7)). (Ⅳ Ⅳ) removal of

359

NO by oxidation of O3/·O from VUV photolysis of O2 (equations (2), (3), (8), (9)); (Ⅴ Ⅴ) removal of NO by direct

360

photolysis of VUV to NO (equation (22)). In these removal routes, based on the contrast in NO removal efficiency

361

and the yield of active species (the share for NO removal efficiency in different removal systems can indirectly

362

represent the importance of the removal routes and active species), the NO removal by oxidation of ·OH from

363

VUV photolysis of H2O2 is the most important route. NO removal by oxidation of O3/·O from VUV photolysis of

364

O2 is the second important route. The other reaction routes above-mentioned only play a small role in NO

365

removal.



366

Because of very high solubility in H2O and good reactivity with H2O2, SO2 achieves complete removal in

367

most of removal systems. However, compared with SO2, NO is much more difficult to remove (it is also the focus

368

of pollutants removal in flue gas). To get a good removal efficiency for NO, an unmatched reactor and a relatively

369

large liquid-gas ratio was supplied to SO2. All of the above-mentioned removal routes may also occur in the

370

reaction system for SO2 removal, but now these factors make we be currently unable to sort their importance for

371

SO2 removal. The related works will be further implemented in the next works by re-designing a reaction system

372

which is suitable for SO2. The above related routes for NO and SO2 removals may be also represented by the

373

following schematic 7.

374

375 376

Figure 6. Comparison on NO and SO2 removal efficiencies in different removal systems: (a) NO removal and (b)

377

SO2 removal. Experimental conditions: VUV power, 36W; H2O2 concentration, 0.2mol/L; solution temperature,

378

318K; Solution pH, 3.96; O2 concentration, 6%; SO2 concentration, 4000mg/m3; NO concentration, 500mg/m3;

379

Liquid-gas ratio, 2.5.


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380 381 382

Figure 7. Reaction routes of NO and SO2 removals using VUV/O2/H2O/ H2O2 removal system 3.12 A preliminary discussion on future application of this technology

383

Emissions of SO2 and NOx from flue gas have been a major environmental concern because of their

384

hazardous effects on human health and ecosystems. To date, SO2 and NOx from coal-fired boilers are mainly

385

controlled by simultaneously installing flue gas desulfurization and denitrification equipments.4 Furthermore,

386

considering the potential requirement for mercury removal in the future (as the two largest economies, both

387

United States and China have already enacted laws to control the emission of mercury from coal-fired flue gas), if

388

coal-fired boilers, industrial furnaces and waste incinerations continue to add mercury removal system, most of

389

small and medium enterprises can not almost bear such a large economic burden. Recently, many results12,13 show

390

that simultaneous removal of NOx, SO2 and Hg0 in a reactor may effectively reduce the equipment space and

391

complexity of systems and save the investment and operating costs. Therefore, studying new technologies and

392

theories about simultaneous removal of NOx, SO2 and Hg0 in a reactor has become one of the hot issues in the area

393

of energy and environment.4

394

Based on our previous results about Hg0 removal using wet UV/H2O2 process24 and the present works,

395

simultaneous removal of Hg0, NO and SO2 using UV/H2O2 process may be feasible. The potential process flow is

396

described as follows (in Figure 8). Containing-SO2/NOx/Hg0 flue gas generated by Boiler, Furnace or Incinerator



397

1 enters Deduster 2 and Heat Exchanger 3 to remove dust and reduce flue gas temperature. Then

398

containing-SO2/NOx/Hg0 flue gas enters UV-Spraying Reactor 5 through Gas Distribution Nozzles 4 to initiate a

399

gas-liquid reaction with the oxidizing medium from Atomizing Nozzles 6. SO2, NOx and Hg0 can be oxidized to

400

H2SO4, HNO3 and Hg2+, respectively, by a series of oxidation reactions. The Hg2+ in mixed solutions can be

401

separated in Hg Separation Tower 11 by adding S2+. The S2+ can react with Hg2+ to produce HgS precipitation,

402

which can be recycled by simple precipitation separation. The remaining H2SO4 and HNO3 mixed solution can be

403

used to manufacture fertilizers, (NH4)2SO4 and NH4NO3, by adding NH3 in a NH3 Neutralizing Tower 12 with

404

evaporation and crystallization in Evaporating and Crystallizing Tower 13 using flue gas waste heat. The produced

405

water vapor will be condensed into water in Water Vapor Condensing Tower 14, and will be recycled by re-adding

406

to Reagent Addition Tower 15. The cleaned flue gas will be discharged into the atmosphere by chimney 16.

407

This removal process has several advantages as follows: (1) it can achieve the simultaneous removal of

408

multi-gaseous pollutants, including SO2, NOx and Hg0 from flue gas, in a reactor; (2) the reaction products can be

409

recycled by producing agricultural fertilizers, such as (NH4)2SO4 and NH4NO3 and industrial raw materials HgS;

410

(3) compared with the dry UV radiation removal process (the surface of quartz tubes is very easy to glue the

411

products and dust/dirt from flue gas, which will hinder the propagation of UV-light and damage the UV lamps),

412

the products and dust/dirt on the surface of quartz tubes of the wet removal process can be easily washed by

413

high-speed solution spraying, thereby being able to keep good propagation of UV-light and long-running of

414

photochemical system; (4) removal process has no secondary pollution, and even water can also be recycled; (5)

415

most of the devices, such as light source, spraying tower and product post-processing system, are very mature

416

products, which have been widely applied in water treatment and flue gas purification industries, and can be

417

almost applied directly on this new technology in the future.

418

According to the statistics,4,39 there are about more than 800000 widely used small and medium size


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419

coal-fired boilers, industrial furnaces and refuse incinerators only in China. It is very difficult for these

420

small/medium-scale burners to simultaneously install flue gas desulfurization, denitrification and mercury

421

removal equipments due to the huge costs.39 Therefore, although there are still a large number of engineering or

422

industrial amplification problems to be solved, this new removal process has a good prospect for simultaneous

423

removal of multi-pollutants (SO2, NOx and Hg0) from these small/medium-scale burners. In the next works, the

424

related engineering or industrial amplification problems for this removal process will be systematically studied.

425 426

1. Boiler, Furnace or Incinerator; 2. Deduster; 3. Heat Exchanger; 4. Gas Distributors; 5. UV-Spraying Reactor; 6. Atomizing Nozzles;

427

7. Defogger; 8. UV Lamps; 9. Quartz Tubes; 10. Circulation Pumps; 11. Hg Separation Tower; 12. NH3 Neutralizing Tower; 13.

428

Evaporating and Crystallizing Tower; 14. Water Vapor Condensing Tower; 15. Reagent Addition Tower; 16. Chimney.

Figure 8. Process flow of SO2/NOx/Hg0 simultaneous removal using a wet UV-spraying reactor.

429 430

Acknowledgements

431

This study was supported by National Natural Science Foundation of China (No.51576094; No.51206067),

432

and Training Project of Jiangsu University Youth Backbone Teacher.

433

References

434 435 436 437

(1)

Liu, Y.X.; Zhang, J.; Sheng, C.D. Simultaneous removal of NO and SO2 from coal-fired flue gas by UV/H2O2 advanced oxidation process. Chem. Eng. J. 2010,162,1006–1011.

(2)

Liu, Y.X.; Zhang, J.; Pan, J.F.; Tang, A.K. Investigation on the Removal of NO from SO2‑Containing Simulated Flue Gas by an Ultraviolet/Fenton-Like Reaction. Energy Fuels 2012, 26, 5430−5436.



438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481

(3)

Adewuyi, Y.G.; Owusu, S.O. Ultrasound-Induced Aqueous Removal of Nitric Oxide from Flue Gases: Effects of Sulfur

(4)

Liu, Y.X. Study on Integrated Desulfurization and Denitrification by UV/H2O2 Advanced Oxidation Process. Nanjing:

(5)

Wilde, J.D.; Marin, G.B. Investigation of simultaneous adsorption of SO2 and NOx on Na- γ -alumina with transient techniques.

Dioxide, Chloride, and Chemical Oxidant. J. Phys. Chem. A 2006, 110, 11098-11107.

Southeast University, 2010.

Catalysis Today 2000,62,319–328. (6)

Ding, J.; Zhong, Q.; Zhang, S.L. Catalytic efficiency of iron oxides in decomposition of H2O2 for simultaneous NOx and SO2

(7)

Obradović, B.M.; Sretenović, G.B.; Kuraica, M.M. A dual-use of DBD plasma for simultaneous NOx and SO2 removal from

removal: Effect of calcination temperature. J. Mol. Catal. A-Chem. 2014, 393, 222–231.

coal-combustion flue gas. J. Hazard. Mater. 2011,185,1280–1286. (8)

Ye, J.H.; Shang, J.; Li, Q.; Xu, W.W.; Liu, J.; Feng, X.; Zhu, T. The use of vacuum ultraviolet irradiation to oxidize SO2 and NOx for simultaneous desulfurization and denitrification. J. Hazard. Mater. 2014, 271, 89–97.

(9)

Cha, C.Y. Microwave induced reactions of SO2 and NOx decomposition in the char-bed. Research on Chemical Intermediates 1994,20,13–28.

(10)

Yoon, H.J.; Park, H.W.; Park, D.W. Simultaneous Oxidation and Absorption of NOx and SO2 in an Integrated O3 Oxidation/Wet Atomizing System. Energy Fuels DOI: 10.1021/acs.energyfuels.5b02924.

(11)

Liu, H.; Yu, X.X.; Yang, H.M. The integrated photocatalytic removal of SO2 and NO using Cu doped titanium dioxide supported by multi-walled carbon nanotubes. Chem. Eng. J. 2014,243,465–472.

(12)

Fang P, Cen CP, Wang XM, Tang ZJ, Tang ZX, Chen DS. Simultaneous removal of SO2, NO and Hg0 by wet scrubbing usingurea+ KMnO4 solution. Fuel Process. Technol. 2013;106:645–653.

(13)

Pillai, K.C.; Chung, S.J.; Raju, T.; Moon, IS. Experimental aspects of combined NOx and SO2 removal from flue-gas mixture in an integrated wet scrubber-electrochemical cell system. Chemosphere. 2009,5,657–664.

(14)

Long, X.L.; Xiao, W.D.; Yuan, W.K. Simultaneous absorption of NO and SO2 into hexamminecobalt(II)/iodide solution. Chemosphere 2005,59,811–817.

(15)

Zhao, Y.; Wen, X.Y.; Guo, T.X.; Zhou, J.H. Desulfurization and denitrogenation from flue gas using Fenton reagent. Fuel Process. Technol. 2014,128,54–60.

(16)

Adewuyi, Y.G, Sakyi, N.Y. Simultaneous Absorption and Oxidation of Nitric Oxide and Sulfur Dioxide by Aqueous Solutions of Sodium Persulfate Activated by Temperature. Ind. Eng. Chem. Res. 2013, 52,11702−11711.

(17)

Zhao, Y.; Zhao, L.; Han, J.; Xu, Y.Y.; Wang, S.Q. Study on method and mechanism for simultaneous desulfurization and denitrification of flue gas based on the TiO2 photocatalysis. Science in China Series E: Technol. Sci. 2008,3, 268–276.

(18)

Su, C.Y.; Xu, R.; Hu, J.L.; Shao, C.L. Photocatalytic Process of Simultaneous Desulfurization and Denitrification of Flue Gas by TiO2−Polyacrylonitrile Nanofibers. Environ. Sci. Technol. 2013, 47, 11562−11568.

(19)

Xia, D.H.; Hu, L.L.; He, C.; Pan, W.Q.; Yang, T.S. Simultaneous photocatalytic elimination of gaseous NO and SO2 in a BiOI/Al2O3-padded trickling scrubber under visible light. Chem. Eng. J. 2015, 279, 929–938.

(20)

Lasek, J.; Yu, Y. H.; Wu, J. C.S. Removal of NOx by photocatalytic processes. J. Photochem. Photobiolo. C: Photochem. Reviews 2013, 14, 29–52.

(21)

Tsuji, M.; Kawahara, T.; Kawahara, M.; Kamo, N.; Hishinuma, N. Photochemical removal of SO2 and CO2 by 172 nm Xe2

(22)

Tsuji, M.; Kawahara, M.; Kawahara, T.; Kamo, N.; Hishinuma, N. Photochemical removal of NO, NO2 and N2O by146 nm

and 146 nm Kr2 excimer lampin N2 or air atatmosphericpressure.Jap.J.Appl.Phys. 2008, 47, 8943–8949. Kr2 excimer lamp in N2 at atmospheric pressure, Bull.Chem.Soc.Jpn. 2009,82, 277–284. (23) Tsuji, M.; Kawahara, M.; Noda, K.; Senda, M.; Sako, H.; Kamob, N.; Kawahara, T.; Kamarudin, K. S. N. Photochemicalremoval of NO2 by using172-nm Xe2 excimer lamp in N2 or air atatmospheric pressure. J. Hazard. Mater. 2009, 162,1025–1033. (24)

Ye, J.H.; Shang, J.; Song, H.; Li, Q.;, Zhu, T. Generation of reactive oxygen species in simulated flue gas under vacuum


Page 24 of 26

Page 25 of 26

482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525


ultraviolet radiation. Chem. Eng. J. 2013,232,6–33. (25)

Liu, Y.X.; Zhang, J,; Sheng, C.D. Study on Kinetics of NO Removal from Simulated Flue Gas by Wet UV/H2O2 dvanced Oxidation Process. Energy Fuels 2011, 25, 1547–1552.

(26)

Liu, Y.X.; Pan, J, F.; Zhang, J.; Tang, A.K.; Liu, Y. Study on Mass Transfer-Reaction Kinetics of NO Removal from Flue Gas by Using UV/Fenton-Like Reaction. Ind. Eng. Chem. Res. 2012, 51, 12065−12072.

(27)

Jia, L.R.; Ko, D.V.; Anthony, E.J. Oxidation of Mercury under Ultraviolet (UV) Irradiation. Energy Fuels 2010, 24, 4351– 4356.

(28)

Granite, E. J.; Pennline, H.W. Photochemical Removal of Mercury from Flue Gas. Ind. Eng. Chem. Res. 2002, 41, 5470– 5476

(29)

Liu, Y.X.; Pan, J.F.; Wang, Q. Removal of Hg0 from Containing-SO2/NO Flue Gas by Ultraviolet/H2O2 Process in A Novel Photochemical Reactor. AIChE Joural 2014, 6, 2275–2285.

(30)

Owusu, S.O.; Adewuyi, Y.G. Sonochemical Removal of Nitric Oxide from Flue Gases. Ind. Eng. Chem. Res. 2006, 45, 4475− 4485.

(31)

Logager, T.; Sehested, K. Formation and decay of peroxynitrous acid: A pulse radiolysis study. J. Phys. Chem. 1993, 97,

(32)

Huie, R.E.; Neta, P. Rate constants for some oxidations of S(IV) by radicals in aqueous solutions. Atmos. Environ. 1987, 21,

6664–6669.

1743–1747. (33)

Lagrange, J.; Pallares, C.; Lagrange, P. Electrolyte effects on aqueous atmospheric oxidation of sulphur dioxide by ozone. J. Geophys. Res., D, Atmos. 1994, 99, 14595–14600.

(34)

Buxton, G.V.; Greenstock, C.L.; Helman, W.P.; Ross, A.B. Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (·OH/·O-) in aqueous solution. J. Phys. Chem. Ref. Data. 1988,17, 513– 886

(35)

Elliot, A.J.; Buxton, G.V. Temperature dependence of the reactions OH + O2- and OH + HO2 in water up to 200 °C. J. Chem. Soc., Faraday Trans. 1992, 88, 2465–2470.

(36)

Christensen, H.; Sehested, K. HO2 and O2- radicals at elevated temperatures. J. Phys. Chem. 1988, 92, 3007–3011.

(37)

Zhang, C. F. Gas-liquid reaction and reactor. Beijing: Chemical Industry Press 1985, 27–31.

(38)

Liu, Y.X.,; Wang, Q. Removal of Elemental Mercury from Flue Gas by Thermally Activated Ammonium Persulfate in A

(39)

Liu, Y.X.; Adewuyi. Y.G. A review on removal of elemental mercury from flue gas using advanced oxidation process:

Bubble Column Reactor. Environ. Sci. Technol. 2014, 48, 12181−12189.

Chemistry and process. Chem. Eng. Res. Des. 2016, 112, 199–250.



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Novel Process of Simultaneous Removal of Nitric Oxide and Sulfur

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