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Investigation of SO2 Oxidation in Humid Air Stream by High Current Density Pulsed Electron Beam
Abstract
The electron beam and impulse corona discharge technology of air flow purification from SO2 and NOx are investigated now in many countries (Leonhardt et al. 1984; Svedchikov et al. 1988; Tokunaga et al. 1981; Baranchicov et al. 1990). One of the main problems considerably influenced on a perspective of practical using of this method is the reduction of oxidation energy cost. In this work it is shown that the energy cost weakly depends on current density j, if j < 10-4 A/cm2 and equals 10 eV/molecule. In this case, for example, it is necessary to use one hundred twenty 100-kW accelerators for gas stream (0.1% SO2) purification of a 300 MW electric power plant. That is why the realization of this project is very difficult for this energy cost of purification. This paper is dedicated to a new chain gas-cluster oxidation mechanism with theoretical investigation of this one realization. The results of experiments realized for the verification of this mechanism are presented here. The role of droplet-phase effect there are also presented.
... First, this is connected with a well-known, from environmental chemistry, liquid-phase chain mechanism and secondly with a specially proposed ionic chain oxidation mechanism in a cluster. The phenomena were discussed by Baranchicov et al. [27], ...
Emission of gaseous pollutants, mostly during combustion of fossile fuels, creates a threat to
the environment.New, economical technologies are needed for flue gas treatment. A physico-chemical basis of the process using electron beam for the simultaneous removal of nitrogen and sulfur oxidesand volatile organic compounds are presented in this report. Development of the process and itsupscaling has been discussed.
... First, this is connected with a well-known, from environmental chemistry, liquid-phase chain mechanism and secondly with a specially proposed ionic chain oxidation mechanism in a cluster. The phenomena were discussed by Baranchicov et al. [27], ...
A review of Authors' works covering the description of the com. installation designed and constructed for electron beam purification of flue gases, the chemical reactions involved, and the reactor design and operation intended to remove simultaneously SO2 and NOx from the flue gases.
... First, this is connected with a well-known, from environmental chemistry, liquid-phase chain mechanism and secondly with a specially proposed ionic chain oxidation mechanism in a cluster. The phenomena were discussed by Baranchicov et al. [27], ...
Summary form only given, as follows. High energy electrons create thousands of ions and free radicals along their path. In consequence radiolytical processes take place that with usage of additional reactants at proper physical gas conditions may lead to new air pollution control technologies. Three examples are discussed: SO2 and NOx removal (combustion flue gases); volatile organic compounds removal (industrial off-gases and vapor from ground water stripping); SO2 high concentration flue gas treatment (copper industry off-gases). The experimental tests, depending on the subject has been performed at two different units. One is an industrial pilot plant constructed in an electropower station on a coal fired boiler, with gas flow up to 20,000 cNmph, equipped in two electron accelerators, 50 kW power and 800 keV each. The second is a laboratory installation with the flow up to 400 cNmph, in this case flue gases are produced by two gas fired boilers and research setup is furnished in an accelerator of 20 kW beam power and electrons energy up to 2 MeV. The results of the tests performed at laboratory and industrial pilot plant are discussed. On this basis technical and economical evaluation of full size industrial installation has been prepared
A flow process with electron beam (EB) irradiation carried out the removal of NO in air by adding microwave (MW) to improve the removal efficiency of NO. The EB irradiation combined with MW irradiation was very effective in the range of NO removal efficiency of 70–80% and reduced required doses up to more than 30%, compared to the flow process without MW. On the other hand, MW irradiation was unlikely to affect the NO removal above 90% of removal efficiency. In addition, MW effect appeared definitely in the dose ranges of 8–24 kGy, whereas the effect became minor below 8 kGy and above 24 kGy. This study found that MW irradiation can play an auxiliary role in NO removal with EB irradiation and the effect of MW on the NO removal is based on an intrinsic kinetic to the exclusion of a thermal effect. The concentrations of removed NO could be linearly correlated as ΔC=k[NO]o+ko. Where, k was proportional to dose and ko could be related to ko/Dn=aD+b, giving n value of 0.7 without MW irradiation and 0.4 with MW irradiation, respectively.
Many authors have investigated simultaneous reduction of SO2 and NOx from flue gas stack emissions. Because of his high costs, this technology has been applied only in few countries (Japan, China, and Poland). Small countries, consumers of cheap combustibles, produce a great deal of atmospheric pollutants: SO2 and NOx. For this reason there is a great interest for implementation of cheaper technologies, with same impact as electron beams processing has. The paper presents a series of experimental data for SO2 and NOx removal of flue gas by electron beams, electric discharge. It also presents an economic study for an installation of simultaneous SO2 and NOx removal pilot plant at a 550 MWe power plant (CET-SOUTH-Bucharest), with an electron beam device and processing capacity of about 10,000 Nm3/h and 106 Nm3/h, respectively.
The biggest source of air pollution is the combustion of fossil fuels, where pollutants such as particulate, sulfur dioxide (SO2), nitrogenoxides (NOx), and volatile organic compounds (VOC) are emitted. Among these pollutants, sulfur dioxide plays the main role in acidification of the environment. The mechanism of sulfur dioxide transformation in the environment is partly photochemical. This is not direct photooxidation, however, but oxidation through formed radicals. Heterogenic reactions play an important role in this transformation as well; therefore, observations from environmental chemistry can be used in air pollution control engineering. One of the most promising technologies for desulfurization of the flue gases (and simultaneous denitrification) is radiation technology with an electron accelerator application. Contrary to the nitrogen oxides (NOx) removal process, which is based on pure radiation-induced reactions, sulfur dioxide removal depends on two pathways: a thermochemical reaction in the presence of ammonia/water vapor and a radiation set of radiochemical reactions. The mechanisms of these reactions and the consequent technological parameters of the process are discussed in this paper. The industrial application of this radiation technology is being implemented in an industrial pilot plant operated by INCT at EPS Kaweczyn. A full-scale industrial plant is currently in operation in China, and two others are under development in Japan and Poland.
Diesel-flue-gas treatment has been demonstrated by using an intense, pulsed relativistic electron beam (IREB). A flue gas treatment chamber, 1.6-m isolated from the IREB source, is filled up with the diesel flue gas with the pressure of 200 kPa, and is irradiated by IREB (2 MV, 0.12 kA, 65 ns (FWHM)). The maximum kinetic energy of IREB injected into the gas chamber is experimentally estimated to be -0.23 MeV. When the diesel flue gas is irradiated by firing 10 shots of the IREB, the concentration of NOx, SO2, and CO are decreased from 75, 14, and 770 ppm to 5, 11, and 690 ppm, respectively. It is found that - 93 % of NOx is removed by firing 10 shots of the IREB irradiation. We have obtained the energy efficiency of NOx removal of 256 g/kWh.
A flow process with electron beam (EB) irradiation carried out the removal of NO in air by adding microwave (MW) to improve the removal efficiency of NO. The EB irradiation combined with MW irradiation was very effective in the range of NO removal efficiency of 70–80% and reduced required doses up to more than 30%, compared to the flow process without MW. On the other hand, MW irradiation was unlikely to affect the NO removal above 90% of removal efficiency. In addition, MW effect appeared definitely in the dose ranges of 8–24 kGy, whereas the effect became minor below 8 kGy and above 24 kGy. This study found that MW irradiation can play an auxiliary role in NO removal with EB irradiation and the effect of MW on the NO removal is based on an intrinsic kinetic to the exclusion of a thermal effect. The concentrations of removed NO could be linearly correlated as ΔC=k[NO]o
+ko
. Where, k was proportional to dose and ko could be related to ko
/Dn
=aD+b, giving n value of 0.7 without MW irradiation and 0.4 with MW irradiation, respectively.
The results of calculation showed that SO2 oxidation in irradiated humid air can be intensified by electrical field application (E/n= 10−15) due to chain reaction which takes a place in such conditions.
This review addresses the production of nano-particles and the processing of particles injected in atmospheric pressure electrical discharges (APED). The mechanisms of formation and the evolution of particles suspended in gases are first presented, with numerical and experimental facilities. Different APED and related properties are then introduced for dc corona, streamer and spark filamentary discharges (FD), as well as for ac filamentary and homogeneous dielectric barrier discharges (DBD). Two mechanisms of particle production are depicted in APED: when FD interact with the surface of electrodes or dielectrics and when filamentary and homogeneous DBD induce reactions with gaseous precursors in volume. In both cases, condensable gaseous species are produced, leading to nano-sized particles by physical and chemical routes of nucleation. The evolution of the so-formed nano-particles, i.e. the growth by coagulation/condensation, the charging and the collection are detailed for each APED, with respect to fine powders production and thin films deposition. Finally, when particles are injected in APED, they undergo interfacial processes. Non-thermal plasmas charge particles for electro-collection and trigger heterogeneous chemical reactions for organic and inorganic films deposition. Heat exchanges in thermal plasmas enable powder purification, shaping, melting for hard coatings and fine powders production by reactive evaporation.
Present-day applications of ionizing radiation to environmental protection are surveyed. This part of the review summarizes
new data on the radiation treatment of sewage sludge and on the radiation-chemical purification of gaseous and solid systems.
A method of simultaneously removing sulfur dioxide and nitrogen oxides from high sulfur, coal-fired utility boiler combustion gases is discussed. Process development history is briefly presented and salient details of a commercial demonstration unit currently under construction at an electric utility power plant in Indiana are given. Detailed discussion on the design details and performance requirements of a cable connected set of 80 kW electron beam sources precedes a discussion of the projected economics of the process. Requirements for future electron beam machine configurations and capacities as well as impact on the radiation machine manufacturing industry, assuming acceptance of the process by the electric utilities, are presented.
A flowing afterglow system has been used to measure 296°K reaction rate constants and equilibrium constants for a number of negative ion reactions with atmospheric constituents. Three‐body association reactions of O−, OH−, O2−, O3−, Cl−, CO3−, OH−(H2O), and O2−(H2O) with H2O have been measured and association rate constants for several ions with CO2 and SO2 have been measured. A number of binary reactions for these ions and their hydrates have been measured with H2O, CO2, SO2, NO2, O3, and NO. Some equilibrium constants for negative ion hydration and some equilibrium constants for solvent (H2O, CO2, and SO2) exchange to several negative ions are reported.
Electrons penetrating gas create /nhonugeneous dose distributions by their interaction with gas
molecules. This behaviour becomes more pronounced for decreasing electrons energies. Thus, according
to dose rate measurements for electrons from 300 kV scanners, dose rates up to 150 Mrad/sec
may occur.
A computer model of the homogeneous gas phase reactions of the electron beam dry scrubbing (EBDS)
process has been developped. The model is capable of handling dose distributions which involve
high dose rates. This is accomplished by a modulation of the dose rate between zero and a preset
maximum, while keeping the total applied dose constant. Extensions of this model allow the treatment
of 3-dlmensional dose distributicms.
The calculations show that radical concentrations are correlated both to dose and dose rate. With
increased dose, more NO
The application of radiation effects in SO2-containing gases for pollution control and SO2-removal from exhaust gases is discussed. Some new prospects to improve the energetical yields of the radiation induced SO2-oxidation by electrical fields are reported.
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Plasma-catalysis SO2 oxidation in air
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