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Plasma-catalysis SO2 oxidation in an air stream by a relativistic electron beam and corona discharge
Abstract
The results of theoretical and experimental investigations of SO2 oxidation in an air flow by a high current pulse electron beam and impulse corona discharge are presented in this work. It was shown that in non-equilibrium plasma and in a certain range of current density and humidity the energy cost of oxidation is significantly reduced to a value corresponding to the chain character of the process. These results were explained by realization of the ion-molecule chain SO2 oxidation mechanism and confirm the effect of non-equilibrium plasma catalytic activity in chemical reactions. It was shown that ion-molecular chain processes in droplet phase can also cause additional reduction of oxidation energy costs.
... It is useful to point out that one other example is known where the existence of a water droplet enhances the plasma chemical conversion. In the oxidation of SO 2 in a plasma reactor with a superimposed electron beam (to generate electrons and radicals in the liquid phase droplets formed from the sulfuric acid), [299] shows that the cyclic chain mechanism with oxygen enhances efficiency and leads to 0.8 eV per molecule. This work suggests that the presence of water droplets (formed in the sulfuric acid case or introduced in other cases) enhances gas-plasma production of condensable products. ...
... The answer to this shortcoming may be the inclusion of chemical reactions in the liquid phase, as happens in the atmosphere when acid rain is formed [25). This proces is also mentioned as a possibility to obtain higher cleaning efficiencies (upto a factor 101) [26]. ...
Some modern electron-beam based technologies and their use in industry and environmental protection are reviewed. Among the examples discussed is the treatment of wastewater of various origins (e.g. municipal, industrial and agricultural) and the removal of toxic SOx and NOx, from power plant flue gases, metallurgical plants etc. As these are relatively new industrial applications, three projects are described: the improvement of the quality and durability of cement, the pretreatment of wood chips in paper industry and the electron beam activation of oil and mazut cracking. Some important problems related to the construction of high power industrial electron accelerators are also discussed.
A new method based on microwave (MW) energy addition to accelerated electron beam (EB) energy for material processing was developed. In order to investigate this method, several specially designed facilities which permit separate, successive, and simultaneous MW and EB irradiation were carried out. These facilities as well as the associated MW and EB injection systems are described. In comparison with separate EB or MW irradiation, the simultaneous EB and MW irradiation of the acrylamide-acrylic acid aqueous solution leads to the highest molecular weight values simultaneously with the smallest Huggins' constant values. Also, the absorbed dose is reduced from 0.8 kGy in the separate EB irradiation case to 0.4 kGy in the simultaneous EB and MW irradiation applied to acrylamide-acrylic acid co-polymerization. Significant higher vulcanization degrees are obtained only for higher EB irradiation doses, especially in terms of the values of the 300% modulus and tensile strength. By using simultaneous EB and MW irradiation, compared to separate EB irradiation, the same maximum value of 300% modulus is obtained for EB absorbed dose and irradiation time of 2.5 times lower at 60-W MW power and five times lower at 100-W MW power. Also, the same maximum value of tensile strength is obtained for EB absorbed dose and irradiation time of four times lower at 60-W MW power and 5.33 times lower at 100-W MW power. The combined EB and MW irradiation applied to the SO2 and NOx removal from the simulated flue gases demonstrated that for the same removal efficiency of 98% for SO2 and 76% for NOx at separate EB irradiation of 40 kGy, the required absorbed dose is about two times smaller for simultaneous EB and MW irradiation.
The relationship is examined between three important middle UV auroral emissions, the electron energy spectrum, and the neutral atmosphere. Calculated emission rates are displayed for the Vegard-Kaplan and second positive band systems of N2 and the OI (1S greater than 3P) 2972-angstrom line. All three features are proportional to the incoming energy flux, but they have different dependences on the characteristic energy of the incident electron spectrum and on the concentration of atomic oxygen. In principle, observations of the intensities of these features could be used to characterize the incident electron spectrum, but uncertainties in the chemistry of certain states of oxygen and nitrogen make this difficult. The uncertainties are discussed along with alternative far UV features (such as OI 1356 angstroms and 1304 angstroms and the N2 Lyman-Birge-Hopfield bands.
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.
For the purpose of elucidation of radiation chemical reactions of Nox and SO2 removals in irradiation of flue gas, the reactions of NOx and SO2 were studied under irradiation with electron beams in various systems ranging from a simple system (NO-nitrogen) to the complex (NO-SO2-water vapour-oxygen-nitrogen) which was close to the composition of an flue gas. Reaction mechanisms of NOx and SO2 were changed markedly by oxygen and water vapour. In nitrogen, NO was decomposed to oxygen and nitrogenthrough reactions with N atom and NO2 was also decomposed to NO, dinitrogen oxide, oxygen and nitrogen. The decompositions were retarded markedly in the presence of oxygen, and an oxidation of NO and a reduction of NO2 became predominant reactions. In the moist mixture of oxygen and nitrogen, fast oxidation of NO took place through the reactions with O, OH and HO2 radicals, leading to the formation of NO2, followed by oxidation of NO2 to produce HNO3. The SO2 was also oxidized to H2SO4 through the reactions with O and OH radicals in the moist mixture. An addition of ammonia enhanced markedly the NOx and SO2 removals in the moist mixture. Reactions of NO and SO2 with NH2 radical took place in irradiation of the moist mixture containing ammonia in addition to the oxidations of No and NO2. The HNO3 and H2SO4 produced through the oxidations were converted to solid NH4NO3 and (NH4)2SO4 and some parts of SO2 itself reacted with ammonia, leading to the SO2 removal.
The process by which sulphur dioxide is oxidised in atmospheric droplets has been studied in laboratory experiments designed to collect a large amount of chemical data pertinent to the atmospheric situation. Thus the oxidation of sodium sulphite solutions by oxygen, ozone and hydrogen peroxide has been studied at different pH's and temperatures. In all cases the reaction is first order with respect to sulphite ion but the order with respect to oxidant differs. For oxygen the order is zero whereas the order for ozone and hydrogen peroxide is one. Varying the hydrogen ion concentration has little effect on the oxygen reaction rate between pH 6 and 9; the ozone reaction rate is inversely proportional to the square root of the hydrogen ion concentration and the hydrogen peroxide rate is almost directly proportional to the hydrogen ion concentration. These last two observations are very important since in the case of ozone it indicates that the reaction proceeds via a free radical mechanism involving hydroxyl radicals and in the case of hydrogen peroxide it is the only oxidation process of sodium sulphite so far investigated that shows a positive response to the presence of hydrogen ions.
Maтeмaтичecкoe мoдeлиpoвaниe кaтaлитичecкoгo oкиcлeния SO2 пoд дeйcтвиeм пyчкa peлятивиcтcкиx элeктpoнoв
- Potapkin
- Backstrom