Simultaneous removal of NO and SO₂ by absorption into aqueous mixed solutions

Abstract

Currently, nitric oxide and sulfur dioxide emitted from stationary combustion facilities have been removed separately by selective catalytic reduction processes and wet scrubbing processes. There is no practical process successful for simultaneous removal of N O and SO2. Since scrubbing soiutions for wet NO removal also remove SO,, wet scrubbing processes are potential candidates for simultaneous NO and SO, removal. For instance, by use of liquid-phase reaction sequences in which both dissolved N O and SO, participate, simultaneous removal of both the gases can be achieved effectively in a single step or equipment. Aqueous solutions of Na,SO, with added Fe(I1)EDTA (ferrous ion coordinated to ethylenediaminetetraacetic acid) seem to be promising absorbents to fulfill such a possibility. To establish the procedure for inevitable regeneration or treatment of spent adsorbent, it is necessary to clarify the whole scheme of the liquid phase complicated reactions.In our previous work (Sada et al., 1984(Sada et al., , 1986, the pathways of the liquid-phase reactions were completed and presented in the form of a map. The degree of removal of NO was found to depend on the concentration of Fe(II), which was determined from a balance of oxidation and reduction rates of iron. The removal of N O during simultaneous absorption of NO and SO, could be predicted from corresponding experimental results for absorption of only NO into an absorbent of the same pH value. Regarding reaction kinetics, the reduction of Fe(II1) to Fe(I1) by HS03-with coexisting EDTA, the oxidation of Fe(1I) to Fe(II1) by N O in the presence of Na,SO,, and the oxidation of Fe(I1)EDTA by dissolved oxygen were investigated (Sada et al., 1986(Sada et al., , 1987.In view of the results of our earlier fundamental work cited above, there are two important considerations that emerge in the simultaneous N O and SO, removal process: 1. To keep the level of the concentration of Fe(I1) as high as possible and for this purpose, to reduce a portion of the effluent Correspondence concerning this paper should be addressed to E. Sada stream by sulfite a t the boiling temperature in the outer loop of the absorberThe former is required from the'experimental result that the degree of N O removal mainly depends on the concentration of Fe(I1). The latter is necessary because of the pH of the absorbent is decreased by simultaneously absorbed SO,.In the present work, the process flow diagram for simultaneous removal of N O and SO2 by absorption into an aqueous solution of Na,SO, with added Fe(I1)EDTA was first proposed on the basis of our earlier fundamental work. Secondly, to put this simultaneous removal process into practical application, long-term absorption tests and the regeneration of (simulated) spent liquor by reduction at its boiling temperature were undertaken.2. to control the pH of the absorvent. Background of Simltaneous NO and SO, Removal ProcessThe wet scrubbing method generally has a significant disadvantage of inevitable waste-liquor treatment, so that the proce...

Kinetic Study of Ambient-Temperature Reduction of FeIIIedta by Na2S2O4

“…9,12,[27][28][29][30][31][32][33][34] Hydrazine has also been shown to be an efficient compound for reduction of ferric ions within Fe III edta complexes. 35 However, the results of the abovementioned researches do not allow one to start the commercialization of this method presumably because of inevitable complicated and expensive treatment of spent absorption solutions.…”

Simultaneous absorption of carbon dioxide, sulfur dioxide and nitrogen dioxide into aqueous 2-amino-2-methy-1-propanol

“…Gas mixtures containing NO and SO 2 [16] or NO 2 and SO 2 [17] emitted from stationary combustion facilities, and H 2 S and SO 2 [18] from natural, coal, and refinery gases, have been separated by simultaneous absorption into aqueous slurries or alkaline solutions. Most of this work has been done towards determining the absorption mechanism and reaction kinetics in the simultaneous absorption of two gases, proposed by Goetter and Pigford [19] and Hikita et al [20].…”

Simultaneous absorption of carbon dioxide, sulfur dioxide, and nitrogen dioxide into aqueous 1, 8-diamino-p-menthane

“…Gas mixtures containing two gases such as NO and SO 2 [19] or NO 2 and SO 2 [20] emitted from stationary combustion facilities, and H 2 S and SO 2 [21] from natural, coal, and refinery gases, have been separated by simultaneous absorption into aqueous slurries or alkaline solutions. CO 2 and SO 2 were simultaneously separated using 2-amino-methyl-1-propanol (AMP) [22] and 1,8-diamino-p-menthane (DAM) [23] containing two amino functional groups as an absorbent of acid gas with a larger capacity than AMP, and CO 2 and NO 2 [24] using AMP.…”