Experimental study on Fe II Cit enhanced absorption of NO in (NH 4 ) 2 SO 3 solution

Study on NO Removal Characteristics of the Fe(II)EDTA and Fe(II)PBTCA Composite System

Fe²⁺ complexation wet denitrification technology has become a research hotspot. It is very important to achieve efficient regeneration of the absorbent and increase NO absorption in the Fe²⁺ complexation system. They are the key to the industrial application of the Fe²⁺ complexation absorption process. In this paper, 2-phosphonate-butane-1,2,4-tricarboxylic acid and ethylenediamine tetraacetic acid were used as ligands to prepare a composite system for the first time. The characteristics of NO removal were investigated under different temperatures, pHs, Fe²⁺ concentrations, O₂ contents, NO concentrations, CO₂ contents, and SO₂ concentrations. Compared with the single ligand, the results show that the denitrification performance of the solution with a complex ligand is significantly improved. In this system, pH 9, 40 °C temperature, and 20 mmol/L Fe²⁺ concentration are the economic ideal conditions for NO removal. The system can realize simultaneous removal of NO and SO₂, but SO₂ in flue gas has a dual effect on the NO removal reaction.

Highly efficient absorption of nitric oxide by RuIII(edta) aqueous solutions at low concentrations

In this paper, Ru^III(edta) was used as a highly efficient absorbent for the removal of NO due to its desirable properties of high NO affinity and oxygen insensitivity. The effects of the Ru^III(edta) concentration, reaction temperature, initial solution pH, oxygen concentration, inlet NO concentration, and liquid-to-gas ratio on denitration performance were examined. The results indicated that Ru^III(edta) showed excellent denitration performance at low concentrations and that an increase in the concentration of Ru^III(edta) resulted in an increase in NO removal efficiency. In addition, NO removal efficiency increased to its optimum value at first and then declined as both the reaction temperature and initial solution pH rose. The optimal reaction temperature and ideal initial solution pH were determined to be 45°C and 5.0 respectively. The suitable liquid-to-gas ratio was found to be 51.5 L/m³. NO removal efficiency was less affected by the oxygen concentration in the range of 0-12% due to a superior anti-oxidation performance at pH = 5.0. Furthermore, the NO removal efficiency decreased significantly as the inlet NO concentration increased. The addition of 5 wt% urea to an aqueous solution of Ru^III(edta) enhanced denitration performance, and an Ru^III(edta) and urea mixed solution were able to exceed 65.07% NO removal efficiency within 30 min under optimal experimental conditions. This work proposed an alternative absorbent for NO removal and provided fundamental data for industrial denitration with Ru^III(edta) absorbents.

A novel method of pH-buffered NaClO2-NaCl system for NO removal from marine diesel engine

Marine diesel engines produce a lot of exhaust gas (NO, SO₂). Based on the situation that wet scrubbing methods have been already applied to ship desulfurization and seawater is easily accessible around the ships, this paper proposed a novel AOP (advanced oxidation process) of NaClO₂ (sodium chlorite) with Cl^- (abundant Cl^- exist in seawater) to remove NO from the flue gases of marine engines. The buffer capacity of NaAC (sodium acetate), the effect of Cl^- concentration, and Cl^- promotion mechanism on NO removal were investigated. The result showed that the existence of NaAC in solution could inhibit the rapid decline of the solution pH. The addition of Cl^- achieved a remarkable promotion to NO removal at lower NaClO₂ concentration, which was due to the fast generation of ClO₂ from the promotion decomposition of NaClO₂ by Cl^- in acidic condition. Then, the thermodynamic and dynamic mechanism of the generation of ClO₂ was intensively analyzed. And the mechanism of NO removal was discussed finally.

Simultaneous removal of SO2 and NO by FeII(EDTA) solution: promotion of Mn powder and mechanism of reduction

The effect of Mn powder addition on the simultaneous removal of SO₂ and NO coupled with Fe^II(EDTA) absorption was investigated in this work. In the NO absorption system with Fe^II(EDTA), SO₂ reduced Fe^II(EDTA)-NO to Fe^II(EDTA) with a reduction efficiency reaching 88.5% under the conditions of 4000 mg/m³ SO₂, pH 8.0, 44 °C, and the flow rate of 1.2 L/min within 60 min. Introducing 0.1 M Mn powder with SO₂ increased the Fe^II(EDTA)-NO reduction efficiency to 96.8% within 5 min. SO₂ was also removed by reducing Fe^II(EDTA)-NO and converted into SO₄^2- at a removal efficiency of 100%. After adding Mn powder, NO was removed through the following reaction: [Formula: see text]. Mn powder functioned as a reductant to regenerate the absorption of solution, and the coordinated NO in Fe^II(EDTA)-NO was reduced to NH₄⁺. The resource utilization rate of N reached approximately 77.2%. The integrated technology is a potential solution for flue gas treatment in industrial sectors with coal-fired power plants and industrial boiler. Graphical abstract.

Promoting Effect of H+ and Other Factors on NO Removal by Using Acidic NaClO2 Solution

In this study, NaClO2 was selected as a denitration oxidant. In order to clarify the mechanism of NaClO2 as an oxidation agent for NO removal efficiency, the effects of H+ and other factors (NaClO2 concentration, temperature, and the other gas) on the NO removal efficiency were investigated. NaClO2 showed a promotional ability on NO removal, whose efficiency increased with the increase of NaClO2 concentration. One hundred percent removal efficiency of NO could be achieved when the NaClO2 concentration was 0.014 mol/L. Furthermore, raising the reaction temperature benefited the removal of NO. The lower the pH, the better the NO removal efficiency. The promoting effect of H+ on the NO removal was studied by the Nernst equation, ionic polarization, and the generation of ClO2. Under the optimal conditions, the best removal efficiency of NO was 100%. Based on the experimental results, the reaction mechanism was finally speculated.

Nitric oxide removal by combined urea and FeIIEDTA reaction systems

(NH₂)₂CO as well as Fe^IIEDTA is an absorbent for simultaneous desulfurization and denitrification. However, they have their own drawbacks, like the oxidation of Fe^IIEDTA and the low solubility of NO in urea solution. To overcome these defects, A mixed absorbent containing both (NH₂)₂CO and Fe^IIEDTA was employed. The effects of various operating parameters (urea and Fe^IIEDTA concentration, temperature, inlet oxygen concentration, pH value) on NO removal were examined in the packed tower. The results indicated that the NO removal efficiency increased with the decrease of oxygen concentration as well as the increase of Fe^IIEDTA concentration. The NO removal efficiency had little change with a range of 25-45 °C, and sharply decreased at the temperature of above 55 °C. The NO removal efficiency initially increases up to the maximum value and then decreases with the increase of pH value as well as the raise of urea concentration. In addition, the synergistic mechanism of (NH₂)₂CO and Fe^IIEDTA on NO removal was investigated. Results showed that urea could react with Fe^IIEDTA-NO to produce Fe^IIEDTA, N₂, and CO₂, and hinder oxidation of Fe^IIEDTA. Finally, to evaluate the effect of SO₃^2- on NO removal, a mixed absorbent containing Fe^IIEDTA, urea, and Na₂SO₃ was employed to absorb NO. The mixed absorbent could maintain more than 78% for 80 min at 25 °C, pH = 7.0, (NH₂)₂CO concentration of 5 wt%, Fe^IIEDTA concentration of 0.02 M, O₂ concentration of 7% (v/v), and Na₂SO₃ concentration of 0.2 M.

An investigation on NO removal by wet scrubbing using NaClO2 seawater solution

The experiments were conducted to investigate the NO removal by wet scrubbing using NaClO2 seawater solution in a cyclic scrubbing mode. Results show that, when the concentration of NaClO2 in scrubbing solution is higher than 10 mM, a complete removal of NO can be achieved during the cyclic scrubbing process. The breakthrough time for seawater with 15 mM NaClO2 is enhanced by 34.3 % compared with that for NaClO2 freshwater. The extension of the breakthrough time for NaClO2 seawater is mainly ascribed to the improved utilization of NaClO2 in the solution. The good buffering ability of seawater could suppress the acidic decomposition of NaClO2 into ClO2 effectively. The analysis of reaction products indicates that the main anions in the spent liquor are chloride ions and nitrate ions. The calculation of NaClO2 utilization according to the ion chromatography also agrees well with the experimental results of breakthrough times.

Kinetics of FeIIIEDTA complex reduction with iron powder under aerobic conditions

The kinetic model of Fe^IIIEDTA complex reduction with iron powder under aerobic condition is deduced and validated. It was .