Wet Flue Gas Desulfurization Process Research Articles

Investigation of iron oxide supported on activated coke for catalytic reduction of sulfur dioxide by carbon monoxide

In view of the low utilization rate of by-product in limestone-gypsum wet flue gas desulfurization process, a method of catalytic reduction of SO2 to elemental sulfur was proposed. In this work, supported iron catalyst using activated coke as supporter was prepared and characterized. Moreover, the performance of SO2 reduction using CO as reducing agent at various Fe loadings, temperatures, gaseous hourly space velocities and CO/SO2 molar ratios was studied. Research shows that, compared with other metals, the highest catalytic activity is achieved over Fe-based catalyst. The iron sulfide is the main active component during the catalytic reduction reaction, hence the catalyst needs to be presulfided before use. The micropores of activated coke become more abundant after loading Fe, whereas excessive increase of Fe loading may bloke the mesopores and weaken the catalytic activity. Higher reaction temperature, lower GHSV and a stoichiometric molar ratio are conducive to the improvement of SO2 conversion and S yield. The catalytic performance at lower temperatures was further improved by loading Co. When the Co loading is 4 wt%, the SO2 conversion rate reaches 90.9% at 400 °C because loading Co enhances the redox performance of the catalyst surface. The findings are instructive for the development of cost-effective carbon-based catalysts for resource recovery of sulfur.

ZIF-67-derived Co@NC as an efficient catalyst for magnesium sulfite oxidation in the flue gas desulfurization process

Magnesium desulfurization is a wet flue gas desulfurization (WFGD) technology widely used in China, however, the low oxidation rate of magnesium sulfite (MgSO3), a byproduct of WFGD, causes the subsequent oxidation and crystallization process to require amount energy. Here, we prepared a cobalt-based nitrogen-doped porous carbon catalyst (Co@NC) using ZIF-67 as a precursor for the efficient catalytic oxidation of MgSO3 generated during magnesium desulfurization. The performance of Co@NC catalysts obtained at an optimal calcination temperature of 650 °C showed that the catalysts with oxidation rates up to 0.1332 mmol·L−1·s−1 of MgSO3 were considerably better than those previously studied, which outperformed the catalysts described in earlier research by a considerable margin. Further studies revealed that the Co@NC’s exceptional catalytic activity was attributed to both its special porous structure and the exposed active Co sites in the organic skeleton. The uniformly dispersed Co species act as the active sites of the Co@NC that can be fully contacted with the reactant. The presence of 0.5 g·L−1 Co@NC increases the MgSO3 oxidation rate by about 14 times compared to the noncatalytic benchmark. A practical tactic is furnished by this research for energy saving and emission reduction in the WFGD process, especially for the efficient oxidation and resource conversion of the by-product MgSO3.

Formation and migration of soluble ions in condensable particulate matter in limestone-gypsum wet flue gas desulfurization system

In this work, the emission characteristics of condensable particulate matter (CPM) and soluble ions in the inorganic components after wet flue gas desulfurization (WFGD) were investigated by adjusting the operating parameters of the limestone-gypsum WFGD system. Using a combination of US Method 202 and US EPA Method 5 as the primary measurement method, the study is an experimental study and analysis of the properties of CPM emitted from a limestone-gypsum WFGD system. Based on the measurement results, the influence of some important WFGD operating parameters on CPM emissions was evaluated. The results showed that CPM accounts for 84% of total particulate matter (TPM) emissions in desulfurized flue gas. The composition of CPM is primarily inorganic, comprising 96% of the components, with only a small portion being organic at 4%. The CPM that condensed to a solid state was generally less than 1 μm in diameter and mostly came from WFGD process. The analysis of soluble ions showed that Ca2+ and SO42- were the main ionic components in CPM. By adjusting the desulfurization operating parameters (inlet flue gas temperature, desulfurization solution temperature, desulfurization solution concentration), the concentration of soluble ions can be reduced to different degrees, so as to achieve the purpose of reducing CPM emission. This demonstrated that the CPM emission problem of limestone-gypsum WFGD system could be relieved by operating parameter optimization.

Data‐based learning control for optimization of nonlinear systems

Data‐based learning control for optimization of nonlinear systems

Investigation on SO3/sulfuric acid mist conversion in WFGD process

SO3 and sulfuric acid mist generated in coal-fired boilers and wet flue gas desulfurization (WFGD) processes can adversely affect boiler facilities, while detection and absorption is an important issue. Factors affecting the conversion of SO3 to sulfuric acid mist (SO3/sulfuric acid mist) during wet desulfurization were studied and evaluated in a simulated experimental system, including the effects of flue gas composition, temperature and humidity on the SO3/sulfuric acid mist conversion rate. The certain concentrations of SO3, water vapor, SO2, NO, NH3, O2 and N2 were mixed thoroughly to simulate the flue gas of WFGD under the special temperature conditions in this experiment. The sulfuric acid droplets, sulfuric acid vapor and sulfuric acid aerosol in the simulated flue gas were absorbed and intercepted by NaCl and quartz wool, gaseous SO3 was absorbed by isopropanol solution, and thorium-barium titration method was used to measure SO42− concentration. The results showed that the increase of temperature significantly decreased the SO3/sulfuric acid mist conversion rate, the increase of humidity significantly increased the SO3/sulfuric acid mist conversion rate, and O2 concentration had little effect on the SO3/sulfuric acid mist conversion rate. In addition, the increase concentration of NH3, NO and SO2 also improved the conversion rate of SO3/sulfuric acid mist to some extent.

Utilization of steel slag as a highly efficient absorbent for SO2 removal at coal-fired power stations

• Steel slag was tried in wet flue gas desulfurization using a bubbling-bed reactor. • Kinetics of SO 2 absorption in steel slag slurry was studied. • The maximum SO 2 absorption capacity of the steel slag is 0.68g/g. • The Mn 4+ , Fe 3+ and Mg 2+ in steel slag promote the oxidation of SO 2 into SO 4 2− . • Mechanism of SO 2 absorption in steel slag slurry was also revealed. In this study, steel slag, a waste generated from steelmaking processes, was used as an absorbent for the removal of SO 2 in coal-fired flue gas. The results showed that SO 2 could be removed completely in the bubbling-bed reactor by the steel slag slurry under certain operating conditions. Effort was then made to study the kinetics of SO 2 absorption in steel slag slurry. It is found that the gas-liquid absorption model fits well with the experimental data and can be used to predict the SO 2 absorption process. Results also demonstrated that the maximum SO 2 uptake capacity of steel slag reaches 0.68 g, which is about 36 wt% higher than that of the traditional limestone-gypsum desulfurization process under similar conditions, while the SO 2 breakthrough time reaches the maximum of 951 min under a flow rate of 420 mL/min, an initial SO 2 concentration of 700 ppm, and a solid-liquid ratio of 1.5 g/100 mL. Moreover, it was found that SO 4 2− , was the main anions detected in the liquid phase after desulphurization and the pH of the solution decreased from 12.9 to 3.2. This study proved that steel slag is of the potential to replace limestone in the wet flue gas desulfurization process, which contributes to the mitigation of global CO 2 emissions and solves environmental problems associated with the disposal of steel slag.

Model‐free adaptive control based on switching mechanism for multi‐input multi‐output wet flue gas desulfurization system

SummaryThe wet flue gas desulfurization (WFGD) process is a complex controlled system with nonlinear and time‐varying characteristics. There are a variety of external disturbances in the desulfurization process, which can easily cause a jump in system parameters and even structure. In response to this problem, a model‐free adaptive control scheme based on a switching mechanism is proposed, and the convergence analysis is given. In the scheme, firstly, the operating conditions of the WFGD system are divided into n kinds based on multiple external disturbances, and the mathematical models of the multi‐input multi‐output WFGD system under different operating conditions are established. Then the MFA controllers of the WFGD system under multiple operating conditions are established, respectively. Finally, a switching index function is designed to switch the controller of the WFGD system according to different operating conditions, so that the desulfurization system is always controlled by the most appropriate controller. In the simulation experiment, according to the actual data of the WFGD system of a 1000 MW coal‐fired power station in Beijing, the modeling test and algorithm simulation of the WFGD system under three operating conditions are carried out. The simulation results show that this method can effectively reduce the transient error of the WFGD system output and improve the desulfurization effect.

Catalytic Oxidation and Desulfurization of Calcium-Hydroxide Gypsum Wet Flue Gas Using Modified MIL-53(Fe)

MIL-53(Fe) was prepared and modified with benzoic acid to prepare MIL-53(Fe)-BA additive, which was used to improve the catalytic oxidation rate of sulfite, prevent the scaling of the desulfurization tower, and improve the desulfurization efficiency during the wet flue gas desulfurization (WFGD) process of power plants. MIL-53(Fe)-BA exhibits abundant Lewis acid sites because of the appearance of coordination unsaturated Fe atoms. Due to the excellent sorption capacity, Ca(OH)2 was used as the main SO2 desulfurizer. The composite desulfurizers were prepared by mixing MIL-53(Fe)-based additives and Ca(OH)2, and were characterized by SEM, XRD, and FT-IR. A desulfurization unit was set up at laboratory scale to study the effect of catalytic oxidation additives on sulfite oxidation and desulfurization efficiency. The results showed that the addition of MIL-53(Fe)-BA can increase the oxidation capacity of sulfite by 159%, and greatly improve the desulfurization efficiency. These composite desulfurizers broaden the adaptability of the desulfurizing system to high-sulfur coals, and provide support for improving the desulfurizing efficiency of power plants.

Enhancement of citric acid on low-grade limestone wet desulfurization performance coupled with spray and partial bubble technology

Developing low-grade limestone as absorbents has been recognized as a prerequisite for industrial application of wet flue gas desulfurization (WFGD) due to the serious depletion of high-grade limestone for SO2 capture. In this research, citric acid was utilized as additive in order to improve the SO2 removal efficiency of low-grade limestone. The enhancement of citric acid on desulfurization performance and the effects of citric acid concentration were investigated based on the spray and partial bubble technology. The results show that the addition of citric acid into low-grade limestone slurry can significantly improve the desulfurization efficiency and the optimal blending ratio between citric acid and low-grade limestone was 1:5. The spent absorbents and reacted liquid phase products were analyzed by X-Ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ion chromatography (IC) and inductively coupled plasma luminescence spectrometry (ICP-OES). These characterizations illustrated that the oxidation of SO32− into SO42− ions along with formation of gypsum was inhibited in the presence of citric acid because of its strong reducibility, whereas the reaction between SO2 and SO32− was greatly promoted, leading to the high SO2 removal efficiency. Furthermore, molecular dynamics (MD) calculation was conducted to provide the microscopic information including the self-diffusion and hydration behavior of SO2 and the gas-liquid interface microstructure. These investigations are of significant importance in providing enhancement mechanism of citric acid on low-grade limestone WFGD process.

Deep neural network-based optimal selection and blending ratio of waste seashells as an alternative to high-grade limestone depletion for SOX capture and utilization

• Wet flue gas desulfurization process was optimized using waste oyster shell. • Deep neural network–based surrogate model is used to cost optimization. • Seashells with low-grade limestone could fully replace high-grade limestone. • At an optimal blending ratio, total annualized cost could be reduced by US$788,469. • The results facilitate cost-effective and eco-friendly SO x capture and utilization. In wet flue gas desulfurization system, the resource depletion of high-grade limestone, used as conventional SO x absorbent, is becoming serious for SO x capture and utilization. This paper proposes optimal selection and blending ratio of waste seashells as an alternative to high-grade limestone depletion using a deep neural network (DNN)-based surrogate model. Cost optimization proceeds as follows: data generation, data preprocessing, development of DNN-based surrogate model, and derivation of cost optimal selection and blending ratio. First, a process model is developed to generate the datasets, which are gypsum purity according to selection and blending ratio of each seashell and limestone. In addition, a mathematical model is proposed to calculate the total annualized cost (TAC) considering the pretreatment cost of seashell, and the TAC is added to the datasets to predict the gypsum purity as well as TAC. Second, the generated datasets are preprocessed to intensify prediction performance of the DNN-based surrogate model using the z-score normalization method. Third, a DNN-based surrogate model is developed to predict the gypsum purity and TAC according to the selection and blending ratio. Finally, the cost optimal selection and blending ratio are derived from 2.4 billion data generated by the developed DNN-based surrogate model under two constraints: gypsum purity and total SO x absorbent consumption. As a result, the derived selection and optimal blending ratios are low-grade limestone (80.86%), oyster shells (10.78%), scallop shells (0.216%), cockle shells (0.323%), clam shells (2.426%), and mussel shells (5.391%), reducing the TAC by US$788,469.

Improved Lignite Predrying System Integrated with Heat and Water Recovery from Wet Flue Gas at Lignite-Fired Power Plants: Energy and Water Conservation

To improve energy efficiency and reduce water consumption simultaneously in lignite-fired power plants, an improved lignite predrying system integrated with heat and water recovery from wet flue gas is proposed in this study. In the proposed system, the heat source for the lignite predrying system was the latent heat from the flue gas instead of the extracted steam, so the extracted steam could return to the turbine to generate more power. Moreover, both the water from the raw lignite and wet flue gas desulfurization (WFGD) processes were recovered, which minimized the water consumption of lignite-fired power plants. This study evaluated the energy- and water-saving potential of the proposed system at both air-cooling and wet-cooling power plants firing three types of lignite separately. The results showed that the higher the moisture content of lignite, the larger the net efficiency improvement and the make-up water rate reduction. The net efficiency improvement and make-up water rate reduction in power plants firing Yimin lignite reached 2.33% points and 0.370 t/MWh, respectively, at wet-cooling power plants, and 2.18% points and 0.443 t/MWh at air-cooling power plants. This means that zero water consumption can be achieved, and water and electricity can be output at the same time at air-cooling power plants. The technical and economic analysis showed that the net present value in 10-years of power plants firing different lignite types could reach 49.31, 36.19, and 16.44 million USD depending on the predry degree. The discounted payback period was 2.34–3.67 years, which showed good economic viability in all cases.

High efficiency desulfurization behavior by the sustainable low carbon utilization of carbide slag

For the purpose of the gradual decrease of calcium carbonate resources and reduction of carbon emissions in wet flue gas desulfurization process, the utilization process of carbide slag to replace limestone is systematically analyzed. The properties of carbide slag and limestone have been analyzed, and the mass transfer and reaction behaviors in desulfurization process have been calculated and comprehensively evaluated. Desulfurization performances have been also compared through response surface analysis method. The results show that the calcium content and specific surface area of carbide slag are higher than limestone, which is conducive to the dissolution and mass transfer rate. Therefore, carbide slag is suitable for the treatment of flue gas with high SO2 concentration. Desulfurization efficiencies of the two desulfurization agents of carbide slag and limestone under the optimal process are 99.15% and 96.53%, respectively. In conclusion, carbide slag can be used in desulfurization process to replace limestone. The consumption of carbide slag slurry in the desulfurization process is about half of limestone slurry at the same conditions, and the higher desulfurization efficiency of carbide slag is attributed to the higher mass transfer and dissolution rate. Utilization of carbide slag also reduces the carbon emission in desulfurization process and economic cost. The reduction amount of CO2 emission can reach to about 0.76 t /t carbide slag. This work provides a basis for the industrial application and desulfurization efficiency improvement of carbide slag as the desulfurizer.

Simultaneous Removal of SO2 and NO x Using Steel Slag Slurry Combined with Ozone Oxidation.

In this work, steel slag slurry was used in combination with O3 oxidation for the simultaneous removal of SO2 and NOx in a laboratory-scale wet flue gas desulfurization process. The effects of the oxidation temperature, steel slag concentration, initial SO2 concentration, and pH value on the desulfurization and denitrification efficiencies were studied. The results showed that the highest NOx removal efficiency occurred at an oxidation temperature of 90 °C. With an increase of the oxidation temperature above 90 °C, the denitrification efficiency decreased due to the decomposition of N2O5. The effect of the SO2 concentration on denitrification was complicated. When the concentration of SO2 was 500 ppm, generation of SO32– promoted the absorption of NO2. However, higher SO2 concentrations strengthened the competitive absorption of SO2 and NOx. In the pH range of 8.5–4.5, the denitrification efficiency was maintained at about 96%. The component analyses of the aqueous solution and the solid residue were conducted to investigate the compositions of the absorption products. The results showed that NO3– and SO42– were the major anions in the aqueous solution. The nitrogen balance was analyzed to be 95.8%, clearly illustrating the migration and transformation path of nitrogen. In the solid residue, most alkaline substances were consumed, and the final products were mainly CaSO4 and FeO. Accordingly, the reaction mechanism of simultaneous desulfurization and denitrification using steel slag combined with ozone oxidation was proposed.

Physical, Chemical and Geotechnical Characterization of Wet Flue Gas Desulfurization Gypsum and Its Potential Application as Building Materials

In South Africa, coal represents the primary source of energy used for electricity generation. Coal power plants use the wet flue gas desulfurization (WFGD) process to remove sulfur dioxide (SO2) from their flue gas. However, this technology produces a large amount of synthetic gypsum, resulting in waste disposal and environmental pollution. This study investigated the physical, chemical and geotechnical properties of WFGD gypsum and its potential application to develop cement-free bricks. WFGD gypsum was collected from a coal power plant in South Africa. It was found that the principal oxides of WFGD gypsum were sulfur trioxide (SO3) and calcium oxide (CaO), which represented more than 90% of the total weight. Calcium sulfate (CaSO4) and calcium di aluminate (CA2) were the predominant minerals in the raw material. The density of the WFGD gypsum was 2.43 g/cm3. The maximum dry density and optimum moisture content values were 1425 kg/m3 and 18.5%, respectively. WFGD gypsum had a liquid limit of 51% but did not display any plasticity characteristics. The optimum curing temperature of gypsum bricks was 40 °C. WFGD gypsum-based bricks exhibited compressive strength of up to 2.3 MPa and a density of about 28% less than that of typical clay bricks. Additionally, there was no significant decrease in compressive strength after seven wet/dry cycles. These results show that WFGD gypsum could be used to produce lightweight building materials with low strength requirements.

Water recovery from wet flue gas by combining the amplification tube condensation and inlet particle-sorting cyclone separation

• A novel technical route was used to recovery of water from flue gas. • The amplification tube and separators were designed to enhance mass transfer process. • The amplification tube and separators have relatively economic performances. The wet flue gas which is generated after the Wet flue gas desulfurization process contains huge amount of water vapor, soluble salts and insoluble particles. Direct discharging will not only lead to the significant waste of water resources, but also causes continuous smog. Therefore, a series of amplification tube with different sizes (length of 40 mm, 80 mm, 120 mm, 160 mm and 200 mm) were designed to condense water vapor by changing the partial pressure. Meanwhile, a particle storing classifier combining with cyclone was used for improving the collection efficiency of condensed water. The result showed that the water collection efficiency raised first with increasing the length of amplification tube and dropped after it reached to the maximum point (11.2%) at the length of 120 mm with the pressure drop lower than 72.5 Pa. Furthermore, after classifier and cyclone separator were incorporated with the optimized amplification tube, the highest water collection efficiency increased by 9.4%, reaching about 19.4% which is equivalent to reducing the flue gas temperature by 4 °C by conventional heat exchange technique. This novel technology was successfully applied to recover water and deep purify wet flue gas for the first time and has great potential in industrial wet flue gas pollution control.

Mechanism of SO3/H2SO4 transformation and reduction in wet flue gas desulfurization systems

In this study, a unique sampling unit combining quartz wool filtration and salt adsorption, which can measure aerosol and gaseous H2SO4 simultaneously, was adopted to reveal the transformation and reduction of SO3/H2SO4 in a lab-scale wet flue gas desulfurization (WFGD) scrubber. The results showed that H2SO4 in flue gas at the inlet of the WFGD scrubber is in both gaseous and aerosol states, and the gaseous state constitutes a larger proportion, differing from the conventional realization that all H2SO4 at WFGD scrubber inlets is gaseous. The experiments showed that the amount of H2SO4 aerosols increased, and that of H2SO4 vapor decreased in the scrubber, indicating H2SO4 transformation from a gaseous to an aerosol state after quenching. However, there is always a small portion of H2SO4 vapor that could be detected at the outlet, suggesting that H2SO4 cannot be completely converted to aerosols in the scrubber, differing from traditional assumption. We also found that spraying droplets could reduce H2SO4 but with low efficiency. The demister installed at the scrubber outlet is more efficient at reducing H2SO4 than the droplets, which inspires a new understanding of the mechanism of H2SO4 reduction in WFGD processes.

Constrained nonlinear model predictive control of pH value in wet flue gas desulfurization process

AbstractIn wet flue gas desulfurization (WFGD) process, the pH value of the absorption tower slurry is a crucial factor to the efficiency of desulfurization system. Aiming at the nonlinearity and large lag of the pH change in WFGD process, a predictive control strategy based on Hammerstein–Wiener inverse model compensation is proposed. During the calculation of optimal control, an anti‐model of Wiener nonlinearity unit is adopted to transform the output setting values and sampling values. Similarly in the control process, the controller output is applied to the actual controlled object after inverse transformation of the static nonlinear Hammerstein model. Through the above two inverse transformations, the controller output is identical with the input of linear link in the closed‐loop system. In this article, the inverse model compensation method is utilized to transform nonlinear process control into linear system control, avoiding the large computation of nonlinear model optimization. Finally, the feasibility and effectiveness of the proposed scheme are verified by simulation.

Environmental and economic impact assessment of three sintering flue gas treatment technologies in the iron and steel industry

Increasingly stringent pollutant emission standards pose a new challenge to the control of air pollutants in China's iron and steel industry (ISI). This study quantified and compared the environmental and economic effects of three typical sintering flue gas ultra-low emission treatment technologies in China's ISI, namely, semi-dry flue gas desulfurization + semi-dry flue gas denitration with O3 + bag filter (SSOB), wet flue gas desulfurization + wet electrostatic precipitator + selective catalytic reduction denitration (WWS), and semi-dry flue gas desulfurization + bag filter + selective catalytic reduction denitration (SBS) by conducting a life cycle assessment coupled with life cycle costing method. Using 1 ton of sinter as the functional unit and “cradle to gate” as the system boundary, the environmental impact of the three treatment technologies is 0.1822, 0.1298, and 0.117, respectively and the total economic cost is 11.622, 10.353, and 10.435 RMB, respectively. The ozone oxidation, semi-dry flue gas desulfurization (FGD), and semi-dry flue gas denitration processes are the key processes of SSOB with electricity, liquid oxygen, and sodium sulfite as key substances. Wet flue gas desulfurization process and selective catalytic reduction (SCR) denitration process are the key processes in WWS while electricity is the key substance. Semi-dry FGD and SCR denitration are the key processes in SBS, with electricity and lime as the key substances. SBS has optimal environmental performance, while WWS has lowest economic costs. Optimization suggestions for each technology are presented based on the influence degree of key processes. The research findings will be valuable for the selection and optimization of ultra-low emission technologies of ISI.

The distribution and conversion of selenite and selenate with the bubbling of simulated flue gas in simulated WFGD slurry

Selenium is one of the hazardous trace elements emitted from coal-fired power plants. The distribution of selenium in Wet Flue Gas Desulfurization (WFGD) process is still unclear and even in controversial, impeding the development of selenium removal technologies. This research has found that the selenite in simulated slurry could be reduced by SO2 while selenate has not been affected. Characterization methods including X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to provide an evidence that the product of the reduction reaction is amorphous elemental selenium. Meanwhile, the influences of other gaseous components, pH, temperature and S2O82− in simulated slurry has also been considered in this research. It is found that with the increase of SO2 concentration in flue gas, the reduction of selenite increased and the reduction reaction is an exothermic reaction. Meanwhile, the oxidation effect of S2O82− competes with the reduction effect of SO2. This study introduced the influence of flue gas into the research of the conversion of selenium in FGD slurry and indicate the effect of flue gas on the potential emission treatment techniques of selenium in FGD slurry.

Numerical investigation on distribution characteristics of oxidation air in a lime slurry desulfurization system with rotary jet agitators

Rotary jet agitator is an effective device for mixing, dispersing, dissolving, and suspending dispersed phases in liquid, and is particularly advantageous to the homogenization of oxygen-enriched air within the lime slurry desulfurization system. The distribution of oxygen-enriched air in agitators is vital for the process of gypsum crystallization and the homogeneous and sufficient oxygen-enriched air can promote the formation of an economically useful by-product. The present study investigated the diffusion performance of oxygen-enriched air in a rotary jet agitator during the wet flue gas desulfurization process by utilizing computational fluid dynamics. The consistency of numerical and experimental results is validated under identical conditions. Investigation results show that the rotation velocities and the inlet velocities of rotary jet machines significantly affect the distribution and homogeneity of the oxygen-enriched air distribution. However, these effects deteriorate with increasing rotation angular and jet outlet velocities. Under the optimal condition, the oxygen-enriched air concentration, within the cross-sections, fluctuates by approximately 20%. The Rotary jet agitator appears to be a remarkable method for the homogenization of oxygen-enriched air in the lime slurry tank, and in other gas-liquid stirring tanks, due to its high efficacy and good stirring effect.