Energy Technology 2021

Electrode polarization potential is an important factor of cell voltage during electrowinning, which can affect the total energy consumption of the zinc hydrometallurgy process. In this work, we creatively use a metal-free oxygen evolution catalyst of water electrolysis to the hydrometallurgy system. An amino-rich hierarchical-network carbon(Amino-HNC) electrocatalyst was prepared by a simple two-step method of amino-assisted polymerization and carbonization process. The surface morphology, phase composition, and electrochemical properties were characterized. The results show that Amino-HNC is an electrocatalyst for oxygen evolution reaction with an amino-rich network structure, and the oxygen evolution overpotential in 0.5 mol L⁻¹ H₂SO₄ electrolyte is 389 mV (@ 10 mA cm⁻²). Meanwhile, the prefabricated catalyst is directly used as an anode in the zinc electrowinning system (50 g L⁻¹ Zn²⁺  + 150 g L⁻¹ H₂SO₄) to measure the cell voltage. Compare with the traditional pure lead anode, the cell voltage decreased in a short time during the zinc electrowinning process.

Globally, coal is the largest primary source of electricity. As per the global demand for coal production, coal ash has also subsequently increased. The coal by products such as fly ash and bottom ashes are the main sources for rare earth and other metals. The tremendous benefits of recycling these ashes have wide energy applications. In this paper, we reported characteristic studies of critical rare earth such as scandium and yttrium from the circulating fluidized bed combustion fly ashes. The preliminary study investigated the performance of three reagents, HCl, H₂SO₄, and HNO₃ on rare earth leaching from a Korean circulating fluidized bed combustion fly ash. Hydrochloric acid was selected as the proper reagent used for subsequent experiments. The variables including reagent concentration, leaching time, and temperature in the range of 1.5–4 mol/L, 5–120 min, and 25–80 °C were optimized. The leaching efficiency of scandium and yttrium were at 48 and 45% under the optimized conditions.

Coronavirus disease (COVID-19) has spread around the world like wildfire, impacting health, industry, the global economy, and the environment. This paper focuses on climate change, discussing the global trend in CO₂ emissions and how COVID-19 is impacting climate change. Global warming is the greatest environmental challenge our planet has ever faced. According to the International Energy Agency (IEA), CO₂ emissions declined by 8% during 2020. Of the wide range of sustainable technologies available for carbon capture, mineralization technology is the first to produce carbonate minerals by directly reacting minerals with low concentration CO₂. This long-term technology affords extended capacity for CO₂ storage. We consider the extensive guidelines required for climate change during the battle against COVID-19.

Iron and steelmaking consumes large amounts of fuel and CO₂ emissions are also huge. In this paper, a new calculation model was proposed to calculate CO₂ emissions based on process analysis, and the technical emission and combustion emissions were distinguished to reflect the CO₂ emission characteristics in iron and steel production. As for electric arc furnace (EAF) steelmaking, the results of the CO₂ emissions calculation show that the CO₂ emission intensity of the enterprise’s EAF process was 53.84 kg/t-cs, including electric emissions and non-electric emissions. The electric emissions were calculated as 41.09 kg/t, accounting for 76% of the total emissions. Considering the complexity of power consumption in iron and steel enterprises, a calculation method based on electric power structure was applied to determine the power emission factor. Finally, the carbon flow of the entire process was analyzed, and the possible ways for carbon reduction in steel complexes was discussed.

In order to efficiently remove the fine particles in the smelting flue gas, especially PM2.5, this paper designed and built a dynamic wave scrubber dust removal device. Through the optimization of equipment, nozzle structure, and operating conditions (liquid–gas flow rate ratio, dust mass concentration), the final dust removal efficiency has been achieved. The effects of liquid–gas flow rate ratio, gas–liquid flow pattern, dust mass concentration on the dust removal efficiency were studied. The results show that the dust removal efficiency increases with the increase of liquid–gas flow rate ratio and initial dust mass concentration. When the foam flow pattern is formed in the washing zone, the performance of the dynamic wave scrubber is better than its performance when forming other flow patterns. The total dust removal efficiency can be more than 99%, the classification efficiency of PM2.5, the particles above 5 μm, and the particles above 10 μm are more than 98.35%, 99%, and almost 100%, respectively, when the liquid–gas volume ratio is more than 0.004.

A possible approach to the carbon dioxide removal from flue gases is application of the dense composite membrane (matrix: polymer material; dispersed phase: zeolite powder). This type of membrane is based on a solution-diffusion mechanism. Carbon dioxide is dissolved in the membrane bulk, and then diffuses to the permeate side. A successful membrane should have high permeability of the carbon dioxide and low permeability for all other gasses commonly present in the combustion process (oxygen, nitrogen, hydrogen…). The main challenge is to provide good contact between long and usually hydrophobic polymer chains and relatively small, but electrically charged, zeolite particles. Two different polymers and four different zeolites were tested for this purpose. As the polymer bulk material, different co-polymers of ethylene-oxide and phthalimide were used. Five different zeolite powders in combination with two different potential additives were tested.

The efficient separation of fine particles from industrial flue gas is still a challenging task. Reverse spray washing technology is gradually used in dust removal due to its advantages of simple structure and large interphase contacting area. In this paper, the lab-scale reverse spray washing device was established. The changes of gas–liquid two-phase flow pattern, pressure drop, and structure characteristics under different operating conditions were studied. It was found that four types of flow regimes (hollow tapered, foaming, annular, and column types) will form. The foaming type has fast surface renewal speed and large contacting area, which is more conducive to the removal of fine particles in the flue gas. The operation and performance diagram of the nozzle was drawn. The formation of different flow patterns can be controlled by controlling the ratio of liquid to gas and the axial and tangential liquid flow ratio of the nozzle.

In this research, using the carbon composite briquette (CCB) containing carbon: 20.30 wt%, Fe₃O₄: 29.70 wt%, FeO: 39.70 wt%, metallic iron: 1.57 wt%, and gangue: 8.73 wt%. the reaction behavior of the CCB in BF and the influence of coal reactivity was examined by the numerical investigation. Results showed that the development of the CCB reaction in BF was divided into six stages. The initial temperature of the CCB self-reduction was 850 K, the dominant temperature range in CCB reaction being effective for BF energy-saving was from 1000 K to 1150 K, its final reduction fraction, and final carbon conversion was 1.0 and 0.9, respectively. By decreasing the activation energy of coal gasification, the initial temperature of CCB self-reduction became lower, the effective temperature range of CCB reaction for BF energy-saving was wider, and the final carbon conversion increased, indicating to improve the coal reactivity in CCB could intensify the effect of its reaction on BF energy-saving. By increasing the activation energy of coal gasification, the initial temperature became higher, the effective temperature range of CCB reaction for BF energy-saving was narrower, and the final carbon conversion decreased, reflecting that to reduce coal reactivity in CCB could weaken the effect of its reaction on BF energy-saving.

The increasing industrial demands for mesoporous silica warrant the continuous development of less energy intensive, cheaper, and eco-friendly technologies. Mesoporous silica from an indigenous kaolinite ore was synthesized by hydrochloric acid dissolution. Experimental reaction parameters were optimized to maximize silica recovery and the solid product was characterized using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Brunauer–Emmett–Teller (BET) Nitrogen adsorption–desorption measurements. The dissolution data show the rate of reaction increase with increasing concentration temperature but with decreasing solid-to-liquid ratio. The Avrami model proved most suitable model for describing the leaching process with Avrami parameter n value of 0.8 and calculated apparent activation energy of 7.22 kJ/mol suggested a diffusion controlling rate mechanism. The mesoporous product as characterized gave a pore size of 3.67 nm at the maximum probability and possessed suitable morphological applications as additive in polymers and catalysis.

Oxygen consumption prediction for steelmaking converter is essential for optimal scheduling and energy saving of oxygen systems. To improve the prediction accuracy of oxygen consumption, an integrated prediction method based on feature space recursive division and feature selection is proposed. The feature space containing the whole converter production data is recursively divided into several feature subspaces containing the training subset. And the complexity of the data distribution will be reduced in each subspace. The simple data distribution will be more easily fitted by the prediction model. Based on recursive feature elimination, the appropriate feature variable combination and the corresponding oxygen consumption prediction models of the converter will be selected for each subset. For the test sample, it will be matched to a corresponding feature space by recursive division conditions. Then oxygen consumption is predicted by the corresponding prediction model based on the optimal combination of feature variables. A converter production data of a steel enterprise are used for testing. SVR and MLP will be used, respectively, for comparison in two groups of comparative experiments. The results show that the prediction performance of the integrated model is better than that of a single prediction model in multiple indicators.

Low-temperature reduction of hematite to metallic iron by hydrogen is an essential process for ironmaking based on the blast furnace and non-blast furnace technologies. In this work, the reduction behaviors of Brazilian hematite in 20%H₂–80%Ar at 400–570 °C were investigated in a micro-fluidized bed. Results indicate that the effect of the gaseous external diffusion can be eliminated as the gas flow rate reaches 400 mL/min at 500 °C. According to the conversion X, the reaction from hematite to metallic iron can be divided into two stages, which include the first stage that corresponds to the process of Fe₂O₃ → Fe₃O₄ with X < 1/9 and the second stage that corresponds to the reaction of Fe₃O₄ → Fe. During the reduction process, magnetite is formed gradually and a large number of pores and fissures are observed on the surface of the ore and peripheral part of the unreacted core of hematite. The rate constants of all individual reactions tend to increase with increasing temperature, and the reaction rate of the entire reduction process is suggested to be determined by the phase boundary reaction.

Aiming at the harmful gas pollutants of low concentration sulfur dioxide and fluoride in electrolytic aluminum flue gas, the process of fluorine and sulfur removal was simulated by NaOH-CO₂gas–liquid absorption system, and the influence of operation and structure parameters such as gas flow rate, liquid flow rate, size, and type of filler on gas-liquid mass transfer process was explored. The results show that the gas flow rate is 1.5–2.0 m³/h, the liquid flow rate is 10–12 m³/h, and the filler is a Bauer ring with the nominal diameter (DN) of 16 mm, the gas–liquid mass transfer effect is the best and the maximum CO₂utilization rate is about 46%. According to the simulation results, when ammonia system is used to absorb sulfur dioxide and hydrogen fluoride, the concentration of sulfur dioxide and hydrogen fluoride can be reduced to 42 mg/m³ and 0.8 mg/ m³, respectively.

With the rapid development of the phosphorus chemical industry, the accumulation of by-product phosphogypsum has increased year by year. The comprehensive utilization of phosphogypsum has received extensive attention. In this paper, physical simulation is used to investigate the effects of the shape of agitator, stirring speed, inlet gas flow, eccentric stirring (the ratio of the distance from the center of the agitator to the radius of the cylinder), and height of agitator (the distance between the agitator and the bottom of the reactor) on the bubble size distribution. The optimized conditions are: the agitator is SSB-D, and the stirring speed is 600 r/min, inlet gas flow is 0.12 m³/h, eccentric stirring is 0.4, and the height of agitator is 3 cm, the size of the bubbles is distributed between 0.5 and 3 mm. Under this condition, the conversion rate of phosphogypsum can reach 91.95%. The experiment has certain guiding significance for the resource utilization of phosphogypsum.

To reduce the CO₂ emission in ironmaking, H₂ is suggested to be the best alternative to the fossil fuels used in the blast furnace, and it attracts increasing attention in recent decades. It is well known the reduction behavior of iron oxides with hydrogen is significantly different from that with carbon. Thus, the operation of the blast furnace will change greatly if hydrogen is injected into the blast furnace. However, the influence of hydrogen injection on the reduction process in the blast furnace is seldom addressed in the literature. In this work, the principle of minimum Gibbs free energy is applied to analyze the thermodynamics under working conditions in the lower part of the blast furnace taking into account hydrogen injection. Results indicate that the addition of H₂ plays a crucial role in the thermal balance of the system and the reduction process of wustite. When the amount of heat supplied by hydrogen injection is less than 25%, the gas utilization ratio increases by injecting hydrogen. In this circumstance, wustite can be completely reduced by carbon, and no water is formed because H₂ only acts as a transmission medium. The situation becomes totally different when it is over 25%, and the coexistence of carbon and wustite can be observed.