Volume 18, Issue 12

The high and fluctuation property of sulfur content in hot metal (HM) is a prominent problem in COREX process. The precise prediction of sulfur content in HM of COREX can provide a theoretical basis and technical reference for stabilizing and reducing the sulfur content in HM. In this work, a three-layer back propagation (BP) neural network was developed to predict the sulfur content in HM of COREX. The main affecting factors regarded as input parameters of the model are determined by the statistical analysis, and the hysteretic heats corresponding to each input parameters are analyzed by calculating the Deng’s correlation degree. The final structure of the BP neural network model is 20-37-1. The results show that when the error of BP neural network model for predicting sulfur content in HM of COREX is ±0.1%, the hit rate is 86.7%. In order to further improve the prediction accuracy of the model, the time series process method is adopted to update the training samples in real time and optimize the model. When the prediction error of the improved model is ±0.1%, the hit rate increases to 96.7%. The improved BP model can provide technical guidance for judging the change of sulfur content in HM and subsequent operations.

Batch and packed bed adsorption of 4-chloro-2-methylphenoxyacetic acid (MCPA) herbicide was performed using bagasse fly ash (BFA) as an adsorbent. In batch process, characteristics of adsorbent, and the influence of adsorbent dosage, initial herbicide concentration, time, pH, particle size of adsorbent and temperature on adsorption were studied. Results disclose higher removal of MCPA on bigger particles of BFA owing to higher specific surface area because of greater carbon and lesser silica percentage in bigger particles. Application of isotherm models in present study indicates the best fitting of Langmuir and Temkin isotherms whereas the kinetic models suggest the suitability of pseudo second order and Elovich models. Thermodynamic study specifies the temperature preferred adsorption process. In packed bed technique, the effect of influent concentration, flow rate and bed height were investigated. The deactivation kinetic model which was previously considered only for studies in gas-solid adsorption is applied in this study to solid-liquid adsorption along with conventional packed bed models. In packed bed study, Bohart-Adams and Wolborska models are appropriate to explain the experimental data upto 60% saturation of the column. The deactivation kinetic model is found the best to elucidate the nature of breakthrough curves till the complete saturation of column. Batch capacity and packed bed capacity per m 2 specific surface area of BFA is found about two and three times greater than the previously used adsorbents for MCPA respectively.

Fluidization characteristics of wide-size-distribution particles in the gas-solid fluidized bed reactor are investigated by applying experiment and computational fluid dynamics (CFD) methods. In this study, three types of narrow-cut particles and two sets of wide-size-distribution particles are used. A model considering particle size distribution is developed in the Eulerian frame, and good agreement between numerical results and experimental data is observed. The particle size distribution has an important effect on the average bed voidage. The axial particle diameter profiles along bed height have a “S” type feature. Minimum fluidization velocity is determined from the standard deviation of pressure fluctuations and bubble dynamics are analyzed based on power spectra. Results indicate that fine particle composition can reduce the minimum fluidization velocity of wide-size-distribution particle system and the bubble diameter in the fluidized bed.

The separation and recovery of copper and indium from a solution arising from the reductive leaching of a zinc leaching residue was studied. Copper was enriched into a copper precipitate produced by iron powder precipitation; indium was hydrolyzed and enriched into a gypsum indium precipitate produced by limestone adjustment of pH. Separation and recovery of both copper and indium were achieved. The results showed that precipitation of copper(II) and arsenic(III) as Cu 2 O and Cu 3 As is thermodynamically feasible by adding iron powder to the reductive leach of a zinc leaching residue. Increasing the iron powder addition and reaction temperature promoted the formation of Cu 2 O and Cu 3 As. In the process of neutralizing and precipitating indium by adjusting the pH using limestone, indium was mainly concentrated in the precipitate by hydrolytic precipitation. The pH of the neutralization endpoint plays a decisive role in this hydrolytic enrichment. The extent of indium precipitation exceeded 98%, and the indium content of the precipitate reached 3.6 kg/t. Addition of limestone balances the acid across the entire production process. The main phase in the gypsum indium precipitate was CaSO 4 ·2H 2 O, the stable properties of which create favorable conditions for the recovery of indium in subsequent steps.

The oxidative coupling of methane (OCM) is a potential option for conversion of excess natural gas to higher value products or useful feedstocks. The preferred or ideal OCM stoichiometry is: 2CH 4  + O 2  → C 2 H 4  + 2H 2 O, but real OCM produces a variety of species. Using a detailed mechanism from the literature for OCM over a La 2 O 3 /CeO 2 catalyst that combines coupled elementary gas phase and surface reactions, a reactor engineering study has been done. Adiabatic packed bed reactor (PBR, modeled as plug flow) and continuous stirred tank reactor (CSTR, perfect mixing) simulations using this mechanism are presented. Each reactor simulation used the same total number of catalyst sites. Process variables included CH 4 /O 2 feed ratio (7, 11), feed temperature (843–1243 K), and feed rate. All runs were conducted at 1.01E5 Pa pressure. The results show the CSTR produces high conversions at much lower feed temperatures than those required by the PBR. Once full PBR “light off” occurs, however, its CH 4 conversions exceed CSTR. The simulations reveal OCM over this catalyst at these conditions gives a mixture of synthesis gas (CO, H 2 ) and C 2 H x (primarily C 2 H 4 plus small quantities of C 2 H 6 and C 2 H 2 ). The CSTR favors the production of synthesis gas, while the PBR favors C 2 H x . Within the suite of CSTR cases, C 2 H x is favored at the lowest feed temperature and highest CH 4 /O 2 feed ratio.

Adsorption as an air purification method is widely employed to remove volatile organic compounds with low concentration using zeolites. In this study, ZSM-5 and LSX zeolites modified by alkali metal cations (Li + , Na + and K + ) were used as adsorbents for the abatement of toluene. The adsorption behaviors of toluene onto adsorbents with different pore sizes and cation contents were evaluated systematically based on the experiments of adsorption equilibrium, kinetic diffusion and desorption. Besides, Langmuir and Freundlich model, constant-pattern wave propagation model and Kissinger method were applied to fit with the above experimental data. The adsorption amount followed the sequence of Li-LSX > Na-LSX > K-LSX > Li-ZSM-5 > Na-ZSM-5 > K-ZSM-5 obtained from equilibrium isotherms. LSX zeolites showed twice adsorption capacity on unit volume compared to ZSM-5. The mechanisms of steric hindrances and electrostatic interactions controlling the diffusion rate under high and low concentrations were proposed, respectively. At relatively low loadings of toluene, the diffusion resistances were primarily affected by electrostatic interaction due to preferential adsorption of toluene on cationic sites. While at relatively high loadings, the diffusion resistance was mainly restricted by steric effect because of saturated cationic sites. The strength of adsorbate-adsorbent interactions was assessed by temperature programmed desorption experiments. It showed that both adsorption sites and microporous walls contributed to the desorption energy.

In this work, the esterification of glycerol with acetic acid (HOAc) was investigated under sulfonated polyphenylene sulfide non-woven fabric (SPSF) as a solid catalyst. The effects of the amount of catalyst, reaction temperature, molar ratio of glycerol to HOAc and the reaction time on the esterification were studied in detail. It was found that SPSF has good catalytic activity and stability. Under the reaction conditions of the molar ratio of glycerol/HOAc of 1:6 (glycerol 0.1 mol), the reaction temperature of 110 °C, the amount of catalyst of 3 g, and the reaction time of 2 h, the glycerol conversion and the selectivity to diacetin (DAG) reached upto 96 and 56.1%, respectively. Reusability test of SPSF showed that no significant declination in the glycerol conversion and the selectivity was observed after five reaction cycles. The experimental results proved the esterification of glycerol with HOAc by SPSF a promising and green process.

In this study, the effect of height/diameter ( H / D ) ratio and type of impeller on the power consumption of the agitator in the Continuous Stirred Tank Reactor (CSTR) was analyzed. CSTR in the process of producing nitrocellulose from cotton linters with a production capacity of 10,000 tons/year was used as a case study. In designing a CSTR, power consumption is also considered because it is related to techno-economics. The results show that it is necessary to adjust the amount of impeller related to the H / D ratio value because it can affect the level of liquid in the reactor during the stirring process so that it also affects the reaction conversion. This work shows that with the higher H / D ratio, the greater number of impellers needed and increase the agitator power consumption. For specific applications, the number of impellers (NT) must be increased to meet the minimum power consumption. As the result, this work recommends the optimal H / D ratio for CSTR design is the maximum H / D ratio to get the NT-calculation as close as to the NT-taken while satisfying the minimum power consumption required. The optimal H / D ratio can be different depending on the impeller type and application.