Calcination temperature is the key factor affecting the quality of calcined petroleum coke and dominated by calcination parameters in a shaft calciner. In this study, a method for evaluating the effects of various factors on the temperature distribution in shaft calciners is proposed. A two-dimensional transient mathematical model was developed to describe the complex gas–solid coupled mass and heat transfer problems that occur during petroleum coke calcination in shaft calciners. In this model, a three-parallel-distributed activation energy model (DAEM)-reaction model was used to describe the pyrolysis kinetics of petroleum coke, and a dichotomy method was used to guarantee constant temperature in the flue of Layer 2 (T2) to meet the operational control requirements in actual production. Then, a statistical method called orthogonal design-based grey relational analysis was used to quantize the influence degree of salient factors (discharge rate per pot [DRPP], moisture content [MC], volatile content [VC], and volatile distribution ratio [VDR] in the flue of Layer 1) on the temperature distribution in the shaft calciner. An analysis of variance of the grey relational degree showed that VC was the most influential factor, followed by DRPP and MC; VDR was the least influential factor behind calcination temperature. Therefore, VC is the key factor affecting the calcination temperature and must be strictly controlled during production.
The feasibility of selective recovery of titanium and scandium from a high acidic content lixivium by solvent extraction was verified in this study. Amongst the extractants, which were investigated for the selective extraction of scandium and titanium from the acidic lixivium in this study, D2EHPA and primary amine N1923 performed best. 2-Octanol and sulfonated kerosene were used as modifier and diluents, respectively, scandium and titanium were stepwise extracted by D2EHPA and primary amine N1923. More than 98% of scandium was extracted selectively by using 10% (v/v) D2EHPA, 5% (v/v) 2-octanol, and 85% (v/v) sulfonated kerosene under the O/A ratio of 1 : 6 for 5 min. After the purification processes, the Sc2O3 with a purity of 99.9% was obtained. More than 96% of titanium was extracted selectively by using 10% (v/v) N1923, 5% (v/v) 2-octanol, and 85% (v/v) sulfonated kerosene under the O/A ratio of 2 : 1 for 5 min. After the process of scrubbing and stripping, a concentration of titanium solution of 64.1 g/L was obtained. Finally, a solvent extraction flowsheet was established.
Adsorptive removal of As(III) and As(V) from a water environment has been investigated, employing Diaion CRB05, with N-methylglucamine functional group, and Lewatit FO 36, with a FeOOH functional group. Batchwise adsorption of arsenic elucidated that the adsorption was affected by the pH of aqueous solution, and the optimal pH for high adsorption amount was determined to be in range 3.0–4.5 for adsorption of As(V) and 7.0–8.5 for adsorption of As(III). Adsorption isotherms of both As(III) and As(V) followed the Langmuir mechanism, and FO 36 was revealed to possess high adsorption capacities for both As(V) (122 mg/g) and As(III) (98 mg/g). Desorption of the loaded arsenic from both adsorbents could be performed by either diluted HCl or NaOH solution. Chromatographic studies for the arsenic removal indicated that both adsorbents could be used repeatedly.
Platinum group metals (PGMs) play an important role in the automotive industry as key components of exhaust catalysts. Recycling of PGMs from secondary resources, such as waste products, is encouraged to ensure their sustainability. A highly efficient and environmentally benign technique for the separation of PGMs is currently required. In the present study, the recovery of PGMs from a spent automotive catalyst was investigated using the trioctyldodecyl phosphonium chloride (P8,8,8,12Cl) ionic liquid (IL) as the PGM extraction solvent. First, leaching from the catalyst was investigated. Pt and Pd are selectively extracted into undiluted P8,8,8,12Cl from the 5 mol L−1 HCl leachate containing various metals together with Pt, Pd, and Rh. Subsequently, Rh is extracted into fresh P8,8,8,12Cl from the raffinate adjusted to an appropriate HCl concentration. Mutual separation of Pt and Pd is possible by stripping processes. Some common metals co-extracted with PGMs, such as Fe, Cu, and Zn, are removed by each stripping process. Recovery of high purity Pt, Pd, and Rh is achieved by the proposed recycling process. The results demonstrate that separation using phosphonium-based ILs is useful for recycling PGMs.
Early detection of anomalies is crucial for maintaining high productivity in industrial plants. To meet that requirement, anomaly detection systems based on adaptive resonance theory (ART) have been developed. Although various anomaly detection methods based on ART have been proposed, their performances have not yet been evaluated systematically. A new anomaly detection criterion is proposed, and the performances of ART-based anomaly detection systems, using different anomaly detection criteria and different anomaly detection structures, are evaluated. The performance evaluation results show that distributed model based systems, which use an ART model for each part of the plant, attain higher anomaly detection performance than that of systems using an ART model for the entire plant. They also show that an anomaly detection system using a new anomaly detection criterion, based on the distance between samples, attains almost the same anomaly detection performance as that of a system using generation of new categories.
In this study, biochars were prepared from Japanese cedar sawdust with a mechanical compression at different temperatures in an air atmosphere. The compression pressure at a given constant value was applied to the raw material during the torrefaction process. Experimental results indicated that the compression positively improved the fuel properties of the biochar obtained. The carbon content in biochar increased; whereas the oxygen and hydrogen contents decreased. The H/C ratio of biochar was generally proportional to its O/C ratio, and biochars prepared at temperatures of more than 300°C were in proximity to bituminous or sub-bituminous coals in the van Krevelen diagram. Torrefaction at 300°C and 3 MPa gave biochar with a higher heating value of 29.8 MJ/kg and an energy yield of 0.85. Furthermore, the differential thermal analyses showed that the peaks corresponding to the release of volatile matters from biochar decreased with an increase in the compressive load. Consequently, torrefaction of Japanese cedar sawdust with compression in an air atmosphere would be a promising method to produce biochars as an alternative fuel.
An analysis of the chemical form of mercury in the by-products produced from a coal-fired power plant was performed by a combining temperature programmed desorption (TPD) method and cold vapor atomic absorption. The TPD curve of the model sample for each mercury compound showed a unique peak temperature, and the chemical form of mercury was identified by comparing the peak temperature with that of the by-product sample. A linear combination of the TPD curve of each model sample was curve-fitted to that of the by-product sample. The ratio of each form of mercury present in the by-products was calculated from the area ratio of the TPD curve of the model sample used in the analysis. The mercury in the fly ash used in this study mainly existed in a form bound to sulfur, and the mercury that adsorbed on carbon was not found despite the very high unburned carbon content. In contrast, the study found that the mercury adsorbed to carbon was the main form of mercury in desulfurization gypsum. These findings suggested that mercury-adsorbed carbon was formed when the mercury that transitioned into the liquid phase in a desulfurization equipment was adsorbed onto the unburned carbon.