Category Archives: Chemical Engineering & Technology

Novel Corncob‐Based Catalytic Biodiesel Production Process: Experiments, Modeling, and Simulation

Posted on 11 October 2023 by nZakir Hussain, nJoji Reddy Lingareddy, nNazleen Sulthana, nShashi Kanth Boddun

A highly active corncob-based solid acid catalyst was used for the esterification of oleic acid. The study involves the design and synthesis of the new catalyst, optimization of experimental conditions, modeling of experimental data to obtain kinetic parameters, and simulation of the continuous biodiesel production process in Aspen Plus software by incorporating the obtained kinetic parameters.

Abstract

A functionalized catalyst for catalyzed biodiesel production via a heterogeneous route is a highly focused area to lower the cost of production and mitigate the drawbacks of homogeneously catalyzed reactions. Production aspects such as parameter study, kinetics modeling, and simulation of continuous process flowsheets incorporating kinetic parameters are scarce in the literature. In the current work, a sulfonic group-functionalized porous carbonaceous catalyst based on corncob was used for the esterification of oleic acid. The Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetic model was found to best fit to correlate the experimental data and thus applied to deduce the kinetic parameters. The obtained kinetic parameters were incorporated into the Aspen Plus simulator to simulate the continuous biodiesel production process. The catalyst showed a strong affinity for oleic acid which enhances the reaction rate.

Thermal Performance Analysis of a Mounded Liquid Ethylene Storage Tank

Posted on 10 October 2023 by nBiping Xin, nJian Wen, nAimin Zhou, nSimin Wangn

A model is established to investigate the temperature field distribution of a mounded liquid ethylene storage tank system under long-term placement. The effects of external environment, number of storage tanks, tank spacing, and thickness of the cold insulation structure on the temperature field distribution are analyzed. Reference for the design of heat tracing devices in such tank systems is provided.

Abstract

A model including the tank body and the external environment is developed to investigate the temperature field of a mounded liquid ethylene storage tank system during long-term placement. Since the external environment always changes, it is introduced by writing user-defined functions (UDFs). The effects of external environment and structural parameters on the temperature field are analyzed to provide reference for the design of the heat tracing devices of the storage tank system. The results indicate that the increase of tank quantities substantially reduces the outer-surface temperature of the cold insulation structure. The increase in tank spacing and thickness of the cold insulation structure weakens the interaction of adjacent tanks and raises the outer-surface temperature of the cold insulation structure.

Lead Adsorption by Fly Ash Geopolymer: Isotherm, Kinetic, and Thermodynamic Studies

Posted on 9 October 2023 by nMurali Pujari, nRohinikumar P, nSudharshan Reddy Manyam, nAdarsh Kumar Aryan

Adsorption is an effective method for removing heavy metals from water. Herein, a geopolymer synthesized from biomass fly ash was tested as an adsorbent for removing Pb from solution. The effects of contact time, pH, adsorbent dosage, and initial Pb concentration were tested. The results showed that this is a viable option for removing Pb from solution and reducing the accumulation of biomass fly ash.

Abstract

The effectiveness of low-cost fly ash geopolymer (FAGP) adsorbents synthesized from biomass fly ash in lead removal from aqueous solution was studied. The synthesized FAGP was characterized by the Brunauer-Emmett-Teller method and energy dispersive spectroscopy. The adsorption experiments were performed in batch mode under various conditions, and the maximum removal efficiency and uptake were found at an optimum time of 120 min and pH 5. Adsorption isotherm studies confirmed that lead removal is best fitted by both Langmuir and Freundlich isotherms. A kinetic analysis showed that pseudo-second-order kinetics governs lead adsorption. Lead adsorption was determined to be an endothermic, spontaneous process through thermodynamic analysis.

Vivianite for Phosphorus Recovery from Digester Supernatant in Wastewater Treatment Plants

Posted on 29 September 2023 by nSalman Amjad, nMorten Lykkegaard Christensen, nKasper Reitzel, nHaiyan Qun

Phosphate recovery in vivianite proved to have great potential for phosphorus recovery from digester supernatants. However, the size of the recovered vivianite was found to be very small (< 20 μm), impeding further processing. A process was developed to increase the crystal size of vivianite by controlled Fe²⁺ dosing and seeding effect, which can be a promising way for vivianite growth.

Abstract

Phosphorus (P) recovery by crystallization of vivianite in digester supernatant (DS) was investigated. A high recovery yield (> 90 %) was obtained with vivianite even for DS with low P concentration (74 mg L⁻¹), as opposed to the formation of struvite and hydroxyapatite where the yield was lower than 50–60 %. Various strategies were tested to produce vivianite with large sizes and narrow size distribution, such as a controlled reagent dosing profile, self-seeded crystallization, and multistage cascade-seeded crystallization. The obtained results demonstrated that the main challenge in the development of vivianite P recovery is to promote crystal growth and to suppress secondary nucleation of vivianite during the crystallization process.

Data‐Driven Analysis of Amine‐Based Sorbents for CO2 Removal from the Atmosphere

Posted on 29 September 2023 by nAli M. Bahmanpour, nEd B. Tegeler, nTyler Colbert, nMansour Masoudin

CO₂ sorbents are considered key components of the direct air capture (DAC) process. Various types of amines are widely applied for CO₂ capture from the atmosphere. Their activities and efficiencies depend on various factors including their support material, operating conditions, and environment. Statistical data analysis is done to provide more insights into the performance of these amines for DAC.

Abstract

Available data on amine-based sorbents used for the direct air capture (DAC) process were gathered and analyzed to identify the correlations between various aspects of these sorbents and the operating conditions they are used in. It is demonstrated that a moderately high temperature (∼ 50 °C) can help with higher CO₂ capture capacity. The effect of sorbent preparation method on its activity and stability was studied. Also, the influence of amine groups and support choice on amine efficiency and CO₂ capture capacity was discussed. The DAC process conditions proved to play a major role in determining the optimal sorbent. An outlook for characteristics to be sought for in future DAC sorbents for CO₂ removal is proposed.

Modeling of the Bioleaching of Process Silver Pulp

Posted on 28 September 2023 by

A new model for the bioleaching process of silver is used to theoretically describe available experimental data. The model is based on the two-moving-front description of mineral bioleaching. The model quantitatively predicts the evolution of the silver mass fraction and the minimum in the biofilm mass fraction, related to the maximum in the rheological properties.

Abstract

Modeling of the bioleaching process applied to the system silver-manganese (Ag-Mn) was carried out. The two-moving-fronts model was used to describe the main stages of the process. Bioleaching involves a catalytic process carried out by bacteria to dissolve the mineral ores. Initially, the bacteria interact with the mineral to dissolve manganese, leading to the precipitation of silver. The Ag-Mn compound is dissolved by the bacteria in two stages. First, the bacteria dissolve the manganese and form a biofilm composed mostly of exopolysaccharides. In the second stage, the biofilm is consumed by the bacteria, ending up in dissolved manganese and silver precipitation. At 48 h, the viscosity of the pulp reaches a maximum attributed to the maximum concentration of extracellular polysaccharides in the medium. Predictions describe the basic issues of the bioleaching process in this system.

Characterization of Sprays Generated by the Expansion of Emulsions with Liquid Carbon Dioxide

Posted on 26 September 2023 by nClara Lauscher, nAlexander Licau, nGerhard Schaldach, nMarkus Thommesn

An approach to generate aerosols by expanding emulsions with water and liquid carbon dioxide was investigated regarding the local droplet size, the droplet velocity, and the mass concentration in the spray cone. The high-pressure emulsion was expanded not only through an orifice but also through swirl nozzles, and the differences in the droplet formation process were determined.

Abstract

Expanding emulsions with liquid CO₂ facilitates the creation of aerosols with an average droplet diameter in the low micrometer size range, which is challenging with conventional atomizers. The droplet formation process of the expansion of high-pressure emulsions was investigated using a plain-orifice atomizer and different swirl nozzles. The local droplet size and droplet velocities were measured and used to estimate the local Weber number and thus infer the droplet size reduction. Measurements of the local mass concentration in the aerosol showed that, for the swirl nozzle, the highest concentration was found outside of the central axis, indicating radial momentum generated by the swirl nozzle. Furthermore, it was shown that the type of expansion nozzle used has an influence on the resulting median droplet size in the aerosol. For a water mass load of 0.01, the median droplet diameter was reduced from 8 to 3 μm by increasing the swirl number from 0.01 to 0.1.

Study on the Turbulent Vortex Structure Characteristics of a Two‐Layer Impinging Stream Reactor

Posted on 25 September 2023 by nJianwei Zhang, nMingyang Liu, nXin Dong, nYing Fengn

The intensity of the vortex structure in a two-layer impinging stream reactor was quantitatively analyzed according to the Liutex method. The bound vortex, trapped vortex, and longitudinal vortex in the reactor were studied for the first time. The formation of vortices is related to the velocity field and pressure field. In this paper, the field synergy theory is used to evaluate their synergy.

Abstract

The structure of the turbulent vortex in a two-layer impinging stream reactor was studied by large eddy simulation. The distributions of vortex intensity, turbulent kinetic energy, and shear stress at different Reynolds numbers Re, nozzle spacings L, and nozzle layer spacings are discussed. The relationship between vortex structure and mixing effect in the flow field is revealed. The effects of longitudinal swirls and shear flow characteristics are analyzed. Finally, the field synergy theory is used for evaluation. With increasing Re, the vortex intensity and average shear stress increase. The nozzle spacing and layer spacing affect the mixing effect in the reactor by controlling the change of vortex structure in the flow field. When L/D = 3, where D is the nozzle diameter, the energy loss is the smallest and the mixing effect is the best. The research results provide a theoretical reference for the structural optimization of the impinging stream reactor.

Research Progress on Direct Contact Evaporation Heat Transfer between Two Immiscible Working Fluids

Posted on 25 September 2023 by nHailing Fu, nWenlin Xiong, nWenwen Liu, nTingduoduo Qian, nAocheng Liun

Simulation methods, experimental results, and enhancement pathways for direct contact vaporization heat transfer of organic workpieces in the past fifteen years are summarized, focusing on the dispersed phase of organic working fluids and the continuous phase of immiscible inorganic fluids. The changes in droplet population state and methods of enhanced heat transfer are discussed.

Abstract

The direct contact evaporation heat transfer of two immiscible fluids can realize low-temperature differential heat transfer, which is an important method to improve the heat transfer coefficient. This article focuses on the dispersed phase of organic working fluids and the continuous phase of immiscible inorganic fluids and summarizes the research on direct contact evaporation heat transfer in the past 15 years. The main research methods include theoretical analysis, numerical models, and experimental research. The evaporation process of a single droplet mainly involves bubble droplet growth, droplet configuration and discriminant, droplet shape change, rising speed and path, etc. In practice, dispersed phases mostly exist in populations, and the research mainly focuses on collisions, coalescence, and rupture between droplets and bubbles, as well as on the number and size distribution. The volumetric heat transfer coefficient is used to reflect the heat transfer capacity of the heat exchanger. The factors affecting evaporation heat transfer performance are complex, and increasing the uniform mixing of bubbles is an important method to improve the heat transfer coefficient. In the future, direct contact evaporation heat transfer is expected to be promoted to multiple fields.

Liquid‐Liquid Phase Equilibrium of Glycerolysis Precursors: Experimental and Modeling Study

Posted on 22 September 2023 by nKapil Mamtani, nChristian L. da Silveira, nMohammed M. Farid, nKaveh Shahbazn

Glycerol and oleic acid are mutually immiscible components. Their rigorous reaction produces glycerol esters and water. Such mutual immiscibility of glycerol and free fatty acids limits glycerolysis, a reaction capable of upgrading waste-derived oils. The glycerol solubility in the fatty phase increases when glycerol esters are added to the immiscible mixture of glycerol and oleic acid.

Abstract

The mutual immiscibility of glycerol and free fatty acids limits glycerolysis, a reaction capable of upgrading waste-derived oils. In the present work, the liquid-liquid phase equilibrium data for the glycerol-water-oleic acid and glycerol-monoolein-oleic acid ternary systems were determined experimentally and compared with predictions of the UNIFAC-LLE and COSMO-SAC models. Monoolein was found to affect the glycerol solubility in oleic acid strongly. None of the models investigated adequately determined phase equilibria for the glycerol-monoolein-oleic acid system. COSMO-SAC predictions showed the best trend for glycerol solubility in the fatty phase. For the glycerol-water-oleic acid system, UNIFAC-LLE predictions were in good agreement with experimental data.