Conceptual Flowsheets Research Articles

Kinetics of One-Pot Regioselective Cohydrogenation of Styrene Oxide and Aryl Alkenes: A Step toward Sustainable Development of a Novel Integrated Process for 2-Phenylethanol Production

A strategy of one-pot regioselective cohydrogenation of styrene oxide (STOX) and aryl alkenes (styrene and alpha-methylstyrene) in the presence of aralkyl alcohols (1-phenylethanol and 2-phenyl-2-propanol) is proposed. It would help reduce capital and operational expenditure in the aralkyl hydroperoxide-based 2-phenylethanol (2PEA) manufacturing process. Reactions are performed in a stirred tank reactor in the presence of a 5% Pd/C catalyst. A range of operating conditions are proposed wherein STOX is converted to 2PEA, whereas the aryl alkenes are converted to their corresponding alkylbenzenes. Interestingly, the rate of hydrogenation of STOX is much slower than the rapid hydrogenation of the aryl alkenes. The kinetic model for the reaction is proposed based on the experimental data, and the associated parameters are estimated by nonlinear regression. The apparent activation energy for STOX hydrogenation over the range of operating conditions is calculated as 47.65 kJ mol–¹. The estimated kinetic parameters are apposite for the technocommercial feasibility study and subsequent scaling-up issues of the aralkyl hydroperoxide-based novel scheme of 2PEA production. Based on the observations, conceptual flowsheets for 2PEA manufacturing using cumene hydroperoxide and ethylbenzene hydroperoxide are also proposed.

Comparison of extractive distillation flowsheets for methanol–tetrahydrofuran–water mixtures

Objectives. Synthesis and comparative analysis of the extractive distillation flowsheets for aqueous mixtures of solvents utilized in pharmaceutical industries using the example of a methanol−tetrahydrofuran−water system with various compositions. The ternary system contains two minimally boiling azeotropes that exist in a vapor–liquid phase equilibrium. To evaluate the selective effect of glycerol, the phase equilibria of the methanol–tetrahydrofuran–water and methanol–tetrahydrofuran–water–glycerol systems at 101.32 kPa were studied.Methods. The calculations were carried out in the Aspen Plus V.9.0 software package. The vapor–liquid equilibria were simulated using the non-random two-liquid (NRTL) equation with the binary interaction parameters of the software package database. To account for the non-ideal behavior of the vapor phase, the Redlich–Kwong equation of state was used. The calculations of the extractive distillation schemes were carried out at 101.32 kPa.Results. The conceptual flowsheets of extractive distillation are proposed. The flowsheets consist of three (schemes I–III) or four (scheme IV) distillation columns operating at atmospheric pressure. In schemes I and II, the extractive distillation of the mixtures is carried out with tetrahydrofuran isolation occurring in the distillate stream. Further separation in the schemes differs in the order of glycerol isolation: in the third column for scheme I (traditional extractive distillation complex) or in the second column for scheme II (two-column extractive distillation complex + methanol/water separation column). Sсheme III caters to the complete dehydration of the basic ternary mixtures, followed by the extractive distillation of the azeotropic methanol–tetrahydrofuran system, also with glycerol. Sсheme IV includes a preconcentration column (for the partial removal of water) and a traditional extractive distillation complex.Conclusions. According to the criterion of least energy consumption for separation (the total load of the reboilers of distillation columns), sсheme I (a traditional complex of extractive distillation) is recommended. Additionally, the energy expended for the separation of the basic equimolar mixture using glycerol as the extractive agent was compared with that expended using another selective agent: 1,2-ethanediol. Glycerol is an effective extractive agent because it reduces energy consumption, in comparison with 1,2-ethanediol, by more than 5%.

Scaleup of pressure oxidation processes

The successful commercialization of a pressure oxidation (POX) process for recovering metal values, including gold, copper, zinc, nickel and molybdenum, is the result of a carefully planned development program. The initial task involves developing one or more conceptual flowsheets, including the POX autoclave and downstream purification and recovery steps. A laboratory program is completed to determine the technical viability of the flowsheets, define the operating parameters for each step and provide information for an initial economic assessment of the process. The process is then confirmed during a continuous pilot plant program, providing engineering design data and other information for the commercial design. A well-thought-out development program has been shown to be critical for reducing the risk of commercializing POX processes. Experiences developing POX processes for refractory gold ores and copper concentrates are briefly discussed.

Processing of Goethitic Iron Ore Fines

In the present investigation an attempt has been made to beneficiate goethitic iron ore containing 59.02 % Iron, 6.51 % Alumina, 4.79 % Silica, 0.089 % Phosphorus with 7.11 % loss on ignition. For this purpose, different beneficiation techniques such as gravity and magnetic separation processes have been employed. During the process two conceptual flow sheets were also developed for the beneficiation of goethite iron ore fines. In the prsent work it was possible to enhance grade of iron to 63.35, 63.18, and 65.35 % from Jigging, Multi Gravity Separation (MGS) and Wet High Intensity Magnetic Separator (WHIMS) respectively.

Beneficiation of Indian High Alumina Iron Ore Fines – a Case Study

Beneficiation of high alumina iron ore fines from Noamundi, India is studied for producing sinter/ pellet grade concentrate. The iron ore fine sample has a feed grade of 59.77%Fe, %4.71SiO<SUB>2</SUB>, and % 5.89Al<SUB>2</SUB>O<SUB>3</SUB> with % 5.53 of LOI (Loss on Ignition). From the characterisation studies, it is revealed that the sample contains huge quantity of goethite which is partially weathered, interlocked with hematite and gangue minerals like gibbsite, kaolinite and quartz at different proportions. Two conceptual flow sheets have considered for the beneficiation of Indian high alumina iron ore fines. The first option, consisting of hindered settling classifier followed by two stage gravity concentration results in a product quality with 66.82%Fe and 2.1%Al<SUB>2</SUB>O<SUB>3</SUB> content ensuring 25.15% iron recovery. In the second option, the iron ore fines treating in the similar approach but the second stage gravity concentration replaced by magnetic separation results in a product quality with 67.77% Fe, 1.53% Al<SUB>2</SUB>O<SUB>3</SUB> with 28.95% of iron recovery. Mineralogical studies revealed that the concentrate product quality depends on presence of the goethite in the product.

PYROPROCESSING FLOWSHEETS FOR RECYCLING USED NUCLEAR FUEL

Two conceptual flowsheets were developed for recycling used nuclear fuel. One flowsheet was developed for recycling used oxide nuclear fuel from light water reactors while the other was developed for recycling used metal fuel from fast spectrum reactors. Both flowsheets were developed from a set of design principles including efficient actinide recovery, nonproliferation, waste minimization and commercial viability. Process chemistry is discussed for each unit operation in the flowsheet.

ISASMELT™ TSL – Applications for nickel

The ISASMELT™ process is a top submerged lance (TSL) bath smelting technology which has been developed and optimised over the last 25 years. By the end of 2011, the total installed capacity of the ISASMELT™ technology will exceed 9,000,000 tonnes per year of feed materials in copper and lead smelters around the world. The technology is equally effective for smelting nickel sulfide concentrates, converting nickel mattes, and producing ferronickel from lateritic ores. This paper demonstrates how the features that make ISASMELT™ attractive for copper and lead smelting may be applied equally to nickel smelting and converting operations. Conceptual flowsheets are presented, supported by results from recent pilot plant and bench-scale testwork.

Heat Integration Strategy for Economic Production of Combined Heat and Power from Biomass Waste

The objective of this work was to design a heat integrated, cost-effective, and cleaner combined heat and power (CHP) generation plant from low-cost, fourth-generation biomass waste feedstocks. The novelty lies in the development of systematic sitewide heat recovery and integration strategies among biomass integrated gasification combined cycle processes so as to offset the low heating value of the biomass waste feedstocks. For the biomass waste based CHP plant technical and economic analysis, the process was based on low-cost agricultural wastes like straws as the biomass feedstock and further established for a more predominant biomass feedstock, wood. The process was modeled using the Aspen simulator. Three conceptual flowsheets were proposed, based on the integration of the flue gas from the char combustor, which was separately carried out from the steam gasification of biomass volatalized gases and tars, and carbon dioxide removal strategies. The cost of energy production included detailed levelized discounted cash flow analysis and was found to be strongly influenced by the cost of feedstock. On the basis of a combined energy generation of ∼340−370 MW using straw wastes priced at 35.3 £/t or 40 Euro/t, with 8.5% and 8.61% by mass moisture and ash contents, respectively, the cost of electricity generation was 4.59 and 5.14 p/(kW h) for the cases without and with carbon capture respectively, with a 10% internal rate of return and 25 years of plant life. On the basis of the carbon capture value assigned by the Carbon Credits Trading scheme, a much constrained viable price of 22 £/t of such agricultural waste feedstocks for CHP generation was obtained, while up to 60 £/t of waste feedstocks can be economically viable under the UK Climate Change Levy, respectively.

State-of-the-art Adsorption and Membrane Separation Processes for Carbon Dioxide Production from Carbon Dioxide Emitting Industries

With the growing concern about global warming placing greater demands on improving energy efficiency and reducing CO2 emissions, the need for improving the energy intensive, separation processes involving CO2 is well recognized. The US Department of Energy estimates that the separation of CO2 represents 75% of the cost associated with its separation, storage, transport, and sequestration operations. Hence, energy efficient, CO2 separation technologies with improved economics are needed for industrial processing and for future options to capture and concentrate CO2 for reuse or sequestration. The overall goal of this review is to foster the development of new adsorption and membrane technologies to improve manufacturing efficiency and reduce CO2 emissions. This study focuses on the power, petrochemical, and other CO2 emitting industries, and provides a detailed review of the current commercial CO2 separation technologies, i.e., absorption, adsorption, membrane, and cryogenic, an overview of the emerging adsorption and membrane technologies for CO2 separation, and both near and long term recommendations for future research on adsorption and membrane technologies. Flow sheets of the principal CO2 producing processes are provided for guidance and new conceptual flow sheets with ideas on the placement of CO2 separations technologies have also been devised.

Electrochemical Processing of Carbon Dioxide

With respect to the negative role of carbon dioxide on our climate, it is clear that the time is ripe for the development of processes that convert CO(2) into useful products. The electroreduction of CO(2) is a prime candidate here, as the reaction at near-ambient conditions can yield organics such as formic acid, methanol, and methane. Recent laboratory work on the 100 A scale has shown that reduction of CO(2) to formate (HCO(2)(-)) may be carried out in a trickle-bed continuous electrochemical reactor under industrially viable conditions. Presuming the problems of cathode stability and formate crossover can be overcome, this type of reactor is proposed as the basis for a commercial operation. The viability of corresponding processes for electrosynthesis of formate salts and/or formic acid from CO(2) is examined here through conceptual flowsheets for two process options, each converting CO(2) at the rate of 100 tonnes per day.

Hydrometallurgical processing of lead-bearing materials for the recovery of lead and silver as lead concentrate and lead metal

Hydrometallurgical processing of lead-bearing materials generated at zinc plants is described. Two types of lead sulphate generated at the smelters of Hindustan Zinc (HZL) have been used, in addition to other types of lead–silver-bearing residues. Two approaches have been selected in view of the complexities of the material. In the first approach, a simple double-decomposition technique was selected for treatment of one of the lead-sulphate residues by reacting with sodium-sulphide solution after the removal of acid-soluble metal values to produce a high-quality lead concentrate. In the second approach, the lead-sulphate residue was treated with brine solution and the resultant filtrate was reacted with sodium-sulphide solution to obtain lead concentrate or cemented-out lead as lead sponge using aluminium scrap, which was then briquetted and melted into lead metal. Alternatively, the lead sponge was subjected to roasting to obtain litharge as a value-added product. The processes developed are very simple, easy to implement and cost-effective, eco-friendly with cleaner technology. The recoveries are excellent. The lead concentrate obtained by the proposed processes can be used directly in the lead circuit and the lead sponge obtained can be melted and cast into lead ingot or roasted to produce lead oxide. The quality of lead concentrate, lead metal and lead oxide produced by the processes are also incorporated. Based on the results, conceptual flowsheets have been developed to treat 3–5 tons/day lead-bearing materials. A similar method was applied to other lead–zinc–cadmium–silver-bearing materials generated at HZL plants. The results are presented along with the flowsheet.