Process synthesis operations

Sundmacher, K., Kienle, A., Seidel-Morgenstem, A. (Eds.). Integrated Chemical Processes Synthesis, Operation, Analysis, and Control. Wiley-VCH, Weinheim, 2005. 

Conventional Transportation Fuels. Synthesis gas produced from coal gasification or from natural gas by partial oxidation or steam reforming can be converted into a variety of transportation fuels, such as gasoline, aviation turbine fuel (see Aviation and other gas turbine fuels), and diesel fuel. A widely known process used for this appHcation is the Eischer-Tropsch process which converts synthesis gas into largely aHphatic hydrocarbons over an iron or cobalt catalyst. The process was operated successfully in Germany during World War II and is being used commercially at the Sasol plants in South Africa. 

Chemical Flowsheet Basic unit operation selection with flow rates, conversion factors, temperatures, pressures, solvents and catalyst selection Process synthesis route Laboratory and pilot scale trials Knowledge of existing processes... 

That benzene hexachloride isomer mixture is then the raw material for lindane production. The production of lindane per se is not a chemical synthesis operation but a physical separation process. It is possible to influence the gamma isomer content of benzene hexachloride to an extent during the synthesis process. Basically, however, one is faced with the problem of separating a 99%-plus purity gamma isomer from a crude product containing perhaps 12 to 15% of the gamma isomer. The separation and concentration process is done by a carefully controlled solvent extraction and crystallization process. One such process is described by R.D. Donaldson et al. Another description of hexachlorocyclohexane isomer separation is given by R.H. Kimball. 

When compared to purely chemical synthesis, bioprocesses are operated under relatively mild conditions and in aqueous solvents they are essentially low temperature processes with operating temperatures usually below 40°C. The pH of most bioprocesses is between 6 and 8 and the pressure is usually one atmosphere. Under these conditions, substrates (eg oxygen) can be poorly soluble in water, which may limit productivity. Since reactions can generate considerable amounts of heat, waste heat generated during bioprocesses often has to be adequately dissipated to ensure high temperatures do not damage enzymes or cells. 

The methanation process commonly operates at pressures up to 30 atm, and, with the nickel catalyst which is almost universally used for the process, the inlet temperature is about 300°C ( 570°F). Almost complete conversion of the oxides of carbon occurs giving a product synthesis gas containing less than 5 ppm CO + C02. The temperature rise for the exothermic methanation reactions is typically 35 °C (63°F). 

AGB stars constitute excellent laboratories to test the theory of stellar evolution and nucleosynthesis. Their particular internal structure allows two important processes to occur in them. First is the so-called 3(,ldredge-up (3DUP), a mixing mechanism in which the convective envelope penetrates the interior of the star after each thermal instability in the He-shell (thermal pulse, TP). The other is the activation of the s-process synthesis from alpha captures on 13C or/and 22Ne nuclei that generate the necessary neutrons which are subsequently captured by iron-peak nuclei. The repeated operation of TPs and the 3DUP episodes enriches the stellar envelope in newly synthesized elements and transforms the star into a carbon star, if the quantity of carbon added into the envelope is sufficient to increase the C/O ratio above unity. In that way, the atmosphere becomes enriched with the ashes of the above nucleosynthesis processes which can then be detected spectroscopically. 

Steve Walsh and John Perkins, Operability and Control inn Process Synthesis and Design... 

Fischer-Tropsch A process for converting synthesis gas (a mixture of carbon monoxide and hydrogen) to liquid fuels. Modified versions were known as the Synol and Synthol processes. The process is operated under pressure at 200 to 350°C, over a catalyst. Several different catalyst systems have been used at different periods, notably iron-zinc oxide, nickel-thoria on kieselgtihr, cobalt-thoria on kieselgiihr, and cemented iron oxide. The main products are C5-Cn aliphatic hydrocarbons the aromatics content can be varied by varying the process conditions. The basic reaction was discovered in 1923 by F. Fischer and... 

Process synthesis is a task of formulating the process configuration for a purpose by defining which operations or equipment are used and how they are connected together. There are two basic approaches for process synthesis 1) classical process synthesis, analysis and evaluation, and 2) optimization of process structure by using a suitable objective function. 

ISI can be used also as an objective function in computerized process synthesis. Process synthesis can be considered as an optimization task. Because the model is uncontinuous, ordinary optimization methods could not be used, but a genetic algorithm was employed instead. In a genetic algorithm the structure of the process was represented as a string of integers, which describes the operations required and how they are connected together. 

Product-centered Process Synthesis and Developoment Detergents Table 12. Examples of dependence of structural attributes on operating variables. 

SCFs will find applications in high cost areas such as fine chemical production. Having said that, marketing can also be an issue. For example, whilst decaffeina-tion of coffee with dichloromethane is possible, the use of scCC>2 can be said to be natural Industrial applications of SCFs have been around for a long time. Decaffeination of coffee is perhaps the use that is best known [16], but of course the Born-Haber process for ammonia synthesis operates under supercritical conditions as does low density polyethylene (LDPE) synthesis which is carried out in supercritical ethene [17]. 

The process is operated at a platinum electrode and a reduced efficiency due to side reactions is observed. A maximum yield of 55% is reported. The use of in situ generated NBS and bromine for the synthesis of nucleosides from silylated pyrimidines has been studied. Nokami etal. [125] suggest the use of only catalytic amounts of NBS or bromine and regeneration of the catalyst by anodic electrolysis in an undivided cell system. 

Prewar Development of Synthesis Operation in Germany. The production of significant quantities of liquid hydrocarbons from synthesis gas over a cobalt catalyst was first reported by Fischer and Tropsch (6) in 1926. In 1932 a catalyst, useful for commercial operations, was described by Fischer and Koch (4), and in 1935 Ruhrchemie built the first full scale synthesis plant, which operated, at atmospheric pressure. In 1936, the process was modified by the work of Fischer and Pichler (5) to operate at. 5 to 15... 

Mitchell used chemiosmotic to describe enzymatic reactions that involve, simultaneously a chemical reaction and a transport process. The operational definition of coupling is shown in Figure 19-18. When isolated mitochondria are suspended in a buffer containing ADP, Pi, and an oxidizable substrate such as succinate, three easily measured processes occur (1) the substrate is oxidized (succinate yields fumarate), (2) 02 is consumed, and (3) ATP is synthesized. Oxygen consumption and ATP synthesis depend on the presence of an oxidizable substrate (succinate in this case) as well as ADP and Pi. 

An industrial process to produce methanol from carbon monoxide and hydrogen was developed by BASF in 1923 using a zinc oxide-chromia catalyst.361 362 Since this catalyst exhibited relatively low specific activity, high temperature was required. The low equilibrium methanol concentration at this high temperature was compensated by using high pressures. This so-called high-pressure process was operated typically at 200 atm and 350°C. The development of the process and early results on methanol synthesis were reviewed by Natta 363... 

In eukaryotes, most of the reactions of aerobic energy metabolism occur in mitochondria. An inner membrane separates the mitochondrion into two spaces the internal matrix space and the intermembrane space. An electron-transport system in the inner membrane oxidizes NADH and succinate at the expense of 02, generating ATP in the process. The operation of the respiratory chain and its coupling to ATP synthesis can be summarized as follows ... 

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