Temperature process optimization

Mineral acids are used as catalysts, usually in a concentration of 20— 40 wt % and temperatures of 30—60°C. An efficient surfactant, preferably one that is soluble in the acid-phase upon completion of the reaction, is needed to emulsify the a-pinene and acid. The surfactant can then be recycled with the acid. Phosphoric acid is the acid commonly used in the pine oil process. Its mild corrosion characteristics and its moderate strength make it more manageable, especially because the acid concentration is constandy changing in the process by the consumption of water. Phosphoric acid is also mild enough to prevent any significant dehydration of the alcohols formed in the process. Optimization of a process usually involves considerations of acid type and concentration, temperature, surfactant type and amount, and reaction time. The optimum process usually gives a maximum of alcohols with the minimum amount of hydrocarbons and cineoles. 

While process design and equipment specification are usually performed prior to the implementation of the process, optimization of operating conditions is carried out monthly, weekly, daily, hourly, or even eveiy minute. Optimization of plant operations determines the set points for each unit at the temperatures, pressures, and flow rates that are the best in some sense. For example, the selection of the percentage of excess air in a process heater is quite critical and involves a balance on the fuel-air ratio to assure complete combustion and at the same time make the maximum use of the Heating potential of the fuel. Typical day-to-day optimization in a plant minimizes steam consumption or cooling water consumption, optimizes the reflux ratio in a distillation column, or allocates raw materials on an economic basis [Latour, Hydro Proc., 58(6), 73, 1979, and Hydro. Proc., 58(7), 219, 1979]. 

In this case, there are n process variables with equality constraints and inequahty constraints. Such problems pose a serious challenge to performing optimization calculations in a reasonable amount of time. Typical constraints in chemical process optimization include operating conditions (temperatures, pressures, and flows have limits), storage capacities, and produc t purity specifications. 

The hydrogasification reactor operates at pressures of 1000-1500 psig and at temperatures of 760°-982°C in order to obtain the proper reaction rates and yields of methane required for process optimization. About 50% of the feed carbon is converted to gases in the hydrogasifier. 

As little as three factors can confront the investigator with an intractable situation if he chooses to proceed classically. One way out is to use the factorial approach, which can just be visualized for three factors. An example from process optimization work will illustrate the concept. Assume that temperature, the excess concentration of a reagent, and the pH have been iden-... 

Lee G-C (2001) Optimal Design and Analysis of Refrigeration Systems for Low-temperature Processes, PhD Thesis, UMIST, UK. 

Lee G-C, Smith R and Zhu XX (2003) Optimal Synthesis of Mixed-refrigerant Systems for Low-temperature Processes, Ind Eng Chem Res, 41 5016. 

Microwave-assisted synthesis is attractive to researchers for many reasons, including speed, yields, and the potential for reduced solvent use. Raman monitoring offers a convenient way to elucidate the chemical mechanism while instantly, continuously monitoring reaction kinetics. This enables rapid, data-driven process optimizations without concerns about safely and accurately sampling out of a microwave vessel stopped mid-reaction. Pivonka and Empheld of AstraZeneca Pharmaceuticals describe the continuous acquisition of Raman spectra of an amine or Knoevenagel coupling reaction in a sealed microwave reaction vessel at elevated temperatures and pressures [134]. 

Moreover, reaction time was reduced from hours to minutes or even seconds. Indeed, the carbonylation of aryl halides 335 was completed in 10 s to give symmetrical diaryl ketones 336 in excellent yields (Equation (31)). The process optimization to reduce the amount of catalyst disclosed the fact that this carbonylation reaction followed a radical pathway, initiated by the homolytic cleavage of Co2(CO)8 into -00(00)4. It also appeared that the amount of the Oo catalyst had a direct correlation with the internal temperature reached during the reaction. These findings are critical for the development of extremely fast synthesis using carbonylations. 

Technically, COSMO-RS meets all requirements for a thermodynamic model in a process simulation. It is able to evaluate the activity coefficients of the components at a given mixture composition vector, x, and temperature, T. As shown in Appendix C of [Cl 7], even the analytic derivatives of the activity coefficients with respect to temperature and composition, which Eire required in many process simulation programs for most efficient process optimization, can be evaluated within the COSMO-RS framework. Within the COSMOt/ierra program these analytic derivatives Eire available at negligible additionEd expense. COSMOt/ierra can Eilso be csdled as a subroutine, Euid hence a simulator program can request the activity coefficients and derivatives whenever it needs such input. 

Process optimization of the thermal treatment of an ablation polymer material, based on phenolformaldehyde resins, was done by time and temperature, by the application of simplex optimization. 

But via, for instance, high-heat exchange reactors (HEX reactors) that allow a much shorter reaction time and at the optimal temperature, process intensification can also reduce the formation of by-products considerably. A by-product reduction by a factor of 4 is achieved via a HEX reactor (46). This means a considerable reduction in feedstock cost and waste handling. 

The manufacture of a ceramic composite generally requires high temperatures. Destruction of carbon nanotubes using a hot-press technique was reported by Flahaut etal. [39], Therefore, the high-temperature degradation process of CNTs has to be further optimized to achieve proper protection of CNTs in high-temperature processes. 

In order to start the multiscale modeling, internal state variables were adopted to reflect void/crack nucleation, void growth, and void coalescence from the casting microstructural features (porosity and particles) under different temperatures, strain rates, and deformation paths [115, 116, 221, 283]. Furthermore, internal state variables were used to reflect the dislocation density evolution that affects the work hardening rate and, thus, stress state under different temperatures and strain rates [25, 283-285]. In order to determine the pertinent effects of the microstructural features to be admitted into the internal state variable theory, several different length scale analyses were performed. Once the pertinent microstructural features were determined and included in the macroscale internal state variable model, notch tests [216, 286] and control arm tests were performed to validate the model s precision. After the validation process, optimization studies were performed to reduce the weight of the control arm [287-289]. 

---