Sustaining the process

The van Arkel-De Boer process is widely used to refine metals. A transporting agent such as Ij reacts with the metal (M) to be refined to form a volatile iodide. This iodide is then decomposed at a higher temperature into the refined metal and I2, which becomes available again to react with the impure metal, thus sustaining the process ... 

Tables 2 and 3 show an antibody purification process scale-up from laboratory scale (1 mL) to intermediate scale (500 mL) to large scale of 10-85 L column volumes, maintaining the column bed height constant. Product quality and biocontaminant levels were maintained throughout the scale-up, though operational flow rates were significantly changed, demonstrating the consistency of the overall purification process. Thorough analysis of each coliunn performance is essential in order to sustain the process robustness at different scales of operation.

To activate the char produced in the pyrolysis step, a portion of the carbon is reacted with steam as in Reaction (6) to develop the internal pore structure which gives the carbon its high adsorptive properties. The percent of carbon that is reacted will depend upon the final properties desired but 25% to 50% is a typical range. This reaction between steam and carbon is highly endothermic so that heat must be supplied to sustain the process. The following list represents alternatives for generating or supplying this heat,... 

In terms of sustainability, the process starting from propene would be preferable, since it avoids the risks connected with the use of HCN in the butadiene route, even if produced on demand. However, the butadiene route to produce adiponitrile (ADN) is more cost-effective, owing to the need to use an electrochemical reaction for acrylonitrile dimerization. The problem of cost, however, is highly dependent on several factors, including sensitivity to natural gas prices (which influences butadiene cost), the market for acrylonitrile, and soon. The acrylonitrile route is used by Solutia, BASF and Asahi Kasei. New plants to make caprolactam, using ADN as intermediate, are under construction in Asia. 

Throughout the problem-solving process, we consider a host of feasibility criteria other than money. These include (1) market feasibility (the product provides customers with benefits they want and are willing to buy), (2) technical feasibility (the process must work, the desired amount and purity of the target product must be produced), (3) sustainability (the process should use our world s resources wisely so that we evolve toward sustainable development), (4) operability and controllability, (5) minimal hazards. 

Already at an early stage of the research in the semiconductor dispersions, attempts have been made to carry out water splitting, CO2 reduction, etc., in other words, the same photoelectrochemical processes as in the macroscopic PEC cells. The results obtained are summarized in [51-55]. We shall confine ourselves, however, to the processes that might underly some methods of purification, eg., of waste waters etc. These processes are stimulated by electrons and holes produced in the particles by light. As only one type of the current carriers is consumed in the "useful" reaction, measures should be taken to remove the other type from the particle in order to preserve its electroneutrality and sustain the process. For this purpose a sacrificial electron donor (or acceptor) is to be introduced into the electrolyte solution. Often it is the solvent that plays sacrifice. Some examples are listed below. 

The plasma-catalytic effect in non-equilibrium methane CO2 reformation (10 ) by sustaining the process with a combination of plasma energy and low-temperature preheating was demonstrated by Mutaf-Yardimci (2001) using an atmospheric-pressure pulsed eorona discharge. 

The occurrence of SHS reactions is predicated upon the ability of a reaction front to produce heat at a magnitude and a rate which can raise the temperature of the adjacent layer to the ignition point, and thus sustain the process in the form of a moving reaction front or combustion wave. However, for thermodynamic and kinetic reasons this process may not be possible, as is the case for the synthesis of many important materials. Referring to Eq. (1), a thermodynamic limitation is operative when the reaction enthalpy, Q, is low and this is the general basis for the use of the empirical limit of the adiabatic temperature discussed in an earlier... 

That the heat produced by the combustion is sufficiently in excess of heat losses to sustain the process. 

Knowledge/information the knowledge or information required to initiate and sustain the processes composing the CE system. This comprises the tacit and explicit knowledge available in people as well as information systems. It may include internal and/or external information sources. 

---