Process Routes

Once the process route has been chosen, it may be possible to synthesize flowsheets that do not require large inventories of materials in the process. The design of the reaction and separation system is particularly important in this respect, but heat transfer, storage, and pressure relief systems are also important. 

Future Methanol Processes. The process route for methanol synthesis has remained basically unchanged since its inception by BASF in 1923. The principal developments have been in catalyst formulation to increase productivity and selectivity, and in process plant integration to improve output and energy efficiency while decreasing capital cost. 

Rhodium was about three times the price of gold through 1988—1989 until skyrocketing to 74/g ( 2300/troy oz) in early 1990. Thus precious metal catalyst costs requite an absolute minimum level of use and maximum number of catalyst recycle uses when batch processing is employed. Starting material contaminants may effect catalyst poisoning, though process routes to overcome this by feed stream pretreatment may be devised (37,60). 

Contaminant by-products depend upon process routes to the product, so maximum impurity specifications may vary, eg, for CHA produced by aniline hydrogenation versus that made by cyclohexanol amination. Capillary column chromatography has improved resolution and quantitation of contaminants beyond the more fliUy described packed column methods (61) used historically to define specification standards. Wet chemical titrimetry for water by Kad Eisher or amine number by acid titration have changed Httle except for thein automation. Colorimetric methods remain based on APHA standards. 

AH commercial processes for the manufacture of caprolactam ate based on either toluene or benzene, each of which occurs in refinery BTX-extract streams (see BTX processing). Alkylation of benzene with propylene yields cumene (qv), which is a source of phenol and acetone ca 10% of U.S. phenol is converted to caprolactam. Purified benzene can be hydrogenated over platinum catalyst to cyclohexane nearly aH of the latter is used in the manufacture of nylon-6 and nylon-6,6 chemical intermediates. A block diagram of the five main process routes to caprolactam from basic taw materials, eg, hydrogen (which is usuaHy prepared from natural gas) and sulfur, is given in Eigute 2. 

Product Process route tons/year X Itf metric ton/yr of product metric tons/year ... 

Increasing use is now being made of alternative processing routes. In powder metallurgy the liquid metal is atomised into small droplets which solidify to a fine powder. The powder is then hot pressed to shape (as we shall see in Chapter 19, hot-pressing is... 

Briefly describe the processing route which you would specify for making the pressure hull of Problem 27.2 from each of the materials listed in the table. Comment on any particular problems which might be encountered. [You may assume that the detailed design will call for a number of apertures in the wall of the pressure hull.]... 

Is selection of a specific process route, or other design option, more appropriate on safety grounds ... 

There are two process routes for making steel in the UK today the electric arc furnace and the basic oxygen converter. The latter requires a charge of molten iron, which is produced in blast furnaces. The raw materials for producing molten iron are iron ore, coking coal, and fluxes (materials that help the chemical process) - mainly limestone. 

Increasingly today, steels after they have been tapped (poured) from the furnace undergo a further stage of processing called secondary steelmaking before the steel is cast. This applies to both the basic oxygen process route and to the electric arc furnace route. 

Edwards, D. W., D. Lawrence, and A. G. Rushton (1996). Quantifying the Inherent Safety of Chemical Process Routes. 5th World Congress of Chemical Engineering, July 14-18,1996, San Diego, CA, Paper 52d. New York American Institute of Chemical Engineers. 

Edwards, D. W., and D. Lawrence (1995). Inherent Safety Assessment of Chemical Process Routes. The i995 IChemE Research Event, First Eur. Conf Young Res. Chem. Eng., 62-64. Rugby, UK The Institution of Chemical Engineers. 

The process designer must be aware of costs as reflected in the (1) selection of a basic process route (2) the equipment to be used in the process and (3) the details incorporated into the equipment. The designer must not arbitrarily select equipment, specify details or set pressure levels for design wdthout recognizing the relative effect on the specific cost of an item as well as associated equipment such as relieving devices, instruments, etc. 

As a result of following the pyrochemical recycle route rather than the aqueous waste processing route, the plutonium values in the residues can be returned very expeditiously to the main process sequence. The form of the plutonium is metal, which is most desirable from a production standpoint. 

FAME may in the future become a possible organic feedstock to the sulfonated to fatty acid methyl ester sulfonate (FAMES). This feedstock is naturally renewable as it is produced from oils/fats or fatty acids. There are several possible process routes for the manufacture of FAME. 

Identify the major safety hazards and eliminate them, if possible Locate critical areas on the flow diagrams and layout drawings Is selection of a specific process route, or other design option, more appropriate on safety grounds ... 

Safety risk of incidents miniature plants novel process routes industrial and academic examples of use HTE standardization LEGO-type plants [207]. 

Edwards, D.W. Lawrence, D. (1993) Assessingthe Inherent Safety ofChemical Process Routes Is There a Relation between Plant Costs and Inherent Safety Transactions of the Institute ofChemical Engineers, 71(B), 252-258. 

Raw materials and auxiliary products used in a process as well as materials of construction for equipment items can be the eause of scale-up effects . Pure raw and auxiliary materials must be used in laboratory studies to eliminate the influence of impurities on the ehoice of the process route, catalyst selection, and search for satisfactory process conditions. However, pure chemicals are usually too expensive to use for manufacture on a commercial scale. It is common practice to use raw materials of technical grade in a full-scale plant. These materials contain impurities, which can act as catalysts or inhibitors. They can react with reactants or intermediates, thereby decreasing yields and selectivities of desired produets. Therefore, raw materials of technical grade, even from different suppliers must first be tested on laboratory scale. 

The process objectives defined earlier must relate to the process routes. A process route essentially consists of several sequential steps with the ultimate aim of achieving the process objective. There are one or more of basic objectives, namely, separation, production of a compound intermediate, metal reduction, and metal refining. With a given starting source material the four basic objectives can be pursued singly or in combination to arrive at the ultimate aim. For example, if the ultimate aim is to prepare a concentrate for the market then it is only the separation that is required for reaching to the product. If, on the other hand, purified metal production is the ultimate aim then possibly all the four objectives have to be fulfilled. 

Figure 1.26 Process route for treatment of low-grade oxidic copper ore.

---