Process design majorization

At the heart of a leaching plant design at any level—conceptual, pre-liminaiy, firm engineering, or whatever—is unit-operations and process design of the extraction unit or hne. The major aspects that are particular for the leaching operation are the selection of process and operating conditions and the sizing of the extrac tion equipment. 

Like Bruce, I am here to share the perspective of the field. Shortcut equipment design methods play a major role in process equipment installations. Virtually all process designs employ these methods and shortcut techniques are developed from many sources. 

The application of the science of human factors to eliminating error in all aspects of process design, management, operation, and maintenance is the focus of this work. Human error has been a major cause of almost all of the catastrophic accidents that have occurred in the chemical process industries (CPI). If one adopts the broad view of human error as being the result of a mismatch between human capabilities and process demands, then clearly management s role is critical in the following areas ... 

The purification of value-added pharmaceuticals in the past required multiple chromatographic steps for batch purification processes. The design and optimization of these processes were often cumbersome and the operations were fundamentally complex. Individual batch processes requires optimization between chromatographic efficiency and enantioselectivity, which results in major economic ramifications. An additional problem was the extremely short time for development of the purification process. Commercial constraints demand that the time interval between non-optimized laboratory bench purification and the first process-scale production for clinical trials are kept to a minimum. Therefore, rapid process design and optimization methods based on computer aided simulation of an SMB process will assist at this stage. 

Steam cracking is of special importance as a major process designed specifically for producing light olefins. It is discussed separately later in this chapter. 

Since 1977, Reza Sadeghbeigi has been involved in various aspects of cat cracking at major and independent oil companies focusing on technical services, troubleshooting, process design, and project management—including major FCC revamps. 

The first step in devising a new process design will be to sketch out a rough block diagram showing the main stages in the process and to list the primary function (objective) and the major constraints for each stage. Experience should then indicate what types of unit operations and equipment should be considered. 

When using the operability study technique to vet a process design, the action to be taken to deal with a potential hazard will often be modifications to the control systems and instrumentation the inclusion of additional alarms, trips, or interlocks. If major hazards... 

To do this, not only must he know the chemistry of the reactions but he must know the rates at which the reactions occur and what affects those rates. The study of this is called chemical kinetics. By the proper choice of raw materials and operating conditions for the reaction stage the process designer can manipulate the ratio of products formed. One major variable is the temperature. An increase in temperature usually causes the reaction rates to increase, but some increase faster than others. Thus, the product mix in the reactor is dependent on the temperature. The pressure and the time the material spends in the reactor also affects the results. In the gaseous phase ahigh pressure will impede those steps in which the number of moles is increased and assist those in which the number of moles is decreased. A... 

The major approach to inherently safer process designs is divided into the following categories ... 

This subcommittee prepared the broad outline for the book, identified the scope and major key references, and selected the title "Guidelines for Chemical Reactivity Evaluation and Application to Process Design" as representative of the concepts desired. The TNO Prins Maurits Laboratory, Rijswijk, The Netherlands, was chosen as the contractor with Dr. A. Henk Heemskerk as the project manager. 

In this thesis an Inherent Safety Index for conceptual chemical process design is presented. This is required, since inherent safety should be considered in the early phases of design when the major decisions on the chemical process are made. The presented methodology allows such a consideration since the index is based on the knowledge available in the preliminary process design stage. 

Edwards and Lawrence (1993) have developed a Prototype Index of Inherent Safety (PIIS) for process design. The inherent safety index is intended for analysing the choice of process route i.e. the raw materials used and the sequence of the reaction steps. This method is very reaction oriented and does not consider properly the other parts of the process even they usually represent the majority of equipment. 

Many different alternative process configurations can be created for a process in the conceptual design phase. In choosing the most feasible alternative safety should be one of the major evaluation criterias. Therefore information on the safety features of alternative process structures are needed on preliminary process design. 

The SRC-II process, developed by Gulf Oil Corp., was an improved version of the SRC-I process, designed to produce more valuable liquid products, rather than a solid. The major difference between SRC-II and the typical process described above was the recycle of a portion of the fractionator bottoms to the slurry feed tank. This increased the ash content of the reactor feed. This ash, particularly the iron pyrites in the ash, acted as a catalyst and improved product yield and quality. 

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