Process and Operations

FIGURE 6.1. Micro reactor and heat exchanger (heat transfer coefficient 20kW/mVk). 

Process intensification has several advantages (Stankiewicz and Moulijn, 2000 Simons, 2004), including 

Process intensification is achieved through the application of one or more of the following intensification principles  

PI not only leads to reductions in capital expenditure (Green, 1999) but also produces several other benefits  

Move from hatch to continuous mode of processing, which may he very relevant to the pharmaceutical and fine chemical industries. Fine chemicals accounted for U.S. 70 billion in sales in the year 2003, and 60% of those sales came from the pharmaceutical sector (Mullin, 2004). 

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Pilot-plant start-up is different from principal process plant start because of the smaller scale of the unit, smaller resources committed, lack of advance start-up planning, and limited experience with the pilot-plant process and operation. 

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. 

Process and Operating Conditions The major parameters that must be fixed or identified are the solvent to be used, the temperature, the terminal stream compositions and quantities, leaching cycle (batch or continuous), contact method, and specific extractor choice. 

Because of the wide variability in sludge characteristics and the variation in acceptability of treated sludges for ultimate disposal (this is a function of the location and characteristics of the ultimate disposal site), it is impossible to prescribe any particular sludge-management plan. In the sections below, general performance of individual sludge-treatment processes and operations is presented. 

Process Hazard Analysis (PHA) An organized effort to identify and evaluate hazards associated with chemical processes and operations to enable their control. This review normally involves the use of qualitative techniques to identify and assess the significance of hazards. Conclusions and appropriate rec-... 

An industrial hall is an indoor space that is enclosed by walls, ceiling, and floor. Such an enclosure is normally perforated by openings for supply and extract of ventilation air, pipes for industrial processes, and operable hatches, windows, and doors for regular or occasional use. 

For a given experiment and configuration, the mixing time will depend upon the process and operating variables as follows ... 

Batch fermentation means the cultivation of microorganisms, where the sterile growth medium in desired volume is inoculated with the microorganisms into the bioreactor and no additional growth medium is added during the fermentation. The product will be harvested at the end of the process. Typically, PHA s production is performed using batch fermentation because of low cost for investment and no special control. In addition, sterilization of the feed stock is easier than other fermentation processes, and operation is flexible. 

In this section we will discuss a systematic approach for the representation of processes and operating steps. These representations, or models, conform to the general requirements presented in Section I,B they can... 

Until about the second World War chemical processes were developed in an evolutionary way by building plants of increasing size and capacity. The capacity of the next plant in the series was determined by a scale-up factor that depended mainly upon experience gained from scale-ups of similar plants. Due to a lack of predictive models for chemical processes and operations, processes had to be scaled up in many small steps. This procedure was very expensive and the results unreliable. Therefore, large safety margins were incorporated in scale-up procedures, which often resulted in a significant unintended overcapacity of the designed plant. 

Operating costs can be estimated based on statistical analysis of operating costs in existing plants. Costs of waste disposal can be evaluated in the same way as costs for any chemical process since procedures for disposal include, in fact, unit chemical processes and operations. Costs of utilities and maintenance are best assessed based on the company data banks. Typical utility figures per m capacity of reactors in MPPs are 800-1100 kg steam/h, 60-80 kW power, and 7,000-8,000 kJ/h refrigeration capacity. 

In the simplest cases, the solvent may consist of one specified component, although in fact in a steady-state cyclic process it is highly unlikely that the solvent will ever come back to the initial composition at time zero. Rather, perhaps, one can say that make-up will entail addition of one material only. Again, clearly this need not be a pure compound, but its composition should be consistent. The single solvent offers limited scope for manipulating the system since it alone must meet all process and operational requirements. In other words, it must satisfy all aspects that will lead to an overall viable system. These aspects include selectivity, capacity, solubility, mass transfer, phase separation, costs, among others. The solvent is, therefore, a mixture components. The solvent components are extractant, (ii) diluent, (iii) modifier, and (iv) synergist. 

This paper deals with the advanced CFD of turbulent stirred vessels. The advances attained in recent years in the field of CFD really matter for the degree of accuracy and confidence at which the performance of stirred reactors and of other operations carried out in stirred vessels can be simulated, as these processes and operations may strongly depend on the details of the physics and chemistry involved. The latter details require the more advanced CFD techniques indeed. 

Each PrHA must be updated and revalidated at least every 5 years to make sure it accurately reflects current processes and operating experiences. 

The basic idea is to let the mind go free in a controlled fashion in order to consider all the possible ways that process and operational failures can occur. 

ALCOA A process proposed for manufacturing aluminum metal by the electrolysis of molten aluminum chloride, made by chlorinating alumina. It requires 30 percent less power than the Hall-Heroult process and operates at a lower temperature, but has proved difficult to control. Developed by the Aluminum Company of America, Pittsburgh, in the 1970s and operated in Palestine, TX, from 1976 abandoned in 1985 because of corrosion problems and improvements in the efficiency of conventional electrolysis. 

Human Factors—Included here are human error assessment, operator/process and operator/equipment interfaces, and administrative controls versus hardware. 

Once both latent conditions and precursors are identified in the company s control process and operational process, the effects on the company s safety barriers can be retrieved. Therefore, the safety barriers present around the transformation process will be identified, i.e. technical, human, and organizational safety barriers. Subsequently, the identified types of latent conditions are used to check if they affect the identified safety barriers either positively, negatively, or not at all (as discussed in the previous Chapter). How safety barriers are affected is illustrated by the example of the re-... 

Of course, it can be argued that these so-called unit processes may be split into the physical unit operation with modifications made necessary by chemical reactions. It should be remembered, however, that all of the physical unit operations can in turn be split into two subjects 1) material flow, and 2) heat flow. It is more satisfactory from a pedagogical standpoint no to reduce these processes and operations to their ultimate subdivisions, principally because the lack of data handicaps the presentation of the subject in such a manner (48). 

OSHA/USEPA requires employers, such as the chemical industry service sector, to perform an initial process hazard analysis (PHA) on processes covered by PSM/RMP standards. The PHA must be appropriate to the complexity of the process and must identify, evaluate, and control the hazards involved in the process. Employers are required to determine and document the priority order for conducting process hazard analyses based on a rationale that includes such considerations as extent of the process hazards, number of potentially affected employees, age of the process, and operating history of the process. 

In a further paper, Howards" classifies the processes and operations which occur in the manufacture and supply of products using an appropriate length scale as follows ... 

Kaminskii, A. A., Crystalline Lasers Physical Processes and Operating Schemes, CRC Press, Boca Raton, Florida (1996). 

This section provides a comprehensive overview of recent efforts in physical theory, molecular modeling, and performance modeling of CLs in PEFCs. Our major focus will be on state-of-the-art CLs that contain Pt nanoparticle electrocatalysts, a porous carbonaceous substrate, and an embedded network of interconnected ionomer domains as the main constituents. The section starts with a general discussion of structure and processes in catalyst layers and how they transpire in the evaluation of performance. Thereafter, aspects related to self-organization phenomena in catalyst layer inks during fabrication will be discussed. These phenomena determine the effective properties for transport and electrocatalytic activity. Finally, physical models of catalyst layer operation will be reviewed that relate structure, processes, and operating conditions to performance. 

The root cause of dark color streaks in gray-colored parts can sometimes be more difficult to determine since both poorly dispersed pigments and resin degradation products can be the source. In these cases, removing the color masterbatch from the process and operating with just the natural resin will allow the root cause to be identified. That Is, If the dark color streaks still occur in the product after the color masterbatch is removed, then the source of the problem is related to resin degradation. Two case studies are shown in Section 11.12 to illustrate these defects. 

During the operation of a polymer-electrolyte fuel cell, many interrelated and complex phenomena occur. These processes include mass and heat transfer, electrochemical reactions, and ionic and electronic transport. Only through fimdamental modeling, based on physical models developed from experimental observations, can the processes and operation of a fuel cell be truly understood. This review examines and discusses the various regions in a fuel cell and how they have been modeled. 

Normally, isolation valves should be designed to fail closed. However, depending on the process and operating conditions, the valve failing closed may create more problems and the failure position should be reviewed by process personnel. Examples of where the valve should fail open include on ... 

Because of the variety and uniqueness of pesticide manufacmring processes and operations, the flow and characteristics of wastewater generated from production plants vary broadly. In 1978, 1979, 1980, 1982, and 1984, the USEPA conducted surveys to obtain basic data concerning manufacturing, disposal, and treatment as well as to identify potential sources of priority pollutants in pesticide manufacmrers [7]. The results of these surveys and USEPA s interpretations and evaluations are summarized in the following. 

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