Detailed Equipment Design

Flare systems are subject to potential flashback and internal explosion since flammable vapor/air mixtures may be formed in the stack or inlet piping by the entry of air, and the pilot constitutes a continuous ignition source. Flares are therefore always provided with flashback protection, which prevents a flame front from travelling back to the upstream piping and equipment. Design details are described later. 

Based on the pre-conceptual designs of the U.S. ceramic process, a summary of the technical safety issues is given below. It should be emphasized that the results are preliminary and generic because the facility and equipment design details are not yet available. 

A number of engineering Arms around the world design and manufacture deodorizers to meet the needs of the vegetable oil industry, in many instances offering unique equipment designs, detailed descriptions of which can be readily found in the literature [35]. The following sections summarize the general characteristics of the three classes of deodorizers batch, semicontinuous, and continuous. 

Process simulators stop generally at the process specifications for the equipment. For the detailed mechanical design of the equipment, such as heat exchangers and distillation columns, stand-alone programs are often used. They make process calculations, size the equipment, calculate thermal and mechanical stresses, design mechanical support of the parts of the equipment, design inlet and outlet nozzles, etc. 

References are noted throughout the book for further information. Particular attention is given to Web site sources where detailed equipment design information and chemical property data bases exist. 

The safe design and operation of chemical processing equipment requires detailed attention to the hazards inherent in certain chemicals and processes. Chemical plant hazards can occur from many sources. Principal hazards arise from ... 

The SRK model can also be used as part of a approach for the elimination of errors that have serious consequences proactive for the plant. Once specific errors have been identified, based on the SRK model, interventions such as improved procedures, training or equipment design can be implemented to reduce their likelihood of occurrence to acceptable levels. This strategy will be discussed in more detail in Chapter 4. 

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. 

The purpose of these 3 volumes is to present techniques of process design and to interpret the results into mechanical equipment details. There is no attempt to present theoretical developments of the design equations. The equations recommended have practically all been used in actual plant equipment design, and are considered to be the most reasonable available to the author, and still capable of being handled by both the inexperienced as well as the experienced engineer. A conscious effort has been made to offer guidelines to judgment, decisions and selections, and some of this will be found in the illustrative problems. 

Before presenting design details, we will review a summary of the usual equipment found in process plants. 

Product size is limited to available equipment that can handle the size and pressure as well as other processing requirements. Also involved are factors such as packaging and shipment to the customer. The ability to achieve specific shapes and design details is dependent on the way the process operates. 

The capillary tube method initially involves packing a powdered sample into a glass capillary tube of uniform diameter and length, carefully sealed at one end so that it forms a rounded tube of uniform thickness. The tube is then attached to a standardized thermometer so that the end of the tube reaches the middle of the thermometer reservoir bulb. This assembly is then inserted into a vessel contg a suitable liq which is uniformly heated so that the temp rises at a rate of about 1° per minute. Ref 1 discusses in detail equipment design and thermometer calibration. It should be noted that this technique is the method most widely used by organic chemists... 

In this book the discussion of optimisation methods will, of necessity, be limited to a brief review of the main techniques used in process and equipment design. The extensive literature on the subject should be consulted for full details of the methods available, and their application and limitations see Beightler and Wilde (1967), Beveridge and Schechter (1970), Stoecker (1989), Rudd and Watson (1968), Edgar and Himmelblau (2001). The books by Rudd and Watson (1968) and Edgar and Himmelblau (2001) are particularly recommended to students. 

The life of equipment subjected to corrosive environments can be increased by proper attention to design details. Equipment should be designed to drain freely and completely. The internal surfaces should be smooth and free from crevasses where corrosion products and other solids can accumulate. Butt joints should be used in preference to lap joints. The use of dissimilar metals in contact should be avoided, or care taken to ensure that they are effectively insulated to avoid galvanic corrosion. Fluid velocities and turbulence should be high enough to avoid the deposition of solids, but not so high as to cause erosion-corrosion. 

Whenever possible, experimentally determined values of physical properties should be used. If reliable values cannot be found in the literature and if time, or facilities, are not available for their determination, then in order to proceed with the design the designer must resort to estimation. Techniques are available for the prediction of most physical properties with sufficient accuracy for use in process and equipment design. A detailed review of... 

Other examples of this type of program are those for equipment design— for instance, the detailed design of heat exchangers or fractionating columns. 

In this approach accident cases and design recommendations can be analysed level by level. In the database the knowledge of known processes is divided into categories of process, subprocess, system, subsystem, equipment and detail (Fig. 6). Process is an independent processing unit (e.g. hydrogenation unit). Subprocess is an independent part of a process such as reactor or separation section. System is an independent part of a subprocess such as a distillation column with its all auxiliary systems. Subsystem is a functional part of a system such as a reactor heat recovery system or a column overhead system including their control systems. Equipment is an unit operation or an unit process such as a heat exchanger, a reactor or a distillation column. Detail is an item in a pipe or a piece of equipment (e.g. a tray in a column, a control valve in a pipe). 

As discussed in Chapter 1, optimization of a large configuration of plant components can involve several levels of detail ranging from the most minute features of equipment design to the grand scale of international company operations. As an example of the size of the optimization problems solved in practice, Lowery et al. (1993) describe the optimization of a bisphenol-A plant via SQP involving 41,147 variables, 37,641 equations, 212 inequality constraints, and 289 plant measurements to identify the most profitable operating conditions. Perkins (1998) reviews the topic of plantwide optimization and its future. 

HPLC equipment has been designed and produced to assure correct volumetric delivery of the mobile phase, including the injected sample, and has low-noise detectors so that low concentrations of samples can be analyzed conveniently. Discussed below, briefly, are some of the important considerations for the HPLC equipment. More detailed discussion can be found in a recent text (see Chapter 3 of reference 3). 

In this chapter reference has been made to a few issued patents but many do not appear in the bibliography. Practically all the issued patents involving the use of hydrogen fluoride as a catalyst are for details of equipment design or operation, and no chemical principles are involved. The number of these patents has now become very large. 

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