Case study Equipment design

Equipment Cracking Failure Case Studies Equipment fails either alone or in combination with other factors, including substandard materials, improper material selection, poor design, equipment abuse, unexpected stresses or environmental conditions, and poor maintenance practices and/or neglect. Many failures, in one way or another, involve human error to some extent. 

A final note is with regard to flat bottom cyclones which have gained acceptance in recent years. The installation of a flat bottom in place of the conical section will coarsen the separation by more than twofold. Additionally, the sharpness of the recovery curve will decrease significantly. As such, flat bottom cyclones should be restricted to those applications in which coarse separations are required. The flat bottom cyclone does produce a very clean underflow but at the expense of a large amount of misplace coarse solids in the overflow. An illustration of a flat bottom cyclone is shown in Figure 58. The reader should refer to the reference section of this chapter for citations that provide more in-depth coverage of this equipment, as well as design case studies and example. 

The first set of case studies illustrates errors due to the inadequate design of the human-machine interface (HMI). The HMI is the boundary across which information is transmitted between the process and the plant worker. In the context of process control, the HMI may consist of analog displays such as chart records and dials, or modem video display unit (VDU) based control systems. Besides display elements, the HMI also includes controls such as buttons and switches, or devices such as trackballs in the case of computer controlled systems. The concept of the HMI can also be extended to include all means of conveying information to the worker, including the labeling of control equipment components and chemical containers. Further discussion regarding the HMI is provided in Chapter 2. This section contains examples of deficiencies in the display of process information, in various forms of labeling, and the use of inappropriate instrumentation scales. 

Case Study — Summary for Part II Detailed Equipment Design... 

Following the detailed equipment design, a few amendments need to be made to the information presented in Part I of the Design Project Report (Case Study). The two main areas needing amendment are detailed as follows. 

Note Chapters 9 to 12 contain case study material for the detailed design of equipment for the nitric acid plant. There are no accompanying text notes. References are included at the end of each chapter. Details of the calculations performed and additional information are included in Appendices G to J. 

Part II contains the design of a major item of equipment (in this case study, it is a sieve-tray absorption column (Chapter 9) ), including the mechanical design, fabrication, materials specification, detailed engineering drawing, HAZOP study, control scheme and associated instrumentation. In summary, as complete and professional a design as... 

Then, a survey of micro reactors for heterogeneous catalyst screening introduces the technological methods used for screening. The description of microstructured reactors will be supplemented by other, conventional small-scale equipment such as mini-batch and fixed-bed reactors and small monoliths. For each of these reactors, exemplary applications will be given in order to demonstrate the properties of small-scale operation. Among a number of examples, methane oxidation as a sample reaction will be considered in detail. In a detailed case study, some intrinsic theoretical aspects of micro devices are discussed with respect to reactor design and experimental evaluation under the transient mode of reactor operation. It will be shown that, as soon as fluid dynamic information is added to the pure experimental data, more complex aspects of catalysis are derivable from overall conversion data, such as the intrinsic reaction kinetics. 

This case study presents the design of a biochemical process for NO removal from flue gases, where an absorber and a bioreactor are the main units. Based on a rough estimation of Hatta numbers, it was concluded that a spray tower offering a large G/L interfacial and a small liquid fraction is the best type of equipment, favoring the main chemical reaction. The bioreactor was chosen as a CSTR. 

The job of designing power generation equipment usually falls to mechanical engineers, but the analysis of combustion reactions and reactors and the abatement and control of environmental pollution caused by combustion products like CO, CO2, and SO2 are problems with which chemical engineers are heavily involved. In Chapter 14, for example, we present a case study involving the generation of electricity from the combustion of coal and removal of SO2 (a pollutant) from combustion products. 

In the process industries, material balances assist in the planning for process design, in the economic evaluation of proposed and existing processes, in process control, and in process optimization. For example, in the extraction of soybean oil from soybeans, you could calculate the amount of solvent required per ton of soybeans or the time needed to fill up the filter press, and use this information in the design of equipment or in the evaluation of the economics of the process. All sorts of raw materials can be used to produce the same end product, and quite a few different types of processing can achieve the same end result, so that case studies (simulations) of the processes can assist materially in the financial decisions that must be made. 

Figure 1.9 shows different kinds of flowsheets which mark the start and the end of the part of the overall design process which is covered by the case study. At the beginning, the chemical process is described by an abstract flowsheet which decomposes the process into basic steps without considering the equipment to be used (upper part of Fig. 1.9). The process consists of three steps reaction of caprolactam and water, separation of input substances which are fed back into the reaction, and compounding, which manipulates the polymer produced in the reaction step such that the end product meets the requirements. The lower part of Fig. 1.9 shows a process flowsheet which consists of chemical devices and therefore describes the chemical plant to be built - still at a fairly high level of abstraction. The process flowsheet serves as input for detail engineering, which is beyond the scope of the case study.

Based on the tuned models, equipment performance could be evaluated and compared with design. The models could then be readily adapted to simulate an additional process fired heater (to unload the methanol superheater) and to evaluate it s inpact on the overall MTG unit performance. Multiple case studies were performed to determine optimum heater size with regard to maximising heat recovery and providing unit heat balance flexibility. The additional heat balance flexibility allows the ZSM-5 catalyst outlet temperature to be reduced hence maximising gasoline yield. 

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