Design flow diagrams

Fig. 3. Design Flow Diagram to Produce Products. (Source DVR.)...

A simplified flow diagram for a typical UOP linear detergent alkylation unit is shown in Figure 7. The design of this unit is similar to a unit that produces branched-chain detergent alkylate. 

Once the candidate corrective measure alternatives have been identified, a more detailed evaluation of each alternative needs to be undertaken. From an engineering perspective, the first step in the evaluation process would include the development of a conceptual design for each alternative. The conceptual design would consist of a process description, a process flow diagram and a layout drawing. Preliminary sizing of equipment and utility and land requirements would be developed. In addition, chemical requirements and residuals produced can be estimated. From the conceptual design, permitability and residuals disposal issues can be identified and addressed. 

Figure 1.1. Simplified flow diagram of activities in planning and implementing process and plant design projects.

Process flow diagrams are more complex and show all main flow streams including valves to enhance the understanding of the process as well as pressures and temperatures on all feed and product lines within all major vessels and in and out of headers and heat exchangers, and points of pressure and temperature control. Also, information on construction materials, pump capacities and pressure heads, compressor horsepower, and vessel design pressures and temperatures are shown when necessary for clarity. In addition, process flow diagrams usually show major components of control loops along with key utilities. 

The process flow diagram, or PP D. is a pictorial description of the process. It gives the basic processing scheme, the basic control concept, and the process information from which equipment can be specified and designed. It pror ides the basis for the der elopment of the P l diagram and also serves as a guide for the plant operator. The process flow diagram usiuilly includes... 

Figure 40.42 shows a flow diagram in a manifold that provides both pressure and return passages. One common line provides pressurized fluid to the manifold, which distributes the fluid to any one of five outlet ports. The return side of the manifold is similar in design. This manifold is provided with a relief valve, which is connected to the pressure and return passages. In the event of excessive pressure, the relief valve opens and allows the fluid to flow from the pressure side of the manifold to the return side. 

In planning a control system, a flow diagram is needed to indicate what may influence each item of plant. In many diagrams it will be seen that complexity arises and two items work in conflict. A typical instance is the cooling and dehumidifying of air, to a room condition lower than design, with concurrent operation of a humidifier. 

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 ... 

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