Petroleum Refining Design and Applications Handbook. A. Kayode Coker

      14.1 Introduction

      Process engineering design is the application of chemical, mechanical, petroleum, gas, and other engineering talents to the process-related development, planning, designs, and decisions required for economical and effective completion of a process project [1]. Although process design engineers are organizationally located in research, technical service, economic evaluation, as well as other specific departments, the usual arrangement is to have them available to the engineering groups concerned with developing the engineering details as well as to evaluate bids for the various equipment items. Process design is usually a much more specific group responsibility in engineering contractor organizations than in a chemical or petrochemical production company, and the degree of distinction varies with the size of the organization.

      The average process engineer has the following responsibilities:

      1 1. Prepares studies of process cycles and systems for various product production or improvements or changes in existing production units; prepares material and heat balances.

      2 2. Prepares economic studies associated with process performance.

      3 3. Designs and/or specifies equipment items required to define the process flowsheet or flow system; specifies corrosion resistant materials of construction.

      4 4. Evaluates competitive bids for equipment.

      5 5. Evaluates operating data for existing or test equipment.

      6 6. Guides flowsheet draftsmen in detailed flowsheet preparation.

      The process engineer also develops tests and interprets data and information from the research pilot plant. He/she aids in scaling-up the research type flow cycle to one of commercial feasibility.

      The process engineer must understand the interrelationship between the various research, engineering, purchasing, expediting, construction, and operational functions of a project. He/she must appreciate that each function may and often does affect or influence the process design decisions. For example, it is futile to waste time designing or calculating in detail, when the basic components of the design cannot be economically fabricated, or if capable of being fabricated, cannot possibly be delivered by the construction schedule for the project. Some specific phases of a project that require process understanding include plant layout, materials of construction for corrosion as well as strength, start-up operations, troubleshooting, maintenance, performance testing and so forth.

14.2 Organizational Structure

      The process design function may be placed in any one of several workable locations in an organization. These locations will be influenced by the primary function of the overall company, i.e., chemical production, engineering, engineering sales, design and manufacture of packaged or specific equipment manufacture, and so on. For best efficiency, regardless of the business nature of the company, the process design being a specialty type operation, works best when specifically identified and given the necessary freedom of contact within and without the company to maintain a high level of practical, yet thorough direction.

A typical working arrangement is shown in Figure 14.1 [1]. In a refinery, consulting or engineering contractor organization, process design and/or process engineering is usually a separate group responsible for developing the process with the customer, or presenting the customer with a turnkey proposed process. In the case of a refinery, the process engineers in various disciplines as the crude distillation and vacuum units, aromatics and reforming units, hydrocracking units, monitor the performance of these units daily and often provide technical information should there be major upsets, mal-operation or a reduction in the performance of these units to the relevant managers who are responsible for overseeing the operation of these units.

      In an operating or producing chemical or petrochemical company, the process engineering and design may be situated in a research, technical service, or engineering department. In most cases it is associated with an engineering department if new projects and processes are being planned for the company. If located elsewhere, the designs and planning must be closely coordinated with the engineering activity.

Most current thinking establishes a project team headed by a project engineer or manager to oversee the accomplishment of a given plant development for a process company. If the projects or jobs are small, then the scope of activity is limited and may often be consolidated in a single individual for project and process responsibility. For projects larger than $500,000, the project and process responsibility usually are best kept separate in order to expedite the specific accomplishment of the process design phase. When the process design engineer is required to interpret calculations and specification development and to follow some electrical, structural or even expediting delivery question or problem, the design work cannot be completed at best efficiency and often the quality of process design suffers, assuming there is a fixed target date for completion of the various phases as well as the overall project.

Figure 14.1 A process engineering section supervision chart (Ludwig [1]).

Figure 14.2 Typical organization of “engineering planning team” [2].

Figure 14.2 diagrammatically suggests a team arrangement for accomplishing the planning of a process project. The arrows indicate directions of flow of communications and also the tie-in relationship of the process design function in the accomplishment of an assignment. The planning team in the box works to place the proper perspective on all phases of the engineering functions by developing a working atmosphere of understanding for accomplishing the engineering design. This is physically represented by mechanical vessels, piping, structures, electrical, instrumentation, civil and any other specialized functions. In many projects, the Lead Process Engineer and the Project Lead Engineer are the only individuals who see the details of the overall scope of the project.

      14.2.1 Process Design Scope

      The project engineer appoints a chief process engineer who puts together a process design team to be responsible for all the chemical engineering aspects of the plant. The term “process design” is used here to include what is sometimes referred to as process engineering. Yet in some process engineering operations, all process design functions may not be carried out in detail. As discussed, process design is intended to include the following:

      1 1. Process material and heat balances.

      2 2. Process cycle development, correlation of pilot or research data, and correlation of physical property data.

      3 3. Auxiliary services material and heat balances.

      4 4. Flowsheet development and detailed completion.

      5 5. Chemical engineering performance design for specific items of equipment required for a flowsheet, and mechanical interpretation of this to a practical and reasonable specification. Here, the process requirements are converted into hardware details to accomplish the process end results at each step in the product production process.

      6 6. Instrumentation as related to process performance, presentation, and interpretation of requirements to instrument specialists.

      7 7. Process interpretation for proper mechanical, structural, civil, electrical, instrument, and so on, handling of the respective individual phases of the project.

      8 8. Preparation of specifications in proper