Process Engineering and Plant Design

The Complete Industrial Picture

Siddhartha Mukherjee

• Publisher: CRC Press
• Year: 2021
• Print ISBN: 9780367248413
• eBook ISBN: 9781000470048
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

The book provides the whole horizon of process engineering and plant design from concept phase through the execution to commissioning of the plant in the real practice. Providing a complete industrial perspective, the book:

• Covers the guidelines and standards followed in the industry and how engineering documents are generated using these standards
• Describes Hazardous Area Classification, Relief System Design, Revamp Engineering, Interaction with Other Disciplines, and Pre-commissioning and Commissioning
• Contains several illustrated practical examples, which clarify the fundamentals to a raw chemical engineer
• Includes description of a complete chemical project from concept to commissioning

Treating the topic from the perspective of an industrial employee with extensive experience in process engineering and plant design, it aims to aid chemical and plant engineers to deal with decision making processes on strategic level, management tasks and leading functions beside the technical know-how.

1 Executing a Process Plant: In a Nutshell

DOI: 10.1201/9780429284656-1

1.1 Introduction

Since the middle of the twentieth century, the design and construction of chemical plants have become more and more specialized. The activities start with the potential triggering of the idea of a new facility. Complex market conditions and interconnections with the economy demand a critical analysis of the project regarding feasibility, economic relevance and environmental impact. This is normally carried out with the aid of a feasibility study.

Based on the results of the feasibility study, once the decision has been made to proceed with the project, the owner/client prepares an elaborate definition of the plant also called the “process design basis” (explained later). The process design basis is used to invite bids from process licensors. The selection of the process licensor marks the end of the conceptual phase of the project.

The selected process licensor is asked to prepare the basic engineering package (BEP). The BEP serves as the basis for detail engineering and construction. The project execution phase starts with the process engineers carrying out the front-end engineering. The engineering team then transforms these into detailed drawings and specifications for all the components of the plant. The procurement group orders the equipment and all other components from specialist manufacturers. Construction companies are then contracted to build and install the plant and components. The final activity involves the commissioning and start-up of the plant. This involves several parties, particularly the process engineers from the process licensing company which has provided the technology. After a successful test run, the plant is handed over to the owner/client [1].

1.2 Feasibility Study

At the beginning of the project, there is very little or only preliminary knowledge planning. No company would like to incur costs unless it knows whether the project is feasible. A small group is formed consisting of engineers from various disciplines to carry out a pre-feasibility study. Usually, this group later becomes responsible for implementation of the project in case the company makes a decision to proceed.

1.2.1 Pre-feasibility Study

Before a project moves into the detailed feasibility study stage, companies sometimes conduct a co-called “pre-feasibility study.” Such a study is carried out if the economics of the investment appears doubtful and the investors wish to be sure before incurring time and cost in carrying out a detailed feasibility report. Further, such a study is particularly useful when there is more than one route for a particular product, and the company wants to know which one is the best, both technically and financially [2].

A comprehensive pre-feasibility study should include design and description of the plant and its operation for each of the routes, as well as cost estimates, project risks, safety issues and other important information.

1.2.2 Detailed Feasibility Study

If the selected scenario is considered feasible, it is recommended to carry out a detailed feasibility study to get a deeper analysis of the selected project scenario.

In a detailed feasibility study, the technical, commercial, financial, economic and environmental pre-requisites for the proposed project are critically examined on the basis of the findings of the pre-feasibility study.

A detailed feasibility study typically consists of the following:

• Preparation of basis of study
• Identification of the most appropriate location for the facility
• Description of technology including process description, block flow diagram, raw materials and utilities, catalysts and chemicals consumption
• Identification of utilities and offsites facilities
• Assessment of plot area requirements
• Preparation of project organization chart, project description, project schedule and execution methodology
• Estimation of major quantities of material for civil, mechanical and electrical instrumentation items
• Assessment of human resources, managerial staff, labor cost and other overhead costs
• Estimation of fixed and variable costs for the proposed facility
• Conduction of financial analysis
• Recommendations for Implementation

1.3 Appointment of the Project Management Consultant

At this stage, the owner needs to decide whether he has enough manpower and expertise to handle all the complexities involved in the execution of the project including experienced design engineers, procurement personnel and construction experts. In most cases, the owner appoints an outside agency to act as the project management consultant, widely called PMC. The PMC works as an extended arm of the owner in the execution of the project.

1.4 Preparing the Process Specifications

Once the desired operating hours per annum have been finalized (say 8000 hours per annum), the design capacity of the plant is defined. The next step is to compile the specifications for the feedstock, end products, utilities, catalysts and chemicals. These specifications include relevant physical and chemical properties as well as battery limit conditions of all streams entering and leaving the proposed complex. Appendix 1 illustrates typical process specifications.

1.5 Licensed Technologies and Selection of the Process Licensor

“Process licensor” is an individual or a company that has exclusive rights of a particular proprietary technology. It allows another party, called the “licensee,” to use the technology in its process plant. In return for the process license, the licensee pays the licensor a “license fee” that is normally a percentage based on the plant capacity.

The selling of a process license alone, however, does not carry any meaning. It is normally sold along with a BEP which contains all the details about the technology in the form of drawings, descriptions and data sheets. For this, an additional fee is charged by the licensor called the “basic engineering fee.” The BEP is explained in detail in Section 1.7.

1.6 Types of Execution Strategies

A chemical plant can be executed in several ways. Accordingly, different types of contracts are signed with the client depending on the type of execution strategy. For small and simple plants, while clients normally get the basic engineering (discussed later) done by process licensors, they would rather get the detail engineering executed by local contractors who are sufficiently competent to execute such plants. In this way, they save on the detail engineering cost. For such small plants, clients normally have sufficient manpower to get the procurement and construction executed by their own resources. In another option, the client gets the basic and detail engineering carried out by the same party. In this way, while they incur a higher detail engineering cost, they minimize the number of interfaces.

For larger plants, while the clients get the basic engineering executed by the process licensor, they club the detail engineering (E), procurement (P) and construction (C) in a single contract. Such a contract is called an “EPC contract.” Such contracts are nowadays more popular. In large complexes such as refineries or petrochemical complexes, such type of contracts are quite common. The whole complex in clubbed into sections depending mainly on the process flow or proximity to each other. A particular section may have three units provided by three different process licensors. However, the client may appoint one EPC contractor to execute the entire section.

In another type of contract, the entire range of activities are awarded to one EPC contract, including the process license and basic engineering. In this case, instead of the client selecting the process licensor, it is the EPC bidder who collaborates with a process licensor and offers the entire package. Such a contract is called an “L-EPC contract,” with ‘L’ standing for process licensing.

1.7 Basic Engineering

Now that the PMC has been appointed, the process licensor selected and the process design basis prepared, it is time to commence the basic engineering activities. In some cases, there can be two or more units in the project whereby the product from one unit feeds the next one. If there are different process licensors for the various units, the situation becomes even more complicated. In such cases, the execution of the basic engineering from the different process licensors would have to be executed in a staggered and partially overlapping manner. The PMC needs to play a major role in the coordination of such an activity in order not to waste time in the overall project cycle.

1.7.1 Process Simulation

Process design calculations for processes involving multiple units and the interconnected processes with material and energy balance may become very complex. Nowadays, computer programs are available that model unit operations mathematically and allow them to be interconnected [1]. A plant can thus be simulated as a network of unit operations with material and energy balance. Often in such programs, the licensors build up their own proprietary thermodynamic packages that have been developed after years of laboratory work and operating experience.

1.7.2 Process Flow Diagram

A process flow diagram describes the unit from the process engineer’s point of view. All the major lines and equipment are shown. Each line has a stream number. All the stream numbers are linked to a separate document called the “heat and mass balance.” In the heat and mass balance, each stream is described with respect to its composition, temperature, pressure and relevant important properties. The major control loops are also illustrated.

1.7.3 Piping and Instrumentation Diagram

Piping and instrumentation is an extension of the process flow diagram and provides detailed information for down-the-line engineering to follow. For example, unlike a process flow diagram, the piping and instrumentation diagram (P&ID) shows all the lines in the unit. For each line, the line number, line size, pipe class (refer to Chapter 2 for details) and the insulation requirements are provided. Slopes required from the process point of v...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Contents
• Preface
• Acknowledgements
• About the Author
• List of Abbreviations
• 1 Executing a Process Plant: In a Nutshell
• 2 Flow Sheets, Equipment Lists and Line Lists
• 3 Plot Plan and Equipment Layout
• 4 Piping and Mechanical Considerations
• 5 Flow of Fluids
• 6 Vessels and Tanks
• 7 Heat Exchangers
• 8 Air Coolers and Fired Heaters
• 9 Mass Transfer Equipment
• 10 Hazardous Area Classification
• 11 Instrumentation and Controls
• 12 Safety and Relief System Design in Process Plants
• 13 Hazard and Operability Study
• 14 Revamp Engineering and Capacity Augmentation
• 15 Interaction and Coordination with Detail Engineering Disciplines
• 16 Pre-commissioning, Commissioning and Start-up
• 17 Execution of Large Process Plants
• 18 Cost Estimation
• Appendix 1 Process Specification
• Appendix 2 Basic Design Data
• Appendix 3 Frequently Used Conversion Factors
• Appendix 4 List of YouTube Links
• Index