ChE 4106 Lesson 1

DESIGN

Begins with a specific objective or customer need in mind, and by developing and evaluating possible designs, arrives at the best way of achieving that objective

DESIGN

One of the most rewarding and satisfying activities by an engineer and does not exist at the start of the project.

Fixed and invariable constraints

Those that arise from physical laws, government regulations, and standards.

Less rigid constraints

Can be relaxed by the designer as part of the general strategy for seeking the best design.

External constraints

Constraints outside the designer’s influence; set the outer boundary of possible designs

Internal constraints

Constraints within the designer’s control, e. g. choice of process, choice of process conditions, materials, and equipment

Major Design Constraints

1. Economic considerations

2. Time

Stages in the development of a design

1. Determine Customer Needs

2. Set Design Specifications

3. Generation of Possible Design Concepts

4. Fitness Testing

5. Economic Evaluation, Optimization and Selection

6. Detailed Design and Equipment Selection

7. Procurement and Construction

Determine Customer Needs

Before starting work, the designer should obtain a complete and unambiguous statement of the requirement

Set Design Specifications

The most important step in starting a process design is translating the customer need into a design basis.

Information on constraints that will influence the design

1. System of units

2. National, local or company design codes

3. Available raw materials

4. Information on potential plant sites

5. Information on utility services

True

TRUE OR FALSE

No design is entirely novel

Fitness Testing

The design engineer builds a mathematical model of the process, usually in the form of computer simulations of the process, reactors and other key equipment.

Economic performance

The primary criterion for design selection

The Anatomy of a Chemical Manufacturing Process

1. Raw Material Storage

2. Feed Preparation

3. Reaction

4. Product Separation

5. Product Purification

6. Product Storage

Continuous processes

Designed to operate 24 hours a day, 7 days a week, throughout the year.

Plant Attainment or Operating Rate

The percentage of the available hours in a year that the plant operates (usually 90-95%).

Batch processes

Designed to operate intermittently, with some, or all, of the process units being frequently shut down and started up.

1. Process design

2. Plant design

The design work required in the engineering of a chemical manufacturing process can be divided into two broad phases.

Process Design

Covers the steps from the initial selection of the process to be used, through to the issuing of the process flow-sheets

Process Design

Includes the selection, specification and chemical engineering design of equipment.

Plant Design

Includes the detailed mechanical design of equipment, the structural, civil and electrical design, and the specification and design of the ancillary services

Project Manager

Ensure that intermediate deliverables identified in the project plan are completed on time and that the project is kept close to the planned budget

Project Design

Starts with a clear specification defining the product, capacity, raw materials, process and site location.