FOOD ENGINEERING DESIGN AND ECONOMICS

CHAPTER I

ENGINEERING DESIGN

Engineering Design

Engineering design is planning a system a part of a system or a process in the way which corresponds the needs. Design is a job of making decisions. Where the data at hand are integrated with basic sciences, mathematics and engineering knowledge in the most suitable manner and the target is achieved.

Stages of Design

Determination of the aim(s) and desired criteria (need)

Collection of data and bring up them together (synthesis)

Detailed investigation of the subject (analysis)

Regulation and starting the application (construction)

Trials (testing)

Examination of the results (evaluation)

Engineering design is an imaginary jump from the realities of today to the probabilities of future.Engineering design is a creative activity; it supplies the formation of new and helpful things that was not present before.Engineering design is the conversion of data in the form of needs to data in the form of technical systems by the help of human and technical power.Engineering design is a problem solving activity directed to a target.

A sample model for Engineering Design

Step 1. Recognizing the need.Step 2. Defining the problem.Step 3. Planning the project.Step 4. Gathering information.Step 5. Conceptualizing alternative approaches.Step 6. Evaluating the alternatives.Step 7. Selecting the best alternative.Step 8. Communicating the design.Step 9. Implementing the preferred design.

Process Design Development

Types of Design

Preliminary or quick estimate designs

Detailed estimate designs

Firm process or detailed designs.

i. Preliminary or quick estimate designs

Preliminary designs are ordinarily used as a basis for determining whether further work should be done on the proposed process. The design is based on approximate process methods and rough cost estimates are prepared. Few details are included and the time spent on calculations is kept at a minimum.

ii. Detailed estimate designs

If the results of the preliminary design show that further work is justified, a detailed estimate design may be developed. In this type of design, the cost and benefit potential of an established process is determined by detailed analysis and calculations. However, exact specifications are not given for the equipment and drafting work is minimized.

iii. Firm process designs or detailed designs

When the detailed estimate design indicates that the proposed project should be a commercial success, the final step before developing construction plans for the plant is he preparation of a firm process design. Complete specifications are presented for all components of the plant and accurate costs based on quoted prices are obtained. The firm process design includes blue prints and sufficient information to permit immediate development of the final plans for constructing the plant.

Feasibility survey

In a feasibility survey process involved must be considered along with the existing and potential market conditions for the particular product. A preliminary feasibility survey gives an indication of the probable success of the project and also shows what additional information is necessary to make a complete evaluation.(A need does not mean that, it is;

reasonable

desirable

possible to fulfill that need)

Following is a list of items that should be considered in making a feasibility survey:

Raw materials (availability, quantity, quality, cost)

Chemical an physical processes (equilibrium, yields, rates, optimum conditions)

Facilities and equipment available at present

Facilities and equipment which must be purchased

Estimation of production costs and total investment

Profits (probable and optimum, based per mass of product and per year or return on investment)

Materials of construction

Safety considerations

Markets (present and future supply and demand, price changes, location and number of possible customers)

Competition (overall production statistics, comparison of manufacturing processes, product specifications of competitors)

Properties of products

Sales and sale service (distribution, advertisement, technical services)

Shipping restrictions and containers

Plant location

Patent situation and legal restrictions

+ time of the project

Process development

In many cases, the preliminary feasibility survey indicates that additional research, laboratory or pilot plant data are necessary and a program to obtain this information may be initiated. Process development on a pilot-plant or semi-work scale is usually desirable in order to obtain accurate design data.

By process development the following information are obtained:

material and energy balances

process conditions

yields

rates

grades of raw materials and products

batch versus continuous operation

materials of construction

operating characteristics

and other design variables.

Preliminary (or quick estimate) designs

The primary step in preparing the preliminary design is to establish the bases for design. The basic items are;

the properties of the product and the manufacturing process

availability and quality of raw material

annual operating factor

energy requirements

valuable by-products

The next step consists of preparing a simplified flow diagram showing details of the process. Flow rates and stream conditions for the remaining cases are evaluated by:

material balances

energy balances

raw material-product relationships and properties

yields

The final stage of preliminary design is writing a report which will present the results of the design work. This report shows calculations and design details therefore improves communication.As soon as sufficient data are available from feasibility survey or process development the preliminary design should be carried out so that money and time losses for undesirable projects are eliminated.

Before detailed estimate design;

manufacturing process

material and energy balances

temperature and pressure ranges

raw material and product specifications

yields, reaction rates, time cycles, capacity

materials of construction

utility requirements

plant site

are to be established.

Detailed estimate designs

The preliminary design leads the accurate estimation of

required capital investment

manufacturing costs

potential profits

Based on these the following factors should be determined in detailed estimate design stage.

types of buildings, heating, ventilating, lighting, power supply, drainage, waste disposal, safety facilities and instrumentation.

Firm process design or Detailed design

At this stage all detailed drawings are prepared and real investments are determined.A complete plant layout (production lines, facilities etc), blueprints and instructions for construction are developed.Specifications are given for warehouses, laboratories, guard-houses, fencing, change houses, transportation facilities etc.MUST BE DEVELOPED WITH THE ASSISTANCE OF PERSONS SKILLED IN VARIOUS ENGINEERING FIELDS.

Construction and Operation

When a definite decision to proceed with the construction of a plant is made, there is usually immediate demand for a quick plant start-up. (why?)The design engineer should work closely with construction personnel during the final stages of construction and purchasing.During construction of the plant, the design engineer should visit the plant site to assist in interpretation of the plans and learn methods for improving future designs.

The engineer should also be available during the initial start up of the plant and the early phases of operation. Thus, by close team work between design, construction and operational personnel, the final plant can develop from the drawing board stage to an operating unit that can function both efficiently and effectively.

Comparison of Different Processes

Technical factors

Process flexibility

Continuous operation

Special controls involved

Commercial yields

Technical difficulties involved

Energy requirements

Special auxiliaries required

Possibility of future developments

Health and safety hazards involved.

Raw Materials

Present and future availability

Processing required

Storage requirements

Materials handling problems.

Waste products and by-products

Amount produced

Value

Potential markets and uses

Manner of discard

Environmental aspects

Equipment

Availability

Materials of construction

Initial costs

Maintenance and installation costs

Replacement requirements

Special designs

For specification: identification, function, operation (continuous or batch), materials handled (quantity, composition, physical properties), basic design data, essential controls, insulation (temperature, air, noise), requirements, allowable tolerances, special information and details are to be given.

Plant location

Amount of land required

Transportation facilities

Nearness to markets and raw material sources

Availability of services and power facilities

Availability of labor

Climate

Legal restrictions and taxes

Costs

Raw materials

Energy

Depreciation

Other fixed charges

Processing and overhead

Special labor requirements

Real estate

Patent rights

Environmental controls.

Time factor

Project completion deadline

Process development required

Occurrence at right time from market standpoint

Value of money.

Process considerations

Technological availability

Raw materials common with other processes

Consistency of product within company

General company objectives.