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
1.Determination of the aim(s) and desired criteria (need)
2.Collection of data and bring up them together (synthesis)
3.Detailed investigation of the subject (analysis)
4.Regulation and starting the application (construction)
5.Trials (testing)
6.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
1.Preliminary or quick estimate designs
2.Detailed estimate designs
3.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:
1.Raw materials (availability, quantity, quality, cost)
2.Chemical an physical processes (equilibrium, yields, rates, optimum conditions)
3.Facilities and equipment available at present
4.Facilities and equipment which must be purchased
5.Estimation of production costs and total investment
6.Profits (probable and optimum, based per mass of product and per year or return on investment)
7.Materials of construction
8.Safety considerations
1.Markets (present and future supply and demand, price changes, location and number of possible customers)
2.Competition (overall production statistics, comparison of manufacturing processes, product specifications of competitors)
3.Properties of products
4.Sales and sale service (distribution, advertisement, technical services)
5.Shipping restrictions and containers
6.Plant location
7.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;
1.manufacturing process
2.material and energy balances
3.temperature and pressure ranges
4.raw material and product specifications
5.yields, reaction rates, time cycles, capacity
6.materials of construction
7.utility requirements
8.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
1.Technical factors
2.Process flexibility
3.Continuous operation
4.Special controls involved
5.Commercial yields
6.Technical difficulties involved
7.Energy requirements
8.Special auxiliaries required
9.Possibility of future developments
10.Health and safety hazards involved.
1.Raw Materials
2.Present and future availability
3.Processing required
4.Storage requirements
5.Materials handling problems.
1.Waste products and by-products
2.Amount produced
3.Value
4.Potential markets and uses
5.Manner of discard
6.Environmental aspects
1.Equipment
2.Availability
3.Materials of construction
4.Initial costs
5.Maintenance and installation costs
6.Replacement requirements
7.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.
1.Plant location
2.Amount of land required
3.Transportation facilities
4.Nearness to markets and raw material sources
5.Availability of services and power facilities
6.Availability of labor
7.Climate
8.Legal restrictions and taxes
1.Costs
2.Raw materials
3.Energy
4.Depreciation
5.Other fixed charges
6.Processing and overhead
7.Special labor requirements
8.Real estate
9.Patent rights
10.Environmental controls.
1.Time factor
2.Project completion deadline
3.Process development required
4.Occurrence at right time from market standpoint
5.Value of money.
1.Process considerations
2.Technological availability
3.Raw materials common with other processes
4.Consistency of product within company
5.General company objectives.