1.1: Nature of Design -Design is a creative activity -Begins with specific objective or customer needs in mind, and by developing and evaluating possible designs, concludes the best way of achieving that objective; be it a better chair, a new bridge, or in your case, a new bio-chemical product or production process. -Designer, will be constrained by many factors, which will help to narrow down the possible designs. -Rarely, there will be only one solution to the problem, just one design. Several alternative ways of meeting the objective will normally possible,

-Constrains can appear in many forms; some will be fixed and invariable, and some will be less rigid. Figure 1.1 -Economic consideration are a major constraint: plant must make a profit. Process costing and economics will be discussed -Time also is a constraint. -Fig 1.2 shows the design stages, which must be done within the time limit.

-Figure 1.1

-Figure 1.2

1.1.1Setting the Design Basis 1)Production rate 2)Purity specification Together with the constraints that will influence the design such as: 1)The system of units to be used 2)The national, local or company codes that must be followed 3)Details of raw materials that are available 4)Information on potential sites where the plant might be located, including climate data, seismic conditions, infrastructure availability, etc.

5) Information on the conditions, availability and price of utility services such as fuel gas, steam, cooling water, process air, process water, electricity, etc Possible Design Concept a)Modifications, and additions, to existing plant b)New production capacity to meet growing sales demand. Repetition of existing designs, with only minor design changes, including designs of competitors to understand whether they have compelling better cost of production. c)New processes, develop from laboratory research, through pilot plant, to a commercial process. Even here, most of the unit operations and process equipment will be use established design.

1.1.3Fitness Testing When design is suggested, it must be tested for fitness for purpose In our case (process engineer) it is usually prohibitive and expensive to do the prototyping, which is common in other engineering field. Instead, the engineer build a model, from computer simulation. The engineer must assemble all the information needed to model the process so as to predict its performance against the identified objective.

1.1.3Fitness Testing Once the working model has been established, the engineer can begin to determine equipment size and cost Economic Evaluation Usually entails analysing the capital and operating costs of the process to determine the return of investment.

1.1.5Detailed Design and Equipment Selection - Detailed specification of equipment such as vessel, heat exchanger, pumps etc. -This is where process engineer work with other disciplines, i.e civil engineer for site prep, mech eng for design of vessel and structure, piping, electrical eng for instrumentation and control. -Detailed design usually focus mainly on equipment selection, rather than changes to the flow-sheet. -Example: Use shell and tube, or plate HE. Trays or packing for distillation column.

1.1.6Procurement, Construction and Operation -Last stage in design. -Must have start-up and shutdown procedure.

1.2The Anatomy of Chemical/ Bioprocess Manufacturing Process Fig 1.3

1.2The Anatomy of Chemical/ Bioprocess Manufacturing Process Stage 1: Raw Material -Some provision will have to be made to hold several days, or weeks, storage to smooth out fluctuations and interruptions in supply. - The storage required depends on the nature of the raw materials, the method of delivery. Example: If delivered by tanker, several weeks’ stocks may be necessary. If received by road/ rail, may be less storage required.

1.2The Anatomy of Chemical/ Bioprocess Manufacturing Process Stage 1: Feed Preparation -Some purification/ preparation usually necessary before they are ready for the process. - For example: acetylene produced by carbide process contains arsenic and sulphur compound. This must be removed by scrubbing with concentrated sulphuric acid before the reaction with hydrochloric acid to produce dichloroethane. -Feed contaminants that can poisoned catalysts, enzymes, micro-organism must be removed.

1.2The Anatomy of Chemical/ Bioprocess Manufacturing Process Stage 2: Feed Preparation -Liquid feeds need to be vaporized before being fed to gas-phase reactors, for example. -Solids probably need to be crushed, ground and screened.

1.2The Anatomy of Chemical/ Bioprocess Manufacturing Process Stage 3: Reaction -Heart of bioprocess/ chemical manufacturing process. In the reactor, the raw materials are brought together under conditions that promote the production of the desired product. Some by-products will also be formed.

1.2The Anatomy of Chemical/ Bioprocess Manufacturing Process Stage 4: Product Separation -Separation of the products and by products from unreacted material. If in sufficient quantity, the unreacted material will be recycled to the reaction stage/ or to the feed preparation stage. - The by-products may also be separated at this stage. - In some fine chemical process, it could be multiple reaction steps, followed by one or more separation steps.

1.2The Anatomy of Chemical/ Bioprocess Manufacturing Process Stage 5: Purification -Before sale, the main product will often need purification to meet the product specification. - By product also can be purified, if it produced in economic quantities.

1.2The Anatomy of Chemical/ Bioprocess Manufacturing Process Stage 5: Product storage -Some inventory of finished product must be held to match production with sales. - Provision for product packaging and transport is also needed. - Liquids are normally dispatched in drums and in bulk tanker. Solids in sacks, cartoon or bales. -Example: Ibuprofen plant

1.2.1 Continuous and Batch Processes -Continuous processes are design to operate 24 hrs/day, 7 days/ week throughout the year. - Down time will be allowed for maintenance, catalyst/ enzyme regeneration, replacement. - The plant operating rate usually between 90-95%. Attainment% = hours operated/ 8760 x 100

1.2.1 Continuous and Batch Processes -Batch processes are designed to operate intermittently, with some, or all, of the process units being frequently shut down and started up. - It is quite common for batch plants to use a combination of batch and continuous operation. -For example, batch reactor may be used to feed a continuous distillation column.

1.2.1 Continuous and Batch Processes -Continuous process will usually be more economical for large scale production. - Batch processes are used when some flexibility is wanted in production rate or product spec.

1.2.1 Continuous and Batch Processes -Advantages of batch: a)Allows production of multiple different products or product grades in the same equipment. b)In a batch plant, the integrity of a batch is preserved as it moves from operation to operation. This is very useful for quality control purpose. c)The production rate of batch plant is very flexible. Can be operating at low output. d)Easier to clean and maintain sterile operation

1.2.1 Continuous and Batch Processes -Advantages of batch: e)Batch processes are easier to scale up from chemist’s recipe. f) Batch plants have low capital for small production volumes.

1.2.1 Continuous and Batch Processes -Disadvantages of batch: a)Scale of production is limited. b)Difficult to achieve economies of scale by going to high production rate. c)Batch-to batch quality can vary, leading to high production of waste / off spec product. d)Recycle and heat recovery are harder, making batch plants less energy efficient and more likely to produce waste by-products.

1.2.1 Continuous and Batch Processes -Continuous Vs Batch -Batch processes usually make sense for products that have high value and produced in small quantities. Batch plants are commonly used for: a)Food products, e.g. french fries b)Pharmaceutical products, e.g. drugs, vaccine, hormones c) Personal care products, e.g. d) Specialty chemicals: Rynex-for dry cleaning, Lonza- emulsifier for ice cream, Basotect, absorb sound under Ferrari hood, Bimaz-monomers for contact lens

1.2.1 Continuous and Batch Processes -Even in these sectors, continuous production is favoured if the process is well understood, the production volume is large and the market is competitive.