This is an introductory course to chemical engineering deign. The block flow diagram, process flow diagram and P& ID have been discussed. Relevant examples have been made.

1. INDUSTRIAL CHEMICAL
PROCESS DESIGN
FLOWSHEETING

2. FLOWSHEETING
• The flowsheet is the key document in process design. It shows the arrangement of
the equipment selected to carry out the process; the stream connections; stream
flow-rates and compositions; and the operating conditions.
• It is a diagrammatic model of the process.
• The flow-sheet is drawn up from material balances made over the complete process
and each individual unit. Energy balances are also made to determine the energy
flows and the service requirements.
• Manual flow-sheeting calculations can be tedious and time consuming when the
process is large or complex, and computer-aided flow-sheeting programs are being
increasingly used to facilitate this stage of process design.

3. USES OF A FLOWSHEET
• The flow-sheet will be used by the specialist design groups as the basis for their designs
which includes; piping, instrumentation, equipment design and plant layout.
• It will also be used by operating personnel for the preparation of operating manuals and
operator training.
• During plant start-up and subsequent operation, the flow-sheet forms a basis for
comparison of operating performance with design.

4. TYPES OF FLOWSHEETS
• Block flow diagram: A block diagram is the simplest form of presentation. Each
block can represent a single piece of equipment or a complete stage in the
process.
• Process flow diagram: The process flow-sheet shows the arrangement of the
major pieces of equipment and their interconnection. It is a description of the
nature of the process
• Piping & Instrumentation diagram: is a detailed diagram in the process
industry which shows the piping and process equipment together with
the instrumentation and control devices.

5. BLOCK FLOW DIAGRAM
• A block diagram is the simplest form of presentation. Each block can represent a single piece of
equipment or a complete stage in the process.
• They are useful for showing simple processes. With complex processes, their use is limited to
showing the overall process, broken down into its principal stages.
• Block diagrams are useful for representing a process in a simplified form in reports and
textbooks, but have only a limited use as engineering documents.
• The stream flow-rates and compositions can be shown on the diagram adjacent to the stream
lines.
• The blocks can be of any shape, but it is usually convenient to use a mixture of squares and
circles, drawn with a template.

6. SAMPLE BLOCK FLOW DIAGRAM

7. PROCESS FLOW DIAGRAM
• On the detailed flow-sheets used for design and operation, the equipment is normally drawn
in a stylised pictorial form sometimes called a Process flow diagram.
• A Process Flow Diagram (PFD) is a type of flowchart that illustrates the relationships between
major components at an industrial plant. It's most often used in chemical engineering and
process engineering, though its concepts are sometimes applied to other processes as well.
• The PFD symbols are adopted from;
• British Standard, BS 1553 (1977) “Graphical Symbols for General Engineering” Part 1, “Piping
Systems and Plant” are recommended; though most design offices use their own standard
symbols.
• The American National Standards Institute (ANSI) has also published a set of symbols for use
on flow-sheets.
• In Europe, the German standards organisation has published a set of guide rules and symbols
for flow-sheet presentation, DIN 28004 (1988).

8. Essential information for stream representation in a flowsheet
1. Stream composition, either:
(i) the flow-rate of each individual component, kg/h, which is preferred, or
(ii) the stream composition as a weight fraction.
2. Total stream flow-rate, kg/h.
3. Stream temperature, degrees Celsius preferred.
4. Nominal operating pressure (the required operating pressure).
USES of a PFD
• It clarifies the working procedure for all workers. A PFD simplifies the process scope and
basic information. Critical data such as feedstock and stream flow rates are easier to
follow.
• Second, the chart highlights fatal flaws and bottlenecks to improve quality control. This
advancement paves the way for better models in the future. Furthermore, PFDs solidify
the interdependence of the organization with external systems.

9. PFD FOR A POLYMER PROCESS

10. PFD SYMBOLS FOR VESSELS

11. PFD SYMBOLS FOR VESSELS

12. PFD SYMBOLS

14. PIPING & INSTRUMENTATION DIAGRAM
• A piping and instrumentation diagram (P&ID or PID) is a detailed diagram in
the process industry which shows the piping and process equipment together with
the instrumentation and control devices.
• The Piping and Instrument diagram (P and I diagram or PID) shows the engineering
details of the equipment, instruments, piping, valves and fittings; and their
arrangement.
• It is often called the Engineering Flow-sheet or Engineering Line Diagram or
Mechanical flowsheets.
• P&IDs are originally drawn up at the design stage from a combination of process flow
sheet data, the mechanical process equipment design, and the instrumentation
engineering design.

15. THE P AND I DIAGRAM COMPONENTS
The P and I diagram shows the arrangement of the process equipment, piping, pumps, instruments, valves and other fittings. It
should include:
1. All process equipment identified by an equipment number. The equipment should be drawn roughly in proportion, and the
location of nozzles shown.
2. All pipes, identified by a line number. The pipe size and material of construction should be shown. The material may be
included as part of the line identification
number.
3. All valves, control and block valves, with an identification number. The type and size should be shown. The type may be shown
by the symbol used for the valve or included in the code used for the valve number.
4. Ancillary fittings that are part of the piping system, such as inline sight-glasses, strainers and steam traps; with an identification
number.
5. Pumps, identified by a suitable code number.
6. All control loops and instruments, with an identification number.

16. USES OF A P& ID
• They are also vital in enabling development of;
• Control and shutdown schemes
• Safety and regulatory requirements
• Start-up sequences
• Operational understanding.
• P&ID provides the basis for the development of system control schemes, allowing for
further safety and operational investigations, such as a Hazard and operability
study (HAZOP).

17. SAMPLE P&ID

18. P&ID SYMBOLS

19. MORE P&ID SYMBOLS

20. COMPUTER AIDED DRAFT SOFTWARE FOR PFD &
P&ID
• The computer programs available for flow-sheeting in process design can be classified
into two basic types:
1. Full simulation programs, which require powerful computing facilities. E.g Aspen
Hysys/Plus, Chemcad, CHEMPRO
2. Drafting softwares which draw the flowsheet but cannot calculate the material balance e.g
Autocad Plant 3D, Microsoft Visio
• The full simulation programs are capable of carrying out rigorous simultaneous heat and
material balances, and preliminary equipment design: producing accurate and detailed
flow-sheets.
• In the early stages of a project the use of a full simulation package is often not justified
and a simple material balance program is more suitable.

21. THE END
REFERENCES:
1. Chemical Engineering Design by R.K Sinnot Volume 6