The most effective way of communicating information about

The most effective way of communicating information about a process is through the use of flow diagrams. • Block Flow Diagram (BFD) • Process Flow Diagram (PFD) • Piping and Instrumentation Diagram (P&ID)

Three Levels of Representation • Block Flow Diagram (BFD) • Process Flow Diagram (PFD) • Piping and Instrumentation Diagram (P&ID) – often referred to as Mechanical Flow Diagram Complexity Conceptual understanding Chemical engineers are most familiar with BFD and PFD.

Toluene (10, 000 kg/h) Hydrogen (820 kg/h) Reactor Gas Separator Mixed Gas (2, 610 kg/h) Benzene (8, 210 kg/h) Conversion 75% Toluene Mixed Liquids Toluene Reaction : C 7 H 8 + H 2 = C 6 H 6 + CH 4 Block flow diagram (BFD) for the production of benzene • Toluene and hydrogen are converted in a reactor to produce benzene and methane. • The reaction does not go to completion, and excess toluene is required. • The non-condensable gases are separated and discharged. • The benzene product and the unreacted toluene are then separated by distillation. • The toluene is then recycled back to the reactor and the benzene removed in the product stream.

Conventions and format recommended for laying out a block flow diagram (BFD) 1. Operations shown by blocks. 2. Major flow lines shown with arrows giving direction of flow. 3. Flow goes from left to right whenever possible. 4. Light stream (gases) toward top, while heavy stream (liquids and solids) toward bottom. 5. Critical information unique to process supplied. 6. If lines cross, then the horizontal line is continuous and the vertical line is broken. 7. Simplified material balance provided.

Process Flow Diagram (PFD) C 6 H 5 CH 3+H 2 C 6 H 6 + CH 4

Process Flow Diagram (PFD) A PFD includes the following items: 1. major equipment; 2. principal flow route and control involved from raw material feed to final product; 3. key temperature and pressure corresponding to anticipated normal operation; 4. material flow rates and compositions; 5. design duties and sizes of major equipment.

Equipment Numbering • XX-YZZ A/B/… – XX represents a 1 - or 2 -letter designation for the equipment (P = pump) – Y is the 1 or 2 digit unit number (1 -99) – ZZ designates the equipment number for the unit (1 -99) – A/B/… represents the presence of spare equipment

The Process Flow Diagram (cont’d) Conventions Used for Numbering Process Equipment General Format XX-YZZ A/B XX are the identification letters for the equipment classification C - Compressor or Turbine E - Heat Exchanger H - Fired Heater P - Pump R - Reactor T - Tower TK - Storage Tank V - Vessel Y designates an area within the plant ZZ are the number designation for each item in an equipment class A/B identifies parallel units or backup units not shown on a PFD Additional description of equipment given on top of PFD R. Turton and J. A. Shaeiwitz Copyright 2008

Equipment Numbering (cont’d) T-905: the 5 th tower in unit 900 P-301 A/B: the 1 st Pump in unit 300 plus a spare • Use unambiguous letters for new equipment – Ex. Turbine use Tb or J not T (used for tower) – Replace old vessel V-302 with a new one of different design – Ø use V-319 (e. g. ) not V-302 – since it may be confused with original V-302

Equipment Drawing

Equipment Information • Equipment are identified by number and a label (name) positioned above the equipment on the PFD • Basic data such as size and key data are included in a separate table (Equipment Summary Table)

Equipment Information Equipment Summary Table Vessel V-101 V-102 Temperature (ºC) 55 38 Pressure (bar) 2. 0 24 Orientation Horizontal Vertical MOC CS CS Height/Length (m) 5. 9 3. 5 Diameter (m) 1. 9 1. 1 Size Internals s. p. (splash plate)

Stream Numbering and Drawing • Number streams from left to right as much as possible • Horizontal lines are dominant yes no no

Stream Numbering and Drawing (cont’d) • Add arrows for – Change in direction – Inlet of equipment • Utility streams should use convention, e. g. lps, cw, fg, etc.

Stream Information • Since diagrams are small, not much stream information can be included • Include important data – around reactors and towers, etc. – Flags are used – see toluene HDA diagram – Full stream data are included in a separate flow summary table

Stream Information - Flags R. Turton and J. A. Shaeiwitz Copyright 2008

Process Streams Mass flow rate: 0. 82 tonne/h Temp. : 25 o. C Pressure: 25. 5 bar

Utility Streams 18

The Process Flow Diagram (cont’d) Flow Summary Information Essential Information Stream Number Temperature (°C) Pressure (bar) Vapor Fraction Total Mass Flow Rate (kg/h) Total Mole Flow Rate (kmol/h) Individual Component Flow Rates (kmol/h) Optional Information Component Mole Fractions Component Mass Fractions Individual Component Flow Rates (kg/h) Volumetric Flow Rates (m 3/h) Significant Physical Properties Density Viscosity Other Thermodynamic Data Heat Capacity Stream Enthalpy K-values Stream Name R. Turton and J. A. Shaeiwitz Copyright 2008

The Process Flow Diagram (cont’d) Simplified Flow Summary Table 1 Temperature (°C) 25 Pressure (bar) 1. 90 Vapor Fraction 0. 0 10. 0 Mole Flow(kmol/h) 108. 7 Mass Flow(tonne/h) Component Mole Flow (kmol/h) 2 Stream Number 3 59 25 25. 8 25. 5 4 5 225 6 41 7 600 8 41 9 38 10 654 90 25. 2 25. 5 25. 0 25. 5 23. 9 24. 0 2. 6 1. 00 1. 0 1. 0 0. 0 13. 3 0. 82 20. 5 6. 41 20. 5 0. 36 9. 2 20. 9 11. 6 144. 2 301. 0 1204. 4 758. 8 1204. 4 1100. 8 1247. 0 142. 2 42. 6 Hydrogen 0. 0 286. 0 735. 4 449. 4 735. 4 25. 2 651. 9 652. 6 0. 02 Methane 0. 0 15. 0 317. 3 302. 2 317. 3 16. 95 438. 3 442. 3 0. 88 Benzene 0. 0 1. 0 0. 0 7. 6 6. 6 7. 6 0. 37 9. 55 116. 0 106. 3 Toluene 108. 7 143. 2 0. 0 144. 0 0. 7 144. 0 0. 04 1. 05 36. 0 35. 0 R. Turton and J. A. Shaeiwitz Copyright 2008

Basic Control Loops Often the basic control loops (those involving maintaining material balance and reactor controls) are included on the PFD; instrumentation and other control loops are not shown

PFD Summary • PFD, Equipment Summary Table, and Flow Summary Table represent a “true” PFD • This information is sufficient for a preliminary estimation of capital investment and operating cost to be made.

Conventions Used for Identifying Process Equipment General Format XX-YZZ A/B XX are the identification letters for the equipment classification C - Compressor or Turbine E - Heat Exchanger H - Fired Heater P - Pump R - Reactor T - Tower TK - Storage Tank V - Vessel Y designates an area within the plant ZZ are the number designation for each item in an equipment class A/B identifies parallel units or backup units not shown on a PFD Supplemental Information Additional description of equipment given on top of PFD

Conventions for Identifying Process and Utility Streams Process Streams All conventions shown in the first table (conventions for BFD) apply. Diamond (square) symbol located in flow lines. Numerical identification (unique for that stream) inserted in diamond (square). Flow direction shown by arrows on flow lines. Utility Streams lps Low Pressure Steam: 3 -5 barg (sat)‡ mps Medium Pressure Steam: 10 -15 barg (sat)‡ hps High Pressure Steam: 40 -50 barg (sat)‡ htm Heat Transfer Media (Organic): to 400 C cw Cooling Water: From cooling tower 30 C returned at less than 45 C+ wr River Water: From river 25 C returned at less than 35 C rw Refrigerated Water: In at 5 C returned at less than 15 C rb Refrigerated Brine: In at -45 C returned at less than 0 C cs Chemical Waste Water with high COD ss Sanitary Waste Water with high BOD, etc. el Electric Heat (specify 220, 440, 660 V service) ng Natural Gas fg Fuel Gas fo Fuel Oil fw Fuel Water ‡These pressure are set during the preliminary design stages and typical values vary within the ranges shown. +Above 45 C, significant scaling occurs.

Information Provided in a Flow Summary Essential Information Stream Number Temperature ( C) Pressure (bar) Vapor Fraction Total Mass Flow Rate (kg/h) Total Mole Flow Rate (kmol/h) Individual Component Flow Rates (kmol/s) Optional Information Component Mole Fractions Component Mass Fractions Individual Component Flow Rates (kg/h) Volumetric Flow Rates (m 3/h) Significant Physical Properties Density Viscosity Other Thermodynamic Data Heat Capacity Stream Enthalpy K-values Stream Name

Equipment Descriptions for PFD and P&ID Equipment Type Description of Equipment Towers Size (height and diameter), Pressure, Temperature Number and Type of Trays Height and Type of Packing Materials of Constructions Heat Exchangers Type: Gas-Gas, Gas-Liquid, Liquid-Liquid, Condenser, Vaporizer Process: Duty, Area, Temperature, and Pressure for both streams. No. of shell and Tube Passes Materials of Construction: Tubes and Shell Tanks See vessels Vessels Hight, Diameter, Orientation, Pressure, Temperature, Materials of Construction Pumps Flow, Discharge Pressure, Temperature, P, Driver Type, Shaft Power, Materials of Construction Compressors Actual Inlet Flow Rate, Temperature, Pressure, Drver. Type, Shaft Power, Materials of Construction Heaters (fired) Type, Tube Pressure, Tube Temperature, Duty, Fuel, Material of Construction Others Provide Critical Information

Piping and Instrumentation Diagram (P&ID)

Piping and Instrumentation Diagram (P&ID) 1. All process equipment and piping required for start-up, shut-down, emergency and normal operation of the plant, including valves, blinds, etc. 2. An id number, an identifier of the material of construction, diameter and insulation requirements for each line. 3. Direction of flow. 4. Identification of main process and start-up lines. 5. All instrumentation, control and interlock facilities with indication of action on instrument air failure. 6. Key dimensions or duties of all equipment. 7. Operating and design pressures and temperatures for vessels and reactors. 8. Equipment elevations. 9. Set pressure for relief valves. 10. Drainage requirements. 11. Special notes on piping configuration as necessary, e. g. “gravity drainage. ”

Conventions in Constructing Piping and Instrumentation Diagrams For Equipment - Shown Every Piece Including Spare units Parallel units Summary details of each unit For Piping - Include All Lines Including Drains, Sample Connections and Specify Size (use standard sizes) Schedule (thickness) Materials of construction Insulation (thickness and type) For Instruments - Identify Indicators Recorders Controllers Show instrument lines For Utility - Indentify Entrance utilities Exit to waste treatment facilities

THE NATURE OF PROCESS DESIGN A Creative Activity ！

Activities of Process Design (1)Synthesis The step where one conjectures the building blocks and their interconnections to create a structure which can meet the stated design requirements. structure (2)Analysis (Simulation) The activity of modeling and then solving the resulting equations to predict how a selected structure should behave if it were constructed. (3)Evaluation The activity of placing a worth on the structure where the worth might be its cost, its safety, or its net energy consumption. (4)Optimization The systematic searching over the allowed operating conditions to improve the evaluation as much as possible. Parameter

Process Synthesis A design task where one conjectures the building blocks and their interconnections to create a structure which can meet the stated design requirements.

Importance of Process Structure

Figure 1. 1 (a) Synthesis is the creation of a process to transform feed streams into product streams. (b) Simulation predicts how it would behave if it was constructed.

An Example of Process Synthesis: Hydrodealkylation of Toluene

A Hierarchical Approach Toluene + H 2 Benzene + CH 4 2 Benzene Diphenyl + H 2 1150 F ～ 1300 F 500 psia

Toluene feed ENERGY INTEGRATION

Alternatives?

ALTERNATIVES OF DISTILLATION TRAIN (1) Recycle Diphenyl (2) (3)

ALTERNATIVES OF VAPOR RECOVERY SYSTEM (1) Condensation; (2) Absorption; (3) Adsorption; (4) Membrane.

Vapor recovery system H 2 , CH 4 Toluene Reactor system Purge H 2 , CH 4 Design Phase Alternatives split ? Liquid separation system Benzene Dipheny 1 Simplified Flowsheet for Separation Systems

Gas recycle H 2 , CH 4 Toluene Purge H 2 , CH 4 Benzene Reactor system Separation system Design Alternatives? Dipheny 1 Toluene recycle Recycle Structure of the Flowsheet

Purge H 2 , CH 4 Benzene Toluene Dipheny 1 Input-Output Structure of the Flowsheet

Hierarchy of Decisions

Block Flow Process Diagram n Similar to sketches in material and energy balances Input Reactants Output Products Excess toluene is required Hydrodealkylation of toluene to produce benzene

Block Flow Diagram n Similar to sketches in material and energy balances Input Reactants Excess toluene is required The noncondensable gases are separated and discharged Output Products The benzene product and unreacted toluene are separated by distillation. The toluene is recycled back to the reactor and the benzene removed in the product stream

Generic Structure of Process Flow Diagrams C 6 H 5 CH 3+H 2 C 6 H 6 + CH 4 58

R. Turton and J. A. Shaeiwitz Copyright 2008

Basic Control Loops R. Turton and J. A. Shaeiwitz Copyright 2008

Exclusions from Piping and Instrumentation Diagram 1. Operating conditions T, P 2. Stream flows 3. Equipment locations 4. Pipe routing a. Pipe lengths b. Pipe fittings 5. Supports, structures, and foundations

Reactor Separation and Recycle System Heat Exchanger Network Utilities Figure 1. 6 The “onion model” of process design. A reactor design in needed before the separation and recycle system can be designed, and so on. (From Smith and Linnhoff, Trans. IChem. E, Ch. ERD, 66: 195, 1988; reproduced by permission of the Institution of Chemical Engineers. )