THE NATURE OF PROCESS DESIGN A Creative Activity ！ [ Example ] CH3 + Toluene Toluene (10,000 kg/h) Hydrogen (820 kg/h) H2 + Hydrogen Reactor Benzene CH4 Methane Gas Separator • Block Flow Diagram (BFD) • Process Flow Diagram (PFD) • Piping and Instrumentation Diagram (P&ID) Mixed Gas (2,610 kg/h) Benzene (8,210 kg/h) Conversion 75% Toluene The most effective way of communicating information about a process is through the use of flow diagrams Table 1.1 Conventions and Format Recommended for Laying out a Block Flow Process Diagram Mixed Liquids Toluene Reaction : C7H8 + H2 = C6H6 + CH4 Figure 1.1 Block flow process diagram for the production of benzene Toluene and hydrogen are converted in a reactor to produce benzene and methane.The Operations shown by blocks Major flow lines shown with arrows giving direction of flow Flow goes from left to right whenever possible Light stream (gases) toward top with heavy stream (liquids and solids) toward bottom Critical information unique to process supplied If lines cross, then the horizontal line is continuous and the vertical line is broken Simplified material balance provided reaction does not go to completion, and excess toluene is required The noncondensable 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 Process Flow Diagram (PFD) A PFD includes the following items: major equipments; principal flow route and control involved from raw material feed to final product; key temperature and pressure corresponding to anticipated normal operation; material flow rates and compositions; design duties and sizes of major equipments CuuDuongThanCong.com https://fb.com/tailieudientucntt Table 1.2 Conventions Used for Identifying Process Equipment Process Equipment Supplemental Information Table 1.3 Conventions for Identifying Process and Utility Streams Process Streams All conventions shown in Table 1.1 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 lps mps hps htm cw wr rw rb cs ss el ng fg fo fw Utility Streams Low Pressure Steam: 3-5 barg (sat)‡ Medium Pressure Steam: 10-15 barg (sat)‡ High Pressure Steam: 40-50 barg (sat)‡ Heat Transfer Media (Organic): to 400°C Cooling Water: From cooling tower 30°C returned at less than 45°C+ River Water: From river 25°C returned at less than 35°C Refrigerated Water: In at 5°C returned at less than 15°C Refrigerated Brine: In at -45°C returned at less than 0°C Chemical Waste Water with high COD Sanitary Waste Water with high BOD, etc Electric Heat (specify 220, 440, 660V service) Natural Gas Fuel Gas Fuel Oil Fuel Water ‡These pressure are set during the preliminary design stages and typical values vary within the ranges shown 45°C, significant scaling occurs +Above Table 1.6 Equipment Descriptions for PFD and P&IDs 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, rP, Driver Type, Shaft Power, Materials of Construction Compressors Actual Inlet Flow Rate, Temperature, Pressure, DrverType, Shaft Power, Materials of Construction Heaters (fired) Type, Tube Pressure, Tube Temperature, Duty, Fuel, Material of Construction Others Provide Critical Information CuuDuongThanCong.com 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 Table 1.4 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 Piping and Instrumentation Diagram (P&ID) All process equipments and pipings required for start-up, shut-down, emergency and normal operation of the plant, including valves, blinds, etc An id number, an identifier of the material of construction, diameter and insulation requirements for each line Direction of flow Identification of main process and start-up lines All instrumentation, control and interlock facilities with indication of action on instrument air failure Key dimensions or duties of all equipments Operating and design pressures and temperatures for vessels and reactors Equipment elevations Set pressure for relief valves 10.Drainage requirements 11.Special notes on piping configuration as necessary, e.g “gravity drainage.” https://fb.com/tailieudientucntt Table 1.8 Exclusions from Piping and Instrumentation Diagram Operating conditions T,P Stream flows Equipment locations Pipe routing a Pipe lengths b Pipe fittings Supports, structures, and foundations Table 1.9 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 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 (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 structure Exit utilities Exit to waste treatment facilities Process Synthesis IMPORTANCE OF PROCESS STRUCTURE (1) Recycle？ A→P Ｒ A design task where one conjectures the building blocks and their interconnections to create a structure which can meet the stated design requirements or Ｒ Ａ Ｐ Ａ Ｓ Ｐ (2)separation Sequence ? A (propane) A B (1-Butene) A AB or ABC BC C(n-Butane) B ABC C C B C (3)Heat Recovery ? or H CuuDuongThanCong.com https://fb.com/tailieudientucntt Feed Streams Product Streams PROCESS ? (a) Process design starts with the synthesis of a process to convert raw 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 IChemE, ChERD, 66:195, 1988; reproduced by permission of the Institution of Chemical Engineers.) materials into desired products Reactor Feed Streams Product Streams ? PROCESS Separation and Recycle System Heat Exchanger Network (b) Simulation predicts how a process would behave if it was constructed Figure 1.1 Synthesis is the creation of a process to transform feed streams into product streams Simulation predicts how it would behave if it was constructed Utilities A HIERARCHICAL APPROACH Example Hydrodealkylation of Toluene CH3 ＋ CH4 ＋ H2 Toluene Benzene ＋ H2 Benzene Toluene + H2 ® Benzene + CH4 Diphenyl Benzene Diphenyl + H2 1150 ° F ～ 1300 ° F 500 psia Vapor Recovery System H2 Feed H2, CH4 Benzene product Flash hh FIGURE 1.2-2 Hydrodealkylation of toluene; maximum energy recovery ENERGY INTEGRATION Stablizer CW Benzene Col Gas recycle Reactor CuuDuongThanCong.com Toluene Recycle Toluene Col furnace Flash Drum Benzene compressor Diphenyl Reactor Toluene Feed Purge Purge compressor Liquid recycle H2, feed Toluene feed Diphenyl Distillation Train https://fb.com/tailieudientucntt ALTERNATIVES OF DISTILLATION TRAIN (1) Recycle Diphenyl H2, CH4 Benzene (2) Feed ALTERNATIVES OF VAPOR RECOVERY SYSTEM Toluene (recycle) Diphenyl (3) H2 CH4 (1) Condensation; Benzene (2) Absorption; Toluene (recycle) (3) Adsorption; (4) Membrane Diphenyl Gas recycle Vapor recovery system H , CH H , CH H , CH Reactor system Purge H , CH Purge Phase split Toluene Benzene Reactor system Separation system Dipheny1 Toluene Liquid separation system Benzene Toluene recycle Dipheny1 Simplified Flowsheet for the Separation System Purge H , CH Recycle Structure of the Flowsheet Hierarchy of decisions Batch versus continuous Input-output structure of the flowsheet H , CH Benzene Toluene Dipheny1 Recycle structure of the flowsheet General structure of the separation system a Vapor recovery system b Liquid recovery system Heat-exchanger network Ch Ch.5 Ch.6, Ch.7, Ch.16 Input-Output Structure of the Flowsheet CuuDuongThanCong.com https://fb.com/tailieudientucntt ... operation of the plant, including valves, blinds, etc An id number, an identifier of the material of construction, diameter and insulation requirements for each line Direction of flow Identification of. .. (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. .. Streams Product Streams PROCESS ? (a) Process design starts with the synthesis of a process to convert raw Figure 1.6 The “onion model” of process design A reactor design in needed before the separation