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BFD, PFD, P&IDDavide MancaLab 7 of “Process Systems Engineering” – Master Degree in Chemical Engineering – Politecnico di MilanoLAB7—

Diagrams in process engineering There are three main diagrams used by chemical engineers to design anddescribe the processes– Block Flow Diagram BFD Starting from an input-output diagram of the process we divide it into its mainfunctional blocks such as: the reaction section, the separation section, etc Then we add the recycle streams and the preliminary material balances.– Process Flow Diagram PFD The next step is to evaluate and quantify efficiently the material and energybalances for all the process streams. Then we add the preliminary designspecifications of the equipment.– Piping and Instrumentation Diagram P&ID We introduce the specific details describing the mechanics and the processinstrumentation. Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—2

Diagrams in process engineering The most efficient way to communicate information related to a chemicalprocess is to use flow charts. Visual information is the best way to presentdesign data and it avoids misunderstandings and ambiguities. When possible it shall be adopted the English terminology and symbology sincein most cases the documentation produced by an engineering company is forforeign orders. We refer to symbols and diagrams from the text: R. Turton, R. Bailie, W. Whiting, J. ShaeiwitzAnalysis, Synthesis and Design of Chemical ProcessesPrentice Hall, New Jersey, 1998 Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—3

BDF: Block Flow DiagramReaction: C7H8 H2 C6H6 CH4 International conventions and recommended formats for the realization of BFDs The unit operations are indicated by blocks The main streams are identified by lines with arrows indicating the flow direction When possible, the direction of the streams is from left to right Light currents (gas) upwards, heavy currents (liquids and solids) downwards of the blocksrepresenting the single portions of the plant Provide basic and most important information of the process If the process lines intersect, the horizontal ones are held whilst the vertical one are broken Provide simplified material balances and main reactions Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—4

PFD: Process Flow Diagram The PFD is greatly enhanced compared to the BFD. It is the most important and useddiagram to describe with an adequate level of detail the structure of the process. There is not a universally accepted nomenclature. In general, a PFD contains thefollowing information:1.The important equipment is shown together with a short description. Each device isidentified by a code.2.The streams are shown and identified with a number. Every stream shows the processconditions and composition. These data can be entered directly on the PFD or in asummary attached table. 3.The utilities of the equipment are shown and described4.The main control loops are shownThe information provided by a PFD can be summarized as follows: Topology of the process Information on streams Information on equipment Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—5

PFD: Process Flow DiagramPFD for the production of benzene by the hydrodealkylation of toluene (HDA) Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—6

PFD: Process Flow Diagram We define as “topology of the process” the position and the interaction among theunits and the streams of the process.The equipment is represented by icons. The ASME (American Society of MechanicalEngineers) periodically publishes a list of symbols to be used in the production of thePFD. Nevertheless, engineering companies are used at adopting custom symbols inorder to make their own PFD recognizable and distinguishable from those of theircompetitors.Each piece of equipment is identified by a number on the PFD.For example, the toluene pump P-101A/B provides the following information: P-101A/B means that the equipment as a pumpP-101A/B means that the pump is located in the area 100 of the plantP-101A/B means that the specific pump is number 01 of the area 100P-101A/B means that there are two pumps: P-101A and P-101B. The second oneis a spare part that works as a back-up (i.e. normally is not working but it startsrunning when the former breaks or needs to be serviced).The word “Toluene pump” is the colloquial name that identifies P101 and is usedin discussions about the process. Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—7

PFD: Process Flow DiagramLibrary of equipment symbols for a PFD Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—8

PFD: Process Flow DiagramConventions used to identify the equipment of the process General format: XX-YZZ A/BXX are the identification letters for the classification of the equipment C – Compressor, turbine E – Heat Exchanger H – Fired Heater P – Pump R – Reactor T – Tower TK – Storage Tank V – VesselY shows the area of the plant where the equipment is placed ZZ reports the sequential number of the specific process unit A/B means a parallel/spare/back-up equipment Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—9

PFD: Process Flow DiagramConventions used to identify the streams of the process Each process stream is identified by a number in a diamond above it. The direction isdefined by one or more arrows. The utilities include: electricity, compressed air, cooling water, chilled water, steam,condensate, inert gas, chemical sewer, water treatment and flares. We use thefollowing symbols: lpsmpshpshtmcwwrrwrbcssselngfgfofwlow pressure steam 3-5 barg (sat)medium pressure steam 10-15 barg (sat)high pressure steam 40-50 barg (sat)heat transfer medium (organic): to 400 Ccooling water: from cooling tower 30 C returned at less than 45 Criver water: from river 25 C returned at less than 35 Crefrigerated water: in at 5 C returned at less than 15 Crefrigerated brine: in at -45 C returned at less than 0 Cchemical waste water with high CODsanitary waste water with high BODelectric energy (specify 220, 380, 440, 660V service)natural gasfuel gasfuel oilfire water Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—10

PFD: Process Flow DiagramAs already stated, each stream is identified by a number. A summary table whichaccompanies the PFD provides the data on the process streams. Essential information Stream numberTemperature [ C]Pressure [bar]Vapor FractionTotal Mass Flow Rate [kg/h]Total Mole Flow Rate [kmol/h]Individual Component Flow Rates [kmol/h]Optional information Component Mole FractionsComponent Mass FractionsIndividual Component Flow Rates [kg/h]Volumetric Flow Rates [m3/h]Significant Physical Properties: Density, Viscosity, Thermodynamic Data: Heat Capacity, Enthalpy, K-values, Stream name Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—11

PFD: Process Flow DiagramThe last element of the PFD is a summary of the equipment which allowsestimating the costs and provides the starting point to carry out a detaileddesign.Equipment typeDescription of the equipmentTowersSize (height and diameter), Pressure, Temperature, Number and type oftrays, Height and type of packing, Materials of constructionHeat ExchangersType: gas-gas, gas-liquid, liquid-liquid, Condenser, VaporizerProcess: Duty, Area, Temperature and Pressure for both streamsNumber of shell and tube passesMaterials of construction: shell and tubesTanks, VesselsHeight, Diameter, Orientation, Pressure, Temperature, Materials ofconstructionPumpsFlow, Discharge, Pressure, Temperature, P, Driver type, Shaft power,Materials of constructionCompressorsActual inlet flow rate, Pressure, Temperature, Driver type, Shaft power,Materials of constructionHeaters (fired)Type, Tube pressure, Tube temperature, Duty, Fuel, Materials ofconstructionOthersProvide critical information Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—12

PFD: Process Flow DiagramThe PFD can include explicit information of the process streams by means of special “flags”. These“flags” are attached to the streams which they refer to, with text boxes in different shapes to indicatethe value of measures such as:STREAM IDPRESSUREMOLAR FLOW RATETEMPERATURELIQUID FLOW RATEMASS FLOW RATEGAS FLOW RATE Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—13

P&ID: Piping & Instrumentation DiagramA synonymous of P&ID is MFD, Mechanical Flow Diagram. It contains the dataneeded to start planning the construction of the plant. Mechanical andfunctional data are given for each piece of equipment.Exceptions are:1.Operating conditions: T and P2.Stream values3.Equipment positioning4.Piping: lengths and fillings5.Supports, Foundations and StructuresThe following bits of information must be reported:For Equipment – show every piece including:Spare units, Parallel units, Summary detail on eachunitFor piping – show all lines including Drains,and specify:Size (standard), Thickness, Materials ofconstruction, Insulation (thickness and type)For instruments – Identify:Indicators, Recorders, Controllers, Show instrumentlinesFor utilities – Identify:Inlet and outlet utilities, Waste treatment facilities Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—14

P&IDField instrumentationPositioning of the instrumentation:Instrumentation on the fron of Control Panel inthe control roomInstrumentation on the back of Control Panel inthe control roomMeaning of identifying lettersXYYFirst letter: XSecond and third letters: YAAnalysisABBurner flameBCConductivityCDDensity or specific gravityDEVoltageEFFlowrateFHHand (manually initiated)HHighICurrentIIndicatorJPowerJKTime or time scheduleKControl stationLLevelLLight or lowMMoisture or humidityMMiddle or intermediateOOrificeOAlarmControlElement Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—15

P&IDMeaning of identifying lettersXYYFirst letter: XSecond and third letters: YPPressure or vacuumPQQuantity or eventQRRadioactivity or ratioRRecord or printSSpeed or lve, damper or louverWWeightWWellYRelay or computeZDriveYZPositionPointIdentification of instrumental connectionsCapillaryPneumaticElectric Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—16

P&ID Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—17

P&IDLoop control structure for the tank level V-102 LE LTlevel transmitter positioned on the tank V-102Transfer the signal via an electric line - - - - - - to the control roomLIClevel indicator and controller in the control roomTransfer an electrical signal - - - - - - to the instrument LYLYinstrument able to calculate the exact valve openingTransfer a pneumatic signal (solid line) to the control valve LCVLAHtoo high level alarm in the control room (front panel)LALtoo low level alarm in the control room (front panel) level sensor positioned on the tank V-102 Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—18

Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—19

References R. Turton, R. Bailie, W. Whiting, J. Shaeiwitz, “Analysis, Synthesis and Design of Chemical Processes”, PrenticeHall, New Jersey, 1998 Davide Manca – Process Systems Engineering – Master Degree in ChemEng – Politecnico di MilanoLAB7—20

LAB7—3 The most efficient way to communicate information related to a chemical process is to use flow charts. Visual information is the best way to present design data and it avoids misunderstandings and ambiguities. When possible it shall be adopted the English terminology and symbology since in most cases the documentation produced by an engineering company is for