Exam (elaborations) TEST BANK FOR Analysis, Synthesis and Design of Chemical Processes 3rd Edition By Richard Turton, Richard C. Bailie, Wallace B. Whiting and Joseph A. Shaeiwitz (Solution Manual)

Exam (elaborations) TEST BANK FOR Analysis, Synthesis and Design of Chemical Processes 3rd Edition By Richard Turton, Richard C. Bailie, Wallace B. Whiting and Joseph A. Shaeiwitz (Solution Manual) Chapter 1 1.1 Block Flow Diagram (BFD) Process Flow Diagram (PFD) Piping and Instrument Diagrams (P&ID) (a) PFD (b) BFD (c) PFD or P&ID (d) P&ID (e) P&ID 1.2 P&ID 1.3 It is important for a process engineer to be able to review a 3-dimensional model prior to the construction phase to check for clearance, accessibility, and layout of equipment, piping, and instrumentation. 1.4 (1) Clearance for tube bundle removal on a heat exchanger. (2) NPSH on a pump – affects the vertical separation of feed vessel and pump inlet. (3) Accessibility of an instrument for an operator – must be able to read a PI or change/move a valve. (4) Separation between equipment for safety reasons – reactors and compressors. (5) Crane access for removing equipment. (6) Vertical positioning of equipment to allow for gravity flow of liquid. (7) Hydrostatic head for thermosiphon reboiler – affects height of column skirt. 1.5 Plastic models are no longer made because they are too expensive and difficult to change/revise. These models have been replaced with virtual/E-model using 3-D CAD. Both types of model allow revision of critical equipment and instrument placement to ensure access, operability, and safety. 1.6 Another reason to elevate the bottom of a tower is to provide enough hydrostatic head driving force to operate a thermosiphon reboiler. 1-1 1.7 (a) PFD or P&ID (b) PFD (c) PFD (d) P&ID (e) BFD (or all PFDs) 1.8 A pipe rack provides a clear path for piping within and between processes. It keeps piping off the ground to eliminate tripping hazards and elevates it above roads to allow vehicle access. 1.9 A structure – mounted vertical plant layout is preferred when land is at a premium and the process must have a small foot print. The disadvantage is that it is more costly because of the additional structural steel. 1.10 (a) BFD – No change PFD – Efficiency changed on fired heater, resize any heat exchanger used to extract heat from the flue gas (economizer) P&ID – Resize fuel and combustion air lines and instrumentation for utilities to fired heater. Changes for design changed of economizer (if present) (b) BFD – Change flow of waste stream in overall material balance PFD – Change stream table P&ID – Change pipe size and any instrumentation for this process line (c) BFD – No change PFD – Add a spare drive, e.g. D-301 → D-301 A/B P&ID – Add parallel drive (d) BFD – No change PFD – No change P&ID – Note changes of valves on diagram 1.11 (a) A new vessel number need not be used, but it would be good practice to add a letter to donate a new vessel, e.g. V-203 → V-203N. This will enable an engineer to locate the new process vessel sheet and vendor information. (b) P&ID definitely PFD change/add the identifying letter. 1-2 1.12 1-3 1.13 (a) (i) Open globe valve D (ii) Shut off gate valves A and C (iii)Open gate valve E and drain contents of isolated line to sewer (iv)Perform necessary maintenance on control valve B (v) Reconnect control valve B and close gate valve E (vi)Open gate valves A and C (vii) Close globe valve D (b) Drain from valve E can go to regular or oily water sewer. (c) Replacing valve D with a gate valve would not be a good idea because we loose the ability to control the flow of process fluid during the maintenance operation. (d) If valve D is eliminated then the process must be shut down every time maintenance is required on the control valve. 1-4 1.14 1.15 1-5 1.16 (a) For a pump with a large NPSH – the vertical distance between the feed vessel and the pump inlet must be large in order to provide the static head required to avoid cavitating the pump. b) Place the overhead condenser vertically above the reflux drum – the bottom shell outlet on the condenser should feed directly into the vertical drum. c) Pumps and control valves should always be placed either at ground level (always for pumps) or near a platform (sometimes control valves) to allow access for maintenance. d) Arrange shell and tube exchangers so that no other equipment or structural steel impedes the removal of the bundle. e) This is why we have pipe racks – never have pipe runs on the ground. Always elevate pipes and place on rack. f) Locate plant to the east of major communities. 1.17 1-6 1.17 HT area of 1 tube = πDL = π 1 12 ⎛ ⎝ ⎜ ⎞ ⎠ ⎟( 12 ft)= 3.142 ft2 Number of tubes = (145 m2) ⋅ 3.2808 ft m ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ 2 1 3.142 ft2 ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ = 497 tubes Use a 1 1/4 inch square pitch ⇒ Fractional area of the tubes = π 4 1 m 1.25 in ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ 2 = 0.5027 m in ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ 2 AVAP = 3 ALIQ ∴CSASHELL = 4 ALIQ ALIQ = 497 0.5027 ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ in m ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ 2 π 4 ⎛ ⎝ ⎜ ⎞ ⎠ ⎟( 1 m)2 = 777 in2 CSASHELL = (4)(777)= 3108 in2 ⇒ π 4 D2 SHELL = 3108 in2 DSHELL = (4)(3108 in2) π = 62.9 in = 1.598 m Length of Heat Exchanger = (2 +12 + 2) ft =16 ft = 4.877 m Foot Print = 1.598 × 4.877 m 1-7 1.18 From Table 1.11 towers and reactors should have a minimum separation of 15 feet or 4.6 meters. No other restrictions apply. See sketch for details. 1-8 1.19 1-9 1.20 1-10 1.21 (a) A temperature (sensing) element (TE) in the plant is connected via a capillary line to a temperature transmitter (TT) also located in the plant. The TT sends an electrical signal to a temperature indicator controller (TIC) located on the front of a panel in the control room. (b) A pressure switch (PS) located in the plant sends an electrical signal to … (c) A pressure control valve (PCV) located in the plant is connected by a pneumatic (air) line to the valve stem. (d) A low pressure alarm (PAL) located on the front of a panel in the control room receives an electrical signal from … (e) A high level alarm (LAH) located on the front of a panel in the control room receives a signal via a capillary line. 1-11 1.22 2” sch 40 CS LE LT LIC PAL LAH LY 1 3 2 V-302 2” sch 40 CS 4” sch 40 CS 1 To wastewater treatment 2 To chemical sewer P-401 P-402 3 Vent to flare 2 LE LT LIC LAL LAH LY 3 2 2 2 P-401A P-401B V-302 2” sch 40 CS 2” sch 40 CS 4” sch 40 CS To wastewater treatment To chemical sewer Vent to flare 1 2 3 List of Errors 1. Pipe inlet always larger than pipe outlet due to NPSH issues 2. Drains to chemical sewer and vent to flare 3. Double-block and bleed needed on control valve 4. Arrows must be consistent with flow of liquid through pumps 5. Pumps in parallel have A and B designation 6. Pneumatic actuation of valve stem on cv is usual 7. Level alarm low not pressure alarm low 1-12 = Error Corrected P&ID Chapter 2 2.1 The five elements of the Hierarchy of Process Design are: a. Batch or continuous process b. Input – output structure of process c. Recycle structure of process d. General separation structure of process e. Heat-exchanger network/process energy recovery 2.2 a. Separate/purify unreacted feed and recycle – use when separation is feasible. b. Recycle without separation but with purge – when separation of unused reactants is infeasible/uneconomic. Purge is needed to stop build up of product or inerts. c. Recycle without separation or purge – product/byproduct must react further through equilibrium reaction. 2.3 Batch preferred over continuous when: small quantities required, batch-to-batch accountabilities required, seasonal demand for product or feed stock availability, need to produce multiple products using the same equipment, very slow reactions, and high equipment fouling. 2.4 One example is the addition of steam to a catalytic reaction using hydrocarbon feeds. Examples are given in Appendix B (styrene, acrylic acid.) In the styrene process, superheated steam is added to provide energy for the desired endothermic reaction and to force the equilibrium towards styrene product. In the acrylic acid example, steam is added to the feed of propylene and air to act as thermal ballast (absorb the heat of reaction and regulate the temperature), and it also serves as an anti-coking agent – preventing coking reactions that deactivate the catalyst. 2-1 2.5 Reasons for purifying a feed material prior to feeding it to a process include: a. If impurity foul or poison a catalyst used in the process. e.g. Remove trace sulfur compounds in natural gas prior to sending to the steam reforming reactor to produce hydrogen. CH4 + H20 → CO+ 3H2 b. If impurities react to form difficult-to-separate or hazardous products/byproducts. e.g. Production of isocyanates using phosgene. Production of phosgene is Remove trace sulfur Platinum catalyst v. susceptible to sulfur poisoning CO+ Cl2 → COCl2 The carbon monoxide is formed via steam reforming of CH4 to give CO + H2. H2 must be removed from CO prior to reaction with Cl2 to form HCl, which is highly corrosive and causes many problems in the downstream processes. c. If the impurity is present in large quantities then it may be better to remove the impurity rather than having to size all the down stream equipment to handle the large flow of inert material. e.g. One example is suing oxygen rather than air to fire a combustion or gasification processes. Removing nitrogen reduces equipment size and makes the removal of CO2 and H2S much easier because these species are more concentrated. 2.6 IGCC H2O+ CaHbScOdNe + O2 → pCO2 + qH2 + rH2O+ sCO + tNH3 + uH2S Coal In modern IGCC plants, coal is partially oxidized (gasified) to produce synthesis gas CO + H2 and other compounds. Prior to combusting the synthesis gas in a turbine, it must be “cleaned” or H2S and CO2 (if carbon capture is to be employed.) Both H2S and CO2 are acid gases that are removed by one of a variety of physical or chemical absorption schemes. By removing nitrogen from the air, the raw synthesis gas stream is much smaller making the acid gas removal much easier. In fact, when CO2 removal is required IGCC is the preferred technology, i.e. the cheapest. 2-2 2.7 Ethylebenzene Process a. Single pass conversion of benzene Benzene in reactor feed (stream 3) = 226.51 kmol h Benzene in reactor effluent (stream 14) = 177.85 kmol h Xsp =1− 177.85 kmol h 226.51 kmol h = 21.5% b. Single pass conversion of ethylene Ethylene in reactor feed (stream 2) = 93.0 kmol h Ethylene in reactor effluent (stream 14) = 0.54 kmol h Xsp =1− 0.54 kmol h 93.0 kmol h = 99.4% c. Overall conversion of benzene Benzene entering process (stream 1) = 97.0 kmol h Benzene leaving process (stream 15 and 19) = 8.38 + 0.17 kmol h Xov =1− 8.55 kmol h 97.0 kmol h = 91.2% d. Overall conversion of ethylene Ethylene entering process (stream 2) = 93.0 kmol h Ethylene leaving process (stream 15 and 19) = 0.54 + 0 kmol h Xov =1− 0.54 kmol h 93.0 kmol h = 99.4% 2-3 2.8 Separation of G from reactor effluent may or may not be difficult. (a) If G reacts to form a heavier (higher molecular weight) compound then separation may be relatively easy using a flash absorber or distillation and recycle can be achieved easily. (b) If process is to be viable then G must be separable from the product. If inerts enter with G or gaseous byproducts are formed then separation of G may not be possible but recycling with a purge should be tried. In either case the statement is not true. 2.9 Pharmaceutical products are manufactured using batch process because: a. they are usually required in small quantities b. batch-to-batch accountability and tracking are required by the Food & Drug Administration (FDA) c. usually standardized equipment is used for many pharmaceutical products and campaigns are run to produce each product – this lends itself to batch operation. 2-4 2.10 a. Single pass conversion of ethylbenzene Ethylbenzene in reactor feed (stream 9) = 512.7 kmol h Ethylbenzene in reactor effluent (stream 12) = 336.36 kmol h Single pass conversion = 1− 336.36 kmol h 512.7 kmol h = 34.4% b. Overall conversion of ethylbenzene Ethylbenzene entering process (stream 1) = 180 kmol h Ethylbenzene leaving process (stream 19, 26, 27 & 28) = 3.36 + 0.34 = 3.70 kmol h Overall conversion = 1− 3.70 kmol h 180 kmol h = 97.9% c. Yield of styrene Moles of ethylbenzene required to produce styrene = 119.3 kmol h Moles of ethylbenzene fed to process (stream 1) = 180 kmol h Yield = 119.3 kmol h 180 kmol h = 66.3% Possible strategies to increase the yield of styrene are (i) Increase steam content of reactor feed – this pushes the desired equilibrium reaction to the right. (ii) Increasing the temperature also pushes the equilibrium to right but increases benzene and toluene production. (iii) Remove hydrogen in effluent from each reactor – this will push the equilibrium of the desired reaction to the right and reduce the production of toluene from the third reaction – use a membrane separator, shown on following page. 2-5 2-6 2.11 Route 1: 2A → S + R Key features are that no light components (non-condensables) are formed and only one reactant is used. Therefore, separation of A, R, and S can take place using distillation columns. Route 2: A + H2 → S + CH4 Unlike Route 1, this process route requires separation of the non-condensables from A and S. If hydrogen is used in great excess (as with the toluene HDA process), then a recycle and purge of the light gas stream will be required. Otherwise, if hydrogen conversion is high, the unreacted hydrogen along with the methane may be vented directly to fuel gas. Route 1 – PFD sketch S Route 2 – PFD sketch – gas recycle shown dotted since it is only needed if H2 is used in (considerable) excess and must be recycled. R A Recycled A Tower 1 Reactor Tower 2 S H2 + CH4 A Reactor Recycled A Tower Gas Separator Compressor 2-7 Route 1 is better since: • Simpler PFD • No gas recycle (no recycle compressor) • No build up of inerts (CH4) so recycle stream is not as large • All products are valuable – fuel gas in Route 2 has a low value 2-8 2.12 a. Good when product(s) and reactant(s) are easily separated and purified (most often by distillation.) Any inerts in the feed or byproducts can be removed by some unit operation and thus recycle does not require a purge. b. When unused reactant(s) and product(s) are not easily separated (for example when both are low boiling point gases) and single pass conversion of reactant is low. c. This is only possible when no significant inerts are present and any byproducts formed will react further or can reach equilibrium. 2-9 2.13 a. b. Alternative 1 Alternative 1 assumes butanol and acetic acid can be sold as a mixed product ⇒ very unlikely so probably have to add another column to separate. H C2H5OH → C2H4O + H2 Acetaldehyde C2H4 C2H5O 2C2H5OH → C4H8O2 + 2H2 Ethyl Acetate H2 2C2H5OH → C4H10O + H2O C4H8O Butanol C C4H10 2H5OH + H2O → C2H4O2 + 2H2 Acetic Acid C2H4O Order of volatility is acetaldehyde, water, ethyl acetate, ethanol, isobutanol, acetic acid. 2-10 Alternative 2 This alternative recycles C2H5OH and produces “pure” acetaldehyde – the remaining streams are considered waste – incineration of organics or wastewater treatment are possible ways to remove organics. 2-11 2.14 • A and R are both condensable and may be separated via distillation • C may be separated by absorption into water • R will be absorbed into water • G and S cannot be separated except at very high pressure or low temperature • After reaction, cool and condense A and R from other components. • Separate A from R using distillation and recycle purified liquid A to the front end of the process • Treat remaining gas stream in a water absorber to remove product C • Separate C and from water via distillation • Recycle unused G containing S – since S does not react further – we must add a purge to prevent accumulation of S in the system. This stream must be recycled as a gas using a recycle gas compressor. Reactor Flash Distillation Absorber G+S Purge (to WT) G+S Recycle R Water (to WT) C A+R C+G+S Feed A Feed G Water Distillation If the value of G was very low, then consider not recycling G (and S.) 2-12 2.15 Malt Whiskey Process Grain Whisky Process 2-13