Preliminary Chemical Engineering Plant Design WilliamD.Baasel Professor of Chemical Engineering Ohio University ELSEVIER New York/Oxford/Amsterdam Contents xi Preface INTRODUCTION TO PROCESS DESIGN Other Sources of Innovations, Research, Process Engineering, Professional Responsibilities, Competing Processes, Typical Problems a Process Engineer Tackles, Comparison with Alternatives, 14 Completing the Project, 16 Units, 17 References, 18 Bibliography, 18 23 SITE SELECTION Other Site Location Factors, 34 Major Site Location Factors, 25 Study: Site Selection, 48 References, 54 Case THE SCOPE 57 The Product, 60 Capacity, 60 Quality, 66 Raw Material Storage, 67 Product Storage, 68 The Process, 69 Waste Disposal, Utilities, Shipping and Laboratory Requirements, 70 Plans for Future Expansion, 70 Hours of Operation, 71 Completion Date, 71 Safety, 71 Case Study: Scope, 72 Scope Summary, 75 References, 78 PROCESS DESIGN AND SAFETY 79 Chemistry, 79 Separations, 80 Unit Ratio Material Balance, 84 Detailed Flow Sheet, 85 Safety, 89 Case Study: Process Design, 97 Change of Scope, 103 References, 103 EQUIPMENT LIST Sizing 111 113 114 117 105 Planning for Future Expansion, of Equipment, 106 Materials of Construction, 113 Temperature and Pressure, Laboratory Equipment, 114 Completion of Equipment List, Rules of Thumb, 114 Case Study: Major Equipment Required, References, 133 Change of Scope, 132 141 LAYOUT New Plant Layout, 141 Expansion and Improvements of Existing Facilities, 152 Case Study: Layout and Warehouse Requirements, 153 References, 158 vii Contents viii 159 PROCESS CONTROL AND INSTRUMENTATION Plant Safety, Product Quality 160 Product Quantity, 160 Control System, 161 Manual or Automatic Control, 161 Final Control Element, 162 Variables to be Measured, 162 Averaging versus Set 163 Control and Instrumentation Symbols, 164 Tempered Heat Point Control, 166 Material Balance Control, 167 Cascade Control, 170 Feedforward Control, Transfer, 168 Pneumatic versus Elec171 Blending, 172 Digital Control, 172 Case Study: Instrumentation and Control, tronic Equipment, 173 174 References, 180 ENERGY AND UTILITY BALANCES AND MANPOWER NEEDS 181 Energy Balances, 183 Sizing Energy Conservation of Energy, 182 Equipment, 191 Planning for Expansion, 204 Lighting, 205 Ventilation, Space Heating and Cooling, and Personal Water Requirements, 207 Utility Requirements, 209 Manpower RequireCase Study: Energy Balance and ments, 210 Rules of Thumb, 11 References, 232 Utility Assessment, 213 Change of Scope, 231 COST ESTIMATION 237 Cost Indexes, 237 How Capacity Affects Costs, 239 Factored Cost Estimate, 246 Improvements on the Factored Estimate, 249 Module Cost Estimation, 254 Unit Operations Estimate, 258 Detailed Cost Estimate, 263 Accuracy of Estimates, 264 Case Study: Capital Cost Estimation, 264 References, 10 279 ECONOMICS Capital, 284 Elementary ProfitaCost of Producing a Chemical, 28 Compound Interest, bility Measures, 285 Time Value of Money, 293 Rate of 295 Net Present Value-A Good Profitability Measure, 307 Comparison of Net Return-Another Good Profitability Measure, 311 Present Value and Rate of Return Methods, 316 Proper Interest Rates, Case Study: Economic 317 Expected Return on the Investment, 323 Evaluation, 324 Problems, 330 References, 338 11 DEPRECIATION, AMORTIZATION, DEPLETION AND INVESTMENT CREDIT 339 Depreciation, 339 Amortization, 348 Depletion 348 Special Tax Rules, 350 Investment Credit, 349 The Net Present Value and Rate of Return, 350 351 References, 352 12 Allowance, Case Study: Problems DETAILED ENGINEERING, CONSTRUCTION, AND STARTUP Detailed Engineering, 363 References 367 353 353 Construction 361 Startup, Contents 13 PLANNING TOOLS-CPM AND PERT ix 369 CPM, 370 Manpower and Equipment Leveling, 376 Cost and Schedule Control, 380 Time for Completing Activity, 380 References, 390 Computers, 381 PERT, 382 Problems, 386 14 OPTIMIZATION TECHNIQUES 391 Single Variable Starting Point, 392 One-at-a-Time Procedure, 393 End Game, Gptimizations, 396 Multivariable Optimizations, 396 Optimizing Optimizations , 409 Algebraic Objective Functions, 409 409 Optimization and Process Design, 410 References, 412 15 DIGITAL COMPUTERS AND PROCESS ENGINEERING 415 Program Sources, Computer Programs, 416 Sensitivity, 420 References, 422 420 Evaluation of Computer Programs, 421 16 POLLUTION AND ITS ABATEMENT 423 Determining Pollution Standards, What is Pollution?, 424 Air Pollution Abatement 425 Meeting Pollution Standards, 428 BOD and Methods, 431 Water Pollution Abatement Methods, 437 COD, 447 Concentrated Liquid and Solid Waste Treatment Procedures, 452 References, 454 Appendices 459 Index 479 Preface The idea for this book was conceived while I was on a Ford Foundation residency at the Dow Chemical Company in Midland, Michigan I was assigned to the process engineering department, where I was exposed to all areas of process engineering, project engineering, and plant construction My previous industrial experiences had been in pilot plants and research laboratories Much to my surprise, I found that what was emphasized in the standard plant design texts was only a part of preliminary process design Such areas as writing a scope, site selection, equipment lists, layout, instrumentation, and cost engineering were quickly glossed over After I returned to Ohio University and began to teach plant design, I decided a book that emphasized preliminary process engineering was needed This is the result It takes the reader step by step through the process engineering of a chemical plant, from the choosing of a site through the preliminary economic evaluation So that the reader may fully understand the design process, chapters dealing with planning techniques, optimization, and sophisticated computer programs are in cluded These are meant merely to give the reader an introduction to the topics TO discuss them thoroughly would require more space than is warranted in an introductory design text They (and other sophisticated techniques, like linear programming) are not emphasized more because before these techniques can be applied a large amount of information about the process must be known When it is not available, as is often the case, the engineer must go through the preliminary process design manually before these newer techniques can be used It is to this initial phase of design that this book is directed Three types of design problems fit this situation One is the design of a plant for a totally new product The second is the design of a new process for a product that currently is being produced The last is the preliminary design of a competitor’s plant, to determine what his costs are In each of these, little is known about the process, so that a large amount of educated guessing must occur As time goes on, more and more people are being involved in these types of plant design Most chemical companies estimate that 50% of their profits 10 years hence will come from products not currently known to their research laboratories Since these will compete with other products now on the market, there will be a great need for improving present processes and estimating a rival’s financial status This book deals mainly with chemical plant design, as distinct from the design of petroleum refineries For the latter, large amounts of data have been accumulated, and the procedures are very sophisticated It is assumed that the reader has some xi xii PREFACE familiarity with material and energy balances A background in unit operations and thermodynamics would also be helpful, although it is not necessary No attempt is made to repeat the material presented in these courses This book applies a systems philosophy to the preliminary process design and cost estimation of a plant In doing so, it tries to keep in perspective all aspects of the design There is always a tendency on the part of designers to get involved in specific details, and forget that their job is to produce a product of the desired quality and quantity, at the lowest price, in a safe facility What is not needed is a technological masterpiece that is difficult to operate or costly to build For those using this book as a text, I suggest that a specific process be chosen Then, each week, one chapter should be read, and the principles applied to the specific process selected The energy balance and economic chapters may each require two weeks The pollution abatement chapter may be included after Chapter 8, or it can be studied as a separate topic unrelated to the over-all plant design Each student or group of students may work on a different process, or the whole class may work on the same process The advantage of the latter method is that the whole class can meet weekly to discuss their results This has worked very successfully at Ohio University In the discussion sections, the various groups present their conclusions, and everyone, especially the instructor, benefits from the multitude of varied and imaginative ideas Initially, this procedure poses a problem, since in most college courses there is a right and a wrong answer, and the professor recognizes and rewards a correct response In designing a plant, many different answers may each be right Which is best often can be determined only by physically building more than one plant, and evaluating each of them Of course, no company would ever this It would build the plant that appears to contain fewer risks, the one that seems to be best economically, or some combination of these Since the student will build neither, and since the professor probably cannot answer certain questions because of secrecy agreements or lack of knowledge, the student must learn to live with uncertainty He will also learn how to defend his own views, and how to present material so as to obtain a favorable response from others These learning experiences, coupled with exposure to the process of design as distinct from that of analysis and synthesis, are the major purposes of an introductory design course Besides students, this book should be useful to those in industry who are not intimately familiar with process engineering Researchers should be interested in process design because their projects are often killed on the basis of a process engineering study Administrators need to have an understanding of this because they must decide whether to build a multi-million-dollar plant designed by a process engineering team Operating personnel should know this because they must run plants designed by process engineers Similarly, project engineers and contractors need to understand process engineering because they must take the resultant plans and implement them Finally, pilot plant and semi-plant managers and operators need to know the problems that can arise during process design because they often APPENDIX B 10 loo 1,000 C/H factor, gpm Required Capacity, gpm Differential pressure, psi Suction pressure, psig Body material Figure B-7 Time base Mid.1968 Exponent Averageexponent 0.70 10,000 x psi Recipa.tlw Included Pumping unit Driver and coupling Base plate Reciprocating pumps and drivers Source: Guthrie, K.M.: “Capital Cost 1969, p 114 100,000 Pup Cat, I = ,8src COII Ad,“‘tmsnt factam ldnrcrlsl ,; cart iran 1.00 Brnnzc 25 C.rt steel I.55 suidc.,s Estimating,” Operating Llmlrr Suction p’c”we pi Syrtrrn ‘Lmperrturc, OF F.