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23-Chem-A5 Chemical Plant Design and Economics · May 2017

Question 3 of 6: Scope of Information for a Chemical Process Design

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

Notes on this paper

Closed-book exam, 3 hours; one aid sheet permitted. Six questions of equal value (20 marks each); five constitute a complete paper — full solutions to all six are given here. Questions 1 and 2 are quantitative (plant material balance and discounted-cash-flow return); Questions 3–6 are design-practice list/essay questions.

Reference texts: M.S. Peters, K.D. Timmerhaus & R.E. West, Plant Design and Economics for Chemical Engineers (5th ed., McGraw-Hill) — the exam's named primary text (process design development Ch. 2, general design considerations: plant location, safety, materials Ch. 3, interest and profitability Ch. 7–10, materials-transfer/pumps Ch. 14); R.H. Perry & D.W. Green, Perry's Chemical Engineers' Handbook (9th ed.) — pump types and selection (Sec. 10), pyrolysis kinetics data; O. Levenspiel, Chemical Reaction Engineering (3rd ed.) — first-order plug-flow space-time behind the reactor sizing in Question 1; supporting Canadian practice from CCOHS and the CSA Z767 / provincial OH&S process-safety-management framework for Question 5.

Question 3: Scope of Information for a Chemical Process Design (20 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

Given / Find. A qualitative design-management question. The answer is the "design-basis" or project-scope information set agreed before detailed design begins, conventionally split into basic design data (what the plant must do) and specific design data (the fixed local/technical conditions it must do it under). At least 20 items are listed below, grouped for clarity.

A. Basic design data (product, capacity, and process definition)

  1. Product(s) and specifications — chemical identity, purity, grades, form (solid/liquid/gas).
  2. Production capacity / rate — design throughput (e.g. tonnes/yr) and turndown range.
  3. Raw materials — identity, specification, and required purity of each feed.
  4. Process chemistry / route — reactions, yields, selectivity, catalyst, by-products.
  5. Overall material and energy balances — the process flow sheet basis.
  6. Physical-property data — for all streams (density, viscosity, VLE, Cp, latent heats).
  7. Operating conditions — temperatures, pressures, and residence times of each unit.
  8. Process yield and conversion targets — per-pass and overall.
  9. Recycle and purge philosophy — streams recovered vs. rejected.
  10. By-product and waste streams — quantities, disposition, saleability.

B. Specific design data (site, utilities, and constraints)

  1. Plant location / site — geography, climate, seismic and soil data.
  2. Utilities available — steam levels, cooling water, electricity, fuel, instrument air, nitrogen.
  3. Raw-water source and quality — and any water-treatment needs.
  4. Feed-stock and product storage / logistics — tankage, shipping mode, inventory days.
  5. Battery-limit conditions — the state (T, P, composition) of streams entering and leaving the plant.
  6. Materials of construction constraints — corrosion, temperature, and pressure service limits.
  7. Effluent and emission limits — permitted liquid, gaseous, and solid discharges (regulatory).
  8. Safety and hazard data — flammability, toxicity, reactivity, relief and containment requirements.
  9. Health, environmental and regulatory requirements — permits, codes, provincial OH&S / environmental law.
  10. Applicable codes and standards — ASME, CSA, API, local building and electrical codes.
  11. Economic basis — capital budget, expected rate of return, feed/product/utility prices, project life.
  12. Project schedule and completion date — start-up target and milestone dates.
  13. Degree of instrumentation / control and automation philosophy.
  14. Future-expansion and flexibility provisions — space, spare capacity, alternate feeds.
  15. Operating labour, maintenance, and manning philosophy.

Twenty-five items are given above (more than the twenty required). In practice these are captured in a formal design basis or basis-of-design document signed off by all participating functions before detailed engineering proceeds, so that engineering, research, operations, safety, environmental, and management are working to one agreed target.