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23-Chem-A5 Chemical Plant Design and Economics · May 2018

Question 5 of 6: Protective Linings for Chemical Plant Equipment

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

Notes on this paper

Closed-book exam, 3 hours; one aid sheet (both sides) permitted; approved calculator. Six questions of equal value (20 marks each); five constitute a complete paper — full solutions to all six are given here. Question 1 is process synthesis (draw a flowsheet), Question 2 is quantitative (separation-train economics), and 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 synthesis & flowsheet development Ch. 2–4, general design considerations incl. materials of construction Ch. 3–4, cost & depreciation Ch. 6–9); R. Turton et al., Analysis, Synthesis, and Design of Chemical Processes (4th ed., Prentice Hall) — separation sequencing heuristics and pollution-prevention hierarchy; R.K. Sinnott & G. Towler, Chemical Engineering Design (Coulson & Richardson Vol. 6) — distillation column design and column-internals selection; D.A. Crowl & J.F. Louvar, Chemical Process Safety (4th ed.) — batch-reactor procedures and inherently safer design. Canadian practice framed by CCOHS/WHMIS 2015 and provincial OH&S process-safety expectations.

Question 5: Protective Linings for Chemical Plant Equipment (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.

A lining lets a cheap structural substrate (usually carbon steel) be used in service it could not otherwise survive, by presenting a corrosion- or abrasion-resistant surface to the process fluid. Five commonly used linings are:

  1. Rubber lining (natural or synthetic elastomer). Soft or hard rubber (ebonite), or synthetics such as neoprene, butyl and chlorobutyl, bonded to steel. Excellent against dilute mineral acids, chlorides and slurries, and its resilience resists abrasion. Examples: hydrochloric-acid storage tanks, brine and pickling vessels, slurry pipelines and pump bodies.
  2. Glass-lined (glassed / vitreous enamel) steel. A fused glass coating gives near-universal chemical inertness and a smooth, easily cleaned, non-contaminating surface. Examples: pharmaceutical and fine-chemical reaction vessels, sulphuric- and nitric-acid duties, and food/pharma service where product purity is critical (limited by thermal-shock and impact sensitivity).
  3. Plastic / thermoplastic linings (PVC, PP, PTFE, PVDF, FRP). Loose or bonded thermoplastic sheet, or fibre-reinforced plastic, chosen for the specific chemical. PTFE resists almost everything to high temperature; PVC/PP suit many acids and alkalis. Examples: PTFE-lined pipe and valves for aggressive acids, FRP or PP tanks for hypochlorite and caustic, ducting for corrosive vapours.
  4. Lead lining (and lead alloys). Traditional for sulphuric acid, where a protective sulphate film forms; dense and durable but heavy and toxic, now largely superseded but still specified for some strong-acid duties. Examples: sulphuric-acid towers and drains, pickling tanks, radiation and some effluent lines.
  5. Acid-resistant brick and chemical-resistant refractory lining. Ceramic/carbon brick set in acid-proof mortar over a membrane, giving both chemical resistance and thermal/abrasion protection at high temperature. Examples: acid-storage tank floors, absorption-tower and reactor linings, flue-gas ducts and stacks handling hot corrosive gas.

Selection matches the lining to the specific chemical, temperature, abrasion and purity requirement: rubber and plastics for wet chloride/acid abrasion service, glass for purity-critical or broadly corrosive duty, lead for concentrated sulphuric acid, and acid brick where heat and abrasion accompany the chemical attack.