Chemical Engineering Plant DesignCHE 441

Dr. Asim Laeeq Khan

Assistant Professor

Email: alaeeqkhan@ciitlahore.edu.pk

Materials and Fabrication Selection

3

Material of construction Severe operating conditions Corrosive materials Selection of appropriate material

Resistant to conditions and environment Economical

Role of Chemical Engineering and Metallurgist

4

Iron and Steel Economy vs suitability Impurities in product (Iron salts) Cast Iron and Carbon Steel AISI Standards Steel

5

Stainless Steel Many different types High corrosion and heat resistance High conc. of Ni and Cr Addition of Mo to further increase

resistance Cr : Resistance to Oxidizing agents

(HNO3) Good fabrication properties S and P improve machinability

characteristics

6

Stainless Steel Improvement by oxidization into passive

state (HNO3 + H2O) Susceptible to localized corrosion

7

Hastelloy 56% Ni, 17 % Mo, 16 % Cr, 5% Iron Excellent material but expensive Production of phosphoric acid (Involving Halides) Valves, piping, heat-exchangers, vessels

8

Copper Cheap, easily machineable Good resistant to atmospheric oxygen Susceptible to acids in presence of oxygen Good resistance to all alkalis (except

NH4OH) Copper alloys (Brass, bronze etc)

9

Nickel alloys (200 and 201) Resistant to many alkalis Vessels handling caustic soda Susceptible to corrosion in oxidizing

condition Monel (67% Ni, 30% Cu)

Application in food industry, better resistance to H2SO4 and brine. (Desalination)

Stronger than Ni and Cu Inconel (77% Ni and 17 % Cr)

Better resistance in oxidizing conditions

10

Aluminium Resistant to many acids Al2O3 film formation Oxidation film different from steel Susceptible to halogen acids and extreme pH Application in refrigeration industry

11

Tantalum (Ta) Works at very high temperatures upto

3000 deg C Good fabrication properties Properties similar to glass

12

Glass Resistant to almost all types of fluids except

HF Brittle Low thermal stability Glass-Steel; A possible solution Glass-lined reactors: Pharmaceutical industry Nucerite

Ceramic material Thermal stability upto 650 Deg C 18 times strength

13

14

Graphite Highly resistant except highly oxidizing

conditions Good heat-transfer properties Used in heat-exchangers and other heat transfer

equipment (piping) Low tensile strength

Porcelain & Brick lining Good resistance like glass but better mechanical

stability Brick-lined construction for highly corrosive

environment

15

Rubbers and elastomers Mainly used as liners Varying degree of hardness Natural rubber & Styrene rubber

Resistant to dilute acids and alkali Susceptible to oxidizing conditions and oils

Nitrile rubber For oil and under oxidizing conditions

16

Plastics Very low thermal and mechanical stability Light weight Easy to fabricate and good insulators No electrochemical corrosion as in metals Resistant to inorganic salt solutions Tetrafluoroethylene (Teflon) FRP

Good chemical resistance Cheap Vastly used

17

Gasket Materials Metallic and non-metallic Properties of fluid Operating conditions Frequency of opening of joint

18

Selection of materials Preliminary selection Laboratory experiments

Effect of operating conditions Effect of impurities Other mechanical and thermal tests

Economic comparison Material cost Maintenance costs Probable life

Final selection

19

Selection of materials Coating or Metal itself Selection based on the cost Reliability of coatings

22

Fabrication of equipment Layout of materials

Using flat sheets Cutting and forming Material loss due to operations Location of outlets and attachments

Cutting Shearing Burning (Oxyacetylene flame) Powder of flux burning

23

Fabrication of equipment Forming

Rolling Bending Pressing Spinning in a die Hot or cold working, Lubrication

Fastening Manual shield arc process Heliarc welding