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PROCESSING TECHNOLOGY 1

PROCESSING TECHNOLOGY 1. UNITS AND BASIC CONCEPTS. UNITS AND BASIC CONCEPTS. Introduction to units commonly used in chemical engineering includes non S.I. Units Inter-relationship of and conversion between common units. Units Relating to MOLES.

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PROCESSING TECHNOLOGY 1

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  1. PROCESSING TECHNOLOGY 1 UNITS AND BASIC CONCEPTS

  2. UNITS AND BASIC CONCEPTS • Introduction to units commonly used in chemical engineering • includes non S.I. Units • Inter-relationship of and conversion between common units

  3. Units Relating to MOLES • By definition a mole of any substance contains 6.023 x 1023 molecules (or atoms, ions, electrons) • Avogadro’s number = 6.023 x 1023

  4. Units Relating to MOLES • Molar mass is the mass of a mole of a substance. • Molecular weight is the mass of a compound or element per mole. • Atomic weight is generally the mass of a mole of atoms in grams.

  5. Units Relating to MOLES • Gram Mole (g mol): • 1 gram mole of H2O has a mass of 18 g

  6. Units Relating to MOLES • Kilogram Mole (kmol): • 1 kg mole H2O has a mass of 18 kg • The kilogram mole is comprised of 1,000 moles

  7. Units Relating to MOLES • Pound Mole (lb mole). • 1 lb mole H2O has a mass of 18 lb

  8. Mixtures of Substances • A number of definitions • mole concentration %

  9. Mixtures of Substances • Mole fraction

  10. Mixtures of Substances • Mass concentration (%)

  11. Mixtures of Substances • Volumetric concentration (%)

  12. Keypoint • All units used in a mass balance must be compatible

  13. 100 cm 100 cm 100 cm Units of Volume • S.I. Unit = cubic metre (m3) • 1 m3 103 litre  106 ml (cm3)

  14. Flowrates of Fluids • Volumetric flow rate, Q (m3 /s) • Mass flow rate, G (kg /s) • Molar flow rate, M (kmol/s) • Density, r (kg /m3.

  15. Flowrates of Fluids • density r (kg /m3) = mass (kg)/volume (m3) • G (kg/s) / Q (m3/s) has units of kg/m3 Keypoint: G = rQ

  16. Flowrates of Fluids • Molar flow rate (M)

  17. 1m3 of Water 2m3 of Ethanol-Water Mixture Mix 1m3 of Ethanol Volumes and Mixtures of Liquids

  18. Volumes and Mixtures of Liquids

  19. Mixtures of Similar Liquids • If the liquids have similar molecular structures, it may be assumed, for purposes of estimation, that the volumes are additive as well as the masses.

  20. Mixtures of Similar Liquids • This assumption permits mass balances on a volume basis to be carried out, and also allows the density of mixtures to be estimated if the densities of the pure liquids are known.

  21. Mixtures of Similar Liquids • Consider a liquid system consisting of two similar liquid components A and B, with defined masses (mA and mB), volumes (VA and VB) and densities (rA and rB).

  22. Mixtures of Similar Liquids • define the ratio of the mass of one component to the total mixture mass mTOT as the mass fraction (x) then, • xA = mA / mTOT (1) • xB = mB / mTOT (2)

  23. Mixtures of Similar Liquids • rA = mA / VA (3) • rB = mB / VB (4) • rTOT = mTOT / VTOT (5)

  24. Mixtures of Similar Liquids • Inverting • Assuming volume is conserved (6) (7)

  25. Mixtures of Similar Liquids • Rearrange (3) and (4) (9) (8)

  26. Mixtures of Similar Liquids • Substitute (8) and (9) into (7) (10)

  27. Mixtures of Similar Liquids • Substitute expressions (1) and (2) for mass fraction into (10) (11)

  28. Mixtures of Similar Liquids • This can be generalised for any number n of components

  29. Pressure

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