1 / 29

Understanding Units and Basic Concepts in Chemical Engineering

This resource provides an introduction to the units commonly used in chemical engineering, covering both S.I. and non-S.I. units. It explores the concept of moles, Avogadro's number, and the relationship between molar mass, molecular weight, and atomic weight. The document details various units relating to moles, including gram mole, kilogram mole, and pound mole. It also discusses properties of mixtures of substances including concentration, flow rates, and density, providing a foundation for performing mass balances and understanding liquid mixture behavior in chemical processes.

morse
Télécharger la présentation

Understanding Units and Basic Concepts in Chemical Engineering

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related