Unit operations in chemical engineering

The individual processes used by chemical engineers (e.g. distillation or chlorination) are called unit operations and consist of chemical reaction, mass-, heat- and momentum- transfer operations.

In chemical engineering and related fields, a unit operation is a basic step in a process. A process may have many unit operations to obtain the desired product.

In 1923 William H. Walker, Warren K. Lewis and William H. McAdams wrote the book “The Principles of Chemical Engineering” and explained the variety of chemical industries have processes which follow the same physical laws. They summed-up these similar processes into unit operations. Each unit operation follows the same physical laws and may be used in all chemical industries. The unit operations form the fundamental principles of chemical engineering. Most unit operations are based mechanistically upon the fundamental transport processes of mass transfer, heat transfer, and fluid flow (momentum transfer). Unit operations based on fluid mechanics include fluid transport (such as pumping), mixing/agitation, filtration, clarification, thickening or sedimentation, classification, and centrifugation. Operations based on heat transfer include heat exchange, condensation, evaporation, furnaces or kilns, drying, cooling towers, and freezing or thawing. Operations that are based on mass transfer include distillation, solvent extraction, leaching, absorption or desorption, adsorption, ion exchange, humidification or dehumidification, gaseous diffusion, crystallization, and thermal diffusion. Operations that are based on mechanical principles include screening, solids handling, size reduction, flotation, magnetic separation, and electrostatic precipitation.

Therefore, chemical engineering unit operations consist of five classes:

1. Fluid flow processes, including fluids transportation, filtration, solids fluidization

2. Heat transfer processes, including evaporation, condensation

3. Mass transfer processes, including gas absorption, distillation, extraction, adsorption, drying

4. Thermodynamic processes, including gas liquefaction, refrigeration

5. Mechanical processes, including solids transportation, crushing and pulverization, screening and sieving

Chemical engineering unit operations also fall in the categories such as combination (mixing); separation (distillation); reaction (chemical reaction). Chemical engineering unit operations and chemical engineering unit processing form the main principles of all kinds of chemical industries and are the foundation of designs of chemical plants, factories and equipment used.

4. Answer the questions to the text:

1. What is a unit operation in chemical engineering and related fields?

2. What did William H. Walker et al explain in the book “The Principles of Chemical Engineering”?

3. What fundamental transport processes are most unit operations based upon?

4. What classes do chemical engineering unit operations consist of?

5. What do chemical engineering unit operations and chemical engineering unit processing form?

5. Form derivatives from the following words and translate them into Ukrainian:

1. Nouns from:
a) to crush
b) to cool
c) to grind
d) to require
c) to blow
d) to dry
e) to exchange
f) to utilize

6. Fill in the gaps using the terms denoting unit operations from the table below:

a) distillation b) absorption c) sedimentation d) screening e) filtration f) evaporation

1. _____ is a physical water treatment process used to settle out suspended solids in water under the influence of gravity.

2. _____ is a type of phase transition; it is the process by which molecules in a liquid state (e.g., water) spontaneously become gaseous

3. _____ is a method of separating mixtures based on differences in their volatilities in a boiling liquid mixture.

4. _____ is commonly the mechanical or physical operation which is used for the separation of solids from fluids (liquids or gases) by interposing a medium through which only the fluid can pass.

5. _____ is the incorporation of a substance in one state into another of a different state

6. _____ is the practice of taking granulated ore material and separating it into multiple grades by particle size.

7. Match the columns to make up word combinations and translate them into Ukrainian:

1) related	a) industries	1)
2) fluids	b) laws	2)
3) basic	c) principles	3)
4) chemical	d) step	4)
5) fundamental	e) fields	5)
6) physical	f) transportation	6)
7) centrifugal	g) transfer	7)
8) heat	h) pump	8)

8. Translate into English using a technical dictionary:

1. При хімічній абсорбції компонент, який абсорбується, зв'язується в рідкій фазі у вигляді хімічної сполуки.

2. Ректифікацію застосовують у хімічній, нафтовій, спиртовій промисловості, а також для розділення ізотопів, виділення індивідуальних речовин тощо.

3. До теплообмінного апарату належать випарники, економайзери, льодогенератори, парогенератори, повітронагрівачі, градирні тощо.

4. Застосовують теплообмінні апарати у теплоенергетиці, промисловості, сільському господарстві, системах вентиляції та опалення тощо.

5. Простим типом лабораторного холодильника є повітряний, що представляє собою зазвичай просто скляну трубку, яка охолоджується навколишнім повітрям.

6. Екструзія — процес отримання виробів шляхом екструдування розплаву матеріалу через формуючий отвір.

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