Questions and Answers
Which of the following is NOT a technique used in chemical metallurgy?
In the context of the provided content, what is the primary function of 'Smelting' in chemical metallurgy?
Which of these is NOT a method used in pharmaceutical extraction as mentioned in the content?
What is the main difference between 'Maceration' and 'Infusion' as pharmaceutical extraction methods?
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According to the provided content, which of the following best describes the purpose of 'Centrifugal Extraction'?
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Based on the provided references, which of these authors is associated with the book 'Plant Design and Economics for Chemical Engineers'?
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Which of the following is NOT a source of information about liquid-liquid extraction as mentioned in the content?
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Which of these steps in chemical metallurgy is most closely related to the process of separating valuable minerals from their ores?
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Based on the content, which of the following best describes the relationship between 'Centrifugal Extraction' and 'Liquid-Liquid Extraction'?
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Which of the following methods is MOST LIKELY to be used for extracting a volatile compound from a plant material?
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Study Notes
Absorption
- Absorption separates gas components by transferring them to a non-volatile liquid solvent.
- Types of absorption based on interaction between absorbent and absorbate:
- Physical Solution: Absorbate solubility is higher in the absorbent, with equilibrium dependent on gas phase partial pressure and temperature.
- Reversible Reaction: A chemical reaction forms a compound with substantial vapor pressure.
- Irreversible Reaction: A permanent reaction occurs between absorbate and absorbent.
- Physical absorption favors high-pressure large gas quantities; chemical absorption is suited for low-concentration scenarios.
Absorption Operation
- Conducted in equilibrium stages where gas and liquid phases interact.
- Simpler design than distillation, without needing condensers or reboilers.
- The process involves:
- Gas mixture entering an absorber where a solvent absorbs the desired gas component.
- The saturated solvent is sent to a stripper to remove the absorbed component using a stripping gas, such as steam.
Stripping Cycles
-
Temperature-Swing Cycle: Uses temperature changes for regeneration; energy-intensive; suitable for low adsorbate concentrations.
- Typical capacity exceeds 1 kg of adsorbate per 100 kg of adsorbent.
- Inert-Purge Cycle: Employs a non-adsorbing gas to lower partial pressure for desorption; cycle times are short; energy-efficient but limited capacity.
- Displacement Purge Cycle: Involves a similar adsorbing gas or liquid for regeneration; maintains nearly isothermal conditions with short cycle times.
Equipment Design and Costs
- Gas-liquid separation equipment includes cyclones, knockout drums, and spray towers.
- Costs influenced by energy requirements and design considerations like baffles.
- Gas-solid separation involves cyclones, scrubbers, and bag filters; efficiencies range from 90-99%.
- Liquid-liquid separation uses decanters and hydrocyclones; costs involve coalescence promoters.
- Solid-solid separation techniques include leaching and froth flotation, influenced by particle size and energy needs.
- Solid-liquid separation equipment consists of settlers and filters; costs depend on settling characteristics and vapor pressures.
Extraction
- Extraction utilizes a solvent to isolate components based on differential solubility in immiscible phases.
- Key factors affecting extraction include:
- Solvent Selection: Critical for selectivity and distribution coefficients.
- Temperature: Influences solubility and mass transfer.
- Phase Ratio: Affects extraction efficiency based on solvent to feed phase volume.
- Contact Time and Mixing: Essential for effective mass transfer.
Liquid-Liquid Extraction Methods
- Continuous Counter-Flow Contractors: Enable efficient phase contact but require optimal conditions to lessen viscosity impacts.
- Spray Extraction Towers: Feature large axial dispersion with limited stages; low-cost but rarely utilized.
- Packed Extraction Towers: Reduce axial mixing; more efficient for fewer stages.
- Perforated-Plate Extraction Towers: Enable efficient dispersion and coalescence; specific diameter and spacing requirements enhance performance.
Applications of Extraction
- Chemical Metallurgy: Involves mining, crushing, grinding, and various metallurgical techniques such as hydrometallurgy and pyrometallurgy.
- Pharmaceuticals: Methods include maceration and Soxhlet extraction for component isolation.
Conclusion
- Understanding absorption and extraction processes are crucial for effective separation and purification in chemical engineering applications, addressing both theoretical underpinnings and practical applications.
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Description
This quiz covers the basics of absorption and stripping in separation processes, including the concept of gas absorption and the role of solvents.
