Natural Resources, Manufacturing & Environmental Management
Item 11: Natural Resources and Manufacturing
Natural Resources
Water, air, minerals, rocks, oil, natural gas, timber, and agricultural products are examples of natural resources.
Manufacturing
Key processes involve acids and bases under specific conditions (durable, accessible, abundant).
Classification of Resources
Resources are classified based on their durability:
- Inexhaustible: Air (separation of components by distillation, nitrate combination, electrical discharges, ozone), Water (desalination, potable water recovery, mineral sales)
- Non-renewable: Oil (fractional distillation: petrol/gasoline, kerosene/gasoil, asphalt/fuel oil), Natural gas (mixture of hydrocarbons, synthesis gas), Minerals
- Renewable: Resources of plant or animal origin. Examples include bauxite, corundum, aluminum, pyrite, magnetite, hematite (iron), sodium silicate, and albite.
Carbon
Carbon is formed from organic, slowly decomposing plant matter buried at high pressure and temperature.
- Types: Peat (low energy), Lignite (high percentage of volatiles), Coal (used for steel coke), Anthracite (lighter, high carbon content)
- Applications: Obtaining carbon monoxide, synthesis gas, or producer gas.
Sources of Energy
- Non-renewable: Fossil fuels (coal, oil, natural gas) produce high heat upon burning, releasing substantial energy. However, they generate significant carbon emissions and solid waste, contributing to pollution.
- Renewable: Alternative energy sources offer clean energy options, often derived directly or indirectly from solar energy. Examples include wind, solar, marine, biomass, and fuel cell/battery technologies.
Electrical energy is generated from hydroelectric or thermal power stations (coal combustion).
Environmental Issues
Key environmental concerns include the greenhouse effect, acid rain, ozone depletion, air and water pollution, soil contamination, and climate change.
Gaseous Effluent Treatment
Two main approaches exist:
- Transforming contaminants into safer forms.
- Removing contaminants from the gas stream.
Composting
Composting is a natural process that reduces the volume, weight, and reactivity of biodegradable waste, resulting in a stable and sanitized organic fraction called compost.
Compostable materials include the organic fraction of municipal solid waste, pruning and mowing debris, sewage sludge, agricultural and agro-industrial waste, forestry residues, and livestock waste.
Item 12: Chemical Properties and Unit Operations
Chemical processes involve properties like concentration, density, temperature, and velocity.
Operating Regime
- Steady State: Properties do not change over time.
- Unsteady State: Properties vary with time.
Modes of Operation
Continuous Regime: Input and output flows are continuous without interruption.
Advantages: Economies of scale, easy recovery, reduced manual labor, elimination of loading/unloading time, and greater product uniformity.
Flow and Contact Models
- Continuous parallel flow with differential contact.
- Continuous counter-current flow with differential contact.
- Continuous cross-flow with differential or intermittent contact.
Unit Operations
- Pumping, grinding, sieving (particle size separation), heat exchange, compression.
- Chemical reactions: Electrochemical processes, combustion, depolymerization, precipitation.
- Separation operations: Distillation, absorption, evaporation, extraction, adsorption.
Basic Operations
Mass Transfer
- Absorption (separating gas mixture components by dissolving them in a liquid)
- Adsorption (separating liquid or gas mixture components using a solid adsorbent)
- Reverse osmosis (separating/concentrating electrolytes by applying pressure)
- Distillation/rectification (separating liquids by partial vaporization and condensation)
- Liquid-liquid extraction (separating a component from a liquid mixture using another liquid)
- Solid-liquid extraction (separating a component from a solid using a liquid)
- Ion exchange (chemical reactions between ions in a solvent and a solid resin)
CDM Controlled Transport
- Agitation and mixing, pumping, filtration, flotation (three-phase separation, removing metals from aqueous streams), sedimentation (solids settling).
Mass and Heat Transfer
- Lyophilization (freeze-drying by sublimation under vacuum)
- Humidification (contacting a pure gas with a liquid in which it is insoluble)
Phase Criteria
- Single-phase operations: Screening, milling, pumping, agitation.
- Two-phase operations: Absorption, adsorption, evaporation (heat transfer controlled), filtration, sedimentation, flotation, liquid-liquid extraction.
- Three-phase operations.
Item 13: Material Balance
Material balance can be analyzed at two levels:
- Macroscopic: Determining measured values of velocity, temperature, or concentration using non-differential equations.
- Microscopic: Calculating point values of velocity, temperature, or concentration using differential equations.
Material Balance Equation
(Input per unit time) – (Output per unit time) + (Generation per unit time) = (Accumulation per unit time)
- Batch process: Input = Output = 0
- Steady state: Accumulation = 0
- Unsteady state: Accumulation ≠ 0
- No chemical reaction: Generation = 0
- Chemical reaction: Generation ≠ 0