Coal Gasification - Environment Notes

Coal Gasification – UPSC Notes – Economy

Coal Gasification is the transformative method that converts coal and water into syngas, a mixture containing carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2), methane (CH4), and water vapour (H2O). This process involves subjecting coal to high pressure while simultaneously exposing it to oxygen and steam. The interaction of oxygen and water molecules with coal results in the oxidation process, producing syngas as the output. Understanding the intricacies of Coal Gasification is crucial for individuals preparing for the UPSC IAS exam.

Coal Gasification

  • Coal Gasification: A Key Energy Transformation Process
    • Process: Partial oxidation of coal with air, oxygen, steam, or carbon dioxide
    • Output: Fuel gas utilized for electricity generation
  • In-situ Gasification: Underground Coal Gasification (UCG)
    • Definition: Coal transformation into gas within the seam
    • Retrieval: Through wells
  • Benefits of Gasification over Direct Burning
    • Transformation: Coal carbon converted into electricity, hydrogen, and diverse energy forms
    • Method: Partial oxidation used instead of direct burning
  • Syngas Production
    • Composition: Predominantly includes methane (CH4), carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2), and water vapor (H2O)
    • Applications: Can be converted into various products like fertilizers, fuels, solvents, and synthetic materials
Coal Gasification

Coal Gasification – Process

  • Gasification Process Dynamics
    • Mechanism: Oxygen and steam (water vapor) forcefully applied to coal
    • Conditions: Heating and potential pressurization
  • Allothermal vs. Autothermal Techniques
    • Allothermal: Coal heated by external heat sources
    • Autothermal: Coal heated by exothermic chemical processes within the gasifier
  • Critical Oxidizer Control
    • Importance: Oxygen supply should be insufficient for complete fuel oxidation
  • Outcome of Oxidation
    • Result: Coal oxidized by oxygen and water molecules
    • Gaseous Mixture: Includes carbon dioxide (CO2), carbon monoxide (CO), water vapor (H2O), and molecular hydrogen (H2)

By Products of Coal Gasification

  • By products of Syngas Production
    • Inclusion: Coke, coal tar, sulphur, and ammonia
    • Utility: Valuable byproducts with various applications
  • Diverse Applications of Coal Gas
    • Usage: In the production of colours, pharmaceuticals (especially sulfa drugs), saccharin, and various chemical compounds
  • Coke’s Multifaceted Role
    • Feature: Non-smoking fuel
    • Applications: Used in manufacturing water gas and producer gas
  • Chemical Extraction from Coal Tar
    • Method: Fractional distillation
    • Output: Various chemicals including tar (used for road paving), benzole (a type of vehicle gasoline), and creosote (a phenol-based wood preservative)
  • Sulphur and Ammonia Applications
    • Sulphur: Utilized in the production of sulfuric acid
    • Ammonia: Commonly employed in the manufacture of fertilizers
  • Additional Uses of Coal Byproducts
    • Disinfectants and cresols are derived from coal tar.

Underground Coal Gasification

  • Definition of UCG
    • Description: Industrialized gasification process
    • Location: Occurs in unmined coal seams
  • Process Steps
    • Injection: Gaseous oxidizing agent, often oxygen or air
    • Transport: Product gas moved to the surface through production gas wells
  • Utilization of Gas Product
    • Purpose: Gas can serve as a chemical feedstock or an energy source
  • Economic Viability
    • Advantage: Enables harvesting of materials that would otherwise be prohibitively costly
    • Alternative: Feasible substitute for traditional coal mining methods
  • Environmental Considerations
    • Comparative Impact: Lower environmental and social effects compared to conventional coal mining with gasification
    • Concerns: Includes the risk of aquifer contamination

Significance of Coal Gasification

  • Usage in Steel Industry
    • Common Application: Utilized in the manufacturing process of steel businesses
    • Sourcing Challenge: Majority imported, leading to high costs
  • Syngas as Coking Coal Substitute
    • Alternative Source: Syngas from coal gasification facilities
    • Cost-Saving Strategy: Allows facilities to save expenses
  • Syngas Applications
    • Primary Uses: Generating energy and serving as a chemical feedstock
  • Hydrogen Production via Coal Gasification
    • Significance: Hydrogen produced can be applied in various sectors, such as ammonia production and supporting a Hydrogen Economy
  • Hydrogen Consumption Outlook in India
    • Projection: Expected increase in India’s hydrogen consumption from 6.7 million tonnes per year to 11.7 million tonnes by 2030
  • Current Users of Hydrogen
    • Dominant Sectors: Refineries and fertiliser factories, primarily from natural gas sources
    • Potential Shift: Hydrogen production through coal gasification techniques
  • Advantages of Coal Gasification
    • To be explored in subsequent discussion on Coal Gasification

Advantages

  • Addressing Local Environmental Issues
    • Impact: Helps alleviate local environmental issues
    • Recent Concerns: Significant enough to bring portions of the country to a halt
  • Leveraging Coal’s Chemical Qualities
    • Capability: Gasification makes it easier to utilize coal’s chemical qualities
  • Green Alternative to Coal Combustion
    • Perceived Benefit: Seen as a greener alternative compared to traditional coal combustion
  • Diverse Applications of Coal Gas
    • Transformation: Coal gas converted into chemical energy
    • Utilization: Used to produce iron from iron ore, as well as methanol and urea
  • Advantage of Carbon Capture and Storage
    • Capability: Allows for separation of components
    • Flexibility: Enables the selection of components to retain and discard
    • Specific Term: Known as Carbon Capture and Storage (CCS)

Disadvantages

  • CO2 Emissions Comparison
    • Finding: According to research, coal gasification emits more CO2 than a typical coal plant
    • Intensity: Exhibits a higher total carbon intensity
  • Climate Change Implications
    • Perspective: Deemed unappealing from the standpoint of climate change
  • Water Intensity of Coal Gasification
    • Characteristic: Recognized as one of the more water-intensive modes of energy generation
    • Challenge: Notable concern given the country’s existing water scarcity

Steps taken by the Government in Coal Gasification

  • Revenue Share Concession
    • Incentive: 20% revenue share concession on coal used for gasification
    • Objective: Encourage the adoption of clean fuels
  • CIL’s Expansion Plans
    • Expansion Projects: Building three additional gasification facilities (apart from Dankuni) on a BOO basis
    • Collaboration: MOU with GAIL for synthetic natural gas sales
  • Optimizing Resource Utilization
    • Goal: Harnessing the nation’s reserves for maximum utilization
    • Sustainability Objective: Moving towards sustainability in line with global norms
  • Technological Advancements
    • Impacts: Better coal recovery, operational flexibility, increased productivity, enhanced safety, and cost-effectiveness
    • Role: Technological developments play a crucial part in achieving these improvements
  • National Coal Gasification Mission
    • Establishment: Decision to set up the National Coal Gasification Mission
    • Purpose: Raise awareness among stakeholders and develop a workable roadmap with clear responsibilities

Conclusion

  • Process: Partial oxidation of coal with air, oxygen, steam, or carbon dioxide
    • Outcome: Generates a fuel gas
  • Impact: Helps relieve local environmental difficulties
    • Recent Significance: Noteworthy impact on parts of the country in recent months
  • Enabler: Gasification facilitates the utilization of coal’s chemical properties
  • Transformation: Coal gas can be converted into chemical energy
    • Applications: Used in the production of iron from iron ore, methanol, and urea

FAQs

Q: What is Coal Gasification?

A: Coal gasification is a process that involves the transformation of coal into a gaseous mixture, known as syngas, through partial oxidation. This method typically utilizes air, oxygen, steam, or carbon dioxide to produce a fuel gas that can be employed for various applications such as energy generation and chemical production.

Q: What is Underground Coal Gasification (UCG)?

A: Underground Coal Gasification (UCG) is an industrialized gasification process that occurs directly within unmined coal seams. This technique involves injecting a gaseous oxidizing agent, often oxygen or air, into the coal seams, and then extracting the resulting product gas through wells dug from the ground. UCG offers an alternative to traditional coal mining methods.

Q: What are the Disadvantages of Coal Gasification?

A: While coal gasification has several advantages, it is important to consider its drawbacks. Some disadvantages include a higher carbon intensity leading to increased CO2 emissions compared to traditional coal plants, environmental concerns related to water usage, and potential risks of aquifer contamination. Additionally, the process may face challenges in terms of economic feasibility and public acceptance due to its environmental impact.

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