Coal gasification — key advantage of the Lurgi gasifier Which of the following describes a major advantage of the Lurgi fixed-bed (dry-ash) coal gasifier in industrial service?

Introduction / Context:
The Lurgi gasifier is a pressurized, moving-bed (fixed-bed) unit widely used for producing synthesis gas and town gas. Understanding its strengths and limitations guides gasifier selection for feed type, scale, and downstream use.

Given Data / Assumptions:

• Configuration: pressurized moving-bed with dry-ash removal.
• Feeds: best with non- or weakly-caking coals; strongly coking coals can cause channeling or agglomeration.
• Operating traits: low particulate carryover, methane-rich gas at higher pressure, robust scale.

Concept / Approach:
Lurgi units are valued for large-scale, continuous operation with high reliability. Their design favors low entrainment compared with entrained-flow systems, and carbon conversion is generally good given residence times. However, they are not ideal for strongly caking coals unless special measures are used.

Step-by-Step Solution:
Compare options to known traits.Throughput/scale: a recognized advantage → option (d) matches.Coking coal tolerance: limited in standard Lurgi → option (a) false.Carbon conversion: not “only low” → option (b) false.Entrainment: moving-bed has relatively low fines carryover → option (c) false.

Verification / Alternative check:
Published performance data: Lurgi’s pressurized operation and bed configuration enable large plant capacities with manageable particulate load in raw gas.

Why Other Options Are Wrong:

• (a) Overstates feed flexibility; caking is problematic.
• (b) Mischaracterizes performance; conversions are acceptable for the type.
• (c) Opposite of reality; entrained-flow systems show higher fines in raw gas.

Common Pitfalls:

• Confusing Lurgi with entrained-flow gasifiers (opposite solids behavior).
• Ignoring coal caking behavior in gasifier selection.

Final Answer:
It can process large quantities of coal at high throughput