India’s largest-capacity nitrogenous fertilizer ammonia plants (about 2,700 tons NH3 per day each) are located at which pair of sites?

Introduction / Context:
Ammonia capacity is a key metric for the fertilizer sector, influencing urea production and national nutrient availability. Knowledge of major sites and operators is frequently tested in chemical technology examinations in India.

Given Data / Assumptions:

• Question references large single-train capacities around 2,700 tons NH3 per day.
• Operators include public-sector and cooperative majors such as RCF (Rashtriya Chemicals & Fertilizers) and IFFCO (Indian Farmers Fertiliser Cooperative).
• Site pairs in options correspond to well-known fertilizer hubs.

Concept / Approach:
The pair of locations that match the cited capacity class and operator identity is Thal-Vaishet (RCF) in Maharashtra and Hazira (IFFCO) in Gujarat. These complexes are prominent for large-scale ammonia-urea operations and have historically belonged to the top capacity bracket in India.

Step-by-Step Solution:
Identify operator and geography in each option.Match with known mega-capabilities: RCF Thal-Vaishet and IFFCO Hazira meet the ~2,700 t/d specification.Exclude others that either have different capacities or are associated with different corporate entities or older capacities.Select the pair Thal-Vaishet and Hazira.

Verification / Alternative check:
Industry reports and plant profiles place these locations among the largest ammonia producers by single-train capacity in India, supporting the selection.

Why Other Options Are Wrong:
Talcher/Ramagundam and Korba/Talcher as FCI options do not correspond to the cited largest single-train capacity category.Haldia/Namrup under HFC represent different capacity and corporate contexts, not the named largest installations.

Common Pitfalls:
Mixing up corporate acronyms (RCF, IFFCO, FCI, HFC) or assuming all legacy sites share the same modern capacities.

Final Answer:
Thal-Vaishet (RCF, Maharashtra) and Hazira (IFFCO, Gujarat)