From an economic standpoint in modern fertilizer complexes, what is the approximate optimum single-train size for an ammonia plant (in tons NH3 per day)?

Introduction / Context:
Plant “optimum size” balances economies of scale with capital intensity, reliability, and market/logistics constraints. Historically, single-train ammonia units scaled from a few hundred to over a thousand tons per day as technology improved and global demand rose.

Given Data / Assumptions:

• “Optimum” refers to a commonly cited economic sweet spot in classical exam literature.
• Comparative options span 10, 100, and 1000 t/d, representing small pilot, mid, and large commercial scales.
• We ignore cutting-edge mega-trains and focus on standard textbook benchmarks.

Concept / Approach:
Economies of scale favor larger trains up to a point, beyond which risks, logistics, and capital costs temper benefits. Traditional chemical technology texts cite about 1000 t/d as the representative optimum size for an ammonia plant, reflecting a balance of compressor size, loop equipment, and downstream urea integration at the time of reference.

Step-by-Step Solution:
Review capacity ranges used in industry and textbooks.Recognize diminishing returns in scale-up costs beyond around 1000 t/d in classical analyses.Match to provided choices: 1000 t/d fits the cited optimum.Select 1000.

Verification / Alternative check:
While modern mega-plants can exceed 2000 t/d per train, exam problems traditionally anchor “optimum” at 1000 t/d. The answer reflects that conventional teaching benchmark.

Why Other Options Are Wrong:
10 and 100 t/d are too small to capture economies of scale for world-scale ammonia.“1000C” is not a valid capacity figure; appears to be a typographical decoy.

Common Pitfalls:
Applying current mega-train capacities to legacy “optimum size” questions without noting the exam’s conventional context.

Final Answer:
1000