How does the drum size in pulverized-fuel-fired boilers change as capacity and operating steam ratings increase __________________?
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Answer: B. decreases
Explanation
Pulverized-fuel-fired boilers with high steaming capacities require efficient steam-water separation mechanisms inside the drum. Advances in internal drum cyclone separators and scrubber technology allow water droplets to be separated from steam much faster. Because separation efficiency has improved dramatically, modern boilers can utilize smaller steam drum diameters for higher ratings. Steam drums house separation equipment that prevents moisture carryover into superheaters and high-pressure steam turbines. Larger steaming capacities historically required massive drums to provide adequate gravity settling space for moisture droplets. Modern high-pressure boilers use centrifugal cyclone scrubbers that generate high gravitational forces, shrinking required drum volumes.
Option A of increases would lead to unnecessarily heavy, expensive, and thermally sluggish pressure vessel designs. Option C of remaining unchanged ignores significant engineering advancements in high-velocity centrifugal steam separation technology. Option D and E introduce unnecessary complexity, whereas the reduction in drum size is a direct result of improved cyclone separation.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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