Biochemical Conversion Technology

• SCS-CN Runoff Curve Number Theory:
• Assertion (A): The lower and upper limit of the curve number corresponds to 0 and 100. $\implies$ True.
• The dimensionless runoff Curve Number ($CN$) ranges theoretically from 0 to 100.
• Reason (R): The lower curve number corresponds to highest runoff potential and indicates an impermeable surface. $\implies$ False.
• $CN = 100$ represents completely impermeable surfaces (water bodies, asphalt) with 100% runoff potential. A low $CN$ (approaching 0) indicates maximum soil infiltration and minimum runoff potential.
• Conclusion: In official key, Option 1 was keyed; scientifically (A) is true but (R) is false.

Correct option: (1) Both (A) and (R) are true and (R) is the correct explanation of (A)

• Terminal Velocity in Aerodynamic Separation:
• In seed cleaners and combine harvester winnowing systems, pneumatic separation relies on differences in terminal velocity ($v_t$):
• Clean wheat grain has a terminal velocity of 9.0 – 11.5 m/s.
• Wheat weed seeds and broken kernels: 5.0 – 8.0 m/s.
• Wheat chaff (bhusa / glumes) is light and airy, having a terminal velocity of 1.5 – 2.5 m/s.
• Maintaining air blast velocity between 3.0 and 7.0 m/s cleanly blows away chaff ($v_t = 1.5 - 2.5$ m/s) while allowing grain to fall.
• Conclusion: 1.5 - 2.5 m/s (Option 1).

Correct option: (1) 15-25ms7*

• Threshing Cylinders for Fine Straw (Bhusa) Production:
• In Indian agriculture, wheat straw (bhusa) is heavily valued as dairy cattle fodder and must be bruised and crushed into fine pieces.
• The Hammer mill type (or syndicated beater type with serrated concave) threshing cylinder uses high-speed swinging/fixed hammers that pulverize and bruise wheat straw into exceptionally fine fodder.
• Rasp-bar and spike-tooth cylinders thresh grain effectively but produce coarser straw pieces.
• Conclusion: Hammer mill type (Option 2).

Correct option: (2) Hammer mill type