Subtopic: Bio-fuels and their use in farm mechanization
Question Statement:
In commercial biogas purification units for bottling bio-CNG (compressed biomethane) for farm tractor fuel, pressurized water scrubbing is widely used primarily because:
Options:
(A) Carbon dioxide is significantly more soluble in pressurized water than methane
(B) Water chemically reacts with methane to form methanol
(C) Nitrogen is completely liquefied by water at room temperature
(D) Water increases the percentage of carbon monoxide in the gas
Answer Key:
A
Step-by-Step Solution & Explanation
- **Water Scrubbing Principle:**
- At $20^\circ\text{C}$ and $8\text{--}10\text{ bar}$ pressure, the solubility of $\text{CO}_2$ in water is roughly $25\text{--}30$ times higher than that of methane ($\text{CH}_4$).
- By passing pressurized raw biogas counter-currently through a packed water absorption column, $\text{CO}_2$ and $\text{H}_2\text{S}$ dissolve preferentially into the water, upgrading methane purity from $\approx 60\%$ to over $97\%$.