Question

Comparing sulphate process with sulphite process it is found that

• A. Both temperature and pressure in the former is less than that in the later
• B. Both temperature and pressure in the former is more than that in the later
• C. Temperature is more in the former whereas pressure is more in the later
• D. Pressure is more in the former whereas temperature is less in the later

Hint:

The Kraft (sulphate) process requires aggressive chemical environments and higher cooking conditions (higher $T$ and $P$) to handle all types of wood fibers and produce exceptionally high-strength paper products.

Answer 1

The Correct Option is B

Concept: In the chemical pulp manufacturing industry, wood chips are converted into paper pulp by chemically dissolving the binding lignin matrix. The two predominant industrial chemical methodologies are:
• Sulphate (Kraft) Process: An alkaline digestion method utilizing an active cooking liquor blend of sodium hydroxide ($\text{NaOH}$) and sodium sulphide ($\text{Na}_2\text{S}$).
• Sulphite Process: An acidic or neutral digestion method using sulfurous acid ($\text{H}_2\text{SO}_3$) combined with bisulphite salts (e.g., $\text{Ca(HSO}_3)_2$).

Step 1: Comparing process operating parameters.

• Sulphate (Kraft) Process Conditions: Operates at elevated digital intensities to successfully break down tough, resinous woods. Typical cooking temperatures range from $160^\circ\text{C}$ to $180^\circ\text{C}$ and pressures reach $700\text{ kPa}$ to $1000\text{ kPa}$.
• Sulphite Process Conditions: Operates under relatively milder thermo-mechanical cooking regimes. Typical temperatures range from $125^\circ\text{C}$ to $145^\circ\text{C}$ with pressures averaging around $300\text{ kPa}$ to $600\text{ kPa}$. Therefore, both operating temperature and operating pressure in the sulphate process (the former) are greater than those in the sulphite process (the latter). This matches option (2).