“kraft process”的概念、定义、翻译、参考文献-科学参考

kraft process

Chemical Engineering

A process used for the conversion of wood into wood pulp that was invented by Carl Dahl in 1879. The process is also known as the sulfate process and consists of cooking wood in a basic solution of sodium hydroxide, sodium sulphide, and sodium carbonate. The process involves the hydrolysis of lignin to acids and alcohols. Both sodium hydroxide and sodium hydrosulphide (NaSH) are formed by the reaction:
$N a_{2} S + H_{2} O \to N a O H + N a S H$

which are active in breaking down the bonds between the lignin and cellulose. The pulping takes place in a continuous digester. Spent cooking liquor known as black liquor contains all the chemicals used in the digestion, and is recovered and concentrated by multiple effect evaporation before being burnt in a recovery furnace. A fused salt melt known as green liquor is collected at the bottom, which is treated with burned lime to convert sodium carbonate to sodium hydroxide:
$\begin{array}{l} C a O + H_{2} O \to C a {(O H)}_{2} \\ N a_{2} C O_{3} \to C a {(O H)}_{2} \to C a C O_{3} + 2 N a O H \end{array}$

The calcium carbonate precipitate is removed by filtration. Calcination is then used to produce calcium oxide in a lime kiln:
$C a C O_{3} \to C a O + C O_{2}$

After treatment with calcium oxide the filtrate serves as fresh cooking liquid for the digester. With the small loss of sodium salts in the digestion process, sodium sulphate is added to the recovery furnace as the make-up chemical, hence the alternative name for the process:
$N a_{2} S O_{4} + 2 C \to N a_{2} S + 2 C O_{2}$

单词	kraft process
释义	kraft process Chemical Engineering A process used for the conversion of wood into wood pulp that was invented by Carl Dahl in 1879. The process is also known as the sulfate process and consists of cooking wood in a basic solution of sodium hydroxide, sodium sulphide, and sodium carbonate. The process involves the hydrolysis of lignin to acids and alcohols. Both sodium hydroxide and sodium hydrosulphide (NaSH) are formed by the reaction: $N a_{2} S + H_{2} O \to N a O H + N a S H$ which are active in breaking down the bonds between the lignin and cellulose. The pulping takes place in a continuous digester. Spent cooking liquor known as black liquor contains all the chemicals used in the digestion, and is recovered and concentrated by multiple effect evaporation before being burnt in a recovery furnace. A fused salt melt known as green liquor is collected at the bottom, which is treated with burned lime to convert sodium carbonate to sodium hydroxide: $\begin{array}{l} C a O + H_{2} O \to C a {(O H)}_{2} \\ N a_{2} C O_{3} \to C a {(O H)}_{2} \to C a C O_{3} + 2 N a O H \end{array}$ The calcium carbonate precipitate is removed by filtration. Calcination is then used to produce calcium oxide in a lime kiln: $C a C O_{3} \to C a O + C O_{2}$ After treatment with calcium oxide the filtrate serves as fresh cooking liquid for the digester. With the small loss of sodium salts in the digestion process, sodium sulphate is added to the recovery furnace as the make-up chemical, hence the alternative name for the process: $N a_{2} S O_{4} + 2 C \to N a_{2} S + 2 C O_{2}$
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