| 摘要 |
<p>A cyclic process for pulping wood chips comprises treating the wood with an ammoniasulphur dioxide cooking liquor, separating the waste liquor, treating the liquor with an acidneutralizing agent, suitably calcium oxide, to obtain a pH of at least 7.5, separating the precipitate (A), if any, which forms, and heating the neutralized liquor at a temperature above 150 DEG C., preferably 235-300 DEG C., at a pressure of more than 200 p.s.i., which may be the autogenous pressure of the reaction mixture, in the presence of at least sufficient oxygen, suitably as air, to convert all the carbon present to carbon dioxide and all the hydrogen to water. The condensable and non-condensable portions are separated, for example, in a flash chamber, and the ammonia from the non-condensable portion is separated from other gases, preferably by absorption in water. The condensable portion is treated with sufficient alkaline earth hydroxide, desirably calcium hydroxide, to liberate any more bound ammonia, which is then combined with the ammonia previously liberated, and the precipitate (B) of alkaline-earth sulphate is separated. This precipitate (B) may be mixed with the previous precipitate (A) referred to above, and the mixture kilned at about 1530 DEG C. to yield sulphur dioxide and alkaline earth oxide. This sulphur dioxide may be mixed with the recovered ammonia and the resulting liquor re-used in the digestion process. The alkaline earth oxide is also reused.</p> |
