低臭気クラフト蒸解について

抄録

The problem of odorous effluent gas at kraft mill is caused by some nasty-smelling compounds, chiefly containing of hydrogen sulfide, methyl mercaptan, dimethyl sulfide, dimethyl disulfide.
The removal of odour has been commercially executed by the so-called external treatments, including burning of gas, black liquor oxidation or steam stripping of condensates etc.
The authors studied on the less odorous kraft pulping methods that could depress the amount of volatile organic sulfur compounds (VOS) formed on digestion. The results are as follows :
(1) High temperature-short time method : The cooking was performed at temperature ranging from 175 to 190°C for 3080 minutes. On cooking at 180°C, amounts of VOS formed were 45% of those of a standard KP. Properties of pulp obtained were nearly equal to those of a standard KP.
(2) Liquor exchange method : Exchange of white liquor for black liquor in cooking schedule gave a dramatic reduction of amounts of VOS. The process variables, namely low temperature- high active alkali in initial stage of cooking and high temperature- low active alkali in final stage exhibited the most reduction of amounts of VOS. The amount of VOS by this method was about 10% of that of a standard KP. Properties of pulp showed no appreciable difference from those of a standard KR
(3) Vapour phase method and H₂S-pretreatment method : These method gave about 1 and 4% higher pulp yield than a standard KP respectively. However, both methods do not give reduction of VOS-formation.