(3) Wet cracking method
The recovery of black liquor from rice straw pulp by wet cracking method is a new technology in China. the black liquor was wet cracked at about 20 MPa,360 c for 15~30 min,. the organic matter in the black liquor was converted into gas, tar, carbon powder and organic acid, and sodium silicate was converted into Si2 precipitation at high CO2 partial pressure. Then the cracking product is separated by sedimentation method under normal pressure, and the separated liquid can be causticized to recover alkali.
(4) SCA- comparison
The basic principle of this method is similar to that of air oxidation method. The black liquid concentrated to 50~60% was separated by instant heat in the thermal decomposition furnace under the condition of insufficient oxygen. The decomposition product was Na2CO3、H2S、C.
(5) Integrated Black Liquid Utilization
Recovery of sulfate turpentine, preparation of humic acid ammonia with black liquor, recovery of tarot oil, preparation of dimethyl alum with black liquor, etc. In addition, lignin can be recovered to produce alcohol and yeast.
2. Pulping Machine Waste Water Recycling
The waste water discharged by pulp beating machine contains the same composition as black liquid, but the concentration is low. Due to the small amount of organic substances (fibers and bases, etc.) contained, it is difficult to recover, but the total solids, suspended matter and BOD5 in the wastewater are still very high, and the direct discharge is still very serious for water pollution, so it needs to be treated. and the main treatment methods include coagulation sedimentation, air floatation, activated sludge, stabilization pond, biofilter and A/O.
3. Paper Machine Wastewater Recycling
The waste water discharged from the paper machine contains a large amount of fiber, if it is not recycled, it will cause a great waste. Therefore, the waste water of the paper machine must be fully recovered and reused. These water parts can be used to dilute pulp (such as white water discharged by case Kun), partly to be used in beating engineering (water absorption tank and waste water pressed by Fu Kun), and waste water that can not be used in beating engineering should be sent to the recovery device for feed recovery.
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