Process for treating hardwood black liquor and hardwood black liquor treated according to the process
A hardwood and black liquor technology, applied in fiber raw material treatment, pulping liquid regeneration, concentrated waste liquid, etc., can solve the problems of not reducing the amount of fouling, increasing fouling of evaporation devices, etc.
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[0035] 1. A method of treating hardwood black liquor from hardwood pulp manufacture to precipitate calcium ions present in said liquor, wherein said method comprises the steps of:
[0036] - supply of hardwood black liquor from hardwood pulp manufacture,
[0037] - treating at least a part of said liquor at a temperature higher than 160°C, wherein said calcium compounds present in the black liquor, such as calcium carbonate, will precipitate.
[0038] 2. The method of item 1, wherein the hardwood is eucalyptus, poplar, poplar, acacia or birch or a combination thereof.
[0039] 3. The method of any one of the preceding, wherein the temperature during said treatment is 160-190°C, preferably 165-185°C, most preferably 170-180°C.
[0040] 4. The method of any of the preceding, wherein the treatment lasts less than about 2 hours, preferably less than 60 minutes, most preferably less than 40 minutes, especially preferably 5-30 minutes.
[0041] 5. The method of any preceding item,...
Embodiment 1
[0048] Black liquor from the eucalyptus kraft cooking process was evaporated to 34.5% dry solids and treated at temperatures of 140°C, 170°C and 180°C for 30 minutes.
[0049] Table 1 below shows the results of measurements of soluble calcium in black liquor after heat treatment according to the invention.
[0050] Calcium content was measured by inductively coupled plasma optical emission spectrometry (ICP-AES).
[0051] Table 1 : Comparison of soluble calcium in untreated black liquor as reference and black liquor treated at different temperatures for 30 minutes.
[0052]
[0053]
[0054] It can be seen from Table 1 that the amount of soluble calcium decreased significantly after treatment at 180°C for 30 minutes. It can also be seen from Table 1 that the amount of soluble calcium was not affected after treatment at 140°C for 30 minutes, and that treatment at 170°C was able to reduce the amount of soluble calcium.
Embodiment 2
[0056] Black liquor from the eucalyptus kraft cooking process was evaporated to 34.5% dry solids and treated at 180°C for 5, 10, 20 and 30 minutes.
[0057] Table 2 below shows the results of measurements of soluble calcium in black liquor after heat treatment according to the invention.
[0058] Calcium content was measured by inductively coupled plasma optical emission spectrometry (ICP-AES).
[0059] Table 2: Comparison of soluble calcium in untreated black liquor as reference and black liquor treated at 180°C for different times.
[0060]
[0061] It can be seen from Table 2 that the amount of soluble calcium decreased after treatment at 180 °C. The effective treatment time leveled off after 20 minutes, ie, there was no need to treat this eucalyptus black liquor for more than 20 minutes.
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