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Process for removing silica from cellulosic material

a cellulosic raw material and cellulosic technology, applied in pulp liquor regeneration, papermaking, pretreatment with alkaline reacting compounds, etc., can solve the problems of limiting the commercial use of non-wood cellulosic raw materials, and none of the prior art references discussed above disclose a simple and economical method of de-silicating cellulose raw materials, etc., to achieve simple and economical manner, simple and economical

Inactive Publication Date: 2006-10-12
WESTERN MICHIGAN UNIVERSITY +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013] It is an object of the present invention to provide a method for removing silica from a cellulosic raw material, which can be performed in a simple and economical manner.
[0014] It is a further object of the present invention to provide a method from removing silica from a non-wood cellulosic material in a simple and economical manner.
[0015] It is still a further object of the present invention to provide a method for removing silica from a non-wood cellulosic raw material selected from straw, bagasse, bamboo, reed and cornstalks in a simple and economical manner to produce a processed non-wood cellulosic material which can be used subsequently in pulp manufacture.
[0017] The present invention is concerned with the removal of silica from a cellulosic raw material, particularly, a non-wood cellulosic material which can be straw, bagasse, reed, bamboo, cornstalks, and combinations thereof. Initially, the cellulosic raw material should be cut into long pieces of approximately 10 to 30 millimeters in length and then screened. This significantly reduces the content of silica in the raw materials up to 50%. After washing, the raw materials are then moisturized and preheated by steam or hot water to help improve the kinetics of the impregnation of the cellulosic raw material with a silica leaching agent to thereby improve the efficiency of silica removal.
[0028] After the causticization step, precipitated silica-enriched calcium carbonate can be separated from the causticized impregnation liquor by any suitable type of separation process, with sedimentation and filtration techniques being preferred. Although there is no critical time, temperature and pressure conditions required for separation of the precipitated silica-enriched calcium carbonate from the causticized impregnation liquor, as is generally known, higher temperatures have a positive effect on the settling velocity in a sedimentation process and higher pressures have a positive effect on separation in filtration processes. The separated causticized impregnation liquor is considered to be silica-free and can be used as a washing liquor, dilution media or make-up media in different steps in the process.

Problems solved by technology

The greatest impediment to the use of non-wood cellulosic raw materials in commercial pulping is the ash, and more specifically silica, contained therein.
However, none of the prior art references discussed above disclose a simple and economical method of de-silicating a cellulose raw material that is to be used in the pulp manufacture.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example i

[0035] In a step of causticizing impregnation black liquor containing predominantly residual sodium carbonate and dissolved silica, 25 mL of filtered impregnation black liquor was treated in a 50 mL PE ampoule under the conditions described above. 0.0778 g of powdered calcium oxide (quick lime) was added into the sample, which contained dissolved silica at a concentration of 0.582 g / L. The amount of quick lime added was 71.2% stoichiometrically equivalent to the amount of sodium carbonate present in the sample. After the causticizing reaction, an analysis of centrifuged and clarified spent liquor was provided. 42.4% of causticizing efficiency was determined, and the concentration of dissolved silica in the liquor dropped to a level of 0.542 g / L. Thus, the amount of dissolved silica was reduced by 9.3%.

example ii

[0036] The following experiment was provided under the same conditions, except the calcium oxide (quick lime) was added at the amount of 120% stoichiometrically equivalent to the amount of sodium carbonate present in the sample. After the causticizing reaction, an analysis of centrifuged and clarified liquor was provided. 100% causticizing efficiency was determined and the concentration of dissolved silica in the liquor dropped to a level of 0.014 g / L. The treatment was effective in that the dissolved silica was reduced to 2.4% of the silica dissolved in the original impregnation black liquor. The concentration of residual dissolved silica (0.014 g / L) most probably comes from quick lime used for the causticizing steps, which contained 0.13% silica by weight. Taking that into consideration, the residual silica content may come from sources other than the raw material (wheat straw), so the desilication efficiency in this example may be considered to be 100%.

example iii

[0037] For the impregnation / desilication of wheat straw, under the same conditions as mentioned above, the impregnating liquor with a Total Titratable Alkali of 10.0 g Na2O / L was used with a ratio of Na2CO3:NaOH of 3:1 (in Na2O equivalents). The impregnating black liquor contained residual sodium carbonate at a concentration of 5.5 g Na2O / L and dissolved silica at a concentration of 0.595 g SiO2 / L. Into the sample containing dissolved silica at the concentration of 0.595 g / L, calcium oxide (quick lime) was added at the amount of 120% stoichiometrically equivalent to the amount of sodium carbonate present in the sample of impregnation black liquor (the same as in Example II). After the causticizing reaction, an analysis of centrifuged and clarified liquor was provided. 56.8% of causticizing efficiency was determined and the concentration of dissolved silica in the liquor dropped to a level of 0.249 g / L. The treatment had been effective in that the dissolved silica had been reduced to...

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Abstract

A method of cellulosic raw material desilication involves the steps of impregnating the cellulosic raw material with a solution containing sodium carbonate to form a silica-containing impregnation black liquor and an at least partially desilicated raw material, separating the silica-containing impregnation black liquor from the at least partially desilicated raw material, causticizing the separated silica-containing impregnation black liquor to precipitate silica-enriched calcium carbonate and separating the precipitated silica-enriched calcium carbonate from the causticized impregnation liquor. Up to 100% of the silica contained in the cellulosic raw material can be removed before the raw material is processed by any of conventional pumping methods.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method of removing silica from a cellulosic raw material, such as bamboo, bagasse, reed and straw, prior to the cellulosic raw material being converted into a pulp by a chemical or mechanical delignification processes. BACKGROUND OF THE INVENTION [0002] Non-wood cellulosic fibers are a percentage of the world's pulp source, representing less than 10% of the total pulp production. Non-wood pulp production primarily utilizes straw, bagasse, bamboo and reed. Agricultural by-products make up 73% of the world's non-wood pulp capacity while natural plants such as reed and bamboo account for 18% and the remainder consists mainly of industrial crops. [0003] Current trends indicate that the global consumption of paper making fibers would increase to approximately 425,000,000 tons by the year 2010. At the present time, it is not known where the estimated millions of tons of fiber needed by the year 2010 will come from. An abunda...

Claims

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Application Information

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IPC IPC(8): D21C11/00
CPCD21C5/00D21C1/06
Inventor PEKAROVIC, JANPEKAROVICOVA, ALEXANDRA
Owner WESTERN MICHIGAN UNIVERSITY
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