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Production of calcium carbonate from waste sludge

A technology of calcium carbonate and sludge, applied in the direction of calcium carbonate/strontium/barium, combustion methods, chemical instruments and methods, etc., can solve problems such as not giving product quality, and achieve excellent rheological effects

Inactive Publication Date: 2013-06-12
CASSIE TECH SYNTHETIC MINERALS LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

It has been disclosed that calcium-rich aqueous solutions can be treated with carbon dioxide to produce calcium carbonate, but no detailed product quality is given

Method used

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  • Production of calcium carbonate from waste sludge
  • Production of calcium carbonate from waste sludge
  • Production of calcium carbonate from waste sludge

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0126] This example demonstrates how temperature and time affect the composition of the ash obtained from paper sludge in terms of the amount of freely available calcium oxide present in the sludge.

[0127] For paper sludge using deinked fibers from a German paper mill, 50 g of the sample was burned in an experimental electric furnace at temperatures of 700 °C, 800 °C, 900 °C and 1000 °C for different times. In order to reduce material layer thickness and increase heat flow, small samples are evenly distributed over large trays.

[0128] The effect of these combustion conditions on the amount of freely available calcium oxide in the PSA was determined by adding 8.799 g of ash to 250 g of an aqueous solution containing 25% sorbitol. The mixture was then stirred in a 1 L laboratory beaker for 30 minutes, and insolubles were removed by filtration using a Buchner funnel. The remaining clear filtrate was titrated with 0.1 M hydrochloric acid to determine the concentration of calc...

Embodiment 2

[0136] 150 g of deinked sludge from Aylesford Newsprint were heated under atmospheric conditions in a laboratory furnace. The initial heating was at 600°C for 15 minutes to dry and burn the organic components of the sludge. This is followed by a second heating stage at 800° C. for 2 hours to ensure that all calcium carbonate contained in the sludge is decomposed into calcium oxide. The resulting ash was then cooled and then ground in a Janke & Kunkel mill for 1 minute.

[0137] XRD analysis of this PSA confirmed that all calcium carbonate was decomposed and no glassy complex silicate was formed. PSA has the following composition:

[0138] 0% calcium carbonate

[0139] 60% lime (CaO&Ca(OH) 2 )*

[0140] 1% Quartz

[0141] 39% amorphous metakaolin

[0142] *Some hydration reactions occur when the hot ash cools in the humid atmosphere.

[0143]30 g of the ground powder were added directly to 505 g of an aqueous solution containing 25% by weight sorbitol.

[0144] The mix...

Embodiment 3

[0156] Embodiment 3 (comparative)

[0157] Paper sludge (PSA) from Ayersford Newsprint was characterized as having a brightness of 68% (R457) and a very wide range of particle sizes between 1-200 microns. This PSA has an approximate composition as determined by XRD.

[0158]

[0159] The equivalents of CaO (expressed as mass percent of ash) provided by each of the above components is illustrated in Table 2 below.

[0160] Table 2

[0161] components Equivalent of CaO (%) Lime (expressed as CaO) 23.4 Ca(OH) 2 1.6 calcium carbonate 9.7 Calceolite 3.6 Alpha wollastonite 10.8 calcium aluminate 1.3 quartz - Metakaolin -

[0162] Thus, an ash comprising 50.4% by weight equivalent of lime relative to 100 g of ash represents 90 g of calcium carbonate in the initial sludge (i.e. (50.4 / 56*100, where 56 is the molecular weight of calcium oxide and 100 is the molecular weight of calcium carbonate). molecular weight). ...

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Abstract

A method of producing calcium carbonate from a waste sludge containing calcium carbonate and at least one silicate mineral. The method comprises the steps of: (i) incinerating the sludge to an ash in which at least 60 % of the calcium carbonate present in the sludge is converted to free calcium oxide which is unreacted with the silicate mineral(s), (ii) optionally slaking the ash to convert at least a portion of the free calcium oxide therein to calcium hydroxide, (iii) treating either the ash from step (i) or the slaked ash from step (ii) with an aqueous solution of a polyhydroxy compound to provide a solution of dissolved calcium hydroxide, (iv) separating insoluble material from the solution of calcium ions obtained in step (iii), (v) dispersing carbon dioxide through the solution obtained from step (iv) so as to produce calcium carbonate, and (vi); separating the calcium carbonate produced in step (v). The silicate mineral may be kaolin. The invention allows the production of metakaolin substantially devoid of free lime as an additional product stream.

Description

Background technique [0001] In the most general sense, the present invention relates to the preparation and / or recovery of industrially useful products from sludge comprising calcium carbonate and at least one silicate mineral (eg kaolin). More specifically, the present invention relates to the production and / or recovery of industrially useful products from ash produced by incineration of sludge. In one aspect, the invention relates to the production of calcium carbonate from sludge by converting it to ash. In another aspect, the present invention recovers silicate minerals from relatively lime-free ash. [0002] The present invention relates in particular (but not exclusively) to a method for the preparation and / or recovery of useful substances from sludge produced in paper mills, more particularly by paper mills using recycled paper as raw material, which involves Ash is prepared from sludge as an "intermediate". The primary concern of calcium carbonate prepared from such...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01F11/02C01F11/06C01F11/18F23G5/00
CPCC01F11/02C01F11/06C01F11/18C01F11/181C01F11/183C01P2004/52C01P2004/62C01P2006/64F23G7/001
Inventor R·P·希格斯
Owner CASSIE TECH SYNTHETIC MINERALS LTD
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