Method of preventing or reducing aluminosilicate scale in a bayer process

a technology of aluminosilicate and aluminosilicate, which is applied in the direction of aluminium compounds, chemistry apparatus and processes, and the nature of treatment water, etc., can solve the problems of scale having low thermal conductivity, slow rate at which desilication products precipitate out, and high concentration of dissolved silica, so as to reduce or eliminate aluminosilicate scaling, reduce and even completely prevent the formation of aluminosilicate scal

Active Publication Date: 2005-01-13
CYTEC TECH CORP
View PDF21 Cites 66 Cited by
  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0011] The present invention solves the aforementioned problems and others by providing materials and a process whereby polymers with the pendant group or end group containing --Si(OR)3 (where R is H, an alkyl group, Na, K, or NH4) are used to reduce or eliminate aluminosilicate scaling in a Bayer process. W

Problems solved by technology

The rate at which the desilication products precipitate out, however, is slow and even when a lengthy "predesilication" step is used, concentrations of dissolved silica remain well above equilibrium values.
The scale has low thermal conductivity compared to the steel of the walls and heat transfer is severely reduced as scale builds up.
This reduced heat transfer caused by aluminosilicate scaling is sufficiently severe that the heat exchange units have to be taken out of service and cleaned frequently, as often as every one to two weeks.
The situation is however complicated by the fact that silica in the solution or liquor is not necessarily proportional to the silica in the starting bauxite.
Cleaning of the heat exchangers with acid is itself a high maintenance cost.
The acid cleaning also reduces the life of the heat exchangers, therefore adding cost due to frequent replacement of the heat exchangers.
Moreover, the reduced heat exchanger efficiency caused by scaling leads to higher demand and cost for energy in the form of steam.
The scaled pipes al

Method used

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
View more

Image

Smart Image Click on the blue labels to locate them in the text.
Viewing Examples
Smart Image
  • Method of preventing or reducing aluminosilicate scale in a bayer process
  • Method of preventing or reducing aluminosilicate scale in a bayer process
  • Method of preventing or reducing aluminosilicate scale in a bayer process

Examples

Experimental program
Comparison scheme
Effect test

examples

[0040] Test procedure

[0041] A synthetic Bayer liquor is made by adding 12 ml of a sodium silicate solution (27.7 g / l of a sodium silicate solution that is 28.9% SiO2) to 108 ml of a sodium aluminate solution that contains sodium aluminate, excess sodium hydroxide, and sodium carbonate. After mixing, the solution contains 0.8 g / l SiO2, 45 g / l Al2O3, 150 g / l NaOH, and 40 g / l Na2CO3. If a scale reducing additive is used, it is added just before the silicate is added to the aluminate solution (generally the additive is used as a solution containing 1-10% of active reagent). This solution is put into a polyethylene bottle along with a strip of pre-weighed clean mild steel (25 mm x 95 mm) and the sealed bottle is heated with agitation at 100º for 18 + 2 hours. Eight to twelve such tests (bottles) are done at one time. At the end of the 18 hours, the bottles are opened, the steel strip is thoroughly rinsed and dried, and the solution is filtered (0.45( filter). Considerable aluminosi...

example 1

[0045] A polymer with the structure

[0046] is made as follows: 42 g of a styrene-maleic anhydride (SMA) copolymer, with a mole ratio of styrene to maleic anhydride of 2.0, is dissolved in 87 g of acetone. A separate solution is made with 3.03 g of gama-aminopropyltriethoxysilane, 8.02 g of diethylamine and 21 g of acetone. The amine solution is then added to the polymer solution and allowed to react for 15 minutes at ambient temperature. One hundred eighty milliliters (180 ml) of deionized (D.I.) water is mixed with 20 ml of 28% aqueous ammonia and heated to 70º. The aqueous ammonia is then added to the polymer solution and the mixture heated to 65º to evaporate the acetone. The result is a solution containing 23.4% polymer based on the total weight of SMA polymer and the two amines. It is tested in accordance with the Test Procedure described above with the following results reported in Table B.

TABLE BScale on steel,Total sodalite formed,Dosage, mg / l% vs. blank*% vs. blank*300005...

example 2

[0048] A 25.0 g aliquot of the polymer solution from Example 1 is added to 200 ml of isopropanol to precipitate the polymer, which is washed with isopropanol and dried. The dried polymer contains 0.80% silicon. A 2% solution of the isolated polymer is made in a mixture of NaOH and aqueous ammonia. It is tested in accordance with the Test Procedure with the results reported in Table C.

TABLE CScale on steel,Total sodalite formed,Dosage, mg / l% vs. blank*% vs. blank*300005000.21000.1

*no additive

[0049]

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to view more

PUM

PropertyMeasurementUnit
Fractionaaaaaaaaaa
Fractionaaaaaaaaaa
Concentrationaaaaaaaaaa
Login to view more

Abstract

Abstract of the Disclosure
Materials and a process are provided whereby polymers with the pendant group or end group containing --Si(OR")3 (where R" is H, an alkyl group, Na, K, or NH4) are used to control aluminosilicate scaling in a Bayer process. When materials of the present invention are added to the Bayer liquor before the heat exchangers, they reduce and even completely prevent formation of aluminosilicate scale on heat exchanger walls. The present materials are effective at treatment concentrations that make them economically practical.

Description

Detailed Description of the InventionBACKGROUND OF THE INVENTION[0001] The Bayer process is almost universally used to manufacture alumina. In this process raw bauxite ore is first heated with caustic soda solution at temperatures in the range of 140 to 250º. This results in the dissolution (digestion) of most of the aluminum-bearing minerals, especially the alumina trihydrate gibbsite and alumina monohydrate boehmite, to give a supersaturated solution of sodium aluminate (pregnant liquor). Resulting concentrations of dissolved materials are very high, with sodium hydroxide concentrations being greater than 150 grams / liter and dissolved alumina being greater than 120 g / l. Any undissolved solids are then physically separated from the aluminate solution, and a polymeric flocculant is used to speed the removal of the fine solid particles. Residual suspended solids are removed by a filtration step. The filtered clear solution or liquor is cooled and seeded with alumina trihydrate...

Claims

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to view more

Application Information

Patent Timeline
no application Login to view more
IPC IPC(8): C01F7/0606C07F7/06C01F7/0633C02F5/12C23F14/02
CPCC01F7/0606C01F7/0633C02F5/10C02F5/12C23F14/02C02F2103/16C08G73/0206C08G73/0213C02F2103/023
Inventor SPITZER, DONALD P.ROTHENBERG, ALAN S.HEITNER, HOWARD I.KULA, FRANK
Owner CYTEC TECH CORP
Who we serve
  • R&D Engineer
  • R&D Manager
  • IP Professional
Why Eureka
  • Industry Leading Data Capabilities
  • Powerful AI technology
  • Patent DNA Extraction
Social media
Try Eureka
PatSnap group products

Browse by: Latest US Patents, China's latest patents, Technical Efficacy Thesaurus, Application Domain, Technology Topic.

© 2024 PatSnap. All rights reserved.Legal|Privacy policy|Modern Slavery Act Transparency Statement|Sitemap