CN103274419A

CN103274419A - Removal method of amorphous silicon dioxide in high-aluminum fly ash

Info

Publication number: CN103274419A
Application number: CN2013102189634A
Authority: CN
Inventors: 谭蔚; 朱国瑞; 刘丽艳; 刘颖
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2013-06-04
Filing date: 2013-06-04
Publication date: 2013-09-04

Abstract

The invention relates to a removal method of amorphous silicon dioxide in high-aluminum fly ash. The method comprises the following steps of: adding the high-aluminum fly ash into circulating mother liquor according to the mass ratio of 1:3, wherein the NaOH concentration in the circulating mother liquor is 110-140g/L and the current reaction temperature is 40-50 DEG C; stirring with the speed of 300-350r/min, and reacting for 20-24 hours, wherein the reaction is considered as the pretreatment for a desilicication reaction; then, increasing the temperature to 90-95 DEG C, and ending after reacting for 4 hours. According to the method, the SiO2 content in the desilicication liquid is increased from 80g/L to about 140g/L; the ratio of aluminum to silicon in the desilicication fly ash is increased to about 2.00 from 1.83; the amorphous SiO2 with relatively higher activity in the high-aluminum fly ash is fully extracted for further generating a secondary product with higher value in use, the yield of the secondary product, namely, silico-calcium residue in the follow-up aluminum oxide extraction process is reduced effectively, moreover, most of the reaction heat comes from the residual heat of the circulating mother liquor, and the aim of saving energy is realized.

Description

The removal methods of amorphous silicon di-oxide in the aluminous fly-ash

Technical field

The present invention relates to the aluminous fly-ash production technical field, particularly relate to non-crystalline state SiO in the aluminous fly-ash ₂Removal methods.

Background technology

Aluminous fly-ash is a kind of new flyash type that occurs along with the construction of the exploitation of the western coal resources of China and large-size thermal power plant in the last few years, its Al ₂O ₃Content can reach about 50% usually.Along with the worsening shortages of bauxite resource, utilize aluminous fly-ash to produce aluminum oxide and more and more be subject to people's attention.Can know that by test aluminous fly-ash mainly is made up of mullite, corundum and amorphous carbon/silicon dioxide, wherein the content of amorphous silicon di-oxide has reached more than 25%.The solution of the technological line success of current employing the problem of abundant extraction silico-calcium salt and aluminum oxide.At first deviate from the flyash glassy phase with further raising flyash Al/Si ratio with NaOH solution, desiliconization liquid adds milk of lime and is used for preparing active silicic acid calcium and reclaims NaOH.Flyash after the desiliconization can adopt soda-lime sintering process to prepare aluminum oxide, can be used to produce cement clinker after the last residue silico-calcium slag dealkalize.

The first step at the processing aluminous fly-ash is that this part amorphous silicon di-oxide is removed by the constant pressure hydro-thermal method, its primitive reaction condition is, under the normal pressure in the circulating mother liquor NaOH concentration be 110～140g/L, circulating mother liquor and flyash mass ratio are 3:1, temperature of reaction is 95 ℃.In this production technique, through SiO in the desiliconization liquid that obtains behind the desilication reaction ₂Content be 80g/L, SiO in the aluminous fly-ash ₂Content drops to about 25% SiO from 40% ₂Extraction yield is about 37.5%; Al ₂O ₃Content drops to about 47% Na from 50% ₂O content is about 12%.Alumina silica ratio is increased to about 1.80 from about 1.28.Find in reaction process, to have formed a large amount of hydroxysodalite (Na by test ₈Al ₆Si ₅O ₂₄(CO ₃) _0.5(OH) _XH ₂O), cause part silicon not enter in the middle of the liquid phase by effective elimination, and then had influence on desiliconization effect.

Forefathers adopt the constant pressure hydro-thermal method to handle to flyash a lot of researchs, and for example all there are direct influence grey alkali ratio, temperature, time etc. to side reaction, but wherein temperature effect is particularly important.Kesraoul etc. discover and generate zeolite (zeolite) and sodalite (hydroxyl sodalite) at low temperatures that high temperature easily generates cancrinite (cancrinite).Find in flyash synthetic zeolite forming process: the crystallisation process of flyash synthetic zeolite mainly is to occur in to be partly dissolved or undissolved fly ash grain remains surface, and the crystal of generation has hindered OH ^-With contacting of flyash inside, thereby make the further dissolving of flyash stop gradually.Therefore have only the Si and the Al that have dissolved could participate in synthesizing of zeolite, and the situation of dissolving Si and Al depend on that the condition of reaction and resultant are in the coating situation of particle surface.

This paper is intended to utilize before the pre-desilication reaction flyash with the residence time of circulating mother liquor in make-up tank and allocates temperature as research object, the desilication method of studying refers to and removes amorphous carbon/silicon dioxide in the aluminous fly-ash, observe temperature and time simultaneously to the influence of pre-desiliconization effect, and then optimize pre-desilication process, effectively utilized the surplus heat in the circulating mother liquor simultaneously.

Summary of the invention

Technical problem to be solved by this invention is the removal methods of amorphous silicon di-oxide in the aluminous fly-ash that proposes at existing technical background, he to the effect that handles this part at desiliconization in the aluminous fly-ash Production Flow Chart, aluminous fly-ash is improved through the desiliconization effect after the pre-desiliconization, compare SiO in the desiliconization liquid with former desiliconization effect ₂Content is increased to about 140g/L from 80g/L.Alumina silica ratio is increased to about 2.00 from 1.80 in the desiliconization flyash.

The invention solves the technical scheme that above-mentioned technical problem adopts is:

Aluminous fly-ash is put into circulating mother liquor, and mass ratio is 1:3, and NaOH concentration is 110～140g/L in the circulating mother liquor, this moment, temperature of reaction was 40～50 ℃, and accompany by 300～350r/min stirring, and the reaction times is 20～24h, this section reaction is as the pre-treatment of desilication reaction.Improve temperature to 90～95 ℃ then, finish behind the reaction 4h.

Compared with prior art, the present invention studies optimizing desiliconization effect from reaction mechanism.Only consider always in the former study that single temperature is to the influence of desiliconization effect, as producing a large amount of hydroxysodalites more than 95 ℃, contain a certain amount of element silicon in the hydroxysodalite, cause this part element silicon can not be dissolved in the liquid phase, reduced derailing efficient.And the reaction times that desiliconization effect is not obvious and needs are long under the lesser temps, so forefathers never consider under study for action.

The break the normal procedure thinking of single reaction temperature of this paper, add pre-treatment before in pyroreaction (90～95 ℃), seek optimum low temperature (20～65 ℃) temperature of reaction, the aluminium element silicon that fly ash grain remains surface is comparatively active dissolves in advance, and then the generation of novel substance when hindering pyroreaction, promote amorphous SiO ₂Be dissolved in the liquid phase.Adopting cryogenic temperature when the flyash of this paper carries out desiliconization is 20 ℃, 35 ℃, and 45 ℃, 55 ℃, 65 ℃, react and improve temperature to 90～95 ℃ reaction 4 hours after 24 hours again, whether the desiliconization flyash that obtains is observed by XRD has novel substance to generate, and the result as shown in Figure 2.As can be seen from the figure, the non-crystalline state upwarped district of aluminous fly-ash in 2 θ=10～30 ° represents non-crystalline state SiO ₂Existence, non-crystalline state SiO in 45 ℃ of samples ₂The most obvious and the novel substance peak value minimum that the peak bag disappears, growing amount is minimum, and in other temperature samples or generated multiple novel substance, perhaps the novel substance crest of Sheng Chenging is obvious, and namely growing amount is bigger.So this paper determines that pretreatment temperature control is at 40～50 ℃.

Compared with prior art, the invention has the advantages that: SiO in the back desiliconization liquid of adopting new technology ₂Content is increased to about 140g/L from 80g/L; Alumina silica ratio is increased to about 2.00 from 1.83 in the desiliconization flyash; With active higher non-crystalline state SiO in the aluminous fly-ash ₂Fully extract, and then produce usury more with the byproduct that is worth, can effectively reduce simultaneously the generation of cheap byproduct silico-calcium slag in the subsequent extracted alumina process, also can realize effective extraction and the utilization of silicon resource in the aluminous fly-ash synchronously, the heat of reaction major part comes from the surplus heat of circulating mother liquor in addition, has reached purpose of energy saving.

Description of drawings

Fig. 1: schematic flow sheet of the present invention.

Fig. 2: flyash carries out the XRD synoptic diagram of desiliconization differing temps.

Embodiment

The invention will be further described below in conjunction with example, but should be noted that these several embodiment only are used for explanation system and method for the present invention, and scope of the present invention can not be confined to this.

Embodiment 1:

Technological line as shown in Figure 1, before entering heating jacket, in make-up tank, circulating mother liquor and the desiliconization flyash mass ratio with 3:1 is mixed, wherein NaOH concentration is 110g/L in the circulating mother liquor, stirring velocity is 300r/min, is incubated 20 hours down at 40 ℃.Entering heating jacket then reacted 4 hours down at 90 ℃.SiO in the desiliconization liquid that obtain this moment ₂Content is 115g/L, and alumina silica ratio is 1.99 in the desiliconization flyash.

Embodiment 2:

Technological line as shown in Figure 1, before entering heating jacket, in make-up tank, circulating mother liquor and the desiliconization flyash mass ratio with 3:1 is mixed, wherein NaOH concentration is 120g/L in the circulating mother liquor, stirring velocity is 330r/min, is incubated 22 hours down at 45 ℃.Entering heating jacket then reacted 4 hours down at 93 ℃.SiO in the desiliconization liquid that obtain this moment ₂Content is 148g/L, and alumina silica ratio is 2.13 in the desiliconization flyash.

Embodiment 3:

Technological line as shown in Figure 1, before entering heating jacket, in make-up tank, circulating mother liquor and the desiliconization flyash mass ratio with 3:1 is mixed, wherein NaOH concentration is 140g/L in the circulating mother liquor, stirring velocity is 350r/min, is incubated 24 hours down at 50 ℃.Entering heating jacket then reacted 4 hours down at 95 ℃.SiO in the desiliconization liquid that obtain this moment ₂Content is 121g/L, and alumina silica ratio is 2.07 in the desiliconization flyash.

The removal methods of amorphous silicon di-oxide can also make other changes in different forms on the basis of the above description for those of ordinary skill in the field in a kind of aluminous fly-ash of the present invention.Here need not also can't give all embodiments exhaustive.The replacement that all are similar and change apparent to those skilled in the artly, they are regarded as being included in spirit of the present invention, scope and the content.

Claims

1. the removal methods of amorphous silicon di-oxide in the aluminous fly-ash, it is characterized in that aluminous fly-ash is put into circulating mother liquor, mass ratio is 1:3, NaOH concentration is 110～140g/L in the circulating mother liquor, temperature of reaction is 40～50 ℃, insulation 20～24h, and accompany by 300～350r/min stirring, improve temperature to 90～95 ℃ then, reaction 4h.