DD276671A1 - METHOD FOR PRODUCING SULFUR SILICONE SOLUTIONS FROM TISSUE POCKETS - Google Patents

Abstract

The invention relates to a process for the preparation of sodium silicate solutions from rice husk ash, which is used as a water glass for the extraction of aluminosilicates of the zeolite type and of silica gels, as a binder and in the ceramic industry. The rice husk ash is hydrothermally reacted with sodium hydroxide at temperatures of 50 to 150C under the action of shear forces at reaction times of 5 to 100 minutes.

Description

avoid, is suspended by the action of shear forces in aqueous solution of caustic soda. The alkali concentration of the aqueous solution must, so that technically acceptable reaction times of 5 to a maximum of 100 minutes can be realized, 100 to 200g / l Na ₂ O, more favorable over 150g / l Na ₂ O amount. At temperatures of 50 to 150 ⁰ C, preferably 90 to 120 ^c C, the silicate content of the ash reacts with the alkali and goes into solution as sodium silicate.

In continuous process control in a Ruhrwerkskaskade the alkali metal hydroxide is heated in heat exchangers on reaction off-time, and added in the first stirred tank of the cascade continuously stirring with rice husk ash. The reaction mixture leaving the cascade undergoes solid-liquid separation, preferably by centrifugal separators, filter presses or rotary drum filters.

The obtained water-clear silicate solution, which contains up to 200 g / l SiO ₂ at a single throughput, is again used as starting liquor until, in the resulting alkali silicate solution, a Na ₂ O / SiO ₂ ratio which is between 0.2 and 0.4 , is obtained.

An increase in the reaction rate is triggered by

- a mechanical activation, for. B. at Aufmahlung of the ashes. At the same time, the sintering aggregates created by the thermal process of combustion of the rice husks are destroyed. The activation is conveniently done in disintegrators.

- Increasing the temperature to above 100 ⁰ C. The then running in a few minutes reaction increases the throughput and opens up the possibility of using flow or tubular reactors.

The utilization of the by-product rice husk ash brings economic advantages in that a feedstock is used which otherwise has to be dumped. This saves on loading costs, which have a cost-effective effect on the process. The high-purity water glass solution obtained in accordance with the ongoing reaction opens up opportunities for high-quality applications.

embodiments example 1

I.Stufe: 500g rice hull ash with 91.3% of SiO _2, are suspended in 21 wäßrigor solution of caustic soda, which 150g / l Na ₂ O and was heated to 95 ⁰ C. The reaction mixture is stirred vigorously for 90 minutes at the reaction temperature and then a solid-liquid separation is carried out via a frit.

The resulting silicate solution contains 195 g / l SiO ₂

2nd stage: 500 g of rice husk ash (composition see stage 1) are suspended in 21 of the silicate solution heated to 95 C obtained after the 1st stage and stirred vigorously at this temperature for 90 minutes. The alkali silicate solution obtained after separation of the solid contains 380 g / l SiO ₂ having a Na ₂ 0 / Si0 ₂ of 0.38 -Molverhältniss and can be used as a water glass solution.

Example 2

500 g Reisschalenaoche (composition see Example 1) are activated in a vibrating mill and with 21 an aqueous solution of caustic soda, which contains 150g / l Na ₂ O and was heated to 95 ^C , added and stirred vigorously at this temperature for 20 min. After removal of the solid, the alkali silicate solution contains 198 g / l of SiO ₂ . The silicate solution obtained is again placed in a 2nd otnfo with 500g activated rice husk ash and at 95 ⁰ C is SiO obtained after 20 minutes, a water glass solution having a concentration of 390g / l _2, and a Na ₂ 0 / Si0 ₂ molar ratio of 0.37.

Example 3

500 g rice husk ash (composition see Example 1) are mixed with 21 aqueous solution of caustic soda, in which a Na ₂ O tether of 110 g / l is realized. The suspension is placed in an autoclave, heated with stirring to 150 C and left for 15 min at reaction temperature under stirring. After cooling to 70 to 80 C, the suspension is removed from the autoclave and subjected to a solid-liquid separation. The resulting alkali silicate solution contains 378 g / l SiO ₂ and has a Na ₂ 0 / Si0 ₂ -Molverhältr.is of 0.28.

Claims (4)

claims: 1. A process for the preparation of sodium silicate solutions from rice husk ash, which are used as water glass for the production of aluminosilicates of the zeolite type and silica gels, as a binder and in the ceramic industry, characterized in that they from Reisschalenaschen by reacting with aqueous solutions of caustic soda, the 100 bis 200g / l Na ₂ O contained, at temperatures of 50 to 15O ⁰ C, preferably 90 to 120 ⁰ C, are obtained under the action of shear forces at reaction times of 5 to 100min and the sodium silicate solutions in recycling a Na ₂ O / SiO ₂ ratio from 0.2 to 0.4: 1. 2. The method according to claim 1, characterized in that to increase the purity of the waterglass solution by a classification, the carbonaceous constituents of the rice husk ashes are removed. 3. The method according to claim 1, characterized in that the rice husk ashes are pulled to increase the reaction rate of a mechanical activation. 4. The method according to claim 1, characterized in that to reduce the reaction time, the reaction takes place at temperatures> 100 ⁰ C in autoclaves. Field of application of the invention The invention relates to a process for the preparation of sodium silicate solutions from rice husk ash, which is used as a water glass raw material for a variety of products, such as for the production of aluminosilicates of the zeolite type and Kieselgcle.i. used as a binder and in the ceramics industry. Characteristic of the known state of the art Sodium silicate solutions, known as water glass, are prepared by fusing quartz sand with soda at temperatures of 1200 to 1400 C and subsequent steam treatment or pulverization dor melt and treatment with water (Ulmann Encyclopedia of Industrial Chemistry Volume 1811967], p 733ff). The production of water glass by this means is a very energy-intensive process which places high demands on the materials to be used. Particularly disadvantageous are the high reaction temperatures and the implementation of the reaction in pressure vessels. Further, it can not be prevented that impurities of the ashes react with the reaction, so that the obtained water glass is impure. The burning of rice husks for energy production produces ashes which consist almost exclusively of SiO; consist. US Pat. No. 4,319,911 describes the preparation of a solid sorbent from such rice husk ash by mixing with a metal hydroxide and subsequent thermal treatment. This wild but only used as an adsorbent and can not wio wio a water glass solution for a variety of syntheses use. Rice husk ash is also used as a starting material for the production of diatomaceous earth products, such as insulating stones and for the production of cement and other building materials (Cement and Concrete Research Vo116, 1986, pp. 67 to 73). Object of the invention It is the object of the invention to produce sodium silicate solutions from ashtrays of rice husks which find use as water glass. This is on the one hand to save Verinddungskoston and on the other hand, a high-quality product can be obtained, which is oinsetzbar for the recovery of aluminosilicates of the zeolite type of silica gel, as a binder and in the ceramics industry. Explanation of the essence of the invention The invention is based on the object of Roisschalon, which is more than 90% SiO 2; consist of producing a sodium silicate solution. Aschon, dio in the burning of hot husks, z. B. for energy production incurred. It has been reported by gofundon that dioso Aschon oingohon with aqueous solution of alkali metal hydroxides boi ontiprochondon Bodingungon löslicho Vorbindungon.
Dio Moisschalonaschen are made up of: 90-97ToSiO; 2-5% carbon 1-5% CuO
about 0.5% Fo ^ O ₁ Major proportion of silicic acid accounts for more than 95% of amorphous SiO; and cristobalite, in Spuron quartz also occurs. Dio Ascho, from which previously the kohligon Bustandtoilo ontfornt benton, by order to lorluin;