SU833832A1 - Method of producing refractory powder from caustic magnesial dust - Google Patents

Description

(54) METHOD FOR REFRACTORY POWDER FROM CAUSTIC MAGNETESITE DUST

one

The invention relates to refractory production and can be used in the manufacture of dense materials, such as magnesite powder.,

In the production of sintered magnesite powders by roasting; magnesite in Rotary kilns produce a large amount of caustic magnesia, commercial dust, which is the main source of contamination of the heating surfaces of waste heat boilers and the air basin. When disposing of dispersed caustic dust, caught by electrostatic precipitators and cyclones, by repeated burning in rotary kilns, dust deposits are formed in the duct and on the outer surface of the pipes of the waste-heat boilers before their overgrowth and stopping of the kiln. unit.

Caustic dust in the kiln system initially has valuable properties. It is an active adsorbent that cleans Exhaust flue gases from sulfur dioxide, alkali vapors and fluorine with the formation of coniferous suphates. and alkaline earth metals and magnesium fluoride, harmful to the environment, and enriched with them, exhibits negative properties — becomes a source of dust deposits along the gas flow path.

There is a known method for obtaining dense sintered powders, including the operations of fine grinding caustic magnesite dust; moistening it, pressing the resulting mass and burning the briquette ij.

However, this method requires a lot of energy for grinding and does not eliminate the formation of dust deposits on the pipes of waste heat boilers, which complicates the firing process

5 briquettes, makes it more energy-intensive and low-productive.

The closest to the invention is a method for producing crumb from caustic magnesite dust, which consists in grinding caustic dust followed by dewatering of the sludge using vacuum filters and roasting in rotary kilns with furnaces 2.

five

However, this method involves the energy-intensive grinding operation of the material, and also does not eliminate the formation of sulfates and dust deposits on the pipes of the waste heat boilers. Besides

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In addition, the finished product has an increased porosity.

The purpose of the invention is to improve the quality of the powder, eliminate the formation of dust deposits on the KU pipes, utilize sulphates and reduce their environmental pollution.

The goal is achieved by the fact that caustic dust collected from the exhaust flue gases is moistened with water heated to 4070 ° C at a ratio of t: f 1: 13-17, mixed, filtered on vacuum filters obtained after dehydrating tcek with moisture more than 40% is mixed with dry caustic dust to obtain a mixture with a moisture content of 6-1.8%, then the mixture is briquetted at a pressure of 3001000 kgf / cm and the briquettes are roasted at 1650 ° C.

The method is carried out as follows.

The mixing is carried out with water at a temperature of 40-70 ° C in a ratio of dust 1.

---- fjrfv slurry stirred

Sludge preparation parameters and component content

Water temperature for mixing, with

Ratio 1 eu-water Time of stirring into ani ala aKek, obtained by sludge dewatering on a vacuum filter at a specific pressure of 15-20 kgf / cm, is mixed with dry caustic dust obtained during roasting natural magnesite to a moisture content of 7-8% and pressed at

27.9 29.9

more than 0.5 h. When mixing and stirring, the salts dissolve and the particles disperse. After dewatering the sludge on a vacuum filter at a specific pressure of at least 15 KG / cm, a cake is obtained (dry mass content is at least 60%), which is mixed in a mixture with a certain amount of dry caustic dust into a mass with a moisture content of 6-18%. Briquette the mixture at a specific pressure of 300-1000 kgf / cm. Briquette fired at a temperature of more. Alkali and alkaline earth metal sulfates are removed from the clarified solution, free of suspended particles, by precipitation or evaporation.

Example. The original caustic magnesite dust, which contains SiO. 0.9-1.9; , 61, 9 /, 0.4-0.9, CaO 1.8-2.5, MgO 60.6-82.0; SO 2.0-17.5; 611, 6; F 0.2-1.2 / PP.P. 5.1-8.7, shut off with water and mix.

Contents 50z and. in the material, depending on the parameters of the preparation of sludge are given in Table. one.

Table 1

Composition

20 1/7

40 1/13

70 1/17

specific pressure 1000 kgf / cm. The obtained samples are burned at 1650 C.

The average values of physico-technical properties of the raw and calcined samples are given in Table. 2

.Table

59.3

3h, oh oh

1.63 60.8 3.03 1.66 As can be seen from the table. 2, the quality of the “heated samples” (porosity is open and density is apparent); manufactured according to the proposed method is significantly higher than that of the known physical and technical properties of the material obtained by methods 2 and 3, is significantly higher than that of the samples according to methods 1 and 4. After evaporation, the washings form a crystalline salt of the following composition, wt.% : CaO 4.7-7.7; MDO 5.5-18.4; 50z 44.2-47.2; R „O 7, 34.7; ppt 3.4-17.9 (). The use of the proposed method of obtaining refractory powder from caustic magnesite dust provides, in comparison with the known method, the possibility of improving the quality of the powder by increasing the density during firing, for example, in a rotary kiln, reducing the formation of dust deposits on the heat recovery boiler pipes and the possibility of increasing equipment utilization and feedstock entering and burning, as well as reducing emissions of harmful emissions into the environment through the disposal of sulfates.

Continued table. 2 Claims A method for producing a refractory powder from caustic magnesite dust collected from flue gases by moistening, mixing, filtering on vacuum filters, briquetting, and fading, so that powder quality, eliminating the formation of dust deposits on surfaces. After a dream of waste-heat boilers, they are moistened with water heated to 40-70t at a ratio of t: f 1: 13-17, obtained after dewatering the cake with a density of not more than 40% is mixed with dry caustic dust to obtain a mixture with a humidity of 6-18%, briquetting the mixture is carried out at a pressure of 3001000 kgf / cm, and briquette roasting at a temperature of 1650-1850 C. Sources of information taken into account during the examination 1. Briquetting of caustic magnesite on industrial smooth press rolls. - Refractories, 1974, No. 3, p. 49-55. 2. Chikurov I.F. Some results of work and prospects for the development of the plant Magnesite, - Refractories, 1964, № b. S. 241-243 (prototype).

Claims (1)

Claim A method of producing a refractory powder from caustic magnesite dust captured from flue gases by moistening, mixing, filtering with vacuum filters, briquetting and subsequent firing, characterized in that, in order to improve the quality of the powder, eliminate the formation of dust deposits on surfaces heating of waste heat boilers, humidification is carried out with water heated to 40-70 ° C at a ratio of m: w = 1: 13-17, the cake obtained after dehydration with a moisture content of not more than 40% is mixed with dry caustic dust until mixture with a moisture content of 6-18%, briquetting the mixture is carried out at a pressure of 3,001,000 kg / cm ^2, and firing the briquettes at a temperature of 1650-1850 ° C.