CS269679B1 - Method of sintered burnt dolomite production - Google Patents

Abstract

sintered burned dolomite (SED). charac- : terizovaný content oxide magnesium and Your Penati lows. 98.5 wt.% and volume hmotnoetou lows. 3.15 g.cm - · 5 the uses on the manufacturing refractory materials for metallurgical and cement industry. IN comparing. Nani with known jednostupnovyoi procedures j manufacturing SED, which ones lie in grinding, bri- : ketácii and firing výtvorky eu head of 9posobu manufacturing SED higher strength výtvor- ' · metal at at 600 until 1200 ° C and and team They are- hanging higher return SED, hmmogénne rozlo- ■ drives oxide ferric which catalyzes . 9linovanie. increase content oxide magnesium and th in a sintered product and lower technical; ka severity production. Spísoh manufacturing SED aa · features by that the dolomite served on the zrnoj Come 0.2 mm, najmfi Come 0.06 mm, During mle- with tia, or after grind the agitate e magnesia, ; containing 5 until 8 wt.% oxide · iron ' and lows. 80 wt.% oxide magnesium in after-: Bere 92 until 96 wt.? » dolomite to 4 until 8 hmot.?í magnesia, mixture the is moistened water but bo known roztokml binders, try the on the : výtvorky. which ones the burned at at 1600 : until 1900 C.

Description

The invention relates to a process for the production of sintered calcined dolomite, which is used as a base material for the production of refractory shaped moldings and monolithic masses for the lining of furnaces and vessels in the production of steel and cement. It is characterized by the content of magnesium and calcium oxide CaO + MgO minima. 98.5 wt. % * by volume by weight min. 3.15 g.cra "\

The simplest currently known process for the production of sintered calcined dolomite is the so-called direct firing of lump dolomite in shaft or rotary kilns. However, its usefulness is limited to the processing of rare and occurring types of solid fine-crystalline dolomite, usually with a high content of accompanying oxides. The co-crystalline types of pure dolomites cannot be processed by said epSaob, because even at the high firing temperatures achieved by the enrichment of the combustion air in the firing units, a sufficiently dense sintered product is not obtained. For the above reasons, the so-called a two-stage process according to which ea dolomite is calcined at a temperature of 11C0 to 1300 ° C, after calcination it is usually ground to a grain size * below 0.06 mm, it is briquetted and the briquettes are fired at a temperature of 1600 to 1900 ° C. Some technological processes use hydration instead of grinding the calcine, as a result of which the calcine disintegrates into fine-grained particles. Unhydrated and oversized particles are separated by an air classifier. The disadvantages of these processes are high production costs due to investment intensity, complexity of technological equipment and high energy consumption. A simpler one-step process for the production of sintered calcined dolomite is known, in which the dolomite is ground to a grain size of less than 0.06 mm, briquetted and the briquettes washed at a temperature of 1600 to 1900 ° C. The excessive occurrence of drift due to the etrata of briquette strength in the temperature range of 600 to 1200 ° C and the low yield of granular parts needed for the production of shaped refractory moldings are a disadvantage of this technological process.

The process for the production of sintered calcined dolomite according to the invention, which obviates the said disadvantages, consists in that the dolomite is ground to a grain size below 0.2 mm, preferably below 0.06 mm and during grinding or after grinding and mixing with sintered, or caustic magnesia of the same grain size, weighing 5-8 wt. £ iron oxide, max. 2 wt. % silica and min. 80 wt. of magnesium oxide, in a ratio of 92 to 96 wt. £ dolomite to 4 to 8 wt. Magnesium, the mixture is moistened with water or solutions of known binders, e.g. sulphite leachate, magnesium sulphate and the like, which is briquetted into products which, after drying, are fired in shaft or rotary kilns at a temperature of 1600 to 1900 ° C. The production method according to the invention has several advantages over the known processes for the production of sintered calcined dolomite. The process is one-stage, technically significantly simpler, less energy-intensive than two-stage. Magnesium is a binder which significantly reduces the disintegration of briquettes when staying in the firing unit in the temperature range of 600 to 1200 ° C. Iron oxide is introduced into the dolomite and homogeneously decomposes in an amount which effectively catalyzes sintering without significantly deteriorating the thermotechnical properties of the products of this base material. On the other hand, the beneficial effect of the added magnesium is immobile in that it increases the total magnesium oxide content in the sintered product. As a source of iron oxide, ferrous sintered magnesium, used for the production of shaped moldings, or so-called steel magnesium, containing about 80 wt. % of magnesium oxide, 5 to 8 wt. £ iron oxide, max. 2 wt. % of silica, possibly flight from rotary kilns firing low-silica magnesite. The advantage of briquetting a mixture with a binder in comparison with briquetting a dry mixture lies in lower formation pressures and thus less demands on the construction of the briquetting device, less wear of its hoops, considerably higher yield of briquettes from the briquetting mixture and less return.

Example:

Crystalline dolomite with the chemical composition was used:

SiO _and 0.13 wt.%.

Al 2 O 3 0.03 wt%

PegO ^ 0.06 wt%

CaO 31.41 wt.%

KgO 21.86 wt.% Loss on ignition 46.51 wt.% And sintered magnesium of the following chemical composition:

CS 269 679 Bl

S1C ₂ ai ₂ o ₃ ^Fe 2 ° 3 MgO

0.72 wt. #

0.25 wt. #

7.32 wt. #

88.63 wt. #

Dolomite and sintered magnesium in a ratio of 94 parts by weight of dolomite to 6 parts by weight of magnesium with a particle size of less than 2 mm were ground to a particle size of less than 0.06 mm. The ground mixture contained 14 wt.% Of residue on a sieve with 0.06 mm holes. The prepared mixture ea was moistened by adding 6 l of an aqueous solution of sulphite extract with a density of 1.07 g.cm ^-3 per 100 kg of dry ingredients, briquetted at a pressure of 40 kN / cm. After drying, the briquettes were fired in a gas oven at 1700 ° C and held for 1.5 hours. Firing of the obtained sintered burnt dolomite in a density of 3.20 g.cm ^- ^ and chemical composition:

SiO ₂ 0.29 wt. # Ai ₂ o ₃ Pe ₂ ° ₃ CaO

MgO

0.09 wt. #

0.88 wt. #

52.76 wt. #

45.97 wt. #

The sintered calcined dolomite according to the invention can be used in the production of refractory materials for the metallurgical and cement industries.

Claims (2)

PRE DME T V Y N Á L E Z U Process for the production of sintered calcined dolomite containing 0.1 to 0.6 wt.% Of silica SiO ₂ , 0.4 to 1.3 wt.% Of iron oxide Pe ₂ O ₃ and a minimum of 98.5 wt.% Magnesium and calcium oxide, with a bulk density of min. 3.15 g.cm ^- ^ characterized in that the dolomite e and ground to a particle size below 0.2 mm, najmtí below 0.06 mm during grinding or after grinding is mixed and sintered, or caustic magnesia same grain size of 5 to 8 mass # iron oxide, max. 2 wt. # Of silica S10 ₂ and min. 80 parts by weight of magnesium oxide MgO, in a ratio of 92 to 96 parts by weight of dolomite to 4 to 8 parts by weight of magnesium, the mixture is moistened with water or a solution of known binders such as sulphite leachate, magnesium sulphate, etc. , which are dried after drying in shaft or rotary kilns at a temperature of 1600 to 1900 ° C. '