DE2232719A1 - Refractory stones - contg refractory oxide and/or carbide grains and silicon carbide binder - Google Patents

Abstract

Refractory stone for cladding bottom shaft pt. of blast furnaces contains (a) granular basic material of refractory oxides and/or carbides, pref. sinter corundum, -mullite, -magnesia, Cr-magnesia, sillimanite, Zr oxide and/or SiC, and (b) a SiC binder structure, pref. prepd. by reacting Si powder with coked electrode pitch and coke powder in deep by-prod. coking ovens. Si- or FeSi powder used pref. contains >70% Si and has 0.2 mm grain-size.

Description

Refractory brick The invention relates to a refractory brick and its use in blast furnaces.

The delivery of blast furnaces for the extraction of pig iron can currently divide into two main sections. In the lower part of the blast furnace, i.e. in the ground, The frame and detent are mainly carbon or fire-resistant lining also partially used graphite blocks. The upper part of the blast furnace, i.e. the Sohacht, In contrast, it is almost exclusively made with oxide-ceramic fire-resistant products delivered. In this case, particularly in the lower part of the manhole, there are high levels of aluminum oxide Stones used. The blast furnace gases contain CO 2 in the blast furnace shaft an atmosphere that is oxidizing to carbon stones. That is why carbon stones point in the shaft only a short shelf life. On the other hand, stones are made of fireclay, Sillimanite, mullite or similar refractory materials little or no in the Rast, built into the frame or the floor of the blast furnace because they are there in contrast carbon stones are subject to heavy wear due to slagging.

In addition, there are signs of wear and tear that occur in the individual blast furnace zones the refractory lining different.

A major cause of destruction of the heavy clay stones on the base of alumina / silica is based on the action of potassium and sodium compounds in the form of oxides, carbonates, cyanides, etc., which are mainly the silicate bond attack the stones. The storage of zinc oxide via the gas phase, Lead oxide or fission carbon can be another cause of destruction of the refractory bricks be. The shelf life of the delivery is also ensured by good temperature change resistance and abrasion resistance of the stones increased.

After all, an essential quality feature of the refractory bricks is the thermal conductivity, because the remaining wall thickness is subject to wear Lining is decisively influenced by the coefficient of thermal conductivity.

The invention relates to refractory bricks, which compared to the named signs of wear are particularly resistant.

The excellent resistance of the stones according to the invention is achieved thereby. that the granular base material consists of refractory oxides and / or Carbides and the binding structure consists of silicon carbide. The silicon carbide bond the stones leads to an increase in thermal conductivity, resistance to temperature changes as well as the abrasion resistance. The silicon carbide bond also shows a favorable one Behavior towards attack by alkalis.

The basic refractory materials that make up the inventive Stones are made, for example, coarse and fine grains of sintered round, Sintered mullite, sillirianite, magnesia, chromium magnesia, zirconium oxide and / or silicon carbide. The stones according to the invention are particularly suitable because of their properties for lining the lower part of the shaft of blast furnaces.

The stones according to the invention are produced, for example, in the Way that the coarse and fine-grained base material with the addition of commercial Silicon or ferrosilicon powder with a tar pitch binder to form a plastic one Mass is mixed. The oxidic or carbidic base material consists of processed Grain classes in the range of e.g. O - 8 mm grain size.

The silicon or ferrosilicon powder has a grain size smaller 200 µm, preferably below 90 µm. Its addition to the basic material is aimed on the one hand according to the grain fineness of the base material and on the other hand according to the requirements, which are placed on the silicon carbide bond. The silicon content in the starting mixture is usually 5 to J40 nó. In addition to pure silicon there are ferro-silicon types with at least 75% Silicon content into consideration. Used as a binder Electrode pitches with softening points between 50 and 90 ° C are used.

The heap of base material, silicon powder and electrode pitch is used in a warm, plastic state on presses or vibration compressors desired stone formats. The green moldings are then in Burned ring kilns, as they are generally used for the burning or glowing of charcoal products are common. When firing, the final temperatures are 1,100 to 1,300 ° C. While of the firing process occurs at the upper temperatures through the reaction of the silicon with the coke of the coked electrode pitch silicon carbide. This forms the binding framework of the refractory bricks according to the invention. The recipe for the production of the Refractory brick is usually matched to become the base material amount of silicon powder added and the amount of coke formed from the pitch are stoichiometric correspond. In the case of higher silicon contents of the mixture, something should optionally Coke powder can be added.

Example 1: The oxide ceramic base material consists of granular Sinternullite, a dense mixture of four grain fractions from 0 to 5 mm is put together. On sintered mullite, the proportion of which in the dry matter is 78%, 2G% silicon powder under 0.1 mm tube size and 2% petroleum coke powder are added. The desiccant components are heated to 160 with the addition of 10 V electrode pitch oC thoroughly mixed in a mixer and kneading machine. The mix is on a Vibration compactor compressed into a shaped body, with a bulk density of 2.3 - 2.5 g / cm3 is reached.

The moldings are then sealed up to 1,250 oC in the absence of air burned. The fired stones have the following average property values on: bulk density 2.35 g / cm3 open porosity 14.5% compressive strength 800 kp / cm2 thermal conductivity 4 k@al/m.h. ° C at 100 ° C temperature change resistance according to DIN 51068 40 temperature change until the destruction Example 2: The basic material is one in grain classes silicon carbide grain size used of 0 s @@ 3 @@. 68, di @@@@ Materials will be included 23% pure silicon powder and 9% petroleum coke powder with the addition of around 10) electrode pitch mixed. The molding and firing are carried out in the same way as in the example 1 is described.

The resulting silicon carbide brick is characterized by great hardness and high strength mainly due to excellent thermal conductivity. The following property values were determined: bulk density 2.5 - 2.6 g / cm3 open Porosity 14 - 15 Compressive strength 1,000 kp / cm2 Thermal conductivity 25 kcal / m.h. ° C at 100 ° C

Claims (5)

P a t e n t a n s p r ü c h e 1) Refractory stone, characterized by it, that the granular base material consists of refractory oxides and / or carbides and the binding framework consists of silicon carbide. 2) stone according to claim 1, characterized in that the binding frame from silicon carbide through the reaction of silicon powder with coked electrode pitch and coke powder is produced in deep chamber furnaces for burning charcoal products. 3) stone nech claim 1 - 2, - characterized in that the granular Base material sintered corundum, sintered mullite, sintered magnesia, chrome magnesia, sillimanite, Is zirconium oxide and / or silicon carbide. 4) stone according to claim-l - 3, characterized-in that the used Silicon or ferrosilicon powder has a silicon content of at least 70% and has a grain fineness of less than 0.2 mm. 5) Use of the refractory brick according to claims 1-4 for Lining the lower part of the shaft of blast furnaces.