DE2262654A1 - Refractory particles - bound with pitch and ligno sulphonate - Google Patents

Abstract

Refractory particles are bound by pitch, to which is added Na or Ca lignosulphonate. The particles may contain dolomite and/or periclase. Bodies may be made by heating some basic refractory particles to 260-315 degrees C mixing the pitch and lignosulphonate with the hot particles and shaping. The refractory material can undergo combustion without appreciable migration of the pitch, thus obviating weak zones.

Description

"Refractory material and process for the production of shaped bricks The invention relates to a refractory particles made of pitch-bound refractory material and a method for producing shaped bricks with this.

The use of tar- or pitch-bound refractory materials or of refractory materials, consisting of refractory, particles passing through a coking carbonaceous binder material has been linked in recent years Years. This is principally due to the use of this type of refractory material in vessels for steel production through the basic oxygen fresh process In the basic oxygen fresh process, it is essentially purer Oxygen is introduced into the bath through a water-cooled blowing lance made from molten Iron, flux and scrap or iron ore is made up of the reduction of iron to effect steel. The process is different from most other steelmaking processes in that no external fuel is supplied. The required heat will be released by the exothermic reactions of oxygen with carbon, silicon, Phosphorus and some metals. Because basic additives are used in the process are for the lining of the vessels is based on basic refractory materials necessary. Pitch bonded bricks are mostly used as a refractory lining for such vessels are used. The pitch binder confers in such refractory materials the stones green strength and forms under operating conditions and high temperature a carbon compound that develops as a result of the coking of the pitch. The pyrolysis of the pitch in the stones occurs during use, when the lining heated to the high temperatures characteristic of steelmaking.

After installing a new refractory lining in a fresh basic oxygen stove the lining must be baked to pyrolyze the pitch. This is done by placing hot coke in a bed of cold coke at the bottom of the stove. The oxygen lance is then lowered into the stove, and oxygen under low pressure and low Throughput is used to release some of the heat from the coke the volatile constituents from the coal-tar-pitch binder in the refractory lining releases, and the hydrocarbons cracks into carbon, which binds for forms the refractory material. The one normally required for this operation Time is between 45 minutes and 2 hours. The operation is critical because the Bad luck goes through a softening state in which the bad luck can begin to flow. If the burn-in process is continued at too low a temperature, then bad luck cracking in carbon results in oxidation or loss of bond, which results in a substantial amount of the liner being lost.

The coal tar pitch used in conventional pitch-bonded refractory materials is used, melts and flows or creeps out of the refractory structure and leaves Back parts of the structure that have a high pitch content and other parts that have a low pitch.

The pyrolysis of the pitch is the amount of carbon that is in the Areas of low pitch remains small and soft results Zone or a low strength refractory material. This soft area can do not resist the impact when introducing the batch. There are jumps in the rock a few centimeters from the hot surface, and loosen the loose areas away from the jar after a few batches, leaving a hole that repairs must become. Furthermore, the poorly bonded refractory material can by the effect the aggregates and the metal are eroded, which leads to rapid wear.

The pitch flows or creeps between 110 ° C and 5000C. The damage caused by the flowing of the pitch can be a The consequence of inaccurate heating of the stove or other factors that affect the temperature gradient influence through the pitch-bonded refractory lining. The coal-tar pitch becomes more fluid as the temperature rises.

The object of the present invention is to provide a pitch-bound refractory particles to create refractory material without any noticeable Creeping pitch can be branded. To solve this problem, the Pitch additives added, namely calcium and / or sodium lignosulfonate.

The most common pitch is coal-tar-pitch, but you can too use other types of pitch, such as aromatic hydrocarbon pitch. The invention is explained under Reference to carbon pitch. The lignosulfonate does not prevent the pitch from melting, but prevents the pitch from flowing and thus maintains a rather uniform distribution of the pitch within the material upright, as well as the resulting carbon bond during the baking process. Calcium lignosulfonate is preferred and reference is made to this in the following explanation.

The pitch with the added lignosulfonate melts at the usual temperature, and the viscosity remains the same as that of pitch without addition at the start of melting. As the burn-in process proceeds, the pitch reacts with the finely divided one Lignosulfonate and the viscosity gradually increases. The contact angle between the However, the pitch and the refractory particles remain approximately the same as the pitch without lignosulfonate. As a result, the refractory particles are completely through the pitch mixture wets, and there is a uniform coating with Pitch on the particles and a corresponding filling of porous cavities.

It is believed that the calcium lignosulfonate with the unsaturated aromatic hydrocarbons reacts, so that a series of highly viscous aromatic hydrocarbons. This also leads to an increased yield of carbon in the pyrolysis because the more volatile components of the pitch are lost when the temperature is brought to the level at which pyrolysis occurs.

The preferred composition of a pitch-bonded doloutite brick and the range for the amounts of each insert material in parts by weight is the following: Ingredient typical value range low-closing 65 35-85 dolomite periclase L-grain 35 20-65 size 0.23 coal-tar-pitch mixture 6 0.5-15.0 The chemical analysis of the molded stones from this preferred composition results in percentages by weight: calcined base magnesium oxide 61, 10 calcium oxide 36.70 Silica 0.51 Alumina 0.47 Iron Oxide 1.21 The preferred composition a pitch-bound molded stone on the basis of high-purity periclase and the areas the amounts of each ingredient in parts by weight are as follows.

Component typical value range periclase (4 x 2, o grain size) 25 10-45 periclase (loxo, 62 "30 20-40 periclase (up to o, 23") 45 30-60 coal-tar-pitch mixture 6 0.5-15.0 The chemical analysis of the shaped stones from this preferred composition shows in percent by weight: calcined base magnesium oxide (MgO) 95.82 Calcium Oxide (CaO) 0.87 Silicon Oxide (Sio2) 1.75 Aluminum Oxide (A1203) 0.60 iron oxide (Fe203) o.96 The coal-tar-pitch mixture (mixture of pitch and Lignosulfonate) is preferably prepared by finely grinding pitch with a Softening point of about 143 to 1480 C (cube-in-air method) and mixing with powdered calcium lignosulfonate. Both materials are preferably so fine grind so that they have a grain size of less than 0.6 mm.

The following is a typical composition and range for the amounts of each constituent given in percent by weight: typical value range Coal tar pitch 90 80-99 Calcium lignosulfonate 10 1-20 The specifications for a typical coal-tar pitch are the following: insoluble benzene-toluene 34, o % Coking value nacii Conradson 47.4% specific weight at 150 ° C. 1.330 melting point (Kubus-in-Luft) 1460 C fldc} volatile combustible components 52.8% solid carbon 47, o s ash 0.2% ground to a grain size of less than 0.6 mm The specifications for a typical calcium lignosulfonate are the following: calcium lignosulfonate 74 - 76% sugar acids 20% calcium oxide 7.5% sulfur 5, °% The molded stone mixture is prepared for pressing by mixing the correct proportions of the refractories Particles, heating the particles to a temperature of 260-315 ° C, and then quickly Mixing the coal-tar-pitch mixture with the heated particles in about one Sigma type mixer.

If desired, coal tar distillate oil can be added to the mixture of refractory particles and the coal-tar-pitch mixture are added, and then one can into the desired Press the shape with about 560 at. An alternative method for mixing the material before pressing consists in bringing the refractory particles to a temperature of 260-315 ° C and then the coal-tar pitch as a hot liquid or even as a Add solids. The refractory particles and coal-tar pitch then become getttcht until the refractory particles are well coated, after which the pulverized Calcium lignosulfonate is added.

To demonstrate the advantages of the refractory material below Using an additive made from calcium lignosulfonate, you have one Formed stone made of pitch-bound dolomite with the dimensions 60 cm x 15 cm x 9 cm in an oven with an area of 15 x 9 cm 2 is used, in which the temperature is at 2050 C. In addition to this shaped stone, a conventional coal-tar-pitch-bound-he was used Shaped stone the same composition, but without the addition of calcium lignosulfonate, offset. Both stones were exposed to the same temperature for 24 hours and then cooled. On top of each stone was on the 15 x 9 cm2 area one sample taken and another sample from the lower surface of 15 x 9 cm2, which was 60 cm from the top. A determination of loss Solderability was carried out on each stone and compared with an unheated one Stein, who just came out of the press. The following numerical values show the percentage Loss of flammability top bottom side freshly pressed stone 5.4% 5.4% conventional ZCohlen-tar- 1 9% 8 5% pitch-bound stone coal-tar-pitch-calcium-lignosulfonate-mixture-mixed 5, o% 5.2% bonded stone The higher the value, the higher the coal-tar-pitch content of the refractory material. This experiment clearly shows the effectiveness of the mixture of coal-tar-pitch and calcium lignosulphonate for the production of homogeneous shaped bricks for stoves for the purpose of basic oxygen freshening.

Shaped stones, which are bound with this Gemich, lead to a longer life and lower costs because of the repairs and the downtime can be brought to a minimum.

(Patent claims)

Claims (6)

Claims 1) Made of pitch-bound refractory particles Refractory material, characterized by the addition of calcium and Z or sodium lignosulphonate. 2) Refractory material according to claim 1, characterized by a Weight fraction of pitch of 80. 99% and a weight fraction of lignosulfonate of 1 .. 20%. 3) Refractory material according to claim 2, characterized in that about 0.5 .. 15 parts by weight of the material consist of pitch with lignosulfonate. 4) Refractory material hach one of claims 1 to 3, characterized characterized in that the refractory particles are made of dolomite, periclase or a mixture both exist 5) Process for the production of refractory moldings with the Material according to any one of the preceding claims, characterized by the following Steps: (a) Heating a batch of basic refractories to a Temperature of 260 .. 315 ° C, (b) mixing pitch and lignasulfonate, (c) manufacturing of molded bodies from the mixture. 6) A method for the production of shaped bricks according to claim 5, with a Material composition according to claims 2 and 3, characterized in that pitch and lignosulfonate with a grain size below 0.6 mm are used