FR2593170A1 - REFRACTORY MATERIAL CONTAINING IRON AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Abstract

Disclosed are an iron-containing refractory material, which further contains an additive which acts as a poison of the catalyst, and a method of making the same. The poison is especially sulfur. Application to refractory linings of furnaces.

Description

The present invention relates to refractory materials. The materials

  refractory coatings are often contaminated with metallic iron, oxides of

  iron or other compounds containing iron, referred to

  after simply under the name "iron". Iron is good

  naked as a catalyst for the reaction (Fe)

2 CO CO2 + C4

  which, depending on the concentration of CO in the gas,

kills between 450 and 900 C.

  As the iron possibly present is

  naked throughout the mass of the refractory material, when the refractory coating comes into contact with a hot gas containing CO, the carbon deposit occurs on the

  iron particles that act as catalytic sites

  inside the refractory lining. A deposit of

  prolonged carbon results in expansion,

  suration and finally to a complete rupture of coatings

  otherwise mechanically sound refractories.

  It should be noted that there are many applications

  industrial processes in which an oven or reactor

  contains carbon monoxide, either from a

  incomplete combustion of fuel, either deliberately

  trimmed, or added to the process to perform for example a reduction of metal ores. For example, CO is commonly found in the petrochemical industry, in coal conversion and coal gasification, as well as in the plasma arc and magnetohydrodynamic facilities. Similarly, in the direct reduction of iron ore, the hot ore is brought into contact with hot gases containing Co in straight or rotary kilns. In many cases, in direct reduction processes, gaseous CO is

  produced in external regenerators coated with

  fractary, while in the more traditional blast furnace process, gaseous CO is produced indoors

  by means of coke in contact with the ore.

  Demand for resistant refractory materials

  so relatively cheap CO is therefore consid-

  and tests have been developed, notably in BS 1902-310: 1981 and ASTM C 288/78, to establish the resistance of a refractory material to

disintegration by CO.

  On the other hand, most of the

  refractory materials contain iron as a contami-

  in one form or another. All the proci

  known iron removal are either expensive,

  as is the case for acid washing, either inef-

  as is the case for the use of a

  magnet. Refractory materials can be prepa-

  They are designed to meet strict specifications for low iron content, but these are generally expensive, as is the case for molten mullite, fused alumina and tubular alumina. It is well known that even low iron content materials will bind iron during blending

  refractories by contamination from the apparatus

  steel crushing mill, and during grinding

  with steel balls. The normal fixation of

  The quantities of abraded iron are sufficient to cause a high carbon deposit in CO atmospheres. In addition, most aggregates, for example calcined clay, andalusite, bauxite,

  high content of alumina, magnesia or chromium

  will normally hold a certain proportion of oxide

of iron as a contaminant.

  In some cases, CO resistance may

  conferred on refractory aggregates or bricks

  refractory materials calcined in calcinat at a temperature

  high temperature, at which all iron is oxidized to oxide

  of iron and reacted to form an iron silicate (2FeO.

  SiO2), which is well known for being resistant to

  carbon deposit. Here again, the calcination at high temperature of the aggregate is expensive, and during the calcination of a refractory brick at high temperature, other properties, such as

  chipping resistance, may be affected.

  Many refractory coatings are

  put in place in unburned form. These include

  refractory concretes, refractory rammed earths and coating compounds for which it is not possible to treat the composition at room temperature.

  high before setting up. Because of their natural

  same, the materials are put in place at the temperature

  ambient temperature and heated to the operating temperature

  in the temperature range of 450 to 900C, during which time a CO attack may occur. In addition, establishing a gradient of

  temperature in the coating, when the coating

  reached the operating temperature, requires

  that a large part of the mass of the refractory coating

  be in the temperature range of 450 to

  900 throughout the life of the coating.

  One of the aims of the invention is to provide a

  refractory material which is protected against

by the CO.

  According to the invention, a material

  fractary that contains iron is characterized in that

  that it contains an additive acting as a poison

iron stripper.

  According to the invention, the additive is

  elemental sulfur, or a compound containing sulfur

  such as potassium sulphide or a sulfur compound

  which is reactive with iron and any iron compound that can be reduced to metallic iron in the presence of CO to poison the catalyst at

  iron by formation of iron sulphide. -

  Thus, the invention comprises in its field a refractory material, either in the form of an aggregate or in the form of a shaped body, containing iron and

  sulfur; it also covers refractory materials

  in which iron and sulfur have already

to form iron sulphide.

  In the preferred embodiment of the invention,

  vention, the material poisoning the catalyst with iron,

  of sulfur, is present in excess

  of the iron contained in the material

  refractory material. It is more particularly found that good CO resistance is given to unshaped refractories if the sulfur is present in

  slight stoichiometric excess over metal iron

  present due to contamination by the

  crushing and grinding machinery.

  The sulfur or reactive sulfur compound may be added to the non-calcined refractory composition in the form of a solid or liquid component such as, by heating to about 400 ° C in a furnace or

  in situ, formation of iron sulphide occurs.

  Soluble sulphide solution can also be used

  for the impregnation of a preformed body which is subsequently

  calcinated or heated in situ.

  The refractory material or composition of the invention can be used to produce refractory concretes or shaped bodies having high mechanical strength and abrasion resistance, so that they are particularly useful for coating furnaces in which the coating is

  in continuous contact with heavy masses of charge.

  In this case, and also in the case of reactions in

  which hot gases are treated, the refractory

  re of the invention is made resistant to CO attack in the range of dangerous temperatures by

  inactivation of the iron contained in the refractory material

silent.

  The invention also includes in its field

  a method of forming a refractory material

  holding iron for use as a refractile body

  resistant to atmospheres containing CO, including

  the stage of adding catenary poison

  iron to this refractory material.

  All refractory compositions prepa-

  in accordance with the invention satisfy the tests

  standardized resistance to CO. The illustration is

  lustred by the following examples. In the examples, chamotte containing iron is used for the formation of two refractory concrete compositions "Mixture A" and "Mixture B" respectively, containing

  or not the poison of the iron catalyst of the invention.

  After casting under the conditions indicated in BS 1902, the samples were subjected to CO resistance tests according to the standard

3S 1902-310: 1981 and ASTM C 288/78.

Example 1

  Natural clays are calcined or

  sintered at a relatively high temperature to eliminate

  combined water and to densify the chamotte obtained

  so that it is suitable for the manufacture of

  dense refractory bricks or recycled concrete

  dense fractaries. Iron compounds are contagious

  common minerals in raw clay, and in many

  in many cases, the calcination temperature of the clay

  is insufficient to turn all iron into silicon

  Inactive iron cate. The addition of 0.3% sulfur flower to react with iron, forming iron sulphide, has a marked effect on the CO resistance of

  refractory bricks made from the chamotte.

  Calcined Chamomile Blend Ii Alumina Cement Sulfur Chemical Composition S io2 Al2O3 Fe2O3 TiO2 CaO MgO Alkali S Co-Assay -1.40 + 3.96mm 3.96mm 3.32mm%%%% Blend B by weight 30% by weight "i 45%" I "5%" l

"20%"

+ 0.3% "

than

42.1% "

48.7% "

0.6% "

1.83% "

6.17% "

O, 11% "

0.19%

  carbon deposition after 2 hours. After 40 hours. camplete disintegration.

42.1% "

48.7% "

0.6% "

1.83% "

6.17% "

O, 11% "

0.19% "

+ 0.3% "

After hours,

: no dice

handover

bone nor disintegration

Example 2

  During crushing and fine grinding with balls in conventional crushers and grinders, up to 0.25% Fe can be fixed

  by generally abrasive refractory materials.

  Andalusite contains minerals containing natural iron, but generally has some

CO resistance.

  Fine grinding releases the iron-containing minerals from the material, but it also contaminates the latter with metallic iron. The addition of 0.3% of

  S confers on a mixture of refractory concrete a resistance

total CO.

  Andalousite -2,36 + 3,96 n "1,08 mm" il 3,33 mm Aluminous cement Sulfur Chemical composition SiO2 Al2O3 Fe2O3 TiO2 CaO MgO alkali S Coil test Mixture A Mixture B _26% by weight 26% _- by weight 46% by weight 46% by weight 4613% by weight 4613% by weight% by weight 15% by weight - + 0.3% by weight + 0.3% by weight

29.5% "29.5%"

62.3% "62.3%"

0.7% "0.7%"

0.12% "0.12%"

6.49% "6.49%"

0.49% "0.49%"

0.16% "0.16%"

- 0.3% "

  Carbon deposit No deposit of

after 2 hours. carbon.

After 100 hours: No disintegration

  disintegration gration at the complete end of 200 h.

Example 3

  It is well known that, in order to obtain a

  maximum resistance to CO in refractory concrete, the

  Alumina should be low in iron content.

  tal, and in particular of low iron

  than. Many refractory aluminous cements, especially for low temperature applications, have a high iron content, for example cement

  Well-known fade contains about 16% Fe203. AIN-

  if, even for low temperature applications in which CO is present, a low refractory, white refractory aluminous cement should be used

iron more expensive.

  In this example, it is shown that the invention

  allows the use of the cheaper high iron content cement in CO-resistant mixtures if at least a stoichiometric amount of sulfur

  is added to the mixture to allow the poisoning

  iron as a catalyst for the CO reaction.

  os05 Blend A Blend B Chamotte -1.40 + 3.96mm 3.96-0 mm 3.33mm Molten Cement Sulfur Flower Chemical Composition Sio2 A1203 Fe203 TiO2 CaO MgO Alkali S CO Test

________________________________

% by weight 30% by weight

% "I 45%" I

% n 5% "

% "20%"

- + 0.6% "

  41.0% 42.0% 4.66% 1.55%, 30% 0.3% 0.4% Deposit from end to end Complete disintegration at 3 hours

"41.0%

"42.0%

"4.66%"

"1.55%

,30%

"0.3%"

  "It 0.4%" + 0.6% arbo- Takes a color

for lh. dark, but

tion satisfies the test

u after 200 hours.

  s. Although the invention has been illustrated by examples referring to clay, andalousite and aluminous cement, it will be appreciated that any

  desired refractory materials can benefit from the pre-

  prevention of attack by the CO according to the invention.

Claims (15)

  1. Refractory material containing iron, characterized in that it contains an additive which acts   as an iron catalyst poison.   2. Refractory material according to the   cation 1, characterized in that the additive is eng.   3. Refractory material according to claim   cation 2, characterized in that the additive is elementary fre.   4. Refractory material according to claim   cation 2, characterized in that the additive is a compound   poses sulfur that reacts with iron and any iron compound that can be reduced to metallic iron   in the presence of CO, to form iron sulphide.   5. Refractory material according to any one   conque of claims 1 to 4, characterized in that   the additive is present in an amount of at least   chiometrically equivalent to iron.   6. Refractory material according to any one   conque of claims 1 to 5, characterized in that   the additive has reacted with iron to poison this last deny as a catalyst.   7. Refractory body comprising a material   refractory according to any of the claims 1 to 6.   8. Refractory body according to claim   7, this body comprising a poured container liner.   The refractory body according to claim 7, said body being shaped prior to use in the form   of container coating element.   10. A method of manufacturing a recycled material   fractary containing iron for use as a refractory body resistant to atmospheres containing CO, characterized in that it comprises the step of adding a catalyst poison to iron to this refractory material. 11. The process of claim 10   characterized in that sulfur is added as a its iron catalyst.   12. The process of claim 11   characterized in that elemental sulfur is added to refractory materials.   13. The process of claim 11   characterized in that a sulfur compound which is reacted   against iron and any iron compound that can be reduced to metallic iron in the presence   of CO, is added to the refractory material.   14. Process according to any one of   Claims 10 to 13, characterized in that a quantity   of the additive at least stoichiometrically equivalent   slow iron is added to the refractory material.   15. Process according to any one of   10 to 14, characterized in that the material   refractory material is heated to allow the additive to react with the iron to poison the latter as catalyst.