CA1048268A - Stove of blast furnace - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A stove comprises a metal jacket the inner surface of which has a Gunite* coating with a layer of metal or a heat-resistant synthetic material sprayed on the surface of said coating to form a continuous gastight cover. The gas-tight cover is superimposed by heat-insulating and refractory layers. The heat-insulating layer immediately adjacent to the gastight cover is made of kaolin wool which prevents the cover against mechanical damages.

Description

`~ ~

31L~4~2~ 1 `
.
STOYE OF B~AST FURNAC~' ;
1 .~
~e prese~t invention relates to an advanced blast ~urnace and, more precisel~, to stove~ of th~ blast furnace5 -~ he stoves are provided to heat the air which is ~ed into the bla~t ~urnace. ~he temp~rature of blasting at modern blast furnaces reaches as much as 1,~00C, with th~ pressure o~ blasting from 3 to 5 kg/sg.¢m.
~ he stove comprises a~ outer jacket o~ metal sheet a~d a~ inner lining made of heat-insulating and refractory ma- ~
terials. ;
~ he structure and thickness o~ the inn~r lining depend o~ the maximum operating blast temperature and on the most admissible temperature of heatin~ o~' the metal jacket. Normal-1~, the operating temperature of the jacket e~ceeds the am-bie~t temperature by 20~50Cr ~ ~ i Thc inner li~ing i~ not gastlght there~ore water vapour ! -:
and various gases pene~rate through it from the inner work-i~g space of the stove; when reaching the in~er sur~ace of the jacket these gases and vapour are condensed on it in the for~ of solutions of dif~erent acids and alkalies.
Th~ ~ater vapour gets into the u~orking space o~ the stove together with the~air blast and also ~rom the heat~g gas w ~ ch 1" ' ~ ~

~, ,' : ' I :',:

~:

~:^
:~
~;)48;26B
, is consumed ~or heatin~; the lining. During burning o~ the heating gas arl additional amount o~ moisture appears due to the presence of hydrogen in the stovels wor~in~ space.
In addition, not all water evaporates ~rom the lining and mortars used for lining operations during construction and in the period o~ drying and warr~ing-up o~ the stove be~
~ore its commissioning. ~here~ore the remaininp, amount of the moisture penetrates through the lining in the direction of the outer metal àacket and is condensed on it as water.
It is known that ~vater causes cansiderable corrosion o~ steels o~ ~hich the iackets of stoves are usually made. ~he corrosion e~eot o~ water is, however9 intensified by chemical agents which get into the ~orking space of the stove together with the heating gas and air blast, and which are also gene-rated as a result of ga9 burning. For e~ample, alkalies~ chlo-rine and sulphur compounds get into t~e stove.to~ether with j gas, dust a~d.air~ During the burning o~ heating gas, ~hich i is taking place wlth the excess o~ air and o~yge~, alkalies, chlorine and sulphur compound~ are bein~ oxidized. Combined ~ il with the condenced water on the inner sur~ace of the metal .
jacket they ~orm a variety o~ corrosive solutiQns, causing .
..
it~ general or local corrosionO Recent obser~ations ha~e shown ~' :
~:

-20 .
.
~ . ~ .
.
:~:

~ ::

that at a high temperature of blasting nitrogen gets oxidized, I
too. The oxidation o~ nitroge~ begins at temperatures o~ ~rom 1,150 to 1~200C, and it goe~ stronger with a ~urther increa5e ~9 in t~e blasting temperature.`In combination with water ~itro-gen oxides ~orm corresponding acids which also cause ge~eral and local corrosion o~ the inner sur~ace o~ the jacket.
Gorrosion can expand over very large areas, practically in all zones o~ the stovo where the tcmperature o~ ~he iacket i9 below the dew point ~or water and the above-mentioned corrOsive solution~. In the points of the jacket where internal stresses are high the processes of corrosion proceed especial-,ly rapidly (in the stress concentrators within regions of weld :
seams, as well as in places where the jacket deviates ~rom ~:
its right geometrical shapej. Intercristalline corrosio~ which give-~ rise to a rapid fracturing a~d cracking in the metal ¦ :
jacket is ~aki~g place under a simultaneous impact of the cor~
rosive medium and high lnternal stresses complemented by a !
cyclic nature o~ loads brouy;ht about by special ~eatures of the stove operation in varied blasting and heatin~ conditio~s~
Several techniques are known to pxevent damages caused ~
by corrosion~ e.gO ~ the painting or metallization o~ the i~ner .
sur~aGe of the metal jacket9 the use of jackets made o~ acid- I ;
a~d-alkali-resista~t steels, an i~crease i~ the temperature ' of the jacket over the value of the dew point of potential .
.

~:

, ,, -`- 1 ' ;
.. .. . , : ,, , ,- , , , . ~ ' ~

32~
condensates, etc. However, all of them are either insufficient ly reliable or unjustifiably expensive. Recently it has become a common practice to shotcreate the inner surface of the metal jackets of stoves with a special compound (a mixkure of mortar, cement, and asbestite with watar) over a metal gauze secured to the jacket. The term "to shotcreate" means to apply a concrete layer on a surface with the help of a concrete gun. Asbestos article, such as asbestos board, cord and the like, are commonly known. If asbestos is formed into light-weight fibres (powder), instead of an article, it is called "asbestite". The thickness of Gunite* coating is in the range of 60-100 mm, and it has a sufficiently good adhesion to the metal jacket and does not crack in the process of operation~
The applying of Gunite* coating on the inner surface of the jacket undoubtedly slows down the propagation rate of corrosion and at the same time reliably protects the jacket from being overheated when there emerge local defects in the lining. Gunite* coatings are applied as a continuous layer, as a rule, in the stoves' zones with high temperatures. However, in case of a high pressure of the air blast (up till 5 kg/sq. cm), a Gunite* coating which has considerable porosity cannot be regarded as a sufficient protection against the penetration of some amount of water vapour and corrosive elements to the inner surface of the metal jacket.
One of the further relatively simple and sufficiently effective methods of protection against corrosion is the pro-vision of a gastight cover in the form of metal or heat-resist-* - Trade mark ::
.

~48~68 ,1 snt ~ynthetic foil between the heat-in~ulating layera o~ the ~ g. Such a foil cover works at temperatures over 180-200C, iOe~ ~ higher thaG the dew point of corrosive vapour and, whils it preYents the corrosiYe conde~sates from penetrating to the iacket, it, thus, protects itself from corrosion9 as w~ll.
A shortcoming o~ ~uch a design lies in the fact that tbe foil cover is composed of separate sheets which must be glued to~ather to provide desired gastightness. This is a ~ery delicate a~d time-consuming job~ as the ~i~est sheets ,-o~ foil uhich must be glued together o~ an area of 1,500

-2,000 sq,m. during the construction o~ one stove should be handled with the greatest care. Practically, the integrity o~
these foil sheets can be damaged even duri~g the erectio~ of the stove. ~here is also a possibility for untight glue joi~ts.
~11 this substantiall~ reduces the ~astig~tness o~ the foil !
.- i cover and, conseque~tly, the reliabilit~ o~ jacket protec-tionc -I ;-Besides, due to temperature moveme~ts in the hot lining, some ~ ~
., ruptures may occur i~ the ~oil cover during the operatio~ pro- ~
cess. ~he e~pedlenc~ o~ compensators in the form o~ folds a~d ;
corrugations o~ the foil sheets is dubious takin~ account of signi~ioa~t radiaL compresaive stresses (~rom 2 to 7 kg~/sq.cm).
acting betwee~ all layers of the li~ing. This leads to a crump-, .
lin~ of ~olds and corrugations,and 9 as the foil will be tig~t ;~ ~
_~ . ' ' : :.~
~:

.

, .
I

..
- . .. - . . .. .

8Z6~
ly pinched between the heat-inswlating layers, this can result in breaking the foil sheets. Thus, the provision of compensat-ors practically gives no advantages.
The object of the invention is the creation of such a stove of the blast furnace wherein a more reliable protection of the jacket from the impact of corrosive condensates be ensured Another object of the present invention is to make the design of the gastight cover simpler and chea~er.
These and other objects and advantages are achieved by the fact that in the stove of the blast furnace with a metal jacket and inner lining which comprises a Gunite* coating, heat- ~-insulating la~ers with a gastight cover, placed over one of the heat-insulating layers, and refractory layers said gas tight cover, accordlng to the invention, is provided in the form of a layer of a metal or heat-resistant synthetic material sprayed on the surface of the Gunite* coating.
Such a design of the gastight cover makes it possible to more reliably protect the metal jacket from water vapour and gases which penetrate from the working space of the stove to the metal jacket through the lining. Thanks to this, the carrying capacity of the metal jacket is preserved for a longer peri~d.
The thickness of the Gunite* coating is chosen so that * - Trade mark .. . . ... . .

the gastight cover sprayed on its surface should work in a zone of temperatures higher than the dew point of corrosive vapour. In order to prevent any possibility of mechanically breaking the integrity of the gastight sprayed cover it is highly expedient to place a layer of an elastic, soft, heat-insulating and readily-strained material, for instance, kaolin wood, over the sprayed layer which, in the process of its forma- ;
tion, is densely connected with the surface of the Gunite*
coating, closing all its surface pores.
The invention will further be explained by a particular embodiment thereof, with reference to the acaompanying draw-ings, wherein:
Figure 1 shows the scheme of the stove (longitudinal section);
Figure 2 - unit A in Figure 1.
A stove 1 denoted as a whole (Fig. 1) comprises an outer metal jacket 1~ and an inner lining 2 0 Said stove 1 com~
prises a combustion chamber 3, a checkerwork chamber 4 and a dome 5 common for them. The burning of heating gas occurs in the com-bustion chamber 3, as a result of which porous refractoryblocks 6 ~illing said checkerwork chamber 4 are heatedO As Fig. 2 shows, said lining 2 comprises a Gunite* coating 7 which is a mixture of refractory mortar, asbestite and cement with * - Trade mark wa-ter. Said Gunite* coating 7 is applied on a metal gauze (not shown) secured to the inner surface of said metal ~acket 1'. A gastight cover 8 in the form of a continuous sprayed layer of metal or a synthetic material is provided on the inner surface of said Gunite* coating 7, perfectly repeating the shape of this surface.
Aluminium, æinc or a synthetic material, e.g., silicone compounds of the type of heatproof enamels are, for example, used as materials for spraying. I~ese materials are applied on the surface of the Gunite* coating by means of devices of the known design for electric-arc or gas-plasma metallization or with the help of usual paint-sprayers in 3-4 operations.
The thickness of the layer which is sprayed in one operation is from 60 to 80~u.
~ .;
- The gastight cover 8 is followed by a layer 9 made ofan elastic, soft, readily-strained heat-insulating material, for example, of kaolin wool, over which there are several layers of refractory materials 10 made, for instance, of refractory `
brick. The composition o~ kaolin wool încludes A1203 and SiO
In the operating condition "heating" the refractory ; blocks 6 positioned in said checkerwork chamber 4 are heated `~
as a result of the burning of heating ga~ in said combustion chamber 3. In the operating condition "blasting" -the air pass~

~.
'~

* - Trade mark ':~

~g~4~3~61~
ing through the checkerwork chamber 4 1-akes the heat from the ~;
refractory blocks 6 and is fed in a heated state into the blast `;;
furnace. Under both operating conditions of said stove l the vapour of water, gases and dust particles penetrate, through said lining 2, to said gastight layer 8 which, thanks to an appropriate selection of the thickness of the Gunite* coating ;~
7 and said layer 9 is in the range of temperatures from 180C ~, to 300C. Thus, the vapour and gases do not cool down below 180C, that is, below the dew point and are not able to reach the cooler zone of said jacket l~. The gastight layer 8 ~hich, in the process of its formation, is densely connected with the ~ :
: surface of the Gunita* coating 7 and closes all its surface - ~ :
pores is a continuous layer and has no seams (including glue ;~ ~-~ ones) on the entire protected surface of the stove l. The sur~
; face of said Gunite* coating 7 to be metallized does not require :.
preliminary preparation, but in the process of metallization it must be protected against precipitation and must have a temperature not lower than minus 5C.
The spraying of the gastight layer which forms the 20 cover-8 with silicone compounds of the type of heatproof enamels is carried out with the help of usual paint-sprayers, with the temperature of the ambient air being higher than 0C and re-;. ~.
lative humidity not higher than 80%. The surface of the Gunite*

' '`; -~;.''' ;. ~ .: .

' ~
* - Trade mark , `::~
'`' ~"~
~4 ~9~

:

~3 48 i~ !
, ~,,' coating 7 neither ne~ds pr~ inary prepara~ion. The thickness 1 o~ the sprayed gastight layer 8 depends on the valu~ o~ the sur-plus pressure of the air blast. Sa~d layer 9 ~ade o~ an ela~tic, .
so~t and readily-strained ma-terial, for e~ample, o~ kaolin ~ool reliably protects the gastî~ht layer 8 Prom ~echanical damagas both in the procass o~ the electron o~ the re~ractory lining and i~ th~ process of the operation of said stove 1~
~ husy a more reliable protect~on of the inner su~ace of said metal aacket 1' a~ainst the impact of corrosive condensat-es is e~surea.

. .

~ ~ .
!
:
, -10- ' ' j ~ , ~
' ; :::

~ C;~

, . ; . . .

Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A stove of a blast furnace with a metal jacket and an inner lining which comprises: a Gunite*coating on an inner surface of said jacket; a gastight cover in the form of a layer sprayed on the surface of said Gunite* coating, this layer is chosen from a group consisting of metal or a heatproof synthetic material, heat-insulating layers adjacent to said gastight cover from the inner side of the stove; refractory layers positioned over said heat-insulating layers from the inner side of the stove.

2. A stove of the blast furnace as of claim 1 wherein the heat-insulating layer immediately adjacent to the gastight cover is made of a soft elastic material.

3. A stove of the blast furnace as of claim 2 wherein the heat-insulating layer immediately adjacent to the gastight cover is made of kaolin wool.