Heating – Work chamber having heating means – Combustion products heat work by contact
Reexamination Certificate
2001-07-27
2003-10-07
Wilson, Gregory (Department: 3749)
Heating
Work chamber having heating means
Combustion products heat work by contact
C432S138000, C075S477000
Reexamination Certificate
active
06629839
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a technique for charging raw materials, carbonaceous materials, and the like into a moving hearth furnace. More particularly, this invention relates to a material charging method and apparatus for use in a moving hearth furnace wherein raw materials comprising metal-containing materials such as ores containing metals, e.g., Fe, Cr and Ni, iron manufacturing dust and sludge, and industrial wastes (collectively sometimes hereinafter referred to as a “raw material”), are charged/deposited on a moving hearth along with carbonaceous materials comprising solid reductants such as coal, coal char, and coke (collectively sometimes hereinafter referred to as a “carbonaceous material”), and then the deposited raw material is heated for reduction and melting during movement of the moving hearth within a heating furnace, thereby recovering reduced metals continuously. The method and apparatus of the invention reliably and easily performs production, separation and discharge of reduced metals after melting.
2. Description of the Related Art
A reduced metal, e.g., steel, is generally produced by a converter or an electric furnace. According to the process using an electric furnace, scrap and reduced iron are melted under heating with electric energy and then refined, if necessary, for production of steel. Recently, however, there is a tendency to employ reduced iron instead of scrap because of a stringent relation between demand and supply of scrap and an increasing demand for higher quality steel.
As one of the processes for producing reduced iron, etc., the so-called “moving hearth furnace” is known in which an iron ore and a solid reductant are charged/deposited on a horizontally moving hearth, and the iron ore is heated for reduction by radiant heating from above, thereby producing reduced iron (Japanese Unexamined Patent Publication No. 63-108188). The moving hearth furnace used in the above known process is of the type that the charged and deposited raw material is heated during horizontal movement of a hearth within a heating furnace. Usually, the horizontally moving hearth is constructed to move along a ring-shaped locus (i.e., to make a revolution) as shown in FIG.
1
.
A rotary hearth furnace will be described below as one example of moving hearth furnaces.
As shown in
FIG. 1
, a conventional rotary hearth furnace has a ring-shaped furnace body
10
partitioned into a preheating zone
10
a
, a reducing zone
10
b
and a cooling zone
10
d
, which are arranged in that order from the supply side of raw materials toward the discharge side. Within the furnace body
10
, a ring-shaped moving hearth
11
is disposed to be able to rotate. A mixture of a raw material, e.g., iron ore, and a carbonaceous material serving as a solid reductant is charged onto the moving hearth
11
under rotation.
It is to be noted that raw material pellets including carbonaceous materials therein are suitably used as the mixture of both the materials. A refractory is placed on the surface of the hearth
11
, but a particulate refractory, for example, may be laid on the hearth surface. Burners
13
are disposed in an upper portion of the furnace body
10
. By using the burners
13
as heat sources, metal-containing oxides, such as iron ores, deposited on the moving hearth
11
are heated for reduction in the presence of reductant, thereby obtaining reduced iron. Additionally, in
FIG. 1
, numeral
14
denotes a charging apparatus for charging the raw material onto the hearth, and numeral
15
denotes a discharging apparatus for discharging the reduced material.
Meanwhile, general metal-containing materials, e.g., iron ores, contain many gangue components which are different depending on the places of their production, whereas coal, coal char, and coke as typical solid reductants also contain ashes. In the moving hearth furnace, gangues are unavoidably mixed in the reduced iron having been produced, and ashes contained in the reductants also remain affixed to the reduced iron. This has imposed restrictions that only those raw materials and solid reductants having high-grade quality must be employed in the moving hearth furnace.
Further, if reduced iron containing gangues and ash in large amounts is introduced as a raw material to an electric furnace, the amount of lime to be used for adjustment of the basicity of slag must be increased in the operation of the electric furnace. This necessarily increases not only the cost due to an increase in the amount of lime used, but also the amount of consumed energy, e.g., electric power, due to an increase in the amount of heat required for removing the lime in the form of slag. From that point of view, it has also been essential in the operation of a conventional moving hearth furnace to use only high-grade iron ores containing gangue components as small as possible, and to use reductants containing ashes in smaller amount.
Recently, however, the use of lower-grade materials has been obliged due to exhaustion of resources, such as iron ore and coal, and changes in properties thereof. Thus, this situation has created a problem to be solved as quickly as possible.
Because of those reasons including the necessity of using higher-grade raw materials and carbonaceous materials, there has been a need for development of techniques capable of effectively separating metal components and gangue and other unnecessary components from each other. For example, one method for separating metal components and gangue and other unnecessary components is melting separation of gangues and ash from reduced iron, the separated gangues and ash being treated to turn to slag for removal.
Melting reduced iron on the hearth, however, causes the problem that the melted metal adheres by fusion to the hearth refractory or enters fine cracks or the like and, hence, damages the hearth refractory when the solidified metal is discharged. In particular, because the interior of the moving hearth furnace is subjected to fairly high temperatures for ore reduction, an expensive refractory capable of enduring high temperatures is employed to form the hearth. From the viewpoint of suppressing the production cost of products, therefore, due consideration must be paid so that the hearth refractory will not be damaged for a long period of time.
To overcome the above-mentioned problems, the assignee of this application proposed, in Japanese Unexamined Patent Publication No. 11-106815, “A method of operating a moving hearth furnace, in which a raw material mainly consisting of a powdery iron ore and a powdery solid reductant is deposited on a horizontally moving hearth to form a layer, and the iron ore is reduced by radiant heating from above within the furnace, the method comprising the steps of depositing a powder mixture of the powdery iron ore and the powdery solid reductant, or a powder mixture of the powdery iron ore, a powdery assistant raw material and the powdery solid reductant on the hearth in the form of scattered small divisions such that the powdery mixture will not be brought into direct contact with the hearth by the presence of the powdery solid reductant therebetween, and then melting reduced iron on the hearth at least once.” With those features, the proposed method is intended to “produce reduced iron containing neither gangues nor ash mixed therein, i.e., reduced iron highly suitably used in an electric furnace, while employing a simple installation and ensuring smooth operation without damaging the installation”.
However, Japanese Unexamined Patent Publication No. 11-106815 does not specifically describe a method for charging the raw material in the form of small divisions scattered in the carbonaceous material as illustrated in
FIGS. 3
,
5
,
6
and
7
thereof. An intricate process is used to achieve the method for properly charging the raw material in each recess of the carbonaceous material such that the raw material will not come out from the recess and will be kept from mixing with the raw materials charge
Ozawa Tatsuya
Sawa Yoshitaka
Yamamoto Tetsuya
Kawasaki Steel Corporation
Piper Rudnick LLP
Wilson Gregory
LandOfFree
Method and apparatus for charging raw and carbonaceous... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for charging raw and carbonaceous..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for charging raw and carbonaceous... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3132976