Patent Grant
8690987
This is a §371 of International Application No. PCT/JP2010/063143, with an international filing date of Jul. 28, 2010 (WO 2011/018964 A1, published Feb. 17, 2011), which is based on Japanese Patent Application Nos. 2009-185410, filed Aug. 10, 2009, and 2010-167786, filed Jul. 27, 2010, the subject matter of which is incorporated by reference.
This disclosure relates to a method and an apparatus for producing carbon iron composite (ferrocoke) in which a formed product of a carbon-containing substance and an iron-containing substance is continuously carbonized in a vertical carbonization furnace to produce metallic iron in coke.
Metallurgical coke produced by coal carbonized in a coke oven is generally used in the operation of a blast furnace. In recent years, from the viewpoint of improving the reactivity of coke, there has been known a technique for using metallurgical carbon iron composite produced by carbonizing a mixture of coal and iron ore in the operation of a blast furnace. Carbon iron composite can increase the CO2 reactivity of coke in the carbon iron composite by the catalytic effect of reduced iron ore and can decrease the percentage of a reducing material as a result of a decrease in thermal reserve zone temperature.
Studies have been carried out on a technique for carbonizing a carbon-containing substance such as coal, and an iron-containing substance such as iron ore, in a common chamber coke oven to produce carbon iron composite, for example, a) a method for feeding a mixture of coal and iron ore fines into a chamber coke oven or b) a method for cold-forming coal and iron ore at room temperature and feeding the formed product into a chamber coke oven (see, for example, Fuel Society of Japan, “Kokusu Gijutsu Nenpou (annual report on coke technology),” 1958, p. 38).
However, since conventional coke ovens are constructed of silica stone bricks, iron ore in a chamber coke oven can react with the main component of the silica stone bricks, silica, to form low-melting-point fayalite, causing damage to the silica stone bricks. Thus, a technique for producing carbon iron composite in a chamber coke oven has not been industrially employed.
As a substitute for a method for producing coke in a chamber oven, a method for continuously producing formed coke has been developed. In the method for continuously producing formed coke, a vertical shaft furnace constructed of chamotte bricks in place of silica stone bricks is used as a carbonization furnace. Coal is cold-formed in a predetermined size and fed into a vertical shaft furnace. The briquettes are carbonized by heating with a circulating heating gas to produce formed coke. It has been demonstrated that coke having a strength comparable to that of coke produced with a conventional coke oven can be produced even by using a large amount of naturally abundant and inexpensive non- or slightly-caking coal.
One known method for continuously producing formed coke is characterized in that a top gas of a vertical carbonization furnace is utilized as a coolant gas into a lower portion of a cooling chamber directly coupled to a carbonization chamber of the vertical carbonization furnace. Most of the gas passing through the cooling chamber is exhausted from an upper portion of the cooling chamber and supplied as a heating gas to an inlet in an intermediate portion of the carbonization furnace (see, for example, Japanese Examined Patent Application Publication No. 56-47234). This method requires three gas inlets (an intermediate portion of the carbonization chamber, a lower portion of the carbonization chamber, and a lower portion of the cooling chamber) and one gas outlet (an upper portion of the cooling chamber), which makes the equipment complicated. Sensible heat generated by the cooling of high-temperature coke after carbonization is recovered with a gas and reused by supplying the heat to an intermediate portion of the carbonization furnace. However, there is a problem of heat loss. To simplify the equipment, another method for producing formed coke is disclosed which does not require the removal of gas from an intermediate portion of a vertical carbonization furnace (see Japanese Unexamined Patent Application Publication No. 52-23107). In accordance with that method, coke after carbonization is cooled in a water tank instead of using a gas. One of characteristics of carbon iron composite is that iron ore can be reduced to metallic iron during carbonization, and its catalytic effect can increase reactivity. A water cooling method may cause reoxidation of metallic iron and therefore cannot be employed for the production of carbon iron composite.
As described above, chamber coke ovens constructed of silica stone bricks are difficult to use in the production of carbon iron composite. It is therefore desirable to use a vertical carbonization furnace having multiple tuyeres using the same type of gas as in formed coke as a heating medium, for example, a vertical shaft furnace constructed of chamotte bricks. However, considering the use of a vertical continuous carbonization furnace having a cooling function, a conventional carbonization furnace for formed coke requires gas removal at some point of the furnace which makes the equipment complicated. Furthermore, carbon iron composite requires the reduction of an iron-containing substance. Thus, a conventional method for producing formed coke cannot be directly used for carbon iron composite. The operational specifications such as gas distribution in tuyeres must be reconsidered. Furthermore, energy conservation cannot be avoided in future iron-manufacturing processes, necessitating a design concept of minimizing energy required for the production of carbon iron composite.
Accordingly, it could be helpful to provide a method and an apparatus for producing carbon iron composite in which production of metallurgical carbon iron composite with a vertical carbonization furnace can be performed with simplified equipment with decreased energy consumption.
We thus provide:
(1) A method for producing carbon iron composite, including the steps of:
Carbon iron composite can be continuously produced with simplified equipment with decreased energy consumption. Thus, reactive carbon iron composite can be used in the operation of a blast furnace, thereby effectively decreasing the percentage of a reducing material.
As described above, we concluded that vertical continuous carbonization furnaces having a cooling function are more suitable for production of carbon iron composite than chamber coke ovens. As illustrated in
Thus, in production of carbon iron composite containing metallic iron by continuously carbonizing a formed product of a carbon-containing substance and an iron-containing substance in a vertical carbonization furnace to produce metallic iron in coke, we employ simplified equipment to produce carbon iron composite in which an upper portion of the vertical carbonization furnace serves as a carbonization zone, a lower portion serves as a cooling zone, a heating medium gas is supplied from three points, that is, an intermediate portion and a lower portion of the carbonization zone and a lower portion of the cooling zone, a furnace gas is exhausted only through a top portion, and thereby a coolant-gas-removal tuyere installed in production of formed coke is eliminated.
In
In production of carbon iron composite, a formed product of a carbon-containing substance and an iron-containing substance is fed with a formed product feeder 1 from the top portion of the vertical carbonization furnace main body 2, carbonized in the carbonization zone, cooled in the cooling zone, and discharged from the lower portion. A heating gas for the carbonization of the formed product is blown into the furnace through the low-temperature-gas-blowing tuyere 5 and the high-temperature-gas-blowing tuyere 6. The gas blown into the furnace through the high-temperature-gas-blowing tuyere 6 has a higher temperature than the gas blown into the furnace through the low-temperature-gas-blowing tuyere 5. A coolant gas for cooling carbon iron composite is blown into the furnace through the coolant-gas-blowing tuyere 9. The gas blown into the furnace is exhausted only through the furnace gas outlet in the top portion.
The furnace gas exhausted only from the top portion is cooled in circulating gas coolers 3 and 4. Part of the exhausted furnace gas is heated in a low-temperature gas heater 7 and blown into the furnace through the low-temperature-gas-blowing tuyere 5. Another part of the exhausted furnace gas is heated in a high-temperature gas heater 8 and blown into the furnace through the high-temperature-gas-blowing tuyere 6. The remainder of the exhausted furnace gas is blown into the furnace through the coolant-gas-blowing tuyere 9.
A formed product of a carbon-containing substance and an iron-containing substance is continuously carbonized to produce carbon iron composite in the vertical carbonization furnace having the three tuyeres disposed at different heights and no gas outlet other than the gas outlet in the top portion while a low-temperature gas is blown into the furnace through the tuyere disposed in the intermediate portion of the carbonization zone, a high-temperature gas is blown into the furnace through the tuyere disposed in the lower portion of the carbonization zone, and a coolant gas is blown into the furnace through the tuyere disposed in the lower portion of the cooling zone. Production of carbon iron composite in this manner can decrease the amount of heat required to produce carbon iron composite.
The low-temperature gas blown into the furnace through the low-temperature-gas-blowing tuyere 5 is blown to control the top gas temperature and the heating rate of the solid in the carbonization furnace and preferably has a temperature of approximately 400° C. to 700° C. The high-temperature gas blown into the furnace through the high-temperature-gas-blowing tuyere 6 is blown to heat the solid to the maximum temperature and preferably has a temperature of approximately 800° C. to 1000° C. The coolant gas blown into the furnace through the coolant-gas-blowing tuyere 9 is blown to cool carbon iron composite produced by carbonization in the furnace and preferably has a temperature of approximately 25° C. to 80° C.
The circumstances leading up to our methods and apparatus will be described in detail below. In the following description, the carbon-containing substance is a carbon material, coal, and the iron-containing substance is iron ore (ore).
In producing carbon iron composite, not only carbonization of coal, but also reduction of ore therein require heat. Thus, the operational specifications for production of formed coke cannot be employed without modification. The operational specifications for a vertical carbonization furnace in producing carbon iron composite were examined on the basis of studies on the basic characteristics of carbonization and reduction and simulation for a carbonization furnace based on the studies.
First, as basic characteristics, reduction behavior of iron ore was examined in the carbonization process of a formed product. Reduction of iron oxide in producing carbon iron composite can be broadly divided into direct reduction with solid carbon (see the following formula (1)) and gas reduction with CO gas and H2 gas generated from coal (see the following formulae (2) and (3)):
Fe2O3+3C→2Fe+3CO-ΔH298=−676.1 (kcal/kg-Fe2O3) (1)
Fe2O3+3H2→2Fe+3H2O-ΔH298=−142.5 (kcal/kg-Fe2O3) (2)
Fe2O3+3CO→2Fe+3CO2−ΔH298=+42.0 (kcal/kg-Fe2O3) (3).
Direct reduction of the formula (1) involves a highly endothermic reaction.
A formed product of coal and iron ore was carbonized in a small batch furnace while N2 flowed. The type of reduction was determined on the basis of the composition of exhaust gases.
The temperature distribution of the furnace was estimated using a one-dimensional numerical formula model on the basis of the relationship shown in
In
In
In the case of the conventional equipment having the coolant-gas-removal tuyere 10 illustrated in
Table 1 shows the ratio of the gas flow rate of the low-temperature-gas-blowing tuyere to the gas flow rate of the high-temperature-gas-blowing tuyere to produce formed coke with the conventional equipment as described in JP '234 illustrated in
The amount of gas through the high-temperature tuyere is higher in producing carbon iron composite than in producing formed coke. This is because production of carbon iron composite requires a larger amount of heat in the high-temperature portion than production of formed coke because of reduction of ore. This clearly shows that even with the same vertical furnace the operational designs for producing conventional formed coke and producing carbon iron composite must be different.
The example described above considers the reuse (blowing into the furnace through each tuyere) of the top gas temporarily cooled to the vicinity of normal temperature. We prefer to circulate a gas exhausted from the vertical carbonization furnace. The top gas blown into the high-temperature-gas-blowing tuyere and the low-temperature-gas-blowing tuyere must therefore be heated to a predetermined temperature. This heating requires partial combustion of the top gas or combustion of fuel such as LNG, supplied from the outside. This process requires energy. Table 2 shows the sensible heat of gas blown through a tuyere in the presence or absence of the coolant-gas-removal tuyere illustrated in
Energy corresponding to the sensible heat shown in Table 2 must be supplied from the outside. In both cases, the high-temperature gas is the top gas cooled to 35° C. and then heated in the outside of the furnace. In the absence of the coolant-gas-removal tuyere as illustrated in
In the case of a known vertical carbonization furnace used in a method for continuously producing formed coke in which a coolant gas is removed, a technique for producing carbon iron composite is also disclosed (see Japanese Unexamined Patent Application Publication No. 6-65579). However, blowing conditions and energy supplied are not specified. Our method for decreasing energy required for producing carbon iron composite was found as a result of examination of a difference in equipment structure, more specifically, the presence or absence of the coolant-gas-removal tuyere. Thus, our apparatus cannot be deduced from equipment structures having a coolant-gas-removal tuyere.
The test production of carbon iron composite was performed with a test apparatus for producing carbon iron composite illustrated in
Table 3 shows the operational specifications for an carbon iron composite production volume of 50 t/d. The target carbonization temperature ranged from 800° C. to 950° C., and the temperature of a high-temperature blast from a high-temperature-gas-blowing tuyere was altered. The carbonization temperature is the mean value of temperatures measured during the operation at heights of 0.1 and 1 m with respect to the high-temperature tuyere. Table 3 also shows the reduction rate of iron and percentage of metallization in carbonized carbon iron composite measured for each condition.
At a carbonization temperature of 800° C. or more, the reduction rate is 40%, and the percentage of metallization is more than 25%, indicating that iron ore in the carbon iron composite is reduced to form metallic iron.
Regardless of the presence or absence of the coolant-gas-removal tuyere 10, carbon iron composite thus produced had a target strength without any problem in the production. Table 4 shows the amount of heat required to increase the temperature of gases blown through the low-temperature-gas-blowing tuyere and the high-temperature-gas-blowing tuyere for each condition. The definition is the same as described above, that is, the sensible heat of gas blown through each tuyere with respect to 35° C.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-185410 | Aug 2009 | JP | national |
| 2010-167786 | Jul 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/063143 | 7/28/2010 | WO | 00 | 5/1/2012 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2011/018964 | 2/17/2011 | WO | A |
| Number | Date | Country |
|---|---|---|
| 52-023102 | Feb 1977 | JP |
| 52-023107 | Feb 1977 | JP |
| 54 062203 | May 1979 | JP |
| 6-065579 | Mar 1994 | JP |
| 7 188667 | Jul 1995 | JP |
| 2004359718 | Dec 2004 | JP |
| 4078771 | Apr 2008 | JP |
| 4218426 | Feb 2009 | JP |
| 2010 202838 | Sep 2010 | JP |
| 2011122535 | Oct 2011 | WO |
| Entry |
|---|
| Machine translation of JP 2004-359718 by Okada et al, published Dec. 24, 2004. |
| “Kokusu Gijutsu Nenpou (annual report on coke technology),” Fuel Society of Japan, 1958, cover and index and pp. 35-41 (1 page of partial English translation). |
| Anyashiki, T. et al.,“Development of Carbon Iron Composite Process,” JFE Technical Report, May 1, 2009, pp. 1-6. |
| Number | Date | Country | |
|---|---|---|---|
| 20120204678 A1 | Aug 2012 | US |
