JPH04342401A - Method for reforming gas - Google Patents

Abstract

PURPOSE:To economically maintain a stationary driving condition without stopping a gas reforming device in direct reducing iron production by using part of reducing gas formed by the gas reforming device as a fuel gas of the gas reforming device during the operation of a reducing furnace in suspension. CONSTITUTION:In a gas reforming method wherein a reducing gas obtained from a gas reforming device 1 is fed to a reducing furnace 2 for direct iron production, an iron ore is reduced and a furnace top gas 7 discharged from the reducing furnace 2 for direct iron production is used (7 3 4 26 8) as a fuel gas for the gas reforming device 1, during the operaiton of the reducing furnace 2 in the suspension, the reducing gas obtained from the gas reforming device 1 is partially used (6 23 21 25 34 8) as the fuel gas of the gas reforming device 1.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a gas reforming method for obtaining reducing gas when implementing a direct reduction iron manufacturing method, and in particular, the present invention relates to a gas reforming method for obtaining reducing gas when carrying out a direct reduction iron manufacturing method. The present invention relates to a gas reforming method that allows gas reforming to continue in a stable state without causing any damage, etc., and to prepare for a stable supply of reducing gas when restarting operations.

0002

[Prior Art] FIG. 3 is a flowchart illustrating a known direct reduction iron manufacturing method, in which a mixture of hydrocarbon gas and steam is supplied from a line 5 to a gas reformer 1, and a reforming tube filled with a catalyst is A high temperature reducing gas produced by passing through 1a is supplied from line 6 to reduction furnace 2 for direct reduction of iron ore.

The top gas discharged from the top of the reduction furnace 2 is sent from the line 7 to the scrubber 3 for cleaning, cooling, and water removal, and then a part of it is passed from the line 9 to the line 8 for gas reforming. The gas is sent to the device 1 and used as fuel gas, and the remainder is discharged outside the system through the pressure regulating valve 13. Further, as shown in the figure, a part of the furnace top gas can be pressurized by the compressor 4 and then sent from the line 10 to the reducing gas supply line 6, where it can be mixed with the reducing gas and reused.

Furthermore, in the example shown in FIG. 4, even when the operation of the reduction furnace 2 is interrupted, the steady operation of the gas reformer 1 is not stopped, and the reducing gas is discharged outside the system, so that when the operation is restarted, the reduction has a stable composition. A line 23 is branched on the upstream side of the valve 20 provided in the line 6 so that the gas can be supplied immediately, and the gas cooler 2 is connected to the line 23.
1. A line is provided to discharge reducing gas through line 24 and valve 22.

[0005] That is, interrupting the operation of the gas reformer 1 each time the operation of the reduction furnace 2 is interrupted (for example, when iron ore raw material is introduced or when an abnormal situation occurs) is important for the stability of the reformer 1. This is not desirable for maintaining operation, and fluctuations in the composition of the reformed gas cannot be ignored, so even when the operation of the reduction furnace 2 is interrupted, the gas reformer 1 continues to operate steadily and the valve 20 is closed. By closing the valve 22 and opening the valve 22, the reducing gas is extracted from the system. When the operation of the reduction furnace 2 is resumed, the valve 20 is opened and the valve 22 is closed, so that reducing gas having a stable composition can be immediately supplied to the reduction furnace 2.

[0006]

[Problems to be Solved by the Invention] However, the following problems arise in the equipment shown in FIGS. 3 and 4. That is, when the valve 20 is closed to stop the supply of reducing gas to the reduction furnace 2 during an interruption of operation, the top gas discharged from the reduction furnace 2 through the line 7 is stopped, and therefore the top gas is discharged through the line 8 to the gas reformer 1. The top gas that is returned as fuel gas also stops. In addition, when restarting operation thereafter, it is necessary to ignite the top gas (fuel gas) that has been resumed being supplied to the gas reformer 1 to bring it to a steady state, but during this period the unstable operation Problems sometimes arise in that carbon adheres to the inside of the reforming reaction tube, or that the life of the reforming tube is shortened due to repeated sudden changes in the temperature inside the tube each time the operation is interrupted and restarted.

Therefore, as a means to avoid such problems, natural gas is supplied from the outside to the gas reformer 1 when the operation is interrupted.
A method of switching and supplying the fuel as fuel is also considered. However, the calorific value of furnace top gas and natural gas is significantly different (
The calorific value of natural gas is approximately three times that of furnace top gas), and the air-fuel ratio is also significantly different. Therefore, when switching from furnace top gas fuel to natural gas fuel, there may be a shortage or excess of combustion air, or there may be problems near the burner nozzle. Problems such as backfire may occur. Moreover, during this time, the reducing gas produced in the gas reformer 1 is generally dissipated into the atmosphere, so fuel costs increase by the amount of natural gas consumed that is switched to the top gas. , it is uneconomical.

The present invention has been made by focusing on the problems of the prior art as described above, and its purpose is to maintain stable gas reforming equipment without stopping the gas reformer even when the operation of the reduction furnace is interrupted. We have established an economical method that can maintain a steady state of operation, without causing problems such as unfavorable thermal shock or carbon adhesion in the gas reformer, and producing a reducing gas with a stable composition when the reduction furnace resumes operation. The purpose of the present invention is to provide a gas reforming method for direct reduction iron making that can immediately supply .

[0009]

[Means for Solving the Problems] The structure of the gas reforming method according to the present invention that can solve the above problems is to directly supply reducing gas obtained in a gas reformer to a reduction furnace for iron ore production. In a gas reforming method in which stone is reduced and the furnace top gas discharged from the reduction furnace is used as fuel gas for the gas reformer, when the operation of the reduction furnace is interrupted, the gas obtained by the gas reformer is The gist is that a part of the reduced reducing gas is used as fuel gas for the gas reformer.

0010

[Operation] As described above, in the present invention, the gas reformer, which was conventionally discharged outside the system, can be used as an alternative fuel for the top gas fuel, which stops being fed to the gas reformer due to the interruption of operation of the reduction furnace. It uses the reducing gas from the reduction furnace, and the fuel gas for gas reforming is produced by the top gas from the reduction furnace when the reduction furnace is in operation, and by the gas reformer when the operation is interrupted. Reducing gases are used in each case, and a self-sufficiency system for fuel gas for gas reforming can be established within the reduction ironmaking facility throughout the entire period.

[0011] Since the furnace top gas is the exhaust gas that has been used to reduce iron ore in the reduction furnace, its calorific value is naturally higher than that of the reducing gas produced in the gas reformer. low. However, the average composition and calorific value of both are shown in Table 1 (for reference, the average composition and calorific value of natural gas are also shown in Table 1).
), and the difference between the two is extremely small compared to the difference between natural gas and furnace top gas, so even if both are switched and used as gas reforming fuel when the reduction furnace operation is interrupted or restarted. , it does not have a significant effect on the operating status of the gas reformer, and does not cause the problems pointed out when switching to natural gas.

0012

[Table 1]

[0013] As will be described in detail in Examples below, the reducing gas produced in the gas reformer may be supplied as is to the reduction furnace, but if the reducing gas contains a large amount of water (steam). If this occurs, the reduction efficiency in the reduction furnace may be adversely affected, so either the reducing gas is cooled and dried to remove moisture and then reheated, or some of the top gas discharged from the reduction furnace is It is desirable to decarburize the part and reheat it to increase its reducing power, mix it with the reducing gas, and then supply it to the reduction furnace. Hereinafter, the configuration and effects of the present invention will be explained in detail with reference to the drawings.

[0014]

[Example] Fig. 1 is an overall flow diagram illustrating reduction iron manufacturing equipment in which the present invention is implemented.The basic configuration is the same as the conventional example shown in Fig. 4, so the same parts have the same structure. A symbol is attached.

In FIG. 1, during steady operation of the reduction furnace 2, hydrocarbons and steam fed from the line 5 are passed through the reforming tube 1 filled with a reforming catalyst in the gas reformer 1.
a, is reformed by receiving heat from the outside, becomes a reducing gas, and is sent to the reducing furnace 2 from the line 6 via the valve 20. The top gas discharged from the top of the reduction furnace 2 is sent from the line 7 to the scrubber 3 to remove dust and moisture, and then a portion of it is moderately pressurized by the compressor 4.
The fuel gas is sent from the line 8 to the gas reformer 1 via the check valve 26. Further, the remainder of the furnace top gas is discharged outside the system through the flow control valve 13, and is sent to nearby reducing gas demand equipment as the case may be.

On the other hand, when some kind of trouble occurs in the operation of the reduction furnace 2, the valve 20 is immediately closed to interrupt the supply of reducing gas to the reduction furnace 2, and the gas is sent from the line 8 to the gas reformer 1 as fuel gas. As the furnace top gas stops,
The valve 34 is opened and the reducing gas produced in the gas reformer 1 is allowed to flow from the line 6 to the line 23, and the gas cooler 2
After cooling the gas to an appropriate temperature in step 1, it is sent to line 8 through line 25, valve 34, and line 25, and is returned from line 8 to gas reformer 1 as fuel gas. The amount of reducing gas returned as fuel gas is adjusted by adjusting the opening degree of the pressure regulating valve 22, and the remaining reducing gas is discharged to the outside of the system.

[0017] In place of the valve 34, a solenoid valve or the like is used,
Of course, it is also effective to incorporate an automatic control mechanism that automatically opens and closes depending on fluctuations in the back pressure in the line 8, or that closes and opens in synchronization with the opening and closing of the valve 20. Furthermore, when preparations for restarting the operation of the reduction furnace 2 are completed, the valve 20 is opened and the supply of reducing gas to the reduction furnace 2 is resumed. However, immediately after restarting, the furnace top gas has not yet reached the check valve 26. ,
Wait until the furnace top gas pressure in the upstream line of the check valve 26 rises to a predetermined pressure, and then close the valve 34 so that the supply of fuel gas to the gas reformer 1 will not be interrupted. do.

As mentioned above, there is not much difference in calorific value between the furnace top gas and the reducing gas, so even when the above two gases are switched and supplied as fuel gas, there is no thermal shock in the gas reformer 1. There is no risk of such occurrence, thermal deterioration of the gas reforming tube is suppressed, and problems such as carbon adhesion do not occur. Moreover, even when the operation of the reduction furnace is interrupted, fuel gas can be self-sufficient without supplying fuel gas from outside.
It is also extremely advantageous economically.

FIG. 2 shows another embodiment of the present invention, in which a cooling dryer 28 and a reheater 29 are provided in the supply line 6 of the reducing gas produced by the gas reformer 1. After water is removed in the cooling dryer 28 to increase the reducing power, the temperature is raised to a predetermined temperature in the reheater 29 so that it can be fed to the reduction furnace 2, and it can be opened and closed when the operation of the reduction furnace 2 is interrupted. This embodiment is substantially the same as the example shown in FIG. 1, except that a pressure regulating valve 27 is used instead of the valve 34 shown in FIG.

In other words, if the reducing gas produced by the gas reformer 1 has a high water content, the reduction efficiency in the reduction furnace 2 will be adversely affected, so if there is such a possibility, the above It is desirable to provide a cooling dryer 28 and a reheater 29 of various types.

FIG. 3 shows still another embodiment of the present invention, in which top gas discharged during steady operation of the reducing furnace 2 can be re-supplied to the reducing furnace 2 as reducing gas. There is. That is, the exhaust gas line 8 is branched into a line 30 on the upstream side of the check valve 26, and the furnace top gas extracted from the line 30 is passed through a decarbonation gas tower 31 to increase its reducing power, and then heated to a predetermined level by a heater 32. After the temperature has been raised to a certain temperature, it is made to join the reducing gas flowing in the line 6 from the line 33 and is sent to the reduction furnace 2.

[0022] With this configuration, when the amount of furnace top gas sent as fuel gas to the gas reformer 1 is relatively small and the amount of furnace top gas discharged from the pressure control valve 13 to the outside of the system is large, the furnace The advantage is that the top gas can be effectively utilized within the equipment, and the reducing gas generator can be downsized. Also in this figure, when the operation of the reduction furnace 2 is interrupted, the gas cooler 21 and the line 25 are connected to the line 23 branched from the line 6.
The point that the reducing gas is sent to the line 8 via the flow rate control valve 27 and returned as fuel gas to the gas reformer 1 is as shown in FIG.
, 2 is the same as the example.

[0023]

Effects of the Invention The present invention is constructed as described above, and when the operation of the reduction furnace is interrupted, the reducing gas produced by the gas reforming apparatus is used as the fuel for gas reforming. Problems such as thermal shock and carbon adhesion in the reformer can be resolved and stable gas reforming operations can be continued at all times. Moreover, the fuel gas for gas reforming can be self-sufficient within the facility during steady operation and during interruptions of the reduction furnace, and there is no need to replenish fuel from outside, which is extremely advantageous economically.

[Brief explanation of drawings]

FIG. 1 is a flow diagram illustrating a direct reduction iron manufacturing method employing the present invention.

FIG. 2 is a flow diagram illustrating another direct reduction iron manufacturing method employing the present invention.

FIG. 3 is a flow diagram illustrating still another direct reduction iron manufacturing method employing the present invention.

FIG. 4 is a flow diagram illustrating a conventional direct reduction iron manufacturing method.

[Explanation of symbols]

1 Gas reformer 2　Reduction furnace 3 Scrubber 4 Pressurizer 5 Raw material supply line

Claims (1)

[Claims] [Claim 1] Reducing iron ore is carried out by directly supplying reducing gas obtained from a gas reforming device to a reduction furnace for iron-making, and
In a gas reforming method in which the furnace top gas discharged from the direct steelmaking reduction furnace is used as fuel gas for a gas reformer, when the operation of the reduction furnace is interrupted, the reducing gas obtained in the gas reformer is A gas reforming method for direct steelmaking, characterized in that a part of the gas is used as fuel gas for the gas reformer.