KR20100082696A - Process for making iron in a blast furnace and use of top gas resulting from said process - Google Patents

Abstract

PURPOSE: A method for making iron in a blast furnace and a use method of upper gas obtained from said method are provided to enable upper gas after purification to be used directly for a power plant by increasing the heating value of the upper gas and by enabling a user to control the heating value. CONSTITUTION: A method for making iron comprises next steps. Iron ore and cokes are supplied to a blast furnace(1). Air is sent to the bottom of the blast furnace. Fuel is injected into the bottom of the blast furnace. In order to supply heat to molten metal and to produce fritted iron, the cokes and the fuel are burnt by air. The oxygen content of the air is 30~100 volume %. The injected fuel amount is 220~500kg per molten metal ton. The oxygen content of the air is 35~70 volume %. The oxygen is injected by a cold air unit.

Description

Process for producing iron in furnaces and use of top gas obtained from the process

The present invention relates to a method for producing iron in a furnace and a method for using the upper gas of a furnace obtained from this production method as a fuel for a power plant, in particular a combined cycle power plant.

The top gas obtained from traditional furnace processes is a relatively low calorific gas which is in most cases treated and treated as a byproduct. Some of the top gas can be used to heat the hot blast for the furnace, and the remainder is used for applications requiring low calorific value gas but is sometimes burned as waste gas.

However, burning the top gas does not apply in all cases. According to the known method, this low calorific value overhead gas is mixed with a gas having a high calorific value such as natural gas to be suitable for use in a power plant for generating electricity and steam.

According to a recent development, a power plant is for example a coke oven and / or after a cleaning and mixed top gas is supplied to a multi-cycle power plant for producing electricity, in particular a gas turbine designed for low calorific value synthesis gas. Or near the steel mill of Silva Steelworks, Taranto, Italy, mixed with the gas from the oxygen steelmaking furnace. These devices, operating on low calorific gas, are suitable for known integrated gasification combined cycles in which syngas is used for the gasification of coal or waste materials. In all these devices, certain gas turbines are used to design for low calorific gas. Because of the efficiency of the combined cycle technology, it is economically installed in power plants.

It is an object of the present invention to provide a method for producing iron in a furnace with increased iron production by improving productivity.

Another object of the present invention is to provide a method for producing iron in a furnace for obtaining a top gas having a high calorific value.

Another object of the present invention is to provide a method for manufacturing iron in a furnace that can easily control the calorific value of the upper gas.

It is a further object of the present invention to use the top gas as fuel for a power plant, more preferably a combined cycle power plant.

One or more of these purposes

In the iron manufacturing method in the furnace,

Providing iron ore and coke in the furnace,

Blasting at the bottom of the furnace,

Injecting fuel into the bottom of the furnace,

Combusting coke and fuel with a blower to provide heat to the melt and produce molten iron,

The oxygen content of the blow is 30-100% by volume and the amount of fuel injected is achieved by being in the range of 220-500 kg per ton of hot metal.

Increasing the calorific value of the upper gas by injecting oxygen with blowing air of 30-100% by volume and injecting a predetermined amount of fuel at the same time. At the same time, the total tonnage of the produced hot metal is increased. The high calorific value top gas obtained from the production process according to the invention does not need to mix this gas with other gases and can be supplied directly to the combined cycle power plant after purification. In this way, very effective combined operation of the furnace and combined cycle power plant is achieved.

According to another aspect of the present invention, the oxygen content of the blowing is preferably from 30 to 70% by volume, more preferably from 35 to 70% by volume.

The oxygen content of 30% by volume is the lowest content, which is high enough to make it possible to use the top gas in the power plant without mixing this gas with other gases with high calorific value such as natural gas or coke-oven gas. It is possible to produce the upper gas having. For this reason, it is preferable that the lower limit is 35 vol% oxygen content to ensure that the top gas having a high calorific value is generated so that the power plant can be operated without special measurement.

Blowing with a 100% by volume oxygen content produces a top gas with a sufficiently high calorific value, but the furnace process will be inefficient. Too much oxygen in the blow means little or no nitrogen in the blow. Since nitrogen acts as a heat transfer medium for transferring heat from the bottom to the top of the furnace, it is preferable to have a predetermined amount of nitrogen in the blower. Too little nitrogen in the furnace leads to inadequate preheating and pre-reduction material, which in turn reduces the efficiency of the furnace. This heat transfer problem can also be solved by injecting heated gas into the top stack of the furnace to achieve the desired heat balance, but using less than 100% oxygen and achieving sufficient heat transfer by the desired nitrogen content desirable.

According to another aspect of the invention, a portion of the oxygen is injected as a cold blast. Since it is difficult to inject hot air having a very high oxygen content, at least a part of the oxygen can be injected into the cold wind when a high oxygen level is required to realize the upper gas having a predetermined calorific value.

A second feature of the process of the invention is the high proportion of injected fuel. Various fuels of various types, such as coal, gas, oil, etc., injected through a tuyere for injecting hot air into the furnace may be used. In the production method according to the present invention, at least 250 kg of fuel per ton of molten metal is injected to realize a top gas having a desired minimum calorific value. Depending on the fuel quality and the operating environment, the fuel injection ranges from 300-400 kg per tonne of melt or 350-400 kg per tonne. The production method according to the invention focuses on conditions in raceways, flocculation zones and furnace stacks to allow gasification and to effectively use large amounts of fuel in the furnace without letting gas out through the top.

According to another aspect of the invention, burnt lime is injected at the time of manufacture. The injection of quicklime achieves a low liquidus temperature of the primary slag, which results in easier discharge of the slag into the hearth of the furnace, thus reducing the pressure difference in the furnace. Quicklime is infused in an amount of 5-20 kg per tonne of melt.

According to another aspect of the invention, pre-reduced iron fines are injected. The injection of iron leads to a higher calorific value in the upper gas. The injected cold pre-reduced iron requires heat to melt, which is provided by burning hot air and / or oxygen injection with high oxygen content and extra injection fuel. The amount of pre-reduced iron injected is in the range of 20-200 kg per tonne of molten iron, with iron having a minimum metallization of 90%.

The top gas obtained by the production process according to the invention has a sufficient calorific value that can be used directly in the gas turbine of the power plant. Preferably, the top gas is used in the combined cycle power plant to further increase the overall efficiency of the combined process.

In the drawings, the process flow diagram shows a possible realization of a furnace and power plant employing the process of the invention.

The furnace 1 is supplied with coke and iron ore from the material supply 2, hot air is supplied through the blowing system 3 and the blowing heating system 4, and excess oxygen can be supplied from the oxygen plant 5. have. The oxygen plant 5 is equipped with an additional oxygen outlet 9 which is connected to a system for injecting cold air into the furnace so as to realize a highly complex total blowing with a very high oxygen content.

By the fuel injection device 6, fuel is injected into the lower part of the furnace 1 through the tuyeres. The additive injection 7 is also provided by means for injecting quicklime and iron into the furnace 1.

The upper gas discharged into the iron manufacturing process in the furnace 1 is led to a gas purification system 8 having dry and wet purification devices. By the upper pressure recovery turbine, the pressure of the upper gas is also used to generate electricity.

Some of the purified upper gas can be returned to the breeze heating system 4 and used to heat the hot air.

In the gas purification system 8, the top gas is purified and sent to the combined cycle power plant 10. Combined cycle power plant 10 produces electricity and steam.

The operation of the furnace process is adjusted by controlling the injection of oxygen, fuel and additives according to the load of the furnace so that the combined process of the furnace and the combined cycle power plant is optimized. This also depends on the actual power required by the combined cycle power plant.

The energy content of the upper gas is maximized by satisfying a combination of a predetermined specific calorific value (J / m 3) of the upper gas and a predetermined volume (m 3 / tHM) produced at m 3 per ton of melt. This allows for maximum output of combined cycle power plants and the most efficient combined operation of furnaces and combined cycle power plants.

Chemical control of slag basicity is achieved by injected quicklime. This allows a very quick response in situations requiring the stopping of the furnace.

Control of the gas flow in the furnace is achieved by load distribution similar to normal furnace operation.

Thermal control of the furnace is achieved by coal injection by adjusting the heat balance of the raceway.

1 is a process flow diagram illustrating a furnace and a power plant employing the process of the present invention.

* Explanation of symbols for the main parts of the drawings

1: furnace 2: material supply

3: blowing system 4: blowing heating system

5: oxygen plant 6: fuel injection device

7: additive injection 8: gas purification system

9: oxygen outlet 10: combined cycle power plant

Claims (10)

In the iron manufacturing method in the furnace, Providing iron ore and coke in the furnace, Blowing at the bottom of the furnace, Injecting fuel into the bottom of the furnace, Combusting coke and fuel with a blower to provide heat to the melt and produce molten iron, The oxygen content of the blowing is 30 to 100% by volume, the amount of fuel injected is iron production method characterized in that the 220 to 500 kg per ton of molten metal. The method of claim 1, Oxygen content of the blowing is iron production method, characterized in that 35 to 70% by volume. The method according to claim 1 or 2, The oxygen production method characterized in that the oxygen is injected by cold wind means. The method according to any one of claims 1 to 3, The amount of fuel injected is in the range of 300-400 kg per ton of molten iron manufacturing method. The method according to any one of claims 1 to 4, And the injected fuel comprises coal, gas and / or oil. The method according to any one of claims 1 to 5, Iron production method characterized in that the quicklime is injected in the manufacturing method. The method of claim 6, Quicklime is iron manufacturing method characterized in that the injection of 5 to 20 kg content per ton of molten metal. The method according to any one of claims 1 to 7, Iron production method characterized in that the pre-reduced iron powder is injected. The method of claim 8, The injection amount of the pre-reduced iron powder is characterized in that 20 to 200 kg per ton of molten iron. A method for using a top gas obtained from the production method according to any one of claims 1 to 9 as a fuel for a combined cycle power plant.

Images