Patent Application
20170211160
The present invention relates to pulverized coal for iron making, which comprises cow manure, and a method for producing pig iron using the same, and more particularly to pulverized coal for iron making comprising cow manure which can improve combustibility and increase the efficiency and stability of a blast furnace operation, and to a method for producing pig iron using the same.
Iron making is a process that produces pig iron by smelting iron ore. In this process, iron ore, coke and limestone are charged into a blast furnace, and then hot air with a temperature of 1100 to 1300° C. is blown into the furnace to burn the coke and smelt and reduce the iron ore to thereby melt iron contained in the iron ore. The iron produced by this process is known as pig iron.
Coke is obtained by introducing coal into a furnace and burning the coal at a high temperature of about 1,000 to 1,300° C., and serves not only as a heat source to melt iron ore (that is a compound of iron and oxygen) in a blast furnace, but also as a reducing agent to separate iron from iron ore.
In recent blast furnace operations for iron making, owing to the development of technology, a significant reduction in the production cost has become possible by injecting pulverized coal into the furnace bottom through the tuyere level in an operation in which expensive coke is used. Coke serves to ensure gas permeability by supporting a reducing agent, a heat source and a charged material in a blast furnace. On the other hand, pulverized coal consisting of very fine particles which are injected through the tuyere level functions as a reducing agent and a heat source by inducing combustion at an early stage within milliseconds.
The background art of the present invention is disclosed in Korean Patent No. 10-1198619 (Nov. 11, 2011; entitled “Coal Briquette Comprising Coal and Pulverized Coal and Production Method Thereof”).
Embodiments of the present invention provide pulverized coal for iron making, which comprises cow manure.
Embodiments of the present invention also provide a method for producing pig iron using pulverized coal for iron making, which comprises cow manure.
Other objects and advantages of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings.
In accordance with one aspect of the present invention, there is provided pulverized coal for iron making, which comprises, based on 100 parts by weight of coal powder, 76 parts by weight or less of dried and crushed cow manure having a size of 50 mm or less and a water content of 20% or less.
In accordance with another aspect of the present invention, a method for producing pig iron, comprising the steps of: (1) drying cow manure; (2) crushing the dried cow manure in a pulverizer; (3) mixing the cow manure with coal powder to prepare pulverized coal; and (4) injecting the pulverized coal into a blast furnace.
According to embodiments of the present invention, pulverized coal may comprise cow manure to reduce the amount of coal contained in the pulverized coal, thereby reducing greenhouse gas emissions and blast furnace operation costs.
In addition, the combustibility of existing pulverized coal may be greatly improved, making an efficient blast furnace operation possible. Particularly, combustion of pulverized coke can be promoted to prevent the gas permeability and liquid permeability of the blast furnace from being further reduced by accumulation of the coke powder, thereby making a stable blast furnace operation possible.
When cow manure that is agricultural livestock waste is used according to embodiments of the present invention, the agricultural livestock waste can be recycled as resources so that advantages in environmental terms can be obtained. In addition, reducing gas can be easily produced, making it possible to reduce iron ore at high speed.
The present invention can be variously modified and can have various forms, and specific embodiments are shown in the drawings and described in detail in the specification. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that the present invention includes all modifications, equivalents or replacements that fall within in the spirit and technical scope of the present invention. In the following description, the detailed description of related known technology will be omitted when it may obscure the subject matter of the present invention.
The terms “first”, “second”, etc., may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing a component from other components.
Terms used in the specification are used only to describe a specific embodiment and are not intended to limit the scope of the present invention. Singular expressions include plural expressions unless specified otherwise in the context thereof. In the specification, the terms “comprise”, “have”, etc., are intended to denote the existence of mentioned characteristics, numbers, steps, operations, components, parts, or combinations thereof, but do not exclude the probability of existence or addition of one or more other characteristics, numbers, steps, operations, components, parts, or combinations thereof.
Hereinafter, pulverized coal for iron making comprising cow manure according to the present invention, and a method for producing pig iron using the same, will be described with reference to the accompanying drawings. In the following description made with reference to the accompanying drawings, like components will be denoted by like reference numerals, and the overlapping description of the components will be omitted.
In accordance with one aspect of the present invention, there is provided pulverized coal for iron making, which comprises, based on 100 parts by weight of coal powder, 76 parts by weight or less of dried and crushed cow manure having a size of 50 mm or less and a water content of 20% or less.
Cow manure that is used as a replacement for coal in the present invention generally contains a large amount of volatile matter, and thus has a characteristic in that the fixed carbon content thereof is significantly lower than that of coal. Particularly, the calorific value of cow manure is about 50% of existing coal. However, it was shown that the volatile matter of cow manure is thermally decomposed at an earlier stage and contains a higher concentration of oxygen, compared to carbon, and thus can be used as an additive capable of promoting the combustion of existing carbon (see Table 1 below). Furthermore, as shown in Table 2 below, cow manure has advantages in that it is generated in significantly large amounts and is steadily supplied, and thus it can be used continuously in a blast furnace.
In addition, existing cow manure has been mostly used as compost and the like, but the amount of cow manure generated is significantly larger than the amount of cow manure used, and thus livestock raisers have experienced difficulty in disposal of cow manure. Accordingly, the present invention can considerably contribute not only to solving environmental problems, but also to reducing production costs, because cow manure which has been disposed of as livestock waste is applied to a blast furnace operation.
When cow manure is used in pulverized coal according to the present invention, it can significantly improve the combustibility of the pulverized coal.
In addition, when cow manure is used according to the present invention, it can improve the calorific value of pulverized coal. Although the combustibility of pulverized coal is also associated with the accumulation of the pulverized coal powder in a blast furnace, the combustion efficiency of the pulverized coal has a significant effect on the initial calorific value of the pulverized coal. Thus, in order to more closely examine the effect of such cow manure on the improvement in combustibility and the change in initial calorific value by cow manure, the change in calorific value of each kind of pulverized coal as a function of the rate of replacement with cow manure was examined, and the results of the examination are shown in
Meanwhile, it is important that the pulverized coal comprises cow manure so that the Bosh gas volume (BGV) of a blast furnace in an iron making process will be lower than a critical limit. Thus, in the present invention, the pulverized coal preferably comprises, based on 100 parts by weight of coal powder, 76 parts by weight or less of cow manure.
If a portion of pulverized coal is replaced with cow manure, the highly volatile components of the cow manure can increase the Bosh gas volume (BGV), and thus increase the pressure of the blast furnace. If the pressure of the blast furnace increases, it will be difficult to ensure good gas permeability, and it can be impossible to perform a stable blast furnace operation. For this reason, for a stable blast furnace operation, the pulverized coal preferably comprises, based on 100 parts by weight of coal powder, 76 parts by weight or less of cow manure (see
In addition, cow manure has a high ash content, but it was shown that, when a portion of pulverized coal was replaced with cow manure, the replacement cow manure had no great effect on the blast furnace slag volume (see
In the present invention, the crushed cow manure preferably has a particle size of 50 mm or less, but is not limited thereto. If the particle size of the crushed cow manure is more than 50 mm, a large amount of energy will be required to dry the cow manure, and it will be difficult to mix the cow manure uniformly with coal powder.
The pulverized coal comprising cow manure according to the present invention may further comprise, in addition to coal powder and cow manure, various components that are added to conventional pulverized coal. A person skilled in the technical field to which the present invention pertains may suitably add additional components depending on blast furnace operation conditions without difficulty.
Meanwhile, embodiments of the present invention illustrate cow manure as a component that is added to pulverized coal, the scope of the present invention is not limited only to cow manure, and may be expanded to the manure of other livestock animals, including dogs, pigs, goats, horses and the like.
In accordance with another aspect of the present invention, a method for producing pig iron, comprising the steps of: (1) drying cow manure; (2) crushing the dried cow manure in a pulverizer; (3) mixing the cow manure with coal powder to prepare pulverized coal; and (4) injecting the pulverized coal into a blast furnace.
According to a specific aspect of the present invention, drying of cow manure in step (1) may be performed by primarily drying the cow manure to a water content of 65% or less in a yard under conditions in which no fermentation occurs, and secondarily drying the cow manure, crushed by the pulverizer in step (2), to a water content of 20% or less in a dryer. If the cow manure is naturally dried in the yard and then further dried in the dryer as described above, the drying cost can be reduced. Namely, the yard in which the cow manure is dried may be a roofed accommodation capable of preventing penetration of water upon raining, and the yard can save the cost caused by a relatively expensive dryer. In addition, if the cow manure is primarily dried, and then is crushed in the pulverizer, and then introduced into the dryer, the drying efficiency can further be improved.
According to another specific aspect of the present invention, the cow manure is passed through a particle size separator before introduction into the pulverizer of step (2) so that cow manure having a particle size of 50 mm or less will be transferred directly to the dryer, and the cow manure is crushed in the pulverizer in step (2) so as to have a particle size of 50 mm or less. If the cow manure is passed through the particle size separator before introduction into the pulverizer as described above so that a cow manure portion having a particle size of 50 mm or less will be transferred directly to the dryer, the crushing efficiency can be improved.
According to still another specific aspect of the present invention, the dryer can be heated using either waste heat from an iron making process including an existing blast furnace or byproduct gas such as blast furnace gas, coke gas or electric furnace gas. Thus, according to the present invention, cow manure can be dried using either waste heat generated in an iron making process or byproduct gas, and thus the amount of coal used can be reduced while additional costs can be minimized.
Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Comparison of Major Characteristics of Cow Manure and Pulverized Coal for Blast Furnace
In the present invention, various replacement fuels were selected in order to improve the combustibility of pulverized coal, and the major characteristics thereof were compared with those of conventional pulverized coal as shown in Table 1 below.
Biomass considered as a replacement for coal generally contains a large amount of volatile matter, and thus has a characteristic in that the fixed carbon content thereof is significantly lower than that of coal. Particularly, the calorific value of biomass is about 50% of existing coal. However, the volatile matter of biomass is thermally decomposed at an earlier stage and contains a larger amount of oxygen, compared to carbon, and it is considered that the volatile matter can be used as an additive capable of promoting the combustion of existing coal. Table 1 below shows the characteristics of major biomass and pulverized coal for a blast furnace.
Meanwhile, coal manure is preferably used as a replacement for coal. As shown in Table 2 below, cow manure has advantages in that it is generated in significantly large amounts and is steadily supplied, and thus it can be used continuously in a blast furnace. The amount of cow manure generated in Korea is estimated to be 23,291,745 tons per year. Cow manure has a water content of about 85%, and thus the amount of cow manure remaining after complete drying is estimated to be 3,493,780 tons per year. Table 2 below shows the amount of cow manure generated in Korea.
In addition, existing cow manure has been mostly used as compost and the like, but the amount of cow manure generated is significantly larger than the amount of cow manure used, and thus livestock raisers have experienced difficulty in disposal of cow manure. Accordingly, the present invention can considerably contribute not only to solving environmental problems, but also to reducing production costs, because cow manure which has been disposed of as livestock waste is applied to a blast furnace operation.
Change in Combustibility of Pulverized Coal as a Function of Rate of Replacement with Cow Manure
In order to more closely examine the effect of replacement with cow manure for each kind of pulverized coal, the combustion rate at a cow manure rate of 25% at which the combustibility was linearly increased was compared, and the results of the comparison are shown in
Change in Calorific Value of Pulverized Coal as a Function of Rate of Replacement with Cow Manure
Although the combustibility of pulverized coal is also associated with the accumulation of the pulverized coal powder in a blast furnace, the combustion efficiency of the pulverized coal has a significant effect on the initial calorific value of the pulverized coal. For example, when combustion rate of pulverized coal YQ0 having a calorific value of 7,665 Kcal/kg is 65.1%, the initial calorific value of the pulverized coal is only 4,990 Kcal/kg, which is disadvantageous for a highly efficient operation. Thus, in order to closely examine the effect of such cow manure on the improvement in combustibility and the change in initial calorific value by cow manure, the change in caloric value of each kind of pulverized coal as a function of the rate of cow manure was examined, and the results of the examination are shown in
It was shown that, when ZH0 and CUP, which showed low combustibility before addition of cow manure, were placed with cow manure, the initial calorific value thereof was steadily increased due to their greatly improved combustibility as the rate of replacement with cow manure increased up to 30%. Meanwhile, it was shown that in the case of YQ0, the initial calorific value thereof steadily decreased until the rate of replacement with cow manure reached 25%, even though the combustibility of cow manure was improved. This is believed to be because the initial calorific value of YQ0 was better than that of other two kinds of pulverized coal and was influenced by the low calorific value (3,742 Kcal/kg) of the cow manure added.
Change in Bosh Gas Volume as a Function of Rate of Replacement with Cow Manure
If a portion of pulverized coal is replaced with cow manure, the highly volatile components of the cow manure can increase the Bosh gas volume (BGV), and thus increase the pressure of the blast furnace. If the pressure of the blast furnace increases, it will be difficult to ensure good gas permeability, and it can be impossible to perform a stable blast furnace operation.
The change in BGV as a function of the rate of replacement with cow manure for each kind of pulverized coal was examined in a blast furnace having an internal volume of 5,250 m2 under the following operating conditions: air flow rate: 7,000N m3/min; moisture amount: 25 g/Nm3; oxygen load: 32,100N m3/min; and pulverized coal rate (PCR): 165 kg/thm. The results of the examination are shown in
Change in Slag Volume as a Function of Rate of Replacement with Cow Manure
Cow manure has a high ash content. For this reason, if a portion of pulverized coal is replaced with cow manure, the blast furnace slag volume can increase. If the slag volume increases, problems, including poor molten iron and an increase in the reducing agent cost, can arise. Thus, it is needed to examine a suitable critical limit required for a smooth blast furnace operation.
The change in the blast furnace slag volume as a function of the rate of replacement with cow manure for each kind of pulverized coal was examined in a blast furnace having an internal volume of 5,250 m2 under the following operating conditions: air flow rate: 7,000N m3/min; moisture amount: 25 g/Nm3; oxygen load: 32,100 N m3/min; and pulverized coal rate (PCR): 165 kg/thm. The results of the examination are shown in
Comparison of Injectability Indices of Cow Manure and Conventional Pulverized Coal
Injectability is an index that indicates whether pulverized coal after crushing can be easily injected into a blast furnace when the pulverized coal is transferred to the blast furnace through a plurality of pipes. The injectability can be influenced by factors, including the frictional force between the pulverized coal and the inner wall of the pipes, resistance, etc. As shown in
Comparison of Particle Shape after Combustion of Conventional Pulverized Coal and Cow Manure
In comparison with this, cow manure has a relatively spherical particle shape compared to YQ0, and this spherical shape suggests that cow manure has a completely combustion property.
Method for Producing Pig Iron Using Pulverized Coal for Iron Making Comprising Cow Manure According to Embodiment of the Present Invention
This embodiment illustrates a method in which cow manure is applied by simultaneous injection to a pulverized coal injection process that uses conventional coal. This embodiment has an advantage in that cow manure can be easily applied while minimizing the addition of facilities to a pig-iron production process in which conventional pulverized coal is injected.
Hereinafter, a method for producing pig iron using pulverized coal for iron making comprising cow manure according to an embodiment of the present invention will be described with reference to
Referring to A of
Referring to B of
Next, the naturally dried cow manure 110 is stored in a cow manure storage hopper 120, and then crushed in a pulverizer 140 so as to have a particle size of 50 mm. Herein, a particle size separator 130 may be disposed below the cow manure storage hopper 120 so that cow manure having a particle size of 50 mm or less can be transferred directly to a dryer 150 without passage through the pulverizer 140, thereby increasing the crushing efficiency of the pulverizer 140.
Next, the cow manure is dried in a dryer 150 at a temperature of at least 100° C. For drying, a indirect heating method employing either waste heat from an existing blast furnace or other iron making process or a byproduct gas such as blast furnace gas, coke gas or electric furnace gas is used. However, if collected cow manure has a water content of about 20%, the above-described process may be omitted, and the cow manure may be subjected directly to an existing process that uses coal.
The cow manure stored as described above is primarily stored in a cow manure storage silo 160, and it is discharged through the bottom of the silo in a predetermined amount according to a desired blending ratio and introduced into the mixed coal storage hopper 20.
According to some other embodiments, the cow manure 110 may be naturally dried to a water content of 20% or less. The cow manure 110 naturally dried to a water content of 20% or less may be stored in the cow manure storage hopper 120, and then crushed in the pulverizer 140 so as to have a particle size of 50 mm or less. The cow manure 110 crushed to a particle size of 50 mm or less may be stored in the cow manure storage silo 160. In addition, through the particle size separator 130 disposed below the cow manure storage hopper 120, cow manure determined to have a particle size of 50 mm or less may be transferred to the cow manure storage silo 160 without passage through the pulverizer 140.
Next, the cow manure 110 is subjected to the above-described pulverized coal injection process and injected into the blast furnace 80 through the tuyere level from the pulverized coal injection hopper 70, thereby producing pig iron.
As described above, according to embodiments of the present invention, pulverized coal may comprise cow manure to reduce the amount of coal contained in the pulverized coal, thereby reducing greenhouse gas emissions and blast furnace operation costs.
In addition, the combustibility of existing pulverized coal may be greatly improved, making an efficient blast furnace operation possible. Particularly, combustion of pulverized coke can be promoted to prevent the gas permeability and liquid permeability of the blast furnace from being further reduced by accumulation of the coke powder, thereby making a stable blast furnace operation possible.
When cow manure that is agricultural livestock waste is used according to embodiments of the present invention, the agricultural livestock waste can be recycled as resources so that advantages in environmental terms can be obtained. In addition, reducing gas can be easily produced, making it possible to reduce iron ore at high speed.
Meanwhile, embodiments of the present invention illustrate cow manure as a component that is added to pulverized coal, the scope of the present invention is not limited only to cow manure, and may be expanded to the manure of other livestock animals, including dogs, pigs, goats, horses and the like.
Although the present invention has been described with respect to the embodiments, any person skilled in the technical field will appreciate that the present invention can be variously modified or altered by the addition, modification or deletion of components without departing from the scope of the present invention as disclosed in the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2014-0028554 | Mar 2014 | KR | national |
| 10-2015-0034093 | Mar 2015 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2015/002377 | 3/11/2015 | WO | 00 |
