Method for preparing feed gas for directly reducing iron and coke oven raw gas collecting device

Abstract

The invention relates to a method for preparing feed gas for direct reduction iron, which comprises the following steps in sequence: step 1): from the beginning of coking of a coke oven carbonization chamber, closing a second turning plate (201) of a hot gas pipe (20) in a gas collection unit connected with the coke oven carbonization chamber through a pipeline, opening a first turning plate (101) of a gas collection pipe (10) in the gas collection unit, and starting from the beginning of coking of the coke oven carbonization chamber; the gas from the raw gas in the carbonization chamber is introduced into the gas collecting pipe (10) for gas refining; and 2) closing the first turning plate (101) and opening the second turning plate (201) in a time period from more than 60% of the total coking time to the total coking time, and introducing the raw gas from the carbonization chamber into the hot gas pipe (20) to be used as raw gas for directly reducing iron. The invention also discloses a coke oven raw gas collecting device for implementing the method. According to the invention, the raw gas generated in the middle-rear period of the coking time of the carbonization chamber is collected, so that the raw gas for direct reduction of iron can be obtained.

Description

Technical Field

[0001] This invention relates to the field of non-blast furnace ironmaking technology, and more particularly to a method for preparing feed gas for direct reduction of iron and a coke oven. Background Technology

[0002] Direct reduced iron (DRI) is a process that directly reduces iron ore to iron in a solid state. It can serve as a pure raw material for smelting high-quality and special steels, and also as an iron-containing raw material for processes such as casting, ferroalloys, and powder metallurgy. Traditional steelmaking processes will gradually be replaced by the shorter direct reduction electric arc furnace (DRI) steelmaking process. This technology can achieve the metallurgical industry's dual-carbon goals, promote industrial upgrading in the steel industry, save energy and reduce emissions, and is an important direction and pathway for sustainable development. Currently, among mature DRI processes, the vertical shaft furnace method is the main production process, with the Midrex process and the HYL / Energiron process being typical examples.

[0003] Most vertical shaft furnaces used natural gas as feedstock for direct reduced iron (DRI) production. However, my country faces a shortage of natural gas resources, making it unsuitable as a feedstock for DRI. Therefore, developing vertical shaft furnace processes using coke oven gas and pyrolysis gas as feedstocks is the future direction for DRI production technology in my country. However, coke oven gas cannot be directly used as a DRI feedstock: firstly, it contains 20-30% CH4, requiring reforming into H2 and CO before it can be effectively used as a reducing gas; secondly, even after conventional purification, coke oven gas still contains trace amounts of heavy hydrocarbon impurities (tar, naphthalene, BTX (benzene, toluene, xylene)). These impurities can cause coking and carbon buildup during gas pressurization and heating, affecting equipment operation.

[0004] The HYL-ZR process is a method for producing DRI (Dry Reduction) from coke oven gas. It achieves CH4 conversion through self-reforming in a reduction shaft furnace. Therefore, this process places high demands on the shaft furnace and has relatively low reduction efficiency. For heavy hydrocarbon impurities in the coke oven gas, the process first purifies the gas by passing it through the cooling section of the shaft furnace, then reheating it before re-entering the shaft furnace. However, because the enthalpy of the DRI in the cooling section is insufficient to handle excessive amounts of coke oven gas, only about 30% of the coke oven gas can be utilized using this method. These two drawbacks are related to the compositional characteristics of coke oven gas, namely, high CH4 content and high aromatic hydrocarbon impurity content. Therefore, reducing the CH4 and aromatic hydrocarbon impurity content in coke oven gas for DRI production is crucial.

[0005] Existing invention patents have limited research on reducing CH4 and aromatic impurities in coke oven gas. For example, Chinese patents CN200510012823.7, CN200810226076.0, CN201010195863.0, and CN201210064998.2 relate to methods and equipment for producing DRI from coke oven gas. These patents introduce heated and / or purified coke oven gas into a vertical shaft furnace or converter for reduction, and the reduced top gas is returned to the heating furnace and / or vertical shaft furnace; CN201210064 Patent 993.X discloses a method for producing direct reduced iron (DRI) using coke oven gas. This method uses coke oven gas as both a reducing gas and a cooling gas. The two streams of coke oven gas mix at the bottom of the reduction section of a vertical shaft furnace and participate in the reaction to complete the reduction of iron ore. Patent CN201110112050.5 discloses a method for co-producing DRI using coke oven gas in dry quenching. This method uses coke oven gas as a heat transfer medium to cool red-hot coke and introduces it into the dry quenching coke oven. After heating, it serves as a hydrogen-rich reducing gas. All of these patent applications disclose methods for producing DRI using coke oven gas as a reducing gas. However, they focus more on the reforming of coke oven gas into CH4, rather than on increasing the H2 content of the reducing gas itself and reducing the content of aromatic impurities. Furthermore, the production processes and equipment are complex, requiring a series of purification treatments from the raw coke oven gas, such as tar removal, naphthalene removal, benzene removal, desulfurization, and ammonia removal, before finally obtaining purified coke oven gas (COG) suitable for DRI. Summary of the Invention

[0006] The gas composition of raw coal gas produced during the coking process in modern coke ovens changes with the coking time. In the later stages of coking, the raw coal gas is mainly composed of H2 with low CH4 content, and only trace amounts of heavy hydrocarbons such as tar, naphthalene, and BTX. The raw coal gas in this coking stage has both good reducing gas components (H2) and high sensible heat, making it very suitable as feed gas for DRI production in vertical shaft furnaces. However, existing technologies do not address how to effectively utilize the raw coal gas in the later stages of coking, and it is difficult for current coke ovens to extract and utilize the raw coal gas in the later stages of coking.

[0007] Figure 1The structure of a conventional coke oven raw gas extraction and collection device in the prior art is shown, wherein the raw gas escapes from the carbonization chamber (not shown) and enters the gas collection pipe (10) via the riser pipe (40) and the bridge pipe (30). The bridge pipe (30) is equipped with an ammonia water nozzle (301), and a flap (101) controls the opening and closing of the gas collection pipe (10). When the flap (101) is open, the carbonization chamber is connected to the gas collection pipe (10) through the riser pipe (40) and the bridge pipe (30). The raw gas from the carbonization chamber enters the bridge pipe (30) via the riser pipe (40), and after being cooled by ammonia water sprayed from the ammonia water nozzle (301), it directly enters the gas collection pipe (10). This conventional coke oven cannot collect the raw gas in the early and late stages of the coking time separately, and cannot directly utilize the sensible heat contained in the raw gas itself.

[0008] Therefore, in order to overcome the problems existing in the prior art, the present invention provides a method and a coke oven for preparing feed gas for direct reduction of iron. The feed gas has a high H2 content, a low CH4 content, only trace amounts of heavy hydrocarbon compounds, and can maintain a physical sensible heat of 700-800°C. It can be directly used as a reducing gas in vertical shaft furnace for DRI production or other reduction processes, and has the characteristics of simple process and low energy consumption.

[0009] A first aspect of the present invention provides a coke oven raw gas collection device, comprising a riser pipe and a gas collection unit. The riser pipe is located above and connected to the coke oven carbonization chamber. The riser pipe is connected to the gas collection unit via a bridge pipe. The gas collection unit comprises:

[0010] A gas collecting pipe (10), the inlet of which is controlled by a first flap (101); and

[0011] Hot air pipe (20), the inlet of which is controlled by a second flap (201);

[0012] From the moment coking begins in the carbonization chamber, the first flap (101) is in the open state, the second flap (201) is in the closed state, and the carbonization chamber is connected to the gas collecting pipe (10);

[0013] During the period from 60% or more, preferably 2 / 3 or more, more preferably 70% or more of the total coking time in the carbonization chamber to the total coking time, the first flap (101) is in the closed state, the second flap (201) is in the open state, and the carbonization chamber is connected to the hot gas pipe (20).

[0014] The above-mentioned coke oven raw gas collection device can be used to prepare and collect raw gas for direct reduction of iron. It is a gas collection unit used to export and collect raw gas from the coke oven carbonization chamber. In this article, "pipeline" includes any pipe that connects the carbonization chamber to the gas collection unit and allows gas to flow, such as riser pipe, bridge pipe, etc. By controlling the first flap (101) and the second flap (201), the gas from the carbonization chamber can be allowed to enter the gas collecting pipe (10) or the hot gas pipe (20), respectively.

[0015] Preferably, the bridge pipe is equipped with an ammonia water nozzle (301). At the beginning of coking, since the raw coal gas from the carbonization chamber contains a large amount of gaseous tar, it can be cooled by spraying ammonia water. The ammonia water evaporates rapidly and absorbs a large amount of heat, which lowers the temperature of the raw coal gas to 80-100°C and promotes tar condensation.

[0016] Preferably, the outlet of the gas collecting pipe (10) is connected to the gas refining unit. The gas collected in the gas collecting pipe (10) contains tar, naphthalene, BTX, CH4, etc. The gas collected in the gas collecting pipe (10) can be further detarized, denaphthalene removed, debenzene removed, desulfurized, deammoniated, etc. in the gas refining unit to finally obtain purified coke oven gas (COG) for further reuse.

[0017] Preferably, the outlet of the hot gas pipe (20) is connected to the direct reduced iron unit. The raw coal gas collected in the hot gas pipe (20) mainly contains H2 gas, with a low CH4 content and only trace amounts of heavy hydrocarbon compounds such as tar, naphthalene, and BTX. It can be directly used as a reducing gas in the direct reduced iron process.

[0018] Preferably, the coke oven includes multiple carbonization chambers and multiple gas collection units, with each carbonization chamber corresponding to one of the gas collection units. Typically, a coke oven contains more than one carbonization chamber, each with an independent coking time; therefore, each carbonization chamber can correspond to one gas collection unit, ensuring maximum H2 collection.

[0019] A second aspect of the present invention provides a method for preparing a feed gas for direct reduction of iron, comprising the following steps performed sequentially:

[0020] Step 1): Starting from the coking chamber in the coke oven, close the second flap (201) of the hot gas pipe (20) in the gas collection unit connected to the coking chamber through the pipe, open the first flap (101) of the gas collection pipe (10) in the gas collection unit, and introduce the gas from the raw coal gas in the coking chamber into the gas collection pipe (10) for coal gas refining.

[0021] Step 2): During the period from 60% or more, preferably 2 / 3 or more, more preferably 70% or more of the total coking time in the carbonization chamber to the total coking time, close the first flap (101) of the gas collecting pipe (10) and open the second flap (201) of the hot gas pipe (20) to introduce the raw coal gas from the carbonization chamber into the hot gas pipe (20) as the raw material gas for direct reduction of iron.

[0022] Typically, when the coking time is more than 60% of the total coking time (preferably more than 2 / 3, more preferably more than 70%), the raw coal gas in the carbonization chamber has a low content of CH4 and heavy hydrocarbons and a high content of H2, which can be directly collected for direct reduction of iron.

[0023] Preferably, the method further includes step 2.1): the gas collected in the gas collecting pipe (10) is introduced into the gas refining unit, and the gas is further detarted, denaphthalene removed, debenzene removed, desulfurized, deammoniated, etc. in the gas refining unit to finally obtain purified coke oven gas (COG) for further reuse.

[0024] Preferably, the method further includes step 2.2): introducing the raw coal gas collected in the hot gas pipe (20) into the direct reduced iron unit.

[0025] Preferably, in step 1), ammonia water is sprayed when the first flap (101) of the gas collecting pipe (10) is opened, and in step 2), ammonia water spraying is stopped when the first flap (101) of the gas collecting pipe (10) is closed. In step 1), the raw coal gas from the carbonization chamber has a high content of tar and heavy hydrocarbons, so spraying ammonia water can cause the tar and heavy hydrocarbons to condense; while in step 2), the raw coal gas from the carbonization chamber in the later stage of coking time has a lower content of tar and heavy hydrocarbons, so there is no need to spray ammonia water for condensation, and the sensible heat of the gas during coking can be retained while ensuring the H2 content.

[0026] Preferably, in step 1), the gas collected in the gas collecting pipe (10) includes the following components: H2 ≤ 55% by volume, CH4 ≥ 25% by volume, CO: 2-6% by volume, CO2: 3-8% by volume, tar: ≥ 200 mg / Nm, naphthalene: ≥ 300 mg / Nm, BTX: ≥ 2000 mg / Nm.

[0027] Preferably, in step 2), the raw coal gas collected in the hot gas pipe (20) includes the following components: H2 ≥ 70% by volume, CH4 ≤ 15% by volume, CO: 2-10% by volume, CO2: 1-6% by volume, tar: ≤ 10 mg / Nm, naphthalene: ≤ 30 mg / Nm, BTX: ≤ 300 mg / Nm.

[0028] Preferably, in step 2), the temperature of the raw coal gas collected in the hot gas pipe (20) is 700-800℃.

[0029] Preferably, the total coking time in the carbonization chamber is 19 to 25 hours.

[0030] In summary, the coking time is determined by the specifications of the coke oven. In this invention, a top-loading regenerative coke oven (with a carbonization chamber height of more than 6m) is generally used.

[0031] Beneficial effects of this invention:

[0032] 1) This invention obtains the raw gas for direct reduction of iron by collecting the portion of raw coal gas with high H2 content, which can be obtained directly or by further modifying and purifying the gas. After reducing iron, the raw gas can produce low carbon emissions, effectively solving the shortcomings of high CH4 content and high aromatic impurity content in the coke oven gas currently used for direct reduction of iron.

[0033] 2) This invention can effectively utilize the sensible heat of raw coal gas, which can be retained in the subsequent direct reduction iron process, thus saving energy. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of a conventional coke oven raw gas collection device;

[0035] Figure 2 This is a schematic diagram of a coke oven raw gas collection device for preparing raw gas for direct reduction of iron, according to an embodiment of the present invention.

[0036] Reference numerals: 10-Gas collecting pipe; 20-Hot gas pipe; 101-First flap; 201-Second flap; 30-Bridge pipe; 301-Ammonia water nozzle; 40-Rising pipe. Detailed Implementation

[0037] The following description, with reference to the accompanying drawings, illustrates several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the invention is not limited to the embodiments mentioned herein. Furthermore, unless otherwise stated, features of the various embodiments can be suitably combined with each other.

[0038] In the description of this embodiment, it should be noted that the terms "upper," "front," "inner," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product of the invention is usually placed in during use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0039] In the description of this embodiment, it should also be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly, for example, it can be a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above term in this embodiment based on the specific circumstances.

[0040] Gas composition detection methods

[0041] The collected gas was sampled and then analyzed by gas chromatography to determine the content of the main components in the coke oven gas, such as GB / T28901-2012 Gas Chromatographic Analysis Method for Coke Oven Gas Components.

[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0043] As mentioned above, Figure 1 The diagram shows the structure of a conventional coke oven. The carbonization chamber is connected to the gas collecting pipe (10) through the riser pipe (40) and the bridge pipe (30). During the coking time, the gas from the carbonization chamber is introduced into the gas collecting pipe (10).

[0044] Figure 2 A schematic diagram of the structure of a coke oven for preparing feed gas for direct DRI according to the present invention is shown, wherein the carbonization chamber is connected to a gas collection unit via a pipe, the gas collection unit includes: a gas collecting pipe (10), the inlet of which is controlled by a first flap (101); and a hot gas pipe (20), the inlet of which is controlled by a second flap (201).

[0045] In the coke oven of the present invention, from the start of coking in the carbonization chamber, the first flap (101) is in the open state and the second flap (201) is in the closed state, and the carbonization chamber is connected to the gas collecting pipe (10); during the period from 60% or more, preferably 2 / 3 or more, more preferably 70% or more of the total coking time to the total coking time, preferably to 80% of the total coking time, more preferably to 75% of the total coking time, the first flap (101) is in the closed state and the second flap (201) is in the open state, and the carbonization chamber is connected to the hot gas pipe (20).

[0046] The pipeline includes an ascending pipe (40) and a bridge pipe (30). The carbonization chamber is connected to the gas collecting pipe (10) and the hot gas pipe (20) via the ascending pipe (40) and the bridge pipe (30), respectively. An ammonia water nozzle (301) is provided on the bridge pipe (30). By controlling the first flap (101) of the gas collecting pipe (10) and the second flap (201) of the hot gas pipe (20), the present invention allows gas from the carbonization chamber to enter the gas collecting pipe (10) or the hot gas pipe (20).

[0047] In the coke oven of the present invention, the outlet of the gas collecting pipe (10) can be connected to the gas refining unit, and the outlet of the hot gas pipe (20) can be connected to the direct reduced iron unit or the reduction unit.

[0048] Example 1

[0049] A steel plant needs to produce pre-reduced Fe pellets with a metallization rate of over 85%, requiring an annual output of 300,000 tons. This invention collects raw coal gas from the latter part of the coking time in a 200-hole, 6-meter coke oven as feed gas for direct reduction of iron. In this embodiment, the final coking time in the carbonization chamber is 21 hours. Specifically, the method includes the following steps performed sequentially:

[0050] Step 1): When coking begins in the carbonization chamber, close the second flap (201) of the hot gas pipe (20) and open the first flap (101) of the gas collecting pipe (10) to introduce the gas from the raw coal gas in the carbonization chamber into the gas collecting pipe (10).

[0051] Before the coking time in the coke oven reaches 12.6 hours (i.e., 60% of the total coking time), ammonia water is sprayed by the ammonia water nozzle (301) on the bridge pipe (30). The first flap (101) located before the inlet of the gas collecting pipe (10) is in the open state, and the second flap (201) located before the inlet of the hot gas pipe (20) is in the closed state. The raw coal gas from the carbonization chamber is cooled and condensed into tar after being sprayed with ammonia water. Then, the mixture of gas and tar is introduced into the gas collecting pipe (10). The gas collected in the gas collecting pipe (10) contains the following components: H2: 54.5 vol%, CH4: 20.9 vol%, CO: 4.4 vol%, CO2: 7.1 vol%, tar: 385 mg / Nm, naphthalene: 260 mg / Nm, BTX: 3100 mg / Nm.

[0052] Step 2): When the coking time is 60% of the total coking time, close the first flap (101), open the second flap (201), and introduce the raw coal gas from the carbonization chamber into the hot gas pipe (20).

[0053] When the coking time of the carbonization chamber reaches 12.6 hours, close the ammonia water nozzle (301) on the bridge pipe (30), stop spraying ammonia water, close the first flap (101) located at the inlet of the gas collecting pipe (10), open the second flap (201) located at the inlet of the hot gas pipe (20), and introduce the raw coal gas from the carbonization chamber into the hot gas pipe (20) until the coking time reaches 21 hours (final coking time);

[0054] Subsequently, the gas collected in the gas collecting pipe (10) is introduced into the coal gas refining unit, and the raw coal gas collected in the hot gas pipe (20) is directly introduced into the DRI unit or other reduction units as reducing gas.

[0055] This method can collect approximately 25,000 Nm³ / h of raw gas from raw coal gas, which can be used for direct reduction of iron. The raw coal gas collected in the hot gas pipe (20) has a temperature of 800 °C and contains the following components: H₂: 70.8 vol%, CH₄: 14.5 vol%, CO: 9.2 vol%, CO₂: 2.7 vol%, tar: 10 mg / Nm³, naphthalene: 30 mg / Nm³, and BTX: 300 mg / Nm³.

[0056] Example 2

[0057] A steel plant needs to produce pre-reduced Fe pellets with a metallization rate of over 85%, requiring an annual output of 300,000 tons. This invention collects raw coal gas from the later stages of coking time in a 200-hole, 6-meter coke oven as feed gas for direct reduction of iron. In this embodiment, the final coking time in the carbonization chamber is 21 hours. Specifically, the method includes the following steps performed sequentially:

[0058] Step 1): Starting from the coking of the carbonization chamber, close the second flap (201) of the hot gas pipe (20) and open the first flap (101) of the gas collecting pipe (10) to introduce the gas from the raw coal gas in the carbonization chamber into the gas collecting pipe (10).

[0059] Before the coking time in the coking chamber of the coke oven reaches 14 hours (i.e., 2 / 3 of the total coking time), ammonia water is sprayed by the ammonia water nozzle (301) on the bridge pipe (30). The first flap (101) located in front of the gas inlet of the gas collecting pipe (10) is in the open state, and the second flap (201) located in front of the hot gas pipe (20) is in the closed state. The raw coal gas from the coking chamber is cooled and condensed into tar after being sprayed with ammonia water. Then the mixture of gas and tar is introduced into the gas collecting pipe (10). The gas collected in the gas collecting pipe (10) contains the following components: H2: 55.5 vol%, CH4: 21.8 vol%, CO: 4.9 vol%, CO2: 6.6 vol%, tar: 408 mg / Nm, naphthalene: 366 mg / Nm, BTX: 3900 mg / Nm.

[0060] Step 2): When the coking time is 2 / 3 of the total coking time, close the first flap (101) and open the second flap (201) to introduce the raw coal gas from the carbonization chamber into the hot gas pipe (20).

[0061] When the coking time of the carbonization chamber reaches 14 hours, close the ammonia water nozzle (301) on the bridge pipe (30) to stop spraying ammonia water, close the first flap (101) located at the inlet of the gas collecting pipe (10), open the second flap (201) located at the inlet of the hot gas pipe (20), and the raw coal gas from the carbonization chamber enters the hot gas pipe (20) until the coking time reaches 21 hours (final coking time);

[0062] Subsequently, the gas collected in the gas collecting pipe (10) is introduced into the coal gas refining unit, and the raw coal gas collected in the hot gas pipe (20) is directly introduced into the DRI unit or other reduction units as reducing gas. By this method, approximately 18,000 Nm / h of raw gas can be collected from the raw coal gas, which can be used for direct reduction of iron. The raw coal gas collected in the hot gas pipe (20) has a temperature of 800°C and contains the following components: H2: 74.5 vol%, CH4: 11.9 vol%, CO: 7.2 vol%, CO2: 2.2 vol%, tar: 5 mg / Nm, naphthalene: 10 mg / Nm, BTX: 150 mg / Nm.

[0063] Example 3

[0064] A steel plant needs to produce DRI with a metallization rate of over 90%, requiring an annual output of 500,000 tons. This invention collects raw coal gas from the later stages of coking time in a 200-hole, 7-meter coke oven as feed gas using the following method. In this embodiment, the final coking time in the carbonization chamber is 24 hours.

[0065] Specifically, the method includes the following steps performed sequentially:

[0066] Step 1): Starting from the coking of the carbonization chamber, close the second flap (201) of the hot gas pipe (20) and open the first flap (101) of the gas collecting pipe (10) to introduce the gas from the raw coal gas in the carbonization chamber into the gas collecting pipe (10).

[0067] Before the coking time in the coking chamber of the coke oven reaches 16.8 hours (i.e., 70% of the total coking time), ammonia water is sprayed by the ammonia water nozzle (301) on the bridge pipe (30). The first flap (101) at the inlet of the gas collecting pipe (10) is in the open state, and the second flap (201) at the inlet of the hot gas pipe (20) is in the closed state. The raw coal gas from the coking chamber is cooled and condensed into tar after being sprayed with ammonia water. The mixture of gas and tar enters the gas collecting pipe (10). The gas collected in the gas collecting pipe (10) contains the following components: H2: 57.5 vol%, CH4: 20.3 vol%, CO: 6.5 vol%, CO2: 3.6 vol%, tar: 212 mg / Nm, naphthalene: 305 mg / Nm, BTX: 2800 mg / Nm.

[0068] Step 2): When the coking time is 70% of the total coking time, close the first flap (101), open the second flap (201), and introduce the raw coal gas from the carbonization chamber into the hot gas pipe (20).

[0069] When the coking time of the carbonization chamber reaches 16.8 hours, close the ammonia water nozzle (301) on the bridge pipe (30), stop spraying ammonia water, close the first flap (101) located at the inlet of the gas collecting pipe (10), open the second flap (201) located at the inlet of the hot gas pipe (20), and introduce the raw coal gas from the carbonization chamber into the hot gas pipe (20).

[0070] Subsequently, the gas collected in the gas collecting pipe (10) is introduced into the gas refining unit, and the raw coal gas collected in the hot gas pipe (20) is used as reducing gas and sent to the DRI unit or other reduction units.

[0071] This method can collect approximately 24,000 Nm³ / h of raw gas from raw coal gas, which can be used for direct reduction of iron. The raw coal gas collected in the hot gas pipe (20) has a temperature of 700 °C and contains the following components: H₂: 73.8 vol%, CH₄: 10.7 vol%, CO: 8.3 vol%, CO₂: 2.0 vol%, tar: 8 mg / Nm³, naphthalene: 12 mg / Nm³, and BTX: 180 mg / Nm³.

[0072] While the present invention has been illustrated and described with reference to certain preferred embodiments, those skilled in the art should understand that the above description is a further detailed explanation of the invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the invention to these descriptions. Various changes in form and detail can be made by those skilled in the art, including several simple deductions or substitutions, without departing from the spirit and scope of the invention.

Claims

1. A coke oven waste gas collection device, characterized in that, The coke oven raw gas collection device includes a riser pipe and a gas collection unit. The riser pipe (40) is located at the top of the coke oven carbonization chamber and is connected to the coke oven carbonization chamber. The riser pipe (40) is connected to the gas collection unit via a bridge pipe (30). The gas collection unit includes: A gas collecting pipe (10), the inlet of which is controlled by a first flap (101); and Hot air pipe (20), the inlet of which is controlled by a second flap (201); From the moment coking begins in the carbonization chamber, the first flap (101) is in the open state, the second flap (201) is in the closed state, and the carbonization chamber is connected to the gas collecting pipe (10); During the period from 60% or more, preferably 2 / 3 or more, more preferably 70% or more of the total coking time in the carbonization chamber to the total coking time, the first flap (101) is in the closed state, the second flap (201) is in the open state, and the carbonization chamber is connected to the hot gas pipe (20).

2. The coke oven gas collection device according to claim 1, characterized in that, The bridge pipe is equipped with an ammonia nozzle (301).

3. The coke oven gas collection device according to claim 1, characterized in that, The outlet of the gas collecting pipe (10) is connected to the gas refining unit.

4. The coke oven gas collection device according to claim 1, characterized in that, The outlet of the hot gas pipe (20) is connected to the direct reduced iron unit.

5. The coke oven gas collection device according to claim 1, characterized in that, The coke oven includes multiple carbonization chambers and multiple gas collection units, with each carbonization chamber corresponding to one of the gas collection units.

6. A method for preparing feed gas for direct reduction of iron, characterized in that, The method includes the following steps performed sequentially: Step 1): Starting from the coking of the coke oven carbonization chamber, close the second flap (201) of the hot gas pipe (20) in the gas collection unit connected to the coke oven carbonization chamber through the pipeline, open the first flap (101) of the gas collection pipe (10) in the gas collection unit, and introduce the gas from the raw coal gas in the carbonization chamber into the gas collection pipe (10) for coal gas refining. Step 2): During the period from 60% or more, preferably 2 / 3 or more, more preferably 70% or more of the total coking time to the total coking time, close the first flap (101) of the gas collecting pipe (10) and open the second flap (201) of the hot gas pipe (20) to introduce the raw coal gas from the carbonization chamber into the hot gas pipe (20) as the raw material gas for direct reduction of iron.

7. The method according to claim 6, characterized in that, The method further includes step 2.1): introducing the gas collected in the gas collecting pipe (10) into the gas refining unit.

8. The method according to claim 6, characterized in that, The method further includes step 2.2): introducing the raw coal gas collected in the hot gas pipe (20) into the direct reduced iron unit.

9. The method according to claim 6, characterized in that, In step 1), ammonia water is sprayed when the first flap (101) of the gas collecting pipe (10) is opened, and in step 2), ammonia water spraying is stopped when the first flap (101) of the gas collecting pipe (10) is closed.

10. The method according to claim 6, characterized in that, In step 1), the gas collected in the gas collecting tube (10) includes the following components: H2 ≤ 55% by volume, CH4 ≥ 25% by volume, CO: 2-6% by volume, CO2: 3-8% by volume, tar: ≥ 200 mg / Nm, naphthalene: ≥ 300 mg / Nm, BTX: ≥ 2000 mg / Nm.

11. The method according to claim 6, characterized in that, In step 2), the raw coal gas collected in the hot gas pipe (20) includes the following components: H2 ≥ 70% by volume, CH4 ≤ 15% by volume, CO: 2-10% by volume, CO2: 1-6% by volume, tar: ≤ 10 mg / Nm, naphthalene: ≤ 30 mg / Nm, BTX: ≤ 300 mg / Nm.

12. The method according to claim 6, characterized in that, In step 2), the temperature of the raw coal gas collected in the hot gas pipe (20) is 700-800℃.

13. The method according to claim 6, characterized in that, The total coking time in the carbonization chamber is 19-25 hours.

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