Production equipment and production method of direct reduced iron

Abstract

The invention relates to production equipment and a production method for preparing direct reduced iron. 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 directly reducing iron can be obtained, and the method has the advantages of simple process, low energy consumption and the like.

Description

Technical Field

[0001] This invention relates to the field of non-blast furnace ironmaking technology, and in particular to a production equipment and method for direct reduced iron. 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 given the current coke oven riser pipe structure, it is difficult 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 direct reduced iron production apparatus, comprising a coke oven and an iron reduction unit, wherein the coke oven includes a carbonization chamber and a gas collection unit, the carbonization chamber being connected to the gas collection unit via a pipeline, and the gas collection unit comprising:

[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 iron reduction unit is connected to the hot gas pipe (20), and the iron reduction unit includes the following devices connected in sequence:

[0015] A heating furnace (50) is used to heat gas from a hot gas pipe (20);

[0016] The reduction shaft furnace (60) is used to reduce oxide pellets to produce direct reduced iron.

[0017] The coke oven described above can be used to prepare and collect raw gas for direct reduction of iron, and then pass the raw gas into the iron reduction unit to reduce iron oxide pellets to obtain direct reduced iron. The raw gas 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 reduction of iron process. It is worth noting that the temperature required to reduce iron oxide pellets is usually above 900℃. Therefore, regardless of the type of raw gas used for reduction, the raw gas must be heated. The raw gas collected in the coke oven of this invention has a physical sensible heat of 700-800℃. Therefore, compared with conventional raw gas, it consumes less fuel during heating, thereby achieving the purpose of energy saving. 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.

[0018] Preferably, the pipeline includes a riser pipe and a bridge pipe, and 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.

[0019] 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.

[0020] 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 the collection of more reducing gas that can be used for direct reduction of iron.

[0021] Preferably, the direct reduced iron production equipment further includes a purification furnace (70) between the hot gas pipe (20) and the heating furnace (50), wherein the purification furnace (70) is equipped with a cracking catalyst for cracking and purifying the gas from the hot gas pipe (20).

[0022] Although the raw gas collected in the hot gas pipe (20) can be used for direct reduction of iron, the raw gas can optionally be further cracked and purified again through the purification furnace (70) to reduce the content of heavy hydrocarbons such as tar, naphthalene, and BTX.

[0023] Specifically, the composition range of the purified gas is as follows: CH4 content ranges from 0-15% by volume, H2 content ranges from 70-85% by volume, CO content ranges from 2-10% by volume, CO2 content ranges from 0-3% by volume, N2 content ranges from 0-4% by volume, and C... n H m Content range 0-1% by volume, tar ≤5mg / Nm, naphthalene ≤10mg / Nm, BTX ≤100mg / Nm.

[0024] Preferably, the pre-reduced pellets are reduced pellets with a TFe content of ≥80% by mass.

[0025] From a cost perspective, reduced pellets with a TFe content of ≥80% by mass are preferred. Because they contain more than 80% by mass of Fe, they exhibit catalytic cracking properties, further purifying heavy hydrocarbon impurities. In this article, "TFe" refers to the total Fe content in the pellets.

[0026] Preferably, the direct reduced iron production equipment further includes an oxygen heating unit (80) between the heating furnace (50) and the reduction shaft furnace (60) for secondary heating of the gas from the heating furnace (50).

[0027] Since the raw material gas collected by the hot gas pipe (20) contains a large amount of H2, the heated raw material gas can be passed into the oxygen heating unit (80) to consume a small amount of H2 in the raw material gas and further increase the temperature of the gas, thereby promoting the subsequent reduction of iron oxide pellets.

[0028] Preferably, the direct reduced iron production equipment further includes a tail gas treatment unit (90), the inlet of which is connected to the reduction shaft furnace (60) for treating the tail gas from the reduction shaft furnace (60), and the outlet of which is connected to the heating furnace (50) to introduce the treated tail gas into the heating furnace (50) to realize the recycling of tail gas.

[0029] After reducing iron oxide pellets, the tail gas in the reduction shaft furnace (60) can be introduced into the tail gas treatment unit to remove components such as H2O and CO2 generated during the reduction process. The treated tail gas is then combined with the gas in the heating furnace and reheated before entering the shaft furnace to produce reduced iron in a cycle.

[0030] Preferably, the heating furnace is a tubular heating furnace.

[0031] Using a tubular furnace can improve gas heating efficiency, therefore a tubular furnace is preferred.

[0032] A second aspect of the present invention provides a method for producing direct reduced iron, comprising the following steps performed sequentially:

[0033] 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.

[0034] 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).

[0035] Step 3): The gas in the hot gas pipe (20) is introduced into the heating furnace of the iron reduction unit and heated in the heating furnace; preferably, the gas is heated to 900-1000°C in the heating furnace.

[0036] Step 4): The heated gas is introduced into the reduction shaft furnace to reduce the iron oxide pellets in the furnace to obtain direct reduced iron; preferably, the pressure of the reduction shaft furnace is 0.6 to 1.0 MPa.

[0037] 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. It can be directly collected and passed into the heating furnace and the reduction shaft furnace in sequence for direct reduction of iron (i.e., reduction of iron oxide pellets).

[0038] Preferably, the method further includes step 2.1): the gas collected in the gas collecting pipe (10) in step 1) 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.

[0039] Preferably, in step 1), ammonia is sprayed into the bridge pipe of the pipeline when the first flap (101) of the gas collecting pipe (10) is opened, and in step 2), ammonia spraying into the bridge pipe of the pipeline 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 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 for condensation, and the sensible heat of the gas during coking can be retained while ensuring the H2 content.

[0040] Preferably, in step 1), the gas collected in the gas collecting tube (10) contains 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.

[0041] Preferably, in step 2), the raw coal gas collected in the hot gas pipe (20) contains 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.

[0042] Preferably, in step 2), the temperature of the raw coal gas collected in the hot gas pipe (20) is 700-800℃.

[0043] Preferably, the total coking time in the carbonization chamber is 19 to 25 hours.

[0044] 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.

[0045] Preferably, the method further includes step 2.2) between step 2) and step 3): introducing the gas in the hot gas pipe (20) into the purification furnace (70) to obtain purified gas, and then introducing the purified gas into the heating furnace (50).

[0046] Preferably, the method further includes step 3.1) between step 3) and step 4): introducing the heated gas into the oxygen heating unit (80) to obtain a secondary heated gas, and introducing the secondary heated gas into the reduction vertical furnace (60); preferably, the temperature of the secondary heated gas is 1050-1100℃.

[0047] Preferably, the method further includes step 5): introducing the tail gas in the reduction shaft furnace into the tail gas treatment unit (90), treating the tail gas in the tail gas treatment unit, and introducing the treated tail gas into the heating furnace (50).

[0048] Preferably, the metallization rate of the direct reduced iron is 85% to 95%. The feed gas obtained by the present invention can achieve the same direct reduced iron metallization rate as existing methods, and is less expensive than conventionally purchased H2 feed gas.

[0049] Beneficial effects of this invention:

[0050] 1) This invention can directly obtain raw material gas for direct reduction of iron by collecting the portion of raw coal gas with high H2 content. After reducing iron, the raw material gas can produce low carbon emissions, effectively solving the shortcomings of the current coke oven gas used for direct reduction of iron, which has low H2 content, high CH4 content and high content of heavy hydrocarbon impurities.

[0051] 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

[0052] Figure 1 This is a schematic diagram of the structure of a conventional coke oven;

[0053] Figure 2 This is a schematic diagram of the structure of a coke oven for preparing feed gas for direct DRI according to an embodiment of the present invention.

[0054] Figure 3 This is a flowchart of an iron reduction unit according to an embodiment of the present invention.

[0055] 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; 50-Heating furnace; 60-Reduction vertical furnace; 70-Purification furnace; 80-Oxygen heating unit; 90-Tail gas treatment unit. Detailed Implementation

[0056] 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.

[0057] 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.

[0058] 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.

[0059] Gas composition detection methods

[0060] 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.

[0061] 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.

[0062] 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).

[0063] 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).

[0064] 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).

[0065] 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).

[0066] 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.

[0067] Figure 3 A flowchart of the iron reduction unit of the present invention is shown, wherein a hot gas pipe (20) is sequentially connected to an optional purification furnace (70), a heating furnace (50), an optional oxygen heating unit (80), and a reduction shaft furnace (60). Optionally, the outlet of the reduction shaft furnace (60) is connected to a tail gas treatment unit (90) for introducing tail gas into the tail gas treatment unit (90) for treatment, and the outlet of the tail gas treatment unit (90) is connected to the heating furnace (50) to introduce the treated tail gas into the heating furnace (50), thereby achieving tail gas recycling.

[0068] Example 1

[0069] 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:

[0070] 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).

[0071] 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.

[0072] 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).

[0073] 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);

[0074] 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.

[0075] 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 by volume: H₂: 70.8 vol%, CH₄: 14.5 vol%, CO: 9.2 vol%, CO₂: 2.7 vol%, tar: 10 mg / Nm³, naphthalene: 30 mg / Nm³, BTX: 300 mg / Nm³.

[0076] Example 2

[0077] 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:

[0078] 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).

[0079] 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.

[0080] 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).

[0081] 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);

[0082] 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.

[0083] Example 3

[0084] 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.

[0085] Specifically, the method includes the following steps performed sequentially:

[0086] 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).

[0087] 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.

[0088] 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).

[0089] 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).

[0090] 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.

[0091] 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.

[0092] Example 4

[0093] The raw material gas prepared in Example 2 was heated to 900°C in a heating furnace (50), and then the heated gas was passed into a reduction shaft furnace (60) to reduce the iron oxide pellets therein. The TFe content of the iron oxide pellets was 65% by mass, and the pressure of the reduction shaft furnace was 0.6 MPa. After the reduction, the tail gas was treated by a tail gas treatment unit (90) to remove H2O and CO2, and then mixed with the raw material gas again and entered the heating furnace (50) for heating, and then entered the reduction shaft furnace (60) to circulate and produce reduced pellets. The final DRI metallization rate was 88%.

[0094] Example 5

[0095] The raw material gas prepared in Example 2 was heated to 900°C in a heating furnace (50), and then the heated gas was passed into an oxygen heating unit (80) to raise the gas temperature to 1050°C. The gas, after being heated a second time, was then passed into a reduction shaft furnace (60) to reduce the iron oxide pellets therein. The iron oxide pellets had a TFe content of 65% by mass, and the reduction shaft furnace pressure was 0.8 MPa. The tail gas after reduction was treated by a tail gas treatment unit (90) to remove H2O and CO2, and then mixed with the raw material gas again before being heated in the heating furnace (50). The mixture was then passed into the oxygen heating unit (80) and the reduction shaft furnace (60) in sequence to produce reduced pellets. The final DRI metallization rate was 90%.

[0096] Example 6

[0097] The raw material gas prepared in Example 2 was heated to 1000°C in a heating furnace (50), and then the heated gas was passed into an oxygen heating unit (80) to raise the gas temperature to 1100°C. The gas was then passed into a reduction shaft furnace (60) to reduce the iron oxide pellets therein. The iron oxide pellets had a TFe content of 65% by mass, and the reduction shaft furnace pressure was 1.0 MPa. The tail gas after reduction was treated by a tail gas treatment unit (90) to remove H2O and CO2, and then mixed with the raw material gas again before being heated in the heating furnace (50). The mixture was then passed into the oxygen heating unit (80) and the reduction shaft furnace (60) in sequence to produce reduced pellets. The final DRI metallization rate was 92%.

[0098] Example 7

[0099] The raw material gas prepared in Example 2 was introduced into the purification furnace (70) to obtain purified gas. The composition of the purified gas was: CH4 content 11% by volume, H2 content 76% by volume, CO content 5.5% by volume, CO2 content 4% by volume, N2 content 3% by volume, C n H m The gas contains 0.2% by volume, 2 mg / Nm of tar, 5 mg / Nm of naphthalene, and 50 mg / Nm of BTX. The purified gas is then heated to 900°C in a heating furnace (50), and then passed into an oxygen heating unit (80) to raise the gas temperature to 1050°C. The reheated gas is then passed into a reduction shaft furnace (60) to reduce the iron oxide pellets. The iron oxide pellets contain 65% by mass of TFe, and the reduction shaft furnace pressure is 0.8 MPa. The reduced tail gas is treated by a tail gas treatment unit (90) to remove H2O and CO2, and then mixed again with the raw material gas before being heated in the heating furnace (50). This mixture is then sequentially passed into the oxygen heating unit (80) and the reduction shaft furnace (60) to circulate and produce reduced pellets. The final DRI metallization rate is 95%.

[0100] 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 direct reduced iron production apparatus, comprising a coke oven and an iron reduction unit, characterized in that, The coke oven includes a carbonization chamber and a gas collection unit. The carbonization chamber is connected to the gas collection unit via a pipeline. 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). The iron reduction unit is connected to the hot gas pipe (20), and the iron reduction unit includes the following devices connected in sequence: A heating furnace (50) is used to heat gas from a hot gas pipe (20); The reduction shaft furnace (60) is used to reduce oxide pellets to produce direct reduced iron.

2. The direct reduced iron production equipment according to claim 1, characterized in that, The pipeline includes an ascender pipe (40) and a bridge pipe (30), and the bridge pipe is provided with an ammonia nozzle (301).

3. The direct reduced iron production equipment according to claim 1, characterized in that, The outlet of the gas collecting pipe (10) is connected to the gas refining unit.

4. The direct reduced iron production equipment 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.

5. The direct reduced iron production equipment according to claim 1, characterized in that, The direct reduced iron production equipment also includes a purification furnace (70) between the hot gas pipe (20) and the heating furnace (50), wherein the purification furnace (70) is filled with pre-reduced pellets for cracking and purifying the gas from the hot gas pipe (20).

6. The direct reduced iron production equipment according to claim 5, characterized in that, The pre-reduced pellets are reduced pellets with a TFe content of ≥80% by mass.

7. The direct reduced iron production equipment according to claim 1, characterized in that, The direct reduced iron production equipment also includes an oxygen heating unit (80) between the heating furnace (50) and the reduction shaft furnace (60) for secondary heating of the gas from the heating furnace (50).

8. The direct reduced iron production equipment according to claim 1, characterized in that, The direct reduced iron production equipment also includes a tail gas treatment unit (90). The inlet of the tail gas treatment unit (90) is connected to the reduction shaft furnace (60) for treating the tail gas from the reduction shaft furnace (60), and the outlet of the tail gas treatment unit (90) is connected to the heating furnace (50) to introduce the treated tail gas into the heating furnace (50) to realize the recycling of tail gas.

9. The direct reduced iron production equipment according to claim 1, characterized in that, The heating furnace (50) is a tubular heating furnace.

10. A method for producing direct reduced iron, characterized in that, The method includes the following steps performed sequentially: 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. 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). Step 3): The gas in the hot gas pipe (20) is introduced into the heating furnace (50) of the iron reduction unit and heated in the heating furnace (50); preferably, the gas is heated to 900-1000°C in the heating furnace (50); Step 4): The heated gas is introduced into the reduction shaft furnace (60) to reduce the oxide pellets in the reduction shaft furnace (60) to obtain direct reduced iron; preferably, the pressure in the reduction shaft furnace (60) is 0.6 to 1.0 MPa.

11. The method according to claim 10, characterized in that, The method further includes step 2.1): introducing the gas collected in the gas collecting pipe (10) in step 1) into the gas refining unit.

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

13. The method according to claim 10, characterized in that, In step 1), the gas collected in the gas collecting tube (10) contains 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.

14. The method according to claim 10, characterized in that, In step 2), the raw coal gas collected in the hot gas pipe (20) contains 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.

15. The method according to claim 10, characterized in that, In step 2), the temperature of the raw coal gas collected in the hot gas pipe (20) is 700-800℃.

16. The method according to claim 10, characterized in that, The total coking time in the carbonization chamber is 19-25 hours.

17. The method according to claim 10, characterized in that, The method further includes step 2.2) between step 2) and step 3): the gas in the hot gas pipe (20) is introduced into the purification furnace (70) to obtain purified gas, and then the purified gas is introduced into the heating furnace (50).

18. The method according to claim 10, characterized in that, The method further includes step 3.1) between step 3) and step 4): the heated gas is introduced into the oxygen heating unit (80) to obtain the secondary heated gas, and the secondary heated gas is introduced into the reduction vertical furnace (60); preferably, the temperature of the secondary heated gas is 1050-1100℃.

19. The method according to claim 10, characterized in that, The method further includes step 5): introducing the tail gas in the reduction vertical furnace into the tail gas treatment unit (90), treating the tail gas in the tail gas treatment unit, and introducing the treated tail gas into the heating furnace (50).

20. The method according to claim 10, characterized in that, The metallization rate of the direct reduced iron is 85% to 95%.

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