A method for producing high temperature coal gas based on an arc plasma torch

Abstract

This invention provides a method for generating high-temperature coal gas based on an electric arc plasma torch, comprising the following steps: feeding carbon-containing powder and at least one energy-carrying medium into different inlets of the electric arc plasma torch; the carbon-containing powder being carried circumferentially and uniformly into the arc channel within the electric arc plasma torch by a carrier gas; the at least one energy-carrying medium, after entering the electric arc plasma torch, passing through a fluid passage on the arc channel wall and entering the arc channel; initiating an electric arc in the arc channel to generate plasma; the energy-carrying medium and the carbon-containing powder being heated together by the plasma, and then ejected together from the nozzle of the electric arc plasma torch. This invention utilizes the energy-carrying medium to perform divergent cooling, evaporative cooling, or endothermic chemical reactions near the arc channel wall, directly absorbing the radiation and convection heat transfer to the pipe wall from the plasma, greatly improving the thermal efficiency of the plasma torch, and inhibiting coking of the gasified carbon-containing powder on the arc channel wall of the plasma torch.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature gas processing technology, and specifically relates to a method for generating high-temperature gas based on an electric arc plasma torch. Background Technology

[0002] Using renewable energy to generate plasma energy for heating, the carbon dioxide produced during iron smelting reduction and cement limestone decomposition is reduced to coal gas, and the energy required for iron smelting reduction and limestone decomposition is provided, which can achieve near-zero carbon emissions in iron smelting and cement production.

[0003] During blast furnace ironmaking, coal gas is used as the energy carrier to provide the heat required by the blast furnace, with coal gas temperatures reaching as high as 3000K. An effective method is to use an electric arc plasma torch to heat the coal gas or reduce carbon dioxide to produce coal gas. The electric arc plasma torch is connected to a dedicated coal gas generator and blast furnace. For example, patent ZL202210468187.2 discloses an electric arc channel that directly feeds carbon dioxide and pulverized coal into the plasma torch. The high temperature of the electric arc plasma directly heats the carbon dioxide and pulverized coal, generating coal gas within the plasma torch. This improves the conversion rate of pulverized coal, and the absorption of electric arc radiation by the pulverized coal enhances the thermal efficiency of the plasma torch. The main components of the coal gas are CO and H2, and it also includes small amounts of C2H2, CH4, etc., as well as incompletely reacted CO2, H2O, aromatics, other small organic molecules from coal pyrolysis, and incompletely gasified carbonaceous solid powder slag. However, due to the high temperature of the electric arc and its edge, the carbon-containing powder is rapidly pyrolyzed and vaporized, producing active C, H and their compound small molecules, which will further diffuse and cause the arc channel wall to heat up further. At the same time, the high-temperature carbon-containing powder and CH compound small molecules are very easy to deposit and coke on the arc channel wall.

[0004] In addition, the heat loss of high-power plasma torches requires cooling, and the cooling power is enormous, reaching 10%-40%. Therefore, reducing the heat loss of plasma torches and improving their thermal efficiency has great economic benefits and practical value. Summary of the Invention

[0005] To address the technical problems existing in the background art, this invention proposes a method for generating high-temperature coal gas based on an electric arc plasma torch. This invention solves the cooling problem of the arc channel wall of the electric arc plasma torch during coal gas heating and improves thermal efficiency.

[0006] The specific technical solution of the present invention is as follows:

[0007] The objective of this invention is to provide a method for generating high-temperature coal gas based on an electric arc plasma torch, which includes the following steps:

[0008] S1. Carbon powder and at least one energy-carrying medium are fed into different inlets of the electric arc plasma torch.

[0009] S2. The carrier gas carries carbon-containing powder into the arc channel of the arc plasma torch in a circumferential and uniform manner.

[0010] S3. After at least one energy-carrying medium enters the arc plasma torch, it passes through the fluid passage on the arc channel wall and enters the arc channel.

[0011] S4. Initiating an electric arc in the arc channel to generate plasma;

[0012] S5. The energy-carrying working medium and carbon-containing powder entering the electric arc channel are heated together by the plasma, and then ejected together from the nozzle of the electric plasma arc torch.

[0013] The high-temperature coal gas ejected from the nozzle of the electric arc plasma torch provides the energy required for the ironmaking reduction and limestone decomposition processes. It also reduces the carbon dioxide produced during the ironmaking reduction and cement limestone decomposition processes to coal gas, thus achieving near-zero carbon emissions in ironmaking and cement production.

[0014] In a further embodiment, the energy-carrying medium in this invention can be one of the following three types:

[0015] The first method uses an oxidizing medium as the energy-carrying medium. Carbon-containing powder flows toward the electric arc in a centripetal flow manner. Some of the carbon-containing powder is pyrolyzed and gasified into CH small molecule compounds. The CH small molecule compounds react with the oxidizing medium to generate high-temperature coal gas.

[0016] The oxidizing medium includes liquid water, water vapor, liquid carbon dioxide, and carbon dioxide gas.

[0017] The carbon-containing powder entering the arc channel flows centripetally towards the arc. The plasma generated by the arc completely pyrolyzes the carbon-containing powder near the arc column, partially vaporizes the fixed carbon, and generates CH small molecule compounds. The high temperature at the edge of the arc can also partially pyrolyze the carbon-containing powder. The energy-carrying medium enters the arc channel through the fluid passage on the arc channel wall. It has oxidizing properties and reacts with CH small molecule compounds near the arc channel wall to generate coal gas. The unpyrolyzed carbon-containing powder and energy-carrying medium are heated by the arc and then mixed with the generated coal gas before being ejected.

[0018] In addition, since the reaction is endothermic, it can reduce the temperature near the arc channel wall; at the same time, the unpyrolyzed carbon powder in the lower temperature area near the arc channel wall can also shield the plasma from radiation to the pipe wall, thereby reducing the heat transfer of the arc plasma to the pipe wall, reducing the loss of the plasma torch, and inhibiting the coking of CH small molecule compounds on the arc channel wall.

[0019] In the second scenario, the energy-carrying medium is a reducing medium, and the carbon-containing powder enters the arc channel uniformly in a centrifugal manner; that is, the carbon-containing powder enters the arc channel along the arc channel wall, away from the arc column, reducing its pyrolysis, while isolating the arc radiation and convection from heat transfer to the pipe wall; then it is mixed with the energy-carrying medium, heated, and then sprayed out.

[0020] The reducing medium includes carbon monoxide, hydrogen, blast furnace gas, coke oven gas, water gas, natural gas, or any mixture thereof;

[0021] The carrier gas carrying the carbon powder is CO2, O2, air, or water vapor. Preferably, the ratio of the sum of the molar flow rates of C and H elements in the carrier gas, carbon powder, and energy-carrying medium to the molar flow rate of O element is less than 1, so as to reduce carbon enrichment and wall coking.

[0022] In the third scenario, when the energy-carrying medium is of two types, namely a liquid medium and a gaseous medium: the liquid medium and the gaseous medium enter the arc plasma torch from two non-directly connected fluid channels, wherein the liquid medium cools the arc channel wall, and the gaseous medium enters the arc channel through the fluid passage and is heated by the plasma together with the carbon-containing powder.

[0023] When the working gas is oxygen, the carbon powder carried by the gas is CO2, and the carbon powder enters the arc channel uniformly by centrifugation to mix with the working gas; the working liquid is liquid water or carbon dioxide.

[0024] When the carbon-containing powder is mixed with oxygen and uniformly enters the arc channel and mixes with the gaseous working medium in a rotating centrifugal flow manner, the gaseous working medium is CO or coal gas, and the liquid working medium is liquid water or carbon dioxide.

[0025] Oxygen can be directly mixed with carbon-containing powder and introduced into the arc channel, in which case the working gas can be CO or coal gas; alternatively, oxygen can be introduced into the arc channel from another inlet and mixed with carbon-containing powder, in which case the gas carrying the carbon-containing powder must be CO2. In both methods, carbon-containing powder and oxygen are mixed to achieve oxygen-thermal coal powder, which can significantly reduce plasma energy and thus reduce power load.

[0026] The gaseous energy carrier can also be carbon dioxide, water vapor, or a mixture of gases containing carbon dioxide and / or water vapor, with carbon powder entering the arc channel uniformly in a radial-centripetal manner; the liquid working medium is liquid water or carbon dioxide.

[0027] The gaseous energy carrier can also be carbon monoxide, coal gas, or a mild gas containing carbon dioxide / or water vapor. The carbon powder enters the arc channel uniformly in a rotating centrifugal flow manner. The liquid working medium is liquid water or carbon dioxide.

[0028] In a further embodiment, when a through hole is provided on the wall of the arc channel, the through hole is a micropore in a mesh-like multi-micropore structure, and the liquid working fluid passes through the wall of the arc channel to enter the arc channel and evaporate and cool the wall of the arc channel.

[0029] When the liquid working medium is an oxidant, it passes through the wall of the electric arc channel and enters the electric arc channel to react with some of the carbon-containing powder that has been pyrolyzed and gasified by the plasma to form CH small molecule compounds, thereby generating coal gas and reducing the temperature near the wall of the electric arc channel.

[0030] In a further embodiment, the energy-carrying medium described in step S3 passes through the fluid passage on the wall of the arc channel and enters the arc channel. The fluid passage is a micropore in a mesh-like microporous structure, which diffuses and cools the wall of the arc channel.

[0031] In a further embodiment, the carbon-containing powder includes at least one of the following: coal powder, coal coke powder, petroleum coke powder, waste plastics, rubber granules, low-hydrogen carbon powder, and biomass pellets; wherein the low-hydrogen carbon powder includes anthracite powder, biomass carbon powder, coke powder, and semi-coke powder.

[0032] The carrier gas in the carbon-containing powder is CO2, CO, water vapor, coal gas, nitrogen, or air; the molar flow ratio of the carrier gas to the energy-carrying medium is less than 0.5, preferably less than 0.2. High concentration of carbon-containing powder is beneficial for direct arc heating of the carbon-containing powder, improving the degree of carbon powder vaporization, and the vaporization energy of the carbon-containing powder can increase the electric field strength and power density of the arc.

[0033] In this invention, carbon-containing powder flows towards the electric arc in a centripetal flow manner or enters the electric arc channel uniformly in a centrifugal flow manner. The centripetal flow and centrifugal flow are relative; that is, the centripetal flow can have tangential and axial components, with the radial centripetal component being the largest. The centrifugal flow can also have axial and radial flow components, with the angular flow component being greater than the radial centripetal flow component. When the energy-carrying medium is an oxidizing medium such as carbon dioxide or water, the carbon-containing powder enters the electric arc channel in a radial centripetal flow manner, and the carbon-containing powder enters the electric arc column, increasing the carbon content of the powder. The carbon-containing powder undergoes final gasification and reacts with the oxidizing medium to generate coal gas. When the energy-carrying medium is a reducing gas such as carbon monoxide or coal gas, the carbon-containing powder enters the arc channel via a rotating centrifugal flow, separates from the arc column, and concentrates near the arc channel wall, reducing the gasification of the carbon-containing powder. The carbon-containing powder also isolates the arc from heat transfer to the arc channel wall, and the arc mainly heats the carbon monoxide or coal gas. When the gaseous medium is oxygen, or when the carbon-containing powder is mixed with oxygen, the carbon-containing powder enters the arc channel via a rotating centrifugal flow, concentrates near the arc channel wall, and isolates the arc from heat transfer to the arc channel wall.

[0034] In this invention, the carbon-containing powder can flow towards the electric arc in a centripetal manner or enter the electric arc channel uniformly in a centrifugal manner, which can be achieved by setting the entry direction of the inlet.

[0035] In this invention, after the energy-carrying medium enters the electric arc plasma torch, it passes through the fluid passage on the wall of the electric arc channel and enters the electric arc channel. The fluid passage is set on the wall of the electric arc channel, such as the wall of the electric arc channel being made of a porous material, or a through hole being opened on the wall of the electric arc channel. The diameter of the through hole can be set according to the actual situation.

[0036] The electric arc plasma torch used in this invention is existing. To achieve the technical solution of this invention, the structure of the electric arc plasma torch can be improved according to the purpose of this invention. For example, the number of inlets, the direction of entry, and the composition of the arc channel walls can all be set according to different needs. For instance, setting one or two channels on the outer periphery of the arc channel is based on the number of energy-carrying media. However, its structure is not the focus of this application. The core of this application is a method for generating high-temperature coal gas based on an electric arc plasma torch. Therefore, this application will not describe the structure of the electric arc plasma torch in detail.

[0037] To meet the radiative cooling requirements of the arc channel wall, the mass flow rate of the energy-carrying working fluid is much greater than the mass flow rate of the carrier gas carrying carbon-containing powder, while also meeting the requirements for coal gas production and heating.

[0038] The present invention realizes the use of plasma from an electric arc plasma torch to heat coal gas, generating high-temperature coal gas, and utilizes the energy-carrying working medium to enter the electric arc channel through the fluid passage on the wall of the electric arc channel to diffuse and cool the wall of the electric arc channel.

[0039] In addition, during heating, some carbon-containing powder is pyrolyzed and vaporized by plasma into CH small molecule compounds. These CH small molecule compounds react with the oxidizing medium to generate high-temperature gas. Since this reaction is endothermic, it can lower the temperature near the arc channel wall. This allows the unvaporized carbon-containing powder in the lower temperature region near the arc channel wall to also shield the tube wall from plasma radiation, thereby reducing heat transfer from the arc plasma to the tube wall, reducing plasma torch wear, and inhibiting the coking of CH small molecule compounds on the arc channel wall.

[0040] This invention can also include a dedicated liquid working fluid for cooling. The liquid and gaseous working fluids enter the arc plasma torch through two separate, non-directly connected fluid channels. The liquid working fluid cools the arc channel walls, while the gaseous working fluid enters the arc channel through the fluid pathway and is heated by the plasma along with the carbon-containing powder. Alternatively, the liquid working fluid can pass through the micropores in the mesh-like microporous structure of the arc channel wall to achieve evaporative cooling of the arc channel wall.

[0041] Therefore, the method of the present invention can be used to form the following process for generating high-temperature coal gas:

[0042] 1) High-temperature water gas is produced by plasma heating of carbon powder and water;

[0043] 2) Plasma heating of carbon powder and CO2 reduces CO2 to produce high-temperature gas;

[0044] 3) Cold coal gas enters the electric arc plasma torch and is heated into high-temperature coal gas by the plasma;

[0045] 4) High-temperature coal gas is produced from plasma-induced oxygen-thermal carbon powder;

[0046] 5) Oxygen-heated coal gas.

[0047] In addition, the raw materials mentioned in 1), 2), and 3) above can be combined with each other to still generate high-temperature coal gas; such as water + CO2 + carbon powder, water + clean coal gas + carbon powder, water + furnace top gas (CO + H2 + CO2) + carbon powder, etc.

[0048] This invention centrifuges carbon-containing powder into the arc channel, where it absorbs radiation from the arc plasma onto the channel wall, reducing plasma torch losses. Furthermore, by reducing the amount of gas carried in the powder, a high concentration of carbon-containing powder is formed, increasing the powder's residence time in the arc channel and allowing the arc to directly heat it, thus improving the degree of carbon powder vaporization and increasing the plasma enthalpy. This, in turn, increases the power density of the plasma generator and improves the thermal efficiency of the plasma torch. Simultaneously, the vaporization of the carbon powder enhances the electric field strength and power density of the arc.

[0049] This invention employs an energy-carrying medium to perform divergent cooling, evaporative cooling, or endothermic chemical reactions near the arc channel wall, directly absorbing the heat transfer from plasma radiation and convection to the pipe wall, greatly improving the thermal efficiency of the plasma torch, and inhibiting the coking of carbon-containing powder gasified substances on the arc channel wall of the plasma torch.

[0050] This invention reduces the heat loss of the plasma torch and improves the heat utilization rate of the plasma, allowing the heat energy to be fully utilized in industrial kilns. Combined with chemical energy storage, the process of this invention has an energy efficiency of over 95%. Therefore, the high-temperature gas produced by the method of this invention has extremely high energy efficiency and can operate in various variable power load modes, and can directly absorb a large amount of intermittent renewable energy power. This invention can be used for low-carbon ironmaking in blast furnaces, cement limestone decomposition, and carbon dioxide reduction, and can also be used to produce gas in combination. Detailed Implementation

[0051] The present invention will be further described in detail below through specific embodiments.

[0052] Example 1:

[0053] A method for generating high-temperature coal gas based on an electric arc plasma torch includes the following steps:

[0054] S1. Carbon powder and an energy-carrying medium are fed into the two inlets of the electric arc plasma torch, respectively; wherein the carbon powder is coal powder and the energy-carrying medium is water vapor.

[0055] S2, CO2 gas carries pulverized coal into the arc channel of the electric arc plasma torch in a circumferentially uniform manner; specifically, it flows towards the arc in a centripetal flow manner.

[0056] S3. After the energy-carrying working medium enters the electric arc plasma torch, it passes through the fluid passage on the wall of the electric arc channel and enters the electric arc channel to conduct divergent cooling of the electric arc channel wall.

[0057] S4. Initiating an electric arc in the arc channel to generate plasma;

[0058] S5. The working medium and carbon-containing powder entering the arc channel are heated by plasma together. The carbon-containing powder entering the arc column is completely pyrolyzed, and the remaining fixed carbon is partially vaporized to generate CH small molecule compounds. The working medium reacts with the CH small molecule compounds near the arc channel wall to generate high-temperature gas. Then, the high-temperature gas, along with the unpyrolyzed carbon-containing powder and the unreacted working medium, is ejected from the nozzle of the plasma torch.

[0059] Since the reaction is endothermic, it can absorb a large amount of heat, thus reducing the temperature near the arc channel wall. At the same time, the unpyrolyzed and unvaporized carbon powder in the lower temperature area near the pipe wall mainly acts to shield the plasma from radiation to the pipe wall, thereby reducing the heat transfer of the arc plasma to the pipe wall, reducing the loss of the plasma torch, and inhibiting the coking of the vaporized substances in the carrier gas carbon powder on the arc channel wall.

[0060] The specific reaction process is as follows:

[0061] The oxidizing medium is generally carbon dioxide or water. The main component of carbon powder is carbon, or carbon powder contains hydrocarbons that undergo pyrolysis to produce carbon. The main reaction formula is as follows:

[0062] C+CO2→2CO ΔH=172.5kJ / mol-C

[0063] C + H₂O (g) →CO + H₂ ΔH=131.3kJ / mol⁻¹

[0064] The main components of the generated coal gas are CO and H2, and it also includes small amounts of C2H2, CH4, etc., as well as unreacted CO2, H2O, aromatics, other small organic molecules from coal pyrolysis, and incompletely gasified coal slag.

[0065] For industrial carbon capture and utilization, CO2 is reduced by hydrogen decomposed in carbon-containing powder and absorbs heat to lower the temperature near the arc channel wall:

[0066] CO2 + H2 → CO + H2O (g) ΔH = 54.4 kJ / mol-H2

[0067] In this embodiment, the main energy-carrying working fluid oxidant is water, and the gas carrying a small amount of pulverized coal is CO2, thus mainly producing water gas. The oxygen content entering the arc channel is usually slightly greater than the carbon and hydrogen content, so that the carbon element can be fully utilized.

[0068] The average temperature of the generated gas is between 1000 and 4000 K, and the waste heat is utilized in subsequent processes.

[0069] To meet the cooling requirements of the arc channel wall, the mass flow rate of the energy-carrying medium is much greater than the mass flow rate of the gas carrying carbon powder; wherein the molar flow rate ratio of the gas carrying carbon powder to the energy-carrying medium is less than 0.2, for example, the flow rate of the gas carrying carbon powder is 50 Nm³. 3 / h / MW, the energy-carrying working fluid steam quantity is 250Nm 3 / h / MW, with an output gas temperature of approximately 3000K.

[0070] The average particle size of pulverized coal is 40 μm, and the radial velocity of the particles entering the arc channel is 8 to 10 m / sec. Large particles can easily enter the arc column, while most small particles are blocked outside the arc column due to the thermal surge force.

[0071] Because the amount of gas carrying carbon powder is relatively small, the carbon powder is highly vaporized in the arc channel of the arc plasma torch, with a vaporization rate of generally 20-70%, and reacts rapidly with the oxidant in the energy-carrying medium to generate coal gas; the temperature near the tube wall is low, and the unvaporized carbon powder in this area mainly serves to shield the tube wall from plasma radiation.

[0072] Unvaporized carbon-containing powder near the arc channel wall shields the arc channel wall from radiation from the plasma, high-temperature gas, and high-temperature carbon-containing powder, reducing convective heat transfer from the plasma to the tube wall. Water vapor, the energy-carrying medium, diffuses through micropores in the arc channel wall, cooling the tube wall. The oxidant undergoes a heat-absorbing reduction reaction with the vaporized carbon-containing powder near the tube wall, further reducing convective heat transfer from the plasma to the tube wall. Heat loss from the plasma to the tube wall can be reduced to below 5% of the arc power, and the tube wall temperature can be controlled below 1000K. The heat transferred to the arc channel tube wall is absorbed by the energy-carrying medium and returns to the plasma torch, ensuring full energy utilization.

[0073] Because the arc channel is primarily composed of high-enthalpy CH plasma, with carbon vapor reaching 300–800 kJ / mol, it possesses extremely high energy density. Simultaneously, the high thermal conductivity of atomic hydrogen and gaseous carbon at the arc edge, through their cooling and compression effect, significantly enhances the arc's electric field strength and power density. The arc electric field strength is also related to the arc channel diameter and the magnitude of the arc current, typically ranging from 10 to 50 V / cm. For high-power arc plasma torches, increased arc voltage is necessary, requiring an arc channel length-to-diameter ratio greater than 5, preferably greater than 10. Arc voltages are typically higher than 1–10 kV. However, higher voltages are detrimental to operational safety.

[0074] Due to the current tolerance of electrode materials, the arc current is usually less than 5000A. High current is beneficial to increase the arc range and improve the gasification rate of carbon-containing powder, but high current will affect the electrode life. A current of 500 to 5000A is preferred.

[0075] Example 2:

[0076] Same as Example 1, except that the carbon-containing powder is coal coke powder, which is transported by coal gas; and the energy-carrying medium is carbon dioxide gas.

[0077] Example 3:

[0078] A method for generating high-temperature coal gas based on an electric arc plasma torch includes the following steps:

[0079] S1. Carbon powder and an energy-carrying medium are fed into the two inlets of the electric arc plasma torch respectively; wherein the carbon powder is anthracite powder and the energy-carrying medium is carbon monoxide.

[0080] S2. The pulverized coal carried by CO2 gas enters the arc channel of the electric arc plasma torch in a circumferential manner; specifically, it enters the arc channel in a centrifugal manner; that is, the carbon-containing powder enters the arc channel along the arc channel wall, away from the arc column, reducing its vaporization by the plasma.

[0081] S3. After the energy-carrying working medium enters the electric arc plasma torch, it passes through the fluid passage on the wall of the electric arc channel and enters the electric arc channel to conduct divergent cooling of the electric arc channel wall.

[0082] S4. Initiating an electric arc in the arc channel to generate plasma;

[0083] S5. The CO and carbon-containing powder entering the arc channel are heated together by the plasma and then ejected together from the nozzle of the plasma torch.

[0084] In this embodiment, CO and carbon-containing powder are heated together by plasma into a high-temperature gas, which is then used as the reaction gas in the subsequent process.

[0085] Choose an arc current of 800A to reduce arc radiation.

[0086] The pulverized coal flow rate is 50–100 kg / h / MW, and the carrier gas CO2 flow rate is approximately 50 Nm³. 3 / h / MW. Pulverized coal is concentrated near the arc channel wall to isolate arc radiation and convection from heat transfer to the arc channel wall. The heat transfer to the channel wall is approximately 5-10% of the arc power, and the working fluid gas flow rate is 1000 Nm³. 3 / h / MW, the gas temperature is approximately 2800K.

[0087] Example 4:

[0088] Same as Example 3, except that the carbon-containing powder is waste plastic powder, which is carried by CO; the energy-carrying medium is the clean coal gas after CO2 is separated from the nitrogen-free blast furnace gas, which mainly includes CO and a small amount of H2, CO2, CH4, N2, etc. The coal gas has undergone deep purification treatment, including desulfurization, deacidification, dust removal and removal of organic molecules above C2.

[0089] Example 5:

[0090] A method for generating high-temperature coal gas based on an electric arc plasma torch includes the following steps:

[0091] S1. Carbon powder and two energy carriers are fed into the three different inlets of the electric arc plasma torch respectively; the carbon powder is anthracite powder, and the energy carriers are oxygen and liquid water.

[0092] S2. The anthracite is carried by CO2 gas into the arc channel of the electric arc plasma torch in a circumferential and uniform manner; specifically, it enters the arc channel in a centrifugal manner; that is, the carbon powder enters the arc channel along the wall of the arc channel, away from the arc column, reducing its vaporization by the plasma.

[0093] S3. Two types of energy-carrying media enter the arc plasma torch through two non-directly connected fluid channels. Liquid water cools the arc channel walls after entering the arc plasma torch, while oxygen enters the arc channel through a fluid passage.

[0094] S4. Initiating an electric arc in the arc channel to generate plasma;

[0095] S5. The oxygen and carbon powder entering the arc channel are heated by the plasma together. Some of the carbon powder and O2 burn and react with water to produce CO and H2, which are then ejected together from the nozzle of the plasma torch.

[0096] In this embodiment, oxygen and carbon-containing powder are mixed together and ignited by plasma, achieving the generation of water gas from oxythermal pulverized coal. The plasma energy mainly serves to ignite the carbon-containing powder, thereby reducing power consumption. The ungasified pulverized coal is then fed into the blast furnace for further gasification. Compared with existing pulverized coal injection technology, the pre-gasification of pulverized coal within the plasma torch improves the carbon utilization rate of the pulverized coal and can increase the pulverized coal injection ratio while reducing the blast furnace coke ratio.

[0097] Example 6:

[0098] Same as Example 5, except that the carbon-containing powder is petroleum coke powder, which is carried by CO2; the energy carrier is oxygen and liquid carbon dioxide; wherein the energy carrier liquid CO2 passes through the micropores on the arc channel wall and absorbs heat to evaporate and cool the arc channel tube wall.

[0099] Example 7:

[0100] A method for generating high-temperature coal gas based on an electric arc plasma torch includes the following steps:

[0101] S1. Carbon powder and two energy carriers are fed into the three different inlets of the electric arc plasma torch respectively; the carbon powder is coal powder mixed with oxygen, and the energy carriers are coal gas and liquid water.

[0102] S2. CO2 gas carries pulverized coal into the arc channel of the electric arc plasma torch in a uniform circumferential direction. Oxygen is introduced into the arc channel of the electric arc plasma torch from the nearest point in the plasma torch. Oxygen and pulverized coal begin to mix at the entrance of the arc channel. Specifically, it enters the arc channel uniformly in a centrifugal manner. That is, it enters along the wall of the arc channel, away from the arc column, reducing its vaporization by the plasma.

[0103] S3. Two energy-carrying media enter the arc plasma torch through two non-directly connected fluid channels. Liquid water cools the arc channel walls after entering the arc plasma torch, while coal gas enters the arc channel through a fluid passage.

[0104] S4. Ignite the gas in the arc channel or initiate an electric arc to generate plasma;

[0105] S5. Oxygen, carbon powder, water and gas entering the arc channel are heated together by oxygen-fueled gas or plasma, and then ejected together from the nozzle of the plasma torch.

[0106] The mass flow rate of the coal gas is greater than the mass flow rate of the carbon-containing powder; the O / C molar ratio in the mixture of oxidant liquid water and coal powder is preferably less than 1.

[0107] In this embodiment, oxygen, carbon powder, water, and coal gas are mixed together and heated by oxygen-fueled coal gas or plasma to generate high-temperature coal gas from oxygen-heated coal powder. This significantly reduces plasma energy, thereby reducing or eliminating power consumption.

[0108] In this example, some oxygen or some coal gas can be fed into the plasma torch, and any additional oxygen or coal gas required can be fed into the blast furnace through other auxiliary channels.

[0109] Example 8:

[0110] Same as Example 7, except that the carbon-containing powder is a mixture of waste plastic and oxygen; and the energy carrier is CO and liquid carbon dioxide. The liquid carbon dioxide, after entering the arc plasma torch, passes through the arc channel wall and enters the arc channel to evaporate and cool the arc channel wall. The mass flow rate of the coal gas is greater than the mass flow rate of the carbon-containing powder; the O / C molar ratio in the mixture of the oxidant liquid CO2 and coal powder is preferably less than 1.

[0111] Example 9:

[0112] Same as Example 7, except that the carbon-containing powder is a mixture of waste plastic and oxygen; and the energy carrier is CO and liquid carbon dioxide. The liquid carbon dioxide enters the arc plasma torch, passes through the arc channel wall, and enters the arc channel to react with some of the carbon-containing powder, which is pyrolyzed and vaporized by the plasma into small CH molecules, generating high-temperature gas. This endothermic reaction cools the arc channel wall.

[0113] When the high-temperature gas produced by this invention is used in a blast furnace for ironmaking, the energy-carrying medium in this invention can also be at least one of the following: blast furnace top gas, CO2 separated from blast furnace top gas, and purified gas after CO2 separation from blast furnace top gas, thereby achieving its recycling. Specific examples are as follows:

[0114] Application Example 1:

[0115] In this embodiment, the carbon-containing powder is anthracite powder, and the energy-carrying medium is CO2 separated from the blast furnace top gas;

[0116] The anthracite pulverized coal has a volatile matter content of 4% and a pulverized coal flow rate of 200 kg / h / MW.

[0117] The gas carrying the pulverized coal is CO2, with a flow rate of approximately 50 Nm³. 3 / h / MW, the mass flow rate ratio of pulverized coal to the mass flow rate of the pulverized coal carrier is approximately 2.

[0118] Alternatively, the carrier gas carrying pulverized coal can be water vapor, with a flow rate of approximately 100 Nm³. 3 / h / MW, the mass flow rate ratio of pulverized coal to the gas carrying the pulverized coal is approximately 2.

[0119] The preparation method is as described in Example 1. For a plasma operating power of approximately 5MW, each arc plasma torch is supplied with gaseous CO2 (separated from blast furnace top gas) and anthracite powder, with the gaseous CO2 injection rate being 1200 Nm³. 3 The anthracite pulverized coal feed rate is 600 kg / h; approximately 50% of the anthracite pulverized coal is gasified within the plasma torch and reacts with gaseous CO2 to generate coal gas, with approximately 2000 Nm³ of gas entering the blast furnace. 3 / h (components include CO, OH, CO2, H2O, O, H, O2, H2, etc.); unreacted anthracite pulverized coal and CO2 continue to react after entering the blast furnace, and the excess CO2 is reduced by coke.

[0120] Application Example 2:

[0121] Multiple pairs of transfer arc plasma torches are installed on the blast furnace; the rated power of a pair of arc plasma torches is 10MW (the average rated power of each arc plasma torch is about 5MW), and the processing capacity of molten iron is 5t-HM / h (t-HM, ton of molten iron); the design current is 600~1400A, and the voltage between a pair of arc plasma torches is 8kV.

[0122] Each arc plasma torch is supplied with smokeless pulverized coal at a flow rate of 600 kg / h (75% carbon content, less than 5% volatile matter); the pulverized coal injection ratio is 240 kg / t-HM, and the blast furnace coke ratio is 220 kg / t-HM.

[0123] The gas carrying pulverized coal is blast furnace top gas, and the gas flow rate is 60 Nm³. 3 / h, the mass flow rate ratio of pulverized coal to the gas carrying the pulverized coal is approximately 6.

[0124] The preparation method is the same as in Example 1. For each arc plasma torch, gaseous CO2 (separated from the blast furnace top gas) is introduced as the energy-carrying medium at a rate of 1200 Nm³. 3 / h; Anthracite pulverized coal feed rate 600 kg / h; Approximately 50% of the pulverized coal is gasified in the plasma torch and reacts with CO2 to generate coal gas, with a gas volume of 2000 Nm³ entering the blast furnace. 3 / h (components include CO, OH, CO2, H2O, O, H, O2, H2, etc.); complete reduction of CO2 requires approximately 900 kg / h of pulverized coal. Unreacted pulverized coal and CO2 continue to react after entering the blast furnace, and excess CO2 is reduced by coke.

[0125] CO2 is also used as a coolant for the arc pipe wall; when the cooling capacity is insufficient, external water cooling is used for the arc pipe wall.

[0126] The required gas volume, gas temperature, and gas energy carrying capacity are limited by the blast furnace process conditions. The required gas enthalpy is 3–4 MJ / Nm³. 3 The average temperature of the gas entering the blast furnace is generally less than 3000K.

[0127] The pressure difference between the plasma torch arc channel tube and the blast furnace is approximately 20 kPa.

[0128] The number of plasma torch pairs is designed based on the blast furnace capacity. In this embodiment, twelve pairs of plasma torches can process approximately 60 t-HM / h of molten iron (calculated as Fe2O3).

[0129] The reducing agent, pulverized coal, can also be bituminous coal with a high volatile matter content, such as 20-30%. Due to the high hydrogen content, the hydrogen from pulverized coal cracking can be directly reduced in the blast furnace, thus improving the reduction efficiency. Correspondingly, the CO2 content in the blast furnace top will also decrease, and the amount of CO2 entering the plasma torch will also decrease, but the pulverized coal flow rate will not change significantly. Since the energy consumption for pyrolysis of hydrocarbons in pulverized coal is much lower than that for CO2 reduction, the energy consumption of the plasma torch is reduced.

[0130] Plasma heating and pulverized coal are used to reduce CO2 separated from the blast furnace top gas into high-temperature gas, mainly composed of CO and a small amount of H2. This gas is fed into the blast furnace as a reducing agent and provides the energy required for the blast furnace reaction. The net gas yield after CO2 separation from the top gas mainly consists of CO and a small amount of H2, with a yield of ~700 Nm³. 3 / t-HM.

[0131] The calculation results for the operating conditions of a specific blast furnace and raw materials in this implementation example are scaled proportionally. The actual values ​​will vary significantly depending on factors such as the parameters of each blast furnace, raw materials, operating parameters, and process adjustments.

[0132] Application Example 3:

[0133] Referring to the methods in Examples 8 and 9, pulverized coal is introduced into the electric arc plasma torch and then uniformly enters the arc channel in a circumferential direction. The gas carrying the pulverized coal is CO2.

[0134] Under pressure, liquid water in the energy-carrying medium passes through the arc channel wall and enters the arc channel to evaporate and cool the arc channel wall, and also acts as a partial oxidant.

[0135] The coal gas, CO2, or coal gas + CO2 in the energy-carrying medium directly enter the electric arc channel through the fluid passage, generating a rotating flow within the electric arc channel;

[0136] To recycle blast furnace gas, there are four operating modes:

[0137]

[0138] Note: *: Carbon utilization rate 0.8; **: PE, plasma energy (thermal efficiency 94%)

[0139] Coal powder parameters: C, 70%; H, 1%; O, 5%; calorific value 23.6 MJ / kg; carbon utilization rate of coal powder 0.8. Iron ore is Fe2O3, carbonate CO2 content 3 kmol / t-HM.

[0140] The cooling water volume is 175 kg in operating condition 1 and 105 kg in other operating conditions.

[0141] The molar ratio of CO / H2 in the reducing agent of the system is >3.

[0142] 50 Nm is used for each operating condition. 3 The CO2 carries pulverized coal, and the rest is the energy-carrying medium.

[0143] Operating condition 1 involves the recycling of CO2 from the blast furnace top gas, meaning that no CO2 in the blast furnace tail gas is emitted; instead, it is entirely used as a gas carrying pulverized coal and as an energy-carrying medium in the electric arc plasma torch. The plasma energy is 2.1 MWh. The CO2 recycling rate is 448 Nm³. 3 50Nm 3 The coal powder is used to carry the pulverized coal, while the remainder is fed into the electric arc plasma torch. It then enters the arc channel through a fluid passage. Water passes through the arc channel wall and enters the arc channel to evaporate and cool the wall. 376 kg of pulverized coal is input. Some of the pulverized coal is pyrolyzed and gasified by the plasma into CH small molecule compounds. These CH small molecule compounds react with CO2 and H2O in the arc channel to generate high-temperature coal gas, producing 718.6 Nm³ of coal gas. 3 .

[0144] Operating condition 2 involves the recycling of clean blast furnace top gas, where all the clean blast furnace top gas is fed into the electric arc plasma torch as an energy carrier, with a recycling gas volume of 802 Nm³. 3 The pulverized coal is fed into an electric arc plasma torch; 76 kg of CO2 is fed into the arc channel, which enters the arc channel evenly by centrifugation, moving away from the arc column along the arc channel wall to reduce its vaporization by the plasma; water passes through the arc channel wall to evaporate and cool the arc channel wall; the pulverized coal and coal gas are heated together by the plasma, with a plasma energy of 1.2 MWh. 361 Nm³ of CO2 is produced. 3 .

[0145] Operating condition 3 uses oxy-thermal pulverized coal, with a plasma energy of 0.68 MWh. The supplementary gas volume is 220 Nm³. 3 The coal is fed into the electric arc plasma torch and then into the electric arc channel; 400 kg of pulverized coal and 200 Nm³ of oxygen are added. 3 It needs to be fed separately from the coal gas into different inlets in the electric arc plasma torch; water passes through the arc channel wall and enters the arc channel to evaporate and cool the arc channel wall; due to the reduction of plasma energy, 361 Nm of coal gas is produced. 3 It generates 382 Nm³ of CO2 emissions. 3 .

[0146] Operating condition 4: Clean gas recycling from the top of the oxygen-thermal blast furnace; plasma energy: 0.31 MWh. Supplementary coal: 233 kg; oxygen supply: 200 Nm³. 3 Entering the electric arc channel; circulating gas volume 797 Nm 3The gas passes through the wall of the electric arc channel and enters the electric arc channel; the coal gas, pulverized coal, and oxygen are heated together and then enter the blast furnace, producing CO2 emissions of 556 Nm³. 3 .

[0147] The above operating conditions demonstrate that the plasma device of this invention for blast furnaces can flexibly adjust the electrical load to accommodate changes in power supply while meeting the blast furnace's operational requirements. As the plasma input energy increases, blast furnace CO2 emissions decrease, and / or the amount of gas produced increases.

[0148] The calculation results for the operating conditions of a specific blast furnace and raw materials in this implementation example are scaled proportionally. The actual values ​​will vary significantly depending on factors such as the parameters of each blast furnace, raw materials, operating parameters, and process adjustments.

[0149] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for generating high-temperature coal gas based on an electric arc plasma torch, characterized in that: Includes the following steps: S1. Carbon powder and at least one energy-carrying medium are fed into different inlets of the electric arc plasma torch. S2. The carrier gas carries carbon-containing powder into the arc channel of the arc plasma torch in a circumferentially uniform manner. S3. After at least one energy-carrying medium enters the electric arc plasma torch, it passes through the fluid passage on the wall of the electric arc channel and enters the electric arc channel. S4. Initiating an electric arc in the arc channel to generate plasma; S5. The energy-carrying working medium and carbon-containing powder entering the arc channel are heated together by the plasma and then ejected from the nozzle of the arc plasma torch. The energy-carrying medium is an oxidizing medium. The carbon-containing powder flows toward the electric arc in a centripetal flow manner. Some of the carbon-containing powder is pyrolyzed and vaporized by the plasma into CH small molecule compounds. The CH small molecule compounds react with the oxidizing medium to generate high-temperature coal gas. The unpyrolyzed carbon-containing powder in the low-temperature area near the arc channel wall plays a role in shielding the plasma from radiation to the tube wall. The energy-carrying medium is a reducing medium, and the carbon-containing powder is uniformly introduced into the arc channel by centrifugation.

2. The method according to claim 1, characterized in that: The oxidizing medium includes liquid water, water vapor, liquid carbon dioxide, and carbon dioxide gas.

3. The method according to claim 1, characterized in that: The reducing medium includes carbon monoxide, hydrogen, blast furnace gas, coke oven gas, water gas, natural gas, or any mixture thereof.

4. The method according to claim 1, characterized in that: The energy-carrying medium is of two types: a liquid medium and a gaseous medium. The liquid medium and the gaseous medium enter the arc plasma torch through two non-directly connected fluid channels. The liquid medium cools the walls of the arc channel, while the gaseous medium enters the arc channel through the fluid channel and is heated by the plasma together with the carbon-containing powder.

5. The method according to claim 4, characterized in that: The working gas in the oxidizing medium is mixed with carbon dioxide or water vapor, and the carbon powder enters the arc channel in a radial-centripetal manner to mix with the working gas. The working fluid is liquid water or carbon dioxide.

6. The method according to claim 4, characterized in that: The reducing medium contains oxygen as the working gas, and the carrier gas carrying the carbon powder is CO2. The carbon powder enters the arc channel and mixes with the working gas in a centrifugal manner. The working fluid is liquid water or carbon dioxide.

7. The method according to claim 4, characterized in that: The carbon-containing powder is mixed with oxygen and is uniformly introduced into the arc channel and mixed with the gaseous working medium by centrifugation. The energy-carrying gaseous working medium is CO or coal gas, and the liquid working medium is liquid water or carbon dioxide.

8. The method according to claim 4, characterized in that: The liquid working fluid passes through the arc channel wall and enters the arc channel to evaporate and cool the arc channel wall.

9. The method according to claim 4, characterized in that: The liquid working fluid passes through the wall of the electric arc channel and enters the electric arc channel to react with CH small molecule compounds generated by the plasma pyrolysis and gasification of some carbon-containing powder to generate high-temperature coal gas.

10. The method according to any one of claims 1-3, characterized in that: In step S3, the energy-carrying medium passes through the fluid passage on the wall of the electric arc channel and enters the electric arc channel to dissipate cooling to the wall of the electric arc channel.

11. The method according to any one of claims 1-3, characterized in that: The carbon-containing powder includes at least one of the following: coal powder, coal coke powder, petroleum coke powder, waste plastics, rubber granules, low-hydrogen carbon powder, and biomass pellets. The carrier gas carrying the carbon-containing powder is CO2, CO, water vapor, coal gas, nitrogen, or air; The molar flow ratio of the carrier gas to the energy-carrying working fluid is less than 0.

5.

12. The method according to claim 11, characterized in that: The molar flow ratio of the carrier gas to the energy-carrying working fluid is less than 0.2.

Images