CN205838931U - A kind of preparation system of gas-based shaft kiln reducing gases - Google Patents

Abstract

The utility model relates to a reducing gas preparation system for a gas-based shaft furnace. The system includes a regenerative rotary bed, a gasification furnace, a conversion device and a gas-based shaft furnace; the regenerative rotary bed passes through the gasification furnace in sequence. , a waste heat recovery device and a water washing tower are connected to the conversion device; the regenerative rotating bed is also connected to the conversion device through a cooling separation device, a gas purification device and a reformer; the conversion device is connected to the conversion device through the waste heat recovery The unit is connected to a gas-based shaft furnace. The system provided by the utility model recycles and utilizes the heat generated in the semi-coke gasification process to heat the reducing gas, and at the same time, utilizes the by-product saturated steam in the gasification process to complete the methane steam reforming reaction, comprehensively utilizes the heat generated by the system, and improves The energy efficiency and economic benefits of the system are improved.

Description

A reducing gas preparation system for a gas-based shaft furnace

technical field

The utility model relates to the fields of chemical industry and metallurgical production, in particular to a reduction gas preparation system for a gas-based shaft furnace.

Background technique

Non-blast furnace ironmaking technology is an ironmaking method that mainly uses non-coking coal as fuel and does not use coke or uses a small amount of coke to produce iron products. The main purpose of developing non-blast furnace ironmaking technology is to get rid of dependence on metallurgical coke, expand the proportion of non-coking coal used in ironmaking production, and promote efficient recycling of metallurgical energy and resources.

In areas such as Xinjiang and Inner Mongolia where there is a lack of coking coal rather than rich and cheap coking coal resources, the combined process of large-scale coal-to-gas and shaft furnace sponge iron has strong competitiveness. Due to the lack of natural gas and rich ore resources, my country has not yet built a mature and energy-saving large-scale gas-based direct reduction shaft furnace, fine ore direct reduction industrial production and other cutting-edge technology production equipment for ironmaking, and there is still a lack of mature large-scale gas-based direct reduction shaft furnace However, there are companies in Shanxi Province, Inner Mongolia and Jiangsu Province that are preparing to build coal-to-gas shaft furnace direct reduction projects.

my country's energy structure is "rich in coal, poor in oil, and low in gas", which is suitable for the development of direct reduction ironmaking technology with coal gasification as the gas source. The large-scale shaft furnace direct reduction process technology using the latest generation of clean coal gasification technology is currently the most energy-saving, low-emission, and high-efficiency large-scale advanced ironmaking process. The process avoids the most serious environmental pollution sintering and coking processes. Compared with the blast furnace process, the combined process has obvious advantages in terms of energy consumption and emission, and is the development direction of my country's iron and steel industry and direct reduction industry.

The traditional gas-based shaft furnace direct reduction process is based on natural gas, which limits its popularization and application, and can only be industrialized in countries and regions rich in natural gas. In recent years, with the development of technology, the technology of using COREX output gas, coal gasification gas and coke oven gas as reducing gas source for direct reduction iron production has been proposed and gradually matured. In particular, the development of coal gasification gas as the source of reducing gas is of great significance to those areas or iron and steel enterprises that lack natural gas and do not have the conditions to use coke oven gas as the source of reducing gas.

The main coking coal resources are extremely limited and unevenly distributed, accounting for only about 25% of the total coal resources in my country. Although my country is a country with large coal resources, with the rapid development of my country's iron and steel production, according to the forecast of relevant parties, my country's coking coal resources are only enough for 30 years.

Compared with the traditional blast furnace process, the gas-based shaft furnace direct reduction/scrap electric furnace process has the technical advantages of relatively short process, no need for coking coal, large output of a single set of equipment, energy saving, and obvious CO ₂ emission reduction effect. The fetters of coking coal resources, reducing energy consumption and reducing _CO2 emissions are the mainstream of cokeless ironmaking technology.

Utility model content

The purpose of this utility model is to provide a system and method for preparing reducing gas for a gas-based shaft furnace, which is suitable for preparing sponge iron by direct reduction of a gas-based shaft furnace through pyrolysis and upgrading-gasification of medium and low-rank coal raw materials. Gas, comprehensive utilization of heat generated by the system, not limited to coal types and high value-added by-product tar can be obtained, which improves the energy utilization rate and economic benefits of the system.

Specifically, the utility model provides a reducing gas preparation system for a gas-based shaft furnace, and the system includes a regenerative rotary bed, a gasifier, a conversion device and a gas-based shaft furnace.

The top view of the regenerative rotary bed described in the utility model can be referred to as shown in Figure 2. The regenerative rotary bed uses a regenerative radiant tube to increase the temperature in the rotary bed, and the medium and low rank coal passes through the feeding device in the feeding area. It enters the regenerative rotating bed, passes through the heating zone for pyrolysis upgrading reaction, and reacts to obtain gas products and solid products. The gas product enters the cooling and separation device after exiting the furnace roof and/or the gas collecting pipe on the side of the furnace for subsequent reaction; the solid product is discharged out of the furnace through the discharge device in the discharge area, and enters the The gasifier carries out subsequent reactions.

Specifically, the regenerative rotating bed passes through a gasifier, a waste heat recovery device, and a water washing tower in sequence, and is connected to the conversion device. The solid product (semi-coke) produced in the regenerative rotary bed is discharged out of the furnace through the discharge device, and is discharged after being cooled to ~40°C by dry coke quenching, and is prepared by the coal grinding system to a particle size of more than 90%. The coal coke powder between 5 and 95 μm is transported to the gasification furnace through dense phase carbon dioxide to complete the gasification reaction, and the high-temperature syngas generated is recovered by the waste heat recovery device, and then cooled and purified by the water washing tower to obtain ~40 The normal temperature syngas at about ℃, the normal temperature syngas is mixed with the following reducing gas 1 and enters the shift system for shift reaction.

At the same time, the heat-storage rotary bed also passes through the cooling and separation device, the gas purification device and the reformer in sequence, and is connected with the conversion device. The gas product (raw coal gas) produced in the regenerative rotary bed is collected by the furnace top and/or the gas collecting pipe on the side of the furnace, and then sent to the gas cooling device (such as: oil-gas cooling tower), and after cooling and separation, tar and non-condensable Gas, the non-condensable gas is purified by a gas purification device (including desulfurization, benzene removal, etc.) to obtain clean gas (mainly containing CO, H ₂ , CH ₄ , etc., wherein the content of CH ₄ is about 20% to 50%), The clean coal gas enters the reformer to complete the steam reforming reaction to obtain a reducing gas 1, and the reducing gas 1 is mixed with the normal-temperature synthesis gas and enters a shift system for a shift reaction. As a preferred solution, the gas purification device can be connected to the regenerative rotating bed through the combustion raw gas pipeline, so that part of the clean coal gas that does not participate in the reaction of preparing reducing gas can supply energy for the regenerative rotating bed; specifically , part of the clean coal gas enters the reformer for reaction to generate reducing gas 1, and the remaining part is sent back to the regenerative rotating bed as combustion raw material gas for increasing the temperature in the regenerative rotating bed.

The conversion device is connected to the gas-based shaft furnace through the waste heat recovery device, so that the reducing gas 2 after the conversion reaction is heated to a suitable temperature through the waste heat recovery device, and then directly sent into the gas-based shaft furnace to complete the reduction reaction ; Specifically, the waste heat recovery device recovers the high-temperature heat in the high-temperature synthesis gas, and then uses this part of the high heat to heat the reducing gas to 2 to 780-950°C, and then sends it into the gas-based shaft furnace to reduce the pellets to the target The product sponge iron. There are two or more sets of heat storage recovery devices, which are used alternately to ensure the stable operation of the system.

The gasification furnace described in the utility model is preferably a water-jacketed water-cooled wall entrained-bed gasification furnace capable of generating saturated water vapor, and its structure can be referred to as shown in FIG. 3 . The gasification agent is used in the gasification furnace; the gasification agent is pure oxygen or oxygen-enriched air and superheated steam, and the gasification agent is sent into the combustion chamber of the gasification furnace through the gasification agent channel of the above-mentioned overhead burner. The oxidizing agent pure oxygen or oxygen-enriched air and superheated steam can be mixed uniformly and fed through the same channel of the burner, or can be fed through two channels of the burner separately. Cooling water (saturated water) is used in the gasifier, and the cooling water (saturated water) comes from the steam drum, and the saturated water is circulated between the water jacket and the steam drum through a hot water circulation pump, and Add fresh water to the steam drum in time to ensure the stable operation of the water jacket-steam drum system.

In the gasification furnace, cooling water (saturated water) enters from the bottom of the water jacket, exits from the top of the water jacket, and then enters the steam drum to generate saturated steam. As a preferred solution, the gasifier can be connected to the reformer through a steam pipeline, so that the saturated steam generated in the above process is sent to the reformer to reform and react with CH ₄ in the clean gas to generate CO and H ₂ .

The utility model also provides a method for preparing a gas-based shaft furnace reducing gas by using the system; the method includes the following steps:

(1) After the raw coal is crushed, it is input into a regenerative rotary bed for heating and upgrading to obtain solid products and gas products; the raw coal is preferably medium and low-rank coal, more preferably lignite or/and long-flame coal;

(2) After the solid product is pulverized, it is sent to a gasification furnace for gasification reaction to obtain high-temperature synthesis gas, and after waste heat recovery, water washing and cooling, normal-temperature synthesis gas is obtained;

At the same time, the gas product is separated after cooling to obtain tar and non-condensable gas; after the non-condensable gas is purified, clean coal gas is obtained;

(3) The clean coal gas and saturated steam undergo methane-steam reforming reaction in the reformer to obtain reducing gas 1, which is then mixed with the normal temperature synthesis gas obtained in step (2) and then undergoes shift reaction to obtain _H2 /CO>0.7 The reducing gas 2 is directly fed into the gas-based shaft furnace after being heated.

The raw coal of the utility model is preferably medium and low-rank coal, such as lignite or/and long-flame coal.

In the method described in the utility model, the heat-storage rotary bed uses a heat-storage radiant tube to control the temperature inside the rotary bed, and is preheated to 500-700°C.

In order to ensure the smooth progress of the reaction and obtain the desired product, the temperature in the gasifier is controlled at 1100-1400°C.

The high-temperature synthesis gas recovers waste heat through a waste heat recovery device, cools down to 200-300°C, and then enters a water washing tower to cool down to below 40°C.

In the step (3), the reducing gas 2 is heated to 780-950° C. by the waste heat recovery device, and then directly sent into the gas-based shaft furnace.

In order to realize the full utilization of energy, in the clean coal gas obtained in the preferred step (2) of the utility model, part participates in the reaction described in step (3), and the remaining part is used as the fuel for the regenerative rotary bed radiant tube combustion, which is the regenerative rotary bed Energy Supply.

In order to realize the full utilization of energy, the utility model preferably passes the saturated steam generated in the gasification furnace into the reformer, and performs methane-steam reforming reaction with clean coal gas.

Specifically, the raw coal is crushed and sent to the regenerative rotary bed through the feeding device, and the regenerative rotary bed is heated to 500-700°C in advance, and the raw coal is heated and upgraded to obtain solid product semi-coke and gas Product shortage of gas.

The raw coal gas, the gas product, is collected by the gas collecting pipe on the top of the furnace and/or on the side of the furnace, and then sent to the oil-gas cooling tower, where tar and non-condensable gas are obtained after cooling and separation. The resulting tar can be further processed to produce light gasoline and diesel. The obtained non-condensable gas is further purified, including desulfurization, benzene removal and other processes, to obtain clean gas, and a part of the clean gas is returned to the regenerative rotary bed as combustion raw material gas, which is used to increase the temperature in the regenerative rotary bed; Part of it is sent to the reformer, and undergoes reforming reaction with steam to obtain reducing gas 1, which is then mixed with synthesis gas obtained from semi-coke gasification, and used as reducing gas 2 after treatment.

The solid product semi-coke is discharged out of the furnace through the discharge device, and is discharged after being cooled to ~40°C through dry coke quenching. The resulting finished semi-coke is prepared by a coal grinding system into coal coke powder with a particle size of more than 90% between 5 and 95 μm, and then transported into the entrained-flow gasifier through dense-phase inert gas (nitrogen or carbon dioxide) for gasification. The resulting high-temperature synthesis gas is cooled and purified by a waste heat recovery device and a water washing tower, and then mixed with the reducing gas 1 from the above-mentioned reformer. After conversion treatment, the H ₂ /CO ratio in the reducing gas 2 obtained is 0.5~ 4.0, preferably >0.7, suitable for preparing sponge iron by direct reduction of iron ore in gas-based shaft furnace.

The raw material is pumped to the top of the gasification furnace by dense-phase conveying, and sprayed into the combustion chamber of the gasification furnace through the top burner and the gasification agent through different channels to complete the gasification reaction. The temperature in the furnace is 1100-1400 °C. The high-temperature syngas recovers the waste heat through the waste heat recovery device, reduces the temperature of the high-temperature syngas to 200-300°C, and then sends it to the water washing tower to cool down to ~40°C normal-temperature syngas. The normal-temperature syngas is mixed with the reducing gas 1 from the above-mentioned reformer and then sent to the shift process to obtain a reducing gas 2 with H ₂ /CO=0.5-4.0, preferably H ₂ /CO>0.7, after water-vapor shift reaction. The ash enters the separation chamber below the combustion chamber, the high-temperature ash is preliminarily cooled by the water seal in the separation chamber, and then enters the slag lock hopper for further cooling before being discharged out of the furnace.

The technical solution provided by the utility model has the following significant advantages:

(1) The system provided by the utility model mainly deals with middle and low rank coal, which has the characteristics of high volatile matter and high water content, and cannot directly enter the entrained flow bed for gasification reaction. The method provided by the utility model has no requirements on the type of coal to be fed into the furnace, and in addition to obtaining highly efficient and clean synthesis gas, it can also effectively recover high value-added tar produced by middle and low-rank coal, and the tar can be obtained through further processing. gasoline and diesel;

(2) The system provided by the utility model adopts medium and low-rank coal pyrolysis-gasification to prepare reducing gas for direct reduction of iron in a gas-based shaft furnace. The coal type has strong adaptability, and pellets are the main iron raw materials;

(3) The system provided by the utility model recycles and utilizes the heat generated in the semi-coke gasification process to heat the reducing gas. Heat, which improves the energy utilization rate and economic benefits of the system.

Description of drawings

Fig. 1 is the schematic diagram of the preparation system of the gas-based shaft furnace reducing gas provided in Example 1; in the figure: 1, regenerative rotary bed; 2, gasifier; 3, waste heat recovery device; 4, water washing tower; 5, cooling Separation device; 6. Gas purification device; 7. Reformer; 8. Conversion device; 9. Gas-based shaft furnace;

Fig. 2 is the top view of the regenerative rotating bed provided by embodiment 1;

FIG. 3 is a schematic structural diagram of the gasifier provided in Example 1.

detailed description

The following examples are used to illustrate the utility model, but not to limit the scope of the utility model.

Example 1

This embodiment provides a preparation system for reducing gas in a gas-based shaft furnace, as shown in Figure 1, comprising a regenerative rotary bed 1 (its top view is shown in Figure 2) and a conversion device 8;

The regenerative rotating bed passes through the gasification furnace 2, waste heat recovery device 3 and water washing tower 4 successively, and is connected with the conversion device 8; the regenerative rotating bed also passes through the cooling separation device 5 and the gas purification device 6 in sequence And reformer 7, link to each other with described conversion device 8;

The gasifier 2 is a water-jacketed water-cooled wall entrained-bed gasifier, the structure of which is shown in Figure 3; the gasifier 2 is connected to the reformer 7 through a steam pipeline;

The gas purification device 6 is connected to the regenerative rotating bed 1 through a combustion raw gas pipeline;

The waste heat recovery device 3 is composed of two sets of alternate heat storage body recovery devices; the conversion device 8 is connected to the gas-based shaft furnace 9 through the waste heat recovery device 3 .

Example 2

This embodiment provides a method for preparing gas-based shaft furnace reducing gas using the system described in Embodiment 1, specifically:

The raw lignite is crushed and sent to the regenerative rotary bed through the feeding device. The regenerative rotary bed is heated to 500-700°C in advance, and the raw coal is heated and upgraded to obtain solid product semi-coke and gas product raw gas. The gas product raw coal gas is collected by the gas collecting pipe on the furnace top and/or side of the furnace and then sent to the oil and gas cooling tower. After cooling and separation, tar and non-condensable gas are obtained. The non-condensable gas is purified by desulfurization and benzene removal to obtain clean gas. Part of the clean gas is sent back to the regenerative rotary bed as combustion raw material gas to increase the temperature in the regenerative rotary bed; the other part is converted into a reducing gas 1 after steam reforming in the reformer, and then mixed with semi-coke gas The resulting synthesis gas is mixed and used as reducing gas 2 after treatment.

The solid product semi-coke is discharged out of the furnace through the discharge device, and is discharged after being cooled to ~40°C through dry coke quenching. The finished semi-coke is prepared by the coal grinding system into coal coke powder with a particle size of more than 90% between 5 and 95 μm, which is transported to the entrained bed gasifier through dense phase carbon dioxide to complete the gasification reaction. After the recovery unit and the water washing tower are cooled and purified, normal temperature syngas at ~40°C is obtained. The synthesis gas is mixed with the reducing gas 1 from the above-mentioned reformer and then enters the water vapor shift process. The ratio of H ₂ /CO in the mixed gas is adjusted to 1.5 to obtain the reducing gas 2 suitable for direct reduction in the gas-based shaft furnace. The reducing gas 2 is heated to about 850°C by the aforementioned waste heat recovery device, and then directly sent into the gas-based shaft furnace to complete the direct reduction reaction to obtain sponge iron.

Example 3

This embodiment provides a method for preparing gas-based shaft furnace reducing gas using the system described in Embodiment 1, specifically:

The raw long-flame coal is crushed and sent to the regenerative rotary bed through the feeding device. The regenerative rotary bed is heated to 500-700°C in advance, and the raw coal is heated and upgraded to obtain solid product semi-coke and gas product waste. gas. The gas product raw coal gas is collected by the gas collecting pipe on the furnace top and/or side of the furnace and then sent to the oil and gas cooling tower. After cooling and separation, tar and non-condensable gas are obtained. The non-condensable gas is purified by desulfurization and benzene removal to obtain clean gas. Part of the clean gas is sent back to the regenerative rotary bed as combustion raw material gas to increase the temperature in the regenerative rotary bed; the other part is converted into a reducing gas 1 after steam reforming in the reformer, and then mixed with semi-coke gas The resulting synthesis gas is mixed and used as reducing gas 2 after treatment.

The solid product semi-coke is discharged out of the furnace through the discharge device, and is discharged after being cooled to ~40°C through dry coke quenching. The finished semi-coke is prepared by the coal grinding system into coal coke powder with a particle size of more than 90% between 5 and 95 μm, which is transported to the entrained bed gasifier through dense phase carbon dioxide to complete the gasification reaction. After the recovery unit and the water washing tower are cooled and purified, normal temperature syngas at ~40°C is obtained. The synthesis gas is mixed with the reducing gas 1 from the above-mentioned reformer and then enters the water vapor shift process. The H ₂ /CO ratio in the mixed gas is adjusted to 2.0 to obtain the reducing gas 2 suitable for direct reduction in the gas-based shaft furnace. The reducing gas 2 is heated to about 900°C through the aforementioned waste heat recovery device, and then directly sent into the gas-based shaft furnace to complete the direct reduction reaction to obtain sponge iron.

Although, the utility model has been described in detail with general description, specific implementation and test above, but on the basis of the utility model, some modifications or improvements can be made to it, which is a must for those skilled in the art. Obvious. Therefore, the modifications or improvements made on the basis of not departing from the spirit of the utility model all belong to the protection scope of the utility model.

Claims (7)

1. the preparation system of a gas-based shaft kiln reducing gases, it is characterised in that include heat accumulating type rotating bed, gasification furnace, conversion Device and gas-based shaft kiln；

Described heat accumulating type rotating bed sequentially passes through gasification furnace, waste-heat recovery device and water scrubber and is connected with described converting means； Described heat accumulating type rotating bed also sequentially passes through refrigerated separation device, gas cleaning plant and reburner and described converting means phase Even；

Described converting means is connected with gas-based shaft kiln through described waste-heat recovery device.

Preparation system the most according to claim 1, it is characterised in that described gasification furnace is water-jacket water-cooling wall air flow bed Gasification furnace.

Preparation system the most according to claim 2, it is characterised in that described gasification furnace by water vapour pipeline with described turn Change stove to be connected.

Preparation system the most according to claim 1, it is characterised in that described heat accumulating type rotating bed built-in regenerative radiates Pipe, is used for improving temperature in revolving bed.

5. according to the preparation system described in claim 1 or 4, it is characterised in that described gas cleaning plant passes through combustion material Feed channel is connected with described heat accumulating type rotating bed.

Preparation system the most according to claim 1, it is characterised in that described waste-heat recovery device is by two groups or more Heat storage retracting device forms.

Preparation system the most according to claim 1, it is characterised in that arrange between described heat accumulating type rotating bed and gasification furnace Dry coke quenching auxiliary.