CN110982542A - Method for preparing blast furnace blowing semicoke from low-rank coal based on hydrothermal reaction - Google Patents
Method for preparing blast furnace blowing semicoke from low-rank coal based on hydrothermal reaction Download PDFInfo
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- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
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Abstract
The invention relates to a treatment method for dewatering and upgrading low-rank coal with high moisture and high volatile content, and discloses a method for preparing blast furnace blowing semicoke by upgrading low-rank coal based on high-pressure hydrothermal reaction. The invention utilizes a high-pressure hydrothermal reaction upgrading technology to convert low-calorific-value low-rank coal into high-quality blast furnace injection upgrading semicoke, the air drying base moisture of the semicoke is less than 6%, the volatile component is less than 25%, the Haw's grindability index is greater than 60, the high-order calorific value is greater than 24000kJ/kg, soluble potassium salt, sodium salt and sulfate components in ash are dissolved out, organic sulfur in coal is effectively decomposed and separated out, and the upgrading semicoke can meet the performance index requirements of blast furnace injection coal. The method provided by the invention effectively solves the problems of high water and volatile content, low heat value and high content of harmful elements in the low-rank coal subjected to blast furnace injection, and provides a clean, efficient, low-energy-consumption and high-added-value product utilization method for improving the quality of the low-rank coal.
Description
Technical Field
The invention relates to a treatment method for dewatering and upgrading low-rank coal with high moisture, high volatile matter and low calorific value, in particular to a method for preparing blast furnace blowing semicoke by upgrading the low-rank coal based on hydrothermal reaction.
Background
The exploitation and utilization of fossil fuels play an important role in the progress and development of human society, and coal resources are one of three fossil fuels and are important energy sources and chemical raw materials for industrial production and life. Compared with petroleum and natural gas, the traditional coal utilization process has the defects of low energy utilization efficiency and large pollutant discharge amount. From the long-term goal, "coal removal" is the development direction of energy transformation in China, but the characteristics of "rich coal, lack of oil and little gas" of energy reserves in China determine that coal is still the most important basic energy and raw material in China for a long time in the future. How to develop and utilize coal resources well becomes an important problem which needs to be solved urgently in economic development of China.
China is rich in coal resources, the coal powder ratio reaches over 90 percent in the total amount of fossil energy resources, and the occupation amount of petroleum and natural gas resources is less than 10 percent, so that the coal resources are the most economic energy resources in China. In the aspect of energy consumption structure, the coal powder accounts for less than 60% of primary energy consumption, the consumption proportion of petroleum and natural gas exceeds 25%, and the external dependence of petroleum and natural gas in China exceeds 65%, so that the coal has the characteristics of strong resource guarantee capability and high energy safety. For a long time, extensive and plunder mining modes in China not only cause great waste of coal resources, but also cause serious damage and pollution to social environments, so that the development of a clean and efficient utilization technology of the coal resources is very important, and particularly, the clean and efficient utilization of lignite and bituminous coal (including non-caking coal, weakly caking coal and long flame coal) with low metamorphism degree accounting for more than 46% of the reserved resource reserves is realized.
The technology of blowing coal powder at a blast furnace tuyere is a main technical means for reducing the cost, reducing the pollutant discharge and enhancing the competitiveness of iron and steel enterprises in the prior iron-making production. The blast furnace coal powder injection process is mainly used for replacing expensive metallurgical coke, and requires high calorific value, good combustibility and low ash content and harmful element content of the injected coal powder. The anthracite has high fixed carbon and high calorific value, which just meets the requirement of replacing coke with coal, but the production cost and pressure are increased due to limited storage amount of the anthracite and continuous rising of the price, and the average amount of coal injected by a domestic blast furnace reaches 150kg/t iron, so how to ensure that a large amount of coal powder injected into the blast furnace is completely combusted in limited time and space at the front end of an air port becomes the focus of attention of ironmaking producers. The method for efficiently applying the low-rank coal resource with rich reserves and low price to the blast furnace injection field is a main method for expanding ironmaking fuel resources and reducing ironmaking production cost at present. However, the low-rank coal carbon resources (including non-caking coal, weakly caking coal and long flame coal) have high moisture and volatile content, low calorific value, low ignition point and strong explosiveness, and the high content of harmful elements in part of coal species limits the high proportion of the coal species in the blast furnace injection technology. The quality improvement treatment of the low-rank coal is an important technology for clean and efficient utilization of low-rank coal resources at present, the medium-low temperature pyrolysis technology is a common method for quality improvement and utilization of the low-rank coal at present, the content of moisture and volatile matters in the low-rank coal can be effectively reduced through the medium-low temperature pyrolysis treatment, the calorific value is improved, but the problems that the process energy consumption is high, the waste heat is difficult to recycle, the ash content in the semi-coke after the pyrolysis quality improvement is greatly increased, the moisture reabsorption is easily caused by a porous structure, and the grindability of the upgraded semi-coke is poor exist. The method can not only effectively remove the moisture and the volatile components in the low-rank coal, improve the heat value, but also effectively control the ash content, reduce the moisture reabsorption capability of the upgraded semicoke and improve the grindability of the upgraded semicoke, and is a problem commonly related to coal chemical industry and iron-making workers.
Hydrothermal carbonization is a low-rank coal dehydration quality-improving treatment method which is rapidly developed in recent years, and belongs to a non-evaporation drying quality-improving technology. The method comprises the steps of placing low-rank coal and distilled water in a closed high-pressure reaction kettle for heating, providing saturated vapor pressure by the distilled water, discharging water in the low-rank coal in a liquid form, and simultaneously partially removing organic tube energy clusters and inorganic mineral substances, thereby achieving the purposes of improving the rank and the calorific value of the coal and reducing the ash content. It should be noted that the hydrothermal upgrading process can remove a large amount of alkali metals such as soluble potassium salt, sodium salt and the like and chloride ions in the coal, and sulfur, heavy metal elements and some polar organic matters in the coal also appear in liquid-phase products. Research shows that the hydrothermal carbonized carbocoal has similar properties to anthracite and can be used as high-quality raw materials and fuels in the fields of chemical industry and metallurgy. But the technology still has a large promotion space in the aspects of process flow (system energy consumption/water consumption, hydrothermal upgrading semicoke yield, continuous operation rate, waste heat recovery utilization rate and the like) and product quality optimization at present.
Disclosure of Invention
The invention provides a clean, environment-friendly, rapid and efficient method for producing blast furnace injection fuel by hydrothermal upgrading of low-rank coal, wherein the method has the advantages that the product quality can meet the requirements of a blast furnace injection process, and the product quality can meet the requirements of the blast furnace injection process.
In order to solve the defects of the prior art, the invention is solved by the following technical scheme:
the method for preparing blast furnace blowing semicoke from low-rank coal based on hydrothermal reaction comprises the following steps:
(1) pretreating raw coal of low-rank coal: crushing raw low-rank coal, conveying crushed coal powder to a slurry storage tank through a pipeline, and adding water into the coal powder in the slurry storage tank to stir and mix uniformly;
(2) preheating coal slurry: pressurizing the coal slurry in the slurry storage tank through a high-pressure coal slurry pump, and conveying the coal slurry to a coal slurry heat exchanger through a pipeline to preheat the coal slurry;
(3) hydrothermal carbonization treatment: injecting the pressurized and preheated coal slurry into a hydrothermal treatment system by using a pipeline, wherein the core device of the system is a hydrothermal carbonization tank, the reaction temperature in the hydrothermal carbonization tank is controlled to be 280-400 ℃, and the hydrothermal carbonization time is 1-5 h;
(4) and (3) waste heat recovery treatment: conveying the high-temperature and high-pressure material subjected to the hydrothermal carbonization treatment to a condensing system for cooling and depressurizing treatment, and conveying the depressurized high-temperature steam to a coal slurry heat exchanger and a thermal drying device;
(5) and (3) dehydration and drying treatment: the hydrothermal carbonized material subjected to cooling treatment by the condenser is reduced to normal pressure by a pressure reduction system, the normal pressure mixed material is conveyed to a solid-liquid separation system for dehydration treatment, the obtained liquid phase is purified and recycled, the obtained mud-cake-shaped solid-phase separator is conveyed to a thermal drying device for drying to obtain hydrothermal upgraded semicoke, the air drying base moisture of the upgraded semicoke is less than 6%, the volatile matter is reduced by 25%, the sulfur content is less than 0.5%, the alkali metal (K + Na) is less than 0.1%, the Haw's grindability index is greater than 60, the high-order heating value is greater than 24000kJ/kg, and the upgraded semicoke is conveyed to a steel plant and can be directly ground into medium-speed mill powder for blast furnace injection.
The low-rank coal is crushed, pulped and subjected to waste heat treatment, so that the complete implementation of the raw material conveying and the hydrothermal carbonization reaction is facilitated. Compared with the traditional low-rank coal pyrolysis treatment method, the hydrothermal carbonization treatment of the low-rank coal is adopted, the hydrothermal process is a non-evaporation drying quality-improving technology, water is removed in a liquid form, phase change heat consumption in the evaporation drying quality-improving technology is reduced, and system energy consumption is reduced; the hydrothermal process can remove hydrophilic oxygen-containing functional groups such as-OH, -COOH and > C ═ O and the like while removing the water in the low-rank coal, change the surface performance of the low-rank coal and reduce the volatile content in the low-rank coal; the hydrothermal process can dissolve alkali metals such as soluble potassium salt and sodium salt, chloride ions, partial organic sulfur and heavy metal elements in the low-rank coal into a water solution, and the ash content and the harmful element content in the upgraded coal are reduced.
The method for preparing the blast furnace injection semicoke by using the low-rank coal based on the hydrothermal reaction has the advantages of short flow, less investment, simple equipment, convenience in operation and strong adjustability of application scale, and can meet the scale requirements of large-scale industrial production such as chemical industry, metallurgy and the like. On the other hand, after high-temperature and high-pressure materials obtained after the low-rank coal is subjected to hydrothermal carbonization are subjected to pressure reduction and temperature reduction treatment by a flash tank, a part of heat can be further applied to the waste heat of the low-rank coal slurry and the drying of the upgraded semicoke, the energy recovery rate is high, and the energy consumption of the whole system is further reduced.
Preferably, the low-rank coal is high-moisture high-volatile low-metamorphic coal powder such as brown coal, non-caking coal, weakly caking coal, long-flame coal and peat. The low-rank coal is subjected to high-temperature hydrothermal carbonization treatment in a hydrothermal carbonization tank, most of water is removed in a liquid state, organic functional groups on the surface of the coal are partially decomposed, and partial soluble salts, organic sulfur and other harmful elements are dissolved out, so that the high-quality requirement of the upgraded semicoke as blast furnace injection fuel is met.
Preferably, the pulverized coal in the step (1) is crushed to a level of less than 1mm, and the moisture of the coal slurry in the slurry storage tank is controlled to be 30-70%.
Preferably, the pressurizing pressure of the high-pressure coal slurry pump in the step (2) is controlled to be 0.1-3.5MPa, and the coal slurry is preheated to 50-180 ℃.
Preferably, the heating mode of the hydrothermal carbonization tank in the step (3) can adopt one or more combination modes of electric heating, high-temperature steam heating and hot waste gas heating. .
Preferably, the core device in the step (4) is a secondary flash tank, the high-temperature steam with the temperature of 200-240 ℃ generated by decompression of the primary flash tank is partially conveyed to the heat exchanger, and the low-temperature steam with the temperature of 120-160 ℃ generated by decompression of the secondary flash tank is conveyed to the thermal drying equipment.
By adopting the technical scheme, the invention has the following advantages:
low energy consumption and high heat recovery efficiency. According to the invention, the water in the low-rank coal is discharged in a liquid state by using a hydrothermal carbonization principle, so that the heat consumed by steam gasification in an evaporation drying process is reduced; the waste heat generated after the low-rank coal is subjected to hydrothermal carbonization treatment is utilized in a gradient manner, and is dried by the waste heat of the raw coal slurry and the carbonized semicoke, so that the heat recovery utilization rate is high.
The equipment is simple to operate, and the process is flexible to control. According to the invention, a high-pressure coal slurry pump is combined with a hydrothermal carbonization tank through a pipeline to realize hydrothermal carbonization reaction, and a high-temperature steam-assisted electric heating mode is adopted to realize rapid temperature rise and accurate temperature control; the method can realize the regulation and control of the performance of the hydrothermal carbonization semicoke by controlling the hydrothermal carbonization reaction time and temperature according to the characteristics of the low-rank raw coal; and the high-temperature material cooling treatment after the low-rank coal hydrothermal carbonization treatment adopts a secondary flash tank, and the preheating of the raw coal slurry and the drying steam temperature of the carbonized semicoke are flexibly controlled.
The raw material source is wide, and the quality of the upgraded semicoke is uniform and controllable. Lignite, non-caking coal, weakly caking coal, long flame coal, peat and the like can be used as raw materials, raw coal is crushed and pulped and then is subjected to hydrothermal carbonization treatment, slurry in a hydrothermal carbonization tank can be fully stirred and uniformly heated, and the prepared semicoke has uniform and stable performance; according to the property difference of raw coal, the hydrothermal semicoke performance can be controlled by optimizing the hydrothermal carbonization time and temperature to meet the blast furnace injection requirement.
The value of low-rank coal is improved, and the types of fuel injected by the blast furnace are expanded. The low-rank coal is subjected to hydrothermal upgrading and semicoke to replace expensive anthracite and bituminous coal for blast furnace injection, so that the blast furnace smelting cost can be reduced, and meanwhile, the utilization value of the low-rank coal is improved; the range of the types of the blast furnace injection fuel is further expanded, and low-rank coal such as brown coal, non-caking coal, weakly caking coal, long flame coal, peat and the like can be applied to blast furnace ironmaking production, so that the high-value utilization of the low-rank coal and the cost reduction and efficiency improvement of the blast furnace ironmaking production are promoted.
Drawings
FIG. 1 is a process flow diagram of a method for preparing blast furnace injection semicoke by using low-rank coal based on hydrothermal reaction.
Detailed Description
The technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.
The invention is further described with reference to the following figures and examples.
Example 1
The method for preparing blast furnace blowing semicoke from low-rank coal based on hydrothermal reaction, as shown in figure 1, comprises the following steps:
(1) pretreating raw coal of low-rank coal: crushing low-rank coal raw coal to a level smaller than 1mm, conveying the crushed coal powder to a slurry storage tank through a pipeline, adding water into the coal powder in the slurry storage tank, stirring and uniformly mixing, and controlling the water content of the coal slurry in the slurry storage tank to be 40%;
(2) preheating coal slurry: pressurizing the coal slurry in the slurry storage tank to 0.1MPa through a high-pressure coal slurry pump, conveying the coal slurry to a coal slurry heat exchanger through a pipeline for preheating, and preheating the coal slurry to 80 ℃;
(3) hydrothermal carbonization treatment: injecting the pressurized and preheated coal slurry into a hydrothermal treatment system by using a pipeline, electrically heating a hydrothermal carbonization tank by using high-temperature steam in an auxiliary manner, and controlling the reaction temperature in the hydrothermal carbonization tank to be 280 ℃ and the hydrothermal carbonization time to be 5 hours;
(4) and (3) waste heat recovery treatment: conveying the high-temperature and high-pressure material subjected to hydrothermal carbonization treatment to a condensing system for cooling and depressurizing treatment, conveying the high-temperature steam part at 200 ℃ generated by depressurization in a primary flash tank to a heat exchanger, and conveying the low-temperature steam at 120 ℃ generated by depressurization in a secondary flash tank to a thermal drying device;
(5) and (3) dehydration and drying treatment: the hydrothermal carbonized material subjected to cooling treatment by the condenser is reduced to normal pressure by a pressure reduction system, the normal pressure mixed material is conveyed to a solid-liquid separation system for dehydration treatment, the obtained liquid phase is purified and recycled, the obtained mud-cake-shaped solid-phase separator is conveyed to a thermal drying device for drying to obtain hydrothermal upgraded semicoke, the air drying base moisture content of the upgraded semicoke is 3.5%, the volatile matter is 25.6%, the sulfur content is 0.33%, the alkali metal (K + Na) is 0.08%, the Haw abrasion coefficient is 65, the ash content is 6.6%, the high-order calorific value reaches 24600kJ/kg, and the upgraded semicoke is conveyed to a steel plant and can be directly ground into powder for blast furnace injection.
Wherein the low-rank coal is lignite; steam generated by decompression of the first-stage flash tank in the step (4) is recycled for preheating the coal slurry in the step (2); and (4) utilizing steam generated by decompression of the secondary flash tank in the step (4) in the solid material heating and drying process in the step (5).
Examples 2 to 5
Examples 2 to 5 provide a method for preparing blast furnace injection semicoke from low-rank coal based on hydrothermal reaction, which is different from example 1 in that the moisture content of the coal slurry, the conveying pressure of the high-pressure coal slurry pump and the preheating temperature of the coal slurry in the step (1) and the step (2) are changed, and specific values of the moisture content of the coal slurry, the conveying pressure of the high-pressure coal slurry pump and the preheating temperature of the coal slurry corresponding to each example are shown in table 1.
TABLE 1 coal slurry moisture content, high pressure slurry pump delivery pressure and slurry preheat temperature for examples 2-5
The upgraded semicoke produced in each example was tested and the results are shown in table 2:
TABLE 2 Properties of upgraded semicoke produced in example 2-5, step (5)
As can be seen from Table 2, the air drying base of the upgraded semicoke prepared in examples 2 to 5 has a hydrothermal content of 3.2 to 3.5%, a volatile matter content of 25.3 to 25.6%, a sulfur content of 0.32 to 0.34%, an alkali metal (K + Na) content of 0.07 to 0.08%, a Hawski grindability coefficient of 65, an ash content of 6.6 to 6.7%, and a high calorific value of 24480 to 24660 kJ/kg. The comparison can find that the content of moisture, volatile components, ash content, sulfur and alkali metal in the obtained semicoke can be reduced by increasing the moisture content of the coal slurry, improving the conveying pressure of a high-pressure coal slurry pump and the preheating temperature of the coal slurry, the high-order heating value is improved, the Haw grindability coefficient is not influenced, and the performance of blast furnace blowing of the upgraded semicoke is improved integrally.
Examples 6 to 13
Examples 6 to 13 provide a method for preparing blast furnace injection semicoke from low-rank coal based on hydrothermal reaction, which is different from example 1 in that the hydrothermal carbonization temperature and the treatment time in the step (3) are changed, and specific values of the hydrothermal carbonization temperature and the treatment time in each example are shown in table 3:
TABLE 3 hydrothermal carbonization temperature and treatment time for examples 6 to 13
| Examples | Heating temperature of | Treatment time, h |
| Example 6 | 300 | 4 |
| Example 7 | 320 | 3.5 |
| Example 8 | 340 | 3 |
| Example 9 | 360 | 2 |
| Example 10 | 380 | 1.5 |
| Example 11 | 400 | 1 |
| Example 12 | 340 | 4 |
| Example 13 | 340 | 2 |
The upgraded semicoke produced in each example was tested and the results are shown in table 4:
TABLE 4 Properties of upgraded semicoke produced in example 6-13, step (5)
As can be seen from Table 4, the air-dried base of the upgraded semicoke prepared in examples 6 to 13 has a hydrothermal content of 2.5 to 3.4%, a volatile matter content of 19.8 to 25.1%, a sulfur content of 0.29 to 0.33%, an alkali metal (K + Na) content of 0.04 to 0.07%, a Hawski grindability coefficient of 65 to 75, an ash content of 5.8 to 6.7%, and a high-order calorific value of 25330 to 29350 kJ/kg. The comparison shows that the content of moisture, volatile components, ash content, sulfur and alkali metal in the semicoke obtained by increasing the hydrothermal carbonization temperature is reduced, the high calorific value is increased, the Haugh grindability coefficient is gradually increased along with the increase of the hydrothermal carbonization temperature, and the performance of blast furnace blowing of the upgraded semicoke is improved. The contents of moisture, volatile components, ash, sulfur and alkali metals in the obtained semicoke are slightly reduced by prolonging the hydrothermal carbonization treatment time, the high calorific value is slightly increased, the Haw grindability coefficient is slightly increased, and the improvement range of the quality-improved semicoke performance is small.
The influence of the increase of the hydrothermal carbonization temperature and the prolongation of the treatment time on the performance of the upgraded semicoke is caused by that in the hydrothermal carbonization process, the higher the temperature is, the longer the treatment time is, the crystal water and organic functional groups contained in the low-rank coal are broken and decomposed to form CO2、CO、H2O and the like enter the liquid phase and the gas phase, and the content of moisture and volatile matters is reduced. In the process, the sulfur and alkali metals in organic forms are released and removed, more small molecular gases are released in the hydrothermal carbonization process, the porosity is improved, and a good channel is provided for the escape of the sulfur and alkali metals, so that the removal of the sulfur and alkali metals is promoted. Water-soluble mineral substances in the low-rank coal gradually enter the hydrothermal carbonization processThe liquid phase reduces the ash content of the upgraded semicoke, and the reduction of the ash content and the increase of the porosity of the semicoke also help to improve the Haw grindability coefficient. The fixed content in the upgraded semicoke is increased due to the reduction of the content of volatile matters and ash, and the high calorific value is increased.
Example 14
The method for preparing blast furnace blowing semicoke from low-rank coal based on hydrothermal reaction, as shown in figure 1, comprises the following steps:
(1) pretreating raw coal of low-rank coal: crushing low-rank coal raw coal to a level smaller than 1mm, conveying the crushed coal powder to a slurry storage tank through a pipeline, adding water into the coal powder in the slurry storage tank, stirring and uniformly mixing, and controlling the water content of the coal slurry in the slurry storage tank to be 60%;
(2) preheating coal slurry: pressurizing the coal slurry in the slurry storage tank to 2.75MPa by a high-pressure coal slurry pump, conveying the coal slurry to a coal slurry heat exchanger through a pipeline for preheating, and preheating the coal slurry to 170 ℃;
(3) hydrothermal carbonization treatment: injecting the pressurized and preheated coal slurry into a hydrothermal treatment system by using a pipeline, electrically heating a hydrothermal carbonization tank by using high-temperature steam in an auxiliary manner, and controlling the reaction temperature in the hydrothermal carbonization tank to be 360 ℃ and the hydrothermal carbonization time to be 2 hours;
(4) and (3) waste heat recovery treatment: conveying the high-temperature and high-pressure material subjected to hydrothermal carbonization treatment to a condensing system for cooling and depressurizing treatment, conveying the part of high-temperature steam at 230 ℃ generated by depressurization in a primary flash tank to a heat exchanger, and conveying low-temperature steam at 150 ℃ generated by depressurization in a secondary flash tank to thermal drying equipment;
(5) and (3) dehydration and drying treatment: the hydrothermal carbonized material subjected to cooling treatment by the condenser is reduced to normal pressure by a pressure reduction system, the normal pressure mixed material is conveyed to a solid-liquid separation system for dehydration treatment, the obtained liquid phase is purified and recycled, the obtained mud-cake-shaped solid-phase separator is conveyed to a thermal drying device for drying to obtain hydrothermal upgraded semicoke, the air drying base moisture content of the upgraded semicoke is 2.1%, the volatile matter is 19.5%, the sulfur content is 0.23%, the alkali metal (K + Na) is 0.03%, the Haw abrasion coefficient is 77, the ash content is 5.2%, the high-order calorific value reaches 28600kJ/kg, and the upgraded semicoke is conveyed to a steel mill and can be directly ground into powder for blast furnace injection.
Wherein the low-rank coal is long bituminous coal; steam generated by decompression of the first-stage flash tank in the step (4) is recycled for preheating the coal slurry in the step (2); and (4) utilizing steam generated by decompression of the secondary flash tank in the step (4) in the solid material heating and drying process in the step (5).
Examples 15 to 18
Examples 2 to 5 provide a method for preparing blast furnace injection semicoke from low-rank coal based on hydrothermal reaction, which is different from example 1 in that the conveying pressure of the high-pressure coal slurry pump, the coal slurry preheating temperature and the steam temperature generated by the primary and secondary flash tanks in steps (2) and (4) are changed, and specific values of the conveying pressure of the high-pressure coal slurry pump, the coal slurry preheating temperature and the steam temperature generated by the primary and secondary flash tanks corresponding to each example are shown in table 5.
Table 5 delivery pressure and slurry preheating temperature of high-pressure slurry pump and steam generation temperature of primary and secondary flash tanks corresponding to embodiments 15 to 18 of embodiment
The upgraded semicoke produced in each example was tested and the results are shown in table 6:
TABLE 6 Properties of upgraded semicoke produced in example 15-18, step (5)
As can be seen from Table 2, the air-dried base of the upgraded semicoke prepared in examples 2 to 5 has a hydrothermal content of 1.8 to 2.3%, a volatile matter content of 19.4 to 20.3%, a sulfur content of 0.21 to 0.25%, an alkali metal (K + Na) content of 0.02 to 0.04%, a Hawski grindability coefficient of 75 to 81, an ash content of 5.3 to 5.5%, a high-order calorific value of 27650 to 29180kJ/kg, and the upgraded semicoke can be transported to a steel plant to be directly ground into powder at a medium speed for blast furnace injection. The higher steam temperature of the first-level flash tank improves the preheating efficiency of the coal slurry and can reduce the energy consumption of the system. The higher steam temperature of the secondary flash tank improves the drying effect of the upgraded semicoke, further reduces the moisture content of the upgraded semicoke and is beneficial to improving the blowing performance of the upgraded semicoke blast furnace.
While the invention has been described with respect to specific embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention; meanwhile, any equivalent changes, modifications and alterations of the above embodiments according to the spirit and techniques of the present invention are also within the scope of the present invention.
Claims (7)
1. A method for preparing blast furnace injection semicoke from low-rank coal based on hydrothermal reaction comprises the following steps:
(1) pretreating raw coal of low-rank coal: crushing raw low-rank coal, conveying crushed coal powder to a slurry storage tank through a pipeline, and adding water into the coal powder in the slurry storage tank to stir and mix uniformly;
(2) preheating coal slurry: pressurizing the coal slurry in the slurry storage tank through a high-pressure coal slurry pump, and conveying the coal slurry to a heat exchanger through a pipeline for preheating treatment;
(3) hydrothermal carbonization treatment: injecting the pressurized and preheated coal slurry into a hydrothermal treatment system by using a pipeline, wherein the core device of the system is a hydrothermal carbonization tank, the reaction temperature in the hydrothermal carbonization tank is controlled to be 280-400 ℃, and the hydrothermal carbonization time is 1-5 h;
(4) and (3) waste heat recovery treatment: conveying the high-temperature and high-pressure material subjected to the hydrothermal carbonization treatment to a condensing system for cooling and depressurizing treatment, and conveying the depressurized high-temperature steam to a coal slurry heat exchanger and a thermal drying device;
(5) and (3) dehydration and drying treatment: and (3) reducing the temperature of the hydrothermal carbonized material subjected to the cooling treatment of the condenser to normal pressure through a pressure reduction system, conveying the normal-pressure mixed material to a solid-liquid separation system for dehydration treatment, purifying the obtained liquid phase for cyclic utilization, conveying the obtained mud-cake-shaped solid-phase separated substance to a thermal drying device for drying to obtain hydrothermal upgraded semicoke, and conveying the upgraded semicoke to an iron and steel plant to directly feed the upgraded semicoke into a medium-speed mill to prepare powder for blast furnace injection.
2. The method for preparing blast furnace injection semicoke from low-rank coal based on hydrothermal reaction according to claim 1, characterized by comprising the following steps: the low-rank coal includes, but is not limited to, high-moisture and high-volatile low-metamorphic coal powder such as brown coal, non-caking coal, weakly caking coal, long-flame coal and peat.
3. The method for preparing blast furnace injection semicoke from low-rank coal based on hydrothermal reaction according to claim 1, characterized by comprising the following steps: in the step (1), the pulverized coal is crushed to a level less than 1mm, and the moisture of the coal slurry in the slurry storage tank is controlled to be 30-70%.
4. The method for preparing blast furnace injection semicoke from low-rank coal based on hydrothermal reaction according to claim 1, characterized by comprising the following steps: and (3) controlling the pressurizing pressure of the high-pressure coal slurry pump in the step (2) to be 0.1-3.5MPa, and preheating the coal slurry to 50-180 ℃.
5. The method for preparing blast furnace injection semicoke from low-rank coal based on hydrothermal reaction according to claim 1, characterized by comprising the following steps: the heating mode of the hydrothermal carbonization tank in the step (3) can adopt one or more combination modes of electric heating, high-temperature steam heating and hot waste gas heating.
6. The method for preparing blast furnace injection semicoke from low-rank coal based on hydrothermal reaction according to claim 1, characterized by comprising the following steps: and (4) the core device is a secondary flash tank, the high-temperature steam with the temperature of 200-plus-240 ℃ generated by decompression of the primary flash tank is partially conveyed to the coal slurry heat exchanger, and the low-temperature steam with the temperature of 120-plus-160 ℃ generated by decompression of the secondary flash tank is conveyed to the thermal drying equipment.
7. The method for preparing blast furnace injection semicoke from low-rank coal based on hydrothermal reaction according to claim 1, characterized by comprising the following steps: and (3) drying in the step (5) to obtain the air drying base water content of the hydrothermal upgraded semicoke is less than 6%, the volatile component is less than 25%, the sulfur content is less than 0.5%, the alkali metal (K + Na) is less than 0.1%, the Hastelloy index is greater than 60, and the high-order calorific value is greater than 24000 kJ/kg.
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