Method for preparing hydrogen-rich gas by using waste plastics gasified with waste heat of steelmaking and reducing CO2 emissions

Abstract

A method for preparing hydrogen-rich gas by gasifying waste plastics with the waste heat of steelmaking and reducing CO2 emissions is carried out according to the following steps: (1) Pour the molten converter slag into a rotary disk granulation device, and introduce air from the bottom of the rotary disk granulation device; the converter slag shrinks into ellipsoidal or spherical particles, and thus is broken into fine high-temperature solid steel slag particles; (2) Mix the converter flue gas with steam to obtain a mixed gas; (3) Introduce the high-temperature solid steel slag particles into a fluidized bed reactor; under the action of the waste heat of the steel slag and the mixed gas, the polyethylene plastic particles undergo pyrolysis gasification reaction to generate pyrolysis gas and low-temperature solid steel slag particles; (4) Introduce the low-temperature solid steel slag particles into a fluidized bed heat exchanger for heat exchange and cooling. The present invention uses a rotary disk granulator to granulate the molten steel slag and carry out primary waste heat recovery treatment, and uses a waste heat boiler and a fluidized bed heat exchanger to recover and utilize the waste heat of the steel slag particles and the syngas.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel metallurgy, and particularly relates to a method for preparing hydrogen-rich gas by gasifying waste plastics with the waste heat of steelmaking and reducing CO2 emissions. Background Art

[0002] At present, the molten slag waste heat recovery processes mainly include water quenching method, drum method, thermal insulation method, gas quenching method, mechanical stirring method, etc. These methods only consider the waste heat recovery of molten slag singly and do not consider the problem of carbon dioxide emission reduction synergistically, and have the following defects: (1) Low waste heat recovery rate: The existing molten slag waste heat recovery technologies have low heat recovery efficiency, all lower than 65%; (2) Poor uniformity of slag particle size: The uniformity of slag particle size after treatment by the existing molten slag waste heat recovery technologies is poor, and the molten slag treatment efficiency is low; (3) Difficult to efficiently utilize the low-temperature sensible heat during the molten slag heat exchange process: After the conventional molten slag treatment process recovers the sensible heat of molten slag, the remaining temperature of the slag particles reaches about 300°C, and it is difficult to efficiently utilize the low-temperature sensible heat below 300°C; (4) Long treatment cycle: The traditional hot pouring and slag insulation processes often take several days to complete. Summary of the Invention

[0003] In view of the above problems existing in the existing recovery and utilization of converter slag waste heat technology, the present invention provides a method for preparing hydrogen-rich gas by gasifying waste plastics with the waste heat of steelmaking and reducing CO2 emissions. The liquid steel slag is effectively granulated to save the cost of secondary crushing. Using converter flue gas and water vapor as gasification media, waste plastic particles are gasified with the waste heat of steel slag particles to prepare hydrogen-rich syngas, and at the same time, carbon dioxide in the flue gas is reduced; achieving the effect of energy conservation and emission reduction.

[0004] The method of the present invention is carried out according to the following steps:

[0005] (1) Pour the molten converter slag into a rotating disk granulation device, and at the same time, introduce air from the bottom of the rotating disk granulation device; under the action of the centrifugal force of the rotating disk and the air, the converter slag shrinks into ellipsoidal or spherical particles, and thus is broken into fine high-temperature solid steel slag particles; the air forms hot air after heat exchange with the converter slag and is introduced into a waste heat boiler.

[0006] (2) Mix the converter flue gas and water vapor to obtain a mixed gas; in the mixed gas, the molar ratio of CO + CO2 in the converter flue gas to H2O of the water vapor is 1.8 - 9.0.

[0007] (3) Introduce the high-temperature solid steel slag particles into a fluidized bed reactor; polyethylene plastic particles and the mixed gas are introduced from the bottom of the fluidized bed; under the action of the waste heat of the steel slag and the mixed gas, the polyethylene plastic particles undergo a pyrolysis gasification reaction in the fluidized bed reactor to generate pyrolysis gas and low-temperature solid steel slag particles; the pyrolysis gas is discharged and enters a first waste heat boiler; the temperature of the low-temperature solid steel slag particles is 500 - 700°C.

[0008] (4) Introduce the low-temperature solid steel slag particles into the fluidized bed heat exchanger for heat exchange and temperature reduction. The high-temperature air after heat exchange enters the second waste heat boiler through the gas guide pipe.

[0009] In the above step (1), the temperature of the molten converter slag is 1350 - 1650 °C.

[0010] In the above step (1), the air flow rate is 0.01 - 5 m / s.

[0011] In the above step (1), the rotational speed of the rotating disk of the rotating disk granulation device is 1500 - 2000 r / min.

[0012] In the above step (1), the temperature of the hot air is 1000 - 1300 °C.

[0013] In the above step (2), in the converter flue gas, the molar percentage of CO is 55 - 80%, the molar percentage of CO2 is 10 - 18%, the molar percentage of H2 is 2 - 10%, and the molar percentage of N2 + Ar is 8 - 26%.

[0014] In the above step (2), the temperature of the mixed gas is 100 - 150 °C.

[0015] In the above step (3), the diameter of the polyethylene plastic particles is 0.1 - 5.0 mm.

[0016] In the above step (3), when the polyethylene plastic particles and the mixed gas are introduced from the bottom of the fluidized bed, using the mixed gas as the carrier gas, the flow rate of the mixed gas is 0.01 - 5 m / s.

[0017] In the above step (3), during the pyrolysis gasification reaction, the polyethylene plastic particles generate H2 and CO, and the CO2 in the flue gas is consumed during the reaction.

[0018] In the above step (3), the hydrogen yield in the pyrolyzed gas is 45 - 65%.

[0019] In the above step (3), the CO yield is 85 - 100%.

[0020] In the above step (4), after the low-temperature solid steel slag particles are introduced into the fluidized bed heat exchanger for heat exchange and temperature reduction, the temperature ≤ 100 °C.

[0021] In the above step (3), after the pyrolyzed gas enters the waste heat boiler for heat exchange and temperature reduction, the temperature is 100 - 150 °C.

[0022] In the above step (4), in the hydrogen-rich gas, H2 / CO ≥ 1.5 by volume ratio.

[0023] The device for implementing the above method of the present invention includes a rotary disk granulation device 2, a fluidized bed reactor 8, a first waste heat boiler 13, and a second waste heat boiler 21; inside the rotary disk granulation device 2, there are a rotary disk 3, a primary fluidized bed 4, and a secondary fluidized bed 6; above the rotary disk granulation device 2, there is a feed cylinder, the outlet of the feed cylinder faces the rotary disk 3, and the inlet of the feed cylinder is opposite to the slag receiving tank 1 outside the rotary disk granulation device 2; the outlet at the lower part of the rotary disk granulation device 2 is communicated with one end of a first solid slag conduit 7, and the other end of the first solid slag conduit 7 is communicated with the inlet at the lower part of the fluidized bed reactor 8; at the bottom of the fluidized bed reactor 8, there is a fluidized bed air distribution plate 10; the upper outlet of the fluidized bed reactor 8 is communicated with the first waste heat boiler 13 through a first gas conduit 12; the lower outlet of the fluidized bed reactor 8 is communicated with a fluidized bed heat exchanger 17 through a second solid slag conduit 16.

[0024] In the above device, the outlet at the upper part of the fluidized bed heat exchanger 17 is communicated with the inlet at the bottom of the second waste heat boiler 21 through a second gas conduit 20.

[0025] In the above device, the outlet at the upper part of the first waste heat boiler 13 is communicated with the inlet of a gas storage tank 15 through a syngas conduit 14.

[0026] In the above device, both the primary fluidized bed 4 and the secondary fluidized bed 6 are circular rings. Horizontally, the secondary fluidized bed 6 is located between the primary fluidized bed 4 and the rotary disk 3, and vertically, the primary fluidized bed 4 is located between the secondary fluidized bed 6 and the rotary disk 3.

[0027] The usage method of the above device is as follows:

[0028] (1) Pour the converter slag into the rotary disk granulation device 2 through the slag receiving tank 1 via the feed cylinder, pour it onto the rotary disk 3, start the rotary disk 3, and disperse the converter slag above the primary fluidized bed 4 and the secondary fluidized bed 6; by introducing air 5 at the bottom of the rotary disk granulation device 2, make the air blow upward from the bottom of the primary fluidized bed 4 and the secondary fluidized bed 6 to cool the converter steel slag.

[0029] (2) The generated high-temperature solid steel slag particles 9 enter the fluidized bed reactor 8 through the first solid slag conduit 7; introduce a mixed gas 11 carrying polyethylene plastic particles from the bottom of the fluidized bed reactor 8 for pyrolysis gasification reaction; after the pyrolyzed gas is discharged, enter the first waste heat boiler 13 through the first gas conduit 12 to recover waste heat; the heat-exchanged mixed gas enters the gas storage tank 15 through the syngas conduit 14; (3) The generated low-temperature solid steel slag particles 18 enter the fluidized bed heat exchanger 17 through the second solid slag conduit 16; introduce normal-temperature air 19 from the bottom of the fluidized bed heat exchanger 17 to exchange heat with the low-temperature solid steel slag particles 18; the heat-exchanged normal-temperature air generates high-temperature air and enters the second waste heat boiler 21 through the second gas conduit 20 to recover waste heat.

[0030] In the above method, the H2 yield is 44.82 - 64.13%; the formula for calculating the H2 yield is as follows: (1); where moles of H2 in the produts is the number of moles of H2 in the hydrogen-rich gas, Input H2 is the number of moles of H2 in the converter gas, and moles of theoretical H2 is the number of moles of theoretical hydrogen.

[0031] In the above method, the CO yield is 88.88 - 135.69%; the formula for calculating the CO yield is as follows:

[0032] (2); where COout is the number of moles of CO in the hydrogen-rich gas, inputCO is the number of moles of CO in the converter gas, and moles of C in plastic is the number of moles of C in the polyethylene plastic particles.

[0033] In the above method, the CO2 emission reduction efficiency in the converter gas is 75 - 17 - 90%, and the formula for calculating the CO2 emission reduction efficiency is as follows:

[0034] (3); where CO2in is the number of moles of CO2 in the converter gas, and CO2out is the number of moles of CO2 in the hydrogen-rich gas.

[0035] In the above method, the thermal recovery rate of the converter slag is 80 - 100%; the formula for calculating the thermal recovery rate of the converter slag is as follows:

[0036] (4);

[0037] In formula (4), ; c is the specific heat capacity of the thermal recovery rate of the converter slag, with the unit J / (kg·℃); m is the mass of the thermal recovery rate of the converter slag, with the unit kg; Δ t is the temperature difference of the thermal recovery rate of the converter slag to form low-temperature solid steel slag particles, with the unit ℃; Q1 represents the sensible heat of the converter slag; η 1 represents the utilization rate of the sensible heat of the converter slag, with a value of over 90%; η 2 represents the heat recovery rate of the mixed gas, with a value of over 80%; η 3 represents the thermal efficiency of the first waste heat boiler, with a value of over 90%; η 4 represents the heat exchange efficiency of the fluidized bed heat exchanger, with a value of over 90%.

[0038] In the above method, the gasification reaction equation involved in the fluidized bed reactor is as follows:

[0039] Boudouard reaction (BD): C(s)+CO2(g)⇋2CO(g) ΔH=168.9 kJ / mol (5),

[0040] Primary water gas (PWG): C(s)+H2O(g)⇋CO(g)+H2(g) ΔH=135.8 kJ / mol (6),

[0041] Water gas shift (WGS): CO(g)+H2O(g)⇋CO2(g)+ H2(g) ΔH= -33.1 kJ / mol (7),

[0042] Methane formation (MF): C(s)+ 2H2(g)⇋CH4(g) ΔH= -91.3 kJ / mol (8),

[0043] MSR: CH4(g)+H2O(g)⇋CO(g)+3H2(g) ΔH=227.1 kJ / mol (9) and

[0044] MDR: CH4(g)+ CO2(g)⇋2CO(g)+2H2(g) ΔH=260.2 kJ / mol (10).

[0045] This patent has the following features and innovations:

[0046] High efficiency of waste heat recovery: Different methods are used for step-by-step waste heat recovery in different temperature sections of converter slag. For molten converter slag above 1000°C, a rotating disc granulator is used for granulation while the heat of the molten converter slag is recovered by physical methods. The sensible heat of slag particles at 700-1000°C is recovered by polyethylene plastic gasification reaction. The sensible heat of slag particles below 700°C is recovered by fluidized bed heat exchanger and waste heat boiler.

[0047] Reducing CO2 emissions in flue gas while preparing hydrogen-rich synthesis gas: The method of the present invention utilizes high-temperature steel slag as a heat carrier and converter flue gas as a gasifying agent to gasify polyethylene waste plastics, thereby achieving the effect of reducing CO2 emissions in flue gas while preparing hydrogen-rich synthesis gas.

[0048] Good product quality: In the method described in the present invention, the rotating disk granulator has a uniform rotation speed, is easy to handle, safe and efficient, and the slag particle size is small and uniform.

[0049] The waste heat recovery from molten metallurgical steel slag is the key point for energy conservation and emission reduction in iron and steel enterprises and is crucial for realizing the waste heat recovery and utilization in all links of iron and steel enterprises. In the present invention, a rotary disk granulator is used for granulating molten steel slag and performing primary waste heat recovery treatment. Further, in a fluidized bed reactor, the waste heat of steel slag particles at 700 - 1000°C is recovered by using the gasification reaction of waste plastics, carbon dioxide in the flue gas is reduced, and hydrogen-rich syngas is prepared. Finally, a waste heat boiler and a fluidized bed heat exchanger are used for recovering and utilizing the waste heat of steel slag particles below 700°C and syngas. The method described in the present invention is an innovation in liquid steel slag treatment and heat recovery and has broad prospects. Description of the Drawings

[0050] Figure 1 It is a schematic diagram of the implementation device for the method of preparing hydrogen-rich gas by gasifying waste plastics with waste heat from steelmaking and reducing CO2 in an embodiment of the present invention;

[0051] In the figure, 1, slag receiving tank; 2, rotary disk granulator; 3, rotary disk; 4, primary fluidized bed; 5, air; 6, secondary fluidized bed; 7, first solid slag conduit; 8, fluidized bed reactor; 9, high-temperature solid steel slag particles; 10, fluidized bed air distribution plate; 11, mixed gas carrying polyethylene plastic particles; 12, first gas conduit; 13, first waste heat boiler; 14, syngas conduit; 15, gas storage tank; 16, second solid slag conduit; 17, fluidized bed heat exchanger; 18, low-temperature solid steel slag particles; 19, normal-temperature air; 20, second gas conduit; 21, second waste heat boiler. Detailed Embodiments

[0052] In the examples of the present invention, the example composition of the converter slag used contains, by mass percentage, 39 - 50% CaO, 17 - 42% SiO2, 0.8 - 18% Fe2O3, 0.1 - 13% MgO, 3 - 5% Al2O3, 0 - 1.2% SO3, 1.2 - 2.8% P2O5, and 0 - 2.5% CaCO3.

[0053] In the examples of the present invention, the flue gas used is the converter flue gas generated in the converter workshop, with the molar percentage of CO being 55 - 80%, the molar percentage of CO2 being 10 - 18%, the molar percentage of H2 being 2 - 10%, and the molar percentage of N2 + Ar being 8 - 26%.

[0054] In the examples of the present invention, the water used for preparing steam has a purity of more than 99.999%.

[0055] In the examples of the present invention, the diameter of the polyethylene plastic particles used is 0.1 - 5.0 mm;

[0056] In the examples of the present invention, the rotational speed of the rotary disk of the rotary disk granulator is 1500 - 2000 r / min.

[0057] The device in the embodiment of the present invention is as follows Figure 1 shown, and it includes a rotary disk granulation device 2, a fluidized bed reactor 8, a first waste heat boiler 13, and a second waste heat boiler 21; inside the rotary disk granulation device 2, there are a rotary disk 3, a primary fluidized bed 4, and a secondary fluidized bed 6; above the rotary disk granulation device 2, there is a feed cylinder, the outlet of the feed cylinder faces the rotary disk 3, and the inlet of the feed cylinder is opposite to the slag receiving tank 1 outside the rotary disk granulation device 2; the outlet at the lower part of the rotary disk granulation device 2 is communicated with one end of a first solid slag conduit 7, and the other end of the first solid slag conduit 7 is communicated with the inlet at the lower part of the fluidized bed reactor 8; at the bottom of the fluidized bed reactor 8, there is a fluidized bed air distribution plate 10; the upper outlet of the fluidized bed reactor 8 is communicated with the first waste heat boiler 13 through a first gas conduit 12; the lower outlet of the fluidized bed reactor 8 is communicated with a fluidized bed heat exchanger 17 through a second solid slag conduit 16;

[0058] The outlet at the upper part of the fluidized bed heat exchanger 17 is communicated with the inlet at the bottom of the second waste heat boiler 21 through a second gas conduit 20;

[0059] The outlet at the upper part of the first waste heat boiler 13 is communicated with the inlet of a gas storage tank 15 through a synthesis gas conduit 14;

[0060] Both the primary fluidized bed 4 and the secondary fluidized bed 6 are circular rings. Horizontally, the secondary fluidized bed 6 is located between the primary fluidized bed 4 and the rotary disk 3, and vertically, the primary fluidized bed 4 is located between the secondary fluidized bed 6 and the rotary disk 3.

[0061] The usage method of the device in the embodiment of the present invention is as follows:

[0062] (1) Pour the converter slag into the rotary disk granulation device 2 through the slag receiving tank 1 via the feed cylinder and onto the rotary disk 3. Start the rotary disk 3 to disperse the converter slag above the primary fluidized bed 4 and the secondary fluidized bed 6; by introducing air 5 at the bottom of the rotary disk granulation device 2, make the air blow upward from the bottoms of the primary fluidized bed 4 and the secondary fluidized bed 6 to cool the converter slag.

[0063] (2) The generated high-temperature solid steel slag particles 9 enter the fluidized bed reactor 8 through the first solid slag conduit 7; introduce a mixed gas 11 carrying polyethylene plastic particles from the bottom of the fluidized bed reactor 8 for pyrolysis gasification reaction; after the pyrolyzed gas is discharged, it enters the first waste heat boiler 13 through the first gas conduit 12 to recover waste heat; the heat-exchanged mixed gas enters the gas storage tank 15 through the synthesis gas conduit 14;

[0064] (3) The generated low-temperature solid steel slag particles 18 enter the fluidized bed heat exchanger 17 through the second solid slag conduit 16; introduce normal-temperature air 19 from the bottom of the fluidized bed heat exchanger 17 to exchange heat with the low-temperature solid steel slag particles 18; the heat-exchanged normal-temperature air generates high-temperature air and enters the second waste heat boiler 21 through the second gas conduit 20 to recover waste heat. Example

[0065] The molten metallurgical steel slag is the steel slag produced in the converter shop. Its composition contains 46.92% CaO, 17.96% SiO2, 17.73% Fe2O3, 8.99% MgO, 3.73% Al2O3, 1.76% P2O5, 1.23% TiO2, and 1.68% MnO by mass percentage;

[0066] The method is as follows:

[0067] Pour the converter slag molten at 1450 °C into the spinning disk granulation device (SDA), and at the same time, introduce air from the bottom of the spinning disk granulation device; under the action of the centrifugal force of the spinning disk and the air, the converter slag shrinks into ellipsoidal or spherical particles, and thus is broken into fine high-temperature solid steel slag particles; after the air exchanges heat with the converter slag, hot air is formed and introduced into the waste heat boiler; the flow rate of the air is 0.6 m / s; the rotation speed of the spinning disk of the spinning disk granulation device is 1800 r / min;

[0068] Mix the converter flue gas and water vapor to obtain a mixed gas; in the mixed gas, the molar ratio of CO + CO2 in the converter flue gas to H2O of the water vapor is 1.8; in the converter flue gas, the molar percentage of CO is 62%, the molar percentage of CO2 is 18%, the molar percentage of H2 is 5%, and the molar percentage of N2 + Ar is 15%; the temperature of the mixed gas is 130 °C;

[0069] Introduce the high-temperature solid steel slag particles into the fluidized bed reactor; the polyethylene plastic particles and the mixed gas are introduced from the bottom of the fluidized bed; under the action of the waste heat of the steel slag and the mixed gas, the polyethylene plastic particles undergo pyrolysis gasification reaction in the fluidized bed reactor to generate pyrolysis gas and low-temperature solid steel slag particles; the pyrolysis gas is discharged and then enters the waste heat boiler; the temperature of the low-temperature solid steel slag particles is 700 °C; the diameter of the polyethylene plastic particles is 0.4 mm; when the polyethylene plastic particles and the mixed gas are introduced from the bottom of the fluidized bed, the mixed gas is used as the carrier gas, and the flow rate of the mixed gas is 0.6 m / s; during the pyrolysis gasification reaction, the polyethylene plastic particles generate H2 and CO, and the CO2 in the flue gas is consumed during the reaction;

[0070] Introduce the low-temperature solid steel slag particles into the fluidized bed heat exchanger for heat exchange and temperature reduction; after the pyrolysis gas passes through the waste heat boiler for heat exchange and temperature reduction, rich hydrogen gas is generated; after the low-temperature solid steel slag particles are introduced into the fluidized bed heat exchanger for heat exchange and temperature reduction, the temperature ≤ 100 °C; in the rich hydrogen gas, H2 / CO ≥ 1.5 by volume ratio;

[0071] After being processed by the above process steps, the H2 production rate is 64.13%, the CO production rate is 88.88%, the CO2 emission reduction rate is 80.18%, and the waste heat recovery rate is 95.28%. Example

[0072] The molten metallurgical steel slag is the steel slag produced in the electric furnace workshop. Its composition contains 49.64% CaO, 41.64% SiO₂, 0.83% Fe₂O₃, 0.16% MgO, 4.23% Al₂O₃, 0.62% SO₃, 2.76% P₂O₅, and 0.12% MnO by mass percentage;

[0073] The method is the same as that in Example 1, and the differences are as follows:

[0074] (1) Pour the molten converter slag at 1480 °C into the rotary disk granulation device; the air flow rate is 0.4 m / s; the rotational speed of the rotary disk of the rotary disk granulation device is 2000 r / min;

[0075] (2) In the mixed gas, the molar ratio of CO + CO₂ in the converter flue gas to H₂O in water vapor is 9.0; in the converter flue gas, the molar percentage of CO is 64%, the molar percentage of CO₂ is 16%, the molar percentage of H₂ is 5%, and the molar percentage of N₂ + Ar is 15%; the temperature of the mixed gas is 120 °C;

[0076] (3) The temperature of the low-temperature solid steel slag particles is 690 °C; the diameter of the polyethylene plastic particles is 0.2 mm; the flow rate of the mixed gas is 0.4 m / s;

[0077] (4) After being processed by the above technological steps, the H₂ production rate is 45.82%, the CO production rate is 135.69%, the CO₂ emission reduction rate is 90%, and the waste heat recovery rate is 98.64%. Example

[0078] The molten metallurgical steel slag is the steel slag produced in the refining workshop. Its composition contains 39.89% CaO, 31.68% SiO₂, 3.86% Fe₂O₃, 12.73% MgO, 1.13% SO₃, 4.92% Al₂O₃, 2.42% CaCO₃, 1.23% P₂O₅, and 2.14% MnO by mass percentage;

[0079] The method is the same as that in Example 1, and the differences are as follows:

[0080] (1) Pour the molten converter slag at 1430 °C into the rotary disk granulation device; the air flow rate is 0.8 m / s; the rotational speed of the rotary disk of the rotary disk granulation device is 1600 r / min;

[0081] (2) In the mixed gas, the molar ratio of CO + CO2 in the converter gas to H2O in water vapor is 5.0; in the converter gas, the molar percentage of CO is 66%, the molar percentage of CO2 is 15%, the molar percentage of H2 is 4%, and the molar percentage of N2 + Ar is 15%; the temperature of the mixed gas is 110 °C;

[0082] (3) The temperature of the low-temperature solid steel slag particles is 680 °C; the diameter of the polyethylene plastic particles is 0.6 mm; the flow rate of the mixed gas is 0.8 m / s;

[0083] (4) After being treated by the above process steps, the H2 yield is 56.38%, the CO yield is 105.3%, the CO2 emission reduction rate is 85.62%, and the waste heat recovery rate is 91.58%.

Claims

1. A method for preparing hydrogen-rich gas and reducing CO2 emissions by gasifying waste plastics with steelmaking surplus heat. The device for preparing hydrogen-rich gas and reducing CO2 emissions by gasifying waste plastics with steelmaking surplus heat includes a rotary disk granulation device (2), a fluidized bed reactor (8), a first waste heat boiler (13), and a second waste heat boiler (21); inside the rotary disk granulation device (2), there are a rotary disk (3), a primary fluidized bed (4), and a secondary fluidized bed (6); above the rotary disk granulation device (2), there is a feed cylinder, the outlet of the feed cylinder is opposite to the rotary disk (3), and the inlet of the feed cylinder is opposite to the slag receiving tank (1) outside the rotary disk granulation device (2); the outlet at the lower part of the rotary disk granulation device (2) is communicated with one end of a first solid slag conduit (7), and the other end of the first solid slag conduit (7) is communicated with the inlet at the lower part of the fluidized bed reactor (8); at the bottom of the fluidized bed reactor (8), there is a fluidized bed air distribution plate (10); the upper outlet of the fluidized bed reactor (8) is communicated with the first waste heat boiler (13) through a first gas conduit (12); the lower outlet of the fluidized bed reactor (8) is communicated with a fluidized bed heat exchanger (17) through a second solid slag conduit (16), characterized in that Proceed as follows: (1) Pour the molten converter slag into the rotary disk granulation device, and at the same time introduce air from the bottom of the rotary disk granulation device; under the action of the centrifugal force of the rotary disk and the air, the converter slag shrinks into ellipsoidal or spherical particles, and thus is broken into fine high-temperature solid steel slag particles; after the air exchanges heat with the converter slag, hot air is formed and introduced into the waste heat boiler. (2) Mix the converter gas with steam to obtain a mixed gas; in the mixed gas, the molar ratio of CO + CO2 in the converter gas to H2O of the steam is 1.8 - 9.

0. (3) Introduce the high-temperature solid steel slag particles into the fluidized bed reactor; the polyethylene plastic particles and the mixed gas are introduced from the bottom of the fluidized bed; under the action of the waste heat of the steel slag and the mixed gas, the polyethylene plastic particles undergo pyrolysis gasification reaction in the fluidized bed reactor to generate pyrolysis gas and low-temperature solid steel slag particles; after the pyrolysis gas is discharged, it enters the first waste heat boiler; the temperature of the low-temperature solid steel slag particles is 500 - 700 °C. (4) Introduce the low-temperature solid steel slag particles into the fluidized bed heat exchanger for heat exchange and cooling, and the high-temperature air after heat exchange enters the second waste heat boiler through the gas guide pipe.

2. The method for preparing hydrogen-rich gas and reducing CO2 emissions by gasifying waste plastics with the waste heat of steelmaking according to claim 1, wherein In step (1), the temperature of the molten converter slag is 1350 - 1650 °C.

3. The method for preparing hydrogen-rich gas and reducing CO2 emissions by gasifying waste plastics with the waste heat of steelmaking according to claim 1, characterized in that In step (1), the air flow rate is 0.01 - 5 m / s.

4. The method for preparing hydrogen-rich gas and reducing CO2 emissions by gasifying waste plastics with the waste heat of steelmaking according to claim 1, characterized in that In step (1), the rotation speed of the rotary disk of the rotary disk granulation device is 1500 - 2000 r / min.

5. The method for preparing hydrogen-rich gas and reducing CO2 emissions by gasifying waste plastics with the waste heat of steelmaking according to claim 1, characterized in that In step (1), the temperature of the hot air is 1000 - 1300 °C.

6. The method for preparing hydrogen-rich gas and reducing CO2 emissions by gasifying waste plastics with the waste heat of steelmaking according to claim 1, wherein In step (2), in the converter gas, the molar percentage of CO is 55 - 80%, the molar percentage of CO2 is 10 - 18%, the molar percentage of H2 is 2 - 10%, and the molar percentage of N2 + Ar is 8 - 26%.

7. The method for preparing hydrogen-rich gas and reducing CO2 emissions by gasifying waste plastics with the waste heat of steelmaking according to claim 1, wherein In step (3), when the polyethylene plastic particles and the mixed gas are introduced from the bottom of the fluidized bed, using the mixed gas as the carrier gas, the flow rate of the mixed gas is 0.01 - 5 m / s.

8. The method for preparing hydrogen-rich gas and reducing CO2 emissions by gasifying waste plastics with the waste heat of steelmaking according to claim 1, wherein In step (3), the CO yield is 85 - 100%.

9. The method for preparing hydrogen-rich gas and reducing CO2 emissions by gasifying waste plastics with the waste heat of steelmaking according to claim 1, characterized in that Include the following steps: (1) Pass the converter slag through the slag receiving tank (1) and introduce it into the rotary disk granulation device (2) through the feed cylinder, pour it on the rotary disk (3), start the rotary disk (3), and disperse the converter slag above the primary fluidized bed (4) and the secondary fluidized bed (6); by introducing air (5) from the bottom of the rotary disk granulation device, make the air blow upward from the bottom of the primary fluidized bed (4) and the secondary fluidized bed (6) to cool the converter steel slag. (2) The generated high-temperature solid steel slag particles (9) enter the fluidized bed reactor (8) through the first solid slag conduit (7); introduce the mixed gas (11) carrying polyethylene plastic particles from the bottom of the fluidized bed reactor (8) for pyrolysis gasification reaction; after the pyrolysis gas is discharged, it enters the first waste heat boiler (13) through the first gas guide pipe (12) to recover waste heat; the mixed gas after heat exchange enters the gas storage tank (15) through the syngas conduit (14). (3) The generated low-temperature solid steel slag particles (18) enter the fluidized bed heat exchanger (17) through the second solid slag conduit (16); normal-temperature air (19) is introduced from the bottom of the fluidized bed heat exchanger (17) to exchange heat with the low-temperature solid steel slag particles (18); the normal-temperature air after heat exchange generates high-temperature air, which enters the second waste heat boiler (21) through the second gas conduit (20) to recover waste heat.

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