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CN-122012920-A - Functionalized core-shell structure binder for hydrogen-based direct reduction pellets, preparation method thereof and oxidized pellets for hydrogen-based direct reduction

CN122012920ACN 122012920 ACN122012920 ACN 122012920ACN-122012920-A

Abstract

The application provides a functional core-shell structure binder for hydrogen-based direct reduction pellets, a preparation method thereof and oxidized pellets for hydrogen-based direct reduction, and relates to the technical field of green metallurgy and pellet binders. The binder is a core-shell structure unit formed by a composite functional core and a chemically grafted polymer shell, wherein the polymer shell is a polyacrylamide crosslinked network bridged and covalently bonded to the surface of the composite functional core, and the binder comprises 50-85% of bentonite matrix, 10-25% of dispersion enhancer and 5-25% of magnesium-containing grain boundary enhancer calculated by 100% of the total mass of the raw materials of the composite functional core. The application solves the core problem of easy failure under shearing force and thermal stress caused by weak interface combination in the physical mixture, remarkably improves the structural stability and reliability of the product, and endows the pellet with special functions of actively inhibiting hydrogen reduction expansion and improving high-temperature strength by the innovative design of a core-shell structure and the introduction of a magnesium-containing grain boundary reinforcing agent.

Inventors

  • Yue Shouyan
  • HUANG HAO
  • LING SHISHENG
  • HE WEI
  • ZHANG YINXUE
  • LI DA
  • LI HAN
  • LI MENGYU
  • LI XIANG
  • CHEN JIAXIU

Assignees

  • 矿冶科技集团有限公司
  • 北矿化学科技(沧州)有限公司

Dates

Publication Date
20260512
Application Date
20260414

Claims (10)

  1. 1. The functional core-shell structure binder for the hydrogen-based direct reduction pellet is characterized in that the binder is a core-shell structure unit formed by a composite functional core and a chemically grafted polymer shell, wherein the polymer shell is a polyacrylamide crosslinked network bridged and covalently bonded to the surface of the composite functional core; The composite functional core comprises 50-85% of bentonite matrix, 10-25% of dispersion enhancer and 5-25% of magnesium-containing grain boundary enhancer by taking the total mass of the raw materials of the composite functional core as 100%.
  2. 2. The functionalized core-shell structured binder for hydrogen-based direct reduction pellets of claim 1, wherein the bentonite matrix comprises sodium bentonite and/or calcium bentonite.
  3. 3. The functionalized core-shell structured binder for hydrogen-based direct reduction pellets of claim 1, wherein the dispersion enhancer comprises at least one of lignosulfonate, humate, polycarboxylate.
  4. 4. The functionalized core-shell structured binder for hydrogen-based direct reduction pellets of claim 1, wherein the magnesium-containing grain boundary enhancer is at least one of magnesium oxide, magnesium hydroxide, magnesium carbonate, and light burned magnesite powder.
  5. 5. The functionalized core-shell structured binder for hydrogen-based direct reduction pellets according to any one of claims 1 to 4, wherein the polyacrylamide cross-linked network is formed by polymerizing an acrylamide monomer with a cross-linking agent.
  6. 6. The functionalized core-shell structured binder for hydrogen-based direct reduction pellets of claim 5, wherein the cross-linking agent is N, N' -methylenebisacrylamide and/or ethylene glycol dimethacrylate.
  7. 7. A method for preparing the functionalized core-shell structure binder for hydrogen-based direct reduction pellets according to any one of claims 1 to 6, comprising: Dispersing bentonite matrix, dispersion enhancer and magnesium-containing grain boundary enhancer in water according to a proportion to obtain uniform slurry, adding cationic surfactant for intercalation and surface organic modification to obtain organic composite functional core powder; dispersing the organic composite functional core powder in an organic solvent, and adding a silane coupling agent containing vinyl into the organic solvent under inert atmosphere for reflux reaction to obtain a silanized modified core; And dispersing the silanized modified core in water, mixing with an acrylamide monomer, a cross-linking agent and a water-soluble initiator, and carrying out free radical polymerization reaction to obtain the adhesive.
  8. 8. The method for preparing a functionalized core-shell structured binder for hydrogen-based direct reduction pellets according to claim 7, wherein at least one of the following conditions is satisfied: A. the cationic surfactant comprises cetyl trimethyl ammonium bromide or cetyl amino trimethyl ammonium chloride, and the addition amount of the cationic surfactant is 30-60% of the mass of the bentonite matrix; B. The silane coupling agent comprises at least one of vinyl trimethoxy silane, vinyl triethoxy silane and gamma- (methacryloyloxy) propyl trimethoxy silane, wherein the mass ratio of the silane coupling agent to the organic composite core powder is 0.15-0.35:1; C. The mass ratio of the acrylamide monomer to the silanized modified core is 3-10:1; D. The addition amount of the cross-linking agent is 0.2-1.0% of the mass of the acrylamide monomer; E. the water-soluble initiator comprises at least one of ammonium persulfate, potassium persulfate and azo diisobutyl amidine hydrochloride, and the addition amount of the water-soluble initiator is 0.1-0.8% of the mass of the acrylamide monomer.
  9. 9. An oxidized pellet for hydrogen radical direct reduction, characterized in that the raw material of the oxidized pellet comprises the functionalized core-shell structure binder for hydrogen radical direct reduction pellet according to any one of claims 1 to 6; the reduction expansion rate of the oxidized pellets is lower than 15 percent, and the compressive strength of the oxidized pellets is not lower than 350N/min after isothermal reduction for 30min in pure hydrogen or hydrogen-rich atmosphere at 800-900 ℃.
  10. 10. The oxidized pellet of claim 9, wherein the total amount of SiO 2 +Al 2 O 3 incorporated by the binder in the oxidized pellet is less than 0.5% of the total mass of the pellet.

Description

Functionalized core-shell structure binder for hydrogen-based direct reduction pellets, preparation method thereof and oxidized pellets for hydrogen-based direct reduction Technical Field The application relates to the technical field of green metallurgy and pellet binders, in particular to a functional core-shell structure binder for a hydrogen-based direct reduction pellet, a preparation method thereof and an oxidized pellet for the hydrogen-based direct reduction. Background In the context of global iron and steel industry efforts to achieve this goal, hydrogen-based direct reduction techniques with hydrogen as the primary or sole reductant are recognized as the most potential subversion of the process. However, the unique reaction kinetics of hydrogen reduction place near-stringent demands on the metallurgical properties of its raw material, oxidized pellets. Firstly, in a hydrogen reducing atmosphere, iron oxides (Fe 2O3) in the pellets are rapidly reduced to metallic iron (Fe), and due to the lack of CO inhibition, the newly formed α -Fe whiskers tend to overgrow and interweave with each other, creating a tremendous internal stress, leading to severe volume expansion of the pellets, i.e. "reduction expansion". Too high a reduction expansion rate (typically > 20%) can lead to pulverization of the pellets, worsening the gas permeability of the shaft furnace or reactor, disrupting normal production, which is one of the core technical bottlenecks faced by hydrogen metallurgy. Secondly, to ensure reduction efficiency and stable operation of the reactor, the pellets must have extremely high room temperature strength to withstand the column pressure, and excellent medium and high temperature strength to maintain integrity during rapid temperature rise and reduction. In addition, to obtain high quality Direct Reduced Iron (DRI) and to reduce the energy consumption of the subsequent electric furnace smelting, the pellets themselves are required to have as high an iron grade and a low gangue content as possible. The pellet binder is a key auxiliary material affecting pellet quality, energy consumption and final iron-making economic and technical indexes. At present, pellet binders (such as bentonite) widely used in industry and physical compounding improved types thereof mainly aim at improving falling strength and bursting temperature of green pellets, and design thinking and performance targets of the pellet binders are derived from the traditional oxidizing roasting-blast furnace smelting process, so that the pellet binders are difficult to adapt to high-temperature reduction working conditions of hydrogen metallurgy. The binder has two fundamental defects that firstly, the addition amount of high-silicon aluminum minerals such as bentonite and the like is generally 1.5% -3.0%, the grade of pellet iron is obviously reduced, and secondly, the components are mostly physically adsorbed or weakly bonded, and can not provide durable and stable microstructure support under the severe working condition of high-temperature reduction, and the binder does not have the function of actively regulating and controlling the reduction behavior of the pellet (such as inhibiting whisker growth). Therefore, the novel special adhesive which builds a stable synergistic structure through chemical bonding, has high-efficiency bonding and low impurity introduction and can actively improve the high-temperature reduction metallurgical performance of the pellets is developed, and is a key material problem which is to be solved urgently for pushing the hydrogen-based direct reduction technology to be applied to large-scale industrialization from a laboratory. Disclosure of Invention The application aims to provide a functionalized core-shell structure binder for hydrogen-based direct reduction pellets, a preparation method thereof and oxidized pellets for hydrogen-based direct reduction, so as to solve the problems. In order to achieve the above purpose, the application adopts the following technical scheme: The application provides a functional core-shell structure binder for hydrogen-based direct reduction pellets, which is a core-shell structure unit formed by a composite functional core and a chemically grafted polymer shell, wherein the polymer shell is a polyacrylamide crosslinked network bridged and covalently bonded to the surface of the composite functional core; The composite functional core comprises 50-85% of bentonite matrix, 10-25% of dispersion enhancer and 5-25% of magnesium-containing grain boundary enhancer by taking the total mass of the raw materials of the composite functional core as 100%. Optionally, the bentonite matrix comprises sodium bentonite and/or calcium bentonite. Optionally, the dispersion enhancer comprises at least one of lignosulfonate, humate, polycarboxylate. Optionally, the magnesium-containing grain boundary strengthening agent is at least one of magnesium oxide, magnesium hydroxide, magnesium ca