Patent ID: 12195334

DETAILED DESCRIPTION OF THE EMBODIMENTS

To further explicitly demonstrate the purpose, characteristics and performance of this application, a further explanation will be combined with attached figures in order to fully illustrate the detailed concept, concrete arrangement and technical purposes of the system.

With respect to one of the embodiments for systems of producing hydrogen and biochar using biomass assisted by iron and steel slag extract shown inFIG.1, the flowsheet is described as follows:

Pretreatment system (10): the reactants, including the biomass, iron-based catalyst and alkaline reagent, are pretreated and fully mixed at a specific ratio in the pretreatment system.

Thermal reactor (20): the mixed reactants are fully reacted in the thermal reactor.

Solid residue collector (40): the solid residue is collected by the solid residue collector (40) at the discharge outlet of the thermal reactor (20) after the reacted mixture is separated.

Gas collection system: the generated hydrogen-based gas is collected by the gas collection system from the exhaust port of the thermal reactor (20).

In this embodiment, the iron and steel slag extract are prepared by a carbon dioxide based hydrometallurgical process.

In this embodiment, the Ca/Mg alkaline reagent contained in the iron and steel slag extract as one of reactants is used to absorb the moisture in the biomass which is beneficial to the fracture of the biomass structure and the production rate of hydrogen and simplifies the pretreatment process of biomass. In addition, the iron-based catalyst extracted from the stainless steel slag are used to replace the nickel-based catalyst. Although the overall conversion rate of the reactions using iron-based catalyst is lower compared to that using nickel-based catalyst, the iron-based catalyst has the advantages of low price and mass production rate since the iron-based catalyst is a by-product from the iron and steel slag.

Furthermore, the pretreatment system (10) addressed above also comprises a biomass dehydration treatment unit. The moisture content of the biomass can be adjusted by oven drying, freeze drying and other techniques.

Pretreatment system (10) also comprises a 2-hour reduction pretreatment of iron-based catalyst in hydrogen at 500° C.

In this embodiment, the chemical equation of the reaction using the molecular formula of biomass C5H10O5(s) as an example is shown blow:
C5H10O5(s)+5Ca(OH)2(s)→10H2(g)+5CaCO3(s)

The addressed biomass and alkaline reagents are mixed at a specific stoichiometric ratio which is 1 mole to 5 mole according to the theoretical molecular formula and chemical reaction equation. The amount of iron-based catalyst added in the reaction is between 5% and 15% by weight of the mixture.

In the thermal reactor (20), the mixture is fully reacted either at 500° C. for 1 hour or at 300° C. for 2 hours in order to ensure the reactants are fully mixed and reacted.

Furthermore, if the biomass is relatively dry, additional steam is needed for keeping the humidity of the reaction environment which is between 10% and 30%.

The solid residue is a mixture of biochar, calcium and magnesium carbonates and iron-based catalyst.

This embodiment also comprises an iron-making sintering system (40) where solid residue is mixed with the raw material at the ratio of no more than 30% by total weight for the sintering preparation. The solid residue, which is a mixture of biochar, calcium/magnesium carbonates and iron-based catalyst, can be fully used in the sintering process and the blast furnace reduction reaction.

This embodiment also comprises a gas separation and purification system (50) where the hydrogen-based gas collected by the gas collector system is transferred in for separation and purification in order to obtain high-purity hydrogen product.

Furthermore, this embodiment also comprises a mixed gas reuse system where the hydrogen-based gas collected by the gas collector system is transferred into an iron-making blast furnace for direct reduced iron reaction, heating reaction, reduction reaction and etc. The hydrogen-based gas collected by the gas collection system contains impurity gases such as CH4, C2H4, C2H6, CO, CO2and ect., which can be used as fuels in the furnace to heat up the direct reduced iron reaction. A small portion of CO can also be used to participate in reduction reaction directly. The reaction temperature is between 750° C. and 1000° C. which is more energy efficient comparing with the temperature of traditional furnace reaction which is higher than 1500° C.

The chemical equation of the reduced iron reaction using hydrogen as a reactant is shown below:
3Fe2O3+H2→2Fe3O4+H2O
Fe3O4++H2→3FeO+H2O
FeO+H2→Fe+H2O

Furthermore, in this embodiment, the pretreatment system addressed above also comprises an iron-based catalyst collecting system, which is composed of:

Pre-washing device (A10): the feedstock, such as industrial solid waste, mineral and mine tailings, is continuously added and fully mixed with auxiliary reagents and water at a specific ratio into the pre-washing device (A10).

Reactor (A20): the washed slurry from the pre-washing device (A10) is continuously transferred into the reactor (A20) by a pump unit. Carbon dioxide is bubbled into the reactor (A20) under a specific pressure in order to be fully mixed and reacted with the washed slurry. The treated slurry is continuously discharged from the reactor (A20).

Multistage product preparation unit: the treated slurry from the reactor (A20) is filtered by multistage solid-liquid separators, where the unreacted solids are recycled as feedstock into the next stage of reaction and separation.

Purifier (A50): Besides the target calcium and magnesium ions, the filtrate from the multistage product preparation unit contains other impurities such as ferrite ion. The filtrate from multistage product preparation unit is continuously transferred into the purifier (A50). Precipitation is performed to remove impurities from the filtrate by physically and/or chemically changing the pH value of the solution. The iron-based catalysts can be obtained by collecting iron-containing impurities.

The pretreatment system also includes a by-product preparation unit (A70), where the filtrate from the multistage separator containing target ions of calcium and magnesium is continuously added in order to generate Ca/Mg based products, and a water recirculation device, where remaining liquor is recirculated to the system after that by-products are collected.

In this embodiment, the whole system is able to continuously and consistently react at the maximum capacity through continuous slurry feeding and CO2bubbling into the reactor (A20) which also enables multistage circulating reaction. Meanwhile, the emissions and losses of carbon dioxide derived from the discharging process during the batch reaction can be reduced. Moreover, CO2loss and unnecessary time loss derived from the repetitive feeding and discharging can be minimized which is the current technical limitation led to the underperformance of the whole system.

Furthermore, the added feedstock, such as industrial solid waste, mineral and mine tailings, added into the pre-washing device (A10) should be less than 10% by weight of the slurry and the added auxiliary reagents should be less than 5% by weight of the slurry. In practical application, the proportion of auxiliary reagents can be adjusted depending on actual component of the feedstock.

The industrial solid waste addressed above comprises steel slag, iron slag, fly ash, bottom ash, red mud, waste concrete/cement, tailings and etc.

The feedstock addressed above comprises various types of calcium and magnesium bearing minerals.

The auxiliary reagents addressed comprise at least one of acids, salts or the combination containing organic acid anions. The anions or acids consist of: oxalate, citrate, picolinate, gluconate, glutamate, formic acid, acetic acid, propionate, valerate, lactate, succinate, phosphate, pyrophosphate, ascorbic acid, and phthalic acid.

The added water is fresh water or the recycled water treated by the water recirculating device.

The added carbon dioxide is continuously bubbled into the reactor (A20) under a pressure of less than 100 bars and is fully mixed and reacted with the washed slurry, where the whole reaction temperature is controlled under 90° C. This embodiment provides a continuous leaching process of target ions by adjusting the pressure of carbon dioxide bubbling process, ratio of auxiliary reagents and reaction temperature, which eliminates the usage of strong acid or highly corrosive acid such as nitric acid, hydrochloric acid, sulfuric acid and hydrofluoric acid.

In this embodiment, the bubbled carbon dioxide is from the flue gas generated by power plants, blast furnaces, basic oxygen furnaces/converters, refining furnaces, lime kilns, coal-to-chemicals manufacturing plants or petrochemical manufacturing plants. The content of carbon dioxide varies between 15% and 98% based on the source of flue gas.

Furthermore, the multistage product preparation unit addressed above comprises a primary coarse separation module (A30) and a secondary fine separation module (A40), where the size of particles separated by the primary coarse separator module (A30) is larger than 5-10 μm and the size of particles separated by the secondary fine separator module (A40) is smaller than 1 to 5 μm. In particular, the combined reaction time of each separation module in total is less than 1 hour. This embodiment ensures that the whole system is able to continuously and consistently separate solids from the slurry at a maximum capacity through the optimized multistage solid-liquid separation processes for a wide distributed particle sizes which shortens the total separation time and increases the likelihood of the separation system to operate continuously and consistently. Technical issues of single-stage separation caused by the requirement of removing solid particles of all sized at once is minimized. Moreover, sedimentation centrifuge is proved to be inefficient in single-stage separation for particles with sizes under 5 μm which affects the maximum treatment capacity per unit time of the whole system and leads to a high energy consumption. In the case that a filter press is used in a single-stage separation, filter cloth is frequently clogged with various sizes of solid particles which also affects the maximum treatment capacity per unit time of the whole system and increases operating cost since frequent filter replacement is required.

Thereinto, the multistage solid-liquid separators can be applied comprising of either the combination of a sedimentation centrifuge and a disk-stack centrifuge, the combination of two filter press, or the combination of a sedimentation centrifuge and a filter press.

The CO2treated slurry discharged from the reactor (A20) is filtered by multistage solid-liquid separators where the unreacted solids (M31) are recycled as feedstock into the next stage of reaction and separation. The frequency of recycling the unreacted solids (M31) is less than 5 times.

Furthermore, in this embodiment, the filtrate is continuously transferred into the purifier (A50) after processing through the multistage solid-liquid separators. Besides the target ions of calcium and magnesium, the filtrate from the multistage solid-liquid separators also contains other impurities such as iron, silicon, aluminum and etc. Impurities are precipitated from the filtrate by physically and/or chemically changing the pH value of the solution through either continuously adding alkaline reagents, acid reagents, coagulant and/or flocculant which is less than 1% by weight of solution, injecting air/steam or heating the solution.

Furthermore, in this embodiment, multistage solid-liquid separators also comprise a third stage solid-liquid separation module (A60) which is arranged after the purifier (A50). The third stage solid-liquid separation module (A60) is able to continuously separate the precipitated particles from the filtrate containing target ions of calcium and magnesium by using either dish-stack centrifuge, filter press or filtration. The remaining filtrate containing target ions of calcium and magnesium is transferred into the by-product preparation unit (A70) which is described below.

Thereinto, if the remaining filtrate after third stage solid-liquid separation module (A60) is enriched with iron after passing through the third stage solid-liquid separation module, iron is collected as ferric and/or ferrous hydroxides precipitation (A61) for recycling and reusing.

The filtrate containing target ions of calcium and magnesium is transferred into by-product preparation unit (A70) to generate calcium and magnesium products which are in the formation of calcium magnesium carbonate, calcium carbonate and magnesium carbonate, calcium hydroxides and magnesium hydroxides, calcium and magnesium sulfates or calcium and magnesium nitrates.

Furthermore, the remaining liquor is recirculated to the system after the by-product is collected and the recycle frequency of water is larger than 2 times.

In this embodiment, the pretreatment system addressed above also comprises an alkaline reagent separation system including a product preparation device (C20) and a thermal decomposition unit (C30), which is shown inFIG.3. The filtrate from multistage separators containing target ions of calcium and magnesium is added in the product preparation device (C20) in order to generate Ca/Mg based products. The Ca/Mg based product (C22) is calcined by the thermal decomposition unit (C30) to produce a calcium and magnesium based alkaline reagent (M). The alkaline reagent (M) is recycled into the precipitation reactor (C10) for the next cycle of reaction.

The alkaline separation system addressed above also comprises a precipitation reactor (C10), the leached solution containing calcium and magnesium is continuously added and fully mixed with the alkaline reagent (M) at specific mole ratios. The precipitation reactor (C10) also comprises a CO2bubbling module where CO2is captured and recirculated from the thermal decomposition process as a supplement. The treated slurry transferred from the precipitation reactor (C10) is filtered by the product preparation unit (C20) to produce the calcium and magnesium based precipitated products (C21) and the recycled water (B) is circulated back and used in the next cycle of slurry preparation.

In this embodiment, the leached Ca/Mg containing solution is prepared by a CO2-based hydrometallurgical process and the pH value of the leached solution is nearly neutral or slightly acidic (pH<7) with certain level of dissolved CO2.

The leached Ca/Mg containing solution is continuously added into the precipitation reactor (C10) at a mole ratio<1 per unit time between the alkaline reagents (M) and the leached Ca/Mg containing solution. Furthermore, the CO2generated from the thermal decomposition unit (C30) is transferred back into the CO2bubbling module where CO2is captured and recirculated back into the precipitation reactor (C10) as a supplement to precipitate calcium and magnesium carbonate products.

In this embodiment, the precipitated calcium and magnesium carbonate products (C21) acquired by the product preparation unit (C20) is partially proceeded to be prepared into Ca/Mg carbonate slurry or is formulated into Ca/Mg carbonate powder by a drying module. Moreover, the rest of the precipitated calcium and magnesium carbonate products (C22) is transferred into the thermal decomposition unit (C30) for the alkaline reagents (M) preparation and the alkaline reagents (M) are recycled into precipitation reactor (C10).

Furthermore, the temperature of the calcination in the thermal decomposition unit (C30) is between 800-900° C.

Thereinto, the alkaline reagent (M) contains calcium and magnesium oxides.

The thermal decomposition unit (C30) comprises a fluidized bed unit. After dispersion in the fluidized bed, more than 99% of the Ca/Mg carbonate could have particle sizes less than 300 μm and the particle sizes after calcination are mostly less than 100 μm.

Thereinto, the density of calcium and magnesium carbonates is between 2.8×103kg/m3to 2.9×103kg/m3and the density of calcium and magnesium oxides is between 3.3×103kg/m3to 3.4×103kg/m3.

During the process of calcination of calcium and magnesium carbonate products (C22) in the fluidized bed unit, the average minimum fluidization velocity of calcium and magnesium carbonate particles is U1, the average minimum fluidization velocity of calcium and magnesium oxide particles is U2, the entrainment velocity of calcium and magnesium oxide particles is U3, and the inlet fluidizing gas velocity is Ug.

When U3>Ug>U1>U2, the bed height of the dense phase will significantly increase after the calcination of calcium and magnesium carbonates starts. The bed height increases until the thermal decomposition of Ca/Mg carbonate particles is completed. At this point, the calcined Ca/Mg based oxide particles can be entrained and collected by increasing Ug.

The calcined calcium and magnesium oxide particles can be entrained and collected when Ug>U3>U1>U2.

During the process of calcination in the fluidized bed, when Ug>U2>U1, Ugneeds to be tuned less than U3. Meanwhile, the bed height of the dense phase will significantly decrease when the thermal decomposition of Ca/Mg carbonate particles begins and will last until the thermal decomposition is completed. The calcined Ca/Mg based oxide particles can be entrained and collected by increasing Uglarger than U3.

Thereinto, the inlet fluidizing gas comprises hot air and optional CO2of which CO2is collected and recirculated from the CO2outlet on the top of the fluidized bed unit after the calcination process.

In this embodiment, the carbon dioxide generated from the thermal decomposition unit (C30) is transferred back into the CO2module where CO2is collected and recirculated into the precipitation reactor (C10) as a supplement to precipitate calcium and magnesium carbonates.

The present invention utilizes the Ca/Mg based reagent contained in the iron and steel slag extract as one of reactants to absorb the moisture in biomass which is beneficial to the facture of the biomass structure and the production rate of hydrogen and simplifies the pretreatment process of biomass. Moreover, iron-based catalyst is extracted from the stainless steel slag to replace nickel-based catalyst. Although the overall conversion rate of the reactions using iron-based catalyst is lower comparing with using nickel-based catalyst, the iron-based catalyst has the advantages of low price and mass production since the iron-based catalyst is a by-product from the iron and steel slag. The solid residue generated from the present invention as a by-product can be mixed with the raw materials in the sintering system of iron-making process prior to the reduction reaction of blast furnace as a substitute of reaction reagents comprising coking coal, slag-making agents limestone/dolomite and iron ore. The biochar in the solid residue can be used as a substitute or extra supplement of coking coal as a reducing reagent. Meanwhile, the calcium and magnesium based carbonates in the solid residue can also be fully recycled as a slag-making reagent. As a substitute of iron ore, the iron-based catalyst in the solid residue will participate in the reduction reaction of iron-making process in the blast furnace. The present invention also produces a hydrogen-based gas mixture containing other gases as CH-based gas and CO-based gas from hydrogen production reaction by using biomass. The mixed gas produced from the reaction can be applied directly on site in the reducing iron process, thermal reactor and reduction reaction in iron and steel mills otherwise the gas product needs to be prepared as a high-purify hydrogen through the process of separation, purification and extraction which will increase the total cost.

The embodiment addressed above is intended to explain the concrete arrangement of the present invention in details with reference to one of the best modes for carrying out the invention, but the invention is not limited by this embodiment. It should be understood by technicians in this field that embodiments of the present invention can be modified or equivalently replaced without departing from the spirit and scope of this invention which shall be all included in the claims of the invention.