Field of the Invention

The present invention relates to a method of producing solid composites, especially composites containing minerals.

Background of the Invention

Many industrial processes are both energy-intensive and carbon intensive. Examples of such processes include the production of iron and steel from iron ore minerals and the production of silicon from silica minerals. Fossil fuels such as coal are often the main sources of energy and carbon. For example, metallurgical coke from the coking of high-quality bituminous caking coal is the main form of carbon used in the iron and steel industry, especially in the feedstock into a blast furnace. These industrial sectors are major emitters of greenhouse gases (especially CO ₂₎ and actively seek alternative and low-emission means of supplying the energy and carbon required in the processes .

Whilst many renewable energy sources may be used to meet the energy demand of such industrial process to reduce their CO ₂ emissions, biomass is the only renewable that can be used directly to meet the carbon demand of these industrial processes.

Beneficiation is a process commonly used to improve the quality (purity) of raw minerals such as iron ore. It normally involves pulverisation and thus produces fine minerals. The fines must then be made into large particles, e.g. through pelleting or briquetting, in order for the fines to become a feed in the forms of large particles such as pellets and briquettes that are suitable for the intended processes, e.g. as a feed into a blast furnace. Clays such as bentonite are commonly used as a binder. However, such inorganic binders would tend to introduce undesirable inorganic impurities into the process, which may negatively impact the main process and eventually be discharged from the process as slag, requiring disposal. An organic binder would be desirable, especially if the organic binder can also form a composite with the mineral to be processed, via physical and/or chemical interactions, and become part of the carbon required in the process. Chemical reactions between binder and mineral would be advantageous in producing a composite of high mechanical strength .

The "carbon" required by the above-mentioned industry sectors is normally a reactant, e.g. as a reductant to reduce iron ore into iron or reduce silica into silicon, although the carbon can also be a source of energy. The "carbon", as used herein, is not necessarily pure carbon but mainly refers to carbonaceous material rich in carbon. Metallurgical coke and charcoal are typical examples of these "carbon" materials. An intimate contact in the composite between the

carbonaceous material and the mineral to be reacted (reduced) would have many beneficial effects in speeding up the process and improving the process efficiency.

A lot of fines can be generated during the production of carbon materials and/or during the subsequent preparation of the carbon materials so that the carbon materials in the required particle size ranges can be fed into the intended industrial processes, e.g. a blast furnace or an electrical arc furnace. For examples, a lot of metallurgical coke fines can be generated when the metallurgical coke is crushed so that coke in the required particle size range can be produced and fed into a blast furnace. These coke fines may not be fed directly into the blast furnace and are of lower commercial values than the coke lumps. Another example is the production of biochar fines during the production and preparation of biochar as a feedstock that can be fed into an electrical arc furnace to produce silicon. Again, the biochar fines cannot be fed into the arc furnace and are of lower commercial values than the biochar lumps. The production of lump carbon materials using the corresponding fines would be an important commercial outcome. In particular, the lump carbon materials produced from the fines should meet the quality requirement for the intended uses, e.g. the coke lumps should have sufficient mechanical strength required for use in a blast furnace to produce iron and steel or the biochar lumps should have sufficient mechanical strength required for use in an electric arc furnace to produce silicon.

The scope of the present invention should by no means be limited by the examples cited above. Other examples can be cited where the fines should be made into large particles because the large particles are of higher commercial values than the fines.

A bio-crude can be produced from the thermal treatment of biomass at elevated temperature and used as a binder or as an ingredient in the binder. A typical type of bio-crude is bio-oil from the pyrolysis of biomass, which also simultaneously produces a solid co-product called biochar. On heating, the bio-oil can devolatilise and harden. The bio oil contains abundant reactive structures and functional groups, which may react with the mineral to result in a very strong bond between the mineral and the components derived from the bio-crude. The

hydrothermal liquefaction of biomass can also produce a reactive bio crude. The bio-crude may also act as a binder for other materials such as metallurgical coke fines and/or biochar fines.

The organic binders may decompose at high temperature, releasing combustible volatiles. The use of carbon as a reductant may also produce gases such as CO that are of useful heating value. The recovery of the energy value of these volatiles and gases would be important for the overall process energy efficiency. The carbon in the organic binders can also become part of the carbon required in the process to upgrade the mineral, for example, as reductant to reduce iron ore into iron in a blast furnace or similar processes .

There is thus a need for the development of an organic binder from biomass and/or for bringing the carbon in intimate contact with the ore (or other materials to be bound) in the composite into the high temperature process, e.g. for the reduction of iron ore into iron.

Summary of the Invention

In accordance with a first aspect of the present invention, there is provided a method of producing a solid composite, the method comprising :

providing a bio-crude formed from the heat treatment of a carbonaceous feedstock comprising biomass, the bio-crude being capable of hardening at elevated temperature;

mixing the bio-crude with a solid or paste to form a green composite; and

heating the green composite to produce a hardened solid composite .

Embodiments of the present invention have significant advantages. In particular, the produced solid composite may have a relatively high density and strength. Furthermore, the produced solid composite may have a relatively low sulphur content and the bio-crude may not introduce undesirable impurities into the composite. Furthermore, the bio-crude may contain useful species that can act as fluxing agents, e.g. in the subsequent steelmaking process.

The term "biomass", as used herein, refers to any material derived from living or recently living organisms. While biomass is a preferred feedstock for the production of an organic binder due to the potential carbon-neutrality of biomass and other properties of biomass, other carbonaceous feedstocks may also be used as the feedstock, which include a variety of carbon-containing renewable and non-renewable feedstock including but not limited to coal, solid wastes or their mixtures. The solid wastes may include but are not limited to agricultural wastes, forestry wastes and domestic/municipal solid wastes or residues from the processing of carbonaceous feedstocks. In fact, many solid wastes are considered as biomass in the broad sense. Alternatively, biomass is at least a significant component in many solid wastes .

The term "heat treatment", as used herein, is intended to include within its scope any process at elevated temperature, in the presence or absence of additional substances. For example, the pyrolysis of biomass in an inert, oxidative or reductive atmosphere is a heat treatment process. The hydrothermal treatment of biomass in

subcritical, critical or supercritical water is another heat treatment process .

The term "bio-crude", as used herein, is intended to include any liquid or paste product from the heat treatment of biomass or other carbonaceous feedstocks. The bio-oil from the pyrolysis of biomass is a typical bio-crude.

The term "biochar" (or "char"), as used herein, is intended to include the solid product from the heat treatment of biomass or other carbonaceous feedstocks.

The term "composite", as used herein, is intended to include within its scope, any material consisting of two or more constituent materials with different properties. 'Green composite" refers to the mixture of precursors to make the final solid composite. The green composite may be in the shape of pellets and balls or any other regular or irregular shapes and in any size.

The method in the present invention may be conducted over a wide range of relative ratios between bio-crude and solid to produce solid composites having widely different compositions and properties. In an embodiment, the solid comprises a mineral such as iron ore or silica. For example, the solid may be a magnetite iron ore.

In another embodiment, the solid comprises a solid carbon material.

For example, the solid may be a metallurgical coke, a biochar or a char . In one embodiment, the solid may have a wide range of particle sizes. For example, beneficiated magnetite iron ore fines alone or together with magnetite ore lumps may be mixed with bio-oil to make green composites. The solid may contain impurities including but not limited to water. In a further embodiment, the solid may be in the form of a slurry with water or other chemicals.

In an embodiment, the solid comprises mixed solids. For example, the solid may be a mixture of magnetite and hematite iron ores together with other impurities. Alternatively, the solid may be a mixture of ore and biochar or a mixture of ore and metallurgical coke. In a further embodiment, the green composite may comprise fluxing agent ( s ) such as lime to aid the subsequent processing of the composite .

In a yet further embodiment, the green composite may comprise additional chemicals, including a catalyst, to speed up the hardening of the composite.

The step of heating the green composite may be carried out by heating the green composite to a temperature between 100 and 600°C, preferably between 150 and 450°C and still more preferably between 200 and 350°C. The heating may be carried in an inert or reducing or oxidising atmosphere .

In another embodiment, the step of heating the green composite may be carried out by heating the green composite to a temperature above 600°C in an inert or reducing or oxidising atmosphere.

In an embodiment, the step of heating the green composite is conducted in a step wise manner. For example, the temperature may be increased gradually at different heating rates and with various holding periods at selected temperature levels.

The method may comprise a further step of carbonising the composite at high temperature, preferably above 600°C, more preferably above 800°C and still more preferably above 1000°C, especially but not limited to, to carbonise the bio-crude-derived carbonaceous components in the composite .

The method may comprise a further step of burning the composite through reactions with an oxidising agent, e.g. air, to cause the solid in the composite to at least partially melt or recrystallise to achieve a better mechanical strength.

In accordance with a second aspect of the present invention, there is provided a method of producing a solid composite, the method comprising :

providing a bio-crude formed from the heat treatment of a carbonaceous feedstock comprising biomass, the bio-crude being capable of hardening at elevated temperature;

providing a biochar formed from the heat treatment of the carbonaceous feedstock comprising biomass;

mixing the bio-crude and biochar with a solid or paste to form a green composite; and

heating the green composite to produce the hardened solid composite . The inclusion of biochar in the green composite can advantageously increase the carbon content of the composite. The biochar and bio crude may be produced from the heat treatment of the same or different carbonaceous feedstocks. In accordance with a third aspect of the present invention, there is provided a method of producing a solid composite, the method comprising :

providing a bio-crude formed from the heat treatment of a carbonaceous feedstock comprising biomass, the bio-crude being capable of hardening at elevated temperature;

mixing the bio-crude with a solid or paste to form a green composite;

heating the green composite to produce the hardened solid composite; and

recovering the volatiles released from the heating of the green composite .

In accordance with a fourth aspect of the present invention, there is provided a method of producing a solid composite, the method comprising :

providing a bio-crude formed from the heat treatment of a carbonaceous feedstock comprising biomass, the bio-crude being capable of hardening at elevated temperature;

providing a biochar formed from the heat treatment of the carbonaceous feedstock comprising biomass;

mixing the bio-crude and biochar with a solid or paste to form a green composite;

heating the green composite to produce the hardened solid composite; and

recovering the volatiles released from the heating of the green composite.

The biochar and bio-crude may be produced from the heat treatment of the same or different carbonaceous feedstocks.

In an embodiment of the third or fourth aspect of the present invention, the step of recovering the volatiles comprises feeding the volatiles into a combustion device to provide the thermal energy to heat up the green composite.

In a further embodiment of the third or fourth aspect of the present invention, the step of recovering the volatiles comprises the cooling of volatiles to form a liquid and a non-condensable gas mixture. The liquid or the non-condensable gas mixture can be used, individually or together, as a fuel to supply the thermal energy required to heat up the green composite or for other purposes. In a specific embodiment of the third or fourth aspect of the present invention, the recovered volatiles are used as fuel for generating electricity. Any suitable electricity generating method known now or in the future, e.g. using a gas engine or a gas turbine, may be used for this purpose.

Brief Description of the Figures

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figure:

Figure 1 is a flow diagram of a method of producing a solid composite in accordance with an embodiment of the present invention;

Detailed Description of an Embodiment of the Present Invention

Embodiments of the present invention relate to a method of producing a solid composite. For producing the solid composite, a bio-crude is provided that is formed through the heat treatment of biomass or other carbonaceous feedstock or their mixtures, wherein the bio-crude is capable of hardening upon heating. Without necessarily subscribing to any particular theory, the hardening process includes complicated chemical reactions involving reactive species and functional groups in the bio-crude as well as involving the solid that forms part of the green composite, in addition to the evaporation of water and light species from the bio-crude. The description of embodiments herein is focused on the bio-oil from the pyrolysis of biomass although the bio crude in this invention is not limited to bio-oil alone. A variety of biomass pyrolysis technologies, known now or to be invented in the future, may be used to produce the bio-oil. For example, the grinding pyrolysis technology ( PCT/AU2011/ 000741 ) works very well to produce the bio-oil for the production of composite using the method in the present invention. The pyrolysis processes commonly also produce a solid co-product biochar and a gaseous co-product comprising non condensable gases. The biochar can also be used as a feedstock for the production of a solid composite in the present invention.

Bio-oil is mostly a liquid although those skilled in the art would recognise that a bio-oil can contain colloids and even solids

(including biochar) . In addition to water, bio-oil may contain a large number of organic compounds containing a wide variety of chemical functional groups, especially functional groups containing oxygen. Bio-oil may also contain dissolved inorganics and inorganic solids, such as sodium, potassium, magnesium and calcium salts. They may have beneficial effects for the subsequent processes using the composite as a feedstock. For example, they may act as fluxing agents in a blast furnace in the iron and steel industry. In some pyrolysis processes, bio-oil is produced in the form of a paste or slurry. A slurry of bio oil and biochar is directly produced in some pyrolysis processes. The bio-oil is mixed with a solid to produce a green composite. In an embodiment, the bio-oil is mixed with magnetite iron ore to produce a green composite comprising the bio-oil and magnetite. In another embodiment, the bio-oil and biochar is mixed with magnetite ore to produce a green composite. In a further embodiment, various additional chemical species are also added to the mixture to produce green composites having different properties.

In a further embodiment, bio-oil is mixed with a carbon material to produce a green composite. The carbon material may be a metallurgical coke or biochar or any solid from the heat treatment of a carbonaceous feedstock. Additional chemicals, including a catalyst, may also be ingredients of the green composite.

The mixing process can be carried out in a variety of ways and the green composites can be produced in variety of shapes. The bio-oil and solid may be pressed into a green composite with the required shapes. In an embodiment, a pelletising disc is used to mix and roll the bio oil and iron ore, which may also include biochar or any other ingredient chemicals as mentioned above, into balls. In a further embodiment, a pelletising drum is used.

The relative ratios of bio-oil, iron ore and other ingredients, including biochar and additional chemicals, in the composite can be varied over a wide range to suit the need of subsequent processes using the composites.

The green composite is then heated to produce the final solid composite product. The heating can be carried out in a variety of ways in an inert, reducing or oxidising atmosphere to cause the composite to harden.

A large number of physical processes and chemical reactions may take place during heating. The moisture, e.g. the moisture in the bio-oil or in the iron ore, would evaporate. Some light components in the bio oil would also evaporate. Depending on the temperature, the reactive functional groups in the bio-oil would also undergo various reactions, especially cracking reactions and polymerisation reactions, to produce additional lighter components and heavier components . The heavy components are particularly important for binding the solid (e.g. ore) particles together.

Without necessarily subscribing to any particular theory, the components in bio-oil might also react with the solid (e.g. iron ore, biochar or other carbon materials) to form some new chemical bonds between the bio-oil components and the iron ore. This type of chemical bonds would be much stronger than the physical interactions / forces , greatly contributing to the mechanical strength of the composite product . The heating of green composite can be carried out in a variety of ways. In an embodiment, the green composite is heated in an oxidising atmosphere to cause at least some bio-oil components to combust. The combustion would heat the green composite to high temperature to cause some extents of melting/sintering of the iron ore where

recrystallization or other physico-chemical processes can take place to result in a composite of high mechanical strength. Concurrently with the combustion, some iron ore may also be at least partially reduced. The combustion process may be carried out on the green composite or on the final composite product.

The composite derived from bio-oil and iron ore and/or the composite derived from bio-oil and metallurgical coke can be used as part of the feedstock into a blast furnace in the iron and steel industry. The composite derived from the bio-oil and solid biochar (or other types of char) may be fed into an electric arc furnace to produce silicon.

The volatiles released from the heating of green composite can contain a large number of combustible components. If the heating is carried out at relatively low temperatures (e.g. below about 600°C), some of these volatile components may be condensed to produce a liquid fuel and a non-condensable gaseous fuel.

The iron ore may be an excellent catalyst for the reforming of the released volatiles into light gases. Therefore, in a specific embodiment, the composite production in the present invention is used to integrate with a power generation process where the volatiles and gaseous released from the heating of green composite are used to generate electricity using power generation devices. The examples of these power generation devices include, but are not are not limited to, gas engines, gas turbines and fuel cells.

Referring now to Figure 1, there is shown a flow chart illustrating a method 100 in accordance with a specific embodiment of the present invention .

In a first step 102, a bio-crude that is formed through the heat treatment of biomass and is capable of hardening is provided. In this particular embodiment, the bio-crude is bio-oil obtained from the pyrolysis of biomass.

In step 104, a biochar is provided. While bio-oil and biochar are commonly produced simultaneously from the pyrolysis of the same biomass, bio-oil and biochar can also be produced from different biomasses and using different heat treatment processes.

A particular example of a pyrolysis process is described in further detail in PCT international patent application No. PCT/AU2011/ 000741. In a next step 106, the bio-oil and the biochar are mixed together with a solid to form a green composite. In this particular embodiment, the solid is a magnetite iron ore, especially magnetite iron ore fines after beneficiation . Instead of biochar and iron ore, the solid may also be the biochar fines, which are generated during the production and preparation of biochar for the silicon production process. In a further embodiment, silica may be added to form the green composite so that the silica in the final composite product is in intimate contact with carbon to facilitate its reduction to form silicon in an electric arc furnace. The mixing may be conducted at room temperature. In this particular example, the mixing is conducted to form the desired shape. The green composite may be formed through pressing.

The green composite is then heated in step 108 to a temperature at which the bio-oil undergoes complicated physical and chemical processes to harden. The binding between the C-containing components, including the reaction products from bio-oil, and magnetite ore include physical forces and chemical bonds.

In step 110, the volatiles released from the reactions involving bio oil are recovered to extract their energy values. They may also be used as chemical feedstocks for other chemical processes.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.