Carbonaceous material for use in a process for producing activated carbon - Patents.com

Abstract

Activated carbon (AC) is provided that is produced from an agglomerated purified carbonaceous product (PCP). The PCP is in granular form, with at least about 90% by volume (%v) of the particles being about 25 μm or less in diameter, and the PCP has an ash content of less than about 5%m and a moisture content of up to about 60%m. The PCP may be used to make AC or may be utilized as an additive for the production of AC from other carbonaceous feedstocks.

Description

[Technical field]

[0001] The present invention relates to a method for producing activated carbon material, particularly from a coal feedstock. [Background technology]

[0002] Activated carbon (AC) has become a large market for coal-based materials, with approximately 1.4 million tons sold in 2018. Feedstock for AC can be from agricultural materials such as coconut shells, biomass, sawdust, and coal. Coal differs from other feedstocks because it already contains inherent micropores and does not need to be carbonized first to form the micropores. In general, non-fusible lower rank coals (lignites and subbituminous coals) have greater porosity and surface area than higher rank coals and are used to make AC. AC from coal is generally made from low fluidity coals where no melting or plastic phase transition occurs, because this closes the porous structure. AC can be made from these materials if the structure is stabilized by oxidation before devolatilization and further activation.

[0003] Coal flour, including fines, and ultra-fines are small particles of coal obtained from larger lumps of coal during the mining and coal preparation process. Although coal fines maintain the same energy potential as coal, they are generally considered waste because the particulate nature of the product makes them difficult to sell and transport. The mining industry produces as much as 70-90 million tons of coal fines annually in the United States alone as a waste by-product (Baruva, P., Losses in the coal supply chain, IEA Clean Coal Centre Rep. CCC / 212, p. 26, December 2012, ISBN 978-92-9029-532-7), the majority of which remains unused. Coal fines are therefore generally disposed of as slag near coal mines, forming large waste piles, or are placed in large ponds that require careful future management to avoid environmental pollution.

[0004] High ash coal seams are abundant throughout the world from many geological reserves, sometimes as thick coal seams maintained over wide geographic areas, but many are not economically available for use in the production of AC due to high ash content (>20% m dry basis), which reduces adsorption efficiency.

[0005] Clean coal technology has led to the development of new types of specialty fuels with higher energy density and lower emission levels, including upgraded clean coal blends as described in International Patent Application WO 2020 / 065341 or complex liquid-solid mixtures as described in US Pat. No. 9,777,235. There is a further need to recognize additional uses of clean coal compositions derived from waste and low-grade solid hydrocarbons that can contribute to the improvement of the expanding global green economy. It is therefore desirable to provide an alternative economical source of high-quality feedstock for non-fuel technologies, which will provide a longer-term, more sustainable and greener future for societies that depend on the coal industry for their economic well-being.

[0006] The conventional production of AC from coal is briefly summarized in the prior art process shown in Figure 1. The coal feedstock is typically crushed and crushed to pass 10 mesh US standard size (i.e., particle size less than 2 mm) prior to the oxidation and devolatilization steps. A sieving and dedusting step ensures the removal of particle sizes <75 microns (e.g., fines) since these size ranges are usually considered too small to handle during activation. The granular coal is activated by either chemical or physical means. In Figure 1, activation is performed by using hot steam. The AC product can be further classified and subjected to additional grinding steps if finer granular AC is required for a particular application. For example, in US Patent 10,029,235 B1, the AC preparation is subjected to jet mill grinding and another finer grinding step to reduce the particle size of the AC to <28 microns, suitable for use as a sorbent in the removal of mercury from flue gases. Therefore, in conventional manufacturing processes for finer AC, the larger particle size composition is activated before being ground to the finer grades. Summary of the Invention [Problem to be solved by the invention]

[0007] It would be desirable to provide improved feedstocks for use in the production of AC. It would also be desirable to provide improved feedstocks that include a greater diversity of origins but that meet the strict specifications of AC products used in pharmaceutical manufacturing, chemical synthesis processes, and other highly specialized industries. Additionally, it would be desirable to utilize feedstocks derived from materials that would otherwise be classified as waste or previously considered unsuitable, thereby allowing for the upcycling of industrial waste and reducing the further accumulation of waste fines as a by-product of coal mining activities. [Means for solving the problem]

[0008] The present invention relates to improvements in the process for producing high surface area AC from subfine coal feedstock.

[0009] The present inventors have developed a process that provides for the utilization of very high quality (low ash, sulfur and water content) refined carbonaceous products that were previously considered undesirable for the production of AC. These refined carbonaceous products are typically upgraded from waste materials from coal tailings ponds, impoundments or dumps and reject materials from current coal production processes (e.g., denser underflow or tailings underflow waste streams), high ash lower layer coals that were previously not economically exploitable.

[0010] According to a first aspect of the present invention, there is provided a process for producing activated carbon (AC), comprising the steps of: (i) providing an agglomerated purified carbonaceous product (PCP), the PCP being in granular form, with at least about 90% by volume (%v) of the particles being about 25 μm or less in diameter, the PCP having an ash content of less than about 5%m and a moisture content of up to 60%m; (ii) subjecting the agglomerated PCP to at least one heat treatment, thereby forming a heat-treated agglomerated PCP; and (iii) subjecting the heat-treated agglomerated PCP to at least one activation process to produce AC; A process is provided that includes:

[0011] A second aspect of the invention is an activated carbon composition prepared by the process described herein, comprising at least 500 ml 2 The activated carbon composition has a BET surface area of ​​100 / g.

[0012] In a third aspect, the present invention provides an activated carbon composition prepared by the process described herein, the activated carbon composition having an average molecular weight of at least 1000 m 2 The activated carbon composition has a BET surface area of ​​100 / g.

[0013] A fourth aspect of the present invention is a process for producing an AC product, comprising the steps of: (i) providing a carbonaceous feed material in granular form; (ii) agglomerating the carbonaceous feedstock with a binder, thereby forming an agglomerated feedstock, the binder comprising a purified carbonaceous product (PCP), the PCP being in granular form, at least about 90% by volume (%v) of the particles being about 25 μm or less in diameter, and the PCP having an ash content of less than about 5%m; (iii) subjecting the agglomerated feedstock to at least one heat treatment, thereby forming a heat-treated agglomerated feedstock; and (iv) subjecting the heat-treated agglomerated feedstock to at least one activation process to produce an AC composition; The present invention provides a process including:

[0014] A fifth aspect of the present invention is an activated carbon composition prepared by the process described herein, comprising at least 500 ml 2 The activated carbon composition has a BET surface area of ​​100 / g and an ash content of less than 5% m.

[0015] A sixth aspect of the invention provides a process for adsorbing a substance contained in a fluid stream, the process comprising exposing the fluid stream to an activated carbon product prepared by a process described herein.

[0016] A seventh aspect of the present invention provides the use of an agglomerated purified carbonaceous product (PCP) as an additive feedstock to increase the BET surface area of ​​a biochar-derived activated carbon product, wherein the PCP is in granular form, at least about 90% by volume (%v) of the particles are less than about 25 μm in diameter, and the PCP has an ash content of less than about 5%m and a moisture content of up to about 60%m.

[0017] It will be appreciated that the invention may be directed to additional combinations of features disclosed herein but not expressly set forth above.

[0018] The invention is further illustrated by reference to the accompanying drawings. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a process flow diagram illustrating a prior art method for producing activated carbon material from bituminous coal feedstock. [Diagram 2] 1 is a graph showing how BET surface area increases with increasing activation time for activated carbons prepared from four types of PCP samples according to an embodiment of the present invention. [Diagram 3] 1 is a graph showing the yield of activated carbon prepared from various types of PCP samples according to an embodiment of the present invention at various activation times. [Figure 4] 1 is a graph showing the removal efficiency of the contaminant 2-methylisoborneol (MIB) from drinking water compared for PCP-derived activated carbon and a commercial benchmark activated carbon. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] All references cited herein are incorporated by reference in their entirety. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0021] Before describing the invention in more detail, some definitions are provided that will be helpful to an understanding of the invention.

[0022] As used herein, the term "comprising" means that any recited elements are necessarily included, and may optionally include other elements. "Consisting essentially of" means that any recited elements are necessarily included, and that elements that materially affect the basic and novel characteristics of the recited elements are excluded, and that other elements may optionally be included. "Consisting of" means that all elements other than those recited are excluded. Embodiments defined by each of these terms are within the scope of the present invention.

[0023] As used herein, the term "about" when used in combination with an absolute value means a tolerance of 1% above or below the stated absolute value.

[0024] The term "coal" is used herein to refer to solid hydrocarbonaceous materials derived from sedimentary minerals that are readily combustible, including, but not limited to, hard coals, e.g., anthracite, bituminous, subbituminous coals, and lignite, e.g., lignite (as defined in ISO 11760:2005). "Natural" or "feedstock" coal means coal that has not been subjected to extensive processing and includes a physical composition (e.g., maceral content) that is substantially unchanged from the time of mining. In contrast, the terms "coal-derived products," "coal replacement products," and "refined coal compositions" are used herein to refer to various coals that have been subjected to one or more processes that alter the physical and / or chemical composition of the coal so that it is substantially different from the time of mining, i.e., natural, state.

[0025] As used herein, the term "hydrocarbonaceous material" refers to a material containing hydrocarbons, which are organic compounds consisting essentially of the elements hydrogen and carbon. Hydrocarbonaceous materials may include aliphatic and aromatic hydrocarbons. Carbonaceous materials tend to contain mostly carbon and have a lower hydrogen content, e.g., <5% m hydrogen, typically less than 2% m hydrogen. Carbonaceous and hydrocarbonaceous materials can be used as feedstocks for producing activated carbon. For example, bituminous coal is a representative natural feedstock of hydrocarbonaceous origin, while biochar or charcoal, both derived from the pyrolysis of biomass, represent mostly, though not exclusively, carbonaceous feedstocks. It will thus be understood that hydrocarbonaceous materials are a subclassification of carbonaceous materials in that they also contain hydrogen in addition to their carbon content.

[0026] As used herein, the term "refined carbonaceous product" or "PCP" refers to a material composed of carbonaceous matter of geological or biological origin, e.g., coal, coke, petroleum coke and / or biochar. PCP is typically subjected to various process steps that reduce the non-carbonaceous matter present, such as ash or sulfur, to a minimum. As previously mentioned, refined coal compositions differ from coal in their natural or unrefined state. Similarly, carbonaceous matter can be refined from a starting feedstock of coke, petroleum coke or biochar and subjected to processes to reduce the non-carbonaceous content, such as ash, sulfur and / or water. Typically, PCP of geological or biological origin according to embodiments of the present invention comprises an ash content of less than 5%m, suitably less than 4%m, optionally less than 3%m, in some cases less than 2%m, and in certain embodiments less than or equal to 1%m.

[0027] As used herein, the term "ash" refers to the inorganic, e.g., non-hydrocarbon, mineral components found in most types of fossil fuels, especially in coal. Ash is included in the solid residue remaining after the combustion of coal, and is sometimes called fly ash. The sources and types of coal are very diverse, and therefore the composition and chemistry of the ash is also very diverse. However, typical ash includes several oxides, such as silicon dioxide, calcium oxide, iron (III) oxide, and aluminum oxide. Depending on its source, coal may further contain trace amounts of one or more substances that may be included in the subsequent ash, such as arsenic, beryllium, boron, cadmium, chromium, cobalt, lead, manganese, mercury, molybdenum, selenium, strontium, thallium, and vanadium.

[0028] As used herein, the term "low ash coal" refers to a natural coal that has a lower proportion of ash forming components than another industry standard coal. Typically, low ash natural or feedstock coal contains less than about 12%m ash. The term "demineralized coal" or the related term "demineralized coal" is used herein to mean a coal that has a lower proportion of inorganic mineral matter than its natural state. Ash content can be determined by proximate analysis of the coal composition as described in ASTM D3174-12 Standard Test Method for Ash in the Analysis Sample of Coal and Coke from Coal. In embodiments of the invention, the ash content in the refined carbonaceous product derived primarily from coal is less than 5%m, less than 3%m, less than 2%m and less than 1.5%m, or even less than 1%m is obtained. Indeed, the inventors have found, quite unexpectedly, that very low ash products of about 1%m or less than 1%m can be obtained from ash starting materials up to 50%m without having to pay the price of yield levels that make the process non-commercial.

[0029] Low rank coal is a term used in geological surveys of coal seam quality (e.g. UK coal survey, 1937) to refer to inherent ash in a coal zone or seam above 15.1%m and below 40.0%m. Coal zones or seams consisting of low rank coal contain intimately mixed mineral matter within the coal itself and, as a result, are very difficult to refine using conventional coal processing techniques.

[0030] As used herein, the term "coal fines" refers to coal in granular form, typically having a maximum particle size of less than 1.0 mm. The terms "ultrafine coal", or "ultrafine coal", or "ultrafine powder" refer to coal, typically having a maximum particle size of less than 0.5 mm (500 microns (μm), about 0.02 inches). The terms "coal fines", or "fine coal", or "fine powder" refer to coal, typically having a maximum particle size of less than 20 μm.

[0031] Most suitably, the maximum average particle size of the PCP, whether derived from coal or other source, may be up to 75 μm, 50 μm, 40 μm, 30 μm, 20 μm, 25 μm, 20 μm, 15 μm, 10 μm or 5 μm, and the minimum average particle size may be 0.01 μm, 0.1 μm, 0.5 μm, 1 μm, 2 μm or 5 μm.

[0032] Another measure of particle size is to indicate a maximum particle size and the percentage of the volumetric proportion of particles in a sample that are below that particle size, i.e. the "d" value. Suitably, the particle size of the PCP material is in the ultrafine range. Most suitably, the particle size of the PCP is in the fine range. In particular, the maximum particle size may be up to 500 μm. More suitably, the maximum particle size may be up to 300 μm, 250 μm, 200 μm, 150 μm or 100 μm. However, most typically, the maximum particle size may be up to 75 μm, 50 μm, 40 μm, 30 μm, 20 μm, 10 μm or 5 μm. The minimum particle size may be 0.01 μm, 0.1 μm, 0.5 μm, 1 μm, 2 μm or 5 μm. Any "d" value may be associated with any one of these particle sizes. Suitably, the "d" value associated with any of the above maximum particle sizes may be d99, d98, d95, d90, d80, d70, d60 or d50. For example, in one particular embodiment of the invention, the PCP has a d90 of <70 μm, <50 μm, optionally <20 μm, suitably <10 μm. Suitably, the PCP has a d95 of <25 μm, <20 μm, <15 μm, <12 μm, optionally <10 μm.

[0033] As used herein, the term "moisture content" refers to the total amount of water in a sample, expressed as a concentration or mass percentage (%m). When the term refers to moisture content in a PCP sample, it includes the inherent or residual moisture content of the material and any water or moisture absorbed from the environment, for example as a result of the PCP refining process. As used herein, the term "dehydrated coal" refers to coal that has a lower absolute percentage of water than its natural state. The term "dehydrated coal" may also be used to refer to coal that has a naturally occurring low percentage of water. Moisture content can be determined by analysis of natural or refined coal compositions as described in ASTM D3302 / D3302M-17 Standard Test Method for Total Moisture in Coal.

[0034] As used herein, the term "thermal treatment" refers to a thermal pretreatment that can be carried out below the normal pyrolysis temperature of 600° C., suitably below 550° C., typically below 500° C., and optionally at about 450° C., without affecting the ability to obtain a high surface area material during subsequent activation. The thermal treatment effects devolatilization of the PCP, at which point the resulting material can be subjected to chemical or physical activation to produce an AC composition.

[0035] As used herein, the term "activation" and its derivatives refer to a process in which a hydrocarbonaceous or carbonaceous material, such as PCP, becomes more porous as a result of physical or chemical treatment, or both. Thus, as used herein, the terms "activated carbon" (AC) or "activated carbon particles" and their derivatives are intended to mean carbon particles that have been subjected to an activation process, resulting in an increase in porosity and a corresponding increase in the effective surface area (SA) of the particles.

[0036] AC is a form of carbon that is highly porous across a wide range of pore sizes, from visible cracks and fissures to those of molecular dimensions, resulting in a very large internal surface area, making it ideal for use in adsorption. AC is one of the largest markets for carbon materials produced from coal, coke and biochar. It is used in a variety of applications for water, food, chemical, pharmaceutical, blood and gas purification. Each application requires AC with different surface area properties, pore morphology, purity levels and surface functionalization. At the most basic level, the uses and value of AC are largely determined by the surface area achievable by a particular carbon source. AC is appropriately defined by ASTM D2652-11 (Reapproved 2020) Standard Terminology Relating to Activated Carbon as "a series of carbonaceous materials produced by processes that produce adsorption properties." Activation is appropriately defined by ASTM D2652-11 (Reapproved 2020) as "any process by which a material is treated so as to develop adsorption properties."

[0037] As used herein, the term "activated carbon product" is used to define activated carbon produced from two or more feedstocks of carbonaceous material. For example, activated carbon products can be produced from carbonaceous feedstocks that include natural coal, biochar, or wood charcoal in combination with PCP, particularly a PCP binder.

[0038] Powdered activated carbon (PAC) is suitably defined by ASTM D2652-11 (Reapproved 2020) Standard Terminology Relating to Activated Carbon as "activated carbon having an average particle size of less than 45 μm." PAC is typically made from larger particles of activated carbon that are then crushed, ground or milled to a smaller size range. The adsorption kinetics of activated carbon increases as the particle size decreases. PAC is often used in water and gas treatment.

[0039] Granular activated carbon (GAC) is appropriately defined by ASTM D2652-11 (Reapproved 2020) Standard Terminology Relating to Activated Carbon as "activated carbon with a majority of particle size greater than 80 mesh (175 microns)." GAC therefore has a relatively larger particle size than powdered activated carbon, and therefore a smaller external surface for adsorption. GAC is well suited for adsorption of gases and vapors due to its rapid diffusion. GAC is used in water treatment, deodorization, and separation of components in flow systems.

[0040] Demineralization and dewatering of carbonaceous materials such as coal fines to produce PCPs, which can be used as a direct feedstock to produce AC compositions or as a binder to be used with another feedstock, can be achieved by a combination of froth flotation separation, specifically designed for ultrafine and fine particles, and mechanical and thermal dewatering techniques. Typically, PCPs can be produced from a granular coal feedstock by a process that includes size reduction, demineralization, dewatering, and optionally drying. Some or all of these steps can be changed or modified to meet the specifications of the starting material or the desired end product. The key process steps are summarized below in conjunction with a typical starting coal material derived from the underflow of a reservoir, tailings pond, or production tailings.

[0041] particle size reduction The starting material is reduced to a particle size of d80=30-50 microns (or finer for some coals) to achieve efficient separation to a target mineral (ash) content of 5-8%m. To achieve this, the feed containing the starting material is diluted with water to achieve a solids content in the range of 20-40%m and then ground in a ball mill or bead mill depending on the maximum size of the feedstock. The product is sieved to a size range of about 100 microns to eliminate particles above this size. Dispersing additives may be included to optimize the use of energy during size reduction (e.g. lignin-based dispersing agents such as Borresperse, Ultraazine and Vanisperse manufactured by Borregaard, 1701 Sarpsborg, Norway). Suitable equipment for size reduction is manufactured by Metso Corporation, Fabianinkatu 9 A, PO Box 1220, FI-00130 Helsinki, FIN-00101, Finland, Glencore Technology Pty. Ltd., Level 10, 160 Ann St, Brisbane QLD 4000, Australia and FLSmidth, Vigerslev Alle 77, 2500 Valby, Denmark.

[0042] ash removal One or a series of froth flotation stages are performed to reduce the entrained mineral content to a target level. For some coals with mineral matter distributed primarily in the sub-10 micron size region, further comminution followed by two or more stages of flotation may be required to achieve low ash levels.

[0043] During froth flotation, the coal slurry is typically further diluted with water to a range of 5-20% m solids and then collected in a tank where a froth flotation agent known as a foaming agent (e.g., methyl isobutyl carbinol and pine oil) and a collector (e.g., diesel fuel or another hydrocarbon oil and Nasmin AP7 from Nasaco International Co., Petite Rue 3, 1304 Cossonay, Switzerland) are added using controlled dosages. A microparticle separator (e.g., flotation testers manufactured by Eriez Manufacturing Co., 2200 Asbury Road, Erie, Pa. 16505, USA; FLSmidth, Vigerslev Alle 77, 2500 Valby, Denmark; Metso Corporation, Fabianinkatu 9 A, PO Box 1220, FI-00130 Helsinki, Finland; and GTEK Mineral Technologies Co. Ltd.) filled with process water and filtered air from a closed air compressor is used to separate the hydrophobic carbonaceous material from the hydrophilic mineral material. The froth containing the hydrocarbonaceous particles overflows the tank and is collected in an open top trough. The mineral pulp is kept in the separation tank until discharged, while the demineralized coal slurry is deaerated and then subjected to further processing.

[0044] dehydration The concentrate from the froth flotation is dewatered using a filter press or tube press under pressure or vacuum, optionally with air blowing, to a target range of 20-50% m depending on the actual particle size to remove water by mechanical means to produce the feed for the extruder. Suitable filter press equipment is manufactured by Metso, FI-00130 Helsinki, Finland, FLSmidth, Valby, Denmark and Outotec. Rauhalanpuisto 9, 02230 Espoo, Finland.

[0045] In some cases, flocculants (or thickeners, such as anionic polyacrylamide additives manufactured by Nalco Champion, 1 Ecolab Place, St. Paul, MN 55102-2233, USA) are added to optimize settling characteristics and underflow density. To optimize the procedure, settling tests are performed to measure settling velocity, generate settling curves, and track underflow density over time.

[0046] Filtration may also be required depending on the filtration rate and the resulting cake moisture. To optimize the procedure, the feed % solids (with / without thickening), feed viscosity, pH and filtration pressure are measured. The filter fabric is selected after evaluating the cake drainage and clogging performance. A suitable filter fabric is manufactured by Clear Edge Filtration, 11607 E 43rd Street North, Tulsa, Oklahoma 74116 USA.

[0047] In some circumstances, a decanter centrifuge can be incorporated into the process design to concentrate the solids prior to the filter press. Suitable equipment is manufactured by Alfa Laval Corporate AB, Rudeboksvaegen 1, SE-226 55 Lund, Sweden.

[0048] The product at this stage is called PCP wet cake and typically contains 50-60%m moisture. At a moisture content of about 50%m the material becomes cohesive and dry to the touch.

[0049] Drying The PCP product can be thermally dried to reduce the moisture content to less than 10%m. This can be accomplished directly on the PCP or by first pelletizing it for easier handling and conveying it to a belt dryer where hot, oxygen-depleted process air is blown directly onto the pulverized coal. Suitable equipment is manufactured by STELA Laxhuber GmbH, Oettingerstr. 2, D-84323 Massing, Germany or GEA Group Aktiengesellschaft, Peter-Mueller-Str. 12, 40468 Duesseldorf, Germany.

[0050] According to further specific embodiments of the invention, at least about 90% by volume (%v) of the PCP particles are about 25 μm or less in diameter, optionally about 15 μm or less in diameter, optionally about 5 μm or less in diameter. Suitably, the PCP has an ash content of less than about 2%m, suitably less than about 1.5%m, optionally 1%m or less. Optionally, the PCP has a sulfur content of less than about 2%m, optionally about 1% or less, optionally 0.5% or less.

[0051] agglomeration According to an embodiment of the present invention, a process is provided in which solid particulate material of PCP is blended, either as a dry or wet mixture (e.g. as a wet cake or partial wet cake), with or without an organic or inorganic binder material, to agglomerate the fine particles prior to the thermal process steps required for pre-oxidation, devolatilization and / or physical or chemical activation. The wet mixture may include PCP in the form of a so-called "wet cake", obtained directly from the aforementioned dewatering step, with a water content of about 50%m to 60%m of PCP. One advantage of the fine-powdered nature of the PCP particles is that the PCP material can be produced either dry or at various water contents. When a higher water content is preferred, the water maintained on the surface, such as in the wet cake, results in a PCP with additional intrinsic binder properties that are usefully exploited when the PCP is added as a minor component with another AC feedstock. At lower water contents, a partially dried wet cake can be used with a water content of at least 10%m of PCP, up to 40%m of PCP, suitably about 30%m of PCP.

[0052] Agglomeration of PCP occurs when primary particles are loosely bound to each other by adhesion (weak physical interactions) to form larger agglomerates. These agglomerates can be broken by mechanical forces. Agglomerates are collections of smaller primary particles that can change size and shape due to the conditions of the surrounding medium (pressure, temperature, viscosity, etc.). Larger agglomerates can be broken into smaller agglomerates or vice versa, and smaller agglomerates can reform larger agglomerates. Extrusion is a process used to form objects of a constant cross-sectional profile, and is a technique that can be used to agglomerate fine particles by applying a compressive force to the material, suitably causing it to flow through an orifice or die. Agglomeration of PCP with an average particle size of less than 25 microns results in AC products with unexpected properties, such as improved activation surface area and no inherently nonactivatable binder material.

[0053] However, in addition to the water maintained on the surface, in some circumstances suitable binder materials can be utilized for the aggregation of the PCP granular composition, which can be of organic or inorganic origin or a combination of both. Inorganic binders can include lime, calcium hydroxide, hydrated lime, alumina, clay, iron oxide, calcium oxide, silica and silicates. Organic binders can include carbohydrates such as refined or unrefined sugar, molasses and starch; alginates; cellulose, lignocellulose, sawdust and cellulose derivatives; coal tar pitch, petroleum pitch, ethylene cracker bottoms, Gilsonite, coal gasification bottoms, epoxy resins; vegetable oils or fatty acids; glycerol and glycerol esters; natural gums (e.g., xanthan gum, shellac); biomass pyrolysis products; latex; lignosulfonates; polyacrylates and polyacrylamides; polyalkylene glycols; polyester resins; polyurethanes; and styrene polymers. Typically, the use of inorganic binders contributes to an increase in the ash content of the agglomerated PCP composition and the AC obtained therefrom after activation. However, another advantage of the present invention is that this increase in ash content can be partially offset by the inherent low ash of the PCP itself. This can therefore extend the range of potential inorganic binders that can be used, especially when their use is required for desired physicochemical properties such as pellet strength.

[0054] In one particular embodiment of the present invention, the feedstock comprises granular coal, such as bituminous coal, having an average particle size of more than 50 microns, suitably more than 70 microns, and optionally at least 75 microns. The bituminous coal feedstock can be mixed with PCP as a binder component at up to 50% m, i.e., in a 1:1 mixture by mass. In one embodiment, the PCP can be a minor component in the mixture, i.e., less than 50% m. Without wishing to be bound by theory, the combination of PCP with a d90 particle size <20 microns in the agglomerated co-mixed solid-solid blend with larger size coal particles allows optimal volumetric packing, further increasing the available surface area per unit mass of the AC composition after activation. In another embodiment, a composition is provided containing up to 50% m of PCP as a binder and the remainder of the granular biochar feedstock with an average particle size >50 microns. In one embodiment, the PCP can be a minor component in the mixture, i.e., less than 50% m. Similar to the above, optimal volumetric loading can result in a large available surface area per unit mass of the AC composition after activation from the combination of larger biochar particles and smaller PCPs.

[0055] According to one embodiment of the present invention, a process for making an AC composition may include combining PCP with a binder to agglomerate the PCP particles, thereby forming an agglomerated PCP.

[0056] The agglomeration step, with or without a binder, can begin with a PCP that is substantially or partially dry (e.g., with a water content of up to 10% m or less), or with a PCP that is structured in a wet cake (e.g., with a water content of <60% m), or with a composite mixture with water between about 20% m or 30% m. The agglomeration step can be incorporated into a pelletization process, where pelletization of the PCP occurs, such as by an extrusion process. The agglomerated composition is then subjected to one or more heat treatment steps, also called pyrolysis, which may include pre-oxidation and devolatilization before chemical or physical activation. Pyrolysis is the thermal decomposition of a material at high temperatures in an inert atmosphere, which changes its chemical composition. During pyrolysis, which typically occurs in the temperature range of 400° C. to 900° C. for carbonaceous materials such as PCP, volatile liquid and gaseous compounds are evolved, leaving behind a solid residue that is mainly carbon. Pre-oxidation is an oxidation process that occurs before chemical or physical activation.

[0057] In one embodiment of the present invention, thermal pretreatment can advantageously be carried out at lower temperatures than would be expected due to the relatively small particle size of PCP, thereby allowing for more efficient char formation.

[0058] The AC compositions produced according to embodiments of the present invention surprisingly have a high surface area, suitably over 500 m 2 / g, appropriately >700m 2 / g, typically >800m 2 / g, optionally about 1000m 2 / g, typically at least >1300m 2 / g.

[0059] Thus, in certain embodiments, PCP can be utilized as an organic binding agent (i.e., as a "binder") by itself, in combination with PAC or GAC obtained from another carbonaceous source, as described above. The PCP binder can be present in a composition comprised of carbonaceous material derived from natural coal (e.g., bituminous coal) or biomass (e.g., biochar). The PCP binder can be present in an amount of about 1%m or more, 2%m or more, 5%m or more, 10%m or more, 15%m or more, 20%m or more, and up to about 25%m. The PCP binder can be present in an amount of about 50%m or less, 30%m or less, 25%m or less, 20%m or less, 15%m or less, and 10%m or less. In one particular embodiment, the carbonaceous feedstock can be mixed with up to 25%m of PCP, i.e., a 3:1 mixture based on the weight of the carbonaceous feedstock to the PCP binder. The high activation levels achievable with PCPs give them a significant advantage over organic binders (such as polymers) or inorganic binders (such as clays or silicas), neither of which are activated, and thus, when used as a binder in the production of activated carbon compositions, PCPs contribute to a total activated surface available for adsorption in the final AC product.

[0060] In certain embodiments of the invention, PCP may be present as an additive, such as an additive feedstock or "binder," particularly to increase the BET surface area of ​​biochar-derived activated carbon products. In such embodiments, PCP is present in granular form, typically with at least about 90% by volume (%v) of the particles being about 25 μm or less in diameter, with an ash content of less than about 5%m, and a moisture content of up to about 60%m. As shown in the examples below, the addition of PCP to biochar-derived activated carbon can result in at least a two-fold increase in the BET surface area, optionally more than a two-fold increase, and even up to a three-fold increase.

[0061] Activated carbon comprised of the compositions and materials described herein can find utility in a range of applications. For example, activated carbon can be used to remediate various sources of environmentally damaging pollutants, such as those in improperly disposed wastewater from industrial plants and chemical processing facilities, surface runoff containing fertilizers and pesticides used on agricultural areas, fire retardants used in cleaning detergents and fire fighting foams. Many industrial chemical pollutants are known to persist in nature for decades before breaking down, and even very low concentrations can be very harmful to plants, animals and humans, especially when present in mobile water supplies. Thus, the activated carbon compositions described herein can be used in methods for removing "pollutants" or "pollutants" from fluid streams, such as those containing water. In the context of the present invention, "pollutants" are intended to include substances that can be harmful to human or animal health or the environment. As a result, derivatives are defined accordingly, for example, a contaminated fluid is a fluid that contains a pollutant. In some embodiments, the contaminants include organic compounds, and optionally include pharmaceutical or pesticide molecules, including one or more selected from the group consisting of diclofenac, erythromycin, estrogen, oxadiazon, and thiamethoxam. In some embodiments, the contaminants are perfluorinated compounds, such as perfluoroalkyl and polyfluoroalkyl substances (PFAS). In some embodiments, the contaminants can be metal or metalloid ions, optionally selected from copper, iron, lead, mercury, chromate, or arsenate.

[0062] The activated carbon compositions described herein are suitable for contact with a fluid stream containing contaminants, whereby the activated carbon adsorbs or otherwise captures and separates substances from the fluid stream. In certain embodiments, the activated carbon material is placed in a filter / purifier and / or bed or packed column (e.g., including multiple stacked filters) and the fluid stream is passed or traversed through the filter, bed or packed column. The activated carbon can be placed in a mixed bed in combination with another adsorbent material, such as an ion exchange resin. In one embodiment, the activated carbon is included in a prepared component, such as a filter cartridge, which can conveniently confine the activated carbon and adsorbed contaminants when used, as well as allowing replacement or replenishment of the activated carbon material with new activated carbon material as needed. Alternatively, the activated carbon can be added to the fluid stream as a dispersion. The activated carbon can be in the form of granules, flakes, beads, pellets or tablets. The activated carbon material can be in the form of a powder, which can advantageously provide a larger accessible surface area. The activated carbon material can be incorporated into a membrane or membrane-like filter. Typically, the activated carbon material when used in a composition for fluid improvement is in particulate or granular form, suitably the average diameter size of the particles or granules (as measured by the maximum diameter of the particle) is greater than about 0.01 mm, suitably greater than about 0.1 mm and typically less than about 5 mm, less than about 3 mm, optionally less than about 1 mm or even less than about 500 μm.

[0063] The invention is further illustrated by the following non-limiting examples. EXAMPLES

[0064] Example 1: Activation of powdered PCP The PCP samples used in this study were derived from pond tailings waste generated from US bituminous coal originating primarily from Harlan County (East Kentucky). As-produced PCP had particle sizes of d80<5 microns, d98<10 microns, and ash content of 1%m.

[0065] Surface area (SA) and mesopore (1.7-300 nm) characteristics of PCP and other samples were investigated by standard nitrogen adsorption using a Micromeritics instrument Tristar 3000. SA and pore volume were measured using the BET (Brunauer-Emmett-Teller) method and average pore diameter was measured using desorption isotherms using the BJH (Barrett, Joyner and Halenda) method (R. Bardestani, GS Patience & S. Kaliaguine, Experimental methods in chemical engineering: specific surface area and pore size distribution measurements-BET, BJH, and DFT, Can. J. Chem. Eng. 2019, Vol 97, pp 2781-2791).

[0066] For example, for untreated PCP, 20.6 m 2 / g and similarly sized BJH SA values ​​(21.6m 2 / g) is the pore volume (0.091 cm 3 / g) and average pore size (16.0 nm) were measured (Table 1 (Test No. 1)).

[0067] Effect of pre-oxidation and devolatilization Samples of PCP powder were oxidized in an open crucible in an oven at a preset temperature of 250° C. for 6 hours and then pyrolyzed at 500° C. for 1 hour to remove volatiles (e.g., Tests Nos. 3 and 4). Test No. 2, which was devolatilized only, had a BET SA of 20.6 m. 2 / g to 8.3m 2 / g, and the pore volume is 0.091 cm 3 / g to 0.021cm 3 / g. This is expected to be due to swelling of the bituminous coals, as their plastic phase transition occurs and the coal material flows, which may result in pore collapse.

[0068] Oxidation can be used to reduce or eliminate the swelling and flow behavior of bituminous coal. Surprisingly, a simple combination of pre-oxidation and devolatilization steps reduced the 289m 2 / g~293m 2 / g (Tests 3 and 4). The pore volume is nearly the same, but the average pore size is significantly reduced from 16.0 nm to 9.5 nm. The oxidation step results in a 40% weight loss and an 84% yield from devolatilization, giving a net yield of about 50%.

[0069] [Table 1]

[0070] Preoxidation of PCP was also carried out in an autoclave at 250 °C for 6 h under an air flow of 0.3 liters / min, followed by devolatilization at 500 °C for 1 h under the same nitrogen flow. This procedure also resulted in a BET SA of 20.6 m 2 / g to 208m 2 / g (Test No. 5). This procedure resulted in the largest pore volume, i.e., 0.45 cm 3 / g was realized.

[0071] Therefore, by the above pre-oxidation and devolatilization techniques, the BET SA of the PCP powder is 200m 2 / g~300m 2 / g range. This is within the lower end of the SA range for commercial activated carbons, but most products have a BET SA in the range of 500-1500 m 2 / g range. Therefore, the effect of three activation methods to increase the BET SA was further examined.

[0072] Effects of chemical activation A sample of oven preoxidized and devolatilized PCP was impregnated with aqueous KOH and placed in a custom-built 316 stainless steel reactor made with tubing and Swagelok parts and maintained in the reactor using a stainless steel frit with pores of approximately 0.5 microns. The reactor was plumbed into a manifold that supplied nitrogen for Test 6 and CO2 gas for Test 7. Prior to activation, the sample and reactor were purged with the desired gas and for activation, the reactor was placed in a preheated oven under gas flow. A thermocouple was attached to the outlet of the reactor that extended into the oven so that the temperature of the gas exiting the reactor could be monitored. A flow meter was used to control the gas flow rate. The activation temperature was 850° C. and the flow rate was 0.3 liters / min.

[0073] Under these conditions, 1266m 2 Powdered AC with high BET SA of 1368 m / g (final yield 17%) was prepared under nitrogen (Test 6). 2 Higher BET SA of 0.1% / g (final yield 27%) was obtained. These SA values ​​are in the very high range of commercial AC. The pore volumes were similar for both AC products (0.29 and 0.25 cm for nitrogen and CO, respectively). 3 / g). The average pore size obtained from the nitrogen test is much larger (21.3 nm) than that obtained from the CO2 test (8.7 nm) and is larger than the starting PCP itself. In contrast, the average pore size from the CO2 test was the smallest of all tests.

[0074] Example 2. Activation of extruded PCP-containing pellets Alternatively, PCP can be agglomerated prior to activation, which can improve handling of the final AC and also facilitate the use of PCP as a binder component for another carbonaceous material such as biochar. In this example, we focus on PCP wet cake (>50% moisture content).

[0075] PCP wet cake and PCP powder samples were used. The main difference between them is the moisture content, which is 59%m for the wet cake and 2%m for the powder. The analysis of the two samples is shown in Table 2, along with available analytical data for the biochar and low ash US bituminous coal samples (see Examples 4 and 5, respectively). Moisture content was determined by ASTM D2867, ash by ASTM D2866, volatile matter content by ASTM D5832 or thermogravimetric analysis (tga), ignition temperature by tga in air, and BET surface area and pore structure were determined using a NOVA surface analyzer.

[0076] The bulk density of the PCP wet cake was determined by conventional oven drying to obtain an agglomerated product which was then ground to a powder to give a value of 430 kg / m 3 Powdered PCP is produced by ring drying techniques which keep the individual fine particles apart, resulting in a much lower yield of 250 kg / m 3 It has a bulk density of

[0077] The density of the raw pellets was measured by placing the pellets in a 1 L graduated cylinder at a time, approximately 250 mL, and gently tapping the cylinder on a hard surface to allow the pellets to settle and improve packing. The final pellet density after activation was determined by filling a 50 mL cylinder with the entire sample and tapping the cylinder to optimize packing. The mass and volume were then recorded.

[0078] [Table 2]

[0079] agglomeration There are two forms of physical activation: agglomerated and direct. Agglomerated activation uses fine coal particles in PCP in combination with a binder to ensure uniform activation across and within the particle, whereas direct activation, unlike Example 1, typically uses coarse granular material (>175 microns) as the base raw material.

[0080] The various agglomerated formulations were prepared by standard extrusion using a Bonnet extruder (https: / / www.thebonnotco.com / extruders / ) with a 4 inch (10.2 cm) auger, which produced pellets of 4 mm diameter that were cut into lengths of 4-6 mm. These pellets were dried in a 60°C oven for at least 24 hours until dry: 1. As-received PCP wet cake was broken into smaller aliquots and then agglomerated - Sample P1; 2. 90%m of PCP wet cake was mixed with 10%m of inorganic binder (standard bentonite clay with particle size <44 microns) - sample P2; 3. The PCP wet cake was divided into small coin-sized pieces and then oven-dried at 60°C to reduce the moisture content to 10%m - Sample P3, 4. PCP powder was used as a binder and mixed 1:1 with a feedstock of high volatile bituminous coal having a volatile matter content of 35%m (dry basis) and a moisture content of 1-5%m - sample P4.

[0081] Pellets P1 and P2 were produced without problems, but they were very sticky and clumped together due to the high moisture content. Despite the inorganic binder in P2, both formulations clumped similarly with no difference in appearance. After drying, the pellets separated easily, but they were brittle and broke when lightly touched. Both formulations P3 and P4 processed well and gave better initial pellet quality than P1 or P2. The pellet properties are shown in Table 3.

[0082] [Table 3]

[0083] All formulations had relatively similar ignition temperatures and volatile matter contents, but there were significant differences in ash content and density. The inorganic binder used in P2 resulted in a density 50 kg / m3 lower than that of P1. 3The moisture content in P3 (10%m) was much lower than that in P1 (59%m), but the bulk density of P3 was 550 kg / m 3 The PCP / bituminous coal blend P4 achieved the highest bulk density of these pellets at 580 kg / m 3 was obtained.

[0084] Heat Treatment - Pyrolysis and Steam Activation The agglomerated pellets P1-P4 were first pyrolyzed and then steam activated. During pyrolysis, the samples are heated in a furnace under nitrogen gas to remove the volatiles. After activation, the pellets have shrunk to a diameter of 2-3 mm.

[0085] For each pyrolysis test, 20 grams of the dried sample was first sieved so that all particles were larger than 4 mesh (>4.7 mm). This resulted in a more uniform size distribution of the pellets. After the furnace reached the desired temperature, the pellets were loaded into a 1 inch (2.54 cm) diameter quartz reactor. The sample was pyrolyzed for 20 minutes, after which the furnace was shut off and the sample was cooled to 150°C. It was then removed from the furnace, weighed, and analyzed for horizontal compressive strength and volatile content.

[0086] Samples were prepared at different pyrolysis temperatures ranging from 450°C to 750°C, but all were heated for 20 min under 3 L / min nitrogen gas to maintain an inert environment.

[0087] The second step of the heat treatment was steam activation, where the charcoal was introduced into steam. The activation furnace parameters were 850 °C for 30 to 90 min. Approximately 10 grams of pyrolytic charcoal was used for each steam activation. As with pyrolysis, the furnace reached an internal temperature of 850 °C with an equilibrium steam flow rate of 4 mL / min before the samples were loaded into the reactor and activated for the planned time. After activation, each sample was cooled under a nitrogen flow and then removed from the furnace at a temperature below 150 °C.

[0088] After pyrolysis, the mass loss was recorded and the density and volatile matter content of the pyrolysis pellets were measured. The low volatile matter content indicates that the sample was well carbonized. After activation, the mass loss was recorded again, along with the diameter shrinkage (as a percentage value) and the total yield. Table 4 shows these pyrolysis and activation results of PCP samples P1-P4 under various conditions, as well as the main activated carbon properties (BET surface area, total pore volume, average pore size, ash content and volatile matter content) of the products from the same set of pyrolysis and activation conditions.

[0089] Effect of temperature (Tests 1-4) For comparative testing, the effect of temperature on P1 (feed material with the highest moisture) was investigated from 450°C to 750°C to determine the ideal temperature conditions (Tests 1-4 in Table 4). Granular activated carbon with surprisingly high surface area and unusually low ash content was produced, and an optimum temperature of 550°C was identified.

[0090] BET surface area: 677m 3 / g~1103m 3 / g values ​​were obtained, with larger values ​​obtained at the two lower temperatures (450° C. and 550° C.). These values ​​are comparable to commercial grades Calgon 400 and Calgon 600.

[0091] Pore ​​size and pore volume: 0.62 cm at the two lower temperatures (450°C and 550°C) along with a larger surface area at the lower temperatures. 3 / g and 0.60cm 3 A larger pore volume of 1000 nm / g and a larger average pore diameter (22.5 Å) were obtained, which are comparable to the two commercial grades of Calgon (Table 4).

[0092] Yields: Mass loss during pyrolysis increased with increasing temperature from 22%m (450°C) to 33%m (750°C), but this trend was reversed during activation where mass loss decreased with increasing temperature from 62%m (450°C) to 42%m (750°C). As a result, the total yields of activated carbon were more similar, but the actual yields increased with increasing temperature from 30%m (450°C) to 42%m (750°C), which is a high yield for the coal-based pyrolysis / steam activated carbon process, see the yield of about 20%m for Calgon F400 (Table 4).

[0093] Ash content: Ash content is reduced from 5.1%m to 4.2%m at higher temperatures, consistent with increasing yield with increasing temperature. These ash contents are much lower than typical commercial grades which have ash of 8-9%m. PCP has been prepared from waste coal with ash contents as low as 0.3%m (dry basis). Thus, this method can produce activated carbon with ash contents of 1.0% or even less.

[0094] Volatile content: During pyrolysis, lower volatile content was obtained at higher temperatures, and indeed Test 1 at 450°C was not completely pyrolyzed as volatilization occurred at the end of 20 minutes. During activation, these differences were eliminated as the volatile content of Tests 1-4 were all very similar, ranging from 2.0m to 2.6%m (dry basis).

[0095] Effect of pellet type and moisture content Surprisingly, P1 (tests 1-6) containing 60% moisture not only failed to pelletize, but also had a pellet size of >1000m in three tests (numbers 1, 2 and 6). 3A very high surface area of ​​1000m3 / g was also obtained. In the case of activated carbon, the ash content was very low, ranging from 4.2%m to 7.1%m3. Here, the water retained on the surface present in P1 (PCP wet cake) contributes to the binding capacity of PCP due to capillary forces (Sastry, KVS, Pelletization of fine coals, DOE Grant No. DE-FG-22-89PC89766, Univ. of California, 1995, https: / / www.osti.gov / servlets / purl / 171245).

[0096] P2 (Test 7), which contained an inorganic binder, had the smallest surface area of ​​activated carbon (only 537 m 3 / g) but also had an unacceptably high ash content of approximately 37%m. This formulation was not subjected to further testing.

[0097] P3 (Tests 8–10), which contained 10% moisture PCP wet cake, produced the activated carbon with the highest surface area (1349 m in Test 9). 3 / g), the largest average pore diameter (27.9 Å) and pore volume (0.94 cm 3 / g) were obtained. The high BET surface area is achieved by the large total pore volume, larger pore diameter, and larger BJH pore volume. Samples 8 and 9 were heat treated at a starting moisture content of about 20%. Sample 10 was dried to about 1% moisture before pyrolysis. Drying the samples before heat treatment resulted in high yields, densities (0.44 g / cm for test 10). 3 It was confirmed that pellets having high hardness and small diameter shrinkage after activation were obtained. The ash content was very low in the case of activated carbon, ranging from 3.0%m to 5.9%m.

[0098] Based on data from Harlan County coals taken from Ruppert, LF et al,, Chapter G, A Digital Resource Model of the Middle Pennsylvanian Pond Creek Coal Zone, Central Appalachian Basin Coal Region, US Geological Survey Paper 1625-C, 2000, (https: / / pubs.usgs.gov / pp / p1625c / CHAPTER_G / CHAPTER_G.pdf), for typical seams from which this PCP is obtained, approximately 3% m of moisture is inherently retained in the pores. For this class of vitrinite-rich coal, data from JF Ensworth, C.S. Fowler & L.F. Jones, Moisture in Coal. 2, Maceral effects on pore structure., Fuel, 68, 18 (1989) estimate that the macroporosity destroyed during crushing is 1% m. The remaining 8% is water retained at the surface, and the resulting capillary forces contribute to the binding tendency of the PCP. Some PCP particles also bind to one another themselves due to particle-particle interlocking resulting from electrostatic or van der Waals forces. This binder property results from the fine particle size distribution of the PCP, which results in a large number of particle-particle interlockings.

[0099] In P4 (Tests 11-18), which contained 50% PCP wet cake with 60% moisture and 50% dry bituminous coal, the ash content was >1000 m in five tests (Nos. 13, 14, 15, 17 and 18). 2 In tests 11-15, the samples were pyrolyzed at an initial moisture content of about 15%, whereas in tests 16-18, they were dried to about 1% solution moisture before heat treatment. This difference in pre-drying resulted in a higher density (0.51 g / cm for test 16). 3 ) was obtained. Comparing all the tests, the preliminary drying test gave a value of 0.42 g / cm 3 ~0.51g / cm 3The activated carbons obtained had densities in the range of 0.26 g / cm3 (Tests 10-18), whereas those without pre-drying (Tests 1-9) had densities of 0.26 g / cm3. 3 ~0.39g / cm 3 Although there are bituminous coals that contain more ash, the ash content for activated coal is very low, ranging from 4.6%m to 6.6%m.

[0100] Not only does PCP allow for the production of binder-free pellets suitable for activation, but it also acts as a binder for the coarser sized bituminous coal particles, again resulting from the particle size distribution of the PCP fines, which results in particle-particle interlocking between the PCP and the bituminous coal and between the PCP and the PCP.

[0101] P5 (Tests 20-22) contained PCP-B wetcake, which was prepared from the same waste coal source as PCP, but with one less ash removal step. The PCP-B wetcake had the following properties: Higher ash content (2.7%m) than PCP wet cake (1.3%m); Lower moisture content (18.1%m) than PCP wet cake (59%m); Coarser particle size distribution (d80=9.5μm) than PCP wet cake (d80=5μm).

[0102] Smaller surface area (512-611m 2 / g) and higher activated carbon yield (45–41%), respectively, were confirmed for the P5 sample. Test 22 showed the highest surface area (611 m) after 120 min activation time. 2 These surface areas are less than those obtained with PCP, but many commercial activated carbons, such as Norit Darco™, are manufactured to this specification, which allows a trade-off between the degree of processing required to produce the PCP and the properties required for the AC end product.

[0103] [Table 4]

[0104] As can be seen from Table 4, P2, the only sample containing an inorganic binder, has the smallest surface area of ​​all the samples tested after activation.

[0105] Activation time Figure 2 shows how the BET surface area increases with increasing activation time for activated carbons prepared from the four types of PCP samples: P1 (Test 5 at 30 min, Test 2 at 60 min and Test 6 at 90 min), P3 (trial 8 at 60 min and trial 9 at 90 min), P4 wet (average of two tests 11 and 12 at 60 min and average of three tests 13, 14 and 15 at 90 min) P4 dry (average of test 16 at 60 min and tests 17 and 18 at 90 min).

[0106] In most cases, the pore volume shows a similar trend with the surface area being at higher values ​​at longer activation times, e.g. P1: 0.32cm at 30 minutes 3 / g to 0.60 cm at 60 min 3 / g and 0.60 cm at 90 min 3 / g, P3: 0.38cm at 60 minutes 3 / g and 0.92 cm at 90 min 3 / g, P4 wet: 0.41cm at 60 minutes 3 / g and 0.57 cm at 90 min 3 / g, P4 dry 60 minutes 0.37cm 3 / g and 0.51 cm at 90 min 3 / g.

[0107] There is a similar trend of increasing average pore size with increasing activation time.

[0108] Figure 3 shows how the yield decreases with increasing activation time for activated carbons prepared from the same four types of PCP samples. This is to be expected, since longer contact times result in greater mass loss. One small exception is P1, where the yield after 90 min is seen to be slightly higher than at 60 min.

[0109] Thus, there is a trade-off between lower yields and higher surface area, larger pore volume and larger average pore size for increasing activation time.

[0110] Example 3. Activation of hydraulically compressed PCP discs Another material (D1) was prepared by hydraulically pressing dry PCP powder into three small cylindrical disks of approximately 25 mm diameter and 8 mm height. The individual calculated volumes and measured masses of these disks gave a mass of 895 kg / m 3 The average bulk density of the pellets was measured (Table 3), which was higher than that of any of the extruded pellets P1 to P4.

[0111] The disks were broken into smaller pieces for pyrolysis and activation, the results of which are shown in Table 4. The resulting activated carbon had a mass of 930 ml. 2 / g and a large surface area of ​​0.46 cm 3 / g pore volume, average pore diameter of 19.9 Å (angstroms) and 0.43 g / cm 3 %. Thus, the activated carbon had a density similar to that of the activated carbon prepared from pellets containing moisture as a binder.

[0112] In D1, the dry PCP particles are effectively bound together by particle-particle interlocking resulting from electrostatic or van der Waals forces (Sastry, KVS, 1995). The nature of this binder is a function of the fine particle size distribution of the PCP.

[0113] Example 4. Activation of extruded pellets prepared from PCP and biochar blends Biochar chunks obtained from sawmill debris, specifically sawdust, were ground to powder in a vertical air swept hammer mill (Raymond mill). The resulting biochar powder was 356 m 2 / g BET surface area, see also Table 2 (supra) for additional properties. Biochar powder was blended with PCP in three different ratios, A, B and C, as shown in Table 5 below. 50 g dried samples of blends A, B and C were subjected to pyrolysis at 550°C for 30 minutes with a nitrogen flow rate of 3 L / min, followed by steam activation at 850°C for 120 minutes with a steam flow rate of 4 mL / min. Each blend was tested in duplicate and the calculated average results are shown in Table 5.

[0114] [Table 5]

[0115] These surprising results show that the addition of PCP to biochar increases the BET surface area of ​​the resulting activated carbon by 356 m 2 / g to 916~982m 2 The results show that the average pore size can be significantly increased to values ​​in the range of 0.3-0.6 cm / g. Biochar contains mainly mesopores, whereas char from PCP is mainly micropores. Table 4 shows that for activated carbon prepared from PCP, the average pore size values ​​are mainly in the range of 18-22 Å and 0.3-0.6 cm. 3 / g. Thus, both the average pore size and the total pore volume are increased by 28-29, respectively, by adding biochar to the PCP. This allows tuning of the pore structure of the activated carbon to best perform for a particular application.

[0116] Example 5. Activation of extruded pellets prepared from blends of PCP and low ash bituminous coal. Low ash bituminous coal, the properties of which are shown in Table 2, was blended with PCP in three different ratios, D, E and F, as shown in Table 6 below. Pyrolysis and activation were carried out on 50 g dried samples of blends D, E and F under the same conditions as in Example 4, and the test was repeated twice, with the average results shown in Table 6.

[0117] [Table 6]

[0118] These results were obtained by mixing PCP with low-ash bituminous coal in various ratios and measuring the temperature range of 845 to 977 m 2 / gが343.18 ...

[0119] Example 6. Performance of PCP-derived activated carbon in water treatment applications The ability of PCP-derived activated carbon to remove 2-methylisoborneol (MIB) from drinking water is a standard measurement used to evaluate the effectiveness of activated carbon for use in drinking water applications, such as the removal of taste, color, and odor forming compounds as well as other trace contaminants (AWWA B600-2016 Standard For Powdered Activated Carbon, which describes powdered activated carbon (PAC) for use in adsorption of impurities for water supply service applications). The method involves using various concentrations of activated carbon in a stirred jar apparatus. Synthetic water was prepared (US EPA method 600 / 4-90 / 027F). The synthetic freshwater with medium hardness used contained 1 mg / L sodium humate to simulate organic carbon competition commonly found in real-world applications. These waters contained 50 ng / L of MIB in the influent. Figure 4 shows the %MIB removal efficiency with increasing amounts of activated carbon used for both PCP-derived activated carbon and commercial activated carbon. It is clear that PCP-derived activated carbon removes a higher percentage of MIB at all use levels. For example, a PCP dose of 20 mg / L is required to remove 70% of MIB, while commercial options require a much higher dose of 26 mg / L to achieve the same level of MIB removal. This makes PCP-derived activated carbon a very effective method for improving water quality.

[0120] Overall conclusion 1) The fine particle size of PCP and PCP wet cake makes it suitable for subsequent pyrolysis and activation to produce activated carbon, with a density of 350g / cm 3 ~895g / cm 3 Cohesive pellets in the range of sizes can be prepared. PCP not only produces binder-free cohesive pellets suitable for activation, but also acts as a binder for the coarser sized bituminous coal particles. The cohesiveness is achieved through the fine particle size distribution of the PCP.

[0121] 2) The surface water present in the PCP wet cake and partially dried PCP wet cake acts as a binder to hold the PCP particles together due to capillary forces. In the absence of water, the dry PCP particles will clump together due to particle-particle interlocking resulting from electrostatic or van der Waals forces.

[0122] 3) Potassium hydroxide chemical activation after pre-oxidation of PCP as powder resulted in up to 1369 m 2 Activated carbon with a very high surface area of ​​1000 nm / g was obtained.

[0123] 4) Pyrolysis and steam activation of PCP-derived extruded pellets or hydro-pressed disks to produce up to 1,349 m 2 A very high surface area of ​​0.1 g / g was obtained and had a low ash content of 3%.

[0124] 5) Thus, the process of the present invention provides a means for producing high surface area activated carbons having the following novel properties: Ash content is less than 3% in Example 2, but in some cases less than 1%m, and is refined from PCP preparations to 0.3%m ash. · Activation of activated carbon is achieved through the center of the particle due to the small size of the primary particles in the carbon itself, in contrast to fine activated carbon, which is produced by grinding much larger activated particles, which inevitably exposes non-activated surfaces that are not permeated by the activation reagent.

[0125] 6) Due to the absence of inorganic or organic binders, binderless agglomerated pellets and moisture-bound pellets of PCP are advantageous for higher yields (dry basis) of activated carbon with larger surface area. To produce activated carbon, additives are always used to bind the carbonaceous powder into an agglomerated form, typically added in amounts ranging from a few percent to 30%m or even 50%m (see, for example, US Pat. No. 5,332,426A, US Pat. No. 3,544,507A, US Pat. No. 3,901,823A, CN Patent Publication No. 102,674,341A, CN Patent Publication No. 103,011,158A, CN Patent No. 103,787,329B, CN Patent Publication No. 103,060,053A and US Pat. No. 5,389,325A). Inorganic binders do not affect yield when they remain within the activated carbon structure, but the ash from the inorganic binders is not activated and proportionally reduces the surface area of ​​the product. Organic binders are lost during processing as volatiles, resulting in lower yields. By avoiding the use of binders, the potential activated carbon yield and surface area is maximized. As with the impact of inorganic binders, the low ash content of PCP minimizes the percentage of inactive material, further contributing to improved activated carbon yield and surface area.

[0126] Although specific embodiments of the present invention have been disclosed in detail herein, this is done by way of example and for the purpose of illustration only. The above-mentioned embodiments are not intended to be limiting on the scope of the present invention. It is contemplated by the inventors that various substitutions, changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention.

Claims

1. A process for manufacturing activated carbon (AC), comprising: (i) providing an agglomerated purified carbonaceous product (PCP), wherein the PCP is in granular form and at least about 90 volume % (%) v of the particles have a diameter of about 25 μm or less, and the PCP has less than about 5% m ash and a water content of up to about 60% m; (ii) subjecting the agglomerated PCP to at least one heat treatment to form a heat-treated agglomerated PCP; and (iii) subjecting the heat-treated agglomerated PCP to at least one activation process to produce the AC. A process as described above.

2. The process according to claim 1, wherein at least about 95% v of the PCP particles have a diameter of about 25 μm or less.

3. The process according to claim 1, wherein the average particle size of the PCP is 10 μm or less.

4. The process according to claim 1, wherein the PCP has less than about 3% m ash, typically less than about 2% m ash, and suitably less than 1% m ash.

5. The process according to claim 1, wherein the PCP has a water content of up to about 50% m, typically up to 30% m, suitably up to 20% m, and optionally up to 10% m.

6. The process according to claim 1, wherein the at least one heat treatment includes a preliminary oxidation and / or pyrolysis stage.

7. The process according to claim 1, wherein the at least one heat treatment includes a devolatilization stage.

8. The process according to claim 1, wherein the at least one heat treatment is carried out at a temperature of about 500 °C or less.

9. The process according to claim 8, wherein the at least one heat treatment is carried out at a temperature of about 450 °C or less.

10. The process according to claim 1, wherein the activation process includes an activation selected from the group consisting of physical activation and chemical activation.

11. The process according to any one of claims 1 to 10, wherein the PCP is contained in a wet cake, and the wet cake contains up to about 60% m water.

12. The process according to claim 1, wherein the PCP is contained in a partially dried wet cake, and the partially dried wet cake contains up to about 30% m water.

13. The process according to claim 1, wherein the agglomeration of the PCP particles includes the further addition of an organic or inorganic binder material.

14. The process according to claim 1, wherein the agglomeration of the PCP particles is carried out in the absence of any additional binder material.

15. The process according to claim 1, wherein the PCP is obtained from froth flotation of waste pulverized coal.

16. Activated carbon prepared by the process according to claim 1, having a BET surface area of at least 500 m ２ / g of activated carbon.

17. Activated carbon prepared by the process according to claim 1, having a BET surface area of at least 800 m ２ / g, suitably 900 m ２ / g, optionally 1000 m ２ / g.

18. A process for manufacturing an activated carbon (AC) product, comprising: (i) providing a carbonaceous feedstock in granular form; (ii) agglomerating the carbonaceous feedstock with a binder to form an agglomerated feedstock, wherein the binder comprises a purified carbonaceous product (PCP), the PCP is in granular form, at least about 90 volume % (%) v of the particles have a diameter of about 25 μm or less, and the PCP has an ash content of less than about 5% m; (iii) subjecting the agglomerated feedstock to at least one heat treatment to form a heat-treated agglomerated feedstock; and (iv) subjecting the heat-treated agglomerated feedstock to at least one activation process to produce an AC composition. A process as described above.

19. The process according to claim 18, wherein the carbonaceous feedstock is selected from natural coal, biochar, and charcoal.

20. The process according to claim 18, wherein the at least one heat treatment is carried out at a temperature of 500 °C or lower.

21. The process according to claim 18, wherein the at least one heat treatment is carried out at a temperature of 450 °C or lower.

22. The process according to claim 18, wherein the activation process comprises an activation selected from the group consisting of physical activation and chemical activation.

23. The process according to claim 18, wherein the PCP is contained in a wet cake, and the wet cake contains up to 60% m of water.

24. The process according to claim 18, wherein the PCP is contained in a partially dried wet cake, and the partially dried wet cake contains up to 30% m of water.

25. The process according to claim 18, wherein the binder further comprises an inorganic binder material.

26. An activated carbon product prepared by the process according to claim 18, having a BET surface area of at least 500 m ２ / g and an ash content of less than about 5% m of ash.

27. An activated carbon product according to claim 26, having an ash content of less than about 2% m.

28. A process for adsorbing a substance contained in a fluid stream, the process comprising exposing the fluid stream to an activated carbon product prepared by the process according to claim 1.

29. The process according to claim 28, wherein the fluid stream comprises water.

30. The process according to claim 28, wherein the substance is selected from one or more of the group consisting of organic compounds, optionally pharmaceutical or pesticide molecules, perfluorinated compounds, and metal or metalloid ions optionally selected from copper, iron, lead, mercury, chromate or arsenate.

31. The process according to claim 28, wherein the activated carbon product is contained in a filter / cleaner, a bed or a packed column.

32. A process for adsorbing a substance contained in a fluid stream, the process comprising exposing the fluid stream to an activated carbon product prepared by the process according to claim 18.

33. The process according to claim 32, wherein the fluid stream comprises water.

34. The process according to claim 32, wherein the substance is selected from one or more of the group consisting of organic compounds, optionally pharmaceutical or pesticide molecules, perfluorinated compounds, and metal or metalloid ions optionally selected from copper, iron, lead, mercury, chromate or arsenate.

35. The process according to claim 28, wherein the activated carbon product is contained in a filter / cleaner, a bed or a packed column.

36. Use of an aggregated purified carbonaceous product (PCP) as an additive feedstock for increasing the BET surface area of an activated carbon product derived from biochar, wherein the PCP is in granular form and at least about 90 volume % (%) v of the particles have a diameter of about 25 μm or less, and the PCP has an ash content of less than about 5% m and a water content of up to about 60% m.

37. The use according to claim 36, wherein the PCP is present in an amount of up to about 50% m.

38. The use according to claim 36, wherein the PCP increases the BET surface area of the activated carbon product derived from biochar by at least 2-fold compared to the BET surface area of the activated carbon product derived from biochar alone.

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