Pyrolysis and carbon deposition method and system

Abstract

The present invention provides a method for sequential pyrolysis and carbon deposition to produce a composite carbonaceous product, the method comprising: a pyrolysis process step, which comprises pyrolyzing a pyrolyzable organic feed in a first reaction zone at a pyrolysis temperature in the presence of a non-oxidizing gas to produce hot char and pyrolysis gas, wherein the pyrolysis gas and the non-oxidizing gas are combined to form a gas mixture; discharging the gas mixture from the first reaction zone to a combustion zone, and combusting at least a portion of the pyrolysis gas in the combustion zone, wherein the heat generated by the combustion of the pyrolysis gas is transferred from the combustion zone to the first reaction zone to provide at least a portion of the pyrolysis heat; and a decomposition process step, which comprises directly contacting a hydrocarbon-rich organic gas with the hot char after the hot char is produced in the pyrolysis process step, wherein the hydrocarbon-rich organic gas is catalytically decomposed on the hot char at a decomposition temperature higher than the pyrolysis temperature, thereby producing a gaseous decomposition product and a composite carbonaceous material, the gaseous decomposition product comprising hydrogen, and the composite carbonaceous material comprising char having carbon deposits thereon.

Description

Technical Field

[0001] The present invention relates to a method and system for sequential pyrolysis and carbon deposition to produce a composite carbonaceous product. The method includes pyrolyzing an organic feed to produce hot char and pyrolysis gases, burning the pyrolysis gases and transferring heat from the combustion to provide at least a portion of the pyrolysis heat, and catalytically decomposing the hydrocarbon-rich organic gas directly on the hot char at a temperature above the pyrolysis temperature after the hot char is produced. A composite carbonaceous material is thereby produced, which includes a char having a carbon deposit thereon. Background Art

[0002] Carbon emissions are a growing concern in many industrial processes, including those seeking to remediate or monetize biomass or carbon-containing waste feedstocks. Gasification and incineration have been proposed as thermal methods for processing such feedstocks, but nearly all of the carbon is ultimately emitted as carbon dioxide.

[0003] Another method by which a portion of the feedstock carbon can be advantageously retained in a stable solid product is pyrolysis. Pyrolysis is a high temperature decomposition process used to convert pyrolyzable organic feeds (i.e., any feed containing at least a portion of organic carbon-based materials) under non-oxidative conditions, particularly where the oxygen content is sufficiently low that endothermic cracking reactions dominate over exothermic oxidation reactions. Industrial pyrolysis is typically operated at moderate to high temperatures (350-900°C) to produce products for energy, fuel, or chemical applications. Pyrolysis produces three product streams: a solid carbonaceous product (char), a condensable pyrolysis oil portion, and a non-condensable gas portion.

[0004] Pyrolysis is considered particularly useful for treating potentially contaminated waste or biomass streams, including biosolids as a product of wastewater treatment plants. High temperature pyrolysis advantageously sterilizes potentially harmful microorganisms in the feedstock, as well as permanently sequesters a portion of the carbon in the (bio)char product. However, other carbon-containing streams, including biogas, that are often co-produced with the solid feedstock are typically combusted.

[0005] The pyrolysis products can be converted into useful derivatives or can be used in their original form for many applications. For example, the char can be used for soil improvement, soil remediation, water purification, composite materials or as a fuel. However, considering the cost of operating processes to repair or utilize low-value waste feedstocks, there is a need to increase the value of the product range, especially the solid pyrolysis products.

[0006] In the pyrolysis process where charcoal is the main target product, the oil portion and / or the gas portion can be burned to provide the energy required to drive the endothermic pyrolysis reaction. The excess energy can be used to generate electricity or utility steam. A further problem in such pyrolysis systems is that the heat transfer between combustion and pyrolysis may be unsatisfactory, resulting in poor heat distribution, so that the pyrolysis rate is low and / or the charcoal product quality is poor or inconsistent. In addition, there is still a need to improve the overall energy balance of the pyrolysis system.

[0007] Chemical vapor deposition (CVD) is another method of carbon sequestration, in this case by carbon deposition in the form of carbon nanomaterials. Gaseous hydrocarbon vapors are passed over a catalyst to produce carbon nanomaterials and hydrogen-rich decomposition gas products. Synthetic catalysts for this process have been reported, including catalytic metals such as Ni, Fe, and Co. However, such catalysts are easily deactivated and, since they are expensive, must be regenerated. They also leave metallic impurities in the carbon nanomaterials.

[0008] Therefore, lower cost carbon-based catalysts such as activated carbon, graphite and carbon black have been proposed as alternatives to metal catalysts. However, the conversion rates obtained using carbon-based catalysts are relatively low compared to synthetic catalysts. In addition, carbon-based catalysts are purchased or produced from specialized raw materials in a separate process before being used for CVD. Therefore, the cost of producing carbon-based catalysts with sufficient performance remains a limiting factor in implementing large-scale CVD processes.

[0009] Pyrolysis processes have been reported in which increased overall carbon recovery is obtained by re-adsorbing and dehydrogenating the pyrolysis vapors on the char pyrolysis products, either simultaneously with the pyrolysis reactions occurring in the pyrolysis reaction zone or separately in a downstream process unit. However, at typical pyrolysis temperatures where these dehydrogenation reactions occur, amorphous coke deposits that block pores are formed on the char, rather than value-added carbon materials such as carbon nanomaterials.

[0010] Thus, there continues to be a need for new methods and systems of pyrolysis and carbon deposition that at least partially address one or more of the above-mentioned shortcomings or provide useful alternatives.

[0011] The reference herein to a patent document or other matter cited as prior art should not be taken as an admission that the document or matter was known or that the information it contained was part of the common general knowledge at the priority date of any claim. Summary of the invention

[0012] According to a first aspect, the present invention provides a method for sequential pyrolysis and carbon deposition to produce a composite carbonaceous product, the method comprising: a pyrolysis process step, which comprises pyrolyzing a pyrolyzable organic feed in a first reaction zone at a pyrolysis temperature in the presence of a non-oxidizing gas to produce hot char and pyrolysis gas, wherein the pyrolysis gas and the non-oxidizing gas are combined to form a gas mixture; discharging the gas mixture from the first reaction zone to a combustion zone, and combusting at least a portion of the pyrolysis gas in the combustion zone, wherein the heat generated by the combustion of the pyrolysis gas is transferred from the combustion zone to the first reaction zone to provide at least a portion of the pyrolysis heat; and a decomposition process step, which comprises directly contacting a hydrocarbon-rich organic gas with the hot char after the hot char is produced in the pyrolysis process step, wherein the hydrocarbon-rich organic gas is catalytically decomposed on the hot char at a decomposition temperature higher than the pyrolysis temperature, thereby producing a gaseous decomposition product and a composite carbonaceous material, the gaseous decomposition product comprising hydrogen, and the composite carbonaceous material comprising char having carbon deposits thereon.

[0013] Advantageously, an integrated pattern of sequential pyrolysis and carbon deposition process steps can provide a high degree of sequestration of the overall carbon from two carbonaceous feeds in a stable and potentially useful composite carbonaceous product. Immediate use of the formed hot char pyrolysis product as a carbon deposition catalyst can provide improved catalytic performance compared to superficially similar preformed materials because cooling-induced degradation mechanisms are minimized. In addition, a high degree of thermal efficiency can be achieved because the intermediate char product, which already contains process heat, is used as a catalytic substrate for high-temperature carbon deposition. The temperature increase between the pyrolysis and decomposition process steps helps to form high-quality crystalline carbon materials, including carbon nanomaterials. Combustion of the pyrolysis gases and optionally also the decomposition gases is used to provide the heat required for the endothermic reaction.

[0014] In some embodiments, the method further includes separating a gas composition comprising gaseous decomposition products and any residual hydrocarbon-rich organic gas from the composite carbonaceous material and combusting at least a portion of the combustible components therein, wherein heat generated by the combustion of the combustible components is transferred to provide at least a portion of the decomposition heat.

[0015] In some embodiments, the pyrolyzable organic feed comprises biomass such as biosolids.

[0016] In some embodiments, the hot char is continuously maintained at a temperature above 300°C, or above 400°C, or above 600°C, or above 700°C between generating the hot char in the pyrolysis process step and catalytically decomposing the hydrocarbon-rich organic gas on the hot char in the decomposition process step.

[0017] In some embodiments, the pyrolysis in the pyrolysis process step and the catalytic decomposition in the decomposition process step are carried out successively in the first reaction zone. The catalytic decomposition can be initiated by introducing the hydrocarbon-rich organic gas into the first reaction zone. When the hydrocarbon-rich organic gas stream is introduced, the non-oxidizing gas stream flowing into the first reaction zone can be reduced or stopped. The solid in the first reaction zone can be continuously fluidized in a fluidizing stream comprising non-oxidizing gas and / or hydrocarbon-rich organic gas during the pyrolysis and catalytic decomposition.

[0018] In some embodiments, the first reaction zone is separated from the combustion zone by a heat transfer baffle, wherein the heat transferred from the combustion zone to the first reaction zone to provide at least a portion of the pyrolysis heat is transferred through the heat transfer baffle. The heat transfer baffle may include a plurality of holes, wherein the gas mixture flows from the first reaction zone to the combustion zone through the holes.

[0019] In some such embodiments, the catalytic decomposition in the decomposition process step is carried out in a first reaction zone, and a gas composition comprising gaseous decomposition products and any residual hydrocarbon-rich organic gas is discharged to a combustion zone to combust combustible components in the combustion zone, wherein heat generated by the combustion of the combustible components is transferred through a heat transfer baffle to provide at least a portion of the decomposition heat.

[0020] In some embodiments, the hydrocarbon-rich organic gas is substantially free of pyrolysis gas or its components produced in the pyrolysis process step. Thus, all or substantially all (e.g., greater than 90%) of the hydrocarbon-rich organic gas may be provided from a source external to the pyrolysis process step that produces the hot char. In some embodiments, the hydrocarbon-rich organic gas is selected from biogas and plastic pyrolysis gas.

[0021] In some embodiments, the method further comprises: pyrolyzing the polymer to produce hot pyrolysis vapors, wherein the hot pyrolysis vapors form at least a portion of a hydrocarbon-rich organic gas; separating a gas composition comprising gaseous decomposition products and any residual hydrocarbon-rich organic gas from the composite carbonaceous material; and cooling the gas composition to condense the pyrolysis oil portion.

[0022] In some embodiments, the method further includes exhausting a portion of the gas mixture from the first reaction zone, wherein the pyrolysis gas in the first reaction zone forms at least a portion of the hydrocarbon-rich organic gas.

[0023] In some embodiments, the decomposition temperature is at least 700° C., or at least 750° C., or at least 800° C., such as at least 850° C. In some embodiments, the decomposition temperature is no more than 200° C., or no more than 100° C. higher than the pyrolysis temperature.

[0024] In some embodiments, the method further comprises introducing an activation additive into the first reaction zone before or during pyrolysis, wherein the activation additive causes the surface area of ​​the hot char to increase relative to the hot char produced in the absence of the additive. The activation additive may be selected from NaOH and KOH.

[0025] In some embodiments, the composite carbonaceous material comprises at least 5 wt% carbon deposits, or at least 10 wt% carbon deposits, or at least 20 wt% carbon deposits.

[0026] In some embodiments, the carbon deposit is crystalline.In some embodiments, the carbon deposit comprises a carbon nanomaterial, for example selected from carbon nanotubes, carbon nanofibers, and carbon nanospheres.

[0027] In some embodiments, at least 30% or at least 40% of the total carbon in the pyrolyzable organic feed and the hydrocarbon-rich organic gas is sequestered in the composite carbonaceous material.

[0028] In some embodiments, the method includes separating and recovering at least a portion of the hydrogen.This method may include separating a gas composition comprising gaseous decomposition products and any residual hydrocarbon-rich organic gas from the composite carbonaceous material, and separating hydrogen from the gas composition.

[0029] In some embodiments, the method further comprises generating electricity and / or steam from heat generated by combustion of combustible components in the pyrolysis gas and / or the gas composition comprising the gaseous decomposition products and any residual hydrocarbon-rich organic gas.

[0030] According to a second aspect, the present invention provides a system for sequential pyrolysis and carbon deposition to produce a composite carbonaceous product, the system comprising: (i) a first endothermic reactor comprising a first reaction zone, a first gas inlet and one or more first gas outlets, wherein the first endothermic reactor is configured for a pyrolysis process step, the pyrolysis process step comprising: feeding a non-oxidizing gas into the first reaction zone via the first gas inlet; pyrolyzing a pyrolyzable organic feed at a pyrolysis temperature in the first reaction zone in the presence of the non-oxidizing gas to produce hot char and pyrolysis gas, wherein the pyrolysis gas and the non-oxidizing gas are combined to form a gas mixture; and discharging the gas mixture from the first reaction zone through the first gas outlet, and (ii) a burner comprising a combustion zone, wherein the burner is configured to: receive the gas mixture discharged from the first reaction zone in the combustion zone; feed an oxygen-containing gas into the combustion zone; and burn at least a portion of the pyrolysis gas in the combustion zone, wherein the heat generated by the combustion of the pyrolysis gas is transferred from the combustion zone to the first reaction zone to provide at least a portion of the pyrolysis heat, wherein either of the following two: (iii) the first endothermic reactor further The step is configured for a decomposition process step, and the decomposition process step includes: after hot char is generated in the first reaction zone in the pyrolysis process step, directly introducing a feed of a hydrocarbon-rich organic gas into the first reaction zone through the first gas inlet or another gas inlet; catalytically decomposing the hydrocarbon-rich organic gas on the hot char in the first reaction zone at a decomposition temperature higher than the pyrolysis temperature, thereby producing gaseous decomposition products and composite carbonaceous materials, wherein the gaseous decomposition products contain hydrogen, and the composite carbonaceous materials contain char with carbon deposits thereon, or: (iv) the system further includes a second reaction zone and a second gas inlet, wherein the second reaction zone is configured for a decomposition process step, and the decomposition process step includes: after hot char is generated in the pyrolysis process step, directly receiving the hot char from the first reaction zone in the second reaction zone; introducing a feed of a hydrocarbon-rich organic gas into the second reaction zone through the second gas inlet; catalytically decomposing the hydrocarbon-rich organic gas on the hot char in the second reaction zone at a decomposition temperature higher than the pyrolysis temperature, thereby producing gaseous decomposition products and composite carbonaceous materials, wherein the gaseous decomposition products contain hydrogen, and the composite carbonaceous materials contain char with carbon deposits thereon.

[0031] In some embodiments, option (iii) applies.

[0032] In some embodiments, the first endothermic reactor is configured to fluidize solids in the first reaction zone during pyrolysis. In some embodiments, the first endothermic reactor is configured to continuously fluidize solids in the first reaction zone in a fluidizing stream comprising a non-oxidizing gas and / or a hydrocarbon-rich organic gas during pyrolysis and catalytic decomposition. The system may include one or more heat exchange conduits configured to transport combustion product gases from the combustion zone through the first reaction zone to heat the fluidized solids used.

[0033] In some embodiments, the first reaction zone is separated from the combustion zone by a heat transfer baffle, wherein heat can be transferred from the combustion zone to the first reaction zone through the heat transfer baffle. The heat transfer baffle may include a plurality of holes to allow the gas mixture to flow from the first reaction zone into the combustion zone through the holes.

[0034] When the terms "comprises", "comprising" and "containing" are used in the specification (including claims), they should be interpreted as specifying stated features, integers, steps or components, but not excluding the presence of one or more other features, integers, steps or components, or groups thereof.

[0035] As used herein, the terms "first," "second," "third," etc., in connection with various features of the disclosed apparatus are arbitrarily designated and are intended only to distinguish between two or more features that the apparatus may incorporate in various embodiments. These terms themselves do not imply any particular orientation or order. Furthermore, it should be understood that the presence of a "first" feature does not imply the presence of a "second" feature, the presence of a "second" feature does not imply the presence of a "first" feature, and so on.

[0036] Further aspects of the invention emerge from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Embodiments of the present invention will herein be described by way of example only with reference to the accompanying drawings, in which:

[0038] Figure 1 A system for sequential pyrolysis and carbon deposition in the same reaction zone according to an embodiment of the present invention is schematically depicted.

[0039] Figure 2 Systems for sequential pyrolysis and carbon deposition in different reaction zones according to other embodiments of the present invention are schematically depicted.

[0040] Figure 3 and Figure 3A An endothermic reactor configured for sequential pyrolysis and carbon deposition with a heat integrated burner according to an embodiment of the present invention is schematically depicted in side and plan view.

[0041] Figure 4 and Figure 4A An endothermic reactor configured for sequential pyrolysis and carbon deposition with a heat integrated burner according to other embodiments of the present invention is schematically depicted in side and plan view.

[0042] Figure 5 A process scheme for implementing the systems and methods of the present invention in a wastewater treatment plant is schematically depicted.

[0043] Figure 6 A process scheme for implementing the systems and methods of the present invention in combination with a plastic waste pyrolysis process is schematically depicted.

[0044] Figure 7 and Fig. 7A Schematically depicted are side and plan views of an endothermic reactor configured for sequential pyrolysis and carbon deposition with a heat integrated burner according to another embodiment of the present invention.

[0045] Figure 8 is a graph of the simulated effect of temperature on the equilibrium composition in the decomposition reactor when the feed gas consists of 1:1 CH4:N2.

[0046] Fig. 9 Graphs of methane conversion over the biochar catalyst produced in Example 2 during the first 30 minutes of catalytic methane decomposition for feeds of 10 wt%, 50 wt% and 90 wt% CH4 in N2 at (a) 700°C and (b) 900°C.

[0047] Fig.10 Graphs of methane conversion over the activated biochar catalyst produced in Example 3 during the first 30 minutes of catalytic methane decomposition for feeds of 10 wt%, 50 wt% and 90 wt% CH4 in N2 at (a) 700°C and (b) 900°C.

[0048] Fig.11 Graphs of methane conversion over the biochar catalyst produced in Example 2 for feeds of 10 wt%, 50 wt% and 90 wt% CH4 in N2 during 30 minutes to 6 hours of catalytic methane decomposition at (a) 700°C and (b) 900°C.

[0049] Fig.12 is a graph of the amounts of aliphatic, aromatic, and polycyclic aromatic hydrocarbon (PAH) fractions in the condensed pyrolysis oil after contacting the polymer pyrolysis vapors with hot biochar in Example 9 at 500, 700, and 900°C.

[0050] Fig.13 A transmission electron microscope image of carbon nanotubes produced by decomposing polymer pyrolysis vapors on hot biochar at 900° C. in Example 9 is shown. DETAILED DESCRIPTION

[0051] The present invention relates to a method for sequential pyrolysis and carbon deposition to produce a composite carbonaceous product. The method includes a pyrolysis process step, which includes pyrolyzing a pyrolyzable organic feed in a first reaction zone in the presence of a non-oxidizing gas to produce hot char and pyrolysis gas. The pyrolysis gas and the non-oxidizing gas are combined to form a gas mixture, and part or all of the gas mixture is discharged from the first reaction zone to a combustion zone. At least a portion of the pyrolysis gas is burned in the combustion zone, and the heat generated by the combustion is transferred from the combustion zone to the first reaction zone to provide at least a portion of the pyrolysis heat. The method further includes a decomposition process step, which includes directly contacting a hydrocarbon-rich organic gas with the hot char after the hot char is produced in the pyrolysis process step. The hydrocarbon-rich organic gas is catalytically decomposed on the hot char at a decomposition temperature higher than the pyrolysis temperature, thereby producing a gaseous decomposition product and a composite carbonaceous material, the gaseous decomposition product comprising hydrogen, and the composite carbonaceous material comprising char with carbon deposits thereon.

[0052] Figure 1 Depicted in is a system 100 according to an embodiment of the present invention. System 100 includes a reaction vessel having a first reaction zone 120, a feed inlet 122 for introducing an organic pyrolyzable feed 124, a gas inlet 126, a solid product outlet 128, and one or more gas outlets 130. Gas inlet 126 is supplied by a gas manifold that includes valves 132 and 134 that control the flow of non-oxidizing gas 136 and hydrocarbon-rich organic gas 138, respectively. Alternatively, valves 132 and 134 can control the addition of gases 136 and 138 to the first reaction zone through separate gas inlets. In some embodiments, reaction zone 120 is configured to fluidize solids in a gas stream introduced through inlet 126.

[0053] The system 100 further includes a combustion zone 140, which can be a separate reaction zone in the same reaction vessel as the first reaction zone 120 or in a different reaction vessel. The combustion zone 140 is provided with one or more feed gas inlets 142 for feeding a gas mixture 144 discharged from the first reaction zone 120, an oxidizing gas inlet 146 for introducing an oxygen-containing gas 148, and a combustion gas outlet 150 for discharging a combustion product gas 152.

[0054] The combustion zone 140 and the first reaction zone 120 are thermally integrated so that the heat 154 generated by the exothermic combustion reaction in the combustion zone 140 can be transferred to the first reaction zone 120 to drive the endothermic reaction therein. This can be accomplished in a variety of ways, including using a heat exchanger to preheat the feed gas entering the first reaction zone 120 or by using a heat transfer baffle between the reaction zone 120 and the combustion zone 140, as will be described in more detail below.

[0055] In use, by opening valve 132 while keeping valve 134 closed, non-oxidizing gas 136 such as nitrogen is fed to first reaction zone 120. Pyrolyzable organic feed 124 such as biosolids in particle form is fed to first reaction zone 124 to be pyrolyzed in the presence of non-oxidizing gas. Optionally, solid feed is fluidized in non-oxidizing gas stream. Pyrolysis is carried out to produce char and pyrolysis gas at conventional pyrolysis temperature such as 350°C to 900°C (depending on feed). In contrast to undesirable oxidation reactions, the low oxygen content in non-oxidizing gas 136 is advantageously conducive to the selectivity of desired pyrolysis cracking reaction. In this way, pyrolysis reaction is carried out, through a period of time sufficient to convert feed 124 into char, typically a solid residence time of 30 minutes to 6 hours. During this period, pyrolysis gas is combined with non-oxidizing gas 136 to form gas mixture 144, which is discharged from first reaction zone 120 through gas outlet 130.

[0056] The gas mixture 144 is fed into the combustion zone 140 through the feed gas inlet 142, where it is contacted with an oxygen-containing gas 148 (e.g., air) introduced through the oxidizing gas inlet 146. At least some of the combustible pyrolysis gas components in the gas mixture are combusted in the combustion zone 140 to form combustion product gases 152 and heat. The combustion product gases 152 are discharged from the combustion zone 140 through the combustion gas outlet 150. The heat 154 generated in the combustion is transferred from the combustion zone 140 to the first reaction zone 120 to provide all or part of the pyrolysis heat, thereby maintaining the desired pyrolysis reaction temperature.

[0057] In some embodiments, combustion in the combustion zone 140 is controlled so that all pyrolysis gases are substantially completely combusted. Oxygen-containing gas 148 is therefore added in excess so that the combustion product gas 152 contains a large amount of residual oxygen. The excess combustion heat generated in the combustion zone 140 can optionally be used to generate electricity or steam by conventional means. The combustion product gas 152 can then be sent directly for post-combustion cleanup and exhaust.

[0058] In other embodiments, the addition of oxygen-containing gas 148 to combustion zone 140 is limited so that a significant amount of residual unburned (or partially burned) components are present in combustion product gas 152. For example, the addition of gas 148, and therefore the degree of oxidation in combustion zone 140, can be a controllable variable for maintaining the pyrolysis temperature in reaction zone 120 within a desired range. In this case, the partially burned product gas 152 can be sent to another burner (not shown) where the remaining combustible products therein are burned to extinction in the presence of excess oxygen, optionally using the heat to generate electricity or steam.

[0059] After the selected time period for converting the organic feed 124 into char, valve 134 is opened to introduce a stream of hydrocarbon-rich organic gas 138 (e.g., biogas) into the first reaction zone. Optionally, the stream of non-oxidizing gas 136 is reduced or completely stopped at the same time. In a fluidized bed embodiment, the solids in the first reaction zone can therefore be continuously fluidized in the fluidizing stream of gas, ensuring continuous good mixing and heat transfer. The hot char in the reactor is preferably not substantially cooled during the change in gas feed composition, and in fact, the system 100 is operated, for example, by increasing the transfer heat 154 or by preheating the hydrocarbon-rich organic gas 138, to raise the temperature in the reaction zone 120 to the desired decomposition temperature before or after the introduction of the hydrocarbon-rich organic gas 138.

[0060] Thus, at least a portion of the hydrocarbons in the hydrocarbon-rich organic gas 138 are catalytically decomposed on the hot char in the first reaction zone 120 at a decomposition temperature that is higher than the pyrolysis temperature (or temperature range) used to produce char, thereby forming a carbon nanomaterial deposit on the char and producing hydrogen. Compared to pyrolysis, the elevated decomposition temperature can help form higher quality, more carbon-rich and crystalline materials and produce a higher yield of hydrogen. Without wishing to be bound by any theory, it is also believed that the carbon deposition reaction is assisted by the release of volatile components from the char itself, which occurs at the elevated temperature.

[0061] The decomposition process step may be performed at a temperature in excess of 600° C., such as 700° C. to 1000° C. The decomposition temperature may affect the rate of decomposition as well as the morphology of the carbon deposits. The inventors have found that at 700° C., methane decomposes on certain biochars to produce carbon nanofiber deposits, while at 900° C., methane or other organic gases decompose on biochar to produce carbon nanospheres or carbon nanotube deposits. Therefore, higher decomposition temperatures, such as above 800° C., or 900° C. and higher, may be particularly desirable. In contrast to undesirable oxidation reactions, the low oxygen content already present in the first reaction zone 120 and in the feed of the hydrocarbon-rich organic gas 138 advantageously favors the selectivity of the desired decomposition reaction.

[0062] The decomposition reaction is carried out in this manner for a period of time sufficient to form carbon deposits on the char. Due to the rapid deactivation rate, this period of time may be less than 5 hours, or less than 1 hour, such as less than 30 minutes. During this period, hydrogen and any other gaseous products combine with the residual gas 138 to form a gas mixture 144a, which is discharged from the first reaction zone 120 through the gas outlet 130.

[0063] The gas mixture 144a is fed into the combustion zone 140 through the feed gas inlet 142, where it is contacted with an oxygen-containing gas 148 (e.g., air) introduced through the oxidizing gas inlet 146. At least some of the combustible components in the gas mixture (including hydrogen) are combusted in the combustion zone 140 to form combustion product gas 152a and heat. The combustion product gas 152a is discharged from the combustion zone 140 through the combustion gas outlet 150.

[0064] The heat 154a generated in the combustion is transferred from the combustion zone 140 to the first reaction zone 120 to provide all or part of the decomposition heat, thereby maintaining the desired decomposition reaction temperature. As during the pyrolysis stage, the combustion can be controlled during the decomposition stage so that all combustible components in the gas mixture 144a are completely or partially burned. If the combustion is limited so that a large amount of residual hydrogen remains in the combustion product gas 152a, the hydrogen can be burned in a more downstream combustion unit or recovered as a hydrogen source.

[0065] Once the decomposition process step is complete, valve 134 may be closed and valve 132 opened. Composite carbonaceous product 146, which comprises char having carbon deposits thereon, is unloaded from the first reaction zone. A further amount of organic feed 124 is then added to initiate a new pyrolysis process step. The system 100 is thus operated by successive cycles of pyrolysis and carbon deposition.

[0066] Advantageously, the integrated mode of sequential pyrolysis and carbon deposition that can be implemented in system 100 provides a high degree of sequestration of total carbon from pyrolyzable organic feed and hydrocarbon-rich organic gas in a stable composite carbonaceous product. It is estimated that 30% to 50% of the total carbon can be sequestered. The composite material has a wide range of potential applications in soil improvement, soil remediation, water purification, environmental remediation, and advanced materials (e.g., for battery storage and catalysts).

[0067] It is also believed that sequential pyrolysis-carbon deposition involving the immediate use of hot char pyrolysis products as carbon deposition catalysts will provide higher hydrocarbon-rich gas conversion and / or higher quality carbon nanomaterial deposits in the decomposition reaction compared to the use of superficially similar preformed materials. Cooling of the pyrolytic char results in a permanent reduction in the size of the pores due to uneven condensation, solidification, nucleation and polymerization reactions. In addition, gaseous pyrolysis vapors can condense and react on the char surface to form an amorphous carbonaceous layer or tar layer and block the pores. This undesirable change is irreversible upon reheating.

[0068] A high degree of thermal efficiency is achieved in the system 100 because i) the intermediate char product is immediately used as a substrate for high temperature carbon deposition in subsequent reactions without extensive cooling, and ii) the combustion of pyrolysis gases and decomposition gases is used to maintain a continuous high temperature and drive the endothermic reaction in the reaction zone. Thus, the energy requirements of the system 100 are low and a favorable positive energy balance can actually be achieved, allowing the generation of electricity and / or steam.

[0069] System 100 has the further advantage of process simplicity, which is highly desirable in many environments where pyrolysis (particularly pyrolysis of biomass such as biosolids) is performed. A single reaction zone is used in a gas feed switching mode to sequentially perform pyrolysis and catalytic decomposition reactions without the need to transfer solids from one reaction zone to another. The conversion is easily controlled by simply introducing a hydrocarbon-rich organic gas feed into the reaction zone, while optionally reducing the initial feed of non-oxidizing gas accordingly.

[0070] Figure 2 Depicted in FIG. 1 is a pyrolysis system 200 according to another embodiment of the present invention. Like numbered objects of system 200 are as described herein with respect to Figure 1 The system 100 depicted in FIG.

[0071] However, in the system 200, the first reaction zone 220 is not necessarily configured for feeding a hydrocarbon-rich organic gas. Instead, the system 200 includes a second reaction zone 260, which can be a separate reaction zone in the same reaction vessel as the first reaction zone 220 or in a different reaction vessel. The second reaction zone 260 is provided with a char inlet 262, an organic gas inlet 264, a solids outlet 266, and one or more decomposition gas outlets 268. The system 200 is configured so that the hot char 246 can be discharged from the first reaction zone 220 into the second reaction zone 260. For example, the system 200 can include a rotary kiln or an augur-type reactor that transfers the pyrolyzable organic feed through the first reaction zone 220, where it is subjected to pyrolysis conditions in the presence of a non-oxidizing gas 236, for a suitable residence time, and into the second reaction zone 260.

[0072] System 200 also includes a combustion zone 240, which can be a separate reaction zone within the same reaction vessel as first reaction zone 220 or in a different reaction vessel. As described for system 100, combustion zone 240 and first reaction zone 220 are thermally integrated such that heat 254 generated by the exothermic combustion reaction in combustion zone 240 can be transferred to first reaction zone 120 to drive the endothermic pyrolysis reaction therein.

[0073] The system 200 may optionally include an additional combustion zone 280 configured to receive and combust the gas mixture exhausted from the second reaction zone 260. The combustion zone 280, if present, may optionally be heat integrated with the second reaction zone 260 such that heat 274 generated by the exothermic combustion reaction in the combustion zone 280 may be transferred to the second reaction zone 260 to drive the endothermic decomposition reaction therein.

[0074] In use, a pyrolyzable organic feed 224 is fed to the first reaction zone 220 and pyrolyzed in the presence of a non-oxidizing gas 236 to form hot char and pyrolysis gases. The system 200 can be operated in a continuous mode so that the feed 224 can be fed continuously. The pyrolysis gases are combined with the non-oxidizing gas 236 to form a gas mixture 244, which is discharged from the first reaction zone 220 into the combustion zone 240. At least a portion of the pyrolysis gases are then burned in the combustion zone 240 as described for the system 100, and the heat is used to drive the endothermic pyrolysis reaction in the first reaction zone 220.

[0075] After a suitable residence time for the conversion of the organic feed 224, the hot char is discharged into the second reaction zone 260 through the solid product outlet 228 and the char inlet 262. The hot char is preferably not substantially cooled during the transfer process, and the transfer can optionally be carried out continuously. A hydrocarbon-rich organic gas 238, such as biogas or plastic pyrolysis gas, is fed to the second reaction zone 260, where at least a portion of the hydrocarbons in the gas are catalytically decomposed on the hot char at a decomposition temperature higher than the pyrolysis temperature (or temperature range) in the first reaction zone 220 where char is produced. Thus, a carbon nanomaterial deposit is formed on the char and hydrogen is produced. The decomposition can be carried out at a temperature exceeding 600°C, preferably exceeding 650°C, such as 700°C to 1000°C. Hydrogen and any other gaseous products are combined with the residual gas 238 to form a gas mixture 272, which is discharged from the second reaction zone 260 through the decomposition gas outlet 268. After a suitable residence time in the second reaction zone 260, a composite carbonaceous product 270 is unloaded from the second reaction zone, which includes char with carbon deposits thereon. Although the system 200 can be operated continuously, it is still a process for sequential pyrolysis and carbon deposition because the char is first formed in the pyrolysis process step and then the carbon deposit is deposited thereon in the decomposition process step.

[0076] The gas mixture 272 may optionally be sent to a burner 280 to burn the combustible components therein, and the heat of combustion 274 may optionally be transferred to the second reaction zone 260 to drive the endothermic decomposition reaction therein. Alternatively, the second reaction zone 260 may be heated by alternative means, and hydrogen may be recovered from the gas mixture 168.

[0077] Like system 100, system 200 also provides an integrated mode of sequential pyrolysis and carbon deposition, which sequesters a large amount of carbon from two carbon-containing feeds in a stable carbonaceous composite. Similarly, system 200 also provides thermal efficiency due to the transfer of hot carbon intermediates without substantial cooling and the heat integration between combustion and at least pyrolysis reactions. In addition, system 200 provides the potential advantage of continuous operability. Continuous operation is advantageous in terms of process stability, particularly in larger scale units.

[0078] In a variation of process 200, a pyrolysis gas stream 244a containing a portion of the pyrolysis gas product mixed with a non-oxidizing gas 236 is discharged from the first reaction zone 220 and transported outward to form at least a portion of the hydrocarbon-rich organic gas 238, which is fed to the second reaction zone 260. There, at least a portion of the hydrocarbons in the pyrolysis gas are catalytically decomposed on the hot charcoal at a decomposition temperature higher than the pyrolysis temperature in the first reaction zone 220, thereby forming a carbon nanomaterial deposit on the charcoal and producing hydrogen. The elevated decomposition temperature is conducive to the desired decomposition reaction to form a high-quality crystalline carbon deposit, preferably including carbon nanomaterials. In contrast, the pyrolysis temperature may be too low to allow the pyrolysis gas to decompose significantly during the pyrolysis process step. Also in this embodiment, a portion of the pyrolysis gas is sent to the combustion zone 240 via the gas mixture 244 and burned in the combustion zone to drive the endothermic pyrolysis reaction.

[0079] Further details of each processing unit in the system of the present invention and the steps of the method of the present invention will now be described.

[0080] Pyrolysis

[0081] The method of the present invention involves the step of pyrolyzing a pyrolyzable organic feed in the presence of a non-oxidizing gas in a reaction zone, the reaction zone being configured for a high temperature endothermic reaction. The solid feed is pyrolyzed at a high temperature, i.e., a pyrolysis temperature, to produce hot char and pyrolysis gas. The non-oxidizing gas typically has a low oxygen content, thus providing a suitable environment for the pyrolysis cracking reaction to occur, thereby producing high-quality char (solid carbonaceous material). The pyrolysis gas and the non-oxidizing gas are combined in the reaction zone to form a gas mixture, which is then discharged for combustion.

[0082] The non-oxidizing gas is suitably non-oxidizing to provide a favorable environment for the occurrence of pyrolysis reaction. It can be an inert gas such as N2, CO2, Ar and mixtures thereof. Therefore, the non-oxidizing gas should generally have low oxygen (O2) content, such as less than 4 % by weight, or less than 2 % by weight, or less than 1 % by weight, because the desired pyrolysis reaction selectivity is obtained by the endothermic cracking reaction without the presence of an oxidant. However, it is not necessarily required to exclude oxygen completely. For example, the non-oxidizing gas can include the recycled flue gas from combustion as at least one component, which contains some residual oxygen. In certain embodiments, the advantages provided by using this gas (for example, by heat integration and / or reducing the consumption of external inert gas supply) can exceed the disadvantages of introducing some oxygen into pyrolysis.

[0083] In some embodiments, a non-oxidizing gas flows into and through the reaction zone during pyrolysis. This flow can contribute to the positive pressure difference between the pyrolysis reaction zone and the downstream combustion zone. This can advantageously facilitate the forward flow of the gas mixture into the combustion zone while preventing or substantially limiting the undesirable reverse flow of the oxidizing gas from the combustion zone to the pyrolysis reaction zone. In embodiments where the organic feed is fluidized in the pyrolysis reaction zone, the solid organic feed and the resulting char can be fluidized in the non-oxidizing gas stream. This can advantageously improve mixing and heat transfer in the pyrolysis reaction zone.

[0084] The present invention is applicable to a wide range of solid pyrolyzable organic feeds, including 1) waste, such as plastics, tires or any other solid hydrocarbon-containing waste or blends thereof; 2) biomass, such as wood, straw, rice husks, coffee husks and any other type of biomass material; 3) coal, such as anthracite, bituminous coal, sub-bituminous coal, lignite or any other coal blend; 4) dried algae; 5) biosolids or sewage sludge; 6) food waste; 7) any type of solid organic or inorganic waste from humans; 8) biomass waste, such as green waste or agricultural residues or blends thereof; and 9) mixed inorganic and organic wastes, such as municipal solid waste. For the avoidance of doubt, the term "pyrolyzable organic feed" as used herein refers to any feed containing at least a portion of organic carbonaceous material from any source, including synthetic, mineral and bio-based sources, which can be pyrolyzed to produce pyrolysis products.

[0085] Industrial pyrolysis reactions can be carried out at 350-900°C, depending on the feed and the target product, and the pyrolysis step of the present invention can be operated within this temperature range. For example, where the feed is waste plastic, relatively low temperatures such as 350°C to 550°C may be suitable. Where the feed is biomass, such as biosolids from sewage, relatively high reaction temperatures such as 500°C to 900°C may be preferred. Pyrolysis of the pyrolyzable organic feed can occur within a temperature range in the pyrolysis process step, for example, by a temperature ramp with a final hold temperature. The pyrolysis temperature in this case refers to the temperature or temperature range at which pyrolysis of the pyrolyzable organic feedstock to charcoal primarily occurs.

[0086] The pyrolysis reaction generally produces a product mixture, which contains a solid carbonaceous product (charcoal), an oil (condensable) portion, and a gas (non-condensable) portion when cooled. The portion of gas, oil, and charcoal produced as primary products during the pyrolysis process varies with the heating rate, pyrolysis temperature, and feedstock, and the pyrolysis process can be divided into three process types accordingly: slow pyrolysis, fast pyrolysis, and flash pyrolysis. Slow pyrolysis generally produces more charcoal, fast pyrolysis produces more oil portions, and flash pyrolysis produces more gas portions. It will be understood that when produced at the high reaction temperature in the pyrolysis zone, the oil product portion of the pyrolysis reaction is substantially in vapor form. Therefore, where the present disclosure refers to the production of "pyrolysis gas" or its further reaction by combustion, the "pyrolysis gas" will be understood to include a non-condensable gas portion and a vaporized (but condensable) oil portion.

[0087] The pyrolysis organic feed can be continuously, periodically or initially added to the pyrolysis reaction zone. Suitable residence time of the solid in the pyrolysis reaction zone can be 10 minutes to one hour, for example 25 to 30 minutes. Suitable pressure in the pyrolysis reaction zone can be 1 to 10 bar, for example 1 to 3 bar.

[0088] Pyrolysis is an endothermic reaction and therefore requires energy input, namely the heat of pyrolysis (or enthalpy). At least a portion of the required energy input is provided by the combustion of combustible components (including pyrolysis gas products) in the gas mixture sent from the pyrolysis reaction zone to the combustion zone. As will be described in more detail below, the pyrolysis reactor and the combustion reactor are therefore thermally integrated.

[0089] In some embodiments, an activation additive may be added to the pyrolysis reaction zone before or during the pyrolysis reaction. The activation additive results in an increase in the surface area of ​​the product char, for example relative to a hot char produced under the same conditions without the additive. Suitable additives may include, but are not limited to, metal hydroxides such as KOH and NaOH. Optionally, the activation additive may be mixed with or added together with the pyrolyzable organic feed.

[0090] The system according to the present invention comprises at least one reactor for carrying out endothermic reaction. The reactor for pyrolysis comprises a reaction zone, one or more gas inlets and one or more gas outlets, and is configured to feed non-oxidizing gas to the reaction zone through at least one gas inlet and receive pyrolyzable organic feed in the pyrolysis reaction zone. Solid feed can be fed to the reaction zone through the solid feed inlet. A gas mixture containing pyrolysis gas and non-oxidizing gas is discharged from the reaction zone through the gas outlet.

[0091] In some embodiments, the reactor is a fluidized bed reactor or a packed bed reactor. In the case of a fluidized bed reactor, the reactor can be configured to fluidize the solid in the non-oxidizing gas stream. The reactor is configured to carry out the endothermic pyrolysis reaction, and therefore heat is flowed into the reaction zone. As will be described in more detail below, the endothermic reactor is therefore integrated with the combustion reactor heat to allow the combustion heat generated therein to drive the pyrolysis reaction.

[0092] combustion

[0093] The method of the present invention involves the steps of discharging a gas mixture from a pyrolysis reaction zone to a combustion zone and burning at least a portion of the pyrolysis gas in the combustion zone. The heat generated by the combustion of the pyrolysis gas is transferred from the combustion zone to the pyrolysis reaction zone to provide at least a portion of the pyrolysis heat.

[0094] The system of the present invention includes at least one burner including a combustion zone, one or more feed gas inlets for receiving a gas mixture discharged from a first reaction zone to the combustion zone, an oxidizing gas inlet for introducing an oxygen-containing gas into the combustion zone, and a combustion product gas outlet for discharging combustion flue gas. The burner is thermally integrated with the endothermic reactor so that heat generated by the combustion pyrolysis gas is transferred from the combustion zone to the first reaction zone to provide at least a portion of the pyrolysis heat.

[0095] The gas mixture from pyrolysis can be the only source of combustible products introduced into the burner during the pyrolysis phase, at least during continuous operation (i.e. after startup). Optionally, however, the burner can be configured to feed and burn another fuel source (e.g. natural gas or biogas). This may be particularly useful during startup to achieve the appropriate temperature in the combustion zone or pyrolysis zone, or to maintain the desired temperature during lower pyrolysis gas production rates.

[0096] The oxygen-containing gas is most conveniently air, but other sources of oxygen are not excluded.For thermal efficiency, the oxygen-containing gas may be preheated, for example by indirect contact with hot flue gases.

[0097] The combustion zone of the burner is operated at a temperature at which the combustible components in the gas mixture will undergo a combustion reaction. The operating temperature may therefore be 700° C. to 1300° C., or 700° C. to 1100° C., such as 800° C. to 1000° C., for example about 900° C. During continuous operation, such a temperature may be maintained by the exothermic oxidation reaction occurring in the combustion zone.

[0098] In some embodiments, the burner is operated to provide substantially complete combustion of all combustible products in the combustion zone. Therefore, excessive oxygen is added, and high combustion temperature can be conducive. Sufficient oxygen can be added so that the combustion product gas contains at least 5% by weight of oxygen, or at least 10% by weight of oxygen. This condition is conducive to the high conversion rate of combustible products. The excess combustion heat generated in the combustion zone can be used to generate electricity or steam. This can be completed using a heat exchanger inside the combustion zone or thermally coupled to the combustion zone, or can be completed using the heat carried in the discharged combustion gas downstream of the burner.

[0099] In other embodiments, the burner is operated to provide only partial combustion of the combustible components fed to the combustion zone. The oxygen supply can be limited so that a large amount of residual unburned (or partially oxidized) components are present in the combustion product gas. The degree of combustion can be controlled by adjusting the oxygen feed, so that the temperature in the pyrolysis reaction zone is maintained within the target range. The residual combustible products in the combustion product gas can be burned in the burner downstream, optionally generating electricity or steam.

[0100] Heat integrated pyrolysis and combustion

[0101] The endothermic reactor and combustor are heat integrated so that the heat of combustion provides part or substantially all of the heat of pyrolysis. The manner of heat integration is not considered to be particularly limited. For example, hot flue gases from combustion can be used to heat the endothermic reaction zone using a heat exchanger.

[0102] In some embodiments, the pyrolysis reaction zone and the combustion zone are separated by a heat transfer baffle that allows heat to flow from the combustion zone operating at a higher temperature to the pyrolysis zone operating at a lower temperature. As will be described below, the baffle may be impermeable or contain a plurality of holes.

[0103] Figure 3 and Figure 3A Depicted in FIG. 1 is an integrated endothermic reactor-combustor according to an embodiment of the present invention. The endothermic reactor includes a reaction zone 342 for pyrolysis, which is configured to receive a pyrolyzable organic feed 352 and a non-oxidizing gas 332. The flow of the non-oxidizing gas is regulated by a valve 334. The combustor includes a combustion zone 362 adjacent to the pyrolysis reaction zone 342, and an impermeable metal partition 301 defines a boundary between the pyrolysis zone and the combustion zone. Figure 3 Side view and Figure 3AAs schematically depicted in the plan view in FIG. , the pyrolysis reaction zone is cylindrical and the combustion zone is the annular space between the outer wall 302 and the cylindrical partition 301 .

[0104] In use during the pyrolysis process step, an organic feed 352 and a non-oxidizing gas 332 are fed to a pyrolysis reaction zone 342. Optionally, a solid feed is fluidized in a non-oxidizing gas. The organic feed is pyrolyzed at a pyrolysis temperature of 350°C to 900°C to produce pyrolysis gas and char. The pyrolysis gas is combined with the non-oxidizing gas to form a gas mixture 356, which is discharged from the pyrolysis reaction zone and transported to a combustion zone 362 via an external conduit 303. There, the combustible components in the gas mixture are at least partially burned with oxygen introduced into the air feed 370. As described herein, the combustion product gas 372 is discharged from the combustion zone and can be sent to a further burner, energy recovery or post-combustion treatment. A portion of the combustion heat is transferred from the combustion zone 342 through the metal baffle 301 by conduction, thereby driving the endothermic pyrolysis reaction in the reaction zone 342. The metal baffle 301 can be configured to increase heat transfer, such as by fins, etc.

[0105] Figure 4 and Figure 4A Depicted in FIG. 1 is an integrated endothermic reactor-combustor according to other embodiments of the present invention. The endothermic reactor includes a reaction zone 442 for pyrolysis, which is configured to receive a pyrolyzable organic feed 452 and a non-oxidizing gas 432. The combustor includes a combustion zone 462 adjacent to the pyrolysis reaction zone 442, and a heat transfer metal partition 401 defines a boundary between the pyrolysis zone and the combustion zone. Figure 4 Side view and Figure 4A As schematically depicted in the plan view in FIG. 4 , the pyrolysis reaction zone is cylindrical and the combustion zone is the annular space between the outer wall 402 and the cylindrical partition 401. The partition 401 is preferably made of a thermally conductive material (typically metal) and includes a plurality of holes 405 that provide fluid communication between the pyrolysis reaction zone and the combustion zone.

[0106] In use during the pyrolysis process step, an organic feed 452 and a non-oxidizing gas 432 are fed to a pyrolysis zone 442. Optionally, a solid feed is fluidized in the non-oxidizing gas. The organic feed is pyrolyzed at a temperature of 350° C. to 900° C. to produce pyrolysis gases and char. The pyrolysis gases are combined with the non-oxidizing gas to form a gas mixture 456, which is discharged from the pyrolysis reaction zone by flowing through the hole 405 into the combustion zone 462. There, the combustible components in the gas mixture are at least partially burned with oxygen introduced into the air feed 470. As described herein, the combustion product gas 472 is discharged from the combustion zone and can be sent to a further burner, energy recovery or post-combustion treatment.

[0107] The distribution and size of the baffle 401, and in particular the holes 405 therein, are configured to maintain a pressure differential between the reaction zone 442 and the combustion zone 462. The flow rate of the resulting gas mixture through the holes is sufficient to prevent or appropriately limit the entry of oxygen from the combustion zone into the pyrolysis zone.

[0108] As the higher temperature is maintained in the combustion zone, heat is transferred from the combustion zone 462 to the pyrolysis reaction zone 442 through the baffle 401. Heat transfer occurs through conduction through the thermally conductive baffle material and convection through the holes 405, thereby providing a portion of the heat required to drive the endothermic pyrolysis reaction in the pyrolysis reaction zone. The degree of combustion in the combustion zone 462 can be controlled to adjust the temperature in the pyrolysis zone. For example, the control can be responsive to the temperature measured in the endothermic pyrolysis zone so as to maintain a constant or range-limited reaction temperature. In practice, the temperature in the combustion zone may be about 50 to 300°C, or 100 to 200°C higher than the temperature in the pyrolysis reaction zone.

[0109] Heat transfer through the baffles 401 is highly efficient due to the combined convection and conduction heat transfer modes. In addition, the heat of combustion transferred from the combustion zone to the pyrolysis zone is generally sufficient to provide the pyrolysis heat, thereby eliminating the need to input external energy into the process. Other benefits such as reduced weight and cost are also envisioned, such as by using simple mesh baffles. The complexity and / or operability of the system may also be improved because there is no need to pipe hot, unstable pyrolysis gases from outside the pyrolysis reaction zone to the combustion zone.

[0110] The integrated pyrolyzer-combustor reaction system is described in more detail in the applicant's co-pending PCT application PCT / AU2019 / 050548, which is incorporated herein by reference. The pyrolyzer and combustor of the present invention can be configured and operated according to any embodiment disclosed therein.

[0111] When the endothermic reactor is a fluidized bed reactor, the combustion zone can be extended by heat transfer ducts or other conduits that transport the hot flue gas through the fluidized bed in the pyrolysis reaction zone. This arrangement provides a higher heat transfer surface area (through the ducts) between the pyrolysis zone and the combustion zone, thereby improving the overall heat integration between the pyrolysis reaction and the combustion reaction. In this case, the heat transfer mode can be dominated by an additional particle convection term (in addition to gas convection, radiation and conduction) at moderate temperatures. The higher heat transfer from the particle convection term is mainly attributed to the increased particle motion through the heat transfer wall (i.e., the duct).

[0112] Figure 7 and Fig. 7ADepicted in FIG is an integrated endothermic reactor-combustor according to this embodiment of the invention. The endothermic reactor includes a pyrolysis zone 942 configured to receive a pyrolyzable organic feed 952 via a feed line 903 and fluidize the feed and resulting char product in a non-oxidizing gas 932. The gas 932 is distributed by a distribution plate 904 so that the solids are fluidized in a bed 906.

[0113] The burner includes a combustion zone 962 adjacent to the pyrolysis reaction zone 942, and the heat transfer metal partition 901 defines the boundary between the pyrolysis zone and the combustion zone. Figure 7 Side view and Fig. 7A As schematically depicted in the plan view in FIG. 9 , the pyrolysis reaction zone is cylindrical and the combustion zone is the annular space between the outer wall 902 and the cylindrical partition 901. The partition 901 is preferably made of a heat conductive material (usually metal) and includes a plurality of holes 905 at the top of the partition that provide fluid communication between the pyrolysis reaction zone and the combustion zone. Air 970 is fed to the burner through the air inlet 910. As shown in FIG. Fig. 7A As seen in FIG. 9 , the inlet 910 is configured to feed an air jet 970 tangentially into the annular combustion zone 962. Thus, in use, a cyclone or vortex-like flow is generated near the outer wall 902, as depicted by arrows 909. The combustion reaction in the combustion zone 962 can therefore occur primarily near the outer wall 902, and therefore away from the partition 901. The integrated reaction system includes a plurality of heat transfer conduits 912 that direct the hot combustion flue gas from the combustion zone 962 through the fluidized bed 906 in the pyrolysis reaction zone 942, and ultimately exit the reactor system through the outlet 916 as a combustion product gas 972. Fig. 7A Three such conduits are depicted in a spaced-apart configuration in FIG, but it will be understood that one, two, or more than three conduits may be used.

[0114] In use during the pyrolysis process step, an organic feed 952 and a non-oxidizing gas 932 are fed to a pyrolysis reaction zone 942, and the solid feed is fluidized by the non-oxidizing gas in a fluidized bed 906. The organic feed is pyrolyzed at a temperature of 350° C. to 750° C. to produce pyrolysis gases and hot char. The pyrolysis gases are combined with the non-oxidizing gas to form a gas mixture 956, which is discharged from the pyrolysis reaction zone by flowing through holes 905 into a combustion zone 962. There, the combustible components in the gas mixture are at least partially combusted with oxygen introduced into the air feed 970. The hot combustion gases flow downwardly in the combustion zone (in the form of a vortex), then upwardly through the heat transfer conduit 912 and out through an outlet 916 (see Figure 7 As described herein, the combustion product gas 972 can be sent to further burners, energy recovery, or post-combustion processing.

[0115] Heat from the combustion reaction is thus transferred to the pyrolysis reaction zone through the baffles 901 and through the walls of the heat transfer conduits 912. Heat transfer occurs by conduction through the thermally conductive baffle and conduit materials, convection through the holes 905, and by additional particle convection terms, as described herein. At least a portion of the heat required to drive the endothermic pyrolysis reaction is thus provided in the pyrolysis zone with excellent heat transfer efficiency.

[0116] In a further variant of the integrated endothermic reactor-burner, the pyrolysis is carried out in a plurality of heat exchange pipes which are spaced apart, arranged vertically and pass through the combustion zone. The pyrolyzable organic feed is fluidized in the heat exchange pipes by an upward flow of non-oxidizing gas. The heat exchange pipes comprise a tube wall having a plurality of holes (which constitute a heat transfer baffle), preferably above the level of the fluidized bed, through which a mixture of pyrolysis gas and non-oxidizing gas flows into the combustion zone for burning a portion of the pyrolysis gas. This shell-and-tube arrangement of the burner and the pyrolysis zone provides excellent heat integration between the combustion reaction and the pyrolysis reaction.

[0117] Catalytic decomposition

[0118] The method of the present invention involves a decomposition process step, which includes directly contacting a hydrocarbon-rich organic gas with the hot charcoal after the hot charcoal is produced in the pyrolysis process step. The hydrocarbon-rich organic gas is catalytically decomposed on the hot charcoal at a decomposition temperature higher than the pyrolysis temperature, thereby producing a gaseous decomposition product and a composite carbonaceous material, the gaseous decomposition product including hydrogen, and the composite carbonaceous material comprising charcoal with carbon deposits thereon. As used herein, the hydrocarbon-rich organic gas is in the gas phase during the decomposition process and can be condensable or non-condensable under ambient temperature conditions. The catalytic decomposition of a range of hydrocarbons can be considered to be a chemical vapor deposition (CVD) process, or in the specific case of a methane-rich feedstock, the process can be considered to be a catalytic methane decomposition (CMD) process.

[0119] In some embodiments, the hydrocarbon-rich organic gas is substantially free of pyrolysis gases or components thereof produced in the pyrolysis process step, which are sent to combustion. As will be explained below, this process configuration provides an opportunity to upgrade another hydrocarbon-containing stream (e.g., biogas or plastic pyrolysis gas).

[0120] In the case of methane-rich feedstocks such as biogas, the methane decomposition reaction will be catalyzed on the hot charcoal surface according to equation (1):

[0121] CH4→C+2H2ΔH 298K =74.52 kJ / mol (1)

[0122] A similar reaction occurs for larger hydrocarbon molecules, such as those produced by pyrolysis of plastic (polymer) materials. In this case, a mixture of hydrocarbon and hydrogen gaseous decomposition products is formed. The inventors have experimentally found that methane or polypropylene pyrolysis product gas (mainly containing linear C1-C 10 hydrocarbons), thereby forming carbon nanomaterial deposits on the carbon.

[0123] The catalytic decomposition reaction occurs directly on the hot char after it is produced by pyrolysis. As used herein, "directly after..." means that the process steps are continuous because the hot char is immediately contacted with the hydrocarbon-rich organic gas after it is produced in pyrolysis. Although some loss of char temperature between process steps is not excluded, the char remains hot throughout its formation and subsequent use for carbon deposition. In particular, the char is not cooled to ambient conditions nor stored between formation and use as a catalyst.

[0124] In some embodiments, between the generation of hot char in pyrolysis and the catalytic decomposition of hydrocarbon-rich organic gas on the hot char, the hot char is continuously maintained at a temperature above 300° C., or above 400° C., or above 600° C., such as above 700° C. In some embodiments, the time between the start of pyrolysis of the pyrolyzable organic feedstock and the start of decomposition of the hydrocarbon-rich organic gas on the resulting char product does not exceed 1 hour.

[0125] The sequential mode of pyrolysis and carbon deposition used in the present invention provides many advantages. In particular, the decomposition catalyst is generated in situ in the process, so there is no need to purchase or separately produce the catalyst. This is particularly advantageous in environments where pyrolysis is already attractive, such as in wastewater treatment plants where pyrolysis is used to treat biosolids. In addition, since the hot char products of pyrolysis already possess a large amount of process heat when used as carbon deposition catalysts, a high degree of thermal efficiency is obtained. In addition, the immediate use of the hot char pyrolysis products can provide improved catalyst performance, i.e., higher conversion of hydrocarbon-rich organic gases to carbon deposits and / or higher quality carbon nanomaterial deposits, compared to the use of superficially similar preformed materials. Due to uneven condensation, solidification, nucleation and polymerization reactions, the cooling of pyrolytic char leads to morphological changes, including a permanent reduction in the size of the pores. In addition, gaseous pyrolysis vapors can condense and react on the char surface to form a carbonaceous layer or tar layer and block the pores. This undesirable change is irreversible upon reheating.

[0126] The hydrocarbon decomposition reaction is endothermic and requires input energy, namely the heat of decomposition (or enthalpy). In some embodiments, at least a portion of this energy is provided by the combustion of gaseous decomposition products (including hydrogen) and any residual unreacted hydrocarbons in the feed.

[0127] High reaction temperatures (typically in the range of 600°C to 1100°C) are required to produce significant conversion rates. In some embodiments, catalytic decomposition is carried out at a decomposition temperature of at least 700°C, such as at least 800°C. The decomposition temperature is higher than the pyrolysis temperature at which the precursor char is produced in the pyrolysis process step. Compared with pyrolysis, the elevated temperature in the decomposition can contribute to the formation of higher quality, more carbon-rich and crystalline materials, and produce a higher yield of hydrogen. In contrast, amorphous coke that hinders the porosity of the char can be formed at typical pyrolysis temperatures. Without wishing to be bound by any theory, it is also believed that the carbon deposition reaction that forms carbon nanomaterials is assisted by the release of volatile components from the char itself due to further pyrolysis that occurs due to the increase in temperature. In some embodiments, the catalytic decomposition temperature is no more than 200°C, or no more than 100°C, higher than the temperature during pyrolysis.

[0128] It will be appreciated that carbon deposition should generally be carried out in an inert or reducing atmosphere, wherein the carbon deposition reaction predominates over the exothermic oxidation reaction.Thus, the hydrocarbon-rich organic gas generally has a low oxygen content, for example less than 4 wt%, or less than 1 wt%, or substantially zero.

[0129] The hydrocarbon deposition reaction produces gaseous decomposition products including hydrogen. In the case of a methane-rich feed, hydrogen can be the main gaseous product. As will be described below, the gaseous decomposition products can be optionally burned to provide decomposition heat. However, optionally, the method of the present invention can include the steps of separating the gaseous decomposition products and any residual hydrocarbon-rich organic gas from the composite carbonaceous material and separating hydrogen from the gas composition. Hydrogen can therefore be a product of the process. The recovered hydrocarbons can be recycled for further decomposition reactions.

[0130] Decomposition reaction zone

[0131] As already described herein, for example with reference to Figure 1 , the catalytic hydrocarbon decomposition reaction can be carried out in the same endothermic reaction zone where the char is produced. The char is thus continuously produced under pyrolysis conditions and once produced is exposed to a hydrocarbon-rich organic gas to decompose it in the same reaction zone. Suitable configurations for this method may include fluidized bed and packed bed reactors.

[0132] Alternatively, for example, refer to Figure 2 As described, the char can be directly transferred from the pyrolysis reaction zone where the char is produced to a different reaction zone to contact and decompose the hydrocarbon-rich organic gas. Non-limiting examples of suitable configurations for the method may include a rotary kiln or an augur-type reactor that transfers the pyrolyzable organic feed through the pyrolysis reaction zone and into the different decomposition reaction zones.

[0133] In each case, the heat of reaction of the endothermic decomposition reaction can be provided by a burner that is thermally integrated with the corresponding endothermic reaction zone. The reaction system is also configured to allow the temperature to be increased between consecutive pyrolysis and decomposition process steps. This can be achieved, for example, by controlling the corresponding burner to increase the heat flow from the decomposition reaction zone and / or by preheating the hydrocarbon-rich organic gas before contacting with the hot char.

[0134] Figure 3 and Figure 3A Depicted in FIG. 1 is an integrated endothermic reactor-combustor according to an embodiment of the present invention. The system and the method in which hot char is produced from a pyrolyzable organic feed 352 in a reaction zone 342 using heat input from an adjacent combustion zone 362 have been described. Once the hot char is formed in the reaction zone 342, a catalytic decomposition reaction is initiated by introducing a hydrocarbon-rich organic gas 336 into the reaction zone by opening valve 338. Optionally, valve 334 is simultaneously closed to reduce or stop the flow of non-oxidizing gas 332. If the char is fluidized in the reactor, the fluidization can therefore continue with minimal interruption despite changes in the composition of the fluidizing gas. For example, immediately before or after the introduction of the hydrocarbon-rich organic gas 336 into the reaction zone, the temperature in the reaction zone 342 is raised to a decomposition temperature that is higher than the pyrolysis temperature between the pyrolysis step and the decomposition step. At this elevated temperature in the range of 700° C. to 1100° C., hydrocarbons in the feed gas 338 are catalytically decomposed on the surface of the hot char in the reaction zone 342, producing gaseous decomposition products including hydrogen and forming carbon deposits such as carbon nanomaterials on the char.

[0135] Gaseous decomposition products and unreacted hydrocarbons in the feed are discharged from the reaction zone 342 and transported to the combustion zone 362 through the external pipeline 303. There, the combustible components including hydrogen are at least partially combusted with oxygen introduced into the air feed 370. The combustion product gas 372 is discharged from the combustion zone and can be sent to further burners, energy recovery or post-combustion processing. A portion of the combustion heat is transferred from the combustion zone 342 through the metal partition 301 by conduction, thereby driving the endothermic carbon decomposition reaction in the reaction zone 342. Therefore, the decomposition heat is provided to the reaction zone 342 in a manner substantially similar to the pyrolysis heat during the pyrolysis stage.

[0136] After the carbon deposition reaction is complete, the flow of hydrocarbon-rich organic gas 336 may be replaced with the flow of non-oxidizing gas 332 and the composite carbonaceous product 354 unloaded.

[0137] Similarly, in Figure 4 and Figure 4AIn the system depicted in FIG. 4 , after valve 438 is opened to introduce hydrocarbon-rich organic gas 436 and thereby initiate decomposition and raise the temperature to an elevated decomposition temperature, gaseous decomposition products and unreacted hydrocarbons in the feed are discharged from reaction zone 442 to combustion zone 462 via aperture 405. Heat generated by the combustion of the combustible components, including hydrogen, is transferred back to reaction zone 442 by conduction through the thermally conductive baffle material and convection through aperture 405. The advantages of this arrangement in the carbon deposition stage are similar to those described for the pyrolysis stage.

[0138] Similarly, in Figure 7 and Fig. 7A In the system depicted in , the decomposition process step can be initiated after the pyrolysis process step (as described herein) by introducing the hydrocarbon-rich organic gas into the endothermic reaction zone 942 through the distribution plate 904. The hot char is thus maintained continuously fluidized in the fluidized bed 906, and the temperature of the char is raised to the desired decomposition temperature. The hydrocarbon-rich organic gas is catalytically decomposed on the hot char, and the gaseous decomposition products and unreacted hydrocarbons in the feed are discharged from the reaction zone 942 to the combustion zone 962 through the holes 905. There, the combustible components in the gas mixture are at least partially combusted with oxygen introduced into the air feed 970, and the hot combustion gases are transported through the endothermic reaction zone in the heat exchange conduit 912. As described for the pyrolysis process step, the heat from the combustion reaction is thus transferred to the endothermic reaction zone through the partition 901 and through the wall of the transfer conduit 912. After the decomposition process step, the composite carbonaceous material 954, which includes the char having carbon deposits thereon, is unloaded through the outlet 907.

[0139] It will be appreciated that similar heat integration methods of endothermic decomposition and exothermic combustion may be used when the char is transferred to a second reaction zone for a decomposition reaction.

[0140] Composite carbonaceous products

[0141] The catalytic decomposition reaction produces a carbon deposit on the char previously formed in the pyrolysis. The method of the present invention therefore produces a composite carbonaceous material comprising char and a carbon deposit formed thereon. The carbon deposit is typically a crystalline carbon-rich material and may advantageously be in the form of a carbon nanomaterial, such as carbon nanofibers, carbon nanospheres, carbon nanotubes or other crystalline carbon nanostructures. As used herein, a carbon nanomaterial refers to a solid carbon material structure having at least one nanometer (1-100nm) size. This composite material has a wide range of potential applications in soil improvement, soil remediation, water purification, environmental remediation, and advanced materials (e.g., for battery storage and catalysts).

[0142] The inventors have experimentally shown that biochar, for example, produced from biosolids or other biomass, can be used to catalyze the formation of a variety of carbon nanostructures. One method of controlling the morphology of carbon nanomaterials is to control the temperature of the hydrocarbon decomposition reaction.

[0143] The composite carbonaceous material may contain at least 5 wt % carbon deposits, such as at least 10 wt % carbon deposits, or at least 20 wt % carbon deposits. Higher deposition temperatures may be beneficial for increasing yields. Surprisingly, the inventors have found that at 900° C., up to 25 wt % carbon deposits may be deposited on biosolids derived biochar.

[0144] It is believed that a particular advantage of the present invention is that carbon from the pyrolyzable organic feed and the hydrocarbon-rich organic gas is sequestered in a stable composite carbonaceous product. In some practical use cases, it is estimated that 30% to 50% of the total carbon in both feeds can be sequestered, which is a very favorable result compared to other options of incinerating one or both feeds.

[0145] Process for pyrolysis of biosolids and decomposition of biogas on charcoal

[0146] The method and system of the present invention can be applied to wastewater treatment plants. Figure 5 A process scheme 500 for such an application is depicted in . Sewage-derived sludge 550 is fed to and treated in a conventional wastewater treatment plant 575. The treatment produces a biosolids stream 524 and a methane-rich biogas stream 538. The biosolids stream 524 is pyrolyzed in an endothermic reactor 520 in the presence of a non-oxidizing gas 536 to form hot biochar. The resulting gas mixture 544, comprising pyrolysis gases and inert gases, is exhausted to a combustion reactor 540 where it is combusted with air 548. The heat of combustion drives the pyrolysis reaction in the reactor 520. The hot flue gas 552 is used to generate electricity.

[0147] The hot charcoal product of pyrolysis is then contacted successively with biogas stream 538 in the depicted reactor 520 or in a second reactor. At a decomposition temperature higher than the pyrolysis temperature for producing hot charcoal, the methane in the biogas is catalytically decomposed to form hydrogen and carbon nanomaterial deposits on the charcoal. A portion of the carbon dioxide in the biogas can also be converted into carbon and carbon monoxide. A gas mixture 544a comprises hydrogen, unreacted biogas 538 and any carbon monoxide and is discharged into a combustion reactor 540 where it is burned with air 548. The combustion heat drives the decomposition reaction in the reactor 520. In the process, an inert and stable carbonaceous composite material 570 is produced, which comprises carbon sequestered from biosolids and biogas feed streams. Optionally, a portion of the hydrogen in the gas mixture 544a (or residual hydrogen in the flue gas 552) can be separated and recovered as a product of the process.

[0148] It will be understood that the system 500 process equipment for pyrolysis, combustion and carbon decomposition can be according to any embodiment disclosed herein, such as reference Figure 1 , Figure 2 , Figure 3 and Figure 3A ,and Figure 4 and Figure 4A As described.

[0149] Process of pyrolysis of biosolids on charcoal and decomposition of waste plastic pyrolysis gases

[0150] In another application, the method and system of the present invention are used to process municipal waste or polymer (plastic) waste. In some embodiments, the unrecyclable waste plastic part is pyrolyzed to produce a hydrocarbon-rich organic gas stream (plastic pyrolysis gas). The feed gas can then be catalytically decomposed on (bio) char produced by biomass or other organic waste streams, and the residual condensable pyrolysis gas is optionally condensed and recovered as pyrolysis oil.

[0151] Figure 6 A process scheme 600 for such an application is depicted in . A biomass stream 624, such as municipal waste biomass, is pyrolyzed in an endothermic reactor 620 in the presence of a non-oxidizing gas 636 to form hot biochar. The resulting gas mixture 644, comprising pyrolysis gases and inert gases, is exhausted to a combustion reactor 640 where it is combusted with air 648. The heat of combustion drives the pyrolysis reaction in the reactor 620. The hot flue gas 652 can be used to generate electricity.

[0152] Waste polymer 650, such as non-recyclable plastic municipal waste, is fed separately to a conventionally designed plastic pyrolysis unit 675, where it is pyrolyzed in the presence of an inert gas 626 at a suitable pyrolysis temperature, such as 400 to 600° C. A solid pyrolysis residue 628 is discharged after a suitable residence time. After hot pyrolysis char is produced by pyrolysis of the biomass stream 624, hot plastic pyrolysis gas 638 (including condensable and non-condensable vapor components) is then fed into the reactor 620 where the pyrolysis char is produced (as depicted) or in a second reactor to contact it successively with the pyrolysis char. At a decomposition temperature above the pyrolysis temperature at which the hot char is produced, methane and / or other hydrocarbon components in the pyrolysis gas 638 are catalytically decomposed to form hydrogen and carbon nanomaterial deposits on the char.

[0153] After a suitable residence time for conversion on hot charcoal, a gas mixture 644a containing hydrogen and residual pyrolysis gas 638 is discharged to a condenser 680, where pyrolysis oil 682 is condensed and discharged. The pyrolysis oil 682 can advantageously have a low polycyclic aromatic hydrocarbon (PAH) content, particularly a lower PAH content than when the gas 638 is condensed without contacting the charcoal. Experimental findings show that polycyclic aromatic hydrocarbons (PAH) or their precursors present in the plastic pyrolysis gas can be catalytically converted on pyrolysis charcoal, thereby reducing the presence of PAH components in the condensed pyrolysis oil. Optionally, a portion of the hydrogen can also be separated and recovered as a product of the process. The non-condensable gas portion 684 can be sent to a combustion reactor 640, where it is burned with air 648. The heat of combustion drives the decomposition reaction in the reactor 620. Thus, an inert and stable carbonaceous composite material 670 is produced in the process, which contains carbon sequestered from the biomass and plastic pyrolysis gas feed streams.

[0154] Example

[0155] The present invention is described with reference to the following examples.It will be understood that these examples are intended to illustrate and not to limit the invention described herein.

[0156] Example 1. Thermodynamic calculations

[0157] Thermodynamic calculations of the methane decomposition reaction were performed to determine the effect of temperature and to allow comparison of equilibrium values ​​with experimental values. Thermodynamic calculations were performed using a Gibbs reactor run in Aspen Plus software. A temperature range of 300 to 1000 °C at atmospheric pressure was chosen in order to understand the relationship between the equilibrium flow rates of the mixture and the products. 100 kmol h -1 The total flow rate of is used as the inlet flow rate of the Gibbs reactor, and the outlet equilibrium flow rate is calculated by minimizing the Gibbs free energy of the reactor under isothermal conditions. The gas consists of a mixture of CH4 and N2 (10 wt%, 50 wt% and 90 wt% methane, the remainder being nitrogen).

[0158] Figure 8 The effect of temperature on the equilibrium of a gas composed of 1:1 CH4 and N2 (i.e. 50 wt% CH4) is shown. At temperatures below 300°C, the equilibrium CH4 flow rate is proportional to the inlet CH4 flow rate (100 kmol h -1 ) is similar to that of the methane decomposition reaction, since the methane decomposition reaction is very endothermic and requires relatively high temperatures. The CH4 product flow rate drops rapidly above 300°C, and only above 700°C does the conversion exceed 90%, so the H2 and carbon product flows increase. As expected, N2 remains unchanged due to its inert properties.

[0159] Example 2. Preparation of biochar

[0160] The biosolids were obtained from a wastewater treatment plant. The proximate and final analyses of the biosolids are shown in Table 1, and the chemical composition is shown in Table 2.

[0161] Table 1.

[0162]

[0163] a Values ​​based on dry weight. b Value based on dry ash free basis

[0164] Table 2.

[0165]

[0166] Biochar was produced by pyrolyzing biosolids using a vertical fluidized bed quartz reactor with an inner diameter of 27 mm and a reaction zone height of 680 mm. The distributor plate was placed at 320 mm from the bottom to ensure that the gas was preheated before entering the reaction zone. The fluidized bed was heated using an electric furnace. In each experiment, 40 g of biosolids were loaded into the reactor and nitrogen was purged through the fluidized bed reactor at a flow rate of 1000 ml / min to ensure an inert atmosphere before heating. The pyrolysis run was performed using a heating rate of 35°C / min to provide slow pyrolysis conditions, and the conditions were maintained isothermally at a final temperature of 700°C for 60 min. A nitrogen flow was fed during the heating process, which provided an apparent velocity of 3.69 times the minimum fluidization velocity to produce a bubbling fluidization state.

[0167] Example 3. Preparation of activated biochar

[0168] Activated carbon was prepared by chemical activation of the biochar produced in Example 2 by NaOH. Initially, 3 g of biochar was mixed with 40 mL of 4 M NaOH, and the mixture was shaken intermittently at room temperature for 2 hours to impregnate the NaOH. The excess solution was removed by vacuum filtration, and the treated biochar was dried overnight in a 105 ° C oven. The biochar sample was then heated from room temperature to 800 ° C at a heating rate of 4 ° C / min in a quartz tube furnace under inert conditions (300 mL / min N2 flow) and maintained at 800 ° C for 1 hour. The furnace was then turned off and the sample was cooled under a N2 flow of 100 mL / min. The sample was then treated with 2L deionized (DI) water, followed by 200mL0.1M HCl (200mL) solution. The final washing step was performed with DI water until the pH of the filtrate was found to be 7.0. The washed sample was dried overnight in a 105 ° C oven before use.

[0169] Example 4. Characterization of biochar

[0170] The biochars and activated biochars of Examples 2 and 3 were characterized by Fourier transform infrared (FT-IR spectroscopy) and scanning electron microscopy (SEM) using a FEI Verios 460L instrument. The BET surface area and pore structure properties were determined by a Micromeritics physical adsorption apparatus at 77 K using N2 adsorption.

[0171] The FT-IR results showed that the biochar produced in Example 2 had significantly higher amounts of surface oxygen species than the activated biochar produced in Example 3. By comparing the surface oxygen species at about 1002 cm -1 This is evident from the FT-IR band at 400 nm attributed to the carboxylic acid stretching mode.

[0172] The SEM results qualitatively show that the activated carbon has a highly porous active structure (i.e., a large number of smaller pores) compared to the non-activated carbon. This is consistent with the BET results shown in Table 3, which show that the surface area of ​​the activated carbon is almost twice that of the non-activated carbon. The pore size of the activated carbon was also found to be much smaller, close to the average diameter reported for methane molecules (i.e., 0.38 nm).

[0173] Table 3.

[0174] sample Biochar (Example 2) Activated carbon (Example 3) <![CDATA[Total surface area (m 2 / g)]]> 90.97±5.82 180.54±11.19 <![CDATA[Micropore volume (cm 3 / g)]]> 0.028±0.002 0.018±0.001 Pore ​​size (nm) 1.3±0.083 0.38±0.024

[0175] Example 5. Catalytic methane decomposition reaction

[0176] Catalytic methane decomposition (CMD) experiments were conducted in a fixed bed reactor with an inner diameter of 27 mm and a length of 650 mm, heated by a three-zone electric furnace. In each test, 1 g of fresh catalyst (biochar or activated biochar produced in Examples 2 and 3) was loaded into the reactor, and 10, 50, and 90 wt% CH4 in N2 was passed through the reactor at a flow rate of 100 ml / min, with a weight hourly space velocity (WHSV) of 6 L g -1 h -1 The reaction was carried out under isothermal conditions at different temperatures (700°C and 900°C) for 6 hours (initial heating rate was 35°C / min). The post-reaction gases were collected in Tedlar bags every 5 minutes for the first 30 minutes and every 30 minutes thereafter. The gases were analyzed using a gas chromatograph.

[0177] In blank experiments without carbon catalyst, the conversion of methane at both 700 °C and 900 °C was found to be negligible, indicating that the uncatalyzed reaction rate was extremely low under the reaction conditions.

[0178] In the catalytic reaction, GC analysis showed no CO2 signal in all cases, indicating that methane was decomposed in one step to produce H2 and carbon without CO2. Trace CO signals were obtained in some cases, probably due to the reaction of oxygen-containing functional groups in biochar. Methane conversion was calculated by the area under the curve of the methane peak area, and hydrogen yield (%H2) can be calculated using Equation 1, because other product gases can be ignored.

[0179]

[0180] Fig. 9 Methane conversion during the first 30 minutes of CMD for the biochar catalyst produced in Example 2 at (a) 700°C and (b) 900°C for feeds of 10 wt%, 50 wt% and 90 wt% CH4 in N2 is shown. A high initial methane conversion is observed during the first 30 minutes and drops off quickly. Higher conversion values ​​are observed for lower concentrations of methane (i.e., 10% CH4 in N2). Significantly higher conversions are obtained at 900°C compared to 700°C.

[0181] Fig.10 Equivalent results are shown for the activated biochar catalyst produced in Example 3 at (c) 700°C and (d) 900°C. The activated carbon has a slightly higher initial methane conversion but a higher deactivation rate compared to the non-activated biochar.

[0182] Fig.11 Shown at (a) 700°C and (b) 900°C over the entire 6-hour reaction process Fig. 9 The results are a continuation of the results described in (for the non-activated biochar produced in Example 2). After the first 30 minutes, the deactivation rate was significantly lower. The long-term methane conversion activity of the biochar was better than that of the activated biochar (results not shown).

[0183] The conversion rate obtained in the experiment is much lower than the result predicted by the thermodynamic equilibrium calculation in Example 1. This is consistent with the following hypothesis: methane cracking on carbon is a surface reaction and is more dependent on the diffusion of methane from the gas phase to the catalytic carbon surface as the methane concentration increases.

[0184] At the end of the reaction, the carbonaceous product material was recovered and the total amount of carbon deposits was calculated by comparing the initial mass and the final mass. The results are shown in Table 4 below. At higher temperatures, higher amounts of carbon deposits were produced on the surfaces of biochar and activated carbon. At constant temperature, carbon deposits increased with increasing methane partial pressure (i.e., concentration). Due to the lower deactivation rate, the total carbon deposits produced by inactivated biochar were slightly higher than those of activated carbon at all temperatures and methane concentrations studied.

[0185] Table 4.

[0186]

[0187] Example 6. Characterization of composite biochar with CMD carbon deposits

[0188] The carbonaceous product materials of the CMD reaction in Example 5 were characterized by BET measurements, SEM, and transmission electron microscopy (TEM) using a JEOL-1010 microscope. For TEM analysis, the sample was first finely ground, dispersed in isopropyl alcohol (IPA), and then a drop of the solution was dropped on a classic TEM carbon grid.

[0189] The BET results are shown in Table 5. The surface area of ​​all materials was significantly reduced compared to the starting carbon (as reported in Example 4), consistent with the formation of carbon deposits on the carbon surface.

[0190] Table 5.

[0191]

[0192] SEM and TEM analysis revealed the formation of crystalline carbon nanomaterials. Short-length carbon nanofiber (CNF) aggregates with uniform diameter of 10-100 nm were found to be deposited on the biochar and activated carbon surfaces at 700 °C. The CNFs were found to be highly bent and randomly entangled together. Carbon nanospheres (CNS) with a diameter of about 40 nm were found to be deposited on the biochar and activated carbon surfaces at 900 °C. Some CNS aggregation was noted due to the small diameter.

[0193] Example 7. Catalytic biogas decomposition reaction

[0194] Catalytic decomposition experiments of synthetic biogas were conducted in the fixed bed reactor described in Example 5. 5 g of fresh catalyst (biochar produced in Example 2) was loaded into the reactor, and a gas mixture containing 60 wt % CH4 and 40 wt % CO2 was passed through the reactor at a flow rate of 100 ml / min, with a weight hourly space velocity (WHSV) of 1.2 L g -1 h -1 The reaction was carried out at 900°C isothermally for 6 hours (initial heating rate was 35°C / min). The post-reaction gas was collected in a Tedlar bag every 5 minutes for the first 30 minutes and every 30 minutes thereafter. The gas was analyzed using a gas chromatograph.

[0195] A methane conversion of 60-70% was initially obtained, which dropped to 40-45% conversion after 6 hours. Hydrogen (H2) was detected in the gaseous products. Excellent CO2 conversion was also obtained under the reducing conditions of the decomposition process, with an initial conversion of 90-95% and a drop to 65-70% conversion after 6 hours. The expected reduction product carbon monoxide (CO) was detected together with H2 in the gaseous products. Analysis of the composite carbonaceous products by SEM and TEM again indicated the formation of carbon nanospheres.

[0196] Example 8. Catalytic pyrolysis gas decomposition reaction

[0197] The reactor was charged with granular polypropylene (0-600 micron particle size). The reactor was purged with nitrogen, the nitrogen flow rate was set to 100 ml / min, and then heated to a temperature of 500°C at an initial heating rate of 35°C / min. The polypropylene was thus pyrolyzed to form vaporized hydrocarbon species, mainly linear C1 to C 10 molecular.

[0198] 1 g of fresh biochar catalyst (as produced in Example 2) was again charged into the fixed bed reactor described in Example 5. A hydrocarbon-rich gas stream containing polypropylene pyrolysis products was then passed over the char under isothermal conditions at different temperatures (700°C and 900°C) for 6 hours (initial heating rate of 35°C / min).

[0199] The carbonaceous product material is recovered at the end of the reaction. The product consists of carbon nanomaterial deposits on the charcoal, including carbon nanofibers and carbon nanospheres.

[0200] Example 9. Catalytic pyrolysis gas decomposition reaction

[0201] The decomposition of plastic pyrolysis gases on biochar was investigated in more detail in this example. The biochar catalyst was pre-made by pyrolyzing woody biomass (sawdust) in a muffle furnace at 700° C. The biochar thus produced was sieved to produce a fraction with a particle size in the range of 1-100 microns (excluding nano- and 100-300 micron fractions).

[0202] A quartz tube reactor (27 mm inner diameter; 1000 mm length) was placed in an electric heating furnace with three independent heating zones. Waste polypropylene copolymer (PPC) was washed, air-dried and chopped into small pieces, and 10 g of PPC was placed in the second (middle) reaction zone. 10 g of biochar was placed in the third reaction zone of the quartz tube reactor. The first zone remained empty and was used to preheat the N2 gas flow flowing through the reactor.

[0203] Sequential pyrolysis and carbon deposition reactions were then performed by flowing N2 (100 mL / min) through the quartz reactor (in the order: zone 1-zone 2-zone 3) and heating the reaction zones independently. The temperature of PPC pyrolysis in zone 2 and the temperature of hydrocarbon vapor decomposition in zone 3 were controlled using two different electrical controllers, with an initial ramp rate of 35°C / min for both zones to reach the target holding temperature. In all experiments, PPC pyrolysis was performed at a holding temperature of 500°C, while the effect of hydrocarbon vapor decomposition temperature was studied in the holding temperature range of 500°C to 900°C.

[0204] During the reaction, the condensable products were recovered in the condenser downstream of the reactor, and the non-condensable gases were analyzed using an online micro GC analyzer. After the reaction was completed, the carbon material in the third zone was recovered after cooling to room temperature under a continuous N2 flow. The condensed products were analyzed by GC-MS. The results are shown in Table 6.

[0205] Table 6.

[0206]

[0207] In the absence of a downstream steam decomposition catalyst, the product composition of PPC pyrolysis at 500 °C contains non-condensable gases and condensable liquid products in a ratio of about 3:1 (w / w). In the experiment where the PPC pyrolysis vapors were passed through the biochar, it was clear that the reaction of the pyrolysis vapors on the biochar catalyst was negligible at 500 °C and slow at 700 °C. At 900 °C, the transition to gaseous products was obvious, and a large amount of solid carbon was deposited on the biochar.

[0208] Analysis of the product gases showed that H2 was formed at 700°C and 900°C biochar temperatures, but not at 500°C or in the absence of biochar catalyst. Other gaseous products included methane (increased amounts at higher biochar temperatures), ethane, ethylene, propane, propylene, and isobutylene.

[0209] The condensed liquid product was divided into three components by GC-MS analysis: aliphatic, aromatic and polycyclic aromatic hydrocarbons (PAH). Aliphatic includes alkanes and alkenes, aromatic mainly consists of benzene and its derivatives and o-xylene, and PAH includes perylene, naphthalene, indene and its derivatives. The composition of the liquid part produced in the experiment is shown in Fig.12 (where the composition at 500°C was almost identical to that obtained in the absence of the biochar catalyst). In addition to carbon formation, the biochar catalyst also significantly inhibited the formation of PAH components in the liquid product (reduced from 36% to 1% at 900°C). PAH compounds are undesirable components of pyrolysis oils, and thus the process of the present invention advantageously provides a method for reducing their presence in liquid products of pyrolysis processes, for example for beneficiation of polymer wastes.

[0210] The solid product in the reactor zone 3 was recovered and analyzed by SEM and TEM. Uniformly distributed filamentous carbon nanomaterials were formed at 700°C and 900°C. Fig.13 The TEM micrograph depicted shows carbon nanotubes formed at 900°C that are almost defect-free and have a smooth surface.

[0211] Example 10. Use of carbon composite biochar with CMD carbon deposits as absorbent

[0212] The use of biochar and carbon composite biochar with carbon deposits as absorbents for per- and polyfluoroalkyl substances (PFAS) was investigated and compared with commercial activated carbon. In each experiment, 1 g of absorbent was contacted with 50 ml of water contaminated with PFAS compounds for 48 hours. The PFAS components were perfluorohexane sulfonic acid (PFHX), perfluorooctane sulfonic acid (PFOS), and perfluorooctanoic acid (PFOA). The test results are shown in Table 6. It is clear that the carbon composite provides an increased absorption capacity for PFAS compounds compared to its biochar precursor and has the potential to replace the high-cost absorbents used commercially in this application.

[0213] Table 6.

[0214]

[0215] Those skilled in the art will appreciate that the invention described herein is susceptible to changes and modifications other than those specifically described. It should be understood that the invention includes all such changes and modifications that fall within the spirit and scope of the invention.

Claims

1. A method of sequential pyrolysis and carbon deposition to produce a composite carbonaceous product, the method comprising: a pyrolysis process step comprising pyrolyzing a pyrolyzable organic feed in a first reaction zone in the presence of a non-oxidizing gas at a pyrolysis temperature to produce hot char and pyrolysis gas, wherein the pyrolysis gas and the non-oxidizing gas combine to form a gas mixture; discharging the gas mixture from the first reaction zone to a combustion zone and combusting at least a portion of the pyrolysis gases in the combustion zone, wherein heat generated by the combustion of the pyrolysis gases is transferred from the combustion zone to the first reaction zone to provide at least a portion of the pyrolysis heat; and a decomposition process step, comprising contacting a hydrocarbon-rich organic gas with the hot char directly after the hot char is produced in the pyrolysis process step, wherein the hydrocarbon-rich organic gas is catalytically decomposed on the hot char at a decomposition temperature higher than the pyrolysis temperature, thereby producing a gaseous decomposition product and a composite carbonaceous material, wherein the gaseous decomposition product comprises hydrogen, and the composite carbonaceous material comprises char having carbon deposits thereon, wherein at least 90% of the hydrocarbon-rich organic gas is provided from a source external to the pyrolysis process step that produces the hot char, wherein the decomposition temperature is at least 600°C, and The carbon deposits include carbon nanomaterials.

2. The method of claim 1 further comprises separating a gas composition comprising gaseous decomposition products and any residual hydrocarbon-rich organic gas from the composite carbonaceous material and burning at least a portion of the combustible components therein, wherein the heat generated by the combustion of the combustible components is transferred to provide at least a portion of the decomposition heat.

3. The method of claim 1, wherein the pyrolyzable organic feed comprises biosolids from sewage.

4. The method according to claim 1, wherein between generating hot char in the pyrolysis process step and catalytically decomposing the hydrocarbon-rich organic gas on the hot char in the decomposition process step, the hot char is continuously maintained at a temperature above 300°C.

5. The method according to any one of claims 1 to 4, wherein the pyrolysis in the pyrolysis process step and the catalytic decomposition in the decomposition process step are carried out sequentially in the first reaction zone.

6. The process of claim 5, wherein when the hydrocarbon-rich organic gas stream is introduced, the flow of the non-oxidizing gas to the first reaction zone is reduced or stopped.

7. The process of claim 5, wherein the solids in the first reaction zone are continuously fluidized in a fluidizing stream comprising a non-oxidizing gas and / or a hydrocarbon-rich organic gas during the pyrolysis and catalytic decomposition.

8. The method according to any one of claims 1 to 4, wherein the first reaction zone is separated from the combustion zone by a heat transfer partition, and wherein the heat transferred from the combustion zone to the first reaction zone to provide at least a portion of the pyrolysis heat is transferred through the heat transfer partition.

9. The method of claim 8, wherein the heat transfer baffle comprises a plurality of holes through which the gas mixture flows from the first reaction zone to the combustion zone.

10. The method of claim 8, wherein the catalytic decomposition in the decomposition process step is carried out in a first reaction zone, and wherein a gas composition comprising gaseous decomposition products and any residual hydrocarbon-rich organic gas is discharged to a combustion zone to combust combustible components in the combustion zone, wherein heat generated by the combustion of the combustible components is transferred through a heat transfer baffle to provide at least a portion of the decomposition heat.

11. The method according to any one of claims 1 to 4, wherein the hydrocarbon-rich organic gas does not contain pyrolysis gas or components thereof produced in a pyrolysis process step.

12. The method according to any one of claims 1 to 4, wherein the hydrocarbon-rich organic gas is selected from biogas and plastic pyrolysis gas.

13. The method according to any one of claims 1 to 4, further comprising: pyrolyzing the polymer to produce hot pyrolysis vapors, wherein the hot pyrolysis vapors form at least a portion of the hydrocarbon-rich organic gas; separating a gas composition comprising the gaseous decomposition products and any residual hydrocarbon-rich organic gas from the composite carbonaceous material; and The gas composition is cooled to condense the pyrolysis oil portion.

14. The method according to any one of claims 1 to 4, wherein the decomposition temperature is 700°C to 1000°C.

15. The method of any one of claims 1 to 4, wherein the decomposition temperature is at least 700°C.

16. The method of any one of claims 1 to 4, wherein the decomposition temperature is at least 800°C.

17. The method of any one of claims 1 to 4, wherein the decomposition temperature is no more than 200°C higher than the pyrolysis temperature.

18. The method of any one of claims 1 to 4, further comprising introducing an activation additive into the first reaction zone prior to or during pyrolysis, wherein the activation additive causes the surface area of ​​the hot char to increase relative to the hot char produced in the absence of the additive.

19. The method of any one of claims 1 to 4, wherein the composite carbonaceous material comprises at least 5 wt% carbon deposits.

20. The method according to any one of claims 1 to 4, wherein the carbon nanomaterial is selected from carbon nanofibers, carbon nanospheres and carbon nanotubes.

21. The method of any one of claims 1 to 4, wherein at least 30% of the total carbon in the pyrolyzable organic feed and hydrocarbon-rich organic gas is sequestered in the composite carbonaceous material.

22. The method of any one of claims 1 to 4, further comprising separating a gas composition comprising the gaseous decomposition products and any residual hydrocarbon-rich organic gas from the composite carbonaceous material, and separating hydrogen from the gas composition.

23. The method of any one of claims 1 to 4, further comprising generating electricity and / or steam from heat produced by combustion of combustible components in the pyrolysis gas and / or the gas composition comprising the gaseous decomposition products and any residual hydrocarbon-rich organic gas.

24. A method according to any one of claims 1 to 4, wherein all of the hydrocarbon-rich organic gas is provided from a source external to the pyrolysis process step that produces the hot char.

Images