Hydrothermal oxidation process

Abstract

The present disclosure provides methods and apparatus for hydrothermal oxidation of organic matter. The method includes pumping organic matter in an aqueous stream into a first section of a reactor, pumping a gaseous oxidant into the first section of the reactor, maintaining conditions in the reactor at a pressure in a range from about 2 bar to about 250 bar and a temperature in a range from about 100°C to about 373°C, subjecting the organic matter in the aqueous stream and the gaseous oxidant to high intensity mixing in the first section of the reactor, transferring the organic matter in the aqueous stream and the gaseous oxidant to a second or subsequent substantially horizontally arranged tubular section of the reactor, wherein at least some of the organic matter containing aqueous stream is in a liquid phase and at least some of the gaseous oxidant is in a gas phase, and maintaining a rate of the liquid phase traveling through at least a portion of the second or subsequent section of the reactor at a maximum velocity of about 0.1 m / sec or maintaining a Reynolds number of the liquid phase traveling through at least a portion of the second or subsequent section of the reactor in a range from about 0 to about 10,000.

Description

Technical Field

[0001] This invention relates to hydrothermal oxidation methods, and more particularly to continuous methods for the hydrothermal oxidation of organic matter. The invention also relates to hydrothermal oxidation reactors. Background Technology

[0002] Wet oxidation is an industrial process applied to organic matter suspended in a predominantly aqueous environment. Typically, it involves oxidative conversion, where the organic matter undergoes a chemical reaction with an oxidant such as oxygen (O2). The conversion occurs at temperatures below the critical point of water (373°C); therefore, the process is also known as subcritical wet oxidation. During wet oxidation, the system pressure is maintained above the vapor saturation point of water at a given process temperature, to accommodate the overpressure of the oxidant, which is typically applied in gaseous form (e.g., air or pure oxygen). The oxidation reaction leads to the degradation of the organic matter, with carbon dioxide and water as the final products. Depending on the system temperature and processing time, a range of intermediate components may form, including short-chain fatty acids such as acetic acid and formic acid.

[0003] Wet oxidation is used industrially to treat wet organic waste containing contaminants such as microplastics and pathogens. This conversion breaks down suspended organic solids present in the waste, producing a final product containing an inorganic ash fraction and an aqueous fraction, which can be readily treated using conventional biological wastewater treatment systems. The benefits of successfully treating wet organic waste include reducing the amount of organic solids that need to be disposed of in landfills or land applications, and extracting value from the final product. One example of such value extraction could be utilizing the aqueous fraction to generate methane gas as an energy product. Therefore, wet oxidation enhances the opportunities for sustainable waste management practices and a bio-based economy.

[0004] There are issues associated with wet oxidation. Wet oxidation and hydrothermal oxidation processes are typically operated under highly turbulent conditions at high temperatures and pressures. However, it has been observed that even under such conditions, wet oxidation is not a rapid process. Some components of organic matter are more difficult to oxidize than others, and such reactions may follow multiple reaction pathways before breaking down the organic matter into smaller carbon molecules. This can depend on the feedstock and the type of mineral ash and nitrogenous material utilized.

[0005] Oxygen is the most commonly used oxidant in wet oxidation processes, typically added as pure oxygen or air. Under these conditions, the process is characterized as a gas-liquid system. Due to the poor solubility of oxygen in water, gas-liquid mass transfer may be the rate-limiting step in the oxidation reaction. Gas-liquid mass transfer, among other factors, is controlled by the intensity of the mixing interactions occurring within a given system. Therefore, the mixing turbulence of the fluids within the system is an important consideration in the design of wet oxidation systems.

[0006] The reaction cycle in wet oxidation typically takes 10 to 120 minutes, and the reaction kinetics are relatively slow compared to supercritical water oxidation. Supercritical water oxidation is another hydrothermal process used for the destruction of organic waste, with reaction times measured in seconds.

[0007] Current wet oxidation practices typically involve large-scale deployments of continuous flow reactors, using fully mixed reactor system configurations such as continuous stirred tank reactors (CSTRs) or bubble columns. Because they are fully mixed, such reactors operate at a single rate, controlled by the reactant concentration in the mixing vessel. Coupled with the possibility of reactions being limited by gas-liquid mass transfer, these reactor designs are characterized by vigorous mechanical or hydraulic mixing to ensure a good interface between the gaseous oxidant and the liquid environment in which the reaction occurs.

[0008] Hybridization is an energy-intensive process and presents significant operational challenges in high-temperature and high-pressure systems (e.g., wear of mechanical seals in the hybridizing elements). Reducing these energy and operational cost requirements will provide new impetus for the deployment of this technology. Therefore, innovation in hydrothermal oxidation methods and equipment remains essential.

[0009] One possible option involves using a plug flow reactor configuration. Plug flow reactors (PFRs) can be deployed within tubular reactor configurations. They offer advantages in reaction kinetics and therefore require smaller processing volumes. Furthermore, the main building elements (i.e., tubes or pipes) offer the possibility of achieving construction efficiency by sourcing tubes or pipes as standardized materials.

[0010] However, tubular PFRs may struggle to provide the turbulent environment of CSTRs or bubble columns. The primary means of improving mixing within the tube is to reduce its diameter. However, to maintain the total PFR volume (crucial for achieving wet oxidation), reducing the diameter necessitates increasing the tube length. Given the quadratic relationship between diameter reduction and length increase, this can present logistical and cost challenges in tubular PFR design. This may explain the near-total dominance of CSTRs and bubble columns in wet oxidation system design.

[0011] Improvements in turbulent mixing in tubular PFR designs can also be achieved through methods such as adding static mixers that disrupt the flow patterns through the tubes. However, these methods involve additional components of the reactor design, thus increasing the system's investment and maintenance costs.

[0012] This invention provides a useful alternative to known wet oxidation methods and reactors. Summary of the Invention

[0013] This disclosure provides a continuous method for the hydrothermal oxidation of organic matter, comprising:

[0014] Organic matter in the aqueous stream is pumped into the first section of the reactor.

[0015] The gaseous oxidant is pumped into the first section of the reactor.

[0016] The conditions in the reactor are maintained at a pressure ranging from about 2 bar to about 250 bar and a temperature ranging from about 100°C to about 373°C.

[0017] In the first section of the reactor, the organic matter and gaseous oxidant in the aqueous stream are subjected to high-intensity mixing.

[0018] The organic matter and gaseous oxidant in the aqueous stream are transferred to a second or subsequent substantially horizontally arranged tubular section of the reactor, wherein at least some of the aqueous stream containing the organic matter is in the liquid phase and at least some of the gaseous oxidant is in the gaseous phase.

[0019] as well as

[0020] The rate of the liquid phase traveling through at least a portion of the second or subsequent section of the reactor is maintained at a maximum velocity of approximately 0.1 m / s, or

[0021] The Reynolds number of the liquid phase traveling through at least a portion of the second or subsequent section of the reactor is maintained at about 0 to about 10,000.

[0022] In one aspect, the liquid phase containing organic matter travels through the tubular reactor section at a maximum speed of approximately 0.05 m / s.

[0023] In one aspect, the liquid phase containing organic matter travels through the tubular reactor section at a maximum speed of approximately 0.02 m / s.

[0024] In one aspect, the Reynolds number of the liquid phase in the tubular reactor section is from about 0 to about 4000.

[0025] The Reynolds number of the liquid phase in the tubular reactor section can also be from about 0 to about 400.

[0026] In one aspect, the pressure in the reactor is maintained in the range of about 10 bar to about 200 bar, and the temperature is maintained in the range of about 160°C to about 350°C.

[0027] In one aspect, the pressure in the reactor is maintained in the range of about 20 bar to about 200 bar, and the temperature is maintained in the range of about 200°C to about 350°C.

[0028] In one aspect, the pressure in the reactor is maintained in the range of about 30 bar to about 120 bar, and the temperature is maintained in the range of about 220°C to about 300°C.

[0029] In one aspect, the liquid and gas phases exist as separate or segregated layers in at least a portion of a tubular reactor section. In another aspect, the liquid and gas phases exist as a sequence of liquid slugs separated by gas slugs. In yet another aspect, the liquid and gas phases exist as a mixture of laminar and slug flows.

[0030] In one aspect, the gas phase moves at a speed equal to or greater than that of the liquid phase.

[0031] In one aspect, the ratio of gas phase velocity to liquid phase velocity is in the range of about 1.01:1.00 to about 10:1.

[0032] In one aspect, the ratio of gas phase velocity to liquid phase velocity is in the range of about 1.1:1 to about 10:1.

[0033] In one aspect, the ratio of gas phase velocity to liquid phase velocity is approximately 3:1 to approximately 6:1.

[0034] In one aspect, the ratio of gas phase velocity to liquid phase velocity is approximately 2:1 to approximately 5:1.

[0035] In one aspect, the gaseous oxidant is oxygen.

[0036] In one aspect, the gaseous oxidant is air.

[0037] In one aspect, the gaseous oxidant is oxygen-rich air, such as about 40% O2.

[0038] In one aspect, the gaseous oxidant is oxygen, and the ratio of the gas phase velocity to the liquid phase velocity is about 1.1:1 to about 10:1.

[0039] In one aspect, the gaseous oxidant is oxygen, and the ratio of the gas phase velocity to the liquid phase velocity is about 2:1 to about 5:1.

[0040] In one aspect, a highly soluble supplemental oxidant is added. Optionally, the highly soluble supplemental oxidant is added to the reactor near the aqueous inlet of the reactor.

[0041] In one aspect, the highly soluble supplementary oxidant is peroxide.

[0042] In one aspect, the highly soluble supplementary oxidant is nitrogen oxides.

[0043] In one aspect, the flow direction of the gas phase in the reactor is countercurrent to the flow direction of the liquid phase.

[0044] In one aspect, the aqueous stream contains about 0% by weight to about 15% by weight of organic matter.

[0045] In one aspect, the aqueous stream contains about 0% by weight to about 10% by weight of organic matter.

[0046] In one aspect, the aqueous stream contains about 0% by weight to about 8% by weight of organic matter.

[0047] In one aspect, the volume of the liquid phase is equal to approximately 40% to approximately 70% of the internal volume of the tubular section of the reactor.

[0048] In one aspect, organic matter comprises or is composed of dissolved organic molecules.

[0049] In one aspect, organic matter includes or consists of suspended solids.

[0050] In one aspect, organic matter comprises both dissolved organic molecules and suspended solids, or is composed of both dissolved organic molecules and suspended solids.

[0051] In one aspect, organic matter is one or more of wastewater, industrial effluent, farm effluent, food waste, packaging materials, and plant residues.

[0052] In one aspect, a continuous hydrothermal oxidation process is followed by a settling stage to allow for the settling and separation of inorganic ash particles.

[0053] In one aspect, the liquid output of the process is fed into an anaerobic digester to produce biogas.

[0054] In one aspect, the aqueous stream is preheated before being injected into the tubular reactor.

[0055] In one aspect, residence time and processing conditions were designed to optimize the yield of C1 to C5 short-chain fatty acids.

[0056] This disclosure also provides a hydrothermal oxidation reactor comprising a first section and a second or subsequent substantially horizontally arranged tubular section, an aqueous inlet port, a gaseous oxidant inlet port, an aqueous outlet port, and a gaseous outlet port.

[0057] In one aspect, the first segment includes a tubular segment.

[0058] In one aspect, the first section includes a stirred tank reactor.

[0059] In one aspect, the second or subsequent substantially horizontally arranged tubular sections comprise a plurality of tubular sections.

[0060] In one aspect, the first section includes a tubular section, and a second or subsequent tubular section arranged substantially horizontally has a larger diameter than the first section.

[0061] In one aspect, the second or subsequent substantially horizontally arranged tubular section includes one or more bends.

[0062] In one aspect, the axis of the tubular reactor section of the second or subsequent substantially horizontally arranged tubular section is horizontal or inclined or descending with less than about 15 degrees relative to the horizontal.

[0063] In one aspect, the axis of the tubular reactor section of the second or subsequent substantially horizontally arranged tubular section is horizontal or has an inclination or descent of less than about 5 degrees relative to the horizontal.

[0064] In one aspect, the axis of the tubular reactor section of the second or subsequent substantially horizontally arranged tubular section is horizontal or has an inclination or descent of less than about 1 degree relative to the horizontal.

[0065] In one aspect, the curved sections of the second or subsequent substantially horizontally arranged tubular sections are adapted to receive liquid and gas phases and to transport water and gas layers flowing in substantially parallel flow to adjacent tubular sections.

[0066] In one aspect, the reactor or part of the reactor is housed within a heat-sealed enclosure.

[0067] In one aspect, the reactor includes an additional oxidant port.

[0068] Other embodiments of the invention will become apparent from the following detailed description of several aspects of this disclosure. Attached Figure Description

[0069] The invention and the following detailed description will be further understood when read in conjunction with the accompanying drawings. Exemplary embodiments of the disclosed methods and apparatus are described with reference to the accompanying drawings to illustrate the methods and apparatus. However, the methods and apparatus are not limited to the specific embodiments disclosed.

[0070] Figure 1 This diagram illustrates the different reaction zones during the wet oxidation process.

[0071] Figure 2: Shows the chemical oxygen demand (COD) along the time process of the wet oxidation reaction. Figure 2a ), Volatile Suspended Solids (VSS) Figure 2b ) and acetic acid concentration distribution ( Figure 2c ).

[0072] Figure 3 shows an alternative arrangement for the combination of mass transfer (MT) confinement and kinetic confinement in a tubular PFR.

[0073] Figure 4 This illustrates a tubular reactor with substantially horizontal and curved sections.

[0074] Figure 5 The process flow chart is shown.

[0075] Figure 6 A schematic diagram of a reactor according to one aspect of this disclosure is shown.

[0076] Figure 7 This shows a representative temperature distribution across the reactor length.

[0077] Figure 8 The value indicates the total chemical oxygen demand (COD) concentration in the reactor.

[0078] Figure 9 The figure shows the total COD removal rate in the reactor. Detailed Implementation

[0079] definition

[0080] The Reynolds number is a dimensionless quantity used to classify the flow pattern in a system passing through a pipe as laminar (smooth) or turbulent. It is defined by the ratio of inertial forces to viscous forces and is determined by the following formula:

[0081] ,in

[0082] Re = Reynolds number (-)

[0083] Fluid velocity (m / s)

[0084] d = pipe diameter (m)

[0085] =Fluid density (kg / m3)

[0086] = Fluid viscosity (Pa·s)

[0087] Subscript i = fluid i (in this case, gas or liquid phase, or the entire mixed multiphase).

[0088] The fluid velocity is determined by the following formula: ,in

[0089] = Fluid volumetric flow rate (m³) 3 / Second)

[0090] = Pipe inner diameter (m) 2 )

[0091] In this specification, it should be noted that velocity and / or Reynolds number are used as indicators of laminar and turbulent flow, and their values ​​are applicable to actual reactor diameters. The true measure cannot be simply described because it depends on many variables.

[0092] The terms “comprise”, “comprised”, or “comprising” used in this specification are used in an inclusive sense, that is, to specify the presence of the stated feature but not to exclude the presence of additional or other features.

[0093] The use of examples or exemplary language (e.g., "for example") is intended only to better illustrate the invention and does not constitute a limitation on the scope of the invention.

[0094] Unless otherwise stated, all figures used in this specification to represent amounts of components, reaction conditions, etc., should in all cases be understood to be modified by the term "about". Therefore, unless otherwise indicated, the numerical parameters listed in the following description are approximate values ​​and may vary depending on the desired properties sought to be obtained by the present invention. At a minimum, each numerical parameter should be interpreted according to the number of significant figures and general rounding conventions.

[0095] The description of numerical ranges is intended only as a shorthand method for individually referring to each individual value falling within that range. Unless otherwise stated, each individual value is incorporated into this specification as if it were described separately. For example, if the range is from about 1 to about 50, it is considered to include, for example, 1, 7, 34, 46.1, 23.7, or any other value or range within that range.

[0096] illustrate

[0097] In view of the limitations of currently available hydrothermal oxidation methods and equipment, this disclosure provides means for hydrothermal oxidation that allows for relatively low engineering requirements, improved efficiency and / or cost-effectiveness.

[0098] This disclosure provides a hydrothermal oxidation method, and particularly a continuous method for the hydrothermal oxidation of organic matter. This disclosure also provides a hydrothermal oxidation reactor in which the method of this disclosure is carried out.

[0099] In this specification, the terms "hydrothermal oxidation" and "wet oxidation" are used interchangeably.

[0100] A complete bibliographical list of cited references is provided at the end of this manual.

[0101] As mentioned above, enhanced turbulence is generally considered beneficial during wet oxidation to ensure sufficiently efficient treatment by increasing the gas-liquid mass transfer rate. Implicit in this method is the concept that the gas-liquid mass transfer rate limits the oxidation process. In contrast, the method disclosed herein utilizes a reactor that provides a low-mixing-intensity environment during certain stages of the process. This method allows hydrothermal oxidation to proceed successfully even when certain stages of oxidation are carried out under low-mixing-intensity conditions.

[0102] Unbound by theory, it has been found that oxygen transport demand may not completely dominate the entire wet oxidation reaction cycle. When the reaction is considered to occur along the course of the tubular reactor, it can be divided into distinct regions characterized by the presence of reaction rate limiting types. The course of wet oxidation exhibits an initial transitional heating zone, followed by a region characterized by high oxygen demand, and then a transition to a region where the oxidation rate decreases significantly and therefore the oxygen demand decreases (see [link to relevant documentation]). Figure 1 The identified area includes:

[0103] Transition Zone 1 - Heating: In this zone, the reactor contents rise from ambient temperature to the reaction temperature. The reaction rate limitation shifts from kinetic limitation to mass transfer limitation.

[0104] Mass transfer confinement region: In this region, the hydrothermal oxidation reaction is underway, and the transport of oxygen from the gas phase to the liquid phase is critical. Sufficiently high mixing intensity or turbulence is required to minimize the gas-liquid mass transfer rate limitations on the overall process reaction.

[0105] Transition region 2: This region appears between two main regions (mass transfer confinement region and kinetic confinement region) and is characterized by a mixture of confinement between the two regions.

[0106] Kinetic limiting region: In this region, the rate of oxygen-consuming hydrothermal oxidation slows down, and the reaction rate is limited by fundamental kinetics and stoichiometry. Here, oxygen transport from the gas phase to the liquid phase is not a major rate-limiting factor, and the absolute requirements for mixing intensity or turbulence are significantly lower than in the mass transfer limiting region.

[0107] The method disclosed herein utilizes these different speed limit phases.

[0108] Experimental data support this analysis. For illustrative purposes only, Figure 2 provides an analysis of the batch wet oxidation of biomass at a temperature setpoint of 230 °C. The use of batch data is appropriate because the reaction kinetics are comparable to those of a plug flow reactor, which is a reasonable representative of a tubular reactor. The oxidation of the organic components, as expressed by total COD (total chemical oxygen demand), is initially rapid until 0.2 h. Suspended solids (VSS) decrease in approximately 0.1 h. The kinetic limitation zone appears in the time period after 0.3 h, showing a slow but non-zero rate of change for key parameters. The benefits of the kinetic limitation zone are shown by the continued decrease in total COD and soluble COD and VSS within this zone until the end of the reaction (t = 1 h), and the continuous increase in acetic acid concentration throughout the reaction.

[0109] The methods and reactors of this disclosure will now be further described.

[0110] As already noted, the methods and apparatus of this disclosure incorporate low mixing intensities in at least a portion of the wet oxidation reactor, compared to the relatively and persistently high turbulent mixing conditions of conventional wet oxidation reactors. This is achieved through a combination of gas and liquid flow rates, combined with the tubular reactor geometry (e.g., diameter), and operating temperature and pressure, resulting in low liquid-phase turbulence within at least a portion of the reactor, where the requirements for transferring oxygen to the liquid phase via gas-liquid mass transfer are relatively low.

[0111] method

[0112] The method disclosed herein is continuous and includes:

[0113] Organic matter in the aqueous stream is pumped into the first section of the reactor.

[0114] The gaseous oxidant is pumped into the first section of the reactor.

[0115] The conditions in the reactor are maintained at a pressure ranging from about 2 bar to about 250 bar and a temperature ranging from about 100°C to about 373°C.

[0116] In the first section of the reactor, the organic matter and gaseous oxidant in the aqueous stream are subjected to high-intensity mixing.

[0117] The organic matter and gaseous oxidant in the aqueous stream are transferred to a second or subsequent substantially horizontally arranged tubular section of the reactor, wherein at least some of the aqueous stream containing the organic matter is in the liquid phase and at least some of the gaseous oxidant is in the gaseous phase.

[0118] as well as

[0119] The rate of the liquid phase traveling through at least a portion of the second or subsequent section of the reactor is maintained at a maximum velocity of approximately 0.1 m / s, or

[0120] The Reynolds number of the liquid phase traveling through at least a portion of the second or subsequent section of the reactor is maintained at about 0 to about 10,000.

[0121] In one aspect, at least a portion of the tubular reactor section contains separate liquid and gas phases. Preferably, the gas phase moves at a velocity equal to or greater than that of the liquid phase. This is achieved by managing the reactor temperature and pressure, the reactor geometry (e.g., diameter), and the relative mass flow rates of the liquid and gaseous materials entering the reactor.

[0122] Providing a relatively low-velocity liquid phase in the second or subsequent sections of the reactor results in an increased residence time relative to the section length of the tubular reactor, which allows for relatively short and low-cost reactors.

[0123] Typical tubular reactors operating hydrothermal oxidation (characterized by significant reaction rate limitations due to oxygen transfer from the gas phase to the liquid phase) are operated using highly mixed turbulent flow to enhance this oxygen transfer rate. To achieve this high turbulence in a tubular wet oxidation reactor, residence times of 30 to 120 minutes typically manifest as extremely long reactor lengths with narrow-diameter tubular sections. This logically becomes difficult to fit within the space footprint, and the resulting high pressure drop across the reactor length leads to increased pumping costs.

[0124] Conventional implementations of hydrothermal oxidation utilize highly mixed tubular systems with long reactor lengths, or highly mixed continuous stirred tank reactors (CSTRs, such as bubble columns) requiring long residence times to match tubular kinetics. The low-rate tubular process of this disclosure is less expensive than highly mixed tubular and CSTR systems.

[0125] In one aspect, the liquid phase containing organic matter preferably travels through the reactor at a maximum velocity of about 0.1 m / s, for example, a maximum velocity of about 0.05 m / s or about 0.02 m / s. This is controlled by selecting the pipe diameter relative to the pump flow rate of the liquid phase. The velocity is a function of these parameters and is also controlled by the temperature and pressure environment of the reactor, the gas flow rate, and the orientation of the reactor itself, which determines the relative distribution of the gas and liquid phases within the pipe. The flow rate of such a complex mixed-phase system can be predicted using, for example, empirical correlations given by Beggs and Brill.

[0126] In one aspect, the method of this disclosure generates relatively low turbulence in a second or subsequent reactor section by selecting the reactor pipe / tube diameter based on the desired volumetric fluid flow rate through the pipe. One measure of this is the Reynolds number. This dimensionless number provides the ratio of inertial fluid forces to viscous fluid forces. For a given fluid in the pipe, a higher Reynolds number is associated with greater turbulence, which in turn represents mixing energy. Low Reynolds numbers (typically below about 2000) are consistent with observations of laminar fluid flow, while higher values ​​(typically above 4000, but ranging above 10000) are consistent with observations of turbulent flow.

[0127] In one aspect, the Reynolds number of the liquid phase is from 0 to about 10,000, for example, from 0 to about 4,000. Alternatively, the Reynolds number is from 0 to about 400.

[0128] In one aspect, the pressure in the reactor is maintained in the range of about 10 bar to about 200 bar, for example, in the range of about 20 bar to about 200 bar, or in the range of about 30 bar to about 120 bar. The pressure is maintained by controlling the back pressure of the control system.

[0129] In one aspect, the temperature in the reactor is maintained in the range of about 160°C to about 350°C, preferably in the range of about 220°C to about 300°C. The temperature will be maintained and controlled by feedback control of system heat exchange and / or by any external heating method that can be applied to the reactor (e.g., electric heating element).

[0130] In one aspect, the pressure in the reactor is maintained in the range of about 20 bar to about 200 bar, and the temperature is maintained in the range of about 200°C to about 350°C.

[0131] In another aspect, the pressure in the reactor is maintained in the range of about 30 bar to about 120 bar, and the temperature is maintained in the range of about 220°C to about 300°C.

[0132] In one aspect, the ratio of gas phase velocity to liquid phase velocity is in the range of about 1.01:1.00 to about 10:1, preferably in the range of about 1.0:1 to about 10:1, or in the range of about 3:1 to about 6:1.

[0133] In one embodiment, the ratio of gas phase velocity to liquid phase velocity is about 2:1 to about 5:1.

[0134] In one aspect, the gaseous oxidant is oxygen, air, or oxygen-enriched air (air containing 40% oxygen).

[0135] In one embodiment, the gaseous oxidant is oxygen, and the ratio of the gas phase velocity to the liquid phase velocity is from about 1.01:1 to about 10:1.

[0136] In another embodiment, the gaseous oxidant is oxygen, and the ratio of the gas phase velocity to the liquid phase velocity is about 2:1 to about 5:1.

[0137] Gaseous oxidant can be supplied to the reactor and regulated by the total system pressure (the mass of oxygen is greater under high pressure) and / or gas flow rate (a higher flow rate equals more oxygen).

[0138] Oxygen can be delivered using air instead of more expensive oxygen or chemical oxidants and at lower pressures, which reduces safety and engineering requirements for the reactor.

[0139] In one aspect, a highly soluble supplemental oxidant is added to the reactor near the aqueous inlet. Optionally, the highly soluble supplemental oxidant is a peroxide or a nitrogen oxide.

[0140] Highly soluble supplemental oxidants are known in the art and can be selected based on the organic matter and desired output. Examples include air, oxygen-enriched air (i.e., air in which nitrogen has been removed to increase the oxygen concentration), oxygen, ozone, hydrogen peroxide, sodium percarbonate, Fenton's reagent, nitrous oxide, sodium peroxide, potassium persulfate, sodium hypochlorite, and peracetic acid.

[0141] In one aspect, the flow direction of the gas phase in the reactor is countercurrent to the flow direction of the liquid phase. Countercurrent airflow can be used as another means to slow down the liquid phase velocity.

[0142] In one aspect, the volume of the liquid phase in the reactor is equal to about 40% to about 70% of the internal volume of the tubular section of the reactor.

[0143] In one aspect, the aqueous stream can be preheated before being injected into the reactor by recovering heat from the material discharged from the reactor at high temperature.

[0144] reactor

[0145] In one aspect, the hydrothermal oxidation reactor of this disclosure includes a first section and a second or subsequent substantially horizontally arranged tubular section, an aqueous inlet port, a gaseous oxidant inlet port, an aqueous outlet port, and a gaseous outlet port.

[0146] The method disclosed herein utilizes a reactor that includes tubular reactor sections. Optionally, the tubular sections form part of a mixing reactor.

[0147] The axis of the tubular reactor section is preferably horizontal or inclined or descending at less than about 15 degrees relative to the horizontal. For example, the axis of the tubular section of the reactor is horizontal or inclined or descending at less than about 5 degrees relative to the horizontal, or the axis of the tubular section of the reactor is horizontal or inclined or descending at less than about 1 degree relative to the horizontal.

[0148] In one embodiment, the tubular reactor section of the second or subsequent reactor section may be coiled. Optionally, the coiled section is substantially horizontal.

[0149] In one embodiment, the inner diameter of the tubular reactor section immediately following the inlet port is smaller than that of the subsequent tubular section.

[0150] In one embodiment, the second or subsequent substantially horizontally arranged tubular sections include curved sections adapted to receive liquid and gas phases and to convey aqueous and gas phases flowing in substantially parallel flow to adjacent tubular sections. This is a highly stratified system.

[0151] In one aspect, the reactor or a portion thereof is housed within a thermal enclosure to minimize energy loss to the external environment. This thermal enclosure allows added and generated heat to be used to reach and maintain one or more desired temperature setpoints along the length of the tubular reactor, preferably without the addition of any external heating source. Such a thermal enclosure can be exemplified as an insulation layer or external insulation layer around the pipe using a material with poor thermal conductivity, and / or by using a heat storage medium through which thermal energy is stored in an object (e.g., silicone-based sand) to buffer temperature changes in the system.

[0152] In one aspect, the reactor includes additional oxidant ports along the length of the tubular reactor section. This adds control options to the reactor, avoids the risk of oxygen depletion from the initial inlet port, and allows for potential manipulation of the final product by controlling oxidation along the reactor.

[0153] As already noted, the reactor of this disclosure is configured to provide a highly turbulent region within the mass transfer confinement zone, particularly at the front end of the reactor. This highly turbulent region may or may not occur within the tubular reactor element. If not, the reactor is considered a mixing reactor.

[0154] The reactor is also configured to provide a low-turbulence region in the kinetically confined zone, particularly in the section following the high-turbulence region.

[0155] In one aspect, the reactor of this disclosure provides physical elements that induce high turbulent mixing intensity, followed by physical elements that minimize turbulent mixing intensity. These elements may include, for example, a stirred tank providing a first section of the reactor, larger pipe diameters in a second or subsequent section of the reactor, and surface texturing of internal baffles of the reactor.

[0156] Figure 3 illustrates a suitable arrangement. The arrangement shown in Figure 3 allows for high mixing intensity or turbulence in one part of the reactor and low mixing intensity in another part of the reactor.

[0157] Figure 3a The diagram shows the arrangement of a small-diameter tube in the first section. This is followed by a large-diameter tube. The two tube sizes will be characterized by high turbulence (mass-confined region, small-diameter tube) and low turbulence (dynamically confined region, large-diameter tube).

[0158] Figure 3b The alternative mixing reactor presented in the image shows the connection between a stirred tank and a horizontally arranged tubular reactor section. The stirred tank is shown as a mechanical mixing reactor, but it could also be in the form of a bubble column.

[0159] In this implementation, high levels of turbulence are induced in the system during the mass transfer confinement zone (which is independent of the tubular reactor section). The kinetic confinement zone is completed within the tubular section. The advantage of this configuration is that it allows for highly specific control of turbulent mixing intensity, temperature, and reaction rate during the first mechanical mixing phase.

[0160] Figure 3c The diagram illustrates flow through a tube including an internal recirculation loop. The fluid is recirculated back to the front of the reactor, providing enhanced mixing intensity in a first mass transfer confinement zone. Outside the recirculation zone, the rear of the tubular reactor exhibits lower mixing intensity, representing a kinetically confinement zone. In this embodiment, both the mass transfer confinement zone and the kinetically confinement zone can have the same tube diameter, with the internal recirculation of the fluid providing enhanced mixing intensity in the mass transfer confinement zone.

[0161] Materials used for processing

[0162] Organic matter can be one or more of wastewater, industrial effluent, agricultural effluent, food waste, packaging materials, and plant residues. However, it should be understood that any suitable organic matter can be used.

[0163] In one aspect, the aqueous stream contains an organic content of 0% to about 15% by weight, preferably 0% to about 10% by weight, and more preferably 0% to about 8% by weight.

[0164] In one aspect, organic matter includes dissolved organic molecules, suspended solids, or both dissolved organic molecules and suspended solids, or is composed of dissolved organic molecules, suspended solids, or both dissolved organic molecules and suspended solids.

[0165] The reactor output consists of gas, liquid, and solid phases. In the liquid phase, water serves as the carrier fluid and contains a series of soluble organic components that are produced as reaction products. These typically include a range of short-chain fatty acids, ketones, and aldehydes, with acetic acid usually being the largest contributor.

[0166] In the gas phase, it typically consists of residual unreacted oxygen, water vapor, carbon dioxide, inert gases such as nitrogen, and some low amounts of carbon monoxide and volatile organic compounds.

[0167] This process can be followed by a settling stage to allow for the settling and separation of inorganic ash particles.

[0168] The liquid output of this process is fed into an anaerobic digester to produce biogas.

[0169] In one aspect, residence time and processing conditions were designed to optimize the yield of C1 to C5 short-chain fatty acids.

[0170] Acetic acid is quite difficult to handle in wet oxidation, making it an effective endpoint for hydrothermal oxidation processes.

[0171] The final product can be used as a chemical feedstock, and its value can be recovered from the carbon components of the organic feedstock.

[0172] Example

[0173] Figure 4 An example of a second or subsequent tubular reactor section of a reactor according to this disclosure is shown. Figure 5 A process diagram is shown.

[0174] The second or subsequent tubular reactor section comprises a horizontal section of pipe (1) connected by a curved section (2). A liquid inlet (3) and a gas inlet (4) are located at the bottom of the reactor, and the reactor outlet is located at the top (5). Straight pipe sections are connected by multiple L-shaped or U-shaped sections (6). At least one sampling point (7), thermocouple (8), and valve (9) are present along the reactor.

[0175] The process is as follows:

[0176] First, appropriate organic matter is introduced into the front end of the reactor by pumping. Figure 4 (Not shown in the image). This organic matter is primarily found in the substrate, typically comprising 90% to 98% water, with the remainder being the organic matter to be treated.

[0177] This pump is a high-pressure pump, capable of reaching reaction pressures of, for example, 50 bar to 100 bar.

[0178] The feed material is heated to a temperature typically between 50°C and 300°C during the primary heating stage. This heating can come from heat exchange with the exiting reactor contents or from an external heating source (e.g., electricity or hot oil). A gaseous oxidant is added separately before heating or after the primary heating stage. The mass of oxygen added is calculated in proportion to the organic matter content of the feed, expressed as chemical oxygen demand (COD). A typical ratio is an oxygen / COD ratio of 0.6 to 2 (called the λ factor). The oxidant may or may not be preheated before being added to the feed.

[0179] The gas-liquid feed substrate passes through the reactor and its various reaction zones. The heat of the oxidation reaction, combined with the heating supplied to the contents, brings the reactor contents to the desired system temperature. The system pressure is set via back pressure control to ensure that the liquid water does not boil, as boiling would lose all the latent heat of vaporization. The system pressure also ensures that sufficient liquid phase is retained to sustain the oxidation reaction, allowing material to pass through the reactor sections without adhering to the tube walls, and limiting water vaporization to the desired level. At the desired temperature setpoint, the typical system pressure is 5 to 50 bar higher than the vapor pressure of the liquid substrate. The temperature setpoint is typically 200°C to 300°C.

[0180] As the reactor contents pass through the various sections of the tubular reactor, they are restored to ambient temperature and pressure by various means, including heat exchange and back pressure regulator arrangements. Preferably, these arrangements are organized to recover energy from the reactor effluent to maximize the efficiency of the entire reactor system. As part of this process, solids may be separated from the fluid before or after gas-liquid separation, which itself may occur before or after the temperature and pressure reduction. The cooled liquid effluent, consisting of materials for final treatment, can be used for further processing to recover value.

[0181] In an embodiment where the flow of the gaseous oxidant is countercurrent relative to the liquid phase, the countercurrent air transfers heat back to the starting point of the reactor; surface ripples are caused by the sliding velocity that introduces turbulence; the countercurrent flow increases the surface area of ​​the liquid-gas interface; and the residence time of the liquid phase is slowed down due to friction.

[0182] Experimental Example

[0183] This embodiment provides the results of hydrothermal treatment of soluble substances in the tubular reactor of this disclosure.

[0184] Materials and methods

[0185] Starting materials

[0186] The starting material comprises a solution of organic material that is substantially soluble in water. This material, an aqueous mixture of molasses and hydrolyzed fish matter, provides a comprehensive representative of waste samples containing high levels of organic pollutants. Typical pollutant biomass is characterized by its primary chemical category, which can be defined as cellulose-based, carbohydrate-based, protein-based, fat-based, or oil-based, or cellular DNA / RNA fragments. The selected mixture represents biomass with high carbohydrate and protein characteristics.

[0187] Prepare the mixture in water and adjust it to pH 7, then feed the mixture into... Figure 6 In the serpentine tubular reactor shown.

[0188] The reactor is 22.4 m long and has an inner diameter of 15.748 mm.

[0189] The water-based feed rate is 5 L / hour or 10 L / hour.

[0190] The concentration of organic components in an aqueous feed was measured using chemical oxygen demand (COD) units. COD is defined as the amount of oxygen theoretically required to completely oxidize a particular sample, thus providing a measure of the concentration of organic contaminants without requiring measurement of individual components. The feed COD was measured to be 7900 mg / L.

[0191] Heating is provided by electric coils installed outside the reactor for the first three running lengths. For a given experiment, the reactor temperature is set to 250°C.

[0192] The oxidant pumped into the reactor is oxygen supplied from air in a high-pressure gas cylinder. The gaseous air flow is controlled by a thermal mass flow controller, with a flow rate ranging from 7.65 nL / min to 15.31 nL / min (standard liters / min, volumetric flow rate normalized to 101300 Pa and 0 °C).

[0193] The oxygen-to-COD ratio (a key parameter of hydrothermal oxidation) was set from 1.1 g O2 / g COD to 2 g O2 / g COD.

[0194] The reactor pressure was controlled by a back pressure controller. For this experiment, two reactor pressures were tested – 70 bar and 90 bar.

[0195] As shown in Table 1, four experiments were completed.

[0196] Table 1: Experimental Matrix

[0197]

[0198] result

[0199] Temperature distribution across reactor length is presented in Figure 7 middle.

[0200] Flow conditions inside the reactor

[0201] Reactor conditions are defined as a multiphase flow—a mixture of gas and liquid. This multiphase flow characteristic facilitates the transfer of oxygen from the gas phase to the liquid in which it participates in the oxidation reaction. Generally, the greater the interphase mixing, the greater the oxygen transfer between the gas and liquid phases. This mass transfer is a function of mixing or turbulence, which can be defined by the dimensionless Reynolds number correlation as specified above.

[0202] Volumetric flow rate is a function of mass flow rate, material properties, and system environmental conditions (temperature and pressure). For this work, the liquid phase is modeled as water containing certain amounts of dissolved components—acetic acid (a product of the oxidation process), oxygen, nitrogen, and carbon dioxide—while the gas is considered a mixture of gases—oxygen, nitrogen, carbon dioxide, and water (originating from the evaporation of the liquid phase).

[0203] The values ​​were generated based on volumetric flow rates at reaction temperature (240 °C) and pressure (70 bar and 90 bar), taking into account water evaporation into the gas phase. The results were generated using the publicly available chemical process simulator DWSIM (https: / / dwsim.org / ) and applied using the NRTL thermodynamic properties package (Renon and Prausnitz 1968).

[0204] Table 2 provides the parameters used in the analysis and describes the flow based on fluid volumetric flow rate, fluid velocity, and Reynolds number.

[0205] Table 2: Key parameters and flow characteristics obtained from the experiment

[0206]

[0207] Table 2 shows the Reynolds numbers for the liquid phase, which are less than 2000. A generally accepted "rule of thumb" is that laminar flow exists when the Reynolds number is less than 2000, and a transition to turbulent flow occurs above 2000 (Perry and Green, 1984). The gas phase also has low Reynolds numbers, with all numbers below 2050.

[0208] Table 2 includes a description of the flow regime. This is derived from the correlation developed to describe multiphase flow—the Beggs and Brill correlation (Beggs and Brill, 1973). Its calculation is built into the piping tool calculator in many process simulators, including DWSIM, where it is applied in this embodiment.

[0209] Applying this correlation determines that the flow regime in each experiment is "coalescing." Coalescing flow is described as a state in which the gas and liquid phases exist in essentially independent layers within the pipe. Coalescing flow occurs where gas and liquid flow rates are low.

[0210] Reactivity

[0211] Reactor performance is measured by the COD removal rate within the reactor. One property of a serpentine reactor is that it is an example of a plug flow reactor. Once the temperature is reached, the length of the reactor reflects the reaction time and therefore the reaction progress. Therefore, sampling along the length of the reactor can be used to represent the performance of reactors of different lengths or the retention time of materials within the system.

[0212] Each of the three sample points represents a specific time the fluid has spent in the reactor. This liquid retention time can be calculated based on the ratio of the reactor length at each specific sampling point to the predicted liquid velocity through the reactor (from Table 2).

[0213] Calculating liquid retention time allows for plotting a graph of COD concentration as a response to this parameter, such as... Figure 8 As shown. The COD removal rate relative to liquid residence time (as a percentage of the original COD) was also plotted (e.g., Figure 9 (As shown).

[0214] COD decreased from an initial 7900 mg / L to 4000 mg / L after approximately 50 minutes of reaction time. This represents a 50% COD removal rate during that time period, demonstrating robust performance at the given reaction temperature.

[0215] All data fit to a consistent curve, indicating that although the 5 L / h and 10 L / h samples represent different input flow rates, the reactor behaves consistently when the response is normalized based on liquid residence time.

[0216] Under the conditions selected in the current experiment, pressure changes have a minimal impact on COD removal rate.

[0217] The results of the examples demonstrate that wet oxidation can be achieved at a practical level under low turbulence conditions.

[0218] While illustrative embodiments have been shown and described, including the best mode known to the inventors for carrying out the invention, those skilled in the art will recognize that this disclosure can be practiced with variations of the disclosed structures, materials, compositions and methods, and such variations are considered to be within the scope of this disclosure.

[0219] References

[0220]

Claims

1. A continuous method for the hydrothermal oxidation of organic matter, comprising: Organic matter in the aqueous stream is pumped into the first section of the reactor. A gaseous oxidant is pumped into the first section of the reactor. The conditions in the reactor are maintained at a pressure ranging from about 2 bar to about 250 bar and a temperature ranging from about 100°C to about 373°C. In the first section of the reactor, the organic matter and the gaseous oxidant in the aqueous stream are subjected to high-intensity mixing. The organic matter and the gaseous oxidant in the aqueous stream are transferred to a second or subsequent substantially horizontally arranged tubular section of the reactor, wherein at least some of the aqueous stream containing the organic matter is in the liquid phase, and at least some of the gaseous oxidant is in the gaseous phase. as well as The rate of the liquid phase traveling through at least a portion of the second or subsequent section of the reactor is maintained at a maximum speed of about 0.1 m / s, or The Reynolds number of the liquid phase traveling through at least a portion of the second or subsequent section of the reactor is maintained at about 0 to about 10,000.

2. The method of claim 1, wherein the liquid phase comprising the organic material travels through the reactor at a maximum speed of about 0.05 m / s.

3. The method of claim 1, wherein the liquid phase comprising the organic material travels through the reactor at a maximum speed of about 0.02 m / s.

4. The method of claim 1, wherein the Reynolds number of the liquid phase in the tubular reactor section is from about 0 to about 4000.

5. The method according to claim 1, wherein the Reynolds number of the liquid phase in the tubular reactor section may also be from about 0 to about 400.

6. The method of claim 1, wherein the pressure in the reactor is maintained in the range of about 10 bar to about 200 bar, and the temperature is maintained in the range of about 160°C to about 350°C.

7. The method of claim 1, wherein the pressure in the reactor is maintained in the range of about 20 bar to about 200 bar, and the temperature is maintained in the range of about 200°C to about 350°C.

8. The method of claim 1, wherein the pressure in the reactor is maintained in the range of about 30 bar to about 120 bar, and the temperature is maintained in the range of about 220°C to about 300°C.

9. The method of claim 1, wherein the liquid phase and the gas phase exist as separate or segregated layers in at least a portion of the tubular reactor section.

10. The method of claim 1, wherein the liquid phase and the gas phase exist in the form of a liquid slug sequence separated by gas slugs.

11. The method according to claim 9 or claim 10, wherein the liquid phase and the gas phase exist in the form of a mixture of laminar flow and slug flow.

12. The method of claim 1, wherein the gas phase mass moves at a speed equal to or greater than the speed of the liquid phase.

13. The method of claim 1, wherein the ratio of gas phase velocity to liquid phase velocity is in the range of about 1.01:1.00 to about 10:

1.

14. The method of claim 1, wherein the ratio of gas phase velocity to liquid phase velocity is in the range of about 1.1:1 to about 10:

1.

15. The method of claim 1, wherein the ratio of gas phase velocity to liquid phase velocity is about 3:1 to about 6:

1.

16. The method of claim 1, wherein the ratio of gas phase velocity to liquid phase velocity is about 2:1 to about 5:

1.

17. The method according to claim 1, wherein the gaseous oxidant is oxygen.

18. The method of claim 1, wherein the gaseous oxidant is air.

19. The method of claim 1, wherein the gaseous oxidant is oxygen-enriched air, for example, about 40% O2.

20. The method of claim 1, wherein the gaseous oxidant is oxygen, and the ratio of the gas phase velocity to the liquid phase velocity is about 1.1:1 to about 10:

1.

21. The method of claim 1, wherein the gaseous oxidant is oxygen, and the ratio of the gas phase velocity to the liquid phase velocity is about 2:1 to about 5:

1.

22. The method of claim 1, wherein a highly soluble supplementary oxidant is added.

23. The method of claim 22, wherein the highly soluble supplemental oxidant is added to the reactor near the aqueous inlet of the reactor.

24. The method of claim 22 or claim 23, wherein the highly soluble supplemental oxidant is a peroxide or a nitrogen oxide.

25. The method according to claim 1, wherein the flow direction of the gas phase in the reactor is countercurrent to the flow direction of the liquid phase.

26. The method of claim 1, wherein the aqueous stream comprises an organic content of about 0% by weight to about 15% by weight.

27. The method of claim 1, wherein the aqueous stream comprises an organic content of about 0% by weight to about 10% by weight.

28. The method of claim 1, wherein the aqueous stream comprises an organic content of about 0% by weight to about 8% by weight.

29. The method of claim 1, wherein the tortuous section of the reactor is adapted to receive a water layer and a gas layer, and is adapted to transport the water layer and the gas layer, flowing in substantially parallel flow, to an adjacent tubular section.

30. The method of claim 1, wherein the volume of the liquid phase in the reactor is equal to about 40% to about 70% of the internal volume of the tubular section of the reactor.

31. The method of claim 1, wherein the residence time and processing conditions are adapted to optimize the yield of C1 to C5 short-chain fatty acids.

32. A reactor for the hydrothermal oxidation of organic matter, comprising: First section, The second or subsequent tubular sections are basically arranged horizontally. Water inlet port, Gaseous oxidant input port, Water outlet port, and Gas flow outlet port.

33. The reactor of claim 32, wherein the first section comprises a tubular section.

34. The reactor of claim 33, wherein the inner diameter of the tubular section is smaller than that of the second or subsequent tubular section.

35. The reactor of claim 32, wherein the first section comprises a stirred tank reactor.

36. The reactor of claim 32, wherein the second or subsequent substantially horizontally arranged tubular section comprises a plurality of tubular sections.

37. The reactor of claim 32, wherein the first section comprises a tubular section, and the second or subsequent substantially horizontally arranged tubular section has a larger diameter than the first section.

38. The reactor of claim 32, wherein the axis of the tubular reactor section is horizontal or has an inclination or descent of less than about 15 degrees relative to the horizontal.

39. The reactor of claim 32, wherein the axis of the tubular reactor section is horizontal or has an inclination or descent of less than about 5 degrees relative to the horizontal.

40. The reactor of claim 32, wherein the axis of the tubular section of the reactor is horizontal or has an inclination or descent of less than about 1 degree relative to the horizontal.

41. The reactor of claim 32, wherein the second or subsequent substantially horizontally arranged tubular section includes one or more bends.

42. The reactor of claim 41, wherein the curved sections of the second or subsequent substantially horizontally arranged tubular sections are adapted to receive liquid and gas phases and to convey water and gas layers flowing in substantially parallel flow to adjacent tubular sections.

43. The reactor of claim 32, further comprising an additional oxidant injection port.

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