Anti-scaling device for heat exchanger and its use

Abstract

The present disclosure relates to an apparatus for reducing fouling in a heat exchanger tube and a heat exchanger including such an anti-fouling apparatus. The anti-fouling apparatus includes an elongate displacement body that is insertable into the heat exchanger tube to reduce the flow cross-sectional area in a portion of the tube. It also includes a mounting member connected to the elongate displacement body for attaching the apparatus to an end of the heat exchanger tube. The mounting member is configured to hold the displacement body in a spaced-apart relationship with the inner surface of the tube when the displacement body is inserted into the tube. The disclosed anti-fouling apparatus effectively reduces fouling in the heat exchanger in a reliable manner over an extended period of time without maintenance or external control, can be provided at a relatively low cost, is easy to install and can also be retrofitted to existing heat exchangers. It is particularly suitable for alleviating fouling-related problems in heat exchangers exposed to hot combustion or process gases, such as those encountered in the production of carbon black, pyrogenic silica or other particulate materials, without contaminating products recoverable from the process gas or adversely affecting their properties.

Description

TECHNICAL FIELD

[0001] The present invention relates to an anti-scaling device and its use for reducing or avoiding scaling in heat exchangers. The present invention also relates to a heat exchanger comprising such a device and its use in industrial processes, particularly in the production of carbon black. BACKGROUND ART

[0002] Heat exchangers are widely used in various industrial processes to recover energy from hot processes or combustion gases and transfer it to a heat exchange fluid to improve the overall efficiency of the process. For example, the recovered energy can be used to: heat one or more reactants, in which case the reactants can directly serve as the heat exchange fluid; or to help maintain the working or reaction temperature required in the process; or for other purposes, including purposes not directly related to the process itself, such as for power generation or district heating. In some of these processes, the heat exchanger may be subjected to quite high temperatures, such as 1,000 °C or higher, thus imposing strict requirements on material selection. Illustrative examples of such high-temperature processes include the production of carbon black or fumed silica.

[0003] Carbon black is generally produced by the pyrolysis of hydrocarbon feedstocks under controlled conditions. A variety of different methods and reactors for manufacturing carbon black are generally known (see, for example, Jean-Baptiste Donnet, Roop Chand Bansal, Meng-Jiao Wang, Carbon Black, 2nd Edition, CRC Press, 1993). According to the most common type of production process, at one or more locations in a furnace reactor, the hydrocarbon feedstock is injected into a stream of hot combustion gas, which is previously generated upstream by reacting a fuel (usually a hydrocarbon fuel) with an oxidizer (preferably air). Due to the high temperature in the combustion gas, when the mixture of the feedstock and the hot combustion gas passes through the reaction zone of the reactor, the injected hydrocarbon feedstock undergoes pyrolysis and the formation of carbon black takes place. After carbon black with the desired properties has been formed, the pyrolysis is usually stopped by injecting water to quench the process mixture. The resulting carbon black-containing gas is typically passed through a heat exchanger, also known as an air preheater, to further cool the carbon black-containing gas while preheating air, which is then supplied to the combustion chamber of the reactor for reaction with the fuel to form the hot combustion gas. The cooled carbon black-containing gas is then transferred to a filter unit, such as a bag filter, where the carbon black product is separated and collected from the gas stream.

[0004] Conventional heat exchangers for the production of carbon black typically include a plurality of parallel tubes that extend through a vertically arranged cylindrical chamber surrounded by a cylindrical shell, a bottom plate, and a top plate. The chamber is provided with an inlet and an outlet for the air to be preheated, the inlet and the outlet being typically at the bottom and top portions of the shell. When the hot carbon black-containing gas passes through the tubes, heat is transferred through the tube walls to the air stream flowing on the outer surfaces of the tubes inside the chamber. The temperature of the air can thus be increased to a temperature of up to about 950 °C and higher at the outlet. Among other things, the heat exchanger operates mainly in a countercurrent mode, where typically, the hot carbon black-containing gas passes through the tubes from the bottom to the top. The heat exchanger typically includes additional devices, such as baffles for controlling the air flow inside the chamber.

[0005] A common problem encountered with conventional heat exchangers for recovering energy from hot process or combustion gases (e.g., gases obtained from a reactor for the production of carbon black) is that they are prone to fouling under conventional operating conditions. Thus, the process gas or combustion gas typically contains condensed-phase materials or their precursors. Fouling occurs through the deposition of condensed-phase materials, such as particulate matter (e.g., carbon black), on the heat exchange surfaces (e.g., in particular, the inner surfaces of the heat exchanger tubes), which are in contact with the hot combustion or process gas containing the condensed-phase materials. Fouling is typically an autocatalytic process, since the deposits that have formed can act as nuclei and promote the deposition of additional condensed-phase materials on the heat exchange surfaces.

[0006] Fouling can have several adverse effects. Thus, it can, for example, have an adverse effect on the efficiency of heat transfer by reducing the heat transfer coefficient of the heat exchange surface of a heat exchanger. As a result, the achievable outlet temperature of the heat exchange fluid (such as air) may be lower, which may reduce the efficiency of a co-production process, such as leading to lower yields or productivity in carbon black production. To some extent, this lower efficiency of heat transfer can be compensated for by using a higher inlet temperature of the process or combustion gas to achieve the desired outlet temperature of the heat exchange fluid. However, on the other hand, this increases the thermal stress applied to the heat exchanger. Since fouling is a progressive process, the change in the outlet temperature of the heat exchange fluid can also lead to undesired long-term changes in the properties of the product obtainable from the co-production process that utilizes the heat exchange fluid (such as the physical properties of the carbon black product). The deposits on the heat exchange surface can also affect the gas flow characteristics in the heat exchanger. For example, they can increase the pressure drop between the opposite ends of the heat exchanger tubes, which can likewise have an adverse effect on the process efficiency and create additional stress on the heat exchanger material. Ultimately, there is a risk that fouling can lead to a complete blockage of the heat exchanger tubes and / or irreversible damage to the heat exchanger (such as due to cracks or ruptures in the heat exchanger tubes). In addition, over time, the deposits tend to harden and become brittle, so there is a risk that the hardened deposits can detach from the heat exchanger surface and re-enter the process or combustion gas stream, thereby contaminating the product obtained therefrom.

[0007] To avoid these problems and drawbacks and to restore proper functionality, heat exchangers are typically shut down from time to time for regular maintenance to remove the deposits from the heat exchange surface. However, cleaning the heat exchanger tubes mechanically, for example by means of long wire brushes or sandblasting, is laborious and time-consuming and stresses the heat exchanger material. In addition, this method is expensive because the time required for the shutdown and the cleaning operation means a loss of production time.

[0008] Therefore, different technical solutions have been developed in the art to eliminate fouling on the heat exchange surface.

[0009] One option foresees repeatedly heating the heat exchanger tubes in an environment where the oxygen level is below the lower explosion limit to thermally remove the deposits from the inner surface of the heat exchanger tubes. However, this thermal cleaning can impose significant thermal stress on the heat exchanger, including the risk of local overheating, which can lead to the degradation of the heat exchanger and thus shorten its lifespan.

[0010] In addition, the use of various chemical additives as anti-fouling agents has been considered. For example, it has been proposed to add certain polymeric materials to a thermal process or combustion medium that may cause fouling and / or to a precursor material for forming such a medium to avoid fouling on the surface of a heat exchanger. For example, US2014 / 0338254A1 proposes using certain hydroxy-functional polyesters as anti-fouling agents when heat-treating a liquid hydrocarbon medium in the temperature range of 100 °C to 550 °C. Such anti-fouling agents may help delay or avoid the progression of fouling; however, they generally cannot remove deposits that have already formed on the heat exchange surface. Alternatively, the use of sugar-containing cleaning compositions has been foreseen, and thereby the removal of deposits from fouled heat exchanger tubes can be achieved, which is attributed to the abrasive cleaning of the surface. However, the use of chemical additives generally means adding foreign substances to the process medium, which can contaminate or otherwise adversely affect the performance of the product obtained from the process medium.

[0011] Therefore, other methods attempt to minimize fouling through the specific structural design of the heat exchanger. Here, it has been found that a large temperature gradient between the process medium and the heat exchanger surface in contact with it generally promotes fouling, and thus a structural design that maintains a smaller temperature gradient has been designed.

[0012] For example, US Patent No. 6,585,949B1 proposes maintaining the temperature difference between a carbon black-containing combustion gas and the heat exchange surface in contact with it to be no greater than 500 °F, preferably no greater than 100 °F, to prevent fouling on the heat exchanger surface. Here, the temperature difference is controlled by controlling the flow rate of a heat exchange fluid, preferably air. For this purpose, it proposes a heat exchanger structure having an outer casing and an inner casing, wherein the air flow is separated and distributed to different baffle channels in such a way that local cooling of any part of the heat exchange surface is minimized by providing holes with different numbers and diameters.

[0013] EP0777098A2 proposes an alternative specific heat exchanger design, which includes a double-bottom tube sheet and means for covering one or more process gas tubes in an area where relatively cold cooling medium may directly impinge. The covering means may include a gas tube chamber adjacent to the cooling medium inlet and / or a collar disposed around the lower part of the process gas tube within the double-bottom tube sheet, and the collar together with the collar filler provides a thermal barrier between the hot process gas and the bottom area of the process gas tube. This design should avoid sudden local temperature changes and achieve a more uniform internal temperature gradient, thereby reducing the fouling tendency within the process gas tube.

[0014] Furthermore, EP2820366B1 relates to a heat exchanger suitable for the production of carbon black. The heat exchanger has a two-stage design, in which a hot process medium containing carbon black, before entering the tubular heat exchange section, passes through a chamber arranged vertically and surrounded by a cylindrical shell. The shell is suitable for transferring heat to the gas to be preheated flowing outside the shell, and then the preheated gas is sent into the inlet of the tubular heat exchanger through a conduit. Maintaining this preheating reduces the temperature difference between the surface of the tubes in the tubular heat exchange section and the hot process medium containing carbon black flowing inside the tubes, thereby reducing or even eliminating the fouling of the tubes.

[0015] This specific structure of the heat exchanger has brought some improvements in reducing fouling. However, the price is an increase in the complexity and sensitivity of the heat exchanger system. In addition, existing heat exchangers cannot be retrofitted according to such a concept because major structural changes to the heat exchanger are required to adjust them accordingly.

[0016] In addition to making structural changes to the design of the main heat exchanger, auxiliary devices specifically designed to reduce fouling in heat exchangers according to different physical principles have also been proposed.

[0017] Therefore, for example, some devices have been proposed that rely on using short-duration, high-speed (e.g., supersonic) gas pulses (e.g., superheated steam) of a cleaning medium during the operation of the heat exchanger to periodically flush the tubes to clean the fouled heat exchanger. An example of such a device is disclosed in U.S. Patent No. 4,366,003 and includes a series of injection nozzles, such as Laval nozzles, which are arranged in the space above the center of the gas inlet opening of the heat exchanger tubes and are connected to a pipeline provided with a shut-off element for periodically supplying a cleaning gas having a positive pressure relative to the process gas. The periodic gas pulses are described as exerting a decomposing effect on the deposits on the inner surface of the heat exchanger tubes through a cavitation effect and being able to maintain a low pressure drop along the heat exchanger tubes and maintain a high heat exchange efficiency without adversely affecting the quality of the carbon black product.

[0018] Similarly, CN101949545(A) describes an automatic descaling device for a shell-and-tube heat exchanger. The device includes: an air injection tube having a plurality of air injection ports, installed at a position close to and parallel to the plane at the end of the heat exchanger tubes and connected to a compressed air source through a valve; a transmission mechanism including a motor for positioning the air injection tube so that each time it is adjusted, a plurality of air injection ports at different positions face a group of heat exchanger tube openings; and a controller for controlling the relative positioning of the injection tube on the heat exchanger tubes and injecting high-pressure pulses into the heat exchanger tubes to remove the deposits on their inner surfaces.

[0019] In addition, U.S. Patent No. 4,846,894 proposes to intermittently interrupt the flow of the transport gas containing carbon black particles through the heat exchanger tubes for a short period of about one second, so that the solid deposits on the inner surface of the tubes are removed and swept away after the gas flow resumes. It also describes a device for implementing this method, which includes a gate or shut-off assembly, and the gate is adjacent to the discharge end of the tube, so that the plate can slide to a position blocking the discharge end of the tube.

[0020] U.S. Patent No. 4,825,940 discloses an automatic cleaning device for periodically cleaning the inner surface of vertically arranged heat exchanger tubes. The device includes: elastic elements, such as springs permanently arranged in the tubes, and nozzles for jetting compressed gas. These nozzles are arranged at a certain distance in front of the openings of the tubes. The pulsed jet of compressed gas from these nozzles is used to vibrate the elastic members inside the tubes, so as to contact the inner surface of the tubes, thereby mechanically scraping off the deposits to clean these surfaces.

[0021] The above types of auxiliary equipment can at least partially satisfactorily reduce fouling; however, they increase the mechanical complexity and sensitivity of the entire system, require the use of specific materials that can withstand harsh working conditions, especially when withstanding high-temperature process media, and require increased control and maintenance. In addition, such devices are costly and cannot be easily retrofitted to existing heat exchangers.

[0022] Therefore, there has always been a need for new methods that are not affected by the limitations and defects of the above-mentioned prior art technical solutions to effectively reduce or even prevent fouling in heat exchangers. Summary of the Invention

[0023] Therefore, the present invention aims to provide an inexpensive device with a simple structure, which can effectively reduce or even avoid fouling in heat exchangers in a reliable manner over an extended period of time without imposing significant stress on the heat exchangers. The device requires no maintenance control or no additional control, and is easy to install, including options for retrofitting existing heat exchangers. In addition, it should be compatible with high-temperature applications, such as being compatible with hot process gases that are the effluents from reactors for producing carbon black, without the risk of pollution or adverse effects on the performance of products (such as especially carbon black) that can be recovered from the process gases.

[0024] The inventors of the present invention have found through diligent research that this object can be achieved by means of the anti-fouling device described in claim 1.

[0025] Accordingly, the present invention relates to a device for reducing fouling in a heat exchanger tube, the device comprising an elongate displacement body configured to be inserted into the heat exchanger tube to reduce the flow cross-sectional area in a portion of the tube. The device further comprises a mounting member connected to the elongate displacement body for attaching the device to an end of the heat exchanger tube. The mounting member is configured to hold the displacement body in a spaced-apart relationship from the inner surface of the tube when the displacement body is inserted into the tube.

[0026] Surprisingly, it has been found that such a device is capable of effectively reducing or even avoiding fouling in a heat exchanger in a reliable manner over an extended period of time without maintenance, external control, addition of chemical reagents or application of significant stress to the heat exchanger. Herein, the device is fully compatible with high-temperature applications and can be exposed to hot combustion or process gases (such as those encountered in the production of carbon black, fumed silica or other particulate materials) without contaminating the products recoverable from the process gases or having an adverse effect on their performance.

[0027] The device according to the present invention can be provided at a relatively low cost, is easy to install and can also be retrofitted to existing heat exchangers, thus representing an attractive general-purpose device for solving fouling-related problems in heat exchangers.

[0028] Without intending to be limited to any theory, the inventors believe that the device according to the present invention is capable of locally controlling the heat and gas flow characteristics in the heat exchanger tube such that fouling can be effectively eliminated in a portion of the tube where fouling would otherwise preferably occur, for example near the end of the heat exchanger tube or in a region where the thermal gradient between the inner surface of the tube and the process gas flowing through the tube is relatively large. Accordingly, the displacement body can affect the gas flow characteristics in the heat exchanger tube in which it is installed, particularly increasing the gas flow velocity in the case where the displacement body reduces the flow cross-sectional area of the tube. The increased gas flow velocity is believed to impede the deposition of condensed-phase materials on the inner surface of the heat exchanger tube and promote the erosion of existing deposited materials. In addition, the displacement body is heated by the process gas flowing through the heat exchanger tube during operation and can act as an emitter and / or reflector of thermal radiation that causes the temperature of the facing portion of the inner surface of the tube to rise, thereby reducing the temperature gradient between these portions of the inner surface of the tube and the process gas flowing through the tube. The reduced temperature gradient between the inner surface of the tube and the process gas is believed to reduce the driving force for depositing condensed-phase materials from the process gas on the inner wall of the tube, for example by preventing nucleation, condensation and / or thermophoretic processes. In addition, the inserted displacement body can thus also increase the heat transfer rate, i.e., the rate of heat transfer from the process medium on the heat exchanger tube to the heat exchange fluid, i.e., improve the efficiency of heat exchange.

[0029] Accordingly, the present invention also relates to a heat exchanger comprising the anti-scaling device according to the present invention and to the use of the anti-scaling device according to the present invention for retrofitting a tubular heat exchanger. Accordingly, the present invention relates to a heat exchanger comprising at least one tube having a first end as an inlet for a process medium and a second end as an outlet for the process medium. The heat exchanger further comprises a housing through which at least one tube extends. The housing forms a pressurized chamber for causing a heat exchange fluid to flow from an inlet provided in the housing to an outlet provided in the housing, thereby effecting heat exchange between the process medium and the heat exchange fluid on at least one tube. The anti-scaling device according to the present invention is attached via a mounting member to one or more ends of at least one of one or more tubes, wherein a displacement body is inserted into the tube in a spaced-apart relationship with the inner surface of the tube to reduce the flow cross-sectional area in a portion of the tube.

[0030] The present invention also relates to a method for reducing scaling on the inner surface of a heat exchanger tube through which a hot process gas entraining a condensed-phase material passes for heat exchange with a heat exchange fluid outside the tube. The method comprises providing a heat exchanger tube having the anti-scaling device according to the present invention, the anti-scaling device being attached via a mounting member to an end of the tube, such as the outlet end of the tube, wherein a displacement body is inserted into the tube in a spaced-apart relationship with the inner surface of the tube to reduce the flow cross-sectional area in a portion of the tube.

[0031] The heat exchanger having the anti-scaling device according to the present invention can be used in any type of application where heat exchangers are commonly used. However, they are particularly useful in applications where traditional severe problems related to scaling may be encountered, such as when the heat exchanger tubes are subjected to a particulate-containing process gas obtained as an effluent from a reactor for producing particulate materials (such as carbon black, fumed silica or other particulate materials). The heat exchanger according to the present invention has been particularly proven to be beneficial in the production of carbon black. Accordingly, the present invention also relates to the use of a heat exchanger comprising the anti-scaling device as described herein in the production of carbon black. It also relates to a process for manufacturing carbon black. The process comprises reacting a fuel with an oxidant to form a hot combustion gas, injecting a hydrocarbon feedstock into the hot combustion gas to form carbon black by pyrolyzing the feedstock in a reactor, quenching the resulting carbon black-containing process medium in the reactor, passing the quenched carbon black-containing process medium through one or more tubes of a heat exchanger according to the present invention, thereby transferring heat from the process medium to a heat exchange medium, and separating and collecting the carbon black from the cooled process medium that has passed through the heat exchanger. A carbon black production apparatus comprising a combustion reactor and a heat exchanger according to the present invention for implementing the process is also within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] These and further features and advantages of the present invention will be described in more detail below. Reference is made herein to exemplary embodiments and the accompanying drawings, which are included for illustrative purposes to enhance understanding of the present invention and should not be construed as limiting the scope of the present invention, the scope of which will be accorded the full breadth of the appended claims and their equivalents.

[0033] Figure 1 A perspective view showing an exemplary embodiment of an anti-scaling device according to the present invention. The installation of the anti-scaling device to the heat exchanger tube is shown in dashed lines.

[0034] Figure 2 Is Figure 1 A cross-sectional view of the shown anti-scaling device, which is attached to the heat exchanger tube through its mounting member.

[0035] Figure 2a Represents a cross-sectional view of the installed anti-scaling device taken along the plane indicated by line IIa-IIa in Figure 2 The enlarged detail view shows that the contact surface of the spacer of the device is positioned very close to / in loose contact with the inner surface of the heat exchanger tube.

[0036] Figure 3 Schematically depicts a heat exchanger according to the present invention, which includes the anti-scaling device of the present invention as disclosed herein.

[0037] Figure 4 Represents a schematic block diagram of a carbon black production apparatus including a heat exchanger according to the present invention as depicted in Figure 3 The enlarged detail view shows that the contact surface of the spacer of the device is positioned very close to / in loose contact with the inner surface of the heat exchanger tube.

[0038] Figure 5A Shows a representative graph of the heat transfer coefficient k multiplied by the heat transfer area ratio A / A o Versus time, which is measured from a reference experiment for an example of a heat exchanger without the anti-scaling device of the present invention installed on the heat exchanger as presented in the present disclosure. The area ratio is selected such that kA / A o Is 1 kW / m at the start of the experiment 2 K.

[0039] Figure 5B Shows a representative graph of the heat transfer coefficient k multiplied by the heat transfer area ratio A / A o Versus time, which is measured from an experiment for a heat exchanger with the anti-scaling device of the present invention installed on the heat exchanger as presented in the present disclosure. The area ratio is selected such that kA / A o Is 1 kW / m at the start of the experiment 2 K. Specific Embodiments

[0040] As described above, the present invention relates to a device for reducing fouling in a heat exchanger tube, also referred to herein as an "anti-fouling device". The anti-fouling device according to the present invention includes an elongated displacer configured to be inserted into the heat exchanger tube to reduce the flow cross-sectional area in a portion of the tube. As used herein, the term "flow cross-sectional area" refers to the cross-sectional area of the tube that is available for a fluid, such as a gas, to flow through the tube. For clarity, the cross-section of the tube refers to the cross-section in a plane perpendicular to the main axis of the tube. The main axis of the tube refers to the central axis along the direction of the hollow channel formed by the closed tube wall as shown and labeled as axis "A" therein. As used herein, the term "displacer" refers to a physical body that, when introduced into the flow path of a fluid such as a gas, maintains its position and causes the flow of the fluid to conform to its shape. In other words, the volume in the flow path occupied by the displacer serves to block the flow of the fluid, and the fluid is forced to flow along the contour of the displacer. Figure 2 The displacer used in the anti-fouling device according to the present invention is elongated. As used herein, the term "elongated" refers to a rectangle. Thus, the displacer exhibits a preferred direction in which its dimension is greater than the dimensions in other directions in space. The axis along the preferred direction is also referred to herein as the longitudinal axis of the displacer (in

[0041] and Figure 1 and Figure 2shown as axis “A”), and the extension of the replacement body along the longitudinal axis is also referred to as its length. The replacement body typically has two opposite ends along the longitudinal axis, also referred to herein as the first end and the second end of the replacement body. The end of the elongated replacement body near the mounting member is referred to herein as the first end of the replacement body, and the mounting member is connected to the replacement body to attach the device to the end of the heat exchanger tube. The mounting member will be discussed in more detail below. The second end opposite the first end typically represents the leading edge of the replacement body that is inserted farthest into the heat exchanger tube. For uniform heat transfer, a symmetric shape of the replacement body may be advantageous. In particular, the replacement body may have a shape that is rotationally symmetric about its longitudinal axis. The cross-section of the replacement body may be constant along the longitudinal axis, for example, the replacement body may have a cylindrical shape. Alternatively, the cross-section of the replacement body may vary gradually along the longitudinal axis, for example, in the case where the replacement body has a conical or tapered shape, for example, varying gradually in a linear manner, for example, in the case where the replacement body includes an irregular and / or complex shape (such as a cylindrical or conical base with one or more protrusions or depressions), varying gradually in a non-linear manner. Additionally, the cross-section of the replacement body may have any form, for example, circular, elliptical, triangular, square, or higher polygons (such as pentagonal or hexagonal) or star-shaped. The exact shape of the replacement body can be selected according to specific needs. For example, a conical shape may provide aerodynamic benefits, while a cylindrical shape may offer advantages in terms of ease of manufacture, for example. Preferably, the replacement body has a cylindrical or conical shape. Depending on the requirements and desired flow characteristics in a specific case, the first end and the second end of the replacement body can have any type of shape. For example, each of the first end and the second end can be individually straight, blunt, angled, tapered, pyramidal, or circular, however, not limited thereto. A straight end, i.e., a planar end perpendicular to the longitudinal axis, may be beneficial in terms of simplicity and ease of manufacture. Other end configurations such as tapered, pyramidal, or circular can provide enhanced aerodynamic characteristics. A circular shape may be particularly advantageous for the second end because it avoids sharp edges and corners that may serve as nucleation sites for the deposition of condensed-phase materials.

[0042] Figure 1An exemplary embodiment of a scale prevention device (1) according to the present invention is shown. The installation of the scale prevention device to the heat exchanger tube (7) is shown in dashed lines, which include an indication of guiding the device along the inner surface of the tube (7) through the spacer (12) of the device when inserting the device into the tube (7), and an indication of the final installation position where the retaining element (11) of the structural support member (10) engages the end (9) of the heat exchanger tube (7). In the illustrated embodiment, the scale prevention device (1) includes an elongated replacement body (2) having a cylindrical shape with a constant cross-section along the longitudinal axis (A) of the replacement body (2). The replacement body (2) has a first end (3) and a second end (4), which are both straight ends in the illustrated embodiment. The mounting member (5) is connected to the elongated replacement body near the first end (3) for enabling the device (1) to be attached to the end (9) of the heat exchanger tube (7) and for maintaining the inserted replacement body (2) and the inner surface (8) of the tube (7) in a spaced-apart relationship, as Figure 2 shown, which shows the Figure 1 exemplary device after being installed to the heat exchanger tube.

[0043] The replacement body of the scale prevention device is generally made of solid material. Therefore, under operating conditions, it is usually substantially impermeable to the process medium exposed in the heat exchanger tube. The material for manufacturing the replacement body should generally provide suitable properties for the intended application, such as corrosion resistance and resistance to degradation, as well as appropriate thermal and mechanical properties, including sufficient strength at the envisioned operating temperature level, which in some cases, such as when using wastewater treatment media from a carbon black reactor, can be as high as 1,000 °C or even higher, and the material for manufacturing the replacement body will be selected according to specific requirements. For example, inorganic composite materials such as metallic materials, ceramics, cermets, or other refractory materials can be used to form the replacement body. Metallic materials, including metals, alloys, and their combinations, generally offer advantages in terms of cost and / or workability, and are therefore preferably used. Non-limiting examples of metallic materials that can be used to form the replacement body include: for example, nickel-based superalloys such as Inconel, Hastelloy, Inconel, Monel, cobalt-based or iron-based superalloys, or stainless steels such as 1.4828, 1.4876, and alloy 800h. For many applications, including heat exchangers for the production of carbon black using readily available stainless steel, according to the present invention, a cost-effective machinable structural material with high strength and chemical stability can be advantageously used.

[0044] The replacement body of the anti-scaling device according to the present invention can be made into a solid body or a hollow body. For cost efficiency and material conservation, as well as to avoid the high weight burden imposed by the replacement body on the heat exchanger and the support structure, the replacement body is preferably a hollow body. The hollow body can have a closed housing that defines the outer contour and shape of the replacement body and encloses an internal void space. The hollow body can have one or more through-holes to achieve pressure equalization of the internal void space. Such one or more through-holes (if any) are typically provided at the first end of the replacement body where the mounting member is arranged, so that they do not affect the flow of the process medium in the heat exchanger tubes. One or more optional through-holes (if any) typically have a diameter in the range of 1 mm to 10 mm, for example 2 mm to 5 mm, which can generally achieve the desired pressure equalization. In Figure 1 In the exemplary embodiment of the anti-scaling device (1) shown, the replacement body (2) is a hollow body, and a through-hole (6) is formed on the first end (3) of the replacement body (2).

[0045] The elongate replacement body of the anti-scaling device according to the invention is configured to be inserted into the heat exchanger tube. This means that the shape and size are chosen to allow the insertion of a replacement body with its longitudinal axis oriented along the main axis of the tube into the tubes of the heat exchanger to be used in combination with the device. Thus, the cross-section of the replacement body is generally smaller than the flow cross-section of the tube, i.e., the inner diameter of the tube. The size of the replacement body can preferably be designed such that: through the replacement body, the flow cross-sectional area of the tube is reduced by 10% to 90% relative to the flow cross-sectional area of the tube without the inserted replacement body, for example 20% to 80% or 25% to 70%. If the size of the replacement body is designed to be so small that the reduction in the flow cross-sectional area of the tube is less than 10%, the anti-fouling effect exerted by the device according to the invention may be weak or even not obvious. If the size of the replacement body is designed to be so large that the reduction in the flow cross-sectional area of the tube is more than 90%, a significant pressure drop may be caused in the tube, and the throughput of the process medium and the heat transfer efficiency may be adversely affected. The length of the replacement body is generally chosen to correspond to the part of the tube where the flow cross-section should be reduced to eliminate scaling. In principle, the replacement body can extend through the entire heat exchanger tube, i.e., the length of the replacement body can correspond up to 100% of the total length of the heat exchanger tube. However, generally, the length of the replacement body will correspond to less than 100% of the total length of the heat exchanger tube (e.g., nearly 90%, e.g., nearly 75%, nearly 50%, nearly 40%, nearly 30, nearly 20% or nearly 10%). The length of the replacement body can be 1% or more, 2% or more, 5% or more, 10% or more, or 15% or more of the total length of the heat exchanger tube. The length of the replacement body can be in the range between any of the above values, for example in the range of 1% to 70%, or 5% to 50%, or 10% to 40% of the total length of the heat exchanger tube. Given the dimensions of the heat exchanger tubes currently used in the art, thus, the length of the replacement body of the anti-scaling device according to the invention can be, for example, in the range from about 30 cm, or 50 cm, or 1 m, or 2 m to about 10 m, or 7 m, or 5 m, and / or the cross-section can be nearly 20 cm, or nearly 15 cm, or nearly 10 cm, or nearly 7 cm, or nearly 5 cm, for example, it can be in the range from 1 cm to 20 cm, or from 2 cm to 15 cm or from 3 cm to 10 cm.

[0046] As previously mentioned and Figure 1 and Figure 2 as shown, the anti-scaling device (1) according to the invention further comprises a mounting member (5) for attaching the device (1) to the end (9) of the heat exchanger tube (7), which is connected to the elongate replacement body (2). As Figure 2As shown, the mounting member (5) is configured to hold the replacement body (2) in a spaced-apart relationship from the inner surface (8) of the tube (7) when the replacement body (2) is inserted into the tube (7). The term "spaced-apart relationship" as used herein means that in the installed state, the inserted replacement body is positioned at a certain distance from the inner surface of the tube. In other words, the replacement body and the inner surface of the tube do not contact each other directly, thereby ensuring the flow of the process medium through the tube and avoiding undesired contact heat transfer and related thermal and / or mechanical stresses between the tube and the replacement body. The mounting member is preferably configured to arrange the longitudinal axis of the replacement body to be substantially parallel to the main axis of the tube. The term "substantially parallel" as used herein means that there may be a small deviation from the ideal parallel arrangement, such as a deviation of nearly 10°, nearly 5°, nearly 3°, or nearly 1°. The mounting member can in particular be configured to: center the inserted replacement body along the main axis of the tube, such that the longitudinal axis of the replacement body and the main axis of the tube can be Figure 2 aligned with each other as shown (where the main axis of the tube and the longitudinal axis of the replacement body correspond to each other and are both shown by the depicted axis "A"). In the installed state, the replacement body can create a circumferential gap, such as an annular gap, between the outer surface of the replacement body and the inner surface of the tube (see also Figure 2a ). In terms of the uniform flow distribution of the process medium in the region where the flow cross-sectional area of the tube is reduced by the replacement body, a symmetric relative arrangement with equal radial distances between the outer surface of the replacement body and the inner surface of the tube in a cross-sectional plane perpendicular to the main axis of the tube may be desirable and promote effective uniform associated heat transfer in the case of a cylinder. For non-cylindrical bodies, gaps should be formed to ensure uniform flow around the replacement body. This can be achieved, for example, if the axis of the replacement body coincides with the axis of the heat exchanger tube.

[0047] The mounting member (5) generally includes, in any configuration such as described above, one or more structural support members (10) for supporting the weight of the replacement body (2) and holding it in a spaced-apart relationship from the inner surface (8) of the tube (7). Since the mounting member must not seal the ends of the heat exchanger tube to which it is installed, an open support structure that allows fluid to pass through is used. For example, one or more structural support members (10) can include a grid, rods, rings, bars, beams, fins, or assemblies or combinations thereof. The dimensions of one or more structural support members (10) or the assemblies formed by them are generally designed such that: when the device (1) is installed, they extend over the heat exchanger tube (7) such that the load of the device (1) can be supported by the heat exchanger tube (7). The mounting member (5) is connected to the replacement body (2). This connection can be as Figure 1 and Figure 2The above is achieved by one or more support members (10) directly connected to the replacement body (2), and the one or more support members (10) are generally located at or near the first end (3) of the elongated replacement body. The connection can be made in various ways available to those skilled in the art, such as but not limited to: welding, soldering, adhesive bonding, plug connection, fasteners (such as bolts, screws, rivets, etc.), or machined as a single piece. As an alternative to directly connecting the replacement body to one or more support members, the mounting member can optionally include one or more extension members for coupling the replacement body to one or more support members. The optional extension member (not shown in the figure) can be any type of retaining element arranged between the structural support member and the first end of the replacement body, such as a rod, bar, chain, or a combination thereof. Selecting an appropriately sized extension member can position the replacement body at any desired distance from the end of the tube, and the device is installed in the tube through the mounting member, so if necessary, scaling can also be selectively eliminated in the part of the tube away from its end.

[0048] The mounting member can attach the anti-scaling device according to the present invention to the end of the heat exchanger tube. For example, as Figure 2 shown, one or more support members (10) can be configured to be held in place on the heat exchanger tube (7), for example, by providing them with one or more retaining elements (11) that cooperate with the end (9) of the heat exchanger tube (7), such as recesses, grooves, etc. Alternatively, in addition to one or more support members and optional extension members (if any), the mounting member can also include one or more attachment devices (not shown in the figure) for attaching the device to the end of the heat exchanger tube. Suitable attachment devices include any known type of attachment device, such as but not limited to: clips, elastic members, fasteners such as screws, bolts, rivets, welding, soldering, adhesive bonding, or plug connection.

[0049] In a preferred embodiment, the mounting member includes a plurality of, for example, at least three (such as three, four, five, or six) support members, such as fins radially extending from the surface of the replacement body. Preferably, all the support members have the same size and are symmetrically arranged with respect to the longitudinal axis of the replacement body. Optionally, each of the support members has a groove on the side facing the heat exchanger tube, and the groove is configured to cooperate with the wall of the heat exchanger tube. For example, in Figure 1 and Figure 2In the illustrated embodiment, the mounting member (5) includes support members in the form of three fins (10) that extend radially from the surface of the replacement body (2) near the first end (3) of the replacement body (2). The fins (10) are symmetrically arranged with respect to the longitudinal axis (A) of the replacement body (2) such that the angle between two adjacent fins in the transverse plane is 120° each. Each fin has a groove (11) on its bottom side, i.e., the side facing the heat exchanger tube (7). The groove (11) is configured to cooperate with the wall (8) of the heat exchanger tube. In the final installation position, the groove (11) of the structural support member (10) engages the end (9) of the heat exchanger tube (7), as Figure 1 shown by the dashed line in Figure 2 . Thus, the replacement body (2) can be installed at the end (9) of the heat exchanger tube (7) by means of the support member (10) having the groove (11) and is spaced from the inner surface (8) of the tube (7) in a centered manner only by gravity, as shown.

[0050] According to the present invention, the anti-scaling device may further optionally include one or more spacers (12) on the surface of the replacement body. As Figure 1 shown by the dashed line in , the one or more spacers can serve as guiding elements to assist in inserting the replacement body into the heat exchanger tube, wherein the device is guided along the inner surface (8) of the heat exchanger tube (7) by the contact surface (12a) of the guiding element (12), and can help maintain a predetermined spacing relationship between the replacement body and the inner surface of the tube, and reduce or avoid the vibrational movement of the replacement body when the replacement body is installed in the tube. If one or more spacers are present, the one or more spacers may preferably be arranged at or near the second end (i.e., the distal end away from the mounting member) of the replacement body. The spacer includes any type of structural element configured to keep the replacement body spaced from the heat exchanger tube, such as fins, vanes, protrusions, etc. Generally, if one or more spacers are present, the one or more spacers extend from the surface of the replacement body in a direction perpendicular to the longitudinal axis of the replacement body. Preferably, the one or more spacers are symmetrically arranged with respect to the longitudinal axis of the replacement body.

[0051] The device may, for example, include a plurality of spacers, preferably at least three (such as three, four, five, or six) spacers, such as guiding fins that extend radially from the surface of the replacement body. In Figure 1 and Figure 2 the illustrated exemplary embodiment, the device includes spacers in the form of three fins (12) that extend radially from the surface of the replacement body (2) near the second end (4) of the replacement body (2). As Figure 2a shown, the fins (12) are symmetrically arranged with respect to the longitudinal axis (A) of the replacement body (2) such that the angle between two adjacent fins in the transverse plane is 120° each.

[0052] The size of the spacer, such as a fin, can be designed to increase the effective perimeter of the replacement body by the fin to almost correspond to the cross-section of the heat exchanger tube (see also the enlarged view in Figure 2a ). The "effective perimeter of the replacement body" refers to the diameter of the smallest circle in the cross-sectional plane perpendicular to the longitudinal axis, and this cross-section encloses the replacement body including the spacer protruding from the surface of the replacement body. "Almost correspond" means that the effective perimeter of the replacement body basically matches the cross-section of the heat exchanger tube, but is still slightly lower than the latter, so that the replacement body can be directly inserted into the tube without causing mechanical damage. In practice, the size of the spacer can preferably be determined such that the effective perimeter of the replacement body is increased by the spacer to be within the range of 95.0% to 99.9% of the cross-section of the heat exchanger tube. The exact size of the spacer can be selected such that, considering the different thermal expansion coefficients of the heat exchanger tube and the different components of the anti-scaling device, the spacer loosely contacts the inner wall of the tube under the operating conditions of the heat exchanger. "Loosely contact" means direct surface contact without a firm contact force.

[0053] The mounting member and its components and one or more optional spacers (if any) can be made of the same type of material as the material used for the replacement body described above. Preferably, the different components of the anti-scaling device according to the present invention are made of the same material, such as stainless steel.

[0054] The device according to the present invention as described above can be used with any type of heat exchanger including one or more heat exchanger tubes to reduce or eliminate scaling in the tubes. Its structure and size can be designed to match different heat exchangers and the design and / or size of the tubes, so it can be used with almost all types of available tubular heat exchangers. Non-limiting examples of tubular heat exchangers are discussed, for example, in U.S. Patent No. 6,585,949, EP 0777098A2, EP2820366B1, and VDI - Edition 11, Springer Verlag. A specific advantage of the anti-scaling device according to the present invention is that it can be used to retrofit existing tubular heat exchangers, thus providing an effective anti-scaling remedy for heat exchangers in use, which is much cheaper and simpler than investing in a new heat exchanger with a design optimized to reduce scaling or retrofitting with a traditional anti-scaling device (such as a nozzle type). Installing the anti-scaling device of the present invention on a heat exchanger is simple and can be completed by a person in the shortest time.

[0055] A heat exchanger including the anti-scaling device according to the present invention is schematically shown in Figure 3is shown. The heat exchanger (13) includes at least one tube (7) having a first end serving as an inlet for the process medium and a second end serving as an outlet for the process medium. Usually, the heat exchanger includes a plurality of tubes, each having a first end serving as an inlet for the process medium and a second end serving as an outlet for the process medium. In Figure 3 three tubes (7) are shown, however, this is not restrictive and the heat exchanger can in principle have any desired number of tubes. Thus, for certain applications, the heat exchanger can include up to 300 tubes or even more, such as 1 to 300 tubes, 2 to 200 tubes, 10 to 150 tubes or 20 to 100 tubes. The tubes typically have a straight, slender cylindrical shape with a hollow channel extending along their entire length, but in principle other shapes can also be used, such as having a non-circular (e.g. oval) or polygonal (e.g. square) cross-section. The dimensions of the tubes are not particularly limited and tubes of any size commonly used in the art can be employed. Usually, the length of each tube is in the range of 1 m to 20 m (e.g. 3 m to 15 m or 5 m to 12 m). The internal diameter (flow cross-section) of the tubes is typically in the range of 2 cm to 30 cm (e.g. 3 cm to 25 cm, 4 cm to 20 cm, or 5 cm to 15 cm, or 5 cm to 10 cm). The thickness of the tube walls can be, for example, in the range of 1 mm to 10 mm, such as 2 mm to 5 mm. The actual number and dimensions of the tubes will be selected according to the required heat exchange capacity and the flow rate through the heat exchanger. The material of the tubes can be any material known in the prior art that is compatible with the operating conditions of the intended application. Typical materials are stainless steels 1.4828, 1.4876 and alloy 800h.

[0056] As Figure 3 shown, one or more tubes (7) of the heat exchanger (13) extend through a housing (14). The housing (14) of the heat exchanger (13) is an outer shell that forms a pressurized chamber (15) for the heat exchange fluid to flow within the boundaries defined by the inner surface of the housing (14). The housing can include a bottom plate (16) and a top plate (17) that are positioned parallel to each other and at a distance from each other for holding one or more tubes in a fixed spatial arrangement, with one or more tubes extending through the pair of plates. The inlet plate for the carbon black-containing gas can be cooled with a portion of the heat exchange fluid. This flow can then be mixed back into the main heat exchange fluid flow at any point before, during or after the heat exchanger. The housing (14) also includes side walls (18) that connect the bottom plate (16) and the top plate (1), thereby surrounding one or more tubes (7) arranged therebetween. The inlet (19) for the heat exchange fluid and the outlet (20) for the heat exchange fluid are typically provided in the housing (14) as openings in the side walls (18). The inlet (19) and the outlet (20) are preferably provided at remote positions on the housing, where one (e.g. Figure 3The outlet (20) therein is typically arranged close to the bottom plate, and the other one (e.g., Figure 3 the inlet (19) therein) is arranged close to the top plate (17). The described arrangement enables the heat exchange fluid to flow from the inlet (19) provided in the housing through the pressurization chamber (15) of the heat exchange fluid containing one or more tubes (7) to the outlet (20) provided in the housing. Thus, heat exchange can be carried out between the process medium flowing through one or more tubes and the heat exchange fluid flowing outside the tubes through the wall of the tubes. The heat exchanger according to the present invention may optionally further include means for optimizing the flow and distribution of the heat exchange fluid through the pressurization chamber (15). For example, as Figure 3 schematically shown, guide plates or baffles (21) may be provided in the housing (14) to control the flow path of the heat exchange fluid through the pressurization chamber (15). In addition, a fluid distribution structure, such as a double housing design known in the art, may be implemented.

[0057] As a unique feature, the heat exchanger (13) includes an anti-scaling device according to the present invention, which is attached to one end of at least one of the one or more tubes (7) through its mounting member (5), wherein a displacer (2) is inserted into the tube in a spaced relationship with the inner surface of the tube (7) to reduce the flow cross-sectional area in a part of the tube (7). Figure 3A heat exchanger having a scale prevention device according to the present invention is shown. The scale prevention device is installed at the end of each tube of the heat exchanger, and the scale prevention device installed on the central tube is shown in a sectional view for illustration purposes. However, it should be understood that this is only for illustrative purposes and is by no means restrictive. The present invention more precisely anticipates that the scale prevention device according to the present invention can be installed on any desired number of tubes present in the heat exchanger, such as a single tube, corresponding to a plurality of tubes selected from the total number of tubes of the heat exchanger. Since scaling generally involves all the tubes of the heat exchanger, preferably, each tube of the heat exchanger and every tube are provided with a scale prevention device according to the present invention. The scale prevention device according to the present invention can be installed at one or both ends of the heat exchanger tube, such as the first end serving as the inlet of the process medium or the second end serving as the outlet of the process medium, or both ends if required. Generally, scaling mainly occurs in a certain part of the tube, such as near one of its ends, so the scale prevention device can be used to selectively eliminate scaling in that part of the tube. Therefore, in many cases, it is useful to provide a heat exchanger having a scale prevention device according to the present invention installed at one end of one or more tubes (such as the first end serving as the inlet of the process medium or the second end serving as the outlet of the process medium). In a preferred embodiment, the heat exchanger thus includes a plurality of tubes, each tube having a first end as the inlet of the process medium and a second opposite end as the outlet of the process medium, and the scale prevention device of the present invention is attached to one of these ends. Preferably, the scale prevention device of the present invention is provided at the same type of end (inlet or outlet) in the tubes provided with the scale prevention device (such as each and every tube of the heat exchanger). Since it has been observed that in some applications scaling tends to mainly occur on the outlet side of the tube, it may be preferred to connect the scale prevention device according to the present invention to the second end serving as the outlet of the process medium.

[0058] One or more scale prevention devices included in the heat exchanger can each separately have any configuration as detailed above in the context of the scale prevention device, including the shape, size, and arrangement relative to the heat exchanger tubes. Thus, as Figure 2As depicted, the anti-scaling device can be installed, for example, on a pipe such that the longitudinal axis of the displacer is substantially parallel to or even aligned with the main axis of the pipe. The displacer of the device can in particular have a rotationally symmetric shape with respect to its longitudinal axis, such as a cylindrical or conical shape. The length and cross-sectional dimensions of the displacer can be as described above. The dimensions of the displacer can in particular be designed such that: with respect to the flow cross-sectional area of the pipe without the inserted displacer, the flow cross-sectional area of the pipe is reduced by 10% to 90% by the displacer, for example 20% to 80% or 25% to 70%. In addition, the displacer of the anti-scaling device can typically extend over nearly 70%, for example nearly 50%, of the total length of the heat exchanger pipe. For example, its length can be in the range of 10% to 50% of the total length of the heat exchanger pipe. It has been found that in certain applications, if the displacer is configured such that the flow velocity of the process medium in the part of the pipe with the reduced flow cross-sectional area is at least 50 m / s, for example 60 m / s or greater, or 80 m / s or greater, or 100 m / s or greater, then reducing scaling is particularly effective. In some cases, the displacer is configured such that the flow velocity of the process medium in the part of the pipe with the reduced flow cross-sectional area is within the range of + / - 30%, preferably + / - 20%, of the initial flow velocity of the process medium at the pipe inlet.

[0059] The heat exchanger according to the invention can be spatially arranged in any suitable manner. Preferably, one or more pipes of the heat exchanger are arranged substantially vertically, as also Figure 3 shown. With this vertical arrangement, the anti-scaling device of the invention can be supported by the upper end of the corresponding pipe. The anti-scaling device is connected to the upper end of the pipe by a mounting and is held in place by gravity without additional devices, as Figure 2 and Figure 3 shown. However, other spatial arrangements of the heat exchanger are also possible, and the heat exchanger according to the invention can for example be of the horizontal type, where the pipes of the heat exchanger are arranged substantially horizontally with respect to the supporting ground. The terms "substantially vertical" or "substantially horizontal" as used herein mean that there can be a small deviation from the ideal corresponding arrangement, such as a deviation of nearly 5° or nearly 3° or nearly 1°, the ideal corresponding arrangement being an orientation of 90° with respect to the ground in the case of the vertical direction or an orientation of 180° with respect to the ground in the case of the horizontal direction.

[0060] There is no particular limitation on the working mode of the heat exchanger. Thus, the heat exchanger can work, for example, when the process medium and the heat exchange fluid flow in a countercurrent mode, a cocurrent mode or a crossflow mode. However, preferably, the heat exchanger according to the present invention works in a countercurrent mode. In addition, according to the present invention, there is no particular limitation on the type of the process medium and the type of the heat exchange fluid, and the anti-scaling device described herein or the heat exchanger including the anti-scaling device can be used together with any type of process medium and heat exchange fluid type commonly used for corresponding specific applications.

[0061] It has been found that the anti-scaling device according to the present invention can effectively reduce or even eliminate the scaling in the heat exchanger tubes, and can also increase the heat transfer rate.

[0062] As described above, the present invention thus also relates to a method for reducing the scaling on the inner surface of a heat exchanger tube through which a hot process gas entraining a condensed-phase substance flows for heat exchange with a heat exchange fluid outside the tube. The expressions "hot process gas", "hot process medium", etc. refer to gas or fluid media generated during processes such as industrial production processes or combustion processes, which have a temperature higher than the ambient temperature, usually significantly higher than the ambient temperature, for example having a temperature of at least 100 °C or at least 400 °C. The term "condensed-phase substance" refers to a substance in solid or liquid form. The condensed-phase substance can particularly exist in the form of particles. The term "particle" includes particles, droplets, agglomerates and other discrete physical entities of the condensed-phase substance. The condensed-phase substance existing in the form of particles is usually dispersed in the hot process gas and can be deposited on the inner surface of the heat exchanger tube. To avoid such scaling, the method according to the present invention anticipates providing the heat exchanger tube with the anti-scaling device according to the present invention, which is attached to the end of the tube, for example the outlet end of the tube, by means of a mounting, and a displacer is inserted into the tube in a spaced-apart relationship with the inner surface of the tube to reduce the flow cross-sectional area in a part of the tube.

[0063] The anti-scaling device used in the method according to the invention can be any configuration as detailed above in the context of the anti-scaling device and the heat exchanger according to the invention, including the shape, dimensions and arrangement of the heat exchanger tubes. In particular, the anti-scaling device can be mounted, for example, on the tube such that the longitudinal axis of the displacer is substantially parallel to the main axis of the tube, or even aligned with the main axis of the tube. In addition, the displacer of the device can in particular have a shape that is rotationally symmetric with respect to its longitudinal axis, such as cylindrical or conical. The length and cross-sectional dimensions of the displacer can be as described above. In certain applications, the method involves increasing the flow velocity of the process medium in the section of the tube with a reduced flow cross-sectional area through the displacer to at least 50 m / s, such as 60 m / s or higher, or 80 m / s or higher, or 100 m / s or higher. In some cases, the displacer is configured such that the flow velocity of the process medium in the section of the tube with a reduced flow cross-sectional area is adjusted by the displacer of the inserted anti-scaling device to within + / - 30%, preferably + / - 20%, of the initial flow velocity of the process medium at the inlet of the tube. The anti-scaling device according to the invention is compatible with high-temperature applications. The hot process gas entraining the condensed-phase material according to the method of the invention can have, for example, an initial temperature of 400 °C or higher (e.g., in the range of 400 °C to 1,200 °C). The method for reducing scaling according to the invention is, for example, very suitable and effective for heat exchanger tubes that are affected by particulate hot process gases from combustion processes or processes for producing particulate materials (such as carbon black, fumed silica or other particulate materials such as metal oxides). The hot process gas entraining the condensed-phase material can thus be, for example, the effluent from a reactor for producing carbon black.

[0064] As mentioned above, the heat exchanger with the anti-scaling device according to the invention is particularly suitable for applications where traditional serious problems related to scaling may be encountered (e.g., when the heat exchanger tubes are affected by particulate process gases that are the effluent from a reactor for producing particulate materials such as carbon black, fumed silica or other particulate materials), and has been specifically proven to be particularly useful in the production of carbon black. Accordingly, the invention also relates to a process for manufacturing carbon black using the heat exchanger according to the invention and to a carbon black production plant comprising such a heat exchanger, wherein such a manufacturing process can be carried out as described above. These aspects of the invention will be described with reference to Figure 4 describe these aspects of the invention, Figure 4 shows a schematic block diagram of a carbon black production plant comprising a heat exchanger according to the invention.

[0065] Carbon black is formed by pyrolysis of a hydrocarbon feedstock in a reactor under controlled conditions. The reactor can be any type of reactor commonly used for manufacturing carbon black, particularly for the production of furnace black. As Figure 4As shown, the reactor may include different zones, such as a combustion zone, an injection zone, a reaction zone, and a quenching or cooling zone. A fuel and an oxidizer are fed into the reactor, for example into a burner in the combustion zone, to produce hot combustion gases by the reaction of these components. The fuel is typically a hydrocarbon-containing fuel, such as hydrocarbon oil or gas, and the oxidizer is typically air, oxygen, or oxygen-enriched air, preferably air. The oxidizer introduced into the reactor is typically preheated, which will be discussed in more detail below. The hot combustion gases produced by fuel combustion reach a high temperature, for example a high temperature in the range of 1,200 to 2,000 °C or higher. The reactor is typically lined with refractory material capable of withstanding such high temperatures. Then, the hydrocarbon-containing feedstock is injected into the hot combustion gas stream. This can be achieved by injection nozzles at one or more locations in the injection zone downstream of the combustion zone of the reactor. A variety of liquid and gaseous hydrocarbon materials can be used as the feedstock. Suitable feedstocks include, for example, natural gas, mineral oil, vegetable oil, hydrocarbon oils obtained from the processing of coal or crude oil (such as naphtha or gasoline), fractions from coal tar, and oils obtained by cracking petroleum fractions. Due to the high temperature of the hot combustion gases, the injected hydrocarbon-containing feedstock is thermally decomposed, and when the mixture of the feedstock and the hot combustion gases passes through the reaction zone downstream of the injection zone of the reactor, carbon black is formed by pyrolysis of the feedstock. Then, the carbon black-containing process medium produced is quenched in the quenching zone to stop the reaction. Quenching can be achieved by injecting a quenching medium (such as water or steam) into the carbon black-containing process medium received from the reaction zone of the reactor, or by applying a quenching boiler system for this purpose. The injected quenching medium reduces the temperature of the process medium to a level at which the pyrolysis reaction no longer proceeds at a significant rate, for example a temperature below 1,200 °C, typically below 1,000 °C, for example a temperature in the range of 400 °C to 1,200 °C. By adjusting the position of the injection of the quenching medium, the reaction time can be controlled, thereby controlling the properties of the carbon black formed, such as the particle size distribution. Typically, the reaction time is in the range of a few milliseconds to 2 seconds. Generally, carbon black grades with very different properties can be produced by adjusting the reactor design and manufacturing conditions (for example, see Jean-Baptiste Donnet, Roop Chand Bansal, Meng-Jiao Wang, Carbon Black, 2nd Edition, CRC Press, 1993). Those skilled in the art will select a suitable reactor design and reaction conditions based on the desired properties of the specific carbon black to be produced.

[0066] The quenched carbon black-containing process medium as the effluent obtained from the reactor passes through one or more tubes of the heat exchanger according to the invention, thereby transferring heat from the process medium to the heat exchange medium. The heat exchanger according to the invention can have any of the configurations described above, in particular including any shape, size and arrangement of the one or more anti-scaling devices according to the invention contained relative to the heat exchanger tubes. Generally, the heat exchanger used in carbon black production according to the invention includes a plurality of parallel heat exchanger tubes which extend through an enclosed housing which defines a plenum for allowing a heat exchange fluid to flow from an inlet provided in the housing to an outlet provided in the housing. The heat exchanger is preferably arranged vertically, i.e. the tubes are oriented substantially vertically with respect to the ground. One or more or all of the tubes can have anti-scaling devices according to the invention mounted to the ends of the tubes. One or more anti-scaling devices are preferably mounted to the upper ends of the tubes. In this case, for example as described and discussed above in the context of Figure 1 and Figure 2 , they can be held in place relative to the tubes by means of mountings using gravity. When the hot carbon black-containing process medium passes through the tubes, heat is transferred across the tube walls to the heat exchange fluid flow flowing on the outer surfaces of the tubes in the plenum. The heat exchanger generally operates in a countercurrent mode. The quenched carbon black-containing process medium as the effluent obtained from the reactor is typically supplied to the tubes located at the bottom end and exits at its top end at a reduced temperature through the tubes of the heat exchanger. A heat exchange medium such as air is typically introduced into the plenum through an inlet provided in the upper part of the housing and exits the heat exchanger through an outlet provided in the lower part of the housing (e.g. as depicted in Figure 3 ). The temperature of the heat exchange fluid can be increased at the outlet to a temperature of up to about 1,000 °C, for example in the range from 500 to 800 °C, by heat exchange with the process medium present in the plenum.

[0067] Different heat exchange fluids can be used according to the invention. Non-limiting examples include air, oxygen, oxygen-enriched air, nitrogen-enriched air, water or steam. Generally, the heat exchange medium used in the process for manufacturing carbon black according to the invention corresponds to the oxidant used to produce the hot combustion gas in the reactor, for example, preferably air. As shown in Figure 4 , an oxidant such as air can be fed into the reactor after being preheated in the heat exchanger to form a hot combustion gas. Thus, a part of the heat generated by the combustion reaction can be recovered by the heat exchanger and used to preheat the starting materials for carbon black production, thereby improving the overall efficiency of the process.

[0068] Using a heat exchanger according to the invention comprising the anti-scaling devices disclosed herein can effectively reduce fouling on the inner surfaces of the heat exchanger tubes and maintain a high heat exchange efficiency during an extended operating period without the need for maintenance or other complex and / or expensive auxiliary cleaning devices.

[0069] The process medium containing carbon black is conveyed to a device for separating and collecting carbon black from the cooled process medium after being cooled by a heat exchanger. The device for separating and collecting carbon black generally includes a filtration unit, such as a bag filter.

[0070] As Figure 4 shown, the process medium containing carbon black leaving the heat exchanger can optionally pass through one or more auxiliary cooling units, such as additional heat exchangers, which may or may not be heat exchangers according to the present invention, to further cool the process medium, and then carbon black is collected and separated from the process medium.

[0071] Using the heat exchanger according to the present invention can effectively eliminate fouling and improve process efficiency without the risk of contamination or the risk of adversely affecting the performance of the carbon black product.

[0072] The features and advantages of the present invention will be further illustrated by the following non-limiting examples, which show the use of the anti-fouling device according to the present invention as an air preheater in a carbon black production process and the beneficial effects obtained therefrom.

[0073] Example

[0074] Carbon black is produced using a furnace reactor. The reactor includes a combustion chamber, an injection zone, a reaction zone, and a quenching zone. The device used also includes a heat exchanger (a 24-tube, type 900+ single-pass heat exchanger from & Son AB of Sweden) connected to the reactor. The heat exchanger is equipped with a steam cleaning device of a type similar to that described in U.S. Patent No. 4,366,003. In the combustion chamber, natural gas is burned together with air, and the air is preheated to about 620 °C using the heat exchanger. The flue gas (i.e., a mixture of carbon black and the reaction gas obtained from the reactor as the process medium containing carbon black) is supplied to the heat exchanger to generate a hot combustion gas stream, as described in more detail below. In the injection zone downstream of the combustion zone, oil is then injected into the generated hot combustion gas stream. The type of oil used is a coal tar fraction, which has the following analytical characteristics:

[0075] C [wt.%] H [wt.%] N [wt.%] S [wt.%] O [wt.%] <![CDATA[H2O[wt.%]]]> Ash [wt.%] 91.5 5.7 0.9 0.7 1.2 0.03 0.002

[0076] The given elemental mass fractions of carbon, hydrogen, nitrogen, sulfur, and oxygen refer to the dry and ash-free basis. The amount of oil is adjusted so that the STSA of the final carbon black product reaches about 120 square meters per gram. The oil and the hot combustion gas from the combustion chamber are converted into carbon black and tail gas in the subsequent reaction zone. Then, water quenching is used in the quenching zone to stop the reaction and cool the stream to 720 °C.

[0077] Downstream of the quenching zone, the flue gas passes through the above heat exchanger. The heat exchanger tubes are arranged vertically with respect to the ground. The heat exchanger operates in a countercurrent mode, so that the hot process medium containing carbon black, which is obtained from the reactor as an effluent, is supplied to the bottom end of the heat exchanger tubes and passed upward through the tubes to their top ends, while an air stream serving as a heat exchange fluid passes from an inlet near the top of the housing through the outer surface of the tubes enclosed therein to an outlet near the bottom of the housing via the interior of the housing. The heat exchanger is designed to operate with air at 2000 to 3500 Nm 3 / h, and the maximum pressure drop on both the air and flue gas sides is 110 mbar. The temperature of the flue gas and the temperature of the air are measured by thermocouples at the respective inlets of the heat exchanger and at the respective outlets of the heat exchanger. These measured temperature values are then used to determine the heat transfer coefficient k. For this purpose, the set mass flow rate, the isobaric specific heat capacity (given as 1107 J / kgK), the air temperature measured at the outlet of the heat exchanger, and the air temperature measured at the inlet of the heat exchanger (which are denoted by Φ m , c p , T air，out , T air，in respectively) are used to calculate the heat flow transferred to the air according to the following formula:

[0078] Φ q = Φ m c p (T air，out - T air，in ).

[0079] The average temperature difference between the flue gas and the air is further determined by the following formula:

[0080]

[0081] where the flue gas temperature measured at the inlet of the heat exchanger and the flue gas temperature measured at the outlet of the heat exchanger are denoted as

[0082] T smoke，in , T smoke，out .

[0083] Then the heat transfer coefficient k is multiplied by the heat transfer area A, and can be determined using the following formula

[0084] For comparison purposes, kA is related to a reference area A determined according to the following formula o and

[0085]

[0086] where the heat transfer coefficient at the start of the measurement is denoted by k start .

[0087] The steam cleaner of the heat exchanger is used to remove deposits generated from the previous operation from the inner surface of the tube by injecting steam pulses into the tube before each test, thereby creating reproducible start-up conditions. For reference purposes, tests were first conducted with no additional anti-fouling device installed in the heat exchanger. In each test, the heat exchanger typically operates continuously for 6 to 7 hours, as described above, where a carbon black-containing process gas is obtained as the effluent of the reactor, and air is preheated as the heat exchange fluid. During operation, the heat transfer coefficient is determined as an indicator of fouling, as described above. Thus, a total of 10 reference tests were conducted. Subsequently, each tube of the heat exchanger is provided with an anti-fouling device according to the present invention installed at its upper end. The anti-fouling device used has a structure as shown in Figure 1 and has a hollow cylindrical displacer with a length of 4 m. The mounting member includes three fins radially extending from the outer surface of the displacer near one end of the displacer and three guide fins radially extending from the outer surface of the displacer near the opposite end of the displacer. The lateral extension of each guide fin is 22 mm and the height is 54 mm. Each fin of the mounting member has a groove for mating with the tube wall. The tube is mounted on the heat exchanger tube by mounting fins, each fin having a lateral extension of 40 mm, a height of 30 mm, and a slit of 5 mm to engage a heat exchanger tube with an inner diameter of about 82 mm and a length of about 9 m. By inserting the displacer into the tube at the upper end of the tube until it docks in the groove of the fin of the mounting member that mates with the tube wall at the upper end of the tube, one such anti-fouling device is mounted on each tube of the heat exchanger. The anti-fouling device thus installed is held in place by gravity, where the displacer is located at the center of the tube and its longitudinal axis is aligned with the main tube axis, thereby forming an annular gap between the outer surface of the displacer and the inner tube wall. Then the same operating conditions are applied, and the heat transfer coefficient is determined in the same manner as in the above reference tests, using a heat exchanger with an anti-fouling device according to the present invention installed on the tube. One test was conducted for more than 20 hours to evaluate the performance on a longer time scale. The process conditions are summarized in Table 1 below:

[0088] Table 1

[0089] Air mass flow kg / s 1,11 Reactor outlet temperature ℃ 725℃ Air temperature at the inlet ℃ 66

[0090] Figure 5A and Figure 5B shows representative graphs of the heat transfer coefficient as a function of time for the reference tests without the anti-fouling device ( Figure 5A ) and the tests with the anti-fouling device according to the present invention ( Figure 5B ), where the heat transfer coefficient is expressed as kA / A o . As can be seen from Figure 5A , in the case of the reference tests, kA / A o decreases from 1 kW / m in the first 1 - 2 hours2 The initial value of K significantly decreases to approximately 0.88 kW / m 2 K, and then further decreases to approximately 0.85 kW / m after about 6 hours 2 The value of K, i.e., the thermal conductivity has decreased by approximately 15% in total over a 6-hour duration. For longer runs, a further decrease in the heat transfer coefficient was observed, which is also indicated by Figure 5A the continuous negative slope in the graph in. In contrast, Figure 5B it is shown that for the tests using the anti-scaling device according to the present invention, the heat transfer coefficient expressed as kA / A o only slightly decreases by approximately 5% from the initial value of 1 kW / m2K to a value of 0.95 kW / m2K after 6 hours of operation. No significant further decrease was observed in the tests with an extended duration of more than 20 hours. These findings indicate that by using the anti-scaling device according to the present invention, the reduction in the heat transfer coefficient of heat associated with fouling on the inner surface of the tubes of the heat exchanger can be effectively reduced, and stable operating conditions can be achieved. No negative impact on the structural integrity of the heat exchanger was observed for this device.

[0091] To study the potential impact of the anti-scaling device on the quality of the carbon black product, samples of carbon black materials separated and collected from the carbon black-containing process medium after passing through the heat exchanger via a filter were analyzed.

[0092] Table 2 shows the analysis results of the carbon black products obtained in the reference tests and the tests in which the anti-scaling device according to the present invention was installed in the heat exchanger. The reported values are the average and standard deviation of the total number of reference tests or tests conducted, respectively.

[0093] Table 2:

[0094]

[0095] The iodine absorption value was measured according to ASTM D-1510.

[0096] The statistical thickness surface area (STSA) was measured according to ASTM D-6556.

[0097] The oil absorption number (OAN) was determined according to ASTM D2414.

[0098] The BET surface area is the total surface area determined by nitrogen absorption using the Brunauer Emmett Teller (BET) method according to ASTM D-6556.

[0099] The reported transmission value was measured according to ASTM D-1618.

[0100] Comparison of the data in Table 2 shows that in the tests of installing the anti-scaling device according to the present invention on the heat exchanger and the reference tests without such a device, the measured carbon black properties are comparable and there are no differences within the tolerance range. This indicates that using the anti-scaling device of the present invention will not have an adverse impact on the product characteristics.

[0101] List of reference signs

[0102] 1 Anti-scaling device

[0103] 2 Displacement body

[0104] 3 First end of the displacement body

[0105] 4 Second end of the displacement body

[0106] 5 Mounting member [[ID=--]]

[0107] 6 Through hole

[0108] 7 Heat exchanger tube

[0109] 8 Inner surface of the heat exchanger tube

[0110] 9 End of the heat exchanger tube

[0111] 10 Structural support

[0112] 11 Retaining element

[0113] 12 Spacer

[0114] 12a Contact surface of the spacer

[0115] 13 Heat exchanger

[0116] 14 Housing

[0117] 15 Pressurization chamber

[0118] 16 Bottom plate

[0119] 17 Top plate

[0120] 18 Side wall

[0121] 19 Inlet of the heat exchange fluid

[0122] 20 Outlet of the heat exchange fluid

[0123] 21 Guide plate / baffle

[0124] A Main axis of the heat exchanger tube / longitudinal axis of the displacement body

Claims

1. An anti-scaling device for reducing scaling in a heat exchanger tube, comprising: (a) An elongated displacement body configured to be inserted into the heat exchanger tube to reduce the flow cross-sectional area in a portion of the heat exchanger tube. The displacement body is a hollow body having a closed housing that defines the outer contour and shape of the displacement body and encloses an internal void space; And (b) A mounting member connected to the elongated displacement body for attaching the anti-scaling device to an end of the heat exchanger tube. The mounting member is configured to hold the displacement body in a spaced-apart relationship with the inner surface of the heat exchanger tube after the displacement body is inserted into the heat exchanger tube, Wherein the mounting member includes a plurality of support members, each support member having a groove on a side facing the heat exchanger tube, and the groove is configured to cooperate with the wall of the heat exchanger tube.

2. The anti-scaling device according to claim 1, wherein, The mounting member is configured to arrange the longitudinal axis of the displacement body parallel to the main axis of the heat exchanger tube, so that the inserted displacement body is centered along the main axis of the heat exchanger tube.

3. The anti-scaling device according to claim 1 or 2, wherein In the installed state, an annular gap is formed between the outer surface of the displacement body and the inner wall of the heat exchanger tube, and / or wherein, The displacement body has a shape that is rotationally symmetric with respect to the longitudinal axis of the displacement body, and the hollow body has through holes for pressure equalization.

4. The anti-scaling device according to claim 1 or 2, wherein The mounting member includes at least three support members, and the support members are fins extending from the surface of the displacement body.

5. The anti-scaling device according to claim 1 or 2, further comprising one or more spacers on the surface of the displacement body, and the spacers are arranged at or near the distal end of the displacement body relative to the mounting member, Wherein the spacer includes a plurality of guiding fins radially extending from the surface of the displacement body, and the size of the fins is designed such that the effective circumference of the displacement body is increased by the fins to a range from 95% to 99.9% of the cross-section of the heat exchanger tube.

6. The anti-scaling device according to claim 5, wherein, The displacement body, the mounting member and / or the spacer are made of stainless steel, and / or wherein, the length of the displacement body is in the range of 0.5 m to 5 m and / or has a cross-section of up to 20 cm.

7. A heat exchanger, comprising: (a) At least one tube having a first end as an inlet for a process medium and a second end as an outlet for the process medium, (b) A housing through which the at least one tube extends. The housing forms a pressurized chamber for a heat exchange fluid to flow from an inlet provided in the housing to an outlet provided in the housing, and heat exchange between the process medium and the heat exchange fluid is achieved on the at least one tube, (c) The anti-scaling device according to any one of claims 1 to 6, and the anti-scaling device is attached to one or more ends of at least one of the one or more tubes through the mounting member, wherein the displacement body is inserted into the tube in a spaced-apart relationship with the inner surface of the tube to reduce the flow cross-sectional area in a portion of the tube.

8. The heat exchanger according to claim 7, wherein, The displacer reduces the flow cross-sectional area by 10% to 90% relative to the flow cross-sectional area of the tube without the inserted displacer, and / or wherein the extension length of the displacer is at most 70% of the total length of the tube.

9. The heat exchanger according to any one of claims 7 or 8, wherein, The one or more tubes are arranged vertically, and at least one anti-scaling device is supported by the upper end of the corresponding tube. The at least one anti-scaling device is attached to the corresponding tube by a mounting member and is held in place by gravity.

10. A method for reducing fouling on the inner surface of a heat exchanger tube, wherein a hot process gas containing a condensed-phase substance passes through the heat exchanger tube to exchange heat with a heat exchange fluid outside the heat exchanger tube, the method comprising: An anti-scaling device according to any one of claims 1 to 6 is provided for the heat exchanger tube. The anti-scaling device is attached to the end of the heat exchanger tube by the mounting member. The displacer inserted into the heat exchanger tube is spaced from the inner surface of the heat exchanger tube to reduce the flow cross-sectional area in a part of the heat exchanger tube.

11. The method according to claim 10, wherein, Through the displacer of the anti-scaling device, the flow rate of the process medium in the part of the heat exchanger tube with a reduced flow cross-sectional area is increased to at least 50 m / s.

12. The method according to claim 10 or 11, wherein, The hot process gas containing particulate matter is an effluent obtained from a reactor for producing carbon black and / or has an initial temperature in the range of 400 °C to 1,200 °C.

13. A process for manufacturing carbon black, comprising: reacting a fuel with an oxidant to form a hot combustion gas, injecting a hydrocarbon raw material into the hot combustion gas to form carbon black by pyrolyzing the raw material in a reactor, quenching the resulting carbon black-containing process medium in the reactor, passing the quenched carbon black-containing process medium through one or more tubes of a heat exchanger according to any one of claims 7 to 9, thereby transferring heat from the process medium to a heat exchange medium, and separating and collecting the carbon black from the cooled process medium that has passed through the heat exchanger.

14. A carbon black production apparatus, comprising a combustion reactor and a heat exchanger according to any one of claims 7 to 9.

15. Use of an anti-scaling device according to any one of claims 1 to 6 for retrofitting a tubular heat exchanger.

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