System and method for preventing leakage of industrial equipment operating in corrosive environment

Abstract

The invention relates to the field of industrial treatment of high-temperature corrosive liquid from a gas-liquid contactor in the chemical industry. The present invention provides a processing unit for preventing leakage of such liquids from equipment downstream of a gas-liquid contactor and an associated method of preventing leakage.

Description

Technical Field

[0001] The present invention relates to the field of industrial processing of hot corrosive liquids originating from gas-liquid contactors (e.g., falling film towers). In particular, the present invention relates to a system and method in which the risk of leakage of hot and / or corrosive liquids downstream of the gas-liquid contactor can be reduced. Background Art

[0002] In the chemical industry, many processes use aggressive, acidic, alkaline, or other corrosive agents as catalysts, solutions, or working media to drive chemical reactions. Because chemical reactions often perform better or have higher conversion rates at higher temperatures, the reagents exiting gas-liquid contactors (such as falling film towers) are often at high temperatures. If these reagents are corrosive and / or erosive, they may damage downstream processing units by corroding the components of the processing units.

[0003] In the prior art, heat exchangers are frequently used in the chemical industry for the purpose of transferring heat between different media (e.g., corrosive liquids and air, or coolants). For heat exchangers, the thermal conductivity of the material from which they are made is a key factor. Many materials (such as graphite, silicon carbide and glass) are corrosion-resistant and have good thermal conductivity (glass is an exception), but have the disadvantage of being inherently brittle and therefore unsuitable for withstanding high pressures (this mainly results in too low a permissible force around gaskets - since a higher pressure drop increases flow rates and therefore heat transfer) and / or rapid pressure changes due to, for example, start-up and shutdown. When subjected to these conditions, these materials can crack, leading to leakage of the hot, corrosive liquids they are designed to exchange heat for. Leaks in these devices pose a high safety risk to operators operating the equipment and need to be avoided.

[0004] Therefore, there is a need in the industry to prevent leaks in systems containing gas liquid contactors operating in high temperature and / or corrosive environments, where the systems include one or more heat exchangers, by, among other means, operating at lower pressures and changing operating conditions smoothly and slowly. The present invention provides a solution to the above-mentioned problems. Summary of the Invention

[0005] According to a first aspect, the present invention relates to a treatment unit for treating a corrosive medium, such as a corrosive, alkaline or acidic liquid flow, possibly at high temperature, comprising:

[0006] A gas-liquid contactor, such as a falling film tower, suitable for contacting a liquid from an input stream A with a gas (such as air, water vapor) and discharging a liquid stream B, said contactor being located at a height H r Department; and

[0007] - an air trap arranged to receive a liquid stream B and to discharge a liquid stream C, and provided with a headspace that traps a volume of gas, which allows the removal of air bubbles and dampens pressure fluctuations within stream B; and

[0008] a heat exchanger arranged to receive a liquid flow C and to discharge a liquid flow D, said heat exchanger comprising heat exchanging means, said heat exchanger being located at a height H c Department; and

[0009] a first vacuum line L1 suitable for providing a negative gauge pressure to the head space, thereby sucking a liquid flow B into the air trap;

[0010] Among them, H r >H c , in order to deliver the pressure differential that acts as the driving force through the heat exchanger.

[0011] This aspect of the present invention provides several advantages. Specifically, it has been found that a treatment unit configured according to this aspect minimizes the risk of leakage of treated liquid from the heat exchanger, thereby allowing the use of materials for the heat exchange device that would not otherwise withstand pressure and / or pressure fluctuations in prior art treatment units. This aspect of the present invention facilitates maintaining the pressure upstream of the heat exchanger within a preferred pressure range. The specific height difference between the gas-liquid contactor and the heat exchanger also allows the pressure to be maintained within the preferred pressure range without the use of a pump.

[0012] According to one embodiment of the present invention, the processing unit further comprises: a vapor-liquid separator arranged to receive the liquid flow D from the heat exchanger; the vapor-liquid separator is located at a height H s This height is higher than the height H of the heat exchanger. c , thereby allowing static pressure to be applied to the liquid flow D to avoid it undergoing liquid-gas transition.

[0013] According to one embodiment of the present invention, the processing unit further comprises a second vacuum line L2 connected to the gas-liquid contactor, which is suitable for providing a negative gauge pressure to the gas-liquid contactor, thereby sucking the input flow A into the gas-liquid contactor.

[0014] According to one embodiment of the present invention, the first and / or second vacuum line L1 , L2 is connected to a vapor-liquid separator.

[0015] According to one embodiment of the invention, the processing unit comprises one or more at least partially traced pipes.

[0016] According to one embodiment of the present invention, the heat exchange device of the heat exchanger comprises a material selected from the group consisting of graphite (C), silicon carbide (SiC), and silicon dioxide (SiO 2 ).

[0017] According to one embodiment of the present invention, the heat exchange device comprises graphite.

[0018] According to one embodiment of the invention, the heat exchange device is selected from: a tube or a tube bundle, one or more plates.

[0019] According to one embodiment of the present invention, the air trap is located at a height H L Where H r >H c >H L .

[0020] According to one embodiment of the present invention, the gas-liquid contactor is a falling film tower.

[0021] According to one embodiment of the present invention, the pH value of liquid stream B and / or stream C is lower than 2 or higher than 12.

[0022] According to one embodiment of the present invention, the temperature of liquid stream B and / or stream C is between 100°C and 300°C, preferably between 120°C and 250°C.

[0023] According to one embodiment of the present invention, the gas-liquid contactor is a reactor configured to receive a reaction reagent (preferably an inorganic oxygen acid and / or a salt thereof, more preferably polyphosphoric acid (PPA)) and contact the reaction reagent with water.

[0024] According to one embodiment of the present invention, the processing unit further includes:

[0025] - first pumping means adapted to receive the liquid flow C and to pump the liquid flow C in the direction of the heat exchanger; and

[0026] - a pressure measuring device arranged to measure the pressure of the liquid flow C pumped in the direction of the heat exchanger but downstream of the control valve; and

[0027] a pressure control valve located downstream of the first pumping means and the pressure measuring means and arranged to regulate the flow of the liquid stream C to the heat exchanger; and

[0028] - a pressure control device in communication with the first pumping device, the pressure measuring device and the pressure control valve, said pressure control device being adapted to maintain the pressure of the liquid flow C within a predetermined pressure range by actuating the pressure control valve and / or the first pumping device based on the pressure measuring device.

[0029] According to one embodiment of the invention, the first pumping device comprises a motor connected to a variable frequency drive (VFD) adapted to be actuated by the pressure control device. An advantage of this embodiment is that the flow at the heat exchanger can be finely regulated and pressure peaks can be reduced.

[0030] According to one embodiment of the present invention, the heat exchanger is part of an economizer, which is adapted to bring the liquid stream E to be supplied to the gas liquid contactor into thermal contact with the liquid stream C.

[0031] According to a further aspect, the invention relates to the use of an air trap arranged upstream of a heat exchanger having a heat exchanging device, wherein the air trap serves to protect the heat exchanging device from pressure fluctuations.

[0032] According to another aspect, the present invention relates to the use of a vapor-liquid separator arranged downstream of a heat exchanger, the vapor-liquid separator being located at a height H s At the height H s A height above the heat exchanger used to create static pressure at the heat exchanger outlet.

[0033] According to a further aspect, the present invention relates to a method of operating a treatment unit as described in any one of the embodiments of the treatment unit according to the present invention for treating a corrosive liquid, the method comprising:

[0034] a) Provide negative gauge pressure to the headspace of the air trap;

[0035] b) contacting the liquid with the gas in a gas-liquid contactor to produce a reaction product;

[0036] c) discharging the reaction product via liquid stream B;

[0037] d) allowing liquid stream B to flow through the air trap and draining said stream from the air trap via liquid stream C, wherein the liquid stream is allowed to flow under the influence of gravity;

[0038] e) The liquid flow C is driven through the heat exchanger using the driving force generated by the influence of gravity. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] With specific reference now to the accompanying drawings, it should be emphasized that the details shown are exemplary and are intended only to illustrate the discussion of various embodiments of the present invention. These drawings are provided to provide what is considered to be the most useful and easily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to present the structural details of the present invention in a more detailed manner than is necessary to understand the basic principles of the present invention. The description in conjunction with the accompanying drawings will make it clear to those skilled in the art how the various forms of the present invention can be implemented in practice.

[0040] Figure 1 , attached Figure 1 is a schematic diagram of a treatment unit according to one embodiment of the present invention, showing a gas-liquid contactor 1 connected to a gas trap 2, which is further connected to a heat exchanger 3. The gas-liquid contactor 1 and the heat exchanger 3 are located at different heights so that H r >H c, so that the flow of liquid can flow from the gas-liquid contactor 1 to the heat exchanger under the influence of gravity. In other words, the heat exchanger 3 is located at a height lower than the gas-liquid contactor 1.

[0041] Figure 2 , attached Figure 2 is a schematic diagram of a treatment unit according to one embodiment of the present invention, wherein the gas-liquid contactor 1, the gas trap and the economizer are positioned so that the gas trap 2 is located at a height lower than both the heat exchanger 3 and the gas-liquid contactor 1, and the heat exchanger 3 is located at a height lower than the gas-liquid contactor 1, i.e., H r >H c >H L , wherein the processing unit further comprises a vapor-liquid separator 4 connected downstream of the economizer.

[0042] Figure 3 , attached Figure 3 , short for , is a schematic diagram of a treatment unit according to an embodiment of the present invention, in which a series of devices are provided to further reduce the risk of leakage upstream of the economizer.

[0043] Figure 4 , attached Figure 4 , short for , is a schematic diagram of a treatment unit according to one embodiment of the present invention, the treatment unit including a vapor-liquid separator having a series of safety devices located downstream of an economizer. DETAILED DESCRIPTION

[0044] The present invention will now be further described. In the following paragraphs, different aspects of the present invention are defined in more detail. Unless explicitly stated otherwise, each aspect so defined can be combined with any other one or more aspects. In particular, any feature that is indicated as preferred or advantageous can be combined with any other one or more features that are indicated as preferred or advantageous. When describing the compounds of the present invention, the terms used should be interpreted according to the following definitions, unless the context otherwise provides.

[0045] As used herein, the terms "about" or "approximately" when referring to a measurable value (e.g., a parameter, an amount, a duration, etc.) are intended to encompass deviations of ±10% or less, preferably ±5% or less, more preferably ±1% or less, and still more preferably ±0.1% or less from the specified value, so long as such deviations are suitable for practicing the disclosed invention. It is to be understood that the value to which the modifier "about" or "approximately" refers is itself also specifically and preferably disclosed.

[0046] According to a first aspect, the present invention relates to a treatment unit for treating a corrosive medium, such as a corrosive, alkaline or acidic liquid flow, possibly at high temperature, comprising:

[0047] A gas-liquid contactor (e.g., a falling film tower) suitable for contacting a liquid from an input stream A with a gas (e.g., air, water vapor) and discharging a liquid stream B, said contactor being located at a height H r Department; and

[0048] - an air trap arranged to receive a liquid stream B and to discharge a liquid stream C, and provided with a headspace containing a volume of gas which allows the removal of air bubbles and dampens pressure fluctuations within stream B; and

[0049] - a heat exchanger arranged to receive a liquid flow C and to discharge a liquid flow D, said heat exchanger comprising heat exchanging means, said heat exchanger being located at a height H c Department; and

[0050] a first vacuum line L1 suitable for providing a negative gauge pressure to the head space, thereby sucking a liquid flow B into the air trap;

[0051] Among them, H r >H c , in order to deliver the pressure differential that acts as the driving force through the heat exchanger.

[0052] In the context of the present invention, the term "gas-liquid contactor" refers to an industrial device that provides gas and liquid for contact with each other. Gas-liquid contactors suitable for implementing the present invention include differential gas-liquid contactors, in which mass transfer occurs throughout the entire length of the contactor and vapor-liquid equilibrium is not reached at any point in the device, and staged gas-liquid contactors, in which vapor-liquid equilibrium is reached within each stage of the device and mass transfer occurs only in a portion of the volume of each stage. Examples of differential gas-liquid contactors include falling film towers, packed towers, bubble towers, spray towers, and gas-liquid stirred vessels. Examples of staged gas-liquid contactors include plate towers, rotating disk contactors, and venturi tubes. According to one embodiment of the present invention, the treatment unit according to any of the preceding claims, wherein the gas-liquid contactor 1 is a falling film tower. In another embodiment of the present invention, the falling film tower is configured to perform a chemical reaction, such as an exothermic hydrolysis / solvation reaction of polyphosphoric acid (PPA) or an endothermic oligomerization / condensation reaction of orthophosphoric acid / pyrophosphoric acid (PA). In a falling film tower, PPA or PA is arranged to be in close contact with the air and / or water vapor present in the tower, which may cause turbulence downstream of the falling film tower, which is harmful to downstream industrial equipment (such as heat exchangers), thereby causing leakage. The present invention solves this problem. According to one embodiment of the present invention, the gas-liquid contactor 1 is a reactor configured to receive a reaction reagent (preferably an inorganic oxygen-containing acid and / or a salt thereof, more preferably polyphosphoric acid (PPA)) and contact the reaction reagent with water. Through the present invention, the pressure at the heat exchanger 3 is reduced to a significant level, and the influence caused by the presence of gas in the pipeline is also minimized at the location of the heat exchanger 3.

[0053] Because no pumping is required to move liquid between the gas-liquid contactor 1 and the heat exchanger 3, and by providing the gas trap 2, the pressure at the heat exchanger 3 is typically reduced to 2-3 bar. Heat exchangers with relatively low operating pressures, such as those made of graphite, benefit most from the present invention. The maximum operating pressure of heat exchangers containing graphite is about 6-8 bar gauge (barg). Through the present invention, the pressure reaching these heat exchangers can be consistently maintained (i.e., with minimal to no pressure spikes) at less than 50% of the maximum operating pressure. The present invention allows the pressure drop at the heat exchanger 3 to be less than 3 bar, less than 2 bar, and advantageously, even better, in the range of 0.5-1 bar. This will greatly reduce the likelihood of leaks and increase the mean time between leaks to several years of normal operation.

[0054] According to the present invention, a gas-liquid contactor 1 is configured to contact a liquid from an input stream A with a gas and discharge a liquid stream B. Depending on the type of liquid stream A that is contacted with the gas in the gas-liquid contactor, the discharge liquid stream B may leave the gas-liquid contactor at a high temperature. According to the present invention, the gas-liquid contactor 1 is located at a height H. r Place.

[0055] According to the invention, the treatment unit further comprises a gas trap 2 arranged to receive a liquid stream B coming from the gas liquid contactor and to discharge a liquid stream C.

[0056] In the context of the present invention, the term "air trap" refers to an industrial device that is configured to allow a headspace to form when filled with liquid, thereby trapping a certain volume of gas therein. This has been found to allow for the suppression of pressure fluctuations and provide a means for maintaining the pressure downstream of the air trap within a predetermined preferred range. The air trap 2 according to the present invention can take various forms and configurations, such as, but not limited to, a siphon, an expansion vessel, a large pipe with a minimum diameter to allow bubbles to escape, or a restriction orifice for generating a lower pressure to encourage bubble formation. According to one embodiment of the present invention, the air trap 2 is provided with a headspace that traps a certain volume of gas, which allows for the suppression of pressure fluctuations within the flow B. In the context of the present invention, the headspace can be any component suitable for preventing bubbles from advancing further along the unit. For example, if the air trap 2 is a siphon, the headspace can be a calculated pipe to ensure that bubbles are not trapped in the siphon and cannot advance along the unit. In this example, the headspace can have a minimum diameter to ensure that the downward velocity of the liquid is sufficiently low compared to the upward velocity of the bubbles.

[0057] According to another embodiment of the present invention, the treatment unit further comprises one or more pipes at least partially provided with heat tracing. In other words, according to this embodiment, at least one or more pipes connecting one or more components of the unit (e.g. the gas liquid contactor 1 and the gas trap 2) are provided with heat tracing along at least a portion of their length or their circumference. Heat tracing is advantageous in simplifying operation by preventing the liquid in the unit from cooling and increasing viscosity, thereby clogging the pipeline due to, for example, (partial) crystallization of the liquid. This situation may occur during a sudden cessation of operation or blockage of the unit. The heat tracing allows the temperature of the retained liquid therein to be maintained within a specific preferred range until operation can be resumed. The heating of the pipeline can be achieved by heating the pipeline or part thereof using, for example, an electrical conductor, steam or any other heat medium.

[0058] Furthermore, according to the invention, the treatment unit comprises a heat exchanger 3 arranged to receive a liquid flow C and to discharge a liquid flow D, said heat exchanger comprising heat exchanging means.

[0059] According to the present invention, the term "heat exchanger" refers to an industrial component configured to facilitate heat exchange between, for example, two liquids, two gases, or a gas and a liquid. Specifically, according to the present invention, heat exchanger 3 is configured to exchange heat with a liquid stream C via a heat exchange device. According to the present invention, various heat exchange devices can be used. In particular, the present invention allows for the use of heat exchange devices comprising materials such as, but not limited to, graphite carbon, silicon carbide (SiC), silicon dioxide (SiO2), and metals (e.g., steel, such as stainless steel, copper, and aluminum).

[0060] According to a first aspect of the present invention, the processing unit includes a first vacuum line L1 adapted to provide a negative gauge pressure to the headspace of the gas trap 2, thereby drawing a liquid stream B into the gas trap 2. According to the present invention, the vacuum line is a conduit capable of withstanding negative pressure, connected to a negative pressure providing device, such as a vacuum pump. Without such a vacuum line, gas and / or air that breaks through in the absence of an air trap could cause liquid hammer and severely damage the integrity of fragile equipment.

[0061] According to one embodiment of the present invention, the heat exchange means of the heat exchanger comprises a material selected from the group consisting of graphite (C), silicon carbide (SiC), and silicon dioxide (SiO2). According to a preferred embodiment of the present invention, the heat exchange means comprises graphite. The processing unit according to the present invention allows the use of heat exchangers comprising heat exchange means that are particularly susceptible to breakage, such as those comprising heat exchange means selected from the group consisting of graphite (C), silicon carbide (SiC), and silicon dioxide (SiO2).

[0062] According to the present invention, the heat exchanger is located at a height H c Wherein the height H of the gas-liquid contactor r Greater than the height H of the heat exchangerc , so as to deliver a pressure differential as a driving force through the heat exchanger. Therefore, the gas-liquid contactor and the heat exchanger are positioned at a height that allows the liquid introduced into the gas-liquid contactor to flow toward the heat exchanger under the influence of gravity.

[0063] According to one embodiment of the invention, the heat exchange device is selected from the group consisting of: a tube or a tube bundle, one or more plates, a disk, a block.

[0064] According to the present invention, the temperature of the liquid stream B leaving the gas liquid contactor can be higher than the temperature at which the downstream processing units are designed to operate. Therefore, according to the present invention, the reaction can be carried out at a higher temperature than would be possible without the present invention. The possibility of increasing the temperature of the liquid leaving the reaction receiver and conversely the temperature of the reaction itself provides several advantages that are obvious to a person skilled in the art, such as: use of cheaper less reactive substances, use of smaller amounts of reagents, higher conversion, faster reaction times, etc. According to one embodiment of the present invention, the pH value of the liquid stream B and / or stream C is lower than 2 or higher than 12. According to one embodiment of the present invention, the temperature of the liquid stream B and / or stream C is between 100°C and 300°C, preferably between 120°C and 250°C.

[0065] In chemistry, highly reactive substances (e.g., acids and bases) such as H2SO4, HNO3, HCl, Cl2, Br2, HBr, F2, and HF are often used to drive organic reactions, often at temperatures above 150-200°C and in the presence of water (e.g., in hydrolysis reactions). Under such conditions, corrosion of the process units downstream of the gas-liquid contactor must be avoided, which presents a significant challenge for the chemical industry. When the process units are configured to operate under pressure, i.e., when the liquid being processed is provided at a non-atmospheric pressure, rupture of one or more equipment components within the process units can have catastrophic consequences. According to one embodiment of the present invention, the pH of liquid stream B and / or stream C is less than 2 or greater than 12.

[0066] According to one embodiment of the present invention, the temperature of liquid stream B and / or stream C is between 100°C and 300°C, preferably between 120°C and 250°C.

[0067] One aspect of the invention relates to the use of an air trap 2 arranged upstream of a heat exchanger 3 having a heat exchange device, wherein the air trap serves to protect the heat exchange device from pressure variations.

[0068] According to a further aspect, the present invention relates to a method of operating a treatment unit as described in any one of the embodiments of the treatment unit according to the present invention for treating a corrosive liquid, the method comprising:

[0069] a) Provide negative gauge pressure to the headspace of the air trap;

[0070] b) contacting the liquid with the gas in a gas-liquid contactor to produce a reaction product;

[0071] c) discharging the reaction product via liquid stream B;

[0072] d) allowing liquid stream B to flow through the air trap and draining the stream from the air trap via liquid stream C, wherein the liquid stream is allowed to flow under the influence of gravity;

[0073] e) The liquid flow C is driven through the heat exchanger using the driving force generated by the influence of gravity.

[0074] According to this aspect, it has been found to be advantageous to start the operation of the treatment unit according to the invention when a negative gauge pressure has already been established in the headspace of the gas trap. In other words, it has been found to be advantageous to carry out treatment by the treatment unit according to the invention when at least one vacuum line is in an operational state at the start of operation, i.e. when a negative pressure (vacuum) is achieved at the location of the gas trap.

[0075] Figure 1 It is shown how the invention can be implemented and an embodiment of the invention is disclosed, in which a gas-liquid contactor 1 is arranged to receive a liquid (see input stream A, for example at a position located at the top of the contactor) which is contacted with a gas, for example in a falling film tower or the like. Gas-liquid contactors generally include heat exchange means, since chemical reactions are either exothermic (needing cooling) or endothermic (needing heating). This is also true for corrosive, alkaline, and acidic media in industry, which generally need to be diluted with water or with a solvent. This dilution is generally an exothermic reaction and requires cooling, for example by generating steam. In other applications, these media need to be increased in concentration. This is generally an endothermic reaction and requires heating, for example by condensation of steam. In the gas-liquid contactor, a chemical reaction may occur between the liquid and the gas, the liquid may be in contact with the gas to react, or the first liquid may be in contact with another liquid to react. In any case, in the gas-liquid contactor 1, the liquid is in contact with the gas and the liquid may react with the gas. The gas-liquid contactor 1 is located at a height H from the base on which the treatment unit is erected. r The gas trap 2 is connected to the gas-liquid contactor 1 and receives the exhaust liquid flow B from the gas-liquid contactor 1. The gas trap 2 is connected to the heat exchanger 3, which is configured to receive the liquid from the gas trap 2. The heat exchanger 3 is located at a height H from the base. c The heat exchanger 3 is then provided with means for discharging a liquid stream after heat transfer has taken place, thereby discharging a liquid stream D. The heat exchanger 3 and the gas-liquid contactor 1 are adapted (ie positioned) so that the liquid stream can flow from these two plant components under the influence of gravity, i.e. the heat exchanger is gravity fed. This can be achieved by H r >H cis achieved so as to deliver a pressure differential as the driving force through the heat exchanger. Figure 1 Also shown are the first and second vacuum lines L1, L2, which are connected to a negative pressure providing device, such as a vacuum pump (not shown). The vacuum lines, in particular the first vacuum line L1, help to draw the liquid into the gas trap 2. According to the present invention, the first and / or second vacuum lines L1, L2 can be connected to various locations of the treatment unit, but they are suitable for providing negative pressure to the top space of the gas trap 2. The first and / or second vacuum lines L1, L2 can be directly or indirectly connected to the gas trap 2 and / or the gas-liquid contactor 1 so as to promote the absorption of liquid into the gas trap 2 by venting gas and / or air before startup. One or more vacuum lines assist gravity as a displacement driving force for the liquid from the gas-liquid contactor 1 to the heat exchanger 3.

[0076] The term "gravity feed" refers to a system that is adapted to allow a liquid stream to flow from the gas-liquid contactor 1 to the heat exchanger 3 even in the absence of a first pumping device. According to the present invention, a pumping device can be provided downstream of the heat exchanger 3. A pumping device can also be provided to pump the liquid stream from the gas-liquid contactor 1 to the heat exchanger 3 at various locations along the path, but the flow from the gas-liquid contactor 1 to the heat exchanger 3 can occur without the presence of such a pumping device.

[0077] The term "pumping device" refers to a device suitable for moving a liquid. Pumping devices useful in the context of the present invention are centrifugal pumps, positive displacement pumps, or any other type of fluid pump. The pumps can be electrically driven or by means of a steam expander. In a preferred embodiment, the pumps used in the context of the present invention are centrifugal pumps; more specifically, centrifugal pumps made of metallic materials; even more specifically, centrifugal pumps made of PTFE, PFA-lined carbon, or stainless steel. Particularly advantageous are pumping devices comprising a motor connected to a variable frequency drive (VFD).

[0078] In prior art processing equipment, the handling of corrosive, alkaline, and acidic liquid streams, particularly at high temperatures (e.g., above 100° C.), is typically limited by the design temperature and design pressure of equipment such as one or more pumping devices or heat exchangers. If the temperature of the liquid stream is higher than the design temperature of the pumping device, the pump may not operate properly and / or may be damaged by the liquid stream. If the pressure of the liquid stream is higher than the design pressure of the heat exchanger, the internal walls of the heat exchanger may rupture, allowing the liquid to leak. According to the present invention, by providing a height difference between the vapor-liquid separator 1 and the heat exchanger 3, the use of a pumping device can be avoided and the heat exchanger can be protected from rapid pressure changes (i.e., pressure spikes) that may be higher than the design pressure of the heat exchanger. However, gravity-fed systems such as those according to the present invention, in which the liquid is in contact with the gas, have the disadvantage that air entrapment and gas blocking are prone to occur, and their effects can be difficult to mitigate.

[0079] Air and / or gas entrapment, which is one possible cause of pressure peaks, is minimized by the presence of an air trap 2 between the gas liquid contactor 1 and the heat exchanger 3. The air trap 2 is therefore arranged to allow the entrapped air to escape. The use of the air trap 2 and the gravity feed arrangement provides a synergistic effect, namely minimizing both overpressure and pressure peaks, thereby allowing the pressure at the heat exchanger 3 to be maintained within a preferred pressure range. Another effect of the air trap 2 is that, in the event that bubbles may form after the gas liquid contactor 1, these bubbles cannot pass through the air trap 2 towards the heat exchanger 3 and can easily return to the apparatus 1.

[0080] It is therefore an object of the present invention to solve these drawbacks in industrial units treating high temperature and / or corrosive liquids under pressure.

[0081] In the context of the present invention, corrosive, alkaline, or acidic media are media that can damage industrial equipment based on their chemical properties (e.g., corrosive, alkaline, or acidic). Because the reactivity of such media increases with temperature, high-temperature corrosive, alkaline, or acidic media are more likely to cause damage to industrial equipment. Examples of damage to industrial equipment include loosening / breaking gaskets and O-rings, puncture of equipment, and damage to moving parts. Damage to heat exchangers caused by overpressure from high-temperature and / or corrosive liquids is particularly problematic, a problem addressed by the present invention. Heat exchanger designs tend to utilize large heat exchange surfaces, which results in thin heat exchange devices, reducing mechanical rigidity and increasing leak susceptibility. Furthermore, various materials may be highly advantageous in heat exchange but unsuitable for manufacturing heat exchange devices used in heat exchangers. When operating conditions include high temperatures and high pressures, finding heat exchange materials suitable for their tasks becomes a challenge. The present invention provides industrial equipment that allows for the processing of high-temperature and / or corrosive liquids in a process unit comprising a heat exchanger that can be made from materials known to be leak-prone, such as graphite, glass, and silicon carbide.

[0082] Therefore, the treatment unit according to the present invention provides a means for advantageously maintaining the pressure within the unit at a pressure below the maximum operating pressure of the heat exchanger. In the context of the present invention, the maximum operating pressure of a heat exchanger, or the design pressure of a heat exchanger, is the maximum pressure of a fluid that the heat exchanger can process without being damaged. The maximum operating pressure of a heat exchanger is set by the manufacturer of the heat exchanger. For some types of heat exchangers, the maximum operating pressure is determined by the design pressure limitations of the heat exchanger components and / or the materials from which they are made.

[0083] Corrosive, alkaline, acidic media that can be treated by the treatment unit according to the invention include any kind of ionic liquids with any kind of solvents; for example, inorganic oxygen-containing acids (e.g. HNO3, H2SO4, H3PO4) and / or their salts with water; metal halide salts (e.g. lithium bromide / lithium chloride...) with water; ammonium salts with water; in particular inorganic oxygen-containing acids and / or their salts with water; even more particularly orthophosphoric acid / pyrophosphoric acid (PA) with water in an endothermic oligomerization / condensation reaction; or polyphosphoric acid (PPA) with water in an exothermic hydrolysis / solvation reaction.

[0084] Figure 2 One or more embodiments of the present invention are shown, and a processing unit including an economizer 9 and a vapor-liquid separator 4 is shown. Figure 2 In the embodiment of the invention shown, the treatment unit comprises a vapor-liquid separator 4 arranged to receive the liquid flow D from the heat exchanger; the vapor-liquid separator 4 is located at a height H s This height is higher than the height H of the heat exchanger. c, so as to allow a static pressure to be exerted on the liquid flow D in order to avoid its liquid-gas transition. In this particular example embodiment, the gas trap 2 is located at a height H L Where H r >H s >H c >H L It is found that the air pocket 2 is located at the height H L By providing a processing unit according to any embodiment of the present invention, wherein the gas trap 2 is positioned such that H r >H s >H c >H L Placing the gas trap 2 at the lowest point of the unit has been found to be advantageous in preventing gas from entering the heat exchanger 3 .

[0085] It should be understood that the gas-liquid contactor 1 according to the present invention is provided with a plurality of inlets or outlets required for carrying out the present invention. Figure 2 As shown schematically, the gas-liquid contactor receives or is capable of receiving an input stream of a variety of materials (e.g., solid or liquid). For example, the gas-liquid contactor 1 may receive an input stream F of a preheated material from the economizer 9 that has been cooled or preheated by a heat exchange device within the economizer. In other cases, the gas-liquid contactor 1 may be provided with an exhaust port, through which a gas such as water vapor may be provided to exit the gas-liquid contactor.

[0086] In the case of an exothermic reaction, the gas-liquid contactor 1 may need to be cooled. According to one embodiment of the present invention, in order to cool the gas-liquid contactor, a cooling liquid flow can be provided to a heat exchanger located at the gas-liquid contactor 1 and in thermal contact with it. The cooling effect can be achieved by, for example, generating steam. In this case, the hot water entering the heat exchanger will be heated and steam will be generated. In other applications, the corrosive, alkaline or acidic medium in the gas-liquid contactor 1 may need to be concentrated. This can be achieved by evaporation of a liquid (such as water or a solvent). Evaporation is generally an endothermic reaction and needs to be heated by, for example, steam condensation. In this case, the steam entering the heat exchanger will be cooled and condensed.

[0087] exist Figure 2 In the present invention, the economizer is designed so that the liquid leaving the gas-liquid contactor 1 at a high temperature preheats the liquid to be supplied to the gas-liquid contactor 1, while the liquid to be supplied to the gas-liquid contactor 1 at a low temperature cools the stream discharged from the gas-liquid contactor 1. Therefore, according to one embodiment of the present invention, the treatment unit includes a heat exchanger 3, which is part of the economizer 9, and the economizer 9 is adapted to bring the liquid stream E to be supplied to the gas-liquid contactor 1 into thermal contact with the liquid stream C. One advantage of this embodiment is that heat can be effectively reused, thereby providing a more efficient treatment unit.

[0088] Figure 2 The specific embodiment disclosed in the disclosure is further supplemented with a vapor-liquid separator 4 (also known as a flash tank) for evaporating a vapor stream (e.g., water vapor) from the vapor-liquid separator 9 and reducing the temperature of the economizer discharge stream D by evaporative cooling, thereby producing a vapor-liquid separator discharge stream at a lower temperature. In the vapor-liquid separator 4, the pressure of the economizer discharge stream 5 is expanded toward a lower pressure, and thus, for example, water is evaporated, leaving behind a liquid. The evaporation of the solvent cools the stream D. More specifically, the vapor-liquid separator 4 provides a further cooling effect to cool the corrosive, alkaline, or acidic liquid stream originating from the gas-liquid contactor 1 before it reaches further processing stages.

[0089] In one embodiment of the present invention, the vapor-liquid separator used is arranged downstream of the heat exchanger 3 and is located at a height H s The height is higher than the height of the heat exchanger and is used to generate static pressure at the outlet of the heat exchanger 3, such as Figure 2 As shown in Figure 1 . One advantage of this embodiment is that if the temperature of stream D is too high, the static height provides a pressure higher than the vapor pressure of the liquid in stream D, thus preventing flashing of the liquid. It also prevents liquid evaporation in the graphite equipment, as graphite is very sensitive to any type of evaporation at its surface. In other words, this setup provides a sustainable design for all process conditions, such as excessively high temperatures and low pressures during different operating modes.

[0090] Therefore, one embodiment of the present invention provides for the use of a vapor-liquid separator (4) in a treatment unit for treating a corrosive medium, wherein the treatment unit comprises:

[0091] a gas-liquid contactor (1) suitable for contacting liquid from an input stream A with a gas and discharging a liquid stream B, said contactor being located at a height Hr; and

[0092] a heat exchanger (3) arranged to receive a liquid flow C and to discharge a liquid flow D, said heat exchanger comprising heat exchange means, said heat exchanger being located at a height Hc;

[0093] wherein Hr>Hc so as to deliver a pressure difference as a driving force through the heat exchanger; and wherein a vapor-liquid separator (4) is arranged downstream of the heat exchanger (3) and at a height Hs, which is higher than the height of the heat exchanger, for generating a static pressure on the liquid flow D at the outlet of the heat exchanger to avoid it undergoing liquid-to-gas conversion.

[0094] According to one embodiment, a processing unit for processing a corrosive medium is provided, wherein the processing unit comprises:

[0095] - a gas-liquid contactor (1) adapted to bring a liquid from an input stream A into contact with a gas and to discharge a liquid stream B, said contactor being located at a height Hr; and

[0096] - a heat exchanger (3) arranged to receive a liquid stream C and to discharge a liquid stream D, said heat exchanger comprising heat exchange means, said heat exchanger being located at a height Hc;

[0097] wherein H r > H c so as to deliver a pressure difference as driving force through the heat exchanger; and wherein a vapor-liquid separator (4) is arranged downstream of the heat exchanger (3) and at a height H s higher than the height of the heat exchanger for creating a static pressure at the outlet of the heat exchanger on the liquid stream D to avoid a liquid-gas transition thereof.

[0098] According to another aspect of the above embodiment, the treatment unit further comprises a vacuum line L2 connected to the gas-liquid contactor (1) and adapted to provide a negative gage pressure to the gas-liquid contactor (1) so as to suck the input stream A into the gas-liquid contactor (1). In a particular embodiment, this vacuum line is connected to the vapor-liquid separator (4).

[0099] According to another embodiment of the application, the treatment unit comprises:

[0100] - first pumping means 5 adapted to receive the liquid stream C and to pump the liquid stream C in the direction of the heat exchanger 3; and

[0101] - pressure measuring means 6 arranged to measure the pressure of the liquid stream C pumped in the direction of the heat exchanger 3 but downstream of a control valve 7; and

[0102] - a pressure control valve 7 located downstream of the first pumping means 5 and of the pressure measuring means 6 and arranged to regulate the flow of the liquid stream C to the heat exchanger 3; and

[0103] - pressure control means 8 in communication with the first pumping means 5, the pressure measuring means 6 and the pressure control valve 7, said pressure control means being adapted to maintain the pressure of the liquid stream C within a predetermined pressure range by actuating the pressure control valve 7 and / or the first pumping means 5 based on the pressure measuring means 6.

[0104] This embodiment has been found to be advantageous because it provides further control over the pressure reaching the heat exchanger 3, thereby further minimizing the risk of leakage within the heat exchanger. The presence of the first pumping device 5 and the air trap 2 reduces air entrapment in the liquid and minimizes the amount of air bubbles reaching the heat exchanger 3. According to this embodiment, various pumps can be used, however, according to a preferred further embodiment of the present invention, the first pumping device 5 comprises a motor connected to a variable frequency drive (VFD) that is adapted to be actuated by the pressure control device 8. The first pumping device according to this embodiment allows for fine adjustment of the motor, thereby providing a way to gradually increase or decrease the speed of the motor for the first pumping device. In this way, pressure peaks are reduced and the pressure within the heat exchanger is further maintained within its operating pressure range.

[0105] Figure 3 One or more embodiments of the present invention are shown, wherein a series of devices are provided to further reduce the risk of leakage upstream of the economizer. Specifically, Figure 3 Shown Figure 2 The embodiment disclosed in , wherein the processing unit further includes:

[0106] - first pumping means 5 adapted to receive the liquid flow C and to pump it in the direction of the heat exchanger 3 (in this case the economizer 9); and

[0107] a pressure measuring device 6 (also indicated as PIC) arranged to measure the pressure of the liquid flow C pumped in the direction of the heat exchanger 3 but downstream of the control valve 7 ; and

[0108] a pressure control valve 7 located downstream of the first pumping means 5 and the pressure measuring means 6 and arranged to regulate the flow of the liquid stream C directed to the heat exchanger 3; and

[0109] a pressure control device 8 in communication with the first pumping device 5, the pressure measuring device 6 and the pressure control valve 7, said pressure control device being suitable for maintaining the pressure of the liquid flow C within a predetermined pressure range by actuating the pressure control valve 7 and / or the first pumping device 5 based on the pressure measuring device 6.

[0110] Figure 4 An embodiment of the present invention is shown, in which the processing unit includes a vapor-liquid separator provided with a series of safety devices located downstream of the economizer. Specifically, according to one embodiment of the present invention, the vapor-liquid separator 4 is also supplemented with a control system (also called a safety device) to monitor and open / close the flow into and out of the vapor-liquid separator 4. Referring again to Figure 4 , such safety devices include:

[0111] a pressure device, also called PIC, for measuring the pressure of the vapor-liquid separator 4; and

[0112] A valve unit, also called PCV, is located at the vapor leading to the vapor condenser G, between the vapor-liquid separator 4 and the vapor condenser 12 .

[0113] If the vacuum in the vapor-liquid separator 4 is insufficient (because not enough solvent is evaporated and therefore insufficient cooling is provided), the valve unit will open and control the pressure in the vapor-liquid separator 4 accordingly, thereby promoting the evaporation of the solvent. This evaporative cooling will result in cooling of the solvent. The generated solvent vapor will move from the vapor-liquid separator to the vapor condenser 12 via the vapor flow G. Ultimately, this will prevent a medium with too high a temperature and / or too high a pressure from being supplied to the suction line 10 (also called the feed line) of the second pumping device 11. The safety device may optionally further include a temperature device (also called a TIC) for measuring the temperature of the vapor flow G. If the temperature of the medium is too high (for example, higher than the design temperature of the second pumping device 11), the valve unit closes. This additional safety device now ensures that the second pumping device will not operate above its design temperature under all circumstances.

[0114] Example 1 - Production of Hydrochloric Acid

[0115] An example is the absorption of HCl in water to produce hydrochloric acid. The absorption medium is cooled using a graphite plate heat exchanger, which is arranged below the absorber where the steam is generated. This allows the generated hydrochloric acid (typically a 30-50% aqueous HCl solution) to be cooled without a pump. This is to avoid high pressures on the graphite plate / disc heat exchanger, as HCl leaks must be avoided at all times for the safety of the environment and passersby.

[0116] Reference numerals

[0117] 1Gas-liquid contactor

[0118] 2 air traps

[0119] 3Heat exchanger

[0120] 4 Vapor-Liquid Separator

[0121] 5. First pumping device

[0122] 6 Pressure measuring device

[0123] 7 Control valve

[0124] 8 Pressure control device

[0125] 9 Energy Saver

[0126] 10 Pump suction line

[0127] 11 second pumping device

[0128] 12 vapor condenser

[0129] A - input stream to the gas-liquid contactor

[0130] B - output liquid stream from the gas-liquid contactor

[0131] C - output liquid stream from the gas trap

[0132] D - output liquid stream from the heat exchanger

[0133] E - liquid stream to the economizer

[0134] F - liquid stream from the economizer to the gas-liquid contactor

[0135] G - vapor to the vapor condenser

[0136] X - liquid from the vapor-liquid separator

[0137] L1 - first vacuum line

[0138] L2 - second vacuum line

[0139] H c - heat exchanger height

[0140] H r - gas-liquid contactor height

[0141] H s - vapor-liquid separator height

[0142] H L - gas trap height

Claims

1. A processing unit for treating a corrosive medium, the processing unit comprising: - a gas-liquid contactor (1) adapted to contact liquid from an input stream A with a gas and to discharge a liquid stream B, said gas-liquid contactor being located at a height H r Department; and - an air trap (2) arranged to receive the liquid flow B and to discharge the liquid flow C, and provided with a headspace for trapping a volume of gas, said headspace allowing the removal of gas bubbles and dampening pressure fluctuations within the liquid flow B; and - a heat exchanger (3) arranged to receive the liquid flow C and discharge a liquid flow D, said heat exchanger comprising heat exchange means, said heat exchanger being located at a height H c Department; and - a first vacuum line L1 suitable for providing a negative gauge pressure to the head space, thereby sucking the liquid flow B into the air trap (2); Among them, H r >H c , so as to deliver a pressure differential as the driving force through the heat exchanger.

2. The processing unit according to claim 1, further comprising: a vapor-liquid separator (4) arranged to receive the liquid stream D from the heat exchanger; The vapor-liquid separator (4) is located at a height H higher than the heat exchanger. c Height H s at a position so as to allow static pressure to be applied to the liquid flow D to avoid liquid-gas transition of the liquid flow D.

3. The processing unit according to any of the preceding claims, wherein the heat exchange means of the heat exchanger comprises a material selected from the group consisting of: graphite (C), silicon carbide (SiC), silicon dioxide (SiO2).

4. A processing unit according to any preceding claim, wherein the heat exchange means comprises graphite.

5. The treatment unit according to any of the preceding claims, further comprising a second vacuum line L2 connected to the gas-liquid contactor (1), wherein the second vacuum line L2 is suitable for providing a negative gauge pressure to the gas-liquid contactor (1), thereby sucking the input flow A into the gas-liquid contactor (1).

6. The processing unit according to any of the preceding claims, wherein the first vacuum line L1 and / or the second vacuum line L2 are connected to the vapor-liquid separator (4).

7. A processing unit according to any preceding claim, further comprising one or more pipes at least partially provided with heat tracing.

8. Processing unit according to any of the preceding claims, wherein the heat exchange means is selected from: a tube or a tube bundle, one or more plates.

9. A processing unit according to any one of the preceding claims, wherein the gas trap (2) is located at a height H L Where H r >H c >H L .

10. The treatment unit according to any of the preceding claims, wherein the gas-liquid contactor (1) is a falling film column.

11. The treatment unit according to any of the preceding claims, wherein the gas-liquid contactor is a reactor configured to receive a reaction reagent, preferably an inorganic oxyacid and / or a salt thereof, more preferably polyphosphoric acid (PPA), and to contact the reaction reagent with water.

12. The processing unit according to any of the preceding claims, further comprising: - first pumping means (5) adapted to receive said liquid flow C and to pump said liquid flow C in the direction of said heat exchanger (3); as well as - a pressure measuring device (6) arranged to measure the pressure of the liquid flow C pumped in the direction of the heat exchanger (3) but downstream of the pressure control valve (7); and - the pressure control valve (7), located downstream of the first pumping device (5) and the pressure measuring device (6), and arranged to regulate the flow rate of the liquid stream C directed to the heat exchanger (3); as well as - a pressure control device (8) connected to the first pumping device (5), the pressure measuring device (6) and the pressure control valve (7), the pressure control device being suitable for maintaining the pressure of the liquid flow C within a predetermined pressure range by actuating the pressure control valve (7) and / or the first pumping device (5) based on the pressure measuring device (6).

13. Treatment unit according to the preceding claim, wherein said first pumping means (5) comprise a motor connected to a variable frequency drive (VFD) adapted to be actuated by said pressure control means (8) .

14. The process unit according to any of the preceding claims, wherein the heat exchanger (3) is part of an economizer (9) adapted to bring the liquid stream E to be supplied to the gas-liquid contactor (1) into thermal contact with the liquid stream C.

15. Use of an air trap (2) arranged upstream of a heat exchanger (3) having a heat exchange device, wherein the air trap (2) serves to protect the heat exchange device from pressure variations.

16. Use of a vapor-liquid separator (4) in a treatment unit for treating a corrosive medium, wherein the treatment unit comprises: a gas-liquid contactor (1) adapted to bring a liquid from an input stream A into contact with a gas and to discharge a liquid stream B, said gas-liquid contactor being located at a height Hr; and a heat exchanger (3) arranged to receive a liquid flow C and to discharge a liquid flow D, said heat exchanger comprising heat exchange means, said heat exchanger being located at a height Hc; wherein Hr>Hc so as to deliver a pressure differential as a driving force through the heat exchanger; and wherein the vapor-liquid separator (4) is arranged downstream of the heat exchanger (3) and is located at a height Hs higher than the height of the heat exchanger for generating a static pressure on the liquid flow D to avoid liquid-to-gas transition of the liquid flow D.

17. A method of operating a treatment unit according to any one of claims 1 to 14 to treat a corrosive liquid, the method comprising: a) providing negative gauge pressure to the headspace of the air trap (2); b) contacting a liquid with a gas in a gas-liquid contactor (1) to produce a reaction product; c) discharging the reaction product via liquid stream B; d) allowing a flow of liquid stream B to flow through the air trap (2) and discharging the flow from the air trap via liquid stream C, wherein the liquid stream is allowed to flow under the influence of gravity; e) Driving the liquid flow C through the heat exchanger using the driving force generated by the influence of gravity.

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