System and method preventing leakage from industrial equipment operating in corrosive environments

Abstract

The present invention is related to the field of industrial processing of hot corrosive liquids originating from gas–liquid contactors in the chemical industry. It provides a processing unit for preventing leakage of such liquids from equipment downstream of the gas–liquid contactor and a related method for preventing leakage.

Description

[0001] SYSTEM AND METHOD PREVENTING LEAKAGE FROM INDUSTRIAL EQUIPMENT

[0002] OPERATING IN CORROSIVE ENVIRONMENTS

[0003] FIELD OF THE INVENTION

[0004] The present invention is related to the field of industrial processing of hot corrosive liquids originating from gas-liquid contactors, such as falling film columns. In particular, the present invention pertains to a system and a method where the risk of leakage of hot and / or corrosive liquids, downstream of the gas-liquid contactor, is reduced.

[0005] BACKGROUND TO THE INVENTION

[0006] In the chemical industry many processes use aggressive, acidic, caustic or other corrosive agents as catalysts, solutions, or working mediums to drive chemical reactions. As chemical reactions mostly perform better or have higher conversion rates under higher temperatures, the reagents coming out of gas-liquid contactors, such as falling film columns, are often at high temperatures. In case these reagents are aggressive and / or corrosive, they could damage the processing unit downstream of the gas-liquid contactor by attacking the parts said processing unit is made of.

[0007] In the state of the art, heat exchangers are often used the chemical industry with the aim of transferring heat between different media (e.g., a corrosive liquid and air, or a cooling liquid). For heat exchangers, the thermal conductivity of the material they are made of is a key factor. Many materials, such as graphite, SiC and glass, are corrosive -resista nt and having good thermal conductivity (except for glass), but have the disadvantage of being brittle in nature are hence not suitable to withstand high pressures mostly giving raise to too low allowable forces around gaskets - as higher pressure drops increase velocity and thus the heat transfer - and / or rapid pressure changes due to e.g., startup and shut downs. When subjected to those, these materials crack, thereby contributing to the leakage of hot corrosive liquids these are designed to exchange heat with. Leakage in equipment of these present high safety risks for operators operating the equipment needs to be avoided.

[0008] There is hence an industrial need of preventing leakage in systems comprising gas-liquid contactors operating in hot and / or corrosive environments by operating amongst others at lower pressures and changing operating conditions in a smooth and slow way, where the system comprises one or more heat exchangers. The present invention provides for a solution to the aforementioned problem. SUMMARY OF THE INVENTION

[0009] According to a first aspect, the present invention pertains to a processing unit for processing a corrosive media, such as a corrosive-, base- or acid-liquid stream, possibly at high temperature, said processing unit comprising: a gas-liquid contactor, such as a falling film column, adapted to contact a liquid from an input stream A with a gas, such as air, water vapor, and to exit a liquid stream B, said contactor being positioned at a height Hr; and a gas trap arranged to receive the liquid stream B and to exit a liquid stream C and provided with a headspace trapping a volume of gas which allows removal of gas bubbles and dampening of pressure surges within stream B; and a heat exchanger arranged to receive the liquid stream C, and to exit a liquid stream D, said heat exchanger comprising heat exchange means, said heat exchanger being positioned at a height Hc; and a first vacuum line Li adapted to provide a negative gauge pressure to the headspace, thereby providing suction of the liquid stream B into the gas trap; wherein the Hr > Hcsuch that a pressure difference is delivered as a driving force through the heat exchanger.

[0010] The present aspect of the invention provides for several advantages. In particular, it was found that a processing unit configured in accordance with the present aspect minimizes the risk of leakage of processed liquids from the heat exchanger, thereby allowing the use of materials for the heat exchanges means that would otherwise not withstand the pressure and / or pressure oscillations processing unit in the state of the art. By means of the present aspect of the invention the pressure upstream of the heat exchanger is can be easily maintained within a preferred pressure range. The specific height difference between the gas-liquid contactor and the heat exchanger also allows for the pressure to stay within said preferred pressure range by not making necessary the use of pumps.

[0011] According to an embodiment of the present invention, the processing unit further comprises: a vapor-liquid separator arranged to receive the liquid stream D from the heat exchanger; the vapor-liquid separator being positioned at a height Hswhich is higher than the height Hcof the heat exchanger so as to allow a static pressure on liquid stream D to avoid a liquid-gas transition thereof.

[0012] According to an embodiment of the present invention, the processing unit further comprises a second vacuum line L2 connected to the gas-liquid contactor which is adapted to provide a negative gauge pressure to the gas-liquid contactor, thereby providing suction of the input stream A into the gas-liquid contactor. According to an embodiment of the present invention, the first and / or the second vacuum lines Li , L2 are connected to the vapor-liquid separator.

[0013] According to an embodiment of the present invention, the processing unit comprises one or more pipes traced at least partially.

[0014] According to an embodiment of the present invention, the heat exchange means of the heat exchanger comprise a material selected from: graphite (C), silicon carbide (SiC), Siliciumdioxide (SiO2).

[0015] According to an embodiment of the present invention, the heat exchange means comprise graphite.

[0016] According to an embodiment of the present invention, the heat exchange means is chosen from: a tube or a tube bundle, one or more plates.

[0017] According to an embodiment of the present invention, the gas trap is positioned at a height HL, wherein HI>HC>HL

[0018] According to an embodiment of the present invention, the gas-liquid contactor is a falling film column.

[0019] According to an embodiment of the present invention, the liquid stream B and / or stream C has a pH lower than 2 or higher than 12.

[0020] According to an embodiment of the present invention, the liquid stream B and / or stream C has a temperature between 100°C to 300°C, preferably from 120°C to 250°C.

[0021] According to an embodiment of the present invention, the gas-liquid contactor is a reactor configured to receive a reaction reagent, which is preferably an inorganic oxoacid and / or its salts, more preferably a polyphosphoric acid (PPA), and to contact said reaction reagent with water.

[0022] According to an embodiment of the present invention, the processing unit further comprises: first pumping means adapted to receive the liquid stream C and to pump the liquid stream C in the direction of the heat exchanger; and pressure measuring means provided to measure the pressure of the liquid stream C pumped in the direction of the heat exchanger but downstream of the control valve; and a pressure control valve downstream of the first pumping means and the pressure measuring means and provided to regulate the flow of the liquid stream C to the heat exchanger; and pressure controlling means in communication with the first pumping means, the pressure measuring means and the pressure control valve, the pressure controlling means being adapted to maintain the pressure of the liquid stream C within a predefined pressure range by actuating the pressure control valve and / or the first pumping means based on the pressure measuring means.

[0023] According to an embodiment of the present invention, the first pumping means comprise a motor connected to a variable-frequency drive (VFD) which is adapted to be actuated by the pressure controlling means. An advantage of the present embodiment is that the flow at the heat exchanger can be finely regulated and pressure spikes reduced.

[0024] According to an embodiment of the present invention, the heat exchanger is part of an economizer adapted to thermally contact a liquid stream E to be fed to the gas-liquid contactor with the liquid stream C.

[0025] According to a further aspect, the present invention pertains to the use of a gas trap arranged upstream of a heat exchanger having heat exchange means, wherein the gas trap is used for protecting the heat exchange means against pressure changes.

[0026] According to a further aspect, the present invention pertains to the use of a vapor-liquid separator arranged downstream of a heat exchanger and being positioned at a height Hswhich is higher than the height of the heat exchanger for creating a static pressure at exit of the heat exchanger.

[0027] According to yet a further aspect, the present invention pertains to a method of operating a processing unit as described in any one embodiments of the processing unit of the present invention, for processing a corrosive liquid, the method comprising: a) providing a negative gauge pressure to a headspace of a gas trap; b) contacting a liquid with a gas in a gas-liquid contractor and thereby creating a reaction product; c) exiting said reaction product via a liquid stream B; d) allowing a flow of liquid stream B via the gas trap and exiting the flow from the gas trap via a liquid stream C, wherein the flow of liquid is allowed to flow under gravitational influence; e) driving the liquid stream C through a heat exchanger with a driving force created by the gravitational influence. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] With specific reference now to the figures, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the different embodiments of the present invention only. They are presented in the cause of providing what is believed to be the most useful and readily description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention. The description, taken with the drawings, makes apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

[0029] Figure 1 , also abbreviated as Fig. 1 , is a schematic drawing of a processing unit according to an embodiment of the present invention, illustrating a gas-liquid contactor 1 , connected to a gas trap 2, the gas trap 2 being further connected to a heat exchanger 3. The gas-liquid contactor 1 and the heat exchanger 3 are positioned at different heights, so that Hr>Hc, so that a flow of a liquid, under the influence of gravity, can flow from the gas-liquid contactor 1 to the heat exchanger. In other words, the heat exchanger 3 is position at a height lower than the gas-liquid contactor 1 .

[0030] Figure 2, also abbreviated as Fig. 2, is a schematic drawing of a processing unit in accordance with an embodiment of the present invention, wherein the gas-liquid contactor 1 , the gas trap and an economizer are positioned so that the gas trap 2 is at a height lower than both the heat exchanger 3 and the gas-liquid contactor 1 , and the heat exchanger 3 is positioned at a height lower than the gas-liquid contactor 1 i.e. HI>HC>HL, wherein the processing unit further comprises a vapor liquid separator 4 connected downstream of the economizer.

[0031] Figure 3, also abbreviated as Fig. 3, is a schematic drawing of a processing unit according to an embodiment of the present invention wherein a series of means is provided to further reduce the risk of leakage upstream of the economizer.

[0032] Figure 4, also abbreviated as Fig. 4, is a schematic drawing of a processing unit in accordance with an embodiment of the present invention, the processing unit comprising a vapor-liquid separator provided with a series of safety means positioned downstream of the economizer.

[0033] DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will now be further described. In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous. When describing the compounds of the invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

[0035] The term "about" or "approximately" as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of + / - 10 % or less, preferably + / - 5 % or less, more preferably + / - 1 % or less, and still more preferably + / - 0.1 % or less of and from the specified value, insofar such variations are appropriate to perform in 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.

[0036] According to a first aspect, the present invention pertains to a processing unit for processing a corrosive media, such as a corrosive-, base- or acid-liquid stream, possibly at high temperature, said processing unit comprising: a gas-liquid contactor, such as a falling film column, adapted to contact a liquid from an input stream A with a gas, such as air, water vapor, and to exit a liquid stream B, said contactor being positioned at a height Hr; and a gas trap arranged to receive the liquid stream B and to exit a liquid stream C and provided with a headspace trapping a volume of gas which allows removal of gas bubbles and dampening of pressure surges within stream B; and a heat exchanger arranged to receive the liquid stream C, and to exit a liquid stream D, said heat exchanger comprising heat exchange means, said heat exchanger being positioned at a height Hc; and a first vacuum line Li adapted to provide a negative gauge pressure to the headspace, thereby providing suction of the liquid stream B into the gas trap; wherein the Hr > Hcsuch that a pressure difference is delivered as a driving force through the heat exchanger.

[0037] In the context of the present invention, by means of the term “gas-liquid contactor”, reference is made to an industrial equipment where a gas and a liquid are provided to come into contact with each other. Gas-liquid contactors suitable to carry out the present invention comprise differential gas-liquid contactors, wherein the mass transfer happens within the entire length of the contactor, and the vapor-liquid equilibrium is not reached in any point of the equipment, and stagewise gas-liquid contactors, wherein the vapor-liquid equilibrium is reached within each stage of the equipment and mass transfer happens in a part only of the volume of each stage. Examples of differential gas-liquid contactors are: falling-film column, packed column, bubble column, spray tower, gas-liquid agitated vessel. Examples of stagewise gas-liquid contactors are: plate column, rotating disc contactor, Venturi tube. According to an embodiment of the present invention, the processing unit according to any one of the previous claims, wherein the gas-liquid contactor 1 is a falling-film column. In yet a further embodiment of the present invention the falling-film column is provided to carry out a chemical reaction, e.g., the exothermic hydrolysis I solvation reaction of polyphosphoric acid (PPA) or the endothermic oligomerisation I condensation reaction of ortho- 1 pyro-phosphoric acid (PA). In the falling-film column the PPA or PA is provided to come in close contact with air and / or water vapor present in the column, this possibly causing a turbulent flow downstream of the falling-film column, which is detrimental to the industrial equipment downstream, e.g., heat exchangers, thereby causing leaks. The present invention solves this problem. According to an embodiment of the present invention, the gas-liquid contactor 1 is a reactor configured to receive a reaction reagent, which is preferably an inorganic oxoacid and / or its salts, more preferably a polyphosphoric acid (PPA), and to contact said reaction reagent with water. By means of the present invention the pressure at the heat exchanger 3 is reduced to heavily reduced and the effect due to the presence of gas within the piping is also minimized at the location of said heat exchanger s.

[0038] By not requiring the use of pumping means to move liquids between the gas-liquid contactor 1 and the heat exchanger 3, and by providing a gas trap 2, the pressure at the heat exchanger 3 is typically reduced to 2-3 bar. Heat exchangers having relatively low operating pressure, such as those made from graphite, benefit the most from the present invention. Heat exchangers comprising graphite have maximum operating pressure of approximately 6-8 barg. By means of the present invention the pressure reaching these heat exchangers can be consistently (i.e., with minimal to no pressure spiking) maintained at less than 50% of the maximum operating pressure. The present invention allows for pressure drop at the heat exchanger 3 below 3 bar, less than 2 bar, beneficially even better in the range of 0,5-1 bar. This will reduce the possibility of leaks drastically and increase the mean time between leaks to several years of normal operations.

[0039] In accordance with the present invention the gas-liquid contactor 1 is provided to contact a liquid from an input stream A with a gas, and to exit a liquid stream B. Based on the type of liquid stream A contacted with the gas in the gas-liquid contactor, the exit liquid stream B might exit the gas-liquid contactor at high temperatures. The gas-liquid contactor 1 is in accordance with the present invention positioned at a height Hr.

[0040] According to the present invention, the processing unit further comprises a gas trap 2 arranged to receive the liquid stream B coming from the gas-liquid contactor and to exit a liquid stream C.

[0041] In the context of the present invention, by means of the term “gas trap”, reference is made to an industrial equipment provided to allow a headspace to form when filled with a liquid, thereby trapping a volume of gas within. This was found to allow dampening of pressure surges and to provide means to maintain pressure downstream of the gas trap within a predefined preferred range. A gas trap 2 in accordance with the present invention can assume a variety of forms and configurations, such as, and not limited to: a syphon, an expansion vessel, a large pipe with minimum diameter to let escape the gas bubbles, restriction orifice to create lower pressure to enforce gas bubble creation. According to an embodiment of the present invention, the gas trap 2 is provided with a headspace trapping a volume of gas which allows dampening of pressure surges within stream B. In the context of the present invention, the headspace is can be any assembly adapted to provide for gas bubbles to not be proceed further along the unit. For example, in case the gas trap 2 is a syphon, the headspace can be a calculated pipe to make sure gas bubbles are not trapped in the syphon and proceed along the unit. According to the present example, the headspace could be provided with a minimum diameter to insure sufficient low down coming velocity of the liquid compared to the rising velocity of the gas bubbles.

[0042] According to a further embodiment of the present invention, the processing unit further comprises one or more pipes traced at least partially. In other words, according to the present embodiment, at least one or more pipes connecting one or more component of the present unit, e.g., the gas-liquid contactor 1 and the gas trap 2, are provided with tracing, along at least a part of their length or their circumference. The tracing is advantageous in simplifying operations by preventing the liquid within the unit to cool down and increase in viscosity, thereby blocking the line due to e.g. (partial)-crystallization of the liquid. This might take place during sudden operational stop or blockage of the unit. The tracing enables the temperature of the liquid blocked therein to remain within a specific preferred range until operation can be resumed. Tracing of the pipes can be achieved by means heating the pipes or part thereof with e.g., an electrical conductor, steam or any other heat medium.

[0043] Further, in accordance with the present invention, the processing unit comprises a heat exchanger 3 arranged to receive the liquid stream C, and to exit a liquid stream D, said heat exchanger comprising heat exchange means.

[0044] According to the present invention, by means of the term “heat exchanger”, reference is made to an industrial component provided to facilitate the exchange of heat between e.g., two liquids, two gases or a gas and a liquid. In particular, according to the present invention, the heat exchanger 3 is provided to exchange heat with the liquid stream C, by means of the heat exchange means. A variety of heat exchanges means could be used in accordance with the present invention. In particular, the present invention allows to use heat exchange means comprising materials such as, and not limited to: graphite carbon, silicon carbide (SiC), Siliciumdioxide (SiC>2), metals (such as steel e.g., stainless steel, copper, aluminum).

[0045] According to the first aspect of the present invention, the processing unit comprises a first vacuum line Li adapted to provide a negative gauge pressure to the headspace of the gas trap 2, thereby providing suction of the liquid stream B into the gas trap 2. In accordance with the present invention, a vacuum line is a pipe capable of withstanding negative pressure which is connected to negative pressure providing means, such as a vacuum pump. Without the presence of such a vacuum line, gas and or air breaking through without a gas trap could possibly give raise to liquid hammer and severely damage the integrity of the brittle equipment.

[0046] According to an embodiment of the present invention, the heat exchange means of the heat exchanger comprise a material selected from: graphite (C), silicon carbide (SiC), Siliciumdioxide (SiC>2). According to a preferred embodiment of the present invention, the heat exchange means comprise graphite. The processing unit according to the present invention allows for the use of heat exchangers comprising heat exchange means particularly susceptible to breaking, such as those comprising a material selected from: graphite (C), silicon carbide (SiC), Siliciumdioxide (SiO2).

[0047] In accordance with the present invention, said heat exchanger being positioned at a height Hc; and wherein the height of the gas-liquid contactor Hr is greater than the height of the heat exchanger Hc, such that a pressure difference is delivered as a driving force through the heat exchanger. Hence, the gas-liquid contactor and the heat exchanger are positioned at a height allowing for a liquid introduced in the gas-liquid contactor to flow to the heat exchanger under the influence of gravity.

[0048] According to an embodiment of the present invention, the heat exchange means is chosen from: a tube or a tube bundle, one or more plates, discs, blocks.

[0049] In accordance with the present invention, the liquid stream B exiting the gas-liquid contactor can be at a higher temperature than the one the processing unit downstream is designed to operate with. Therefore, in accordance with the present invention, reactions can be carried out at a higher temperature than the temperature possible without it. The possibility of increasing the temperature of the liquid exiting the reaction recipient, and conversely the temperature of the reaction itself, allows for several advantages, evident to the skilled in the art, such as: the use of cheaper less reactive species, the use of a reduced amount of reagents, the higher conversion rates, faster reaction time etc. According to an embodiment of the present invention, the liquid stream B and / or stream C has a pH lower than 2 or higher than 12. According to an embodiment of the present invention, the liquid stream B and / or stream C has a temperature between 100°C to 300°C, preferably from 120°C to 250°C.

[0050] In chemistry, highly reactive species such as H2SO4, HNO3, HCI, CI2, Br2, HBr, F2, HF, among others (e.g., acids, bases), are often used to drive organic reactions, mostly above 150-200°C and in presence of water (e.g., in hydrolysis reactions). In such conditions, the corrosion of the processing unit downstream of the gas-liquid contactor has to be avoided, this being a big challenge for chemical industry. When the processing unit is provided to operate under pressure i.e., when the processed liquid is provided at a pressure other than atmospheric pressure, the breaking of one or more equipment parts within the processing unit could lead to disastrous consequences. According to an embodiment of the present invention, the liquid stream B and / or stream C has a pH lower than 2 or higher than 12.

[0051] According to an embodiment of the present invention, the liquid stream B and / or stream C has a temperature between 100°C to 300°C, preferably from 120°C to 250°C.

[0052] An aspect of the present invention pertains to the use of a gas trap 2 arranged upstream of a heat exchanger 3 having heat exchange means, wherein the gas trap is used for protecting the heat exchange means against pressure changes.

[0053] According to yet a further aspect, the present invention pertains to a method of operating a processing unit as described in any one embodiments of the processing unit of the present invention, for processing a corrosive liquid, the method comprising: a) providing a negative gauge pressure to a headspace of a gas trap; b) contacting a liquid with a gas in a gas-liquid contractor and thereby creating a reaction product; c) exiting said reaction product via a liquid stream B; d) allowing a flow of liquid stream B via the gas trap and exiting the flow from the gas trap via a liquid stream C, wherein the flow of liquid is allowed to flow under gravitational influence; e) driving the liquid stream C through a heat exchanger with a driving force created by the gravitational influence.

[0054] According to the present aspect, it was found beneficial to operate the processing unit of the present invention starting with a negative gauge pressure already established at the headspace of the gas trap. In other words, it has been found beneficial to processing by means of the process unit of the present invention with at least one vacuum line being active at start of operation i.e., with negative pressure (vacuum) being realized at the location of the gas trap.

[0055] Fig. 1 illustrates how the present invention can be caried out, and discloses an embodiment of the present invention wherein a gas-liquid contactor 1 which is provided to receive a liquid (see input stream A e.g., position at the top of the contactor), which is brought into contact with a gas such as in a falling film column. The gas-liquid contactor will typically comprise heat exchange means as the chemical reaction is either exothermic (require cooling) or endothermic (require heating). This is also the case with corrosive-, base-, acid-media in industry, that often need to be diluted with water or with a solvent. This dilution is often an exothermal reaction which needs to be cooled by e.g., steam generation. In other applications, these media need to be increased in concentration. This is often an endothermal reaction which needs to be heated by e.g., condensation of steam. In the gas-liquid contactor a chemical reaction might take place between the liquid and a gas, which the liquid might be brought in contact with so to react, or another liquid with which the first liquid is brought in contact so to react. In any case, in the gas-liquid contactor 1 a liquid is brought in contact with a gas, with which the liquid might react. The gasliquid contactor 1 is positioned at a height Hr from a base on which the processing unit is standing on. Connected with the gas-liquid contactor 1 , a gas trap 2 is provided. The gas trap is connected to the gas-liquid contactor 1 and receives an exit liquid stream B from gas-liquid contactor 1. The gas trap 2 is then connected with a heat exchanger 3, which is provided to receive a liquid form the gas trap 2. The heat exchanger 3 is at a height Hcfrom the base. The heat exchanger 3 is then provided with means to exit the liquid stream after heat transfer as taken place, thereby exiting a liquid stream D. The heat exchanger s and the gas-liquid contactor 1 are adapted i.e., positioned, so that is possible for a liquid stream to flow from these two equipment parts under the influence of gravity i.e., the heat exchanger is gravity fed. This would be made possible by Hr > He such that a pressure difference is delivered as a driving force through the heat exchanger. Fig. 1 illustrates also a first and a second vacuum lines Li, L2, which are connected to negative pressure providing means e.g., a vacuum pump (not shown). The vacuum lines, and in particularthe first vacuum line Li .facilitate the suction of the liquid into the gas trap 2. The first and / or the second vacuum lines Li, L2 can be connected to various locations of the processing unit according to the present invention, but are adapted to provide a negative pressure to a headspace of the gas trap 2. The first and / or the second vacuum lines Li, L2 can be connected to either the gas trap 2 and / or thegas-liquid contactor 1 , either directly or indirectly, so that the suction of the liquid to the gas trap 2 is facilitated by tapping off gas and or air before startup. The one or more vacuum lines assist gravity as a driving force of the displacement of liquid from the gas-liquid contactor 1 to the heat exchanger 3.

[0056] By means of the term “gravity fed” reference is made to a system which is adapted to provide for a liquid stream to flow from the gas-liquid contactor 1 to the heat exchanger 3 even when first pumping means are not present. In accordance with the present invention pumping means might be provided downstream of the heat exchanger 3. Pumping means can also be provided to pump the liquid stream from the gas-liquid contactor 1 to the heat exchanger 3, at various location long this path, but the presence of such pumping means would not be required for said flow from the gas-liquid contactor 1 to the heat exchanger 3 to occur.

[0057] By means of the term “pumping means”, reference is made to means adapted to move a liquid. Pumping means useful in the context of the invention are centrifugal pumps, volumetric pumps or any other type of fluid pumps. Said pumps can be electrically driven or via a steam expander. In a preferred embodiment, the pump used in the context of the invention is a centrifugal pump; more in particular a centrifugal pump made from metallic material; even more in particular a centrifugal pump made from PTFE, PFA lined carbon or stainless steel. Particularly beneficial are pumping means comprising a motor connected to a variable-frequency drive (VFD).

[0058] In processing equipment in the state of the art, the processing of corrosive-, base-, acid-liquid streams, especially at high temperature, such as higher than 100 °C, is often limited by the design temperature and designed pressure of equipment such as one or more pumping means or heat exchangers. If the liquid stream is at a higher temperature than the design temperature of the pumping means, said pump could not operate properly and / or could get damaged by said liquid stream. If the pressure of the liquid stream is higher than the design pressure of the heat exchangers, the internal heat exchanger walls might fracture thereby allowing the liquid to leak. In accordance with the present invention, by providing a difference in height between the gasliquid separator 1 and heat exchanger 3, it is possible to avoid the use of pumping means and to protect the heat exchangers from rapid pressure variation i.e., pressure spiking, which might be higher than the design pressure of the heat exchangers. A gravity fed system such as the one according to the present invention, wherein a liquid is contacted with a gas, has nevertheless the disadvantage that air entrapment and air locks can easily occur and their effects can be difficult to mitigate.

[0059] Air and or gas entrapment, which is one possible cause of pressure spiking is minimized here by the presence of a gas trap 2 between the gas-liquid contactor 1 and the heat exchanger 3. Gas trap 2 is hence provided to allow venting of entrapped air. The use of a gas trap 2 and a gravity fed configuration provide for the synergistic effect of minimizing both overpressure and pressure spiking, thereby allowing the pressure at the heat exchanger 3 to be maintained within a preferred pressure range. Another effect of the gas trap 2 is that in case gas bubbles might be formed after 1 , these bubbles cannot pass the gas trap 2 towards equipment 3 and can easily escape back to the equipment 1

[0060] It is accordingly an object of the present invention of addressing these shortcomings in industrial units for the processing of hot and / or corrosive liquid under pressure.

[0061] In the context of the present invention, corrosive-, base- or acid-media are media capable of damaging industrial equipment, based on their chemical properties e.g., being corrosive, basic, acid. As the reactivity of said media will increase with its temperature, hot corrosive-, base- or acid-media are even more responsible for the damaging of industrial equipment. Damages to industrial equipment are e.g., loosening / cracking of gaskets, O-rings, perforation of the equipment, destruction of moving parts. The damaging of heat exchangers by overpressure of hot and or corrosive liquids is particularly problematic and it is dealt with by the present invention. Heat exchanger designs favor large heat exchange surfaces which result in small thicknesses of heat exchanging means which result reduced mechanical rigidity and propension to leakage. Further, a variety of materials might be highly beneficial at exchanging heat but being unsuited to provide manufacturing of heat exchanging means for heat exchangers. When operating conditions comprise high temperatures and high pressures finding heat exchanging materials suitable to carry out their tasks becomes problematic. The present invention provides for industrial equipment allowing for the processing of hot and / or corrosive liquids in processing units comprising heat exchangers, which might be made of materials known to be prone to leakage, such as those comprising graphite, glass and SiC.

[0062] The processing unit according to the present invention hence provide for means allowing for pressure within said unit to be beneficially maintained at a pressure lower than maximum operating pressure of a heat exchanger. In the context of the present invention, the maximum operating pressure of the heat exchanger, or the design pressure of the heat exchanger, is the maximum pressure of a fluid said heat exchanger can process without being damaged. The maximum operating pressure of the heat exchanger is set by the manufacturer of said heat exchanger. For certain types of heat exchangers, said maximum operating pressure is due to the designed pressure limit for the heat exchanger components and or the material it’s made from.

[0063] Corrosive-, base-, acid- media that can be processed by a processing unit as described in accordance with the present invention, includes any kind of ionic liquids with any kind of solvent; such as an inorganic oxoacid (e.g. HNO3, H2SO4, H3PO4) and / or its salts and water; a metal halogen salt (e.g. LiBr / LiCI...) and water; an ammonium salt and water; in particular an inorganic oxoacid and or its salts and water; even more in particular ortho- 1 pyro-phosphoric acid (PA) and water in an endothermic oligomerisation I condensation reaction; or polyphosphoric acid (PPA) and water in an exothermic hydrolysis I solvation reaction.

[0064] Fig. 2 illustrates one or more embodiments of the present invention, and illustrates a processing unit comprising an economizer 9 and vapor-liquid separator 4. According to the embodiment of the invention illustrated in Fig. 2, the processing unit comprises a vapor-liquid separator 4 arranged to receive the liquid stream D from the heat exchanger; the vapor-liquid separator 4 being positioned at a height Hswhich is higher than the height Hcof the heat exchanger so as to allow a static pressure on liquid stream D to avoid a liquid-gas transition thereof. In this particular exemplified embodiment, the gas trap 2 is positioned at a height HL, wherein Hr>Hs>Hc>HL. A gas trap 2 positioned at a height HL, wherein was found beneficial either in combination with the vapor liquid separator 4 or with other embodiments of the present invention. By providing a processing unit according to any embodiment of the present invention with a gas trap 2 positioned so that Hr > Hs> Hc> HL It was found that having the gas trap 2 at the lowest point of the unit is advantageous in blocking gas from entering the heat exchanger 3.

[0065] The gas-liquid contactor 1 according to the present invention is to be understood as being provided as many inlets or outlets as needed to carry out the invention. As schematically depicted in Fig. 2, the gas-liquid contactor receives or can receive multiple input streams of material (e.g., solid or liquid). For example, the gas-liquid contactor 1 can receive an input stream F of preheated material coming from an economizer 9, and cooled or pre-heated by heat exchange means within said economizer. In other circumstances, the gas-liquid contactor 1 can be provided with vents from which a gas, such as water vapor can be provided to escape from the gas-liquid contactor.

[0066] In case of an exothermic reaction, the gas-liquid contactor 1 might require cooling. In accordance with an embodiment of the invention, to cool the gas-liquid contactor, a stream of cooling liquid might be provided to a heat exchanger at the location of said gas-liquid contactor 1 and in thermal contact with it. The cooling effect can be accomplished by e.g., generating steam. In this case, hot water entering the heat exchanger would be heated with the generation of steam. In other applications, the corrosive-, base- or acid-media in the gas-liquid contactor 1 might need to be concentrated. This can be done by evaporation of the liquid e.g., water or solvent. The evaporation is often an endothermal reaction which needs to be heated by e.g., condensation of steam. In this case, steam entering the heat exchanger would be cooled and would condense.

[0067] In Fig. 2, the economizer is designed so that liquid exiting the gas-liquid contactor 1 at high temperature pre-heat liquid to be fed to the gas-liquid contactor 1 , while at the same time, this liquid at low temperature to be fed to the gas-liquid contactor 1 cools down and exit stream from the gas-liquid contactor 1. Hence, according to an embodiment of the present invention, the processing unit comprises that the heat exchanger 3 is part of an economizer 9 adapted to thermally contact a liquid stream E to be fed to the gas-liquid contactor 1 with the liquid stream C. An advantage of the present embodiment is that heat can be efficiently reused thereby providing a more efficient processing unit.

[0068] The specific embodiment disclosed in Fig. 2 is further complemented with a vapor-liquid separator 4, also known as a flash drum, to evaporate a vapor stream e.g., water vapor, from the vapor-liquid separator from the economizer 9, and to decrease the temperature of the economizer exit stream D by evaporative cooling, yielding a vapor-liquid separator exit stream at a lower temperature. In the vapor-liquid separator 4, the pressure of the economizer exit stream 5 is expanded towards a lower pressure and as a result e.g., water, is evaporated, leaving the liquid behind. The evaporation of the solvent cools stream D. More specifically, by means of the vapor-liquid separator 4, a further cooling effect is provided to cool the corrosive-, base- or acid-liquid stream originating from the gas-liquid contactor 1 , before it reaches further processing stages.

[0069] In an embodiment of the present invention the use of a vapor-liquid separator is arranged downstream of a heat exchanger 3 and being positioned at a height Hswhich is higher than the height of the heat exchanger for creating a static pressure at exit of the heat exchanger 3, as also illustrated in Fig. 2. An advantage of the present embodiment is that in case the temperature of the stream D is too high, the flashing effect of the liquid stream is avoided as the static height provides a pressure above the vapor pressure of said liquid in liquid stream D. It also avoids evaporating liquid in the graphite equipment as graphite is very sensitive to any kind of evaporation at its surface. In other words, the setup provides a sustainable design suitable for all process conditions such as too high temperatures, too low pressures during different operational modes.

[0070] It is thus an embodiment of the present invention to provide the use of a vapor-liquid separator (4) in a processing unit for processing corrosive media, wherein the processing unit comprises: a gas-liquid contactor (1) adapted to contact a liquid from an input stream A with a gas, and to exit a liquid stream B, said contactor being positioned at a height Hr; and a heat exchanger (3) arranged to receive the liquid stream C, and to exit a liquid stream D, said heat exchanger comprising heat exchange means, said heat exchanger being positioned at a height He; wherein the Hr > He such that a pressure difference is delivered as a driving force through the heat exchanger; and wherein the vapor-liquid separator (4) is arranged downstream of a theheat exchanger (3) and being positioned at a height Hs which is higher than the height of the heat exchanger for creating a static pressure at exit of the heat exchangeron liquid stream D to avoid liquid-gas transition thereof.

[0071] According to an embodiment it provides a processing unit for processing corrosive media, wherein the processing unit comprises: a gas-liquid contactor (1) adapted to contact a liquid from an input stream A with a gas, and to exit a liquid stream B, said contactor being positioned at a height Hr; and a heat exchanger (3) arranged to receive the liquid stream C, and to exit a liquid stream D, said heat exchanger comprising heat exchange means, said heat exchanger being positioned at a height He; wherein the Hr > He such that a pressure difference is delivered as a driving force through the heat exchanger; and wherein the vapor-liquid separator (4) is arranged downstream of a theheat exchanger (3) and being positioned at a height Hs which is higher than the height of the heat exchanger for creating a static pressure at exit of the heat exchangeron liquid stream D to avoid liquid-gas transition thereof. According to another aspect of the aforementioned embodiment, the processing unit further comprises a vacuum line L2 connected to the gas-liquid contactor (1) which is adapted to provide a negative gauge pressure to the gas-liquid contactor (1), thereby providing suction of the jnput stream A into the gas-liquid contactor (1). In a particular embodiment this vacuum line is connected to the vapor-liquid separator (4).

[0072] According to another embodiment of the present invention, the processing unit comprises: 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 pressure measuring means 6 provided 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 the pressure control valve 7 downstream of the first pumping means 5 and the pressure measuring means 6 and provided to regulate the flow of the liquid stream C to the heat exchanger 3; and pressure controlling means 8 in communication with the first pumping means 5, the pressure measuring means 6 and the pressure control valve 7, the pressure controlling means being adapted to maintain the pressure of the liquid stream C within a predefined pressure range by actuating the pressure control valve 7 and / or the first pumping means 5 based on the pressure measuring means 6.

[0073] It was found the present embodiment is advantageous in that it provides for further control on the pressure reaching the heat exchanger 3, thereby further minimizing the risk of leaks within the heat exchanger. The presence of first pumping means 5 and a gas trap 2 provides for reduced air entrapment within the liquid and minimizes the amount of gas bubbles reaching the heat exchanger 3. A variety of pumps could be used in accordance with the present embodiment, nevertheless, according to a preferred further embodiment of the present invention the first pumping means 5 comprise a motor connected to a variable-frequency drive (VFD) which is adapted to be actuated by the pressure controlling means 8. First pumping means according to the present embodiment allow for a fine regulation of the motor thereby providing a way to gradually increase or decrease the motor RPM for said first pumping means. In this way, pressure spikes are reduced and the pressure within the heat exchange is further maintained within its operational pressure.

[0074] Fig. 3 illustrates one or more embodiments of the present invention wherein a series of means is provided to further reduce the risk of leakage upstream of the economizer. In particular, Fig.

[0075] 3 illustrates the embodiment disclosed in Fig. 2 wherein the processing unit further comprises: 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 (which is in the present case an economizer 9); and pressure measuring means 6 (also denoted as PIC) provided 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 the pressure control valve 7 downstream of the first pumping means 5 and the pressure measuring means 6 and provided to regulate the flow of the liquid stream C to the heat exchanger 3; and pressure controlling means 8 in communication with the first pumping means 5, the pressure measuring means 6 and the pressure control valve 7, the pressure controlling means being adapted to maintain the pressure of the liquid stream C within a predefined pressure range by actuating the pressure control valve 7 and / orthe first words, pumping means 5 based on the pressure measuring means 6.

[0076] Fig. 4 illustrates an embodiment of the present invention, wherein the processing unit comprises a vapor-liquid separator provided with a series of safety means positioned downstream of the economizer. In particular, in accordance with an embodiment of the present invention the vaporliquid separator 4 is further complemented with a control system, also referred to as safety means, to monitor and open / close the streams entering and leaving the vapor-liquid separator 4. Again, per reference to Fig. 4, such safety means comprise:

[0077] - a pressure device, also known as PIC, to measure the pressure of the vapor-liquid separator 4; and

[0078] - a valve unit, also known as PCV, at the vapor to the vapor condenser G between the vapor-liquid separator 4 and the vapor-condenser 12.

[0079] In case the vacuum in the vapor-liquid separator 4 is not sufficient, because not enough solvent is evaporated, and therefore not enough cooling is provided, the valve unit will open and accordingly control the pressure in the vapor-liquid separator 4 and therefore stimulate evaporation of the solvent. This evaporative cooling will cause the solvent to cool down. The generated solvent vapors will move via a vapor stream G from the vapor-liquid separator to a vapor-condenser 12. Eventually this will prevent media at too hot and / or too high pressure to be fed to the suction line 10, also known as feed line, of the second pumping means 1 1 . The safety means may optionally further comprise a temperature device, also known as TIC, to measure the temperature of vapor stream G. In case the temperature of the media is too high e.g., is higher than the design temperature of the second pumping means 11 , the valve unit is closed. This additional safety means now safeguards the second pumping means from being operated above its design temperature under all circumstances. EXAMPLE 1 - Production of Muriatic Acid

[0080] An example is the absorption of HCI in waterto make muriatic acid. The cooling of the absorbed medium is done with a graphite plate heat exchanger and is placed below the steam generating absorber in such a way that the cooling of the generated muriatic acid (typically 30-50% HCI in water) is done without a pump to avoid high pressure on the graphite plate / disc heat exchanger, as HCI leaks must be avoided any time for safety reasons to environment and persons passing by.

[0081] Legend

[0082] 1 gas-liquid contactor

[0083] 2 gas trap

[0084] 3 heat exchanger

[0085] 4 vapor-liquid separator

[0086] 5 first pumping means

[0087] 6 pressure measuring means

[0088] 7 control valve

[0089] 8 pressure controlling means

[0090] 9 economizer

[0091] 10 pump suction line

[0092] 11 second pumping means

[0093] 12 vapor-condenser

[0094] A - input stream to gas-liquid contactor

[0095] B - exit liquid stream from gas-liquid contactor

[0096] C - exit liquid stream from gas trap

[0097] D - exit liquid stream from heat exchanger

[0098] E - liquid stream to the economizer

[0099] F - liquid stream from the economizer to the gas-liquid contactor

[0100] G - vapor to the vapor condenser

[0101] X - liquid from the vapor-liquid separator

[0102] Li - first vacuum line

[0103] L2 - second vacuum line

[0104] He - heat exchanger height

[0105] Hr - gas-liquid contactor height

[0106] Hs- vapor-liquid separator height

[0107] HL - gas trap height

Claims

CLAIMS1 . A processing unit for processing a corrosive media, said processing unit comprising: a gas-liquid contactor (1) adapted to contact a liquid from an input stream A with a gas, and to exit a liquid stream B, said contactor being positioned at a height Hr; and a gas trap (2) arranged to receive the liquid stream B and to exit a liquid stream C and provided with a headspace trapping a volume of gas which allows removal of gas bubbles and dampening of pressure surges within stream B; and a heat exchanger (3) arranged to receive the liquid stream C, and to exit a liquid stream D, said heat exchanger comprising heat exchange means, said heat exchanger being positioned at a height Hc; and a first vacuum line Li adapted to provide a negative gauge pressure to the headspace, thereby providing suction of the liquid stream B into the gas trap (2); wherein the Hr > Hcsuch that a pressure difference is delivered as a driving force through the heat exchanger.

2. The processing unit according 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) being positioned at a height Hswhich is higher than the height Hcof the heat exchanger so as to allow a static pressure on liquid stream D to avoid a liquid-gas transition thereof.

3. The according to any one of the previous claims, wherein the heat exchange means of the heat exchanger comprise a material selected from: graphite (C), silicon carbide (SiC), silicon dioxide (SiC>2).

4. The processing unit according to any one of the previous claims, wherein the heat exchange means comprise graphite.

5. The processing unit according to any one of the previous claims further comprising a second vacuum line L2 connected to the gas-liquid contactor (1) which is adapted to provide a negative gauge pressure to the gas-liquid contactor (1), thereby providing suction of the input stream A into the gas-liquid contactor (1).

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

7. The processing unit according to any one of the previous claims further comprising one or more pipes traced at least partially.

8. The according to any one of the previous claims, wherein the heat exchange means is chosen from: a tube or a tube bundle, one or more plates.

9. The processing unit according to any one of the previous claims, wherein the gas trap (2) is positioned at a height HL, wherein HI>HC>HL10. The processing unit according to any one of the previous claims, wherein the gas-liquid contactor (1) is a falling film column.

11. The processing unit according to any one of the previous claims, wherein the gas-liquid contactor is a reactor configured to receive a reaction reagent, which is preferably an inorganic oxoacid and / or its salts, more preferably a polyphosphoric acid (PPA), and to contact said reaction reagent with water.

12. The processing unit according to any one of the previous claims, further comprising: 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 pressure measuring means (6) provided to measure the pressure of the liquid stream C pumped in the direction of the heat exchanger (3) but downstream of the control valve (7); and a pressure control valve (7) downstream of the first pumping means (5) and the pressure measuring means (6) and provided to regulate the flow of the liquid stream C to the heat exchanger (3); and pressure controlling means (8) in communication with the first pumping means (5), the pressure measuring means (6) and the pressure control valve (7), the pressure controlling means being adapted to maintain the pressure of the liquid stream C within a predefined pressure range by actuating the pressure control valve (7) and / or the first pumping means (5) based on the pressure measuring means (6).

13. The processing unit according to the previous claim wherein the first pumping means (5) comprise a motor connected to a variable-frequency drive (VFD) which is adapted to be actuated by the pressure controlling means (8).

14. The processing unit according to any one of the previous claims, wherein the heatexchanger (3) is part of an economizer (9) adapted to thermally contact a liquid stream E to be fed to the gas-liquid contactor (1) with the liquid stream C.

15. Use of a gas trap (2) arranged upstream of a heat exchanger (3) having heat exchange means, wherein the gas trap (2) is used for protecting the heat exchange means against pressure changes.

16. Use of a vapor-liquid separator (4) in a processing unit for processing corrosive media, wherein the processing unit comprises: a gas-liquid contactor (1) adapted to contact a liquid from an input stream A with a gas, and to exit a liquid stream B, said contactor being positioned at a height Hr; and a heat exchanger (3) arranged to receive the liquid stream C, and to exit a liquid stream D, said heat exchanger comprising heat exchange means, said heat exchanger being positioned at a height He; wherein the Hr > He such that a pressure difference is delivered as a driving force through the heat exchanger; and wherein the vapor-liquid separator (4) is arranged downstream of the heat exchanger (3) and being positioned at a height Hswhich is higher than the height of the heat exchanger for creating a static pressure on liquid stream D to avoid liquid-gas transition thereof.

17. A method of operating a processing unit as described in any one of claims 1 to 14, for processing a corrosive liquid, the method comprising: a) providing a negative gauge pressure to a headspace of a gas trap (2); b) contacting a liquid with a gas in a gas-liquid contractor (1) and thereby creating a reaction product; c) exiting said reaction product via a liquid stream B; d) allowing a flow of liquid stream B via the gas trap (2) and exiting the flow from the gas trap via a liquid stream C, wherein the flow of liquid is allowed to flow under gravitational influence; e) driving the liquid stream C through a heat exchanger with a driving force created by the gravitational influence.

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