Gas handling equipment of a chemical production plant

Abstract

The present disclosure relates to a gas handling equipment of a chemical production plant, comprising a bottom with a lowest part, and being configured to receive a gas which comprises solid particles, wherein, during operation, the solid particles at least partially are carried over from the gas phase to a condensate phase, and comprising a drain arrangement located in the lowest part of the bottom of the gas handling equipment, which comprises a drain nozzle comprising an drain opening, and a drain pipe which is in liquid communication with the drain nozzle, the drain opening being configured to drain the condensate out of the gas handling equipment towards the drain pipe, and wherein one or more floating ball liquid traps are installed downstream the one or more drain arrangements, each floating ball trap being configured to evacuate the condensate out of one or more of the drain pipes when condensate is present in the drain pipe of the respective drain arrangement(s). The present disclosure further relates to a nitric acid production plant comprising an ammonia oxidizer, an absorption tower, and gas handling equipment. The present disclosure finally relates to a method for handling a gas in a gas handling equipment of a chemical production plant.

Description

Technical field

[0001] The present disclosure relates to gas handling equipment of a chemical production plant, more in particular one or more process pipes and one or more shell and tube heat exchangers in a chemical production plant, and most in particular in a nitric acid production plant.Background

[0002] In a chemical production plant, gas handling equipment are configured to handle gases present in the chemical production plant. This gas handling equipment in a chemical production plant can comprise process pipes which are pipes which transport fluids (liquids or gases) within a chemical production plant. The gas handling equipment can further comprise heat exchangers which are devices that allow a fluid, such as a liquid or a gas, to be heated or cooled without coming into direct contact with the cooling or heating medium, which is typically another fluid. More in particular, heat exchangers of the shell and tube type are often applied in chemical production plants. These heat exchangers are known for their high efficiency and their low pressure drop, the latter being the main reason to choose a shell and tube heat exchanger. Shell and tube heat exchangers allow a fluid, i.e. a liquid or a gas, to be heated or cooled without coming into direct contact with the cooling or heating medium, which is typically another fluid. Shell and tube heat exchangers allow a fluid, i.e. a liquid or a gas, to be heated or cooled without coming into direct contact with the cooling or heating medium, which is typically another fluid. A shell and tube heat exchanger in general comprises a tube side and a shell side. The tube side of the shell and tube heat exchanger comprises a tube bundle comprising a plurality of tubes which are configured to heat or cool a tube-side fluid. The tubes can be of different types, i.e. plain, longitudinally finned, etc. The tube-side fluid enters the shell and tube heat exchanger via a tube-side inlet in a front head, which is located between the tube-side inlet and a front tube sheet. The tube-side inlet is typically an opening or a nozzle on one end of the heat exchanger. The front head thus serves as the entry point of the shell and tube heat exchanger for the tube-side fluid. The tube-side fluid is distributed into the different tubes of the tube bundle via a tube inlet of each of the tubes. After flowing through the tubes, the heated or cooled tube-side fluid leaves the tubes via a tube outlet of each of the tubes whereafter it is collected in a rear head (also known as outlet head or return head). The rear head is formed between a rear tube sheet and a tube-side outlet, which is also typically an opening or a nozzle on the other end of the shell and tube heat exchanger opposite the tube-side inlet. The heated or cooled tube-side fluid then leaves the rear head and thus the heat exchanger via the tube-side outlet, which connects to the next stage of the chemical production process or to a discharge system. The rear head is thus the exit point of the shell and tube heat exchanger for the tube-side fluid. The plurality of tubes is on the one hand supported by baffles, which are plates or guides placed inside the shell to direct the flow of the shell-side fluid. Baffles increase the turbulence of the shell-side fluid, enhancing heat transfer by ensuring that the shell-side fluid flows across the tubes rather than parallel to them. The tubes of the tube bundle are also kept in place by tube sheets, including the front and rear tube sheet. Between the front and the rear tube sheet, a shell which comprises an outer shell, which typically has a cylindrical shape, which encompasses an inner space is present. The front tube sheet physically separates the shell from the front head, while the rear tube sheet physically separates the shell from the rear head. The front and rear tube sheet thus act as a barrier ensuring that the tube-side fluid and the shell-side fluid do not mix while allowing heat transfer to occur. The tube bundle is located in the inner space of the shell. The shell-side of a shell and tube heat exchanger is the space outside the tubes in the outer shell. The shell has a shell-side inlet and a shell-side outlet. The shell-side inlet is the entry point for a shell-side fluid in the shell, while the shell-side outlet is the exit points for the shell-side fluid out of the shell. Between the shell-side inlet and the shell-side outlet, the shell-side fluid flows around the tubes. During the passage of the shell-side fluid through the inner space of the shell, it releases heat from the tube-side fluid flowing in the tubes via the wall of the tubes, in case the tube-side fluid needs to be heated. In case the tube-side fluid however needs to be cooled, the shell-side fluid takes up heat from the tube-side fluid flowing through the tubes. The flow of the tube-side fluid can be arranged in various configurations, such as counterflow (opposite direction to the shell-side fluid), crossflow (perpendicular to the tube bundle) or parallel flow (same direction as the shell-side fluid).

[0003] Shell and tube heat exchangers are types of heat exchangers that are widely used in the industry. They are known for their high efficiency and their low pressure drop, the latter being the main reason to choose a shell and tube heat exchanger. Shell and tube heat exchangers are very suitable to be used in large chemical processes, such as amongst others nitric acid production. Nitric acid has many industrial applications, but its primary function however is the production of ammonium nitrate, which in its turn is then used in the fertilizer industry. In nitric acid plants, shell and tube heat exchangers, amongst others nitric acid cooler condenser shells (hereafter further called "nitric acid cooler condenser"), are commonly used for different purposes such as preheating feed streams and cooling product streams.

[0004] It is remarked that a tube sheet can also serve as a flange with which different devices can be coupled to each other by means of bolts and screws. In shell and tube heat exchangers used in chemical production plants, the tube-side fluid is typically the fluid to be treated, while the shell-side fluid typically is a cooling or heating medium (fluid) for the tube-side fluid.

[0005] Process pipes as well as shell and tube heat exchangers in chemical production plants commonly comprise one or more drain arrangements located at the lowest point of the gas handling equipment. A drain arrangement typically comprises a drain pipe, a drain nozzle which connects the drain pipe to the gas handling equipment, and one or more closing elements to close the drain nozzle.

[0006] In case the chemical production plant is a nitric acid production plant, the process pipe is typically configured to conduct a (hot) process gas through it which amongst others comprise one or more of the following components: comprising nitrogen oxides (NO x ), water (H 2 O) in the form of vapour, and other gaseous components including amongst others as a major part nitrogen (N 2 ) and a minor part oxygen (O 2 ) originating from the ambient air from the air compressor which is used for oxidation of NH 3 to NO, dinitrogen oxide (N 2 O), dinitrogen tetra oxide (N 2 O 4 ), nitrous acid (HNO 2 ) and nitric acid (HNO 3 ).

[0007] A nitric acid shell and tube cooler condenser, hereafter called "nitric acid cooler condenser", comprises a front head, a rear head, and a shell located between the front head and the rear head. The front head is located between a tube-side inlet and a front tube sheet. The rear head is located between a tube-side outlet and a rear tube sheet. The shell is located between the front and the rear tube sheet. The shell comprises an outer shell which encompasses an inner space into which a tube bundle comprising a plurality of tubes are located. In the nitric acid cooler condenser, hot process gas which is typically coming from an ammonia oxidizer, and which more in particular comprises nitrogen oxides (NO x ), water (H 2 O) in the form of vapour, and other gaseous components including amongst others as a major part nitrogen (N 2 ) and a minor part oxygen (O 2 ) originating from the ambient air from the air compressor which is used for oxidation of NH 3 to NO, dinitrogen oxide (N 2 O), dinitrogen tetra oxide (N 2 O 4 ), nitrous acid (HNO 2 ) and nitric acid (HNO 3 ), and which needs to be cooled, enters the front head via the tube-side inlet. This hot process gas is then distributed via a tube inlet of each of the tubes over the different tubes. The hot process gas then flows through the tubes. During the movement of the process gas through the tubes, the following chemical reactions take place: oxidation of NO to form NO 2 , and (in parallel) absorption of the NO 2 in H 2 O forming HNO 3 . A cooled two-phase fluid will then leave the plurality of tubes via a tube outlet and will be collected in the rear head. The cooled two-phase fluid will subsequently leave the heat exchanger via the tube-side outlet. In order to cool the process gas entered in the tubes, cooling water with a temperature which is lower than the dewpoint of the process gas entered in the tubes is entered in the inner space of the shell via a shell inlet. This cooling water will flow around the tubes and will finally leave the shell in a heated form via a shell outlet. During the passage of the cooling water through the shell inner space, the cooling water thus takes up heat from the process gas in the tubes via the tube walls.

[0008] Although in process pipes of a nitric acid production plant, the temperature of the process gas flowing through the process pipe is relatively constant and stays at a relative high temperature within the process pipe, there still can be fluctuations in the flow rate and the temperature of the process gas flowing through the process pipe, which can lead to condensation of the process gas flowing through the process pipes. Also, a lower ambient temperature of around the process pipe which is lower than the dewpoint of the process gas flowing through it, can cause part of the process gas in the vicinity of the wall of the gas handling equipment to condense. This condensate will then, due to gravity, flow to the bottom of the process pipe towards the one or more drain arrangements located at the lowest part of the process pipe. If the temperature within the process pipe drops below the dewpoint of the process gas, NO 2 and N 2 O 4 out of the process gas will be absorbed in the condensate formed out of the vapor present in the process gas, therewith resulting in the formation of liquid HNO 3 . When the temperature within the process pipe increases again due to fresh flowing process gas passing by, the condensed liquid HNO 3 can re-boil, turning back into gaseous HNO 3 potentially corrosion of the drain nozzle(s) and / or the drain pipe(s) of the one or more drain arrangements. This can cause thinning of the drain pipe(s), which in the worst case will result in holes formed therein.

[0009] In the case of a nitric acid cooler condenser, the metal temperature of part of the tubes of the tube bundle is lower than the dewpoint of the process gas flowing through the tubes. The dewpoint is the temperature at which gases in the process gas begin to condense from the gas phase into the liquid phase. Although the temperature of the process gas flowing through the tubes lowers as it transfers heat to the cooling water flowing through the shell side around the tubes, the continuous flow of process gas stays at a relative high temperature within the tubes. Any fluctuations in the flow rate or the temperature of the process gas can cause variations in the temperature of the tubes. For instance, if the flow rate decreases, there might be a temporary drop in the temperature of the tubes, followed by an increase of the tube temperature as the flow stabilizes again. If the temperature within the tubes drops below the dewpoint of the process gas, NO 2 and N 2 O 4 out of the process gas will be absorbed in the condensate formed out of the vapor, through which liquid HNO 3 will be formed. If there are leakages between the tubes and the tube sheets, due to gravity, the condensate including liquid nitric acid will flow out the leakages towards the bottom of the front head of the nitric acid cooler condenser, and subsequently towards the one or more drain arrangements located at the lowest part of the front head. When the temperature in the front head increases again, for instance by the (swirling) hot process gas passing by, the condensate which comes into contact again with this hot process gas can reheat and can thus re-boil, turning back into the gaseous phase including gaseous nitric acid, potentially resulting in corrosion of the drain nozzle(s) and / or the drain pipe(s) of the one or more drain arrangements. This can cause thinning of the drain pipe(s), which can lead to loss of containment. Furthermore, there is the risk of recurrent leaking of flanges.

[0010] The goal of the present disclosure is thus to provide a drain arrangement for a gas handling equipment of a chemical production plant according to the present disclosure, of which the drain nozzle and / or drain pipe of the drain arrangement have a longer lifetime.Summary

[0011] According to a first aspect of the present disclosure, a gas handling equipment comprises a bottom with a lowest part, and is configured to handle a gas which comprises solid particles which, during operation, at least partially are carried over from the gas phase to a condensate, wherein one or more drain arrangements are located at the lowest part of the bottom of the gas handling equipment and each comprise a drain nozzle comprising an drain nozzle opening, a drain pipe which is in liquid communication with the drain nozzle, wherein the drain opening is configured to drain the condensate out of the gas handling equipment towards the drain pipe, and wherein the gas handling equipment comprises one or more floating ball liquid traps located downstream the one or more drain arrangements, each floating ball liquid trap being in liquid communication with one or more of the drain pipes of the one or more drain arrangements, wherein each floating ball trap is configured to discharge the condensate from the one or more drain pipes. A floating ball liquid trap operates on the principle of buoyancy to automatically discharge condensate. Inside the floating ball liquid trap, a ball (float) is provided that rises and lowers again with the level of the condensate present in the trap. When condensate enters the trap, the ball rises due to the increased buoyancy. As the ball rises, it lifts a valve, allowing the condensate to be discharged from the trap. The trap continuously discharges condensate as long as there is condensate present, ensuring efficient removal. This floating ball trap thus has the advantage that any formed condensate comprising amongst others corrosion inducing chemical compounds can be evacuated, thereby avoiding accumulation of such compounds which can lead to (intermitted) re-boiling and condensing of the corrosion inducing chemical compounds, thus avoiding corrosion of the drain nozzle and / or the drain pipe of the drain arrangement.

[0012] Such floating ball liquid trap(s) located downstream the respective drain arrangement(s) according to the present disclosure as described above can be applied in horizontally as well as in vertically oriented gas handling equipment.

[0013] In a specific embodiment of a gas handling equipment according to the present disclosure, a respective one of the one or more floating ball liquid traps is installed further downstream in a respective drain pipe of the drain arrangement(s).

[0014] The one or more floating ball liquid traps are more in particular configured to discharge condensate out of the drain pipe of the respective drain arrangement(s) every time there is condensate in the respective drain pipe(s). In that way, no condensate with corrosion inducing chemical compounds will stand still in the drain nozzle opening and in the drain pipe, which for instance results in thinning of the drain pipe. This prevents amongst others unplanned shut-downs of the chemical production plant, which are very costly.

[0015] In a particular embodiment of a gas handling equipment according to the present disclosure, the floating ball liquid trap(s) is (are) installed further downstream in the drain pipe of the respective drain arrangement(s).

[0016] In a specific embodiment of a gas handling equipment according to the present disclosure, the gas handling equipment comprises an equalizing line which is configured to avoid the accumulation of and to evacuate non-condensables out of the respective floating ball liquid trap(s).

[0017] In an optional embodiment of a gas handling equipment according to the present disclosure, the gas handling equipment comprises a purge tank or other process equipment which is in liquid communication with the one or more floating ball traps and which is configured to collect the condensate which is discharged out of the respective floating ball trap(s).

[0018] When gases flow through the gas handling equipment which can carry solid particles, including but not limited to dust and rust (typically originating from corroded and / or eroded gas handling equipment due to the aggressive nature of some chemical compounds present in the gas and / or the condensate), minerals or other solid particles for instance originating from outside the gas handling equipment when for instance the chemical production plant is in a very dusty environment, together also called "debris", such gases can for different reasons, such as the gas handling equipment being exposed to colder ambient temperatures then the dewpoint temperature of the gas flowing through it, or for instance in a shell and tube heat exchanger, leakages of gas flowing through the tubes occurs, convert from the gas phase into the liquid phase, or in other words form a condensate. During this condensation process, at least a part of the solid particles will be taken along and finally end up in the condensate. The condensate will collect at the bottom of the gas handling equipment, and will consequently flow to the one or more drain arrangements which are provided at the bottom of the gas handling equipment. Also at least part of the solid particles carried with the gas can, depending on the speed with which the gas flows through the gas handling equipment and the density of the particles in the gas, fall out of the gas and finally drop down out of the gas on the bottom of the gas handling equipment. At least part of these solid particles can fall in the drain pipe, and at least another part of these will also be taken along with the condensate towards the drain arrangement. The problem with this is now that this debris can clog in the drain nozzle and / or the drain pipe of a drain arrangement, and when the clogging further continues, in the worst case block the drain nozzle(s) and / or the drain pipe(s). Regular maintenance, for instance at each revision stop, ensures that the drain remains unobstructed. However, lack of regular maintenance can lead to accumulation of the debris in the drain nozzle(s) and / or drain pipe(s) which amongst others can create problems such as amongst others corrosion thereof.

[0019] In an optional embodiment according to the present disclosure, a collar which at least partially surrounds the drain opening of the one or more drain arrangement(s) is provided, the collar comprising one or more collar drain openings, wherein the collar drain openings are located in a side of the collar opposite to the flow direction of the incoming gas in the gas handling equipment, wherein at least part of the solid particles of the condensate are stopped by the collar, thereby obtaining a remaining part of the condensate with a reduced amount of solid particles which will flow towards the respective collar drain opening(s), and subsequently in the respective nozzle opening(s) and finally in the respective drain pipe(s).

[0020] The advantage of having the collar as described above is that the debris in the condensate is stopped by the collar, thereby avoiding that the condensate can flow over the bottom of the gas handling equipment directly into the drain opening, but still having the ability to fully drain the condensate out the gas handling equipment. This has the advantage that the one or more drain pipes cannot clog by the solid particles in the condensate, and even in the worst case can block one or more drain pipes. In that way, no condensate with corrosion inducing chemical compounds will stand still in the drain nozzle opening and in the drain pipe, which for instance results in thinning of the drain pipe. This prevents amongst others unplanned shut-downs of the chemical production plant, which are very costly.

[0021] In a particular embodiment of a gas handling equipment according to the present disclosure, the collar is welded to the lowest part of the bottom of the gas handling equipment.

[0022] The collar more in particular has a circular shape.

[0023] In a specific embodiment of a gas handling equipment according to the present disclosure, the collar has a height, and the one or more collar drain openings are in the form of vertical slits extending at least partially over the height of the collar.

[0024] More in particular, the one or more vertical slits extend over the complete height of the collar.

[0025] In a possible embodiment of a gas handling equipment according to the present disclosure, the collar is a metal ring with one vertical slit extending over the complete height of the ring.

[0026] In an optional embodiment of a gas handling equipment according to the present disclosure, the drain arrangement comprises a cover cap which is configured to be mounted on or over the collar to prevent direct access to the collar from above.

[0027] The advantage of this cover cap is that the collar is closed off from the top, and the drain opening which is at least partially surrounded by the collar is not accessible anymore from the top, thereby preventing solid particles that are carried by the gas would fall out of the gas directly in the collar and subsequently through the drain nozzle in the drain pipe.

[0028] The gas handling equipment of the chemical production plant according to the present disclosure can comprise one or more process pipes. In the light of the present disclosure, process pipe are pipes which transport fluids (liquids or gases) within a chemical production plant.

[0029] The gas handling equipment of the chemical production plant according to the present disclosure can further comprise one or more shell and tube heat exchangers. A shell and tube heat exchanger is a device which transfers heat between two fluids. It consists of a series of tubes (the tube bundle) enclosed within a larger shell. One fluid flows through the tubes, while the other flows around the tubes within the shell, allowing heat exchange between the two. The shell and heat exchanger more in particular comprises first of all a front head with a tube-side inlet which is configured to enter a tube-side fluid which needs to be cooled or heated in the heat exchanger, and which is configured to distribute the tube-side fluid from there in the different tubes via the tube inlet of each of the tubes, wherein the front head comprises the bottom and the lowest part with the drain arrangement, and further a rear head, which is configured to receive the tube-side fluid out of the tubes via the tube outlet of each of the tubes, the rear head comprising a tube-side outlet which is configured to exit the tube-side fluid out of the heat exchanger. Between the front head and the rear head, a shell is present which comprises a shell inner space, the shell being separated from the front head by means of a front tube sheet located in the inner space of the shell at the tube-side inlet, and the rear head by means of a rear tube sheet located in the inner space of the shell at the tube-side outlet. The front tube sheet and the rear tube sheet are configured to hold the tubes in place. The shell comprises a shell-side inlet which is configured to enter a shell-side fluid in the shell inner space, and a shell-side outlet which is configured to exit shell-side fluid out of the shell inner space. The shell inner space is configured to let the shell-fluid flow through the shell inner space around the tubes, which are located in the shell inner space, between the shell-side inlet and the shell-side outlet, therewith releasing heat to the tube-side fluid flowing in the tubes in case the tube-side fluid needs to be heated, or taking up heat from the tube-side fluid flowing in the tubes in case the tube-side fluid needs to be cooled.

[0030] In a particular embodiment of a gas handling equipment according to the present disclosure, the chemical production plant is a nitric acid production plant, and the shell and tube heat exchanger(s) is (are) nitric acid cooler condenser(s), wherein the tube-side fluid is a (hot) process gas which originates from an ammonia oxidizer of a nitric acid production plant, comprising NO x , water vapour, N 2 , oxygen O 2 , dinitrogen oxide (N 2 O), dinitrogen tetra oxide (N 2 O 4 ), nitrous acid (HNO 2 ) and nitric acid (HNO 3 ), and which needs to be cooled, and the cooled process gas is a cooled two-phase fluid consisting of a liquid part with a certain amount of HNO 3 , HNO 2 , H 2 O, and N 2 O 4 , and a gaseous part with a reduced amount of nitrogen oxides (NO x ) and water vapour since there was absorption of the NO x in the condensed vapour, and a reduced amount of O 2 in view of the process gas entering the tubes, the same amount of N 2 , and dinitrogen oxide (N 2 O), dinitrogen tetra oxide (N 2 O 4 ), nitrous acid (HNO 2 ) and nitric acid (HNO 3 ), the shell-side fluid is cooling water.

[0031] According to a second aspect of the present disclosure, a nitric acid production plant is disclosed comprising an ammonia oxidizer, an absorption tower, and a gas handling equipment according to the present disclosure comprising one or more process pipes and one or more nitric acid cooler condensers as described above.

[0032] According to a third aspect of the present disclosure, a method for handling a gas in a gas handling equipment of a chemical production plant is disclosed, wherein the method comprises the steps of condensing of part of the process gas to a condensate, flowing of the condensate towards a drain nozzle with a drain opening of one or more drain arrangements located at a lowest part of a bottom of the gas handling equipment through gravity, collecting the condensate in a drain pipe of one or more drain arrangements, and subsequently in one or more floating ball liquid traps provided downstream the one or more drain arrangements, more in particular further downstream in the drain pipe, discharging the condensate out of a floating ball trap.

[0033] In a specific method according to the present disclosure, the discharge of the condensate out of the drain pipe of the one or more drain arrangement(s) by the respective floating ball liquid trap(s) is done every time there is condensate present in the drain pipe(s).

[0034] In an optional method according to the present disclosure, the method comprises the step of venting the floating ball liquid trap using an equalizing line. This has the advantage that non-condensables (= inerts) which are taken along with the gas, and consequently with the condensate of the gas, will not accumulate in the floating ball liquid trap, but instead are evacuated back to the process.

[0035] In an optional method according to the present disclosure, the method comprises the steps of carrying over part of the solid particles of a gas phase to a condensate phase of the gas, thereby forming a condensate with solid particles, flowing of the condensate with the solid particles towards the one or more drain arrangements, stopping at least a part of the solid particles of the condensate with solid particles by the collar (s), flowing of the remaining part of the condensate with a reduced amount of solid particles towards the drain opening of the respective drain arrangement(s), and subsequently in the respective nozzle opening(s) and finally in the respective drain pipe(s). collecting the condensate in the respective drain pipe(s), and consequently in a floating ball liquid trap provided downstream the respective drain arrangement(s), more in particular in further downstream in the respective drain pipe(s), discharging the condensate out of the respective floating ball liquid trap(s), more in particular every time there is condensate present in the respective drain pipe(s).

[0036] In an optional method according to the present disclosure, the condensate is discharged to a purge tank or other process equipment where the condensate is collected.Description of the figures

[0037] FIG. 1 shows a principle drawing of a shell and tube heat exchanger according to the present disclosure comprising a drain arrangement with a floating ball trap. FIG. 2 shows a detail of the drain nozzle opening surrounded by a collar with a vertical slit which is part of the drain arrangement as shown in Figure 1. Detailed description

[0038] A gas handling equipment of a chemical production plant according to the present disclosure is an enclosure or housing configured to contain and manage gases during various stages of the chemical production process. The gas which is handled in the gas handling equipment according to the present disclosure comprises solid particles which during operation of the chemical production plant at least partially are carried over from the gas phase to a condensate of the gas, thereby resulting in a condensate.

[0039] The gas handling equipment according to the present disclosure comprises a bottom with a lowest part which is provided with one or more drain arrangements. A drain arrangement comprises a drain nozzle with a drain nozzle opening which is in fluid communication with a drain pipe. A drain nozzle is the connection between the outer wall of the gas handling equipment and the drain pipe. The drain opening is configured to drain the condensate out of the gas handling equipment towards the drain pipe of the drain arrangement(s). During operation of the chemical production plant, a part of the solid particles of the gas carrying solid particles can be taken along with the condensing gas. Due to gravity, the condensate, together with the solid particles, will flow to the lowest part of the bottom of the gas handling equipment where the drain arrangement(s) is (are) present. The condensate will further flow towards the one or more drain arrangements. In a drain arrangement, the condensate will flow through the drain nozzle opening in the drain pipe.

[0040] The gas handling equipment further comprises one or more floating ball liquid traps installed downstream the drain arrangement(s), more in particular further down in the drain pipe. Each floating ball liquid trap is configured to discharge the condensate out of one or more of the drain pipes, and more in particular every time when there is condensate present in the drain pipe(s). A floating ball liquid trap will collect the condensate out of the drain pipe with which it is in liquid communication. The condensate will then further be discharged from the floating ball liquid trap towards a purge tank which collects the condensate discharged from the floating ball liquid trap. It is remarked that only liquid can be discharged by a floating ball liquid trap, and no gas.

[0041] The floating ball liquid traps(s) can be installed downstream the respective drain arrangement(s) in a horizontally oriented as well as a vertically oriented gas handling equipment.

[0042] The gas handling equipment of the chemical production plant according to the present disclosure can more in particular comprise one or more process pipes which comprise the bottom with the lowest part which is provided with one or more drain arrangements with a floating ball liquid trap arranged downstream of a respective on or the drain arrangements. As already mentioned above, a process pipe is a pipe which transports fluids (liquids or gases) within a chemical production plant.

[0043] The gas handling equipment of the chemical production plant according to the present disclosure can further comprise one or more shell and tube heat exchangers, which are devices which transfer heat between two fluids. In general, a shell and tube heat exchanger consists of a series of tubes (the tube bundle) enclosed within a larger shell. One fluid flows through the tubes, while the other flows around the tubes within the shell, allowing heat exchange between the two. Examples of such a shell and tube heat exchanger is a cooler condenser in which a process gas is located in the tube side and a liquid is present in the shell side, or a gas-gas heat exchanger in which in the tube side as well as the process side, gas is present.

[0044] The gas handling equipment of the chemical production plant according to the present disclosure can more in particular comprise one or more shell and tube heat exchangers. A shell and tube heat exchanger is a device which transfers heat between two fluids. It consists of a series of tubes (the tube bundle) enclosed within a larger shell. One fluid flows through the tubes, while the other flows around the tubes within the shell, allowing heat exchange between the two. The shell and heat exchanger more in particular comprises first of all a front head with a tube-side inlet which is configured to enter a tube-side fluid which needs to be cooled or heated in the heat exchanger, and which is configured to distribute the tube-side fluid from there in the different tubes via the tube inlet of each of the tubes, wherein the front head comprises the bottom and the lowest part with the drain arrangement, and further a rear head, which is configured to receive the tube-side fluid out of the tubes via the tube outlet of each of the tubes, the rear head comprising a tube-side outlet which is configured to exit the tube-side fluid out of the heat exchanger. Between the front head and the rear head, a shell is present which comprises a shell inner space, the shell being separated from the front head by means of a front tube sheet located in the inner space of the shell at the tube-side inlet, and the rear head by means of a rear tube sheet located in the inner space of the shell at the tube-side outlet. The front tube sheet and the rear tube sheet are configured to hold the tubes in place. The shell comprises a shell-side inlet which is configured to enter a shell-side fluid in the shell inner space, and a shell-side outlet which is configured to exit shell-side fluid out of the shell inner space. The shell inner space is configured to let the shell-fluid flow through the shell inner space around the tubes, which are located in the shell inner space, between the shell-side inlet and the shell-side outlet, therewith releasing heat to the tube-side fluid flowing in the tubes in case the tube-side fluid needs to be heated, or taking up heat from the tube-side fluid flowing in the tubes in case the tube-side fluid needs to be cooled.

[0045] The gas handling equipment according to the present disclosure is very suitable to be used in a nitric acid production process. The gas handling equipment can for instance comprise one or more shell and tube heat exchangers such as a nitric acid cooler condenser to cool a process gas coming from an ammonia oxidizer. It is remarked that the shell and tube heat exchanger according to the present disclosure can however also be used in other applications in a nitric acid production plant to cool and heat different fluids. The shell and tube heat exchanger according to the present disclosure can also be applied in other chemical production processes than nitric acid production process to heat or cool different fluids.

[0046] A nitric acid production plant according to the present disclosure comprises an ammonia oxidizer, an absorption tower, and gas handling equipment comprising one or more process pipes and / or one or more nitric acid cooler condensers as described above. An ammonia oxidizer is a device configured for converting ammonia (NH 3 ) and oxygen (O 2 ) into process gas which serves as the precursor gases for nitric acid synthesis. An absorption tower is a device configured for mixing cooled process gas comprising nitrogen oxides (NO x ) with water to obtain nitric acid and a tail gas.

[0047] In case the shell and tube heat exchanger is in the form of a nitric acid cooler condenser, the tube-side fluid is a process gas that needs to be cooled and that originates from an ammonia oxidizer and when entering the tubes comprises N 2 , O 2 , NOx, N 2 O, N 2 O 4 , H 2 O-vapour, HNO 2 and HNO 3 , and when exiting the tubes is a two-phase process gas consisting of a liquid compartment with a certain amount of HNO 3 , HNO 2 , H 2 O, and N 2 O 4 and a gas compartment with a reduced amount of nitrogen oxides (NO x ) and vapour since there was absorption of the NO x in the condensed vapour, and O 2 in view of the process gas entering the tubes, the same amount of N 2 (is inert), and then further dinitrogen oxide (N 2 O), dinitrogen tetra oxide (N 2 O 4 ), nitrous acid (HNO 2 ) and nitric acid (HNO 3 ), and the shell-side fluid is cooling water.

[0048] A nitric acid production plant according to the present disclosure comprises an ammonia oxidizer, an absorption tower, and gas handling equipment according to the present disclosure comprising one or more process pipes and / or one or more nitric acid cooler condensers as described above.

[0049] In a method for handling a gas in a gas handling equipment of a chemical production plant according to the present disclosure, in a first step part of the solid particles of a gas phase are carried over to a condensate of the gas, followed by flowing of the condensate towards one or more drain nozzles with a drain nozzle opening of one or more drain arrangements through gravity, and collecting the condensate in a drain pipe of the respective drain arrangement(s), and finally discharging the condensate out of the respective drain pipe(s) by means of one or more floating ball traps with which the drain pipe(s) are in liquid communication. The condensate will subsequently be discharged out of the one or more floating ball liquid traps towards a purge tank where the condensate is collected. Optionally, the method can comprise the step of venting the drain pipe of the one or more drain arrangements using an equalizing line in order to remove non-condensables out of the respective drain pipe(s) in case there would be present.

[0050] The present disclosure will now be described in more detail with reference to a specific example of a heat and tube exchanger according to the present disclosure. It should be clear that this is only an example which is not limitative for the scope of the present disclosure.

[0051] A horizontal or vertical heat and tube exchanger (1) according to the present disclosure as shown in Figure 1, comprises a front head (2a), also called a front channel, which is located at the left side of a front tube sheet (5). The front head (2a) is configured to enter a process gas to be heated or cooled, which is the tube-side fluid, via a tube-side inlet (21) in the heat exchanger (1), and to distribute the process gas from there to a horizontal, respective vertical tube bundle comprising a plurality of tubes (4) via the respective tube inlets (4a). The front head (2a) comprises a bottom with a lowest part (10). A rear head (2b) is located at the right side of a rear tube sheet (6). This rear head (2b) is configured to collect the cooled or heated process gas from the plurality of tubes (4) via the respective tube outlets (4b), and to exit the heated or cooled process gas from heat exchanger (1) via a tube-side outlet (22). Between the front tube sheet (5) and the rear tube sheet (6), a shell (3) is present. The shell (3) comprises an inner space (31) in which a tube bundle comprising a plurality of tubes (4) is located. The plurality of tubes (4) are kept in place by the front tube sheet (5) and the rear tube sheet (6). Each of the tubes (4) of the tube bundle comprises a tube inlet (4a) and a tube outlet (4b). The shell (3) comprises a shell inner space (31), and further comprises a shell-side inlet (32) which is configured to enter a shell-side fluid that needs to be heated or cooled in the shell (3b), and a shell-side outlet (33) which is configured to exit the heated or cooled shell-side fluid out of the shell (3b), wherein the shell inner space (31) is configured to let the shell-side fluid flow around the tubes (3) which are located in the shell inner space (31), thereby taking up heat from or releasing heat to the process gas flowing through the tubes (3). It is remarked that the front tube sheet (5) can also be located at the right side of the inner space (3), resulting in the front head (3a) also being located at the right side of the inner space (3), and the rear tube sheet (6) can also be located at the opposite, right side of the inner space (3), resulting in the rear head (3c) being located at the opposite, left side thereof. At the lowest part of the bottom of the front head (3a), a drain arrangement (7) is provided which comprises a drain nozzle (71) comprising a nozzle drain opening (72), a drain pipe (73) which is located outside the shell and tube heat exchanger and which is in liquid communication with the drain nozzle (71). The nozzle drain opening (72) is configured to drain the condensate out of the shell and tube heat exchanger (1) towards the drain pipe (73). In the drain pipe, a floating ball liquid trap (9) is provided which during operation discharges condensate out of the drain pipe (73), more in particular every time there is condensate present in the drain pipe (73). A purge tank (10) or other process equipment is provided in which during operation the condensate is collected which is discharged out of the floating ball liquid trap (9). Furthermore, an equalizing line (11) is provided which serves as a venting line to vent the floating ball trap such that any non-condensables which are taken along with the gas and subsequently with the condensate of the gas are removed again out of the floating ball trap in case any of such non-condensables would be present therein. Furthermore, in case the process gas carries solid particles with it which can be taken along during condensation of the process gas, and subsequently will flow with the condensate towards the drain arrangement due to gravity, in order to prevent clogging of the drain pipe (73), and in the worst case blocking thereof, a ring-shaped collar (74) is provided which at least partially surrounds the drain opening (72). The collar (74) is welded by means of spot-welds (76) to the shell of lowest part of the bottom of the shell of the front head (3a). The collar (74) comprises one vertical extending drain slit (75) which extends over the total height (h) of the collar (74). It is remarked that it would also be possible to provide more than one of such vertically extending drain slits (75) (not shown on Figure 2). The vertically extending drain slit (75) is located in a side of the collar (74) opposite to the flow direction of the incoming gas in the front head of the shell and tube heat exchanger. During operation of the chemical production plant, at least part of the solid particles of the condensate are stopped by the collar (74), thereby obtaining a remaining part of the condensate with a reduced amount of solid particles which will flow towards the vertical extending drain slit (75), and subsequently in the nozzle drain opening (72) and finally in the drain pipe (73). In order to prevent that solid particles in the process gas would fall down directly in the drain nozzle opening (72) and thus in the drain pipe (73), a cover cap (76) can be provided which can be mounted on or over the collar (74). In order to be able to remove the debris which is stopped by the collar (74), a manhole (8) is provided in the shell of the front head (3a). A manhole (8) is provided in the shell (2) of the shell and tube heat exchanger (1) to be able to enter the inner space (31) of the shell (3), for instance to do maintenance or reparations in the inner space (31), and / or to remove the debris which is stopped by the collar (74), if present. Although in Figure 1, a horizontal shell and tube heat exchanger (1) is shown and described in more detail above, it is remarked that the features as described above can also be applied to a vertical shell and tube heat exchanger (1) (not shown on Figure 1).

Claims

1. Gas handling equipment of a chemical production plant, wherein the gas handling equipment comprises a bottom with a lowest part, and is configured to handle a gas which during operation is converted to condensate, wherein one or more drain arrangements are located at the lowest part of the bottom of the gas handling equipment and each comprise - a drain nozzle comprising an drain nozzle opening, - a drain pipe which is in liquid communication with the drain nozzle, wherein the drain opening is configured to drain the condensate out of the gas handling equipment towards the drain pipe, wherein the gas handling equipment comprises one or more floating ball liquid traps located downstream the one or more drain arrangements, each floating ball liquid trap being in liquid communication with one or more of the drain pipes of the one or more drain arrangements, wherein each floating ball trap is configured to discharge the condensate from the one or more drain pipes.

2. Gas handling equipment according to claim 1, wherein the one or more floating ball traps are configured to discharge the condensate out of a respective drain pipe of the one or more drain arrangements every time there is condensate present in the drain pipe(s).

3. Gas handling equipment according to claim 1 or 2, wherein the floating ball liquid trap is installed downstream the drain arrangement, more in particular further downstream in the drain pipe.

4. Gas handling equipment according to any one of claims 1 to 3, wherein the gas handling equipment comprises an equalizing line which is configured to vent the floating ball liquid trap.

5. Gas handling equipment according to any one of claims 1 to 4, wherein the gas handling equipment comprises a purge tank or other process equipment which is in liquid communication with the one or more floating ball traps and which is configured to collect the condensate which is discharged out of the one or more floating ball traps.

6. Gas handling equipment according to any one of claims 1 to 5, wherein the one or more drain arrangements comprise a collar which at least partially surrounds the drain opening and comprises one or more collar drain openings, wherein the collar drain openings are located in a side of the collar opposite to the flow direction of the incoming gas in the gas handling equipment, and wherein at least part of the solid particles of the condensate are stopped by the collar, thereby obtaining a remaining part of the condensate with a reduced amount of solid particles which will flow towards the one or more collar drain openings, and subsequently in the nozzle opening and finally in the drain pipe, more in particular - being welded to the lowest part of the bottom of the gas handling equipment, and / or - having a circular shape, and / or - having a height, wherein the one or more collar drain openings are in the form vertical slits extending at least partially over the height of the collar, even more in particular extending over the whole height of the collar, wherein the collar most in particular is a metal ring with one vertical slit extending over the whole height of the collar, - further comprising a cover cap which is configured to be mounted on or over the collar to prevent access to the collar from above7. Gas handling equipment according to any one of the preceding claims, wherein the gas handling equipment comprises one or more process pipes which comprise the bottom with the lowest part with the drain arrangement and the one or more floating ball liquid traps.

8. Gas handling equipment according to any one of claims 1 to 6, wherein the gas handling equipment comprises one or more shell and tube heat exchangers which each comprise - a front head with a tube-side inlet which is configured to enter a tube-side fluid which needs to be cooled or heated in the heat exchanger, and which is configured to distribute the tube-side fluid from there in the different tubes via the tube inlet of each of the tubes, wherein the front head comprises the bottom with the lowest part with the drain arrangement, - a rear head, which is configured to receive the tube-side fluid out of the tubes via the tube outlet of each of the tubes, the rear head comprising a tube-side outlet which is configured to exit the tube-side fluid out of the heat exchanger, and - a shell between the front head and the rear head, the shell comprising a shell inner space, the shell being separated from • the front head by means of a front tube sheet located in the inner space of the shell at the tube-side inlet, and • the rear head by means of a rear tube sheet located in the inner space of the shell at the tube-side outlet, wherein the front tube sheet and the rear tube sheet are configured to hold the tubes in place, and wherein the shell comprises - a shell-side inlet which is configured to enter a shell-side fluid in the shell inner space, and - a shell-side outlet which is configured to exit shell-side fluid out of the shell inner space, wherein the shell inner space is configured to let the shell-fluid flow through the shell inner space around the tubes, which are located in the shell inner space, between the shell-side inlet and the shell-side outlet, therewith releasing heat to the tube-side fluid flowing in the tubes in case the tube-side fluid needs to be heated, or taking up heat from the tube-side fluid flowing in the tubes in case the tube-side fluid needs to be cooled.

9. Gas handling equipment according to claim 8, wherein the chemical production plant is a nitric acid production plant, and wherein the shell and tube heat exchanger(s) is (are) nitric acid cooler condenser(s), wherein - the tube-side fluid is a (hot) process gas which originates from an ammonia oxidizer of a nitric acid production plant, comprising NOx, water vapour, N2, oxygen O2, dinitrogen oxide (N2O), dinitrogen tetra oxide (N2O4), nitrous acid (HNO2) and nitric acid (HNO3), and which needs to be cooled, and - the cooled process gas is a cooled two-phase fluid consisting of a liquid part with a certain amount of HNO3, HNO2, H2O, and N2O4, and a gaseous part with a reduced amount of nitrogen oxides (NOx) and water vapour since there was absorption of the NOx in the condensed vapour, and a reduced amount of O2 in view of the process gas entering the tubes, the same amount of N2, and dinitrogen oxide (N2O), dinitrogen tetra oxide (N2O4), nitrous acid (HNO2) and nitric acid (HNO3), - the shell-side fluid is cooling water.

10. A nitric acid production plant comprising an ammonia oxidizer, an absorption tower, and gas handling equipment comprising one or more process pipes according to claim 7 and / or one or more nitric acid cooler condensers according to claim 9.

11. A method for handling gas in a gas handling equipment of a chemical production plant, wherein the method comprises the steps of - condensing of the gas to a condensate, - flowing of the condensate towards a drain nozzle with a drain opening of one or more drain arrangements located at a lowest part of a bottom of the gas handling equipment through gravity, - collecting the condensate in a drain pipe of one or more drain arrangements, and consequently in a floating ball liquid trap provided downstream the one or more drain arrangements, more in particular in further downstream in the drain pipe of the respective drain arrangement(s), - discharging the condensate out of a floating ball trap, more in particular every time there is condensate present in the drain pipe of the respective drain arrangement(s).

12. A method according to claim 11, wherein the method comprises the step of venting the floating ball liquid trap using an equalizing line.

13. A method according to claim 11 or 12, wherein the gas which during operation is converted to condensate comprises the steps of - carrying over part of the solid particles of a gas phase to a condensate phase of the gas, thereby forming a condensate with solid particles, - flowing of the condensate with the solid particles towards the one or more drain arrangements, - stopping at least a part of the solid particles of the condensate with solid particles by the collar(s), - flowing of the remaining part of the condensate with a reduced amount of solid particles towards the collar drain opening(s), and subsequently in the nozzle opening and finally in the drain pipe of the respective drain arrangement(s). - collecting the condensate in the drain pipe of respective drain arrangement(s), and consequently in a floating ball liquid trap provided downstream the one or more drain arrangements, more in particular in further downstream in the drain pipe of the respective drain arrangement(s), - discharging the condensate out of a floating ball trap, more in particular every time there is condensate present in the drain pipe of the respective drain arrangement(s).

14. A method according to any one of claims 11 to 13, wherein the condensate is discharged to a purge tank or other process equipment where the condensate is collected.

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