DE102014011274A1 - Plate-shaped heat exchanger - Google Patents

Abstract

The invention relates to a plate-shaped heat exchanger for use within a at a first pressure level pressure-resistant pressure vessel of a reactor, in particular Methanisierungsreaktors in which reacts at least two gas constituents educt gas reacts chemically in the presence of a catalyst to a component of both gas constituents product gas, with a on a second Pressure level of preferably an overpressure, more preferably of 2 bar or higher, in particular 40 bar or higher pressure-resistant outer shell over which a thermal coupling between a flowing inside the outer shell heat transfer medium and the chemical reaction is provided, and within the outer shell of an input to a the first output extending first flow path, in the flow through at least a proportion of the heat carrier due to a taking place via the thermal coupling first heat exchange its A ggregatszustand changes, and with a running within the outer shell, located closer to the first output than at the entrance and opening into a second output deviating from the second output second flow, in the flow through the heat carrier due to a take place via the thermal coupling, compared to the first heat exchange lower second heat exchange changes its temperature.

Description

The invention relates to a plate-shaped heat exchanger for use within a at a first pressure level pressure-resistant pressure vessel of a reactor, in particular Methanisierungsreaktors in which reacts at least two gas constituents educt gas reacts chemically in the presence of a catalyst to a component of both gas constituents product gas, with a second on a Pressure level of in particular 40 bar or higher pressure-resistant outer shell over which a thermal coupling between a flowing inside the outer shell heat transfer medium and the chemical reaction is created, within the outer shell of an input to a first output extending first flow path, in the flow through at least a proportion the heat carrier changes its state of aggregation due to a first heat exchange via the thermal coupling, a heat exchanger arrangement with at least one Such a heat exchanger and such a heat exchanger arrangement having a reactor, in particular methanization, as well as a method for operating such a reactor.

Such generic plate-shaped heat exchangers are well known in the art. For example, a plurality of such plates are arranged inside a methanation reactor, wherein flow paths for the gases of the methanation reaction are formed in the spaces between the plates in which the catalyst bed is located. In this case, for example, a countercurrently flowing within the heat exchanger plates heat transfer medium takes on the heat generated during the exothermic methanation and cools the reaction preferably in such a way that a temperature gradient of a hot spot area near an input range of the educt gases of the reaction towards the output of the gives the product gases of the reactor in order to obtain the most efficient conversion rate possible.

Is used as a heat transfer medium H ₂ O, especially in a pressurized refrigeration cycle, a transition liquid to gaseous part of the medium is achieved with a large part of the heat absorbed, so that at the outlet of the plate reactor, a mixture of water and water vapor exits. This can then be separated in a downstream steam drum in the components of water and water vapor, at the same time a part of the water vapor is decoupled from the cooling circuit and is replaced by fresh boiler feed water.

Further details of the catalytic methanation are, for example, in WO 2011/076315 A2 to which reference is made. A representation of a cooling system with a steam drum as explained above can be found in the still unpublished German patent application 10 2014 015 055.3 ,

The invention has for its object to improve a heat exchanger of the type mentioned in terms of a decoupling of the heat transfer medium from a heat exchange cycle.

This object is achieved by the invention by a development of a heat exchanger of the type mentioned, which is characterized by a running within the outer shell, closer to the first output than at the entrance and opening into a deviating from the first output second outlet second flow path, in the flow through the heat transfer medium due to a taking place via the thermal coupling, compared to the first heat exchange lower second heat exchange changes its temperature.

The plate-shaped heat exchanger according to the invention thus opens up the possibility of still providing a portion of the heat carrier in superheated gaseous form within the heat exchanger and decoupling via the second output, without the heat transfer medium would have to be transferred after exiting the second output in a steam drum. This leads to an increase in the durability of subsequent to the second output pipes and apparatus, as a liquid formation is avoided due to the present superheated gaseous heat transfer medium, in contrast to the case of a saturated steam outlet, for example. When the underlying cycle is a water-steam cycle, a major portion of the heat may be absorbed by passing through the first flow path. Parallel to this, a temperature control of the heat transfer medium / cooling medium can take place in the second flow path.

While in this respect an application for exothermic reactions is preferred, use in reverse endothermic reactions is also conceivable. In this case, an additional heat source is provided with the additional heat exchanger surfaces for coupling consumption heat. In endothermic reactions, however, it should be noted that the direction of flow of the heating medium (eg steam / water / superheated steam) is only possible in the direction of gravity, resulting in a reversal of the direction of flow.

In a particularly preferred embodiment it is provided that the second flow path branches off from the first flow path. Thus, the heat transfer medium first flows through the same entrance to a switch, from which a part of the heat transfer medium continues to flow on the first flow path, whereas another part flows along the second flow path.

In this context, it should be noted that the terms "input", "output" and "flow paths" are to be understood as meaning that the entrance / exit may physically consist of several openings, as well as the flow paths have several "parallel" branches can.

In a particularly preferred embodiment, the branch and / or the second flow path forms a flow obstacle causing a pressure drop. Due to the flow obstacle, a pressure drop occurs for the heat transfer medium passing through the second flow path and thus to a boiling point. Point depression, whereby a heat transfer medium which traverses the second flow path undergoes a very rapid complete transition into the gaseous state as liquid-gas mixture.

It is preferably provided that the ratio of the flow cross-section of the second flow path to that of the first flow path near the first exit is less than 2/3, preferably less than 3/7, in particular less than 1/4 and in particular greater than 1/19 , preferably greater than 1/9, in particular greater 1/7.

In this way it is achieved that a predominant portion of the heat transfer medium continues to follow the first flow path, and thus the global desired temperature control in the reactor is not unduly limited.

Thus, in the case of typical process parameters of catalytic methanation, for example at the first outlet, the heat transfer medium can emerge as a liquid / gas mixture in the ratio of about 4/1, for example a water / steam mixture, whereas saturated steam enters the second flow path, but there immediately into one superheated steam is converted and as such exits through the second exit. With an exchanged amount of heat of 1 kWh, it is possible to vaporize approx. 2.27 kg of water at 273.8 ° C and 59 bar.

In addition, depending on the removal amount of the superheated steam despite the possible relevant span span achievable that no local hot spot forms at the location of the second flow path, since surrounding areas of the first flow path can also decouple excess heat of reaction from the system when the flow on throttled or even stopped the second flow path. In fact, the hot spot areas that occur under normal process conditions in catalytic methanation remain virtually unaffected.

In this context, it is also preferably provided that the ratio of the flow path length of the second flow path to the flow path length lying between the inlet and the branch is less than 2/3, preferably less than 3/7, in particular less than 1/4, and in particular greater is greater than 1/19, preferably greater than 1/14, in particular greater than 1/9.

In this way it is achieved that the entire heat transfer medium for a predominant flow path initially act together in the way of the first heat exchange, so after reaching the boiling temperature increasing proportion of the heat transfer fluid from the liquid to the gaseous phase passes, whereas the branch only to a later point takes place, but still sufficient to ensure the complete phase transition and the second heat exchange flow path length remains.

It can be provided that the second flow path is meandering, or at least according to evaluation criteria of the meandering shape has a higher score than the first flow path after the diversion. Also in this way can be given to the remaining course of the first flow path, a flow obstacle, which causes the leading to the boiling point reduction pressure drop.

In a particularly preferred embodiment, on the other hand, the flow path shape of the second flow path need not differ particularly from that of the remaining flow path after the branch. Thus, the flow obstruction can also be achieved by physical interference surfaces in the flow path, such as a grid, or a metal felt, which acts as a control sponge. Ultimately, a relative pressure loss of 1% or less may be sufficient to achieve the desired effect. At pressure ranges of more than 40 bar, preferably more than 60 bar, in particular in the range between 70 and 80 bar, the pressure loss could for example be 1 bar + -0.4 bar. In this context, it should be considered that a predetermined removal of, for example, superheated steam should also take place when a reactor is operated in partial load, ie with not more than 80%, not even more than 70%, in particular not more than 60% of its maximum power.

In a particularly preferred embodiment of the heat exchanger plates, these can be prepared by a method which can be described as pressure inflation of two connected at their edges plates, for example made of stainless steel, wherein the plates are also connected at intermediate points, for example by spot welding, thereby resulting from the inflation Thermo sheet in the form of a kind of "air mattress form" forms. Such a method is for example in the EP 0 995 491 B1 (in particular 3 ), to which reference is made in this regard to the manufacturing process of the plate.

In this context, it is preferably provided that the structure of the first and second flow paths on the type of connection of the plates before the pressure inflation is given. In particular, it is preferred that the flow obstruction is formed by a grid which is defined, for example, by spot welding the two plates prior to their pressure inflation.

A boundary between the second flow path and the further section of the first flow path after the branch can thus also be prepared by spot welding in advance, which are much closer meshed, so that in this area a gap between the plates during pressure inflation will not arise. On the other hand, in the region of the grid, the distance of the spot welds is sufficiently large that the plates can deform outward during pressure inflation between two adjacent spot welds and thus provide access to the second flow path.

The surfaces forming the thermal coupling to the second flow path thus represent superheater heating surfaces. In that regard, the invention, as the most general protection-worthy, discloses a plate-shaped heat exchanger, in particular in the form of a thermo sheet with an integrated superheater heating surface.

Furthermore, a heat exchanger arrangement with at least one, in particular a plurality of plate-shaped heat exchangers according to one of the aforementioned aspects, as well as a reactor equipped with such a heat exchanger arrangement, in particular a methanization reactor, are also protected. In the latter, the heat exchanger plates can be arranged as usual supported, for example, on a grid spaced, and the gap between the plates have the catalyst bed.

In a preferred embodiment of the reactor, a cooling system is provided, which is connected to the at least one input and the at least two outputs of the at least one heat exchanger plate. The cooling system may in particular have a steam drum, preferably coupled to the at least one input and the first output.

In addition, it is preferably provided that in the reactor, the cooling system decouples heat transfer material, in particular in the form of superheated steam via the second output.

Accordingly, it is preferred as a heat transfer medium H ₂ O used although the invention is not limited to this particular type of heat transfer medium / cooling medium and other heat transfer media or mixtures thereof can be used. For the preferred methanation process boiling point ranges (pressure-dependent) in the temperature range between 200 and 400 ° C, preferably between 200 and 300 ° C should be achievable in the phase diagram of the heat transfer medium.

The volume flow of the heat transfer medium exiting via the second outlet can preferably be adjusted in the reactor via a flow control, in particular via a control. However, it is alternatively or additionally conceivable to monitor the pressure in the steam drum and initially to control a natural circulation. In this context, the invention provides no special restrictions, it is also conceivable, in particular, for a heat carrier medium to be decoupled via the steam drum. As already explained above, the removal amount via the second output in large spans is adjustable, and controlled by appropriate valve arrangements. This can also lead to a longer residence time of heat transfer medium in the second flow path. Due to the continuous further heat input is ensured at the present pressures, for example, 40 bar or more that the heat transfer medium does not fall back below the boiling point and thus does not condense, or in the case of water vapor does not come in the direction of the wet steam area.

From the point of view of an amount of heat exchanger medium flowing through the heat exchanger plate, according to the invention, it is preferred that a portion of the heat transfer medium introduced into the inlet be decoupled from the heat circuit after a single pass through the heat exchanger, without passing through the steam drum once again. This aspect is also considered by the invention as independently disclosed worthy of protection. The invention thus also relates to a reactor having a heat exchanger plates arranged within the reactor cooling system, with a flowable from at least a portion of the heat transfer medium of the cooling system flow path from a steam drum to a plate inlet in the liquid state, a complete conversion into the gaseous phase causing flow the heat exchanger plate and a Auskoppelweg after exiting the heat exchanger plate from the circulation without re-flow of the steam drum.

In terms of process technology, the invention is achieved by a method for operating a reactor according to one of the above-described aspects, in which a chemical reaction takes place in the reactor, influenced by means of a heat carrier, in particular cools, and the heat carrier flow to different outputs of the heat exchanger plate leaves. In the case of endothermic chemical reactions, the ratio output / input turns around.

Furthermore, it is provided in procedural terms in particular that one passes a heat transfer medium, in particular H ₂ O through the plate-shaped heat exchanger to receive in particular from a catalytic reaction occurring in the reactor reaction heat, wherein in particular the guided over the second flow rate in accordance with predetermined criteria adjusts, in particular a desired heat carrier material decoupling.

Process parameters of the reaction taking place in the reactor are preferably coordinated so that the heat transfer stream of the second flow path experiences a pressure drop of at least 0.5%, preferably at least 0.8%, in particular at least 1%, due to the flow obstacle. At a pressure in the circuit of the order of magnitude between 50 and 80 bar thus a pressure drop of less than 1 bar is sufficient, especially in pre-load operation. In particular, the geometrically induced pressure drop should not exceed 20%, in particular not exceed 10%.

The advantages of the method according to the invention will become apparent from the above-mentioned advantages of the plate-shaped heat exchanger according to the invention and the reactor according to the invention.

Furthermore, from a procedural point of view, the production of a plate-shaped heat exchanger according to one of the aforementioned aspects, in which one defines a boundary of the second flow path via connections of two connected at their edges plates and the first and the second flow path by creating a gap between the plates produced by pressure inflation.

Further features, details and advantages of the invention will become apparent from the following description of the accompanying figures, of which

1 shows in a schematic axial view a heat exchanger plate of an embodiment, and

2 a schematic arrangement of a plurality of heat exchanger plates of another embodiment in a perspective view shows.

In the 1 illustrated heat exchanger plate 10 has an entrance 5 on, by a heat transfer medium, such as water near the boiling point, under high pressure of about 70 bar in the heat exchanger plate 10 can be initiated. The heat exchanger plate 10 is pressure resistant at this pressure level, due to its manufacture. In this case, namely, the two were now the side plates of the heat exchanger plate 10 forming metal plates superimposed and interconnected, for example by welding. The connection consists on the one hand at the edges, leaving the inlet and outlet openings, as well as on the with compression points 18 that in the presentation of 1 are shown as X. Due to the between the crimping points 18 formed passages there is a first flow path 5 → 1 to first outputs 1 the heat exchanger plate 10 so that's in the heat exchanger plate 10 in use, for example, a methanation reactor, the heat exchanger plate 10 flows through, for example, in countercurrent process. Since the heat transfer medium, here H ₂ O, is already close to the boiling point on entry, the heat transfer medium undergoes its passage through the first flow path 5 → 1 an aggregate change in that a portion of the liquid is converted to gas at the first exit 1 Thus, a mixture of water and water vapor emerges, for example in the ratio of about 4/1. As far as described so far, the heat exchanger plate is different 10 not particularly of known heat exchanger plates made by a similar technique.

In the area of in 1 upper third has the heat exchanger plate 10 however, an integrated superheater heating surface 16 in the form of a boundary of a second flow path 3 → 2 on, in the place of a switch 3 from the first flow path 5 → 1 branches off and into a second exit 2 the heat exchanger plate 10 empties. Heat transfer medium, which at the second output 2 exit, thus first goes through a section 5 → 3 of the first flow path 5 → 1 and then the second flow path 3 → 2 ,

The soft 3 and the second flow path 3 → 2 are opposite the last section 3 → 1 of the first flow path 5 → 1 configured such that the heat transfer medium undergoes a pressure drop of, for example, just over 1%, as it flows through, z. B. about 1 bar at a process pressure of 70 bar. This pressure loss occurs primarily by flowing through a grid 26 at the beginning of the second flow path 3 → 2 , The grid is made in a similar way as the crimping points 18 but by more closely spaced welds between the two side walls of the heat exchanger plate 10 , In addition, this results schematically by direction reversal arrows 6 illustrated flow pattern for the heat transfer medium the second flow path, which leads to a further proportion of pressure loss.

Due to the pressure loss, the boiling point of the heat transfer medium (PT diagram) changes, so that there is a rapid conversion of saturated steam into superheated steam, and by the integrated Überhitzerheizfläche 16 a further heating to superheated steam takes place, which at the second exit 2 exit.

Not in 1 shown, but downstream of the second output 2 There is a control valve, with which the flow through the second flow path can be set, and also close. In this way, the the second flow path can be 3 → 2 Set proportions of the heat transfer medium, which can then be coupled out as superheated steam from the cooling circuit and normal uses of superheated steam can be supplied.

The first flow path 5 → 1 completely quenching portion of the heat transfer medium, the exit through the first exit 1 in a ratio of water / water vapor of about 4/1 is supplied to a steam drum, from which a material extraction no longer has to be done, since this already on the second output 2 is feasible. Material compensation is carried out as usual by supplying boiler feed water, and the steam drum, not shown, in the usual manner with the input 1 connected for the heat transfer medium.

In the 2 illustrated embodiment differs from the in 1 illustrated embodiment in that the second flow path 4 → 2 ' in the course of which the heat transfer medium is converted into superheated gas during use, not from the first flow path 5 ' → 1' but branches off via a separate entrance 4 in the heat exchanger plate 10 ' is initiated. In this case, the first and second flow paths intersect with each other, and that of the entrance 4 supplied heat transfer medium is introduced as saturated steam at the boundary to superheated steam. Again, in this case forms the boundary of the second flow path 4 → 2 ' one in the heat exchanger plate 10 ' integrated superheater heating surface. With the reference number 7 is in 2 nor the addition of the reaction gases drawn, in the preferred embodiment, an educt gas with hydrogen and carbon dioxide components formed for the catalytic methanation in the correct stoichiometric ratio. In between the heat exchanger plates 10 ' formed interstices is a catalyst bed for catalyzing the methanation.

The invention is not limited to the features illustrated in the description with reference to the figures. Rather, features of the following claims as well as the above description, individually and in combination, may be essential to the practice of the invention in its various embodiments.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2011/076315 A2 [0004]
• DE 102014015055 [0004]
• EP 0995491 B1 [0020]

Claims (17)

Plate-shaped heat exchanger ( 10 ; 10 ' ) for use within a at a first pressure level pressure-resistant pressure vessel of a reactor, in particular Methanisierungsreaktors in which a reactant gas having at least two gas constituents reacts chemically in the presence of a catalyst to a component of both gas constituents product gas, with a pressure at a second level of preferably an overpressure , more preferably of 2 bar or higher, in particular 40 bar or higher pressure-resistant outer shell, over which a thermal coupling between a flowing inside the outer shell heat transfer medium and the chemical reaction is provided, and within the outer shell of an input ( 5 ; 5 ' ) to a first exit ( 1 ; 1' ) extending first flow path, in the flow through at least a portion of the heat transfer medium changes its state of aggregation due to a taking place via the thermal coupling first heat exchange, characterized by a running within the outer shell, closer to the first output ( 1 ; 1' ) as at the entrance ( 5 ; 5 ' ) and into one from the first exit ( 1 ; 1' ) deviating second output ( 2 ; 2 ' ) opening second flow path, in the flow through the heat transfer medium due to a taking place via the thermal coupling, compared to the first heat exchange lower second heat exchange changes its temperature. Heat exchanger according to claim 1, wherein the second flow path branches off from the first flow path. Heat exchanger according to Claim 2, in which the branch ( 3 ) and / or the second flow path forms a pressure drop causing flow obstruction. Heat exchanger according to one of the preceding claims, wherein the ratio of the flow cross-section of the second flow path to that of the first flow path near the first exit is less than 2/3, preferably less than 3/7, in particular less than 1/4, and in particular greater than 1/19, preferably greater than 1/9, in particular greater than 1/7. Heat exchanger according to one of claims 2 to 4, wherein the ratio of the flow path length of the second flow path to the flow path located between the input and the branch is less than 2/3, preferably less than 3/7, in particular less than 1/4, and in particular greater than 1/19, preferably greater than 1/14, in particular greater than 1/9. Heat exchanger according to one of claims 2 to 5, wherein the second flow path is longer than a lying between the branch and the first output portion of the first flow path. Heat exchanger according to one of the preceding claims, in which the space formed inside the outer shell is formed by pressure inflation of two at its edges and in particular at further points ( 18 ) connected plates is formed. Heat exchanger according to one of the preceding claims, in which the flow obstacle is interrupted by a grid ( 26 ) is formed, which is defined in particular by spot welds of the two plates before their Druckaufblasen. Heat exchanger arrangement with at least one, in particular a plurality of plate-shaped heat exchangers according to one of the preceding claims. Reactor with heat exchanger arrangement according to claim 9. Reactor according to claim 10, comprising a cooling system connected to the at least one inlet and the at least two outlets, which in particular comprises a steam drum. Reactor according to claim 11, wherein the cooling system decouples heat transfer material, in particular in the form of superheated steam via the second outlet. Reactor according to claim 11 or 12, wherein downstream of the second outlet a flow control, in particular in the form of a control valve is provided. A method of operating a reactor according to any one of claims 11 to 13, wherein the reactor is allowed to run a chemical reaction, it cools by means of a heat carrier and flow the heat carrier to different outputs of a heat exchanger plate. Process according to Claim 14, in which a heat carrier, in particular H ₂ O, is passed through the plate-shaped heat exchangers in order, in particular, to absorb reaction heat arising from catalytic methanation taking place in the reactor, in particular adjusting the volume flow conducted via the second flow path as a function of predetermined criteria , in particular a desired heat carrier material decoupling. A method according to claim 14 or 15, wherein the process parameters of the reaction taking place in the reactor are coordinated so that the heat transfer flow of the second flow path experiences a pressure drop of at least 0.5%, preferably at least 0.8%, in particular at least 1%, due to the flow obstacle , Fabrication of a plate-type heat exchanger according to any one of claims 1 to 8, wherein defining a boundary of the second flow path via connections of two plates connected at their edges, and the first and in particular also the second flow path created by creating a gap between the plates by means of pressure inflation.

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