Process for producing gas phase methylamine with improved reactor inlet temperature control

Abstract

The invention relates to a method for producing methylamine by a generally exothermic gas-phase reaction of methanol and ammonia as reactants in the presence of a heterogeneous catalyst at a pressure in the range of 15 to 35 bar. The reactants are evaporated in one or more heat exchangers and superheated prior to being fed to the reactor, wherein the heat exchangers in turn are heated with a stream of hotter product gas from the reactor. In addition to methylamine (monomethylamine, dimethylamine, and trimethylamine), the product gas stream contains unconverted reactants, water, and any other reaction by-products. To control the reactor inlet temperature and limit it to a temperature in the range of 350 DEG C to 410 DEG C, a suitable quenching liquid is introduced into the hot product gas stream prior to feeding the hot product gas stream to a heat exchanger for heating the reactants. Evaporation and overheating of the added quenching liquid removes the corresponding amount of energy extracted from the hot product gas stream, with the result of efficient and rapid cooling of the hot product gas stream. As a result, the temperature difference between the cold side and the hot side of the heat exchanger is small, which means less energy is transferred to the reactant stream, and thus its reactor inlet temperature can be adjusted or limited.

Description

[0001] This invention relates to a method for producing methylamine from methanol and ammonia in a continuous gas-phase reaction over a heterogeneous catalyst at an absolute pressure in the range of 15 to 35 bar. For this purpose, a reaction stream containing methanol and ammonia reactants is evaporated and heated to a reactor inlet temperature in the range of 350°C to 410°C via a heat exchanger. Since the reaction of methanol and ammonia to produce methylamine is exothermic, a hot product gas stream from the reactor, containing not only methylamine (monomethylamine, dimethylamine, and trimethylamine) but also water, unconverted ammonia, and unconverted methanol, is passed through one or more heat exchangers to heat the reactants. The method of this invention is characterized by conditioning the reactor inlet temperature by introducing a quench liquid into the hot product gas stream before it passes through the heat exchangers. The quench liquid has a boiling point in the range of -40°C to 120°C at standard pressure and evaporates when introduced into the product gas stream, resulting in the product gas stream being effectively and in a controlled manner cooled to the temperature required for the desired heating of the reaction stream. In a particular embodiment of the invention, the condensate of the product gas stream is used as a quenching liquid for cooling the product gas stream. The invention further relates to a corresponding apparatus for continuously carrying out a generally exothermic reaction, wherein the reactants must reach a specific reactor inlet temperature, the apparatus comprising (a) one or more reactors into which reactants are fed and from which product gas streams are extracted, (b) one or more heat exchangers upstream of the one or more reactors, which are used to bring the reactants to the desired reactor inlet temperature and through which the product gas stream is passed to introduce heat, and (c) a measuring instrument for measuring the reactor inlet temperature of the reactants. The apparatus of the invention is characterized by the controlled introduction of an evaporable liquid into the product gas stream before it passes through the one or more heat exchangers, in which the temperature of the product gas stream is cooled by the evaporation of the liquid, and thus the desired reactor inlet temperature of the reactants can be established.

[0002] Methylamine includes monomethylamine, dimethylamine, and trimethylamine, as well as mixtures thereof.

[0003] Methylamine can be produced from methanol and ammonia in a continuous gas-phase reaction in the presence of a catalyst. Although the reaction is generally exothermic, the reactants must be preheated for use in the reaction. The feed reactants are typically preheated in a heat exchanger upstream of the reactor. Preheating, as described in JP 60045550 A, can be accomplished using the product gas stream obtained in the reaction. For this purpose, the product gas stream is directed through a heat exchanger used for preheating. Because the reaction is generally exothermic, the temperature in the reactor increases between the reactor inlet and the reactor outlet. Due to the higher temperature at the reactor outlet, no additional energy is required to preheat the reactants when the product gas stream is used to heat the reactants in steady-state operation.

[0004] The required temperature in the reactor is fixed by technical constraints. The reactor inlet temperature must be high enough to initiate the conversion on the catalyst immediately, to convert most of the methanol, and to bring the reaction close to thermal equilibrium. On the other hand, the temperature in the catalyst bed must not be too high, otherwise it will increase the decomposition of methylamine into gaseous and solid degradation products, or it will exceed the reactor's maximum permissible temperature. Therefore, precise control of the reactor inlet temperature is crucial for the efficient production of methylamine.

[0005] The reaction of methanol and ammonia to produce methylamine typically results in more trimethylamine than desired. The excess trimethylamine is typically recycled within the unit, added to the reactor feed, and converted to dimethylamine and monomethylamine in the reactor via an endothermic reaction. Therefore, recycling trimethylamine into the reactor results in a process with less overall exothermic activity. The same applies to the recycling of other methylamines.

[0006] In current methods for preheating reactants, fluctuations in ambient temperature, varying amounts of recycled trimethylamine, and changes in load can cause fluctuations in reactor inlet temperature. As a result, these fluctuations lead to fluctuations in reactor temperature. In the worst case, the reactor temperature becomes so high that methylamine decomposes, or exceeds the maximum permissible reactor temperature.

[0007] The theoretical possibility of limiting the reactor inlet temperature of the reactant stream by diverting the preheated product gas stream around the heat exchanger when the upper temperature limit is reached is impractical for engineering reasons. Rapidly and in a controlled manner transferring large volumes of hot and pressurized product gas streams would require extremely complex and expensive control valves.

[0008] WO 2005 / 028416 A describes a method in which the evaporation or condensation temperature is regulated using controlled pressure adjustment of the reactant stream to be heated or the reactor output to be cooled, such that exactly the same amount of energy is transferred in the heat exchanger as is required to reach the desired reactor inlet temperature. The disadvantages of this method are that it is difficult to control, has slow closed-loop control characteristics, and introduces additional pressure drops.

[0009] Furthermore, according to the method of WO 2005 / 028416 A, when heat recovery is improved by preheating the reactive stream with other suitable energy sources available within this method, additional closed-loop control intervention is required, thus further increasing the pressure drop. Under partial load operation of the system, specific heat transfer may increase. To compensate for this increase in specific heat transfer, the process requires closed-loop control intervention, which also causes additional pressure drop.

[0010] Therefore, the object of the present invention is to provide a method for producing methylamine from methanol and ammonia via a gas-phase reaction, wherein the reactor inlet temperature is rapidly, efficiently, and in a controlled manner within a narrow range and without pressure drop. In steady-state operation, energy loss from the process through heat removal should be minimized, and a minimum amount of energy should have to be supplied externally for preheating and superheating the reactants.

[0011] Therefore, the present invention relates to a method for producing methylamine by a continuous gas-phase reaction, wherein a reaction stream comprising reactants methanol and ammonia is evaporated and heated to a reactor inlet temperature in the range of 350°C to 410°C in one or more heat exchangers and optionally additional heating elements, and then fed into one or more reactors, wherein it is converted into methylamine (monomethylamine, dimethylamine, and trimethylamine) at an absolute pressure in the range of 15 to 35 bar in the presence of a heterogeneous catalyst, the methylamine being extracted from the reactor as a product gas stream along with water and any unconverted reactants and any byproducts, wherein the reactor inlet temperature of the reaction stream is regulated by operating at least one of the heat exchangers, wherein the product gas stream is pre-cooled to the temperature required for this purpose by introducing a quenching liquid having a boiling point in the range of -40°C to 120°C at standard pressure into the product gas stream.

[0012] Therefore, the method of the present invention for producing methylamine is based on the concept of reducing the temperature of the product gas stream from the reactor to such an extent that the reaction stream is heated only to the desired reactor inlet temperature before entering the heat exchanger, wherein the required cooling of the product gas stream is achieved by the introduction and evaporation of a suitable quenching liquid that has been completely evaporated. Liquids suitable for this purpose are those that completely evaporate under the conditions of the product gas stream (i.e., at a temperature of at least 350°C and an absolute pressure of 15 to 35 bar). This is the case for liquids having a boiling point in the range of -40°C to 120°C at standard pressure. This reduces the temperature of the product gas stream through the evaporation of the quenching liquid without energy removal and loss.

[0013] To produce methylamine from methanol and ammonia, the reactants are first evaporated and superheated in one or more heat exchangers. The reactants, which have thus been heated to a temperature in the range of 350°C to 410°C, preferably in the range of 350°C to 390°C, and more preferably in the range of 360°C to 380°C, are then supplied to the reactor at this temperature (reactor inlet temperature).

[0014] In addition to methanol and ammonia, methylamine is typically supplied to the reactor, and the degree to which methylamine is formed in the reaction exceeds the current demand. In particular, it may be necessary to recycle trimethylamine, which is typically formed in the reaction, back into the reaction to a greater extent than required, and thus increase the proportion of monomethylamine and dimethylamine in the methylamine used throughout the process. This recycling of trimethylamine and the associated endothermic transmethylation reduce the overall exothermic nature of the reaction in the reactor.

[0015] Since the reaction is generally exothermic, the temperature rises from the reactor inlet to the reactor outlet. To ensure that the temperature in the reactor does not rise above 450°C, the reactor inlet temperature setting of the reaction stream must be monitored. In this case, when the reaction is carried out with low methylamine recirculation, i.e., highly exothermic (preferably a reactor inlet temperature of 350°C to 370°C), a relatively low reactor inlet temperature must be set; or when the reaction is carried out with high methylamine recirculation, i.e., low exothermic (preferably a reactor inlet temperature of 370°C to 410°C), a relatively high reactor inlet temperature must be set. If necessary, excess heat of the reaction can be removed by cooling the reactor. The reaction in the reactor is preferably carried out in such a manner that the product gas stream exits the reactor at a temperature in the range of 390°C to 450°C.

[0016] In the presence of a heterogeneous catalyst, the reactants are converted into monomethylamine, dimethylamine, and trimethylamine in a reactor at an absolute pressure ranging from 15 to 35 bar. This pressure range typically applies not only to the reactor but also to the entire feed stream through a heat exchanger and the discharge of the product gas stream via a heat exchanger including any liquid separator. Therefore, an absolute pressure in the range of 15 to 35 bar is preferably also present at the location where the quench liquid is introduced into the product gas stream.

[0017] The product gas stream is extracted from the reactor and, in addition to methylamine, monomethylamine, dimethylamine, and trimethylamine, also contains water, which is produced as a byproduct during the reaction. The product gas stream typically also contains unconverted methanol, unconverted ammonia, and other byproducts such as carbon monoxide and carbon dioxide.

[0018] The reaction can be carried out in one or more reactors. The reaction is preferably carried out in one reactor. If two or more reactors are used, they can be connected in parallel or in series, or in combination thereof.

[0019] Heterogeneous catalysts are typically alumina doped with silica, such as the N7066 catalyst from BASF. Heterogeneous catalysts are typically used in fixed-bed configurations.

[0020] The product gas stream can then be separated into individual reaction products. Separation is typically carried out by distillation in two or more distillation columns. Methylamine formation usually produces more trimethylamine than desired. The excess trimethylamine can then be fed back into the reaction stream. The reaction of trimethylamine with ammonia to produce monomethylamine and dimethylamine, or with monomethylamine to produce dimethylamine, is endothermic. When other methylamines are recycled, the corresponding endothermic reactions occur. For endothermic reactions, a portion of the heat of reaction released in the exothermic reaction of ammonia and methanol to produce methylamine is consumed. For this reason, the reactor can also be operated adiabatically.

[0021] When heat is released to heat the reaction stream, the product gas stream in the heat exchanger is cooled and at least partially condensed. The condensate can preferably be separated from the gaseous components of the cooled product stream by a liquid separator. This can be a separate liquid separator downstream of the heat exchanger, or preferably a liquid separator integrated into the heat exchanger. By means of such a liquid separator (condensate separator) integrated into a separate heat exchanger or directly downstream therefrom, the erosion of entrained condensate droplets can be avoided. The liquid product stream obtained in the condensate separator is preferably supplied, like the product gas stream leaving the heat exchanger, to further processing for the separation and, optionally, of methylamine.

[0022] The heat required to start the reaction can be supplied by additional heating of the reactants using an externally heated heat exchanger or electric heating element. If the product gas stream cannot adequately heat the reactant stream during steady-state operation, the missing heat can also be supplied by an externally heated heat exchanger or electric heating element.

[0023] The heat exchanger used for preheating the reactant stream can be any type of heat exchanger known to those skilled in the art. Suitable heat exchangers include, for example, shell-and-tube heat exchangers, spiral heat exchangers, or plate heat exchangers. Shell-and-tube heat exchangers are preferred. A modified floating head heat exchanger is particularly preferred for this purpose. The heat exchanger used can operate in co-current, counter-current, or cross-current modes. Furthermore, any combination of cross-current, counter-current, and co-current modes known to those skilled in the art is possible. For example, when using several heat exchangers, at least one heat exchanger can operate in co-current mode while the remaining heat exchangers operate in counter-current mode. The preferred operating mode for the heat exchanger used to heat the reactants is counter-current. The heat exchanger preferably has an integrated condensate separator for removing condensates formed when the product gas stream in the heat exchanger is cooled.

[0024] To control the reactor inlet temperature, measurements are typically recorded at various points within an apparatus used for methylamine production. For example, the flow rates of both the ammonia-containing reactant stream and the methanol stream can be measured before methanol is mixed into the ammonia-containing reactant stream. Furthermore, the flow rates of the individual methanol sub-streams can be measured as methanol is mixed into the ammonia-containing reactant stream at different locations. When the product gas stream is split into multiple sub-streams, the flow rate in each sub-stream can be measured. Flow rate measurements can also be used to measure the amount of any additional steam required to heat the reactants.

[0025] For specific closed-loop control of the reactor inlet temperature, it is necessary to measure the reactor inlet temperature of the reaction stream. In addition to the reactor inlet temperature, the temperatures of the ammonia-containing reaction stream, methanol, the internal temperature of the reactor, and the temperature of the product gas stream at the reactor outlet can also be measured.

[0026] The method of the present invention preferably includes an automatic closed-loop control system that controls the introduction of quench liquid into the product gas stream via a control valve based on the measured reactor inlet temperature. Furthermore, other measurements, such as the flow rates of various process flows, the reactor outlet temperature, and the temperature of the product stream after the introduction of quench liquid, may be included in the closed-loop control system to optimize the control of the reactor inlet temperature.

[0027] For energy-efficient methods in the production of methylamine, it is desirable to heat the reactant stream to the reactor inlet temperature during steady-state operation at both partial and full loads, without operating externally heated heat exchangers or electric heating elements (i.e., solely by means of heat exchangers heated by the hot process stream, particularly the product gas stream). For example, in principle, it is possible to... Figure 1 In the first heat exchanger (3) of the method, the liquid mixture of ammonia and any recycled methylamine is heated and partially evaporated by an external flow, but preferably by means of a hot process flow to be cooled (e.g., a hot wastewater flow from the process).

[0028] Due to ambient temperature fluctuations caused by varying amounts of recycled methylamine or other fluctuations in the operating protocol (especially under partial load), as well as energy fluctuations in the supply to the preheater (heat exchangers and electric heating elements used for heating, evaporating, and superheating the reaction stream), the corresponding energy-saving design of this method can lead to undesirable high reactor inlet temperatures. Therefore, efficient and rapid control of the reactor inlet temperature is essential for the energy-saving configuration of the method.

[0029] In the method for producing methylamine according to the present invention, the temperature of the product gas stream is cooled to such an extent by the introduction and evaporation of a suitable liquid (quench liquid) that the temperature of the reactants leaving one or more heat exchangers heated by the product gas stream does not exceed the value required for the intended operation of the reactor. A suitable quench liquid is a fluid having a boiling point in the range of -40°C to 120°C under standard pressure, preferably in the range of -35°C to 105°C under standard pressure. Such a quench liquid can be a pure substance or a mixture of two or more substances.

[0030] Preferred quench liquids are substances already present in the method, including ammonia, methanol, water, monomethylamine, dimethylamine, and trimethylamine, and mixtures thereof. Particularly preferred quench liquids are substances or mixtures thereof that do not cause any significant additional cost or inconvenience in subsequent separations at the reactor output, such as water, condensates generated during cooling of the product stream, or bottom slurries from the distillation column in such subsequent separations. Very particularly preferred quench liquids are condensates generated during the heating of the reactant stream and the associated cooling of the product gas stream.

[0031] The quench liquid is preferably injected into the product gas stream via a pump and control valve, supplied via a control valve and a powered jet nozzle, or introduced via a control valve through a static water supply. Injection via a pump and control valve is particularly preferred. In the case of injection via a pump and control valve, the pump establishes the positive pressure necessary for injection, and the control valve controls the inlet of the product gas stream. In the case of static water supply, the system components are arranged such that the quench liquid is fed into the product gas stream via static water pressure. The control valve then controls the inlet of the product gas stream. When the quench liquid is introduced via a powered jet nozzle, the liquid is drawn into the product gas stream itself and atomized in the nozzle. The inlet of the product gas stream is here controlled by the control valve. This variant is feasible when the product gas stream has a sufficiently high pressure.

[0032] The purpose of introducing the quench liquid is rapid evaporation. For this purpose, the quench liquid is preferably introduced into the product gas stream at a temperature just below its boiling point at the introduction point, more preferably at a temperature no more than 20°C below that boiling point, and most preferably at a temperature no more than 10°C below that boiling point. Furthermore, for rapid evaporation, the quench liquid is preferably atomized in a nozzle into small droplets with a particularly high surface area. The nozzle used can be of a type known to those skilled in the art for this purpose, such as a flat jet nozzle, a hollow cone nozzle, a full cone nozzle, a spiral nozzle, a mist nozzle, or a powered jet nozzle. The nozzle can be combined with a static mixer. Alternatively, the quench liquid can be distributed over a large surface area, such as random or structured packing used in distillation techniques. The flow through the random packing can be co-current, cross-current, or counter-current with the flow direction of the quench liquid. In a preferred embodiment of the method, the quench liquid is introduced by injection via a pump and a control valve, and the introduced quench liquid is distributed in the product gas stream via a liquid distributor above the random or structured packing, or preferably by means of a nozzle. In a preferred embodiment of the method, the quench liquid is introduced via a static water supply, and the quench liquid to be introduced is distributed in the product gas stream via a liquid distributor above the random or structured packing.

[0033] Cooling the product gas stream requires only a small amount of quenching liquid.

[0034] The present invention also provides a corresponding apparatus for continuously converting reactants into a product gas stream in a generally exothermic reaction, the apparatus comprising:

[0035] a) One or more reactors, into which the reactants are fed and from which the product gas stream is extracted.

[0036] b) One or more heat exchangers upstream of these reactors, used to bring the reactants to the desired reactor inlet temperature and to allow the product gas stream to pass through the heat exchangers to introduce heat.

[0037] c) One or more measuring instruments for measuring the reactor inlet temperature of these reactants.

[0038] The apparatus includes the controlled introduction of an evaporable liquid into the product gas stream before it passes through one or more of these heat exchangers. This introduction allows the temperature of the product gas stream to be cooled by the evaporation of the liquid, limiting heat exchange within the heat exchangers and thus establishing a desired reactor inlet temperature for the reactants.

[0039] In a preferred embodiment, the apparatus of the present invention includes one or more liquid separators and a feeding device, wherein the one or more liquid separators separate condensate from the product gas stream after or during passage through a heat exchanger, and the feeding device supplies the condensate to a controlled introduction, wherein the condensate is introduced into the product gas stream as an evaporable liquid (quench liquid).

[0040] Therefore, the present invention provides an apparatus for continuously converting reactants into a product gas stream in an overall exothermic reaction, the apparatus comprising:

[0041] a) One or more reactors, into which the reactants are fed and from which the product gas stream is extracted.

[0042] b) One or more heat exchangers upstream of these reactors, used to bring the reactants to the desired reactor inlet temperature and to allow the product gas stream to pass through the heat exchangers to introduce heat.

[0043] c) One or more measuring instruments for measuring the reactor inlet temperature of these reactants, and

[0044] d) One or more liquid separators for separating the condensate from the product gas stream after or during passage through these heat exchangers.

[0045] The apparatus includes the controlled introduction of a portion of the condensate into the product gas stream before it passes through one or more of these heat exchangers. This introduction allows the temperature of the product gas stream to be cooled by the evaporation of the condensate, limiting heat exchange within the heat exchangers and thus establishing the desired reactor inlet temperature for the reactants.

[0046] In a preferred embodiment of the apparatus of the present invention, the controlled introduction of evaporable liquids or condensates into the product gas stream comprises (a) a pump with a control valve, (b) a control valve with a powered jet nozzle, or (c) static water feed via a control valve. To ensure rapid evaporation of the evaporable liquids or condensates and thus rapid cooling of the product gas stream, the apparatus of the present invention may include nozzles for introducing the evaporable liquids or condensates into the product gas stream. By means of nozzles, the evaporable liquids or condensates can be introduced into the product gas stream in the form of small droplets that evaporate rapidly due to their relatively large surface area. Nozzles are particularly suitable for introducing condensates via pumps and control valves. Furthermore, nozzles are an inherent element of the introduction via control valves and powered jet nozzles. Alternatively, the apparatus of the present invention may also include random or structured packing at the point where the evaporable liquids or condensates are introduced into the product gas stream, the introduced evaporable liquids or condensates being distributed on the random or structured packing via a liquid distributor. The distribution of the evaporable liquids or condensates over the large surface area of ​​such a bed or packing also enables rapid evaporation. This type of bed or packing is particularly suitable for introducing evaporable liquids or condensates via a control valve using static water feed, and is also suitable for introducing evaporable liquids or condensates via a pump and control valve. Therefore, in this preferred embodiment,

[0047] ● When an evaporable liquid or condensate is introduced via a pump with a control valve, the evaporable liquid or condensate is distributed in the product gas stream via a liquid distributor and random or structured packing, or preferably via nozzles.

[0048] ●When an evaporable liquid or condensate is introduced via a control valve through a static water feed, the evaporable liquid or condensate is distributed in the product gas stream via a liquid distributor and random or regular packing.

[0049] In a particular embodiment of the apparatus of the invention, the condensate passes through one or more purification units before being recycled to the product gas stream. These purification units are preferably distillation columns, in which methylamine is drawn off from the top and then the bottom product from there is returned to the product gas stream as condensate. Alternatively or additionally, the condensate may also be introduced into the product gas stream formed in such purification units by a product gas stream supplied in gaseous form, i.e., for example, liquid bottom product from a distillation column, feeding the gaseous product gas stream into the distillation column and drawing methylamine off from the distillation column from the top.

[0050] This invention is illustrated by the following figures:

[0051] Appendix Figures 1 to 3 A flowchart of a specific embodiment of the method of the present invention for producing methylamine from methanol and ammonia is shown.

[0052] Figure 1 :

[0053] exist Figure 1In the method for producing methylamine shown, a first reaction stream (“ammonia and amine feed”) forms the feed to a first preheater (3). In addition to ammonia, the feed may also contain recycled byproducts from the method and excess methylamine. The reaction stream is heated in the first preheater (3). The heat supplied is provided by a hot process stream (1) to be cooled. To limit the heat transfer if necessary, the hot process stream can be bypassed, wholly or partially, by a management control valve (2). The preheated first feed is then mixed with a methanol feed (“methanol feed”) and fed to a second preheater (4). This stream is also referred to hereinafter as the reaction stream. The second preheater (4) is heated with a product gas stream (“stream 4”). The reaction stream feed, thus further heated, is passed through a third preheater (5) heated with steam (“steam”). This is primarily used to heat the reaction stream during start-up operation. The third preheater is also used when the heat transferred in the two upstream preheaters (3 and 4) is insufficient. In the fourth preheater (6), the reactant stream is superheated to the reactor inlet temperature. This preheater (6) is heated by the product gas stream from the reactor (“Stream 4”). The reactant stream heated to the reactor inlet temperature eventually flows through the last electrically operated preheater (7) and is then fed into the reactor (8) (“Stream 1”). This last preheater (7) is primarily used to heat the reactant stream during start-up operation. It is also used when the reactant stream in the other preheaters does not reach the necessary reactor inlet temperature. Thus, while the first preheaters (3, 4, 5, and 6) are heat exchangers heated by external streams (5 and 3 if necessary) or internal streams (4, 6 and 3 if necessary), the last preheater (7) is heated by electric heating elements. What occurs in the reactor (8) is not only the exothermic conversion of methanol and ammonia to monomethylamine, dimethylamine, and trimethylamine, but also the endothermic conversion of unwanted recycled trimethylamine to dimethylamine and monomethylamine in an endothermic reaction. However, the reaction in reactor (8) is exothermic overall. For this reason, the temperature of the entire reactor (8) is elevated. The temperature of the reactor output (“flow 2”) is higher than the required temperature in the reactor feed (“flow 1”). Therefore, the product gas stream from the reactor output in the preheaters (6 and 4) can be used to heat the reactor feed. For this purpose, the product gas stream (“flow 4”) is directed countercurrently through the fourth preheater (6) and the second preheater (4). Downstream of the second preheater (4), the cooled and now two-phase product stream is separated into liquid and gas phases in a liquid separator (10). The gas stream leaving the liquid separator (10) is sent to post-processing.A portion of the condensate from the liquid separator (10) (“Stream 3”) is injected into the reactor output (“Stream 2”) at point (9.1) upstream of the fourth preheater (6) via a pump (11) and a control valve (12). The injected liquid evaporates and removes the required heat of evaporation from the reactor output, thereby lowering the temperature of the product gas stream (“Stream 4”) leading to the fourth preheater (6). Due to the resulting temperature reduction, a smaller amount of heat is transferred in the fourth preheater (6) to the reactor feed to be heated. Along with temperature measurements in the feed to the reactor (8), closed-loop temperature control can thus be set up. This ensures rapid, immediate control of the reactor inlet temperature. The condensate from the liquid separator (10), which does not require temperature control, is also sent to the methylamine post-treatment.

[0054] In addition to the implementation variant described herein with a total of five preheaters (3, 4, 5, 6 and 7), a variety of variations are possible in the number, arrangement and interconnection of heat exchangers used for preheating the reactive stream.

[0055] Instead of counter-current operation of the preheater as shown here, parallel or cross-flow operation is also possible, as is any combination of counter-current, parallel or cross-flow.

[0056] Figure 2 :

[0057] Figure 2 The method shown is as follows Figure 1 The variation shown is for the production of methylamine, in which liquid from a liquid separator (10) is drawn in and atomized via a powered jet nozzle (9.2). The powered medium used here is the product gas stream (“stream 2”) itself. This variation can be employed when the product gas stream has a sufficiently high pressure.

[0058] Figure 3 : Figure 3 The method shown is as follows Figure 1 The variant shown is for the production of methylamine, in which the preheater is arranged in such a way that liquid from the liquid separator (10) can be statically introduced into the product gas stream (“stream 2”). To generate maximum liquid surface area, the liquid is distributed by a liquid distributor onto random or structured packing (9.3), as is known from distillation techniques.

[0059] Example:

[0060] The following examples illustrate the effect of introducing a quenched liquid into the product gas stream of a method for producing methylamine, such as... Figures 1 to 3As described in detail in the document. The reactor output (product gas stream) typically has the composition shown in Table 1. This composition can vary depending on the design and operating mode of the method.

[0061] Table 1:

[0062] Typical composition of the product gas stream of the method of the present invention for producing methylamine

[0063]

[0064] A typical reactor inlet temperature is, for example, 360°C. With an adiabatic increase in temperature within the reactor of approximately 50°C to 80°C, as is customary with this method, the result is a typical reactor outlet temperature of 410°C to 440°C. Therefore, a decrease in reactor outlet (product gas stream) temperature, for example, by 10°C, already leads to a significant reduction in the temperature difference between the feed and output streams, and consequently, a similarly significant reduction in the energy transferred in the preheater zone. According to the invention, this temperature reduction is achieved by introducing a suitable quench liquid into the product gas stream. Based on the process conditions (reactor outlet: 20.8 bar, 427.2°C, quench liquid temperature: see Table 2) and the thermodynamic data of the product gas stream and the introduced quench liquid, the amount of quench liquid required to cool a specific quantity of product gas stream can be determined. These results are summarized in Table 2 for various possible quench liquids.

[0065] Table 2:

[0066] Determine the amount of liquid to be introduced into the reactor output from various possible quenching liquids required to reduce the temperature of the reactor output by 10°C.

[0067]

[0068] Condensate here refers to the condensate obtained when the reactor output in the heat exchanger of the preheater section is cooled by heat transfer to the reactor feed. In other words... Figures 1 to 3 In the method described, the condensate is used to lower the temperature of the product gas stream. However, in principle, other quenching liquids listed in Table 2 can also be used to lower the temperature.

[0069] For according to Figure 1 For example, Table 3 summarizes the data (composition, pressure, temperature, and state of matter) used to cool the reactor output from 427.2°C to 370°C with condensate for the selected operating conditions of the method.

[0070] Table 3:

[0071] Used for such Figure 1The composition and physical parameters of the streams (streams 1 to 4) for the production of methylamine are shown, wherein the product gas streams are cooled to a certain extent by introducing condensate to ensure the reactor inlet temperature required for the reaction stream.

[0072]

[0073] As shown in this example, the temperature reduction reduces the temperature difference between the process stream leaving the last heat exchanger and the process stream entering the heat exchanger from 67.2°C to 10°C.

[0074] The 85.92 kg of condensate required to cool 57.2°C per ton of reactor output corresponds to approximately 15 kg of condensate per ton of reactor output cooled by 10°C.

Claims

1. A method for producing methylamine via a continuous gas-phase reaction, wherein a reaction stream comprising reactants methanol and ammonia is evaporated and heated to a reactor inlet temperature in the range of 350°C to 410°C in one or more heat exchangers and optionally additional heating elements, and then fed into one or more reactors, wherein it is converted to methylamine, monomethylamine, dimethylamine and trimethylamine at an absolute pressure in the range of 15 to 35 bar in the presence of a heterogeneous catalyst, wherein methylamine is extracted from the reactor as a product gas stream along with water and any unconverted reactants and any byproducts, wherein the reactor inlet temperature of the reaction stream is regulated by operating at least one of the heat exchangers, wherein the product gas stream is pre-cooled to the temperature required for the purpose by introducing a quenching liquid having a boiling point in the range of -40°C to 120°C at standard pressure into the product gas stream.

2. The method according to claim 1, wherein, The inlet temperature of the reactor was continuously measured.

3. The method according to claim 1 or 2, wherein, The reaction in the reactor is carried out in such a way that the product gas stream exits the reactor at a temperature in the range of 390°C to 450°C.

4. The method according to any one of claims 1 to 3, wherein, The evaporation and temperature regulation of the reactants are achieved through two or more heat exchangers, and the quenched liquid is introduced into the product gas stream upstream of the first heat exchanger of the product gas stream.

5. The method according to any one of claims 1 to 4, wherein, The quenching liquid contains one or more components selected from the group consisting of: monomethylamine, dimethylamine, trimethylamine, ammonia, methanol, and water.

6. The method according to any one of claims 1 to 5, wherein, The product gas stream is completely or partially condensed, and the resulting methylamine is then purified via one or more distillation columns, and optionally separated into fractions of individual methylamines or methylamine compositions.

7. The method according to claim 6, wherein, The fraction containing trimethylamine or rich in trimethylamine is recycled back to the reactor for the reaction.

8. The method according to any one of claims 1 to 7, wherein, The quenching liquid used is the liquid flow that occurs within this method.

9. The method according to any one of claims 1 or 7, wherein, The product gas stream is cooled and completely or partially condensed, and the quenching liquid used is the resulting condensate.

10. The method according to claim 6 or 7, wherein, The quench liquid used is a bottom slurry from one or more of these distillation columns.

11. The method according to any one of claims 1 to 10, wherein, The quenching liquid is introduced into the product gas stream in the following manner. a) Injected via pump and control valve b) Supplied via control valve and power nozzle, or c) Static water supply is provided via a control valve.

12. The method according to claim 11, wherein, The injected quenching liquid is distributed in the product gas stream via a liquid distributor above the random or structured packing or preferably by means of a nozzle, or the quenching liquid supplied by static water is distributed in the product gas stream via a liquid distributor above the random or structured packing.

13. An apparatus for continuously converting reactants into a product gas stream in a generally exothermic reaction, the apparatus comprising: a) One or more reactors, into which the reactants are fed and from which the product gas stream is extracted. b) One or more heat exchangers upstream of these reactors, used to bring the reactants to the desired reactor inlet temperature and to allow the product gas stream to pass through the heat exchangers to introduce heat. c) One or more measuring instruments for measuring the reactor inlet temperature of these reactants. in, The apparatus includes the controlled introduction of an evaporable liquid into the product gas stream before it passes through one or more of these heat exchangers. In this way, the temperature of the product gas stream can be cooled by the evaporation of the liquid, heat exchange in the heat exchangers can be limited, and thus the desired reactor inlet temperature of the reactants can be established.

14. The apparatus according to claim 13, wherein, The apparatus of the present invention includes one or more liquid separators and a feeding device, wherein the one or more liquid separators separate condensate from the product gas stream after or during passage through these heat exchangers, and the feeding device supplies the condensate to a controlled introduction, wherein the condensate is introduced into the product gas stream as an evaporable liquid.

15. The apparatus according to claim 13 or 14, wherein, The apparatus for introducing the evaporable liquid into the product gas stream includes a) Pumps with control valves b) A control valve with a powered injection nozzle, or c) Still water feed via a control valve.

16. The apparatus according to claim 15, wherein, - When the evaporable liquid is introduced via a pump with a control valve, the evaporable liquid is distributed in the product gas stream via a liquid distributor and random or structured packing, or preferably via a nozzle. - When the evaporable liquid is introduced via a control valve through a static water feed, the evaporable liquid is distributed in the product gas stream via a liquid distributor and random or ordered packing.

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