Methanol synthesis converter and process

Abstract

A methanol synthesis converter (1) comprising a catalyst bed (4) having an annular shape and configured as an adiabatic or isothermal catalyst bed, with a cooling element disposed downstream of the catalyst bed or immersed in the catalyst, respectively; and a discharge heat exchanger (6) disposed in a central cavity of the annular catalyst bed (4) to transfer heat from a hot gas (12) discharged from the catalyst bed (4) to a cooling medium.

Description

[Technical Field]

[0001] The present invention is in the field of methanol synthesis. In particular, the present invention relates to a methanol synthesis converter and a process for the synthesis of methanol. [Background technology]

[0002] The industrial production of methanol begins in the front-end section of a methanol plant, where make-up gas containing carbon oxides CO, CO2, and hydrogen H2 is obtained by reforming or partial oxidation of a hydrocarbon feedstock. The hydrocarbon feedstock subjected to reforming may come from a variety of sources, but typically includes one or more of the following: natural gas, coal, petroleum coke, waste, and / or biomass.

[0003] The conversion of the make-up gas to crude methanol is carried out in one or more methanol converters that are part of the methanol synthesis loop. Converters are complex devices because the reaction leading to the synthesis of methanol is highly exothermic and must be able to withstand high temperatures and pressures, typically 200°C-300°C and 50-100 bar.

[0004] The methanol converter may include one or more catalyst beds containing a catalyst and may include one or more cooling elements immersed in the catalyst mass and / or one or more heat exchangers positioned downstream of the catalyst beds to remove heat generated by the methanol synthesis reaction.

[0005] In the art, catalytic converters with cooling elements placed in the catalyst mass are called isothermal converters due to the fact that the temperature of the reaction leading to the synthesis of methanol is kept within a suitable temperature range, while converters without cooling elements in the catalyst mass are called adiabatic converters.

[0006] Typically, the methanol synthesis loop includes an isothermal and / or adiabatic converter, along with additional processing equipment upstream or downstream of the converter, such as one or more heat exchangers, that are not part of the catalytic converter.

[0007] The performance of a catalytic converter can be evaluated by considering the converter's active volume, simply the volume of the converter that actively contributes to the synthesis of methanol. The remaining volume can be referred to as the inactive volume. The active volume is the sum of several contributions, including the volume occupied by the catalyst bed and the volume occupied by cooling elements immersed in the catalyst.

[0008] In practice, to evaluate the converter's performance, the active volume of the converter is divided by the converter's internal volume to calculate a parameter called the actively utilized volume ratio. This ratio is an indirect indicator of the proper design of a methanol converter; a higher ratio means lower CAPEX and is favorable for cost optimization.

[0009] Unfortunately, in prior art adiabatic and isothermal converters, not all of the internal volume of the catalytic converter is active for methanol synthesis as a result of mechanical and fluid dynamic constraints and / or maintenance requirements.

[0010] In fact, current technology catalytic converters are designed with a central cavity, which is essentially an empty volume not filled with catalyst and inactive for methanol synthesis. Therefore, in current designs, converters are characterized by a small active utilization volume fraction, resulting in a non-optimized design.

[0011] Patent Document 1 discloses a radial flow reactor including a heat exchanger within the catalyst bed. Patent Document 2 discloses a multi-bed catalytic converter, and Patent Document 3 discloses a catalytic reactor for ammonia, methanol, etc. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] U.S. Patent No. 4,714,592 [Patent Document 2] International Publication No. 2019 / 121155 [Patent Document 3] Japanese Patent Application Publication No. 63-283741 Summary of the Invention

[0013] The present invention aims to overcome the above-mentioned drawbacks of the prior art. In particular, the present invention addresses the challenge of designing a methanol converter with a higher active volume or a higher active utilization volume ratio compared to current technology converters.

[0014] Therefore, one aspect of the present invention is a catalytic converter for the synthesis of methanol as claimed in claim 1.

[0015] A catalytic converter for the synthesis of methanol comprises a pressure vessel containing a catalyst bed having an annular shape and an exhaust heat exchanger installed in the empty central cavity of the converter and arranged to transfer heat from a hot methanol-containing gas present in the catalyst bed to a coolant.

[0016] The converter of the present invention can include one or more catalyst beds. The catalyst beds may include one or more adiabatic or isothermal catalyst beds. An isothermal catalyst bed includes one or more cooling elements, preferably in the form of heat exchange plates, disposed within the catalyst bed to remove heat of reaction from the catalyst. An adiabatic catalyst bed does not have a cooled heat exchange element immersed in the catalyst, and a heat exchanger is preferably provided downstream of the adiabatic catalyst bed to remove heat of reaction from the effluent.

[0017] The exhaust heat exchanger is preferably a feed / effluent heat exchanger configured to transfer heat from the hot methanol-containing gas exhaust from the catalyst bed to the synthesis gas feed so that the synthesis gas feed is preheated before entering the catalyst bed.

[0018] The volume occupied by the feed / effluent heat exchangers in the converter is counted in the definition of active volume.

[0019] Another aspect of the present invention is a process for the synthesis of methanol as claimed.

[0020] The advantages of the present invention are as follows:

[0021] The inactive volume of the converter is reduced by installing a feed / effluent heat exchanger in the central cavity, which also increases the active utilization volume ratio of the converter, which is particularly advantageous for the investment costs of the synthesis loop.

[0022] In particular, the ability to integrate multiple processing functions into a single pressure vessel results in a compact, simplified, and more practical converter. For example, converters of the present invention can be configured to perform a range of functions, including cooling, heating, and in some embodiments, concentration.

[0023] The converter of the present invention is particularly suitable for application in small methanol plants and in methanol plants powered at least in part by renewable energy sources.

[0024] The converter vessel can be designed with a slightly larger diameter than conventional converters. This slight increase in converter diameter makes it possible to include one or more additional processing units within the converter volume. This reduces the cost of external equipment and piping, as well as CAPEX. Furthermore, pressure loss and energy consumption (OPEX) are also reduced. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram of a converter according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] In a broad sense, the present invention relates to a catalytic converter for the synthesis of methanol comprising a pressure vessel containing a catalyst bed having an annular shape and an exhaust heat exchanger.

[0027] An exhaust heat exchanger is installed in the empty central cavity of the converter and positioned to transfer heat from the hot methanol-containing gas exhaust from the catalyst bed to the coolant.

[0028] The coolant can be unreacted syngas (a process stream) fed to the converter itself or an external medium. Suitable external cooling fluids can be cooling water, demi-water, boiler feed water, etc. that can be used in the process for energy recovery or stream generation.

[0029] In a highly preferred embodiment, the exhaust heat exchanger is a feed / effluent heat exchanger positioned in the converter to transfer heat from the hot methanol-containing gas exhaust from the catalyst bed to the unreacted synthesis gas feed, the converter feed being preheated before entering the catalyst bed.

[0030] The exhaust heat exchanger has a first side for a syngas feed and a second side for a hot gas exhaust, the output of the first side being in communication with the inlet of the catalyst bed and the inlet of the second side being in communication with the outlet of the catalyst bed.

[0031] The exhaust heat exchanger may be any of the following, depending on the application:

[0032] In a first option, the discharge heat exchanger is a feed / effluent heat exchanger as defined above, or a unit thereof if the feed / effluent heat exchanger is a multi-unit device or part of a heat exchanger train. In general terms, a feed / effluent heat exchanger is understood as a device comprising one or more units arranged to cover a given heat load, i.e., the heat that must be transferred from the heat exhaust to the inlet gas. The heat exchanger arranged within the pressure vessel and in the cavity of the annular bed may, depending on various embodiments, be the entire feed / effluent heat exchanger arranged to completely cover the heat load, or a unit thereof arranged to cover a certain percentage of the heat load.

[0033] In an interesting embodiment, the exhaust heat exchanger is a plate heat exchanger comprising heat exchange elements in the form of plates, which are relatively thin, smooth heat exchange bodies with a length and width predominantly relative to their thickness.

[0034] In a second option, the exhaust heat exchanger includes a liquid-gas separator located downstream of the feed / effluent heat exchanger.

[0035] A third option includes a feed / effluent heat exchanger and another heat exchanger positioned to remove additional heat from the hot reaction effluent with an external cooling medium such as cooling water.

[0036] In another option, the discharge heat exchanger includes a feed / effluent heat exchanger, an additional heat exchanger, and a liquid-gas separator.

[0037] The converter of the present invention may comprise one or more catalyst beds.

[0038] Preferably, the catalytic converter comprises only a single catalyst bed (single-bed converter). A particularly preferred embodiment is a single-bed isothermal converter having only one catalyst bed with a cooling element immersed in the catalyst mass to maintain the temperature of the reaction zone within a target range. More preferably, the cooling element is in the form of a heat exchanger plate through which a cooling medium traverses. The cooling medium is preferably water.

[0039] In some embodiments, the catalytic converter comprises a single or multiple adiabatic catalyst beds without cooling elements within the catalyst mass.

[0040] In some embodiments, the catalytic converter comprises multiple catalyst beds, each of which is immersed in a dedicated cooling element to maintain the reaction temperature in the respective catalyst bed within a target range (isothermal or quasi-isothermal range).

[0041] According to another embodiment, the converter comprises multiple catalyst beds, some of which are isothermal and others of which are adiabatic, with no cooling elements within the catalyst mass.

[0042] According to one embodiment, the converter comprises two catalyst beds arranged in series, one downstream of the other, the first catalyst bed being an isothermal catalyst bed and the second catalyst bed being an adiabatic bed.

[0043] According to one embodiment, the converter comprises two catalyst beds arranged in series, one downstream of the other, the first catalyst bed being an adiabatic bed and the second catalyst bed being an isothermal catalyst bed.

[0044] According to various embodiments, the feed / effluent heat exchanger is a shell-and-tube heat exchanger, which includes tubes housed within a cylindrical shell, or the exhaust heat exchanger is a plate heat exchanger, in which the cooling elements are in the form of plates.

[0045] The converter may further include a methanol condenser housed in the pressure vessel and positioned in fluid communication downstream of the feed / effluent heat exchanger to receive the cooled methanol-containing gaseous effluent from the second side of the heat exchanger and to produce a liquid methanol-containing product.

[0046] The present invention is applicable to the manufacture of new converters and / or the retrofitting of existing chemical plants, especially when a compact catalytic converter size is required and the available space for its installation is limited. In some embodiments, the methanol converter of the present invention can replace an existing methanol converter during a retrofit process.

[0047] In a further aspect of the invention, a hydrocarbon or biomass feedstock is subjected to a reforming step to obtain a synthesis gas feed comprising a mixture of carbon oxides and hydrogen, which is then subjected to a heating step and then reacted over a catalyst to produce a hot methanol-containing gas. In some embodiments, the production of the synthesis gas feed may involve gasification of a suitable feedstock, preferably a biomass feedstock. The reforming step may be partially or completely replaced by the gasification step.

[0048] The hot methanol-containing gas is then cooled and transferred to a condensation step, and the heating of the synthesis gas feed and the cooling of the hot methanol-containing gas are carried out in a discharge heat exchanger such that the heat retained by the hot methanol-containing gas is indirectly transferred to the synthesis gas feed.

[0049] The reaction of the syngas feed over the catalyst, the heating of the syngas feed, and the cooling of the hot methanol-containing gas are carried out in the catalytic converter, which can be configured to operate under isothermal or adiabatic conditions.

[0050] Isothermal conditions are preferably achieved by transferring the heat generated by the reaction of the synthesis gas feed to a coolant, any suitable coolant may be used, but preferably pressurized water is used.

[0051] In some embodiments, additional hydrogen and carbon oxides can be provided in the process and then reacted in a catalytic converter to increase the production of methanol. In one embodiment, additional hydrogen is produced by electrolysis of water, and carbon oxides can be obtained from a carbon oxide recovery section.

[0052] In one embodiment, condensation of the raw methanol containing gas is carried out within the same pressure vessel of the converter, preferably after cooling in a feed / effluent heat exchanger.

[0053] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The converter 1 shown in FIG. 1 comprises a pressure vessel 3 with a nozzle 16 for a synthesis gas feed 14 and an outlet 17 for raw methanol gas 2 .

[0054] The pressure vessel further contains an annular catalyst bed 4 , heat exchanger plates 5 and a feed / effluent heat exchanger 6 .

[0055] The feed / effluent heat exchanger 6 is located at the center of the converter 1 along the axis of symmetry (AA) of the pressure vessel 3. The catalyst bed 4 has an annular shape and is disposed concentrically around the feed / effluent heat exchanger 6, enveloping the heat exchanger 6.

[0056] The heat exchanger plates 5 are immersed in the catalyst bed 4 and serve to remove the heat generated by the methanol synthesis reaction and maintain the reaction temperature within the desired temperature range.

[0057] FIG. 1 discloses a preferred embodiment of a single-bed, plate-cooled isothermal reactor.

[0058] The feed / effluent heat exchanger 6 has a first side 7 and a second side 8, with the first side 7 in fluid communication with an inlet 9 of the catalyst bed 4 and the second side 8 in fluid communication with an outlet 10 of the catalyst bed 4.

[0059] The feed / effluent heat exchanger 6 is a shell-and-tube heat exchanger with a plurality of tubes 11 disposed within the shell of the heat exchanger. The shell-and-tube heat exchanger is vertically oriented within the converter with the plurality of tubes 11 parallel to the reactor axis of symmetry AA. The tubes 11 are in fluid communication with the outlet 10 of the catalyst bed 4 and with the outlet 17 of the pressure vessel.

[0060] In a variant (not shown), the feed / effluent heat exchanger is also a plate heat exchanger with plate-shaped heat exchange elements instead of tubes.

[0061] The outlet 10 of the catalyst bed 4 communicates with the tubes 11 of the heat exchanger 6 through a recuperator 21. The recuperator 21 is part of the shell of the feed / effluent heat exchanger 6 and extends along the entire length of the heat exchanger 6.

[0062] The shell side of the feed / effluent heat exchanger 6 is in fluid communication with a nozzle 16 of the pressure vessel 3 and with an inlet 9 of the catalyst bed 4 .

[0063] The pressure vessel 3 of the converter 1 may be provided with an opening to allow the feed / effluent heat exchanger 6 to be removed from the pressure vessel 3 for maintenance or replacement.

[0064] The heat exchanger plates 5 also comprise a piping system 18 arranged to supply a coolant 13, such as pressurized water, to said exchanger plates 5, and a collector 19 arranged to collect the coolant 20 outside the converter 1.

[0065] Catalytic converter 1 operates as follows: syngas feed 14 enters the converter through nozzle 16, passes through the shell side of feed / effluent heat exchanger 6, and absorbs heat from hot methanol-containing gas 12 flowing through tubes 11 of heat exchanger 6. As a result of this heat transfer process, the syngas feed is preheated. The preheated syngas then travels sequentially through first side 7 toward catalyst bed inlet 9 and into catalyst bed 4 itself.

[0066] Here, the preheated synthesis gas reacts over catalyst bed 4 to produce hot methanol-containing gas 12, which is then recovered and conveyed to the second side 8 of feed / effluent heat exchanger 6. Hot methanol-containing gas 12 further passes through recovery vessel 21 before being fed to tube 11.

[0067] It can be noted that the hot methanol-containing gas passes through tubes 11 facing against the syngas feed 14 before being discharged outside the converter 1 through outlet nozzle 17 as raw methanol gas 2. As mentioned above, heat is transferred indirectly from the hot methanol-containing gas 12 to the syngas feed 14 in the shell-and-tube heat exchanger 6.

Claims

1. a catalyst bed (4) configured to contain a catalyst and having an annular shape; a set of cooling elements; a discharge heat exchanger (6) arranged to transfer heat from the hot methanol-containing gas (12) discharge from said catalyst bed (4) to a coolant; Including, The catalyst bed (4) is configured either as an adiabatic catalyst bed with a cooling element downstream of the catalyst bed, or as an isothermal catalyst bed with a cooling element arranged so as to be immersed in the catalyst of the catalyst bed (4); The exhaust heat exchanger (6) is arranged in the central cavity of the annular catalyst bed (4) so ​​that the catalyst bed (4) is arranged concentrically around the exhaust heat exchanger (6). A catalytic converter (1) for the synthesis of methanol (2) comprising a pressure vessel (3).

2. the exhaust heat exchanger (6) is a feed / effluent heat exchanger arranged to transfer heat from the hot methanol-containing gas (12) effluent from the catalyst bed (4) to the synthesis gas feed (14) to be reacted, such that the synthesis gas feed (14) is preheated before entering the catalyst bed (4); The exhaust heat exchanger (6) comprises a first side (7) for a synthesis gas feed (14), the output of which is in communication with the inlet (9) of the catalyst bed (4); and a second side (8) for a hot methanol-containing gas (12), the inlet of which is in communication with the outlet (10) of the catalyst bed (4). The converter of claim 1 .

3. 3. Catalytic converter (1) according to claim 2, wherein the exhaust heat exchanger (6) is a shell-and-tube heat exchanger comprising tubes (11) housed in a cylindrical shell.

4. 3. Catalytic converter (1) according to claim 2, characterized in that the exhaust heat exchanger (6) is a plate heat exchanger comprising heat exchange elements in the form of plates, the plates being traversed by the synthesis gas feed.

5. 5. The catalytic converter (1) according to claim 1, further comprising a methanol condenser housed in the pressure vessel (3), the methanol condenser being disposed downstream of the exhaust heat exchanger (6) and in fluid communication with the exhaust heat exchanger (6), the methanol condenser receiving cooled methanol-containing gas from the second side (8) of the exhaust heat exchanger (6) and producing a liquid methanol-containing product.

6. The catalytic converter (1) according to any one of claims 1 to 5, wherein the exhaust heat exchanger (6) is part of a heat exchanger train comprising a plurality of heat exchanger units connected in series either inside or outside the catalytic converter (1).

7. The catalytic converter (1) according to any one of claims 1 to 6, further comprising a liquid-gas separator arranged downstream of the exhaust heat exchanger (6).

8. The converter of claim 7 , wherein the liquid-gas separator is located downstream of the condenser.

9. A catalytic converter (1) according to any one of claims 1 to 8, further comprising a start-up heater.

10. A converter according to any one of claims 1 to 9, wherein the converter is a single bed converter and the catalyst bed (4) is the only catalyst bed of the converter.

11. Converter according to any one of claims 1 to 10, wherein the converter is isothermal and the cooling element immersed in the catalyst bed is in the form of a heat exchange plate through which a coolant is traversed.

12. a synthesis gas feed (14) containing a mixture of carbon oxides and hydrogen is subjected to a heating step and then reacted over a catalyst to produce a hot methanol-containing gas (12); The hot methanol-containing gas (12) is then cooled and transferred to a condensation step, and the heating of the synthesis gas feed (14) and the cooling of the hot methanol-containing gas (12) are carried out in a discharge heat exchanger (6) so that the heat of the hot methanol-containing gas (12) is indirectly transferred to the synthesis gas feed (14); The reaction of the synthesis gas feed (14) over the catalyst, the heating of the synthesis gas feed (14), and the cooling of the hot methanol-containing gas (12) are carried out in a catalytic converter (1) according to any one of claims 1 to 11; and the reaction with the synthesis gas feed (14) over the catalyst is carried out under adiabatic or isothermal conditions; Process for the synthesis of methanol (2).

13. 13. The process of claim 12, wherein the isothermal conditions are achieved by transferring heat generated by the reaction of the synthesis gas feed (14) to a cooling medium (13).

14. 14. The process of claim 13, wherein the condensation of the hot methanol-containing gas (12) is carried out sequentially after the cooling in the catalytic converter (1).

15. The process according to any one of claims 12 to 14, wherein the cooling medium (13) is pressurized water.

Images