Joint production of methanol, ammonia and urea

Abstract

FIELD: chemical production.SUBSTANCE: invention relates to a plant for the combined production of methanol, ammonia and urea from hydrocarbon feedstock. The plant comprises first and second parallel methanol production lines, at least one common methanation reactor, at least one common ammonia synthesis loop and a urea production section for producing urea by reacting CO2 with ammonia.EFFECT: avoiding the emission of carbon dioxide captured from methanol and ammonia synthesis gas into the atmosphere and the use of expensive water gas conversion and carbon dioxide removal steps.13 cl, 1 dwg, 1 tbl

Description

[0001] The present invention relates to a method for the co-production of methanol and ammonia from hydrocarbon feedstock without releasing carbon dioxide captured from the methanol and ammonia synthesis gas into the atmosphere and without using expensive water gas conversion and carbon dioxide removal steps. More specifically, the present invention relates to a sequential and once-through (single pass) method for the co-production of methanol and ammonia without water gas conversion and carbon dioxide removal and without an air separation unit used in the reforming portion of the unit.

[0002] Currently existing methods for co-producing methanol and ammonia typically involve parallel processes, in which a common reforming section is used to produce syngas, which is then split into separate parallel streams, one of which is used for methanol synthesis and the other for ammonia synthesis. Co-production of methanol and ammonia can also be carried out sequentially or in sequence, where the syngas obtained in the reforming section is first converted to methanol, and the unreacted gas, containing carbon oxides and hydrogen, is subsequently used for ammonia synthesis. These processes require water gas shift and / or carbon dioxide removal steps from the syngas stream, which involves the release of CO2 into the atmosphere and investment in expensive and complex conversion and carbon dioxide removal units.

[0003] A first object of the present invention is a method for co-producing methanol, ammonia and urea, which is simpler than the current method and which at the same time ensures minimal emission of carbon dioxide into the atmosphere.

[0004] A second object of the present invention is a method for the co-production of methanol, ammonia and urea, which allows for the optimized use of two parallel methanol production lines.

[0005] These and other advantages are achieved by the method according to the present invention for the joint production of methanol, ammonia and urea from hydrocarbon feedstock, said method comprising the steps

[0006] a) from a first methanol process comprising a first reforming stage and a first methanol synthesis stage, obtaining a first effluent stream comprising methanol and a first off-gas, a stage of nitrogen, hydrogen and unconverted carbon oxides, and

[0007] from a second methanol process comprising a second reforming stage and a second methanol synthesis stage, producing a second effluent stream containing methanol and a second off-gas containing nitrogen, hydrogen and unconverted carbon oxides

[0008] b) obtaining ammonia synthesis gas from the first and / or second off-gas containing nitrogen, hydrogen and unconverted carbon oxides in a common catalytic methanation step, and recovering said ammonia synthesis gas, preferably having a molar ratio of H2:N2 equal to 3:1;

[0009] c) catalytically converting nitrogen and hydrogen of ammonia synthesis gas in a common ammonia synthesis step, and recovering an effluent stream containing ammonia and an effluent gas stream containing hydrogen, nitrogen and methane, and

[0010] d) reacting at least a portion of the effluent stream containing ammonia with at least a portion of the exhaust gas containing CO2 from at least one of the first and second reforming stages to produce urea.

[0011] In other words, the applicant of the present invention provides a method based on two parallel methanol production lines, each comprising a reforming section and a methanol reaction section. Each methanol reaction section contains a methanol product that can be sent for further processing, storage, etc., as well as an off-gas containing nitrogen, hydrogen, and unconverted carbon oxides, which is very suitable as a basis for ammonia synthesis by methanation. Furthermore, the aspect of CO2 emissions from industrial plants and processes is a common problem, making the current process very interesting, since at least a portion of the CO2 from the off-gases from the reforming sections is used to produce urea.

[0012] As used in this application, the term “carbon oxides” means the components carbon monoxide and carbon dioxide.

[0013] As used in this application, in the catalytic methanation step (b), the term "by removing unconverted carbon oxides" means converting unconverted carbon oxides into methane. This is obviously different from the removal of carbon dioxide by using absorbents in acid gas scrubbing, which is excluded according to the present invention.

[0014] Accordingly, as used in this application, the term "carbon dioxide removal" means very expensive CO2 removal steps in the form of acid gas scrubbing, such as conventional MDEA and carbonate scrubbing processes.

[0015] Preferably, the following steps are carried out in each of the first or second methanol processes

[0016] 1) obtaining methanol synthesis gas containing hydrogen, carbon oxides and nitrogen by steam reforming of hydrocarbon feedstock in a reforming section containing a primary and secondary reforming stage;

[0017] 2) catalytically converting carbon oxides and hydrogen of methanol synthesis gas in a once-through methanol synthesis stage and recovering an effluent containing methanol and an exhaust gas containing nitrogen, hydrogen and unconverted carbon oxides;

[0018] In various installations, the secondary reforming stage is an air blowing secondary reforming stage.

[0019] As used in this application, the term “primary reforming stage” means reforming carried out in a conventional steam methane reformer (SMR), i.e., a tubular reformer, wherein the heat required for endothermic reforming is provided by thermal radiation from burners, such as burners located along the walls of the tubular reformer.

[0020] As used in this application, the term “air-blown secondary reforming step” means reforming carried out in an autothermal reformer or a catalytic partial oxidation reactor using air.

[0021] As used in this application, the term “once-through methanol synthesis stage” means that methanol is produced in at least one catalytic reactor operated in a single pass configuration, i.e., without significant recirculation (not more than 5%, i.e., less than 5%, often 0%) of the volumetric flow rate of any gas produced in the methanol synthesis back to the methanol reactor of the methanol synthesis stage, in particular off-gas containing hydrogen and unconverted carbon oxides.

[0022] By providing two parallel methanol production lines and a common methanation step followed by overall ammonia synthesis, a flexible yet very simple process is achieved.

[0023] The ability to control the flow / feed of syngas from each of the two reforming sections to each of the two methanol synthesis sections is advantageous for several reasons.

[0024] For example, the first and second direct-flow methanol synthesis stages of the first and second methanol processes are controlled by at least regulating the amount of synthesis gas from the first and / or second reforming stage fed to the first and / or second methanol production stage.

[0025] The first and second methanol processes may be connected by a syngas line allowing syngas from each of the two first and second reforming stages to be distributed to each of the first and second methanol stages, which, for example, may minimize any synthesis gas combustion in order to optimize energy consumption and thereby operating costs (OPEX) and / or maximize the utilization of the often very expensive portion of the reforming process by using boundaries in the compressor design and voluntarily different deactivation cycles in the first and second methanol stages.

[0026] The process may include additional parallel methanol processes. That is, one or more additional methanol processes may be operated in parallel with the dual methanol process of the present invention. The parallel methanol processes, one, two, three, or more, may be linked by one or more synthesis gas trains.

[0027] In some embodiments of the present invention, at least a portion of the methanol from the first and / or second methanol process is converted to formaldehyde. This formaldehyde, or at least a portion thereof, can be absorbed into an aqueous urea solution based on at least a portion of urea to produce UFC85 or equivalent solutions. UFC85 can be added to urea as a coating material. UFC85 is a concentrate containing 85% formaldehyde + urea and 15% water.

[0028] The present invention also relates to a plant for co-producing methanol, ammonia and urea.

[0029] The plant comprises first and second parallel methanol production lines, at least one common methanation reactor, and at least one common ammonia synthesis stage, as well as a urea production section. Furthermore, the plant preferably comprises an interconnecting synthesis line that allows fluid communication between the first and second methanol production lines.

[0030] The device may contain a formaldehyde production part and / or a UFC85 production part.

[0031] With a simple and low-cost process flowsheet (as in EP 2192082 B1), two methanol trains, each considered large in size, can be allowed and the flexibility that comes with having two trains instead of one large train can be achieved.

[0032] Typically, the reforming section will be the most expensive in terms of capital expenditure (CAPEX), and therefore there will be very limited oversizing of this section. While the synthesis compressor is typically limited in accordance with the relevant code and standard, methanol synthesis will have additional capacity when the catalyst is new and has not yet been deactivated. This can be used to increase flexibility and recover natural gas savings over the lifetime of the methanol catalyst, which is typically 3-4 years. Ammonia synthesis catalysts deactivate much more slowly and typically have a service life of 20 years, and therefore will not follow the life cycle of a catalyst like the methanol synthesis catalyst. In principle, overall ammonia synthesis can be maintained in operation for the entire life of its catalyst, always being supplied with syngas from at least one methanol synthesis.

[0033] Additional flexibility can be achieved by having a syngas interconnector between the two front ends (syngas production). Most likely, the two methanol syntheses will operate in such a way that they do not undergo simultaneous catalyst changes. One methanol synthesizing unit can have its catalyst in end-of-cycle (EOR) condition, while the other is still in a state close to start-up, and the total methanol synthesizing capacity will still be sufficient to utilize the resulting syngas.

[0034] This syngas line can, for example, be used during the start-up of the first methanol process, while the second methanol process is operated by feeding syngas from the first methanol process started before the second methanol process, instead of burning after the first methanol synthesis, since the start-up sequence is not available for operation.

[0035] With methanol processes and syngas interconnection line, the expensive reforming part in both methanol processes can operate at maximum productivity, and the dual methanol synthesis and single overall ammonia synthesis can jointly convert all the syngas produced.

[0036] An ammonia synthesis loop with a capacity of 750-960 tons per day is considered small, so the most obvious advantage is having a single ammonia synthesis train to convert syngas from two methanol synthesis trains. The combined ammonia capacity will then be combined to a nearly world-class ammonia plant capacity of 1,500-1,920 tons per day, achieving significant CAPEX savings.

[0037] Everything else related to ammonia synthesis can also be shared between the two methanol trains, such as (but not limited to) the process air compressor, the methanation section, the hydrogen recovery section, and the ammonia recovery section from the purge gas. At least the same relative CAPEX savings can be achieved for these sections, which are considered small.

[0038] The urea and UFC85 process steps described herein can also be used in connection with a single-stage methanol-ammonia co-production process, such as a process / installation primarily based on one of the methanol processes described herein, together with methanation and ammonia synthesis. For example, the co-production process as described in EP 2192082 B1.

[0039] Preferably, the hydrocarbon feedstock is natural gas, such as in the form of liquefied natural gas (LNG) or substituted natural gas (SNG).

[0040] According to the present invention, reactions controlling reforming, methanol synthesis and ammonia synthesis are directly used, so that methanol and ammonia can be co-produced without removing carbon dioxide captured from the synthesis gas. Hydrogen production by steam reforming is controlled by the endothermic reaction CH4 + H2O = CO + 3 H2, while methanol synthesis in the absence of carbon dioxide is controlled by the reaction CO + 2 H2 = CH3OH. In the presence of carbon dioxide, methanol is also otherwise formed according to the reaction CO2 + 3 H2 = CH3OH + H2O. Ideally, the feed synthesis gas for methanol production is a gas containing the highest possible molar ratio of CO / CO2. Ammonia synthesis occurs according to the reaction N2 + 3 H2 = 2 NH3.Since the entire reforming process produces only 3 moles of hydrogen, while methanol synthesis requires 2 moles of hydrogen, and ammonia synthesis requires 3 moles of hydrogen, the amount of ammonia produced is intentionally limited to one-third to utilize the available hydrogen at a rate of 1 / 3 (N2 + 3 H2 = 2 NH3). Therefore, with the present invention, we intentionally promote minimal flexibility in the separation of methanol and ammonia products.

[0041] This simple and superior solution enables the production of approximately 75-80 wt% methanol and 20-25 wt% ammonia at any given time in a process that is simpler and less expensive than traditional processes. This eliminates the need for very expensive steam reforming steps to convert carbon monoxide to hydrogen and carbon dioxide, as well as very expensive CO2 removal steps, such as acid gas scrubbing, such as conventional MDEA and carbonate scrubbing. Operating costs are also kept to a minimum, as there is no need to replace the reforming catalyst and no need to replenish the solvent in the CO2 removal processes.This contrasts with other combined methanol and ammonia processes, such as the process according to JP 2000063115, which require very expensive carbon dioxide removal using a conventional CO2 stripper or absorber to adjust the CO2 / CO ratio in the syngas, thereby achieving process flexibility. Furthermore, since secondary reforming is carried out in a secondary air-blown reformer (an autothermal air-blown reformer) to provide the necessary nitrogen, there is no need for expensive and massive air separation units (ASUs), making the process less expensive than current processes, where ASUs are often required to supply oxygen to autothermal reformers, and where the co-generated nitrogen is typically used in subsequent nitrogen scrubbing.

[0042] The method according to the present invention is environmentally friendly, as there are no emissions of CO2 captured from the methanol and ammonia synthesis gas. Virtually all of the carbon monoxide (and carbon dioxide) generated in the process is used for methanol synthesis.

[0043] The process is applicable to installations of any capacity, including large installations producing more than 2000 tons per day of ammonia and methanol, such as 3000, 5000 tons per day or even more.

[0044] The methanol synthesis step is preferably carried out by conventional means by passing synthesis gas at high pressure and temperatures, such as 60-150 bar, preferably 120 bar and 150-300°C, through at least one methanol reactor containing at least one fixed bed of methanol catalyst. A particularly preferred methanol reactor is a fixed bed reactor cooled with a suitable cooling agent, such as boiling water, for example a boiling water reactor (BWR). In a particular embodiment of the present invention, the methanol synthesis step in step (b) is carried out by passing the synthesis gas through one boiling water reactor and then through an adiabatic fixed bed reactor or by passing the synthesis gas through a series of boiling water reactors and then through an adiabatic fixed bed reactor.Preferably, the boiling water reactor is a single condensation-methanol reactor which comprises, in a common shell, a fixed bed of methanol catalyst particles and cooling means adapted to indirectly cool the methanol synthesis gas with a cooling agent, and which operates at pressures above 90 bar and below 150 bar, more preferably above 110 bar and below 130 bar, as described in DK patent applications PA 2008 00261 and PA 2008 00260, filed on February 25, 2008. The use of a methanol reactor in accordance with these applications allows operation at pressures much higher than conventional boiling water reactors, which are typically around 80 bar. In addition, this allows the use of a single reactor rather than two conventional boiling water reactors, thereby significantly reducing the cost of the plant.Furthermore, since the operating pressure in the methanol synthesis stage can be maintained at around 120 bar or even higher, there are significant savings in terms of equipment size and overall investment costs, as methanol synthesis is preferred at high pressures.

[0045] Accordingly, the present invention enables the methanol and ammonia synthesis sections to be operated at similar operating pressures, for example, 130 bar, which implies a simplified process with significant savings in equipment size, as mentioned above. However, it is also possible to operate at two different operating pressures, for example, 80 bar in the methanol synthesis stage and 130 bar in the ammonia synthesis stage, which means energy savings in the methanol synthesis stage.

[0046] In step (a), the effluent stream containing methanol is preferably a liquid effluent stream. This effluent stream is obtained by cooling and condensing synthesis gas from the methanol reactors. Accordingly, the method according to the present invention may further include cooling the synthesis gas withdrawn from each methanol reactor to condense methanol and passing the gas through a separator, extracting a bottom fraction from the separator containing crude methanol, extracting an upper fraction containing synthesis gas, which is passed to a subsequent methanol reactor, and forming a single liquid effluent stream containing methanol by combining the bottom fractions of the separators of each reactor containing crude methanol.

[0047] It should be understood that the term “methanol reactor” as used in this application covers adiabatic fixed bed reactors and cooled reactors, such as boiling water reactors and condensation methanol reactors, which contain in a common shell a fixed bed of methanol catalyst particles and cooling means adapted to indirectly cool the methanol synthesis gas with a cooling agent.

[0048] Because the methanol synthesis stage is once-through, there is no need to recycle a portion of the overhead fraction from the separator of the adiabatic fixed-bed reactor back to the first methanol reactor in the methanol synthesis stage. This contrasts with other combined methanol and ammonia processes, such as JP 2000063115, where methanol synthesis involves significant recirculation of the gaseous product.

[0049] In step (b), the catalytic methanation step for converting carbon oxides into methane is carried out in at least one methanation reactor, which is an adiabatic reactor containing a fixed bed of methanation catalyst.

[0050] In step (c), the ammonia synthesis gas from the methanation step, containing the correct proportion of hydrogen and nitrogen (preferably a molar ratio of H2:N2 of 3:1), is optionally passed through a compressor to obtain the required ammonia synthesis pressure, such as from 120 to 200 bar, preferably about 130 bar. Ammonia is then obtained in the usual way using an ammonia synthesis loop containing at least one ammonia converter containing at least one fixed bed of ammonia catalyst, with intermediate cooling. The effluent stream containing ammonia also contains hydrogen, nitrogen and inert substances such as methane and argon. Ammonia can be recovered from the effluent stream containing ammonia as liquid ammonia by condensation and subsequent separation. Preferably, an off-gas stream containing hydrogen, nitrogen and methane is removed from the ammonia synthesis stage, as well as a hydrogen-rich stream (>90 vol.% H2).These streams may, for example, be a stream from a purge gas recovery unit. Preferably, this hydrogen stream is added to the methanol synthesis stage, for example by combining it with methanol syngas. Recycling this hydrogen-rich stream ensures higher process efficiency, as the useful hydrogen is used in methanol synthesis and subsequent ammonia synthesis, rather than simply being used as fuel.

[0051] In order to increase the energy efficiency of the process, the off-gas (purge) stream containing hydrogen, nitrogen and methane from step (c) is returned to step (a), that is, it is returned in the form of off-gas fuel to the reforming part of the plant, in particular, to the primary reforming stage.

[0052] A plant with a combined capacity of 3,000 tons per day of methanol and 750 tons per day of ammonia is considered world-class, but even higher plant capacities are required. The present invention provides a dual-train methanol plant with a capacity of 2 x 3,000 tons per day of methanol and 2 x 750 tons per day of ammonia, which can compete with other technologies generally considered more optimal for producing syngas for methanol synthesis, such as two-stage reforming or ATR.

[0053] The accompanying drawing shows a simplified flow chart of a process according to a specific embodiment of the present invention, including a reforming step, a methanol synthesis step, a methanation step, and an ammonia synthesis step.

[0054] In the first part of the reforming, natural gas 1 is added to the primary reforming stage 20 (steam methane reforming) by adding steam 2. Then, the partially reformed gas is further reformed in the secondary reforming stage with air blowing 21 (autothermal reforming) by adding air 3. Methanol synthesis gas 4 containing hydrogen, carbon oxides and nitrogen is cooled in the exhaust gas boiler(s) by generating steam and then compressed to a methanol synthesis pressure (not shown). In the first methanol synthesis stage 22, methanol synthesis gas 4 is converted in a once-through operation (single-pass operation, no recirculation) to obtain a liquid effluent 5 containing methanol and an off-gas 6 containing nitrogen, hydrogen and unconverted carbon oxides. About 80% by weight of the total capacity of the plant is used to produce methanol from the outlet stream 5.

[0055] In the second part of the reforming, natural gas 1B is added to the primary reforming stage 20B (steam methane reforming) with the addition of steam 2B. Then, the partially reformed gas is further reformed in the secondary reforming stage with air blowing 21B (autothermal reforming) with the addition of air 3B. Methanol synthesis gas 4B containing hydrogen, carbon oxides and nitrogen is cooled in the exhaust gas boiler(s) while generating steam and then compressed to the methanol synthesis pressure (not shown). In the second methanol synthesis stage 22B, methanol synthesis gas 4B is converted in a once-through operation (single-pass operation, no recycle) to obtain a liquid effluent stream 5B containing methanol and an off-gas 6B containing nitrogen, hydrogen and unconverted carbon oxides. About 80% by weight of the total capacity of the plant is used to produce methanol from the 5B outlet stream.

[0056] The carbon oxides in the exhaust gases 6 and 6B are hydrogenated into methane in the common methanation step 23, resulting in the formation of ammonia synthesis gas 7 having a molar ratio of H2:N 2, equal to 3:1. The ammonia syngas 7 is then passed through the ammonia synthesis stage 24 to produce an effluent stream 8 containing ammonia and an effective stream 9 containing hydrogen, methane and nitrogen, which is processed to produce two effluent streams. The first effluent stream 11 is returned as waste gas fuel to the primary reforming stage 20. The second effluent stream 10, a hydrogen-rich stream (>90 vol H2H2), is returned to the methanol synthesis stage 22 by combining with the methanol synthesis stream 4. About 20 wt% of the total plant capacity is devoted to producing ammonia in the effluent stream 8. The plant eliminates the use of an air separation unit (ASU), as well as water vapor reforming and CO2 removal stages.

[0057] The following table shows the temperatures, pressures and flow rates of the various streams for the process according to Fig. 1, which ensures the production of about 3000 tons per day of methanol and 750 tons per day of ammonia, despite the use of complex feedstock. The feedstock used is heavy natural gas (85 vol.% methane):

[0058] Table Position Pace. Pressure Flow rate / kmol / h °C Bar g H2O H2 N2 CH4 CO CO2 Ar 4,4B 947 30.1 5890 12023 1414 419 3147 1043 16 6,6B 35 120.3 2.7 4574 1457 463 17 38 20 7 35 119.3 8742 2914 1036 40 10,10B 35 32 1463 66 61 4 11,11B 35 12 167 477 450 16

[0059] The 25 process air compressor can be one common one or one for each part of the reformer.

[0060] Stream 4 / 4B can be allocated to methanol processes 22 / 22B depending on individual catalyst activity in order to optimize OPEX along line 12.

[0061] The hydrogen-rich stream 10 / 10B and the off-gas 11 / 11B can be distributed to optimize the process requirements in the reforming parts and the methanol synthesis parts.

[0062] Due to the nature of the co-production of methanol and ammonia from natural gas, the process gas recovered for urea production will not contain significant amounts of CO2. If it is desired to use some or all of the resulting ammonia in the process according to the present invention, CO2 from the off-gas from one or more reforming sections can be recovered in the CO2 removal section 27.

[0063] Typically, the off-gas from one reformer section will contain enough CO2 to convert all the ammonia from the combined methanol section's off-gas into urea. Thus, economies of scale can be achieved for the urea unit, section 29.

[0064] A widely used coating material in urea production is urea-formaldehyde concentrate (UFC85), which contains up to 85% urea and formaldehyde, with the remainder being water to prevent caking of the urea product. The synergistic effect of producing the coating material in the present invention is evident, as a small flow of methanol 16 is required to produce formaldehyde and urea solution, and the urea solution is required to absorb formaldehyde to produce UFC85 or more diluted UFC products in Part 28.

Claims

1. A plant for the combined production of methanol, ammonia and urea from hydrocarbon feedstock, comprising first and second parallel methanol production lines, at least one common methanation reactor, at least one common ammonia synthesis loop and a urea production section for producing urea by reacting CO2 with ammonia, where said first methanol production line is configured to carry out a first direct-flow methanol process comprising a first reforming stage and a first methanol synthesis stage to produce a first outlet stream containing methanol and a first outlet gas containing hydrogen, nitrogen and unconverted carbon oxides, and said second methanol production line is configured to carry out a second direct-flow methanol process, including a second reforming stage and a second methanol synthesis stage to produce a second outlet stream containing methanol and a second outlet gas containing hydrogen, nitrogen and unconverted carbon oxides; said at least one common methanization reactor is configured to produce ammonia synthesis gas from the first and / or second exhaust gas in a common catalytic methanation stage and recover said ammonia synthesis gas; said at least one common ammonia synthesis circuit is configured to catalytically convert nitrogen and hydrogen of ammonia synthesis gas in a common ammonia synthesis stage and extract an outlet stream containing ammonia and a purge gas stream containing hydrogen, nitrogen and / or methane; and said urea production section is configured to react at least a portion of the ammonia-containing effluent with at least a portion of the CO2-containing exhaust gas from at least one of the first and second reforming stages to produce urea; wherein said first and second methanol production lines include a reforming section that includes a primary and secondary reforming stage configured to produce methanol synthesis gas containing hydrogen, carbon oxides and nitrogen by steam reforming hydrocarbon feedstock, and wherein said first and second methanol production lines are designed with the possibility of catalytically converting carbon oxides and hydrogen from the methanol synthesis gas at said stage of the direct-flow methanol process.

2. The apparatus of claim 1, further comprising an interconnecting synthesis line allowing fluid communication between the first and second methanol process lines.

3. The plant according to claim 1, wherein said at least one common methanation reactor is configured to produce ammonia synthesis gas having a molar ratio of H2:N2 equal to about 3:

1.

4. The plant according to claim 1, wherein the reforming section of said first and second methanol production lines is designed in such a way that the secondary reforming stage is a secondary reforming stage with air blowing.

5. The plant according to claim 1, wherein the plant is configured to use hydrocarbon feedstock that is natural gas, or a substitute for natural gas (SNG), or a gas containing > 80% methane.

6. The plant according to claim 1, wherein said first and second methanol production lines are configured to control the synthesis of methanol at said first and second stages of the direct-flow methanol synthesis at least by regulating the amount of synthesis gas from the first and / or second reforming stage fed to the first and / or second stage of methanol production.

7. The plant according to claim 1, wherein the plant is configured to synthesize methanol by passing the synthesis gas through one or more fluidized bed reactors and then through one or more adiabatic fixed bed reactors.

8. The plant according to claim 1, wherein the plant is configured to carry out the synthesis of methanol by passing the synthesis gas through one or more fluidized bed reactors and then through one or more gas-cooled reactors.

9. The apparatus of claim 8, wherein the boiling water reactor is in the form of a separate condensation-methanol reactor which contains, in a common shell, a fixed bed of methanol catalyst particles and cooling means adapted to indirectly cool the methanol synthesis gas using a cooling agent.

10. The plant according to claim 8 or 9, wherein the plant is designed such that said co-production of methanol, ammonia and urea further comprises cooling the synthesis gas withdrawn from each methanol reactor to condense the methanol and passing the gas through a separator, extracting a bottom fraction from the separator containing crude methanol, extracting an upper fraction containing the synthesis gas, which is passed to a subsequent methanol reactor, and forming a single liquid effluent stream containing methanol by combining the bottom fractions of the separators of each reactor containing crude methanol.

11. The plant according to claim 1, wherein the plant is designed such that said joint production of methanol, ammonia and urea further comprises extracting a hydrogen-enriched stream from a purge gas stream containing hydrogen, nitrogen and methane, and adding this stream to the first and second methanol production lines.

12. The plant according to claim 1, wherein the plant is designed such that said joint production of methanol, ammonia and urea further comprises extracting off-gas from a purge gas stream containing hydrogen, nitrogen and methane, and adding this stream to the first and second methanol production lines as fuel.

13. The plant according to claim 1, wherein the plant is designed in such a way that said joint production of methanol, ammonia and urea further includes additional parallel methanol processes.

Images