Method and system for the production of methanol

Abstract

A process for preparing methanol by a methanol synthesis reaction of carbon dioxide with hydrogen may involve a distillation step and a condensation step following the synthesis of a crude methanol. A volatile component and water may be separated off from a methanol-containing product stream, and a gas stream containing a volatile component that has been separated off may be discharged at least partially as offgas. At least part of the gas stream that has been separated off may be recirculated into the methanol synthesis reaction. A plant for preparing methanol can store or utilize electric power generated from renewable energy sources and provide facilities for discharging the offgas stream, which can be purified by catalytic after-combustion. Alternatively, the plant can be configured without discharge of an offgas substream, or the offgas streams are so small that they can be released without treatment into the environment at a suitable position.

1 .- 35 . (canceled) 
     
     
         36 . A process for preparing methanol by reaction of carbon dioxide with hydrogen, the process comprising:
 feeding a product stream obtained in a methanol synthesis reaction to at least one of a high-pressure separator or a low-pressure separator where a gas stream is separated off from a methanol-containing product stream;   feeding the methanol-containing product stream, after the gas stream is separated off, to a distillation step where water is separated off from the methanol-containing product stream; and   recirculating volatile components that have been separated off in the distillation step at least partly into a mixing and compression section located upstream of the methanol synthesis reaction.   
     
     
         37 . The process of  claim 36  comprising at least one of
 at least partially discharging a gas stream that contains at least one of the volatile components as offgas, or 
 recirculating at least part of the gas stream that contains the at least one of the volatile components to the methanol synthesis reaction. 
 
     
     
         38 . The process of  claim 36  comprising feeding at least one substream of the gas stream to a catalytic offgas purification. 
     
     
         39 . The process of  claim 38  wherein the catalytic offgas purification comprises a catalytic after-combustion with introduction of a supplementary combustion component. 
     
     
         40 . The process of  claim 39  wherein oxygen obtained by electrolysis is introduced as the supplementary combustion component. 
     
     
         41 . The process of  claim 36  comprising obtaining the hydrogen used as a starter material in the methanol synthesis reaction by electrolysis of water. 
     
     
         42 . The process of  claim 41  wherein water that has been separated off from the methanol-containing product stream in the distillation step, water that has been separated off by condensation, or water that has been separated off via another method is at least partially recirculated for the electrolysis. 
     
     
         43 . The process of  claim 41  comprising treating water that is used as a starter material for the electrolysis by at least one of ion exchange or reverse osmosis. 
     
     
         44 . The process of  claim 36  wherein liquid carbon dioxide is used as a starter material in the methanol synthesis reaction. 
     
     
         45 . The process of  claim 36  comprising vaporizing and heating the carbon dioxide with heat from a return stream of a cooling medium. 
     
     
         46 . The process of  claim 36  comprising:
 feeding the product stream obtained in the methanol synthesis reaction to the low-pressure separator; and 
 feeding the gas stream that has been separated off in the low-pressure separator to the distillation step. 
 
     
     
         47 . The process of  claim 36  wherein the mixing and compression section includes one or more compressors or compressor stages connected in series. 
     
     
         48 . The process of  claim 36  comprising discharging a substream of the volatile components separated off in the distillation step as offgas. 
     
     
         49 . The process of  claim 36  comprising:
 feeding the product stream obtained in the methanol synthesis reaction to the high-pressure separator; 
 at least partially recirculating the gas stream that has been separated off in the high-pressure separator as recycle gas to the methanol synthesis reaction; and 
 feeding a substream from the high-pressure separator to the distillation step. 
 
     
     
         50 . The process of  claim 36  wherein the gas stream is a first gas stream, the process further comprising:
 feeding the product stream obtained in the methanol synthesis reaction to the high-pressure separator where the first gas stream is separated off from the methanol-containing product stream; 
 feeding the methanol-containing product stream to the low-pressure separator where a second gas stream is separated off from the methanol-containing product stream; 
 at least partially recirculating the first gas stream as recycle gas to the methanol synthesis reaction; and 
 feeding the second gas stream and a remainder of the methanol-containing product stream to the distillation step. 
 
     
     
         51 . The process of  claim 36  comprising supplying the mixing and compression section with carbon monoxide or hydrogen or a synthesis gas containing carbon oxides and hydrogen from outside a plant where the process occurs. 
     
     
         52 . The process of  claim 36  comprising:
 recirculating a gas stream that has been separated off in the distillation step to the mixing and compression section; and 
 recirculating water that has been separated off in the distillation step as process water for electrolytic production of hydrogen. 
 
     
     
         53 . The process of  claim 36  comprising:
 recirculating a gas stream that has been separated off in the distillation step into the mixing and compression section where the gas stream is compressed in a first compressor or a first compressor stage, which generates a compressed recirculated stream; 
 combining at least one of the carbon dioxide or the hydrogen as feed gases with the compressed recirculated stream, which generates a resulting combined mixture; 
 feeding the resulting combined mixture to a second compressor or a second compressor stage; and 
 feeding the resulting combined mixture, after the second compressor or the second compressor stage, to the methanol synthesis reaction. 
 
     
     
         54 . The process of  claim 36  comprising supplying the mixing and compression section from outside a plant where the process occurs with carbon monoxide or hydrogen or a synthesis gas containing carbon oxides and hydrogen, hydrogen produced by electrolysis, gaseous carbon dioxide produced from cryogenic dioxide by vaporization, and/or a stream of the volatile components that has been separated off in the distillation step and recirculated. 
     
     
         55 . A plant for preparing methanol by reaction of carbon dioxide with hydrogen, the plant comprising:
 a reactor unit for synthesis of methanol;   a first separation apparatus located downstream of the reactor unit, the first separation apparatus for separating off volatile and/or liquid constituents from a methanol-containing product stream;   a second separation apparatus located downstream of the first separation apparatus, the second separation apparatus for separating off volatile constituents and water by distillation; and   a return conduit connected to the second separation apparatus for at least partial recirculation of a gas stream separated off in the second separation apparatus to a region upstream of the reactor unit.   
     
     
         56 . The plant of  claim 55  comprising:
 an offgas conduit connected to the second separation apparatus for at least partial discharge of an offgas stream; and 
 an apparatus for catalytic offgas purification of at least one of the offgas stream or a purge gas stream to be discharged, wherein the apparatus for catalytic offgas purification is indirectly or directly in active communication with the reactor unit via the offgas conduit. 
 
     
     
         57 . The plant of  claim 56  comprising at least one of:
 a gas conduit from a high-pressure separator to the apparatus for catalytic offgas purification, 
 a gas conduit from a low-pressure separator to the apparatus for catalytic offgas purification, or 
 a gas conduit from a distillation apparatus to the catalytic offgas purification. 
 
     
     
         58 . The plant of  claim 55  comprising:
 an electrolysis apparatus for producing hydrogen from water; and 
 means for feeding the hydrogen produced by way of the electrolysis apparatus to the reactor unit for the synthesis of methanol. 
 
     
     
         59 . The plant of  claim 58  comprising a compressor disposed between the electrolysis apparatus and the reactor unit. 
     
     
         60 . The plant of  claim 58  comprising:
 an apparatus for treating water by removing substances dissolved in the water; and 
 means for feeding the treated water to the electrolysis apparatus. 
 
     
     
         61 . The plant of  claim 55  wherein the first separation apparatus comprises a high-pressure separator that is located downstream of the reactor unit and is configured to separate gaseous constituents from the methanol-containing product stream. 
     
     
         62 . The plant of  claim 55  wherein the first separation apparatus comprises a low-pressure separator that is located downstream of the reactor unit and is configured to separate liquid and/or gaseous constituents from the methanol-containing product stream. 
     
     
         63 . The plant of  claim 55  wherein the second separation apparatus comprises a distillation apparatus and the return conduit for recirculating the gas stream that has been separated off in the distillation apparatus to the region upstream of the reactor unit. 
     
     
         64 . The plant of  claim 55  comprising:
 an apparatus for providing carbon dioxide; 
 a vaporizer located downstream of the apparatus for providing carbon dioxide; 
 a compressor located downstream of the vaporizer; and 
 means for feeding carbon dioxide from the vaporizer and/or the compressor to the reactor unit. 
 
     
     
         65 . The plant of  claim 55  comprising a return conduit that extends from a high-pressure separator and conveys gases to an entry region of the reactor unit and a compressor disposed in a flow path between the high-pressure separator and the entry region of the reactor unit. 
     
     
         66 . The plant of  claim 65  comprising a branch conduit branching off from the return conduit for feeding a substream of volatile constituents separated off in the high-pressure separator into a top region of a distillation apparatus. 
     
     
         67 . The plant of  claim 66  wherein the branch conduit opens into a conduit that serves to feed volatile constituents separated off in a low-pressure separator into the top region of the distillation apparatus. 
     
     
         68 . The plant of  claim 55  comprising a mixing and compression section that is disposed upstream of the reactor unit and is in active communication with the reactor unit, wherein the mixing and compression section includes one or more compressors or compressor stages and that mixes and compresses a carbon dioxide gas stream supplied from a vaporizer with a hydrogen gas stream produced by electrolysis of water and/or a feed gas stream comprising carbon dioxide and or carbon monoxide and/or hydrogen and/or a synthesis gas from outside the plant. 
     
     
         69 . The plant of  claim 55  comprising a store for hydrogen that is disposed downstream of an electrolysis apparatus for producing hydrogen from water. 
     
     
         70 . The plant of  claim 55  comprising an offgas conduit connected to the second separation apparatus for at least partial discharge of an offgas stream.