Methanol Synthesis via Partial Oxidation and Water-Gas Shift
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Solution Overview
Problem
Current methanol production methods from non-catalytic partial oxidation (PDX) face challenges with sub-stoichiometric synthesis gas, leading to hydrogen deficiency, which increases investment and production costs, especially in smaller plants, due to the need for complex equipment and inefficient carbon utilization.
Innovation Solution
A method and apparatus that utilize a partial oxidation (PDX) process followed by a water-gas shift reactor to convert carbon monoxide and water into hydrogen and carbon dioxide, then combine the shifted synthesis gas with a recycle stream to achieve stoichiometric balance, reducing equipment complexity and costs by using a single recycle compressor and common steam drum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If non-catalytic partial oxidation (PDX) is used to produce synthesis gas, then capital expenditure and equipment complexity are reduced, but the synthesis gas becomes sub-stoichiometric with hydrogen deficiency
Solution Approach 1:
The patent applies parameter changes by adjusting the stoichiometric number of the synthesis gas through controlled blending of PDX effluent with hydrogen-rich streams. By varying the composition parameters (hydrogen content, stoichiometric number) rather than changing the entire process configuration, the system achieves suitable gas composition for methanol synthesis while maintaining equipment simplicity. The blending ratio is optimized to reach SN=2.0 while minimizing additional equipment requirements.
Solution Approach 2:
The patent introduces an intermediary approach by using a water-gas shift reactor as a mediating unit between the PDX process and methanol synthesis. This intermediary reactor converts CO and H2O into H2 and CO2, effectively increasing hydrogen content without requiring complex catalytic reforming equipment. The shift reactor serves as a bridge that transforms the sub-stoichiometric PDX output into suitable feed for methanol synthesis.
2Quantity of substance
If catalytic steam reforming with multiple steps is used to achieve stoichiometric balance, then hydrogen content is sufficient, but capital expenditure and investment costs increase significantly
Solution Approach 1:
The patent extracts the essential function of hydrogen production from the complex multi-step catalytic reforming process. By isolating and using only the water-gas shift reaction (which can be performed in a simple reactor without complex catalytic systems), the invention removes the need for pre-reforming, primary reforming, and secondary reforming equipment. This extraction approach maintains sufficient hydrogen content while dramatically reducing equipment complexity and capital expenditure.
Solution Approach 2:
The patent employs a simpler, more economical water-gas shift reactor instead of expensive, complex catalytic reforming equipment. The shift reactor is a more economical alternative that achieves the necessary hydrogen production through a single reaction step rather than multiple catalytic stages. This substitution of a cheaper, simpler unit operation reduces investment costs while maintaining process effectiveness.
3Quantity of substance
If hydrogen recovery units or membranes are used to adjust hydrogen content, then stoichiometric balance is achieved, but carbon efficiency deteriorates and large amounts of tail gas are produced
Solution Approach 1:
The patent converts the harmful effect of CO in the PDX effluent into a beneficial source of hydrogen through the water-gas shift reaction. Instead of treating CO as an impurity to be removed (which would produce tail gas and reduce carbon efficiency), the invention uses CO as a reactant in the shift reaction to generate additional hydrogen. This approach transforms a potential problem into a solution, improving hydrogen content while maintaining carbon efficiency by utilizing all carbon-containing gases productively.
4Quantity of substance
If recycle ratio is reduced to increase hydrogen amount, then stoichiometry improves, but carbon efficiency decreases and fresh synthesis gas demand increases
Solution Approach 1:
The patent applies preliminary action by increasing hydrogen content through the water-gas shift reaction before the synthesis gas enters the methanol synthesis loop. By pre-adjusting the stoichiometric number and hydrogen content in advance, the system eliminates the need for subsequent hydrogen recovery operations and reduces the requirement for fresh synthesis gas make-up. This preliminary hydrogen enrichment improves both stoichiometry and carbon efficiency by minimizing material losses throughout the process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively increases hydrogen content in the synthesis gas, optimizing stoichiometry and reducing production costs by utilizing heat from reaction for steam production, making it suitable for smaller plants and modular plants.
Implementation Method 1
passing, in a water-gas shift reactor, the synthesis gas over a water-gas shift catalyst to convert at least a portion of carbon monoxide (CO) and water (H2O) into hydrogen (H2) and carbon dioxide (CO2)
Implementation Method 2
producing, in a partial oxidation (PDX) chamber, the synthesis gas having a stoichiometric number of less than substantially 1.8 by performing a partial oxidation (PDX) process with a hydrocarbon stream and an oxygen stream
Data Source
AI summary
A method and apparatus for producing methanol from a synthesis gas is provided. The method includes (i) producing, in a partial oxidation chamber, the synthesis gas having a stoichiometric number of less than 1.8 by performing a partial oxidation process with a hydrocarbon stream and an oxygen stream, (ii) passing, in a water-gas shift reactor, the synthesis gas over a water-gas shift catalyst to convert at least a portion of carbon monoxide and water into hydrogen and carbon dioxide, (iii) producing a dry, shifted synthesis gas by separating liquid condensate from shifted synthesis gas, (iv) combining, in a recycle compressor, the dry, shifted synthesis gas with a recycle synthesis gas comprised of unreacted synthesis gas and a hydrogen rich product to form a mixed synthesis gas stream, and (v) converting, in a cooled methanol synthesis reactor, at least a portion of the mixed synthesis gas stream into methanol.