Low-Stoichiometry Methanol Synthesis With Recycled Gas
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Solution Overview
Problem
Existing methanol synthesis processes face challenges with high by-product formation when using synthesis gases with stoichiometry numbers below 2.0, leading to low selectivity and increased energy consumption due to the formation of by-products with similar physical properties, making it difficult to obtain pure methanol.
Innovation Solution
A process that involves recycling unreacted synthesis gas to adjust the stoichiometry number to 0.80 to 2.20, maintaining a maximum catalyst bed temperature of 280°C or lower, and controlling carbon monoxide concentration at 20% or less, along with a multi-reactor concept for methanol synthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If synthesis gas with stoichiometry number below 2.0 is used for methanol synthesis, then the process can handle low stoichiometry synthesis gases including those rich in carbon dioxide, but by-product formation increases significantly leading to low selectivity
Solution Approach 1:
The invention changes the operating parameters by limiting the maximum catalyst bed temperature to ≤ 280 °C and controlling the stoichiometry number SN to 0.80-2.20, which allows the use of low stoichiometry synthesis gases while maintaining high selectivity and reducing by-product formation
Solution Approach 2:
The invention applies preliminary anti-action by pre-controlling the synthesis gas composition and temperature conditions before the reaction occurs, preventing excessive by-product formation from the outset rather than attempting to remove by-products after formation
2Adaptability or versatility
If synthesis gas with stoichiometry number below 2.0 is used, then the process flexibility increases, but the formation of by-products with similar physical properties increases making separation difficult
Solution Approach 1:
By controlling the maximum catalyst bed temperature to ≤ 280 °C and stoichiometry number SN to 0.80-2.20, the invention reduces by-product formation at the source, making subsequent separation easier even when using flexible low stoichiometry synthesis gases
Solution Approach 2:
The invention converts the potential harm of low stoichiometry synthesis gas (which normally causes high by-product formation) into a benefit by establishing specific temperature and composition parameters that enable the use of such gases while maintaining high selectivity
3Ease of manufacture
If conventional methanol synthesis is used with low stoichiometry synthesis gas, then the process can operate with unmodified synthesis gases, but by-product formation becomes so high that sufficiently pure methanol cannot be obtained
Solution Approach 1:
The invention changes the critical parameters of maximum catalyst bed temperature (≤ 280 °C) and stoichiometry number (0.80-2.20) to simultaneously achieve easy operation with unmodified synthesis gases and high methanol purity through reduced by-product formation
4Loss of energy
If high by-product concentrations are present in crude methanol, then the thermal separation process energy consumption increases and methanol loss increases, but conventional processes cannot avoid this when using low stoichiometry synthesis gases
Solution Approach 1:
By establishing specific parameters (maximum catalyst bed temperature ≤ 280 °C, stoichiometry number 0.80-2.20), the invention produces crude methanol with low by-product concentrations, reducing both energy consumption and methanol loss in subsequent separation processes
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 significantly reduces by-product formation to less than 10,000 ppm, achieving high hydrogen conversion rates of 80% or more, suitable for synthesis gases with low stoichiometry, and allows the use of unmodified synthesis gases, including those rich in carbon dioxide.
Implementation Method 1
Passing the synthesis gas at elevated pressure and elevated temperature through a catalyst bed of a methanol synthesis catalyst to convert the synthesis gas to methanol
Implementation Method 2
Cooling the product stream to condense and separate crude methanol comprising at least methanol and water from the cooled product stream
Data Source
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AI summary
The invention relates to a process for the production of methanol, in which a synthesis gas containing carbon oxides and hydrogen is provided, which is passed at elevated pressure and temperature through a catalyst bed of a methanol synthesis catalyst to convert the synthesis gas to methanol, yielding a product stream comprising crude methanol and unreacted synthesis gas, and the product stream is cooled for condensation and separation of crude methanol containing at least methanol and water. Unreacted synthesis gas is returned to the inlet of the catalyst bed and combined with the synthesis gas, resulting in a mixed synthesis gas which is passed through the catalyst bed at elevated pressure and temperature.According to the invention, the mixed synthesis gas at the inlet of the catalyst bed has a stoichiometry number SN of ≥ 0.80, the catalyst bed has a maximum catalyst bed temperature of ≤ 280 °C during the conversion of the mixed synthesis gas to methanol, and the mixed synthesis gas has a carbon monoxide concentration of ≤ 20 vol.% at the inlet of the catalyst bed. The combination of these parameters effectively suppresses the formation of byproducts.