Methanol Synthesis Gas Compression with Recycle Integration
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Solution Overview
Problem
Current methanol production processes face challenges with high energy consumption for gas compressors, increased system parts and costs, hydrogen losses, catalyst deactivation due to high water partial pressure, and high recirculation rates of synthesis gas, especially with high CO2 content, leading to increased investment and operating costs.
Innovation Solution
A process involving a feed gas with at least 80% carbon dioxide, pre-compression of fresh gas, and subsequent compression with recycle gas to synthesis pressure in multiple reactor stages, where unreacted synthesis gas is recycled directly to the compressor stage without additional compression, reducing recirculation and compressor power, and optimizing stoichiometry to minimize hydrogen usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high recirculation rates are used to achieve high conversion with high CO2 content synthesis gas, then conversion efficiency is improved, but energy consumption and operating costs increase significantly
Solution Approach 1:
The synthesis process is divided into multiple reactor stages (first reactor stage, second reactor stage, etc.) with intermediate condensation steps. This segmentation allows the reaction to proceed in steps, achieving high overall conversion without requiring high recirculation rates, thereby reducing energy consumption.
Solution Approach 2:
Intermediate condensation is performed between reactor stages to remove methanol from the gas phase. This phase transition shifts the equilibrium toward product formation, enabling high conversion with lower recirculation rates and reduced energy consumption.
2Productivity
If high recirculation rates are used to process high CO2 content synthesis gas, then conversion is improved, but system complexity and investment costs increase
Solution Approach 1:
The process is segmented into multiple reactor stages with intermediate condensation, eliminating the need for complex high-volume recirculation systems. This reduces device complexity while maintaining high conversion through staged reaction and equilibrium shift.
3Productivity
If multiple reactor stages with intermediate condensation are used to reduce recirculation rate, then recirculation rate is reduced, but device complexity and investment costs increase
Solution Approach 1:
The condensation units are integrated between reactor stages within the same process train, merging the reaction and separation functions into a cohesive system. This approach reduces the number of separate process units compared to conventional designs while achieving lower recirculation rates.
4Stress or pressure
If synthesis gas is pressurized using a gas compressor to over 60 bar, then reaction pressure is achieved, but energy consumption increases
Solution Approach 1:
Pressurization is segmented into multiple stages corresponding to the reactor stages. Gas is pressurized to moderate pressure in the first stage, then further pressurized between subsequent reactor stages. This segmented approach reduces the energy consumption of single-stage high-pressure compression while achieving the required reaction pressures.
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 reduces energy consumption, investment costs, hydrogen losses, and catalyst deactivation, while maintaining high carbon and hydrogen conversion rates, thereby improving the overall economics and efficiency of methanol production.
Implementation Method 1
introducing the feed gas as a first fresh gas stream into a first compressor stage for pre-compression of the first fresh gas stream, yielding a second fresh gas stream
Implementation Method 2
introducing a return gas stream and the second fresh gas stream into a second compressor stage for compression of the return gas stream and the second fresh gas stream to synthesis pressure
Implementation Method 3
Cooling of the product stream obtained from each reactor stage for condensation and separation of methanol from unreacted synthesis gas
Data Source
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AI summary
The invention relates to a process for the production of methanol and a plant for the production of methanol. A first fresh gas suitable for the production of methanol and containing high levels of carbon dioxide is pre-compressed by a first compressor stage, yielding a second fresh gas. This second fresh gas is combined with a recirculated gas stream and further compressed to synthesis pressure in a second compressor stage. By catalytically reacting the synthesis gas stream thus obtained in a plurality of reactor stages arranged in series, with intermediate condensation and separation of the crude methanol, the amount of recirculated gas in the synthesis cycle is reduced to such an extent that the recirculated gas can be directly returned to the second fresh gas stream, thereby eliminating the need for a separate recirculated gas compressor stage and reducing the overall compressor power.