Methanol Synthesis Gas Compression via Liquid Expansion Energy Recovery
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Solution Overview
Problem
Methanol production from synthesis gas with high inert components leads to increased reactor load, pressure drop, and higher energy consumption due to the need for larger compressors and increased operating costs, making it economically and technically challenging without prior separation of inert components.
Innovation Solution
A process that compresses synthesis gas, converts it into methanol using a catalyst, separates the product stream, and then expands the raw methanol stream to generate mechanical or electrical energy, which is used to drive the synthesis gas compression, thereby reducing external energy requirements and minimizing inert component accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high recycling rates are applied in conventional single-stage methanol syntheses, then carbon conversion yield is improved, but inert components accumulate at the reactor inlet, significantly increasing reactor load and pressure drop
Solution Approach 1:
The patent extracts and removes inert gas components from the synthesis gas stream before they can accumulate in the reactor. This is achieved through a gas separation unit that selectively removes inert gases (such as nitrogen, argon, or methane) from the recycled synthesis gas, preventing their accumulation and the associated increase in reactor load and pressure drop while maintaining high recycling rates for improved carbon conversion yield
Solution Approach 2:
The patent changes the composition parameter of the synthesis gas by dynamically adjusting the inert gas content in the recycled stream. By controlling the removal rate of inert components, the system maintains optimal gas composition for methanol synthesis, enabling high recycling rates without the detrimental accumulation effects that would otherwise occur
2Productivity
If high recycling rates are applied, then carbon conversion yield is improved, but load on synthesis gas and recycle gas compressors increases, leading to higher operating costs
Solution Approach 1:
The patent extracts inert gas components from the recycle stream, reducing the total volume of gas that needs to be compressed and recirculated. This extraction before compression significantly reduces the workload and energy consumption of both the synthesis gas compressor and the recycle gas compressor, while still maintaining high recycling rates for improved carbon conversion
Solution Approach 2:
The patent converts the harmful effect of inert gas accumulation into a beneficial separation process. By intentionally removing inert gases that would otherwise be harmful to compressor performance and energy efficiency, the system achieves both high carbon conversion through recycling and reduced energy consumption, as the separated inert gases can be disposed of or utilized elsewhere
3Device complexity
If feed gas is not purified before methanol synthesis, then complex separation process is avoided, but inert components accumulate and increase reactor load and operating costs
Solution Approach 1:
The patent applies preliminary action by performing inert gas removal from the recycle stream before the gas enters the reactor. This prevents inert component accumulation proactively, maintaining optimal reactor conditions and high methanol production efficiency without requiring complex pre-purification of the fresh feed gas, thus balancing device complexity with productivity
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 process reduces the energy needed for the synthesis gas compressor, allows for efficient methanol production with high inert components without prior separation, and decreases operational and investment costs by utilizing internal energy recovery.
Implementation Method 1
expanding at least a portion of the crude methanol stream in a liquid expansion device to a pressure lower than the synthesis pressure, wherein the liquid expansion device performs mechanical work
Implementation Method 2
transferring at least a portion of the mechanical work performed by the liquid expansion device to the synthesis gas compression device to drive the synthesis gas compression device, or converting at least a portion of the mechanical work performed by the liquid expansion device into electrical energy and using the electrical energy to drive the synthesis gas compression device
Implementation Method 3
Compressing the synthesis gas stream to synthesis pressure in a synthesis gas compression device
Implementation Method 4
Converting the compressed synthesis gas stream over a methanol synthesis catalyst to a product stream
Implementation Method 5
Separating the product stream in the phase separation device into a liquid crude methanol stream comprising at least methanol and water, and a residual gas stream
Data Source
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AI summary
The invention relates to a process for the production of methanol, in which at least a portion of the resulting liquid crude methanol stream is expanded in a liquid expansion device to an expansion pressure, wherein the expansion pressure is lower than the synthesis pressure, and wherein the liquid expansion device performs mechanical work. At least a portion of the mechanical work performed by the liquid expansion device is used to drive the synthesis gas compression device required for compressing the synthesis gas to the synthesis pressure. This utilization can be indirect, through the generation of electrical energy, or direct, through the direct use of the mechanical work.