MTO Effluent Heavy Hydrocarbon Separation Process
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Solution Overview
Problem
The methanol to olefins (MTO) process generates heavy hydrocarbons that cause fouling issues in heat exchangers and downstream devices due to their buildup, leading to increased costs and downtime, as they are not effectively separated from the reactor effluent.
Innovation Solution
A process that separates heavy hydrocarbons from the MTO reactor effluent by compressing the vapor stream in multiple stages, causing heavier hydrocarbons to become insoluble and form a separate phase, which is then removed in a separation vessel, reducing their recirculation and subsequent fouling, and includes a DME stripping zone and water wash zone to recover oxygenates and hydrocarbons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the water recycle loop is used to circulate liquid from the MTO effluent, then water recovery and reuse is improved, but heavy hydrocarbons concentrate and cause fouling in heat exchangers and downstream devices
Solution Approach 1:
The patent extracts heavy hydrocarbons from the water recirculation loop by introducing a dedicated extraction zone where heavy hydrocarbons are separated from the aqueous stream. This prevents their accumulation and subsequent fouling of heat exchangers while maintaining water recovery, directly resolving the contradiction between energy efficiency and fouling prevention.
Solution Approach 2:
The patent introduces an intermediary extraction zone with specific chemistry (basic conditions, organic solvent) that mediates between the water recirculation loop and the heavy hydrocarbon removal. This intermediary system enables selective separation of heavy hydrocarbons without disrupting the overall water recovery process, addressing both energy loss and fouling concerns.
2Device complexity
If heavy hydrocarbons are not removed from the MTO effluent, then the process complexity is reduced, but fouling of heat exchangers and downstream devices increases
Solution Approach 1:
The patent segments the MTO effluent treatment process by adding a dedicated extraction zone that specifically targets heavy hydrocarbon removal. This segmentation isolates the fouling problem to a specific process step, allowing effective removal without requiring complete redesign of the entire process, thus balancing complexity and reliability.
Solution Approach 2:
The patent applies preliminary action by removing heavy hydrocarbons early in the process through the extraction zone, before the effluent reaches heat exchangers and downstream devices. This proactive removal prevents fouling issues before they occur, maintaining reliability without adding excessive complexity to the overall system.
3Device complexity
If the liquid with dissolved heavy oil is sent back to the first stage suction drum, then the separation process is simplified, but heavy hydrocarbons form separate phase and require oil skimming
Solution Approach 1:
The patent takes out heavy oil from the recirculation loop through a dedicated extraction zone that uses chemical extraction with organic solvents under basic conditions. This removes dissolved heavy oil before it can form separate phases in the suction drum, eliminating the need for oil skimming while maintaining process simplicity.
Solution Approach 2:
The patent changes parameters in the extraction zone (pH to basic conditions, introduction of organic solvents, temperature control) to alter the solubility and phase behavior of heavy hydrocarbons. This prevents them from forming separate phases upon return to the suction drum, simplifying operation by eliminating oil skimming requirements.
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 buildup of heavy hydrocarbons in the water recirculation loop, improving the operability of the oxygenate stripper/absorber sections and reducing energy losses, thus enhancing the efficiency and reducing maintenance needs.
Implementation Method 1
compressing the vapor stream in a compression zone having a plurality of stages of compression
Implementation Method 2
causing heavier hydrocarbons to become insoluble and form a separate phase
Implementation Method 3
separating the first liquid stream from the product separation zone and the at least one compressed liquid stream from the compression zone in a separation vessel into a hydrocarbon liquid stream and a lean hydrocarbon water stream
Implementation Method 4
includes a DME stripping zone and water wash zone to recover oxygenates and hydrocarbons
Data Source
AI summary
A process is presented for removing the fouling problems associated with the product recovery in a methanol to olefins conversion process. The process includes passing the quenched MTO process stream to a product separator, wherein an intermediate stream is generated and includes water and heavier hydrocarbons. The intermediate stream is processed to remove the buildup of heavier hydrocarbons.