Ethanol Dehydration and Oxidation Process Integration
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Solution Overview
Problem
Current processes for converting ethanol to ethylene oxide are inefficient in terms of energy and water consumption, with existing methods requiring external heat transfer fluids and compression, which increases energy costs and reduces selectivity due to secondary reactions.
Innovation Solution
An integrated process that includes a pretreatment step to reduce nitrogen impurities, followed by vaporization using recycled water, and a multitubular reactor for oxidation, where thermal energy from the oxidation step is used to compress and heat the dehydration load, minimizing external energy input and water usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If external heat transfer fluid (water vapor) is introduced into the dehydration reactor to provide necessary heat, then the temperature of the catalytic bed can be maintained at a level compatible with desired conversions, but the investment cost and operational cost increase due to additional equipment and external water vapor requirements
Solution Approach 1:
The patent combines the heat transfer function with the reaction medium itself by using recycled ethylene and process water vapor as the heat transfer fluid. This eliminates the need for separate external heat transfer systems and reduces equipment complexity while maintaining the necessary catalytic bed temperature for ethanol dehydration conversion.
Solution Approach 2:
The process uses its own effluent (recycled ethylene and process water vapor) to provide the heat necessary for the dehydration reaction. This self-service approach eliminates dependency on external heat sources and reduces both investment and operational costs associated with external heat transfer systems.
2Use of energy by moving object
If ethylene effluent is recycled and mixed with feed to provide heat, then the heat necessary for dehydration is supplied, but the selectivity decreases due to increased ethylene concentration promoting secondary reactions (oligomerization, hydrogen transfer, disproportionation)
Solution Approach 1:
The patent applies different quality requirements to different parts of the system: fresh ethylene feed is introduced at the reactor inlet where conversion is needed, while recycled ethylene is used in the heat exchanger where only heat transfer is required. This local differentiation allows heat recovery without compromising reaction selectivity in the dehydration zone.
Solution Approach 2:
The patent extracts the heat transfer function from the reaction zone by using a separate heat exchanger loop. Recycled ethylene circulates through the heat exchanger to provide heat, then returns to the reactor feed stream after transferring its thermal energy, thus separating the heating function from the reaction function and preventing selectivity loss.
3Productivity
If pressure is increased to 20-40 atm for dehydration reaction, then the reaction efficiency improves, but the equipment requirements and operational complexity increase
Solution Approach 1:
The patent optimizes the pressure parameter by operating at moderately elevated pressures (2-10 bar gauge) rather than extremely high pressures. This parameter change maintains adequate reaction efficiency while significantly reducing equipment complexity and operational requirements compared to conventional high-pressure processes.
4Productivity
If multiple compression stages are used to achieve required pressure and temperature, then the dehydration and oxidation processes can be integrated, but the energy consumption and equipment investment increase
Solution Approach 1:
The patent implements continuous heat recovery and recycling throughout the process. Ethylene effluent is continuously recycled through the heat exchanger to preheat and pressurize the feed stream, creating a continuous cycle of useful action that eliminates the need for multiple separate compression stages and reduces overall energy consumption.
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 integrated process reduces energy and water consumption, enhances mechanical energy efficiency, and maintains high selectivity by utilizing internal heat recovery and recycling, thereby improving the overall conversion efficiency of ethanol to ethylene oxide.
Implementation Method 1
heat exchange with the effluent from the dehydration reactor
Implementation Method 2
vaporizing the ethanol feed mixed with at least part of the water produced by the dehydration of the ethanol
Implementation Method 3
dehydration of the ethanol feed in the presence of a dehydration catalyst
Implementation Method 4
The dehydration reaction of ethanol to ethylene has been known and detailed since the end of the 19th century
Implementation Method 5
oxidizing the ethylene thus produced... step for oxidizing the ethylene produced, characterized in that said oxidation step is carried out in the presence of a oxidation catalyst
Implementation Method 6
oxidation step is carried out in the presence of a oxidation catalyst
Implementation Method 7
compressor driven by a condensation turbine taking in the suction the vaporized quench flow in the oxidation section
Implementation Method 8
compressor driven by a condensation turbine
Data Source
Figure 1
AI summary
The invention concerns a method for dehydrating an ethanol feedstock into ethylene, then oxidising the ethylene into ethylene oxide, comprising a step of vaporising a feedstock comprising said ethanol feedstock and at least a portion of a stream of dilution water comprising recycled ethanol so as to produce a vaporised feedstock, a step of compressing in a compressor driven by a condensing turbine driven by the steam generated by the oxidation step, a step of dehydrating a mixture comprising said compressed vaporised feedstock, a step of separating the effluent from the dehydration step into an effluent comprising ethylene and an effluent comprising water, a step of purifying at least a portion of the effluent comprising water and separating same into at least one stream of treated water and one stream of dilution water comprising ethanol, the latter being recycled upstream from the vaporisation step, and a step of oxidising the ethylene in the effluent comprising ethylene into ethylene oxide, this oxidation step comprising at least one tubular oxidation reactor cooled by vaporising a quenching stream, said vaporised quenching stream being used to drive a condensing turbine.