Cold Box Reboiler Control for Low-Loss Carbon Monoxide Recovery
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Solution Overview
Problem
Conventional methods for separating carbon monoxide from syngas mixtures lack independent control of reboiler duties, leading to increased recirculation and compression of recycle streams, larger compressor requirements, and susceptibility to liquid level excursions in cryogenic separation processes.
Innovation Solution
The method involves cooling and partially condensing syngas in a primary heat exchanger, separating it into hydrogen-rich vapor and carbon monoxide-rich liquid streams, and controlling reboiling duties for independent operation of hydrogen removal and carbon monoxide/methane separation columns, allowing for precise control of reflux flow and reducing equipment size and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional cryogenic separation methods are used without independent reboiler control, then the separation process can operate, but recirculation and compression of recycle streams increase and compressor size requirements increase
Solution Approach 1:
The patent applies parameter changes by independently controlling reboiler duties through separate feed streams, adjusting the thermal parameters of the separation process to optimize component distribution between liquid and vapor phases, thereby reducing recirculation requirements
Solution Approach 2:
The patent segments the reboiler control system into independent control zones, where each reboiler receives a separate controlled feed stream. This segmentation allows independent adjustment of reboiling rates for different separation sections, optimizing the overall process and reducing unnecessary recirculation
2Productivity
If conventional cryogenic separation methods are used without independent reboiler control, then the separation process can operate, but compressor size requirements increase
Solution Approach 1:
By independently controlling reboiler duties through parameter adjustment of separate feed streams, the patent optimizes the vapor-liquid equilibrium conditions, reducing the quantity of gas requiring compression and thereby decreasing compressor size requirements
Solution Approach 2:
The segmentation of reboiler control allows each compression section to be sized according to its specific requirements rather than accommodating maximum recirculation flows, leading to more efficient and smaller compressor installations
3Device complexity
If column operating levels are adjusted to control reboiling amount, then recirculation flows and equipment sizing can be minimized, but the system becomes susceptible to high or low level excursions and liquid level loss during upsets
Solution Approach 1:
The patent provides beforehand cushioning by maintaining columns at optimal control levels with independent reboiler control, creating a buffer that prevents level excursions and liquid level loss during upsets, thereby improving system reliability without requiring oversized equipment
Solution Approach 2:
The independent reboiler control system enables better feedback control of column levels, where each reboiler can be adjusted independently to maintain optimal liquid levels, preventing excursions and improving stability during process upsets
4Ease of operation
If reboiling is not independently controlled, then the process is simpler to operate, but CO losses increase and hydrogen purification equipment size increases
Solution Approach 1:
The patent applies parameter changes by controlling reboiler duties through separate feed streams, precisely adjusting the vaporization rate to minimize CO losses while maintaining effective separation, and optimizing hydrogen purification requirements through controlled component distribution
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 minimizes CO losses, reduces the size and power requirements of hydrogen purification equipment, and enhances the efficiency of carbon monoxide recovery by allowing direct and independent control of reboilers, thereby optimizing the separation process and reducing operational and capital expenses.
Implementation Method 1
cooling and partially condensing the syngas feedstock containing carbon monoxide and hydrogen in a primary heat exchanger
Implementation Method 2
heating the separated cooled feed stream to provide a reboiling duty to a reboiler
Implementation Method 3
feeding the first carbon monoxide rich liquid stream to a hydrogen removal column... separating it into a second hydrogen rich vapor stream and a second carbon monoxide rich stream
Data Source
AI summary
The present invention relates to a cold box cycle which allows for independent control of the heat supplied for reboilers associated with the separation columns. More specifically, the invention relates to the tight control of the hydrogen removal separation, thus avoiding the possibility of excess reboiling in this separation. Optimal reboiling also results in a lower temperature of the hydrogen depleted liquid from this separation. As this stream is used to provide a portion of the cooling at the cold end of the primary heat exchanger, lower temperatures facilitate cooling of the incoming syngas feed, reducing carbon monoxide (CO) losses into the crude hydrogen stream from the high pressure separator. Lower CO in the crude hydrogen allows for smaller hydrogen purification equipment.