CO2 Buffer Vessel Control for Stable Syngas Ratio During Upsets
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Solution Overview
Problem
The industry faces challenges in maintaining the hydrogen to carbon monoxide ratio in syngas during upset conditions, such as a reduction or interruption of carbon dioxide flow, which affects the efficiency and economy of syngas production in Steam Methane Reformer (SMR) plants.
Innovation Solution
A system that detects reductions in carbon dioxide flow using sensors and a controller to adjust valve openings and activate a composition adjustment unit, ensuring the syngas composition ratio is maintained by importing more CO2, adjusting hydrocarbon and steam flow, and utilizing backup streams to mitigate fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If carbon dioxide is imported into the SMR to maintain hydrogen to carbon monoxide ratio, then the syngas composition ratio is improved, but the system becomes vulnerable to flow interruption and reliability deteriorates
Solution Approach 1:
The patent applies preliminary action by storing carbon dioxide in a buffer vessel before it is needed. The buffer vessel is pre-filled with CO2 from alternative sources (flue gas or imported) so that when the primary imported CO2 stream is interrupted, the reformer can immediately draw from the buffer vessel without composition disruption. This anticipatory storage resolves the contradiction by ensuring composition stability (improving manufacturing precision) while protecting against flow interruption (improving reliability).
Solution Approach 2:
The buffer vessel acts as an intermediary between alternative CO2 sources and the reformer. Instead of directly connecting flue gas or imported CO2 streams to the reformer, the buffer vessel mediates by receiving CO2 from these sources and supplying it to the reformer at a steady rate. This intermediary buffer resolves the contradiction by decoupling the reformer from direct dependence on any single CO2 source, thereby maintaining syngas composition ratio while improving system reliability during interruptions.
2Reliability
If a buffer vessel is added to store carbon dioxide, then reliability during flow interruption is improved, but device complexity increases
Solution Approach 1:
The buffer vessel is designed with multi-functionality to justify its addition. It serves multiple purposes: (1) storing CO2 from alternative sources, (2) providing steady CO2 supply to the reformer during interruptions, (3) acting as a mixing chamber for CO2 from different sources, and (4) providing a buffer that can be drawn upon during composition upsets. This multi-functionality resolves the contradiction by making the added device (buffer vessel) perform several critical functions simultaneously, thereby improving reliability without proportionally increasing complexity.
Solution Approach 2:
The buffer vessel system is designed to be self-regulating to minimize control complexity. The level controller automatically manages CO2 transfer from the buffer vessel to the reformer based on vessel level, and the system can automatically switch between different CO2 sources (imported vs. flue gas) without complex external control. This self-service capability resolves the contradiction by providing reliable operation during interruptions while keeping the control system relatively simple.
Data Source
AI summary
A method of maintaining a syngas composition ratio during an upset condition, including detecting a reduction in the import carbon dioxide flow rate with a carbon dioxide import stream flow sensor, evaluating the reduction in carbon dioxide flow rate or carbon dioxide pressure in a controller, performing one or more predetermined corrective actions as instructed by the controller. Wherein the predetermined corrective actions are chosen from the following: opening a CO2 import stream flow valve, opening a hydrocarbon and steam stream feed valve, opening a CO2 backup stream control valve, opening a syngas backup letdown valve, and starting a composition adjustment unit.