FCC Residual Gas CO Oxidation for Easier CO2 Separation
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Solution Overview
Problem
Current methods for CO2 capture in fluidized bed catalytic cracking installations are inefficient and water-intensive, particularly in oxycombustion modes, which are hesitant to adopt due to significant process modifications and energy balance adjustments.
Innovation Solution
The process involves converting carbon monoxide in waste gas to CO2 through combustion with an oxygen-rich gas, followed by adsorption and separation to enrich CO2 concentration, using a combination of conversion, adsorption, and distillation to produce a CO2-rich stream, which is then further processed for easier capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If amine scrubbing is used to capture CO2 from waste gas, then CO2 removal efficiency is improved, but water consumption increases significantly
Solution Approach 1:
The patent applies preliminary action by converting carbon monoxide to carbon dioxide in a combustion chamber before the gas enters the absorption column. This pre-conversion step enriches the CO2 concentration in the waste gas, making the subsequent amine scrubbing process more efficient and reducing water consumption by approximately 50% compared to treating raw waste gas directly
Solution Approach 2:
The patent changes the chemical composition parameter of the waste gas by converting CO to CO2 through combustion with oxygen-rich gas. This parameter change increases the CO2 concentration from typical FCC waste gas levels (10-20%) to higher concentrations (20-35%), thereby improving absorption efficiency and reducing water requirements
2Quantity of substance
If oxycombustion mode is implemented in FCC, then CO2 concentration in waste gas is improved, but process complexity and modification requirements increase
Solution Approach 1:
The patent extracts the CO combustion conversion step from the traditional oxycombustion concept and places it in a separate combustion chamber before the absorption column. This extraction allows the FCC unit to operate in conventional mode while still achieving CO2 enrichment, avoiding the need to modify the core FCC process and reducing overall system complexity
Solution Approach 2:
The patent introduces an intermediary combustion chamber that converts CO to CO2 before the gas enters the absorption system. This intermediary step acts as a bridge, achieving CO2 concentration enhancement without requiring direct integration of oxygen enrichment into the FCC regenerator, thereby simplifying the overall process
3Quantity of substance
If CO is converted to CO2 by combustion with air, then CO2 concentration is improved, but nitrogen content increases and capture efficiency decreases
Solution Approach 1:
The patent uses oxygen-rich gas (pure oxygen or oxygen-enriched air containing 21-96% O2) as the oxidant in the combustion chamber instead of ordinary air. This strong oxidant approach converts CO to CO2 with minimal nitrogen introduction, maintaining higher CO2 concentration in the waste gas and improving subsequent capture efficiency in the absorption column
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 method increases CO2 concentration in the waste gas, simplifying downstream capture and improving efficiency and cost-effectiveness without significant modifications to the existing FCC process.
Implementation Method 1
At least a portion of the carbon monoxide in the waste gas is converted into carbon dioxide to form a carbon dioxide-enriched stream by combustion
Implementation Method 2
At least a portion of the carbon dioxide-enriched stream from step i) is separated by adsorption to form a carbon dioxide-enriched, nitrogen-depleted gas
Implementation Method 3
at least a portion of the carbon dioxide-enriched, nitrogen-depleted gas is separated in a separation apparatus (30) by separation at a temperature below 0°C by partial condensation and/or by distillation to form a carbon dioxide-rich fluid
Implementation Method 4
at least a portion of the carbon dioxide-enriched, nitrogen-depleted gas is separated in a separation apparatus (30) by separation at a temperature below 0°C by partial condensation and/or by distillation to form a carbon dioxide-rich fluid
Data Source
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AI summary
In a method for separating carbon dioxide from a residual gas (3, 11) in a fluidised bed catalytic cracking plant (1) containing carbon dioxide, nitrogen and carbon monoxide, at least a portion of the carbon monoxide in the residual gas is converted into carbon dioxide to form a flow enriched with carbon dioxide (17) by combustion, at least a portion of the flow enriched with carbon dioxide in step i) is separated in order to form a fluid that is rich in carbon dioxide (29, 35) and a fluid that is depleted of carbon dioxide (31, 37), and a gas (41) containing at least 90% oxygen is sent for combustion in step i), as is a gas (39) containing at least 40% carbon dioxide.