Partial Moderator Bypass for IGCC Gasifier Optimization
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Solution Overview
Problem
In integrated gasification combined-cycle (IGCC) systems, the use of excess water moderator in gasifiers leads to cooling of syngas below the slag fusion point, resulting in higher oxygen consumption and decreased syngas production, while recycling CO2 is necessary for increased CO content but also affects syngas production.
Innovation Solution
A partial moderator bypass system is introduced, featuring a secondary reaction chamber that mixes moderator with gaseous byproducts and unburned carbon to increase fuel gas concentration, and a carbon dioxide recycle system to enhance CO content, allowing for optimized syngas production by controlling temperature and oxygen usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If excess water moderator is fed to the gasifier to achieve pumpable slurry concentration and high hydrogen content syngas, then slurry concentration and hydrogen content are improved, but syngas temperature drops below slag fusion point resulting in higher oxygen consumption and decreased syngas production
Solution Approach 1:
The gasifier is divided into two separate reaction chambers: a primary reaction zone for partial oxidation and a secondary reaction chamber for additional moderation. This segmentation allows the primary zone to maintain high temperature for slag fusion and initial syngas production, while the secondary chamber provides the necessary moderation to achieve pumpable slurry concentration without cooling the primary reaction zone below the slag fusion point.
Solution Approach 2:
A bypass stream of moderator is introduced as an intermediary element that connects the moderator supply to the secondary reaction chamber. This bypass stream allows precise control of the moderator flow rate to achieve the desired slurry concentration while preventing excessive cooling of the syngas in the primary reaction zone, thereby maintaining optimal temperature for slag fusion and syngas production.
2Quantity of substance
If excess water moderator is fed to the gasifier to achieve high hydrogen content syngas, then hydrogen content is improved, but syngas temperature drops below slag fusion point resulting in higher oxygen consumption
Solution Approach 1:
The gasifier is divided into two separate reaction chambers: a primary reaction zone for partial oxidation and a secondary reaction chamber for additional moderation. This segmentation allows the primary zone to maintain high temperature for slag fusion and initial syngas production, while the secondary chamber provides the necessary moderation to achieve pumpable slurry concentration without cooling the primary reaction zone below the slag fusion point.
Solution Approach 2:
The system changes the temperature parameter distribution by introducing a bypass stream of moderator that selectively cools the secondary reaction chamber while maintaining the primary reaction zone temperature above the slag fusion point. This parameter change allows the system to achieve high hydrogen content through additional moderation without the penalty of increased oxygen consumption that would result from cooling the primary zone.
3Quantity of substance
If CO2 is recycled to the gasifier to increase CO content and syngas lower heating value, then CO content and LHV are improved, but syngas production is affected
Solution Approach 1:
The recycled CO2 is introduced as an intermediary substance into the secondary reaction chamber where it participates in gasification reactions to increase CO content and syngas lower heating value. The bypass stream configuration ensures that the CO2 addition does not excessively cool the primary reaction zone, thereby maintaining optimal temperature for slag fusion and preventing the decrease in overall syngas production that would otherwise occur.
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 enhances syngas production by maintaining optimal temperatures and reducing oxygen consumption, thereby improving the efficiency and output of IGCC systems.
Implementation Method 1
a partial oxidation reactor including an inlet and an outlet and a primary reaction zone extending therebetween, the partial oxidation reactor configured to direct a flow of products of partial oxidation
Implementation Method 2
known gasifiers convert a mixture of fuel, air or oxygen, steam, and/or limestone into an output of partially oxidized gas, sometimes referred to as 'syngas'
Implementation Method 3
Exhaust from at least some known gas turbine engines is supplied to a heat recovery steam generator that generates steam for driving a steam turbine
Data Source
AI summary
Methods and systems for a gasifier having a partial moderator bypass are provided. The gasifier includes a partial oxidation reactor including an inlet and an outlet and a primary reaction zone extending therebetween, the partial oxidation reactor configured to direct a flow of products of partial oxidation including fuel gases, gaseous byproducts of partial oxidation, and unburned carbon, and a secondary reaction chamber coupled in flow communication with the partial oxidation reactor, the secondary reaction chamber is configured to mix a flow of moderator with the flow of gaseous byproducts of partial oxidation and unburned carbon such that a concentration of fuel gases is increased.