Dry Coal Feed System for Low Rank Gasification
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Solution Overview
Problem
IGCC systems face inefficiencies when processing low rank coals due to high inherent moisture content, leading to dilute coal slurries with low energy content, increased energy consumption, and higher capital costs, as excess water in the slurry decreases thermal efficiency and requires additional oxygen, resulting in less CO and H2 production per unit of coal gasified.
Innovation Solution
A fuel feed system with a feed preparation section to adjust moisture content and grind coal to a predetermined size, a pressurization and conveyance section using solids pumps to increase pressure, and a slag additive section to control water content and ash melting and flow characteristics, allowing for efficient gasification of low rank coals by optimizing coal delivery and ash management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a water-based slurry system is used to feed coal to the gasifier, then the system can handle higher rank coals like bituminous and anthracite, but it becomes less attractive for lower rank coals like sub-bituminous coals due to difficulty in producing slurries with sufficient solids concentration and energy content
Solution Approach 1:
The invention changes the physical state parameter of the coal feed from liquid slurry to dry particulate form. This parameter change enables the system to handle low rank coals with high inherent moisture content that cannot form pumpable slurries, while maintaining efficient gasification by delivering coal with controlled moisture levels (5-15%) directly to the gasifier.
2Ease of operation
If excess water is added to create a pumpable slurry, then the slurry becomes pumpable and can be fed to the gasifier, but the excess water consumes thermal energy to heat up to reaction temperature and decreases overall thermal efficiency
Solution Approach 1:
The invention extracts water from the coal feed system by transitioning from a water-based slurry to a dry feed system. Coal is ground to fine particulates and fed in a dry or minimally moist state (5-15% moisture), eliminating the excess water that would otherwise need to be heated to gasifier temperature, thereby recovering the thermal energy that would be lost.
Solution Approach 2:
The invention performs preliminary drying and size reduction of coal before gasification. Coal is ground to a fine particulate size distribution and moisture is reduced to 5-15% content before feeding to the gasifier. This preliminary preparation eliminates the need for excess water addition and subsequent energy-intensive heating of that water.
3Quantity of substance
If low rank coals with high inherent moisture content are used, then the fuel cost may be reduced, but the energy required for drying the coal increases overall energy consumption and reduces power production
Solution Approach 1:
The invention changes the moisture parameter from high (22-30% inherent moisture in low rank coals) to controlled low levels (5-15% total moisture in feed). By using dry particulate feed instead of slurry, the system eliminates the need for energy-intensive drying equipment while maintaining efficient gasification, thus avoiding the energy penalty associated with conventional drying approaches.
4Ease of operation
If a dry feed system is used to remove inherent moisture from low rank coals, then the flow characteristics improve and consolidation problems are reduced, but the system becomes more complex and expensive with additional drying equipment and storage capacity
Solution Approach 1:
The invention extracts the drying function from the system by eliminating the need for active drying equipment. Instead of using complex drying systems to remove moisture, the approach feeds coal with controlled low moisture content (5-15%) in dry particulate form, achieving good flow characteristics without the complexity and cost of drying equipment, lock hoppers, and additional storage capacity.
5Adaptability or versatility
If sub-bituminous coal slurry is fed to the gasifier, then the system can process low rank coal, but significantly more coal must be gasified compared to bituminous coal to produce the required amount of CO and H2, decreasing plant efficiency
Solution Approach 1:
The invention changes the feed state parameter from wet slurry to dry particulate with controlled moisture (5-15%). This parameter change increases the effective energy content of the feed by eliminating excess water, thereby increasing the amount of CO and H2 produced per unit of coal gasified and improving overall plant productivity when processing low rank coals.
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
The system enhances gasification efficiency by maintaining optimal moisture levels, reducing energy consumption, and minimizing capital costs by avoiding the need for extensive drying or expensive slurry-based systems, enabling more efficient CO and H2 production and improved overall plant performance.
Implementation Method 1
a feed preparation section configured to adjust a moisture content within a particulate fuel
Implementation Method 2
the particulate solids are pneumatically conveyed at high pressure directly to the gasifier feed injector
Implementation Method 3
a gasification system that includes a gasifier configured to convert the solid fuel and oxygen into a clean fuel gas
Data Source
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AI summary
A fuel feed system (110) for use in a gasification system (50) including a gasifier (134) is provided. The fuel feed system (110) includes a feed preparation section (118) configured to grind a particulate fuel to a predetermined size and to adjust a moisture content within the particulate fuel, a pressurization and conveyance section (124) coupled in flow communication with the feed preparation section, the pressurization and conveyance section including at least one solids pump (340) configured to receive a flow of the particulate fuel at a first pressure and discharge the particulate fuel at a second pressure, a conduit (122) configured to channel the pressurized particulate fuel to the gasifier, and a slag additive section (152) configured to feed a slag mixture into the gasifier and substantially control a total water content of a quantity of feeds into the gasifier, and further control melting and flow characteristics of a quantity of particulate fuel ash within the gasification system.