Standpipe-Fluid Bed Hybrid Char Recycle System
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Solution Overview
Problem
Gasification systems face high maintenance costs and inefficiencies due to frequent cycling and batch operations in lock-hopper systems, and erosion issues in rotary valve systems when handling abrasive solids like char, necessitating a more reliable and cost-effective method for recycling char from a lower pressure to a higher pressure environment.
Innovation Solution
A standpipe-fluid bed hybrid recycle system that uses a standpipe to build pressure and a fluidized-bed distribution vessel to facilitate continuous, measurable, and controllable flow of char back to the gasification reactor, eliminating the need for lock-hoppers and minimizing erosion through dense phase transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lock-hopper systems are used to transfer solids from low pressure to high pressure, then char recycling is achieved, but maintenance costs increase and system reliability decreases due to frequent cycling and batch operations
Solution Approach 1:
The patent replaces batch lock-hopper operations with continuous dense-phase pneumatic transport. The system maintains continuous char flow from the gasifier outlet through the standpipe and back to the gasifier, eliminating the start-stop cycling inherent in lock-hopper systems. This continuous operation significantly reduces maintenance requirements while improving reliability.
Solution Approach 2:
The patent employs dense-phase pneumatic transport using a standpipe with controlled gas injection. Gas is introduced at the bottom of the standpipe to fluidize and transport char particles upward against gravity and pressure differential. This pneumatic mechanism eliminates mechanical moving parts like lock-hoppers, reducing maintenance needs.
2Reliability
If rotary valves are used to transfer solids from low pressure to high pressure, then char recycling is achieved, but erosion wear increases due to fine abrasive solids
Solution Approach 1:
The patent replaces mechanical rotary valves with dense-phase pneumatic transport through a standpipe. The char particles are suspended in a gas stream and transported upward, eliminating direct mechanical contact between abrasive char and valve components. This dramatically reduces erosion wear while maintaining effective char recycling.
Solution Approach 2:
The patent changes the transport mechanism from mechanical rotation to pneumatic flow. By controlling gas velocity and flow rate parameters, the system achieves effective char transport without the mechanical contact that causes erosion. The dense-phase regime maintains low particle velocity relative to pipe walls, further reducing erosion.
3Stress or pressure
If lock-hopper systems are used for char transfer, then pressure differential is overcome, but system complexity increases due to multiple vessels and instrumentation
Solution Approach 1:
The patent extracts the core function of pressure differential overcoming from the complex lock-hopper system and implements it through a simplified standpipe with gas injection. The standpipe design naturally handles the pressure differential through the hydrostatic head of the char column, eliminating the need for multiple pressurizable vessels and complex valve instrumentation.
Solution Approach 2:
The patent changes the approach to pressure differential handling from mechanical pressurization of multiple vessels to a single standpipe with controlled gas flow. The pressure balance is achieved through the height of the char column in the standpipe and the gas injection rate, simplifying the system while effectively overcoming pressure differentials.
4Reliability
If batch operations are used in lock-hoppers, then char recycling is achieved, but productivity decreases due to frequent cycling
Solution Approach 1:
The patent replaces batch lock-hopper operations with continuous dense-phase pneumatic transport. The standpipe system maintains uninterrupted char flow from the gasifier outlet back to the gasifier inlet, eliminating the periodic interruptions caused by batch filling and emptying operations. This continuous operation significantly improves productivity while maintaining reliable char recycling.
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 solution enables continuous operation with precise control over char flow, reducing maintenance costs and erosion, while efficiently recycling char to maintain optimal gasification reactor conditions, enhancing process efficiency and flexibility in handling various carbonaceous feedstocks.
Implementation Method 1
The height of accumulated solids in the standpipe results in the pressure build at the bottom of the standpipe
Implementation Method 2
a fluidized-bed distribution vessel disposed below the standpipe and in communication with the standpipe to receive the accumulated solids and to facilitate continuous flow of the solids
Data Source
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AI summary
A system for gasification of a carbonaceous material and recycling char or solids from a gasifier is disclosed. The recycling system may include a standpipe that receives a solids stream from a separator, the standpipe generating a pressure differential across a bed of accumulated char, thereby producing a bottoms stream having a greater pressure than the inlet solids stream. The recycling system may also include a holding vessel that receives the bottoms stream and a fluidized-bed distribution vessel that receives char from the holding vessel and is configured to provide a continuous and precise flow of recycled char to the gasification reactor.