Multistage Fluidized Bed Reactor for Volatile Recovery and Low Erosion
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Solution Overview
Problem
Existing fluidized bed reactor systems face challenges in efficiently circulating and managing large particles, leading to high gas velocities that are costly and erosive, and are incompatible with smaller particles used in bubbling fluidized bed designs, resulting in inefficient reaction rates and bed size requirements.
Innovation Solution
A multistage fluidized bed reactor with separate stages, each with its own fluidization gas and independent pressure control, allowing for controlled transport of bed solids and gas between stages, enabling sequential chemical reactions and efficient extraction of volatile species from fuel streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If CFB reactors utilize smaller particles with high gas velocities for circulation, then particle circulation is achieved, but the system becomes erosive and expensive to operate
Solution Approach 1:
The system is divided into two distinct reactor types: a CFB reactor for volatilization using small particles with high gas velocity, and a BFB reactor for combustion using large particles with low gas velocity. This segmentation allows each reactor to operate under optimal conditions without the harmful effects of the other type on its particle circulation
Solution Approach 2:
A particle transfer system acts as an intermediary between the CFB and BFB reactors, transporting particles from the CFB reactor to the BFB reactor. This intermediary mechanism enables the system to utilize the advantages of both particle sizes while avoiding their respective disadvantages through controlled particle flow
2Temperature
If BFB reactors use larger particles for bubbling, then reaction conditions are improved, but circulation in CFB designs requires very high gas velocities
Solution Approach 1:
The system separates the functions of different particle sizes into dedicated reactors: CFB reactor for volatilization with small particles and high velocity, BFB reactor for combustion with large particles and low velocity. Each reactor is optimized for its specific particle size and operating conditions
Solution Approach 2:
The particle transfer system serves as an intermediary that moves particles between reactors with different operating conditions, enabling large BFB particles to be circulated through the CFB reactor without requiring the system to operate at continuously high gas velocities
3Ease of operation
If high gas velocities are used to circulate large BFB particles, then particle circulation is achieved, but the system becomes expensive and difficult to manage
Solution Approach 1:
The system divides particle circulation into two stages: initial circulation in the CFB reactor using high gas velocity with small particles, followed by secondary circulation in the BFB reactor using low gas velocity with large particles. This segmentation reduces overall energy consumption compared to maintaining high velocities throughout
Solution Approach 2:
The particle transfer system acts as an intermediary that facilitates particle movement between reactors with different velocity requirements, enabling the system to achieve effective particle circulation while operating at lower average gas velocities and reducing energy costs
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 configuration allows for independent control of reaction rates and residence times, enabling efficient extraction of valuable chemical species and improved thermal efficiency, while reducing the need for high gas velocities and minimizing erosion, thus enhancing the overall performance of the reactor system.
Implementation Method 1
Air flows upward through holes in a distributor plate in the floor of the combustion container. Using appropriately sized solid particles, air distribution plate, and air flow, the bed becomes 'fluidized' by the upwardly flowing air.
Implementation Method 2
A combustion plant burns a fuel (e.g., wood, coal, gas, oil, waste products, and the like) to generate useful heat and/or electricity.
Implementation Method 3
Combustion heat is often used to generate steam via a heat exchanger, which may be used directly and/or converted to electricity.
Data Source
AI summary
Various aspects provide for a multistage fluidized bed reactor, particularly comprising a volatilization stage and a combustion stage. The gas phases above the bed solids in the respective stages are separated by a wall. An opening (e.g., in the wall) provides for transport of the bed solids from the volatilization stage to the combustion stage. Active control of the gas pressure in the two stages may be used to control residence time. Various aspects provide for a fuel stream processing system having a pretreatment reactor, a combustion reactor, and optionally a condensation reactor. The condensation reactor receives a volatiles stream volatilized by the volatilization reactor. The combustion reactor receives a char stream resulting from the removal of the volatiles by the volatilization reactor.