Downer-Riser Solids Control via Pneumatic Fluidization
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Solution Overview
Problem
Existing methods for controlling the solids level and temperature in fluidized beds, such as aperture blockers and star feeders, face challenges including mechanical wear, pressure seal issues, and limited directional control, leading to inefficiencies and safety hazards.
Innovation Solution
A method involving a downer and riser system where solids are fluidized by conveying gas, allowing for adjustable solids flow to control the level and inventory in a fluidized bed, and temperature in a mixing tank, using pressure differences and gas flow to maintain a reliable pressure seal and precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an aperture blocker or discharge lance is used to control solids outflow, then the solids level can be controlled, but mechanical moving parts are required which need water cooling and monitoring, increasing device complexity and risk of damage
Solution Approach 1:
The patent replaces the mechanical aperture blocker system with a pneumatic system using a gas-tight valve and gas flow control. Instead of mechanically blocking the outlet, the invention uses gas flow to control the solids discharge, eliminating the need for mechanical moving parts in contact with hot solids, thereby reducing device complexity and improving reliability.
Solution Approach 2:
The invention introduces a pneumatic control system where gas flow through a valve controls the solids discharge rate. The gas flow acts as a controlling medium to regulate the outlet cross-section dynamically, replacing mechanical blockage with pneumatic pressure control to achieve solids level regulation.
2Ease of operation
If an aperture blocker is used to control solids flow, then the outlet cross-section can be adjusted, but pressure seal deterioration occurs when differential pressure exists, reducing control quality
Solution Approach 1:
The patent replaces the mechanical aperture blocker that suffers from pressure seal deterioration with a gas-tight valve system controlled by gas flow. This substitution maintains ease of operation for adjusting outlet cross-section while ensuring reliable pressure sealing through the gas-tight valve mechanism that can maintain seal integrity under differential pressure conditions.
3Temperature
If water cooling is applied to the aperture blocker, then mechanical parts can be cooled, but cooling water flow rate and temperature difference must be monitored, increasing device complexity
Solution Approach 1:
The invention eliminates the need for water cooling by replacing the mechanical aperture blocker with a gas-tight valve system. The gas flow control mechanism inherently handles thermal management without requiring separate cooling systems, thereby reducing device complexity while maintaining temperature control capability.
4Reliability
If a weir or discharge opening is used to maintain constant solids level, then the level can be kept constant, but pressure seal must be realized using float chambers or siphons, increasing device complexity
Solution Approach 1:
The patent replaces complex pressure seal mechanisms like float chambers and siphons with a gas-tight valve system controlled by gas flow. This substitution achieves stable solids level control while simplifying the pressure seal implementation, as the gas-tight valve inherently provides the necessary sealing without requiring additional complex mechanisms.
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 enables reliable and precise control of solids level and temperature, avoiding mechanical wear and safety hazards, with flexible operation across varying pressures and gas atmospheres, ensuring consistent process conditions.
Implementation Method 1
The stream of solids withdrawn from the solids tank is fluidized at a bottom of the downer by supplying a conveying gas so as to convey the withdrawn stream of solids upward via a riser
Implementation Method 2
using pressure differences and gas flow to maintain a reliable pressure seal and precise control
Data Source
AI summary
A method for controlling at least one of a level of solids and an inventory of solids in a solids tank includes withdrawing a stream of solids from the solids tank via a downer. The stream of solids withdrawn from the solids tank is fluidized at a bottom of the downer by supplying a conveying gas so as to convey the withdrawn stream of solids upward via a riser branching off from the downer, a size of the conveyed stream of solids being adjusted by the supplying of the conveying gas. At least one of the level and the inventory of the solids in the solids tank is used as an adjustment variable of a control circuit and a volume flow of the conveying gas is used as an actuating variable of the control circuit.