Direct Recycle Gas Cooling for Shaft Furnace Moisture Control
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Solution Overview
Problem
Existing direct reduction (DR) systems face challenges during startup and normal operation, including temperature control issues, biological fouling, high energy consumption, and capital costs due to the use of refractory-lined ducts and mechanical valves in the bustle gas system, which are prone to failure and inefficiencies.
Innovation Solution
The implementation of a direct recycle line with a packed bed cooler (DRC) to temper and dry the process gas, eliminating the need for refractory-lined ducts and mechanical valves, allowing flexible installation and reducing energy consumption by stopping cooling water supply during idling, and enabling efficient temperature and moisture control of the bustle gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If process gas is cooled and scrubbed in conventional systems, then dust and heavy metals are removed, but the gas loses valuable heat energy and requires large equipment footprint
Solution Approach 1:
The patent combines the cooling, dust removal, and heat recovery functions into a single integrated cyclone separator system. The process gas is cooled and dust is removed through the cyclone separation process while simultaneously recovering heat, merging multiple conventional separate operations into one unified system that eliminates energy loss and reduces equipment footprint
Solution Approach 2:
The patent introduces a heat exchanger as an intermediary device that transfers heat from the hot process gas to the incoming feed material or ambient air. This intermediary mechanism enables heat recovery without requiring direct contact between hot and cold streams, allowing efficient heat energy utilization while maintaining process gas quality for dust removal
2Reliability
If process gas is cooled rapidly, then dust removal efficiency increases, but thermal shock damages equipment and reduces system reliability
Solution Approach 1:
The patent applies preliminary action by pre-cooling the process gas gradually through controlled heat exchange before it enters the cyclone separator. The heat exchanger progressively reduces gas temperature, preparing the gas for effective dust removal without subjecting equipment to sudden thermal shock, thus maintaining system reliability while achieving high dust removal efficiency
Solution Approach 2:
The patent implements dynamic temperature control in the cooling process, adjusting the cooling rate and heat exchange parameters based on real-time process conditions. This dynamic approach allows the system to optimize between cooling speed for dust removal and cooling rate for equipment protection, maintaining both reliability and productivity
3Area of stationary object
If conventional cooling and scrubbing equipment is used, then gas cleaning is achieved, but the equipment footprint and capital costs increase
Solution Approach 1:
The patent enables the process gas to serve its own cooling and cleaning needs through the cyclone separator system. The high-velocity gas flow itself provides the driving force for cyclone separation and dust removal, while the heat exchanger uses the gas's own thermal energy to preheat incoming materials or generate steam, making the system self-sufficient and eliminating the need for external energy inputs or large equipment installations
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 enhances temperature and moisture control during startup and normal operation, reduces energy consumption, minimizes capital costs, and prevents biological fouling, thereby improving the efficiency and reliability of the DR process.
Implementation Method 1
The cyclone separator receives a portion of the process gas from the direct reduction shaft and separates dust and heavy metals therefrom
Implementation Method 2
process gas from the direct reduction shaft is fed to a heat exchanger to preheat feed material to be introduced into the direct reduction shaft or to generate process steam
Data Source
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AI summary
A direct reduction system and process for reducing a metal oxide to a metal, including and utilizing: a process gas line configured to deliver a portion of a process gas to a reformer operable for reforming the process gas to form a reformed gas; a bustle gas line configured to deliver the reformed gas to a shaft furnace as a bustle gas, wherein the shaft furnace is operable for reducing the metal oxide to the metal; and a direct recycle line including a direct recycle cooler configured to selectively deliver a portion of the process gas to the bustle gas line while circumventing the reformer, thereby selectively cooling and lowering the moisture content of the bustle gas delivered to the shaft furnace. Optionally, the direct reduction system further includes a reheat line configured to deliver a portion of the bustle gas to the shaft furnace as reheat gas.