Ejector Gas Recirculation in Direct Reduced Iron Cooling
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Solution Overview
Problem
Current direct reduction processes for iron oxide to metallic iron in the steel industry rely on expensive compressors for gas recirculation, leading to high capital and operational expenses, and inefficient use of natural gas as a motive energy source.
Innovation Solution
Implementing an ejector driven by high-pressure natural gas to recycle the cooling gas in the cooling gas loop, replacing or supplementing conventional compressors, and utilizing the natural gas as a motive fluid to enhance gas recycling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional compressors are used for cooling gas recirculation, then reliable gas recycling is achieved, but capital and operational costs increase significantly
Solution Approach 1:
The patent replaces the mechanical compressor system with a pneumatic ejector system driven by high-pressure natural gas. This substitution eliminates the need for expensive compressor equipment, reduces capital expenditure, and lowers operational costs while maintaining the gas recirculation function through fluid dynamic principles rather than mechanical compression.
Solution Approach 2:
The invention utilizes high-pressure natural gas to drive ejectors that create a pressure differential, enabling cooling gas recirculation through pneumatic action. The ejectors convert the kinetic energy of the high-pressure natural gas into a vacuum effect that draws cooling gas through the system, achieving reliable gas recycling without mechanical compressors.
2Use of energy by moving object
If high-pressure natural gas is used as motive fluid for ejectors, then electrical energy consumption is reduced, but equipment complexity increases
Solution Approach 1:
The system uses high-pressure natural gas, which is already present in the plant as a process material, to drive the ejectors. This self-service approach converts an existing resource into motive power, eliminating the need for separate electrical compression equipment and reducing electrical energy consumption while utilizing materials already available in the process stream.
Solution Approach 2:
The high-pressure natural gas serves dual functions: it acts as both a process material for iron oxide reduction and as a motive fluid for driving the ejector system. This multi-functionality reduces overall system complexity by eliminating dedicated compression equipment and integrating multiple process functions into a single resource.
3Ease of operation
If ejectors are used for cooling gas recirculation, then operational costs decrease, but maintenance requirements change
Solution Approach 1:
The ejector system uses simpler, less expensive components compared to mechanical compressors. The ejectors have fewer moving parts and can be more easily replaced or maintained, reducing operational costs and simplifying maintenance routines despite changes in the nature of maintenance requirements from mechanical to pneumatic systems.
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
Significantly reduces capital and operational costs, simplifies maintenance, and improves process parameters by leveraging natural gas as a 'free' motive energy source, achieving substantial savings in electrical energy and equipment costs.
Implementation Method 1
an ejector for recirculating a portion of the cooled and scrubbed cooling gas back to the cooling zone by utilizing the high-pressure stream of the make-up gas as a motive power for the ejector
Implementation Method 2
an ejector driven by high-pressure natural gas to recycle the cooling gas in the cooling gas loop
Implementation Method 3
a cooling gas is circulated in said cooling gas recycle loop through said cooling zone to cool-down所述DRI
Implementation Method 4
the hydrocarbons present in the natural gas (methane, ethane, propane, aromatics, etc) will in some proportion, depending on the temperatures and time encountered, partially transform into hydrogen and carbon monoxide through the catalytic action of the DRI at the temperatures encountered by said cooling gas in the cooling zone
Data Source
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AI summary
A direct reduction process for producing direct reduced iron (DRI) in a reduction reactor having a reduction zone for reducing iron-oxides-containing particles, such as iron ore pellets, to DRI by reaction of said iron oxides with a high temperature reducing gas, and a cooling zone for lowering the temperature of the DRI produced in said reduction zone, wherein a stream of cooling gas, usually natural gas, is circulated through said cooling zone, a portion of said cooling gas is withdrawn from the cooling zone, cooled and cleaned in a gas cooler and a portion of the cooled gas is recycled to said reduction zone by means of an ejector utilizing the high-pressure natural gas make-up feed as the ejector's motive fluid. Using an ejector for recycling the cooling gas instead of using a mechanical compressor provides significant savings in electricity and in capital, operational and maintenance costs. A direct reduction plant having a DRI cooling zone which uses at least one ejector in recycling at least a portion of cooling gas to the cooling zone.