Direct Reduced Iron Reactor Gas Heating via Spent Stream Heat Exchange
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Solution Overview
Problem
Existing direct reduction processes for producing Direct Reduced Iron (DRI) require additional fuel for heating the reducing gas, leading to increased energy consumption and carbon dioxide emissions, and involve complex gas treatment steps that are costly and inefficient.
Innovation Solution
A method and apparatus that utilize a reducing gas with high carbon monoxide content, where spent gas is cleaned and heated using sensible heat from the reduction reactor, eliminating the need for additional fuel combustion and simplifying gas treatment by avoiding water gas shifters, and using CO2 lean gas for partial combustion to achieve the necessary temperature for reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If additional fuel is used for heating the reducing gas, then the necessary temperature for reduction is achieved, but energy consumption and carbon dioxide emissions increase
Solution Approach 1:
The patent combines the heating function with the reduction reactor itself, where the reduction reactions provide the heat necessary for gas heating. The reactor serves dual purposes: conducting the reduction reaction and providing thermal energy for heating the reducing gas, thereby eliminating separate fuel combustion systems.
Solution Approach 2:
The patent converts the carbon dioxide produced as a byproduct of reduction reactions into a beneficial heating source. Instead of treating CO2 as waste that requires separate combustion to generate heat, the system utilizes the exothermic reduction reactions themselves to provide the necessary thermal energy, turning a harmful emission into a useful energy source.
2Stability of the object's composition
If complex gas treatment steps including water gas shifters are used, then gas composition is adjusted, but process complexity and costs increase
Solution Approach 1:
The patent extracts and eliminates the water gas shifter unit from the traditional gas treatment sequence. By removing this complex equipment, the process is simplified while still achieving the necessary gas composition control through alternative means integrated into the reduction reactor system.
Solution Approach 2:
The reduction reactor is designed to perform multiple functions simultaneously: it conducts the reduction reaction, heats the reducing gas, and controls gas composition. This multi-functionality eliminates the need for separate dedicated units for each function, thereby reducing overall process complexity.
3Temperature
If fired gas heaters are used for heating reducing gas, then temperature is achieved, but capital and operational costs increase
Solution Approach 1:
The patent merges the heating function with the reduction reactor, eliminating the need for separate fired gas heaters. The reactor structure itself provides the thermal energy for heating, reducing capital expenditure on additional heating equipment while maintaining the necessary operating temperatures.
Solution Approach 2:
The reduction reactor serves itself by using the heat generated from reduction reactions to warm the reducing gas. This self-heating capability eliminates dependency on external fuel combustion systems, reducing both capital costs for heater equipment and operational costs for fuel.
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 reduces energy consumption per ton of iron produced, decreases carbon dioxide emissions, and simplifies the process by eliminating the need for fired gas heaters, thereby lowering capital and operational costs while maintaining efficient reduction of iron ore.
Implementation Method 1
Oxygen is removed from the iron ore by chemical reduction for the production of highly metallized DRI
Implementation Method 2
the upgraded CO2 lean reducing gas stream passes through a heat exchanger where only exchanging sensible heat recovered from said spent reducing gas removed from the reduction reactor is heated
Implementation Method 3
This heated CO2 lean reducing gas stream is then partially combusted with a molecular-oxygen-containing gas in order to raise its temperature above 700°C measured at the reactor inlet
Data Source
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AI summary
The present invention concerns a method and an apparatus for producing DRI (Direct Reduced Iron) utilizing a high-oxidation reducing gas containing carbon monoxide and hydrogen, derived directly or indirectly from the gasification of hydrocarbons or coal, with a high content of oxidants (H20 and CO2). The invention provides a more efficient method and plant comprising a reactor in which particulate material of iron ore comes into contact with a high temperature reducing gas to produce DRI, with lower investment and operating costs, avoiding the need for a fired heater for the reducing gas fed into the reduction reactor. The reducing gas is heated to a temperature above 700°C in two steps, a first step at a temperature below about 400°C to prevent the phenomenon of metal dusting, by exchange of sensible heat supplied by the stream of hot spent gas removed from the reduction reactor; and a second step by means of partial or total combustion with oxygen, maintaining the temperature of the combustion gas below the limits established by the construction materials of the combustion chamber.