Hydrogen DRI Cooling and Reduction Control for Lower Heating Demand
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Solution Overview
Problem
Existing methods for producing direct reduced iron (DRI) using hydrogen as both a reduction and cooling gas are not optimized for energy efficiency, particularly in terms of flow rates and heating requirements for the reducing gas introduced directly into the reducing section.
Innovation Solution
A method involving the controlled flow rates and temperatures of hydrogen-based reducing and cooling gases within a direct reduction shaft, including measuring and adjusting gas flow rates and temperatures to optimize heat exchange and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the flow rate of cooling gas is increased to improve heat exchange efficiency, then energy efficiency improves, but the temperature of heated cooling gas may fall below the minimum allowable temperature
Solution Approach 1:
The control system continuously monitors the temperature of heated cooling gas (Tcooltop) and adjusts the cooling gas flow rate accordingly. When Tcooltop approaches Tcooltopmin, the system reduces cooling gas flow rate to maintain the temperature above the minimum threshold, creating a closed-loop feedback control that balances heat exchange efficiency with temperature constraints
Solution Approach 2:
The system dynamically changes the flow rate parameter of cooling gas based on real-time temperature measurements. By adjusting this parameter within operational bounds (maintaining Tcooltop ≥ Tcooltopmin), the system optimizes heat exchange efficiency while respecting thermal constraints on the reduction process
2Loss of energy
If the flow rate of heated reducing gas is decreased to reduce energy consumption, then energy efficiency improves, but the top gas temperature may fall below the minimum required for adequate metallization
Solution Approach 1:
The control system monitors top gas temperature (Ttopgas) and adjusts the heated reducing gas flow rate to maintain Ttopgas ≥ Ttopgasmin. This feedback mechanism ensures that energy consumption is minimized while still achieving the minimum temperature required for adequate metallization of the DRI product
Solution Approach 2:
The system utilizes the heat from cooling gas (after it has absorbed heat from DRI) and recycles it back into the reducing section. This self-service approach allows the system to maintain adequate top gas temperature with reduced external heating requirements, as the cooled gas from the cooling section provides supplemental heat
3Loss of energy
If external heating of reducing gas is reduced to improve energy efficiency, then energy consumption decreases, but the metallization degree of DRI product may fall below minimum allowable values
Solution Approach 1:
The cooling gas serves a dual function: it cools the DRI product and simultaneously preheats before entering the reducing section. This self-service mechanism provides internal heat recycling that maintains reduction temperature and metallization quality with reduced external energy input
Solution Approach 2:
The system optimizes multiple parameters simultaneously - cooling gas flow rate, heated reducing gas flow rate, and their respective temperatures - to achieve the minimum metallization degree (≥96% Fe0) while minimizing external heating energy consumption
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 method enhances energy efficiency by minimizing the energy needed for heating the reducing gas, achieving a desired metallization degree in the DRI product while reducing external heating requirements.
Implementation Method 1
the cooling gas is introduced at an end of the cooling section opposite to the end of the cooling section which is adjacent to reduction section, and thereby cooling the hot DRI, which has a temperature Tdritop when entering the cooling section, to cold DRI and heating the cooling gas to a temperature Tcooltop (through heat exchange with the counterflowing DRI)
Implementation Method 2
permitting the hot cooling gas to enter the reducing section of the direct reduction shaft to mix with the heated reducing gas and form a second component part of the reducing gas
Implementation Method 3
introducing the heated reducing gas into a reducing section of the direct reduction shaft to form a first component part of a reducing gas that reduces the iron ore to hot DRI at a reduction temperature Tred
Data Source
AI summary
A method for producing direct reduced iron (DRI), comprising the steps of: controlling a flow rate of a non-heated hydrogen gas into a cooling section (5) such that Tdriout<Tdrioutmax, wherein Tdrimax is a set maximum allowable temperature of the DRI exiting the cooling section (5), measuring temperature of cooling gas Tcooltop leaving the cooling section and increasing the flow rate of the cooling gas, FRcoolgas, introduced into the cooling section (5) until Tcooltop=Tcooltopmin, adjusting a flow rate of a separately heated reduction gas introduced into a reduction section (4) and measuring the degree of metallization of the produced DRI and measuring the top gas temperature Ttopgas, and determining a minimum top gas temperature, Ttopgasmin, below which the degree of metallization is below a minimum allowable value, and measuring the top gas temperature Ttopgas and controlling at least one of the flow rate of the heated reducing gas and the temperature Tredgas to which the heated reducing gas is heated such that Ttopgasmin≤Ttopgas≤Topgasmax, wherein Topgasmax is a set maximum allowable temperature of the top gas.