Hot Nitrogen Fuel Milling for Lower-Volume Oxy-Fuel Flue Gas
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Solution Overview
Problem
Existing oxy-fuel combustion systems face challenges in efficiently milling fuels while minimizing flue gas volume and reducing the risk of dust explosions, as they often require additional heating and drying steps that increase energy consumption and flue gas volume.
Innovation Solution
A method and system where a hot nitrogen gas stream with high purity is used to mill fuels, providing an inert atmosphere for drying and reducing the risk of explosions, and a significant portion of the nitrogen gas is removed before the fuel reaches the burner, thereby reducing flue gas volume and energy consumption by integrating waste heat from air separation units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional heating and drying steps are used to mill fuel, then fuel drying efficiency is improved, but energy consumption increases
Solution Approach 1:
The patent combines the fuel drying function with the fuel milling operation by introducing a hot nitrogen gas stream into the mill. This integration eliminates the need for separate heating and drying steps, as the milling process itself performs the drying function using the hot inert gas atmosphere.
Solution Approach 2:
The system uses waste heat from the air separation unit's nitrogen gas stream to dry the fuel during milling. This self-service approach utilizes already-heated gas that would otherwise be wasted, converting a byproduct into a useful drying medium without requiring additional external heating energy.
2Reliability
If additional heating and drying steps are used to mill fuel, then fuel drying efficiency is improved, but flue gas volume increases
Solution Approach 1:
The patent combines the fuel drying function with the fuel milling operation by introducing a hot nitrogen gas stream into the mill. This integration eliminates the need for separate heating and drying steps, as the milling process itself performs the drying function using the hot inert gas atmosphere.
Solution Approach 2:
The system uses nitrogen gas from the air separation unit to create an inert atmosphere in the mill. This nitrogen atmosphere prevents combustion during milling while simultaneously drying the fuel, and the nitrogen is later removed before fuel combustion, reducing overall flue gas volume.
3Device complexity
If conventional milling is used without inert atmosphere, then device complexity is reduced, but risk of dust explosions increases
Solution Approach 1:
The system uses nitrogen gas from the air separation unit to create an inert atmosphere in the mill. This nitrogen atmosphere prevents combustion during milling while simultaneously drying the fuel, and the nitrogen is later removed before fuel combustion, reducing overall flue gas volume.
Solution Approach 2:
The hot nitrogen gas stream acts as an intermediary substance that serves dual functions: it creates an explosion-proof inert atmosphere during milling and simultaneously dries the fuel. The nitrogen is introduced into the mill, performs these functions, and is then removed before combustion.
4Use of energy by moving object
If flue gas volume is reduced by removing nitrogen, then energy efficiency is improved, but system complexity increases
Solution Approach 1:
The patent combines the fuel drying function with the fuel milling operation by introducing a hot nitrogen gas stream into the mill. This integration eliminates the need for separate heating and drying steps, as the milling process itself performs the drying function using the hot inert gas atmosphere.
Solution Approach 2:
The system uses waste heat from the air separation unit's nitrogen gas stream to dry the fuel during milling. This self-service approach utilizes already-heated gas that would otherwise be wasted, converting a byproduct into a useful drying medium without requiring additional external heating energy.
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 enhances energy efficiency, reduces flue gas volume, and minimizes the risk of explosions during fuel milling, while also reducing the overall energy consumption and size of flue gas ducts in oxy-fuel power plants.
Implementation Method 1
the hot gas stream acts to dry the fuel
Implementation Method 2
providing an inert environment which reduces the risk of dust explosions during milling/pulverizing the fuel
Implementation Method 3
The oxygen may be obtained from separating air into an oxygen stream and a nitrogen stream by means of an air separation unit (ASU)
Data Source
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AI summary
The present disclosure relates to a method of milling a fuel for an oxy-fuel combustion burner (9), the method comprising: separating air into a hot nitrogen gas stream, having a temperature of at least 150°C and a purity of at least 98 mol-% nitrogen, and an oxygen gas stream; leading at least a part of the nitrogen gas stream to a fuel mill (2); milling the fuel by means of the fuel mill (2) in a nitrogen rich atmosphere formed by means of the nitrogen gas stream; leading the at least a part of the nitrogen gas stream away from the milled fuel; leading the oxygen gas stream to the oxy-fuel combustion burner (9); conveying the milled fuel to the oxy-fuel combustion burner (9); and burning the fuel, by means of the oxy-fuel combustion burner (9), in an oxygen rich atmosphere formed by means of the oxygen gas stream. The present disclosure further relates to a system for milling a fuel for an oxy-fuel combustion burner as well as to a power plant comprising such a system.