Coal Mill Low Load Operation via Gas Recirculation
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Solution Overview
Problem
Coal mills in power plants face challenges in operating at low load conditions due to the risk of explosions and inefficient coal combustion when coal flow rates drop below the minimum required for normal operation, especially when integrated with intermittent renewable energy sources like wind and solar power.
Innovation Solution
A modified coal fed power plant system using a beater wheel mill with flow control devices and a recirculator to manage gas flow and temperature, allowing operation at 25-33% below previous low load levels, ensuring safe and efficient combustion by adjusting gas recirculation and burner ducts to maintain stable coal distribution and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If coal mills operate below minimum coal flow rate, then power plant can accommodate more renewable energy, but explosion risk increases and normal operation is hampered
Solution Approach 1:
The patent converts the harmful hot gas that causes explosion risk into a beneficial drying medium. By recirculating the hot gas through the coal mill, it effectively dries the coal particles, preventing moisture-related combustion issues and reducing explosion risk while enabling low-load operation
Solution Approach 2:
The patent changes the operational parameters of the coal mill by introducing a recirculation system that maintains specific temperature and flow conditions. The recirculated gas temperature is controlled to optimize drying while preventing explosion, allowing the mill to operate reliably at coal flow rates below the traditional minimum
2Adaptability or versatility
If coal mills operate below minimum coal flow rate, then power plant can accommodate more renewable energy, but combustion efficiency decreases
Solution Approach 1:
The patent applies preliminary action by drying the coal particles with recirculated hot gas before they enter the combustion chamber. This pre-drying process ensures that even at low coal flow rates, the coal is in optimal condition for efficient combustion, maintaining productivity while enabling renewable energy integration
Solution Approach 2:
The recirculation system maintains continuous useful action by constantly circulating hot gas through the coal mill to ensure continuous drying of coal particles. This continuous process maintains combustion efficiency regardless of coal flow rate variations, allowing the system to adapt to renewable energy generation patterns
3Adaptability or versatility
If multiple mills are installed to handle load variations, then power plant can maintain operation at different loads, but system cost and space requirements increase
Solution Approach 1:
The patent makes the coal mill universal by enabling it to operate across a wide range of loads through the recirculation system. The single mill performs multiple functions - drying, pulverizing, and temperature control - allowing the power plant to maintain operation at different loads without requiring multiple specialized mills, thus reducing device complexity and space requirements
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
Enables coal fed power plants to operate effectively at lower loads, reducing the risk of explosions and maintaining efficient combustion, allowing them to accommodate high power generation in conjunction with wind and solar power plants, with a retrofit capability for existing systems.
Implementation Method 1
a recirculator configured to recirculate a portion of the hot gas from the furnace to the coal mill
Implementation Method 2
Coal is charged to the mill where it is dried and pulverized
Implementation Method 3
the incoming coal is caught by the rapidly circulating beater plates which are fixed at the perimeter of the beater wheel and comminuted by the impact of the beater plates
Implementation Method 4
Coal is charged to the mill where it is dried and pulverized and then discharged to burners where it is combusted in a furnace
Data Source
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AI summary
Disclosed herein is a coal fed power generation system 200 comprising a mill 202 in fluid communication with a furnace 206; where the mill 202 is operative to pulverize coal and to ventilate the coal; where the furnace 206 contains more than one burner 210, 212, 214, or burner nozzles; where the burner 210, 212, 214, or burner nozzles are operative to receive the coal from the mill 202 and combust it in the furnace 206; and a plurality of flow control devices 216, 218, 220; where at least one flow control device 216, 218, 220, is in fluid communication with the mill 202 and with the burner 210, 212, 214, or burner nozzle; and where the flow control device 216, 218, 220, that is in fluid communication with the mill 202 and with the burners 210, 212, 214, or burner nozzles is closed to prevent fluid communication between the mill 202 and the furnace 206 during the operation of the furnace 206.