Oxyfuel Pulverizer Nitrogen Carrier Gas Drying
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Solution Overview
Problem
In oxyfuel combustion boilers, the use of moist primary recirculated flue gas for drying and pulverizing coal can lead to solidification and reduced fluidity of pulverized fuel, potential erosion of equipment due to acidic gas reactions, and ignition risks with lignite or easily ignitable fuels, necessitating costly cooling and material resistance.
Innovation Solution
Supplying nitrogen gas separated from the air separation unit as a carrier gas to the pulverizer to dry and pulverize fuel, using a powder separation device to separate the pulverized fuel and mixing it with primary recirculated flue gas, while maintaining an inert atmosphere to prevent ignition and using a preheater to ensure effective drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If primary recirculated flue gas is supplied as carrier gas to the pulverizer for drying and pulverization of coal, then the pulverized fuel can be dried and pulverized, but the pulverized fuel may get moist to hinder transportation and reduce fluidity
Solution Approach 1:
The invention extracts and removes moisture from the primary recirculated flue gas before supplying it to the pulverizer. A moisture removal device is installed in the flue gas path to dehumidify the gas, ensuring that the carrier gas remains dry while still providing the necessary drying effect on the coal during pulverization.
Solution Approach 2:
The invention changes the moisture content parameter of the primary recirculated flue gas by introducing a moisture removal device. This parameter change ensures that the flue gas has optimal moisture levels - dry enough to prevent pulverized fuel from getting moist, but still warm enough to provide effective drying during pulverization.
2Productivity
If primary recirculated flue gas containing sulfur oxides is supplied to the pulverizer, then the drying and pulverization process can proceed, but sulfur oxides may react with moisture to form sulfuric acid that erodes instruments and pipings
Solution Approach 1:
The invention extracts moisture from the primary recirculated flue gas through a moisture removal device, thereby preventing the formation of sulfuric acid by removing the reactant (moisture) needed for the corrosion reaction between sulfur oxides and water.
Solution Approach 2:
The invention applies preliminary anti-action by removing moisture before the sulfur oxides can react with it to form corrosive sulfuric acid. The moisture removal device is positioned upstream in the flue gas path to prevent the harmful chemical reaction before it occurs, protecting instruments and pipings from erosion.
3Manufacturing precision
If preheated primary recirculated flue gas is supplied to the pulverizer for lignite drying and pulverization, then drying efficiency is improved, but ignition may occur due to oxygen included in the flue gas
Solution Approach 1:
The invention creates an inert atmosphere in the pulverizer by controlling the oxygen content in the primary recirculated flue gas. By removing moisture and controlling the composition of the carrier gas, the environment becomes less supportive of combustion, preventing ignition of lignite during the drying and pulverization process while maintaining drying efficiency.
4Ease of operation
If cooling is applied to remove moisture from primary recirculated flue gas, then the pulverized fuel can remain dry, but sulfur oxides react with condensed moisture to form acidic drainage that erodes pipings
Solution Approach 1:
The invention extracts moisture from the primary recirculated flue gas in a controlled manner using a moisture removal device positioned upstream, before the flue gas reaches the cooling zone. This prevents the formation of acidic drainage by removing moisture before it can condense and react with sulfur oxides in the cooling section.
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 stabilizes the pulverization of easily ignitable fuels, ensures dry and non-moist pulverized fuel, and prevents equipment erosion, reducing costs by eliminating the need for corrosive-resistant materials and cooling processes.
Implementation Method 1
an air separation unit (ASU) for separating introduced air into oxygen and nitrogen gas
Implementation Method 2
a pulverizer for drying and pulverizing fuel using carrier gas to discharge a fluid mixture of the carrier gas with the pulverized fuel
Implementation Method 3
supplying the fluid mixture of the nitrogen gas from said pulverizer with the pulverized fuel to a powder separation device to separate the pulverized fuel
Implementation Method 4
using a preheater to ensure effective drying
Data Source
AI summary
In an oxyfuel combustion boiler system, nitrogen gas separated by an air separation unit (ASU) is supplied as carrier gas to a pulverizer for drying and pulverization of fuel. A fluid mixture of the nitrogen gas from the pulverizer with pulverized fuel is supplied to a powder separation device where the pulverized fuel is separated. The separated pulverized fuel is mixed with the primary recirculated flue gas and supplied to a burner.