Ceramic Diffuser and Adjustable Flow Conditioner for Coal Burners
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Solution Overview
Problem
Low NOx pulverized coal fired burners face issues with impeller erosion and high temperature degradation due to radiative heat transfer, leading to short service life and non-uniform coal and air distribution, as well as long flames causing unburned combustibles and NOx emissions. Additionally, existing adjustable flow resistors are economically infeasible and difficult to install.
Innovation Solution
A ceramic diffuser with a tapered upstream portion and angled blades is located in the upstream end of the coal nozzle to condition the coal and air flow, combined with an adjustable flow conditioner in the burner elbow to enhance mixing and wear resistance, allowing for improved fuel and air distribution and adjustable pressure drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If standard bladed impellers are placed at or near the exit of the burner coal nozzle to achieve mixing benefit, then NOx emissions are reduced, but the impellers reach high temperatures causing thermal erosion and coal caking, shortening service life to about one year
Solution Approach 1:
A ceramic diffuser is introduced as an intermediary component between the coal nozzle and the impeller. The ceramic diffuser protects the metal impeller from direct exposure to high temperatures and pulverized coal erosion, while still allowing the impeller to perform its mixing function. This mediator extends the impeller service life from about one year to potentially much longer while maintaining NOx reduction benefits.
Solution Approach 2:
The solution uses a ceramic diffuser in combination with a metal impeller, creating a composite material system. The ceramic material provides high temperature resistance and erosion protection, while the metal impeller provides mechanical strength and mixing capability. This composite approach allows both components to发挥 their respective advantages and overcome their individual weaknesses.
2Reliability
If ceramics are used to protect equipment from pulverized coal erosion, then wear resistance is improved, but high temperatures near the exit of the burner coal nozzle prevent effective use of ceramics
Solution Approach 1:
The protective function is segmented between two components: the ceramic diffuser handles the high temperature and erosion exposure, while the metal impeller handles the mixing function in a slightly cooler zone. This segmentation allows each material to operate within its optimal temperature range, with the ceramic providing protection where temperatures are highest.
Solution Approach 2:
The ceramic diffuser acts as a thermal barrier and intermediary, protecting the metal impeller from the full brunt of high temperatures and pulverized coal erosion. The ceramic material absorbs and dissipates thermal energy, creating a more favorable thermal environment for the metal impeller while maintaining erosion resistance.
3Manufacturing precision
If fixed orifices are used to balance flow distribution through coal pipes, then uniform distribution is improved, but the devices have inherent limitations making sustainable uniform distribution not possible
Solution Approach 1:
The invention replaces static fixed orifices with a dynamic adjustable flow conditioner. The flow conditioner can be adjusted to change flow resistance characteristics, allowing adaptation to varying operating conditions and maintaining uniform flow distribution sustainably. This dynamic adjustment capability overcomes the limitations of fixed orifices which cannot adapt to changing system requirements.
Solution Approach 2:
The flow conditioner allows for parameter changes in flow resistance and distribution characteristics. By adjusting the flow conditioner, operators can modify the flow parameters to achieve and maintain uniform distribution across multiple burners, overcoming the fixed limitations of orifices and adapting to different operational scenarios.
4Ease of operation
If adjustable flow resistors are used to balance coal piping flow, then flow distribution can be adjusted, but the devices are economically infeasible and difficult to install
Solution Approach 1:
The flow balancing function is merged with the existing burner assembly structure. The adjustable flow conditioner is integrated into the burner design, combining flow control functionality with the structural components already present in the system. This integration reduces overall device complexity and eliminates the need for separate, complex flow resistor installations.
Solution Approach 2:
The flow conditioner serves multiple functions: it balances flow distribution across burners, controls flame length, and adjusts mixing characteristics. This multi-functionality replaces the need for separate adjustable flow resistors, reducing system complexity while maintaining flow adjustment capability. The same component performs multiple tasks that would otherwise require different devices.
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
The solution extends the service life of burner components, achieves more complete combustion with reduced NOx emissions, and allows for controlled flame length and uniform coal distribution, while being economically feasible and easy to install.
Implementation Method 1
The diffuser promotes the generation of a fuel rich ring of fuel near the walls of the coal nozzle downstream of the conical diffuser, thereby promoting improvements in flame stability and lower NOx emissions
Implementation Method 2
At these locations impellers readily reach high temperatures from radiative heat transfer from the furnace
Implementation Method 3
Pulverized coal is highly abrasive, and erosion from pulverized coal is a consistent problem for burner component in direct contact therewith
Implementation Method 4
These high temperatures are undesirable to impeller longevity as they can thermally erode metal components directly and/or cause coal to stick and cake upon the device
Data Source
AI summary
A coal nozzle assembly for a pulverized coal burner includes a diffuser. A flow conditioner also may be used with the assembly. The assembly conditions the coal/air flow before the coal/air flow is introduced to the furnace. The flow conditioner directs the coal into the diffuser where it is swirled to form a fuel rich outer ring disposed about an air rich inner portion before the fuel is delivered to the coal nozzle.