Integrated Fuel Drying and Combustion for High-Moisture Steam Generation
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Solution Overview
Problem
The efficient use of high-moisture and low-BTU fuels in steam generation systems is limited by reduced flame temperature, poor fuel utilization, and low boiler efficiency due to high moisture content, leading to suboptimal steam generation capacity and increased flue gas volume.
Innovation Solution
A process that thermally integrates a dryer with a boiler, using an oxygen-depleted gas stream for drying the fuel and an inert atmosphere to prevent ignition, combined with oxygen enrichment of the combustion air to enhance combustion efficiency, and includes bypass mechanisms to control heat transfer and moisture levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high-moisture fuel is combusted directly in the boiler, then fuel utilization is poor and flame temperature is reduced, but steam generation capacity falls below design expectations
Solution Approach 1:
The patent applies preliminary action by drying the high-moisture fuel before combustion in the boiler. A separate dryer unit removes excess moisture from the fuel using thermal energy from the boiler system, ensuring that only dried fuel with optimized moisture content enters the combustion chamber. This preliminary drying action prevents flame temperature reduction and maintains design steam generation capacity.
Solution Approach 2:
The patent segments the fuel processing system into distinct functional units: a dryer unit for moisture removal and a boiler unit for combustion and steam generation. This segmentation allows independent optimization of each process - the dryer controls moisture content to prevent flame temperature loss, while the boiler maintains steam generation capacity, resolving the contradiction between these two parameters.
2Loss of energy
If high-moisture fuel is combusted directly, then boiler efficiency is reduced due to latent heat loss in exhaust gases, but flue gas volume flow increases
Solution Approach 1:
The dryer unit performs preliminary moisture removal from fuel before combustion, reducing the amount of water that would otherwise evaporate during burning. This preliminary action decreases flue gas volume and minimizes latent heat loss in exhaust gases, thereby improving boiler efficiency while controlling flue gas quantity.
Solution Approach 2:
The patent converts the harmful effect of fuel moisture into a beneficial process by using the moisture content as a controlled variable. The dryer removes excess moisture to prevent efficiency loss, while the controlled moisture content in dried fuel allows for optimized combustion that reduces flue gas volume and recovers latent heat, turning the previously harmful moisture into a manageable parameter that improves overall system efficiency.
3Power
If oxygen enrichment is applied to combustion air, then flame temperature and combustion kinetics increase, but combustion air flow rate must be controlled
Solution Approach 1:
The patent applies parameter changes by enriching the combustion air with oxygen, changing the compositional parameter of the air supply. This oxygen enrichment increases flame temperature and combustion kinetics (power) while requiring controlled adjustment of the air flow rate parameter to maintain optimal combustion conditions, resolving the contradiction between enhanced combustion rate and operational control.
4Productivity
If fuel moisture is reduced through drying, then boiler efficiency and steam generation improve, but additional drying equipment and energy input are required
Solution Approach 1:
The patent merges the drying function with the existing boiler system by using thermal energy from the boiler's flue gases or steam to power the dryer unit. This integration combines moisture removal with the primary steam generation function, improving steam generation rate while minimizing additional equipment complexity and energy input requirements through synergistic system coupling.
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 improves boiler efficiency and steam generation by reducing fuel moisture, increasing flame temperature, and optimizing steam production, while providing operational flexibility to adapt to varying fuel conditions.
Implementation Method 1
heating the high-moisture solid fuel by indirect heat exchange with a recirculating thermal fluid
Implementation Method 2
contacting a high-moisture solid fuel with an oxygen-depleted gas stream while heating the high-moisture solid fuel by indirect heat exchange... to produce a dried solid fuel
Implementation Method 3
transferring a first portion of the amount of heat to generate steam by indirect heat exchange with the combustion products stream
Implementation Method 4
transferring a first portion of the amount of heat to generate steam by indirect heat exchange with the combustion products stream
Implementation Method 5
transferring a second portion of the amount of heat to preheat the combustion air by indirect heat exchange with the combustion products stream
Implementation Method 6
transferring a third portion of the amount of heat to the recirculating thermal fluid by indirect heat exchange with the combustion products stream
Data Source
AI summary
A process for combusting a high-moisture fuel to generate steam in which the high-moisture solid fuel is first dried by contacting with an oxygen-depleted gas stream while being heated by indirect heat exchange with a recirculating thermal fluid. The dried fuel is then combusted with a combustion air stream to produce a combustion products stream whose heat first is used to generate steam, and then to preheat the combustion air stream by indirect heat exchange in which a portion of the combustion air stream and/or a portion of the combustion products stream bypasses the heat exchanger. The combustion products stream also provides heat to dry the solid fuel via the recirculating thermal fluid.