Integrated Fuel Drying and Oxygen-Enriched Boiler Combustion
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Solution Overview
Problem
The efficient use of high-moisture, low-BTU solid 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 and increased flue gas volume.
Innovation Solution
A thermally integrated dryer and boiler system using an oxygen-depleted gas stream to dry the fuel, combined with oxygen enrichment of the combustion air, and a recirculating thermal fluid for indirect heat exchange to enhance combustion efficiency and steam generation.
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 fuel is dried in a dryer before being fed to the boiler combustion chamber. This preliminary drying action removes excess moisture from the high-moisture fuel, preparing it for efficient combustion and enabling the boiler to achieve design steam generation capacity while maintaining high flame temperatures.
Solution Approach 2:
The moisture content parameter of the fuel is changed from high-moisture state to dried state through the drying process. This parameter change transforms the fuel properties to enable proper combustion, improving both flame temperature and steam generation capacity simultaneously.
2Loss of energy
If high-moisture fuel is combusted, then fuel utilization is poor with high unburned carbon levels, but combustion efficiency remains low
Solution Approach 1:
The dryer performs preliminary moisture removal from the fuel before combustion. This preliminary action ensures that the fuel enters the boiler in an optimized state, enabling complete combustion and minimizing unburned carbon losses, thereby improving combustion efficiency and reducing energy loss.
3Loss of energy
If high-moisture fuel is burned, then latent heat is lost in exhaust gases, but flue gas volume flow becomes extremely large
Solution Approach 1:
By drying the fuel beforehand, the amount of moisture available to vaporize during combustion is significantly reduced. This preliminary moisture removal decreases both the flue gas volume flow and the latent heat loss in exhaust gases, as less water vapor is generated during the combustion process.
4Power
If oxygen enrichment is applied to combustion air, then flame temperature and combustion kinetics increase, but system complexity increases
Solution Approach 1:
The oxygen concentration parameter of the combustion air is changed from ambient levels to enriched levels. This parameter change accelerates combustion kinetics and increases flame temperature, enhancing the boiler's power output and steam generation capability despite the added system complexity.
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 system effectively reduces fuel moisture, increases flame temperature, improves combustion efficiency, and enhances steam generation capacity while maintaining operational flexibility to adapt to varying fuel conditions.
Implementation Method 1
the dryer configured to be heated by indirect heat exchange using the recirculating thermal fluid
Implementation Method 2
an auxiliary heat exchanger in fluid flow communication with the radiant section for heating water by indirect heat exchange with the combustion products stream
Implementation Method 3
an air preheater for preheating the combustion air stream by indirect heat exchange with the combustion products stream
Implementation Method 4
to combust the dried solid fuel with a combustion air stream to produce a combustion products stream and an amount of heat
Data Source
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AI summary
An apparatus for generating steam comprising a dryer configured and arranged to create contact between a high-moisture solid fuel and an oxygen-depleted gas stream and to produce a dried solid fuel, a combustion air system having an air inlet for receiving air and a combustion air outlet for discharging the combustion air stream; a boiler comprising a radiant section, a convective section, and an energy recovery section is disclosed. The apparatus is characterized by the dryer having an inlet section and an outlet section, the inlet section including a high-moisture solid fuel inlet, an oxygen-depleted stream inlet, and a recirculating thermal fluid outlet; the outlet section including a dried solid fuel outlet, an oxygen-depleted stream outlet, and a recirculating thermal fluid inlet, and the dryer is configured to be heated by indirect heat exchange using the recirculating thermal fluid.