Heavy Fuel Boiler Ash Deposition Control via Unburned Carbon Ratio
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Solution Overview
Problem
Heavy fuel-fired boilers experience ash deposition issues due to low-grade fuels like vacuum residual oil and petroleum coke, leading to operational troubles, increased cleaning expenses, and instability in power generation, particularly with increased sulfur content and unburned carbon in fly ash.
Innovation Solution
A heavy fuel-fired boiler system incorporating a denitration device, air preheater, electric precipitator, desulfurization device, ash flowability measuring instrument, and coal-ash supply unit, which adjusts air feed rates based on ash flowability and fuel composition to maintain a constant unburned carbon to sulfur ratio, reducing ash deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If charge to the electric precipitator is increased to decrease fly ash to downstream side, then fly ash amount decreases, but unburned C concentration in fly ash decreases and ash deposition increases
Solution Approach 1:
The invention changes the chemical composition parameter of fly ash by controlling the unburned carbon content through air feed rate adjustment. By maintaining a specific unburned carbon concentration relative to sulfur content, the ash deposition characteristics are modified to prevent sticking to downstream equipment while still achieving dust removal goals.
Solution Approach 2:
The invention implements a feedback control system that monitors fly ash composition (unburned carbon concentration and sulfur content ratio) and adjusts the air feed rate to the boiler accordingly. This closed-loop control maintains the unburned carbon to sulfur ratio within an optimal range to prevent ash deposition while managing fly ash quantity.
2Reliability
If air feed rate is controlled to prevent accidental fire, then boiler safety is improved, but ash deposition on downstream device increases
Solution Approach 1:
The invention modifies the chemical composition of fly ash by adjusting combustion parameters (air feed rate) to change the unburned carbon content. This parameter change transforms the ash from a sticky, deposition-prone material to a free-flowing material that can be safely handled even at controlled air feed rates required for safety.
Solution Approach 2:
The invention uses unburned carbon as an intermediary substance that modifies the properties of fly ash. By maintaining appropriate unburned carbon levels, it acts as a dispersing agent that prevents ash particles from sticking together and depositing on downstream equipment, while still allowing safe operation at controlled air feed rates.
3Power
If S content in fuel increases for energy production, then energy output is improved, but acidic ammonium sulfate increases and causes more ash deposition
Solution Approach 1:
The invention changes the ratio parameters of fly ash composition, specifically maintaining an optimal unburned carbon to sulfur content ratio. This parameter adjustment prevents the formation of sticky ammonium sulfate compounds even when fuel sulfur content is high, allowing energy production from high-sulfur fuels without excessive ash deposition.
Solution Approach 2:
The invention converts the harmful effect of sulfur in fuel (which normally causes sticky ash deposition through ammonium sulfate formation) into a beneficial situation by using controlled unburned carbon levels to modify ash properties. The sulfur that would normally cause problems is transformed into a manageable component when the unburned carbon to sulfur ratio is properly controlled.
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 prevents ash deposition-related troubles by maintaining a consistent unburned carbon to sulfur ratio in fly ash, ensuring stable boiler operation and reducing vibration issues and cleaning expenses.
Implementation Method 1
an electric precipitator that removes dust while adding ammonia into the gas after heat recovery
Implementation Method 2
a denitration device that removes nitrogen oxide in exhaust gas from a heavy fuel-fired boiler
Implementation Method 3
an air preheater that recovers heat in the gas after the nitrogen oxide is removed
Implementation Method 4
a vapor-liquid contact type desulfurization device that removes sulfur oxide in the gas after dust removal
Data Source
AI summary
In an exhaust gas treatment system including a denitration device that removes nitrogen oxide in exhaust gas from a heavy fuel-fired boiler, an air preheater that recovers heat in the gas after the nitrogen oxide is removed, an electric precipitator that removes dust while adding ammonia into the gas after heat recovery, a desulfurization device that removes sulfur oxide in the gas after dust removal, and a stack that exhausts the gas after desulfurization to the outside, an ash-shear-force measuring instrument is provided to measure an ash shear force, which is ash flowability, on the downstream side of the electric precipitator, so that a feed rate of an air supply unit that supplies air to the boiler is reduced according to ash shear-force information.