Fluidized-Bed Furnace With Adjustable Bed Volume for Low Sludge Flow
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Solution Overview
Problem
Existing fluidised bed incineration furnaces face challenges in maintaining optimal operating temperatures and reducing auxiliary fuel consumption due to varying sludge flow rates, particularly during start-up and low production phases, leading to inefficiencies and increased energy losses.
Innovation Solution
A method and furnace design that allows adjustable reduction of the fluidisation zone volume and air flow rate by using a sleeve-like insert to optimize incineration based on varying sludge volumes, maintaining efficient combustion and reducing auxiliary fuel use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the furnace operates with a fixed fluidisation zone volume and air flow rate designed for nominal sludge production, then the furnace can handle future increased production capacity, but during start-up and low production phases the furnace requires excessive auxiliary fuel consumption to maintain operating temperature
Solution Approach 1:
The patent applies the dynamics principle by making the fluidisation zone volume adjustable rather than fixed. A telescopic or movable wall allows the fluidisation zone volume to be dynamically reduced during start-up and low production phases, and expanded for nominal and future production. This dynamic adjustment enables the furnace to adapt its size to the actual sludge input rate, maintaining efficient combustion conditions and reducing auxiliary fuel consumption when processing small amounts of sludge, while preserving the capability to handle future increased production capacity.
2Reliability
If the air flow rate is maintained at nominal operating levels during low sludge production, then sufficient oxygen is available for complete combustion, but the excess air causes excessive heat loss and cooling of the bed
Solution Approach 1:
The patent dynamically adjusts the air flow rate to match the actual sludge production level. During start-up and low production phases, the air flow rate is reduced proportionally to the reduced sludge input, preventing excess air from causing heat loss and bed cooling. When nominal or increased production is achieved, the air flow rate is increased to ensure sufficient oxygen for complete combustion. This dynamic coordination between air flow rate and sludge input rate resolves the contradiction between combustion reliability and energy loss.
3Use of energy by moving object
If the fluidisation zone volume is reduced to match low sludge production rates, then auxiliary fuel consumption is minimized, but the furnace cannot handle future increased production capacity
Solution Approach 1:
The patent employs a movable or telescopic wall that enables dynamic adjustment of the fluidisation zone volume. During start-up and low production phases, the wall position is adjusted to reduce the fluidisation zone volume, minimizing auxiliary fuel consumption. When nominal or increased production is achieved, the wall is moved to expand the fluidisation zone volume, enabling the furnace to handle higher sludge input rates. This dynamic volume adjustment resolves the contradiction between energy efficiency at low production and adaptability to future capacity increases.
4Temperature
If auxiliary fuel is continuously injected to maintain 850°C operating temperature during low sludge production, then the furnace maintains minimum operating temperature, but energy efficiency deteriorates and operating costs increase
Solution Approach 1:
The patent dynamically adjusts the fluidisation zone volume to match the actual sludge production level. During start-up and low production phases, the reduced fluidisation zone volume concentrates the available heat in a smaller space, maintaining the 850°C operating temperature without requiring continuous auxiliary fuel injection. When nominal or increased production is achieved, the fluidisation zone volume is expanded to accommodate higher sludge input rates while maintaining efficient combustion and temperature. This dynamic volume adjustment resolves the contradiction between maintaining operating temperature and energy efficiency.
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
Enables efficient incineration across varying sludge flow rates by minimizing fuel consumption and energy losses, providing economic and environmental benefits while maintaining furnace performance.
Implementation Method 1
A fluidised bed incineration furnace comprises an enclosure in the lower part of which there is a bed of particles, preferably sand constituting the fluidisation zone into which sludge is injected as fuel
Implementation Method 2
The fluidised sand bed is heated to incineration temperature (750-850° C.) and constitutes an extremely turbulent medium in which heat exchanges reach very high transfer coefficients. Organic matter, typically dewatered sludge, generally fed into the base of this bed at one or more points, is very rapidly disintegrated by the turbulence of the sand, evaporation takes place instantaneously and partial combustion of the organic matter takes place with the fluidisation air as oxidant.
Data Source
AI summary
A method for incinerating organic matter derived from the treatment of wastewater, or of industrial or agricultural waste, such as sludge and notably treatment plant sludge, is in a fluidized-bed incineration furnace, the furnace including a chamber in the lower part of which there is a bed of particles, preferentially sand, constituting a fluidization zone, in which fluidization zone the organic matter is introduced as fuel whilst air is injected as oxidizer into the bed of sand from a wind box through a fluidization dome surmounting the box. The air passes through passages made in the fluidization dome, and the furnace is configured to treat a nominal value of volume of organic matter to be treated. The method includes a step of adjusting the volume of the fluidization zone as a function of the volume of organic matter to be treated in which, when the volume of organic matter to be treated is lower than the nominal value, the volume of the fluidization zone is reduced from an initial volume to a reduced volume, and the incoming air flow is reduced by closing air passages so only the passages opening into the thus reduced fluidization zone are left active.