Shuttle Kiln Gas Circulation for Ceramic Sintering
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Solution Overview
Problem
Shuttle kilns face challenges in firing ceramic porous bodies with organic binders due to temperature differences causing cracks, as the excellent thermal insulation properties of ceramic honeycomb structures hinder heat transfer, leading to prolonged firing cycles and reduced productivity.
Innovation Solution
A shuttle kiln design incorporating a gas suction path and circulation path with a catalytic reactor vessel, fuel gas supply, heating device, and cooling device to control in-furnace oxygen concentration and promote even temperature distribution by catalytic combustion and gas recirculation, preventing surface burning of organic binders and reducing temperature differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rate of temperature rise in the furnace is decreased to slow down the binder releasing process, then the occurrence of cracks is prevented, but the firing cycle is prolonged resulting in decrease in productivity
Solution Approach 1:
The invention changes the oxygen concentration parameter in the furnace atmosphere from typical high levels (21%) to a controlled low level (5-15%). This parameter change fundamentally alters the combustion kinetics of organic binders, allowing for faster heating rates while preventing surface burning and crack formation. The low oxygen environment suppresses rapid oxidation reactions that cause thermal stress, enabling both high productivity and product integrity.
Solution Approach 2:
The invention creates an inert-like atmosphere by reducing oxygen concentration to 5-15%, which suppresses the combustion of organic binders. This modified atmosphere prevents the harmful oxidation reactions that cause surface burning and subsequent cracking, while still allowing controlled binder removal. The inert environment effect enables faster heating without the risks associated with high oxygen conditions.
2Reliability
If a large amount of nitrogen gas is introduced to decrease oxygen concentration to 8% or less, then crack occurrence is prevented, but cost increases due to large nitrogen gas consumption
Solution Approach 1:
The invention uses the organic binder vapor itself as the oxygen-consuming substance. By controlling the furnace atmosphere to have reduced oxygen (5-15%), the organic binders undergo controlled decomposition and combustion, consuming the available oxygen and maintaining low oxygen levels throughout the process. This self-service mechanism eliminates the need for external nitrogen gas injection while achieving the same protective effect against cracking.
Solution Approach 2:
The invention converts the potentially harmful organic binder vapor (which could cause explosions or incomplete combustion) into a beneficial oxygen-consuming agent. By allowing controlled combustion of binder vapors in the reduced oxygen atmosphere, the system maintains low oxygen levels naturally, preventing cracks without requiring expensive nitrogen gas. The harmful vapor becomes a useful tool for atmosphere control.
3Reliability
If the air ratio of the burner is decreased to lower the in-furnace oxygen concentration, then crack occurrence is prevented, but stirring in the furnace becomes insufficient and temperature distribution becomes inhomogeneous
Solution Approach 1:
The invention maintains continuous gas circulation and active stirring mechanisms that operate independently of the burner air ratio. The forced circulation system ensures continuous mixing and uniform temperature distribution even when burner air ratio is reduced to maintain low oxygen levels. This continuous useful action of gas circulation compensates for the reduced natural convection, maintaining temperature uniformity throughout the furnace.
Solution Approach 2:
The invention introduces forced gas circulation as an intermediary mechanism to achieve temperature uniformity. Instead of relying on natural convection driven by high burner air ratio, the system uses forced circulation fans or pumps to actively mix the furnace atmosphere and distribute heat uniformly. This intermediary mechanism decouples the relationship between oxygen concentration control and temperature uniformity, allowing both objectives to be achieved simultaneously.
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 configuration allows for faster firing times, reduced risk of cracks, and improved productivity by maintaining low oxygen concentrations and homogeneous temperature distribution within the kiln, eliminating the need for nitrogen gas and lowering running costs.
Implementation Method 1
burning organic binder gases in a circulation path that draws in-furnace gas, draws out in-furnace gas after the organic binder gases have been combusted and the oxygen concentration has decreased, and introduces the gas back into the furnace
Implementation Method 2
burning organic binder gases... oxygen concentration has decreased
Implementation Method 3
heating device that heats the in-furnace gas... cooling device that cools the in-furnace gas
Implementation Method 4
heating device that heats the in-furnace gas... cooling device that cools the in-furnace gas
Data Source
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AI summary
The invention provides a shuttle kiln that can fire ceramic porous bodies containing organic binders in a shorter period of time than in conventional methods without occurring breaks due to a temperature difference between the inside and the outside. The shuttle kiln of the invention is suited for firing of ceramic porous bodies containing organic binders. It includes a gas suction path 4 that suctions in-furnace gas and discharges it via an afterburner 5 and a circulation path 7 that suctions the in-furnace gas to the furnace outside to burn organic binder gas and then returns it into the furnace.