Multipassage Boiler with Moving Ceramic Bed for Corrosion Control
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Solution Overview
Problem
High-temperature corrosion and ash deposits in multi-pass boilers for waste incineration plants limit the service life of superheaters and heat exchangers, reduce heat transfer efficiency, and restrict catalyst effectiveness, necessitating frequent cleaning and temperature limitations.
Innovation Solution
A multi-pass boiler design featuring a slowly descending bed of ceramic or corrosion-resistant balls that decouples superheaters from the flue gas flow, preventing ash deposition and enhancing heat transfer, combined with catalyst-coated balls for efficient nitrogen oxide reduction, allowing higher operating temperatures and continuous self-cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If superheaters and heat exchangers are arranged in the second pass with high flue gas temperatures above 400°C, then heat transfer efficiency is improved, but high-temperature corrosion rates increase and service life is limited
Solution Approach 1:
The patent introduces a moving bed of spherical parts that continuously moves through the second pass, dynamically interacting with the flue gas and heating surfaces. This dynamic system allows the spherical parts to physically remove ash deposits and corrosive components from the superheater and heat exchanger surfaces, enabling operation at higher temperatures without the corrosion limitations of static systems
Solution Approach 2:
The moving bed of spherical parts performs self-cleaning of the heating surfaces through its own movement and gravity-driven flow. The spherical parts automatically scour and remove deposits from the superheater and heat exchanger surfaces as they pass through the second pass, eliminating the need for external cleaning mechanisms and maintaining heat transfer efficiency continuously
2Productivity
If flue gas temperature is maintained above 400°C for efficient heat transfer, then productivity is improved, but ash deposits form on catalyst surfaces rendering them unusable
Solution Approach 1:
The moving bed creates dynamic flow conditions that prevent ash particles from settling and forming static deposits on catalyst surfaces. The continuous movement and turbulence generated by the spherical parts keep the flue gas in constant motion, preventing the formation of stationary ash layers that would block catalyst pores and reduce effectiveness
Solution Approach 2:
The spherical parts act as an intermediary between the high-temperature flue gas and the catalyst surfaces. They physically interact with the flue gas stream, removing corrosive components and ash deposits before they can reach and contaminate the catalyst, thereby protecting the catalyst while allowing high temperature operation
3Reliability
If cleaning devices are used to remove ash deposits from heating surfaces, then purity is improved, but device complexity and discontinuous operation requirements increase
Solution Approach 1:
The moving bed of spherical parts provides self-cleaning functionality through its own movement. As the spherical parts flow through the second pass, they automatically scour and remove ash deposits from the superheater and heat exchanger surfaces. This eliminates the need for separate, complex cleaning devices and allows continuous cleaning operation without interrupting the flue gas flow
Solution Approach 2:
The moving bed of spherical parts serves multiple functions simultaneously: it acts as a heat transfer medium, a flow distributor, and a self-cleaning mechanism. This multi-functionality eliminates the need for separate dedicated cleaning devices, reducing overall system complexity while maintaining continuous cleaning action
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
Significantly reduces corrosion rates, extends superheater life, improves heat transfer, and enhances nitrogen oxide reduction efficiency, eliminating the need for frequent cleaning and slip catalytic converters, while maintaining optimal temperature control.
Implementation Method 1
the corrosive components of the fly ash are removed by the movement of the bed over the surface of the heating surfaces
Implementation Method 2
Heat exchangers or evaporators or superheaters can be located both in the second and in further passes, via the heating surfaces of which thermal energy is transferred to the medium located inside and dissipated
Implementation Method 3
some of the ash particles that were previously carried along by the flow are separated due to gravity and inertia and discharged through an opening into a funnel
Implementation Method 4
some of the ash particles that were previously carried along by the flow are separated due to gravity and inertia
Implementation Method 5
High-Dust SCR catalytic converters are used in a temperature range of below 400 °C to reduce ammonia slippage of the SCR and as the sole device for reducing nitrogen oxides
Data Source
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Figure 2
AI summary
The invention relates to a multipass boiler (2) for cooling, or cooling while simultaneously cleaning, a flue gas (1) of a refuse incinerator, said boiler comprising a first flue (3) having a lower opening (5) into which the flue gas (1) is introduced, and a second flue (4), a superheater (8), a heat exchanger (9), a base with a lower opening (12), and an ascending channel (11) through which the flue gas (1) leaves said second flue, there being a downward-moving feed material (6) consisting of spherical parts in the second flue (4) of the boiler, which is removed through the lower opening (12) of the base and fed into the second flue (4) through an upper opening. The solution according to the invention is advantageous in that, by decoupling the superheater from the flue gas, a higher superheating temperature can be achieved, the rate of corrosion of the superheater can be reduced, continuous cleaning of the heating surfaces is achieved, and deposited ash can be ground up and removed from the boiler.