Two-Stage Refuse Gasification for High Moisture Waste

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Solution Overview

Problem

Conventional combustion systems for municipal solid waste face challenges with high moisture content refuse, leading to unstable combustion, increased energy requirements, and the production of undesirable emissions like NOx, carbon monoxide, and dioxins, due to limitations in controlling gas flow and temperature.

Innovation Solution

A two-stage refuse gasification combustion system that employs a moving grate, primary and secondary air sources, and advanced control systems to regulate oxidant supply and temperature, utilizing a first and second gasifier with a post-combustor, ash collector, and sophisticated gas regulators to optimize combustion efficiency and reduce harmful emissions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If high moisture content refuse is combusted in conventional systems, then energy recovery is attempted, but combustion stability deteriorates and harmful emissions increase

Engineering Contradiction:
Improveenergy recoveryVSAvoidcombustion stability
Core Design Contradiction:
Use of energy by moving objectVSReliability

Solution Approach 1:

The combustion process is divided into two distinct stages: a drying stage where moisture is removed at lower temperatures, and a combustion stage where dry refuse is burned at higher temperatures. This segmentation allows each stage to be optimized independently, ensuring stable combustion even with high moisture content refuse by preventing the interference of moisture during the high-temperature combustion phase

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The refuse is pre-dried in the first chamber before entering the combustion chamber. This preliminary action of removing moisture beforehand prevents the negative effects of high moisture content during combustion, such as temperature reduction and combustion instability, thereby enabling reliable energy recovery

Inventive Principle:
Principle #10Preliminary action

2Use of energy by moving object

If high moisture content refuse is combusted, then energy recovery is attempted, but harmful emissions increase

Engineering Contradiction:
Improveenergy recoveryVSAvoidharmful emissions
Core Design Contradiction:
Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

By separating the drying and combustion processes into different chambers, the system prevents incomplete combustion that would occur if moisture were present during burning. This segmentation ensures that combustion occurs only after moisture removal, thereby reducing harmful emissions while maintaining energy recovery

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The preliminary drying action in the first chamber removes moisture before combustion, creating conditions for complete and clean burning in the second chamber. This preliminary preparation prevents the formation of harmful emissions by ensuring dry refuse enters the combustion zone

Inventive Principle:
Principle #10Preliminary action

3Productivity

If gas flow is increased to dry high moisture refuse, then drying effectiveness improves, but system complexity and energy requirements increase

Engineering Contradiction:
Improvedrying effectivenessVSAvoidsystem complexity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The system segments the drying function into a dedicated first chamber, separating it from the combustion chamber. This allows drying to occur with controlled, lower gas flow rates without compromising the combustion process, thereby maintaining drying effectiveness while avoiding the need for high gas flow rates that would increase system complexity

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The first chamber acts as an intermediary zone between the refuse input and the combustion chamber. It performs the moisture removal function separately, allowing the combustion chamber to operate independently with optimized conditions, thereby simplifying the overall system control while maintaining effective drying

Inventive Principle:
Principle #24Intermediary (Mediator)

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 efficiently processes refuse with high moisture content, minimizing undesirable emissions and enhancing energy conversion efficiency by precisely controlling gasification and combustion processes, thereby creating a more durable and efficient energy conversion system.

Implementation Method 1

a first gasifier (102) for receiving所述 refuse and processing所述 refuse to a volatiles free state

Methodology Applied
Scientific EffectGasification: Pyrolysis

Implementation Method 2

a post-combustor (104) for receiving所述 gas and所述 volatiles free refuse and combusting所述 gas and所述 volatiles free refuse

Methodology Applied
Scientific EffectCombustion: Combustion

Data Source

PatentEP2433053B1Two stage refuse gasification system
Publication Date: 2016.08.10 COVANTA ENERGY CORPORATION
  • EP2433053B1 patent drawingFigure 1
  • EP2433053B1 patent drawingFigure 2
  • EP2433053B1 patent drawingFigure 3

AI summary

A two stage refuse gasification combustion system for processing refuse is disclosed. The system may contain features such as an advancer, a first and second gasifier, a drier, a gas regulator, and a post combustor. Additionally, methods for regulating gas and advancing refuse through a two stage refuse gasification combustion system are disclosed.