Gasification System with Segmented Pyrolysis Zones
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Solution Overview
Problem
Current pyrolysis techniques for carbonaceous feedstock face challenges in achieving high methane concentration and efficient tar cracking, leading to lower product gas purity and increased tar disposal costs due to operating at suboptimal temperatures and inefficient methanation processes.
Innovation Solution
A gasification system with serially connected primary, secondary, and tertiary chambers, where the primary chamber operates at temperatures above 850°C for pyrolysis and tar cracking, the secondary chamber at 700-900°C for methanation, and the tertiary chamber at 700-1100°C for further pyrolysis and gasification, with a catalytic surface and reactant injection ports to enhance methane production and tar cracking, and a process involving pyrolysis and methanation stages to produce a high methane content product gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pyrolysis is operated at excessively high temperature (>1100°C), then thermal cracking of long chain hydrocarbons is enhanced and hydrogen production increases, but methane produced may be pyrolysed resulting in significant waste tar formation and lowered product gas purity
Solution Approach 1:
The pyrolysis chamber is divided into multiple temperature zones (first zone at 850-950°C, second zone at 1000-1100°C) to perform different functions sequentially: the first zone produces methane while the second zone cracks tars without pyrolyzing methane, thus resolving the contradiction between hydrogen production and product gas purity
Solution Approach 2:
Different regions of the pyrolysis chamber are assigned different temperature characteristics: the first zone maintains moderate temperature (850-950°C) for methane production, while the second zone provides high temperature (1000-1100°C) for tar cracking, allowing each zone to optimize its specific function without compromising the other
2Reliability
If pyrolysis is operated at lower temperature (<1100°C), then product gas purity is maintained, but tar cracking efficiency is reduced resulting in lower amount of available carbon and hydrogen for methanation
Solution Approach 1:
The pyrolysis chamber is segmented into two temperature zones where the first zone (850-950°C) protects methane from pyrolysis while the second zone (1000-1100°C) efficiently cracks tars, thus achieving both high product gas purity and high tar cracking efficiency simultaneously
Solution Approach 2:
The first zone performs preliminary methane production at controlled temperature before the gas enters the second zone where tar cracking occurs at higher temperature, ensuring methane is formed before exposure to conditions that would pyrolyze it
3Productivity
If conventional gasification process is used for coal powder, then processing of fine particles is achieved, but product gas has unfavorable low methane concentration
Solution Approach 1:
The process changes the temperature parameter profile by implementing a two-zone pyrolysis system with specific temperature ranges (850-950°C followed by 1000-1100°C) that optimize both fine particle processing and methane concentration in the product gas
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 achieves a high methane concentration in the product gas while reducing tar content and disposal costs by optimizing temperature profiles and reactant injection across multiple chambers, enhancing the efficiency of pyrolysis and methanation processes.
Implementation Method 1
pyrolysing and methanating the feedstock to produce a reaction gas in at least one pyrolysis chamber, wherein the at least one pyrolysis chamber operates at a temperature at or above 850°C
Implementation Method 2
the secondary chamber at 700-900°C for methanation, and the tertiary chamber at 700-1100°C for further pyrolysis and gasification, with a catalytic surface
Implementation Method 3
The thermal cracking of long chain hydrocarbons, efficient at a temperature above 1000° C., results in an increased pool of hydrogen, as well as formation of methane
Data Source
AI summary
Processes and systems are provided for converting a carbonaceous feedstock into a reaction gas and a syngas, involving a step of pyrolysing and methanating the feedstock in a pyrolysis chamber to produce the reaction gas and a step of gasifying unconverted feedstock in the presence of a reactant to produce a syngas.