Gasification of High-Ash Feedstock via Carbon Coating and Acid Gas Stripping
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Solution Overview
Problem
Existing gasification processes face challenges with high ash content feedstocks, leading to equipment damage, short syngas effluent cooler lifetime, and increased risk of plugging due to high carbon-to-ash ratios and ash fouling.
Innovation Solution
A process that gasifies residue streams with lower carbon-to-ash ratios, removes solids from recycled water, and strips acid gases to prevent precipitation, allowing for efficient operation in a non-slagging regime and reducing the risk of plugging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ash content in feedstock is increased to process challenging streams, then economic value is improved through higher-value products, but equipment damage and short lifetime occur due to ash fouling and plugging
Solution Approach 1:
The patent changes the operating temperature parameter to below ash fusion temperature, preventing ash from melting and forming molten slag that causes fouling and plugging, thereby extending equipment lifetime while still processing high-ash feedstock
Solution Approach 2:
The patent introduces a carbon coating layer as an intermediary substance that forms on ash particles, preventing direct contact between ash and equipment surfaces, thus reducing fouling and extending equipment lifetime
2Object-affected harmful factors
If carbon-to-ash ratio is increased to coat ash particles, then fouling is reduced, but downstream solids removal system size increases becoming impractical
Solution Approach 1:
The patent optimizes the carbon-to-ash ratio parameter to a specific range (2:1 to 5:1 by weight), providing sufficient carbon coating to prevent fouling while avoiding excessive carbon that would require oversized solids removal systems
Solution Approach 2:
The patent applies partial carbon coating sufficient to prevent ash particle sticking and fouling, rather than excessive coating that would create agglomeration problems and require larger solids removal systems
3Ease of manufacture
If operation is conducted in slagging regime above ash fusion temperature, then ash forms molten slag that can be separated, but costs increase due to higher oxygen usage and reduced refractory lifetime
Solution Approach 1:
The patent inverts the conventional approach by operating below ash fusion temperature instead of above it, preventing ash from melting and forming molten slag, thus avoiding the need for high oxygen consumption and refractory protection while still enabling effective ash management
4Device complexity
If ash is not coated with sufficient carbon, then carbon coating thickness is reduced, but ash particles stick to surfaces and cause fouling problems
Solution Approach 1:
The patent optimizes the carbon-to-ash ratio parameter to ensure sufficient carbon coating thickness on ash particles, preventing particle sticking and fouling while maintaining manageable system complexity
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 process achieves reduced solids loading in solids removal systems, increased hydrocarbon conversion to syngas, and improved metal recovery by operating at lower carbon-to-ash ratios and minimizing ash fouling.
Implementation Method 1
reacting the residue stream with an oxidant stream in a gasifier to produce a hot syngas stream comprising carbon monoxide, hydrogen, and soot
Implementation Method 2
contacting the hot syngas stream with a quench water stream to produce a quenched syngas stream and a water bath in the gasifier
Implementation Method 3
filtering the concentrated soot water stream to produce a solid filter cake and a liquid filtrate stream
Implementation Method 4
stripping a first sour gas stream from the primary filtrate fraction to produce a stripped water stream
Data Source
AI summary
A residue stream comprising liquid hydrocarbons and metal-rich solid particles is reacted with an oxidant stream in a gasifier to produce a syngas stream that is quenched in a water bath. The risk of plugging in the water lines is reduced by removing solids from the recycled water streams. Acid gases are stripped from at least a portion of the recycled water to reduce the risk of precipitates forming from the reaction of dissolved acid gases with metal ions.