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Slag Management Toolset for Improvised Gasifier Performance

National Energy Technology Laboratory

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Technology Marketing Summary

Research is active on the development of computational tools for slag management during carbon feedstock gasification. This invention is available for licensing and/or further collaborative research from the U.S. Department of Energy’s National Energy Technology Laboratory.


Gasification that relies on carbon feedstocks can face challenges associated with impurities in the feedstock, in the form of mineral and metallic compounds. During gasification, these materials can oxidize and/or melt, forming particles that coalesce at high gasification temperatures to form liquid slags whose viscosity depends on overall chemistry, the gasification temperature, and the gasifier oxygen partial pressure. Liquid slags can also interact with the gasifier liner, which is needed to protect the metal gasification chamber during the gasification process. The slag corrosion of the refractory liner increases with increasing temperature, so gasifier operators typically try to operate the gasifier at low versus high temperatures. As the gasification temperatures decreases, however, the viscosity of a slag increases—becoming so viscous it will not flow from the gasifier. This situation forces a gasifier operator to either increase the gasification temperature to lower slag viscosity so it will flow, or to shut down the gasifier so the slag can be physically removed from it. Both scenarios can cause damage to the refractory liner, shortening its service life. Knowledge of how to control slag viscosity properties is critical to improving and maintaining the on-line performance of a gasifier. 

Currently carbon feedstock is purchased based on carbon content, with little attention paid to its impact on gasification operation or refractory service life. Gasifier operators lack the knowledge to accurately predict slag properties from a specific carbon feedstock, or how to manipulate/manage the feedstock during gasification in relation to controlling the ash chemistry through slag additives or blending of different carbon feedstocks.

This technology describes a slag management computational toolset that enables a user to determine the optimal temperature for gasification of a carbon feedstock based on the chemistry of impurities (or additives) in the carbon feedstock that form slag in the gasifier.

The slag management model works by determining the optimal temperature range for gasification using known slag chemistry, viscosity, and temperature/viscosity relationships. When the slag management toolset is used to control slag properties, it can increase feedstock flexibility and decrease gasifier maintenance costs; changes that can be used to increase gasifier availability and lower syngas production costs. Additionally, the database of the slag chemistry and viscosity information can be expanded by adding public or proprietary information, allowing slag viscosity predictions to be optimized to a specific user needs.   




· The slag management toolset represents a new and unique method to predict slag viscosity for optimal gasifier operation based on carbon feedstock ash and additive chemistry

· The toolset allows for improved predictions of molten slag properties without the need to study slag structure or using regression fitting analysis

· Preliminary testing of the existing slag model by an industrial gasifier user demonstrated the toolset to be superior to commercially available slag models

· The slag management toolset can be customized to a specific user needs based on their slag chemistry/viscosity relationships

· The slag management toolset allows users to know in advance of purchasing a coal how ash impurities in it will impact gasification temperature, allowing a gasifier operator to predict in advance necessary modifications of that coal for their gasification process, and thus know the true cost of using a carbon feedstock

Applications and Industries

· Slag management for gasifier operators, modelers, or coal users that need to control molten ash properties

· Other processes involving control of high temperature slags, such as steel production

· The toolset may be applicable to other processes not related to molten materials, but that are dependent on historical means of process control 

More Information

U.S. Non-provisional Patent Application No. 15/894,885 filed February 12, 2018, titled “A Slag Management Toolset for Determining Optimal Coal Gasification Temperatures.”

 Inventors: Kyei-Sing Kwong and James Bennett

Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Application 20180230390
Embodiments relate to methods, systems and an apparatus for determining an optimal temperature for gasification of a feedstock. The method includes predicting a chemistry of impurities in the feedstock that form a slag; predicting viscosity curves of the impurities in the feedstock that form the slag; predicting a need for one or more additives; and predicting an impact of chemistry changes of the slag based at least partly on temperature vs viscosity behavior during gasification. The method further includes controlling a gasification temperature to achieve a desired viscosity of the slag using at least one of the predicted chemistry changes and the additives.
Technology Status
Development StageAvailabilityPublishedLast Updated

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