Model-Free Control of UCG Based on Continual Optimization of Operating Variables: An Experimental Study

• Published in: Energies (Basel) Vol. 14; no. 14; p. 4323
• Main Authors: Kačur, Ján, Laciak, Marek, Durdán, Milan, Flegner, Patrik
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-07-2021
• Subjects: Adaptation; Air flow; Air temperature; Algorithms; Automation; Calorific value; Carbon monoxide; Chemical reactions; Coal; Coal gasification; Coal mines; Coal mining; Gases; Hydrocarbons; operating variables; Optimal control; Optimization; Reactors; Steam; syngas; Synthesis gas; underground coal gasification (UCG); Variables
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en14144323

The underground coal gasification (UCG) represents an effective coal mining technology, where coal is transformed into syngas underground. Extracted syngas is cleaned and processed for energy production. Various gasification agents can be injected into an underground georeactor, e.g., air, technical oxygen, or water steam, to ensure necessary temperature and produce syngas with the highest possible calorific value. This paper presents an experimental study where dynamic optimization of operating variables maximizes syngas calorific value during gasification. Several experiments performed on an ex situ reactor show that the optimization algorithm increased syngas calorific value. Three operation variables, i.e., airflow, oxygen flow, and syngas exhaust, were continually optimized by an algorithm of gradient method. By optimizing the manipulation variables, the calorific value of the syngas was increased by 5 MJ/m3, both in gasification with air and additional oxygen. Furthermore, a higher average calorific value of 4.8–5.1 MJ/m3 was achieved using supplementary oxygen. The paper describes the proposed ex situ reactor, the mathematical background of the optimization task, and results obtained during optimal control of coal gasification.