Energy-efficient gasification-based multi-generation apparatus, facilities, or systems, and methods of modifying existing gasification-based multi-generation apparatus and the various conventional thermal coupling arrangements, are provided. An exemplary gasification-based multi-generation apparatus includes a gasification system configured to generate raw syngas feed from a carbon-based feedstock, and an acid gas removal system configured to remove acidic contaminants from the raw syngas feed to thereby provide a treated syngas feed. The gasification system includes a gasification reactor, a syngas fluid cooler reactor, and a soot ash removal unit comprising a soot quench column, a soot separator, a soot filter, a soot scrubber, and a gasification system energy management system having a conventional set of heat exchanger unit and an added set of heat exchanger units to enhance energy efficiency. The acid gas removal system includes a reactor, an acid gas contaminant absorber, a solvent regenerator, and an acid gas removal system energy management system having a conventional set of heat exchanger unit and an added set of heat exchanger units to enhance energy efficiency.