Today, as more and more power is required globally, securing a sufficient supply of energy is very important. Coal is one of the energy resources that may be useful in solving the energy crisis. Currently, we have to reduce greenhouse gas emissions. Coal gasification is one of the methods that use coal and at the same time solve the climate problem. This technology produces synthesis gas, which is composed of hydrogen, methane, and carbon monoxide, from coal through procedures of drying, pyrolysis, and gasification. In this study, KIDECO coal (HCK raw coal) and hybrid coal (biomass/coal = 10 wt%) were mixed with water to make a coal slurry. Hybrid coal is a fuel combining coal and sugarcane derived from bioliquid. Transportation of the coal slurry, which is related to slurry viscosity, was considered as an aspect of energy efficiency. Viscosity experiments were performed on the KIDECO coal and hybrid coal by Korea Institute of Energy Research (HCK coal) using a viscometer at 40, 50, and 60 wt% of water content. Simulation analysis was performed by the Aspen Plus program. In this study, the entrained-flow gasifier is the proposed basic model for simulating gasification of HCK raw coal and HCK coal. The carbon conversion and the cold gas efficiency were also calculated to analyze the energy efficiency. Sensitivity analysis was performed according to various conditions such as slurry water content, oxygen ratio, operating temperature, and operating pressure to investigate the process characteristics after verifying the basic model. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.