Experimental investigation on pre-heating technology of coal water slurry with different concentration in shell-and-tube heat exchangers with ladder-type fold baffles

Preheating coal water slurry (CWS) before entering the gasifier can improve gasification efficiency and reduce oxygen consumption. Shell-and-tube heat exchangers (STHXs) with ladder-type fold baffles were applied to preheating of CWS. And experiments were performed when CWS was in shell side and conductive oil flowed in tube side. The different concentration (52.13 wt%, 55.56 wt% and 57.67 wt%) of CWS fitted Bingham model had a significant effect on thermal-hydraulic performance. The experimental results show that, both shell-side temperature difference and overall heat transfer coefficient are the highest when the concentration of CWS is 52.13 wt%, and the shell-side pressure drop is the lowest. The temperature difference per unit pressure drop of CWS with 52.13 wt% and 55.56 wt% increases by 119.3%–290.2% and 55.2%–96.9% compared with that of CWS with 57.67 wt%, respectively, and overall heat transfer coefficient per unit pressure drop also decreases with the increasing of concentration of CWS. Based on experimental data, empirical correlations of Nu and f are obtained and the adjusted coefficient of determination (Adj.R²) is between 0.980 and 0.997. And compared with STHXs with fold baffles, selecting STHXs with ladder-type fold baffles is priority to preheat CWS.