Hydrothermal Treatment of Brown Coal To Improve the Space Time Yield of a Direct Liquefaction Reactor

Abstract

The possibility of hydrothermal treatment (HTT) of brown coal at 200−350 °C was examined as a pretreatment method for improving the space time yield of a Victorian brown coal liquefaction reactor. Main reactions occurring during HTT below 350 °C were decarboxylation and dehydration, by which most of carboxylic groups were decomposed. Sodium and chlorine in the brown coal were almost completely removed below 250 and 300 °C, respectively, during HTT. Around 20−30% of Ca and Mg in the brown coal was also removed by HTT below 350 °C. The viscosity of the coal−solvent slurry prepared from a HTT coal was less than 1 / 10 of the viscosity of the coal−solvent slurry prepared from a just dewatered coal. This enabled the increase of the coal concentration of the coal−solvent slurry from 28 to 40 wt %. The significant increase of the coal concentration of the coal−solvent slurry prepared from the HTT coal was found to be realized mainly by the decrease of the pore volume of the coal particles through HTT. These results suggest that HTT will be a pretreatment method effective not only to increase the space time yield but to suppress the scale formation of the brown coal liquefaction process.

Experimental and simulation study of the temperature distribution in a bench‐scale fixed bed Fischer–Tropsch reactor

“…In general, the plot of the integral STY can be interpreted as how the overall product reaction rate varies with catalyst bed length, while a plot of differential STY shows the axial change in local catalyst bed efficiency. As shown in Figure 11a,b, the integral STY, decreases monotonically along the reactor bed, when either increasing N 2 flow rate or decreasing GHSV; this results is supported by Deckwer's research 38 and is caused by both the decreasing temperature profile and reactant concentration 39,40 . Since the differential STY was calculated based on equal volumes of catalyst, it is proportional to the local C 3+ product formation rate.…”

Upgrading of low rank coal by hydrothermal treatment: Coal tar yield during pyrolysis

“…Moreover, hydrothermal treatment not only promotes the hydro-liquefaction activity in coal liquefaction [24,25] but also increases the coal concentration of coalsolvent slurry [26], then, the oil production cost of liquefaction process is reduced. Shui [27,28] has studied the effect of hydrothermal treatment on modifying caking and coking properties of the sub-bituminous coal.…”

Influence of the hydrothermal dewatering on the combustion characteristics of Chinese low-rank coals

“…Wu et al [13] studied the gas-, solid-, and liquid-phase products obtained after HTD, and analyzed the occurrence of carbon and its migration mechanism during HTD. In recent years, there has been a growing interest of HTD in coal treatment and a number of potential applications of hydrothermal processing have been investigated, such as preparing coal water slurry with the solid and liquid products of HTD [14], improving the space time yield of brown coal liquefaction reactor [15], upgrading and dewatering of raw tropical peat [16], dewatering of sludge [17], generating alternative solid fuel from paper sludge [18], and producing liquid and solid biofuels [19,20].…”