The Effect of Upgrading Processes on Combustion Characteristics of Berau Coal

Abstract

Indonesian coal was upgraded by upgraded brown coal (UBC), hot water drying (HWD), and steam drying (SD) processes to study the combustion characteristics of this coal. The differential thermal-thermogravimetric analysis (DTA-TG) was carried out to obtain some combustion parameters, such as, ignition temperature (T ig ), maximum combustion rate temperature (T max ), maximum combustion rate (R max ), char burn-out temperature (T bo ), and ash yield. The differential thermal analyzer (DTA) curve can be used to estimate the heat released during the combustion process, which corresponds to the high heating value of the coal. The results show that the combustion characteristics of HWD and SD processes are much better than those of the UBC process. This is because the UBC process was conducted at lower temperature and pressure.

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

“…They found that T i of the upgraded coals increased, whereas T max is not so changed, and k max significantly increased. They also treated the brown coal with hot water drying (HWD) and steam drying (SD), and the combustion characteristics of HWD and SD processes were much better than those of the UBC process due to it conducted at lower temperature and pressure [36]. Besides, there were three DTG peaks for all of the brown coals in their study.…”

“…This result demonstrates that several volatile matters turned into char structures during the upgrading process, thus enhancing the char combustion process. Besides, there was another combustion peak around 300 C for ZT-250, which was ascribed to the combustion of volatile matter [35,36] due to its highest volatile matter content (35.58 wt%, Table 1). This provided another evidence that some unstable active compositions in the volatile matter gradually transferred into stable inert components.…”

Preparation and Characterization of the Glycerol-Embedded Hybrid Coal

“…Low-rank coal inherently has many disadvantages for direct application in preconstructed power plants, such as low heating value, low combustion efficiency in the boiler, high shipping cost due to moisture readsorption, and the increase of carbon dioxide emission. For these reason, energy companies are still sometimes hesitant to adopt low-rank coal as fuel. , High moisture content in the low-rank coal, in particular, causes spontaneous combustion during its transportation and storage. , Hence, there have been great efforts to develop the low-rank coal upgrading technologies. , It has been reported that dewatering and prevention of water readsorption into the coal play a key role to improve low-rank coal in terms of heating value and transportation price. , The Korea Institute of Energy Research has proposed an upgraded low-rank coal called HCK, which is a fuel synthesized by the impregnation of bioliquid into low-rank coal followed by torrefaction. First, they suggested molasses as a bioliquid additive.…”

“…5,7 High moisture content in the low-rank coal, in particular, causes spontaneous combustion during its transportation and storage. 8,9 Hence, there have been great efforts to develop the low-rank coal upgrading technologies. 10,11 It has been reported that dewatering and prevention of water readsorption into the coal play a key role to improve low-rank coal in terms of heating value and transportation price.…”

Upgrading Effects of Supercritical Carbon Dioxide Extraction on Physicochemical Characteristics of Chinese Low-Rank Coals

“…Various dewatering and upgrading processes have been developed since the 1920s, such as the upgraded brown coal (UBC) method, hot water drying (HWD) method, steam drying (SD) process, microwave irradiation process, and solvent extraction process. − The general conclusions of the LRC upgrading process are basically known. Several scientific researchers found that Indonesian coal upgraded by UBC, HWD, and SD processes has a higher T i , T max , R max , and calorific value. ,, The oxygen content and moisture of upgraded LRCs decrease, whereas their calorific value increases. , Similar conclusions were shown in upgraded coal by solvent extraction at around 350 °C. , Some researchers investigated the effects of the pore structure and oxygen functional group content on the moisture distribution and found that the removal of free moisture is associated with the collapse of macropore structures, whereas the bound water is reduced because of the removal of oxygen functional groups . Besides, the effects of desulfurization, enhancement of grindability on LRCs, ,, and increase of the rheological characteristics of coal slurries are obtained in the microwave irradiation upgrading process. , …”