Indonesian Lignite Research Articles

ANALISIS DETERMINAN EKSPOR LIGNIT INDONESIA TAHUN 2012-2021

This study aims to analyze; influence of benchmark interest rate and inflation on the USD exchange rate; influence of benchmark interest rate, inflation, coal price reference, and the USD exchange rate on the volume of Indonesia's lignite exports; whether the USD exchange rate mediates influence of benchmark interest rate and inflation on volume of Indonesia's lignite exports. This study uses monthly time series data from 2012-2021 so that 120 observations are obtained, technique used is path analysis. Research shows; 1) the benchmark interest rate and inflation have a negative significant effect on the USD exchange rate in 2012-2021; 2) the benchmark interest rate has a negative significant effect on the volume of Indonesia's lignite exports in 2012-2021, while inflation has no significant effect; 3) the USD exchange rate mediates the influence of the benchmark interest rate and inflation on the volume of Indonesia's lignite exports in 2012-2021.

Investigation of Low-Temperature Copyrolysis of Organic Matter from Huadian Oil Shale and Indonesian Lignite

Investigation of Low-Temperature Copyrolysis of Organic Matter from Huadian Oil Shale and Indonesian Lignite

Effects of Chain Alkanes on Restraining Water Re-Adsorption of Dried Indonesian Lignite

Effects of Chain Alkanes on Restraining Water Re-Adsorption of Dried Indonesian Lignite

Possibility and Process of the Use of Upgraded Coal and Coke from Indonesian Lignite Coal in the Iron Making Process

Possibility and Process of the Use of Upgraded Coal and Coke from Indonesian Lignite Coal in the Iron Making Process

Effects of Changes in Physicochemical Properties Caused by Hydrothermal Treatment on Pyrolysis Performance of Indonesian Lignite

Effects of Changes in Physicochemical Properties Caused by Hydrothermal Treatment on Pyrolysis Performance of Indonesian Lignite

Study on pore structure characteristics of Indonesian lignite during low temperature drying process

ABSTRACT In order to study the effect of temperature on the pore structure of lignite, liquid nitrogen adsorption and scanning electron microscopy (SEM) were used to analyze the change of pore structure of Indonesian lignite after heating, and the relationship between fractal dimension and pore structure of lignite after heating was analyzed. The effect of drying temperature on the pore structure of lignite was investigated by effective moisture diffusion coefficient and X-ray diffraction (×RD). The results show that between 40 and 160 ℃, with the increase of drying temperature, the N2 adsorption and desorption of Indonesian lignite shows a trend of first increasing and then decreasing. The fractal dimensions D 1 and D 2 of some lignites have a linear relationship with the specific surface area and average pore diameter, respectively, and the fractal dimension D 3 has a linear relationship with the average pore diameter. As the drying temperature increases, the moisture transfer resistance decreases and the effective moisture diffusivity of lignite () increases accordingly. There is a linear positive correlation between and the average pore diameter. The increase of the lignite aromatic system and the decrease of the crystallite stacking height have certain effects on the pore structure of lignite.

Preparation of High Strength Coke from Indonesian Lignite by Deeply Pulverized

Coke production from lignite was studied as a continuation of research showing the effectiveness of a sequence of hot briquettes and carbonization on preparations high strength coke from Indonesian lignite. The hot briquetting and carbonization cokes from three Indonesian lignites with a deeply pulverized. Ball milling carried out for 10 hours and 20 hours to obtain a small particle size. Raw lignite hot briquettes at mechanical pressure and temperature of 128 MPa and 200 °C, respectively, allowed cokes to be produced with a tensile strength (TS) of 7-11 MPa. Pretreatment, 10 hour and 20 hour ball milling, respectively increasing TS from the resulting coke to 15-23 and 19-36 MPa. Moreover, it is proved in this study that the structure on the coke fracture has a smooth texture and solid with less pore. There is a strong correlation between TS and coke density of individual lignites.

Pyrolysis and Carbon Dioxide Gasification Kinetics of Pine Cones and Lignite Blends

This study determines the kinetic parameters of blended Pinus kesiya, Pinus elliottii, and Indonesian lignite in co-pyrolysis and co-gasification. Nine binary blends and three ternary blends were tested using a thermogravimetric analyzer. Pyrolysis was carried out in an argon atmosphere and DTG plots showed that Pinus kesiya had the highest maximum pyrolysis rate while Pinus elliottii had the lowest starting decomposition temperature. Similarly, blends with Pinus elliottii had lower maximum pyrolysis rates and lower starting decomposition temperatures than those with Pinus kesiya. Ternary blends, however, have starting decomposition temperatures and maximum pyrolysis rates close to those of pure Pinus elliottii. The Kissinger-Akahira-Sunose (KAS) model was used to obtain the reaction rate constants and activation energies of the pyrolysis reactions of various blends. Co-gasification of the mixtures was also done in a CO2 environment at gasification temperatures of 700°C, 800°C, and 900°C. The conversion-time data obtained were fitted using five different gas-solid reaction models.

Change in Catalytic Activity of Potassium during CO2 Gasification of Char

Potassium (K)-catalyzed CO2 gasification of lignite char was studied with a particular focus on the change in catalyst activity with the char conversion (X) at 800–900 °C. Char samples were prepared from an Indonesian lignite by a sequence of complete removal of inherent metallic species and mineral matter, K-loading by ion-exchange, and pyrolysis. The catalytic activity of K (kcat′) was defined as the rate of catalytic gasification (after elimination of the rate of non-catalytic gasification and that of K volatilization from total mass release rate from char) per amount of K retained by the gasifying char. kcat′ increased by a factor of 5–20 with X over its range up to 0.98–0.99, depending on the initial K concentration in the char (mcat,0), ranging 0.16–1.4 wt %-daf. Such significant increase in kcat′ was due to the change in not the intrinsic reactivity of char but its porous nature, that is, the size and volume of pores that retained the K catalyst. At X < 0.4, the entire portion of the K catalyst was...

The ash formation and attrition characteristics of an Indonesia lignite coal ash for a 550 MWe ultra supercritical CFB boiler

The Samcheok CFBC (circulating fluidized bed combustion) power generation plant, the world largest, consists of 4 units of 550 MWe USC (ultra-supercritical) CFB boilers, started operation since the end of 2016. The years’ operation proves that there lacks circulating material and low solid hold-up in the upper furnace when burning Indonesia coal with low ash content of 4.5%. To solve this problem, the present study studied the mass balance of the Samcheok CFB boiler by investigating the ash formation and attrition characteristics of the feed coal in the lab. The ash formation PSD (particle size distribution) proves that the burnout-produced fly ash and fragmentation-produced fly ash are not the main sources of the production of fly ash. The heterogeneity of specific chemical compositions of particles in terms of particle sizes is proved to be one of the key factors for determining the attrition rate. For large particles, SiO2 and Al2O3 compositions dominate and results in low attrition rate, while for small particles, Fe2O3 and CaO compositions dominate and results in high attrition rate. The fine particles produced due to attrition have very high Fe2O3 contents, indicating that the heterogeneity of chemical composition is enhanced due to attrition. These findings show good agreement with the phenomenon of the high content of Fe2O3 in fly ash in the CFB boiler.

No.1-8 インドネシア褐炭とインドネシア瀝青炭との混炭による自然発熱性緩和の検討

No.1-8 インドネシア褐炭とインドネシア瀝青炭との混炭による自然発熱性緩和の検討

Improving physicochemical properties of upgraded Indonesian lignite through microwave irradiation with char adsorbent

To upgrade Indonesian lignite by significantly reducing volatile matter content, char adsorbent was employed to accelerate lignite pyrolysis through microwave irradiation. Physicochemical properties of pyrolyzed lignite were determined with the assistance of char adsorbent on Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray spectroscopy, N2 adsorption porosimetry, and contact angle analysis. Under the same microwave power of 800 W and irradiation time of 12.5 min, the lignite temperature remarkably increased from 150 °C to 656 °C with the aid of 10 g char adsorbent. Its apparent aromaticity increased from 0.50 to 0.97. The relative content of superficial carbon functional groups attributed to π–π∗ transitions increased from 1.18% to 6.71%. The volatile matter content (dried basis) markedly decreased from 48.94% to 6.47% due to the release of volatile compounds in the lignite.

Combustion Efficiency and Pollution Risk Analysis Based on Different Type of Coal

Air pollution such as PM2.5 and PM10 has become a serious problem for many cities in China. One of the key factors for the causation of air pollution is the exhausts of coal combustion. The combustion efficiency and emission will be affected by different type of coal. Thus, four raw coals include Gaoping anthracite coal, Tangshan bituminous coal, Liupanshui lean coal, and Indonesia lignite coal are selected for the combustion process simulation and analysis based on Aspen Plus. The results show that the combustion heat of anthracite coal reached the highest level based on same combustion condition. According to the emission results of the selected coal, the combustion temperature just has a little impact on the emission of SOX, while the emission of NOX will increase when the combustion temperature increase. The study may provide a constructive strategy for the selection and utilization of different type of coal for relevant industry.

Comparison of catalytic pyrolysis and gasification of Indonesian low rank coals using lab-scale bubble fluidized-bed reactor

Various methods are used in the coal gasification technology for increasing the efficiency of low rank coal to the level of high rank coal through catalytic gasification. The catalyst used in the catalytic gasification process lowers the activation energy required in the coal gasification reaction. Our purpose was to determine the characteristics of the reaction conditions for producing syngas and the characteristics for comparison catalytic pyrolysis and gasification performance. Among various coals, we used Indonesian low rank coals (Indonesian lignite, MSJ, and Roto South) characterized by a large deposit volume and low cost. Catalytic pyrolysis and gasification experiments were run under the same experimental conditions (reactor type, reaction temperature, catalyst content, and catalyst input method), and the characteristics were compared. Taking the conversion and heating values into consideration, the optimal conditions for catalytic gasification in this study were an H2O/C mole ratio of 10, temperature of 800 °C, and 10 wt% catalyst impregnation.

Effect of coal blending and ashing temperature on ash sintering and fusion characteristics during combustion of Zhundong lignite

Ash sintering and fusion characteristics of pulverised Zhundong lignite and its blends combusted at different temperatures in a muffle furnace were investigated. Zhundong lignite (ZL) was blended with an Australian bituminous (AB) and an Indonesian lignite (IL), respectively, at various blending ratios. The blends were then combusted in the muffle furnace in air at 550°C and 815°C. The sintering and fusion temperatures of the ashes of the blends were determined. In addition, the ashes prepared at 550°C were further heated to 850°C, 1050°C and 1250°C in air for different periods of time to study the mineralogical and morphological changes during the ash sintering and fusion. The results showed that the ZL ash at 815°C was rich in basic oxides with Ca-bearing minerals anhydrite, calcium silicate and yeelimite being dominant, incurring relatively low ash sintering and fusion temperatures. Both AB and IL ashes, however, were rich in acidic oxides and dominant with refractory minerals such as quartz or mullite, leading to relatively high ash sintering and fusion temperatures. As the AB or IL addition ratio in the blend increased, the ash sintering temperature also increased, indicating that the addition of AB or IL into ZL decreased the ash sintering tendency. However, as the AB or IL addition ratio increased, the ash softening temperature (ST) and fluid temperature (FT) decreased first and then increased, reaching the lowest values at addition ratios of 40% for AB and 20% for IL. In addition, owing to the higher alkali and alkali earth contents in the forms of fluxing minerals, the sintering and fusion temperatures of the ash samples at 550°C were correspondingly lower than those of the ashes at 815°C. XRD and SEM-EDS analyses of the ash heated at 850°C, 1050°C and 1250°C revealed that the sintering of the ZL ash was attributed to Na- and Cl-bearing minerals whereas the fusion of the ZL ash was attributed to the eutectics enriched with Ca, Al, Fe, and S. The addition of 20% AB into ZL resulted in the formation of hauyne, gehlenite and nepheline of low melting points and thus promoted the fusion of the ZL80AB20 ash, explaining why FT and HT of the ash initially decreased with increasing AB addition.

Comparison of Combustion and Emission Characteristics of an Indonesian Lignite Washery Tailing Slurry with a Bituminous Coal in a Bench-Scale Bubbling/Circulating Fluidized Bed Combustor

In this study, the combustion and emission characteristics of slurry from an Indonesian lignite washery tailing (LWT) and a bituminous coal were studied and compared in both a bubbling fluidized bed (BFB) and a circulating fluidized bed (CFB). The effects of excess air ratio, feeding rate, secondary air ratio, and secondary air location on the flue gas emissions were analyzed to investigate the optimal operating conditions. The results show that it is feasible to directly fire LWT slurry in a CFB. The temperature of the dense-phase bed firing the LWT slurry can reach 800 °C but is lower than that of a normal BFB/CFB firing coal. Both SO2 and NO emissions of bituminous coal are higher than those of LWT slurry, but their emission characteristics are still below the limits for both EU and Chinese regulations. Improved emission characteristics are observed when firing LWT slurry and coal in CFB compared to BFB. Two main differences were found between LWT slurry and coal: (1) Low primary air (PA) flow rates fa...

The influences of moisture on particle ignition behavior of Chinese and Indonesian lignite coals in hot air flow

The effect of moisture content on ignition and combustion behavior of Chinese (HL) and Indonesian (YN) lignite were investigated. Particles with a size range of 75–105μm with different moisture contents were injected in a bench-scale, electrically heated transparent reactor and the combustion of individual particles was observed with a high-resolution high-speed camera. Direct ignition observations indicated that most of the HL lignite particles underwent extensive fragmentation during ignition. Fragmentation was attributed to the explosive diffusion of volatiles and water vapor to the particle surface as a result of fast heating rate. Fragmentation reduced the particle size and increased the possibility of heterogeneous ignition of individual fragments. YN lignite particles on the other hand, underwent one-mode whole particle ignition upon heating. Higher moisture content caused a significant ignition delay in both lignite samples. 10% and 20% moisture in lignite samples resulted in around 83 and 160ms delay in ignition for both coals. Higher intensity of fragmentation of HL particles during combustion compared to YN lignite resulted in shorter total particle combustion time at higher moisture contents. The findings of this study advanced the knowledge of the effects of moisture on ignition and combustion of low-rank coals.

Effects of drying method on self-heating behavior of lignite during low-temperature oxidation

Pore structure changes during pre-drying of lignite affect its low-temperature oxidation and increase the susceptibility to spontaneous combustion. In this study, the effects of drying methods (i.e., vacuum drying and N2 drying) on self-heating of Indonesian lignite during oxidation were investigated using a dual fixed-bed quartz reactor. The variation of coal temperatures was recorded and the release of CO2 and CO was measured by a gas chromatography. The pore volume and surface area of dried samples were measured using Brunauer-Emmett-Teller (BET) method. Mesopores in lignite initially increased and collapsed with further increasing drying intensity during drying in N2, resulting in a rapid self-heating rate of lignite within a critical moisture content range of 6–13%. However, vacuum drying caused a gradual increase in mesopores, which lead to a monotonic increase in self-heating rate with decreasing residue moisture content in lignite. The experimental results indicated that the production rates of both CO2 and CO during oxidation of raw lignite increased with reducing particle size and increasing gas flow rate, but decreased at lower moisture contents. Typically, the variation of production rates of both CO2 and CO as a function of particle size and gas flow rate followed a similar trend to that of raw lignite when the lignite was completely dried by the vacuum drying method. The impacts of lignite particle size and gas flow rate on the yields of CO2 and CO was limited due to less diffusion of O2 into small pores, suggesting that the oxidation reaction between lignite and oxygen has been shifted from diffusion controlled to kinetic controlled reactions.

Activated carbon and graphite facilitate the upgrading of Indonesian lignite with microwave irradiation for slurryability improvement

To upgrade Indonesian lignite by significantly reducing moisture and volatile matter content for the preparation of quality coal water slurry (CWS) gasification fuel, carbonaceous materials with high dielectric permittivity were employed to accelerate heating rate via microwave irradiation. The physicochemical properties of lignite upgraded through microwave irradiation with the addition of activated carbon and graphite were investigated through Fourier transform-infrared spectroscopy, X-ray photoelectron spectra and N2 adsorption porosimetry. The oxygen functional groups of the upgraded lignite decreased remarkably, whereas coal rank increased. Furthermore, the atomic ratio of oxygen to carbon and the molar ratio of carbonyl to the aromatic groups of the lignite upgraded with the aid of activated carbon were both lower than those of lignite upgraded with the inclusion of graphite. On the contrary, the aromaticity and aromatic-to-aliphatic ratio of the first type of upgraded lignite were both higher than those of the second type. The hydrophilic functional groups on the surfaces of lignite upgraded with the aid of activated carbon were lower in number than those on the surfaces of lignite upgraded with the inclusion of graphite; the opposite was true given hydrophobic functional groups. The maximum solid concentration of CWS prepared from upgraded lignite with activated carbon-assisted microwave irradiation increased markedly from 41.3wt% to 66.6wt%.

Optimization of microwave dewatering of an Indonesian lignite

Dewatering of an Indonesian lignite with microwave irradiation was optimized to increase dewatering rate and decrease energy consumption. The energy consumption of the microwave dewatering process was affected by different factors, including addition of microwave absorber, diameter-to-height ratio of lignite pile, particle size and initial moisture content of lignite. The experiment results indicated that adding absorber carbon materials (activated carbon and graphite) and metal oxides (Fe3O4, MnO2, etc.) could increase the dewatering rate and decrease the energy consumption. With increased diameter-to-height ratio of lignite pile, dewatering rate initially increased and then decreased. An optimum value exists for diameter-to-height ratio, which presents maximum dewatering rate but with minimum energy consumption. The enhancement of heat accumulation caused by larger particle size increased the dewatering rate of lignite and decreased energy consumption. The energy consumption decreased with increased lignite weight and initial moisture content. However, the energy consumption initially decreased and then increased with enhanced microwave power. Electric power consumption can be well predicted on the basis of the microwave dewatering kinetics of lignite, which can be well described by the Page model under different conditions.