Characteristics of low-rank and medium-rank Indonesian coal using the TG-DSC method

Low-rank and medium-rank coal are dominant coal resources in Indonesia. Considering the decisive role of coal in coal-fired power plants, it is crucial to examine the combustion characteristics before burning coal in the boiler. This paper presents the effect of moisture content, heating value, and volatile matter on ignition temperature and burn out of five samples of low-rank coal and five samples of medium-rank coal using TG-DSC analysis which was carried out using LINSEIS High-Pressure STA at atmospheric pressure with an air rate of 25 ml/min and heating rate of 10 °C/min. The investigation results show that low-rank coal with the higher volatile matter has tremendous reactivity and is more flammable, and favours of burning through itself than medium-rank coal. Medium-rank coal has better combustion with short residence time because it has a lower burnout temperature (Tbo) value than low-rank coal. However, medium-rank coal burns more instantly because it has a lower temperature interval than low-rank coal. Medium-rank coal, which has fixed carbon and higher heating value, but lower moisture content, has a higher Rmax value than low-rank coal. In conjunction with these properties, it is crucial to examine the implementation in boilers.

Techno-economic analysis study of coal gasification plant into various strategic chemicals

The abundant amount of coal reserves in Indonesia has a great potential to be used as a source of raw materials and energy for industry. However, the use of coal in meeting domestic needs is not optimally utilized, as indicated by the high number of raw coal exports abroad. In addition, the low quality of coal is also one of the reasons for its low utilization. The processing of coal into synthetic gas (syngas) opens the way downstream of coal-derived chemical products, namely dimethyl ether (DME), methanol, ammonia and synthetic natural gas (SNG). The integration of various chemical products is expected to maximize the potential of Indonesian coal. The plant capacity was 11540 tpd (tons per day) low-rank wet coal producing DME 2000 tpd, methanol 2500 tpd, ammonia 600 tpd and SNG 25 MMSCFD (million standard cubic feet per day). These chemical production technologies have been proven and are commercially available. Based on the results of the process and economic simulations, it is found that the establishment of a coal gasification plant into various integrated chemicals is feasible to be established with an internal rate of return (IRR) of 12.46% and a payback period of 6 years and 5 months.

Function of Production, Capital, Labor and Government Policy in The Coal Mining Sector - Case Study of an Indonesian Coal Mining Company

This study aims to determine the effect of labor, capital, and government policies on coal output and the scale of coal business results of PT Indo Tambangraya Megah Tbk. The new thing from this research is the Cobb-Douglas production function which usually uses labor and capital variables, but in this study, it has been expanded by adding policy variable in the form of Law No. 4 of 2009 regarding Mineral and Coal Mining, which is not yet present in other studies. The research method is linear regression using the Cobb-Douglas model function. The results showed that labor did not significantly influence coal production. Capital has a significant effect on model 2 and policy has a significant effect on model 3. The coal mining business of PT Indo Tambangraya Megah Tbk is in decreasing return to scale because if the three variables are combined, it will be worth -0.24. This condition occurs because the additional output produced is smaller than the additional input (δ% output <δ% input).

Numerical Analysis of Longwall Gate-Entry Stability under Weak Geological Condition: A Case Study of an Indonesian Coal Mine

The present research primarily focuses on the investigation of gate-entry stability of longwall trial panel under weak geological condition in Indonesia coal mine by means of numerical analysis. This work aims at identifying appropriate roof support at 100 m and 150 m of depth during gate development. Due to depth depending competency of dominant rock, the stability of gate-entry at 100 m of depth can be optimized by leaving at least 1 m of remaining coal thickness (RCT) above and below the gate-entry. The appropriate support for the trial panel gate-entry is steel arch SS540 with 1 m and 0.5 m spacing for 100 m and 150 m of depth, respectively. The influence of panel excavation on gate-entry is also discussed. Regarding the aforementioned influence, the utilization of additional gate mobile support is recommended at least 10 m from the longwall face.

Coal Pillar Strength Formula in Indonesian coal mines

In underground coal mines, coal pillars play a major rule in sustaining the weight of the overburden and protecting the stability of the entries and crosscut during mine development and production, allowing the miners to safely extract the coal¹. The determination of a coal pillar size is adjusted to the expected load and strength of the coal seam. It needs to consider several factors such as pillar load (stress within the pillar), pillar strength, and safety factors. In this determination, an analysis will be conducted using five similar coal pillar strengths including; Obert-Duvall Equation (1967), Holland Equation (1964), Holland-Gaddy Equation (1956), Salamon-Munro Equation (1967), and Bieniawski (1983). Using AirLaya seam as an example, we can combine the results of various equations. The coal used in the Airlaya research area has a value of k = 425.75, thus the strength of Airlaya insitu seam coal is estimated to be 161,607 Psi.

Preliminary Study of Calorific Value Increase on Lignite Coal Using Dialkyl Carbohydrate Biosurfactant

Indonesian coal consumption is dominated by a low-grade coal quality, and supplied from local coals mining which was composed of lignite. A technological breakthrough has to be main objective to convert low grade coal into upper-class coal. This paper reports on improving the quality of lignite coal by washing with biosurfactant. Di-alkyl carbohydrates were tested on coal sizes of 80, 64, 16 and 6 mesh. The optimum biosurfactant applied to increase the calorific value derived from brown algae, namely isopropyl stearate alginate (ISA) 0.5%. This was able to improve a calorific value of lignite coal up to 27722.74% or increased by 11%. The size of the coal also affects the calorific value of lignite coal. Four coal sizes applied in the study (80, 64, 16, and 6 mesh), indicates coal size 80 mesh has given the best calorific value improvement. Conversely, the smaller of the coal size, increase biosurfactant absorption. Thus, improve the washing capability of biosurfactants.

Experimental Study of Rare Earth Element Enrichment from Indonesian Coal Fly Ash: Alkaline Leaching

Rare Earth Element plus Yttrium (REY) is an critical element in green technology and consumer goods. Due to its limited supply, it is necessary to look for alternative sources of REY which one of the potential candidates is coal fly ash. Two samples of coal fly ash which originated from Indonesia were leached in an alkaline solution in order to remove Si and increase REY content. Samples were collected from pulverized coal power plant in East Java (sample T) and West Java (sample I). Leaching conditions were studied including concentration of NaOH, ratio of volume of liquid (L) to weight of solid (S) and leaching time. It was found that the optimum condition was reached at NaOH concentration of 8M, L/S ratio (10 mL: 1 g) and leaching time of 120 min. At this condition, percent removal of Si and REY enrichment were respectively 56.22% and 30% for sample I, and 33.75% and 24% for sample T.

LEGAL CERTAINTY FOR FOREIGN INVESTORS IN COAL MINING IN INDONESIA

Since 2009, there have been significant regulatory changes in coal mining in Indonesia, beginning with the enactment of Law No.4 of 2009 concerning Mineral and Coal Mining, which replaced the prior system of contracts and mining authorizations (Kuasa Pertambangan; KP) with mining business permits (Ijin Usaha Pertambangan; IUP). There are two types of IUP: exploration and production operation. Then, the mechanism of Clean and Clear was created to reduce the large numbers of overlapping licenses. This article explores Indonesian regulatory changes and court rulings in coal mining and clarifies share divestment requirements for foreign investors in Indonesian coal-mining operations, which should not be classified as indirect expropriations.