Maceral Types and Quality of Coal in the Tuli Coalfield: A Case Study of Coal in the Madzaringwe Formation in the Vele Colliery, Limpopo Province, South Africa

The Madzaringwe Formation in the Vele colliery is one of the coal-bearing Late Palaeozoic units of the Karoo Supergroup, consisting of shale with thin coal seams and sandstones. Maceral group analysis was conducted on seven representative coal samples collected from three existing boreholes—OV125149, OV125156, and OV125160—in the Vele colliery to determine the coal rank and other intrinsic characteristics of the coal. The petrographic characterization revealed that vitrinite is the dominant maceral group in the coals, representing up to 81–92 vol.% (mmf) of the total sample. Collotellinite is the dominant vitrinite maceral, with a total count varying between 52.4 vol.% (mmf) and 74.9 vol.% (mmf), followed by corpogelinite, collodetrinite, tellinite, and pseudovitrinite with a count ranging between 0.8 and 19.4 vol.% (mmf), 1.5 and 17.5 vol.% (mmf), 0.8 and 6.5 vol.% (mmf) and 0.3 and 5.9 vol.% (mmf), respectively. The dominance of collotellinite gives a clear indication that the coals are derived from the parenchymatous and woody tissues of roots, stems, and leaves. The mean random vitrinite reflectance values range between 0.75% and 0.76%, placing the coals in the medium rank category (also known as the high volatile bituminous coal) based on the Coal Classification of the Economic Commission for Europe (UN-ECE) coal classification scheme. The inertinite content is low, ranging between 4 and 16 vol.% (mmf), and it is dominated by fusinite with count of about 1–7 vol.% (mmf). The high amount of inertinite, especially fusinite, with empty cells and semi-fusinite in the coals will pose a threat to coal mining because it aids the formation of dust.

Study on the washability by using float sink test and thermal decomposition of the Mogoin gol bituminous coal

The Mogoin gol bituminous coal properties were determined by proximate and ultimate analysis and thermal behaviors performed using a HITACHI TG/DTA7300 thermogravimetry analyzer. Float sink test carried out by Russian standard GOST 4790-93. Results of the proximate and ultimate analyses showed that the coal has Vdaf=30.7%, Ad=10.6%, Cdaf=76.5% and Qdaf=7532 kcal/kg. According to the coal classification, the coal belongs to the J class of bimuminous coal. The rate of mass loss was maximum in the range 483°С. Yields and ash contents of the fraction were γб=49.9 and 5.6% respectively, when for the separation was used heavy liquid with 1.3g/cm3 density. In general, it can be concluded that the Mogoin gol coal belongs to the category of coals with very good washability. Therefore, it will be advantageous and economically viable to use coal concentrate with low-ash for further chemical processing. Могойн голын ордын нүүрсний халууны задралын болон баяжигдах шинж чанарын судалгаа Хураангуй: Дээд ангилалын чулуун нүүрс болох Могойн голын ордын нүүрсний шинж чанарыг техникийн болон элементийн шинжилгээгээр, халуун, дулаан тэсвэрлэх чанарыг термогравиметр HITACHI TG/DTA7300 маркийн багажийн тусламжтайгаар, нүүрсний баяжигдах шинж чанарыг хүнд шингэний ГОСТ 4790-93 стандарт аргаар тодорхойллоо. Нүүрсний техникийн болон элементийн шинжилгээний үр дүнгүүдээс Ж маркийн чулуун нүүрс болохыг баталж байна. Жингийн алдагдлын хурд ДТГ 483°С-ын температурын мужид хамгийн их байв. Хүнд шингэний нягтыг ихэсгэх тутам баяжмалын үнс болон гарц аажмаар ихэсгэх хандлагатай бөгөөд δ=1.3 г/см3 нягттай хүнд шингэнд нүүрсийг баяжуулбал, үнс бага Aб а=5.6%, гарц өндөртэй γб=49.9% баяжмал гарган авах боломж. Иймд бага үнстэй нүүрсний баяжмалыг цаашид гүн боловсруулалтын чиглэлээр ашиглахад давуу талтай, эдийн засгийн ач холбогдолтой байх болно. Түлхүүр үг: нүүрс, термогравиметр, жингийн алдагдал, баяжуулалт, баяжмал, хөвсөн/ живсэн фракц

Reserves Estimation for Coalbed Methane Reservoirs: A Review

A continuous growth in the global economy and population requires a sustainable energy supply. Maximizing recovery factor out of the naturally occurring hydrocarbons resources has been an active area of continuous development to meet the globally increasing demand for energy. Coalbed methane (CBM), which is one of the primary resources of natural gas, associates complex storage mechanisms and requires some advanced recovery techniques, rendering conventional reserve assessment methods insufficient. This work presents a literature review on CBM in different aspects. This includes rock characteristics such as porosity, permeability, adsorption capacity, adsorption isotherm, and coal classification. In addition, CBM reservoirs are compared to conventional reservoirs in terms of reservoir quality, reservoir properties, accumulation, and water/gas saturation and production. Different topics that contribute to the production of CBM reservoirs are also discussed. This includes production mechanisms, well spacing, well completion, and petrophysical interpretations. The main part of this work sheds a light on the available techniques to determine initial-gas-in-place in CBM reservoirs such as volumetric, decline curve, and material balance. It also presents the pros and cons of each technique. Lastly, common development and economic challenges in CBM fields are listed in addition to environmental concerns.

Determination of mercury thermospecies in South African coals in the enhancement of mercury removal by pre-combustion technologies

Samples of South African bituminous coals were analysed for total mercury (Hg) and Hg thermospecies concentrations using an RA-915 + Zeeman Mercury Analyser. Total mercury concentrations in samples of coals (n = 57) ranged between 10 ng g−1 and 493 ng g−1 with a mean value of 150 ± 53 ng g−1. Thermospecies of Hg were determined by monitoring Hg response as a function of sample temperature, increasing at 0.8 °C/s from ambient to 720 °C. This approach provides important information on thermal release of Hg species, as indicated by their appearance over specific temperature intervals. This permits identification of the presence of Hg thermospecies in coal and their quantification in each time (temperature) interval. It was found that 76% of tested bituminous coal samples release Hg species within low temperature intervals (20–180 °C and180–360 °C). The information generated in this study will aid in the selection of suitable coals for pre-combustion treatment that can lead to significant reduction of atmospheric Hg emission during coal combustion at power stations. This analytical approach can also be used for the creation of a system of coal classification based on the temperature of release of various Hg thermospecies.