Hydrothermal Carbonization of Spent Coffee Grounds

With increasing coffee production and consumption, the amount of coffee by-product is also increasing. Therefore, there is growing worldwide interest in using these by-products as a renewable energy source. In this study, hydrothermal carbonization was conducted with subcritical water to improve the fuel characteristics of spent coffee grounds. The water content was varied, with the mass ratio between the dry sample and water set to 1:1.5 and 1:4. The reaction temperature was increased by 10 °C from 180 to 250 °C. The fuel and thermal characteristics of the reaction products were investigated through mass and energy yields, elemental, proximate, and heating value analysis. In analysis results, as the reaction temperature increased, carbon and fixed carbon content increased, and oxygen and volatile matter content decreased, resulting in an increase in calorific value. Thermogravimetric analysis, derivative thermogravimetry, and Fourier transform infrared spectroscopy were also conducted on the reaction products. To investigate their storage characteristics, chemical oxygen demand analysis was conducted. The results showed that with increasing reaction temperature, the fixed carbon content and heating value increased; also, the fuel characteristics became similar to those of coal. In addition, the reaction products became more hydrophobic as the reaction temperature increased.

Research on Purification Technology of Ultra-Large Flake Graphite Based on Alkali-Acid Method

Graphite is a strategically scarce resource, and the preparation of high-purity graphite is the prerequisite and basis for the application of graphite. In order to determine the optimal purification technology parameters of an ultra-large flake graphite mine pneumatic separation ore with a fixed carbon content of 77.69%, a particle size of mainly 10 to 40 mesh, and main impurities of calcium carbonate, iron oxide and silica , two additional experiments of acid method and alkali method were added on the basis of alkali-acid method, to investigate the purification effect of different technological processes and acid leaching times on graphite raw materials, as well as to analyze the retention extent of different methods and alkali fusion temperature on graphite ultra-large flake structure. The results show that all three methods can increase the fixed carbon content of graphite to above 99%. However, compared with the acid method and the alkali method, the alkali-acid method can obtain high-purity graphite while also better protecting the graphite's ultra-large flake structure. The optimal fusion temperature is 400 °C, the optimal acid leaching time is 30% sulfuric acid thrice and 5% hydrofluoric acid once. After purification, the fixed carbon content of the product exceeds 99.97%.

Characteristics of the Coal Fines Produced from Low-Rank Coal Reservoirs and Their Wettability and Settleability in the Binchang Area, South Ordos Basin, China

By using proximate analysis, X-ray diffraction mineral analysis, scanning electron microscope, contact angle measurement, and settlement simulation experiment, the coal fines produced from the coalbed methane wells of Binchang area were used to study the characteristics including particle size distribution, composition, morphology, wettability, and settleability. The results show that the particle size of coal fines produced from coalbed methane wells are mainly >20 mesh, ranging of 1-400 μm, and the particle size distribution curve is mainly dominated by the main-secondary bimodal type, with the main peak of 30-300 μm. The particle size from large to small is drill cutting coal fines, flowback coal fines, bailing coal fines, and pipeline filter coal fines. In terms of ash content, coal fines are higher than coal seam, and drilling cuttings are higher than bailing coal fines, while the fixed carbon content of the former is lower than that of the latter. The minerals of coal fines are mainly kaolinite, illite, quartz, and other 6 minerals, and the mineral types of drilling coal fines are the most abundant, while the bailing coal fines only contain illite and quartz. The roundness of coal fine particles ranges from excellent to poor in the order of bailing coal fines, pipeline filter coal fines, flowback coal fines, and drilling cuttings. However, the sorting of drilling cuttings is excellent, and the particle edges are straight, neat, and smooth, while the sorting of bailing coal fines is poor, and the particle edges are curved, uneven, and rough. The contact angles of coal fines are 40.25°-69.5°, indicating hydrophilous. The wettability of bailing coal fines is better than that of drilling cuttings. The particle size has a negative correlation with the wettability effect. The more obvious the modification effect of positive wetting agent is, the worse the modification effect of negative wetting agent is. The modification of surfactant has nothing to do with the particle size of the coal fines, but is closely related to organic components and minerals. The larger the coal particle size, the higher the settling rate, and the higher the ash content and the lower the fixed carbon content, the faster the settling rate. With the dividing point 150 mesh, the settling rate of large particles is mainly affected by particle size, while that of small particles is affected by the composition.

"Biopellet" as One of Future Promising Biomassbased Renewable Energy: a Review

The depletion of fossil energy reserves and not environmentally friendly fossil energy emissions makes it necessary to use renewable energy as an alternative to replacing fossil energy. Biopellet is one of the renewable energy based on biomass that exists in Indonesia. Biopellets are produced from a base of abundant biomass. Thus, biopellets have the potential and promise to continue to be used as fuel by humans. The literature review includes the characteristics of biopellets and the application of biopellets as fuel. Biopellets can be made by mixing biomass with an adhesive with a concentration of 15% (w/w) then stirred until homogeneous and put into a pellet mill for printing. The pellets were dried in an oven for 30 minutes. Biopellet characteristically has complied with SNI 8021-2014 for parameters of ash content, fixed carbon content, caloric value, water content, and volatile matter content. The application of biopellet as a stove material also shows good performance for heat, efficiency, and emission parameters. In conclusion, biopellet is a renewable energy fuel based on biomass that has potential in the present and promising in the future.

Investigation on the Structure and Fractal Characteristics of Nanopores in High-Rank Coal: Implications for the Methane Adsorption Capacity

The structure and fractal characteristics of nanopores of high-rank coal were investigated using an approach that integrates N2 adsorption and field emission scanning electron microscopy (FE-SEM). The results indicated that the high-rank coal of the Shanxi Formation has a complex pore-fracture network composed of organic matter pores, mineral-related pores, and microfractures. The pore type of high-rank coal tends to be complicated, and the main pore types are inkbottle pores and open pores, which are more conducive to methane enrichment. The Ro,max has a negative relationship with the total pore volume. In addition, the ash and inertinite contents show a positive correlation with the average pore size (APS), while the fixed carbon content exhibits a negative relationship with the APS. The pore structure of high-rank coal is controlled not only by the degree of metamorphism but also by coal composition, which leads to the variation in pore structure becoming more complicated. With the increase in coal metamorphism, high-rank coal with high amounts of fixed carbon content generally possesses a higher irregularity in pore structure. No obvious relationship was observed between D2 and the coal components, which indicates that the pore structure, ash content, moisture content and other factors controlled by the metamorphism of coal have different effects on D2 that lead to this inapparent relationship. A negative relationship exists between adsorption volume and D1, which indicates that the high irregularity of the pore structure is not conducive to methane absorption and that no obvious correlation exists between the adsorption volume and D2. In the high-rank coal, the high D1 value represents the complexity and heterogeneity of the pore structure and represents a low adsorption affinity for methane molecules; in addition, D2 has no effect on the methane adsorption capacity.

Aprovechamiento de cáscara de piñón (Jatropha curcas L.) y paja de arroz (Oriza sativa L.) para la elaboración de pellets como biocombustible

Use of pine nut husk (Jatropha curcas L.) and rice straw (Oriza sativa L.) for the production of pellets as biofuel Resumen El uso de los biocombustibles sólidos es una de las alternativas para reemplazar a los combustibles convencionales en la producción de energía eléctrica y calorífica. Este trabajo tiene como objeto el aprovechamiento biomásico residual de la cáscara de piñón (Jatropha curcas L.) y paja de arroz (Oriza sativa L) para la producción de pellets como biocombustible sólido. Se aplicó mediante un diseño experimental (Simplex-lattice) la mezcla en proporciones de 100%-0%, 75%-25%, 50%-50%, 25%- 75%,0%-100% respectivamente. Se efectuaron análisis a la materia prima y producto terminado en porcentaje del contenido de humedad, cenizas, volátil, carbono fijo, adicionalmente el contenido de celulosa y lignina a las materias primas. Para la obtención de pellets, se empleó un equipo de pelletizado marca KL 1500, los pellets se elaboraron con recirculación para eliminar el exceso de humedad para el mejoramiento de textura y dureza. Las mezclas de las biomasas lignocelulósicas, que presentaron un mayor contenido de carbono fijo fueron la M2 (75%-25%) =16,53 ±3,2 % y M5 (0%-100%) =23,51 ±0,72%, en lo referente a material volátil fueron la M1 (100%-0%) =82,37±2,0% y M2 (75%-25%) =81,57±3,47%. El poder calorífico calculado reveló que con una mezcla del 75% de paja de arroz con un 25% de cáscara de piñón se obtiene un poder calorífico de 29,21±0,1 Mj/Kg y la mezcla de 50% de paja de arroz y 50% de cáscara de piñón, genera un valor de 29,01±0,01 Mj/Kg. Concluyendo que las mezclas mencionada puede ser aprovechada para la generación de calor. Palabras clave: Biocombustible sólido; biomasa; pellets; arroz; piñón. Abstract The use of solid biofuels is one of the alternatives to replace conventional fuels in the production of electrical and heat energy. The objective of this work is the residual biomass utilization of the pine nut husk (Jatropha curcas L.) and rice straw (Oriza sativa L) for the production of pellets as solid biofuels. The mixture was applied using an experimental design (Simplex-lattice) in proportions of 100% -0%, 75% -25%, 50% -50%, 25% - 75%, 0% -100% respectively. Analysis of the raw material and finished product were carried out as a percentage of the moisture, ash, volatile, and fixed carbon content, in addition to the cellulose and lignin content of the raw materials. To obtain pellets, a KL 1500 brand pelletizing equipment was used, the pellets were recirculated to remove excess moisture to improve texture and hardness. The mixtures of lignocellulosic biomasses, which had a higher fixed carbon content were M2 (75% -25%) = 16.53 ± 3.2% and M5 (0% -100%) = 23.51 ± 0, 72%, regarding volatile material, were M1 (100% -0%) = 82.37 ± 2.0% and M2 (75% -25%) = 81.57 ± 3.47%. The calculated calorific value revealed that with a mixture of 75% of rice straw with 25% of pinion husk, a calorific value of 29.21 ± 0.1 Mj / Kg is obtained and the mixture of 50% of rice straw and 50% of pinion shell, generates a value of 29.01 ± 0.01 Mj / Kg. Concluding that the mentioned mixtures can be used for heat generation. Keywords: Solid biofuel; biomass; pellets; rice; pinion.

THE EFFECT OF BINDER RATIO ON THE PHYSICAL AND COMBUSTION CHARACTERISTICS OF CARBONIZED RICE STALK BRIQUETTES

The selection or choice of agro-waste briquettes for domestic and industrial cottage applications depends on the fuel properties. In this study, the briquette was produced by carbonizing the rice stalk followed by crushing and sieving, the binder was prepared by dissolving the starch in hot water, then mixed with the sieved carbonized rice stalk and then the briquette was produced using the briquetting machine. Proximate analyses, viability, characteristics and combustion were determined to know the average composition of their constituents. From the results obtained it was observed that ash content, moisture content, after glow and ignition propagation decrease as the binder ratio increase while fixed carbon content, volatile matter, calorific value, density and compressive strength increase. The results of this work indicate that briquettes produced using high concentration of the binder would make good biomass fuels. However, it has a high moisture content of 25.00%, high ash content of 23.00%, moderate volatile matter of 44.80%, low fixed carbon content of 32.20%, moderate calorific value of 13.86 MJ/Kg and high density of 0.643g/cm3. The results obtained for all the parameters showed that rice stalks briquettes produced with high concentration of the binder (starch) had a better performance based on their combustion profile.

ANALISA PEMANFAATAN BRIKET LIMBAH ARANG KAYU ALABAN DI DESA TAPUK KECAMATAN LIMPASU KABUPATEN HULU SUNGAI TENGAH

The solution to reduce the use of fossil fuels is by utilizing renewable energy such as solar power, wind power, and hydropower, as well as the utilization of other alternative energy derived from biomass. One of alternative energy from biomass that is very potential is briquettes. Tapuk Village, Limpasu Subdistrict, Hulu Sungai Tengah Regency is one of the producers of Alaban wood charcoal, with grade D charcoal in the form of charcoal flakes and is often regarded as waste. This study aims to determine the physical properties of alaban wood charcoal waste briquettes which include water content, ash content, volatile matter content, fixed carbon content, and calorific value, as well as the potential utilization of alaban wood charcoal waste briquettes. so that residents can use Tapuk Village, Limpasu District, Hulu Sungai Tengah Regency as an alternative fuel to substitute kerosene and LPG. The results showed the physical properties of alaban wood charcoal waste briquettes for 3.66 % water content, 3.15 % ash content, 14.31 % volatile matter content, 78.88% fixed carbon content, 6.259.33 cal / gr calorific value. The use of alaban wood charcoal waste briquettes is able to produce consumption costs efficiency of 60% better than the use of LPG and 70% better than the use of kerosene.

COMPARATIVE STUDIES OF PHYSICAL AND COMBUSTION CHARACTERISTICS OF RICE HUSK BRIQUETTES PRODUCED USING DIFFERENT BINDING AGENTS

Briquettes samples were manually produced using a hydraulic press from rice husk using starch and gum Arabic resin as binders. The proximate analysis of the samples reveals that the briquette produced using starch binder has the moisture value (9.26±0.251), Ash (16.29±0.172), Volatile matter (64.17±0.306), and fixed carbon content of (9.55±0.502) respectively whereas the gum Arabic bonded briquette has the moisture value (10.68±0.214), Ash (19.89±0.775), Volatile matter (60.84±0.250), and fixed carbon content of (8.26±0.535) respectively. The physical characteristics of the samples shows that the starch bonded briquette has the compressive strength of (0.668± 0.012 N/mm2), density (0.68±0,028 g/cm3), ignition time (0.17±0.01 cm/s), afterglow (313±6.123 sec), and calorific value (10.35±0.135 MJ/Kg) respectively whereas the gum Arabic bonded briquette has the compressive strength of (0.559±0.031 N/mm2), density (0.575±0.031 g/cm3), ignition time (0.13±0.007 cm/s), afterglow (187±7.035 sec), and calorific value (9.47±0.095 MJ/Kg) respectively. Water boiling test shows that both the starch and gum Arabic bonded briquettes boil water to 1000C at 18 and 22 minutes respectively. The thermal efficiency of the briquettes during water boiling test shows that the starch bonded briquette has the highest thermal efficiency.