The proximate analysis is the most common form of coal evaluation that reveals the quality of a coal sample. It examines four factors including moisture, ash, volatile matter (VM), and fixed carbon (FC) within the coal sample. Every factor is determined through a distinctive experimental procedure under ASTM specified conditions. These determinations are time consuming and require various laboratory equipment. The calorific value is one of the most important properties of a solid fuel and its experimental determination requires special instrumentation and highly trained operator. This paper develops mathematical and ANFIS models for estimation of two factors of proximate analysis based on the other two factors. Furthermore, the estimation of calorific value of coal samples based on proximate analysis factors is performed using multivariable regression, the Minitab 16 software package, as well as ANFIS and MATLAB software package. The results indicate that ANFIS is a more powerful tool for estimation of proximate analysis factors and calorific value than multivariable regression method. The following equation estimates the calorific value of coal samples with high precision: calorific value (btu/lb)=12204 - 170 Moisture+46.8 FC - 127 Ash.

Peanut shell (PS) waste and plastic waste are abundant in Indonesia and have the potential to pollute the environment. The limited availability of fossil fuels also makes all parties look for other energy sources. This research aims to find a solution to this problem. The effect of adding low density polyethylene (LDPE), polypropylene (PP), and biodegradable plastic to briquettes made from peanut shell waste was investigated in this research. Briquettes were made using starch adhesive and a compaction pressure of 70 N/m2 using a laboratory scale piston. The compression test is essential because, during the stacking process, the briquettes must withstand loads from external pressure, which significantly influences the quality of the briquettes during storage and transportation. This research found that adding biodegradable plastic increased the modulus of elasticity and compressive strength of briquettes, namely 20 MPa and 4.45 MPa, compared to briquettes without plastic. The highest calorific value of briquettes in this study was obtained from the addition of PP plastic, amounting to 6185 cal/g. Based on the quality of the briquettes, the lowest moisture content was obtained from the addition of LDPE plastic at 7.71%, and the lowest ash content was obtained from the addition of biodegradable plastic at 4.01%, the lowest volatile content was obtained from the addition of PP plastic amounting to 15.71%. The most considerable fixed carbon content was obtained from adding PP plastic, amounting to 80.25%.

Rubber wood (Ficus elastica) is one of the biomass waste that can be used as rawmaterial for gasification process, and has a calorific value of 4069 cal/g. Gasification is a process to convert a solid fuels to syngas (CO, CH4, and H2) through a partially combustion process using limited air between 20% to 40% of air stoichiometry. Depending on the direction of airflow, the gasifier are classified as updraft, downdraft, and cross-flow. The downdraft type of gasifier produces a lower tar content than updraft type. The gasification of rubber wood and rubber wood-coal mixture were carried out in this research. The purpose of the research is to determine the effect of Air Fuel Ratio (AFR) and temperature on calorific value and composition of syngas using a downdraft gasifier. The variations of AFR were 0. 64, 0. 95, and 1. 26. The temperature of gasification was varied between 600-1000º C. The result showed that the percentage of CO, H2, and CH4 decreased with increasing of AFR and decrease in calorific value. The calorific value of syngas increased along with the temperature. The use of coal in the gasification process can maintain the stable combustion temperatures and increase the syngas produced. The best-operating conditions in this research occurred at AFR of 0. 64, temperature of 800º C and use of coal as a stabilizer. At this condition, the percentage of syngas of 35. 95% of CO, 15. 95% of H2, 9. 38% of CH4, and caloric value of 9. 42 MJ/m3 was obtained. The highest gasification yield of 35. 75% was also reached.

Densification of biomass materials such as briquette improves the management properties of materials for transportation, storage, and so on. This study aimed to determine the optimal conditions of the briquette production process using a hydraulic press from the combination of bagasse and walnut shell using response surface methodology. The effects of independent variables including bagasse particle size (PS), process temperature (PT), bagasse moisture content (MC), and the composition ratio percentage of the walnut shell to bagasse (CR) were evaluated at three levels on the response variables of the density and tensile strength. The calorific value of the briquette was determined through validated linear and nonlinear equations of the high heat value using the proximate analysis of volatiles, fixed carbon, and ash. The results showed that by decreasing the moisture content of bagasse particles, the density and tensile strength of the briquette increased. Adding walnut shell particles to the briquette produced with the size of fine particles reduces tensile strength. The briquette production significantly reduced the percentage of volatile materials relative to their biomass and increased the percentage of fixed carbon. The calorific value of the raw material sample relative to the briquette produced increased from 16 to 22 MJ/kg. The optimal values of the density and tensile strength of briquettes were equal to 867. 847 kg/m3 and 1. 356 MPa, respectively at the CR of 5%, PS less than 1. 18 mm, MC content of 7%, and PT of 360 °C. At this condition, the calorific value of 22 MJ/kg was obtained.

Due to different reasons, such as the destructive effects of fossil fuel consumption, climate changes, global warming, and threats to human health, biomass is considered as alternate fuel. This biofuel is the most widespread source of renewable energy, and its scientific exploitation is increasing. In this research, pistachio pruning residues including leaves and stems were separately used as a source for biomass and their combustion and heat characteristics were investigated. A TGA device was used for thermal analysis and the combustion properties including enthalpy of combustion, high heating value (HHV) and low heating value (LHV) were measured experimentally and by using regression equations. The amounts of cellulose, hemicellulose, and lignin in stem were 48%, 16%, and 15%, respectively, and the same materials for leaves were 35%, 19%, and 32%, respectively. The high calorific value was calculated using regression equations, which were calculated as 17. 5 MJ/kg for stem and 14. 5 MJ/kg for leaves. The results showed that the two methods for determining the HHV and LHV were in good agreement with each other. The TGA analysis of the samples showed that the thermal decomposition of stem and leaves starts at a temperature of about 220°C, but during the initial stage of decomposition, the decomposition rate for stem is more severe than the decomposition rate of leaves.

The simultaneous utilization of Disulfide Oil (DSO) and Condensate is known as a novel mixture that has drawn researchers’ attention. The usage of such products is applicable when only precise experimental physico-chemical data are available. The DSO is produced as a waste and byproduct of gas sweetening process, which contains several disulfide components. Moreover, condensate is known as a valuable industrial product that is liquid at atmospheric temperature and pressure. Adding condensate to DSO makes it more economically feasible for export and may upgrade thermo-physical properties of DSO. Moreover, adding condensate to DSO promotes its potential applications. In this research work, different volume fractions of these two products from zero (0%) to 100% of DSO were tested by Refractometer, Tensiometer, Rheometer, Salinometer, and Calorimeter. It was found that the obtained refractive indexes linearly decreased from 1. 5215 to 1. 4277 by increasing the volume fraction of condensate at ambient temperature and pressure. Subsequently, the surface tension values decreased from 30. 6 to 19. 9 mN/m via quadratic function. The Rheometer results showed that various mixtures of these two products depicted a Newtonian fluid behavior in which their viscosity increased from 0. 54 to 0. 69 mPa. s by adding DSO at a standard temperature of 15. 5˚ C. The salt concentrations in condensate and DSO were achieved 26. 096 and 30. 265 g/m3 respectively. The calorific value of DSO was almost half of that of condensate value. It was observed that the condensate heat of combustion reduced by adding DSO.