Calorific value, as a key component for fuel quality assessment, directly affects the thermal power plants' efficiency. While high-quality coal is consumed as metallurgical coal, low-rank coals are used by coal-fired power plants. The high moisture content of the thermal coals significantly influences their heating values. In this study, the drying performances of the fixed bed and air dense medium fluidized bed (ADMFB) dryers were investigated under the superficial air velocity of 15-18 cm/s, inlet air temperature of 55-75 ºC, and up to 80 minutes of operation. Low air consumption is an intrinsic characteristic for ADMFB, while a low-temperature range for drying air was selected to address the coal-fired power plants' waste heat. It was found that an increase in air velocity and temperature favored the drying efficiency of both systems (i.e., 18 cm/s and 75 ºC), with the temperature being more effective than the air velocity. The ADMFB dryer removed comparatively more moisture than the fixed bed for the shorter drying durations. For example, for 10% moisture reduction at 75 °C, the ADMFB dryer needed 5 minutes less time than the fixed bed. The fitting quality and goodness of serval well-known thin-layer models for describing fluidized bed and ADMFB coal drying kinetics were assessed by several models and statistical evaluators, respectively. It was found that the Middilli & Kucuk model best describes the fixed bed coal drying (i.e., R2=0.999, RSE=0.001, RMSE=0.008), while the Page model much properly simulates the ADMFB coal drying (i.e., R2=0.998, RSE=0.002, RMSE=0.009).

Summary: The aim of this research is stability analysis of coal pillars in inclined coal seams (the variable pillar width and the variable seam dip) using the finite difference method software (FLAC2D). This aim is achieved by assessing the vertical and shear stresses distribution and their influence on the coal pillar.Introduction: In some mining method such as longwall, room and pillar and stope and pillar, the design of mine is done in such a way that the pillars are left in the seam gradient. Therefore in this case the effect of seam dip must be considered on the stability of pillar. Pillars in dipping strata are under in compression and shear load and therefore require consideration of a failure criterion that accounts for compression and shear load. The stability analysis of coal pillar can be performed by empirical, analytical, statistical and numerical methods.Since the existing empirical methods developed to pillar design have some limitations, the application of numerical methods was widely increasing to optimize pillar size in all mining methods. Applying numerical methods, it is possible to consider seam dip on the stability of coal pillar.Methodology and Approaches: In this study, six numerical models were analyzed in FLAC2D software for 30, 45 and 60 degree steeply coal seams with 10 and 15 m pillar width. It should be noted that 90 m width are considered for stopes in all numerical models. Moreover, exploitation has been started at the first stope and then continued to the second stope. In each step of the analyses, the model is run to equilibrium before creating the second stope.Results and Conclusions: The numerical modeling result on 30, 45 and 60 degree steeply coal seams with 10 and 15 m pillar width showed that the vertical stresses on the pillar decreased by increase of coal seam dip and coal pillar width. Moreover, the shear stresses increased by increases of coal seam dip. Finally, according to the numerical modeling result the pillar width of 15 m on a dip of 30 degree is stable.

2Deficit irrigation is one of the irrigation management methods that is used to increase Water Use Efficiency. Considering the internal plant adaptability characteristic to water shortage, Partial Root Drying method has been introduced in recent years. In this field research improvement of Water Use Efficiency for Soybean was determined. This experiment which was conducted at four furrow irrigation treatments at the Research Field of Tehran University in Karaj in 2008, consists of full irrigation (100% soil moisture deficit compensation), conventional deficit irrigation at 50 and 75 percent soil moisture deficit compensation and Partial Root Drying at 50 percent soil moisture deficit compensation with three replications. The amounts of irrigation used were exactly compensation level (negligible loss). Results indicated that Water Use Efficiency according to Duncan's Multiple Range Test at the five percent level of probability there was a significant difference between partial root drying treatment (PRD50%) and conventional deficit irrigation treatment at fifty percent soil moisture deficit compensation (DI50%),. Water Use Efficiency in PRD50% compared with DI50%, DI75% and full irrigation increased by 48.3%, 61.9% and 70.1% respectively.

Deficit irrigation is one of the irrigation management methods that is used to increase Water Use Efficiency. Considering the internal plant adaptability characteristic to water shortage, Partial Root Drying method has been introduced in recent years. In this field research improvement of Water Use Efficiency for Soybean was determined. This experiment which was conducted at four furrow irrigation treatments at the Research Field of Tehran University in Karaj in 2008, consists of full irrigation (100% soil moisture deficit compensation), conventional deficit irrigation at 50 and 75 percent soil moisture deficit compensation and Partial Root Drying at 50 percent soil moisture deficit compensation with three replications. The amounts of irrigation used were exactly compensation level (negligible loss). Results indicated that Water Use Efficiency according to Duncan's Multiple Range Test at the five percent level of probability there was a significant difference between partial root drying treatment (PRD50%) and conventional deficit irrigation treatment at fifty percent soil moisture deficit compensation (DI50%). Water Use Efficiency in PRD50% compared with DI50%, DI75% and full irrigation increased by 48.3%, 61.9% and 70.1% respectively.

Coal has been used for centuries as a energy source, and it remains a vital fuel for electricity generation in many countries. However, the risks of coal mining are high, and outbursts and gas emissions are two significant hazards associated with underground coal mining. Coal and gas outbursts are sudden and violent ejections of coal, gas, and rock from the working face of an underground coal mine. They occur when high gas levels, such as methane, accumulate in the coal seam and are released rapidly due to the stress and pressure caused by mining activities. Numerical simulation is one of the most powerful methods to study this complex phenomenon. The purpose of this article is to investigate the effect of coal strength parameters on the occurrence of the desired phenomenon in underground coal mines using the finite element numerical method. For the study, the sub-tunnel of the E4 workshop of the Parvade 1 Mine of Tabas, which is located at a depth of 472 meters from the ground, was investigated in the Phase2 simulation software and the possibility of an outburst in this layer assuming the existence of a pocket with a pressure of 0.6 MPa and crushed rock. The unstable failure index has been used to determine outburst-prone areas. In general, the application of UFI is to detect areas prone to brittle failure in phenomena such as Spalling, Rockburt, and Outburst. When this index is greater than 1, there is a possibility of this phenomenon because there is excess energy in the rock. According to the results of this research, strength parameters such as cohesion, angle of internal friction, and modulus of elasticity have a significant effect on the severity of outburst, at the same time the probability of this phenomenon is estimated independently of the tensile strength of coal. Considering that the UFI index used confirmed the results of previous researchers about this phenomenon, it can help predict this phenomenon. For the first time, this criterion is written based on energy components instead of stress and was able to show the effect of different parameters on outbursts.

The coal wastes of Zarand coal washing Plant are accumulated in near of this plant. The rate of extractable Alumina from the coal waste ash is about 27%. The amount of these wastes estimated about 107tons which about 1000 tons are added to them daily. In this study Alumina was extracted from wastes using: Lime-soda sintering, leaching of sinter, desilication of leaching solution, carbonation of desilicate solution with CO2 and precipitation of Al(OH)3 calcined Al(OH)2 processes respectively. The optimum condition achieved for each process as fallows: 1-Sinteringprocess; mol ratio of CaO/SiO2 =1.8. Na2O/Al2O3=1.3 in raw materials, particle size of raw materials: 12.5 % residual of 170 mesh sieve, time=35 minutes, temperature= 1275°C, sinter blain = 250 m2/kg. 2-Leaching process; solvent: NaOH 5.6 g/l solution, solid-liquid ratio =2, time=30 minutes and temperature=60°C 3-Desilication process; reagent: Ca(OH)2 10 g/l suspension, liquid - liquid ratio = 2, time=15 minutes, temperature: environmental temperature. 4-Carbonation process; amount of CO2 for Alumina precipitation in 250ml of 16.5 g/l Alumina solution: 1 liter/minutes for 20 minutes.5- Calcinations of AL(OH)3; temperature= 1250°C, time 30 minutes. The results showed that in optimum conditions about 74 % Alumina holding 99 % purification can be extracted from coal waste ash.

Screening experiments were carried out to isolate bacterial strains capable of solubilizing coal tailings for use in biofuel production from these byproduct wastes. Using enrichment in medium containing coal as sole carbon source, seven bacterial strains able to grow on coal hydrocarbons were isolated. The bacterial consortium was then cultured in mineral salt liquid media containing 1% (w/v) hard coal or coal tailings and incubated for 15 days at 25 degree centigrade on an orbital shaker (150 rpm). Spectrophotometric analysis of supernatants resulted from centrifugation of cultures showed 1.475 increases in absorbance at 450 nm for coal tailing and 0.832 for hard coal, compared to blank lacking bacteria. Gravimetric measurements also performed wich confirmed the solubilization of coal by bacteria.

Weathered coal (WTC) modified asphalts with improved storage stability are prepared by incorporating styrene-butadiene rubber (SBR). The effects of WTC and SBR/WTC are studied on the storage and physical properties, and morphologies of the modified asphalts. It is found that the WTC has marked effect on the increasing of softening point at the content of 3 wt% while SBR has significant effect on the low temperature (5ºC) properties and improvement of aging resistance at SBR content of 4 wt% in the WTC and SBR/WTC modified asphalts. The morphology of SEM and TEM photographs show that WTC was dispersed relatively uniform in asphalt which indicates compatibility and storage stability are improved by producing a homogeneous phase in modified asphalts. The FTIR analysis show new weak peak areas in modified asphalts indicating physical alteration is the main changes in modified asphalts.