1 Biodesulfurization technologies for selective separation of coal Hassanzadeh Ahmad 1 , Farhadi Ebrahim 1 , Hassanzadeh Soheyla 2 , Barani Vahideh 3 1- Department of Mining engineering, Shahid Bahonar University of Kerman, Kerman, Iran. 2- Senior Scientist, Payam Nour, khoy, Iran. 3- Department of Mining engineering, Shahid Bahonar University of Kerman, Kerman, Iran. Abstract The presence of sulfur in coal appears in three basic forms; as sulfates (mostly gypsum), pyrite and organic sulfur. Only pyritic sulfur can be separated from coal in coal preparation plants. Pyritic and organic sulfur may each constitute as much as 40 to 60% of the total removal of total sulfur content, respectively. Thus, removal of an effective portion of this sulfur content prior to coal combustion would substantially reduce the emission of sulfur oxides into the atmosphere. Many grades of coal and petroleum contain large quantities of sulfur compound which form corrosive air and water pollutant products during combustion. Since high temperature, high pressure or corrosion resistant equipment are not required for biological process, inexpensive construction materials can be used leading to low capital costs. Moreover, biological treatment is not likely to significantly alter the structure and the composition of the coal or to substantially reduce the BTU value of the coal. In this paper advantage process were discussed and introduced some effective microorganisms such as M. phlei and mesoacidophilic. Keywords Organic sulfur Coal Desulfurization Biological cleaning Pollution control 1-Introduction In the coal combustion, to generate electric power and process heat, the sulfur is emitted as SO 2, which is seen as one of the main causes of acid rain which leads to the acidification of soils, forests and surface water. When coal is burned, generally 90% or more of sulfur present in it is emitted into the atmosphere as sulfur oxides (mainly SO 2 ); if no desulfurization methods are used before, during and after combustion. Since physical cleaning can be remove the inorganic sulfur alone, biological methods can offer the potential to remove organic sulfur. Parallel to the physical and chemical cleaning methods, alternative biotechniques have been the subject of much investigation during the last decades. Reports results suggest that it is possible to remove up to 90% of either pyritic or organic sulfur from coal using oxidation agent at high temperature and pressure, and microorganisms (the use of bacteria to eat the sulfur in coal). It is known that pyrite can be removed from coal by bioleaching with Thiobacillus ferrooxidans [1]. Hoffman et al. reported that 90% desulfurization can be achieved in 8 to 12 days by grinding below 74 μm [2]. The mixed culture of T.ferrooxidans and T.Thiooxidans high yield sulfur removable was also reported. Butler et al. claims that bacterial cells themselves act as wetting agents and render the pyrite surface hydrophilic and this mechanism does not involve pyrite oxidation [3]. Other bacteria such as Thiobacillus acidophilus and Escherichia coli which do not oxidize pyrite worked even better. In the flotation process with Thiobacillus ferrooxidans preconditioning, Dogan et al. achieved pyrite removal after a conditioning time of 4h [4]. Atkins et al. showed that the time of conditioning at pH 2 could be reduced to 2min [5]. This paper focuses on the reduction methods of SO 2 emissions in the use of coal by biological techniques. In addition, it is intended to review the progress achieved to date in coal biodesulfurization processes. 2-Principles of biodesulfurization