دانلود رایگان مقاله لاتین تولید متان از زغال سنگ از سایت الزویر
عنوان فارسی مقاله:
بهینه سازی تولید متان از زغال سنگ بتمنس از طریق تبدیل کردن به گاز
عنوان انگلیسی مقاله:
Optimization of methane production from bituminous coal through biogasification
سال انتشار : 2016
برای دانلود رایگان مقاله تولید متان از زغال سنگاینجا کلیک نمایید.
مقدمه انگلیسی مقاله:
1. Introduction
The global coal reserve is estimated to be 1,000 Gt [1]. As an abundant and inexpensive resource, coal has been investigated extensively for generating fuels and chemicals through various conversion technologies besides the conventional combustion for power generation. Conversion techniques that attempt to circumvent the negative environmental impacts associated with coal combustion, such as carbon fuel cell [2], coal to synthetic natural gas (SNG) [3], pyrolysis [4] and underground coal gasification [5] typically employ thermal and/or chemical processes under high pressures and/or temperatures with high capital and operating costs [6,7]. To alleviate these problems, coal bioconversion or biogasification has been studied intensively during recent years. Biogasification transforms solid coal to methane gas through actions of microorganisms. Different from in situ gasification where syngas is produced from controlled combustion of coal [8] or ex situ gasification which is generally performed at temperatures higher than 800 C [9], biogasification can be conducted under mild environmental conditions. In addition, coal does not need to be cleaned before biogasification like those prepared for power generation [10]. This technology can be used for both in situ (abandoned or unmineable coal seams) and ex situ (coal wastes or mined out coal) scenarios [11]. Considering the U.S. coal resource of 6 trillion tons [12], if a methane content of 200 ft3 /ton could be achieved, then the total methane from coal would be 1,200 trillion cubic feet (Tcf). This volume of methane is much higher than 158.2 Tcf, estimated by the potential gas committee as of year-end 2012 for coalbed gas resources and would be 53.9% of 2226 Tcf of gas potentially recoverable from traditional reservoirs, such as conventional, tight sands and carbonates and shales [13]. Hence, if methane production from coal through biogasification is successful, it would generate the same volume of methane as that produced from shale gas in 2012, 1,073 Tcf. Considering the fact that coal seams are located at much shallower depth than shales, recovery of methane from charged coalbeds would be relatively inexpensive compared to that from shale. To harness this natural process and make coal biogasification a commercial reality and a clean coal technology [14,15], huge amounts of efforts have been dedicated to microbially enhanced coal bed methane (MECBM). Specifically, these efforts have spanned from understanding the coal conversion pathways [16,17]; improving methane production rate by investigating different microbial communities [18,19], different nutrient solutions [11], different testing conditions; and conducting pilot scale tests by several companies [20]. Under different testing conditions, evaluating effects from different parameters have been investigated intensively. Factors, such as coal loading, medium pH, coal particle size and temperature [21–23], surfactants [24], solvents [22,25] and salinity [23] have been optimized for different coal samples. Although excellent studies have been conducted on elucidating the key factors for increasing methane production rate, all researches so far have only evaluated the effect from variation of single parameters. For example, effect of temperature was detected in cultures having the same pH or effect of pH was studied for cultures at one temperature. Combined effects from multiple parameters, though critical, have not been investigated to the best of our knowledge. In addition, no such studies have been carried out for bituminous coal. Thus, for this study, we conducted experiments designed by the use of Design of Expert (DOE) software to: (1) evaluate effects from single and multiple factors simultaneously; and (2) identify the optimal conditions for achieving maximal methane yield. To achieve this purpose, we started with a 2-level factorial design to screen the most important parameters affecting methane productivity. Once significant parameters were identified, we used response surface methodology (RSM) to identify the optimal conditions for obtaining the highest methane yield. A total of 12 parameters were evaluated in this study. These 12 factors were chosen based on their reported effects on methane production from coal. It needs to be noted that these parameters are strongly tied to ex situ coal bioconversion although valuable information can be applied to in situ scenarios. The selected parameters were: (1) particle size (<420 lm, mesh size 40); (2) pH (6.0–8.0). As demonstrated by our previous study [26], in our enriched microbial consortium, the order of Methanomicrobiales was 90.4% of the methanogenic population. For this order, the optimal pH ranges from 6.0 to 8.0 [27]; (3) temperature (20–40 C). With two exceptions that can tolerate temperatures up to 60 C, the majority of the Methanomicrobiales are mesophiles and have optimal temperatures from 20 to 40 C; (4) mixing (0–75 rpm). As almost all studies on coal biogasification are conducted under static conditions, effect from mixing is unknown. On one hand, mixing can enhance the contact and interaction between coal and microorganisms. On the other hand, mixing may damage the attachment of cells to coal; (5) inoculum size (10–20% of final liquid volume in each reactor). An inoculum size of 10% has been commonly used. But it is unknown whether increased initial cell numbers will enhance methane release from coal; (6) coal loading (200–700 g/L). Different studies have reported different coal loadings ranging from 25 to 800 g/L [28]. Low coal loading requires large consumption of nutrient solutions while high loading may render some coal un-accessed by medium and microbes; (7) mercaptoethanesulfonic acid (coenzyme M, CoM, 0–0.25 g/L). This compound is generally included in nutrient media for anaerobic cultures. It is a reducing agent and also required by an enzyme: methyl-coenzyme M reductase in the final step of methane formation from various substrates in anaerobic environments [11,29]. This chemical accounts for approximately 75% of the total medium cost when used at 0.5 g/L; (8) two surfactants (30–50% of critical micelle concentration (CMC)). Triton X-100 is nonionic and was reported to exert no effect on enhancing methane production from subbituminous coal while its effect on bituminous coals are unclear [24]. Sodium dodecyl sulfate (SDS), is anionic and has not been evaluated in terms of impact on methane production. These two surfactants were chosen due to their low toxicity and low cost. Cationic surfactants were not selected since their solutions can interact with coal and result in decreased pH [30]; and (9) three carbon sources (each at 100 mM). Members of the order of Methanomicrobiales grow by reducing CO2 with H2 and some strains can use formate and alcohols as electron donors. Since H2 is a cleaner fuel than methane, it does not make sense to add large amount of H2 (80% of headspace gas) for the purpose of producing methane, especially considering large scale applications. Thus, in the reported study here, we did not attempt to supply H2 in the headspace. To reduce CO2, we investigated effects from sodium formate, 2-propanol and ethanol. It needs to be noted that: (a) like H2, the two alcohols are also biofuel molecules. But their concentrations in this study were only 100 mM; (b) the two alcohols either being miscible with or having high solubility in water might also serve as solvents to increase coal solubility.
برای دانلود رایگان مقاله تولید متان از زغال سنگاینجا کلیک نمایید.
کلمات کلیدی:
Coal gasification - Wikipedia https://en.wikipedia.org/wiki/Coal_gasification Coal gasification is the process of producing syngas–a mixture consisting primarily of carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2), methane (CH4), and water vapor (H2O)–from coal and water, air and/or oxygen. Historically, coal was gasified using early technology to produce coal gas ..... RSA is rich in Bituminous coal and Anthracite and was able to arrange the ... History · Process · By-products · Commercialization Gasification of Indonesian sub-bituminous coal with different gasifying ... pubs.acs.org/doi/abs/10.1021/acs.energyfuels.6b01329 by S Fan - 2016 - Related articles Oct 25, 2016 - Gasification of Indonesian sub-bituminous coal with different ... were compared with different gasifying atmosphere by using two catalysts. Gasification of Indonesian Sub-bituminous Coal with Different ... pubs.acs.org/doi/full/10.1021/acs.energyfuels.6b01329 by S Fan - 2016 - Related articles Oct 25, 2016 - Syngas, liquid fuels, and chemicals could be obtained through coal gasification. The catalytic effect of K2CO3 and CaCO3 on gasification with ... Results of Bituminous Coal Gasification upon Exposure to a ... pubs.acs.org/doi/pdf/10.1021/ef901596n by F Duan - 2010 - Cited by 11 - Related articles Apr 28, 2010 - gasifications using Chinese bituminous coal, pressurized CFB gasification decreases the carbon content of fly ash much better. Introduction. Catalog of Books and Reports in the Bureau of Mines Technical ... https://books.google.com/books?id=oUsMAQAAMAAJ 1968 - Library catalogs Coal - Gasification Plants, Kenneth D and others Gasification of bituminous coal ... 066 operation Increased thermal efficiency of solid fuel through gasification; ... Catalytic Coal Gasification Using Calcium Oxide https://books.google.com/books?isbn=0542814722 Narcrisha S. Norman - 2006 CHAPTER 1 INTRODUCTION Mild Catalytic Coal Gasification allows for the use ... Chemistry Coal types can be divided into four classes: anthracite, bituminous, ...
