Oil Shale and Coal Combustion inside a Fluidized Bed Combustor

Transcription

1 Interntionl Journl of Mining, Metllurgy & Mechnicl Engineering (IJMMME) Volume 2, Issue 3 (214) ISSN (Online) Oil Shle nd Col Combustion inside Fluidized Bed Combustor Ibrhim I. A., Shbn M. M., And Gd H. M. Abstrct Oil shle, s well s, solid fuels like col nd wood ships is used in fluidized bed technology for wide rnge of pplictions. The chrcteristics of fluidized bed combustion using snd s bed mterils with prticles dimeter of mm were studied experimentlly. An experimentl test rig hs been designed nd mnufctured to produce good fluidiztion in wide rnge of operting conditions. Cold experiments were crried before performing hot experiments to predict the suitble initil bed height, which hs been seen to be 3-cm. LPG fuel, hs been used s gseous fuel. The effects of bed mteril on gs temperture distribution long the combustor height re investigted nd presented in the present work. The combustion of oil shle nd col in fluidized bed combustor were verified by dding continuous flow rtes with reducing the quntities of LPG. The photos of the bed in cold nd hot sttes re presented. The results show the gret dependent of the prmeters under study on the bed chrcteristics nd solid fuel combustion. Keywords Fluidized Bed, Oil shle, Snd, Gseous fuels, Col, Wood ships. O I. INTRODUCTION IL shle is commonly defined s fine-grined sedi mentry rock contining orgnic mtter tht yields substntil mounts of oil nd combustible gs upon destructive distil ltion. Most of the orgnic mtter is insoluble in ordinry orgnic solvents; therefore, it must be decomposed by het ing to relese such mterils. Underlying most definitions of oil shle is its potentil for the economic recovery of energy, including shle oil nd combustible gs, s well s number of byproducts. A deposit of oil shle hving economic poten til is generlly one tht is t or ner enough to the surfce to be developed by open-pit or conventionl underground mining or by in-situ methods [1-4]. The oil shle is ny compct lminted sedimentry rock with more thn 33% sh which is cpble of yielding certin mount of orgnic mtter under suitble process. The min positive sides of the lrge-scle use of oil shle re the security of supply for the stte energy sector nd the reltive price independence from the world mrket. The negtive sides re gret environmentl dmge due to mining nd use of oil shle nd low clorific vlue of oil shle [5-7]. Clssifiction of Oil Shle: There re vrying *Ibrhim I. A., Shbn M. M, And Gd H. M. re Mechnicl Power Engineering Dept., Fculty of Engineering, Port Sid University, Port Sid, Egypt. (corresponding uthor s phone: ; fx: ; e- mil:hem_bb76@yho.com ). clssifictions of oil shles depending on their minerl content, type of Kerogen, ge, depositionl history, nd orgnisms from which they re derived. The ge of the oil shle deposits rnges from Cmbrin to Tertiry ge. Lithologies rnge from shles to mrl nd crbonte rocks, ll of which form mixture of tightly bound orgnic nd inorgnic mterils. Oil shles hve been divided into three ctegories bsed on minerl composition crbonte-rich shle, siliceous shle nd cnnel shle. Crbonte-rich shles derive their nme from the lrge mount of crbonte minerls such s clcite nd dolomite. As mny s twenty crbonte minerls hve been found in oil shle, the mjority of which re considered uthigenic or digentic. Crbonterich oil shles, prticulrly tht of lcustrine-sourced deposits, hve usully the orgnic-rich lyers sndwiched between crbonte-rich lyers. These deposits re hrd formtions tht re resistnt to wethering nd they re difficult to process using ex-situ methods. Siliceous oil shles re usully drk brown or blck shles. They re not rich in crbontes but rther in siliceous minerls such s qurtz, feldspr, cly, chert nd opl [8]. Oil Shle in Egypt: Egypt hs two substntil resources of blck shle which re s shown in Fig. 1: 1- Sfg-Qusier, Estern Desert. 2- Abu Trtur, Western Desert. Blck Oil Shle of Sfg nd Qusier: Blck Shle is restricted phosphte bed in the upper cretceous nd its recorded t the upper prts of Qusier formtion, Duwi formtion nd the lower prt of Dkhl formtion. The clorific vlue of the oil shle used in this pper obtined from the Nekheil mines is 236 Kcl/Kg. Fig. 1 Min loctions of Oil Shle in Egypt Fluidized bed combustion: The bsic im of FBC technology ws to enble utiliztion of cols with high sulphur content, while simultneously fulfilling its strict environmentl protection regultions. From the very 12

2 Interntionl Journl of Mining, Metllurgy & Mechnicl Engineering (IJMMME) Volume 2, Issue 3 (214) ISSN (Online) beginning, work focused on the development of lrge boilers, minly for utility electric energy production. A fluidized-bed (FB) is obtined by pssing fluid t sufficient rte up through mss of solid prticles held in (often cylindricl) vessel. As the nme indictes, the ction of pssing the fluid up through the mss of prticles cuses it to tke on fluid like Properties [9]. Fluidized bed powder: Geldrt [1] clssified powders into four groups ccording to their fluidiztion properties t mbient conditions. The Geldrt Clssifiction of Powders is now used widely in ll fields of powder technology. The fluidiztion properties of powder in ir my be predicted by estblishing in which group it lies. het trnsfer in fluidized-bed combustors is better thn ny combustion system becuse the het trnsfer by rdition from solid prticles [9]. It is importnt to note tht t operting temperture nd pressures bove mbient powder my pper in different group from tht which it occupies t mbient conditions. This is due to the effect of gs properties on the grouping nd my hve serious implictions s fr s the opertion of the fluidized bed is concerned [11-13]. II. EXPERIMENTAL SET UP Test rig: The pprtus used is verticl combustor which is first fed with combustible mixture (LPG nd Air) from the bottom through distributor plte, which is consists of numerous nozzles (5 nozzles ech hs 7 holes with 2 mm dimeter). The combustor is filled by snd prticultes for limited height. The initil height of the bed determined from cold tests. These prticultes re the fluidiztion medium. The prticultes dimeters ly in the rnge of (.6:1.18 mm). Fig.2 shows the schemtic digrm of the pprtus. surrounded by cylindricl wter jcket for cooling. The combustor contins one verticl side, 1 tpping holes of 19 mm dimeter rrnged xilly long the combustor to mesure ny desired phenomen, nd it hs glss window to see the fluidiztion in cold nd hot sttes. There re two feeding cones on the top, one for solid fuels (wood ships nd col). The other cone is for mking-up the fluidized-bed prticultes. Fig. 2 shows the combustor detils. The combustion ir is dmitted from centrifugl ir blower to the combustor through 4 steel pipe. The ir mss flow rte ws controlled by gte vlve. The combustion ir flow rte is mesured by mens of clibrted orifice meter, which is connected to U-tube wter mnometer. The gseous fuel flows from pressurized gs cylinder, with LPG t bout 3 br. The fuel flow rte is mesured by mens of clibrted orifice meter before entering the mixing chmber. Distributor plte, the im of the distributor plte is to ensure tht the mixture distributed cross the re of the bed uniformly. The distributor dimeter is 19 mm. The distributor plte consists of 5 nozzles; ech nozzle hs 7 holes with 2 mm dimeter ech. Six holes re distributed rdilly nd one xilly. The nozzles re distributed in rdil mnner with equl distnce long the cross section re of the distributor. Fig. 3 shows the distributor plte nd nozzles. 1- Gs bottle 2- Pressure regultor 3- Orifice meter 4- U-tube mnometer 5- Gs distributor 6- Distributor plte 7- Glss window 8- Cooling wter out 9- Flme trp 1- U -tube mnometer 11- Orifice meter 12- Air duct 13- Control vlve 14- Air blower Fig. 3 Distribution plte nd nozzles Fig. 2 Experimentl test rig nd combustor The combustor is verticl cylindricl steel tube of 213 mm dimeter nd 12 mm height. The combustor is Flme trp The ide of flme trp is to prevent the combustion wve to rech the mixing chmber where the gseous fuel nd oxidnt re mixed nd being explosive. The flme trp composed of multi copper tube, which quenches the flme wve by incresing the cooling re, which is presented, by circumertil re of the tube. Crushing mchine The crushing mchines, which hve been used for crushing the oil shle nd col, nmed s Los Angeles, Fig. 4 shows the prepring of solid fuel to combustion, The mchine consists of rolled steel drum hving n inside dimeter of 711 mm nd internl length 58 mm, the drum is rotted by speed of between 3 nd 33 R.P.M The motor, controls nd drum re mounted on robust steel frme together with steel try for unloding the specimen. The unit is supplied complete with set of 12 brsive chrges. In the present work fine wire thermocouple of Pltinum - 6 % Rhdium Vr. Pltinum - 3 % Rhdium of.3 mm in dimeter is used for gs temperture mesurements t some sections inside 13

3 Interntionl Journl of Mining, Metllurgy & Mechnicl Engineering (IJMMME) Volume 2, Issue 3 (214) ISSN (Online) furnce volume. The probe hs 14 mm in outer dimeter nd.5 m length. Fig. 6 Fluidiztion height for snd, dimeter =.6 mm Fig. 4 prepring of solid fuel to combustion III. RESULTS AND DISCUSSION 3.1 Cold tests For typicl experiment the cold bed mteril, fter selection for type, mss nd prticle size plced into the combustor. Cold tests were performed by using snd prticultes with dimeter of mm to determine the best initil height of the bed prticultes, to chieve good fluidiztion the best initil height observed to be [3cm]. Figures (5 nd 6) show the fluidiztion of the bed nd the corresponding height with incresing the ir flow rte for snd prticultes. Fig. 7 shows the fluidiztion of the bed with incresing the ir flow rte for snd prticultes with dimeter of.9 mm in glss combustor. () bed height of 3cm (b) bed height of 7cm Fig. 5 Snd cold tests, dimeter =.6 mm Fig.7 Snd cold tests, dimeter =.9 mm 3.2 Hot tes Three experiments were conducted to show the effect of chnging the momentum fluxes of ir-fuel mixture mss flow rte on the fluidiztion chrcteristics, gs temperture distribution long the combustor height nd the combustion efficiency. Figs. 8-1 represent the fluidiztion chrcteristics nd the gs temperture distributions. From the observtion from these figures, it cn see the following: The gs temperture distributions show the sme trend s the mximum gs temperture vlues re observed just bove the fluidized height nd progressively decresed s the distnce from the bed incresed. The mximum gs temperture re slightly incresed with incresing the mixture mss flow rte nd decresed with more increse in the mixture flow rte. Incresing the mixture mss flow rte giving more effective fluidiztion nd the gs temperture vlues t the combustible exit re progressively incresed due to the increse of the input het vlues of the mixtures. 14

4 Interntionl Journl of Mining, Metllurgy & Mechnicl Engineering (IJMMME) Volume 2, Issue 3 (214) ISSN (Online) Gs temperture, C Fig. 8 Gs temperture distribution long combustor height () nd photo for fluidized bed (b) Fuel: LPG, m. f = 1.3 g/s, m. =24 g/s. dimeter =.6 mm dimeter rnging from mm) with using reduced quntities of LPG fuel. The solid fuels re continuously fed by using prticle feeder to the combustor. Figs shows the combustion of different kinds of the solid fuel with the snd bed mteril. It could prove the bility of the experiment test rig to fire ny kind of the solid fuels by using the fluidiztion techniques [14]. In hot tests, the LPG fuel ws burned with snd s bed mterils. The experiments were conducted to show the effect of momentum flux of ir-fuel mixture mss flow rte on the fluidiztion chrcteristics. Without oil shle = 1.3g With oil shle = 1g With oil shle =.6g m m With oil shle =.g = 24g LPG Fig. 11 The combustion steps of oil shle for snd dimeter of.6 mm Without oil shle m LPG = 1.3g With oil shle = 1g With oil shle =.6g m m With oil shle =.g = 24g LPG Gs temperture, C 8 Fig. 9 Gs temperture distribution long combustor height () nd photo for fluidized bed (b) Fuel: LPG, m.f = 1.3 g/s, m. =24 g/s. dimeter =.9 mm Fig. 12 The combustion steps of oil shle for snd dimeter of.9 mm Gs temperture, C Fig.1 Gs temperture distribution long combustor height () nd photo for fluidized bed (b) Fuel: LPG, m.f = 1.3 g/s, m. =52.5 g/s. dimeter =.6 mm Before dding the solid fuel the oil shle nd col crshed using crushing mchine to get suitble size of prticultes to combustion, see Fig. 4. A set of experiments were crried out using crshed oil shle nd col of prticle Fig. 13 The combustion steps of col for snd dimeter of.9 mm 15

5 Interntionl Journl of Mining, Metllurgy & Mechnicl Engineering (IJMMME) Volume 2, Issue 3 (214) ISSN (Online) IV. CONCLUSION A series of experiments hve been conducted out for cylindricl fluidized bed combustor using snd with ( mm) s bed mterils nd LPG s gseous fuel; crry informtion on the combustion process. Bsed on the informtion nd dt presented, the following findings were obtined: For cold tests: Incresing the momentum flux the bed height incresed. The bed height in.6 mm snd is greter thn the bed height in 1.18 mm snd. Incresing the initil bed height the fluidiztion height decrese. For hot tests: The bed height in hot tests is greter thn cold tests for the sme conditions. When incresing the momentum flux the verge temperture increse due to the greter mount of fuel burnt. The temperture difference between the lower section nd the higher section decrese. When incresing the ir mss flow rte the verge temperture decrese. The bility design of the experimentl test rig to fire ny kind of the solid fuels by using the fluidiztion techniques. REFERENCES [1] Yvuzkurt, S., Gutfinger, C. nd Dyn, J., Fluidiztion, John Wiley nd Sons, New York, Vol. 143, (1979). [2] Hmmd, M., Zurigt, Y., Khzi, S., Hmmd, Z. nd Mubydeem, O., Fluidized bed combustion unit for oil shle, Interntionl Oil Shle Conference: Recent Trends in Oil Shle, Ammn, 7-9 November (26). [3] Dyni, J. R., Geology nd Resources of Some World Oil-Shle Deposits, Oil Shle, Vol. 2, pp ,(23). [4] Altun, N. E., Hicyilmz, C., Hwng, J. Y., Sutbgci, A. Kok, M. V., Oil Shles in The world nd Turkey; Reserves, Current Sitution nd Future Prospects: A review, Oil Shle, Vol. 23, pp ,(26). [5] Veski, R., Plu, V. nd Kruusementr. K., Co-Liquefction of Kukersite Oil Shle nd Pine Wood in Supercriticl Wter, Oil Shle, Vol. 23, pp , (28). [6] Sensoz, S., Putun, E. nd Kockr, O. M., Liquid products from pyrolysis of synthetic blends of Turkish oil shles nd lignites, Energy Sources, Vol. 22, pp , (2). [7] Gvin, J. M. Oil Shle, Wshington, etc., (1924). [8] Hutton, A.C., Petrogrphic clssifiction of oil shles, Interntionl Journl of Col Geology, Vol. 8, pp , (1987), [9] Simeon, N. O., Fluidized bed combustion, Mrcel Dekker, Inc. (24). [1] Geldrt D., The design of distributors for gs-fluidized beds, Powder Technology, Vol. 42 pp (1985). [11] Bron, J. Bulewicz E.M., Zukowsk, W. Kndefer S. nd Pilwsk M., Combustion of hydrocrbon fuels in bubbling fluidized bed, Combustion nd Flme Vol.128 pp (22). [12] Wng L., Wu P. nd Ni X., Combustion of liquid petroleum gs in fluidized bed furnce with jetting-mixing distributor, Powder Technology, Vol.17, pp.8693, (26). [13] Zukowski W., Acoustic effects during the combustion of gseous fuels in bubbling fluidized bed, Combustion nd Flme, Vol.117, pp , (1999). [14] Shbn, M.M., Effect of bed mteril type on combustion efficiency of fluidized bed combustor ERJ, Vol.33, pp.97-19, (21). 16