Feasibility Study on Conversion of Indian Bamboo to Activated ...
Feasibility Study on Conversion of Indian Bamboo to Activated ...
Feasibility Study on Conversion of Indian Bamboo to Activated ...
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<str<strong>on</strong>g>Feasibility</str<strong>on</strong>g> <str<strong>on</strong>g>Study</str<strong>on</strong>g> <strong>on</strong> C<strong>on</strong>versi<strong>on</strong> <strong>of</strong> <strong>Indian</strong> <strong>Bamboo</strong> <strong>to</strong> <strong>Activated</strong> Carb<strong>on</strong> carried out byChemical Engineering Department, <strong>Indian</strong> Institute <strong>of</strong> Technology, BombayAbstract<strong>Activated</strong> carb<strong>on</strong> can be used for removal <strong>of</strong> organic chemicals, chlorine, lead, unpleasanttastes and odors in effluent or coloured substances from gas or liquid streams by themechanism <strong>of</strong> adsorpti<strong>on</strong>. Adsorpti<strong>on</strong> can be classically defined as absorpti<strong>on</strong> <strong>on</strong> the surface<strong>of</strong> the material due <strong>to</strong> capillary c<strong>on</strong>densati<strong>on</strong> inside the multitude <strong>of</strong> pores/active sitesavailable.In its effort <strong>to</strong> promote value added bamboo based products, the Nati<strong>on</strong>al Missi<strong>on</strong> <strong>on</strong><strong>Bamboo</strong> Applicati<strong>on</strong>s launched an investigati<strong>on</strong> <strong>to</strong> study the c<strong>on</strong>versi<strong>on</strong> <strong>of</strong> <strong>Indian</strong> bamboospecies <strong>to</strong> activated carb<strong>on</strong> in associati<strong>on</strong> with <strong>Indian</strong> Institute <strong>of</strong> Technology – Bombay.Three comm<strong>on</strong>ly occurring species has been used in the experimentati<strong>on</strong>. These areMelac<strong>on</strong>a baccifera, Bambosa tulda and Oxycelandra s<strong>to</strong>ckii. The study indicating that<strong>Indian</strong> bamboo is a good raw material for c<strong>on</strong>versi<strong>on</strong> <strong>to</strong> activated carb<strong>on</strong> has laid thefoundati<strong>on</strong> for further activity in this area.In the first step, carb<strong>on</strong>isati<strong>on</strong> <strong>of</strong> bamboo has been d<strong>on</strong>e in inert atmosphere using ZincChloride promoter. The carb<strong>on</strong>ised product has been activated chemically using CO 2 . Theactivated product obtained has surface area above 1200m 2 /gm. Performance studies carriedout with methylene blue as coloring agent has indicated that the product has betteradsorpti<strong>on</strong> indices than that <strong>of</strong> the standard activated carb<strong>on</strong> available. The yield <strong>of</strong>carb<strong>on</strong>isati<strong>on</strong> and activati<strong>on</strong> was observed <strong>to</strong> be 40% and 75% respectively. Out <strong>of</strong> the threespecies experimented, activated carb<strong>on</strong> prepared from Bambusa tulda has been found <strong>to</strong> bethe best in terms <strong>of</strong> surface area and adsorpti<strong>on</strong> capacity.BackgroundHigh-grade activated carb<strong>on</strong> can be obtained from woody material like bamboo havinginherent mechanical strength, high carb<strong>on</strong> and low ash c<strong>on</strong>tent. Since India is the sec<strong>on</strong>dlargest producers <strong>of</strong> bamboo, there exists an excellent scope for producing bamboo basedhigh-grade activated carb<strong>on</strong> if appropriate technology is developed and exploited atcommercial level.During assessment <strong>of</strong> technology needs for bamboo based activated carb<strong>on</strong>, it was foundthat no such knowledge base currently exists in the country with reference <strong>to</strong> <strong>Indian</strong> bamboospecies. While there has been much indigenous effort in c<strong>on</strong>verting coc<strong>on</strong>ut shell in<strong>to</strong>activated carb<strong>on</strong>, certain initiatives were necessary for an investigative study <strong>of</strong> c<strong>on</strong>versi<strong>on</strong><strong>of</strong> bamboo.Experimental WorkRaw Material
Three bamboo species available in abundance in the country has been used in theexperiment. These are Melac<strong>on</strong>a baccifera, Bambosa tulda and Oxycelandra s<strong>to</strong>ckii.Methodology□ <strong>Bamboo</strong> is crushed either manually or by Lathe machine <strong>to</strong> a desired mesh size.Particle size <strong>of</strong> bamboo is 60-80 meshes□ The crushed bamboo pieces are washed with water for the removal <strong>of</strong> adherentextraneous matter.□ The washed bamboo pieces are dried in oven at 150 0 C for 4 hrs for removal <strong>of</strong>moisture.□ The dried bamboo pieces are treated with carb<strong>on</strong>izing promoters like phosphoric acid(H 3 PO 4 ) or Zinc chloride (ZnCl 2 ). Then carb<strong>on</strong>izati<strong>on</strong> is carried out in a fixed bedreac<strong>to</strong>r at 400-600 0 C for 4 hrs in the presence <strong>of</strong> nitrogen gas.□ The carb<strong>on</strong>ized mass was washed with water for the removal <strong>of</strong> carb<strong>on</strong>izingpromoter.□ Activati<strong>on</strong> is carried out at 900-1000 0 C in the presence <strong>of</strong> carb<strong>on</strong> dioxide (CO 2 ).Experimental setupFig. 2. Experimental set-up for the producti<strong>on</strong> <strong>of</strong> activated carb<strong>on</strong>. 1. Trap. 2. Cooling bath. 3.Furnace with reac<strong>to</strong>r tube. 4. Carb<strong>on</strong> sample. 5. Support. 6. Flow meter. 7. Valve. 8. N 2 -cylinder. 9. CO 2 -cylinder.Observati<strong>on</strong>s1. CrushingIt is c<strong>on</strong>venient <strong>to</strong> do crushing <strong>of</strong> bamboo in two stages, first by lathe machine and then bymanual crushing. Manual crushing al<strong>on</strong>e is not adequate <strong>to</strong> give the desired size due t<strong>of</strong>ibrous nature <strong>of</strong> bamboo.2. Carb<strong>on</strong>izati<strong>on</strong>During carb<strong>on</strong>izati<strong>on</strong>, the use <strong>of</strong> phosphoric acid (H 3 PO 4 ) as a promoter was found <strong>to</strong> betroublesome because it is an oxidizing and corroding agent, which corrodes the insidesurface <strong>of</strong> the reac<strong>to</strong>r and causes burning <strong>of</strong> bamboo particles thereby producing c<strong>on</strong>tinuousbluish flame at the outlet <strong>of</strong> the reac<strong>to</strong>r. This phenomen<strong>on</strong> was quite violent. It is <strong>to</strong> be notedthat this observati<strong>on</strong> has not been reported in the available literature, but we noticed itseveral times during carb<strong>on</strong>izati<strong>on</strong> using phosphoric acid as a carb<strong>on</strong>izing promoter for all
uns. On other hand, zinc chloride (ZnCl 2 ) as a carb<strong>on</strong>izing promoter was friendly <strong>to</strong> use forcarb<strong>on</strong>izati<strong>on</strong> process. The yield <strong>of</strong> carb<strong>on</strong>izati<strong>on</strong> was typically 40%.3. Activati<strong>on</strong>The yield <strong>of</strong> activati<strong>on</strong> is typically 75% with respect <strong>to</strong> the material charged in the fluidizedbed.5. Results and Discussi<strong>on</strong>Properties <strong>of</strong> <strong>Activated</strong> Carb<strong>on</strong>Table-1 Properties <strong>of</strong> various activated carb<strong>on</strong> analyzed by BET apparatusStandardAssam bamboo samplesactivatedcarb<strong>on</strong>.(<strong>Activated</strong>Melac<strong>on</strong>a BambosaCarb<strong>on</strong>.coBaccifera Tuldam)Sr.No. Parameters1.23.4.4.5.6.Surface area. (m 2 /g)Pore volume. (cc/g)Avg.Pore diameter. (A)Bulk density (gm/cc)Volatile matterAsh c<strong>on</strong>tentIodine No.(ASTM_4607)11000.730.48-3.00900-110012200.499516.52780.21321.33.38950-105013500.961416.63220.23721.33.38950-1100Oxycelandras<strong>to</strong>ckii12800.505716.190.2821.33.38950-11005.1 Effect <strong>of</strong> particle size and activati<strong>on</strong> temperatureSome explora<strong>to</strong>ry work was performed <strong>to</strong> investigate the effect <strong>of</strong> two important processparameters viz particle size and activati<strong>on</strong> temperature. It was observed that if the activatedcarb<strong>on</strong> is prepared by finely crushed bamboo (particle size < 1 mm) then the surface area isabout 8 <strong>to</strong>10% more than that observed for the granules <strong>of</strong> about 3 mm. Activati<strong>on</strong>temperature is a crucial parameter that mainly determines the fete <strong>of</strong> the product. Its effec<strong>to</strong>ver the range 700-900 0 C studied and it was observed that the surface area at 900 0 C is almostdouble the surface area when the activati<strong>on</strong> was performed at 700 0 C under otherwise similarc<strong>on</strong>diti<strong>on</strong>s.5.2 Recovery <strong>of</strong> Zinc Chloride (ZnCl 2 )As seen from characteristics <strong>of</strong> the product zinc chloride has given a substantial increase inthe <strong>to</strong>tal surface area. However, in order <strong>to</strong> recommend this agent for carb<strong>on</strong>izati<strong>on</strong>, it isnecessary <strong>to</strong> look at the ec<strong>on</strong>omical aspects <strong>of</strong> its use.
The quantitative analysis <strong>of</strong> ZnCl 2 in aqueous soluti<strong>on</strong> was performed by the standardmethod <strong>of</strong> titrati<strong>on</strong> with 0.1N AgNO 3 soluti<strong>on</strong>. The results suggested that 9-10 % <strong>of</strong> zincchloride is lost during this operati<strong>on</strong>, which is well in limit <strong>of</strong> ec<strong>on</strong>omical applicati<strong>on</strong>. Thepercentage recovery can still be improved by carefully performing more runs. Since the zincchloride soluti<strong>on</strong> is more dilute than the initial soluti<strong>on</strong>, it is necessary <strong>to</strong> c<strong>on</strong>centrate thesoluti<strong>on</strong> <strong>to</strong> the required strength prior reuse.5.3 Performance study: Comparis<strong>on</strong> <strong>of</strong> different activated carb<strong>on</strong> samplesThe performance studies were c<strong>on</strong>ducted for all the activated carb<strong>on</strong> samples using batchand semi-c<strong>on</strong>tinuous (column) adsorpti<strong>on</strong> for methyl blue dye soluti<strong>on</strong>s. The breakthroughcurve for activated carb<strong>on</strong> from Assam bamboo samples and that <strong>of</strong> the standard activatedcarb<strong>on</strong> by c<strong>on</strong>tact method using methylene blue dye soluti<strong>on</strong> are shown in Fig. 3. Asmenti<strong>on</strong>ed before, the performance is well in agreement with the surface areas given inTable-1.C<strong>on</strong>centrati<strong>on</strong> Vs TimeC<strong>on</strong>centrati<strong>on</strong> (gm/lit)0.70.60.50.40.30.20.100 20 40 60 80Time (min)Not SpecifiedBmabossa TuldaStandardTable 3: Performance <str<strong>on</strong>g>Study</str<strong>on</strong>g> using Methylene BlueC<strong>on</strong>clusi<strong>on</strong>A huge amount <strong>of</strong> waste is generated during processing <strong>of</strong> bamboo in<strong>to</strong> mat, flooring tilesand sticks. The major porti<strong>on</strong> <strong>of</strong> the bamboo pole cannot be used for manufacture <strong>of</strong> suchproducts due <strong>to</strong> poor machinability. Certain bamboo species such as melocanna bacciferathough abundantly available are not suitable for certain applicati<strong>on</strong>s due <strong>to</strong> their poormechanical properties. From the study carried out it can be c<strong>on</strong>cluded that:• The performance <strong>of</strong> bamboo based activated carb<strong>on</strong>, with methylene blue as coloring agentgives better adsorpti<strong>on</strong> indices than that <strong>of</strong> the standard activated carb<strong>on</strong>• <strong>Activated</strong> carb<strong>on</strong> prepared from Bambusa tulda has been found <strong>to</strong> be the best in terms <strong>of</strong>surface area and adsorpti<strong>on</strong> capacity