Title of Invention

"A PROCESS FOR THE RECOVERY OF CAUSTIC SODA FROM WEAK BLACK LIQUORS AND THE APPARATUS THEREOF"

Abstract

The subject invention relates to a process and the apparatus for the recovery of caustic soda from weak black liquor obtained from agricultural residue pulping by evaporating weak black liquor to solids content in multi-effect short tube evaporator, mixing it with agricultural bio mass obtaining thereby a dark colored semisolid mass, burning said semisolid mass to obtain ash, leaching said ash in water and filtering same to obtain solution of sodium silicate and sodium carbonate, heating said solution to a temperature from 80°C - 95°C and bubbling carbon dioxide through said heated solution thereby converting said sodium silicate into sodium carbonate and silica precipitate, separating said silica precipitate , washing the said silica with water and acid, and mixing lime to the sodium carbonate solution to obtain a solution of caustic soda and calcium carbonate precipitate, separating the calcium carbonate precipitate from the said solution , washing said calcium carbonate precipitate with water, mixing the resultant wash with the caustic soda solution, drying and recalcining the calcium carbonate precipitate to recover lime and carbon dioxide for recycling.

Full Text

FIELD OF INVENTION The present invention relates to the recovery of caustic soda from black liquor and more particularly from black liquors obtained from cooking of agricultural residues such as, rice straw, wheat straw, sarkanda, husks and the like with caustic soda. PRIOR ART In the known art so far as paper making is concerned, cellulosic raw materials like wood, bamboo, agricultural residues, are cooked with chemicals, principally caustic soda to separate and obtain cellulosic fibers ( known as pulp) for further processing into paper. The other substances from the above mentioned raw materials, mainly lignin, combine with caustic soda for removal from the pulp solution with water when the pulp is washed for the above mentioned separation. This solution is known as black liquor principally due to its dark blackish colour. The black liquor also contains other substances like pentosans, sugars, fiber fines, silica and other non performing chemicals like salts of magnesium and calcium (obtained from the raw material), and the like, which make up total solids in the black liquor. However, in mills where wood or bamboo is used as raw material, the black liquor obtained as above is concentrated to 60% solids content and burnt in a furnace. The residual ash is obtained as soda ash and is converted into caustic soda by causticizing it with lime. This process is possible because the black liquor contains little or no silica and other non performing chemicals and it can be concentrated to a solid content of 60% or more, at which concentration it can burn on its own. In mills where agricultural residue is used as raw material for paper, the process mentioned above for recovery of caustic soda from black liquor can not be used for the following reasons : The raw materials have very high silica content due to which the ash obtained after burning of concentrated black liquor( soda ash) will contain sodium silicate in substantial quantities. This sodium silicate interferes in causticizing process and prevents formation of clear caustic soda. The black liquor can not be concentrated beyond 45% solids content due to presence of excessive amounts of fiber fines. Concentrated black liquor at this low concentration can not be burned on its own and needs external fuel( like fuel oil) support to burn, which, besides posing process difficulties, becomes a very expensive proposition. Burning of the concentrated black liquor is only known way for recovery of caustic soda from it. Since the black liquor cannot be burned, there is no alternative for the mills using agricultural residues but to discharge the weak black liquor as effluent. This discharge causes tremendous amount of pollution and is an environmental hazard. Various attempts have been made to overcome these disadvantages.The most prominent and extensively used procedure has been to desilicate the black liquor. In this process, the carbon dioxide of the flue gas from the boilers have been used to carbonate the black liquor and thus precipitate silica. Here the black liquor, which is originally obtained at 4% solids content, has to be concentrated to a solids content of 12%.Then the pH of this partially concentrated black liquor is adjusted to 9.5 by addition of additional caustic soda. Flue gas is then passed through this black liquor and the pH is constantly maintained at 9.5 by adding caustic soda at various intervals. After a fixed time , it is adjudged that maximum of silica is precipitated. The precipitated silica is filtered out and the remaining black liquor is further concentrated to a solids content of 60% and conventional recovery process as detailed above followed. The above process has the following basic flaws due to which it has not been successfully implemented till date : In the process of desilication, it is not exactly known when all silica has been precipitated. Either some silica remains behind which interferes with the subsequent recovery process or, due to excessive carbonation besides silica some lignin is also precipitated which lowers the heat value of concentrated black liquor and subsequent combustion even at 60% solids content concentration without external fuel support becomes difficult. It is very difficult to maintain an exact pH level of 9.5 which is an essential requirement of the process. Even slight variation from this pH causes lignin precipitation resulting in lowering of the heat value of the concentrated black liquor. Even after silica precipitation, it is difficult to concentrate black liquor up to 60% solids content since the fiber fines are not removed, causing problems in the evaporator system due to choking. The precipitated silica also is a disposal problem and its disposal is an environmental hazard. Indian patent number 171289 dated 18 December, 1987 describes a process of recovery of caustic soda in which some of the aforesaid disadvantages were overcome. However the following factors have not been taken into consideration by the said patent: A. The combustion of the concentrated black liquor- bio mass mixture can be carried out at higher temperatures in the range of 820 °C- 950 °C instead of earlier range of 750 °C - 820 °C. This elevated temperature results in better and complete combustion and a higher sodium silicate to sodium carbonate ratio leading to higher yields. B. Like in case of other black liquors, multi effect tubular evaporators can be used to concentrate the weak black liquor except that the tubes have to be of shorter length to avoid in tube boiling and at any time this black liquor can not be subjected to a temperature greater than 110 °C. Besides silica and fiber fines there are non performing chemicals like salts of calcium and magnesium contributed from raw materials which do not interfere in the described evaporation process. C. If a counter current leaching of at least three stages is used to dissolve sodium silicate/ sodium carbonate from the ash, a much higher concentration of sodium in terms of Na2O ( 10 - 12 % as against originally proposed 3 - 5% ) resulting in elimination of subsequent concentration step of the sodium carbonate solution. D. If during carbonation instead of stopping the process when a value of 100 % is reached, it is continued further to a value of 105 - 110 % ( which indicates formation of sodium bicarbonate ) a total precipitation of silica is ensured . In the subsequent causticization process the precipitated calcium carbonate obtained can be recalcined to regenerate lime and carbon dioxide gas for recycling without any loss of efficiencies and /or properties. This regeneration process also eliminates the disposal problem of calcium carbonate precipitate. E. It is much more easier and controllable to use enriched carbon dioxide gas having a concentration of more than 80%. This enriched carbon dioxide gas can be easily obtained from the gas generated in recalcination of the calcium carbonate precipitate through absorption and subsequent desorption from mono ethanol amine. The present invention relates to an improved process of producing caustic soda from from black liquors and also enlarging its scope of applicability to sulfite pulping for recovery of sodium sulfite. An advantage of the present invention is that it eliminates the need for concentrating the black liquor of 45% solids content to a higher solids content at any time during the process. Another advantage is to use/mix cheap and abundantly available agricultural bio mass as additional fuel with the low concentrated black liquor for augmenting the heat value of the black liquor. A further advantage of the invention is the ease with which the aforesaid mixture of the agricultural bio mass and black liquor( herein after referred to as wet mixed fuel or WMF) can be handled because of its semisolid state. Yet another advantage of the invention is whether the carbonation of the resultant solution obtained by the leaching of ash after incineration is in excess or not, silica will be precipitated. Another advantage of this process as established is that, the sodium carbonate solution after thorough carbonation is free of silica. Hence , upon causticization, the calcium carbonate precipitate that is obtained cab be recalcined to give both lime and carbon dioxide, both of which can be recycled in the process above. It is to be noted that, in absence of total silica removal, the precipitated calcium carbonate can not be treated in any way and creates a disposal / pollution problem. Also the carbon dioxide gas generated above is of 25 - 35 % concentration and thus becomes easier to enrich. The object of the present invention is therefore an improved process for the recovery of caustic soda from black liquor. Another object of the invention is to provide a process, which eliminates the need for concentration, the black liquor of 45% solids content to higher solids content. A further object of the invention is to provide cheap and abundantly available agricultural bio mass as additional fuel. Yet another object of the invention is to provide rice husk/ cut wheat straw / cut rice straw/ saw dust etc., as additional fuel, which is also cheap and abundantly available. The present invention encapsulates all the above advantages over the known process of recovery of caustic soda. It is more economically viable and energy saver. According to the present invention there is provided an improved process for the recovery of caustic soda from weak black liquor which comprises concentrating by evaporation weak black liquor to solids content of 40-48% by passing through a multieffect short tube evaporators, mixing said concentrated weak black liquor with agricultural bio mass of the kind as herein described in the ratio of 2:0.8 to 2:1.5 by weight obtaining thereby a dark coloured semisolid mass.WMF, burning said WMF to a temperature of from 820° C - 950 °C to form ash, being a mixture of soluble sodium silicate and sodium carbonate, leaching said ash in water and filtering to obtain a solution of sodium silicate and sodium carbonate, heating said solution to a temperature from 80° C - 90° C and bubbling carbon dioxide through said heated solution thereby converting said sodium silicate into sodium carbonate and silica precipitate, separating by known means silica precipitate from the sodium carbonate solution, mixing lime with sodium carbonate solution with agitation at 85°C -95°C to obtain a solution of caustic soda and calcium carbonate precipitate, separating by known means the calcium carbonate precipitate from caustic soda solution, recalcining by known means the calcium carbonate precipitate to obtain lime for causticization above and carbon dioxide gas, enriching it to 80 - 90% by absorption and desorption from mono ethanol amine for use in carbonation step above. Preferably, the agricultural bio mass include cut rice straw, cut wheat straw, and the like. Of these, the most preferably is rice husk. Another important and abundantly available waste would be saw dust. Saw dust either individually or in combination with rice husk in any proportion can be used. Accordingly the present invention relates to a process for the recovery of caustic soda from weak black liquor obtained from agricultural residue pulping,which comprises concentrating by evaporation weak black liquor to solids content of 40 - 48%, mixing said concentrated weak black liquor with agricultural bio mass in the ratio of 2:0.8 to 2:1.5 by weight obtaining thereby a dark colored semisolid mass( WMF ), burning said semisolid mass to temperature of from 820°C -950°C to obtain ash, leaching said ash in water and filtering same to obtain solution of sodium silicate and sodium carbonate, heating said solution to a temperature from 80°C - 95°C and bubbling carbon dioxide through said heated solution thereby converting said sodium silicate into sodium carbonate and silica precipitate, separating said silica precipitate from the sodium carbonate solution, washing the said silica with water and acid, and mixing lime to the sodium carbonate solution while agitating the solution at 85°C - 95°C to obtain a solution of caustic soda and calcium carbonate precipitate, separating the calcium carbonate precipitate from the said solution , washing said calcium carbonate precipitate with water to recover entrapped caustic soda solution and mixing the resultant wash with the caustic soda solution, drying and recalcining the calcium carbonate precipitate to recover lime and carbon dioxide for recycling. Accordingly the subject invention also resides in an apparatus for the recovery of caustic soda from weak black liquor comprising, a pulp mill for making a pulp from the raw material and chemicals, means to condensate weak black liquor obtained from the pulp, a mixer for mixing the black liquor and agricultural biomass to obtain wet mixed fluid, a furnace for burning said wet mixed fuel, a three stage leacher for leaching ash, means for carbonation, means for causticization and calcination. The present invention can better be understood with the reference to the accompanying drawings which are for illustrative purposes and should not in any way be construed to restrict the scope of the invention keeping in view that certain modifications and improvements are possible without deviating from the scope of the invention. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig. 1 Schematic diagram of the process DETAILED DESCRIPTION OF THE INVENTION According to the process, the weak black liquor obtained from the washing of the pulp is concentrated by evaporation in short tube multi effect evaporators having the tube lenghth between 1.8m-3m such that at no point during the evaporation process, the temperature of black liquor exceeds 110° C to solids content of 40 - 48%, preferably 45%. This concentrated black liquor is mixed with agricultural bio mass in the ratio varying from 2:0.8 to 2:1.5, preferably 2:1 on weight to weight basis. After thorough mixing, a dark coloured semisolid mass is obtained, known as WMF (Wet Mixed Fuel). This WMF is then burnt in a suitable preferably travelling grade furnace so that the temperature of oxidation remains at around 820°C and, in any case, does not exceed 950°C. As soon as the combustion is complete, the resultant ash is immediately removed from the furnace. It is important that the ash should not be left in the hot furnace after combustion. The ash thus obtained contains a mixture of soluble sodium silicate and sodium carbonate in the ratio varying from 75:25 to 80:20, preferably 78:22. The resultant ash is atleast three stage counter currently leached with water and the mixture filtered through a suitable medium, or settled to remove insoluble portion of the ash and recover the sodium silicate/sodium carbonate solution. The solution thus obtained contains sodium measured as Na2O as 10- 12 % of the solution. This solution is then heated to from 80 to 95° C preferably above 90°C and carbon dioxide gas bubbled through the solution. The carbon dioxide gas constitutes 25- 35 % as obtained from recalcination of calcium carbonate obtained below. The gas is cooled and concentrated by absorption and desorption from mono ethanol amine to more than 80 % and compressed and then passed through the above mentioned solution.The carbon dioxide gas reacts with the sodium silicate portion of the solution converting it into sodium carbonate and silica.The silica after a while, deposits itself as precipitate. The progress of the conversion process is monitored from time to time by the withdrawal of sample from the solution and titrating it with acid first against phenolphthalein indicator and then against methyl orange indicator ad obtaining values for sodium carbonate as percentage of total sodium present. When this figure attains a value of higher than 105%, then the carbonation process (inclusive of some formation of sodium bicarbonate) is completed and the passing of the carbon dioxide gas stopped. The resulting mixture of sodium carbonate solution and silica precipitate is either centrifuged or filtered to separate silica and sodium carbonate solution. The resultant solution contains 17 - 21 % of sodium carbonate. The silica thus obtained is washed thoroughly with water and with dilute acid, preferably hydrochloric acid and dried. The sodium carbonate solution is mixed with lime and the mixture thoroughly agitated for 15 minutes at 85- 95°C, preferably above 90°C to obtain caustic soda solution and calcium carbonate precipitate. Afterwards, the agitation is stopped and the mixture either centrifuged or filtered or settled to remove calcium carbonate precipitate from caustic soda solution. The calcium carbonate precipitate is thoroughly washed and calcined to regenerate lime for re use and generate carbon dioxide gas for use as mentioned above.This process effects a recovery of caustic soda as a percentage of the sodium obtained from the original black liquor to the tune of 80-85%, generally 83%. EXAMPLE The following examples of various stages of operation are based on pilot plant operation. The data for example are presented on stage wise operations, maintaining a percentage wise link with the sodium content ( measured as Na2O), where ever applicable. The sulfitation results are based on laboratory experiments. Evaporation For evaporation five effect short tube evaporators were used, each having multiplicity of tubes of 0.035 to 0.045 meter inner diameter and 2.5 meter effective length. The steam for this operation was supplied from the main paper plant initially and after wards from the recovery boiler at 1.5 kg/cm2 pressure., For the measured run, a weak mixed black liquor was obtained from the pulp mill from the pulping of rice straw, wheat straw and sarkanda. The solids content in the weak black liquor were around 5% and Na2O content about 1.17%. After evaporation 9.3 m3 of concentrated black liquor was obtained having a solids content of 41.9% and Na2O content of 6.15 % or equivalent to 0.572MT , which is 97.77% of the original. The measured run was operated for 24-28 hours . Mixing and Burning 5 m3 of concentrated black liquor obtained after evaporation were thoroughly mixed with air dry rice husk in continuous single screw mixer of with stub agitators to obtain Wet Mixed Fuel containing Na2O. This slight increase in Na2O was attributed to Na2O present in rice husk. The Wet Mixed Fuel was fed on to a travelling grate furnace. High speed Diesel was burnt through four burners under neath the beginning of the grate travel to heat the fuel to its ignition temperature of 160-190°C. There after air was supplied from underneath the grate to create and carry to end the combustion. A probe was installed approximately mid way of grate travel to note the high temperature of combustion . At the end of the travel, the ash was dropped into a pit to be collected for subsequent operations. The collected ash was weighed and its Na2O content determined. Its weight was found to be 1.11 MT having a Na2O content of 27% or 0.299MT. This corresponds to 97.4 % of Na2O from concentrated black liquor or 95.2 % of original from pulp mill. The sodium silicate to sodium carbonate ratio was found to be 78: 22, the unburnts were determined ( after complete incineration in muffle furnace) to be 4.9 %. The total time taken for the run was 12 to 13 hrs including mixing and furnace preheating time. Leaching For leaching, 1050 kg of ash obtained after burning was leached in three stage counter currently. Each stage is provided with an open barrel, with a closed steam coil for heating, a bottom valve for extraction of leached solution and a cage made up with bottom and sides of almost 15-25 mesh screen whose diameter and height were 60% of that of the drum , with a handle extending at the top to lift the cage up and down for shaking purposes. The cage was such that it would handle 50 kgs of ash at a time to be extracted with initial 100 liters of fresh water. The three barrels were arranged in a triangle, so that each barrel could become stage one. The leaching sequence for initiation was conducted in 14-16 steps and subsequent cyclic operations in 25-27 steps per cycle. After leaching and filtration to remove suspended insolubles , the filtrate obtained was having 95-96% of Na2O from ash or 90-92% of Na2O from pulp mill. The total filtrate contained Na2O, silica, other solubles and water Carbonation The solution after leaching was taken for carbonation. For carbonation , a pair of drums with steam coil for heating and agitators were connected to two 300 mm diameter vertical pipes of 2 meters height , closed at both ends with inlet and CO2 gas distributors spider at the bottom and outlet at top which discharged into a receiving tank, samples from which were drawn for analysis by titration against first phenolphthalein and then methyl orange. If the reaction was not complete, the solution with precipitate would be recycled through the above two drums. Upon completion, the solution will be filtered to remove silica precipitate and sodium carbonate/ bicarbonate solution forwarded for causticization. For the experiment, CO2 gas was supplied from gas cylinder procured from the market. The progress of carbonation reaction is measured by equation C = ( 2P - M )/ M where C is the causticity , P being value of titration against phenolphthalein , M against methyl orange. At C=1, causticity( sodium silicate ) is 100% , at C = 0 , carbonate is 100% , at C 100% ) there is bicarbonate formation. During the run , the heated solution( to 92 °C ) was passed through the tower and CO2 gas introduced co currently. After three passes , carbonate value was found out to be 107% and the solution was taken for filtration. The silica was washed with water and HCI and then oven dried at 110°C . Causticization For causticization , desilicated filtrate from above was taken. Causticization was carried out in a reaction vessel having capacity to treat 760 kg of filtrate at a time.The vessel had a mesh cage (open at top) attached to a side for charging lime, paddle agitator and a discharge valve at the bottom , discharging into a settling tank, from where the top liquid layer of caustic soda solution( with some suspended lime precipitate ) was siphoned off and filtered. The bottom lime precipitate ( calcium carbonate ) was also filtered to recover entrapped caustic soda. The reaction vessel was jacketed to provide for steam heating. The cage was filled with lime of 70% purity and the vessel charged with 720-780 kg of desilicated filtrate, heated to 90-96°C such that lime would react with sodium carbonate and produce caustic soda. After 20-25 minutes of reaction , the solution was transferred to settling tank where the settling process was complete in almost 10 minutes. The top caustic soda layer was siphoned off and filtered. The bottom calcium carbonate sludge was taken out using diaphragm pump and passed through filter press. The filtrate obtained was combined with the siphoned and filtered caustic soda solution above as final recovered caustic soda solution. After processing the total sodium carbonate solution , the recovered caustic soda solution was collected and measured. Calcination Calcination as well as re calcination of calcium carbonate precipitate from causticization step is carried out in a conventional way including in wood based paper industry. Hence its experimentation was not conducted. However, in order to establish repeated recalcinability of the calcium carbonate precipitate, it is important to establish total absence of silica from carbonated solution. Hence the carbonated solution from above was dried in a constant temperature oven first at 60°C and then finished drying at 110°C , to yield solids containing sodium carbonate and balance being other inorganics and organics( from unburnts). The solids were maintained at 850°C in a muffle furnace for a while till constant weight to eliminate organics and other decomposables. The residue was boiled with HCI and filtered. There was no solids left behind, everything passing into filtrate, thereby establishing absence of silica.( Silica is acid insoluble) While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention. We claim: 1. A process for the recovery of caustic soda from weak black liquor obtained from agricultural residue pulping, which comprises concentrating by evaporation weak black liquor to solids content of 40 - 48%, mixing said concentrated weak black liquor with agricultural bio mass in the ratio of 2:0.8 to 2:1.5 by weight obtaining thereby a dark colored semisolid mass (WMF), burning said semisolid mass to temperature of from 820°C - 950°C to obtain ash, a mixture of sodium silicate and sodium carbonate, leaching said ash in water and filtering same to obtain solution of sodium silicate and sodium carbonate, heating said solution to a temperature from 80°C - 95°C and bubbling carbon dioxide through said heated solution thereby converting said soidum silicate into the sodium carbonate and silica precipitate,separating said silica precipitate from the sodium carbonate solution, washing the said silica with water and acid, and mixing lime to the sodium carbonate solution while agitating the solution at 85°C - 95°C to obtain a solution of caustic soda and calcium carbonate precipitate, separating the calcium carbonate precipitate from the said solution, washing said calcuim carbonate precipitate with water to recover entrapped caustic soda solution and mixing the resultant wash with the caustic soda solution, drying and recalcining the calcium carbonate precipitate to recover lime and carbon dioxide for recycling. 2. The process as claimed in claim 1 wherein the said weak black liquor is concentrated to a solids content of 45%. 3. The process as claimed in claim 1 wherein the said agricultural bio mass are rice straw, wheat straw, sarkanda, husk, saw dust and the like. 4. The process as claimed in claim 3 wherein the said husk is the rice husk. 5. The process as claimed in any of the preceding claims wherein the ratio of the concentrated black liquor to agricultural bio mass is 2:1 by weight. 6. The process as claimed in claim 1 wherein the burning of the said semisolid mass (Wet Mixed Fuel) is effected at temperature of 860 - 880°C resulting in ash, being a mixture of soluble sodium silicate and sodium carbonate. 7. The process as claimed in claim 1 wherein the ash is leached with water to obtain 10 - 12% Na2O solution of sodium silicate and sodium carbonate. 8. The process as claimed in claim 7 wherein, the solution is subjected to carbonation by passing CO2 gas at 92°C, precipitating silica and creating sodium carbonate/sodium bicarbonate solution and separating the precipitated silica. 9. The process as claimed in claim 8 wherein the precipitated silica is washed with water and HC1 and dried to make precipitated silica. 10. The process as claimed in claim 7 wherein the ratio of soluble sodium silicate and sodium carbonate is from 75:25 to 80:20. 11. The process as claimed in claim 10 wherein the ratio of soluble sodium silicate and sodium carbonate is 78:22. 12. The process as claimed in claim 1 wherein the said carbon dioxide constitutes 25-35% of flue gases. 13. An apparatus for the recovery of caustic soda from weak black liquor as claimed in claim 1 comprising: a pulp mill for making a pulp from the raw material and chemicals, - means to condensate weak black liquor obtained from the pulp, a mixer for mixing the black liquor and agricultural biomass to obtain wet mixed fuel, - a furnace for burning said wet mixed fuel, - a three stage leacher for leaching ash, - means for carbonation, - means for causticization and calcination. 14. An apparatus for the recovery of caustic soda from weak black liquor as claimed in claim 13 wherein the said means to condensate weak black liquor is a multi-effect short tube evaporator, preferably five effect short tube evaporator. 15. An apparatus for the recovery of caustic soda from weak black liquor as claimed in claim 14- wherein length of the tube of said multi-effect short tube evaporator is between 1.8m to 3m. 16. An apparatus for the recovery of caustic soda from weak black liquor as claimed in claim 13 wherein the said furnace for burning the wet mixed fuel is a travel grading furnace. 17. An apparatus for the recovery of caustic soda from weak black liquor as claimed in claim 13 wherein the said means for carbonation is a combination of agitator and containers. 18. A process for the recovery of caustic soda from weak black liquor substantially as herein before described with reference to the foregoing example. 19. An apparatus for the recovery of caustic soda from weak black liquor substantially as herein before described with reference to the accompanying drawings.

Documents:

618-del-2002-abstract.pdf

618-del-2002-claims.pdf

618-del-2002-Correspondence Others-(06-06-2011).pdf

618-DEL-2002-Correspondence Others-(24-03-2011).pdf

618-del-2002-correspondence-others.pdf

618-del-2002-correspondence-po.pdf

618-del-2002-description (complete).pdf

618-del-2002-drawings.pdf

618-del-2002-form-1.pdf

618-del-2002-Form-16-(06-06-2011).pdf

618-del-2002-form-18.pdf

618-del-2002-form-2.pdf

618-del-2002-form-26.pdf

618-DEL-2002-Form-27-(24-03-2011).pdf

618-DEL-2002-Form-3.pdf

618-del-2002-GPA-(06-06-2011).pdf