Title of Invention

AN INTEGRATED PROCESS FOR PRODUCING CARBON MOLECULAR SIEVES

Abstract

This invention relates to an integrted process for producing carbon molecular sieves. Carbon mkolecular sieves are useful as separators in industrial and bio gas purifiers. The process consists of partially oxidising raw coal, pelletizing, binding and powdering the coal to the desired size. These particles are thermally degraded to produce semicoke which is hydro cracked and/or steam activated to produce carbon molecular sieves of different pore sizes.

Full Text

This invention relates to an integrated process for produc i ng carbon mo I ecular s ieves. Molecular sieves are versatile absorbents used for separation of various mixtures and possess lattice like crystal structures. The shape and size of the crystal lattices can be selected to suit the separati on of given molecules, which are t rapped in "cages" formed by the lattices. Synthet ic zeoli te is one of the commonly used molecular sieves. Carbon molecular sieves are also effectively used for indust rial separation of gases. In view of their excellent mole&ilar sieving absorpti on, h i gh hydrophobi c i ty • therma 1 stabi1i ty, res i stance to acids and bases, carbon mo lecular sieves have many \ inclustr ial app1icas1ions for instance carbon molecular sieves are used in air separtion, molecular a i r cleaning, biogas separation and produce gas separati on. Further, easy avai1abi1ity of raw materials, relatively s impIer processes of manufacturing and the poss i b i t i ty of modifying pore sizes of the sieves for achieving the des i red molecular separation, makes carbon molecular s ieves very attlactive . The present invent inn employs a single step carbonization To I lowed by pore size control. Irrespective of the raw material qua Ii ty , mo I ecular sieves of the desired pore s ize can be obtained by this process. Further, the entire energy is effectively used in this integrated process itself with minimum emissions of env i ronmentally unfriendly polluting gases to the atmosphe re. The integrated process for producing carbon molecu1ar s ieves according to this i riven t i on compresses par t i a 1 oxidation of coal and admixture of t he same with a known binder, subsequent peI 1etication and thermal degradation of the same to produce semicoke, coking and steam activating the said semicoke to produce carbon molecular sieves of the desired pore size. Coal is an excellent starting material, not* only because of its ready availability but also due to the presence of condensed and I aye red strata having imper fec t ions providing enough voidage V and non-uniform porous structure. The aproximate analysis of coal suitable for carbon molecular sieve production is given be I ow: ** Raw coa 1 in t he form of 1umps i s crushed to 5 - 6 mm particle size, preferably in a jaw crusher. The particle size is further reduced to Powdered coal is thren conditioned in a hydrocyclone to produce un i form raw coaI which is a requisite for obtain ing uniformity of the final product. Coal is mixed thoroughly with water to produce a slurry of \% by weight of coal. This slurry i s pumped to a hydro eye lone. By adjust ing the pressure drop of the hydrocyclone cone, particles of uniform size are formed. A two stage hydro cyclone method is preferred as the rejects from the first stage is diluted and processed in the second stage. Accepts from the second stage are fed to the first stage for further processing. The sludge is thickened with a known thickening medium to have 40% to 60% moisture. Tray type dryers may be used for drying the sludge and hot gases are allowed to pass the ret hrough. The t emperature of the dryer and the exhaust gas temperature are maintained below 105 C by providing heat exchangers and the entire system is made integrated by connect ing the dryer exhaust with the air oxidation stage and Poking and steam activation stage. Coal thus dried is crushed to a particle size of >50 urn. 95% to 100% dryness is preferred and the dried and crushed coal may be s to red. Th is dr i ed coal is subjected to partialoxidat ion in a mixer fed continuously with incoming air. A binder such as coal tar pitch is added to the mixer preferably with injection of hot water. Hot water flow is measured to control the addition of binder to the coal powder in the mixer. Partial oxidation and mixing of coal dust with the binder occur simultaneously. Hot coa 1 powder from the blender is transferred to a pe I I e t i 7-er , preferably a hydrau lie pellitzer for forming pellets of the desired size and bulk density. The next stage in the production of carbon molecular sieves is the thermal degradation or carbonization step which is carried out in an inert atmosphere or under vacuum. Carbonization temperature ranges from 400 to 800°C and the reactor may be heated either electrically or by indirect burning of fuel. In a preferred embodiment, two reactors are used for alternate batch wise ope rati on and effective heat utilization. Reactors may be fluidized bed reactors, the outlet of which goes to a fin type heat exchanger for exchanging heat with the incoming flow to the reactor. The pelletized mass gets heated under the flow of inert ni t rogen med i urn for a predetermi ned per iod. As the temperature V rises, t he mass is carbon i zed and volatile matter is re leased t here from in stages. Cont roI Ied heat i ng does not disturb the i nternaI structure of t he carbon i zed mass but uncombustfid vapours and* part ia1 Iy oxidised gases are expeI 1ed therefrom, resulting in un i Form pore size. After t he requ i red carbon i/at ion is achieved, the pe1 let ized mass is subjected to cok i ng and steam activation t reatment. Coking is effected by controlled hydrocracking under known conditions to produce carbon molecular sieves of low pore sizes whereas activation carried out in the presence of steam and carbon dioxide results in molecular sieves of wider pores. Ideally, since the process is integrated, pellets are divided into two streams, one of which is subjected to hydrocarbon cracking to produce sieves of fine porosity, while the other stream is activated with steam in the presence of carbon dioxide. Rejects from the first stream is lead to the activation stream to complete the product ion. The flow chart given herein after shows the different stages of the integrated process according to this invention. However, alterations and modifications known to persons skilled in the art are within the scope of this invention and the appended cI aims. WE CLAIM: 1. An integrated process for producing range of carbon molecular sieves for separating various gas mixtures (N2/02 , N2-O2/CO2 , CH4/CO2 , H2/C02 etc.) based on their molecular size, comprising: a. Sizing the raw material to make a powder of less than 50jim b. Hydro separation of coal powder by making 1% slurry in water and thickening followed by drying of the filter cake. c. The coal powder from above process is transferred to a rotary kiln for partial air oxidation followed by mixing the binder. d. The binder admixture is palletized in a hydraulic pelletizer to get a shape. 2. The process as claimed in claim 1, wherein the palletized material is transferred into a fluidized bed reactor. a. The reactor is connected with a supply of hot inert gas, hydrocarbon bubbling mechanism, steam, booster heaters, heat recovery systems etc. b. The temperature and flow is controlled to the reactor to get desired conditions. c. The material from the reactor is discharged from the bottom discharge chute and packed in air tight bag. 3. The process as claimed in claims 1 and 2, wherein the thermal degradation is carried out in an inert atmosphere at a temperature range of 400°C to 800°C. a. Carbonization is carried out at about 700°C for opening up the pores. b. Hydrocarbon cracking is carried out on carbonized pellets to produce the carbon molecular sieves of fine pore size. c. The extent of hydrocarbon cracking controls the pore size to produce the desired type of carbon molecular sieves. 4. The process as claimed in claims 1 to 3 wherein the reject from the hydrocarbon cracking is fed to the rotary kiln to produce activated carbon. 5. An integrated process for producing different types of carbon molecular sieves substantially as herein described.

Documents:

1157-mas-1998- abstract.pdf

1157-mas-1998- claims duplicate.pdf

1157-mas-1998- claims original.pdf

1157-mas-1998- correspondence po.pdf

1157-mas-1998- correspondence others.pdf

1157-mas-1998- description complete duplicate.pdf

1157-mas-1998- description complete original.pdf

1157-mas-1998- form 1.pdf

1157-mas-1998- form 19.pdf

1157-mas-1998- form 26.pdf