Patent Application: US-25888608-A

Abstract:
this invention describes a complete sequestration of carbon from coal burning plants . in this process , hydrogen can be generated which in turn permits the reduction in the cost of hydride synthesis . the hydrides store hydrogen for on - board application for automobiles and fuel cells . hydrogen generation and synthesis of hydrides is accomplished by using an integrated approach in which coal is used as a fuel and carbon is sequestered in the process . the co and or co 2 produced in coal burning power plants and the heat is used when available for producing hydrogen and hydrides . carbon is used both as a reactant and as a fuel . economically hydrogen production cost is comparable to or less than the current price of hydrogen produced from fossil - fuel with the added benefit of carbon sequestration and reducing global warming . specific processes for synthesizing important hydrogen storage materials , hydrides are described . a hydrogen based automobile becomes viable as the cost of the hydrogen production and hydride synthesis is reduced . although coal - burning power plant is specified here , any power plant , coal - or natural gas - burning , can be subjected to similar treatment .

Description:
the present invention provides a novel method of producing hydrogen with carbon sequestration ; the novelty lies in the fact that gases produced in a coal - burning plant are used both for the energy and for the substance to react with sodium hydroxide reducing the cost simultaneously with eliminating the emission . if we further couple the metal hydride producing reaction with the above reactor system , we can also reduce the cost of metal hydrides for automobile use . 2naoh ( c )+ co ( g )= na 2 co 3 ( c )+ h 2 ( g ) δh =− 1 . 19e5 j ( 600 k ) 4naoh ( c )+ c ( c )+ co 2 ( g )= 2na 2 co 3 ( c )+ 2 h 2 ( g ) δh =− 6 . 62 e4 ( 600 k ) 2naoh ( c )+ c ( c )+ h 2 o ( 1 )= na 2 co 3 ( c )+ 2 h 2 ( g ) δh = 6 . 458 e4 ( 600 k ) 3naoh ( c )+ c ( c )= na 2 co 3 ( c )+ na + 1 . 5 h 2 δh =− 2 . 52e5 j ( 1100 k ) reactions ( 1 ) and ( 2 ) are exothermic . reaction ( 2 ) can be considered as a combination of the boudouard reaction : and reaction ( 1 ). reaction ( 2 ) may also be considered as a combination of co is not produced in coal burning because high ratio of air to coal is used . however if the heating requirement for the plant is fully met with a lower ratio such that co is actually produced in some quantity , we could use the co for producing hydrogen according to the following reaction if naoh costs 42 cents per kg and na 2 co 3 sells for 36 cents per kg , the hydrogen cost will be only the cost of the energy for this exothermic reaction , which would be an excellent value . an equilibrium calculation in fig1 shows that na 2 co 3 also known as soda ash and hydrogen are produced over a wide temperature range starting from 400 to 1100 k . the reaction kinetics may be improved by use of a catalyst such sio 2 and / or continuous stirring as described later . however , if we switch to coal - burning plant design that produces significant co , we will have to burn more coal for the same thermal effect as can be seen by calculating at 1000 k c + air ( n 2 2 , o 2 0 . 5 mole )= 0 . 763 co + 0 . 118 co 2 + 0 . 12 c , δh =− 6 . 628e4 j a comparison of δh shows that 4 times heat is produced when co 2 is maximized . thus in order to maximize co , we will have to burn 4 times carbon ; since in doing so , we will produce as much more hydrogen and na 2 co 3 , the economics would not change . for existing power stations , where co 2 is produced , we may choose another alternative and use co 2 to react with water and sodium hydroxide according to the reaction : one may compare this reaction with the combination of the gasifier reaction c + 2h 2 o = co 2 + 2h 2 and the co 2 absorbing reaction 2naoh + co 2 = na 2 co 3 + h 2 o to accomplish similar result . it is shown in fig2 ( a and b ) that the reaction ( 3 ) has definite advantage being the carbon - sequester and hydrogen producing reaction . the reaction kinetics may be improved by use of a catalyst such sio 2 and / or continuous stirring as described later . a comparison of the two figures shows that much higher temperature is required to obtain a significant amount of hydrogen mixed with co in fig2 a than is required when using reaction ( 2 ) ( fig2 b ). we may consider reaction ( 3 ), if co or co 2 are not available from an industrial plant : while this is an endothermic reaction , less amount of solids are required to produce the same amount of hydrogen . this may be helpful if the cost structure of the sodium compound alters in time . in this process 20 kg of naoh will yield 26 . 5 kg of na 2 co 3 for each 1 kg of hydrogen . reaction ( 3 ) was considered by saxena et al . ( 25 ) followed by ishida et al . ( 26 ). however , this is the first demonstration that the process is cost effective ( see below ). fig3 a shows the equilibrium calculated results while fig3 b and c show the experimental results . fig4 shows one possible construction of a plant comprising of a ceramic - lined steel cylinder . engineering designs of various types may be possible . in this container , a mixture of naoh : pulverized coal in 43 : 12 ratio by weight is introduced . hot co 2 from the power plant is entered from one end . the solid mixture is continually stirred with heating partly provided by the hot air from the coal - burning plant and partly by other heaters until all naoh is converted to na 2 co 3 and h 2 . the exit gases are monitored for the co 2 and the flow rate is adjusted accordingly . reaction ( 1 ) may be similarly carried out and no carbon will be needed . catalysis of the reactions , where coal is involved may be needed and has been discussed in detail in literature ( 17 ) ( e . g . probstein and hicks , 2006 ). a high production rate would result if the hydrogen is formed by continuous flow processes . as envisaged here , the reactor is a closed system with a complete conversion of fixed ratio of reactants and production of the carbonate and hydrogen . catalysis and partial conversion of the reactants will affect the costs . fig5 and table 1 show the cost analysis . through reaction ( 2 ), we will sequester 11 kg of co2 for every 43 kg of sodium hydroxide producing 1 kg of hydrogen and 53 kg of sodium carbonate . if we accept the following per kg prices : if we accept the per kg prices in table 1 , there is an advantage in offsetting the energy costs . the new hydrogen doe cost goal of $ 2 . 00 - 3 . 00 / gge ( delivered , untaxed , 2005 $, by 2015 ) is independent of the pathway used to produce and deliver hydrogen . better cost calculations are needed to insure the economic viability of the project . note that less energy is required to electrolyze sodium chloride to produce sodium hydroxide than to produce sodium . it will be necessary to integrate the production of naoh at the power plants instead of purchasing it from an outside manufacturer . in - house sodium hydroxide manufacturing will provide significant shipping cost savings , efficient process integration , and safety . there are many uses of na 2 co 3 and as long as the use does not release the co 2 to the atmosphere , the carbon sequestration remains effective . this reaction is endothermic with h of 1 . 16e6 j / mol and is largely complete around 1400 k . since we rely on coal to provide the heat , the energy cost is not an issue . if we use this reaction to reduce the amount of sodium carbonate produced in reactions ( 1 )-( 4 ), we will further decrease the dependence on the selling price of na 2 co 3 . united states tops in co 2 - emissions per capita ; in 2003 , 121 . 3 metric tons of co 2 were released in the atmosphere . in 2004 the total carbon release in north america was 1 . 82 billion tons . world - wide industrial nations were responsible for 3790 million metric tons of co 2 ( kyoto - related fossil - fuel totals ). it is clearly not practical to consider that we can sequester all this carbon with reaction ( 2 ) which would require production of naoh on a massive scale which would cause further emission of co 2 if fossil fuel is used in the production . however in all situations where industry is producing carbon gases and heat anyway , the production of hydrogen according to the reactions presented here , would lead to reduction of carbon in the atmosphere . most benefit will be obtained if non - fossil sources of energy ( hydroelectricity , nuclear - energy , solar and wind ) are used for naoh production . more than 100 mt c / yr are vented to the atmosphere as part of the global production of roughly 38 mt of hydrogen per year . through reaction ( 2 ), we will sequester 3 mt carbon ( 11 mt of co 2 ) for every 40 mt of sodium hydroxide producing 1 mt of hydrogen and 53 mt of sodium carbonate . the us production of naoh is currently 16 mt per year . 1300 mt of naoh will be needed to sequester all the carbon which is currently emitted in hydrogen production . in this process 33 mt of h 2 will result . sodium hydroxide is produced ( along with chlorine and hydrogen ) via the chloralkali process . this involves the electrolysis of an aqueous solution of sodium chloride . the sodium hydroxide builds up at the cathode , where water is reduced to hydrogen gas and hydroxide ion . the total h 2 produced in these reactions ( reactions 1 , 2 and electrolysis ) if used in automobiles and other energy devices will have a very large effect on co 2 - emission . we should also consider the possibility of simply removing the co 2 emission by the reaction : in this process , 1 kg of co 2 will be removed as 2 . 41 kg of sodium carbonate consuming 1 . 818 kg of naoh . we will gain 11 cents per kg of co 2 removal in material costs . the energy cost is separate . this is all based on the prices remaining at this level . what is proposed here depends critically on maintaining the cost difference between na 2 co 3 and naoh at the current level . with the availability of hydrogen already at a high temperature ( hydrogen has the same heat capacity as air ), we may use the hot gas in any innovative use in producing a hydride . may be used ; methods of activating a metal for reaction with hydrogen has been described amply in literature ( 1 - 7 ) e . g . for mg by mcclane et al . ( 1 ). with the hot h 2 provided in the present set up , there will be a further reduction in the cost of mgh 2 as is used in the safe hydrogen method ( 1 ). two other methods are proposed here which take the advantage of the available hot hydrogen . in the first method , mgh 2 is synthesized as follows : the addition of water promotes the above reaction to proceed forward vigorously . a method to produce hydrogen on board using a borohydride and methods to synthesize it have been discussed in literature ( 8 - 15 ). millenium cell inc ( 16 ) has demonstrated the use of nabh 4 in fuel - cells which may be usable for running small devices as well as automobiles . for sodium borohydride to be widely utilized as an energy storage medium for hydrogen , the cost must be reduced by at least an order of magnitude from its present price . we propose the following set of reactions to solve this problem : the sodium compound can be synthesized over 300 to 800 k , while the lithium compound over 300 to 600 k . both of these reactions can be modified considering that h 2 is produced cheaply as discussed in this document as follows : nabo 2 + 3 mg + 1 h 2 o + 1 h 2 = nabh 4 + 3 mgo ( δh =− 6 . 9 kj , 600 k ), libo 2 + 3 mg + 1 h 2 o + 1 h 2 = libh 4 + 3 mgo ( δh =− 6 . 5 kj , 600 k ), since nabo 2 or libo2 is the product in the hydrolysis reaction : the major cost is for the reduction of mgo to mg , which is discussed by saxena et al . ( 18 ). they studied the reaction 2mg + h 2 o producing mgh 2 and mgo or mg ( oh ) 2 . with the possible recycling of mgo using the som process [ 19 ], the cost of producing the hydride will be substantially reduced . the energy costs ( which in this case since the reaction is exothermic and we may be able to use hot h 2 ( fig4 ) as well as hot air from coal - burning power plants as used for electric generation or for manufacturing industrial products such as cement ( fig4 - 5 )), the energy cost can be minimized . fig6 shows that the synthesis of a hydride using metal + water + heated h 2 is accomplished in this reactor which may be heated using hot air exhausted from a power plant according to this invention . freshly powdered metal is used with water and the newly produced hydrogen from the reactor is used for the production . andrew w . mcclaine , kenneth brown , sigmar tullmann , chemical hydride slurry for hydrogen production and storage , doe hydrogen program 2 fy 2006 annual progress report . a . w . mcclaine , s . tullman and k . brown : chemical hydrogen slurry for hydrogen production and storage . fy 2005 progress report : doe hydrogen program . a . w . mcclaine , r . w . breault , c . larsen , r . konduri , j . rolfe , f . becker and g . miskolczy , proceedings of the 2000 u . s . doe hydrogen program review nrel / cp - 570 - 28890 . m . klanchar , b . d . wintrode , j . phillips , energy & amp ; 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morigazaki , n . ; liu , b . h . ; suda , s . “ preparation of sodium borohydride by the reaction of mgh 2 with dehydrated borax through ball milling at room temperature ” j . alloys compd ., 2003 , 349 , 232 - 236 . wu , y . process for the regeneration of sodium borate to sodium borohydride for use as hydrogen storage source . report 2005 , contract id #: de - fc36 - 04go14008 . probstein , r . f . and hicks , r . e . synthetic fuels , dover , n . y ., 2006 . s . k . saxena , vadym drozd and andriy durygin , synthesis of metal hydride from water . international journal of hydrogen energy , in press on - line , march 2007 . uday b . pal and adam powell , “ solid oxide membrane technology ( som ) for electrometallurgy ”, j . of metals , 59 ( 5 ), 2007 , p . 44 . gupta , h . ; mahesh , i . ; bartev , s . ; fan , l . s . enhanced hydrogen production integrated with co 2 separation in a single - stage reactor ; doe contract no : de - fc26 - 03nt41853 , department of chemical and biomolecular engineering , ohio state university : columbus , ohio , 2004 . ziock , h - j . ; lackner , k . s . ; harrison , d . p . zero emission coal power , a new concept . proceedings of the first national conference on carbon sequestration , washington , d . c ., may 15 - 17 , 2001 . rizeq , g . ; west , j . ; frydman , a . ; subia , r . ; kumar , r . ; zamansky , v . ; loreth , h . ; stonawski , l . ; wiltowski , t . ; hippo , e . ; lalvani , s . fuel - flexible gasification - combustion technology for production of h 2 and sequestration - ready co 2 ; annual technical progress report 2003 , doe award no . de - fc26 - 00ft40974 . ge global research : irvine , calif ., 2003 . “ the hydrogen economy : opportunities , costs , barriers , and r & amp ; d needs ( 2004 ),)” carbon emissions associated with current hydrogen production : “ national academy of engineering ( nae ), board on energy and environmental systems ( bees ). xu , x , xiao , y . and quaio , c . system design and analysis of a direct hydrogen from coal system with co2 capture . energy & amp ; fuels 2007 , 21 , 1688 - 1694 . saxena , s . k . hydrogen production by chemically reacting species . int . j . hydrogen energy 2003 , 28 , 49 . ishida , m ., toida , m ., shimizu , t ., takenaka , s . and otsuka , k . formation of hydrogen without co x from carbon , water and alkali hydroxide , ind . eng . chem . res . 2004 , 43 , 7204 - 7206 . the references recited here are incorporated herein in their entirety , particularly as they relate to teaching the level of ordinary skill in this art and for any disclosure necessary for the commoner understanding of the subject matter of the claimed invention . it will be clear to a person of ordinary skill in the art that the above embodiments may be altered or that insubstantial changes may be made without departing from the scope of the invention . accordingly , the scope of the invention is determined by the scope of the following claims and their equitable equivalents .