WO2009029292A1

WO2009029292A1 - Hydrogen production with carbon sequestration in coal and/natural gas-burning power plants

Info

Publication number: WO2009029292A1
Application number: PCT/US2008/055586
Authority: WO
Inventors: Surendra Saxena
Original assignee: Surendra Saxena
Priority date: 2007-08-27
Filing date: 2008-03-02
Publication date: 2009-03-05

Abstract

This invention describes a system of reactions for a partial sequestration of carbon (CO2 and CO) from coal burning plants and zero emission production of hydrogen and hydrides. The only raw material to be used is salt (sodium chloride, NaCl), coal and water or a metal for the hydride. Sodium hydroxide (NaOH) generated from the chloride is used for locking carbon dioxide in sodium carbonate and bicarbonate.

Description

APPLICATION

FOR

PATENT

Title of Invention:

HYDROGEN PRODUCTION WITH CARBON SEQUESTRATION

IN COAL AND /NATURAL GAS-BURNING

POWER PLANTS

Inventor: Dr. Surendra Saxena

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority under 119(e) to the provisional application entitled "Carbon sequestration and production of hydrogen and hydride" U.S. serial number 60/982,473, filed Oct. 25, 2007.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

No federal government funds were used in researching or developing this invention.

NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

REFERENCE TO A SEQUENCE LISTING

Not applicable.

BACKGROUND

Field of the Invention

[001] This invention relates to a system of processes for sequestering carbon in coal- burning power plant and producing hydrogen gas that take advantage of emission of CO and CO2 and heat from the plants. The use of this invention will lead to cheap hydrogen and hydride production and carbon sequestration and reduced global warming.

Background of the Invention

[002] The United States leads the world in per capita Cθ2-emissions. 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 CO2 (Kyoto-Related Fossil- fuel totals). There is little doubt that the world is choking with greenhouse gases. [003] No one can deny that there is an urgent need to develop innovative solutions to reduce the emissions from our automobiles and from our coal or gas burning power plants. This invention may well provide an answer to the problem of greenhouse gas emissions and pave the way towards a clean energy future. The invention addresses carbon sequestration in coal or gas burning plants used for power generation or for manufacturing (cement, steel etc.). The chemical process that sequesters carbon gases (thus preventing them from escaping to the atmosphere) generates hydrogen as a byproduct.

[004] Coal burning power plants currently produce electricity to satisfy the needs of a power hungry economy all over the world and in doing so also produce much of the greenhouse gases. While coal is used to generate electric power, it is also used for producing hydrogen by reaction with water. Therefore, its continued use would be of immense help to the world if only we can sequester the carbon. This invention helps to do exactly that and if we develop this technology, we could continue to use coal for many decades without any environmental degradation.

[005] Currently steam methane reforming is the most common and the least expensive method to produce hydrogen [I]. Coal can also be reformed to produce hydrogen through gasification. Hydrogen production by methods that do not emit CO2 are either more expensive compared to those using fossil fuels or are in the very early stages of development [2-4]. Since the United States has more proven coal reserves than any other country, hydrogen production through a coal-based technology is a very attractive prospect. However, effective and low cost carbon sequestration technology has not yet been developed.

[006] Hydrogen is widely regarded as the energy of the future, but to produce and use hydrogen - either by direct combustion or in a fuel cell - it is necessary to use other sources of energy. Thus using hydrogen or any other material to produce energy cannot be environmentally clean and economically viable unless the process by which it's produced sequesters carbon or is otherwise free of greenhouse gas emissions. The use of hydrogen is being promoted on a federal level with financial support, and we may eventually have hydrogen-using technology for our transportation and other energy needs. However, it is a sad fact that the production of the hydrogen to be used in that technology will most likely continue to be dependent on the use of fossil fuels for the foreseeable future, and it may not be viable either economically or environmentally. Solving this problem requires alternative methods of using coal to produce hydrogen and hydrides. Many hydrides are currently being considered for use in the on-board generation of hydrogen, and the cost of producing the hydride is an obviously critical factor in this evaluation. This project would use carbon to produce hydrogen with carbon sequestration.

Coal-burning power-plants are harmful to the environment

[007] Coal is used extensively in producing synthetic fuels [I]. Use of coal in gasifiers is well established and hydrogen may be produced by the reaction: C + 2H₂O = CO₂ + 2H₂. Gasifiers are operated between 500 to 1200⁰C, and use steam, oxygen and/or air and produce a mixture of CO₂, CO, SO₂, NO_x, H₂, CH₄ and water. Treatment systems are available for SO2 and NO_x but CO₂ remains a problem. The CO produced can be further processed by the shift-gas reaction to produce H₂ with production of CO₂: CO +H₂O = CO₂ + H₂. The following is an extract from a report by National Academy of Engineering, Board on Energy and Environmental Systems [5] and shows the importance of the present study: "At the present time, global crude hydrogen production relies almost exclusively on processes that extract hydrogen from fossil fuel feedstock. It is not current practice to capture and store the byproduct CO₂ that results from the production of hydrogen from these feed stocks. Consequently, 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."

[008] It would then appear that when coal is used in gasifiers or in direct burning in power- and other manufacturing-plants, CO₂ and CO are prominent among other gases released to atmosphere. Their emission is not only harming the environment but as considered here is also a waste of resources. For industry this has been an economic issue.

[009] This invention provides a clear economic incentive to sequester carbon (CO₂ and CO) without significantly affecting our current modes of operations i.e. the coal- burning power plants. It will also show that hydrogen will be produced at much lower costs and with zero emission of greenhouse gases.

[0010] Many new coal-burning power plants are now in the offing. This is the right time to act.

[0011] Related patents include the following.

[0012] US 7,132,090, D. Dziedzic, K. B. Gross, R. A. Gorski, J. T. Johnson, Sequestration of carbon dioxide [0013] US patent application 20030017088, W. Downs and H. Sarv Method for simultaneous removal and sequestration of CO2 in a highly efficient manner

[0014] US patent application 20010022952, G. H. Rau and K. G. Caldeira Method and apparatus for extracting and sequestration carbon dioxide [0015] US 5,261,490, T. Ebinuma Method for dumping and disposing of carbon dioxide gas and apparatus therefore

[0016] US 6,667,171, D. J. Bayless, M. L. Vis-Morgan and G. G. Kremer Enhanced practical photosynthetic CO2 mitigation [0017] US 6,598,407, O.R. West, C. Tsouris and L. Liang Method and apparatus for efficient injection of CO2 in ocean [0018] US 5,562,891, D. F. Spencer and W. J. North Method for the production of carbon dioxide hydrates [0019] US 5,293,751, A. Koetsu

Method and system for throwing carbon dioxide into the deep sea [0020] US 6,270,731, S. Kato, H. Oshima and M. Oota Carbon dioxide fixation system [0021] US 5,767,165, M. Steinberg and Y. Dong

Method for converting natural gas and carbon monoxide to methanol and reducing CO2 emission

[0022] US 6,987,134, R. Gagnon

How to convert carbon dioxide into synthetic hydrocarbon through a process of catalytic hydrogenation called CO2 hydrocarbonation [0023] US 7,282,189 B2 Zauderer

Production of hydrogen and removal and sequestration of carbon dioxide from coal- fired furnaces and boilers [0024] US 2006/0048517 Al Fradette et al.

Process and a plant for recycling carbob dioxide emissions from power plants into useful carbonated species [0025] US 2004/0126293 Geerlings et al. Process for removal of carbon dioxide from flue gases [0026] US 6,669,917 B2 Lyon

Process for converting coal into fuel cell quality hudyrogen and sequestration-ready carbon dioxide [0027] US 7,083,658 B2 Andrus Jr. et al.

Hot solids gasifϊer with CO2 removal and hydrogen production

[0028] US 2006/0185985 Al Jones

Removing, carbon dioxide from waste streams through co-generation of carbonate and/or bicarbonate minerals

SUMMARY OF THE INVENTION

[0029] The present invention provides a system of reactions to sequester carbon and produce hydrogen from sodium hydroxide and CO or CO2 and carbon or natural gas. The carbon gases are produced in industrial plants burning coal and thus available at no cost. These gases also can be obtained at relatively high temperature; the reaction of CO or CO2 and carbon with sodium hydroxide is exothermic and hence no additional heating may be required. The CO or carbon or natural gas and CO2 would react to form sodium carbonate and thus carbon will be sequestered. The main points are: We continue to use coal burning power plants for electric generation and other uses; The emitted gases mostly CO and CO2 (the green-house gases causing global warming) at modest temperatures and hydroxide are fed into chemical reactors built adjacent to the power plant; Chemical reactions between gases and hydroxide and carbon or natural gas produce solid carbonate and hydrogen; The reactant NaOH is produced preferably with a non- fossil energy source (nuclear, hydro-, solar- or wind-) and the products carbonate and hydrogen are sold reducing the cost of the power plant and generating electricity ; Electric or thermal power is produced from coal-burning plants with zero emission of greenhouse gases, and Hydrogen is produced economically with zero emission because of the low materials cost and low energy cost due to use of hot gases; use of hydrogen in transport will further reduce CO2- emission.

[0030] An embodiment of the present invention provides for a complete sequestration of carbon and hydrogen production using CO from coal-burning power plant. In such a case, sodium hydroxide reacts with CO producing hydrogen and carbonate and no carbon is released in the environment.

[0031] Another embodiment of the present invention provides the production of carbonate and hydrogen using CO2 from coal-burning power plant and reacted with carbon and sodium hydroxide. In such a case, sodium hydroxide reacts with carbon and CO2 producing hydrogen and carbonate and no carbon is released in the environment.

[0032] Another embodiment of the present invention provides the production of carbonate and hydrogen using CO2 or CO or any mixture thereof from coal-burning power plant and reacted with natural gas, water and sodium hydroxide. In such a case, sodium hydroxide reacts with water, natural gas and CO/CO2 producing hydrogen and carbonate and no carbon is released in the environment.

[0033] Another embodiment of the present invention provides the production of hydrogen if the industrial CO or CO2 is not available. In such a case, sodium hydroxide reacts with water and carbon or natural gas producing hydrogen and no carbon is released in the environment.

[0034] Another embodiment of the present invention provides for further sequestration of CO2 by reaction of the unsold Na₂CO3 with water and CO2. [0035] Another embodiment of the present invention provides for the existing coal- burning power plants to be retrofitted with the reactor design presented in Figure 7 or any such design with better engineering attributes.

[0036] Finally, hydrogen produced in the reactor is used to produce hydrides, specifically magnesium hydride at a low cost,

Relation to other published work and patented processes

[0037] The use of hydroxide in sequestering carbon from processes using fossil-fuel has been suggested in many publications and in some patents (Table 1). A technique to use the carbonation reaction for use with coal-burning power plants has been described by Jones (US 2006/0185985 Al) who uses the reaction:

[0038] NaOH + CO₂ = Na₂CO₃ (or bicarbonate)

[0039] The strategy adopted in this work differs in using several reactions that produce hydrogen as well as form the carbonate. Production of hydrogen with zero emission and using the carbonate gainfully are important aspects of the present invention. Unlike the reactions used in this invention, the Skyonic method relies on a single direct carbonation reaction. Others have used solids such as CaS (US 7,083,658 B2 Andrus Jr. et al.) and CaO (US 6,669,917 B2 Lyon) with different effects. Others use hydroxide reaction with CO2 involving CaO (Lin et al., 11, Xu et al.9), magnesium and calcium silicates (Zevenhoven et al, 10) and alkali hydroxide (Ishida et al. 8). Finally the ZECA (Zero Emission Coal Alliance) process uses Ca(OFTh.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The purpose of this invention and the tremendous advantages it entails for reduction in global warming gases needs to be fully understood from the study of the description along with the drawings herein.

[0041] Fig.l shows in two parts a comparison of the calculated equilibrium compositions, which are easily verified in experiments. Fig. Ia is a well known phase diagram showing the carbon-water system in a gasifier where hydrogen and CO mixture is produced up to very high temperatures. This diagram is included here to show a comparison with the reaction adopted in the present invention shown in Fig.

Ib. The temperature of hydrogen production is much lowered and the gas is pure hydrogen.

[0042] Fig. 2 shows the moles of hydrogen and sodium carbonate produced when sodium hydroxide and carbon monoxide are allowed to react. The carbon monoxide is presumably generated in a coal-burning process providing heat to another manufacturing process, e.g. synthesis of cement.

[0043] Fig.3a shows that in absence of an industrial source of carbon-oxygen gases, this invention provides for the production of hydrogen from water, carbon and sodium hydroxide reaction with no emission of C-O gases.

[0044] Fig. 3b shows the reaction where carbon may be replaced by methane with high production of hydrogen.

[0045] Fig. 4 shows an experimental setup that was used to produce the experimental results shown in the following figures. Equipment for the study of hydrogen generation is used with laser break-down spectroscopy to measure the hydrogen formation.

[0046] Fig. 5a shows experimental data for the reaction (2 NaOH (c) + C(c) + H₂O (1)

= Na₂COs (c) + 2 H₂). The temperature was increased at a rate of 4°C/min starting from 110 ⁰C to reach a maximum of 700 ⁰C in about 150 minutes. [0047] Fig.5b. Hydrogen generation in 2NaOH + C + H₂O → Na₂CO₃ + 2H₂ reaction studied at different temperatures. N₂ carrier gas flow rate 50 mL/min. [0048] Fig.βa. Experimental data for the reaction (2NaOH (c) + CO (g) = Na₂CO₃ (c) + H₂(g)). Temperature was increased at rate of 4°C/min. Two different rates of flow of CO were used. Lower hydrogen yield for higher CO flow could be explained if one takes into account CO disproportionation reaction 2CO →CO₂ + C, the rate of which depends on the CO partial pressure. Released CO₂ will react with sodium hydroxide decreasing amount of the latter available for the reaction with carbon monoxide. [0049] Fig. 6b. Hydrogen generation in 2NaOH (c) + CO (g) = Na₂CO₃ (c) + H₂(g) reaction studied at different temperatures. N₂ carrier gas flow rate 50 mL/min. 90% hydrogen resulted in less than 60 minutes.

[0050] Fig. 6c. Hydrogen flow rates in the CO + 2NaOH reaction measured at different temperatures and CO flow rate of 20 mL/min and N₂ flow rate of 50 mL/min. Hydrogen flow rate vs. time dependence at 300⁰C is characterized by quite long (about 3 h) initialization period. However, after 3 h the reaction accelerated in a tubular furnace with a quartz tube. Nitrogen gas with a flow rate of 50ml/min was used as a carrier to deliver steam to the reactor.

[0051] Fig. 7a. A not-to-scale schematic diagram showing a possible industrial set up of a reactor to be linked to a coal-burning power plant and a sodium hydroxide production plant. The power plant provides hot CO or CO₂ to the reactor. NaOH delivered to the reactor is advanced through the length of the reactor by a screw feeder over the required time period for reaction which could be usually 60 minutes. Since the reaction is highly exothermic, power must be adjusted by monitoring the temperature by use of a thermocouple. Maintaining the temperature at 400⁰C would ensure the result. It is permitted for CO pressure to be built up to some bars and for the newly formed hydrogen to exit through a membrane and be collected for use. The screw feeder delivers the finished product Na₂CO₃ and may be some unused CO and H₂ mixture to a container. The gases from the container may be reused as necessary. This design will also apply to Process IV reactions where carbon is replaced by methane. Additional sequestration of CO₂ is possible through the reaction OfNa₂CO₃, water and CO₂. The product sodium bicarbonate could then be sold or used in landfills. [0052] Fig. 7b. A not-to-scale schematic diagram showing a possible industrial set up of a reactor to be linked to a coal-burning power plant and a sodium hydroxide production plant. The power plant provides electric power for the latter as well as hot CO2 to the reactor. NaOH is delivered to the reactor at the top and CO2 and if needed for reaction (5) the natural gas from the bottom. This is a closed system reactor. The required time period for reaction could be usually 180 minutes. Since the reaction is highly exothermic, power must be adjusted by monitoring the temperature by use of a thermocouple. Maintaining the temperature at 700 ⁰C would ensure the result. It is permitted for CO2 pressure to be built up to some bars. The newly formed hydrogen exits through a membrane and is collected for use. After the reaction is complete with no hydrogen flowing out, the reactor can be emptied into another container. The finished product would be Na2CO3 and some unused CO2. This design will also apply to Process IV reactions where carbon is replaced by methane. Additional sequestration of CO2 is possible through the reaction of Na₂COs, water and CO2. The product sodium bicarbonate could then be sold or used in landfills. [0053] Fig. 7c. A not-to-scale illustration of a screw reactor sketched in Fig. 7a. The reactor could be used for both CO and CO2 and if needed for reaction (5) the natural gas with different times and temperatures as required.

[0054] Fig. 7d. A schematic diagram for the flow of materials using a conveyor belt design. The sodium carbonate may further be used by using Process V to sequester additional CO2, which may be accomplished by passing the gas through series of tanks with water and the carbonate until all gas is adsorbed. [0055] Fig. 8 shows the cost calculations for carbon sequestration assuming that Na₂COs sells for $100 per ton and production cost for NaOH varies from $100 per ton to $200 per ton. This calculation applies to the first several power-plants which use this technique. As the Na2CO3 supply continues to rise, the price structure would change. $2000/ton price of hydrogen is used for carbon sequestration calculation. (See Tables 2 and 3 for detailed calculation).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0056] The present invention provides a novel method of sequestering carbon 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. The invention relies on processes described below.

Process I. CO2 sequestration and hydrogen production

[0057] For existing power stations, where CO₂ is produced, we may choose this alternative and use CO2 to react with water and Sodium hydroxide according to the reaction:

[0058]

(1) 4 NaOH (c) + C (c) + CO₂(g) = 2 Na₂CO₃ (c)+ 2 H₂ (g) ΔH = -6.62 E4 (600 K)

[0059] One may compare this reaction with the combination of the gasifier reaction C+ 2H₂O = CO₂ + 2H₂ and the CO₂ absorbing reaction 2NaOH + CO₂ = Na₂CO₃ + H₂O to accomplish similar result. It is shown in Fig. 1 (a and b) that the reaction (1) has definite advantage as the carbon-sequester and hydrogen producing reaction. A comparison of the two figures shows that much higher temperature is required to obtain a significant amount of hydrogen mixed with CO in Fig. Ia than is required when using reaction (1) (Fig. Ib). Reaction (1) can be considered as a combination of the Boudouard reaction:

[0060]

C + CO₂ = 2 CO

and reaction (1). Reaction (2) may also be considered as a combination of

[0061]

2NaOH + CO₂ = Na₂CO₃ + H₂O and

2 NaOH + C + H₂O = Na₂CO₃ + 2 H₂

Process II. CO sequestration and hydrogen production

[0062] 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

[0063]

(2) 2NaOH (c)+ CO(g) = Na₂CO₃ (c) + H₂ (g) ΔH = -1.19E5 J (600 K)

[0064] An equilibrium calculation in Fig. 2 shows that Na₂CO₃ also known as soda ash and hydrogen are produced over a wide temperature range starting from 400 to 1100 K. 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

[0065]

C + Air ( N₂ 4,O₂ 1 mole)= CO2, ΔH = -2.746E5 J

C + Air ( N₂ 2, O₂ .5 mole) = .763 CO + .118 CO₂ + .12 C, ΔH = -6.628E4 J

Process III. Hydrogen production with zero emission

[0066] We may consider reaction (3), if CO or CO₂ are not available from an industrial plant:

[0067]

(3) 2 NaOH (c)+ C(c) + H₂O (1) = Na₂CO₃ (c)+ 2 H₂ (g) ΔH = 6.458 E4 (600 K)

[0068] Reaction (3) was proposed by Saxena [6]. 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 OfNa₂CO₃ for each 1 kg of hydrogen. Fig.3 shows the calculated phase diagram.

[0069] It is possible to consider a combination of the reactions. For example, reactions (1) and (3) or (1) and (2) may be combined respectively as follows:

[0070]

(3a) 6NaOH + CO₂+ 2C + H₂O=3 Na₂CO₃ + 3 H₂, and (3b) 6NaOH + (1-x) CO₂ + x CO +C = 3Na₂CO₃ + 3H₂.

Combination of the reactions may be optimized by taking into consideration the costs of the energy, products and reactants.

Process IV. Use of natural gas

[0071] We may also consider the use of cheaply available natural gas as follows:

[0072]

(4) 2 NaOH + CH₄ + H₂O = Na₂CO₃ + 4 H₂

for hydrogen production. For sequestration of carbon with hydrogen production, we use

[0073]

(5) 4 NaOH + CH₄ + CO₂= 2Na₂CO₃ + 4H₂

(6) 4 NaOH +CH₄ +C0+H₂0 =2Na₂CO₃+ 5H₂

[0074] Several mixed reactions between (5) and (6) are feasible and may be optimized as before.

Process V. Treatment of NQCO; and additional carbon sequestration

[0075] The excess carbonate can be further used to sequester additional CO₂ according to the reaction:

[0076]

(7)Na₂CO₃ + CO₂ +H₂O = 2 NaHCO₃

[0077] This reaction takes place at 25 ⁰C and does not require heating.

Process VI. Synthesis of hydrides using the hydrogen [0078] Hydrogen formed in the above procedure may be directly used for synthesizing hydrides. A hydride which may be synthesized at the site is Mg +H2 = MgH2. This reaction is exothermic (DH = -76 KJ/mol) and with a well ground metal would proceed rapidly to completion.

EXPERIMENTAL DATA

[0079] Experiments were conducted to verify the theoretical predictions for reactions (2) and (3) using an in-house method involving measurement of evolving hydrogen by break-down laser spectroscopy (Fig. 4). The reaction between carbon, sodium hydroxide (anhydrous sodium hydroxide, supplied by Alfa Aesar (97%)) and water was carried out in a gas-flow system (Fig. 4). Sodium hydroxide was dissolved using a minimal amount of distilled water in an alumina boat and then activated carbon was immersed into this solution. The alumina crucible was put in the quartz tube as shown in Fig. 4.

[0080] The reaction between NaOH and CO was studied using the same experimental setup. Both reactions were first explored with temperature increasing at a fixed rate, reaction (3) between 110 to 700⁰C (Fig. 5a and 5b) and reaction (2) between 110- 400⁰C (Fig. 6). Reaction (3) was studied at two different flow rates of CO (10 and 20 ml/min) (Fig. 6a). Both reactions were complete in less than 200 minutes. Results of isothermal kinetic experiments at several temperatures are shown in Fig. 6b (reaction 2) and 5b (reaction 3). Hydrogen concentration in the effluent gases from the reactor was determined by laser beak-down spectroscopy. Before analysis the gases were passed through liquid nitrogen (NaOH/C/H₂O reaction) or acetone/dry-ice (NaOH/CO reaction) cooled condenser to remove all hydrogen containing species except for H2 gas.

Design of an integrated plant for power and hydrogen generation with zero emission [0081] The only raw material required is coal (or natural gas), sodium chloride and water. To minimize the costs it is essential that an integrated design of the plant is used. It should consist of:

1. A plant to produce sodium hydroxide (NaOH) which uses the electricity preferably from an alternate-energy source(nuclear, hydro-, geothermal, solar or wind; however we note that since all electricity is sold from grids from all sources, this may not always be possible) (byproducts chlorine and hydrogen in this manufacturing process are sold reducing the production cost of NaOH),

2. A coal-burning or natural gas power plant that generates power for electricity or power for manufacturing materials and from which off-peak power can be tapped for forming NaOH, and which gives off CO and CO2,

3. A screw feed reactor (conveyor belt design is shown in Fig.7d) which takes the energy for heating from the coal-burning power plant and from the ensuing gases and permits the reaction between the hydroxide and the gases, and finally

4. A series of reactor tanks for Process V where CO2 is sequestered by bubbling it through a mixture of sodium carbonate and water.

[0082] We can consider the following type of situations. Although we deal with separate reactions below, in actual practice the composition of the feeder stock in the reactor will be determined by optimizing the desired yield of products using the several reactions. Such composition would be variable depending on the supply and demand of the products.

[0083]

1.The coal burning power plant produces mostly CO

[0084] In such a case, we use the reaction (2) and reaction (6) as described under Process II and Process IV. Fig. 7a shows a schematic diagram of the plant design. Stainless steel cylinder may be used with an alumina lining for protection from the corrosive reactants. The dimension of the vessel will have to depend on the size of the coal-burning power plant and the volume of the emitted gases. The reactor will be linked to the exhaust gases from the power plant and the plant for production of NaOH. Hot gases will be fed to the reactor vessel at one end and NaOH at the other end which is advanced by screw feeding mechanism. Temperature inside the reactor is maintained at 400 C. Since this is a highly exothermic reaction, the temperature must be monitored with a thermocouple and power adjusted accordingly. The kinetics of this reaction are such that one can expect the movement of the reactant solid to advance to the end of the vessel in one hour or more as needed for the completion of the reaction. Hydrogen is collected from the top. The electric power from the coal- burning power plant is used for powering the exothermic reaction and for consumers; the production of NaOH is preferably from an alternate non- fossil energy source such as hydro- , geothermal or nuclear.

[0085]

2.The coal-burning power plant produces mostly CCh

[0086] In such a case, we have to consider the reaction in a closed system for the reactions (2) and (5). The reaction (2)

[0087]

4 NaOH (c) + C (c) + CO₂(g) = 2 Na₂CO₃ (c)+ 2 H₂ (g) ΔH = -6.62 E4 (600 K)

[0088] may be considered as a combination of 2NaOH + CO₂ = Na₂CO₃ + H₂O and

2 NaOH + C + H₂O = Na₂CO₃ + 2 H₂

[0089] Catalysis of the reactions was not employed in our experiments but if needed can be used as has been discussed in detail in literature [I]. A high production rate would result if the hydrogen is formed by continuous flow processes. As envisaged here, the equilibrium calculations are for 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.

[0090] We use the steel reactor vessel whose dimension will depend on the size of the coal-burning plant (Figs. 7b and 7c). The vessel has access for the solid (NaOH+ C) feeder at the top, and for CO₂ at the bottom and for taking out the products; the vessel is otherwise sealed. As before the steel vessel is lined on the inside with alumina. After feeding the reactants, the temperature is raised to 700 ⁰C at a rate of few degrees per minute. Since this is an exothermic reaction, the temperature inside the vessel must be monitored with a thermocouple and power adjusted accordingly. The reaction should be complete rapidly.

[0091]

3. The reaction to produce hydrogen with zero-emission

We may use the hot steam from the coal-burning plants and could use the same set up as shown in Figure 7.

[0092]

4.The reactions in Process IV

We may also use natural gas in sequestering carbon and producing hydrogen according to Process IV reactions using the same plant design as shown in Fig.7.

[0093]

5.The bicarbonation reaction

CO2 is bubbled through several tanks with water and carbonate until all of it is absorbed. The size and number will depend on the size of the power plant.

[0094]

6. Hydride production

The evolving hydrogen may be fed into additional reactors with some pressure (~2 atmospheres) with well stirred magnesium metal to form hydrogen. Since the reaction is exothermic no additional heating may be necessary.

[0095] Cost analysis

[0096] The cost of NaOH in the market may fluctuate wildly depending on the supply and demand. The following calculations are based on an assumed cost of producing NaOH which may vary from $50 to $200 per ton and a selling price for Na2CO3. We note that if nuclear, hydro or geothermal energies are used, the price would be much less. Although examples of calculations are given here using separate reactions, in actual practice the composition of the feeder stock in the reactor will be determined by optimizing the desired yield of products using the several reactions. The production of NaOH (chloralkali process) may involve in simplified form a reaction such as

[0097]

2 Na⁺ + 2 H₂O + 2 e- = 2 NaOH + H₂

[0098] In industrial production which employs NaCl, there is formation of chlorine in addition to hydrogen. The energy consumption to produce 1 ton of Cl₂ by electrolysis with diaphragm is around 2720 kWh. This gives us 2413 kWh per 1 ton of NaOH. To produce 1 ton of NaOH one needs 1.463 ton of NaCl. Chlorine (888kg) and H₂ (25 kg) are byproducts of the electrolysis. Thus the cost of 1 ton NaOH production is:

[0099] 1.463 x price of NaCl $/ton + (2413 x Price of electricity $/kWh) - (0.888 x price Cl₂ $/ton) - (25 x price H₂$ /kg)

[00100] Cl₂ price varies from $220 to $240 (http://www.the-innovation- group.com/ChemProfiles/Chlorine.htm). Rock Salt price is ca.$60(http://www.ct.gov/dot/lib/dot/documents/dsalt/winterops.pdf). Construction cost, labor, water etc., which are not included in this estimation, of course, will increase the price of NaOH as well as the supply and demand for chlorine. With price for Cl₂ and NaCl $220 and $60, respectively and electricity cost of $0.09/kWh, the cost of 1 ton NaOH is quite small. However, it must be emphasized that this energy must not be obtained from burning coal, otherwise the CO₂ production would continue to exceed all amounts that we can lock in Na₂COs. It may be possible for several reactors to operate using off-peak power.

[00101] For the reaction:

2 NaOH + C + H₂O = Na₂CO₃ + 2 H₂ [00102] The requirements are 80 kg of NaOH producing 106 kg of Na2CO3 and 4 kg of hydrogen; to the latter we can add the already produced 2 kg of H produced while manufacturing NaOH (sale of chlorine should also be considered). Table 2 shows the material costs. To this we must add the energy costs as well as also consider that this is a zero emission product.

Reaction (3), however, is not useful (in terms of reducing greenhouse gases) for coal- burning power plants even though it is a zero-emission process. For coal-burning power plants, we use the reaction:

[00103]

4 NaOH + CO₂ (or mixture of CO₂ and CO) + C = 2 Na₂CO₃ + 2 H₂ (2)

[00104] The requirements are 160 kg of NaOH producing 212 kg OfNa₂CO₃ and 4 kg of hydrogen; to the latter we can add the already produced 4 kg of H produced while manufacturing NaOH as discussed above. The costs are shown in Table 1 for variously assumed cost of producing the reactant at the plant. To this we must add the energy costs, which will be much less than that for reaction (2) because we will be using hot gases from the power plant. Furthermore, the power plant will be used for generating thermal or electric power.

[00105] We may also consider the use of cheaply available natural gas as follows:

2 NaOH + CH₄ + H₂O = Na₂CO₃ + 4 H₂

[00106] The requirements are 80 kg of NaOH and 16 kg Of CH₄ which produces 106 kg OfNa₂CO₃ and 8 kg of hydrogen; to the latter we can add the already produced 2 kg of H produced while manufacturing NaOH as discussed above. The cost of NaOH is (80x.l5=$12.0), the cost of CH₄ based on ($0.04/kg) is ($0.16) selling price of Na₂CO₃ is $10.6 resulting in $1.86 for 10 kg of hydrogen produced for less than $0.16 per kg. To this we must add the energy costs. A hybrid process (a combination of reactions), which uses hot gases from the power plant, may be possible and energy efficient. Any one reaction or combination of reactions may be employed, adapted to local conditions as appropriate. The cost calculations for the reactions with natural gas are shown in Table 2 and are certainly quite exciting.

[00107] Figure 8 shows plot of calculated costs for carbon sequestration. It is demonstrated that for a range of values for sodium hydroxide, the material costs remain negative i.e. money is actually saved by sequestering carbon gases and producing hydrogen. Note that none of the other costs of manufacturing, such as infra-structure development, energy and labor, are included in the calculations. Finally what if the price structure changes in such a way that we must totally discard sodium carbonate (possibly by burying it in an environmentally safe way)? The material costs would vary from $1.2 to $3.0 per kg of hydrogen. Table 2 shows that for practically every reaction considered, there is a profit if carbon is sequestered. Considering that the hydrogen is produced with zero emissions - and lets us burn coal to generate electric and thermal power, also with zero emissions - this process has enormous beneficial consequences for the world.

Impurities in coal and other exhaust gases

[00108] The invention addresses principally the sequestration of carbon and production of hydrogen. The question of clean air involves minor and trace components of natural fossil- fuels e.g. sulfur, mercury, nitrous oxides etc. The removal of these has been researched very well and can be handled appropriately as needed by adding the necessary reagents to sodium hydroxide.

Tables 2 and 3 show various other models of price variation and the effect on the price of carbon sequestration.

Limitations

[00109] It is to be emphasized that the production of NaOH should be preferably done using electricity from a nuclear or other alternate source (byproducts chlorine and hydrogen in this manufacturing process are sold reducing the production cost of NaOH). If off-peak power is used to advantage, the processes would yield results no matter the source of power. It is possible to use the energy from the same plant but all CO2 emitted will not be sequestered; the advantage of hydrogen produced and used for applications that would otherwise emit CO2 should be considerd. [00110] Reactions (1) to (7) used in this invention or the reaction described by Jones (US 2006/0185985 Al) and other carbonation reactions cannot sequester CO2 effectively if electric energy from coal-burning power plants is to be used for the production of NaOH. It can be easily demonstrated that several tons of CO2 has to be emitted in forming one ton of NaOH if fossil fuel is used. The current market price of NaOH and Na₂COs would permit several coal/natural gas burning power plants to operate with profit but as the products (Na2CO3, and CI2) saturate the market, additional power plants could be retrofitted if NaOH price can be brought down substantially by using alternate energy sources and off-peak power. It is all possible because the raw materials (NaCl and coal) are almost inexhaustible. [00111] An alternative would be to consider only a 10% reduction in CO2 in a power plant 500 megawatt size. In such a situation we will produce about 1 to 1.5 million tons of solid material per year and it will be possible to manage the flow of material through the reactor.

[00112] The chlor-alkali process requires significant energy which must come from some source. If available, the energy can be used from the same power plant, which may amount to 30% of the total plant energy resulting in more CO2 emission than the process can sequester. However, since the energy if not used this way would have resulted in even more CO2 emission. By using this method, we reduce the Cθ2by some percent (depending on the target, see [00108]) and produce hydrogen which will replace the energy from coal in a variety of applications. When hydrogen replaces gasoline in transportation, the overall effect of green-house-gas emission will be substantial.

REFERENCES

1. Probstein, R.F. and Hicks, R.E. Synthetic fuels, Dover, New York, 2006.

2. Gupta, H.; Mahesh, L; 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, OH, 2004.

3. 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, DC, May 15-17, 2001.

4. 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 ofH2 and Sequestration-Ready CO2, Annual Technical Progress Report 2003, DOE Award No. DE-FC26-00FT40974. GE Global Research: Irvine, CA, 2003.

5. "The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs (2004),)"

Carbon Emissions Associated with Current Hydrogen Production: " National

Academy of Engineering (NAE), Board on Energy and Environmental Systems (BEES).

6. Saxena, S. K. Drozd Vadym, Durygin Andriy, Synthesis of metal hydride from water.

Int J. Hydrogen Energy 32 (2007) 2501-2503.

7. Saxena, S.K. (2003) Hydrogen production by chemically reacting species: International J. of Hydrogen Energy ,28,49-53.

8. Ishida, M., Toida, M., Shimizu, T., Takemaka, S., and Otsuka, K. Formation of hydrogen without CO_x from carbon, water, and alkai hydroxide. Ind. Eng. Chem. Res. 2004, 43, 7204-7206.

9. Xu, X., Xiao, Y. and Qiao, C. System design and analysis of a direct hydrogen from coal system with CO2 capture. Energy and Fuels 2007, 1688-1694.

10. Zevenhoven, R. Eloneva, S., and Teir, S. Chemical fixation of CO2 in carbonates: Routes to valuable products and long-term storage. Catalysis Today 115, 2006, 73-79.

11. Lin, S., Harada, M., Suzuki, Y. and Hatano, H. Hydrogen production from coal by separating carbon dioxide during gasification. Fuel 81 (2002) 2079-2085.

[00113] 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.

Claims

WHAT IS CLAIMED IS:

1. A process to sequester carbon from flue gas of a power plant, comprising: reacting sodium hydroxide with an oxide of carbon from the flue gas to form sodium carbonate.

2. The process of claim 1, further comprising wherein the oxide of carbon is carbon monoxide.

3. The process of claim 2, further comprising the step of adding natural gas and water to the sodium hydroxide reaction to produce sodium carbonate.

4. The process of claim 2, further comprising the step of adding water to the sodium hydroxide reaction to produce sodium bicarbonate.

5. The process of claim 1, further comprising wherein the oxide of carbon is carbon dioxide.

6. The process of claim 5, further comprising the step of adding coal to the sodium hydroxide reaction to produce sodium carbonate.

7. The process of claim 5, further comprising the step of adding natural gas and water to the sodium hydroxide reaction to produce sodium carbonate.

8. The process of claim 5, further comprising the step of adding water to the sodium hydroxide reaction to produce sodium bicarbonate.

9. The process of claim 1, further comprising wherein the power plant is a coal- burning power plant.

10. The process of claim 1, further comprising wherein the power plant is a natural gas-burning power plant.

11. The process according to any of the preceding claims, further comprising the step of generating hydrogen from the reaction.

12. The process according to any of the preceding claims, further comprising the steps of: conducting the reaction in a closed system to achieve zero emission of carbon gases, and generating hydrogen from the reaction.

13. The process according any of the preceding claims, further comprising the step of: using a form of energy obtained from the coal-burning plant to conduct said process, wherein said form of energy is selected from hot air, electric energy in off-peak production, or both.

14. The process according to any of the preceding claims, further comprising the steps of: using any gas mixtures exhausting from the power plant; and adjusting the composition of the feed stock (sodium hydroxide) to react with components of gas selected from sulfur dioxide, nitric oxide, or both; and forming removable solids.

15. The process according to any of the preceding claims, further comprising the step of: using one or more catalysts to promote the reaction kinetics.

16. The process according to any of the preceding claims, further comprising wherein the process of carbonation is not a direct conversion of NaOH to Na2CO3 but is a result of a reaction with other solids and gases usually producing hydrogen in important amounts.

17. The process according to any of the preceding claims, further comprising the step of: using an integrated design for the execution of the processes such that the waste-energy provided by the coal burning power plant is used effectively by adhering to energy saving schedules which comprise off-peak utilization.

18. The process according to any of the preceding claims, further comprising the step of: producing the sodium hydroxide at the site using energy selected from the power plant itself, nuclear, solar, wind, hydro-electric, alternate energy sources other than coal or any other fossil fuel, or combinations thereof.

19. The process according to any of the preceding claims, further comprising the step of: recovering additional cost by selling reaction products selected from sodium carbonate, sodium bicarbonate, hydrogen, chlorine, or combinations thereof, at market prices to recover any additional costs that are incurred due to the use of sodium hydroxide.

20. A system for sequestering carbon from flue gas of a power plant, comprising:

(a) a burner for combusting a mixture of oxygen and fuel and generating flue gas and products of combustion;

(b) a stack in communication with said burner for collection and dispersion of the flue gas and the products of combustion; and

(c) a reactor for reacting sodium hydroxide with an oxide of carbon from the flue gas to form sodium carbonate.

21. The reactor of claim 20, further comprising wherein the oxide of carbon is carbon monoxide.

22. The reactor of claim 21, further comprising means for adding natural gas and water to the sodium hydroxide reaction to produce sodium carbonate.

23. The reactor of claim 21, further comprising means for adding water to the sodium hydroxide reaction to produce sodium bicarbonate.

24. The reactor of claim 20, further comprising wherein the oxide of carbon is carbon dioxide.

25. The reactor of claim 24, further comprising means for adding coal to the sodium hydroxide reaction to produce sodium carbonate.

26. The reactor of claim 24, further comprising means for adding natural gas and water to the sodium hydroxide reaction to produce sodium carbonate.

27. The reactor of claim 24, further comprising means for adding water to the sodium hydroxide reaction to produce sodium bicarbonate.

28. The reactor of claim 20, further comprising wherein the power plant is a coal- burning power plant.

29. The reactor of claim 20, further comprising wherein the power plant is a natural gas-burning power plant.

30. The reactor according to any of the preceding claims, further comprising means for generating hydrogen from the reaction.

31. The reactor according to any of the preceding claims, further comprising means for conducting the reaction in a closed system to achieve zero emission of carbon gases, and means for generating hydrogen from the reaction.

32. The reactor according any of the preceding claims, further comprising means for using a form of energy obtained from the coal-burning plant to conduct said process, wherein said form of energy is selected from hot air, electric energy in off-peak production, or both.

33. The reactor according to any of the preceding claims, further comprising means for using any gas mixtures exhausting from the power plant; and means for adjusting the composition of the feed stock (sodium hydroxide) to react with components of gas selected from sulfur dioxide, nitric oxide, or both; and forming removable solids.

34. The reactor according to any of the preceding claims, further comprising means for using one or more catalysts to promote the reaction kinetics.

35. The reactor according to any of the preceding claims, further comprising wherein the reactor of carbonation is not a direct conversion of NaOH to Na₂COs but is a result of a reaction with other solids and gases which produce hydrogen in substantial amounts.

36. The reactor according to any of the preceding claims, further comprising means for using an integrated design for the execution of the processes such that the waste-energy provided by the coal burning power plant is used effectively by adhering to energy saving schedules which comprise off-peak utilization.

37. The reactor according to any of the preceding claims, further comprising means for producing the sodium hydroxide at the site using energy selected from the plant itself, nuclear, solar, wind, hydro-electric, alternate energy sources other than coal or any other fossil fuel, or combinations thereof.

38. The reactor according to any of the preceding claims, further comprising means for recovering additional cost by selling reaction products selected from sodium carbonate, sodium bicarbonate, hydrogen, chlorine, or combinations thereof, at market prices to recover any additional costs that are incurred due to the use of sodium hydroxide.

39. The reactor according to any of the preceding claims, wherein the reactor is a retrofit module for an existing or a new power plant.

40. The process of synthesizing a hydride such as magnesium hydride linked to the hydrogen being produced in the reactor according to any of the previous claims.