WO2014120035A1

WO2014120035A1 - Method for using carbon-containing fuel in system containing high-temperature fuel cell

Info

Publication number: WO2014120035A1
Application number: PCT/RU2013/000074
Authority: WO
Inventors: Александр Анатольевич СТРОГАНОВ; Марина Юрьевна ЗУБКОВА
Original assignee: Stroganov Alexander Anatolyevich; Zubkova Marina Yur Evna
Priority date: 2013-01-31
Filing date: 2013-01-31
Publication date: 2014-08-07

Abstract

The invention relates to generating electricity and producing H₂ by means of using carbon-containing fuel in fuel cells. The goal of the present invention is to increase the efficiency of using carbon-containing fuel in a system containing a high-temperature fuel cell, and also to increase the reliability and extend the service life of the high-temperature fuel cell. This goal is achieved by means of the proposed method for using carbon-containing fuel in a system containing a high-temperature fuel cell, comprising inputting carbon-containing fuel and a converting reagent into a converter, carrying out an endothermic reaction of the carbon-containing fuel and the converting reagent within the converter, producing a mixture of CO and H₂ in the converter, feeding a portion of the mixture (of CO and H₂) and an oxidant to the anode and cathode, respectively, of the high-temperature fuel cell, which is a part of a high-temperature oxidizing system, oxidizing the part of the mixture fed into the high-temperature oxidizing system to produce electrical and thermal energy, transferring the thermal energy produced in the high-temperature oxidizing system to the converter, maintaining the converter temperature within set limits, chosen to be in the range of 800-1300K, wherein a portion of the H₂ from the mixture of CO and H₂ generated in the converter is removed and the quantity of said H₂ which is fed into the high-temperature oxidizing system is reduced in such a way so that the amount of heat emitted during the process of oxidizing the CO and H₂ in the high-temperature oxidizing system is at least sufficient to maintain the set temperature in the converter, and the H₂ released from a separation system is fed into a hydrogen utilization system.

Description

A method of using carbon-containing fuel in a system comprising a high temperature fuel cell.

The invention relates to the production of electrical energy and the production of Ng using carbon-containing fuel in fuel cells.

The prior art. It is known that the production of electricity in a fuel cell using hydrocarbons is possible with internal conversion (reforming) of the fuel, which can occur in a high-temperature fuel cell, for example, in a solid oxide or molten carbonate, operating in the temperature range from 800 to 1300K (RU 2199172, US 6.492. 050). The conversion of hydrocarbons into synthesis gas (a mixture of CO and H ₂ ) at the indicated temperature is an endothermic process, and subsequent anodic reactions of hydrogen oxidation and carbon monoxide are exothermic with the release of a large amount of heat, even the partial use of which significantly affects the overall efficiency of the system.

In some cases, to use the generated heat, hybrid units of high-temperature fuel cells with heat engines are created (US 5.541.014, US 5.811.201, US 20040197612, US 7.097.925, US 20020142208), which improves the balance on the use of heat, but only in part exergy with losses characteristic of any heat engine.

Unlike a heat engine, an endothermic reaction allows you to utilize the total heat, and not just its exergic part. Known solutions (US 7.285.350, US 6.485.852, US) that use the heat of an exothermic oxidation reaction to maintain an endothermic conversion reaction directly in the anode region of a high temperature fuel cell (internal reforming). However, they have significant disadvantages: one . uneven thermal regime of the anode, due to cooling of the zone of the input flows of the endothermic reaction;

2. incomplete use of the generated heat (excess heat of the exothermic reaction of fuel oxidation in a high-temperature fuel cell occurs in comparison with the needs of converter processes for converting fuel);

3. The reaction of CO oxidation at the anode is hindered by the competing oxidation of Hg at the same electrode;

4. carbon deposition on nickel-containing ceramics that catalyze fuel reforming processes.

Preliminary (external) fuel reforming expands the possibilities of conversion by the type of converting reagent (this can be steam or carbon dioxide conversion, partial oxidation of the fuel and their various combinations) and by the types of “burned” fuel (US 5.858.314, US 6.485.852, US 6.492 , 0507, US 7.008.71 1, US 5.079.105, US 7.169.495, US 5.932.181). In this case, the use of coal, requiring mandatory preliminary gasification, becomes very promising and justified. Heat from the fuel cell is transferred to an external converter using both direct heat transfer (US 5.858.314, US 6.485.852, US 6.492.050, US 7.008.71 1, US 5.079.105), and using a coolant, which also allows provide and heating the input streams of the converter (US 20080057359, US 7.169.495).

The additional oxidation of carbon monoxide in a shear reactor allows the production of additional hydrogen (RU 2343109, US 6.589.303, US 7.097.925, US 5.932.181). This reaction is exothermic, but is carried out, as a rule, at lower temperatures (~ 500K), which reduces the possibility of utilization of the heat generated during this

Hydrogen obtained from the conversion of carbon-containing fuel can be used in a low-temperature fuel cell to generate electricity or stored for storage (US 6.623.880, US 20050037245). To do this, CO and H ₂ are separated into separate streams, while under high temperature conditions, shear adsorption under pressure is used (US 7.097.925, US 20040197612, US 20020142208, US 7.087.331) or hydrogen is isolated using a palladium membrane (RU 2394752) . When FeOx, Fe (US 20050037245) is used as a converting reagent, highly pure hydrogen is obtained.

Due to the incomplete oxidation of CO and Hg in a high-temperature fuel cell, in some cases, a fuel burner is included in the fuel cell system and the heat of this stage is used to heat the converter (US 7.169.495).

It is known to use the generated heat for heating fuel and converting reagents to the required temperature with compensation for the costs of the endothermic converter reaction (US 5.079.105, RU 2302287, US 7.008.71 1). A structural solution for organizing heat transfer involving several options for the interaction of a desulfatizer, a converter and an assembly of high-temperature fuel cells, considered by the authors of patent US 7.008.71 1, allows you to more fully use the thermal resource of exothermic processes of high-temperature fuel cells.

The closest analogue of the present invention is US 7.008.71 1, where it is proposed to use carbon-containing fuel (liquid and gaseous, including natural gas methane CH ₄ ) to generate electricity. The fuel enters the desulfatizer, then to the converter, where as a result of endothermic interaction with the converting reagent (water vapor, oxygen, carbon dioxide), synthesis gas (a mixture of CO and Ng) is obtained. Converted fuel (synthesis gas) is fed to the anode of a high-temperature fuel cell (e.g., solid oxide), i.e., to a high-temperature oxidizing system, where an exothermic reaction with the formation of carbon monoxide and water vapor occurs under the influence of atmospheric oxygen. The process of reforming and oxidizing reforming products in a high-temperature fuel cell is arranged in such a way that heat is regenerated to the converter through heat transfer; The process of recycling water vapor and carbon dioxide at the outlet of the anode for reforming was also organized. However, in this case as well, the CO oxidation reaction at the anode is hindered by the competing Hg oxidation reaction on the same electrode, and the generated heat is not fully used, since there is excess heat from the exothermic fuel oxidation reaction in the high-temperature fuel cell compared to the needs of converter fuel conversion processes.

SUMMARY OF THE INVENTION

The objective of the present invention is to increase the efficiency of using carbon-containing fuel in a system containing a high-temperature fuel cell, increasing the reliability and service life of a high-temperature fuel cell.

The problem is solved by the proposed method of using carbon-containing fuel in a system containing a high-temperature fuel cell, which includes placing carbon-containing fuel and a converting reagent in the converter, carrying out an endothermic reaction of carbon-containing fuel with a converting reagent in the converter, obtaining a mixture of CO and H ₂ in the converter, supplying part of the mixture ( СО and Н ₂ ) and an oxidizing agent, respectively, to the anode and cathode of a high-temperature fuel cell, which is part of a high-temperature oxidation system, oxidation of the fed portion of the mixture in a high-temperature oxidation system with the generation of electric and thermal energy, transfer of heat energy generated in the high-temperature oxidation system to the converter, maintaining the temperature in the converter within specified limits, selected in the range 800 - 1300K, and from this mixture and Ng formed in the converter, remove part of H ₂ and reduce its amount supplied to the high-temperature oxidation system so that the amount of heat released In the high-temperature oxidizing system, the reactions of CO and H ₂ oxidation were at least sufficient to maintain the set temperature in the converter, and H ₂ released from the separation system was fed to the hydrogen recovery system.

Coal or methane is placed in the converter as a carbon-containing fuel, water is placed in the converter as a converting reagent and the temperature is maintained within specified limits, selected in the range from 800 to 1000K. As one of the options in the converter, a combination of water with iron oxides is used as a converting reagent for hydrocarbons and the temperature is maintained within specified limits. selected in the range from 900 to 1100K. As a high-temperature fuel cell, a solid oxide or melt-carbonate fuel cell or a combination thereof is used. A portion of H _{2 is} extracted from the mixture of CO and H ₂ formed in the converter and its quantity supplied to the high-temperature oxidizing system is reduced to a level at which the heat released in the high-temperature oxidizing system during the course of the reactions of CO oxidation and additional H ₂ is compensated the heat spent on the endothermic reaction in the converter and heat loss. In a high temperature oxidizing system, part of the mixture is oxidized. The electric and thermal energy obtained in the high-temperature oxidation system is generated and transferred to the converter. Heat from the hot gases leaving the high-temperature oxidizing system is transferred to the oxidizing stream entering the high-temperature oxidizing system, as well as to the carbon-containing fuel and the converting reagent entering the converter. In the high-temperature oxidizing system, CO is oxidized, and the amount of Hg supplied to the high-temperature fuel cell is chosen so that the amount of heat released in the high-temperature oxidizing system during the oxidation of CO and H ₂ is at least sufficient to maintain a given temperature in the converter. The converter maintains the temperature within the selected limits T _! ^pre and t ₂ ^pre-. T ₁ ^{prad is} selected by the condition: 800K <T1 ^prvd <T ₂ ^pre . T ₂ ^before choose by the condition: T- | ^Pre <T ₂ ^pre <1100K. Thus, the converter operates in the following temperature conditions: 800 <Τι ^πρθΑ <T ₂ ^before <1100K.

With a decrease in temperature in the converter below the lower temperature limit T- | ^pre \ selected in the range 800 - 1100K, the amount of hydrogen sent to the high-temperature fuel cell is increased, and when the temperature in the converter rises above the second temperature limit T ₂ ^pre , selected with a margin between Τι ^πρβΑ and 1100K, the amount of hydrogen sent to the high-temperature fuel cell element, reduce. The amount of H ₂ sent to the high temperature oxidizing system is changed in the separation system using a selective membrane (passing H ₂ and not passing CO) or adsorption of shear under pressure (Pressure Swing Absorbtion - PSA), by changing the degree of extraction of H ₂ from the mixture. The degree of H ₂ recovery is changed by changing the pressure drop across the membrane or changing the cycle frequency or pressure drop in the PSA cycle.

In another implementation of the method, the degree of H ₂ extraction in the separation system is kept stably redundant, and an additional part of H ₂ recovered in the separation system is sent to the high temperature oxidation system, and the total amount of H ₂ directed to the high temperature oxidation system is changed by changing said additional part.

Thus, the total amount of hydrogen supplied to the high temperature fuel cell is reduced to a level at least sufficient so that the heat generated in the high temperature oxidation system (including electrochemical oxidation in the high temperature fuel cell) during oxidation of CO and H ₂ compensates for the heat, spent on the endothermic reaction in the converter, heating the input streams and heat loss. To maximize the efficiency of using carbon-containing fuel, the hydrogen released from the separation system is fed into a low-temperature proton-exchange fuel cell included in the hydrogen recovery system.

The essence of the invention is illustrated by drawings, which show:

Figure 1 is a General schematic diagram of a method for processing carbon-containing fuel.

Figure 2-diagram of a method for processing carbon-containing fuel, where a low-temperature fuel cell is used as an H ₂ utilization system, CO oxidation is carried out in a shear reactor.

Fig.Z is a diagram of a method for processing carbon-containing fuel, where low-temperature is used as a system for utilizing H ₂ fuel cell, CO afterburning is performed in the afterburner included in the high-temperature oxidation system.

4 is a diagram of a counterflow heat exchanger.

Figure 5. graphs of the dependences of the total efficiency of the entire system on the efficiency of a real high-temperature fuel cell for various values of the efficiency of a low-temperature fuel cell (from 50 to 70%) for methane when implementing the fuel processing scheme corresponding to FIG. 2.

6 is a graph of the dependences of the total efficiency of the entire system on the efficiency of a real high-temperature fuel cell for various values of the efficiency of a low-temperature fuel cell (from 50 to 70%) for coal when implementing the fuel processing scheme corresponding to figure 2.

Fig.7 is a graph of the dependences of the total efficiency of the entire system on the efficiency of a real high-temperature fuel cell for various values of the efficiency of a low-temperature fuel cell (from 50 to 70%) for methane when implementing the fuel processing scheme corresponding to Fig.Z.

Fig. 8 is a graph of the dependences of the total efficiency of the entire system on the efficiency of a real high-temperature fuel cell for various values of the efficiency of a low-temperature fuel cell (from 50 to 70%) for coal when implementing a fuel processing scheme corresponding to Fig.Z. As examples of the carbon-containing fuel used 1, two boundary variants of the ratio of hydrogen to carbon in the compound formula are considered: coal (C _gr .) (Hydrogen-free compound) and methane (CH ₄ ) (compound containing the maximum amount of hydrogen per carbon atom) , all other types of hydrocarbons can be considered intermediate.

As a converting reagent 2, water (Н ₂ О) is used for coal, water and carbon dioxide (СОg) for hydrocarbons. The following are examples of calculations using 2 Н ₂ О as a conversion reagent according to the reaction for methane: СН ₄ + Н ₂ 0 = СО + ЗН ₂ (1); by reaction for coal: CGR + H ₂ 0 = CO + H ₂ (2).

As a converting reagent 2, it is also possible to use a combination of water with iron oxides. In this case, it is advisable to alternate the reduction of iron from oxides in the interaction with hydrocarbons (at T = 900 - 1100 K), leading to the formation of a gaseous mixture of CO and H ₂ , with the oxidation of iron to oxides in the interaction with water vapor, leading to the formation of H ₂ , already separated from CO.

The implementation of the fuel processing method according to the schemes depicted in FIG. 1, FIG. 2, FIG. 3 is carried out as follows: carbon-containing fuel 1 and converting reagent 2 enter converter 3, where at T = 800-1000K as a result of endothermic reactions (1 ) and (2) synthesis gas is formed (gaseous mixture (CO + H ₂ ) 4). From the converter 3, the synthesis gas 4 enters the separation system 5. In the separation system 5, a part of H ₂ 6 (released H ₂ ) is extracted from the incoming synthesis gas 4 by dividing the incoming synthesis gas 4 stream into at least two output streams: depleted gas mixture (CO and H ₂ ) 7, the content of H ₂ in which is reduced to a predetermined level, and the stream of H ₂ 6 released from the original synthesis gas stream 4 and entering the hydrogen recovery system 8. The preferred content of H ₂ in stream 6 not less than 99%, determined by the quality of used separation system.

The lean gas mixture is directed to a high-temperature oxidizing system (BOC) 9, which includes at least one high-temperature fuel cell (VTTE) 10. In a high-temperature oxidizing system 9, including a high-temperature fuel cell 10, CO and H _{2 are} oxidized at T > T _CO inverter. The hydrogen depleted gas stream 7 is directed to the anode 1 1 of the high-temperature fuel cell 10. An oxygen-containing oxidizing gas mixture (for example, air) 18 is supplied to the cathode 12 of the high-temperature fuel cell 18. At the anode 1 1 of the high-temperature fuel cell 10, electrochemical oxidation of CO occurs by reaction : CO + 1 / 2O ₂ -2e ^ CO ₂ + 5Q + 5Q ^' (3);

and oxidation of H ₂ by reaction:

Н ₂ + 1/20 ₂ -2е— Н ₂ 0 + 6Q + 5Q ^' (4)

with the receipt of electrical energy and heat - (5Q) 15 and (5Q ^' ) 16.

At the exit from the high-temperature fuel cell 10, Н ₂ 0 13 and С0 ₂ 14 are formed as the products of electrode reactions, which can be used as a converting reagent 2 of steam and carbon dioxide conversion.

As a high-temperature fuel cell with anionic conductivity, it is proposed to use, for example, a solid oxide or melt-carbonate fuel cell, or a combination thereof.

The heat generated in this case 15 is sent to the converter 3. The amount of heat generated in the high-temperature oxidation system 9 during the course of the oxidation of CO and the specified amount of H ₂ should be at least sufficient to maintain the desired temperature in the converter.

Changing the amount of H ₂ sent to the high-temperature oxidizing system 9 can be done by changing the degree of extraction of H ₂ from the synthesis gas 4 in the separation system 5. Preferably, in the separation system 5, a fixed degree of extraction of H ₂ from the synthesis gas 4 is maintained. ₂ , sent to the high-temperature oxidation system 9, is realized due to the additional amount of H ₂ from the extracted part 6, which is sent to the high-temperature fuel cell 10 or a separate stream m 17, or by attaching to stream 7.

The amount of hydrogen sent to the high-temperature fuel cell 10 should be at least sufficient to maintain a predetermined temperature in the converter due to the heat generated in the high-temperature oxidation system during CO oxidation reactions and the indicated amount of H ₂ . To increase the temperature of the Converter increase the amount of heat 15 supplied from high-temperature oxidizing system 9 to the converter 3 by increasing the amount of hydrogen supplied to the high-temperature fuel cell 10. To lower the temperature of the converter 3, respectively, reduce the amount of heat 15 supplied from the high-temperature oxidizing system 9 to the converter 3 by reducing the amount of hydrogen 17 supplied to the high-temperature fuel cell 10. Thus, at low heat losses, the heat 15 generated in the high-temperature oxidizing system 9 is practically completely absorbed by endothermic reaction (1) (or (2)) in the converter 3. The high temperature fuel cell 10 utilizes much of the CO and hydrogen with a selected amount of thermodynamic efficiency close to 100%.

The fraction of Ng sent to the high-temperature fuel cell 10 after the separation system 5 is further characterized by the parameter γ — the number of moles of hydrogen (from 1 mole of carbon-containing fuel produced in the synthesis gas by reactions (1) and (2)) sent to the high-temperature fuel cell 10 The value of γ is determined by the value of the efficiency (efficiency) of the high temperature fuel cell. The higher the efficiency of the high-temperature fuel cell 10, the less heat is generated during the oxidation of CO and Hg, the greater is the set γ to maintain the temperature in the converter. The increase in heat loss to the external environment 16 (through thermal insulation), as well as to the heating of the input streams 16 of the carbon-containing fuel 1, the converting reagent 2 and the oxidizing mixture 18 leads to the need to increase γ.

Heat is transferred from the high temperature fuel cell 10 to the converter 3 by heat and mass transfer, heat transfer, radiation, or combinations thereof.

Part of the heat carried away by the output streams (H ₂ O 13, COg 14) is regenerated, that is, used in the counterflow heat exchanger 19 to heat the input streams (Fig. 4). Table 1 for methane and table 2 for coal (based on one mole of carbon-containing fuel) for example presents the dependences of y on the efficiency of the high-temperature fuel cell for the case of complete oxidation of CO and H ₂ in the high-temperature fuel cell 10 and without taking into account losses during heat recovery to reimburse the necessary amount of heat to heat the input streams.

Table 1 .

Table 2.

Coal Efficiency

VTE, (y) The amount of hydrogen supplied to the released hydrogen 6 high-temperature fuel cell

%

10, including:

On To reimburse the costs, mol% of the content in the endothermic heating of the input synthesis gas

reaction in flows, mol /% of

converter, moles of content in synthesis gas

50 Not required 0.224 /22.4 0.776 77.6 55 0.075 0.264 /26.4 0.661 66.1

60 0.227 0.243 /24.3 0.53 53.0

Extraction of H ₂ from the gas mixture is carried out using selective separation membranes or shear absorption under pressure, which typically requires cooling the mixture before the separation process. In this case, it is preferable to carry out heat recovery from the cooled mixture stream to the heated stream of the lean mixture of CO and H ₂ , as well as to the heated oxidizer stream directed to the high-temperature fuel cell 10.

To further increase the efficiency of using carbon-containing fuel 1, as well as to increase the specific power of the system, the oxidation state of CO in the high-temperature fuel cell 10 is preferably maintained in the range of 70 - 90%. Typically, the oxidation of H ₂ in the high temperature fuel cell 10 is maintained at a higher level (~ 99%). Unoxidized in a high temperature fuel cell, CO 20 is sent for further oxidation.

The invention provides two options for CO oxidation, namely, CO oxidation in a shear reactor 21, and CO afterburning in a high temperature oxidizing system 9, namely in an afterburner 22, which is part of a high temperature oxidizing system.

In the embodiment of the invention of FIG. 2 and FIG. 3, it is proposed to use a low-temperature fuel cell (NTTE) 23 as a system for utilizing H ₂ 8. In a low-temperature fuel cell 23 at a temperature of 300 K under the influence of an oxidizing agent (oxygen O ₂ ) 24, a hydrogen oxidation reaction proceeds :

(H ₂ +1/2 O ₂ = H ₂ O) (5),

as a result of which electrical energy is obtained and H ₂ O 25 is formed.

In accordance with the scheme shown in figure 2, unoxidized CO 20 from the high-temperature fuel cell 10 enters the reactor - shear 21, where at T = 500K by the action of water vapor 26 the reaction of oxidation of CO 20 proceeds:

СО + Н ₂ О = СО ₂ + Н ₂ + 5Q ^" (6)

with the formation of CO ₂ 27 and additional H ₂ 28, which enters the low-temperature fuel cell 23. Reaction (6) is exothermic, and its heat (6Q ^" ) 29 is preferably sent to heat the input streams.

Figures 5 and 6 show the dependences of the total efficiency (efficiency) of the entire system (η _Σ ) on the efficiency of a real high-temperature fuel cell (pvtte) for methane and coal, respectively, for different values of the efficiency of a low-temperature fuel cell (Pnte) ( from 50 to 70%) when implementing the fuel processing scheme corresponding to figure 2. It can be seen that with an increase in the efficiency of a high-temperature fuel cell and a low-temperature fuel cell, the total efficiency increases for both methane and coal.

Table 3 for methane presents data on the total efficiency of the entire system (r \), on the useful work of the entire system (change in Gibbs energy) (AGnon), on the amount of hydrogen 17 supplied to the high-temperature fuel cell to offset (compensate) the costs of the endothermic reaction ( 1) in the converter 3 and to make up for the costs of heating the input streams, at different real values of the efficiency of the high-temperature fuel cell (pvtte) and low-temperature fuel cell (pnte) when implementing the fuel processing scheme corresponding to figure 2 . For example, when r) _The TTE = 50% requires a hydrogen feed in an amount of 0.909 mol to a high temperature fuel cell for the converting maturity endothermic reaction. With the growth of Pvtte, the amount of hydrogen supplied to the high-temperature fuel cell to offset the costs of the endothermic reaction in the converter increases. Additional hydrogen to make up the cost of the required amount of heat for heating the input streams in a high-temperature fuel cell is not required for all considered Pvtte values. With the increase in Pnte when it burns the remaining 2.291 moles of Н ₂ (taking into account the 0.2 moles of Н _{2 formed} in the shift reactor), the contribution useful work (AG _n <^) at this stage increases, and the installation increases from 62.2% to 77.0%. A similar trend is observed at d) _In tte = 55 and at Pvtte = 60.

Table 3

Table 4 for coal presents data on the total efficiency of the entire system (η _Σ ), on the useful work of the entire system (AG _non ), the amount of hydrogen 17 supplied to the high-temperature fuel cell 10 to pay off the costs of the endothermic reaction (2) in converter 3 and for replenishment of the cost of heating the input streams at various real the efficiency values of the high-temperature fuel cell (pvtte) and the low-temperature fuel cell (pvtte) when implementing the fuel processing scheme corresponding to figure 2. For example, at Pvtte = 50%, hydrogen is required to supply a high-temperature fuel cell to extinguish the endothermic converter reaction in an amount of 0.182 moles. To compensate for the required amount of heat for heating the input streams in a high-temperature fuel cell, it is necessary to additionally supply 0.222 moles of hydrogen, the thermal component of which extinguishes the heating of cold input streams, creating a positive heat balance = 0.155 kJ. With an increase in d) WTE, the amount of hydrogen supplied to the high-temperature fuel cell to pay off the costs of the endothermic reaction in the converter increases, and, accordingly, the amount of hydrogen supplied to the high-temperature fuel cell to meet the costs of heating the input flows decreases. With the growth of PNTE, when the remaining 0.796 moles of Ng are burned in it (taking into account the 0.2 moles of Ng formed in the shear reactor), the contribution of useful work (AG _n0 n) at this stage increases and the installation increases from 70.1% to 81.6%. A similar trend is observed at pvtte = 55 and at pvtte = 60.

Table 4

COAL

The amount of hydrogen supplied to the high temperature fuel

ΠΣ · (%) DSpole, kJ

item 10, including:

On to

P nte, (%) endothermic replenishment reaction in the cost of heating the converter, moles of input flows, moles

Pvtte = 50

50 70.1 -277.03

60 75.9 -299.78 0.182

65 78.7 -31 1.16 0.222

70 81.6 -322.54 Pvtte - 55

50 74.1 -292.82

60 79.3 -313.24 0.304

65 81.9 -323.45 0.182

70 84.5 -333.66

Pvtte = 60

50 78.7 -310.87

60 82.9 -327.77 0.456

65 85.0 -336.22 0.153

70 87.2 -344.67

In accordance with the fuel processing scheme shown in FIG. 3, an afterburner 22 is used to further oxidize CO 20. CO 20 under-oxidized in the high-temperature fuel cell 10 enters the afterburner 22, where in the atmosphere O ₂ 30 at T> T _{KOH of the} converter ( 900 - ^ - 1200K) combustion reaction of CO proceeds:

СО + 1 / 2О ₂ = СО ₂ + 5Q ^" (7).

At the output, CO ₂ 31 is formed, the heat of the exothermic reaction (7) (5Q ^'" ) 32 is sent to the converter 3 to compensate for the costs of the endothermic reaction (1) (or (2)) in the converter 3 and the cost of the required amount of heat to heat the input fuel flows and reagents The calculation presented in Tables 5 and 6 was made under the assumption of ideal thermal insulation of the high-temperature part and ideal heat recovery of the outgoing gas streams.

Figures 7 and 8 show graphs of the total efficiency of the entire system (η ^) versus the efficiency of a real high-temperature fuel cell (Pvtte) for methane and coal, respectively, for different efficiency values of a low-temperature fuel cell (ptte) (from 50% to 70%) when implementing the fuel processing scheme corresponding to FIG. It can be seen that with an increase in the efficiency of a high-temperature fuel cell, the total efficiency increases.

Table 5 for methane presents data on the total efficiency of the entire system (Π, Σ), on the useful work of the entire system (ΔΘ _ΠΟ η), on the number of hydrogen 17 supplied to the high-temperature fuel cell 10 to pay off the costs of the endothermic reaction (1) in the converter 3 and to make up for the costs of heating the input streams, at different real values of the efficiency of the high-temperature fuel cell (Pvtte) and low-temperature fuel cell (Pntte) during implementation fuel processing circuitry corresponding to FIG. For example, at Pvtte = 50%, N ₂ is required to be supplied to a high-temperature fuel cell to extinguish the endothermic converter reaction in an amount of 0.452 moles. To replenish the cost of the required amount of heat for heating the input streams into the high-temperature fuel cell, it is necessary to additionally supply Ng in the amount of 0.056 moles, the heat component of which extinguishes the heating of cold inlet streams, creating a positive heat balance = 0.03 kJ. With the growth of Pvtte, the amount of hydrogen supplied to the high-temperature fuel cell to pay off the costs of the endothermic reaction in the converter increases, and, accordingly, the amount of hydrogen supplied to the high-temperature fuel cell to compensate for the costs of heating the input flows decreases, and at r | not required. With the growth of PNTE during the burning of the remaining 2.492 moles of Н _{2 in it, the} contribution of useful work at this stage increases, and η _{Σ of the} installation increases from 59.9% to 76.0%. A similar tendency is observed at n, wtwe = 55 and at T | wtte = 60.

Table 5

65 72.0 -639.13 0.452

70 76.0 -674.74

Pvtte - 55

50 61.8 -549.16

60 69.4 -617.07 0.02

0.604

65 73.2 -651.03

70 77.1 -684.99

Pvtte = 60

50 64.0 -569.20

60 71.1 -632.27 Not required

0.793

65 74.6 -663.80

70 78.2 -695.34

Table 6 for coal presents data on the total efficiency of the entire system (g) ^), on the useful work of the entire system (DS _ON l), on the amount of hydrogen 17 supplied to the high-temperature fuel cell 10 to pay off the costs of the endothermic reaction (2) in the converter 3 and to make up for the costs of heating the input streams, at various real values of the efficiency of the high-temperature fuel cell (pvtte) and low-temperature fuel cell (pvtte) when implementing the fuel processing scheme corresponding to FIG. For all the considered Pvtte values, hydrogen supply to the high-temperature fuel cell is not required to extinguish the endothermic converter reaction (taking into account the use of heat from the afterburner to the converter reaction 32), and the excess heat from the combustion of CO in the high-temperature fuel cell is used to heat cold inlet streams. However, for example, at Pvtte = 50%, in order to reimburse the required amount of heat for heating the input streams in the high-temperature fuel cell, it is necessary to additionally supply Н ₂ in the amount of 0.053 mol, the heat component of which extinguishes the heating of cold input streams, creating a positive heat balance = 0.1 19 kJ. With increasing Pvtte, the amount of hydrogen supplied to the high-temperature fuel cell to make up for the heating costs input streams increasing. With the growth of PNTE, when the remaining 0.947 moles are burned in it, the contribution of useful work at this stage increases, and the η of the installation increases from 64.5% to 78.85%. A similar trend is observed at Pvtte = 55 and at Pvtte = 60.

Table 6

A comparison of the above implementations of the method shows that the use of an afterburner simplifies the technical design (oxidation of CO in a high temperature fuel cell 10 and additional oxidation of CO 20 in an afterburner 22 are carried out in the same temperature regime in a single oxidizing system - a high temperature oxidizing system 9), Using a shear reactor and carrying out the CO 20 oxidation process to produce additional hydrogen increases the efficiency of the proposed method, which, with any method for further utilization of the released H _2, leads to an increase in the total efficiency of using carbon-containing fuel (for example, the total electrical efficiency in the utilization of the released H ₂ in low-temperature fuel element).

The proposed solutions increase the fuel efficiency both in the storage mode of H ₂ and in the mode of its use in a low-temperature fuel cell. In the latter case, the total electrical efficiency of the tandem installation, including a fuel converter, a separation system, a high-temperature oxidizing system, a fuel afterburning system, and a hydrogen recovery system, is higher than for each of the fuel cells separately.

The proposed solution, based on preliminary conversion outside the high-temperature fuel cell, eliminates the cooling of the input region of the high-temperature fuel cell by an intense endothermic reaction, which is one of the most important reasons for the accelerated degradation of a high-temperature fuel cell with direct fuel supply.

The proposed methods for using fuel provide a more stable mode of operation of a high-temperature fuel cell, remove temperature gradients, and also eliminates the deposition of coal on the electrodes, which also increases the reliability and service life of a high-temperature fuel cell.

Claims

Claim

1. The method of using carbon-containing fuel in a system containing a high-temperature fuel cell, comprising placing carbon-containing fuel and a converting reagent in the converter, carrying out an endothermic reaction of carbon-containing fuel with a converting reagent in the converter, obtaining a mixture of CO and H ₂ in the converter, supplying part of the mixture (CO and Н ₂ ) and an oxidizing agent, respectively, to the anode and cathode of a high-temperature fuel cell, which is part of a high-temperature oxidizing system, oxidation of one part of the mixture in a high-temperature oxidizing system with the generation of electric and thermal energy, transferring the heat generated in the high-temperature oxidizing system to the converter, maintaining the temperature in the converter within specified limits, selected in the range 800 - 1300K, characterized in that from the specified mixture of CO and H ₂ formed in the converter, part of Н _{2 is} extracted and its quantity supplied to the high-temperature oxidizing system is reduced so that the amount of heat released in the high-temperature When the oxidation reactions of CO and H ₂ were used, the analytical system was at least sufficient to maintain the set temperature in the converter, and the H ₂ released from the separation system was fed to the hydrogen recovery system.

2. The method according to paragraph 1, characterized in that coal or methane is placed in the converter as carbon-containing fuel.

3. The method according to claim 1, characterized in that water is placed in the converter as a converting reagent and the temperature is maintained within predetermined limits, selected in the range from 800 to 1000K.

4. The method according to paragraph 1, characterized in that a combination of water with iron oxides is placed as a converting reagent in the converter and the temperature is maintained within predetermined limits, selected in the range from 900 to 1100K.

5. The method according to paragraph 1, characterized in that as a high-temperature fuel cell, a solid oxide or melt-carbonate fuel cell, or a combination thereof is used.

6. The method according to claim 1, characterized in that the heat from the hot gases leaving the high-temperature oxidizing system is transferred to the oxidizing stream entering the high-temperature oxidizing system, as well as to the carbon-containing fuel entering the converter and the converting reagent.

7. The method according to paragraph 1, characterized in that when the temperature in the converter decreases below the lower temperature limit Ti ^npefl selected in the range of ^{800-1100 K} , the amount of hydrogen sent to the high-temperature fuel cell increases, and when the temperature in the converter rises above the second temperature limit T ₂ ^pre selected between Ti ^npefl and 1 100K, the amount of hydrogen sent to the high temperature fuel cell is reduced.

8. The method according to paragraph 7, characterized in that the amount of H ₂ sent to the high-temperature oxidation system is changed by changing the degree of extraction of H ₂ from the mixture.

9. The method according to paragraph 8, characterized in that H _{2 is} removed from the mixture using a selective membrane (passing H ₂ and not passing

СО), and the degree of Н ₂ extraction is changed, changing the pressure drop across the membrane.

10. The method according to paragraph 8, characterized in that H _{2 is} removed from the mixture using shear adsorption under pressure, and the degree of H ₂ extraction is changed by changing the cycle frequency or pressure drop in the shear adsorption cycle under pressure.

1 1. The method according to claim 1, characterized in that an additional part of H ₂ recovered in the separation system is sent to the high-temperature oxidation system, and the total amount of H ₂ sent to the high temperature oxidizing system is altered by altering said additional portion.

12. The method according to paragraph 1, characterized in that H ₂ released from the separation system is fed into a low temperature proton exchange fuel cell.