Method of and a plant for combusting carbonaceous fuel by using a solid oxygen carrier
View Patent ↗A method of and a plant for combusting carbonaceous fuel, the method including the steps of introducing particulate oxygen selective sorbent, such as a perovskite type material, into an adsorption reactor of the combustion plant to form a first particle bed in the adsorption reactor, fluidizing the first particle bed by an oxygen-containing first fluidizing gas to adsorb oxygen from the fluidizing gas to the sorbent, conveying oxygen-rich sorbent from the adsorption reactor to a combustion reactor of the combustion plant to form a second particle bed in the combustion reactor, fluidizing the second particle bed by an oxygen-deficient second fluidizing gas to desorb oxygen from the sorbent, so as to produce free oxygen gas, and introducing carbonaceous fuel into the combustion reactor to oxidize the fuel with the free oxygen gas.
1. A method of combusting solid carbonaceous fuel in a combustion plant, the method comprising the steps of:
(a) introducing particulate oxygen selective sorbent into an adsorption reactor of the combustion plant to form a first particle bed in the adsorption reactor;
(b) fluidizing the first particle bed by an oxygen-containing first fludizing gas to provide a first partial pressure of oxygen p 1 in the adsorption reactor to adsorb oxygen from the fluidizing gas to the sorbent, so as to produce oxygen-rich sorbent and oxygen-depleted exhaust gas;
(c) discharging oxygen-depleted exhaust gas from the adsorption reactor along a first exhaust gas channel;
(d) conveying oxygen-rich sorbent from the adsorption reactor to a combustion reactor of the combustion plant along a sorbent conveying channel to form a second particle bed in the combustion reactor;
(e) fluidizing the second particle bed by an oxygen-deficient second fluidizing gas consisting mainly of carbon dioxide, to provide a second partial pressure of oxygen p 2 in the combustion reactor, where p 2 is less than p 1 , to desorb oxygen from the sorbent in the combustion reactor, so as to produce free oxygen gas and oxygen-depleted sorbent;
(f) introducing solid carbonaceous fuel into the combustion reactor to oxidize the fuel with the free oxygen gas, and to produce exhaust gas consisting mainly of carbon dioxide and water, and to maintain a low partial pressure of oxygen p 2 ′ in the combustion reactor, where p 2 ′ is less than p 1 , to continue desorbing oxygen from the sorbent;
(g) discharging exhaust gas from the combustion reactor along a second exhaust gas channel; and
(h) obtaining at least a portion of the second fluidizing gas as a side stream of the exhaust gas discharged from the combustion reactor.
2. The method according to claim 1 , wherein the method comprises a further step of returning at least a portion of the oxygen-depleted sorbent from the combustion reactor to the adsorption reactor along a sorbent return channel.
3. The method according to claim 1 , wherein the method comprises a further step of discharging at least a portion of the oxygen-depleted sorbent from the combustion plant so as to remove impurities adsorbed in the sorbent.
4. The method according to claim 3 , wherein the method comprises further steps of regenerating at least a portion of the discharged sorbent by removing impurities adsorbed in the sorbent, and returning at least a portion of the regenerated sorbent in the regenerating step to the adsorption reactor.
5. The method according to claim 1 , wherein the first fluidizing gas comprises air.
6. The method according to claim 1 , wherein the second fluidizing gas comprises steam.
7. The method according to claim 1 , wherein the carbonaceous fuel comprises at least one of coal, biofuel and waste derived fuel.
8. The method according to claim 1 , wherein the adsorption reactor is a slow fluidized bed reactor.
9. The method according to claim 8 , wherein in step (a) the oxygen selective sorbent is introduced at the upper portion of the adsorption reactor and in step (d) the oxygen-rich sorbent is conveyed from the lower portion of the adsorption reactor.
10. The method according to claim 1 , wherein the adsorption reactor is a fast fluidized bed reactor.
11. The method according to claim 10 , wherein the adsorption reactor comprises a particle separator for separating oxygen-rich sorbent from the oxygen-depleted gas, and step (d) comprises conveying the separated oxygen-rich sorbent into the combustion reactor.
12. The method according to claim 2 , wherein the combustion reactor is a slow fluidized bed reactor.
13. The method according to claim 12 , wherein in step (d) the oxygen-rich sorbent is introduced at the upper portion of the combustion reactor and the method further comprises a step of returning oxygen-depleted sorbent from the lower portion of the adsorption reactor.
14. The method according to claim 2 , wherein the combustion reactor is a fast fluidized bed reactor.
15. The method according to claim 14 , wherein the combustion reactor comprises a particle separator for separating oxygen-depleted sorbent from the carbon dioxide containing exhaust gas, and the method further comprises a step of conveying the separated oxygen-depleted sorbent into the adsorption reactor.
16. The method according to claim 1 , wherein the oxygen selective sorbent comprises a perovskite type material.
17. The method according to claim 16 , wherein the perovskite type material has a structural formula A 1-x M x BO 3-δ , where A is an ion of a metal of Groups 3A and 3B of the periodic table of elements or mixtures thereof, M is an ion of a metal of Groups 1A and 2A of the periodic table of elements or mixtures thereof, B is an ion of a d-block transition metal of the periodic table of elements or mixtures thereof, x varies from 0 to 1, and δ is the deviation from a stoichiometric composition resulting from the substitution of ions of metals of M for ions of metals of A.
18. The method according to claim 17 , wherein at least one of (i) A is at least one f-block lanthanide, (ii) M is at least one metal of Group 2a of the periodic table of elements, and (iii) B is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn or mixtures thereof.
19. The method according to claim 17 , wherein x is 0.2 to 1 and at least one of (i) A is La, Y, Sm or mixtures thereof, (ii) M is Sr, Ca, Ba or mixtures thereof, and (iii) B is V, Fe, Ni, Cu or mixtures thereof.
20. The method according to claim 1 , wherein the oxygen selective sorbent comprises ceramic substances selected from the group consisting of Bi 2 O 3 , ZrO 2 , CeO 2 , ThO 2 , Hf 0 2 and mixtures of these, the ceramic substance being doped with at least one of CaO, rare earth metal oxides and mixtures of CaO and rare earth metal oxides.
21. The method according to claim 20 , wherein the ceramic substance is doped with a rare earth metal oxide selected from the group consisting of Y 2 O 3 , Nb 2 O 3 , Sm 2 O 3 , Gd 2 O 3 and mixtures of these.
22. The method according to claim 1 , wherein the oxygen selective sorbent comprises brownmillerite oxides.
23. The method according to claim 1 , wherein the oxygen selective sorbent is treated by a substance that promotes the oxygen adsorption properties of the material.
24. The method according to claim 23 , wherein the promoter substance comprises transition metals of Groups 1B and 8 of the periodic table of elements.
25. The method according to claim 23 , wherein the promoter substance is selected from the group consisting of Cu, Ag, Fe, Ni, Rh, Pt or mixtures of these.
26. The method according to claim 1 , wherein the method comprises a further step of recovering carbon dioxide from the carbon dioxide containing exhaust gas.
27. The method according to claim 1 , wherein the method comprises a further step of generating steam by using heat transfer surfaces in the combustion reactor and in at least one of the adsorption reactor, the first exhaust gas channel and the second exhaust gas channel.
28. The method according to claim 1 , wherein the method comprises a further step of heating the first fluidizing gas with heat recovered from the oxygen-depleted exhaust gas.
29. The method according to claim 1 , wherein the method comprises a further step of heating the second fluidizing gas with heat recovered from the carbon dioxide containing exhaust gas.