Pilot plant for chemical looping hydrogen generation using single-column packed bed and hydrogen generation method

Abstract

A pilot plant for chemical looping hydrogen generation using a single-column packed bed and hydrogen generation method. The plant has a feeding system, reaction system, tail gas treatment and analysis system, and auxiliary system. The reaction system has a packed bed reactor, inside which a thermal storage layer, oxygen carrier layer and supporting layer are arranged successively from top to bottom. The feeding system has a delivery pipe, metering pump, mass flow controller and fuel mixer. The tail gas treatment and analysis system has a cooler, gas-liquid separator, mass flow meter, gas analyzer and tail gas pipe. The packed bed reactor is subjected to fuel reduction, purge, steam oxidation, purge, air combustion and purge stages successively under control of the feeding system. The pilot plant enables evaluation for oxygen carriers and identification for technological difficulties and can generate high-purity hydrogen without using complex gas purification devices.

Claims

1. A method for chemical looping hydrogen generation using a pilot plant, wherein the method comprises following steps: A. feeding stage: a feeding system mixes a fuel I with a fuel II via a fuel mixer and then delivers the mixture into a packed bed reactor of a reaction system, and other raw materials are delivered into the packed bed reactor of the reaction system after passing through corresponding raw material mass flow controllers; B. reaction stage: mixed fuels I and II react with an oxygen carrier in the packed bed reactor and other raw materials enter the packed bed reactor successively under a control of the feeding system, so that the packed bed reactor is subjected to a fuel reduction stage, a first purge stage, a steam oxidation stage, a second purge stage, an air combustion stage and a third purge stage successively, wherein liquid water enters the packed bed reactor after the first purge stage; and C. tail gas treatment stage: gases generated during the fuel reduction stage, the steam oxidation stage and the air combustion stage are cooled, separated, metered and analyzed by a tail gas treatment and analysis system before being discharged.

2. The method according to claim 1, wherein gas generated during the steam oxidation stage is cooled and separated by a tail gas treatment and analysis system to obtain high-purity hydrogen, which is metered and analyzed before being discharged, wherein the high-purity hydrogen comprises at least 98.3% of hydrogen.

3. The method according to claim 2, wherein reaction temperatures of the fuel reduction stage, the steam oxidation stage and the air combustion stage are 800° C.; and gases of the first purge stage, the second purge stage and the third purge stage are nitrogen.

4. The method according to claim 1, wherein the pilot plant comprises a raw material mass flow controller comprising a metering pump, a fuel I mass flow controller and a fuel II mass flow controller, an air mass flow controller and a nitrogen mass flow controller, wherein the metering pump, the air mass flow controller and the nitrogen mass flow controller are each connected to the inlet of the reaction system, and an outlet of the fuel I mass flow controller and an outlet of the fuel II mass flow controller are connected to an inlet of the fuel mixer.

5. The method according to claim 1, wherein a thermal storage layer, an oxygen carrier layer and a supporting layer are arranged successively from top to bottom inside the packed bed reactor, and wherein said liquid water entering the packed bed reactor is then vaporized on the thermal storage layer.

6. The method according to claim 5, wherein the oxygen carrier layer of the packed bed reactor has a length-to-diameter ratio of 4:1 to 12:1.

7. The method according to claim 1, wherein the tail gas treatment and analysis system comprises a cooler, a gas-liquid separator, a mass flow meter, a gas analyzer and a tail gas pipe in successively connection.

8. The method according to claim 7, wherein a packed bed reactor inlet safety valve and a packed bed reactor outlet safety valve are connected with the tail gas pipe, and a packed bed reactor blowdown pipe is provided at a bottom of the packed bed reactor.

9. The method according to claim 1, wherein an internal temperature of the packed bed reactor is measured by a packed bed reactor axial temperature measurement device, and a pressure drop of the packed bed reactor is measured by a packed bed reactor inlet pressure sensor and a packed bed reactor outlet pressure sensor.

10. The method according to claim 1, wherein the feeding system comprises at least one raw material delivery pipe, at least one raw material mass flow controller and the fuel mixer, and wherein at least one outlet of the raw material mass flow controller is connected with an inlet of the fuel mixer, and other remaining outlets of the raw material mass flow controller are connected with an inlet of the reaction system.

11. The method according to claim 10, wherein the tail gas treatment and analysis system comprises a cooler, a gas-liquid separator, a mass flow meter, a gas analyzer and a tail gas pipe in successively connection, and wherein the pilot plant further comprises an auxiliary system that is connected with the feeding system, the reaction system and the tail gas treatment and analysis system, respectively, wherein the auxiliary system comprises a quartz heating furnace, a pilot plant control apparatus and an electrical apparatus.

12. The method according to claim 1, wherein the packed bed reactor has a reaction temperature of 700° C. to 1100° C. at the fuel reduction stage, a reaction temperature of 700° C. to 1100° C. at the steam oxidation stage, and a reaction temperature of 700° C. to 1100° C. at the air combustion stage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The sole FIGURE is a schematic diagram of a pilot plant for chemical looping hydrogen generation using a single-column packed bed in accordance with embodiment 1.

DETAILED DESCRIPTION OF THE INVENTION

(2) The procedure and effect of the inventive method will be further described below in conjunction with the embodiments that are not intended to limit the patent scope of the present invention. Any equivalent implementation or change made without departing from the present invention shall be included within the scope of the present patent.

Embodiment 1

(3) As shown in the sole FIGURE, provided in this embodiment is a pilot plant for chemical looping hydrogen generation using a single-column packed bed, which comprises a feeding system, a reaction system, a tail gas treatment and analysis system, and an auxiliary system, wherein the feeding system comprises: a water delivery pipe 1, a fuel I delivery pipe 2, a fuel II delivery pipe 3, a nitrogen delivery pipe 4, an air delivery pipe 5, a metering pump 6, a fuel I mass flow controller 7, a fuel II mass flow controller 8, a nitrogen mass flow controller 9, an air mass flow controller 10 and a fuel mixer 11.

(4) The reaction system comprises a packed bed reactor 12, a thermal storage layer 13, an oxygen carrier layer 14, a supporting layer 15, a packed bed reactor axial temperature measurement device 16, a packed bed reactor inlet pressure sensor 17, a packed bed reactor inlet safety valve 18, a packed bed reactor outlet pressure sensor 19, a packed bed reactor outlet safety valve 20, and a packed bed reactor blowdown pipe 21.

(5) The tail gas treatment and analysis system comprises a cooler 22, a circulated cooling water inlet pipe 23, a circulated cooling water outlet pipe 24, a gas-liquid separator 25, a condensed water outlet pipe 26, a mass flow meter 27, a gas analyzer 28 and a tail gas pipe 29.

(6) The plant further comprises an auxiliary system, which is connected with the feeding system, the reaction system and the tail gas treatment and analysis system, respectively, and provides auxiliary apparatuses, such as electrical, heating and control apparatuses. The auxiliary system comprises a quartz heating furnace, a pilot plant control apparatus and an electrical apparatus. The quartz heating furnace provides appropriate reaction temperatures for different reaction stages in the reaction system; and the pilot plant control apparatus serves to control coordinated reactions among the various systems, in order to compare different experimental results.

(7) Fuels in the fuel I delivery pipe 2 and the fuel II delivery pipe 3 enter the fuel mixer 11 respectively via the fuel I mass flow controller 7 and the fuel II mass flow controller 8, the outlet of the fuel mixer 11 is connected with the inlet of the packed bed reactor 12; and the water delivery pipe 1, the nitrogen delivery pipe 4 and the air delivery pipe 5 are connected with the inlet of the packed bed reactor 12 respectively via the metering pump 6, the nitrogen mass flow controller 9 and the air mass flow controller 10.

(8) The packed bed reactor 12 has the thermal storage layer 13, the oxygen carrier layer 14 and the supporting layer 15 arranged therein successively from top to bottom, the oxygen carrier layer 14 of the packed bed reactor 12 has a length-to-diameter ratio of 4:1 to 12:1, and such a ratio relationship makes it possible to attain optimal contact areas between oxygen carrier and fuel gas and air and also achieve the largest reaction space and best reaction effect; the temperature within the packed bed reactor 12 is measured by the packed bed reactor axial temperature measurement device 16; the pressure drop of the packed bed reactor 12 is determined by the packed bed reactor inlet pressure sensor 17 and the packed bed reactor outlet pressure sensor 19; the packed bed reactor inlet safety valve 18 and the packed bed reactor outlet safety valve 20 are connected with the tail gas pipe 29; and the bottom of the packed bed reactor 12 is connected with the packed bed reactor blowdown pipe 21.

(9) The packed bed reactor 12 is internally structured in such a manner that the thermal storage layer 13, the oxygen carrier layer 14 and the supporting layer 15 are arranged successively from top to bottom. The temperatures of fuel gas, water and air can be raised to appropriate reaction temperatures, followed by reacting with the oxygen carrier. Thus reaction efficiency is enhanced due to the seamless transition from the heating procedure to the reaction procedure.

(10) Preferably, the packed bed reactor 12 has an inner diameter of 79 mm and is made of 310s stainless steel. The thermal storage layer 13 is loaded with 3 kg of inert alumina balls having a diameter of 10 mm, with the aim of vaporizing liquid water. Also, the supporting layer 15 is loaded with 3 kg of inert alumina balls having a diameter of 10 mm, for ensuring that the oxygen carrier layer 14 is located in a constant temperature area in the middle of the packed bed reactor 12. The oxygen carrier used is cylindrical Fe.sub.2O.sub.3/Al.sub.2O.sub.3 having a diameter of 5 mm and a height of 4-6 mm, with the loading being 4 kg.

(11) The outlet of the packed bed reactor 12 is connected with the material inlet of the cooler 22, the cooling water inlet and outlet of the cooler 22 are connected with the circulated cooling water inlet pipe 23 and the circulated cooling water outlet pipe 24, respectively; the material outlet of the cooler 22 is connected with the inlet of the gas-liquid separator 25, the condensed water outlet of the gas-liquid separator 25 is connected with the condensed water outlet pipe 26, the gas outlet of the gas-liquid separator 25 is connected with the inlet of the mass flow meter 27; the outlet of the mass flow meter 27 is connected with the inlet of the gas analyzer 28 and with the tail gas pipe 29, and the outlet of the gas analyzer 28 is connected with the tail gas pipe 29.

(12) Wherein the packed bed reactor has a reaction temperature of 700° C. to 1100° C. at the fuel reduction stage, a reaction temperature of 700° C. to 1100° C. at the steam oxidation stage, and a reaction temperature of 700° C. to 1100° C. at the air combustion stage.

(13) Under the control of the feeding system, the packed bed reactor 12 is continuously subjected to the fuel reduction stage, the first purge stage, the steam oxidation stage, the second purge stage, the air combustion stage and the third purge stage successively, so as to finish a complete chemical looping hydrogen generation procedure. The oxygen carrier in the packed bed reactor 12 undergoes cyclic oxygen gain and loss during the complete chemical looping hydrogen generation procedure, thereby producing nitrogen.

(14) According to the pilot plant for chemical looping hydrogen generation using a single-column packed bed provided in the embodiment of the present invention, the process flow is simplified in which high-purity H.sub.2 can be obtained by simple condensation and water removal of the H.sub.2 product generated by a chemical looping hydrogen generation unit, without using any complex gas purification device. Thus, the costs for hydrogen generation are low. The arrangement of the tail gas treatment and analysis system enables internal separation of CO.sub.2 at the same time of hydrogen generation, resulting in lower carbon during the hydrogen generation procedure. Implementation of the chemical looping hydrogen generation technique on a large-scale reactor is conducive to evaluation for oxygen carriers and identification for technological difficulties, while at the same time offering a pilot test data support for large-scale application of the technique.

Embodiment 2

(15) As shown in the sole FIGURE, provided in this embodiment is a method for hydrogen generation by applying the pilot plant for chemical looping hydrogen generation using a single-column packed bed, which specifically comprises the following steps.

(16) A. feeding stage: the feeding system mixes a fuel I with a fuel II via the fuel mixer and then delivers the mixture into the packed bed reactor of the reaction system, and other raw materials are delivered into the packed bed reactor of the reaction system after passing through the corresponding raw material mass flow controllers.

(17) B. reaction stage: the mixed fuels I and II react with an oxygen carrier in the packed bed reactor and other raw materials enter the packed bed reactor successively under the control of the feeding system, so that the packed bed reactor is subjected to the fuel reduction stage, the first purge stage, the steam oxidation stage, the second purge stage, the air combustion stage and the third purge stage successively.

(18) C. the tail gas treatment stage: gases generated during the fuel reduction stage, the steam oxidation stage and the air combustion stage are cooled, separated, metered and analyzed by the tail gas treatment and analysis system before being discharged.

(19) Specifically in step A, CO from the fuel I delivery pipe 2 and H.sub.2 from the fuel II delivery pipe 3 enter the packed bed reactor 12 after being uniformly mixed by the fuel mixer 11, and the oxygen carrier reacts with the mixed fuels I and II at a temperature of 800° C.

(20) In step B, upon the completion of reduction of the fuels I and II and the oxygen carrier, the fuel I mass flow controller 7 and the fuel II mass flow controller 8 are closed, the nitrogen mass flow controller 9 is opened, nitrogen that comes from the nitrogen delivery pipe 4 enters the packed bed reactor 12, and the gas from the fuel reduction stage is purged for the first time. Wherein the first purge is aimed at guaranteeing no impact of the fuel gas on hydrogen purity.

(21) Wherein preferably, the packed bed reactor 12 has an inner diameter of 79 mm and is made of 310s stainless steel. The packed bed reactor 12 has the thermal storage layer 13, the oxygen carrier layer 14 and the supporting layer 15 arranged therein successively from top to bottom. The thermal storage layer 13 is loaded with 3 kg of inert alumina balls having a diameter of 10 mm, with the aim of vaporizing liquid water. Also, the supporting layer 15 is loaded with 3 kg of inert alumina balls having a diameter of 10 mm, for ensuring that the oxygen carrier layer 14 is located in a constant temperature area in the middle of the packed bed reactor 12. The oxygen carrier used is cylindrical Fe.sub.2O.sub.3/Al.sub.2O.sub.3 having a diameter of 5 mm and a height of 4-6 mm, with the loading being 4 kg. And the corresponding length-to-diameter ratio of the oxygen carrier layer is 6:1.

(22) After purge is concluded, the nitrogen mass flow control valve 9 is closed, the metering pump 6 is opened, liquid water coming from the water delivery pipe 1 enters the packed bed reactor 12 and then is vaporized on the scorching thermal storage layer 13, and the steam that is quantified in a precise way reacts with the reduced oxygen carrier at a temperature of 800° C.

(23) When the steam oxidation is concluded, the metering pump 6 is closed, the nitrogen mass flow control valve 9 is opened, nitrogen from the nitrogen delivery pipe 4 enters the packed bed reactor 12, and the gas from the steam oxidation stage is purged for the second time. Wherein the second purge is to guarantee no impact of the fuel gas on hydrogen purity. Upon the completion of purge, the nitrogen mass flow control valve 9 is closed, the air mass flow controller 10 is opened, and air from the air delivery pipe 5 enters the packed bed reactor 12 and reacts with the steam-oxidized oxygen carrier at a temperature of 800° C.

(24) When air combustion comes to an end, the air mass flow controller 10 is closed, the nitrogen mass flow control valve 9 is opened, nitrogen from the nitrogen delivery pipe 4 enters the packed bed reactor 12, the gas from the air combustion stage is purged for the third time, and in this way a complete chemical looping hydrogen generation cycle is done. Wherein the third purge is intended to avoid explosion that occurs after air is mixed with the fuel from the reduction stage.

(25) It should be noted that steam oxidation is capable of oxidizing the iron-based oxygen carrier only into Fe.sub.3O.sub.4, which fails to combust the fuel gas completely at the reduction stage as there exists thermodynamic limitations. In order to achieve complete fuel combustion and improve process efficiency while enabling internal separation of carbon dioxide, the air combustion stage needs to be added to further oxidize the steam-oxidized iron-based oxygen carrier into Fe.sub.2O.sub.3.

(26) In step C, CO.sub.2 and H.sub.2O(g) generated during the fuel reduction stage are cooled in the cooler 22 until water is condensed, then enter the gas-liquid separator 25 to remove the condensed water, and are metered by the mass flow meter 27 and subsequently divided into two paths, one of which enters the tail gas pipe 29 directly, and the other of which firstly enters the gas analyzer 28 for gas composition analysis and then makes its way into the tail gas pipe 29.

(27) H.sub.2 and H.sub.2O(g) generated by the reaction during the steam oxidation stage is cooled by the cooler 22 and then subjected to water removal in the gas-liquid separator 25 to obtain high-purity H.sub.2, and the H.sub.2 product is metered by the mass flow meter 27 and analyzed by the gas analyzer 28 before entering the tail gas pipe 29.

(28) The gas generated by the reaction during the air combustion stage is cooled by the cooler 22, water-removed by the gas-liquid separator 25, metered by the mass flow meter 27 and analyzed by the gas analyzer 28 before entering the tail gas pipe 29.

(29) The reactant flows as well as the results of packed bed chemical looping hydrogen generation pilot test in embodiment 2 are listed in Table 1.

(30) TABLE-US-00001 TABLE 1 Implementation conditions and results of pilot plant for chemical looping hydrogen generation using packed bed Implementation conditions CO flow H.sub.2 flow Steam flow Nitrogen flow Air flow 7.5 L/min 7.5 L/min 30 g/min 15 L/min 15 L/min Implementation results H.sub.2 content CO content CO.sub.2 content 98.3% 0.4% 1.3%

(31) Experimental data has demonstrated that high-purity hydrogen can be obtained under the above-mentioned implementation conditions, and the entire hydrogen generation procedure becomes more environmentally friendly since the content of carbon dioxide is dramatically reduced after treatments.

(32) According to the method for hydrogen generation provided in the embodiment of the method, the process flow is simplified, the hydrogen generated has high purity and can be obtained only through condensation, there is no complex gas purification procedure, and thus the costs for hydrogen generation are low. Internal separation of carbon dioxide during the process of reaction can be completed at the same time of high-purity hydrogen generation, leading to lower carbon and better environmental friendliness during the hydrogen generation procedure. The chemical looping hydrogen generation technique can be implemented on a large-scale reactor to offer a pilot test data support for large-scale application. The air combustion stage enables a sufficient reduction of the iron-based oxygen carrier while achieving internal separation of carbon dioxide, and therefore complete fuel combustion and an improvement in efficiency are both accomplished.

(33) The above description illustrates and describes several preferred embodiments of the present invention, but as previously described, it is to be understood that the present invention is not limited to the forms disclosed herein, and that the present invention shall not be considered as excluding other embodiments, and instead can be used in various other combinations, modifications and environments and is capable of modifications within the scope of the inventive concept as expressed herein by the above teaching or techniques or knowledge in related arts. Any modifications and changes made by those skilled in the art that do not depart from the spirit and scope of the present invention shall fall within the scope of the appended claims of the present invention.