AU2003261772A1 - Method of recovering hydrogen from organic waste - Google Patents

Description

VERIFICATION OF TRANSLATION Patent Application No. PCT/JPO3/10878 by Japan Planning Organization Inc. I, Mitsuo Matsui, patent attorney of MATSUI & ASSOCIATES of Nishishinbashi YS Bldg., 3F, 19-2, Nishishinbashi 2-chome, Minato-ku, Tokyo, Japan, am the translator of the documents attached and I state that the following is a true translation to the best of my knowledge and belief of International Patent Application No. PCT/JPO3/10878 filed 27 August 2003. DATED this i7 day of F--. raw. ,2005 .. .(Signa re of translator).. ...... (Signature of translator) METHOD OF RECOVERING HYDROGEN FROM ORGANIC WASTE FIELD OF THE INVENTION The present invention relates to a method to effectively utilize organic wastes, 5 such as unused resources and renewable resources, more particularly to a method to recover hydrogen from the organic wastes. PRIOR ART Thinned wood and waste wood were incinerated in the past. Recently processes to 10 use heat generated in the incineration of these to generate electricity were studied from viewpoints of energy saving and effective use of heat. A process to thermally decompose waste plastics into oil or a process to recycle them as a reducing agent for a blast incinerator was studied and practically applied. Garbage had been incinerated, but recently a process to recover methane from garbage by means of methane fermentation 15 and a process to generate electricity from the methane are being practically used. As a means to dispose thinned wood or waste wood, direct incineration and gasification may be mentioned. In the direct incineration, the above-mentioned materials are completely burnt in an incinerator, such as a stoker incinerator, a bubbling fluidized bed incinerator, a circulating fluidized bed incinerator, and a 20 circulating moving bed combustor. What may be recovered and reused in the direct incineration process is only thermal energy, by which energy hot water or steam may be produced to generate electricity. Meanwhile, in the gasification, the above-mentioned materials are partly oxidized by oxygen or air in a gasification incinerator such as a fixed bed incinerator, a moving bed combustor, a circulating fluidized bed incinerator, a 25 two-staged circulating moving combustor, and an entrained flow bed incinerator. What may be recovered and reused in the gasification process is thermal energy and gas. The thermal energy may be used to obtain hot water or electric power. The gas may be used as a fuel to generate hot water or electric power. In both ways, it is the present situation that generated heat, hot water, or electric power cannot be used effectively since there is 30 no factory to consume it. Due to regulatory measures to reduce dioxin generated in incineration of wastes, simple incineration of industrial wastes, such as thinned wood, waste wood from construction, and general waste has been being restricted and, therefore, is becoming impossible. Meanwhile, the Construction Material Recycling Act proclaims promotion of 35 recycling of waste wood from construction. Therefore, recycling of waste wood from construction is becoming unavoidable. 1 SUMMARY OF THE INVENTION The present invention provides a process to effectively use energy and gas obtained from organic wastes, such as, thinned wood, driftwood, waste wood, waste 5 plastics, garbage, sludge, mown grass, and paper industry sludge. The present inventors have reached an idea of recovering hydrogen from the above-mentioned organic wastes so as to promote recycling of unused resource such as thinned wood, and other organic wastes, such as waste wood, and to further promote effective utilization thereof as an energy resource. It has been found that the recovering 10 of energy in a form of hydrogen makes the energy possible to be stored and transported and, subsequently, to be used to generate hot water or electric power as required. Further this gives the environment a less impact since combustion of hydrogen emits no carbon dioxide, which can contribute to prevention of global warming, and thus the present invention has been completed. 15 Namely, the present invention provides (1) a process for recovering hydrogen, comprising heating organic waste at a temperature of from 500 to 600 degrees C under a non-oxidative atmosphere, mixing a pyrolysis gas thus generated with steam at a temperature of from 900 to 1000 degrees C, and separating hydrogen from a reformed gas thus obtained. 20 As preferred embodiments, mention may be made of (2) the process according to the above-described (1), wherein the organic waste is one selected from the group consisting of thinned wood, driftwood, waste wood, waste plastics, garbage, sludge, mown grass, and paper industry sludge; (3) the process according to the above-described (1), wherein the organic waste is 25 one selected from the group consisting of thinned wood, driftwood and waste wood; (4) the process according to any one of the above-described (1) - (3), wherein a means to separate hydrogen from the reformed gas for recovering hydrogen is one selected from the group consisting of PSA, membrane separation, and cryogenic separation; 30 (5) the process according to any one of the above-described (1) - (3), wherein a means to separate hydrogen from the reformed gas for recovering hydrogen is PSA; (6) the process according to any one of the above-described (1) to (5), wherein the temperature at which said organic waste is heated under a non-oxidative atmosphere is in a range of from 530 to 570 degrees C; 35 (7) the process according to any one of the above-described (1) to (6), wherein the temperature at which the generated pyrolysis gas is mixed with steam is in a range of 2 from 950 to 1000 degrees C; (8) the process according to any one of the above-described (1) to (7), wherein a pressure at which said organic waste is heated under a non-oxidative atmosphere and a pressure at which the generated pyrolysis gas is mixed with steam are 1 MPa or less; 5 (9) the process according to any one of the above-described (1) to (7), wherein a pressure at which said organic waste is heated under a non-oxidative atmosphere and a pressure at which the generated pyrolysis gas is mixed with steam are in a range of from 0.1 MPa to 1 MPa; and (10) the process according to any one of the above-described (1) to (9) further 10 comprising producing hydrogen by reacting carbon monoxide and water with each other both contained in said reformed gas obtained after the mixing with steam. According to the process of the present invention, unused resources or organic wastes can be recycled and used as an energy resource. Conventionally, wastes disposal and energy generation were performed separately. Now energy efficiency can be raised 15 by performing them in one and the same equipment. Hydrogen can also be recovered without generating carbon dioxide. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart of the equipment used in the Example. 20 DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the organic waste used in the present invention include thinned wood, driftwood, bamboo, rice straw, rice hull, corn, sweet sorghum, vegetable, fruits, flower, sea weed, other unused resources such as wood or plants recovered in forests, rivers, 25 dams or sea coasts, as well as waste wood, waste materials from lumber mills, waste bamboo, trimmed branches, mown grass, waste plastics, garbage, food residues, residues from vegetable processing, residues from fruit processing, sewage sludge, animal and human waste sludge, community sewage sludge, activated sludge, and paper industry sludge. Among these, preferably use is made of thinned wood, driftwood, 30 waste wood, waste plastics, garbage, mown grass, and paper industry sludge. Use of thinned wood, driftwood or waste wood is particularly preferred. The organic waste may have a dimension such as that of coarsely crushed one. The organic waste may be in a solid state in the form of, for instance, plate, stick, sheet or other forms with a dimension of from 1 mm to 15 cm. When the organic waste is smaller 35 than 1 mm, it may be in any form of particulates, powder, or sludge. A water content of the organic waste depends on its form and is preferably 50 weight % or less, more 3 preferably 30 weight % or less. In the present invention, the organic waste is first heated under a non-oxidative atmosphere, whereby the organic waste is decomposed to generate a pyrolysis gas. The upper limit for a heating temperature is 600 degrees C, preferably 570 5 degrees C, and the lower limit is 500 degrees, preferably 530 degrees C. The above-described range may increase the amount of the generated gas. If the temperature is lower than the lower limit, the organic waste is not decomposed enough. If the temperature is higher than the upper limit, the amount of the generated gas cannot be raised. The upper limit for the pressure in the heating step is preferably 1 10 MPa, more preferably 0.3 MPa, and the lower limit is preferably 0.1 MPa, more preferably 0.103 MPa. Nitrogen is preferably used as the non-oxidative atmosphere. The form or type of the heating furnace that may be used is not particularly limited as far as it; can heat the raw material organic waste to the above-described 15 temperature. Examples include a retort incinerator, a shaft incinerator, a rotary kiln, a fixed bed incinerator, a moving bed combustor, and a fluidized bed incinerator. Alumina, silica, sand, and so on may be used as a circulating medium in the moving bed combustor and the fluidized bed incinerator, and there is no particular restriction on their shape. 20 In the present invention, the organic waste is heated as described above, and then the pyrolysis gas thus generated is mixed with steam, whereby the pyrolysis gas and steam react with each other to reform the pyrolysis gas into a hydrogen-enriched gas. For the temperature at which the gas is mixed with steam, the upper limit is 1000 degrees C and the lower limit is 900 degrees C, preferably 950 degrees C. If the 25 temperature is lower than the above-described lower limit, the reforming reaction does not proceed. If the temperature is higher than the upper limit, the material of the reforming furnace is adversely affected, which is undesirable. Heat required to promote the above-described reforming reaction is supplied by a heat medium, which has been heated. As a heat source for the heat medium, use is 30 made of heat obtained by burning tar and char, including carbon and ash, which is generated in the heating of the above-described organic waste under a non-oxidative atmosphere. The burning is conducted preferably separately from the aforementioned system in which the organic waste is heated under a non-oxidative atmosphere. Since tar among others tends to disturb a continuous operation in the heating of 35 the above-described organic waste under a non-oxidative atmosphere, the tar is preferably removed at the bottom of the furnace, whereby a continuous operation can be 4 conducted smoothly. If tar and char by-produced simultaneously are withdrawn and burnt, it is possible not only to avoid malfunction of the equipment and secure safe operations, but also to effectively use the tar and char. Steam to reform the pyrolysis gas can be obtained from industrial water or clean 5 water through a heat exchanger by using heat of the hot reformed gas obtained from the reforming furnace. Alternatively, a boiler may be installed to obtain steam. The temperature of the steam supplied is preferably 140 degrees or higher, and the pressure is preferably 0.376 MPa or higher. The temperature and the pressure may be, for instance, 180 degrees C and 1 MPa but are not restricted thereto. Steam may be fed into 10 the reforming furnace by continuous or intermittent spraying. There is no particular limitation on the form or type of the reforming furnace that may be used. Mention may be made of, for instance, a retort incinerator, a shaft incinerator, a rotary kiln, a fixed bed incinerator, a moving bed combustor, and a fluidized bed incinerator. In general, a furnace of the same form as that of the 15 above-described heating furnace is used. However, this is not limitative. For instance, a combination of a rotary kiln as a heating furnace and a retort incinerator as a reforming furnace may be used. As a circulating medium for the moving bed incinerator and the fluidized bed incinerator, use may be made of, for instance, alumina, silica, and sand, and there is no particular limitation on their shape. 20 The reformed gas out of the reforming furnace is passed preferably through a shift reaction bed, whereby carbon monoxide contained in the reformed gas is reacted with an excessive amount of steam, so that more hydrogen is recovered. The shift reaction is known. For instance, a two-stage process is used. In the first stage, the reaction takes place preferably at a temperature of from 350 to 500 degrees C using a high 25 temperature conversion catalyst of iron-chromium system so that a content of remaining carbon monoxide in the gas is 3 -4 volume %. Then in the second stage, the reaction takes place preferably at a temperature of from 200 to 250 degrees C using a low temperature conversion catalyst of copper-zinc system so that the content of remaining carbon monoxide in the gas is 0.3 -0.4 volume %. 30 Pressure during the reaction is preferably 1 MPa or higher, more preferably from 1 to 3 MPa. The pressure may be determined so that it is matched to the pressures of the steps before and after the shift reaction bed. The gas thus obtained is cooled preferably with water and then hydrogen is recovered. As a means to recover hydrogen from the gas, any known method can be used. 35 Mention may be made of, for instance, a pressure swing adsorption method or PSA, a membrane separation method, and a cryogenic separation method. Among these, PSA is 5 suitable since a gas content can be controllable freely and the cost is lower. In PSA, a hydrogen content in the recovered gas can be controlled by changing, for instance, an adsorption time or a height of an adsorption bed. Thus the gas is separated into hydrogen and the other gases to recover hydrogen obtained in the above-described 5 procedures. According to the process of the present invention, unused resources and renewable resources can be utilized effectively. It is also possible to recover hydrogen, which is useful, without generating carbon dioxide. Therefore, the process of the present invention can be used in a variety of industrial fields, such as timber industry, 10 lumbering industry, livestock industry, construction industry, environment conservation industry, transportation industry, fuel supply industry, gas supply industry, and plastic manufacturing industry. The present invention will be further elucidated in detail with reference to the following Example, but is not limited thereto. 15 EXAMPLE The equipment used in the Example is as shown in Fig. 1. Here, A is a heating furnace, B is a reforming furnace, C is a gas cooling instrument, and D is a hydrogen separating instrument, PSA. 1 represents waste wood; 2, steam; 3, a cooling gas; 4, a 20 hydrogen-enriched gas; 5, a waste gas; 6, tar and char; and 7, a heat medium. Retort furnaces with a cone-shaped bottom were used as the heating furnace and the reforming furnace. PSA was used as the hydrogen separating instrument. Example 1 Waste wood of cedar, disposed of from a lumber mill, was used for gasification. The 25 waste wood had been subjected to coarse crushing into a mixture of sticks having almost the same dimension as that of disposable chop sticks, ones of a size of saw dust, and thin plates having almost the same dimension as that of a playing card. Properties of the waste wood are presented in Table 1. 30 35 6 Table 1 Properties of Waste Wood Water content 30 weight % Ash content 5 weight % Total Calorie 19,600 kJ/kg Element Composition C 49.90 weight % H 5.78 weight % N 0.36 weight % O 43.59 weight % S 0.37 weight % Each value in Table 1 was determined according to the methods described below. Water and ash contents: JIS-M8812 (1993) Total calorie: JIS-M8814 (1993) 5 Element composition: JIS-M8819 (1997) The waste wood was continuously introduced into a heating furnace kept at a temperature of 550 degrees C and a pressure of 0.103 MPa. The amount of the waste wood fed was 286 kg/h and an apparent residence time in the heating furnace was about 10 1 hour. The pyrolysis gas generated by thermal decomposition was obtained at the top of the heating furnace at a rate of 244 kg/h. The gas was introduced into the reforming furnace kept at a temperature of 950 degrees C and a pressure of 0.103 MPa. Simultaneously, overheated steam (180 degrees C and 1 MPa) was introduced into the 15 reforming furnace at a rate of 50 kg/h to reform the gas. The reformed gas of 950 degrees C was obtained at a rate of 294 kg/h. Then the gas was brought into contact with water in the cooling instrument to be cooled down to a temperature of 40 degrees C. The composition of the gas is as shown in Table 2. 20 Table 2. Gas Composition after Reformed (in volume %) N2 02 C02 CO H2 CH4 CxHy H20 Gas Composition 0.00 0.00 21.4 16.7 58.5 1.4 0.0 2.0 The gas composition in Table 2 was determined with gas chromatography, from Shiamadzu Co. Ltd., GC8A. 25 Then the cooled gas was introduced into the hydrogen purifying instrument and 7 the hydrogen-enriched gas with a hydrogen content of 95 volume % was recovered at a rate of 30 kg/h. The composition of the hydrogen-enriched gas is as shown in Table 3. 5 Table 3. Gas Composition after the Purification (in volume %) N2 02 C02 CO H2 CH 4 CxHy H20 Gas Composition 0.00 0.00 2.1 1.0 95.5 1.4 0.0 0.0 The gas composition in Table 3 was determined with the same gas chromatography for Table 2. 10 INDUSTRIAL APPLICABILITY The present invention provides a process to effectively utilize energy and gas obtained from organic waste, such as thinned wood, driftwood, waste wood, waste plastics, garbage, sludge, mown grass, and paper industry sludge. With the present invention, unused resources or organic waste can be recycled as energy source. 15 Conventionally, waste disposal and energy production were performed separately but energy efficiency can be raised by performing these in one and the same equipment. It is also possible to recover hydrogen without generating carbon dioxide. 8

Claims (10)

1. A process for recovering hydrogen, comprising heating organic waste at a temperature of from 500 to 600 degrees C under a non-oxidative atmosphere, mixing a pyrolysis gas thus generated with steam at a temperature of from 900 to 1000 degrees C, 5 and separating hydrogen from a reformed gas thus obtained.

2. The process according to Claim 1, wherein the organic waste is one selected from the group consisting of thinned wood, driftwood, waste wood, waste plastics, garbage, sludge, mown grass, and paper industry sludge.

3. The process according to Claim 1, wherein the organic waste is one selected 10 from the group consisting of thinned wood, driftwood and waste wood.

4. The process according to any one of Claims 1 - 3, wherein a means to separate hydrogen from the reformed gas for recovering hydrogen is one selected from the group consisting of PSA, membrane separation, and cryogenic separation.

5. The process according to any one of Claims 1 - 3, wherein a means to separate 15 hydrogen from the reformed gas for recovering hydrogen is PSA.

6. The process according to any one of Claims 1 - 5, wherein the temperature at which said organic waste is heated under a non-oxidative atmosphere is in a range of from 530 to 570 degrees C.

7. The process according to any one of Claims 1 - 6, wherein the temperature at 20 which the generated pyrolysis gas is mixed with steam is in a range of from 950 to 1000 degrees C.

8. The process according to any one of Claims 1 - 7, wherein a pressure at which said organic waste is heated under a non-oxidative atmosphere and a pressure at which the generated pyrolysis gas is mixed with steam are 1 MPa or less. 25

9. The process according to any one of Claims 1 - 7, wherein a pressure at which said organic waste is heated under a non-oxidative atmosphere and a pressure at which the generated pyrolysis gas is mixed with steam are in a range of from 0.1 MPa to 1 MPa.

10. The process according to any one of Claims 1 - 9, further comprising producing 30 hydrogen by reacting carbon monoxide and water with each other both contained in said reformed gas obtained after the mixing with steam. 9