Patent Application
20230174877
This invention involves a biomass gasification device which utilizes heat carriers.
As a gasifier for biomass with high ash content (e.g., sewage sludge containing 20% ash by weight) can be dried and then pyrolyzed in an air-blown fluidized bed pyrolyzer operating at a temperature range of 500 to 800° C. The pyrolysis gas is combusted with air at a high temperature (in the range of 1,000 to 1,250° C.) and the heat produced is used to generate steam for turbine power generation (Japanese Unexamined Patent Application Publication No. 2002-32-2902). The pyrolysis of biomass with high ash content at temperatures in the range of 450 to 850° C. in an air-blown circulating fluidized bed vessel is also used to generate turbine power. On the other hand, the pyrolysis gas containing tar is reformed under the presence of oxygen at temperatures in the range of 1,000 to 1,200° C. (Japanese Unexamined Patent Application Publication No. 2004-51-745). To prevent the flowing heat carriers from sticking to one another, in a similar way as described above, the pyrolysis residue (also referred to as char) is separated from the heat carriers via pyrolysis and is recovered using a cyclone. After that, the char is granulated and then fed into the circulating fluidized reforming vessel, in which it is sintered at a temperature in the range of 900 to 1000° C. (Japanese Granted Patent Publication No. 4155507).
Moreover, in this embodiment, a medium for carrying heat (referred to as heat carrier), a preheater which supplies heat to the heat carriers, a reformer in which the steam methane reforming of the pyrolysis gas occurs, a pyrolyzer which thermally decomposes the raw material (i.e., woody biomass), a char separator which separates the char from the heat carriers, and a hot-air furnace which generates hot air by burning the char produced, are described (Japanese Unexamined Patent Application Publication No.
In addition, a facility is proposed which is characterized by two independent apparatus comprising of a pyrolyzer which operates in the thermal decomposition zone, and a reformer which operates in the reaction zone. These may either be connected in series or in parallel. The heat carrier passes through a heating zone (approximately 1100° C.), a reaction zone (in the range of 950 to 1000° C.), a thermal decomposition zone (in the range of 550 to 650° C.) followed by a char separation stage, and subsequently returns to the heating zone. The char, which was obtained from its separation from the heat carriers exiting the pyrolyzer, is burned in a combustion device to generate a heat-decomposed coke. There is a previously described method for producing gas with high calorific value from an organic substance or its mixture by heating the heat carriers in a heating zone, utilizing sensible heat (Japanese Granted Patent Publication No. 4264525).
Furthermore, the pyrolysis gas is introduced from the pyrolyzer to a pyrolysis gas reformer. A gasification method in which a pipe allowing the introduction of pyrolysis gas is installed on the side of the pyrolyzer, below the top of the preheated heat carriers has also been previously described (Japanese Unexamined Patent Application Publication No. 2019-65160).
In the conventional arrangement, the spherical ceramic balls, which serves as heat carriers in the preheater and the pyrolyzer, can become restricted, preventing it from flowing, hence, becoming stagnant.
Considering this, the present invention describes a biomass gasification device that allows the heat carriers to move smoothly within a temporary-holding vessel such as a preheater or a pyrolyzer.
A biomass gasification device according to the present invention comprises:
a vessel;
a baffle provided within the vessel;
and an outlet provided below the baffle to discharge the heat carriers. A gap for allowing the heat carriers to pass through may be provided between the baffle and the interior side walls of the vessel. Otherwise, piping to allow the heat carriers to pass through the inner wall of the side part of the vessel may be provided.
In the biomass gasification device according to the present invention, the temporary holding vessel is a preheater that preheats the heat carriers, and the outlet is the outlet of the preheater. The heat carrier discharged from the preheater outlet may be fed to the pyrolyzer.
In the biomass gasification device according to the present invention, the temporary holding vessel is a pyrolyzer that receives a supply of heat carriers preheated in a preheater. In the pyrolyzer, the pyrolysis of biomass occurs using with the heat input coming from the heat carriers. The outlet is the pyrolyzer outlet. The heat carriers discharged from the pyrolyzer outlet may be fed to the preheater through a recirculation system.
In the biomass gasification device according to the present invention, the upper surface of the baffle may have its central section positioned higher than its peripheral section, and a sloping surface may be provided between the central section and the peripheral section.
In the biomass gasification device according to the present invention, the bottom surface of the baffle may have its central section positioned lower than the peripheral region, and a sloping surface may be provided between its central section and its peripheral section.
In the biomass gasification device according to the present invention, several fixing members for fixing the main body of the baffle to the interior side walls of the vessel are provided between the main body of the baffle and the interior side walls of the vessel. The gaps between the fixing members may serve as spaces to allow passage of the heat carriers towards the outlet.
In the biomass gasification device according to the present invention, the main body of the baffle is disk-shaped. The main body may be secured to the vessel by fixing members between the main body of the baffle and the interior side walls of the vessel or by fixing members on the back side of the main body.
In the biomass gasification device according to the present invention, the vessel has an upper body and a lower body below the upper body, wherein the cross-section of the lower portion of the upper body is smaller than the cross-section of the upper end of the lower body. The baffle is provided below the lower end of the upper body and a gap may be formed between the baffle and the lower body.
In the present invention, in the case wherein a gap is provided between the baffle and the interior side walls of the vessels for the heat carriers to pass through, or in the case wherein piping is provided in the interior side wall of the vessel for the heat carriers to pass through, the heat carriers contained in the temporary holding section of the preheater, pyrolyzer, or similar vessels, can flow smoothly.
As shown in
The heat carriers (30) (which may be also referred to as the heat carrying medium) are composed of a plurality of granules and/or lumps, preferably made of one or more materials selected from the group consisting of metals and ceramics. As for the metals, there is a preference for iron, stainless steel, nickel alloy, and titanium alloy. There is higher preference for stainless steel. As for the ceramics, there is preference for alumina, silica, silicon carbide, tungsten carbide, zirconia, and silicon nitride. There is higher preference for alumina.
The shape of the heat carriers (30) is preferably spherical (ball), but does not necessarily have to be a perfect sphere; it can be a spherical object with an elliptical or ellipsoidal cross-section. The diameter (i.e., maximum diameter) of the spheres is preferably in the range of 3 to 25 mm, more preferably in the range of 8 to 15 mm. If the upper limit of the diameter of the spherical material (25 mm) were exceeded, there is high likelihood for the heat carriers to become stationary inside the pyrolyzer (20) and cause blockage. On the other hand, if the diameter of the spherical material were less than the lower limit (3 mm), tar and dust adhering to the spherical material in the pyrolyzer (20) may cause the spherical material to stick to each other and cause blockage. For example, if the diameter of the spherical material were less than 3 mm, the tar and dust adhering to the spheres may cause the spheres to also adhere to the inner walls of the pyrolyzer (20). In the worst case, the flow through the pyrolyzer (20) may be blocked. In addition, when the spherical materials with tar attached is pulled out through the valve at the bottom of the pyrolyzer (20), due to the light weight of the spherical material that is less than 3 mm in diameter, and also due to the tar attached to it, they may not fall naturally and stick to the internals of the valve, resulting to blockage.
Biomass referred to in this embodiment refers to the so-called biomass resources. Biomass resources include plant biomass, such as thinned wood, lumber waste, pruning, forest residues, and unutilized lumber discarded from the forestry industries; vegetable residues and fruit tree residues discarded from agricultural industries; rice straw, wheat straw, rice husks, marine plants, and construction waste wood; biological biomass, such as livestock waste and sewage sludge; and miscellaneous domestic discharges, such as dust and food waste. This equipment described in this embodiment is preferably suitable for gasification of the described biomass resources. In any of the biomass resources, the ash content is preferably 5.0% or more (dry weight basis), more preferably 10.0 to 30.0% (dry weight basis), and even more preferably 15.0 to 20.0% (dry weight basis). In particular, the equipment described in this embodiment is suitable for the gasification of high ash content biomass, especially sewage sludge and livestock waste.
The heat carriers (30) that are preheated in the preheater (10), are fed to the pyrolyzer (20) by free fall from the preheater (10) via a valve. In the pyrolyzer (20), the heat from the heat carriers (30) induces the pyrolysis of the biomass fed into the pyrolyzer (20). The heat carriers (30) in the pyrolyzer (20) are discharged from the pyrolyzer (20) by free fall through a valve and preferably recirculated back to the preheater (10).
The biomass gasification device of the present embodiment has temporary holding section (10)(20) for storing the supplied heat carriers (30) and discharging the heat carriers (30). The temporary holding sections (10)(20) consists of: housings or vessels (111)(121); baffles (115)(125) which has a front surface, provided inside the housings (111)(121); and outlet sections (119)(129) provided below the baffles (115)(125) for discharging the heat carriers (30). The gap marked G in
In the present embodiment, as an example, the temporary holding sections refer to a preheater (10) and a thermal decomposition device or a pyrolyzer (20). Baffles (115)(125) may be provided inside the housings or vessels (111)(121) of the preheater (10) and the thermal decomposition device or the pyrolyzer (20).
More specifically, as shown in
Also, as shown in
The heat carriers (30) discharged from the pyrolyzer outlet (29) is returned to the discharge treatment section (240) and through the circulation section (290). The heat carriers (30) are then re-introduced to the preheater (10), which is located at the top (see
In addition, unlike the configurations shown in
More specifically, as shown in
Moreover, as shown in
Furthermore, even when the pipe sections (131)(141) are provided, as shown in
The pyrolyzer (20) and/or preheater (10), which comprises of the upper bodies (111a)(121a) and the bottom cone-shaped lower bodies (111b)(121b) serve as vessels for a moving bed. After the heat carriers (30) in the upper bodies (111a)(121a) moved laterally outwards from the bottom of the upper bodies (111a)(121a) towards the upper part of the lower bodies (111b)(121b), the heat carriers (30) move down along the walls of the lower bodies (111b)(121b). The lower bodies (111b)(121b) may have a structure that allows the discharge of the heat carriers (30) from the lower bodies (111b)(121b).
In the pyrolyzer (20) located below the preheater (10) in the biomass gasification device described in the present embodiment, the upper portion (top portion), preferably at the top-most portion, is provided with an inlet (127) for the heat carriers (30) (see
More specifically, as shown in
Consider the first-set of the two top and bottom damper valves (51a) and (51b) to be in close position. First, the upper first damper valve (51a) is opened to allow the heat carriers to drop and flow through the piping. The heat carriers then fill the space between the second damper valve (51b) and the first damper valve (51a). Next, the first damper valve (51a) is closed, and the second damper valve (51b) is opened. The heat carriers that were filling the space between the second damper valve (51b) and the first damper valve (51a) is introduced into the pyrolyzer (20), or withdrawn from the pyrolyzer (20). By repeating these valve operations, the heat carriers are almost continuously introduced into and almost continuously withdrawn from the pyrolyzer (20). This introduction and withdrawal method is an example and the method that may be considered in this embodiment is not limited to this method.
In the present embodiment, a second set of valves (90) between the pyrolyzer (20) and the discharge treatment section (240) may be provided. The second set of valves (90) may have a pair of damper valves (91a)(91b) and a swing valve (92), which is an example of an adjusting/tuning section. Similar to the first set of valves (50), the second set of valves (90) may also have a swing valve (92), a first damper valve (91a) and second damper valve (91b), which may be arranged in order, from top to bottom. As shown in
Most of the heat required for the pyrolysis of biomass in the pyrolyzer (20) is provided by the heat possessed by the heat carriers (30), which are preheated to the temperatures described previously.
The preheater (10) is preferably installed above the pyrolyzer (20), where all of the heat carriers (30) can be heated to a predetermined temperature. The preheated heat carriers (30) can then be fed to the pyrolyzer (20).
The pyrolyzer (20) and/or the preheater (10) is/are installed in the upper bodies (111a)(121a) and the cone-type lower bodies (111b)(121b) and the heat carriers (30) in the upper bodies (111a)(121a). The heat carriers (30) in the upper bodies (111a)(121a) are transported laterally from the bottom of the upper bodies (111a)(121a) to the outer rim of the lower bodies (111b)(121b), and moves down along the walls of the lower body (111b)(121b). The structure may be configured to enable discharge of the heat carriers (30) from the bottom of the lower bodies (111b)(121b) to the outside.
The above features of the pyrolyzer (20) described solve the problems of conventional moving beds, in which even if the volume is designed to gasify a certain amount of biomass, only a small volume in the center where the heat transfer medium moves can be effectively gasified. In this embodiment, the problem that the preheater (10) does not allow the preheated heat carriers (30) to move smoothly to the pyrolyzer (20) can be solved, and the volume can be used effectively and evenly.
More specifically, by moving the heat carriers (30) so that it is discharged in the circumferential direction, as it does in this embodiment, the heat carriers (30) could fall uniformly in the plane at a uniform speed (see
There are no restrictions on the geometry of the upper bodies (111a)(121a), as long as the heat carriers (30) can move to the lower body. However, cylindrical and rectangular shapes are preferred.
There are no restrictions on the geometry of the lower bodies (111b)(121b), as long as the heat carriers (30) can be discharged at the bottom. However, inverted conical and inverted trapezoidal shapes are preferred.
The cross-section of the lower end of the upper bodies (111a)(121a) may be smaller than the cross-section of the upper end of the lower bodies (111b)(121b). If the cross-section is circular in shape, the lower end of the upper bodies (111a)(121a) diameter may be smaller than the diameter of the upper end of the lower bodies (111b)(121b). The lower bodies (111b)(121b) may be smaller. The top surface of the upper end of the lower bodies (111b)(121b) and the bottom surface of the upper bodies (111a)(121a) are connected and has to be continuous. A connecting wall extending from the outermost portion of (111b)(121b) to the lower end of the upper bodies (111a)(121a) may be provided.
Moreover, it is also not limited to the described configuration, as shown in
A baffle (115)(125) is provided below the lower end of the upper bodies (111a)(121a). The lower bodies (111b)(121b) may be provided around the outer periphery of the baffles (115)(125). In this configuration, the lower end of the upper bodies (111a)(121a) and the barriers (115)(125) in the vertical direction, and an aperture (23) is formed between the lower end of the upper bodies (111a)(121a) and the baffles (see
The baffles (115)(125) may be installed at the center of the lower bodies (111b)(121b). The in-plane centers of the upper bodies (111a)(121a), lower bodies (111b)(121b), and baffles (115)(125) may coincide. In this manner, the heat will be uniformly distributed in the in-plane direction. This is beneficial because it allows the heat carriers (30) to flow uniformly in the in-plane direction.
The baffles (115)(125) are not limited to any particular shape, as long as they achieve the above purposes. When the lower bodies (111b)(121b) are inverted conical or inverted conical trapezoidal in shape, the baffles (115)(125) installed in the upper bodies (111a)(121a) and in the lower bodies (111b)(121b) may have the following preferred shapes: conical, inverted conical, and coma-shaped.
The front surface (top surface in this embodiment) of the baffles (115)(125) may be positioned such that the central region is higher than the peripheral region. A sloping surface may be provided between the central region and the peripheral regions. As an example, a conical (see
Moreover, the back surface of the baffles (115)(125) (the bottom surface in this embodiment) may be positioned such that the central region is lower than the peripheral region. It may be positioned in a position so that a sloping surface is provided between the central region and the peripheral region. As an example, a conical (see
The configurations presented in
Furthermore, note that when the shapes of the lower bodies (111b)(121b) are pyramidal, the baffles installed between the upper bodies (111a)(121a) and the lower bodies (111b)(121b) are preferred to be pyramidal, inverted pyramidal, or its combination (115)(125).
In the conical, inverted conical, and coma-shaped baffles (115)(125), the heat carrier (30) flows along the baffles installed in the lower bodies (111b)(121b) as indicated by the arrows shows in
As shown in
The main bodies (115a)(125a) of the baffles (115)(125) within the vessels (111)(121) may be disk-shaped (see
This form of the system may be incorporated into a conventional biomass gasification device.
The biomass gasification device described in this embodiment includes a pyrolyzer (20) which has a biomass feed inlet with a non-oxidizing gas feed inlet and/or a steam inlet in line. The pyrolysis gas reformer (40) has a steam inlet and a reformed gas outlet. The pyrolysis gas generated in the pyrolyzer (20) is introduced to the pyrolysis gas reformer (40). Piping (200) between the pyrolyzer (20) and the pyrolysis gas reformer (40) that is used to introduce the pyrolysis gas from the pyrolyzer (20) to the pyrolysis gas reformer (40) as described above is provided. The pyrolyzer (20) and pyrolysis gas reformer (40) are each equipped with an inlet and outlet for a preheated heat carriers to perform pyrolysis of biomass and reforming of pyrolysis gas generated by pyrolysis of biomass using the heat from the heat carriers. The pyrolyzer (20) and pyrolysis gas reformer (40) are installed in parallel to the flow of the heat carriers. The pyrolysis gas inlet pipe (200) is provided on both sides of the pyrolyzer (20) and the pyrolysis gas reformer (40), below the surface of the heat carrier bed or layer formed in the pyrolyzer (20) and the pyrolysis gas reformer (40). The pyrolysis gas inlet pipe (200) is installed perpendicularly to the direction of gravity. The pyrolyzer (20) and/or a preheater (10) has a moving bed of heat carriers (30) in the upper bodies (111a)(121a) and the bottom cone-shaped lower bodies (111b)(121b). The heat carriers (30) in the upper bodies (111a)(121a) are moved laterally from the bottom of the upper bodies (111a)(121a), along the wall of the lower bodies (111b)(121b), and then discharged from the bottom of the lower bodies (111b)(121b).
Moreover, the pyrolyzer (20) has a biomass feed inlet with a non-oxidizing gas feed inlet and/or a steam inlet in line. The pyrolysis gas reformer (40) has a steam inlet and a reformed gas outlet. Piping (200) between the pyrolyzer (20) and the pyrolysis gas reformer (40) that is used to introduce the pyrolysis gas from the pyrolyzer (20) to the pyrolysis gas reformer (40) as described above is provided. The pyrolyzer (20) is further provided with an inlet and outlet for the preheated heat carriers to perform pyrolysis of the biomass by the heat coming from the heat carriers. Furthermore, the pyrolysis gas reformer (40) performs steam reforming of the pyrolysis gas generated by the pyrolysis of biomass. The pyrolysis gas reformer (40) is further equipped with an air or oxygen inlet to perform steam reforming by partial oxidation of the pyrolysis gas generated by the pyrolysis of the biomass with the air or oxygen. A pyrolysis gas inlet pipe (200) is provided on the side of the pyrolyzer (20) below the surface of the heat carrier bed or layer formed in the pyrolyzer (20). The pyrolyzer (20) and/or the preheater (10) is equipped with the upper bodies (111a)(121a) and the bottom cone-shaped lower bodies (111b)(121b). The heat carriers (30) in the upper bodies (111a)(121a) are moved laterally from the bottom of the upper bodies (111a)(121a), along the wall of the lower bodies (111b)(121b), and then discharged from the bottom of the lower bodies (111b)(121b).
In another form of this embodiment, the biomass gasification device consists of a pyrolyzer (20) in which biomass is heated in a non-oxidizing gas atmosphere or in a mixed gas atmosphere of non-oxidizing gas and steam; a pyrolysis gas reformer (40) in which the gas generated in the above pyrolyzer (20) is reformed in the presence of steam; and preheated heat carriers (30) that are fed from the pyrolyzer (20). The heat of the heat carriers (30) is used to reform the gas from the pyrolyzer (20) in the presence of steam. The pyrolysis of the biomass is performed, and then the pyrolysis gas generated by the pyrolysis of the biomass is introduced into the pyrolysis gas reformer (40) to perform steam reforming of the pyrolysis gas. The pyrolysis gas generated by the pyrolysis of the biomass is introduced into the pyrolysis gas reformer (40) through the pyrolysis gas inlet pipe. The pyrolysis gas is introduced into the pyrolysis gas reformer (40). At the same time, the pyrolysis gas is partially oxidized by air or oxygen introduced into the pyrolysis gas reformer (40). In the pyrolyzer (20) and/or preheater (10) consisting of the upper bodies (111a)(121a) and a bottom cone-shaped lower bodies (111b)(121b), the heat carriers (30) in the upper bodies (111a)(121a) are moved laterally from the bottom of the upper bodies (111a)(121a), along the wall of the lower bodies (111b)(121b), and then discharged from the bottom of the lower bodies (111b)(121b).
An example of this mode of operation is described below.
The heat carriers (30) are preheated in the preheater (10) before being introduced into the pyrolyzer (20). The heat carriers (30) are preferably heated to 650-800° C., more preferably 700-750° C. The lower limit (i.e., below 650° C.) may lead to the biomass (e.g., high ash biomass) not sufficiently pyrolyzed in the pyrolyzer (20), resulting to a decrease in the amount of the pyrolysis gas generated. On the other hand, if the temperature exceeds the upper limit (i.e., 800° C.), volatilization of phosphorus and potassium may occur, resulting in blockage and corrosion of piping due to the formation of diphosphorus pentoxide and potassium pentoxide. In addition, it only gives off extra heat, and no significant increase in effectiveness can be expected, which in turn only leads to higher cost. It also leads to a decrease in the thermal efficiency of the device.
The heat carriers (30) heated to a predetermined temperature in the preheater (10) is then introduced into the pyrolyzer (20). In the pyrolyzer (20), the heat carriers (30) are brought into contact with the biomass supplied to the pyrolyzer (20) via the biomass feed inlet (220). Contact between the heat carriers (30) and the biomass causes the biomass to be heated and pyrolyzed, producing pyrolysis gas. The generated pyrolysis gas passes through the pyrolysis gas introduction pipe (200) and is introduced into the pyrolysis gas reformer (40). At this point, tar, dust, and other particles contained in the generated pyrolysis gas are captured by the heat carriers (30). With tar and other particulates (soot, dust, etc.) adhering to the heat carriers (30), the heat carriers (30) are then discharged from the bottom of the pyrolyzer (20) leading to removal of most of the adhered tar and particulates.
The pyrolyzer (20) and/or preheater (10), which comprises of the upper bodies (111a)(121a) and the bottom cone-shaped lower bodies (111b)(121b) serves as the vessel for a moving bed. The heat carriers (30) introduced from the preheater (10) into the pyrolyzer (20) first enters the upper bodies (111a)(121a) of the pyrolyzer (20). The heat carriers (30) pass laterally through the upper bodies (111a)(121a) and pass through the opening of the lower body (23). The heat carriers (30) then pass through the baffle between the upper bodies (111a)(121a) and the lower bodies (111b)(121b), and move towards the lower bodies (111b)(121b).
Heat carriers (30) are introduced into the lower bodies (111b)(121b) along the walls of the lower bodies (111b)(121b) and moves to the bottom of the lower bodies (111b)(121b). The heat carriers (30) are discharged from the bottom of the lower bodies (111b)(121b).
Within the lower bodies (111b)(121b), a baffle (115)(125) is provided in the center portion, which facilitate the movement of the heat carriers (30) to the bottom of the lower bodies (111b)(121b). These baffles (115)(125) allow the heat carriers (30) to move towards the bottom of the lower bodies (111b)(121b), preventing them from staying in the interior of the lower bodies (111b)(121b).
By controlling the introduction of the heat carriers (30) into the pyrolyzer (20) and the withdrawal rate of the heat carriers (30) from the pyrolyzer (20), the thickness of the layer or the height of the bed of the heat carriers (30) can be controlled to the appropriate value, while also allowing the temperature of the pyrolyzer (20) to be controlled to the predetermined temperature described above. In this manner, the heat carriers (30) are introduced only in the pyrolyzer (20), and the heat is used for the pyrolysis of the biomass, while the pyrolysis gas reformer (40) is controlled through the introduction of steam and oxygen (or air). The process thereby makes it possible to control the internal temperatures of the pyrolyzer (20) and pyrolysis gas reformer (40) separately. This enables the reforming reaction in the pyrolysis gas reformer (40) to proceed at an appropriate temperature. In parallel, the pyrolysis of biomass in the pyrolyzer (20) can be carried out at an appropriate temperature.
The residence time of the biomass in the pyrolyzer (20) is preferably from 5 to 60 minutes, more preferably from 10 to 40 minutes, and even more preferably from 15 to 35 minutes. Below the lower limit (i.e., 5 minutes), heat is not uniformly transferred to the biomass and pyrolysis cannot uniformly conducted, resulting in a reduction in the amount of pyrolysis gas generated. On the other hand, even if the upper limit (60 minutes) is exceeded, no significant increase in pyrolysis can be observed. In fact, the equipment cost will increase. Here, the residence time of the biomass in the pyrolyzer (20) can be appropriately adjusted via the flow rate of the heat carriers (30) and the biomass feed rate.
When the pyrolysis gas reformer (40) and the pyrolyzer (20) are connected in series, the residence time in each vessel (i.e., the residence time for biomass pyrolysis in the pyrolyzer (20) and the residence time for decomposition of tar in the pyrolysis gas) are both considered. It was impossible to control the residence time required for the reforming reaction between pyrolysis gas and steam in the pyrolysis gas reformer (40) separately. The pyrolysis gas reformer (40) is heated by introducing steam and oxygen or air separately, and the pyrolysis gas is heated by partial oxidation of the pyrolysis gas. By using a system in which the pyrolysis gas is heated by partial oxidation of the pyrolysis gas, the residence time in each of the pyrolyzer (20) and the pyrolysis gas reformer (40) can be controlled independently.
As described above, the heat carriers (30) that have passed through the pyrolyzer (20) are discharged from the bottom of the pyrolyzer (20) together with the pyrolysis residue (char) of the biomass, and a small amount of tar and dust that remain attached to the heat carriers (30). Treatment of the discharged heat carriers (30) is carried out by conventionally known methods, such as separation of char in the discharge treatment section. The treated heat carriers (30) are recirculated to the preheater (10) to be supplied again to the pyrolyzer (20).
In the pyrolysis gas reformer (40), the pyrolysis gas generated by pyrolysis of biomass in the pyrolyzer (20) is introduced through the pyrolysis gas inlet pipe (200). The pyrolysis gas introduced into the pyrolysis gas reformer (40) is partially oxidized by air or oxygen, thereby heating the internals of the pyrolysis gas reformer (40). This allows the pyrolysis gas to react with steam to reform the pyrolysis gas into a hydrogen-rich gas.
The following examples will explain this embodiment in more detail, but this embodiment is not limited by these examples.
The biomass feedstock used in the example, and the gasifier used for pyrolysis of the biomass feedstock and pyrolysis gas reforming are as follows.
Sewage sludge was granulated and used as the biomass feedstock. The maximum size of the granulated sewage sludge was in the range of 6 to 15 mm. The properties of the sewage sludge are shown in Table 1. The composition of the ash obtained by combusting the sewage sludge are shown in Table 2.
For the data presented in Table 1: Moisture, volatile matter, and fixed carbon content were analyzed in accordance with JIS M8812. Ash content was analyzed in accordance with JIS Z7302-4: 2009. Higher Heating Value (HHV) was analyzed in accordance with JIS M8814. Carbon (C), hydrogen (H), and nitrogen (N) were analyzed in accordance with JIS Z 7302-8:2002. Sulfur (S) was analyzed in accordance with JIS Z 7302-7:2002. Chlorine (Cl) was analyzed in accordance with JIS Z 7302-6:1999. Oxygen (O) was determined by subtracting the sum of the mass percentages of C, H, N, S, Cl, and ash from 100. Ash, volatile matter, fixed carbon, and the elemental composition were all calculated on a dry basis. Moisture content was measured at the time of collection of the raw biomass material (sewage sludge).
For the data presented in Table 2: silicon dioxide, aluminum oxide, ferric oxide, magnesium oxide, calcium oxide, sodium oxide, potassium oxide, diphosphorus pentoxide, and manganese oxide were analyzed in accordance with JIS M8815. Mercury, chromium, cadmium, copper oxide, lead oxide, zinc oxide, and nickel were analyzed in accordance with JIS Z 7302-5:2002.
The gasifier basically consists of a pyrolyzer (20), a pyrolysis gas reformer (40), and a preheater (10) (see
In this embodiment, a preheater (10) is provided above the pyrolyzer (20). The preheater (10) preheats the heat carriers (30) supplied to the pyrolyzer (20). The preheater (10) preheats the heat carriers (30) to be fed to the pyrolyzer (20), and the heated heat carriers (30) are fed to the pyrolyzer (20). The preheated heat carriers (30) are fed to the pyrolyzer (20) to provide the heat necessary for the pyrolysis of the biomass. The heat carriers are then discharged from the bottom and recirculated to the preheater (10). On the other hand, the pyrolysis gas generated in the pyrolyzer (20) is introduced through the pyrolysis gas inlet pipe (200) to the pyrolysis gas reformer (40).
In this embodiment, air or oxygen is separately introduced into the pyrolysis gas reformer (40) through the air or oxygen inlet pipes (261)(262). The introduction of air or oxygen causes partial oxidation of the pyrolysis gas. Steam is simultaneously introduced through steam inlet (242). The pyrolysis gas is reformed by steam, and the resulting reformed gas is discharged via the reformed gas outlet (230). Alternatively, air or oxygen, and steam can also be introduced through the air or oxygen inlet pipe (262) and steam inlet pipe (243) provided with the pyrolysis gas inlet pipe (200). All the air or oxygen, and steam can be introduced through the provided air or oxygen inlet pipes (261)(262) and the steam inlet pipes (242)(243).
The inner diameter of the straight body portion of the pyrolyzer (20) is about 550 mm. The height is about 1100 mm. And the internal volume is about 260 liters. On the other hand, the inner diameter of the straight body portion of the pyrolysis gas reformer (40) is about 600 mm. The height is about 1200 mm. And the internal volume is about 360 liters.
Moreover, the pyrolysis gas inlet pipe (200) is provided on the side of the pyrolyzer (20), below the top surface of the bed of heat carriers formed in the pyrolyzer (20). On the other hand, for the pyrolysis gas reformer (40), the pyrolysis gas inlet pipe (200) is provided on the side of the pyrolysis gas reformer (40), below the top surface of the bed of heat carriers formed in the pyrolysis gas reformer (40). The pyrolysis gas inlet pipe (200) is provided on the side near the bottom of the vessel. The pyrolysis gas inlet pipe (200) is provided horizontally, or perpendicular to the direction of gravity. The pyrolysis gas inlet pipe (200) has a length of about 1000 mm and an inner diameter of about 80 mm. The inside of the pipe is covered with heat insulating material, and the protruding portion is also covered with a heat insulating material. The heat carriers (30) are approximate spheres with a diameter (maximum diameter) of 10 to 12 mm. Alumina is used as the material for the heat carriers (30).
The interiors of the pyrolyzer (20) and the preheater (10) are pre-filled with heat carriers (30) to a height of about 70% of the respective vessels. The heat carriers (30) are then heated in the preheater (10) to a temperature of about 700° C. Then, the heat carriers (30) are introduced to the pyrolyzer (20), from the top of the pyrolyzer (20), at a rate of 200 kg/h. The appropriate amount of heat carriers (20) is withdrawn from the bottom of the pyrolyzer (20), and the circulation of the heat carriers (30) is started.
The circulation of the heat carriers (30) gradually raises the temperature of the gas phase inside the pyrolyzer (20), and the temperature of the vessel itself. While continuing the described circulation of the heat carriers (30), the temperature of the heat carriers (30) inside the preheater (10) is gradually raised to 800° C. After reaching this temperature, the circulation of the heat carriers (30) is continued to gradually increase the temperature of the gas phase inside the pyrolyzer (20). The temperature of the gas phase in the pyrolyzer (20) is increased to 550° C. When the temperature of the gas phase in the pyrolyzer (20) exceeds 550° C., raw biomass material, nitrogen gas, and steam are introduced from the raw biomass material feed inlet port (220), non-oxidizing gas inlet port (250), and steam inlet port (241), respectively. The temperature of the pyrolyzer (20) is controlled to be at 600° C.
At this time, the heat carriers (30) are deposited forming beds in the pyrolyzer (20). The deposited amount is about 60% of the volume of the pyrolyzer (20). The amount of the heat carriers (30) withdrawn from the pyrolyzer (20) is the same as the feed rate to the pyrolyzer (20), which is 200 kg/h. The temperature of the heat carriers (30) at the time of withdrawal is 650° C. However, the amount of the heat carriers (30) withdrawn from the pyrolyzer (20) can be controlled depending on the temperature conditions.
In the operation described above, sewage sludge as raw biomass material (biomass feedstock) is fed into a metered feeder. The raw biomass material (biomass feedstock) is continuously introduced into the pyrolyzer (20) from the biomass feed inlet (220) using a feed rate of about 22 kg/h (dry basis).
The temperature of the pyrolyzer (20) gradually decreases as the raw biomass material (biomass feedstock) is introduced. At the same time, nitrogen gas and superheated steam are introduced into the pyrolyzer (20) while adjusting the feedstock supply rate. The temperature of the pyrolyzer (20) is maintained at 600° C. and the pressure in the pyrolyzer (20) is maintained at 101.3 kPa.
In this process, nitrogen gas is introduced through the non-oxidizing gas inlet (250) that located at the top of the pyrolyzer (20), at a final rate of 1000 liters/h at a constant volume. The steam used is superheated (160° C., 0.6 MPa). The steam is introduced at a final constant rate of 1 kg/h via the steam inlet (241) located at the top of the pyrolyzer (20). The residence time of the raw biomass material (biomass feedstock) in the pyrolyzer (20) is about 1 h. This results in 15 kg/h of gas produced by pyrolysis in the pyrolyzer (20). In addition, a total of 6.5 kg/h of char and ash are discharged as pyrolysis residue via the pyrolysis residue (char) outlet (210).
The pyrolysis gas obtained in the pyrolyzer (20) is subsequently introduced into the pyrolysis gas reformer (40) through the pyrolysis gas inlet pipe (200) from the lower side of the pyrolyzer (20).
Although the temperature in the pyrolysis gas reformer (40) becomes unstable when the pyrolysis gas is first introduced, by adjusting the amount of superheated steam introduced through the steam inlet (242), and the amount of oxygen introduced from the air or oxygen inlet (261), the pyrolysis gas is partially oxidized and the temperature inside the pyrolysis gas reformer (40) reaches 1000° C. The temperature inside the pyrolysis gas reformer (40) is adjusted so that the temperature inside the pyrolysis gas reformer (40) reaches 1000° C. At this time, the pyrolysis gas reformer (40) is maintained at a pressure of 101.3 kPa. The superheated steam from the steam inlet (242) provided at the bottom of the pyrolysis gas reformer (40) is introduced at a final constant volumetric rate of 3.7 kg/h. Oxygen from the air or oxygen inlet (261) is introduced at a final constant volumetric rate of 2.3 Nm3/h. However, this amount of oxygen is increased or decreased according to the actual degree of temperature increase inside the pyrolysis gas reformer (40).
In the operation described above, the pyrolyzer (20) is maintained at a temperature of 600° C. and a pressure of 101.3 kPa. The pyrolysis gas reformer (40) is maintained at a temperature of 950° C. and a pressure of 101.3 kPa. As a result of this process, reformed gas, at a temperature of 1000° C., is obtained from the reformed gas outlet (230) at a rate of 31 kg/h.
The produced reformed gas is collected in a rubber bag and the gas composition is analyzed by gas chromatography. Table 3 shows the composition of the collected reformed gas. The operation can be carried out for 3 consecutive days. During the operation period, continuous operation can be maintained without difficulties (e.g., problems caused by tar). Moreover, during the operation period, there were no problems caused by blockage of the heat carriers (30) in the pyrolysis gas inlet pipe (200) due to tar accumulation, etc. Smooth introduction of the pyrolysis gas from the pyrolyzer (20) to the pyrolysis gas reformer (40) was maintained. The amount of tar in the reformed gas taken from the outlet of the pyrolysis gas reformer (40) was about 10 mg/Nm3.
The reformed gas can be obtained in this manner. With the stable and continuous supply of the heat carriers (30) in the gasifier, the pressure fluctuations in the pyrolyzer (20) were reduced which also solves the problem of reduced gas separation capacity, thereby providing gas of stable quality.
In the biomass gasifier described, the heat carriers (30) in the pyrolyzer (20) and/or preheater (10) move laterally from the bottom of the cylindrical body to the outer side of the upper bodies (111a)(121a), and then move down along the walls of the lower bodies (111b)(121b) to its bottom from where the heat carriers (30) are discharged. This mechanism enables effective utilization of the full volume allowing efficient biomass pyrolysis.
This form of biomass gasification system is designed to convert biomass, preferably biomass with relatively high ash content, into reformed gas containing a large amount of hydrogen and other valuable gases. The system not only prevents blockage and corrosion of piping caused by the volatilization of diphosphorus pentoxide and potassium contained in the ash component of the biomass, but also suppresses N2O generation and reduces tar and soot generation. Therefore, it is expected to be used as a gasifier for biomass, especially biomass with relatively high ash content, in the future.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-080397 | Apr 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/017236 | 4/30/2021 | WO |
