Heat exchanger component, heat exchanger system comprising a plurality of such heat exchanger components and device for generating a combustible product gas from carbonaceous feedstocks with such a heat exchanger system

Abstract

Heat exchanger component (2) with a cylindrical main body (4) comprising a jacket (6) made of a heat-conducting material, a gas inlet (12) at one end and a gas outlet (14) at the other end of the cylindrical main body (4), wherein the gas inlet (12) and the gas outlet (14) open into the first cylindrical main body (4) transversely to the longitudinal direction of the cylindrical main body (4), and a rod-shaped component (18) arranged in the cylindrical main body (4) for forming an annular gap-shaped flow channel (16) between the gas inlet (12) and the gas outlet (14) in the cylindrical main body (4) for a gas flow (1) with solid particles, characterized in thatthat the gas inlet (12) has a constant first cross-sectional area (F1) over its length and that the gas outlet (14) has a constant second cross-sectional area (F2) over its length and the first cross-sectional area (F1) is larger than the second cross-sectional area (F2).,

Description

The invention relates to a heat exchanger component and a heat exchanger system having a plurality of such heat exchanger components for controlling the temperature of a gas stream with solid particles, and to a device for producing a combustible product gas from carbonaceous feedstocks, having such a heat exchanger system. Gas streams which are mixed with solid particles occur in the form of flue gas from combustion plants, as product gas stream in chemical reactors and in particular also as combustible product gas in the conversion of carbonaceous solids (wood gasification, coal gasification etc.). As a rule, the hot gas streams must be cooled with solid particles. If this cooling takes place in conventional liquid-gas heat exchangers, there is the risk that the solid particles are partially deposited in heat exchangers and the effectiveness of the heat transfer is thereby considerably impaired. Also, the operating times are reduced since the heat exchangers have to be cleaned from time to time.US 2008 / 0 098 653 A1 discloses a gasifier with a separator, for example a cyclone, which separates the ash or solids from the product gas. US 2006 / 0 054 381 A1 describes an exhaust gas silencer having a heat exchanger with an inlet and an outlet which are arranged in the longitudinal direction.US 2008 / 0 190 593 A1 and EP 1 965 165 A2 show a heat exchanger in which the gas inlet and the gas outlet open into the cylinder transversely to the longitudinal direction.CN 2 01 152 705 Y shows heat exchangers which are suitable for generating a flow running along the longitudinal axis of the heat exchangers.A problem with known heat exchangers is that the volume of the gas stream is reduced by cooling the gas stream in the heat exchanger component. The centrifugal forces in the helical gas flow are thus also reduced and the thickness of the Prandtl boundary layer increases and the heat transfer coefficient decreases. The smaller cross-sectional area of the gas outlet compared to the gas inlet ensures that the helical flow is maintained over the entire length of the annular-gap-shaped flow channel.It is therefore the object of the present invention to specify, starting from EP 1 965 165 A2, a heat exchanger component and a heat exchanger system with such heat exchanger components which, during the temperature control and in particular during the cooling of gas streams, are less easily soiled with solid particles and have a high heat transfer capacity. It is a further object of the present invention to specify a device for producing a combustible product gas from carbonaceous feedstocks with such a heat exchanger system.These objects are achieved by claims 1, 8 and 10.The gas inlet of the heat exchanger component has a constant first cross-sectional area over its length and the gas outlet has a constant second cross-sectional area over its length, wherein the first cross-sectional area is larger than the second cross-sectional area. This takes account of the fact that the volume of the gas stream is reduced by the cooling of the gas stream in the heat exchanger component and thus the flow speed is also reduced with the flow volume remaining the same. The smaller cross-sectional area of the gas outlet compared to the gas inlet ensures that the flow velocity at the gas inlet is approximately equal to the flow velocity in the gas outlet.Due to the annular-gap-shaped flow channel and the gas inlet and gas outlet opening transversely into the annular-gap-shaped flow channel, a helical flow around the rod-shaped component in the middle of the main body results in the annular-gap-shaped flow channel. The flow velocity of the gas stream with solid particles is very high in this case in the vicinity of the gas inlet, with the result that the Prandtl boundary layer on the inner side of the casing of the main body is comparatively thin. Due to the high centrifugal forces due to the high flow velocity, the Prandtl boundary layer is virtually compressed. The heat transfer between the gas stream and the jacket thus increases considerably, i.e. the outer side of the jacket releases more heat to the environment. Due to the high centrifugal forces, the solid particles also concentrate in a narrow region on the inside of the jacket, so that the probability of particle collisions and the caking of smaller particles to larger particles increases sharply. Larger solid particles can be separated more easily in downstream filters. Finally, the high flow velocity also prevents solid particles from depositing on the inside of the jacket, as would be the case with laminar flow.The embodiments according to claims 2 to 5 and 7 promote the formation and maintenance of the desired helical gas flow in the annular-gap-shaped flow channel.By the arrangement according to claim 6, instead of a gas-gas heat exchanger, a gas-liquid heat exchanger is provided which has a higher heat transfer performance.As a result of the volume reduction due to the heat removal, the flow velocity between the gas inlet and the gas outlet decreases. The centrifugal forces in the helical gas flow are thus also reduced and the thickness of the Prandtl boundary layer increases and the heat transfer coefficient decreases. In order to compensate for this undesirable effect, according to claim 8, a plurality, preferably three, heat exchanger components are connected in series to form a heat exchanger system. Here, the gas outlet of the i-th heat exchange member becomes the gas inlet of the (i+1)-th heat exchange member. Because the cross-sectional area of the gas outlet of the i-th heat exchanger component or of the gas inlet of the (i+1)-th heat exchanger component is smaller than the cross-sectional area of the gas inlet of the i-th heat exchanger component, the gas flow is accelerated back to the original flow velocity, so that high centrifugal forces again act in the region of the gas inlet of the (i+1)-th heat exchanger component and the Prandtl boundary layer is pressed tightly against the inner side of the jacket of the main body of the (i+1)-th heat exchanger component.The advantageous embodiment according to claim 9 takes into account the volume of the gas stream that decreases due to the cooling, or the volume of the annular-gap-shaped flow channel is adapted to the decreasing volume of the gas stream to be cooled in each stage of the heat exchanger system.By using the heat exchanger system in a device for generating a combustible product gas from carbonaceous feedstocks, this becomes more effective and, with the same performance, the structural volume is reduced due to the compactness of the heat exchanger system.Claim 10 relates to a compact device for producing a combustible product gas from carbonaceous feedstocks with a heat exchanger system according to claim 8 or 9.The remaining dependent claims relate to further advantageous embodiments of the invention.Further details, features and advantages of the invention are evident from the following description of exemplary embodiments with reference to the drawings.It shows FIG. 1 is a schematic sectional view of a first embodiment of a heat exchanger component according to the present invention; FIG. 2 is a schematic sectional view taken along the line A--A in FIG. 1; FIG. 3 shows a second preferred embodiment of a heat exchanger component according to the present invention; FIG. 4 shows a schematic sectional illustration of an exemplary configuration of a heat exchanger system having three heat exchanger components according to FIG. 1 ; and FIG. 5 shows a schematic sectional illustration of a device for producing a combustible product gas from carbonaceous feedstocks with a heat exchanger system according to FIG. 4.FIG. 1 shows a first embodiment of a heat exchanger component 2 for cooling a hot gas stream 1 with solid particles according to the present invention. The heat exchanger component 2 is a gas-air heat exchanger, i.e. the heat from the gas stream is released to the ambient air. The heat exchanger component 2 comprises a cylindrical main body 4 with a circular cross section, which is surrounded by a jacket 6. The left and right end faces 8a, 8b of the main body 4 are closed with flanges 10a and 10b. The jacket 6 consists of a material that conducts heat well and comprises an outer side 6 aand an inner side 6 b. In the region of the left end face 8 a, a gas inlet 12 opens into the main body 4 perpendicular to the longitudinal direction of the main body 4 and tangentially to the outer periphery of the main body 4; from the region of the right end face 8 bof the main body 4, a gas outlet 14 leads out of the main body perpendicular to the longitudinal direction of the main body 4. The gas inlet 12 has a constant first cross-sectional area F 1 over its length and the gas outlet 14 has a constant second cross-sectional area F 2 over its length. The cross-sectional area F 1 is larger than the cross-sectional area F 2. In the cylindrical main body 4, a rod-shaped component 18 with a circular cross section is arranged centrally in order to form an annular-gap-shaped flow channel 16 with an annular shape. The component 18 is fastened to the two flanges 10 aand 10 b.Due to the annular-gap-shaped flow channel 16 and the gas inlet 12 opening perpendicularly and tangentially into the annular-gap-shaped flow channel 16, a helical gas flow around the rod-shaped component 18 results in the annular-gap-shaped flow channel 16. The flow velocity V of the gas stream 1 with solid particles is very high in this case in the vicinity of the gas inlet 12, with the result that the Prandtl boundary layer 20 on the inner side 6 bof the casing 6 of the main body 4 is comparatively thin. Due to the high centrifugal forces due to the high flow velocity v, the Prandtl boundary layer 20 is quasi compressed. The heat transfer between the gas stream 1 and the jacket 6 thus increases considerably, i.e. the outer side 6 aof the jacket 6 gives off more heat to the environment.Due to the high centrifugal forces due to the forced helical gas flow 1, the solid particles also concentrate in a narrow region on the inner side 6 bof the casing 6, namely heavy solid particles nearer to the inner side 6 bof the casing 6 and lighter solid particles at a somewhat greater distance from the inner side 6 b. This greatly increases the probability of particle collisions and the caking of smaller particles to larger particles. Larger solid particles can be separated more easily in downstream filters. This enhanced particle collision zone is schematically shown in Fig. 2 which is a section taken along the line A-A in Fig. 1.Finally, the high flow velocity v in the gas stream 1 also prevents solid particles from depositing on the inner side 6 bof the jacket 6, as would have to be feared in the case of laminar flow conditions.Since heat is continuously extracted from the gas stream 1 via the jacket 6, the volume of the gas stream 1 is reduced, i.e. the volume flow continuously decreases with a constant mass flow. As a result, the flow velocity v decreases and consequently the centrifugal forces in the gas stream 1 also decrease, the thickness of the Prandtl boundary layer 20 increases and the heat transfer coefficient to the jacket 6 decreases between the gas inlet 12 and the gas outlet 14, This increase in the thickness of the Prandtl boundary layer 20 is illustrated in FIG. 1 along the inner side 6 bof the jacket 6 as a dashed line. This decrease in speed between gas inlet 12 and gas outlet 14 is compensated again by the cross-sectional area F 2 of gas outlet 14 that is reduced in comparison to gas inlet 12, so that flow speed v 2 at gas outlet 14 corresponds substantially to flow speed v 1 at gas inlet 12.FIG. 3 shows a second embodiment of a heat exchanger component which, in contrast to the first embodiment of the heat exchanger component 2, is designed as a gas-liquid heat exchanger. The heat exchanger component differs from the heat exchanger component 2 according to FIG. 1 in that the cylindrical main body 4 is embedded centrally in a cylindrical container 32 with a circular cross section. This results in a circular annular-gap-shaped flow channel 34 for a liquid heat exchanger medium 36, e.g. water, between the outer side 6 aof the jacket 6 and the inner side 32 a. The heat exchanger medium 36 flows turbulently in the annular-gap-shaped flow channel 34. The heat exchanger performance of the heat exchanger component is thereby significantly increased compared to the heat exchanger performance of the heat exchanger component 2.FIG. 4 shows an exemplary embodiment of a heat exchanger system 40 having a first, a second and a third heat exchanger component 30- 1, 30- 2 and 30- 3 and the cylindrical containers 32- 1, 32- 2, 32- 3 thereof and also annular-gap-shaped flow channels 34- 1, 34- 2, 34- 3 according to FIG. 3 ; the three heat exchanger components 30- iare connected in series one behind the other, such that the gas outlet 14- 1 of the first heat exchanger component 30- 1 becomes the gas inlet 12- 2 of the second heat exchanger component 30- 2 and the gas outlet 14- 2 of the second heat exchanger component 30- 2 becomes the gas inlet 12- 3 of the third heat exchanger component 30- 3.The following applies to the cross-sectional areas F sr(1), F sr(2) and F sr(3) of the annular-gap-shaped flow channels 16- 1, 16- 2 and 16- 3 of the three heat exchanger components 30- 1, 30- 2 and 30- 3:F sr(1) > F sr(2) > F sr(3). By reducing the cross-sectional areas F sr(1), F sr(2) and F sr(3) from one heat exchanger component 30- ito the next 30- (i+1), the reduction of the gas volume due to the cooling of the gas stream 1 is compensated.By reducing the cross-sectional areas F 2-i of the gas outlets of the individual heat exchanger components 30- irelative to the cross-sectional areas F 1-i of the gas inlets of the individual heat exchanger component 30- i, the flow velocity v at the respective gas inlets 12- iis kept constant, so that approximately the same centrifugal force conditions are also present in each heat exchanger component 30- i.FIG. 5 shows a schematic representation of an exemplary embodiment of an apparatus 100 for generating a combustible product gas from carbonaceous feedstocks with a heat exchanger system 40 according to FIG. 4 ; the apparatus 100 comprises a tubular gasifier vessel 50 whose ends are closed with an upper cover 52 and a lower cover 54. A tubular carburetor component 56 having an open end 561 and a closed end 562 protrudes with the open end 561 into the carburetor container 50. The closed end 562 of the carburetor body 56 projects through the top cover 52 out of the carburetor body 50. The open end 561 of the carburetor body 56 is positioned approximately in the center of the carburetor body 50. Spaced apart h below the open end 561 of the carburetor body 56 is a rotatable grate 57 which is periodically movable by a motor drive 57a passing through the lower cover 54. Into the closed end 562 of the carburetor component 56 protruding from the carburetor container 50, there open a feed 58 for carbonaceous feedstocks in the form of pourable particles, an air feed 60 for feeding combustion air L into the carburetor container 50, and a fill level sensor 62, with which the fill level of the particles in the tubular carburetor component 56 can be determined and monitored. In the region of the open end 561 of the carburetor component 56, a inspection shaft 64 is provided, which penetrates the outer wall of the carburetor container 50. The inspection shaft 64 is closed by a cover flange 70 which is part of a temperature measuring device 72. The temperature in the carburetor container 50 can be monitored by the temperature measuring device 72. By means of the inspection shaft 64, maintenance work, cleaning work can be carried out in the reactor container interior when the reactor is at a standstill.In the region below the grate 57, product gas is taken off from the gasifier vessel 50 via a product gas outlet 66, cooled in a heat exchanger system 40 according to FIG. 4 and purified in a downstream cyclone separator 74. The ash falling through the grate 57 is discharged from the gasifier vessel 50 by the product gas stream via the product gas outlet 66.Both the tubular carburetor container 50 and the tubular carburetor component 56 have an annular cross section and are arranged concentrically with respect to one another. The tubular carburetor component 56 has an inner diameter d which is smaller than the inner diameter D of the tubular carburetor container 50D = 260 mmd=174 mmh=174 mmList of reference numbers:V Flow speed of the gas stream in the flow duct 16 V 1 Flow speed of the gas stream 1 in the gas inlet 12 V 2 Flow speed of the gas stream 1 in the gas outlet 14 F 1 Cross-sectional area of the gas inlet 12 F 2 Cross-sectional area of the gas outlet 14 F sr(i) Cross-sectional areas of the flow ducts 16 L Combustion air h Distance between the grate 57 and the open end 561 of the gasifier component 56 d Inner diameter of the gasifier container D Inner diameter of the gasifier component 1 Gas stream with solid particles 2 Heat exchanger component 4 Cylindrical main body 6 Jacket of 4 6 a Außenseite of 6 6 b Innenseite of 6 8 a Linke of 4 8 b Rechte of 4 10 a Of the left flange 10 b Right flange 12 Gas inlet 14 Gas outlet 16 Annular gap-shaped flow channel 18 Rod-shaped component 20 Prandtl boundary layer 32 Cylindrical container 32 aInside of container 32 34 Annular gap-shaped flow channel 36 Liquid heat exchanger medium 40 Heat exchanger system 30- 1 Heat exchanger components 12- i Gas inlets 14- i Gas outlets 16- i Annular gap-shaped flow channels 100 Device for generating a combustible product gas from carbonaceous feedstocks 50 Gasifier container 52 Upper cover 54 Lower cover 56 Gasifier component 561 Open end of 56 562 Closed end of 56 57 Grate 57 a Motorized drive of 57 58 Feed for carbonaceous feedstocks 60 Air feed 62 Fill level sensor 64 Inspection shaft 66 Product gas outlet 70 Cover flange 72 Temperature measuring device 74 Cyclone separator

Claims

Heat exchanger component (2) having a cylindrical main body (4) which comprises a jacket (6) made of a heat-conducting material, a gas inlet (12) at one end face and a gas outlet (14) at the other end face end of the cylindrical main body (4), wherein gas inlet (12) and gas outlet (14) open into the first cylindrical main body (4) transversely with respect to the longitudinal direction of the cylindrical main body (4), and a rod-shaped component (18) arranged in the cylindrical main body (4) for forming an annular gap-shaped flow channel (16) between the gas inlet (12) and the gas outlet (14) in the cylindrical main body (4) for a gas stream (1) having solid particles, characterized in that, the gas inlet (12) having a constant first cross-sectional area (F 1) over its length and the gas outlet (14) having a constant second cross-sectional area (F 2) over its length, and the first cross-sectional area (F 1) being greater than the second cross-sectional area (F 2).Heat exchanger component according to claim 1, characterised in that the gas inlet (12) and the gas outlet (14) open into the cylindrical main body (4) perpendicular to the longitudinal direction of the cylindrical main body (4).Heat exchanger component according to one of the preceding claims, characterized in that the gas inlet (12) and / or the gas outlet (14) open tangentially into or out of the cylindrical main body (4).Heat exchanger component according to one of the preceding claims, characterized in that the cylindrical main body (4) has a circular cross section.Heat exchanger component according to one of the preceding claims, characterized in that the rod-shaped component (18) has a circular cross section and is arranged centrally in the first cylindrical main body (4).Heat exchanger component according to one of the preceding claims, characterized in that the cylindrical main body (4) is surrounded by a cylindrical container (32) in such a way that an annular gap-shaped flow duct (34) for a heat exchanger medium (36) is produced.Heat exchanger component according to one of the preceding claims, characterized in that the cross-sectional area (F sr) of the annular-gap-shaped flow channel (16) in the cylindrical main body (4) is constant between gas inlet (12) and gas outlet (14).Heat exchanger system (40) for cooling a gas stream (1) comprising solid particles, comprising a plurality of n heat exchanger components (2-i, 30-1) according to one of the preceding claims, which are connected to one another in series, such that the gas outlet (14-i) of the i-th heat exchanger component (2-i, 30-i) is the gas inlet (14-(i+1)) of the (i+1)-th heat exchanger component (2-(i+1), 30-(i+1)), where i = 1 to n-1.Heat exchanger system according to Claim 8, characterized in that the cross-sectional areas (F sr(1)) of the annular-gap-shaped flow channels (16-i) of the individual heat exchanger components (2-i, 30-i) are F sr ( i ) > F sr ( i + 1 ) where i = 1 to n-1.Device (100) for producing a product gas from carbonaceous feedstocks, in particular from pourable biomass particles, having a gasifier container (50), a feed (58) for the carbonaceous feedstocks in the upper region of the gasifier container (50), a rotatable grate (57) arranged in the lower region of the gasifier container (50) for supporting the carbonaceous feedstocks, an air feed (60) for feeding combustion air into the gasifier container (50), a product gas outlet (66) leading out of the gasifier container (50) from the region below the grate (57) for discharging the product gas from the gasifier container (50), and a heat exchanger downstream of the product gas outlet (66), characterized in that the heat exchanger is a heat exchanger system (40) according to one of the preceding claims 8 or 9.

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