Method and device for flue gas cleaning during the combustion of heavy oil and diesel fuels

Abstract

A method for cleaning flue gases produced during the combustion of heavy oil and diesel fuels for the operation of watercraft and drilling platforms, characterized in that: a) sulfur-containing flue gases produced as combustion residues during the combustion of heavy oil and diesel fuels are fed into a reactor (4''); b) soot particles and dust are separated from the gas stream in a first step by adsorption or absorption on a sorbent; c) sulfur-containing components are removed from the gas stream by dry sorption in a second, subsequent step; d) the gases are subsequently discharged via a chimney (9''), wherein the separation of soot particles and dust and the dry sorption of sulfur-containing components each take place in separate reactor sections (4a'', 4b'') in a reactor housing of a reactor (4'');and the gas stream for the separation of soot particles and dusts by adsorption or absorption onto sorbents is first directed into at least a first reactor area (4a'') and subsequently for the separation of sulfur-containing components into at least a second reactor area (4b''), wherein the areas are separated from each other by at least one partition wall (16'').

Description

The invention relates to a method according to the preamble of claim 1 and a device for carrying out a method according to the preamble of claim 11. Air pollution from ships and oil rigs has historically received less attention than, for example, from land-based industrial facilities. This is primarily due to the limited space required on ships. To reduce emissions of pollutants from ship combustion products into the air, Annex 6 was added to the International Convention for the Prevention of Pollution from Ships (MARPOL) in 1997. This annex specifically addresses air pollution from ships and entered into force on May 19, 2005. This directive, developed by the International Marine Organization, sets high standards for the quality of fuels used and for specific combustion systems. Furthermore, Annex 6 established specific North Sea SOx Emission Control Areas (SECAs). Large vessels such as tankers, luxury liners, and ferries almost exclusively use heavy fuel oil and diesel fuel, which produce exhaust gases with a high sulfur content during combustion. This high sulfur content, however, prevents the efficient afterburning of these exhaust gases by a catalytic converter. Sulfur-containing exhaust gases are known to be catalyst poisons, impairing the catalyst's function. The same applies to soot particles, which are produced in large quantities during the combustion of heavy fuel oil and diesel fuels on transport ships and oil rigs. Each ship has individual space requirements for its exhaust gas cleaning systems. Therefore, large-scale exhaust gas cleaning systems, such as those used in industrial plants, cannot be installed on a ship per se. German patent application DE 10 2008 041 530 A1 discloses a plant with a three-stage cleaning process. The first stage is nitrogen oxide cleaning, the second stage is particle cleaning, and the third stage is catalyzed NOx cleaning. DE 40 02 462 A1 discloses a multi-stage exhaust gas purification system. In this system, a material flow of the filter material first passes through a packed bed cell area on the clean gas side and then through a packed bed cell area on the raw gas side. US Patent 3,589,863 A discloses another method for desulfurizing exhaust gases from heavy oil combustion. The invention addresses the problem of creating a method that enables the cleaning of flue gases produced during the combustion of heavy oil and diesel fuel, and a device that can be installed on a ship. The invention solves this problem through the method of claim 1 and through the device of claim 11. Advantageous embodiments of the invention can be found in the dependent claims. This process is suitable for processing flue gases generated during the operation of watercraft and drilling platforms. Sulfur-containing flue gases, produced during the combustion of heavy fuel oil and diesel, are conveyed as combustion residues, for example, from an engine to a reactor via gas pipelines. In a first step, the soot particles and dust contained in the flue gas are separated from the gas stream by absorption or adsorption onto a sorbent. This is followed by the removal of the sulfur-containing components from the gas stream through dry sorption onto a sorbent, which can be similar to the previous sorbent or different in composition. To further reduce the pollutant emissions of the soot- and sulfur-free gases, the gas is conveyed via gas pipelines to a catalyst. After passing through the catalyst, the gases are discharged through a chimney.The gases discharged through the chimney now comply with the requirements set out by the SECA guidelines and the MARPOL Convention. The process can also be used on ship engines with turbochargers that generate a slight overpressure in the reactor. Additionally, the process according to the invention can be used for a full flow of exhaust gases leading away from the engine, as well as for a partial flow. Further applications include stationary agricultural machinery in which engines are operated with heavy fuel oil or diesel fuel. In this process, both the separation of soot particles and dust, as well as the dry sorption of sulfur-containing components, take place in separate reactor compartments within a single reactor. These reactor compartments are preferably arranged compactly within a single reactor housing, ensuring the continuous transfer of the sorbent from one compartment to another. This results in design advantages for systems constructed and operated using this method. Spent sorbent can then act as a soot particle filter, significantly reducing both material costs and the volume of material required within the reactor. According to an advantageous embodiment, at least one heat exchanger can be arranged in the reactor, whereby the thermal energy recovered from the flue gas can be advantageously used to liquefy the marine fuel. Liquefaction of the marine diesel is always necessary, as it cannot be used otherwise. This also results in a simplification of the equipment and a saving of space by eliminating the need for a separate liquefaction plant. The recovered thermal energy from the flue gas, which is approximately 150–200°C, can also be effectively used in other applications. The reactor is divided into at least two sections by at least one partition wall: one section for soot particle filtration and one section for flue gas desulfurization. The flow velocities of the two sorbent layers in these sections can differ in such a design. Furthermore, spent granular sorbent particles from the desulfurization section can be reused as soot particle filters. Thus, a single sorbent can be used in a material-saving manner, first for desulfurization and then as a soot particle filter. Alternatively, a sacrificial layer of, for example, limestone or pebbles can be used as a soot particle filter material to deposit soot particles on this surface. The sorbent is advantageously used as a continuously or discontinuously flowing granular bed, wherein the granules can have a diameter of 1-8 mm. In desulfurization, a calcium carbonate-containing granulate is advantageously used as a dry sorbent, which forms gypsum when, for example, sulfur trioxide is added. In desulfurization, a calcium hydroxide-containing granulate is advantageously used as a dry sorbent, which advantageously neutralizes acidic gases such as HCl. The purification of flue gas from nitrogen oxides by dry sorption can be advantageously carried out using urea granules, whereby NOx gases are reduced to nitrogen. The following drawings illustrate an embodiment of flue gas cleaning systems with which the inventive method is implemented. They show: Fig. 1 the circuit diagram of a non-inventive flue gas cleaning system with a two-stage reactor, Fig. 2 the circuit diagram of a non-inventive flue gas cleaning system with a single-unit reactor, Fig. 3 the circuit diagram of a flue gas cleaning system according to the invention with a reactor which is divided into two separate layer filter systems, and Fig. 4 a non-inventive flue gas cleaning system, wherein the staged cleaning takes place in two spatially separated reactor areas, Figs. 5a to 5d a sectional front view, a sectional rear view, a sectional side view and a perspective view of a ship with a non-inventive flue gas cleaning system. Fig. 1 shows a flue gas cleaning system 1 for heavy oil and diesel fuel-powered engines, for example on ships and drilling platforms, in which the flue gas is first expelled from the ship's engine 2 at a slight overpressure and directed via a shut-off valve 3 into a section 4a of a multi-part reactor 4. The raw gas temperature is measured by the sensor T1. In the reactor 4, soot particles are filtered in step one. These particles adhere to or are embedded in porous granules 5, which are conveyed through a feed line Z1 into a silo 11 and from there introduced into the reactor 4. In the reactor, intermediate shelves 20 are installed in such a way that the gas flow path is extended to several times the width of reactor 4. These intermediate shelves 20, for example steel plates, are spaced apart from each other in such a way as to allow the transport path of the granules 5. The gas then passes by diversion, with temperature control T2, into a separate area of ​​reactor 4b, where the second stage of the flue gas cleaning, sulfur reduction, takes place. In this stage, dry sorption of the sulfur-containing flue gas occurs on granules containing lime and calcium hydroxide. During combustion, sulfur and sulfur-containing oxides (sulfur dioxide and sulfur trioxide) are formed, which, during the transfer via calcium carbonate, are converted into calcium sulfates (gypsum), sulfites, and other sulfur-containing oxidation compounds (thiosulfates), etc.be converted and finally stored in a collection container 26 after discharge. The sorbent can contain additional additives, such as calcium hydroxide, calcium oxide, magnesium oxide, silicon dioxide, iron oxide, and aluminum oxide. For example, calcium hydroxide provides additional neutralization during the sorption of acidic gas components like HCl and HF, in addition to sulfur oxides. Fe₂O₃ and Al₂O₃ can also enable catalytic afterburning of flue gas components. The sorption and neutralization can be further enhanced by the addition of hydrate components. Urea granules can be used to remove nitrogen oxides from flue gas by dry sorption. These granules are preferably urea-doped limestone grains, but other absorbent, heat-resistant materials doped with urea can also be used as carrier materials. Another additional or alternative possibility for the removal of nitrogen oxides is the addition of platinum / ceramic compounds to the sorbent. If urea granules are used as a component of the sorption material, a catalyst can be integrated into the components, for example in cascade blocks, cascade plates and / or collection hoods of the reactors according to the invention, in order to enable denitrification at the typical ship exhaust gas temperatures of approximately 150-200°C. The catalysis can, for example, take place in a packed layer of catalyst granules. The integration of the catalyst allows for a significant saving of space required for a denitrification plant (DENOX plant) for flue gas denitrification on ships and also on land-based facilities. The sorption material is not limited to these additives and can be supplemented with further additives. Consumption of sorption material is prevented by continuously supplying a constant quantity of granules from a reservoir or silo 11, and by using the spent granules first as absorption and adsorption material in a stage 1 soot filter, before finally discharging them through a discharge opening. The operating principle of a bulk filter system is thus illustrated in the embodiment shown in Fig. 1. A key feature of this embodiment is the division of the reactor into two separate sections. This separation is achieved by a structurally defined barrier layer 4c, which offers such high resistance to the gas pressure that the gas cannot pass through this layer into the section above. At the same time, however, the barrier layer 4c allows the mass transfer of the granules from the upper to the lower section of the reactor. After passing through the two purification stages in reactor 4, the gas, following temperature control T3, is transported to the catalyst 6 by a fan 25 and its sulfur and soot content is checked by a measuring device 7. Depending on the measurement results, the fan 25 can be adjusted accordingly to minimize the sulfur and soot particle load on the catalyst 6.Since the reactivity of the granules, particularly during the dry sorption of SOx-containing gases in stage two, depends, among other things, on the temperature of the flue gas and the composition of the heavy fuel oil burned in the ship's engine, a bypass 8 allows, depending on the composition of the flue gas, less polluted flue gases to be diverted directly to the catalyst 6 and from there to a chimney 9. This can be individually adjusted by the user, for example to save sorption material at low engine power. Figure 2 illustrates another possibility for the two-stage cleaning of heavy oil and diesel flue gases on ships and drilling platforms. A fan 25' in the gas line 10' creates a negative pressure, which directs the resulting flue gas into a reactor 4'. Unlike the previous embodiment, this reactor 4' does not have a spatial separation between the first and second stages of the flue gas cleaning process. The gas is passed over a multitude of granule layers, with soot particle filtration and coarse SOx removal taking place in the lower part of the packed bed system. As the gas line passes through the reactor, the transition from the first to the second stage is gradual, with increasing amounts of SOx derivatives being deposited as gypsum on the calcareous granules, while soot particles are present only in small quantities. While the gas is transported from bottom to top in the reactor, the granule is transported in the opposite direction.At ground level, the reaction product is discharged from the packed bed filter system, primarily as gypsum or CaSO3. In this embodiment as well, a reservoir 11' or a silo is provided for the sorption material. An automatic level sensor 12' controls the discharge quantity of granules and informs the user of the fill level. After the sulfur and soot particle content of the flue gas has been reduced, it is directed to a catalyst 6' and from there released into the environment via a chimney. Temperature (T1', T2') and pressure (14', 15') are also monitored within the reactor. An advantageous design feature of these embodiments is that the respective system can be pressure-resistant. This is achieved by operating the ship's engines with a turbocharger, which generates a slight vacuum that is then transferred to the reactor system. Figure 3 shows a flue gas cleaning system 1'' in which the reactor 4'' is divided into two reactor sections 4a'' and 4b'' by a partition 16''. The partition preferably runs vertically within the reactor 2''. The sorption material is added to only one side of the reactor, while a loop 17'' is constructed at the bottom of this side, which allows the granules to be transported to the top of the second side of the reactor. Thus, even the granules unsuitable for complete sulfur adsorption are used again as a soot filter and for a coarse pre-cleaning of the sulfur-containing flue gas. The gas first passes through the first part of reactor 4a'' and is then transferred to the second part of reactor 4b'', where soot particle filtration takes place in the first part of the reactor and a reduction in sulfur-containing flue gas occurs in the second part.The spent sorbent material is discharged from the reactor at the bottom of the soot particle filter. Following cleaning, the gas is transported by a fan to the catalyst, which ensures the complete combustion of the remaining flue gas components. The gas is then released into the environment via a 9" chimney. Figure 4 shows a reactor or flue gas cleaning system 1"' in which the stages of soot particle filtration and flue gas desulfurization take place spatially separated in two reactor sections 4a"', 4b"' with two reactor casings. The sorption material is initially loaded into a silo located at the top of a second reactor section 4b"' for flue gas desulfurization. After the sorption material has fulfilled its function of desulfurizing the gas and can only filter out a small portion of sulfurous exhaust gases from the flue gas, it is transferred to the first reactor section 4a"', where it refills the silo or reservoir 11"' at the top of this reactor section. The granules 5"' now serve exclusively for soot filtration and coarse desulfurization of the flue gas. Once the granules are completely saturated with sulfur oxides, the silo or reservoir 11"' at the top of this reactor section is filled with sorbent material.Once the sorbent material has transformed into gypsum and absorbed a corresponding amount of soot particles, it is discharged from the packed bed filter system at the bottom into a discharge container 18". Other essential components of the flue gas cleaning system, such as the fan 25", temperature sensor 13", level sensor 12", and automated airlocks 19" for discharging the sorbent material from the packed bed filter system, are provided analogously to the previous embodiments. Pressure monitoring 14" is carried out by pressure sensors, which then regulate the fan 25" to the appropriate speed. The packed bed filter system can be bypassed by a bypass 8"' to direct already low-level pollutants or only small amounts of exhaust gases directly to the catalyst 6" and thus not burden the catalyst function. Figures 5a to 5d depict a flue gas cleaning system 1"" in a ship. The flue gas cleaning system 1"" essentially corresponds to the features already described in embodiment or variant 1 in Figure 1. As can be seen in Figure 5a, the flue gas cleaning system has a lower section for soot particle filtration 4a"", a middle thin section as a barrier layer 4c""", and an upper section 4b"" for flue gas desulfurization. A silo 11"" allows for the storage of granules 5"", which can then be discharged into the flue gas desulfurization section 4b""". The diesel engine and chimney are not shown. A pipe 21 extends from the engine to convey the flue gas to the flue gas cleaning system. This pipe leads via piping to the soot particle filter 4a'''' of the flue gas cleaning system, where soot particles adhere to granules 5''''. A transfer pipe 22 diverts the flue gas to the desulfurization unit 4b''''. From the desulfurization unit, the cleaned flue gas is then directed to the catalyst 6'''', which enables the afterburning of combusted fuel. The flue gas is then released into the environment, primarily as carbon dioxide. The granules are discharged from the system continuously or discontinuously. A peeling drum increases the system's efficiency. The resulting reaction product can then be processed by a mill, preventing a build-up of the product at the discharge flap at the bottom of the reactor. The sorption material can, for example, also consist of limestone chippings, which trickle vertically from the storage reservoir past the horizontally arranged intermediate floors to the reactor. Through a design modification of the described embodiments, exhaust noise can be reduced. Diesel engines, especially those on ships, are equipped with silencers on the exhaust side. These reduce the noise level depending on the size of the diesel engine. This reduction in exhaust noise can be achieved through absorption sound attenuation of the sorption material, whereby, among other things, the insulation of the reactor and / or the mass and particle size of the sorption material, for example, crushed stone, can be determined in such a way that the additional silencers can be eliminated or at least significantly reduced in size. This advantageously reduces the noise level to at least below 45 dB at 100 m. This, in turn, leads to a simplification of the packed bed system and a saving of space, which is a crucial criterion, especially on ships. In a further advantageous embodiment, a heat exchanger is integrated into the flue gas cleaning system to efficiently utilize the thermal energy of the flue gas. Particularly preferably, the heat exchanger is integrated into the exhaust gas cleaning system, with the amount of heat varying depending on the engine type. This thermal energy can then be used, for example, to liquefy the diesel fuel. The effectively recovered and utilized thermal energy ranges from 50 to 300 kW per MW of engine power.

Claims

A method for cleaning flue gases produced during the combustion of heavy oil and diesel fuels for the operation of watercraft and drilling platforms, characterized in that: a) sulfur-containing flue gases produced as combustion residues during the combustion of heavy oil and diesel fuels are fed into a reactor (4''); b) soot particles and dust are separated from the gas stream in a first step by adsorption or absorption on a sorbent; c) sulfur-containing components are removed from the gas stream by dry sorption in a second, subsequent step; d) the gases are subsequently discharged via a chimney (9''), wherein the separation of soot particles and dust and the dry sorption of sulfur-containing components each take place in separate reactor sections (4a'', 4b'') in a reactor housing of a reactor (4'');and the gas stream for the separation of soot particles and dusts by adsorption or absorption onto sorbents is first directed into at least a first reactor area (4a'') and subsequently for the separation of sulfur-containing components into at least a second reactor area (4b''), wherein the areas are separated from each other by at least one partition wall (16''). Method according to claim 1, characterized in that heat exchange takes place in the reactor (4''), wherein heat energy obtained from the flue gases is used to liquefy ship fuel. Method according to one of the preceding claims 1 or 2, characterized in that the separation of soot particles and dusts is carried out by means of spent granular sorbent granules of the sorbent and the separation of sulfur-containing components from introduced flue gases is carried out by means of unused granular sorbent granules of the sorbent. Method according to one of the preceding claims, characterized in that the dry sorption of sulfur-containing gases is carried out by a continuously or discontinuously flowing packed bed granulate. Method according to one of the preceding claims, characterized in that the dry sorption is carried out by a calcium carbonate-containing granulate. Method according to one of the preceding claims, characterized in that the dry sorption is carried out by a calcium hydroxide-containing or calcium oxide-containing granulate. Method according to one of the preceding claims, characterized in that the dry sorption is carried out by means of urea granules. Method according to one of the preceding claims, characterized in that sorbent used in the reactor is discharged from the reactor (4") and new sorbent is supplied from a reservoir. Method according to claim 8, characterized in that the level of sorbent in the reservoir is automatically monitored. Method according to one of the preceding claims, characterized in that the pollutant emissions of the low-soot, low-sulfur gases are further reduced by means of a catalyst (6") which is provided downstream of the reactor (4"). Device for carrying out a method according to one of the preceding claims, for cleaning flue gases produced during the combustion of heavy oil and diesel fuels for the operation of watercraft and drilling platforms, comprising at least one reactor (4") which is filled with at least one sorbent and at least one gas piping device (25") which are fluidically connected to each other; wherein the separation of soot particles and dust and the dry sorption of sulfur-containing components each take place in separate reactor sections (4a", 4b) in a reactor housing of a reactor (4");and the gas stream for the separation of soot particles and dusts by adsorption or absorption onto sorbents is first directed into at least a first reactor area (4a") and subsequently for the separation of sulfur-containing components into at least a second reactor area (4b"), wherein the areas are separated from each other by at least one partition wall (16"). Device according to claim 11, characterized in that the reactor (4'') is pressure-resistant.

Images