WO2006022564A1

WO2006022564A1 - Installation for cleaning of exhaust gas and method for cleaning of exhaust gas

Info

Publication number: WO2006022564A1
Application number: PCT/PL2005/000055
Authority: WO
Inventors: Anna Wysocka; Zygmunt Wysocki
Original assignee: Anna Wysocka; Zygmunt Wysocki
Priority date: 2004-08-23
Filing date: 2005-08-23
Publication date: 2006-03-02
Also published as: EP1787015A1

Abstract

In an installation for cleaning of exhaust gas containing filters, following an inlet of the installation are located a filtering system collecting soot and solid impurities, a catalyst reactor (25, 35) and a filter (24, 34) collecting dust and fine impurities, through which diesel engine exhaust gases are transmitted. The filtering system collecting soot and solid impurities contains a ceramic filter (23, 33) with a chemically active cartridge bounding chemical compounds including calcium oxide CaO.

Description

INSTALLATION FOR CLEANING OF EXHAUST GAS AND METHOD FOR

CLEANING OF EXHAUST GAS

TECHNICAL FIELD

The present invention relates to an installation for cleaning of exhaust gas and method for cleaning of exhaust gas, especially for purifying exhaust gases emitted by diesel engines, in particular combustion engines driven by fuels containing rape seed and animal oils.

BACKGROUND ART

Diesel engines, which can be driven by diesel fuels as well as rape seed and animal oils, enjoy good publicity nowadays, mostly because of their low carbon dioxide emissions. Modern vehicles equipped with diesel engines meet the current standards permitting a fraction of allowed emissions of the early 1990s. Such a high reduction in the emission of harmful substances would not be possible without increasing the injection pressure, exhaust gas return, turbo-charging and catalysts.

However, in future even lower limits are to be expected, enforcing a further significant reduction in exhaust gas emissions. The Euro !V standard imposes the requirement of lowering by half the amount of noxious particle emissions permitted at present. Similarly, the HC and NOx emissions will need to be cut almost in half. Following the enforcement of the Euro IV standard in October 2005, the technological innovations applied in engines will be no longer sufficient. More effective exhaust gas purification will become indispensable, based on particle filters and possible additional DeNOx catalysts. The DeNOx catalysts used at present in passenger cars are container catalysts that are self recovered during a short run with a richer fuel mixture. However, the flow capacity of such catalysts is quite low, and they fail to operate with sulphated fuel. Additionally, the current catalysts are not fitted for purifying exhaust gases with high soot content.

AIM OF THE INVENTION

The purpose of the invention is to create a system for purifying engine exhaust gases of high flow reaching 200 thousand m³/h and containing solid impurities, soot, volatile organic compounds, as well as nitrogen, carbon and phosphorus oxides, which would be more efficient than the currently known systems, while meeting higher natural environment protection requirements set by standards anticipated for the nearest future.

DISCLOSURE OF THE INVENTION

The idea of the invention is that in an installation for cleaning of exhaust gas containing filters, additionally to the filters, the installation is equipped with a catalyst reactor and that one of the filters is a filter collecting dust and fine impurities, and an exhaust gas is transmitted through the catalyst reactor and the filters.

The soot-collecting filter system may constitute a part of the catalytic reactor, while the filter collecting dust and fine impurities is located after the catalytic reactor.

The role of the soot-collecting filter system collecting soot and solid impurities can be played by a ceramic filter of porous structure collecting soot and solid impurities, followed by a ceramic filter with a chemically active cartridge bounding chemical compounds, and a filter collecting dust and fine impurities located before the catalyst reactor with an outlet connected to an inlet of an catalyst reactor. it is advantageous to have the ceramic filter of porous structure collecting soot and solid impurities, the ceramic filter with a chemically active cartridge bounding chemical compounds, and the filter collecting dust and fine impurities form a multipurpose filter.

It is advantageous to have calcium or calcium oxide CaO as a chemically active cartridge bounding chemical compounds in a ceramic filter.

The catalytic reactor may be a thermal reactor or a reverse catalytic, or else a flow or a reverse-flow reactor.

It is advantageous to have a fan or a suction-and-force pump located in the way of the purified gas mixture, which would enforce a flow of the exhaust gases as well as that of the purified gas mixture in the system for purifying exhaust gases from diesel engines.

The catalytic reactor may have additional inlets used for supplying controlled amounts of oxygen, ammonia and/or urea. Preferably, near the soot-collecting filter system is placed at least one cleaning device for cleaning the soot-collecting filter system.

The cleaning device can be a burner for burning the soot and solid impurities and/or a vibrator placed on a vibratory frame connected to a filter housing and/or a water collector producing a stream of water at pressure within the range 0.8 MPa to 1.2 MPa.

Preferably, space surrounding the filter is connected to an outlet of the filter by a branch and serves for removing gases formed during burning of soot and solid impurities.

Preferably, below the filter is situated a soot chamber for collecting sludge flowing down from the filter during its washing.

A further idea of the invention is that in a method for cleaning of exhaust gas, exhaust gases are fed to a filter system collecting soot and solid impurities, and pre-purified exhaust gases leaving the filter system are flameless oxidized in a catalyst reactor.

It is advantageous for the filter system to be located in the catalyst reactor, which, once the soot has settled, with the help of heaters or burners is brought to the temperature at which the settled soot and fine solid impurities are oxidized quickly.

It is advantageous for the filter system to be equipped with a ceramic filter of porous structure collecting soot and solid impurities, followed by a ceramic filter with a chemically active cartridge bounding chemical compounds, and a filter collecting dust and impurities, placed before the catalyst reactor, with its outlet connected to an outlet of the catalyst reactor.

Preferably, in an oxidizing section of the catalyst reactor flameless oxidization of a mixture of organic and other compounds is carried out at a temperature of ca. 500⁰C.

Preferably, in a reducing section, NOx nitrogen compounds are reduced to molecular nitrogen N2 by adding ammonia or urea in strictly predetermined quantities calculated basing on chemical bounding reaction of NOx nitrogen compounds and ammonia or urea.

The soot and the impurities can be burned in temperatures within the range of 850⁰C to 1000⁰C and remaining substances can be removed with the help of vibrator and/or water collectors producing a stream of water at pressure within the range 0.8 MPa to 1.2 MPa.

BRIEF DESCRIPTION OF THE DRAWINGS _:

The invention will now be described by way of example and with reference to the accompanying drawings in which:

Fig. 1 shows an installation flow diagram of the first embodiment of an exhaust gas purification system;

Fig. 2 shows a block diagram of the second embodiment of an exhaust gas purification system;

Fig. 3 shows a structure of a multipurpose filter;

Fig. 4 shows a flow chart of an algorithm for continuous monitoring of multipurpose filter condition

Fig. 5 shows a block diagram of the third embodiment of an exhaust gas purification system; and

Fig. 6 shows a block diagram of the forth embodiment of an exhaust gas purification system.

BEST MODE FOR CARRYING OUT THE INVENTION Exhaust gases emitted by diesel engines 11 , 16, 17 are directed from engine exhaust systems 12 via a transmission line 13 to an exhaust gas purification system shown in Fig. 1 and Fig. 2. In the meaning of the solution presented here, the transmission line 13 consists in a system of pipes, ducts, various kinds of valves, throttles and fittings used for carrying exhaust gases, water vapour and volatile particles. The volume of the gas mixture fed to individual branches 21 , 31 of the exhaust gas purification system is controlled with the help of throttles or valves 14, 15. All parameters concerning the composition, temperature and negative pressure, at which the exhaust gases are sucked in, are transferred via a set of sensors 86, 186 to a control system 80 shown schematically in Fig. 2. The exhaust gas flow, through a multipurpose filter 70, 170 consisting of a soot- collecting filter system 22, 32 collecting or accumulating soot and other impurities, a chemically active filter 23, 33 with a chemically active cartridge bounding chemical compounds, a filter 24, 34 collecting or accumulating dust and fine impurities, as well as through a catalyst reactor 25, 35, is enforced by a fan 28, 38 or a suction-and-force pump. The soot settling on the filter 22, 32 collecting soot is oxidized or reheated from time to time, and, once recovered, the ceramic filter cartridge is fed into the filter again. In turn, any environmentally harmful chemical compounds, with phosphorus in¹ the first place, in the chemically active filter 23, 33 used for bounding chemical compounds are bound to chemical compounds such as calcium oxide CaO 44, 48, and reclaimed in the form of compounds 42, 46 harmless for the environment. Any dust and fine impurities 43, 47 are removed periodically from filter 24, 34, usually together with the filter cartridge. A catalyst reactor 25, 35 of the exhaust gas purification system can be a catalyst reactor of thermal, flow, reverse-flow or another type, constructed like catalytic modules placed one within another or modules separated by partitions. In the catalyst reactor 25, 35, flameless oxidization of the organic compound mixture occurs in the range of temperatures from 100⁰C to 600⁰C₁ advantageously at temperatures below 500⁰C but not less than 250⁰C. The flameless oxidization process is accompanied by the reduction of the NOx nitrogen compounds to molecular nitrogen N₂, with catalysis products removed regularly or in a continuous manner. The temperature of flameless oxidization is controlled by the amount of exhaust gases, ammonia 26, 36, water H₂O or urea and neutral gas, for example carbon dioxide of sufficiently low temperature. The reduction of nitrogen oxide present in the exhaust gases can also take place thanks to the ammonia created in the catalyst under the influence of a water solution of urea added to the hot exhaust gases leaving the engine. The exact dose of urea and/or ammonia is calculated by the control system basing on chemical bounding reaction of NOx nitrogen compounds and ammonia or urea. Once purified in the catalyst reactor 25, 35, the exhaust gases constituting gas mixture 27, 37 containing carbon dioxide, molecular nitrogen and harmless substances are directed to a heat exchanger 50, and then to the atmosphere via a chimney 60. The heat exchange medium is brought to the heat exchanger 50 through a feeding transmission line 51, and carried away along a removal transmission line 52. The heat exchange medium can be water used for heating houses and apartments.

The systems presented in Fig. 1 and Fig. 2 differ in their catalyst reactors as well as in the place where the filter collecting dust and fine impurities is installed. In a catalyst reactor 125, 135 in the system version shown in Fig. 2, molecular carbon settles in the form of soot in a soot-colleting filter system 122, 132 constituting a part of the catalyst reactor 125, 135, whereas the filter 24, 34 collecting dust and fine impurities is placed after the catalyst reactor 125, 135. Once soot has settled in the catalyst reactor in admissible quantities, the catalyst reactor 125, 135 is brought to the temperature at which the settled soot and fine solid impurities are oxidized quickly. During the normal run of the catalyst reactor, in the oxidizing sector 123 of the catalyst reactor 125, 135 flameless oxidization of the organic compound mixture is carried out at the temperature range 100⁰C to 600⁰C, advantageously at the temperature of ca. 500⁰C, and in the reducing section 124 the NOx nitrogen compounds are reduced to molecular nitrogen N₂, while the catalysis products, similarly as in the system shown in Fig. 1 , are removed regularly or in a continuous manner after being purified by filter the 24, 34.

Fig. 3 shows schematically a structure of a multipurpose filter 70, the size of which depends on intensity of the exhaust gas flow. It consists of a casing 73 with an opening 71 for letting exhaust gases in, and an opening 72 for letting the pre- purified exhaust gases out. On the soot-collecting filter system formed by a ceramic filter 75 situated at an inlet of a multipurpose filter 70 mostly settles carbon in the form of soot and major solid impurities. With time, the settling molecular carbon fills up the pores of the ceramic filter 75, which must be replaced or recovered regularly. Another filter is a ceramic filter 76, filled with calcium or its compounds, for example caicium oxide CaO, commonly referred to as burnt lime. The calcium contained in the calcium oxide binds phosphorus contained in the exhaust gases, as well as de-sulfurizing exhaust gases and reacting with other acid gas components, such as hydrogen chlorides or fluorides. After the adsorbing capacity of the ceramic filter 76 diminishes, the latter is replaced with a new one, and the filler can be used as road sub-crust in the form of a harmless substance, for example CaHPO₄. A subsequent filter, when proceeding from the entrance opening, is a filter 77 used for the pre-purification of exhaust gases from dust and fine impurities not collected by the first and second ceramic filters. The filter 77 used for pre-purification is followed by a filter 78 of medium concentration. On the other hand, at the exit of the multipurpose filter 70 there is a filter 79 for accurate exhaust gas purification, which stops dust and the finest impurities. Moreover, the filter is equipped with sensors 81, 82, 83, 84, 85, 86, including negative pressure and temperature sensors as well as sensors detecting the composition of exhaust gases flowing through individual segments of the multipurpose filter 70.

The data transferred by sensors 81 , 82, 83, 84, 85, 86, 186 are directed to a control system 80, which continuously monitors the process of exhaust gas purification as well as the condition of the multipurpose filter. The algorithm of the process of monitoring the condition of the multipurpose filter 70 is shown in a flow chart in Fig. 4. The monitoring process begins with the start in step 91 upon the start-up of diesel engine(s) presented in Fig. 1 and Fig. 2. Step 92 encompasses readouts, for example of negative pressure, and then the readouts are compared with each other in step 93. Should it turn out in step 94 that the differences in readout from respective sensors are higher than admissible amounts or thresholds, then in step 95, information is transferred of a need to replace or purify the excessively polluted filter or its sub-assembly, and the next parameter readout follows.

The process of purifying exhaust gases from diesel engines consists in the precipitation of molecular carbon from exhaust gases in the first phase, followed by the de-sulfurization and binding of phosphorous compounds after the transmission of exhaust gases through the multipurpose filter consisting of the ceramic filter collecting soot and major impurities, the ceramic filter, as well as pre-purification and fine purification filters collecting dust and fine impurities. Pre-purified exhaust gases are directed to the catalyst reactor for the flameless oxidization of the unburned organic compounds, as well as for the reduction of nitrogen compounds to molecular nitrogen through addition of urea and/or ammonia. In another system alternative, once soot has settled in the catalyst reactor in admissible quantities, with the help of electric heaters or inflammable-substance burners, the catalyst reactor is brought to the temperature at which the settled soot and fine solid impurities are oxidized quickly. Regardless of the system alternative, during the normal run of the catalyst reactor, flameless oxidization of the mixture of organic and other compounds is carried out in the oxidizing section of the catalyst reactor at the temperature of ca. 500⁰C₁ while in the reducing section the NOx nitrogen compounds are reduced to molecular nitrogen N₂ through adding ammonia or urea in strictly pre-determined quantities calculated basing on chemical bounding reaction of NOx nitrogen compounds and ammonia or urea.

At an inlet of the installation for purifying exhaust gases, shown in Fig. 5, is placed a flap inlet vaive 114, which distributes exhaust gases 113 to individual branches 121 , 131 of the installation for purifying exhaust gases. The exhaust gases 113 enter into chambers of multipurpose filters 170, 171 separated each other by a partition or a diaphragm 173. At the inlet of each multipurpose filter 170, 171 is situated a soot-collecting filter system or a filter set 122, 132 with little eyes of different size or a set filled with pellets, which collects or accumulates soot and other impurities. The collected molecular carbon with time fills the little eyes 122, 132 and causes decreasing of capacity of the team of filters. To avoid the stopping gas flow through the filters, the soot is removed periodically in a chosen branch using cleaning devices 115, 116 whereas other branches work. The soot and larger impurities can be burned, for example using a burner. To improve the burning of the soot and larger impurities, air and other inflammable mixture can be dosed through inlets 155, 156. The mixture of gases is removed from chambers of the filters 122, 132 through the branches 161 , 181 and valves 162, 182.

The next filter is a chemically active filter 123, 133, for example a ceramic filter filled with calcium or calcium oxide CaO. The calcium is use optionally in the case when the exhaust gases contain phosphoric compounds, for example P2O5 and other acid gas compounds, such as hydrogen chlorides or fluorides. After the adsorbing capacity of the filter 123, 133 decreases, the latter is replaced with a new one, and the filler can be used as road sub-crust in the form of a harmless substance. A subsequent filter, when proceeding from the inlet, is a filter 126, 136 used for the pre-purification of exhaust gases from dust and fine impurities not collected by other filters. Pre-purified gases are driven through flow lines 151 , 152, and then directed through an outlet flap valve 153 and flow lines 191 , 192 to the atmosphere or to the catalyst reactor 25, 35 (shown in Fig. 1) for further processing.

The installations for purifying exhaust gases, shown in Fig. 5 and Fig. 6 differ in their multipurpose filters 270, 271 that are placed back warded and have a common chamber 288 of pre-purified gases. The gases to be purified are directed by a flap inlet valve 214 to individual branches 221 , 231. At the inlet of each multipurpose filter 270, 271 is situated a soot-collecting filter system or a filter set 222, 232 with little eyes of different size or a set filled with pellets, which collects or accumulates soot and other impurities. The collected molecular carbon and the impurities are burned in temperatures within the range of 850⁰C to 1000⁰C. Then, a filter housing 220, 230 of each filter sets 222, 232 is shaken using a vibrator 217, 218 placed on a vibratory frame 247, 248. The burning of the soot can be improved by delivering flammable mixture or air through dosing devices 237, 255, 256 or stopped by neutral gasses, such as carbon dioxide in the sufficiently low temperature. Remaining substances are removed with the help of water collectors 211 , 212 producing a stream of water at pressure within the range 0.8 MPa to 1.2 MPa. Sludge 239, gathering in a chamber being a bottom part of a filter casing, is pumped out through a sludge valve 238 using a sludge pump 229 and collected as waste material. Water used for cleaning the filters 222, 232 is delivered by a water pump 226 through pipes 227 and water collectors 211 , 212, Burning gases 253, 254 are directed through valves and ducts 261 , 281 to an outlet 293 or redirected to inlets of the filters placed in working branches.

The next filter is a chemically active filter 223, 233, for example a ceramic filter filled with calcium and/or calcium compounds, for example calcium oxide CaO. After the adsorbing capacity of the filter 223, 233 decreases, the latter is replaced with a new one, and the filler can be used as road sub-crust in the form of a harmless substance. A subsequent filter, when proceeding from the inlet, is a filter 226, 236 used for the pre-purification of exhaust gases from dust and fine impurities. Pre-purified gases are driven to the common chamber 288, and then directed to the outlet 293 through an outlet flap valve 294.

The process of purifying exhaust gases stars by collecting soot and impurities on suitable filters. The collected molecular carbon and the impurities are burned in temperatures within the range of 850⁰C to 1000⁰C. The remaining substances are removed with the help of water collectors 211 , 212 producing a stream of water at pressure within the range 0.8 MPa to 1.2 MPa.

Claims

1. An installation for cleaning of exhaust gas containing filters characterized in that additionally to the filters, the installation is equipped with a catalyst reactor (25, 35, 125, 135) and that one of the filters is a filter (24, 34, 126, 136, 226, 236) collecting dust and fine impurities, and an exhaust gas is transmitted through the catalyst reactor (25, 35, 125, 135) and the filters.

2. The installation for cleaning of exhaust gas according to claim 1 , characterized in that the catalyst reactor (125, 135) contains a soot-collecting filter system (122, 132) and the filter (24, 34) collecting dust and fine impurities is placed after the catalyst reactor (125, 135).

3. The installation for cleaning of exhaust gas according to claim 1 , characterized in that the filters further includes a soot-collecting filter system being a filter (22, 32, 122, 132, 222, 232) of porous structure collecting soot and solid impurities, followed by a chemically active filter (23, 33, 123, 133, 223, 233) with a chemically active cartridge bounding chemical compounds, and that the filter (24, 34, 226, 236) collecting dust and fine impurities is located before the catalyst reactor (25, 35) with an outlet connected to an inlet of a catalyst reactor (25, 35).

4. The installation for cleaning of exhaust gas according to claim 3, characterized in that the filter (22, 32) of porous structure collecting soot and solid impurities, the chemically active filter (23, 33) with the chemically active cartridge bounding chemical compounds, and the filter (24, 34) collecting dust and fine impurities form a multipurpose filter (70, 170).

5. The installation for cleaning of exhaust gas according to claim 3, characterized in that the chemically active cartridge bounding chemical compounds in the ceramic filter (23, 33) contains calcium and/or calcium compounds.

6. The installation for cleaning of exhaust gas according to claim 3, characterized in that the chemically active cartridge bounding chemical compounds in the ceramic filter (23, 33) contains calcium oxide CaO.

7. The installation for cleaning of exhaust gas according to claim 1^", characterized in that the catalyst reactor (25, 35, 125, 135) is a thermal reactor.

8. The installation for cleaning of exhaust gas according to claim 1 , characterized in that the catalyst reactor (25, 35, 125, 135) is of reverse or flow or reverse-flow type.

9. The installation for cleaning of exhaust gas according to claim 1 , characterized in that in a way of a purified gas mixture is installed a fan (28, 38) or a suction-and-force pump enforcing flow of exhaust gases and a purified gas mixture in the installation.

10. The installation for cleaning of exhaust gas according to claim 1 , characterized in that the catalyst reactor (25, 35, 125, 135) has additional inlets (26, 36, 126, 136) used for supplying controlled amounts of oxygen, ammonia and/or urea.

11. The installation for cleaning of exhaust gas according to claim 2 or 3, characterized in that near the soot-collecting filter system (122, 132, 222, 232) is placed at least one cleaning device (115, 116, 215, 216, 217, 218) for cleaning the soot-collecting filter system (122, 132, 222, 232).

12. The installation for cleaning of exhaust gas according to claim 11 , characterized in that the cleaning device is a burner (216, 217) for burning the soot and solid impurities.

13. The installation for cleaning of exhaust gas according to claim 11 , characterized in that the cleaning device is a vibrator (217, 218) placed on a vibratory frame (247, 248) connected to a filter housing (220, 230).

14. The installation for cleaning of exhaust gas according to claim 11 , characterized in that the cleaning device is a water collector (211 , 212) producing a stream of water at pressure within the range 0.8 MPa to 1.2 MPa.

15. The installation for cleaning of exhaust gas according to claim 12, characterized in that space surrounding the filter (122, 132, 222, 232) is connected to an outlet of the filter (126, 136, 226, 236) by a branch (161 , 181 , 261 , 281) and serves for removing gases formed during burning of soot and solid impurities.

16. The installation for cleaning of exhaust gas according to claim 1 , characterized in that below the filter (222, 232) is situated a soot chamber for collecting sludge (239) flowing down from the filter (222, 232) during its washing.

17. A method for cleaning of exhaust gas characterized in that exhaust gases are fed to a filter system collecting soot and solid impurities, and pre-purified exhaust gases leaving the filter system are oxidized in a catalyst reactor.

18. The method for cleaning of exhaust gas according to claim 17, characterized in that in the catalyst reactor is placed a soot-collecting filter, which, once soot and solid impurities has settled, is brought to a temperature at which the soot and solid impurities are burned quickly using heaters or burners.

19. The method for cleaning of exhaust gas according to claim 17, characterized in that the filter system is equipped with a ceramic filter of porous structure collecting soot and solid impurities, followed by a ceramic filter with a chemically active cartridge bounding chemical compounds, and a filter collecting dust and impurities, placed before the catalyst reactor, with its outlet connected to an outlet of the catalyst reactor.

20. The method for cleaning of exhaust gas according to claim 17, characterized in that in an oxidizing section of the catalyst reactor flameless oxidization of a mixture of organic and other compounds is carried out at a temperature of ca. 500⁰C.

21. The method for cleaning of exhaust gas according to claim 17, characterized in that in a reducing section, NOx nitrogen compounds are reduced to molecular nitrogen N₂ by adding ammonia or urea in strictly predetermined quantities calculated basing on chemical bounding reaction of NOx nitrogen compounds and ammonia or urea.

22. The method for cleaning of exhaust gas according to claim 17, characterized in that the soot and the impurities are burned in temperatures within the range of 850⁰C to 1000⁰C and remaining substances are removed with the help of vibrators and/or water collectors producing a stream of water at pressure within the range 0.8 MPa to 1.2 MPa.