DE2221793C3 - Process for exhaust gas purification - Google Patents

Description

is fed oxygen-containing gas in an amount such ^ that its temperature is raised to at least 34O ⁰ C without the Kohlenmonoxidinteil in the exhaust gas under a stoichiometric amount of the nitrogen oxides contained therein to drop.

According to the teaching of the invention, the exhaust gas emitted by the combustion engine is therefore supplied with air in sufficient quantity that partial amounts of the carbon monoxide and hydrogen contents are oxidized without, however, the carbon monoxide content falling below the stoichiometric amount of nitrogen oxides in the exhaust gas. In other words, the invention proposes the implementation of a limited oxidation before the stage for the catalytic reduction of the nitrogen oxides. As a result of carrying out this limited oxidation, essentially two advantages are achieved without the starting position for carrying out the subsequent reaction stages, in particular the reduction stage, deteriorating in any way. By performing the limited oxidation, the temperature of the exhaust gas can be brought to a value suitable for the effectiveness of the catalysts in the reduction stage (at least 840 ° C.), so that external heating means and heating devices can be dispensed with. In addition, in the first stage of the process according to the invention, that is, in the limited oxidation, partial amounts of the hydrogen in the exhaust gas are oxidized so that this hydrogen can no longer be converted to ammonia with nitrogen oxides in the reduction stage, as is the case with the known two-stage process of Case is. With the method according to the invention, an improved degree of efficiency can therefore be achieved. Regarding the state of the art, reference is also made to DT-OS 20 62 056, in which it is generally described that catalytic oxidation reactions (CO + ι; O ₂ -> CO ₂ ) are carried out after prior admixing of secondary air. In addition, this publication shows that catalytic reductions (NO, NO _2, etc.) are carried out in an oxygen-free atmosphere. However, the teaching is in no way conveyed that catalytic reductions can also be carried out after prior admixing of secondary air. Rather, it is expressly pointed out in this publication that the oxidation process described there differs from the known reduction process precisely in that it is not carried out in an oxygen-free atmosphere like this one.

It has also already been proposed (German patent application P 22 42 588.3) to add oxygen or an oxygen-containing gas to the exhaust gases emitted by the engine and then to transfer the resulting gas mixture one after the other into a hydrogen-oxidizing catalyst bed, a nitrogen oxide-reducing catalyst bed and a carbon monoxide and Introduce hydrocarbons oxidizing catalyst bed. This process differs from the process according to the invention in that, apart from the admixture of the oxygen-containing gas, all process stages, in particular those for the oxidation of H ₂ , take place catalytically, while in the process according to the invention only the reduction of nitrogen oxides is carried out catalytically. In the method according to the invention, air is expediently supplied to the exhaust gas in the oxidation stages before and after the reduction of the nitrogen oxides.

As far as the reduction stage is concerned, the

materials suitable as catalysts in various ways in the device in which the Reduction of nitrogen oxides is carried out, be arranged. As for the method according to the invention Particularly suitable has been an apprenticeship

Proven guide form in which the catalyst is provided on the inner surfaces of this device. Advantageously, copper, nickel, iron, chromium or theirs are used as catalytically active metals Mixtures used. In further development

of the invention come with copper-coated screen meshes made of stainless steel alloys as catalyst arrangements for use.

To better illustrate the method according to the invention, the following detailed description serves

Notation in connection with the figures, of which Fig. 1 is a flow chart of the invention Procedure shows

F i g. 2 schematically shows a device suitable for carrying out the method according to the invention

as shows

3 shows a section along the line 3-3 in FIG. 2 shows

F i g. Fig. 4 is a graph showing the decrease in inlet pressure observed on the exhaust pipe of the post-combustion reactor entering nitrogen oxides depending on the in the first process stage supplied amount of air and the content of oxygen and carbon monoxide in the post-combustion reactor supplied exhaust gas is as described in Example 2 below, and

Figure 5 is a graph of air flow rate for steps 1 and 3 of the method according to the invention is dependent on the vehicle speed, as shown below in Example 3 is described.

The flow diagram shown in FIG. 1 illustrates that in the process according to the invention an exhaust gas from an incomplete combustion of hydrocarbon fuels of the Runs through series of three process stages and then emerges as purified exhaust gas. In procedural stage 1 an oxygen-containing gas is supplied, and in such a sufficient amount that a limited Oxidation of the oxidizable constituents present in the exhaust gas is effected.

In process stage 2, this partially oxidized exhaust gas is subjected to a chemical reduction, where catalytic work is carried out. In process stage 3, this becomes the second stage incoming treated exhaust gas is brought together with an oxygen-containing gas, and it is carried out a further oxidation in which the oxidizable substances still remaining in the treated gas Components are completely removed or 60 whose content in the gas is further reduced.

In the F i g. 2 and 3 is a device suitable for carrying out the method according to the invention shown. An internal combustion engine 10 of the type of a piston engine is shown, 65 which has a cylinder block 11 and a cylinder head. Next to the cylinder head 12 is a hollow one elongated tubular reactor 13 is arranged, which has a flange plate 14 and a plurality of tubes 15, 16 and 17,

with which the reactor 13 with the flange plate 14 sets 31 and / or on the inner surfaces of the is connected, has. Reactor 18 may be present as a cover. The air-

The flange plate 14 is in a suitable manner (not feed pipe 26 reiehl: in that shown by the pipe) attached to the cylinder head 12. Housing of the reactor enclosed by the outer jacket 27 Cylinder head 12 is exhaust gas from the four cylinders, 5 in 18 and is at a point near the plates die are indicated, fed to the tubular reactor 13. Inserts 31 arranged downstream behind these. Figure 2 shows one side of a V-8 engine. One that part32 of the tube26 that is inside the Corresponding arrangement of tubular reactor 13, Ge flange sheet enclosed by the outer tube jacket 27 14 and pipes 15, 16 and 17 housing sits, consists of a perforated or is on the opposite side of the io porous material so that the air is inside Engine. this housing can distribute.

As can be seen from the illustration, when carrying out the inventive method

Tubular reactor 13 generally a cylindrical drive comes out of the tubular reactor 13 flow-out form, and the exhaust gas flows through the piping of the exhaust gas through the connecting pipe 19 into the 15, 16 and 17 in one of this reactor 13 around 15 post-combustion reactor 18. Inside the closed inner zone I. The gas flows through the plate inserts 31 at a distance from the actuator 18. The area arranged in the tubular reactor 13 is an area where the second stage of the invention takes place Afterburning reactor 18 arranged. Procedure, d. H. chemical reduction takes place. In

The tubular reactor 13 is via a connection F i g. 3 is such, altogether as a chemical tube 19 with the afterburning reactor 18 reduction zone II shown arrangement. light in which the chemical reduction is carried out

Air is generated via a motor-driven air pump 9. The main part of the chemical reduction introduced, and this flows through a main air takes place near or within one of the several supply pipe 20 in and through a plurality of plate inserts 31 limited area, however, can branched air supply pipes 21, 22, 23 and 24 35 a part of the chemical reduction also already stromin the tubes 15, 16 and 17, whereby due to the upward take place in front of the plate inserts 31. The line pipe 21 air to the pipe 15 through which gas flows through the plate inserts 31, Line pipes 22 and 23 air the pipe 16 and through comes out of this and is just behind the the supply pipe 24 air is fed to the pipe 17 with the exit point through the perforated pipe end 32 will. When carrying out the air supply method according to the invention introduced into the air supply pipe 26 If the air emerges from the supply pipes 21, it mixes. The introduced air mixes with the 22, 23 and 24 exhaust gas flowing into and out of pipes 15, 16 and 17. This is the beginning of the third intermingling in it with the hot exhaust gases from the driving stage of the method according to the invention, d. H. Cylinders of the machine. This is the first stage of the oxidation. The oxidation takes place essentially according to the invention Method, and it is invented near and downstream of the perfusion according to causing partial oxidation. ured pipe end 32 within reactor 18. The partial oxidation takes place predominantly in this area is designated as zone III, inner zone I of the tubular reactor 13, although to a certain extent the oxidation also goes also part of this limited oxidation on still further downstream behind it, so that part the previous path within the tubes 15, 40 of the oxidation within the outflow tube 30 16 and 17 and also behind the reactor, for example. In the method according to the invention then occurs show a purified exhaust gas within the connecting pipe 19 and in the outflow pipe 30. Combustion chamber 33 takes place. The table below shows the composition

By means of the air supply pump 9, air is drawn in with a typical exhaust gas before and after the and through an air supply pipe 26 to the post-combustion 45 carried out according to the invention limited oxy-combustion reactor 18 supplied. The reactor 18 is shown dation. These numerical values result from Cylindrical design and with a pipe an exhaust gas that is generated during the combustion of a Luty outer jacket 27 is provided. At the inflow end of the gasoline mixture with a weight ratio Reactor 18 is treated exhaust gas from zone I, 10.1 to 1 in steady-state operation of a combustion gas is fed through the connecting pipe 19, 50 engine arose.

introduced into reactor 18. This inflowing what is the second stage or reduction stage

is closed with an end plate 28, apart from concerns, so are for the purposes of the present He from that through the connecting pipe 19 to the invention as catalysts, in particular metals Aktorl8 formed opening. The outflow of the metal oxide as well as alloys and mixtures of voi Reactor 18 is fitted with a closure plate 29 of these groups I-B and IV to VIII of the Periodi closed around the system suitable to see from the exhaust pipe 30, which is based on a support formed opening extends around. be brought or be present without carrier material

In the reactor 18 is a plurality of plates can.

Sets 31 arranged. In the embodiment shown, stainless steel alloys are also suitable catalysts

These perforated or porous analyzers are used for the purposes of the present invention Material or the like existing Plattenein- for example crimped fibers from Monel400, Siet sets 31 within the fabric made of Monel 400 through the pipe outer jacket 27, screen fabric made of Inconel 6 (X arranged in an enclosed housing, screen meshes made of stainless steel 304 SS extend (p. 16, table: up to contact with the pipe outer jacket 27 SAE Handbook, Part 1), screen mesh made of Inconel 6C at right angles to this and are attached to it by means of not 65 with copper coating, sieve mesh made of Edelstal shown facilities attached. If a special 304 SS with copper clad, screen mesh ai Catalyst is used, e.g. B. copper, then stainless steel 330 SS (p. 16, table 1, SAE Handboo the catalyst on the surface of the plate part 1) with and without copper coating.

table
salary 7th
I.
in the exhaust NO
(ppm) HC
(ppm) CO H ₁
(ppm) N ₁ 8th Co CO
(ppm) 93
71 2560
9-39 10.9
15.6 31800
9600 78.1
81.3 temperature
( ⁰ C) 1.
2. 84,000
21000 638
995

1. = before the limited oxidation

2. = after the limited oxidation ')

^a ) Uncorrected with regard to the dilution that occurred as a result of the increase in volume of the exhaust gas caused by the air supplied. The values given, with the exception of N ₁ , must be multiplied by 1.14 if comparable quantities are to be obtained. All values dry.

In addition, various alloys can be mentioned above in the case of the invention,

According to the method, composite catalysts also have their compositions in the following

Use capacitors that are listed from with copper oxide, copper table Ia: or platinum-coated glass fibers.

Table Ia *) Alloy C Ni S Fe Si Cr Cu Mn

Inconel 600 0.15 72 0.015 10 0.50 16 0.5 1.0 Monel 400 0.30 66 0.024 2.5 0.50 - rest 2.0 330 pp 0.05 35 0.015 43 1.25 19th - 1.5 304SS 0.08 10 0.030 rest 1.00 19th - 2.0

*) All parts in% by weight.

The following table II shows the stage and, after the second process stage, the formation of an exhaust gas after the limited oxidation,
i.e. before entering the second procedural

table
salary II
by doing Exhaust·) HC
(ppm) CO ₁
(%) O,
(%) H,
(ppm) N ₁
(%) H, 0
(%) NH,
(ppm) Temp.
( ⁰ C) CO
(ppm) NO
(ppm) 9-39
12th 15.6
15.2 1.3
0.8 9600
3900 81.3
82.0 11.0
13.1 0.5
1.6 995
1010 1.
2. 21000
14,000 71
5

1. = When entering the second procedural stage **)

2. = After leaving the second process stage ··)

·) From the incomplete combustion of hydrocarbon fuel and after limited oxidation in the first process step.

··) Uncorrected with regard to the dilution that occurs as a result of the air supplied in the first process stage and the resulting increase in volume. In order to obtain the comparison quantities, except for nitrogen and oxygen, it must be multiplied by 1. All values dry, with the exception of H ₁ O.

Finally, in Table III below, the air blown in in the third stage is shown Composition of a limited oxidized and as well as at one point in the direction of flow chemically reduced exhaust gas just before the point, the air inlet indicated.

Table III

Content in the exhaust gas *)

CO NO HC CO, 0, H, N, Temp,

(ppm) (ppm) (ppm) (%) (%) (ppm) (%) ( ⁰ C)

When entering the 3rd 14,000 5 12 15.2 0.8 3900 82.0 1010

Process stage ^a )

At the exhaust pipe outletb) 32 12 0 14.5 4.1 700 81.5 865

*) From the incomplete combustion of hydrocarbons after the first and after the second process stage.

^a ) Uncorrected with regard to the dilution that occurred as a result of the air supplied in the first process stage and the resulting increase in volume. In order to obtain the comparison quantities, except for nitrogen and oxygen, it must be multiplied by 1.14. All values in this table are dry values.

^b ) Uncorrected values with regard to the dilution that was present as a result of the dilution caused by the air supplied in the first and third process stage. In order to obtain the comparison quantities, except for nitrogen and oxygen, it must be multiplied by 1.3.

In the process of the present invention, about 2% to 3% carbon monoxide and less than about

a that ₈ Πυ «Κ materials used about 98%, the hydrocarbon content by about

hl kt The 99% used according to the invention and the content of nitrogen oxides around _90/0

can be reduced at the beginning of the procedure. Virtually all of the hydrocarbon

w ^y t erred iedoch irteine such prior activated material was decrease in the first process stage akt.v _ie rtwerden edochistemesocn s ^ ^ ^ ^^ ^ _{CoM n0Xld.}

^ Take up the function shortly after the decrease took place in the first procedural stage, e.ne

SJ Ga from the first process-n ^ stage the second additional small decrease was in de; .second

t Λ JinfP Prn-icht process stage reached, and the remaining acceptance

It i _s r ^ ckmTßig driving step in the place in the second comparison of carbon monoxide used in the third process stage Nachverbrennungsreaktor ₄ °. Insert pieces or similar resistance pieces
^ watch. This becomes the contact area for the B e ι s ρ. e 1 1

? ^ £ It became a vehicle with a 250 CID engine

Z _n fifth contact with the surface of the 45 is used. The vehicle had an automatic

Ma ils S. NonSusually, however, are smaller gears, a machine-driven air pump and

Catalyst surface areas in the carburetor according to the invention of 0.32 m ² .

«Should! Proceed? sufficient to obtain the desired test data

EraiSÄ «OehaUe. to achieve nitrogen oxides. was driven with indole-free fuels and

If, however, the catalysts are tested by several 100 "50 a test cycle (Federal Register, Vol. 33, No. 108

SJr «drive? is carried out an expansion of June 4, 1968). The barometric pressure

SStoiSStoerf nierlich. at the time of testing was 75.68 cm Hg.

What sdS ch the third procedural stage was before and after the test; 22 S C.

In the L ZZn the preferred quantities for the there In idle in the cold the speed was 2000UpIvI

en «lead £ ^ 5» ^{Ulld idling in the heat C} 750 rpm. Dc Em-

08- and making the stoichiometric amount for position was 12 "BTC at 900 rpm with no suction

You complete oxidation of the remaining oxygenation air improvement when idling without fans

Siren Ingredients Isl it is particularly beneficial to have the carbon monoxide content in the spray

M neen to arSSes that are between 1 and 1 times the exhaust gas 3.9 vol%. The analysis of the exhaust gas «

1 7k!,! “Mf-trkrhen Mence let 60 out of the aogas pipe was by means of not strcucnae

^ ntteTl ^ Vwf ^^ ™ -8 ^eset2tc inf-rot-Ana.ysen-devices carried out; according to the

MM «an LuTt corresponds to the rest of such a test cycle, which were measured for each cycle

MenTe which enables an exhaust gas to be corrected according to the raw data and then di for each cycle

^ ₁ zier'ten oxidation at least about 1% carbon values for the hydrocarbon, carbon monoxide

Contains Γη oxide or less than 5% oxygen. 6 ₅ and St. Oxide concentrations totaled. In la

For a particularly useful way of working in the belle IV, the values are cycle for cycle and de

In the second process stage, the limited oxidized totalized final value for these basic experiments should be used

Exhaust gas that is treated therein, at least approximately guided.

Table IV
Basic data

Corrected data

HC NO CO cycle

(ppm) (ppm) (%)

1 25.70 43.19 0.40 2 12.73 58.67 0.18 3 11.61 62.14 0.09 4th 12.61 75.96 0.09 5 (not from had read) 6th 50.01 323.08 0.35 7th 31.96 215.15 0.33 Sum of 144.63 778.18 1.45 Cycles 1-7 1.67 g / 1.79 g / 31.40 g / 1.6 km 1.6 km 1.6 km

After the basic data listed above had been obtained for comparison purposes, the vehicle was additionally modified as follows: "Liners were installed in the cylinder heads to aid in heat retention; the main and idle jets were enlarged. The exhaust pipes and the remainder of the factory installed exhaust system was removed and replaced with a fitting suitable for carrying out the process of the present invention, this fitting consisting of a tubular reactor for each side of the machine for some of the limited oxidation associated with the first process stage an afterburning reactor similar to the embodiment shown in Figures 2 and 3 for carrying out the second process stage, chemical reduction, and the subsequent third process stage, oxidation ear-shaped profile and contained a 0.079 cm thick inner shell made of stainless steel 330 SS (SAE Handbook, Part 1, p. 16, Table 1) with a diameter of 7.62 cm. The inner shell was connected to four outlets on each side of the machine by four 330 SS tubes, two of which were attached to the cylindrical surface of the inner shell and the other two were attached to the ends of the cylindrical reactor . The cylindrical shell of each of the tubular reactors enclosed a volume of approximately 150 cm ³ , and the total surface area in each reactor was approximately 980 cm *. An air injection tube was provided in each exhaust duct of the machine and directed towards the exhaust valve. The outlet tube from the reactor was designed as an extension of one of the end feed tubes. The reactors were externally insulated with three layers of commercially available silica-alumina insulation. A 0.045 cm thick sheet of stainless steel 304 SS (SAE Handbook, Part 1, p. 16, Table 1) was wrapped around the outside of the insulation that surrounded the cylindrical part of the tubular reactor, and the line pipes were additionally provided with insulation. The post-combustion reactors were ovals with diameters of 8 cm and 16 cm and a length of 30 cm. They consisted of 330 SS stainless steel 0.079 cm thick. Arranged in them and at right angles to the direction of flow of the exhaust gas were five catalyst plate inserts. Each insert consisted of twelve layers of copper-clad wire. Immediately downstream of these plate inserts, two air inlet tubes protruded through the side wall into the reactor, and the outlet openings of the tubes were located in the center of the reactor. The outlet tube of the tubular reactor was connected to the upstream end of the post-combustion reactor. An exhaust pipe protruded from the outlet end of the reburning reactor and was connected to an exhaust pipe. The afterburning reactors were also provided with three layers of insulation material and had an outer wrapping of 0.045 cm thick stainless steel 304 SS. All connections and the exhaust pipe over a length of about 0.9 mm downstream of the post-combustion reactor were equipped with the aforementioned silica-alumina insulation. The exhaust pipe was held in place by hangers so that heat expansion could be followed.

The vehicle modified and equipped in this way was then driven with indole-free fuel and the tests were carried out according to the test cycle mentioned above. The setting was adjusted to 0 ° BTC at 620 rpm, with no suction air improvement. During the first approximately 6 seconds of the cycle, air was injected only into the exhaust ducts. When idling, the Kohler monoxide content of the exhaust gas was about 9%, and at high cruising speed it was about 7-8 '(these values were observed when none

Place air was introduced). The barometric pressure at the time of the test was 75.58 cm Hg. The ambient temperature at the start of the experiment was 22.8 ° C. and at the end of the experiment 23.9 ° C. The analysis of the exhaust gas emerging from the exhaust pipe was carried out using an infrared device. The raw data measured according to the test were corrected for each shape of each cycle, and then the concentrations for hydrocarbon, carbon monoxide and nitrogen oxides for each cycle summed up. Table V shows the values cycle by cycle as well as the summed up total values.

Table V
Test values

Corrected values Cycles HC NO CO

(ppm) (ppm) (%)

only reproduce a stabilized mode of operation, excluding the initial period of warming up.

Table VI
Test values

Cycles Corrected values

HC NO CO

(ppm) (ppm) (%)

1 1.17 3.90 0.07 2 0.00 3.38 0.00 3 0.00 2.10 0.00 4th 0.00 2.51 0.00 5 (not read) 6th 0.00 7.31 0.00 7th 0.00 7.10 0.00 Sum of 1.17 26.31 0.07 Cycles 1-7 0.01 g / 0.05 g / 1.42 g / 1.6 km 1.6 km 1.6 km

1 0.95 5.66 0.04 2 0.00 3.89 0.00 3 0.00 3.40 0.00 4th O ₁ Cl ' 2.68 0.00 5 (not read) 6th 0.00 5.87 0.00 7th 0.00 9.03 0.00 Sum of 0.95 30.53 0.05 Cycles 1-7 0.01 g / 0.06 g / 0.95 g / 1.6 km 1.6 km 1.6 km Table VII

35 Observed mean temperatures ( ⁰ C) in the device according to the invention

Attempt test 1 Measurement point on the left No.*)

Test 2 right side left side right side

960

932

954

910

The test described above was repeated in accordance with the test cycle with the same vehicle which had been modified as described above for the purposes of the method according to the invention. The following test changes were made: the idling speed in the cold was 1500 rpm; the setting was fixed at 2.0 ° BTC at 620 rpm with no suction air enhancement; During the first 75 seconds of the test, air was only injected into the exhaust ports; the barometric pressure at the time of the experiment was 75.68 cm Hg, and the ambient temperature at the start of the experiment was 22.2 ⁰ C and at the end of the experiment, 23.3 ° C. The data obtained from this study are shown in Table VI.

The temperature measurements during the previously Both examinations described were with Thermocouples installed in various locations on the device for the purposes of this invention were carried out. Table VII below shows the data for these temperature measurements illustrated. The temperatures given are approximate mean temperatures like them were observed during the driving cycle and

2 1066 1066 1043 1038 3 904 966 893 921

·) Where the thermocouples are used:

1. In line with an exhaust duct near the center of the tubular reactor.

2. Approximately in the middle of the plate inserts in the post-combustion reactor.

3. Downstream of the plate inserts in the post-combustion reactor.

For comparison purposes, Table VIII shows the results from the baseline test and the results illustrated from the two experiments with installation suitable for the purposes of the present invention. All data were according to the test cycle on the vehicle with a 250 CID machine receive.

A comparison of the data given in Table VIII below clearly shows the excellent Purification that the exhaust gas has received through the treatment according to the method according to the invention

Table VIII

Base emission values in the case of the invention

worthy procedures

1st attempt 2nd attempt

HC l, 67g / l, 6km
NO 1.79 g / l, 6 km
CO31.40g / l, 6km

0.01 g / 1.6 km
0.05 g / 1.6 km
1.42 g / 1.6 km

Example 2

0.01 g / 1.6 km
0.06 g / 1.6 km 0.95 g / 1.6 km

To obtain basic data for comparison purposes, a 400-ClD V-8 machine connected to a dynamometer was run as follows: Indole-free fuel was used. The throttle valve was adjusted so that the machine had a vacuum of 40.7 cm Hg in the mixing tube at 1300 rpm. The power output was about 12.2HP. The air flow to the carburetor was 1.32 m ³ per minute and the fuel flow was 0.111 kg / min so that the air-fuel ratio was 14.6 to 1. The following stabilized exhaust gas temperatures ( ^C C) were determined under these working conditions:

Table IX

Job

Exhaust gas temperature, ⁰ C

ίο On exhaust duct 586

0.9 m downstream of the exhaust pipe 500

Just before the exhaust inlet 386

0.6 m downstream of exhaust 304

outlet

Representative basic data obtained by communicating the raw data and converting the wet gas concentrations to dry gas values, with Ausao taking from water, for the various components of the exhaust gas flowing out of the exhaust pipe under the above working conditions are shown in Table X.

Table X

Concentrations of the components in NO HC the base exhaust gas O, H, N, H ₂ O NH, CO (ppm) (ppm) CO ₁ (%) (ppm) (%) (%) (ppm) (ppm) (%)

460

240

14.8

1200

81.5

12.2

2.2

The same 400-CID machine was then modified as follows: Head covers were attached to the Cylinder head attached; the diameter of the main fuel nozzles has been increased from 0.15 cm to 0.18 cm; the openings on the idle mixture adjustment screw were enlarged to a diameter of 0.185 cm; the openings of the idle pipes were enlarged to 0.13 cm in diameter, and there was a vacuum tube in front of the Throttle installed. A thin sheet of metal was installed to prevent the passage of the exhaust gas from one cylinder side to block the other. The setting was from 10 ° BTC to 4 ° BTC at 635 rpm. The idle was adjusted so that the carbon monoxide content in the untreated Exhaust gas increased from about 0.5% to about 9.5%. An additional air supply line was provided, with which a precise and regulated supply of air could be made. Suitable devices to carry out the method according to the invention were installed on one side of the machine. to these suitable devices installed for the purposes of the method according to the invention belonged to one Tube reactor for the limited oxidation to be carried out in the first process stage, which is connected to stood with an afterburning reactor that was used to carry out the chemical reduction in the second procedural stage and the subsequent one Oxidation was used in the third process stage. The post-combustion reactor was in turn with connected to an exhaust pipe to which a conventional exhaust was connected, and with this in turn an approximately 0.9 m long exhaust pipe was connected.

In this example, a tubular reactor and an afterburning reactor were used, which with regard to Construction and dimensions were very similar to those used in Example 1 above had found.

The main differences compared to the: in Example 1 device used were as follows: The tubular reactor used had a length which corresponded to that of the removed exhaust pipes, it had end plates and had egg; cylindrical profile. There were flanges with which the tubular reactor could be attached to the machine. The tubular reactor had a volume of approximately 1800 cm ³ , an internal surface of approximately 1230 cm ¹ and an outlet facing the bottom and at the rear of the tubular reactor; the post-combustion reactor contained five plate inserts, which were in the middle and at right angles to the direction of flow of the exhaust gas

7M 614 / 19S

Yl

were arranged. Each plate insert consisted of four staggered layers! ms expanded metal (0.32 X 0.48 cm openings in 0. ■> cm thick stainless steel 330 SS), which had been provided with a thin coating of copper.

The thus modified and equipped 400-CID machine, which was connected to a dynamometer, was run on indole-free fuel. The throttle adjustment was made so that the engine was operating at 1300 RPM with a vacuum in the carburetor tube of 45.72 cm Hg. The power was about 12.2 HP and was similar to the immediately preceding investigation to determine the basic data, about a continuous speed of 51.5 km / h. equivalent to. 1.08 m ³ / M ' ⁿ · air was measured at the carburetor inlet and the fuel flow was 0.130 kg / min. So that the air / fuel ratio was 10.1 to 1. Through the two air inlet pipes 0.18 m ³ / min. Air ao introduced into the post-combustion reactor. Under these working conditions, the following stabilized exhaust gas temperatures ( ⁰ C) were noted:

Table XII Table XI

Job

Temperature of the exhaust gas ° C

Near the exhaust duct (about 5cm 750

downstream of an air inlet) At the inlet in the afterburning 995 reactor

Iη the center of the plate inserts
Near the air inlet in the night

combustion reactor

0.9 m downstream of the post-combustion reactor

At the exhaust inlet

On the exhaust pipe, 0.6 m from the exhaust

The data given were obtained by averaging the raw values and converting humid gas concentrations on dry gas values, with the exception of water, for the various components of the recovered exhaust gas exiting the exhaust pipe treated under the conditions described above, as follows:

975 933

864

714 528

_N concentrations of the components in the exhaust gas "

CO NO HC CO ₄ O ₈ H ₁ N, H, O

(ppm) (ppm) (ppm) (%) (° / „) (ppm) ( /.) <Z °>

40

0.5

13.1

4.0 600

81.0

11.0

0.5

A comparison of these data with the data of Example 2 obtained from the base exhaust gas makes it clear recognize that the proportions of hydrocarbons, carbon monoxide and nitrogen oxides in the exhaust gas through the treatment according to the method according to the invention can be completely eliminated and / or reduced could.

The analytical data listed in Example 2 are mean values. The method of analysis for the various components of the exhaust gas was as follows: nitrogen oxides using an infrared device, some of the values were confirmed using chemiluminescent methods; HC using a flame ionization detector; Carbon dioxide by streaming infrared device and by means of a mass spectrometer for samples collected in containers; Oxygen by means of a polarographic analyzer and by means of a mass spectrometer; Hydrogen using a mass spectrometer; Nitrogen by mass spectrometer and chromatographic methods; Water using Method 4 of Federal Register Vol. 36, NoI 247, page 24 887, December 23, 1971; and NH ₃ by wet chemical methods including Kjeldahl nitrogen determination.

Fig. 4 graphically illustrates some of the data that in the case of the operation of the machine described in this example when the machine is stationary Works of the same have been obtained using the method according to the invention. By doing Diagram A is the dependence of the percentage decrease in the content of nitrogen oxides at the outlet pipe to the content of nitrogen oxides on entry into the post-combustion reactor 18 of FIGS. 2 and as a function of the amount of air introduced into the first process stage, Zone I. on the abscissa is the amount of air introduced and the ordinate is the ratio of the percentage NO decrease values applied. Diagram B shows the ratio of the percentage decrease in nitrogen oxide content on the exhaust pipe to the nitrogen oxide content when entering the reactor 18 as a function the oxygen content of the exhaust gas upon entry into the post-combustion reactor. on the abscissa is the percentage oxygen content on entry into the reactor 18 and plotted on the ordinate in turn shows the ratio of the percentage NO decrease values. Diagram C shows the Relationship between the percentage decrease in the NO content in the exhaust pipe and the nitrogen oxide content upon entry into the reactor 18 as a function of the carbon monoxide content in the exhaust gas when entering the reactor. Again on the abscissa is the percentage of CO and on the ordinate the ratio of the percentage decrease ar NO is plotted.

For the operation of the machine in a steady state using the method according to the invention it can be seen from diagram A that the amount of air introduced is important for the limited oxidation in the first process stage and should not exceed ^{5.5 -0.028 m 3 per minute} so that at least a 50% decrease in the concentration of nitrogen oxides is achieved. In a similar way, it can be seen from diagram B that the oxygen content of a limited oxidized exhaust gas which is introduced into the post-combustion reactor should not exceed 1.75%, so that an at least 50% decrease in the concentrator of nitrogen oxides is achieved. From diagram C it can be seen that the carbon monoxide content of the limited oxidized exhaust gas that is introduced into the post-combustion reactor should not be less than about 0.75%, so that an at least 50% decrease in the concentration of NO is achieved These graphs show that there is no percentage decrease in the exhaust pipe.

ier concentration of nitrogen oxides results, instead of an increase being observed when the amount of air supplied in ier first process stage ^{exceeds about 5.5 + 0.028 m 3} per minute, the oxygen content in the exhaust gas exceeds 2.5% and the content m carbon monoxide in the Exhaust gas is lower than about D.47% when this is introduced into the post-combustion reactor.

Example 3

A 1972 Pontiac Catalina automobile with a factory-fitted 400-CID V-8 engine with a ^{0.32m 3} carburetor and automatic transmission was modified as follows: a liner was placed in each exhaust duct; a machine-driven air pump was installed; the factory-fitted carburetor has been replaced with a richer air / fuel mixture; the factory-fitted exhaust pipes and the remaining exhaust system were removed and replaced with a system suitable for carrying out the method according to the invention. For each side of the machine, this system had a tubular reactor with a small volume for the limited oxidation in the first process stage, which was in connection with an afterburning reactor, which was used to carry out the chemical reduction in the second process stage and the subsequent oxidation in the third process stage .

The tubular reactors each consisted of 330 SS stainless steel 0.079 cm thick and had an inner shell about 47 cm in length, which had a hoof-shaped profile and was closed by end plates. Each tubular reactor had a volume of approximately 1639 cm ³ and an internal surface area of approximately 1095 cm ² . The tubular reactors were provided with flanges and "pushed through" fasteners with which the tubular reactors could be attached directly to the machine instead of the usual exhaust pipes. An outlet tube was arranged so that it faced the floor and sat at the end of each tubular reactor. The outside of the tubular reactors was provided with three layers of a silica-alumina insulating material wrapped in a 0.079 cm thick cladding sheet made of 330 SS stainless steel. The outlet on each of the tubular reactors was connected to the inlet end of the post-combustion reactor. Each post-combustion reactor was an oval shell measuring 8.9 cm and 17.15 cm in diameter. and 35.56 cm in length are made from 0.079 cm thick 330 SS stainless steel. At a distance of about ¹ l ₃ the length of the reactor from the reactor inlet, five catalyst insert plates, each consisting of twelve layers of copper-coated wire mesh, were installed at right angles to the direction of flow of the exhaust gas. The outlets of two air inlet tubes inserted through the side wall of the reactor were placed in the center of the reactor immediately downstream from the last catalyst insert plate. From the other end of the reactor there was an outlet pipe which was connected to an exhaust pipe. The exhaust pipe, in turn, was connected to a conventional exhaust pipe on which an exhaust pipe was attached. The post-combustion reactors were wrapped with three layers of insulating material and the outer cover was made of 304 SS stainless steel. The connections between the tubular reactors and the post-combustion reactors were also provided with three-layer insulation and an outer wrapping of aluminum foil. There were air supply pipes from the air pump to the air inlets in the exhaust ducts of the engine and to the air inlet pipe leading into the post-combustion reactors.
The vehicle thus modified and equipped was

ίο then drove with indole-free fuel and the subjected to the above test cycle. The choke was adjusted by hand. The basic setting was set at 4 ° BTC at 720 rpm. It was made for No suction air is used for approximately the first 120 seconds of the test cycle, but rather during this Period the suction air is throttled. The speed of the machine was 1300 rpm when idling in the cold and was 600 rpm when idling in the heat. The air supply speeds to the air supply

ao guides in the flow channel and the air supply speeds to the two air inlet pipes in the post-combustion reactor are shown in FIG. 5 illustrated. The inflow quantities give up the entire air supply for process stages 1 and 3

on both sides. The barometric pressure at the beginning of the experiment was 75 cm Hg. The ambient temperature at the beginning of the experiment was 24.4 ° C and at the end of the experiment 25 ° C. The analysis of the exhaust gas emerging from the exhaust pipe was carried out using Infrared device made. According to the test, the measured raw data for each shape were each Cycle corrected and the values for the concentrations hydrocarbon, carbon monoxide and Nitric oxide totaled for each cycle. In Table XIII are the values for each cycle and those as the sum of all Cycles resulting values compiled.

Table XIlI
Concentrations

Cycles Corrected values

HC NO CO

(ppm) (ppm) (%)

A C 50 6th 0.18 5.18 0.02 ⁴⁵ 2 7th 0.00 0.00 0.00 3 Sum of 0.00 0.00 0.00 4th 55 cycles 1—7 0.00 0.47 0.00 5 (not read) 0.00 8.28 0.00 0.00 4.42 0.00 0.18 18.35 0.02 0.00 g / 0.05 g / 0.59 g / 1.6 km 1.6 km 1.6 km

Example 4

A 303-CID V-8 machine was equipped with one for performing the method of the invention suitable device similar to that used in the previous examples. Six post-combustion reactors were assembled, which differed only in that in three reactors Inserts made of 330 SS expanded metal with a thin copper coating and inserts in three reactors made of 330 SS expanded metal without copper coating

were present. When conducting the experiment, one side of the V-8 engine was with a reactor, the had inserts provided with a thin copper coating, and the other side with a reactor without Equipped with copper plating on the inserts. The 307-CI D machine was on a test truck installed and driven according to the test cycle. After the test, the concentrations were increased HC, carbon monoxide and nitrogen oxides measured using NDIR instrumentation. For each of the three pairs These experiments were repeated in the post-combustion reactors. Every couple so investigated was then removed from the 307-CID machine and attached to a 400-CID machine, according to the method according to the invention with a specific fuel, which will be described below is, for a period of 100 hours under stationary conditions at 2500 rpm with a 25.4 cm Hg tube vacuum was operated. After the

Table XV

100 hours of steady-state work according to the specified conditions became each Reactor pair removed from the 400-CID machine and again on the 307-CID machine on the zuvoi chassis dynamometer described. The emission values of HC, carbon monoxide, nitrogen oxides were determined again and compared with those values that were used in the same reactors before dei 100-hour test with the special fuel

ίο had been received.

The test described was completed on three pairs of reactors; every couple was during Tested for 100 hours with various amounts of fuels containing tetraethyl lead. The received Test values are compiled in Table XV. The stated values are average values of two tests on the same pairs of reactors. The characteristics for the fuels used are summarized in Table XVI.

Salary ι NO Indole IA CO Inserts without copper NO Indoles CO of treated exhaust gas (g / 1.6 km) 0.04 free 0.89 HC 0.05 30th 0.63 Inserts with copper plating 0.03 (a) 1.33 0.01 0.03 (C) 0.77 HC 0.03 97.7 0.91 0.01 0.03 104.2 0.68 Before 100 hours of testing ») 0.01 0.01 87.8 0.36 0.01 0.04 95.3 0.47 After 100 hours of testing ») 0.04 - 58.7 - 0.01 58.7 100 hours ago 0.01 0.05 0.744 0.56 - 0.06 0.744 0.34 After 100 hours of testing ¹ ») 0.01 «) Fuel without lead content; ^b ) with low; 8.45 0.01 ^c ) with high lead content. 8.55 100 hours ago - Table XVI 91 90 After 100 hours of testing ⁰ ) 0.01 Indoles 127 5 127 181 (b) 182 Test octane 215 ^Q 9.9 215 Engine octane 240 90.5 241 API density 298 58.3 296 Specific density 401 0.7455 401 Reid vapor pressure 98 8.50 98 Distillation initially 1 90 1 boiling point 1 1 10% 0.063 128 3.171 30% 600+ 183 600+ 50% 216 70% 0.016 240 0.005 90% 2.70 303 2.75 End point 402 % Recovered 5.75 98 5.80 % Residue Residue acidity allowed 1 permitted % Loss corrosion 1 IA Pb (3.785 liters each) 0.560 Oxidation stability 600 + (Min.) Sulfur (wt%) 0.014 20% distillation 2.80 Co-efficient RVP coefficient 5.70 permitted IA For this purpose 4 sheets of drawings

Claims (5)

<s duktionsmittel promotes, below a volume claims: percent to be kept. In any case, the addition of oxygen or a free oxygen 1. Method for reducing the proportion of gas containing before the reduction stage than after Carbon monoxide, hydrocarbons, water - 5 parts viewed. substance. and nitrogen oxides in one of one with Also from US-PS 35 65 574 the teaching emerges, a hydrocarbon fuel operated a two-stage process to clean the exhaust gases Internal combustion engine emitted exhaust gas to bring into use in the first in which the exhaust gas of a treatment to the kata stage reduces the nitrogen oxides contained in the exhaust gas lytic reduction of nitrogen oxides and an- io and in the second stage those contained in the exhaust gas then a treatment for non-catalyzable constituents mixed with air or table oxidation of the remaining oxygen in the exhaust gas. In doing so, the one from the verbalized The exhaust gas stream coming from the internal combustion engine is only very oxidizable is drawn, characterized in that they contain small amounts of free oxygen and that that of the internal combustion engine 15 without the supply of oxygen or air with the emitted exhaust gas before treatment for the reduction catalyst for the reduction of nitrogen oxides in Bezierung the nitrogen oxides are brought to a stirring containing oxygen. Gas is supplied in such an amount that one. correspondingly working pure two-stage the temperature of which is increased to at least 840 ° C, in which in a first stage with addition becomes oxidizable without the carbon monoxide content in the air in a flame reaction Exhaust gas is burned below the stoichiometric amount of the constituents of the exhaust gas and in one the nitrogen oxides present drops. second stage the reaction is completed, in- 2. The method according to claim 1, characterized in that the exhaust gases from the first stage are identified via a catalytic converter, that the exhaust gas is fed into the oxidation analyzer, which reduces the stick levels brings about before and after the reduction of nitrogen oxides, and possibly the oxidation of the oxide air is supplied. Carbon monoxide completed to carbon dioxide, 3. The method according to claim 1, characterized in that US Pat. No. 3,220,179 is known. That in this Indicates that the catalyst underflatten the process described on the indoor publication the device in which the reduction differs from those mentioned above only the nitrogen oxide is carried out, applied 30 in that the reduction and oxidation are not will. be carried out one after the other, but age- 4. The method according to claim 1 or 3, characterized depending on the oxygen content of the exhaust gas characterized in that the catalytically active metals either oxidize predominantly with the addition of oxygen Copper, nickel, iron, chromium or their Mi- (flame oxidation in the first stage and cataschungen be used. 35 lytic residual oxidation in the second stage) or without 5. The method according to claim 3 or 4, characterized in that the supply of oxygen is predominantly reduced catalytically characterized in that sieve is coated with copper (second stage). fabric made of stainless steel alloys as a catalyst- These well-known two-stage processes prove arrangements are provided. plus the removal of nitrogen oxides from the exhaust gas 40 has a relatively poor efficiency. This fact can be attributed to the fact that In the reduction stage, hydrogen combines with the nitrogen oxides to form ammonia, which in the Reduction stage following oxidation stage again 45 is converted into nitrogen oxides. Depending on the The invention relates to a process for Vermin- which amount of hydrogen can therefore in these the proportion of carbon monoxide, carbon bederung known processes always a certain part are the hydrocarbons, hydrogen, and nitrogen oxides is not reduced in a nitrogen oxides into harmless N _a, of a with a hydrocarbon -Fuel In addition, in the reduction stage very operated internal combustion engine must be available at high temperatures, because it is exhaust gas in which the exhaust gas is treated with a catalytic converter with a certain co-catalytic reduction of nitrogen oxides and an- generally a stronger one Closing degree of a treatment for the non-catalytic _{reduction of NO x} achieved, the higher the temperature of the oxidation of the remaining temperature of the exhaust gas in the exhaust gas. In certain cases it must be subjected to oxidizable components. 55 therefore include external heating means and heating devices From DT-OS 21 40 495 it is known that the cleaners are set in order to ensure the effectiveness of the supply of the exhaust gases to achieve a suitable temperature by means of such a two-stage catalytic converter. To carry out the method according to the first nature of the above-mentioned Stage the nitrogen oxides contained in the exhaust gas reduces a relatively low efficiency of the disadvantages and in a second stage the 60 known two-stage processes contained in the exhaust gas, oxidizable constituents mixed with air oxy- The invention is based on the object of a be dated. The method for exhaust gas cleaning is available from this publication It also shows that an excessively high oxygen concentration results in a better degree of efficiency tration in the exhaust gas distinguishes the effectiveness of the catalysts than known processes of this type, lowered to reduce nitrogen oxides. This 65 This task is mentioned at the beginning Concentration should therefore be achieved by bringing the process into contact by removing the exhaust gas with a catalytic converter, the reaction of the internal combustion engine emitted exhaust gas before Oxygen with the re-treatment contained in the exhaust gases to reduce nitrogen oxides