Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – A gas is substance acted upon
Patent
1981-05-27
1983-08-23
Chiesa, Richard L.
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
A gas is substance acted upon
60 395, 60286, 60298, 60299, 422111, 422168, 423212, 423239, C01B 2136
Patent
active
044003528
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method and a device for optimizing purification of diesel exhaust gases, the purification being carried out by using a catalyst.
The diesel exhaust gases are today one of the most serious environmental problems on the work places, especially when diesel operation is used in closed rooms, e.g. mines, storerooms, ships etc. Moreover, a great increase of the number of diesel-driven private cars in traffic above ground is expected in the future. Due to this the diesel exhaust gases are likely to be an environmental problem above ground, at least in the cities.
A known technique for reducing the problems with the discharge of the exhaust gases is connecting special exhaust gas purifiers to the exhaust system. So-called catalytic purifiers are often used, the catalyst compound of which consists up to 99% of alumina, the rest being the active metal, mostly platinum. The good eliminating effect of the catalysts on carbon monoxide (CO) and hydrocarbons (HC) is well documented.
However, in recent years it has been often discussed, particularly in mine circles, whether catalysts are justified. There are several reasons for this, i.e. sometimes an increased content of the dangerous nitrogen dioxide (NO.sub.2) and also bad HC/CO-purification in certain cases. The nitrogen dioxide (NO.sub.2) is the gas component according to which ventilation is dimensioned under ground.
It is the object of the present invention to prevent an increase of NO.sub.2 in the exhaust gases and also to eliminate CO/HC effectively. Reduced irritation of nose and ears is also obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
One example of the invention will be illustrated below with reference to the enclosed drawings, where
FIG. 1 is a graphic illustration of the CO- and HC-contents and the NO.sub.2 -change in a catalyst as a function of the exhaust gas temperature at different r.p.m.;
FIG. 2 is a graph showing the ratio of NO.sub.2 to NO.sub.x (.dbd.NO.sub.2 +NO) in the exhaust gases after a catalyst as a function of the exhaust gas temperature at different r.p.m.; and
FIG. 3 is a schematic view of the construction of a device according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In order to explain the theory behind the present invention reference is made to the diagrams in FIG. 1. These show the contents of CO and HC after a catalyst and the NO.sub.2 -change (.DELTA.NO.sub.2) in the same catalyst as a function of the exhaust gas temperature at different r.p.m.
The uppermost diagram shows the CO-content as a function of the exhaust gas temperature. It can be read from this diagram that the CO-content is very low when the exhaust gas temperature exceeds about 250.degree. C.
The diagram in the middle shows the HC-content as a function of the exhaust gas temperature. It is evident that the HC-content will decrease with increasing exhaust gas temperature up to about 250.degree.-300.degree. C. The HC-content will then be substantially constant even if the exhaust gas temperature increases.
In the lowermost diagram of NO.sub.2 -change (.DELTA.NO.sub.2) in the catalyst is shown as a function of the exhaust gas temperature. At low exhaust gas temperatures, <250.degree. C., the NO.sub.2 -change is negative, i.e. NO.sub.2 is converted into NO and O.sub.2. However, when the exhaust gas temperature exceeds 250.degree. C. a great increase of NO.sub.2 will appear, which increase continues until the exhaust gases have reached a temperature of 350.degree.-400.degree. C. At a still higher exhaust gas temperature a reduction of NO.sub.2 will then appear again.
In FIG. 2 the NO.sub.2 /NO.sub.x (.dbd.NO.sub.2 +NO) ratio in the exhaust gases after a catalyst is shown as a function of the exhaust gas temperature at different r.p.m. Only the points of measurement of the minimum and maximum r.p.m. have been connected. The range marked with vertical lines indicates the calculated NO.sub.2 /NO.sub.x ratio at equilibrium and typical oxygen contents in diesel exhaust gases, 5-20%.
It is apparent from FIG. 2 that the
REFERENCES:
patent: 3779015 (1973-12-01), Maruoka
patent: 4106286 (1978-08-01), Sakai et al.
Rehnberg Ove A.
Sundgren Anders J.
Chiesa Richard L.
Unikat AB
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