Power plants – Internal combustion engine with treatment or handling of... – Methods
Patent
1997-11-06
1999-09-07
Denion, Thomas E.
Power plants
Internal combustion engine with treatment or handling of...
Methods
60276, 60285, 123681, F01N 300
Patent
active
059469056
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an optimization control for gas engines with a three-way catalyst and more in particular to the use of such an optimization control during the operation of gas engines which are provided with a .lambda. sensor and a controlled three-way catalyst.
BACKGROUND
Total energy plants with gas engines show a higher emission of noxious components than other electricity generators. In order to drastically reduce these emissions (NO.sub.x and unbrined components), a three-way catalyst can be used. It is necessary for the proper functioning of the three-way catalyst that the gas-air ratio of the mixture supplied to the gas engine is kept constant. The gas-air ratio can be indicated by the air factor .lambda..
The object of a .lambda. control is to keep the composition of the gas-air mixture supplied to the engine very close to the optimum working point of the three-way catalyst by making use of a closed control circuit. The maximum deviation from the working point is determined by the so-called .lambda. window. Within this window are all the values of .lambda., for which it applies that the emission of all the noxious exhaust gas components remains below the maximum limits fixed for these components.
The lower and upper limits of the .lambda. window are determined by an exhaust gas component which at a lower or higher .lambda. value exceeds the maximum emission permissible for this component. In case of a properly functioning three-way catalyst, the emission of carbon monoxide (CO) is decisive of the lower limit, and the emission of nitrogen oxides (NO.sub.x) is decisive of the upper limit of the .lambda. window. This is shown in FIG. 1.
Earlier research and experiences from demonstration projects show that problems arise with the existing techniques to keep within the .lambda. window. By ageing and wear of the sensor, the air factor gradually changes. The three-way catalyst then no longer works at its optimum working point, and the emissions of noxious substances impermissibly increase. The applicant has done research to solve this problem. This research has led to the development of an optimization method for periodically determining the value of the .lambda. signal which corresponds to the optimum value of the fuel-air ratio for the proper functioning of the three-way catalyst.
In the Netherlands, in contrast to other countries such as Germany, Austria, and Switzerland, few gas engines with a three-way catalyst are used. Much more use is made of another NO.sub.x limiting technique, namely the lean mixture gas engine. Although the potency of these lean mixture techniques is high, the use of particularly catalytic cleaning methods seems unavoidable, if the emission requirements are made more stringent in the future. The branch in which uses with three-way catalysts can be expected soonest is the greenhouse horticulture.
In this branch not only the generated electricity and heat, but also the combustion gases of a total energy plant can be used for CO.sub.2 fertilization, provided these gases do not contain too many noxious components. Apart from saving energy, this is also of economic advantage. For CO.sub.2 fertilization the NO.sub.x emission must be considerably lower then the present legal requirement of 140 g/Gj. Besides, limiting values are also imposed on other noxious components. A three-way catalyst is satisfactory here, as has been demonstrated both in applicant's laboratory and in practice, but exact control of air factor .lambda. by means of a .lambda. sensor is then necessary.
A .lambda. sensor comprises a small sheet of a ceramic material consisting of zirconium dioxide (ZrO.sub.2) stabilized by means of yttrium oxide (Y.sub.2 O.sub.3), provided on both sides with thin platinum electrodes permeable to gas. One of these electrodes comes into contact with the exhaust gases. This electrode functions as a small catalyst. The other electrode is in contact with the ambient air and serves as reference electrode with respect to the oxygen concentration.
REFERENCES:
patent: 4953351 (1990-09-01), Motz et al.
patent: 5233829 (1993-08-01), Komatsu
patent: 5325664 (1994-07-01), Seki et al.
patent: 5542248 (1996-08-01), Iwata et al.
Denion Thomas E.
Gastec N.V.
LandOfFree
Optimization control for gas engines with a three-way catalyst does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optimization control for gas engines with a three-way catalyst, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optimization control for gas engines with a three-way catalyst will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1792282