Heating – Processes of heating or heater operation – Including passing – treating or conveying gas into or through...
Reexamination Certificate
1999-08-20
2001-09-25
Lu, Jiping (Department: 3749)
Heating
Processes of heating or heater operation
Including passing, treating or conveying gas into or through...
C432S106000, C110S215000, C110S203000, C062S171000, C095S016000, C095S023000, C096S251000, C096S252000, C261S115000, C261SDIG009
Reexamination Certificate
active
06293787
ABSTRACT:
The present invention relates to a method of regulating the flue gas temperature in a cement production plant comprising a kiln, a flue gas conditioning device, a mill and an electrostatic precipitator, whereby the flue gas from the kiln is passed through the conditioning device and is from there conveyed either via the mill or directly to the electrostatic precipitator, whereby measurements are carried out in the flow path of the gas of the flue gas temperature before the electrostatic precipitator, and whereby the water is supplied to the flue gas for cooling purposes in the conditioning device as a response to this temperature measurement, provided the temperature is too elevated.
In connection with cement production plants a considerable cooling of the flue gas occurs in the mill during its passage through the mill. Thus, in usual operating conditions where the mill contributes to the cooling of the flue gas, there is only a modest need for further cooling in a flue gas conditioning device in order to hereby obtain the desired gas temperature in the electrostatic precipitator to allow optimum control of the precipitator and thus to obtain the best possible precipitation. In this connection a measurement of the flue gas temperature is usually carried out immediately prior to the flue gas entering the electrostatic precipitator, said measurement being used for controlling the supply of cooling water to the conditioning plant.
However, in some cases the mill is not capable of contributing with this cooling effect. Often, the mill in question has an excess capacity relative to the remaining plant thereby allowing the mill to produce a stock so as to permit exploitation of e.g. the differentiations in electricity prices by eliminating the need to operate in times of high electricity prices. Moreover, unpredicted production shut-downs are not uncommon. In operating conditions when the mill is not in operation, flue gas may occur with a substantially higher temperature than desired for the electrostatic precipitator. The temperature measurement before the electrostatic precipitator will react to this elevated temperature and as a result of this, water will be supplied to the flue gas in the conditioning device. Until the regulation of the temperature has occurred by means of the conditioning device, however, some time will lapse during which the operation of the electrostatic precipitator is not optimal due to the increased gas temperature.
It follows that it is the object of the present invention to provide a method of the type described above wherein the temperature regulation is effected more quickly in order to hereby reduce the duration of the period during which an elevated gas temperature prevails in the electrostatic precipitator.
In accordance with the invention this is obtained by a method of the type described in the introductory part which is characterised in that a measurement of the flue gas temperature is carried out prior to its introduction into the conditioning device, that a flow measurement of the flue gas is carried out, and that, on the basis of this temperature measurement and flow measurement, a required amount of water is established for cooling the flue gas to a desired temperature, and that this water amount is supplied to the flue gas.
By the method thus defined a considerable reduction is obtained of the period of time during which an increased flue gas temperature prevails in the electrostatic precipitator, and consequently a reduction of the amount of particles which, in this non-optimum operative state, passes through the electrostatic precipitator. Considerable savings in the amount of water used are also obtained, since the method according to the invention permits a considerably more accurate determination of the required cooling effect. Of course, this is of particular importance in areas with scarcity of water.
The invention also relates to a cement production plant comprising a kiln, a conditioning device, a mill and an electrostatic precipitator. According to the invention this plant is characterised in comprising means for determining the gas temperature before the conditioning device, means for determining the magnitude of the gas flow, and means for determining the amount of water required to reduce the gas temperature from the value measured to a desired value. By means of such plant it is possible to exercise the method described above and to obtain the advantages discovered in this connection.
REFERENCES:
patent: 3842615 (1974-10-01), Reigel et al.
patent: 4184886 (1980-01-01), Ellingen et al.
patent: 4626261 (1986-12-01), Jorgensen
patent: 4666470 (1987-05-01), Verduyn et al.
patent: 5169611 (1992-12-01), Kupper et al.
Baker & Botts L.L.P.
FLS Miljoa A/S
Lu Jiping
LandOfFree
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