Method for monitoring a combustion process, and corresponding device

This is a continuation of PCT/EP02/13899, which was filed Dec. 7, 2002, designates the U.S., and is incorporated herein by reference.

1) Field of the Invention

The invention relates to a method for monitoring a combustion process, in which, in a oven, a substance arranged in a bed of the oven is converted under the supply of heat by way of firing by a flame, data of the flame and/or the substance in the bed is recorded by way of at least one sensor, and the input of heat into the bed is determined from the data recorded by the sensor and is used for quality determination, as a result of the thermal radiations of the flame and of the bed being recorded as data by the sensor and normalized by way of the supplied and/or produced quantities of energy and material. The invention also relates to a device for carrying out the method for monitoring the combustion process.

2) Description of Related Art

DE 199 50 981 A1 discloses a rotary tubular kiln for converting a substance, in which spectroscopic data of the fired cement is determined. The intensity of the data, in particular that of calcium hydroxide, is used to draw conclusions as to the clinker index (FCAO) as a measure of the quality of the cement.

U.S. Pat. No. 5,997,288 A describes a method of the type described in the above Field of the Invention section for the heat treatment of coal in an externally heated rotary tubular kiln, in which hot gas is passed through the coal in countercurrent and the temperature of the bed of coal in the oven is measured by means of thermocouples arranged at a central lance, in order to control the input of heat into the bed of coal and the quality of the treated coal.

DE 25 15 807 A1 has likewise disclosed a method of the type described in the above Field of the Invention section, in which petroleum coke is heat-treated in a rotary tubular kiln, with pyrometers measuring the radiation intensity of the coke bed or of the kiln wall.

The present invention is based on the object of improving a method and a device of the type described in the above Field of the Invention section. One aspect of the present invention is the provision of a method for monitoring a combustion process, in which, in a oven, a substance arranged in a bed of the oven is converted under the supply of heat by way of firing by a flame, data of the flame and/or the substance in the bed is recorded by way of at least one sensor, and the input of heat into the bed is determined from the data recorded by the sensor and is used for quality determination, as a result of the thermal radiations of the flame and of the bed being recorded as data by the sensor and normalized by way of the supplied and/or produced quantities of energy and material, wherein to control the combustion process the input of heat into the bed is determined from the difference between the normalized thermal radiations of the flame and of the bed and is optimized at a defined temperature.

By virtue of the fact that to control the combustion process, the input of heat into the bed is determined from the difference between the normalized thermal radiations of the flame and of the bed and is optimized at a defined temperature, a measure of the quality of the converted substance which is simpler to determine than the spectroscopic measurement, with the control base thereon, is provided. This is true in particular if the input of heat into the bed or the thermal radiation of the flame and of the bed are recorded optically, i.e. the camera arrangement which is in any case present for flame observation is used. To control the combustion process, it is preferable for the normalized thermal radiations, at a defined temperature, as far as possible to be kept in a constant relationship with respect to one another.

The method and the device of the present invention can be used for all conversion operations in which the conversion, firing, sintering or the like of the substance is dependent on the specific heat input, i.e. for example for the firing of cement or lime or in glassmaking.

In the text which follows, the invention is explained in more detail on the basis of an exemplary embodiment.

The interior of a cement oven designed as a rotary tubular kiln has a bottom region, which is referred to as the bed, sintering zone or clinker bed. During the combustion process, the finished cement is formed in the bed. Above the bed is the region in which, during the combustion process, the flame is formed. The thermal radiation S F of the flame, the thermal radiation S B of the cement formed in the bed, the thermal radiation S Z of the cement (clinker) after the flame and the thermal radiation S W of the rotary tubular kiln wall are recorded at a plurality of locations and for a prolonged period of time by way of a plurality of thermal radiation sensors. Examples of the sensors are a multichip CCD camera, a CMOS camera or a glass fiber camera with a plurality of glass fibers which are independent of one another, in each case with connected image processing, and the data is fed to a computer.

The absolute values for the thermal radiation are then also normalized. Specifically, the thermal radiations S F and S W of the flame and the rotary tubular kiln wall are normalized using the quantity and quality of the fuel, i.e. the calorific value M B . Similarly, the thermal radiations S B and S Z of the bed and the cement are normalized using the quantity of clinker produced (cement quantity) M Z . A control performed by the computer, for example by way of a neural network, uses a function of these different normalized thermal radiations, i.e.

f(S F /M B , S W /M B , S B /M Z , S Z /M Z ).

The combustion process is controlled in such a way that at a defined temperature a relationship which is as constant as possible is maintained between these normalized thermal radiations.

The difference between the normalized thermal radiation S F /M B of the flame and the normalized thermal radiation S B /M Z of the bed substantially determines the input of heat Q B into the bed, i.e. the quantity of heat supplied to the bed. The FCAO value, which is a measure of the quality of the cement, is directly dependent on this (specific) heat input Q B into the bed, in which context the quality may locally differ on account of the locally dependent nature of the input of heat Q B . Therefore, the control of the combustion process is intended to achieve the maximum input of heat Q B into the bed. For this purpose, the computer controls various actuating devices which determine the control variables of the oven, for example the supply of air, fuel, lime and aggregates.