JPH058367B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the flow rate of powder and granular materials in a state in which various powder and granular materials are dispersed in a gas, that is, solid-gas two-phase flow (hereinafter sometimes simply referred to as two-phase flow). The present invention relates to a measuring method, and particularly to a method that can accurately and easily measure the flow rate of the powder without interfering with the flow of the two-phase flow.

An air flow transport method is commonly used as a method for transporting powder and granular materials from a storage container to another location. In this case, the flow rate of the powder or granule is usually measured by measuring the weight loss of the powder or granule in the storage container using a strain gauge attached to the container, and calculating the average flow rate per unit time. It is. For this reason, it is not possible to measure the fluctuation in the flow rate of powder or granular material over a short period of time, for example, several minutes. Furthermore, when pulverized coal is distributed and transported from one storage container to around 30 tuyeres, such as when pulverized coal is injected into a blast furnace, even if the total injection amount can be known, individual It is not possible to grasp the amount of pulverized coal fed from the tuyere, and even if a feeding failure occurs in some transport pipes, the situation cannot be accurately grasped. For this reason, technologies are being developed that can measure the flow rate of powder or granular material for each individual transport pipe, such as a method of measuring the flow rate of powder or granular material from the differential pressure or capacitance within the air flow transport pipe, or For example, an ultrasonic Doppler method has been proposed in which the flow rate is measured by projecting ultrasonic waves onto powder particles transported in a two-phase flow. However, these known methods have problems in measurement accuracy and cannot be said to be satisfactory. In other words, solid-gas two-phase flow is a mixed flow of solid and gas with significantly different specific gravity, so the concentration of powder in the transport pipe is quite uneven. For example, in a horizontal pipe, the upper layer is thinner and the lower layer is thicker, and However, because the particle size is non-uniform, the behavior of each particle is complicated and the flow condition is unstable, which is an inherent problem. Moreover, with the method of arranging the flow rate detection member in the two-phase flow channel, it is not possible to avoid wear of the detection member due to collisions of powder and granules, and furthermore, the flow is obstructed by the detection member, making it easy to cause pipe clogging. There is also the problem.

The present inventors have solved these problems and are able to accurately measure the flow rate of powder and granular materials transported by solid-gas two-phase flow, without impeding the flow of the transport fluid and without causing wear on the detection member. Various studies have been carried out in an attempt to establish a flow rate measurement method that does not cause such problems. The present invention was completed as a result of such research, and its structure is a method for measuring the flow rate of powder and granular material in a solid-gas two-phase flow, and the present invention is a method for measuring the flow rate of powder and granular materials in a solid-gas two-phase flow, and the pressure change in the transportation pipe is measured as pressure vibration. , the pressure vibration is subjected to frequency analysis to obtain the integral value of the vibration energy per unit time, and the flow rate of the granular material is calculated from the correlation between the predetermined integral value of the vibration energy per unit time and the granular material flow rate. The gist lies in the fact that we are aware of the following.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and effects of the present invention will be described in detail below with reference to the drawings. Fig. 1 is a schematic vertical cross-sectional view showing an experimental method when the present invention is used to measure the amount of pulverized coal injected into a blast furnace blow pipe. Pipe 4 indicates a pulverized coal supply pipe, and while supplying pulverized coal C together with a carrier gas such as air from the pulverized coal supply pipe 4, heated air H is blown from the right side of the blow pipe 3 in the drawing. The pulverized coal C is mixed with heated air H, combusted, and blown into the blast furnace through the tuyeres 2. In the present invention, a pressure vibration detector 5 and/or 6 is provided on the side wall of the blow pipe 3 and/or the pulverized coal supply pipe 4 to detect pressure changes in the pipe over time and detect the change as pressure vibration. is installed to continuously detect pressure changes caused by the injection of pulverized coal C.
The pressure vibration is subjected to frequency analysis to obtain an integral value of vibration energy per unit time. For example, in Figure 2 A and B, Figure 3 A and B, and Figure 4 A and B, the amount of pulverized coal injected is 64Kg/hour, 80Kg/hour, and 100Kg/hour.
The pressure vibrations detected by the pressure change detector 5 and the vibration energy obtained by frequency analysis of the pressure vibrations when set to Kg/hour (the figure shows the value obtained by squaring the volt value of the output voltage) As is clear from each figure A, the internal pressure of the blow pipe 3 pulsates within a range of approximately ±1 mmH ₂ O for any blowing amount.
The amplitude of the pulsation increases as the pulverized coal flow rate increases. Therefore, it is considered possible to measure the pulverized coal flow rate based on the magnitude of this amplitude, but in reality, the amount of variation in the amplitude due to changes in the pulverized coal flow rate is extremely small, so this is used to measure the flow rate. It is not possible. However, when the above-mentioned pulsation is subjected to frequency analysis, the vibration energy becomes as shown in each figure (b), and the difference in vibration energy due to the difference in the flow rate of the powder becomes obvious. However, when trying to compare the maximum value of vibration energy in each figure (b), this value is shown as an extremely steep tip value, so there is a slight difficulty in measurement accuracy. Therefore, in the present invention, a specific frequency range (preferably a region where the vibration energy shows the highest value: 100 to 300 in the illustrated example)
The purpose is to reduce errors in measurement accuracy by comparing the integral value of vibration energy at Hz), and convert this integral value to the flow rate of pulverized coal. By the way, Figure 5 shows the pulverized coal flow rate from 0 to
This is a graph showing the correlation between the vibration energy (squared value) and the integral value in the frequency range of 0 to 601 Hz for husband and husband when the pulverized coal flow rate is approximately 20 kg/hour. It can be seen that under conditions exceeding time, there is an excellent correlation between the flow rate and the integral value. Note that the linear equation showing this correlation varies slightly depending on the type of powder or granular material being transported, the type of carrier gas, the flow rate, etc., so the relationship between the flow rate and the integral value should be calculated in advance according to the transport conditions. By creating a standard line shown below, and converting it by applying the integral value of the vibration energy measured during actual transportation of powder and granular material to the above standard line,
It is possible to accurately know the flow rate of powder or granular material at any point in time.

In the above example, the pressure change inside the blow pipe 3 where pulverized coal and heated air are mixed and combusted is detected. In this case, the pressure inside the pipe becomes considerably high due to the gasification reaction caused by combustion. , the accuracy of detecting the flow rate of pulverized coal is extremely high. However, even without using this kind of pressure increase due to combustion,
Of course, it is also possible to similarly determine the flow rate of the powder or granule based on the pressure change during fluid transport of the powder or granule itself.
For example, in FIG. 6, pressure vibrations are detected by the pressure vibration detector 6 installed in the pulverized coal supply pipe 4 of FIG. Vibration energy (square value) at
It shows the correlation between the integral value of Note that the slope of the primary straight line in this case is gentler than in the example shown in Figure 5, and the measurement accuracy is accordingly slightly lower; however, before calculating the integral value, the output voltage volt value of the vibration energy is squared. By increasing the value to the third or fourth power, the gradient of change becomes larger and measurement accuracy can be improved.

As described above, according to the present invention, the measurement member is not installed at the cross-sectional position of the fluid flow path of the powder transport pipe, but is installed on the side wall, and the measurement is performed based on fluctuations in the pressure inside the pipe. Therefore, the flow rate of the powder or granular material can be accurately detected without the risk of abrasion of the measuring device due to contact with the transport fluid or obstruction of the flow, causing blockage of the pipe line. Furthermore, even when granular materials such as pulverized coal used as blast furnace fuel are supplied from multiple pipes and inlets, each pipe is equipped with an individual pressure vibration detector. Since it is possible to accurately grasp the flow rate of powder and granular material for each channel, it is possible to accurately control the operating status of the blast furnace, and even if a partial injection abnormality occurs, the location of the abnormality can be identified. You can know instantly. In addition, when managing the amount of powder and granular material transported through a large number of transport pipes in parallel, a pressure vibration detector is installed for each transport pipe, while a pressure vibration detector is installed for signal processing (frequency analysis and vibration energy analysis). (conversion to flow rate, etc.) is shared by one unit,
It is preferable to measure the amount of powder and granular material transported in each pipe while scanning at regular intervals, since this can significantly reduce the burden on equipment. Furthermore, although the above description has mainly focused on the case where the present invention is used for measuring the flow rate of pulverized coal for blast furnace injection, the present invention is of course not limited to this use, and can be used to measure the flow rate of pulverized fuel in various combustion equipment or simply It can also be used to measure the flow rate of various powders and granules in powder and granule transportation piping.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view of the main parts when the present invention is used for blowing pulverized coal into a blast furnace blow pipe;
Figures 2 to 4 A and B are diagrams showing pressure fluctuations in the blow pipe during pulverized coal injection and vibration energy obtained from frequency analysis, and Figures 5 and 6 are the relationship between the pulverized coal flow rate and the integral value of vibration energy. This is a graph showing. 1... Blast furnace refractory wall, 2... Tuyere, 3... Blow pipe, 4... Pulverized coal supply pipe, 5, 6... Pressure vibration detector.

Claims (1)

[Claims] 1. In a method of measuring the flow rate of powder and granular material transported in a pipe together with a carrier gas, pressure changes in the transport pipe are measured as pressure vibrations, and the pressure vibrations are subjected to frequency analysis to calculate the integral of the vibration energy over a unit time. The flow rate of powder and granular material in a solid-gas two-phase flow is characterized by determining the flow rate of the powder and granular material from the correlation between the integral value of the vibration energy in unit time determined in advance and the flow rate of the powder and granular material. Flow measurement method.