JPH0615002B2 - Control method of multi-stage spray drying tower - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a multi-stage spray-drying tower, in which the bulk density and water content of spray-dried particles are controlled for quality control when spray-drying a detergent slurry or the like. It is about how to control.

[Prior Art] Conventionally, in spray-drying a slurry in a spray-drying tower,
When controlling the bulk density and moisture for quality control, a few operating factors selected from hot air temperature, spray pressure, slurry specific gravity, slurry supply amount, etc. are simultaneously operated.

This constitutes an interfering system in which dry operating factors interfere with each other, that is, even when only one of the operating factors is operated, it affects both the bulk density and the water content. This is because it is not possible to control both of them to the target values, and usually, among the above factors, there are many control systems that simultaneously operate the spray pressure and the hot air temperature to obtain the target bulk density and moisture.

In such control, it is necessary to determine how much the manipulated variables of the above two operating factors, that is, the hot air temperature, and how much the spray pressure is changed. Furthermore, there are two methods of operating the spray pressure, one is to operate the supply amount of the slurry and the other is to operate the number of nozzles. In the former case, it is necessary to control the hot air temperature in consideration of the increase / decrease of the material to be dried. Therefore, the operation amount of the hot air temperature must be increased. In this case, by frequently changing the load of the hot-air generating furnace, it is disadvantageous in terms of the time required to reach a constant temperature and the thermal efficiency of the furnace itself. On the other hand, in the latter, the amount of change in the spray pressure per nozzle is large, and it is difficult to adjust to the target spray pressure, and it can be used only when the desired spray pressure is met. Furthermore, when the spray pressure is changed by the nozzle operation, for example, an increase in the spray pressure results in an increase in bulk density and a decrease in water content, and it is not possible to increase both the bulk density and the water content. I could only move it.

Thus, in the conventional control method, hot air temperature, spray pressure,
Selected from among slurry specific gravity, slurry supply amount, etc. 2
It is necessary to operate the operation factors of 3 to 3 at the same time, which makes the selection of the operation factors complicated, and especially when changing the load of the hot-air generating furnace, there is not only a time delay in control, There was no choice but to be disadvantageous in terms of thermal efficiency.

Further, particularly in the control of a spray drying tower equipped with multi-stage nozzles, the control operation has become more complicated.

[Problems to be Solved by the Invention] As a result of studying the control system of the bulk density and the water content in the spray drying tower described above, particularly in the case of multistage spraying in which spray nozzle groups are provided in multiple stages, It was found that the slurry supply amount ratio of the stage greatly affects the bulk density and the water content. The present invention is based on such knowledge, and in particular, in a spray drying tower in which a spray nozzle group is provided in multiple stages, it is possible to individually control the bulk density and water to target values by simply changing the number of injections of nozzles in each stage. The above-mentioned control method is provided.

[Means for Solving Problems] In order to achieve the above object, a method for controlling a multi-stage spray drying tower according to the present invention is a spray drying method using a spray drying tower. Based on the detection result of the bulk density and water content of the spray-dried particles,
The proper number of sprays in each stage is obtained from the functional expression that expresses the relationship between the number of sprays of the nozzles in each stage and the bulk density and water content of the spray-dried particles. The means of controlling the density and water content within the set range is adopted.

Explaining in more detail, the control method of the present invention is a spray drying tower used for the production of detergents and the like, particularly in the control of a multi-stage spray drying tower, the number of nozzles sprayed in each stage and the bulk density of spray dried particles and An appropriate number of jets is obtained by using a functional expression that expresses the relationship with water, and only the number of jets of nozzles in each stage is operated to control the product quality such as the bulk density of detergent and water.

Specifically, the inventors of the present invention have shown that the upper and lower parts 2 as shown in FIG.
In the spray-drying tower 1 having the two-stage nozzle groups 2 and 3, the upper- and lower-stage slurry supply ratios were changed by using the spray nozzles having the same orifices in both the upper and lower stages and changing the number of nozzles used in the upper and lower stages. In this case, it was confirmed that the bulk density decreased and the water content increased as the number of injections on the lower stage was increased, as can be seen from the examples described later.

From a summary of various examination results, it is estimated that the above phenomenon is substantially related to the effective drying height H of the drying tower. The effective dry height H is an index calculated from the installation positions L ₁ and L _{2 of} the upper and lower nozzle groups 2 and 3 shown in FIG. ₁ and the number of nozzles N ₁ and N ₂ sprayed at each stage. , H = (L ₁ · N ₁ + L ₂ · N ₂ ) / (N ₁ + N ₂ ) · (1).

In FIG. 1, 4 is a hot air inlet, and 5 is an exhaust outlet.

Further, when controlling the slurry supply amount ratio in the upper and lower stages by controlling the number of sprays of the nozzles, the spray pressure is controlled by changing the total number of sprays of the nozzles, thereby changing the product water content. The bulk density can be increased or decreased. In this case, it goes without saying that the hot air temperature and the slurry supply amount are kept constant.

That is, the bulk density and the water content can be individually controlled to the target values only by changing the number of jets from the upper and lower nozzles.

In order to control the bulk density and the water content by adjusting the number of sprayed nozzles in the upper and lower stages, a detector for detecting the bulk density and the water content of the spray-dried particles is provided in the multistage spray drying tower, and the detector is provided. Based on the detection result in, in the arithmetic and control unit, from the deviation from the target bulk density and moisture,
The number of nozzles used in each stage is determined, a signal indicating which nozzle in the upper and lower stages is to be opened or closed is output, and the required nozzle is opened or closed based on the signal.

In the above arithmetic and control unit, for the bulk density and water content of the spray-dried particles, an exponential function formula based on a change in the above-mentioned index H and a change in spray pressure due to a change in the total number of sprayed nozzles is given in advance, and the exponential function thereof is given. A signal for opening and closing the required nozzle is output by the calculation of the formula.

The exponential function formula is given by the following formula, for example.

BD ＝ k ₁・ H ^0.7・ No ^0.26・ P ^0.3・ ・ (2) Mo ＝ k ₂・ H ^-1.6・ No ^1.2・ P ^-0.05・ ・ (3) F ＝ No ・ P ^0.5・ ・ (4) , BD: bulk density, Mo: water, F: slurry supply amount, No: total number of nozzles, P: spray pressure, k ₁ , k ₂ ; constants, each index used in each of these formulas is used by the present inventors. Was obtained in the above spray-drying tower, and their indexes and constants k ₁ and k ₂ show values peculiar to each spray-drying tower.

By such a method, the bulk density and water content can be controlled by simply selecting the number of jets of nozzles in multiple stages while keeping the hot air temperature and the slurry supply rate constant, simplifying the operation and improving the efficiency of stable operation of the hot stove. It can be changed.

Example Using a two-stage spray drying tower as shown in FIG. 1, spray drying was performed under various conditions to measure the bulk density and water content. Table 1 shows the measurement conditions and the measurement results. In addition,
The injection position by the upper and lower nozzles is 11m on the upper stage and 6m on the lower stage.
Is. In addition, the orifice diameter of all spray nozzles is 2.8 mm.
The slurry supply rate was fixed at 9000 (kg / h).

As can be seen from Nos. 1 to 4 in Table 1, when the total number of injections is made constant and therefore the spray pressure is made constant, the volume density decreases and the water content increases as the number of injections on the lower side increases. did.

In addition, the injection pressure is also controlled by changing the condition of No. 2 to the condition of No. 5, that is, changing the total number of injections while keeping the hot air temperature and the slurry concentration constant. By combining the upper and lower slurry supply amount ratios and the control of the injection pressure, the bulk density could be increased without changing the water content of the product. That is, the bulk density and the water content could be individually controlled to the target values only by changing the number of jets from the upper and lower nozzles.

Table 2 defines preset values for bulk density and water in advance,
The result when the upper and lower injection numbers are determined and controlled based on the exponential function formula is shown. From the results shown in Table 2, it can be seen that the bulk density and the water content can be controlled with relatively high accuracy.

[Effect of the Invention] According to such a control method of the present invention, since the bulk density and the water content can be controlled by operating only the number of nozzles in the multi-stage spray drying tower, the hot air temperature, the spray pressure, or the specific gravity of the salary can be controlled. Compared with the conventional method of operating multiple factors in a control system by combining such as, it is very simple and does not require frequent control of hot air temperature, so the furnace is stable and efficient. .

[Brief description of drawings]

FIG. 1 is a block diagram of a multistage spray drying tower controlled based on the present invention. 1 ... Spray drying tower, 2, 3 ... Nozzle group.

Claims (1)

[Claims] 1. In spray drying using a spray drying tower, a spray nozzle group in the spray drying tower is provided in a plurality of stages,
Based on the detection result of the bulk density and water content of the spray-dried particles, by a functional formula representing the relationship between the number of spray nozzles in each stage and the bulk density and water content of the spray-dried particles, to determine the appropriate number of injection of each stage, A method for controlling a multi-stage spray-drying tower, characterized in that the necessary nozzles are thereby opened and closed to control the bulk density and water content of the spray-dried particles within a set range.