JPH03106401A - Water content control method for spray dried powder and spray drying device - Google Patents

Abstract

PURPOSE:To manufacture automatically powder of the given water content by determining the water content control constant in a spray drying area by means of the discharged gas temperature and the spray dried particle temperature and operating said drying area. CONSTITUTION:A spray drying device for drying spray particles by means of hot air or warm air to manufacture powder consists of a hot air or warm air generating means 4, a spray raw material feeding pump 1, an atomizer 2 and a drying chamber 3. The temperature of powder discharged from the drying chamber 3 and the temperature of exhaust gas are respectively measured by temperature measuring means 8 and 9. Further, the water-content-control constant for spray drying is found from the temperature of powder and the temperature of discharged gas measured by the temperature measuring means 8 and 9 by a counting means 10. Based on said value, respective means are provided so that the conditions for spraying such as the temperature of hot air and warm air, flow rate, raw liquid feeding volume and the rotating speed of the atomizer can be automatically set and adjusted by an operation condition adjusting means 11 to control the water content of powder automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a spray drying method for drying sprayed particles using hot air or hot air to obtain powder. More specifically, the present invention relates to a method for controlling the moisture content of a spray-dried granule by determining a moisture content control constant in a spray-drying region to obtain a powder or granule with a predetermined moisture content.

[Conventional technology]

Conventionally, in a spray drying method in which a powder is produced by drying sprayed particles with hot air or hot air, moisture content in the powder is controlled by injecting the spray-dried particles with a specific wavelength of infrared rays, such as l.
43, l. 94, 3. 1 of the infrared rays with a wavelength of 0 p m
Or, use 2 or more to irradiate at a constant rate, calculate the absorbance due to water in the spray-dried particles from the amount of reflected infrared rays, estimate the moisture content of the spray-dried particles from that value, and based on that, the rotation speed in the spray-drying area. The moisture content of the granular material spray-dried was controlled by selecting and operating operating conditions such as , temperature, etc.

[Problem to be solved by the invention]

However, the above-mentioned conventional method requires devices such as an infrared generator, a filter, a photodiode, and a computing machine, making the operation complicated and increasing the equipment cost. In addition, in the method of infrared irradiation at a specific wavelength, in addition to infrared absorption by the water in the spray-dried particles, there is also absorption by the particles themselves, and this is easily influenced by the particle surface condition, making it difficult to accurately measure the water content of the spray-dried particles. was difficult.

Therefore, in view of the above-mentioned problems of the conventional method, the inventors conducted intensive studies on a spray-drying method that is relatively simple and accurate in controlling the moisture content of spray-dried particles to obtain powder with a desired moisture content. The present invention was completed based on the finding that the exhaust gas temperature from the spray drying region and the temperature of the spray-dried particles are deeply related to the moisture content of the resulting powder. [Means for Solving the Problems] According to the present invention, in a spray drying method for drying sprayed particles with hot air or hot air to obtain a powder, the moisture content control constant in the spray drying region is set to A method for controlling the moisture content of a spray-dried granular material is provided, which is characterized by obtaining a granular material with a predetermined moisture content by operating the drying zone determined by the exhaust gas temperature and the spray-dried particle temperature.

Further, there is provided a spray drying apparatus for drying spray particles with hot air or hot air to obtain powder or granular material, which comprises a hot air or hot air generating means, a spray raw material supply pump, an atomizer, and a drying chamber, and is discharged from the drying chamber. A temperature measuring means for measuring the temperature of the powder and granular material and exhaust gas, respectively, and a counting means for determining the moisture content control constant in spray drying from the temperature of the powder and granular material and the exhaust gas measured by the temperature measuring means are provided. A spray drying apparatus is provided.

Hereinafter, the principle of the present invention will be explained with reference to the drawings.

FIG. 1 and FIG. 2 are schematic explanatory views showing one embodiment of the spray drying method and apparatus of the present invention, respectively.

In FIG. 1, the stock solution of the spray raw material is supplied to the atomizer 2 by the stock solution pump 1 of the stock solution quantitative supply device, and is sprayed from the atomizer 2 into the drying area of the drying chamber 3 to become spray-dried particles. On the other hand, hot air is sent into the drying chamber 3 from the hot air generator 4, and the spray-dried particles sprayed by the atomizer 2 are dried and turned into powder. The spray-dried powder and granules are discharged from the drying chamber together with the exhaust gas and fed into the cyclone 6, where they are separated into gas and solid and collected in the powder receiver 5 at the bottom of the cyclone 6. The gas heated by the cyclone 6 is exhausted by the blower 7.

In addition, in FIG. 2, a part of the spray-dried particles is directly taken out from the bottom of the drying chamber 3 to the powder receiver 5°, and the rest is discharged from the drying chamber 3 together with the exhaust gas and sent to the cyclone 6. The process is the same as in FIG. 1 except that the process is performed using

In the above-mentioned spray drying method, the constant drying rate at which moisture in the spray particles evaporates into the air and drying is performed is, if the spray particles receive heat only from hot air, the temperature of the spray dried particles is the same as the wet bulb of the hot air that they contact. Since it is almost equal to the temperature, the temperature of the exhaust gas from the drying area T, and the temperature of the sprayed frost dried particles T. , the humidity at the gas temperature T in the dry region is 06, and the saturated humidity corresponding to the dry spray particle temperature T8 is H. Then, the heat transfer balance between the ejected particulate matter and the heat in the gas is as follows (
! ) is expressed by the formula.

=S/W-k(HW-HG) (+) where S is the surface area of the spray-dried particles [m2}, W is the mass of the spray-dried particles [kgl], and h is the heat transfer coefficient [kcal/hr- m”・”C],
λ0 is the latent heat of vaporization at T,1 [kcal/kglk is the film mass transfer coefficient [kg/hr・II12・Δ111], respectively.

From formula (1), H,4-HG=h/k・ ('r. −'rt., )
(2) Hw = HG + h / k ・(TG −T
u) (3) The water content C of the spray-dried particles is the temperature T of the dry spray particles.

It is considered to be proportional to the saturated humidity H corresponding to
4) T,, HG and T as in Eq. becomes a function of

c= r (TG, I{G.Tw)
(4) In this case, jet 1'fU <'bDuring the drying operationH
G is approximately constant and TG is controllable. Therefore, equation (4) can be expressed by the following equation (5).

c=A(TG TW ) +B (5) However, A represents a constant depending on the substance, device characteristics, etc., and B represents a constant depending on operating conditions.

In addition, FIG. 3 is a drying characteristic diagram in the spray drying area,
It is a graph showing temporal changes in the exhaust gas temperature TO from the drying zone, the spray-dried particle temperature T1, and the water content C of the spray-dried particles from the population of the drying zone to the exit.

As is clear from the above equation (5) and FIG. 3, when spray-dried particles are dried in hot air or warm air, from the middle of the drying period onward, the exhaust gas temperature Tc from the drying region and the spray-dried particle temperature T1 The state of the water content C of the spray-dried particles can almost be estimated.

Therefore, in order to keep the water content of the spray-dried particles constant, the temperature of the exhaust gas from the drying area and the temperature of the spray-dried particles must be adjusted according to (5) above.
It is sufficient to operate while maintaining the dry region so that the relationship shown in the formula is satisfied.

The temperature of the exhaust gas from the drying area can be measured, for example, by measuring the temperature of the exhaust gas from the cyclone 7 in FIGS. 1 and 2 using a thermocouple thermometer or the like.

The temperature of the spray-dried particles can be measured, for example, by measuring the temperature of the powder discharged into the receiver 5 or 5° in FIGS. 1 and 2 using an infrared thermometer or the like. in this case,
When the powder and granules are separated from the drying chamber and the cyclone and taken out to a receiver as shown in FIG. 2, it is sufficient to measure the temperature of the powder and granules in the receiver from which 50% or more of the powder and granules are taken out. Also,
Infrared radiation thermometers for measuring the temperature of granular materials are generally used to measure the surface temperature of objects, and various types are already commercially available, so they can be selected according to the conditions of use. This infrared radiation thermometer has a higher
It is a basket waste and is industrially useful because it is cheap to dig.

The moisture content control constant for the spray drying zone can be determined by, for example, conducting an experiment in advance in the above-mentioned spray dryer, and determining the temperature of the exhaust gas from the drying zone, the temperature of the spray-dried particles, and the moisture content of the obtained powder at two or more points. The water content control constants A and B of Equation (5) can be obtained by actually measuring the water content. Using the moisture content control constants A and B determined here, spraying is performed in the spray dryer so that a powder product having a predetermined moisture content is obtained, that is, the exhaust gas temperature and the powder temperature become the predetermined values. Drying operating conditions can be set.

Further, for example, it can also be carried out by a method of automatically controlling the moisture content of the powder or granular material, as schematically shown in FIG. That is,
The temperature of the powder taken out into the receiver 5 or 5° is measured using an infrared radiation thermometer.The temperature of the exhaust gas from the drying area 3 via the cyclone is measured using a thermocouple thermometer. At the same time, at the same time, the moisture content control constant in the dry area is automatically counted by the counting means 10, and based on that value, hot air or warm air is measured. Various means are installed so that the operating conditions such as temperature, flow rate, raw solution supply amount, atomizer rotation speed, etc. can be automatically set and adjusted in 11,000 steps. You can also control your body's water content.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to this example.

Example 1 Using a spray drying device of the type shown in FIG.
C, and stabilized zirconia (Cao,
lsZrl1. 0501. II5) to stock solution concentration 6
The solution was sprayed from the atomizer 2 into the spray drying chamber 3 through the stock solution pump 1 at a rate of 0% and 150 kg/Hr.

The spray drying area of the spray drying chamber 3 has a cylindrical upper part and a funnel-shaped lower part, and has an inlet diameter of 600 mm, an outlet diameter of 150 mm, a cylindrical part diameter of 2500 m, and a cylindrical part height of 2500 mm. , the funnel height was 2000 rm, and the total height was 4500 mm.

First, the stock solution was spray-dried under the following outlet gas temperature and spray-dried particle temperature conditions at the drying chamber outlet 5 (a) and (b). As a result, the obtained powder had the following moisture content.

(a) (t)) Outlet gas temperature (average) (”C) 120 80
Spray-dried particle temperature ('C) 80 60 Powder moisture content (%) 0.2 0.9 From the above results, determine the moisture content control constants A and B of the above formula (5),
A=0.035, B=1. I got 6.

Based on this, in order to obtain powder with a moisture content of 0.4%,
Using the same spray drying equipment as in (a) and ([)) above, the operating conditions such as hot air volume were adjusted so that the outlet gas temperature was 112°C and the spray-dried particle temperature was 78°C. I got a body.

The average moisture content of the resulting powder was 0.38%.

〔Effect of the invention〕

According to the method of the present invention, in the spray drying apparatus, the predetermined moisture content of the powder obtained by spray drying can be specified by the temperature of the exhaust gas from the spray drying area and the temperature of the spray dried particles. The U1 output gas temperature from the spray drying area and the spray drying particle temperature are adjusted to match the moisture content.
It can be controlled by spray dryer operating conditions such as gas meteor, temperature, and spray conditions.

In addition, the temperature measurement of the exhaust gas from the spray drying area and the temperature of the spray dry smoke particles is a highly reliable temperature measurement, and even though it indirectly determines the moisture content of the powder, it is extremely reliable. .

Furthermore, the present invention is useful because it can be controlled using a simple device, and the equipment cost does not increase.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are schematic explanatory diagrams showing one embodiment of the spray drying device according to the present invention. FIG. 3 is a diagram of drying characteristics in the spray drying region. 1... Raw solution pump 2... Atomizer 3...
・Drying room 4...Hot air generator 5' @1
111 Powder receiver...Cyclone 7...Exhaust fan...Powder temperature measuring means...Exhaust gas temperature measuring means O...Counting means 1 1 -...Operating condition adjusting means 3rd figure

Claims (3)

[Claims] (1) In a spray drying method for drying spray particles with hot air or hot air to obtain powder, a moisture content control constant in a spray drying zone is determined by the temperature of the exhaust gas from the drying zone and the temperature of the spray drying particles, A method for controlling the moisture content of a spray-dried powder or granule, the method comprising obtaining a powder or granule having a predetermined moisture content by operating the drying region. (2) A spray drying device for drying atomized particles with hot air or hot air to obtain powder or granular material, which comprises a hot air or warm air generation means, a spray raw material supply pump, an atomizer, and a drying chamber, and is composed of a hot air or hot air generating means, a spray raw material supply pump, an atomizer, and a drying chamber, and the air is discharged from the drying chamber. A temperature measuring means for measuring the temperature of the powder, granular material and exhaust gas, respectively, and a counting means for determining a moisture content control constant in spray drying from the temperature of the powder, granular material and exhaust gas measured by the temperature measuring means are provided. A spray drying device characterized by: (3) The spray drying apparatus according to claim 2, further comprising operating condition adjusting means for adjusting the operating conditions of the spray drying apparatus according to the moisture content control constant determined by the counting means.