KR20220050694A - Apparatus for vaporizing lactic acid - Google Patents

Abstract

The present specification relates to a device for vaporizing lactic acid. According to a method and a device for vaporizing lactic acid of the present invention, a content of lactic acid oligomers can be reduced within a short time and vaporized lactic acid single molecules can be obtained. The device for vaporizing lactic acid includes: a pretreatment unit; a feed supply unit; a spray unit; a vaporization reactor; and an acquisition unit.

Description

Lactic Acid Vaporizer {APPARATUS FOR VAPORIZING LACTIC ACID}

The present specification relates to a lactic acid vaporization device.

Lactic acid, also called lactic acid or lactic acid, is an organic acid with a relatively simple structure that contains both a hydroxy group and a carboxyl group in a molecule.

Lactic acid is traditionally mainly produced naturally during the fermentation process of lactose or glucose, and has played a role in improving the flavor of fermented foods. It has been used variously in the cosmetic field, such as a skin whitening agent, or in the medical field, such as an intravenous solution, a dialysis solution, and a calcium agent.

Recently, lactic acid polymer and polylactide are biodegradable, so interest is increasing as an eco-friendly alternative polymer that can replace plastics that are not naturally decomposed, such as polyolefin, polystyrene, and polyester manufactured from petroleum. It is also receiving high attention as a precursor of acrylic acid, which is considered to be very important.

Lactic acid can be mainly produced by microbial fermentation or chemical synthesis. Recently, starch-based biomass such as corn, sugar-based biomass such as sugar cane, or cellulose-based biomass obtained from woody or herbaceous plants, etc., Methods for producing lactic acid using biomass resources as raw materials are being studied.

Lactic acid obtained in this way is usually concentrated and stored at a high concentration during storage or distribution after production. Alternatively, water molecules are removed to form an oligomer in the form of dehydration condensation.

A large amount of lactic acid is lost by such dimerization or oligomerization, but the oligomerized lactic acid increases the amount of by-products generated in the chemical reaction using lactic acid and forms coking in the reaction process, which greatly reduces the efficiency of the reaction. There is this.

Therefore, it is necessary to reduce the content of lactic acid oligomers when using concentrated and stored lactic acid as lactic acid itself or adding it to other chemical reactions. , because the equilibrium movement speed is very slow, interest in a pretreatment method for using concentrated lactic acid, that is, a method to reduce the content of lactic acid oligomers in the feed and increase the content of lactate single molecules is increasing.

An object of the present specification is to provide a lactic acid vaporization apparatus capable of reducing the content of lactic acid oligomers in a short time and obtaining a single vaporized lactic acid molecule.

The present specification, a pretreatment unit for heating and pressurizing the lactic acid aqueous solution of a first concentration;

a feed supply unit receiving the lactic acid aqueous solution from the pre-treatment unit and supplying a first stream containing the lactic acid aqueous solution;

a spraying unit for spraying the first stream transferred from the feed supply into the gasification reactor;

a vaporization reactor in which the atomized aqueous lactic acid solution is vaporized; and an harvesting portion for obtaining a third stream comprising vaporized lactic acid molecules;

A lactic acid vaporizer is provided.

According to one embodiment of the invention, the pretreatment unit, the first concentration of the aqueous lactic acid solution at a temperature of about 150 ℃ to about 250 ℃, preferably about 150 ℃ or more, or about 160 ℃ or more, about 250 ℃ or less, or about temperature below 200 ° C; and a temperature control unit and pressure for heating and pressurizing to a pressure condition of from about 1 bar to about 40 bar, preferably greater than about 1 bar, or greater than or equal to about 5 bar, less than or equal to about 40 bar, or less than or equal to about 30 bar, or less than or equal to about 15 bar. It may further include a control unit.

According to one embodiment of the invention, the first concentration is about 20 to about 99 wt%, about 20 wt% or more, or about 30 wt% or more, or about 40 wt% or more, or about 50 wt% or more, or about 60 wt% or more, or about 70 wt% or more, or about 75 wt% or more, and about 99 wt% or less, about 95 wt% or less, or about 90 wt% or less, or about 85 wt% or less. That is, the lactic acid aqueous solution may be concentrated to a high concentration.

According to another embodiment of the invention, the temperature of the first stream in the feed supply may be about 150 to about 300 °C, preferably about 150 °C or more, or about 160 °C or more, and about 300 °C or less, or about It may be 250 ℃ or less, or about 200 ℃ or less, the feed supply unit may further include a feed temperature control unit for controlling the temperature of the first stream.

According to another embodiment of the invention, the atomizing unit, wherein the first stream has a flow rate of about 0.1 g/min to 1.0 g/min, preferably about 0.1 g/min or more, or about 0.15 g/min or more, about and a first stream nozzle adapted to spray at a flow rate of 1.0 g/min or less, or about 0.5 g/min or less, or about 0.3 g/min or less.

According to an embodiment of the invention, the lactic acid vaporization device further includes a steam supply unit for supplying steam, and the second stream of a gas phase containing steam by receiving steam from the spray unit and the steam generating device It may further include a second stream nozzle for spraying into the gasification reactor.

And, the temperature of the second stream may be from about 200 to about 600 °C, preferably from about 250 °C or more, or about 300 °C or more, or about 350 °C or more, or about 400 °C or more, and about 600 °C or less, or about 550 °C or less, or about 530 °C or less.

To this end, the water vapor supply unit may further include a water vapor temperature control unit for controlling the temperature of the second stream.

In this case, the temperature difference between the second stream and the first stream may be about 200 °C or more, or about 250 °C or more, and it may be preferably about 500 °C or less, or about 450 °C or less.

And, the second stream in the spraying unit, the flow rate of 0.1 g / min to 3.0 g / min, preferably about 0.1 g / min or more, or about 0.2 g / min or more, or about 0.3 g / min or more, It may be desirable to adjust the spray to a flow rate of about 3.0 g/min or less, or about 2.0 g/min or less, or about 1.0 g/min or less.

At this time, it may be preferable to adjust the flow rate of the first stream in the spray unit: the flow rate of the second stream = 1: 1.5 to 1: 5.

In the present invention, terms such as first, second, etc. are used to describe various components, and the terms are used only for the purpose of distinguishing one component from another.

In addition, the terminology used herein is used only to describe exemplary embodiments, and is not intended to limit the present invention.

The singular expression includes the plural expression unless the context clearly dictates otherwise.

In the present specification, terms such as “comprise”, “comprising” or “have” are used to describe an embodied feature, number, step, component, or combination thereof, and include one or more other features, number, or step. , components, combinations or additions thereof are not excluded.

Also in this specification, when it is said that each layer or element is formed "on" or "over" each layer or element, it means that each layer or element is formed directly on each layer or element, or other It means that a layer or element may additionally be formed between each layer, on the object, on the substrate.

Since the present invention may have various changes and may have various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific disclosed form, and should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

As used herein, lactic acid is a compound represented by the following formula, and unless otherwise specified in the present specification, is used as a concept encompassing all of lactic acid isomers, naturally occurring lactic acid dimers, and lactic acid oligomers.

Hereinafter, the present invention will be described in detail.

According to an example of the present invention, heating and pressurizing an aqueous lactic acid solution of a first concentration; spraying a first stream of a liquid phase comprising the heated and pressurized aqueous lactic acid solution of a first concentration; vaporizing the lactic acid contained in the first stream through spraying; and obtaining a third stream of gas phase comprising lactic acid molecules.

And the lactic acid vaporization method is implemented by the following device.

According to an aspect of the present invention, a pretreatment unit for heating and pressurizing an aqueous lactic acid solution of a first concentration; a feed supply unit receiving the lactic acid aqueous solution from the pre-treatment unit and supplying a first stream containing the lactic acid aqueous solution; a spraying unit for spraying the first stream transferred from the feed supply into the gasification reactor; a vaporization reactor in which the atomized aqueous lactic acid solution is vaporized; and an harvesting unit for obtaining a third stream comprising vaporized lactic acid molecules.

The inventors of the present invention, in the case of instantaneous vaporization by heating and pressurizing a highly concentrated aqueous solution of lactic acid, making it a high-temperature and high-pressure state, and spraying it in a vaporization reactor under atmospheric conditions, the concentration of the oligomer of lactic acid can be efficiently reduced in a very short time. It was found that it can be lowered to , and the present invention was completed.

Lactic acid is widely used in the production of acrylic acid. When acrylic acid is produced by dehydrating lactic acid, since it proceeds by a gas phase reaction, it is necessary to vaporize lactic acid into lactic acid molecules.

However, as described above, lactic acid is usually stored at a high concentration during storage or distribution after production. dimer) structure, or water molecules are removed to form an oligomer in the form of dehydration condensation.

Such lactic acid oligomer molecules may be carbonized in the vaporization step or reaction step to form coking, thereby reducing the active area of the reaction catalyst, and may be included as a by-product in the final product. Since the content of lactic acid in the form of single molecules that can participate is greatly reduced, it is necessary to convert the lactic acid oligomer into a single molecule in the concentrated lactic acid aqueous solution to lower the content of the oligomer and increase the content of the single molecule lactate.

However, when the concentration is diluted by simply adding water to the concentrated aqueous solution of lactic acid containing a high content of lactic acid oligomers, the equilibrium movement speed is very slow, so it takes a very long time to lower the content of the lactic acid oligomers.

In general, in order to shorten this time, a high concentration of lactic acid aqueous solution is heated and vaporized. Since the vaporization efficiency of lactic acid is lower than that of water, water is vaporized first, and the proportion of vaporized lactic acid is less than about 20 wt% will do In this case, as the water is vaporized first, the concentration of the remaining aqueous lactic acid solution is further increased. Accordingly, there is a problem in that the concentration of the oligomer in the remaining aqueous lactic acid solution is also increased.

Accordingly, in the method for vaporizing lactic acid according to an embodiment of the present invention, the first concentration of the lactic acid aqueous solution is first heated and pressurized to make a high-temperature and high-pressure state, and it is sprayed into the vaporization reactor and included in the first stream through spraying. The vaporized lactic acid can be vaporized instantaneously, and a third stream of gaseous phase comprising vaporized lactic acid molecules can be obtained.

That is, according to one embodiment of the present invention, rather than directly heating and vaporizing a high-concentration aqueous lactic acid solution,

i) Heat and pressurize the high-concentration aqueous lactic acid solution again under high temperature and high pressure conditions to reach the conditions for spraying, but prevent the phenomenon of water vaporizing first in the lactic acid aqueous solution,

ii) By supplying an aqueous solution of lactic acid in a high temperature and high pressure state, it is sprayed in the form of an aerosol or droplet in the vaporization reactor,

iii) As the high concentration of lactic acid sprayed in the form of an aerosol in the vaporization reactor is instantaneously vaporized, a single vaporized lactic acid molecule can be obtained.

On the other hand, the lactic acid vaporization method as described above may be implemented by a device to be described later.

According to an aspect of the present invention, a pretreatment unit for heating and pressurizing an aqueous lactic acid solution of a first concentration; a feed supply unit receiving the lactic acid aqueous solution from the pre-treatment unit and supplying a first stream containing the lactic acid aqueous solution; a spraying unit for spraying the first stream transferred from the feed supply into the gasification reactor; a vaporization reactor in which the atomized aqueous lactic acid solution is vaporized; and an harvesting unit for obtaining a third stream comprising vaporized lactic acid molecules.

The concentration of lactic acid in the third stream may be about 30 wt% or less, or about 25 wt% or less, or about 20 wt% or less, and the lower limit thereof may not be significant depending on process conditions, but about 0.1 wt% or more, or about 5 wt% or more.

wherein the third stream comprising single molecules of lactic acid more specifically comprises, for example, less than about 1 wt%, preferably less than about 0.5 wt%, or less than about 0.1 wt%, of the lactic acid oligomers described above. and, more preferably, substantially free of lactic acid oligomers.

Substantially free of lactic acid oligomer means that the content of lactic acid oligomer is 0 wt% within a detectable limit in the process.

According to one embodiment of the invention, the first concentration is about 20 to about 99 wt%, about 20 wt% or more, or about 30 wt% or more, or about 40 wt% or more, or about 50 wt% or more, or about 60 wt% or more, or about 70 wt% or more, or about 75 wt% or more, and about 99 wt% or less, about 95 wt% or less, or about 90 wt% or less, or about 85 wt% or less. That is, the lactic acid aqueous solution may be concentrated to a high concentration.

This generally corresponds to the usual concentrations of commercially available raw materials for lactic acid, such as the manufacture, storage, distribution, and sale of lactic acid.

Here, the first stream, that is, the aqueous lactic acid solution contained in the lactic acid feed in the process is in a state in which lactic acid is dissolved in water, and as described above, naturally, depending on temperature and concentration conditions, lactic acid single molecule, lactic acid dimer, and lactic acid oligomer It means a state that includes all of the

In addition, the lactic acid concentration described herein also refers to the concentration of a lactic acid-based compound including not only a single lactate molecule, but also a single lactate molecule, a lactic acid dimer, and a lactic acid oligomer.

More specifically, for example, when calculated by computer modeling, the oligomer content for each concentration of the total lactic acid-based compound is shown in Table 1 below.

However, some calculation errors may appear depending on the actual calculation model, and the actual measured values may also have some measurement errors depending on the measurement conditions or measurement method (titration method or HPLC).

Concentration of total lactic acid compounds
(wt%) monomolecular concentration
(wt%) dimer concentration
(wt%) Trimer or higher concentration
(wt%) 5 5.0 0.019 0.001 10 9.9 0.079 0.011 15 14.8 0.187 0.013 20 19.6 0.35 0.05 25 24.3 0.575 0.125 30 29.0 0.874 0.126 35 33.6 1.26 0.14 40 38.0 1.75 0.25 45 42.3 2.35 0.35 50 46.3 3.11 0.59 55 50.2 4.03 0.77 60 53.8 5.18 1.02 65 56.9 6.58 1.52 70 59.6 8.31 2.09 75 61.5 10.4 3.1 80 62.5 13.0 4.5 85 62.2 16.2 6.6 90 60.1 19.8 10.1 95 55.4 23.6 16 100 47.6 26.6 25.8

In the heating and pressurizing step, the first concentration of the aqueous lactic acid solution at a temperature of about 150°C to about 250°C, preferably about 150°C or more, or about 160°C or more, about 250°C or less, or about 200°C or less temperature of; and from about 1 bar to about 40 bar, preferably greater than about 1 bar, or greater than or equal to about 5 bar, less than or equal to about 40 bar, or less than or equal to about 30 bar, or less than or equal to about 15 bar. .

If the temperature and pressure are too low outside the temperature and pressure range in the heating and pressurization step, there may be a problem that the lactic acid is not sufficiently vaporized during spraying due to the low temperature of the mixture, and when the temperature and pressure are too high However, there may be problems in that the pressure to maintain the temperature is excessively high, or the temperature of vaporized lactic acid is too high, so that the lactic acid molecules are converted into other substances.

In this regard, the pretreatment unit may further include a temperature control unit and a pressure control unit for heating and pressurizing the first concentration of the lactic acid aqueous solution at a temperature of 150° C. to 250° C. and a pressure condition of 1 bar to 40 bar.

According to another embodiment of the invention, the temperature of the first stream may be from about 150 to about 300 °C, preferably about 150 °C or higher, or about 160 °C or higher, and about 300 °C or lower, or about 250 °C or lower, or about 200 °C or less.

When the first stream is at an excessively low temperature out of the above temperature range, there may be a problem in that a portion of the vaporized lactic acid is condensed, and if the temperature is too high, a problem in which lactic acid molecules are converted into other substances may occur.

In this regard, the feed supply unit may further include a feed temperature control unit for adjusting the temperature of the first stream.

The aqueous lactic acid solution supplied from the feed is heated and then sprayed in the form of droplets into the vaporization reactor through a transfer line and a nozzle.

That is, according to another embodiment of the invention, the spraying unit may include a first stream nozzle for spraying the first stream into the vaporization reactor.

According to another embodiment of the invention, a flow rate of about 0.1 g/min to 1.0 g/min, preferably about 0.1 g/min or more, or about 0.15 g/min or more, about 1.0 g/min or less, or about 0.5 It may be desirable to spray at a flow rate of g/min or less, or about 0.3 g/min or less.

If the spraying amount and spraying rate of the first stream are too low outside the above range, the flow rate of the supplied lactic acid is too low, and there may be a problem in that an overreaction proceeds in the dehydration reaction proceeding to the next step, and if it is too high, A problem of incomplete vaporization may occur because the heat required for vaporization increases.

And at this time, separately from the first stream, a second stream including high-temperature water vapor may be sprayed into the vaporization reactor through a transfer line and a nozzle separate from the first stream. That is, it may be preferable that the first stream and the second stream are mixed and sprayed together into a gasification reactor.

From this point of view, according to another embodiment of the present invention, the lactic acid vaporization device further includes a water vapor supply unit for supplying water vapor, and the spray unit receives water vapor from the water vapor generator and receives the water vapor from the vapor generating device and contains water vapor (gas phase) ) may further comprise a second stream nozzle for spraying a second stream of.

In this case, the hot water vapor supplied to the second stream can be mixed with the lactic acid supplied to the first stream to instantaneously dilute the lactic acid to a lower concentration, and furthermore, by transferring thermal energy to the lactic acid molecules, the lactic acid It can quickly lower the oligomer content and help the vaporization of lactic acid molecules.

In the case of mixed spraying, after the transfer lines of the first stream and the second stream are first combined before spraying, mixed spraying may be performed through the same nozzle, but rather, the first stream and the second stream are each through separate nozzles It is more preferable to mix and spray into the gasification reactor.

In this regard, the temperature of the second stream may be from about 200 to about 600 °C, preferably from about 250 °C or higher, or about 300 °C or higher, or about 350 °C or higher, or about 400 °C or higher, and about 600 °C or lower; or about 550° C. or less, or about 530° C. or less.

At this time, the temperature difference between the second stream and the first stream may be about 200 °C or more, or about 250 °C or more, and it may be preferably about 500 °C or less, or about 450 °C or less.

If the temperature of the second stream is too low outside the above range, the temperature of the mixture is too low to cause a problem that lactic acid is not sufficiently vaporized, and if the temperature of the second stream is too high outside the above range, in order to maintain the temperature If the pressure is too high, a problem may occur.

In this regard, the water vapor supply unit may further include a water vapor temperature control unit for controlling the temperature of the second stream.

And, the second stream has a flow rate of 0.1 g/min to 3.0 g/min, preferably about 0.1 g/min or more, or about 0.2 g/min or more, or about 0.3 g/min or more, about 3.0 g/min or more. It may be desirable to spray at a flow rate of less than or equal to about 2.0 g/min, or less than or equal to about 2.0 g/min, or less than or equal to about 1.0 g/min.

If the spraying amount and spraying rate of the second stream are too low outside the above range, there may be a problem that incomplete vaporization occurs due to less heat supplied to vaporization. Problems may arise during the process.

In this case, in the mixing spraying step, the first stream flow rate: the second stream flow rate may be preferably about 1: 1.5 to about 1: 5.

According to another embodiment of the invention, before the first stream and the second stream are mixed and sprayed in the form of droplets in the vaporization reactor through a transfer line and a nozzle, respectively, the interior of the vaporization reactor is saturated with water vapor in advance. it may be desirable

Through this method, when the first stream is sprayed into the reactor at a high temperature condition, it is possible to prevent the lactic acid from being concentrated by evaporation of water in the droplets of the first stream instantaneously sprayed under the high temperature condition.

And at this time, it may be preferable to proceed with the reaction while maintaining a temperature condition of about 300 to about 400 °C in the vaporization reactor.

According to the lactic acid vaporization apparatus according to an aspect of the present invention, in a high concentration of lactic acid aqueous solution, the content of lactic acid oligomers can be reduced within a short time, and a single vaporized lactic acid molecule can be obtained.

Hereinafter, through specific examples of the invention, the operation and effect of the invention will be described in more detail. However, these embodiments are merely presented as an example of the invention, and the scope of the invention is not defined thereby.

<Example>

An aqueous lactic acid solution having a concentration of about 80 wt% was prepared.

In the pretreatment unit, the lactic acid aqueous solution was heated and pressurized under the conditions of 180° C. and 10 atm, and prepared to be supplied as a feed.

Concentration of lactic acid aqueous solution
(wt%) oligomer ratio temperature
(℃) enter
(ATM) Example 1 80 0.23 180 10 Example 2 80 0.24 180 10

The lactic acid aqueous solution, that is, lactic acid, lactic acid dimer, and the lactic acid aqueous solution concentration of the feed containing all of lactic acid oligomer was determined by taking each sample, measuring the carbon content through elemental analysis, and dividing this by the carbon content ratio in lactic acid .

The ratio of lactic acid oligomers (including dimers) in the aqueous lactic acid solution is determined by taking each sample and analyzing the content of single lactate molecules through HPLC. It was calculated by dividing by the amount of lactic acid-based compound.

And, a feed supply unit for supplying a first stream containing the lactic acid aqueous solution; a water vapor supply unit for supplying a second stream comprising water vapor; A spray unit in which the lactic acid aqueous solution transferred from the feed supply unit and the water vapor transferred from the water vapor supply unit are mixed and sprayed through each nozzle; a vaporization reactor in which the mixed sprayed aqueous lactic acid solution is vaporized; and a lactic acid vaporizing device in the form of a harvesting unit for obtaining a third stream containing vaporized lactic acid molecules.

The feed supply unit and the water vapor supply unit are equipped with a thermometer and a temperature control device, so that the temperature of the feed (first stream) and water vapor (second stream) can be adjusted, and the temperature of the third stream can be measured in the obtaining unit A thermometer was provided.

First, water vapor was introduced into the vaporization reactor so that the interior of the vaporization reactor was saturated with water vapor.

Thereafter, the aqueous lactic acid solution according to Examples 1 to 7 is supplied as a first stream through the feed supply unit, and water vapor is supplied through the water vapor supply unit, so as to be continuously mixed and sprayed into the vaporization reactor through each nozzle, obtained A third stream comprising vaporized lactic acid molecules was obtained through the portion.

The spray conditions are as summarized in Table 3 below.

lactic acid aqueous solution
temperature
(℃) lactic acid aqueous solution
enter
(ATM) lactic acid aqueous solution
spray amount water vapor temperature
(℃) water vapor atomization Example 1 180 10 0.2 450 0.60 Example 2 180 10 0.2 500 0.35

By analyzing the obtained third stream, the concentration of total lactic acid-based compounds in the third stream and the ratio of oligomers among them were measured and calculated, and summarized in Table 4 below.

third stream
temperature
(℃) lactic acid concentration
(wt%) oligomer ratio Example 1 180 19 0.04 Example 2 180 9 0.03

Referring to Table 4, it can be clearly seen that, according to the embodiment of the present invention, the content of lactic acid oligomer can be reduced in a very short time by continuously vaporizing lactic acid.

Claims (9)

Heating and pressurizing the lactic acid aqueous solution of the first concentration, a pretreatment unit;
a feed supply unit receiving the lactic acid aqueous solution from the pre-treatment unit and supplying a first stream containing the lactic acid aqueous solution;
a spraying unit for spraying the first stream transferred from the feed supply into the gasification reactor;
a vaporization reactor in which the atomized aqueous lactic acid solution is vaporized; and an harvesting portion for obtaining a third stream comprising vaporized lactic acid molecules;
Lactic acid vaporizer.
According to claim 1,
The pretreatment unit, lactic acid vaporization device further comprising a temperature control unit and pressure control unit for heating and pressurizing the first concentration of the lactic acid aqueous solution at a temperature of 150 ° C. to 250 ° C. and a pressure condition of 1 bar to 40 bar.
3. The method of claim 2,
The first concentration is 20 to 99 wt%, lactic acid vaporization device.
According to claim 1,
The feed supply unit further comprises a feed temperature control unit for controlling the temperature of the first stream to 150 to 300 ℃, lactic acid vaporization device.
According to claim 1,
The spray unit, lactic acid vaporization device comprising a first stream nozzle for controlling the first stream to be sprayed at a flow rate of 0.1 g / min to 1.0 g / min.
According to claim 1,
The lactic acid vaporization device further comprises a water vapor supply unit for supplying water vapor,
The spraying unit and a second stream nozzle receiving water vapor from the water vapor generating device and spraying a second stream of a gas phase containing water vapor into the vaporization reactor further comprises:
Lactic acid vaporizer.
7. The method of claim 6,
The vapor supply unit further comprises a water vapor temperature control unit for adjusting the temperature of the second stream to 200 to 600 ℃, lactic acid vaporization device.
7. The method of claim 6,
The second stream in the spraying unit is controlled to be sprayed at a flow rate of 0.1 g/min to 3.0 g/min, lactic acid vaporization device.
7. The method of claim 6,
The first stream flow rate in the spraying unit: The second stream flow rate = 1: 1.5 to 1: 5, lactic acid vaporization device.