CN111748656A

CN111748656A - Sugar juice composite detergent and method for cleaning sugar juice by using same

Info

Publication number: CN111748656A
Application number: CN201910232346.7A
Authority: CN
Inventors: 李利军; 李慰霞; 程昊; 孔红星; 黄文艺; 李彦青; 杨岚风; 毛祥
Original assignee: Guangxi University of Science and Technology
Current assignee: Guangxi University of Science and Technology
Priority date: 2019-03-26
Filing date: 2019-03-26
Publication date: 2020-10-09

Abstract

The invention relates to a sugar juice composite detergent and a method for cleaning sugar juice, wherein the sugar juice composite detergent is composed of magnesium nitrate, phosphoric acid and water, the mass fraction of magnesium ions in the sugar juice composite detergent is 1.0-3.0%, and the mass fraction of phosphoric acid is 1.0-2.5%; the method for purifying the sugar juice comprises the following steps: adding sugar juice composite detergent into sugar juice, wherein the adding amount of the sugar juice composite detergent is 1-3% of the volume of the sugar juice, adjusting the pH value to 10.5-11.5 by using lime milk, stirring and reacting for 5-30min at the temperature of 30-60 ℃, adding polyacrylamide, stirring quickly for 0.5-3min, stirring slowly for 1-10 min, standing, and taking supernatant after flocculation and sedimentation are stable to obtain clean juice. The invention adopts phosphoric acid and magnesium nitrate as the cleaning agent, the magnesium hydroxide is generated by coagulation under high pH, the pigment and the non-sugar components in the sugar juice can be efficiently electrically neutralized and adsorbed, the decolorization rate of the sugar juice is improved, and the coagulation product calcium hydroxy phosphate can accelerate the settling speed, assist flocculation and shorten the settling time.

Description

Sugar juice composite detergent and method for cleaning sugar juice by using same

Technical Field

The invention relates to a sugar juice composite detergent and a method for cleaning sugar juice by using the same, belonging to the field of sugar juice clarification and decoloration.

Background

Cane juice cleaning is an important process in a sugar making process, and the main purpose of the cane juice cleaning is to remove pigment molecules and non-sugar components, so that high-quality clear juice is provided for a sugar boiling process.

The traditional decoloring process comprises a phosphoric acid-sulfurous acid method, a carbonic acid method, a lime method and the like, the phosphoric acid-sulfurous acid method is generally adopted in Chinese sugar mills, sulfur dioxide is generated by burning sulfur for decoloring, the utilization rate is not high, and the environmental pollution is caused. In addition, the decolorization rate of the traditional cleaning process is less than 70 percent, the quality and the yield of sugar are influenced, and the sugar content in the waste honey is high. The honey production coefficients of different substances are researched by Maurandi and Ezekari abroad, and a magnesium-containing compound and calcium nitrate are found to have the honey production resistance. The chitosan is high in cost, and meanwhile, the coagulation product calcium sulfate can scale, so that heat transfer and mass transfer in the later period are influenced. For solving the problem that magnesium hydroxide is difficult to settle, the Yuquan adopts bagasse as a flocculating aid, can reduce the volume to a certain extent, but still needs pressure filtration, has low settling speed, and does not research a cleaning mechanism.

At present, no report about the use of phosphoric acid and magnesium nitrate as composite detergents for cleaning sugar juice is found.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: phosphoric acid and magnesium nitrate are used as the detergents, magnesium hydroxide is generated by coagulation under high pH, pigment and non-sugar components in the sugar juice can be efficiently electrically neutralized and adsorbed, the decolorization rate of the sugar juice is improved, and the coagulation product calcium hydroxy phosphate can accelerate the settling speed, assist flocculation and shorten the settling time.

The technical scheme for solving the technical problems is as follows: the sugar juice composite detergent consists of magnesium nitrate, phosphoric acid and water, wherein the mass fraction of magnesium ions in the sugar juice composite detergent is 1.0-3.0%, and the mass fraction of phosphoric acid is 1.0-2.5%.

The further technical scheme of the invention is as follows: the mass fraction of magnesium ions in the sugar juice composite detergent is 2.0%, and the mass fraction of phosphoric acid is 1.7%.

The other technical scheme of the invention is as follows: adding the sugar juice composite detergent into the sugar juice, wherein the adding amount of the sugar juice composite detergent is 1-3% of the volume of the sugar juice, adjusting the pH value to 10.5-11.5 by using lime milk, stirring and reacting for 5-30min at the temperature of 30-60 ℃, adding polyacrylamide, stirring quickly for 0.5-3min, stirring slowly for 1-10 min, standing, and taking the supernatant after flocculation and sedimentation are stable to obtain the clean juice; the addition amount of polyacrylamide is calculated by adding 0.05-0.20mL of polyacrylamide with the concentration of 1-3 g/L into 100mL of sugar juice.

The sugar juice is sugarcane mixed juice or brown granulated sugar redissolved syrup or raw sugar redissolved syrup.

The rapid stirring speed is 250-350 r/min, and the slow stirring speed is 20-40 r/min.

The stirring speed of the stirring reaction is 80-150 r/min.

The phosphoric acid-magnesium nitrate composite detergent of the invention carries out cleaning treatment on sugar juice, and under the optimal process conditions: the composite detergent (the mass fraction of magnesium ions is 2.0%, the mass fraction of phosphoric acid is 1.7%) is 2.0% (based on the volume of sugar juice), the pH value is 11.0, the dosage of a Polyacrylamide (PAM) aqueous solution (2.0 mg/L) is 0.1%, the temperature is 30 ℃, the decolorization rate is 88.2% under the condition, the sedimentation time is 69s, and the phosphoric acid is used as a green auxiliary agent, so that the sedimentation time can be obviously shortened, the decolorization rate is improved, the introduction decolorization rate of the phosphoric acid is improved by 3.1%, and the sedimentation time is shortened by 52 s. Therefore, the phosphoric acid-magnesium nitrate composite detergent belongs to a high-efficiency green detergent.

According to the invention, SEM, TEM and ZETA potential analysis and XRD representation are carried out on the aggregates of a sucrose system and a sugar juice system, and the calcium hydroxy phosphate and magnesium hydroxide generated by the coagulation reaction of the composite detergent are used for carrying out electric neutralization adsorption, embedding and net capture on non-sugar substances such as pigments and the like, so that the crystallinity of a coagulated product is reduced. The coagulation product calcium hydroxy phosphate can accelerate the sedimentation speed and assist flocculation, the coagulation by-product calcium nitrate has the honey-making resistance, and the filter mud containing calcium nitrate, magnesium salts and the like can be used as a fertilizer for plants, so that the problem of difficult treatment of the sugar filter mud can be solved.

The invention adopts the stirring speed from high to low after adding the polyacrylamide, and is very favorable for the decoloring effect of the sugar juice. The rapid stirring speed is 300-350 r/min, which is beneficial to forming fine alum floc in a very short time by polyacrylamide and sugar juice; the slow stirring speed is 20-40 r/min, so that small alum flocs continuously collide with each other and are greatly beneficial to floc sedimentation.

The technical characteristics of a sugar juice complex detergent and the application thereof of the present invention will be further described with reference to the accompanying drawings and examples.

Drawings

FIG. 1: graph showing the effect of complex detergents with different mass fractions of phosphoric acid on decolorization.

FIG. 2: graph of the effect of complex detergents of different mass fractions of phosphoric acid on settling time.

FIG. 3: and (3) a curve chart of the influence of the dosage of the composite detergent on the decolorization rate and the settling time.

FIG. 4: the influence of pH on decolorization rate and settling time is shown in the graph.

FIG. 5: and (3) a graph of the influence of the mass concentration of PAM on the decolorization rate and the sedimentation time of the sugar juice.

FIG. 6: the influence curve of temperature on the decolorization rate and the sedimentation time of the sugar juice.

FIG. 7: SEM images of the aggregates of detergent in different systems. Wherein, a-SEM of the aggregates in the single detergent sucrose system; b-SEM of aggregates in the brown granulated sugar redissolving syrup system with single detergent; c-SEM of the aggregate of the complex detergent in a sucrose system; d-SEM of the aggregate of complex detergents in brown granulated sugar remelt syrup system.

FIG. 8: TEM image of coagulation product of the composite detergent in different systems. TEM images of aggregates in the sucrose a and b; c. TEM image of a system of d-brown granulated sugar redissolved syrup.

FIG. 9: XRD patterns of aggregates of sucrose system and brown granulated sugar redissolution syrup system.

Detailed Description

Example 1: the sugar juice composite detergent consists of magnesium nitrate, phosphoric acid and water, wherein the mass fraction of magnesium ions in the sugar juice composite detergent is 2.1%, and the mass fraction of the phosphoric acid is 1.7%.

Example 2: taking 100mL brown granulated sugar redissolving syrup with 10 degrees of Bx, putting the syrup into a 250 mL beaker, adding 2 mL of sugar juice composite detergent (the mass fraction of magnesium ions is 2.0 percent, and the mass fraction of phosphoric acid is 1.70 percent), adjusting the pH to 11 by using lime milk with the mass fraction of 10 percent, stirring at the rotating speed (100 r/min) for 5 min at the temperature of 30 ℃, then adding 0.1mL of PAM aqueous solution with the PAM mass concentration of 2mg/L, quickly stirring (300 r/min) for 30s, slowly stirring (30 r/min) for 1min, pouring into a settling tube, standing, and flocculating and settling; and taking supernatant after the flocculation sedimentation is stable to obtain clean juice. The decolorization rate was 88.2% and the settling time was 69 s.

Example 3: taking 100mL brown granulated sugar redissolving syrup with 10 degrees of Bx, putting the syrup into a 250 mL beaker, adding 2.15 mL sugar juice composite detergent (the mass fraction of magnesium ions is 2.0 percent, and the mass fraction of phosphoric acid is 1.70 percent), adjusting the pH to 11.25 by using lime milk with the mass fraction of 10 percent, stirring at the rotating speed (100 r/min) for 5 min at the temperature of 30 ℃, then adding 0.1mL PAM aqueous solution with the mass concentration of 2mg/L PAM, quickly stirring for 30s (300 r/min), slowly stirring for 1min (30 r/min), pouring into a settling tube, standing, and flocculating and settling; and taking supernatant after the flocculation sedimentation is stable to obtain clean juice. The decolorization rate was 88.7% and the settling time was 79 s.

Example 4: taking 100mL brown granulated sugar redissolving syrup with 10 degrees of Bx, putting the syrup into a 250 mL beaker, adding 2 mL of sugar juice composite detergent (the mass fraction of magnesium ions is 2.0 percent, and the mass fraction of phosphoric acid is 1.70 percent), adjusting the pH to 11 by using lime milk with the mass fraction of 10 percent, stirring the mixture at the rotating speed (100 r/min) for 5 min at the temperature of 30 ℃, then adding 0.1mL of PAM aqueous solution with the PAM mass concentration of 2.25mg/L, quickly stirring the mixture for 30s at the speed of 300 r/min, slowly stirring the mixture for 1min at the speed of 30 r/min, pouring the mixture into a settling tube, standing the mixture, and flocculating and settling the mixture; and taking supernatant after the flocculation sedimentation is stable to obtain clean juice. The decolorization rate was 84.2% and the settling time was 75 s.

Example 5: taking 100mL brown granulated sugar redissolving syrup with 10 degrees of Bx, putting the syrup into a 250 mL beaker, adding 1.85 mL sugar juice composite detergent (the mass fraction of magnesium ions is 2.0 percent, and the mass fraction of phosphoric acid is 1.70 percent), adjusting the pH to 11 by using lime milk with the mass fraction of 10 percent, stirring at the rotating speed (100 r/min) for 5 min at the temperature of 30 ℃, then adding 0.1mL PAM aqueous solution with the PAM mass concentration of 2mg/L, quickly stirring at 300 r/min for 30s, slowly stirring at 30 r/min for 1min, pouring into a settling tube, standing, and flocculating and settling; and taking supernatant after the flocculation sedimentation is stable to obtain clean juice. The decolorization rate was 82.3% and the settling time was 65 s.

Example 6: taking 100mL brown granulated sugar redissolving syrup with 10 degrees of Bx in a 250 mL beaker, adding 2 mL sugar juice composite detergent (the mass fraction of magnesium ions is 2.0 percent, and the mass fraction of phosphoric acid is 1.70 percent), adjusting the pH to 11.25 by using lime milk with the mass fraction of 10 percent, stirring at the rotating speed (100 r/min) for 5 min at the temperature of 30 ℃, then adding 0.1mL PAM aqueous solution with the PAM mass concentration of 1.75mg/L, quickly stirring for 30s (300 r/min), slowly stirring for 1min (30 r/min), pouring into a settling tube, standing, and flocculating and settling; and taking supernatant after the flocculation sedimentation is stable to obtain clean juice. The decolorization rate was 86.8% and the settling time was 92 s.

The invention adopts the following method to calculate the decolorization ratio:

the color value measurement was carried out using a wavelength of 560nm in accordance with the regulations of International organization ICUMSA (International Committee for the unified methods for sugar analysis). Adjusting pH of the sugar juice to 7.00, placing in a filter with 0.45 μm pore diameter membrane, vacuum filtering, collecting filtrate, and measuring its refractive index, absorbance and sugar juice temperature. Thereby calculating the color value of the sugar juice, and the calculation formula is as follows:

IU₅₆₀=A₅₆₀/(b×c)×1000

in the formula: IU (International Union of China)₅₆₀-a color value; a. the₅₆₀-absorbance of the sample solution measured at a wavelength of 560 nm; b-thickness of cuvette (cm); c-sample DryThe solid concentration (g/mL) can be calculated using the following formula:

c = refractive brix of the juice x corresponding apparent density (20 ℃)/100.

(1) The decolorization ratio is calculated by the following formula:

D=(IU_{front side}－IU_{Rear end})/IU_{Front side}×100%

In the formula: d-decolorization (%); IU (International Union of China)_{Front side}-pre-treatment sugar juice colour values; IU (International Union of China)_{Rear end}-colour value of the treated juice.

Single factor experiment of the present invention

The experimental method comprises the following steps: taking 100mL brown granulated sugar redissolution syrup with 10 degrees of Bx, putting the syrup into a 250 mL beaker, adding 2 mL of composite detergent, adjusting the pH to 11 by using lime milk with the mass fraction of 10 percent, stirring the mixture for 5 min at the temperature of 30 ℃ at a rotating speed (100 r/min), then adding 0.1mL of PAM aqueous solution with the mass concentration of 2mg/L, quickly stirring the mixture for 30s at the speed of 300 r/min, slowly stirring the mixture for 1min at the speed of 30 r/min, pouring the mixture into a settling tube, standing the mixture, and flocculating and settling the mixture. The time required for the supernatant to reach 60 mL was recorded. And (4) neutralizing the supernatant juice by using dilute nitric acid until the pH value is 7, measuring the absorbance, the brix and the temperature, and calculating the decolorization rate.

1. The influence of the composite detergent of phosphoric acid with different mass fractions on decolorization rate and settling time.

The effect of 2 mL of complex detergent (2% by mass of magnesium ions and 0, 0.85%, 1.70%, 2.55%, 3.40% by mass of phosphoric acid, respectively) on decolorization rate and settling time was added to 100mL of brown granulated sugar redissolved syrup at 10 ° Bx, as shown in fig. 1 and fig. 2.

As can be seen from FIG. 1, the decolorization rate increases as the mass fraction of phosphoric acid increases. This is because phosphoric acid reacts with lime milk under strong alkaline conditions to produce calcium hydroxy phosphate, the surface of which is positively charged to adsorb and embed more negatively charged pigment molecules, and thus the decolorization rate is higher than that of a single detergent (i.e. a magnesium nitrate solution with a magnesium ion mass fraction of 2%). The settling time is shortened and then prolonged along with the increase of the mass fraction of the phosphoric acid. This is because the calcium hydroxy phosphate has an auxiliary flocculation effect, which accelerates the settling rate, and thus the settling time of the composite detergent is shorter. When the phosphoric acid mass fraction exceeds 1.70%, the settling time is prolonged. This is because too much calcium hydroxy phosphate is produced, which results in too fluffy flocs and slow sedimentation. And (3) the decolorization rate and the settling time are integrated, and phosphoric acid with the mass fraction of 1.7% and magnesium ions with the mass fraction of 2% are selected to form the composite detergent, so that compared with a single flocculant detergent, the decolorization rate is improved by 3.1%, and the settling time is shortened by 52 s.

2. The influence of the dosage of the composite detergent on the decolorization rate and the settling time.

The temperature of the system is controlled at 40 ℃, 1.0, 1.5, 2.0, 2.5 and 3.0 mL of composite detergents (phosphoric acid with the mass fraction of 1.7 percent and magnesium ions with the mass fraction of 2 percent) are respectively added into 100mL of brown granulated sugar redissolved syrup with the temperature of 10 DEG Bx, the pH value is adjusted to 11 by lime milk, and 0.1mL of PAM aqueous solution with the PAM mass concentration of 2mg/L is added after 10min of reaction. The influence of the amount of the complex detergent on the decolorization ratio and the settling time is examined, and the result is shown in FIG. 3.

As can be seen from FIG. 3, the decolorization rate is significantly increased with the increase of the amount of the complex detergent, and the decolorization rate is slowly increased when the amount of the detergent is more than 2.0% (based on the volume of the sugar juice, the same applies hereinafter). The magnesium hydroxide and the calcium hydroxy phosphate with positive charges can adsorb pigments and non-sugar components with negative charges in the sugar juice, and the generated magnesium hydroxide and the calcium hydroxy phosphate are increased along with the increase of the using amount of the composite detergent, so that more non-sugar components such as pigments with negative charges can be adsorbed, and the decolorization rate is improved; when the dosage of the composite detergent exceeds 2.0 percent, the dosage is continuously increased, and non-sugar components such as pigment with negative electricity and the like are basically removed, so the decolorization rate is slowly increased. When the using amount of the composite detergent is less than 2.5%, the settling time is rapidly shortened along with the increase of the using amount of the detergent; above 2.5%, the settling time increases rapidly with increasing detergent usage. The consumption of the composite detergent is increased, and the generated magnesium hydroxide and calcium hydroxy phosphate particles are increased, so that the flocculation and sedimentation of PAM are facilitated; when the amount of the complex detergent is more than 2.5%, since the amount of the generated particles is so large that 2mg/L of PAM is insufficient to flocculate all the particles in the sugar juice, the settling time is rapidly increased. The amount of the complex detergent is selected to be 2% in view of cost.

3. Influence of pH on decolorization rate and settling time.

The temperature of the system is controlled at 40 ℃, the adding amount of the mixed detergent is 20 mL/L of sugar juice, the pH is adjusted to 8, 9, 10, 11 and 12 by using lime milk, and 0.1mL of 2mg/L PAM aqueous solution is added after the reaction is carried out for 10 min. The influence of pH on the decolorization rate and the settling time was examined, and the results are shown in FIG. 4.

As is clear from FIG. 4, the decolorization rate was low when the pH was less than 9.5. This is due to Mg²⁺Magnesium hydroxide is not generated when the pH value is lower than 9.5, and only calcium hydroxy phosphate plays a role in decoloring, so that the decoloring rate is low. When the pH value is higher than 10, the amount of generated magnesium hydroxide is increased rapidly, so that the decolorization rate is obviously improved.

As can be seen from fig. 4, when the pH is less than 10, the settling time is long; when the pH value is about 11, the settling time is shortest; after a pH of more than 11, the settling time increases rapidly again. This is because when the pH is less than 10, less magnesium hydroxide particles are generated in the sugar juice, which is not favorable for the action of bridging PAM and the like; when the pH value reaches 11, the generated magnesium hydroxide is the most, and 0.1mL of 2 mg/LPAM aqueous solution just completely reacts with the particles, so that the settling time is the shortest; at pH 12, the juice had a large amount of calcium hydroxide particles, resulting in an excess of particulates in the juice, above the 0.1mL flocculation load of 2 mg/LPAM, and thus increased settling time. The pH is selected to be 11, taking the cost of calcium hydroxide into consideration.

4. Influence of PAM dosage on decolorization rate and settling time.

The temperature of the system is controlled to be 40 ℃, the adding amount of the mixed detergent is 2.0 percent, the pH value is adjusted to 11 by using lime milk, and 0.1mL of PAM aqueous solution with the PAM mass concentration of 1.0, 1.5, 2.0, 2.5 and 3.0 mg/L is added after 10min of reaction. The influence of the quality concentration of PAM on the decolorization rate and the sedimentation time is examined, and the result is shown in figure 5.

As can be seen from fig. 5, PAM was used to reduce the effect on the decolorization rate of brown granulated sugar redissolved syrup. This is because the pigment molecules in the brown granulated sugar redissolved syrup have negative charges and are mainly adsorbed or embedded by magnesium hydroxide and calcium hydroxyphosphate, and thus PAM has little effect on the decolorization rate of the sugar juice. But the influence of PAM on the flocculation settling time is more obvious, and the settling time is rapidly shortened along with the increase of the use amount of PAM; when PAM is 2.0 mg/L, the settling time is shortened. The PAM is in negative charge, and the flocculation of magnesium hydroxide, calcium hydroxy phosphate and other colloidal particles in the brown granulated sugar redissolved syrup is realized through mechanisms such as adsorption, bridging, net catching, rolling and sweeping, and the sedimentation is accelerated; however, when the mass concentration of PAM is more than 2.0 mg/L, the granules in the brown granulated sugar redispersed and dissolved again due to the adsorption of the excessive flocculant, and thus the settling time is prolonged. The PAM mass concentration was chosen to be 2.0 mg/L in view of time cost.

5. Influence of temperature on decolorization rate and settling time.

Adding 20 mL/L mixed detergent into sugar juice at 30, 40, 50, 60, 70 deg.C, adjusting pH to 11 with lime milk, reacting for 10min, and adding 0.1mL PAM aqueous solution with PAM mass concentration of 2 mg/L. The influence of temperature on the decolorization rate and the settling time was examined, and the results are shown in FIG. 6.

As can be seen from fig. 6, low temperature favors decolorization and settling rate. This is because the adsorption of pigment molecules by magnesium hydroxide is a chemical exothermic adsorption, and the increase in temperature is detrimental to the adsorption of pigment molecules, so that the decolorization rate decreases with the increase in temperature. However, the settling time gradually increases with increasing temperature, and after exceeding 60 ℃, the settling time begins to shorten again. The high temperature makes the kinetic energy of the grains increased to overcome the short distance repulsion between grains and to result in easy coagulation of grains, and this is favorable to flocculation and settling and shortens the settling time. The optimum temperature is 30 ℃.

Mechanism analysis of the invention

1. Zeta potential analysis.

The Zeta potentials in the different systems are shown in Table 1.

TABLE 1 Zeta potential List in different systems

As can be seen from Table 1, the Zeta potential of the composite detergent after coagulation of a sucrose system is 37.7 mV, which is higher than the Zeta potential (30.20 mV) of the single detergent after coagulation of a sucrose system. The positive charge magnesium hydroxide is generated after the coagulation of the magnesium ions, and the positive charge calcium hydroxy phosphate is also generated in the coagulation process, so the Zeta potential of the system is increased by the introduction of the phosphoric acid. Thereby increasing the Zeta potential of the system and causing the colloidal particles to be more dispersed and facilitating sufficient contact with the non-sugar component. The Zeta potential of the brown granulated sugar redissolution syrup system is-11.42 mV, which shows that the redissolution syrup system has negatively charged pigment molecules and non-sugar components; the Zeta potential after coagulation became-3.96 mV because the positively charged aggregates neutralized the negatively charged pigments and non-sugar components of the reconstituted syrup, resulting in a smaller absolute value of the Zeta potential. Therefore, the cleaning mechanism of the composite detergent on the brown granulated sugar redissolved syrup is shown to be electric neutralization adsorption.

2. And (4) SEM analysis.

The SEM image of the aggregate is shown in FIG. 7. From the SEM figure, it is seen that the aggregates a and b of the single detergent are massive and have a large volume, and the aggregates c and d of the complex detergent are granular and have a small volume. Possibly, the introduction of phosphoric acid, generates positively charged calcium hydroxy phosphate, thereby making the coagulation product more dispersible. The experimental result shows that the settling time of the composite detergent is obviously shorter than that of a single detergent, and the smaller the size of the aggregate particles, the more favorable the adsorption, bridging, net capturing and sweeping effects of PAM are, so that the settling time is shortened.

3. TEM and XRD analysis.

The TEM image and XRD image of the aggregate are shown in FIG. 8 and FIG. 9, respectively. As can be seen from the XRD spectrogram, the characteristic peaks of magnesium hydroxide and hydroxyapatite are respectively consistent with standard card PDF83-0114 and PDF 84-1998. Besides the characteristic peaks of magnesium hydroxide and hydroxyapatite, other peaks appear, which are found to be the characteristic peaks of calcium hydroxide due to the fact that calcium hydroxide has low solubility, and therefore, a calcium hydroxide crystal peak exists. Comparing the XRD spectrograms of the aggregates corresponding to the sucrose system and the redissolved syrup system, the diffraction peak intensity of the aggregates in the sugar juice system is reduced to be lower, and the peak width is increased, which indicates that the crystallinity of the aggregates in the brown granulated sugar redissolved syrup system is smaller than that of the sucrose system; the coagulation crystallinity in the brown granulated sugar redissolved syrup system is low, which is due to the fact that aggregates in the brown granulated sugar redissolved syrup system trap and embed non-sugar components, thereby causing crystal structure defects. As can be seen from a comparison of TEM images, in the brown granulated sugar reconstituted syrup system, the aggregates hardly observed had a specific morphology and a disappearance of interlamellar spacings, and a part of the pigment molecules was embedded and trapped in the aggregate crystals, which affected the growth of the aggregate particles, and thus became smaller and more disordered. Thus the entrapment and trapping effect also removes the pigment molecules and non-sugar components.

Claims

1. The sugar juice composite detergent is characterized in that: the sugar juice composite detergent consists of magnesium nitrate, phosphoric acid and water, wherein the mass fraction of magnesium ions in the sugar juice composite detergent is 1.0-3.0%, and the mass fraction of phosphoric acid is 1.0-2.5%.

2. A sugar juice complex detergent as claimed in claim 1, characterised in that: the mass fraction of magnesium ions in the sugar juice composite detergent is 2.0%, and the mass fraction of phosphoric acid is 1.7%.

3. A method of using the sugar juice complex detergent as claimed in claim 1 or 2 for cleaning sugar juice, characterized in that: adding sugar juice composite detergent into sugar juice, wherein the adding amount of the sugar juice composite detergent is 1-3% of the volume of the sugar juice, adjusting the pH value to 10.5-11.5 by using lime milk, stirring and reacting for 5-30min at the temperature of 30-60 ℃, adding polyacrylamide, stirring quickly for 0.5-3min, stirring slowly for 1-10 min, standing, and taking supernatant after flocculation and sedimentation are stable to obtain clean juice; the addition amount of polyacrylamide is calculated by adding 0.05-0.20mL of polyacrylamide with the concentration of 1-3 g/L into 100mL of sugar juice.

4. The method for cleaning sugar juice according to claim 3, which is characterized in that: the sugar juice is sugarcane mixed juice or brown granulated sugar redissolved syrup or raw sugar redissolved syrup.

5. The method for cleaning sugar juice according to claim 3, which is characterized in that: the rapid stirring speed is 250-350 r/min, and the slow stirring speed is 20-40 r/min.

6. The method for cleaning sugar juice according to claim 3, which is characterized in that: the stirring speed of the stirring reaction is 80-150 r/min.