阅读说明：本技术 水溶性镁盐-石灰用于糖汁脱色的方法 (Method for decoloring sugar juice by using water-soluble magnesium salt-lime ) 是由 李利军 程昊 李蔚霞 杨岚凤 孔红星 黄文艺 李彦青 冯军 于 2018-08-03 设计创作，主要内容包括：本发明涉及一种水溶性镁盐-石灰用于糖汁脱色的方法,具体步骤是：向糖汁中加入水溶性镁盐,再用石灰乳调pH值,在一定温度下持续搅拌,然后加入聚硅酸锌,分别用不同的速度搅拌一定时间,待絮凝沉降稳定后得到清净汁。本发明提出了水溶性镁盐-石灰法,用于糖汁的澄清脱色,用聚硅酸锌做絮凝剂,脱色率高达92.21%,且工艺简单、成本低、不采用有毒有害物质,属于绿色的澄清脱色工艺,在制糖工业中具有重要的应用前景。其原理：以镁盐作为无机脱色剂,在碱性条件下的混凝反应生成氢氧化镁,吸附或包埋糖汁中的非糖物质,再采用聚硅酸锌作为絮凝剂进行絮凝澄清,取得了满意的结果。(The invention relates to a method for decoloring sugar juice by using water-soluble magnesium salt-lime, which comprises the following specific steps: adding water soluble magnesium salt into the sugar juice, adjusting pH value with lime milk, stirring at a certain temperature, adding zinc polysilicate, stirring at different speeds for a certain time, and obtaining clean juice after flocculation and sedimentation are stable. The invention provides a water-soluble magnesium salt-lime method for clarifying and decoloring sugar juice, which uses zinc polysilicate as a flocculating agent, has the decoloring rate as high as 92.21 percent, has simple process and low cost, does not adopt toxic and harmful substances, belongs to a green clarifying and decoloring process, and has important application prospect in the sugar industry. The principle is as follows: magnesium salt is used as an inorganic decolorant, magnesium hydroxide is generated through coagulation reaction under an alkaline condition, non-sugar substances in sugar juice are adsorbed or embedded, and zinc polysilicate is used as a flocculating agent for flocculation clarification, so that a satisfactory result is obtained.)

1. A method for decoloring sugar juice by using water-soluble magnesium salt-lime is characterized by comprising the following steps: adding water-soluble magnesium salt into the sugar juice to ensure that the content of magnesium ions is 1000mg/L at 300-.

2. The method of claim 1, wherein the water soluble magnesium salt-lime is used for sugar juice decolorization: the water-soluble magnesium salt is magnesium sulfate, magnesium chloride or magnesium nitrate.

3. The method of using water-soluble magnesium salt-lime as claimed in claim 1 or 2 for sugar juice decolorization, characterized in that: the sugar juice is sugarcane mixed juice or brown granulated sugar or raw sugar redissolution syrup.

4. The method of using water-soluble magnesium salt-lime as claimed in claim 1 or 2 for sugar juice decolorization, characterized in that: the rapid stirring speed is 300-350 r/min, the medium stirring speed is 200-250 r/min, and the slow stirring speed is 20-40 r/min.

Technical Field

The invention relates to a method for decoloring sugar juice by using water-soluble magnesium salt-lime, belonging to the field of sugar juice clarification and decoloring.

Background

The brown granulated sugar serving as a final-stage crystallization product in the sugar production process of the sugarcane has high color value and impurity content and low market value, and the quality of the finished white granulated sugar is influenced by directly boiling the brown granulated sugar. Therefore, the need for a new efficient decolorizer to decolorize and remove impurities from brown granulated sugar remelt syrup has become a hot point of research in the sugar manufacturing field in recent years, and is also a difficulty.

At present, clarification and decoloration processes in the sugar industry mainly comprise a lime method, a sulfurous acid method, a carbonic acid method, an activated carbon adsorption method, a hydrogen peroxide oxidation method and the like, but have the defects of poor clarification and decoloration effects, environmental pollution, high cost, complex oxidation products and the like. The seawater resource is rich in China, the sea salt yield is high, the byproduct brine contains a large amount of magnesium sulfate and is not well developed and applied, and the magnesium sulfate of the brine can be treated to obtain slurry magnesium hydroxide which is widely used for decoloring sewage, adsorbing heavy metal ions and the like. At present, the application of magnesium sulfate in the sugar manufacturing field is rarely reported, and the magnesium sulfate and chitosan are compounded and used for clarifying and decoloring the sugarcane secondary pressed juice in the week-minority base and the like, so that a better effect is achieved; lilixun and the like adopt a two-step method to decolorize sugar juice, firstly chitosan is used for primarily treating the sugar juice, then magnesium sulfate is used for further decolorization, but two times of centrifugal separation are needed, and the price of the chitosan is high. Mayuefei and the like use magnesium hydroxide slurry to replace part of calcium hydroxide in a sulfurous acid method for sugar juice decolorization, and the decolorization effect can be improved by replacing part of calcium hydroxide with magnesium hydroxide. The polyacrylamide flocculant is generally adopted in the sugar industry, although the performance is excellent, the monomer acrylamide belongs to a neurotoxic agent, and potential food safety hazards exist. The zinc polysilicate is an inorganic polymeric flocculant, is developed by Liu and Qing and the like at the earliest, replaces phosphoric acid in the sugar preparation process by a sulfurous acid method, has the advantages of quick flocculation and sedimentation, good clarification effect, firm flocculate and the like, and proves that the zinc polysilicate is a nontoxic flocculant, a small amount of residual zinc ions cannot cause harm to human bodies, and the zinc polysilicate is a beneficial trace element. However, no report of using zinc polysilicate as a flocculating agent and using water-soluble magnesium salt-lime for sugar juice decolorization exists at present.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the method uses water-soluble magnesium salt as inorganic decolouring agent, and makes coagulation reaction under the alkaline condition to produce magnesium hydroxide, and can adsorb or embed the non-sugar substances of pigment in the sugar juice, and then uses zinc polysilicate as flocculant to make flocculation and clarification so as to obtain the satisfactory decolouring effect.

The technical scheme for solving the technical problems is as follows: a method for decoloring sugar juice with water-soluble magnesium salt-lime comprises adding water-soluble magnesium salt into sugar juice to make magnesium ion content at 1000mg/L of 300-.

The water-soluble magnesium salt is magnesium sulfate, magnesium chloride or magnesium nitrate.

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

The rapid stirring speed is 300-350 r/min, the medium stirring speed is 200-250 r/min, and the slow stirring speed is 20-40 r/min.

The invention provides a water-soluble magnesium salt-lime method for clarifying and decoloring sugar juice, which has the advantages of high decoloring rate, simple process, low cost, no adoption of toxic and harmful substances, green clarifying and decoloring process and important application prospect in the sugar industry. The principle is as follows: the method is characterized in that water-soluble magnesium salt is used as an inorganic decolorant, coagulation reaction is carried out under alkaline conditions to generate magnesium hydroxide, non-sugar substances such as negatively charged pigments, colloidal particles and the like in sugar juice are adsorbed or embedded, zinc polysilicate with the mass concentration of 1.8-2.2% is used as a flocculating agent for flocculation and clarification, and amphoteric zinc polysilicate has strong flocculation and further decoloration double functions on the sugar juice which is adsorbed and decolored by the magnesium hydroxide, so that a satisfactory result is obtained. Under the optimal process conditions, namely the magnesium ion content is 500mg/L, the zinc polysilicate consumption is 2.2mL/100mL, the pH value is 11, and the decolorization rate is as high as 92.21% (proved by experiments, the process conditions can achieve the same effect in practical production application).

The invention adopts the stirring speed from high to low after adding the zinc polysilicate, and is very favorable for the decoloring effect of the sugar juice. The rapid stirring speed is 300-; the medium-speed stirring speed is 200-; 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 Nano-ZS90 type Nano-particle size and Zeta potential result measured by a ZETA potential analyzer show that the nascent magnesium hydroxide is positively charged when the pH value is less than 12, and the negatively charged colloidal particles and non-sugar components in the adhered sugar juice are mainly neutralized by electricity in the sugar juice with the pH value of 11. FIG. 6 is an SEM image of magnesium hydroxide formed in a blank solution, stacked in hexagonal platelets, with a loose surface. FIG. 7 is an SEM image of magnesium hydroxide formed in sugar juice, still showing stacking of flakes, but with a dense surface. As magnesium hydroxide neutralizes negatively charged non-sugar components in the sugar juice through adsorption, the positive charges on the surfaces of magnesium hydroxide particles are reduced, the electrostatic repulsion is reduced, the aggregation among colloidal particles is caused, and finally, the generation of large and compact flocculating constituents is caused.

The ionic type test result shows that the self-made zinc polysilicate flocculating agent is an amphoteric polymer. FIG. 8 is SEM image of synthesized zinc polysilicate, which shows that spherical floc centers are easy to adhere colloidal particles to form a net floc structure.

The technical characteristics of the method for decoloring sugar juice by using water-soluble magnesium salt-lime of the invention are further described in the following with reference to the accompanying drawings and examples.

Drawings

FIG. 1: the invention relates to a process flow chart.

FIG. 2: the influence curve of the magnesium salt dosage on the decoloration rate of the redissolved syrup when zinc polysilicate flocculation is adopted.

FIG. 3: the influence of zinc polysilicate on the decolorization rate of brown granulated sugar redissolved syrup is shown in the graph.

FIG. 4: the influence curve of the pH value on the decolorization rate of the brown granulated sugar redissolved syrup.

FIG. 5: the influence curve of the system temperature on the decoloration rate of the redissolved syrup.

FIG. 6: SEM image before magnesium hydroxide adsorption.

FIG. 7: SEM image after magnesium hydroxide adsorption.

FIG. 8: SEM image of zinc polysilicate.

Detailed Description