Crossflow feed method for thin juice evaporation in sugar beet sugar production

Abstract

A cross-feed method for evaporating diluted sugar juice in beet sugar production includes the following steps: The purified diluted sugar juice is fed into a four-effect evaporator for evaporation and concentration; the sugar juice output from the four-effect evaporator is fed into a first-effect evaporator for further evaporation and concentration, using exhaust steam from the power plant to heat the first-effect evaporator, with all secondary steam from the first-effect evaporator supplied as a heat source to the second-effect evaporator; the sugar juice output from the first-effect evaporator is fed into the second-effect evaporator for further evaporation and concentration, with all secondary steam from the second-effect evaporator supplied as a heat source to the third-effect evaporator; the sugar juice output from the second-effect evaporator is fed into the third-effect evaporator for further evaporation and concentration, with 60% of the secondary steam from the third-effect evaporator used as a heat source to the fourth-effect evaporator; the sugar juice output from the third-effect evaporator is fed into a fifth-effect evaporator for further evaporation and concentration, with 80% of the secondary steam from the fourth-effect evaporator used as a heat source to the fifth-effect evaporator. This invention offers high production efficiency, higher steam heat utilization, and good production stability.

Description

Technical Field

[0001] This invention belongs to the technical field of beet sugar production methods, specifically relating to a cross-flow feeding method for evaporating dilute juice from beet sugar production. Background Technology

[0002] In the industrial production of sugar beets, multi-effect evaporation is the core unit operation for concentrating sugar juice and recovering sugar. Among them, the five-effect co-current evaporation technology has become the mainstream process widely used in the industry due to its simple process flow and suitability for large-scale continuous production. This process uses the exhaust steam generated by the power plant as the core heating heat source. The overall process adopts a co-current feeding mode in which the sugar juice and heating steam flow in the same direction. Specifically, the diluted sugar juice obtained after beet soaking and cleaning is first fed into the first-effect evaporator with an initial temperature of 15-16°Bx, where it fully exchanges heat with the exhaust steam from the power plant to complete the initial heating and evaporation. Subsequently, relying on the pressure and level differences between the evaporators, the sugar juice flows by gravity into the second, third, fourth, and fifth-effect evaporators in sequence. Through staged heat exchange evaporation, the sugar juice is continuously concentrated, ultimately reaching the concentration required for subsequent sugar production processes.

[0003] The current traditional five-effect evaporation process has significant limitations in its steam distribution and sugar juice concentration matching mode. From the perspective of steam utilization, the secondary steam generated by the three-effect evaporator has a certain pressure (0.13-0.15MPa) and purity, and its quality is relatively stable. In addition to serving as a heat source for the four-effect evaporator, a portion is diverted to the crystallization process for sugar boiling. The crystallization process relies excessively on the secondary steam from the three-effect evaporator for energy, which not only increases the steam diversion pressure of the evaporation system but also requires frequent replenishment of high-quality external steam, resulting in an increase of 15%-18% in the overall system steam energy consumption. The thermal energy utilization efficiency is extremely low. Comprehensive calculations show that within the entire system, one part of the heating exhaust steam can only achieve the evaporation of four parts of water, and the thermal energy is not fully utilized in stages, resulting in persistently high steam energy consumption. On the other hand, the secondary steam generated by the four-effect evaporator, after multiple stages of energy loss, experiences a significant decrease in pressure and temperature, and has a high impurity content. Its steam quality cannot meet the process parameter requirements for crystallization and sugar boiling, making direct recovery and utilization difficult. From the perspective of sugar juice concentration, the sugar juice reaches a high concentration (40-45°Bx) after concentration in the four-effect evaporator. The viscosity of the high-concentration sugar juice in the four-effect evaporator increases sharply, with measured viscosity exceeding 200 mPa•s. This significantly increases the heat transfer resistance of the sugar solution, causing a sharp drop in the heat transfer efficiency of the evaporator by 30%-40%. The amount of water evaporated per unit time is greatly reduced, slowing down the overall production pace. Furthermore, high-concentration sugar juice is prone to problems such as increased boiling point, flow fluctuations, and intensified heat transfer scaling during evaporation. This increases the difficulty of controlling the evaporation parameters of each effect, leading to frequent fluctuations in system operating conditions and insufficient stability of the production system. This directly affects key quality indicators such as the purity and color of the finished sugar, making it difficult to ensure continuous and standardized production. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a cross-flow feeding method for evaporating dilute juice in beet sugar production, which has high production efficiency, higher steam heat utilization rate, and good production stability.

[0005] The objective of this invention is achieved through the following technical solution: a cross-flow feeding method for evaporating dilute juice in beet sugar production, comprising the following steps: a. The purified diluted sugar syrup is sent to a four-effect evaporator for evaporation and concentration; b. The sugar juice output from the four-effect evaporator is sent to the first-effect evaporator for evaporation and concentration. The exhaust steam from the power workshop is used to heat the first-effect evaporator. All the secondary steam from the first-effect evaporator is supplied to the second-effect evaporator as a heating source. c. The sugar juice output from the first-effect evaporator is sent to the second-effect evaporator for evaporation and concentration. All the secondary steam from the second-effect evaporator is supplied to the third-effect evaporator as a heating source. d. The sugar juice output from the double-effect evaporator is sent to the triple-effect evaporator for evaporation and concentration. 60% of the secondary steam from the triple-effect evaporator is used as the heating source for the quadruple-effect evaporator, and 40% of the secondary steam from the triple-effect evaporator is used for boiling sugar. e. The sugar juice output from the triple-effect evaporator is sent to the five-effect evaporator for evaporation and concentration, completing the entire process of sugar juice evaporation and concentration. 80% of the secondary steam generated by the four-effect evaporator is used as the heating source for the five-effect evaporator, and 20% of the secondary steam generated by the four-effect evaporator is used as steam for sugar boiling.

[0006] In step a, the feed weight of the diluted sugar juice is 15-16°Bx, the feed temperature is 95-100℃, the operating pressure inside the tank is 0.10-0.12 MPa, and after preliminary evaporation and concentration to 18-20°Bx, the discharge temperature of the sugar juice is 127-132℃, and the quadruple-effect evaporator produces secondary steam with a pressure of 0.10-0.12 MPa.

[0007] In step b, the feed temperature of the sugar juice is 18-20°Bx, the temperature is 125-130℃, the operating pressure inside the tank is 0.22-0.28 MPa, the sugar juice is concentrated to 25-30°Bx, the discharge temperature of the sugar juice is 120℃, and the first-effect evaporator produces secondary steam at a pressure of 0.25-0.3 MPa.

[0008] In step c, the feed weight of the sugar juice is 25-30°Bx, the feed temperature is 118°C, the operating pressure inside the tank is 0.18-0.20 MPa, it is concentrated to 40-42°Bx, the discharge temperature of the sugar juice is 107.5°C, and the secondary steam produced by the double-effect evaporator is 0.15-0.18 MPa.

[0009] In step d, the feed weight of the syrup is 40-42°Bx, the feed temperature is 105.5℃, the operating pressure inside the tank is 0.14-0.16 MPa, the syrup is concentrated to 50-55°Bx, the discharge temperature of the syrup is 87-94℃, and the steam pressure of the triple-effect evaporator is stabilized at 0.13-0.15 MPa.

[0010] In step e, the feed weight of the syrup is 50-55°Bx, the feed temperature is 85-92°C, and it is concentrated under a vacuum of -0.08 MPa. Under vacuum, the boiling point of the syrup is controlled at 83-90°C, and the final syrup is concentrated to 65-70°Bx, with an outlet temperature of 78-84°C.

[0011] The output steam of the five-effect evaporator is vacuum condensed, and the waste heat of the condensate from the vacuum condensation is used to preheat the feed dilute sugar juice. Then the dilute sugar juice is heated to 95-100℃ by a heat exchanger.

[0012] The beneficial effects of this invention are as follows: 1. This invention breaks the traditional feeding sequence of five-effect evaporation, adopting a cross-flow feeding method. Low-melting-point (15-16°Bx) dilute juice first directly enters the fourth-effect evaporator, then sequentially enters the first, second, third, and fifth-effect evaporators. The temperature and pressure gradient within the fourth-effect evaporator is rationally matched, effectively improving the overall evaporation rate and avoiding the problem of high-concentration sugar juice evaporation attenuation. 2. In this invention, the quality of secondary steam in the fourth-effect evaporator is significantly improved compared to traditional processes. Part of the secondary steam is used for crystallization and sugar boiling, meeting the requirements for crystallization and sugar boiling, and greatly improving boiling efficiency. 3. This invention optimizes the utilization of steam in stages. During the step-by-step concentration process of the sugar juice, the melting-point gradient and evaporation efficiency achieve optimal matching, resulting in high steam heat utilization, reduced overall system energy consumption, and reduced equipment wear caused by high-temperature and high-pressure conditions, extending equipment lifespan. 4. This invention avoids the problems of boiling point increase, efficiency decrease, and operating condition fluctuations caused by the sugar juice reaching a high melting-point (40-45°Bx) in the fourth-effect evaporator, making the evaporation system operate more stably and reliably. 5. This invention saves steam production costs and achieves significant cost reduction and efficiency improvement through efficient steam recovery and process optimization. Attached Figure Description

[0013] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0014] The present invention will now be described in detail with reference to the accompanying drawings.

[0015] like Figure 1 As shown, a cross-flow feeding method for evaporating dilute juice in beet sugar production includes the following steps: a. The purified diluted sugar syrup is fed into a four-effect evaporator for evaporation and concentration. The feed weight of the diluted sugar syrup is 15-16°Bx (40-42°Bx in existing co-current feeding processes), the feed temperature is 95-100℃, and the operating pressure inside the evaporator is 0.10-0.12 MPa (0.04-0.06 MPa in existing co-current feeding processes). After preliminary evaporation and concentration, it is reduced to 18-20°Bx (50-55°Bx in existing co-current feeding processes), and the outlet temperature of the sugar syrup is 127-132℃. The four-effect evaporator generates secondary steam at a pressure of 0.10-0.12 MPa (only 0.05 MPa in existing co-current feeding processes). The diluted sugar syrup first enters the four-effect evaporator for preliminary evaporation. Due to the low feed weight of the diluted sugar syrup, the viscosity of the syrup decreases, and the evaporation efficiency is significantly improved.

[0016] b. The sugar juice output from the four-effect evaporator is fed into the first-effect evaporator for evaporation and concentration. The feed weight of the sugar juice is 18-20°Bx (15-16°Bx in the existing co-current feed process) and the temperature is 125-130℃. The first-effect evaporator is heated using exhaust steam from the power plant, with an operating pressure of 0.22-0.28 MPa. The sugar juice is concentrated to 25-30°Bx (18-20°Bx in the existing co-current feed process), and the outlet temperature is 120℃. The first-effect evaporator produces secondary steam at a pressure of 0.25-0.3 MPa, which is then supplied to the second-effect evaporator as a heat source. The first-effect evaporator uses high-quality exhaust steam from the power plant with higher pressure (0.22-0.28 MPa) and temperature (125-130℃) as a heat source. Although the sugar juice weight is higher than in the existing process, the evaporation efficiency is not reduced under high-quality steam heating, and the sugar juice still has good fluidity.

[0017] c. The sugar juice output from the first-effect evaporator is fed into the second-effect evaporator for evaporation and concentration. The feed slurry has a slurry latitude of 25-30°Bx (18-20°Bx in the existing co-current feed process), a feed temperature of 118℃, and an operating pressure of 0.18-0.20 MPa. It is concentrated to 40-42°Bx (25-30°Bx in the existing co-current feed process), and the outlet temperature is 107.5℃. The second-effect evaporator produces secondary steam at a pressure of 0.15-0.18 MPa, which is then supplied to the third-effect evaporator as a heat source. Although the slurry latitude is slightly higher than in the original process, it is still moderate, and the use of higher-quality secondary steam from the first-effect evaporator avoids the efficiency reduction caused by the increased slurry latitude.

[0018] d. The sugar juice output from the double-effect evaporator is fed into a triple-effect evaporator for evaporation and concentration. The feed slurry has a hammer weight of 40-42°Bx (25-30°Bx in existing co-current feed processes) and a feed temperature of 105.5℃ (slightly lower than the previous stage's discharge temperature due to heat loss in the conveying pipeline). The operating pressure inside the tank is 0.14-0.16 MPa. The sugar juice is concentrated to 50-55°Bx (40-42°Bx in existing co-current feed processes), and the discharge temperature is 87-94℃. The steam pressure in the triple-effect evaporator is stabilized at 0.13-0.15 MPa. 60% of the secondary steam from the triple-effect evaporator is used as a heat source for the quadruple-effect evaporator, and 40% of the secondary steam from the triple-effect evaporator is used for sugar boiling. Although the hammer weight is relatively high at this stage (40-42°Bx), the viscosity of the solution increases slowly and the efficiency is stable because the concentration is gradual in the early stages. 60% of the secondary steam from the triple-effect evaporator is used for heating the quadruple-effect evaporator, and 40% is used for sugar boiling, solving the problem of steam pressure fluctuations in traditional processes. Steam cascade reuse technology is prominently featured in this stage, increasing the amount of water evaporated from 1 part of the power plant's waste steam to 5 parts.

[0019] e. The sugar juice output from the triple-effect evaporator is fed into the five-effect evaporator for evaporation and concentration. The feed temperature of the sugar juice is 85-92℃, with a feed latitude of 50-55°Bx. Concentration is carried out under a vacuum of -0.08 MPa to complete the entire process. 80% of the secondary steam generated by the quadruple-effect evaporator is used as the heat source for the five-effect evaporator, and 20% is used for boiling the sugar. Under vacuum, the boiling point of the sugar juice is controlled at 83-90℃, and the final sugar juice is concentrated to 65-70°Bx, with an outlet temperature of 78-84℃, facilitating subsequent cooling. The five-effect evaporator performs the final evaporation under vacuum conditions, utilizing 80% of the secondary steam from the quadruple-effect evaporator as its heat source to minimize energy consumption. Under vacuum, the boiling point of the solution is lowered to 60-65℃, preventing sugar decomposition caused by high temperatures.

[0020] The output steam from the five-effect evaporator is vacuum condensed, and the waste heat from the condensate is used to preheat the feed dilute sugar juice. The dilute sugar juice is then heated to 95-100°C by a heat exchanger. This step minimizes energy consumption.

[0021] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A cross-flow feeding method for evaporating dilute juice in beet sugar production, characterized in that... Includes the following steps: a. The purified diluted sugar syrup is sent to a four-effect evaporator for evaporation and concentration; b. The sugar juice output from the four-effect evaporator is sent to the first-effect evaporator for evaporation and concentration. The exhaust steam from the power workshop is used to heat the first-effect evaporator. All the secondary steam from the first-effect evaporator is supplied to the second-effect evaporator as a heating source. c. The sugar juice output from the first-effect evaporator is sent to the second-effect evaporator for evaporation and concentration. All the secondary steam from the second-effect evaporator is supplied to the third-effect evaporator as a heating source. d. The sugar juice output from the double-effect evaporator is sent to the triple-effect evaporator for evaporation and concentration. 60% of the secondary steam from the triple-effect evaporator is used as the heating source for the quadruple-effect evaporator, and 40% of the secondary steam from the triple-effect evaporator is used for boiling sugar. e. The sugar juice output from the triple-effect evaporator is sent to the five-effect evaporator for evaporation and concentration, completing the entire process of sugar juice evaporation and concentration. 80% of the secondary steam generated by the four-effect evaporator is used as the heating source for the five-effect evaporator, and 20% of the secondary steam generated by the four-effect evaporator is used as steam for sugar boiling.

2. The cross-flow feeding method for evaporating dilute juice from beet sugar production according to claim 1, characterized in that: In step a, the feed weight of the diluted sugar juice is 15-16°Bx, the feed temperature is 95-100℃, the operating pressure inside the tank is 0.10-0.12 MPa, and after preliminary evaporation and concentration to 18-20°Bx, the discharge temperature of the sugar juice is 127-132℃, and the quadruple-effect evaporator produces secondary steam with a pressure of 0.10-0.12 MPa.

3. The cross-flow feeding method for evaporating dilute juice from beet sugar production according to claim 2, characterized in that: In step b, the feed temperature of the sugar juice is 18-20°Bx, the temperature is 125-130℃, the operating pressure inside the tank is 0.22-0.28 MPa, the sugar juice is concentrated to 25-30°Bx, the discharge temperature of the sugar juice is 120℃, and the first-effect evaporator produces secondary steam at a pressure of 0.25-0.3 MPa.

4. The cross-flow feeding method for evaporating dilute juice in beet sugar production according to claim 3, characterized in that: In step c, the feed weight of the sugar juice is 25-30°Bx, the feed temperature is 118°C, the operating pressure inside the tank is 0.18-0.20 MPa, it is concentrated to 40-42°Bx, the discharge temperature of the sugar juice is 107.5°C, and the secondary steam produced by the double-effect evaporator is 0.15-0.18 MPa.

5. The cross-flow feeding method for evaporating dilute juice from beet sugar production according to claim 4, characterized in that: In step d, the feed weight of the syrup is 40-42°Bx, the feed temperature is 105.5℃, the operating pressure inside the tank is 0.14-0.16 MPa, the syrup is concentrated to 50-55°Bx, the discharge temperature of the syrup is 87-94℃, and the steam pressure of the triple-effect evaporator is stabilized at 0.13-0.15 MPa.

6. The cross-flow feeding method for evaporating dilute juice from beet sugar production according to claim 5, characterized in that: In step e, the feed weight of the syrup is 50-55°Bx, the feed temperature is 85-92°C, and it is concentrated under a vacuum of -0.08 MPa. Under vacuum, the boiling point of the syrup is controlled at 83-90°C, and the final syrup is concentrated to 65-70°Bx, with an outlet temperature of 78-84°C.

7. The cross-flow feeding method for evaporating dilute juice in beet sugar production according to claim 6, characterized in that: The output steam of the five-effect evaporator is vacuum condensed, and the waste heat of the condensate from the vacuum condensation is used to preheat the feed dilute sugar juice. Then the dilute sugar juice is heated to 95-100℃ by a heat exchanger.

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