Product Introduction

　　 Natural circulation evaporator It is a classic evaporation-crystallization device that leverages the density difference within the feed liquid itself to generate circulating动力. At its core, it employs “natural convection + external tube boiling” technology. By creating a temperature difference between the inside and outside of the heating tubes, a density gradient is established, which drives the feed liquid to naturally circulate between the heating chamber and the separation chamber, thereby achieving solution concentration and crystallization. The equipment boasts key advantages—simple structure, reliable operation, low investment cost, and easy maintenance—and is widely used in industries such as chemical engineering, food processing, light industry, and environmental protection for concentrating low-viscosity solutions that are not prone to scaling and contain few suspended solids. It is an ideal choice for small- and medium-scale evaporation processes. We can provide either standardized or customized solutions tailored to the user’s production capacity, material characteristics, and process requirements.

Product Category

　　According to the structure of the heating chamber, the circulation path, and the application scenario, natural circulation evaporators are mainly classified into the following categories:

　　 1. Classified by heating chamber structure

　　 ▪ Vertical shell-and-tube natural circulation evaporator: The heating chamber features a vertical shell-and-tube structure, with the feed liquid circulating in the shell side of the tubes. It boasts a large heat transfer area and a compact footprint, making it the most widely used type in industrial applications.

　 　▪ External-heated natural circulation evaporator: The heating chamber and separation chamber are arranged separately. The heating chamber is installed vertically, while the separation chamber is located on one side. This design features a longer circulation path and a more stable circulation rate, making it suitable for applications with larger production capacities.

　　 ▪ Immersive Natural Circulation Evaporator: The heating tube is directly immersed in the liquid feed tank, featuring an extremely simple structure and ideal for small-scale, low-demand concentration applications (such as laboratories or small workshops).

　　 2. Classification by the state of the fluid within the pipe

　　 ▪ Rising-film natural circulation evaporator: The feed liquid is heated and vaporized inside the heating tube, and the resulting steam carries the feed liquid upward, forming a rising film. This process boasts high heat-transfer efficiency and is well-suited for low-viscosity materials.

　 　▪ Falling-film natural circulation evaporator (natural falling film): The feed liquid descends along the inner wall of the tube under gravity, combined with natural convection circulation, making it suitable for low-viscosity materials that are slightly heat-sensitive (as opposed to falling-film evaporators that rely on forced liquid distribution).

　 　3. Combine and classify according to the process.

　 　▪ Single-effect natural circulation evaporator: Simple structure, low investment, and quick results—suitable for small-scale batch production (evaporation capacity: 0.3 t/h to 10 t/h).

　 　▪ Multi-effect natural circulation evaporator (2-3 effects): By utilizing steam in a cascaded manner, energy consumption is reduced by 30% to 60% compared to single-effect equipment, making it suitable for medium- and large-scale continuous production.

Performance Features

　 　1. Simple and reliable structure: It features no complex components such as forced-circulation pumps or liquid distributors, has few moving parts, low failure risk, and a long equipment lifespan (under normal maintenance, it can operate for 8 to 10 years).

　 　2. Low investment and operation & maintenance costs: The equipment manufacturing cost is 20%–40% lower than that of forced-circulation evaporators. It eliminates the energy consumption associated with circulation pumps, resulting in significant savings on operating electricity costs. Additionally, maintenance is simple and does not require frequent inspections by specialized technicians.

　　 3. Stable and safe operation: The feed liquid circulation is driven by natural forces, requiring no manual intervention. It has a low operational threshold and can run continuously for long periods, thereby avoiding downtime caused by pump failures in forced-circulation equipment.

　　 4. Gentle and uniform heat transfer: During the feed liquid circulation process, heat is distributed uniformly, with no local overheating occurring. This makes it suitable for handling materials with good stability and also provides some adaptability to mildly thermosensitive materials (by operating under vacuum to lower the boiling point).

　 　5. Compatible with specific materials: Suitable for handling solutions with low viscosity (<100 mPa·s), that are not prone to scaling, and contain minimal suspended solids (≤1%), such as clear water, low-concentration salt solutions, and neutral organic solutions.

　 　6. Flexible operation: It can operate under atmospheric pressure or reduced pressure (vacuum) conditions, with an operating temperature range of 50℃ to 120℃. By adjusting the flow rate of the heating medium, the evaporation rate can be flexibly controlled, making it suitable for both batch and continuous production processes.

Application scenarios

　　Thanks to their simple and reliable nature and low-cost advantages, natural circulation evaporators are widely used in the following industries:

　　 1. Chemical industry: Concentration of low-concentration salt solutions (such as dilute ammonium chloride and sodium nitrate solutions), concentration of neutral chemical raw materials (such as ethylene glycol and propylene glycol), and treatment of simple organic wastewater (non-corrosive and non-scaling).

　 　2. Food industry: Sugar industry (concentration of sucrose and beet molasses solutions), auxiliary concentration in dairy products (pre-concentration of milk and goat’s milk), and preliminary concentration of fruit and vegetable juices (such as tomato juice and carrot juice);

　 　3. Light industry: White water recovery in the paper-making industry (concentration of pulp washing wastewater); treatment of dilute wastewater in the dyeing and printing industry (free of high-salt content and large amounts of suspended dye particles); concentration of surfactant solutions in detergent production.

　　 4. Environmental Protection Industry: Concentration of low-salt, low-COD wastewater (such as advanced treatment of domestic sewage and lightly polluted wastewater from chemical industrial parks); concentration and reuse of industrial cooling water.

　 　5. Other fields: Small-scale concentration tests in laboratories, concentration equipment for small beverage plants, and processing of agricultural by-products (such as concentration of starch syrup and honey).