The LD2000-6 is a six-effect counter-current multi-effect distilled water machine with a production capacity of 2000 L/h. It improves secondary steam utilization through six-stage counter-current heat exchange. The overall process is divided into four stages: feed preheating, multi-effect counter-current evaporation, distillate condensation and collection, and vent gas and vacuum control.
1. Feed Preheating Stage
Purified water pretreated by sand filtration, carbon filtration, and reverse osmosis enters the feed water tank and is pressurized to 0.3–0.4 MPa by the feed pump. The pressurized purified water first enters the preheating coil of the sixth effect, where residual heat from the secondary steam discharged from the sixth effect preheats the water to about 85°C. It then passes counter-currently through the preheating coils from the fifth effect to the first effect, with the temperature rising step by step. By the time the water enters the tube side of the first effect, its temperature is close to the boiling point at that effect's pressure.
Preheating coils and connecting flanges need to maintain dimensional stability under high temperature, negative pressure, and frequent thermal cycling. We can custom-machine these non-standard components according to customer drawings to meet interface matching requirements for different machine models.
2. Multi-Effect Counter-Current Evaporation Stage
Saturated pure steam at 0.4–0.6 MPa is used as the primary heat source in the first effect. The steam enters the shell side of the first-effect heating chamber, releases latent heat, condenses into condensate, and is discharged through a steam trap. The preheated purified water enters the tube side of the first effect, is heated to boiling, and produces secondary steam. This secondary steam is sent to the shell side of the second effect. The purified water in the tube side of the second effect is further heated and vaporized, producing new secondary steam that is sent to the third effect. This process continues until the sixth effect. The evaporation pressure and boiling point decrease progressively in each effect, ensuring that the secondary steam from the previous effect can effectively condense and release heat in the next effect.
Heating tube bundles, tube sheets, and vapor-liquid separation components directly affect heat exchange efficiency and distillate quality. Hansheng Automation supports single-piece and small-batch precision machining based on customer drawings, helping users maintain stable equipment operation.
3. Distillate and Condensate Collection Stage
The pure steam generated in the tube side of each effect condenses into liquid distillate in the condensation section and is collected in the distillate tank by gravity or negative pressure difference. The result is water for injection that meets pharmacopoeia standards. The steam condensate generated on the shell side of each effect is collected in a condensate tank and can be reused for boiler makeup water or as makeup water for the purified water preparation system.
4. Vent Gas Treatment and Vacuum Control
The uncondensed secondary steam discharged from the sixth effect enters the vent gas condenser and is condensed by circulating cooling water. A small amount of non-condensable gas is discharged through the vacuum exhaust system, and a 0.22 μm sterilizing filter is installed at the exhaust port to prevent microbial contamination. A water-ring vacuum pump maintains negative pressure in each effect, so that the first effect has a gauge pressure of about 0.05 MPa and a boiling point of about 110°C, while the sixth effect has a gauge pressure of about -0.09 MPa and a boiling point of about 60°C, thereby ensuring the temperature difference required for staged heat exchange.
If non-standard modification or replacement is needed for vent gas condenser end covers, filter connections, or vacuum piping fittings, we can also machine these parts according to user-provided drawings to reduce downtime.
