I. Salt Crystallization Blockage: The most frequent failure, directly obstructing equipment flow

This is the most common issue encountered when low-temperature evaporation equipment processes high-salinity wastewater, affecting nearly all long-term operational units. During low-temperature evaporation of high-salinity wastewater, continuous water vaporization gradually increases salt concentration until saturation is reached. Excess salts then precipitate as crystals (e.g., sodium chloride, calcium chloride crystals) If not promptly removed, these crystals preferentially adhere to the inner walls of heating tubes, the shell side of evaporators, inlet/outlet pipes, and valve connections. On one hand, the crystalline layer on heating tube walls forms an “insulating barrier,” causing a sharp drop in heat exchange efficiency (reductions of 30%–50%), slowing evaporation rates while increasing energy consumption. On the other hand, crystalline buildup within pipes gradually reduces flow cross-sectional area and may completely block pipelines, preventing normal wastewater inflow/outflow and forcing equipment shutdown for cleaning.

The risk of crystalline blockage is particularly high when wastewater contains readily precipitable calcium and magnesium ions. These ions combine with carbonate and sulfate ions in the water to form calcium carbonate and calcium sulfate crystals, which are highly hard and possess strong adhesion, making them far more difficult to remove than ordinary sodium chloride crystals.

II. Declining Heating System Efficiency: Reduced Heat Exchange Capacity and Soaring Operating Costs

The heating system serves as the “core power source” of low-temperature evaporation equipment, with its efficiency directly determining evaporation performance. High-salinity wastewater readily causes rapid deterioration in heating system performance. Two primary causes exist: First, salt crystallization adhesion. As previously described, salt crystals coating heating tubes (e.g., titanium or stainless steel) significantly increase thermal resistance. A system capable of evaporating 100L of water per hour may drop below 50L. Second, scale deposition occurs when calcium and magnesium ions in high-salinity wastewater react with carbonate ions generated during heating, forming dense scale (primarily calcium carbonate). Scale has a thermal conductivity only 1/10 to 1/50 that of metal; even a 1mm layer reduces heating efficiency by over 20%.

Additionally, if the equipment employs “heat pump heating,” high-salinity wastewater containing oil residues or suspended impurities may adhere to the heat pump evaporator surface. This reduces heat transfer efficiency, further exacerbating energy waste in the heating system.

3. Vacuum Pump Failure: Destruction of Vacuum Environment, Inability to Maintain Low-Temperature Conditions

Low-temperature evaporation relies on vacuum pumps to maintain a negative pressure environment within the system (typically at a vacuum level of -0.08 to -0.095 MPa) to lower the boiling point of water (reducing it to 40–60°C). If the vacuum pump malfunctions, the system vacuum level will rapidly decrease, causing the evaporation temperature to rise and deviate from the core requirement of “low-temperature operation.” In high-salinity wastewater treatment scenarios, vacuum pump failures primarily stem from two causes:

First, corrosion by volatile acidic gases: Certain high-salinity wastewater streams (e.g., electroplating wastewater, acid pickling wastewater) contain volatile acidic substances (e.g., hydrochloric acid mist, nitric acid mist). These substances enter the vacuum pump via steam, corroding metal components (e.g., rotors, cylinders), leading to wear, compromised sealing performance, and inability to maintain vacuum levels.

Second, salt mist entrainment: If mist removal devices (e.g., wire mesh demisters, cyclone demisters) fail, droplets generated during high-salinity wastewater evaporation enter the vacuum pump with the vapor. Salts in these droplets deposit inside the pump, potentially jamming rotors or clogging exhaust lines, causing pump overload and tripping.

IV. Substandard Condensate Water Quality: Impedes reuse/discharge, undermining treatment objectives

A core objective of low-temperature evaporation is separating high-salinity wastewater into “concentrated salt slurry” and “compliant condensate water” (reusable or dischargeable). However, high-salinity wastewater often causes condensate salt content to exceed standards, rendering it unusable. Primary causes include:

First, severe mist carryover: During evaporation of high-salinity wastewater, excessive gas flow velocity (e.g., from oversized circulation pumps) or mist eliminator issues (large or clogged orifices) allow wastewater droplets to bypass the mist barrier. These droplets enter the condensation system with secondary steam, The salts in these droplets dissolve into the condensate, causing its TDS (Total Dissolved Solids) to exceed acceptable limits (e.g., rising from the ideal level below 10 mg/L to over 100 mg/L).

Second, equipment seal failure: If gaskets age or bolts loosen at connections between evaporators and condenser pipes, or at flange interfaces, high-salinity concentrate may leak into condensate pipelines, contaminating the condensate. Additionally, if condenser pipes corrode and perforate, concentrate can directly mix with condensate, degrading water quality.

V. Equipment Corrosion Damage: Shortened Component Lifespan and Safety Hazards

The highly corrosive nature of high-salinity wastewater (particularly its high chloride ion content) is a key factor causing equipment component damage and reduced service life. Specific manifestations include:

First, electrochemical corrosion of metal components: If the evaporator shell, heating tubes, pipes, etc.,