Low-temperature evaporation equipment has clear applicable ranges for material viscosity and suspended solids (SS). Exceeding the limits will directly lead to a sharp drop in efficiency, pipe blockage, scaling, and shutdown. The following two sections clarify the standard requirements, critical values, consequences, and corresponding solutions.

## I. Requirements for Material Viscosity

### 1. General Standards (Stable Operation Range)

- Ordinary low-temperature evaporation (falling film / natural circulation):

  Most stable at ≤ 150–200 cP (centipoise)

- Forced-circulation low-temperature evaporation:

  Capable of stable treatment at ≤ 500–1000 cP

- Scraped film / specially designed wide-channel systems:

  Up to 3000–5000 cP at maximum

### 2. Consequences of Excessively High Viscosity

- Thickened liquid film, extremely poor heat transfer, and drastically reduced evaporation capacity

- High flow resistance, surging pump load, and susceptibility to cavitation

- High viscosity + high salinity → rapid wall adhesion, scaling, and coking-induced pipe blockage

- Severe foaming and entrainment, resulting in deteriorated condensate quality

### 3. Solutions for High-Viscosity Materials

- Preheating for viscosity reduction: Preheating to 40–60°C can significantly lower viscosity

- Switch to forced circulation: High flow velocity (1.5–3 m/s) scours the pipe walls

- Scraped film evaporation: Forced film formation to prevent wall adhesion

- Dilution pretreatment: Proper water addition to reduce concentration and viscosity

## II. Requirements for Suspended Solids (SS)

### 1. General Standards (Stable Operation Range)

- Ordinary low-temperature evaporation (falling film / small-diameter pipes):

  SS ≤ 50–100 mg/L

- Wide-channel / forced-circulation systems:

  SS ≤ 500–2000 mg/L (higher levels acceptable short-term)

- Extreme working conditions (special design):

  Operable with solid content of 5%–15%

### 2. Consequences of Excessively High SS

- Direct blockage of distributors, nozzles, and small-diameter pipes

- Deposition on heating surfaces → thickening scale layer and failed heat transfer

- Abrasion to pumps, valves, and seals → increased leakage and frequent maintenance

- Foam + solids → severe entrainment, material loss, and deteriorated vacuum performance

### 3. Solutions for High SS

#### Pretreatment (Mandatory)

- Bag / cartridge filtration (precision: 50–100 μm)

- Dosing flocculation + sedimentation / air flotation

- Plate-and-frame filter pressing, centrifugal separation

#### Equipment Selection Adaptation

- Selection of large-diameter pipes, wide flow channels, and anti-clogging distributors

- Forced circulation (high flow velocity prevents deposition)

- Equipped with online backwashing / CIP cleaning

## III. Quick Reference (For On-Site Direct Use)

- Viscosity:

  Ordinary materials < 200 cP;

  Forced circulation < 1000 cP;

  Higher viscosity requires scraped film + preheating + dilution.

- Suspended Solids (SS):

  Ordinary equipment < 100 mg/L;

  Wide-channel / forced circulation < 2000 mg/L;

  Higher SS requires filtration + filter pressing pretreatment.

## IV. Key Judgment of Your Current Wastewater

If you can provide:

- Viscosity (approximate cP or visual fluidity)

- SS concentration (mg/L)

- Whether it is high-salinity, high-oil, or high-organic matter type