What anti-freeze measures should be taken for DAF Sludge Dewatering System in low temperature environment - Wuxi Wanchuan Environmental Equipment Technology Co., Ltd.

DAF System Freeze Protection in Low-Temperature Environments

Targeted anti-freezing measures are required to prevent equipment damage and operational failures in low-temperature conditions.

1

Pipeline & Valve Protection

Thermal Insulation:

Apply 50–80 mm thick Armaflex or rock wool insulation to all process pipelines (especially dissolved air lines and sludge transfer pipes), coupled with aluminum cladding for moisture resistance. Valves (ball valves, check valves) should use electric trace heating (20–30 W/m) maintained at 5–10°C above ambient.

Drainage Design:

Install sloped pipelines (≥3°) with automatic drain valves at low points to prevent water accumulation.

Example: A 100 m DN80 pipeline without drainage can hold 600 L of water, which freezes to 630 L ice, potentially bursting the pipe.
2

Key Equipment Freeze Protection

Dissolved Air Tank:

Equip with electric heating jackets (power density 1–2 kW/m²) and thermostat controls (set to 5–10°C). In extreme cold (-10°C 以下), use glycol-based anti-freeze solutions in the pressure gauge lines to prevent pointer jamming.

Air Compressor:

Install aftercoolers with automatic drain traps and heater cartridges (1–3 kW) in the compressed air storage tank to remove moisture. A 22 kW compressor in -5°C may generate 20 L/day of condensate, risking ice blockages in distribution lines.

Pumps & Agitators:

Use low-viscosity lubricants (e.g., ISO VG 32 synthetic oil) and maintain minimal rotation (10–15 rpm) during shutdowns to prevent impeller freezing. Submersible pumps should be equipped with anti-freeze coatings (e.g., nickel-chrome plating) on wetted parts.
3

System Operational Adjustments

Recirculation Strategy:

Increase dissolved air water recirculation ratio to 30–40% (from standard 15–25%) to maintain fluid motion.

A 10 m³/h recirculation flow at -5°C can raise pipeline temperature by 2–3°C via frictional heating.

Sludge Conditioning:

Add glycol (5–10% by volume) to the sludge feed to lower freezing point, or preheat sludge to 10–15°C using waste heat exchangers. For industrial sludge with high lipid content, heating prevents viscosity spikes that impede pump performance.
4

Control & Monitoring Systems

Temperature Sensors:

Deploy Pt100 sensors at critical points (pump casings, pipeline bends, valve bodies) with alarms set at 2°C. PLC systems should automatically activate heating when temperatures drop below 5°C.

Anti-Freeze Drainage Protocol:

Implement timed drainage cycles (e.g., every 2 hours) for non-operational lines, using solenoid valves controlled by humidity-temp sensors.

In a case study, this reduced freeze-related shutdowns by 80% in a -15°C environment.
5

Emergency & Backup Solutions

Standby Heating Units:

Install diesel-fired hot water boilers (50–100 kW) as backup for electric systems, connected to a bypass loop for quick activation.

Insulated Enclosures:

Encase small components (pressure gauges, flow meters) in heated shelters (maintained at 10–15°C) with weatherproof seals.