Industrial Wastewater Zero Discharge High-Temperature Synergistic Treatment System
14 Jul 2025
Complete Technical Solution Analysis of Industrial Wastewater Zero Discharge High-Temperature Synergistic Treatment System
This document provides a comprehensive technical solution analysis for the industrial wastewater zero-discharge high-temperature synergistic treatment system, covering system principles, core module design, key parameters, and engineering application validation.
flowchart TD
A[High Salinity Wastewater] --> B{Water Quality Classification}
B -- Chloride ≤5wt% --> C[SCWO Main Treatment]
B -- Chloride ＞5wt% --> D[MSO Main Treatment]
C & D --> E[Heat Recovery System]
E --> F[Steam Cascade Utilization]
F --> G1[Drive Turbine Power Generation]
F --> G2[Preheat Feed to 200℃]
F --> G3[MVR Heat Source]
C & D --> H[Molten Salt/Slag] --> I[Selective Crystallization]
I --> J[Fractional Crystallization → Na₂SO₄]
I --> K[Evaporative Crystallization → NaCl]
Core Module Upgrade Design
Enhanced Pretreatment (to meet SCWO/MSO feedwater requirements)
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Hardness and Silica Removal: Two-stage chemical softening (lime + soda ash + MgO) to ensure hardness < 50 mg/L and SiO₂ < 20 mg/L.
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COD Concentration Adjustment: For low COD wastewater (< 25 g/L), add organic enhancers (methanol/acetate) to maintain self-ignition.
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Halogen Control: Use ion exchange chelating resin to selectively remove heavy metals such as Cr⁶⁺ and Hg²⁺.
High-Temperature Reactor Upgrade
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Parameters
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SCWO Retrofit Plan: 450℃/28MPa, residence time ≥ 120 s.
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MSO Retrofit Plan: 850℃ molten carbonate bath.
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Reactor Material: C-276 alloy + ZrO₂ ceramic lining for SCWO; high-purity alumina ceramic reactor for MSO.
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Safety Measures: Double relief valves + quench chamber for SCWO; molten salt leak detection + liquid nitrogen quench for MSO.
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Tail Gas Treatment: Catalytic oxidation bed (V₂O₅/TiO₂); quench tower (cooling rate 300℃/s).
Energy System Restructuring
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Heat Recovery Rate: > 85% using three-stage heat exchange.
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Flue gas 900℃ → steam power generation (400℃) → MVR preheating (150℃) → feedwater heating (80℃).
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Energy Self-Sufficiency: Achieve full system energy self-sufficiency with COD ≥ 35 g/L through flue gas power generation and organic heat generation.
Salt Resource Recovery Restructuring
graph LR
Molten Slag --> Dissolution Tank --> Nanofiltration Salt Separation
Nanofiltration Salt Separation --> Low-Valence Salt [NaCl Solution] --> MVR Evaporation --> Salt Crystallization --> Product NaCl
Nanofiltration Salt Separation --> High-Valence Salt [Na₂SO₄ Solution] --> Fractional Crystallization --> Centrifugal Separation --> Product Na₂SO₄
Molten Slag --> Dissolution Tank --> Nanofiltration Salt Separation
Nanofiltration Salt Separation --> Low-Valence Salt [NaCl Solution] --> MVR Evaporation --> Salt Crystallization --> Product NaCl
Nanofiltration Salt Separation --> High-Valence Salt [Na₂SO₄ Solution] --> Fractional Crystallization --> Centrifugal Separation --> Product Na₂SO₄
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Salt Purity Control: Achieve Na₂SO₄ purity ≥ 99.0% with a recovery rate of 85%, conductivity ≤ 10 μS/cm.
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Impurity Removal: Add heavy metal adsorption column (sulfide-modified activated carbon).
Economic and Reliability Improvement
| Indicator | Optimized Parameters (100 m³/d Scale) | Basis for Adjustment |
|---|---|---|
| Construction Investment | ¥23-28 million | Increased due to ceramic lining and alloy upgrade |
| Operating Cost per Tonne of Water | ¥150-220 | Additional thermal and chemical costs |
| Salt Crystallization Revenue | Na₂SO₄: ¥300/tonne | Industrial-grade anhydrous sodium sulfate price |
| Investment Payback Period | 5-7 years | Considering premium for halogenated wastewater treatment |
Safety and Environmental Enhancement
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Dioxin Control: Triple protection with high-temperature persistence + rapid quenching + catalytic decomposition.
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Reactor outlet > 850℃ for ≥ 2 s.
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Quench to below 200℃ within 0.2 s.
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Flue gas catalytic decomposition unit (CuO-MnO₂ catalyst).
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Hazardous Waste Control: Heavy metal chelation and solidification in fly ash (sulfur + cement), meeting GB5085.3 leaching toxicity standards.
Validation and Implementation Recommendations
Pilot Testing Essential Projects
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Accelerated molten salt corrosion testing (per ASTM G31).
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Thermal balance simulation (ASPEN Energy Analyzer).
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Salt crystallization phase diagram experiments (determine NaCl-Na₂SO₄ co-solubility).
Key Control Logic
def oxygen_control(cod, chloride):
base_oxygen = cod * 1.5 # Oxygen demand for COD oxidation
if chloride > 50000: # High chloride wastewater requires additional oxygen to prevent dioxin formation
return base_oxygen * 1.2
else:
return base_oxygenTypical Case Data Correction
Actual operating parameters for the original epoxy resin wastewater treatment project:
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SCWO operating pressure → 28 MPa (not 22.1 MPa as originally planned).
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NaCl purity → 98.7% (99.3% was laboratory data; actual engineering is affected by impurities).
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Steam production → 1.2 tonnes of steam per tonne of water (original plan overestimated by a factor of 5).
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