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Ⅰ. Scheme Background and Waste Gas Characteristics
Complex organic waste gas is generated during rubber production processes such as rubber mixing, vulcanization and shaping. The main components include volatile organic compounds (VOCs), hydrogen sulfide (H₂S), ammonia (NH₃) and a small amount of dust. This type of waste gas is characterized by complex composition, severe concentration fluctuation, strong peculiar smell and flammability. Direct discharge will cause atmospheric pollution, endanger human health and lead to strict environmental penalties. Therefore, efficient and stable treatment technology is required to achieve compliant discharge. With high purification efficiency and low energy consumption, Regenerative Thermal Oxidizer (RTO) has become the preferred treatment technology for rubber waste gas.
Ⅱ. Treatment Objectives and Design Basis
1. Treatment Objectives
The VOCs removal efficiency ≥99%. The exhaust concentration after treatment complies with theEmission Standard of Pollutants for Rubber Products Industry (GB 27632-2011) and local environmental requirements (VOCs emission concentration ≤30mg/m³).
The odor removal efficiency ≥95% to eliminate pungent odor generated in rubber production.
The emission concentration of hydrogen sulfide and ammonia shall not exceed 1mg/m³ and 15mg/m³ respectively.
The system operates stably to adapt to waste gas concentration fluctuation (design concentration range: 1000-10000mg/m³) without secondary pollution.
2. Design Basis
Air Pollution Prevention and Control Law of the People's Republic of China and Emission Standard of Pollutants for Rubber Products Industry (GB 27632-2011).
Basic parameters such as waste gas emission and concentration provided by the customer (designed air volume: 10000-50000m³/h, adjustable according to actual working conditions).
Technical Requirements for Regenerative Thermal Oxidizer (RTO) (HJ 1286-2023) and relevant industrial technical specifications.
Ⅲ. Core Treatment Principle of RTO
The core principle of Regenerative Thermal Oxidizer (RTO) is that under high temperature (760-850℃), sufficient residence time (≥1.5s) and sufficient oxygen conditions, organic pollutants such as VOCs and inorganic odorous substances such as H₂S in rubber waste gas undergo oxidation reaction, and are decomposed into harmless carbon dioxide (CO₂), water (H₂O) and a small amount of sulfate to achieve thorough purification.
Meanwhile, the regenerator (ceramic regenerative brick) recovers heat from high-temperature flue gas to preheat raw waste gas, which greatly reduces system energy consumption. The working process of the three-chamber RTO is divided into three stages:
1. Preheating Stage
Raw waste gas enters the first regenerative chamber and is preheated to nearly combustion temperature by ceramic regenerative bricks.
2. Combustion Stage
The preheated waste gas flows into the combustion chamber, reaches the oxidation temperature with the heating of auxiliary fuel (natural gas/diesel), and the pollutants are completely decomposed.
3. Heat Regeneration Stage
The purified high-temperature flue gas enters the second regenerative chamber, transfers heat to the regenerative bricks, and then is discharged through the chimney at low temperature. The three chambers work alternately to realize continuous heat recovery with a thermal efficiency of 90%-95%.
Ⅳ. Overall System Configuration
1. Pretreatment System
A small amount of dust and oil mist contained in rubber waste gas will block the RTO regenerator and affect system operation. The pretreatment unit is configured as follows:
(1) Filtration Device
Primary and medium-efficiency filter cotton is adopted to intercept dust (particle size ≥10μm) and oil mist with a filtration efficiency ≥90%. The filter cotton shall be replaced regularly for daily maintenance.
(2) Condensation and Dehydration Device
For high-humidity waste gas, a condensation heat exchanger is installed to control the dew point ≤5℃ and avoid condensation and blockage of regenerators.
2. Main RTO Equipment
(1) Structural Form
Three-chamber square RTO is selected. The main material is Q235B equipped with high-temperature pouring material (inner wall temperature ≤1000℃) to ensure high temperature resistance and corrosion resistance.
(2) Regenerator
Honeycomb ceramic regenerative bricks are adopted with specific surface area ≥300m²/m³ and compressive strength ≥10MPa. It features excellent thermal stability and efficient heat recovery performance.
(3) Combustion System
Low-nitrogen burner is configured (NOₓ emission ≤30mg/m³), compatible with natural gas and diesel. It has functions of automatic ignition, flame monitoring and flameout protection.
(4) Switching Valve
Pneumatic ceramic sealing valve is adopted with excellent tightness (leakage rate ≤0.5%) and switching service life ≥1 million times to ensure continuous and stable system operation.
3. Auxiliary System
(1) Control System
PLC automatic control system with touch screen interface is equipped to realize real-time gas concentration monitoring, automatic temperature adjustment, valve switching and fault alarm, supporting remote monitoring and operation.
(2) Safety System
Flame detector, pressure sensor, temperature sensor, explosion relief device (explosion relief pressure ≤0.02MPa), nitrogen purging device and emergency discharge valve are installed to deal with abnormal conditions such as excessive concentration, flameout and overpressure to ensure operational safety.
(3) Waste Heat Utilization System
If heating demand is required, an additional waste heat exchanger can be installed to recover flue gas waste heat (flue gas temperature: 120-150℃) for workshop heating and production water preheating to reduce energy consumption.
4. Tail Gas Discharge System
(1) Chimney
Made of stainless steel with height ≥15m (meeting environmental standards), equipped with online monitoring sampling port.
(2) Online Monitoring System
Online monitoring equipment for VOCs, temperature, pressure and oxygen content is installed. Monitoring data is uploaded to the environmental protection monitoring platform in real time to ensure compliant discharge.
Ⅴ. Key Design Parameters
Design Parameters | Value Range |
|---|---|
Treatment Air Volume | 10000-50000m³/h (customizable) |
Gas Residence Time | ≥1.5s |
Combustion Temperature | 760-850℃ |
Heat Recovery Efficiency | ≥90% |
VOCs Removal Efficiency | ≥99% |
System Operating Pressure | -300~+300Pa |
Auxiliary Fuel Consumption (Natural Gas) | No supplementary combustion required when VOCs concentration ≥2000mg/m³ |
Equipment Operating Noise | ≤85dB(A) |
Ⅵ. Operation Guarantee and Maintenance
1. Operation Control
During system startup, the combustion chamber is heated to the set temperature (≥760℃) by auxiliary fuel before waste gas intake to avoid incomplete low-temperature combustion.
Monitor waste gas concentration in real time. The auxiliary combustion system automatically starts for heat supplement when the concentration is lower than 1000mg/m³. The dilution air valve opens to reduce inlet concentration and prevent overheating when the concentration is higher than 10000mg/m³.
Switch regenerative chambers regularly (switching cycle: 300-600s) to ensure uniform heat recovery and avoid local overheating.
2. Maintenance Plan
Filter Cotton: Replace in a timely manner when the pressure difference ≥500Pa, with a conventional replacement cycle of 1-3 months.
Regenerator: Inspect every 6 months to remove surface dust and replace damaged bricks.
Burner: Clean the nozzle every 3 months and inspect ignition electrodes and flame detectors to ensure stable combustion.
Switching Valve: Check tightness and pneumatic actuator every quarter and lubricate to ensure flexible switching.
Ⅶ. Scheme Advantages and Environmental Benefits
1. Core Advantages
High Purification Efficiency: VOCs removal rate ≥99% with excellent deodorization performance, meeting strict environmental protection standards.
Low Energy Consumption: The heat recovery efficiency is over 90%. Self-sustaining combustion can be realized without additional auxiliary fuel when VOCs concentration ≥2000mg/m³.
Strong Adaptability: It can treat rubber waste gas with different concentrations and components, operating stably within the concentration fluctuation range of 1000-10000mg/m³.
Stable Operation: Three-chamber structural design with long switching valve service life and low failure rate. The annual operating time is ≥8000 hours.
Environmental Compliance: Low-nitrogen burner design reduces NOₓ emission without secondary pollution.
2. Environmental Benefits
Taking the working condition with air volume of 20000m³/h and inlet VOCs concentration of 5000mg/m³ as an example, this scheme can reduce VOCs emission by approximately 876 tons annually. It completely eliminates rubber production odor, effectively improves the surrounding atmospheric environment and assists enterprises in realizing green production.
