The petrochemical industry, which uses petroleum fractions and natural gas as raw materials to produce organic chemicals, synthetic resins, synthetic fibers, and synthetic rubber, often generates large amounts of VOC waste gas during production.
As a major precursor of PM2.5, VOCs are one of the primary causes of haze formation. Therefore, the petrochemical industry has become a key sector for national VOC control.
Regarding VOC treatment in the petrochemical industry, China has issued a series of standards such as GB31571-2015 "Emission Standard of Pollutants for Petroleum Chemistry Industry" and GB 31572-2015 "Emission Standard of Pollutants for Synthetic Resin Industry". These standards require VOC removal efficiency to be ≥97% and specify emission limits for characteristic organic pollutants in waste gas, such as benzene ≤4mg/m³ and acrylonitrile ≤0.5mg/m³.
In September 2020, China Petroleum & Chemical Corporation issued the No. 1 Order of General Manager "Special Action Plan for Ozone Pollution Prevention and Control", requiring VOC emission limits for incineration methods to be ≤20mg/m³. Some local standards also require VOCs emission limits to be ≤20mg/m³ (For example, petrochemical enterprises in Beijing should implement DB11/447 "Emission Standard of Air Pollutants for Petroleum Refining and Petrochemical Industry", which stipulates that the maximum allowable VOCs emission concentration from all organic waste gas exhaust stacks should be ≤20mg/m³ for incineration treatment).
Therefore, the petrochemical industry strictly implements the VOC emission limit standard of ≤20mg/m³
To meet the ultra-low emission requirements for VOCs and specific organic pollutants in the petrochemical industry, the following optimized combinations can achieve strict compliance with industry emission standards:
Optimized Design of Rotary Valve RTO Equipment to Improve VOC Removal Efficiency
To ensure high-efficiency VOC removal, the "Three T's and One O" principle must be satisfied:
- Residence time
- Combustion chamber temperature
- Turbulence intensity
- Oxygen content
For rotary valve RTOs, optimization focuses on three aspects: residence time, combustion chamber temperature, and turbulence intensity to enhance VOC removal efficiency.
Based on experience and relevant data, when residence time ≥0.75s (as shown in the figure below), with the oxidation chamber temperature 300°C above the ignition point, purification efficiency can exceed 99%.
Therefore, the design ensures:
- RTO combustion chamber residence time ≥1.2s
- Oxidation chamber temperature set at the highest ignition point among combustible components +300°C
- Simulation and optimization of flow and temperature fields in rotary valve RTO regenerative oxidation chambers to maximize treatment capacity, achieving purification efficiency ≥99.3%
Software simulation optimization diagrams:
a. Combustion chamber flow field optimization for efficient oxidation combustion
b. Regenerative chamber flow and temperature optimization for thorough waste gas preheating
Process Flow Design
1. Tank Farm and Loading Area Emissions
Characteristics: Highly concentrated with significant fluctuations in flow rate and concentration. Direct air dilution would result in large waste gas volumes.
Recommended treatment processes:
- "Low-temperature diesel wash + oxygen supplementation + rotary valve RTO"
- "Low-temperature condensation + oxygen supplementation + rotary valve RTO"
Case Study: A Sinopec refinery adopted the "low-temperature diesel wash + oxygen supplementation + rotary valve RTO" process, achieving compliant emissions with NMHC ≤20mg/m³.
Process flow diagram
Project implementation photo:
2. High-volume Process Emissions
Organized emission sources in petrochemical production include:
- PTA production tail gas
- Acrylonitrile production tail gas
- Rubber production tail gas
- PO/SM production tail gas
- Heater flue gas
- Waste gas incinerator flue gas
- Flare gas
Characteristics: Large flow rates, high concentrations, and contains characteristic pollutants.
Due to high concentrations and strict characteristic pollutant requirements, single-stage treatment is typically insufficient for compliance. The oxygen correction requirement for safety-diluted waste gas makes compliance particularly challenging.
Solution: For high-concentration waste gas, adopt:
- "Flue gas recirculation + RTO returning"
- "RTO + RTO" two-stage incineration processes
① "Flue Gas Recirculation + RTO Reburning" Process
A PetroChina PO/SM plant implemented this process to achieve NMHC ≤20mg/m³ after oxygen correction.
Process flow diagram
② "RTO + RTO" Process
A PetroChina synthetic resin plant adopted this process to meet NMHC ≤20mg/m³ and characteristic pollutant emission requirements.
Process flow diagram
3. Oxygen Content Correction Avoidance
In July 2023, the Ministry of Ecology and Environment released draft amendments to three standards (GB 31570-2015, GB 31571-2015, and GB 31572-2015), improving provisions for oxygen content correction.
The amendments added a second working condition: "For process gases with high oxygen content (e.g., environmentally collected gases approaching ambient air levels that meet combustion oxygen requirements), no additional air supplementation is needed." In this working condition, the actual measured concentration is used as the basis for compliance, and no oxygen content conversion is required.
Therefore, to avoid oxygen correction:
- For oxygen-free or high-concentration waste gas requiring dilution below 25% LEL, utilize factory wastewater tank emissions or workshop fugitive emissions.
Media Contact
Company Name: Xi'an Yangling Yurcent Environmental Technology Co., Ltd.
Email: Send Email
Country: China
Website: https://www.yurcentrto.com/
