Hotline: +8618266696519In the process of industrial intensive development in China, industrial concentration areas save land resources and reduce infrastructure costs, yet they also give rise to compound air pollution problems, which seriously impair the indoor air quality of office and residential buildings in the parks.
Taking the fresh air system renovation project of the administrative building and apartment building of a thermal power plant as an example, this paper addresses the compound odor pollution caused by the project’s proximity to industrial centralized control areas, waste incineration plants and printing and dyeing factories, as well as the defects of the original ventilation system. It conducts an in-depth study on the integrated purification technology of clean heat pump type rooftop all-air conditioning units, the optimized renovation scheme of the air duct system, and operation and maintenance adaptation strategies.
Adopting a multi-stage purification process including primary filtration, electrostatic dust removal, photocatalytic catalysis, dual activated carbon adsorption and medium-efficiency filtration, combined with heat pump temperature control and positive pressure air supply design, the renovation achieves the goals of qualified indoor air quality, appropriate temperature and humidity, and low-noise long-term operation under industrial pollution environments. It provides a replicable technical approach and practical reference for the fresh air system renovation of buildings in similar industrial agglomeration areas.
Ⅰ. Project Overview and Renovation Background
1.1 Project Location and Pollution Source Analysis
A thermal power plant is located in the core area of Wubao Industrial Centralized Control Zone in a certain town. Within the range of 300m to 2000m around the site, there are multiple pollution sources including printing and dyeing enterprises in Wubao Industrial Centralized Control Zone and Jinshang Industrial Centralized Control Zone, as well as Hongfeng Waste Incineration Plant. This forms compound air pollution dominated by formaldehyde, ammonia, sulfur dioxide, hydrogen sulfide, benzene series, TVOC and PM10. Affected by the northeast monsoon, odor dispersion intensifies in winter, leading to a marked rise in peak pollution concentration.
The project consists of two main buildings: an administrative building and an apartment building, both with seven floors.
The administrative building covers a construction area of approximately 7,000 square meters and serves public functions such as office work and conferences.
The apartment building has a floor area of about 9,100 square meters, accommodating staff dormitories, a canteen, activity rooms and other living facilities.
Completed in 2009 and put into service in 2010, both buildings have long been affected by the intrusion of outdoor industrial pollutants. Severe indoor odor and poor air quality have caused health problems among employees including dizziness and respiratory discomfort, making it an urgent livelihood and engineering problem to be solved.
1.2 Core Defects of the Original Ventilation System
Problems of the administrative building system
It adopts a fan coil unit plus fresh air system. Fresh air handling units are hoisted at both ends of the corridors, with outdoor air directly taken in through external wall rainproof louvers, without advanced air purification. The operating noise of the units exceeds the standard and disturbs the office environment. The fresh air is supplied without temperature control, resulting in excessively low supply air temperature in winter and failure to meet usage requirements.
Problems of the apartment building system
Only one-to-one split air conditioners are equipped, with no dedicated fresh air system. Indoor ventilation relies entirely on window opening natural ventilation, allowing industrial pollutants to invade the rooms directly. Lacking temperature control and purification devices, the living environment suffers from poor comfort and hidden health risks.
Common existing problems
No dehumidification measures are designed for the coastal high-humidity environment, causing building decoration materials to be prone to mildew and deterioration. There is no positive pressure protection design, so outdoor pollutants easily infiltrate indoors through building gaps. The absence of dedicated purification and operation & maintenance solutions makes it impossible to cope with compound air pollution.
Ⅱ. Core Renovation Requirements and Technical Selection Basis
2.1 Core Renovation Requirements
- Air Purification: Efficiently remove complex indoor pollutants such as formaldehyde, ammonia, sulfides, benzene series compounds, TVOCs, and particulate matter, while eliminating unpleasant indoor odors.
- Temperature Control Adaptation: Heat fresh air to around 20°C during winter to suit coastal climate conditions and employee comfort requirements.
- System Optimization: Resolve noise issues in the office building’s fresh air system, and install a complete fresh air ventilation system for the apartment building with centralized treatment and independent air supply for each unit.
- Operation & Maintenance Adaptation: Reduce long-term consumable costs and maintenance difficulty, ensuring compatibility with industrial facility maintenance capabilities.
- Environmental Adaptation: Integrate dehumidification functions to prevent mold growth in high-humidity environments and extend the service life of interior decoration and building materials.
2.2 Comparison and Selection of Purification Technologies
Complex pollutants in industrial clusters cannot be effectively treated by a single purification technology. After comprehensive technical evaluation, a multi-stage integrated purification solution was selected for this renovation project. The core technology selections are as follows:
Dust Removal Technology: Electrostatic Precipitation Replacing Physical Filtration
Traditional physical filtration systems have a lower initial investment cost, but filter elements generally require replacement every two months, which can easily lead to secondary pollution and higher maintenance requirements.
In contrast, electrostatic precipitators can capture dust particles ranging from 0.05–50 μm, with a filtration efficiency of over 97% for 0.3 μm particles. The air resistance is only 25 Pa, approximately one-tenth that of conventional physical filters. The dust collection components are washable and reusable, requiring no consumable replacement for up to five years. In addition, the system features low noise levels and simplified maintenance, making it highly suitable for industrial facility operation and maintenance conditions.
Odor and Harmful Gas Treatment: Photocatalyst + Dual Activated Carbon Adsorption
The photocatalyst technology uses nano-sized titanium dioxide as the base material. Under 388 nm light irradiation, it generates a photocatalytic reaction capable of decomposing organic pollutants such as formaldehyde, benzene, and sulfides. It also provides antibacterial, deodorizing, and anti-fouling functions, while operating with no self-consumption for long-term effectiveness.
Standard wood-based activated carbon is used to adsorb common harmful gases, while chemically modified activated carbon impregnated with potassium permanganate specifically targets sulfur oxides and malodorous gases generated by fossil fuel combustion. Together, the system forms a triple-protection mechanism combining adsorption, oxidation, and backup purification.
3. Fresh Air System Upgrading and Optimization Plan
3.1 Air Duct System Optimization Design
3.1.1 Apartment Building Fresh Air System Renovation
The apartment building adopts a centralized rooftop air supply combined with independent constant air volume distribution for each unit:
- Two clean-type heat pump rooftop full fresh air air-conditioning units are installed on the rooftop. Fresh air is purified and temperature-controlled before being delivered into the main fresh air duct system.
- New branch air ducts are added through the balcony outdoor AC unit platforms, and each room is equipped with household branch ducts featuring constant air volume valves to achieve independent and quantitative air supply.
- A positive indoor pressure environment is maintained, allowing polluted indoor air to be discharged outdoors through bathroom exhaust shafts and door gaps, effectively preventing outdoor pollutants from flowing back indoors.
3.1.2 Office Building Fresh Air System Renovation
The office building adopts a north-south split air supply system combined with optimization and reuse of the existing ventilation infrastructure:
- Two purification heat pump units are installed on the rooftop, supplying treated fresh air separately to the north and south main duct systems.
- The north-side vertical duct is installed outdoors. Existing rainproof louvers and filters are removed, and outdoor air is introduced through wall openings. The duct decoration is designed to match the building facade.
- The south-side vertical duct passes through the pantry floor slab. After rooftop openings are created, waterproof layers are restored, and horizontal ducts are connected to the existing fresh air duct system, maximizing reuse and reducing renovation costs.
- Existing suspended corridor units are removed to eliminate noise sources and improve the office acoustic environment.
3.2 Multi-Stage Purification Process Optimization
The clean-type heat pump rooftop full fresh air air-conditioning unit adopts a 13-stage integrated design with a fully optimized fresh air treatment process:
- Primary Protection: Fresh air inlet section combined with coarse filters intercepts dust particles larger than 5 μm, protecting downstream electrostatic dust removal equipment.
- Deep Dust Removal: The electrostatic precipitator uses 10–12 KV high-voltage electrostatic ionization to capture particles, sterilize contaminants, and remove fine dust and microorganisms.
- Catalytic Decomposition: The photocatalyst section decomposes harmful organic pollutants while providing sterilization and deodorization functions with long-term operation and no consumable replacement.
- Dual Adsorption: Two-stage cylindrical activated carbon filtration combines standard adsorption with chemical oxidation to effectively remove industrial odors and sulfur compounds.
- Final Fine Filtration: Medium-efficiency filters capture fine particles released from activated carbon, ensuring clean and high-quality supply air.
- Temperature-Controlled Air Delivery: The coil section and fan section provide fresh air heating and cooling, while the airflow equalization section ensures uniform air distribution.
3.3 Heat Pump Temperature Control and High-Humidity Environment Adaptation
To address the project’s coastal high-humidity environment and low winter temperatures, the heat pump temperature control and dehumidification functions are specially enhanced:
- The heat pump unit provides precise temperature regulation, maintaining winter supply air temperatures at approximately 20°C to ensure indoor comfort.
- Purification and temperature control operate simultaneously to effectively reduce fresh air humidity, preventing mold growth and deterioration of walls and interior finishing materials.
- The integrated unit design minimizes on-site piping connections, reducing the risk of equipment corrosion caused by coastal high-salinity environments.
4. Renovation Performance Evaluation and Operation Optimization
4.1 Air Quality Testing Results
After the renovation, professional testing agencies were commissioned to evaluate indoor air quality. The pollutant concentrations at all sampling points in the office building, apartment building, and cafeteria were found to be significantly lower than the national standard limits. Key indicators are as follows:
- Formaldehyde: 0.014–0.038 mg/m³
- Ammonia: 0.013–0.038 mg/m³
- Sulfur Dioxide (SO₂): 0.015 mg/m³
- Hydrogen Sulfide (H₂S): 0.001–0.004 mg/m³
- Benzene Series Compounds: 0.022–0.041 mg/m³
- TVOC: 0.040–0.068 mg/m³
- PM10: 0.017–0.026 mg/m³
Testing conditions included temperatures of 18.3–19.0°C, atmospheric pressure of 101.5 kPa, and relative humidity of 57%–58%. All measured indicators met high-quality indoor air standards, and indoor odors were completely eliminated.
4.2 Advanced Operation and Maintenance System Design
- Consumable Management:
Electrostatic dust collection components are washable and reusable, photocatalyst modules operate without material loss, and the activated carbon section adopts a modular design for convenient periodic replacement and filter media upgrades. - Simplified Maintenance:
The units are centrally installed on the rooftop for easy inspection and servicing, eliminating the need for frequent in-room maintenance operations and reducing disruption to office and residential environments. - Energy Efficiency Optimization:
The low air-resistance design reduces fan energy consumption, while the heat pump system provides highly efficient temperature control. Overall operating costs are lower than those of traditional fresh air and air-conditioning combined systems.
5. Renovation Conclusions and Application Value
This fresh air system renovation project addressed three major challenges: complex pollution in industrial clusters, high-humidity environmental conditions, and defects in the original ventilation system. Through an integrated solution combining advanced purification technology, optimized duct systems, heat pump temperature control, and positive-pressure air supply, the project achieved three major breakthroughs:
- Breakthrough in Pollution Control:
The multi-stage purification process effectively handled complex industrial pollutants, including odors, harmful gases, and particulate matter, achieving a 100% indoor air quality compliance rate. - Breakthrough in System Performance:
The renovation successfully resolved previous issues such as excessive noise, lack of fresh air supply, uncomfortable temperature and humidity conditions, and mold problems, significantly improving overall building functionality and indoor comfort. - Breakthrough in Operation and Maintenance Adaptation:
Featuring low consumable usage, simplified maintenance, and long service life, the system is highly compatible with industrial facility maintenance conditions while offering excellent cost performance.
This renovation solution was specifically designed according to the project’s location, building characteristics, pollution types, and user requirements. It provides a proven technical model for fresh air system upgrades in office and residential buildings located in industrial parks, chemical industry zones, and areas surrounding waste treatment facilities. The project demonstrates significant engineering application and promotional value in improving working and living environments while protecting occupational health in industrial areas.
