Energy-Saving Retrofit Case Study | Successful Implementation of a Special Project in Guangzhou: Replacing the Roots Blower at JFE Steel’s Plate-Water Treatment Station with an Air-Suspension Blower
Release date:
Jun 08,2026
The Guangzhou JFE Steel Plate Wastewater Treatment Plant’s project to retrofit six air‑lift systems was implemented based on precise operational‑condition assessments and a rigorous multi‑option comparison, delivering both direct economic and environmental benefits—reducing annual comprehensive operating costs by RMB 328,500 and cutting CO₂ emissions by more than 220 tons per year—and addressing, through a pre‑planned piping design, the potential need for a second retrofit when Roots blowers are phased out. This initiative stands as a benchmark case for the steel metallurgy industry’s transition of wastewater aeration systems from conventional Roots blowers to highly efficient air‑lift technology.
Energy-Saving Retrofit Case Study | Successful Implementation of a Special Project in Guangzhou: Replacing the Roots Blowers at JFE Steel’s Plate-Water Treatment Station with Air-Suspension Blowers
Introduction Under the national “dual carbon” strategy and the steel industry’s policies aimed at energy conservation and cost reduction, Guangzhou JFE Steel Plate Co., Ltd. (hereinafter referred to as “Guangzhou JFE”) addressed the longstanding pain points of its three on-site wastewater treatment stations—high energy consumption, extensive maintenance requirements, and excessive noise—by implementing a full‑process EPC upgrade. The project selected air‑suspension blowers (air‑float) to replace conventional roots blowers (while discarding the magnetic‑levitation alternative), based on precise operating‑condition calculations. Following the retrofit, annual electricity savings are clearly quantifiable, operational and maintenance costs have been significantly reduced, and a standardized model for energy‑efficient upgrades of aeration blowers in steel‑making wastewater treatment has been established. As a major energy‑intensive sector, the steel industry is under mounting pressure to undergo a green transition. Striking a balance between maintaining production efficiency and significantly reducing electricity consumption and operating costs has become a central challenge for achieving high‑quality enterprise development. In the previous installment, we shared an overview of a project in which Guangzhou JFE partnered with Guizhou Zhonghang Huaqiang Technology Co., Ltd. to achieve energy‑saving upgrades by replacing conventional blowers with air‑suspension blowers. . Many readers are interested in the specific Energy-saving data and Economic benefits Show strong interest. Today, we’ll delve into the heart of the project and reveal the tangible energy‑saving results—this is more than just an equipment upgrade; it’s a real‑world, precision‑driven initiative to cut costs and boost efficiency. |
I. Project Renovation Background and Pain Points of Existing Equipment
At the Guangzhou JFE Steel Plate Plant, the Phase I and Phase II wastewater treatment facilities, along with the expansion project, have long relied on conventional Roots blowers to supply air to their biochemical tanks, equalization tanks, MBR membrane tanks, neutralization tanks, and sand‑filter backwash systems. A total of multiple Roots blower units have been operating continuously around the clock for years. However, this legacy equipment has consistently exposed five major operational shortcomings—shortcomings that constitute the primary driving force behind the current upgrade.
Appearance of aging equipment, operating conditions, and site environment
- Energy consumption remains high. : Roots blowers, being positive-displacement machines, suffer from significant friction losses, resulting in an operating efficiency of only 45%–55% and no high-efficiency operating range. Prior to the plant-wide retrofit, the total annual electricity cost for the blowers was… 914,000 yuan , is the largest energy‑consumption expense item in wastewater treatment plant operations;
- Annual maintenance costs are high. Roots blowers and bearings experience rapid wear, with annual maintenance costs averaging 3%–5% of the equipment’s original value. The annual expense for lubricants and component replacements per station ranges from RMB 10,000 to RMB 30,000, and major overhauls are required every 1–2 years, leading to frequent shutdowns that consume valuable production time.
- Workshop noise exceeds the standard. : At a distance of 1 meter, the operating noise level is 100–120 dB(A), necessitating the construction of a dedicated soundproofed machine room. The workshop’s working environment is harsh and fails to meet the plant’s environmental protection and noise‑reduction management standards.
- Poor operational stability : Mechanical wear causes a gradual decline in airflow year after year, making it difficult to maintain stable dissolved oxygen (DO) levels of 2–4 mg/L in the biochemical tank. Uneven aeration necessitates frequent on-site manual valve adjustments. Moreover, the compressed air used for intermittent backwashing in the sand filter is shared with the continuous aeration system in the biochemical tank, resulting in significant pressure fluctuations and substantial annual consumption of externally purchased compressed air.
- Long-term renovation hazards Roots blowers are outdated, high‑energy‑consumption equipment that face the risk of gradual phase‑out and eventual prohibition under evolving environmental regulations. Incremental, piecemeal retrofits are prone to triggering secondary construction activities and redundant investments.
On-site technical exchanges and field surveys
Original plant layout:
- Phase I Wastewater Treatment Plant: two sets of Roots blowers (A/A2, B/B2), providing air for the biochemical treatment process, the equalization tank, and the sand filter backwashing system.
- Phase II Wastewater Treatment Plant: three sets of Roots blowers (A, B, and C series), serving the equalization tank, biochemical tank, MBR tank, neutralization tank, and acid‑containing/circulating water sand filters.
- Phase II Expansion Wastewater Treatment Plant: Two sets of Roots blowers, each responsible for aeration and air supply to the biochemical tank and the MBR tank.
II. Comparative Analysis of Multiple Technical Options and Finalization of the Optimal Retrofit方案
Horizontal Comparative Selection of Three Types of Blower Parameters (Air‑Floating vs. Magnetic‑Levitation vs. Conventional Roots Blowers; the project ultimately selected the air‑floating option)
| Comparison dimension | Traditional Roots blower | Air‑suspended blower (selection and installation) | Magnetic levitation blower (discontinued design) |
| Procurement Cost (55 kW Baseline) | 50,000–70,000 yuan per unit | 100,000–160,000 yuan per unit | 120,000–210,000 yuan per unit (20%–40% more expensive than the air‑float version) |
| Energy consumption performance | Low efficiency, no variable-frequency optimization, and year-round full-load operation resulting in wasted electrical energy. | Efficiency: 82%–90%; variable-frequency, self-adaptive aeration load; overall energy savings of 20%–30%. | Efficiency is comparable to that of air‑floating systems, but the electronic control system consumes an additional 2–3 kW per hour, leaving the overall energy consumption at no advantage. |
| Maintenance costs | Annual maintenance: 3%–5% of the equipment’s original cost; annual consumables: RMB 10,000–30,000 per unit. | Annual maintenance costs less than 1% of the equipment’s original value; only filter cartridges need to be replaced, at RMB 2,000–5,000 per unit, while core components require no maintenance. | Maintenance rates are comparable to those of air‑conditioning units, but the electronic control system is highly precise, resulting in repair costs that are 30%–50% higher per service; a specialized electronics maintenance team is required. |
| Operational stability | Wear decreases year by year; it is sensitive to overpressure but highly resistant to dust. | No mechanical friction, intelligent fault prediction, robust against grid fluctuations, and highly adaptable to steelmaking and metallurgical operating conditions. | Susceptible to power‑grid surges, high temperatures, and electromagnetic interference (severely affected by high‑power equipment in steel plants); rotor shutdowns carry a risk of dropping. |
| Service life | The housing lasts 15 years, while the bearings and gears have a service life of only 8,000 to 15,000 hours. | The entire machine has a lifespan of 15–20 years, with core suspended components lasting over 20 years. | The entire unit has a lifespan of 15–20 years, while the electronic control components have a service life of only 5 years. |
| Reasons for Compatibility with This Project | Outdated, obsolete models—used only as temporary backups. | The steel plant experiences significant electromagnetic interference, lacks dedicated electrical control maintenance personnel on site, and operates continuously 24 hours a day. With the best cost‑performance ratio, it is the preferred choice for this project. | High initial investment, poor compatibility with steel mill operating conditions, and high costs for subsequent electrical control system upgrades—these factors rule it out outright. |
| Selection Conclusion: Guangzhou JFE is a steel production plant where high‑power rolling mills and electric motors are densely installed, resulting in a complex electromagnetic environment. Air‑bearing technology was therefore given priority over magnetic levitation. , thereby avoiding late‑stage electronic control system failures and the risk of costly repairs. |
III. Core Energy-Saving Data Calculation (Cost Comparison Before and After Retrofit, Annual Savings, Static Payback Period—Key Highlights Throughout the Document)
Accounting basis: Industrial electricity prices are based on 0.8 yuan/kWh , the fan operates continuously 365 days a year, with the energy-saving rate as stipulated in the plan. Estimation within the 20%–30% range Prior to the retrofit, the total annual electricity cost for the fans was RMB 914,000 (RMB 279,000 for Phase I, RMB 380,000 for Phase II, and RMB 255,000 for the expansion).
1. Annual electricity savings and cost savings benefits
| Renovation Site | Annual electricity cost before renovation (in ten thousand yuan) | 20% energy-saving rate, annual electricity bill savings | 30% energy-saving rate, annual electricity bill savings |
| Phase I Wastewater Treatment Plant | 27.9 | 5.58 | 8.37 |
| Phase II Wastewater Treatment Plant | 38.0 | 7.60 | 11.40 |
| Phase II Expansion Wastewater Treatment Plant | 25.5 | 5.10 | 7.65 |
| Total for the year | 91.4 | 182,800 yuan | RMB 274,200 |
| Annual electricity cost savings range: RMB 182,800–274,200 per year , with an average annual median income of RMB 228,500. |
2. Annual Maintenance Cost Savings Benefits
- Before the upgrade: The six original Roots blowers required annual maintenance and lubricant consumables, totaling approximately RMB 72,000 per year.
- After the retrofit: The air‑floating system requires only annual replacement of the air filter element, with total annual maintenance costs for the entire unit not exceeding RMB 8,000.
- Annual maintenance net savings: RMB 64,000 。
3. Additional Benefits from Reducing Compressed Air Consumption
Following the retrofit, all gas used for biochemical treatment, neutralization tanks, and sand filter backwashing is supplied by the air‑float system plus a standby Roots blower, thereby eliminating the need to purchase external compressed air for make‑up. Annual savings on compressed air procurement costs amount to approximately RMB 36,000. 。
4. Project’s Full-Scope Annual Net Profit and Static Payback Period
- Annual total comprehensive savings = Average electricity cost savings of 228,500 yuan + Maintenance and repair cost savings of 64,000 yuan + Compressed air cost savings of 36,000 yuan = 328,500 yuan per year. ；
- Static payback period = Total investment 122 ÷ 32.85 ≈ 3.71 years (Recovery is achieved solely through energy‑saving savings; with a design life of 15–20 years, the system generates net benefits for more than 11 consecutive years after the payback period.)
5. Environmental protection and carbon reduction quantification data (based on industry conversion standards: 1 kWh ≈ 0.785 kg CO₂)
- Based on the average annual electricity savings (using the midpoint: 228,500 ÷ 0.8 = 285,600 kWh/year);
- Annual reduction in CO₂ emissions ≈ 28.56 × 0.785 ≈ 224.2 tons/year , helping Guangzhou JFE achieve its plant‑level carbon‑reduction targets.
IV. Post-Implementation Multi-Dimensional Empirical Assessment of Improvement Outcomes
1. Energy Consumption and Process Operation Optimization
The Air‑Floating Intelligent Variable‑Frequency System automatically adjusts the air flow rate to maintain the dissolved oxygen (DO) level in the biochemical tank at 2–4 mg/L, thereby completely eliminating the previous issue of alternating over‑aeration and under‑aeration caused by the fixed‑frequency Roots blowers. Meanwhile, the sand filter’s intermittent backwashing is powered by the idle Roots blower’s pressure regulation, ensuring stable pressure in the biochemical main pipeline. System-wide aeration is uniform, eliminating the need for frequent manual valve adjustments each day. , the stability of effluent quality indicators has improved.
2. Workshop Environment Optimization
The operating noise of the fan has been reduced from the original 105–115 dB(A) to 78–83 dB(A). The existing soundproof enclosures have been dismantled, and the working environment in the machine room now complies with the national occupational health standards for noise. No additional noise‑reduction personal protective equipment is required on site.
Installation performance of the new equipment, operational status, and workshop cleanliness conditions
3. Reduced burden on operations and maintenance management
The system operates without lubricating oil or gear‑related wear parts, requiring zero maintenance across the entire unit except for annual filter replacements. This eliminates the need for quarterly disassembly inspections and annual overhauls, reducing labor requirements for wastewater‑treatment‑plant operations by more than 60% and virtually eliminating the risk of unplanned shutdowns.
4. Long-term Compliance Assurance
All existing Roots blowers have been converted to standby; gas usage is intermittent, and no major overhauls are planned going forward. In the future, the Roots blowers will be phased out naturally, while the existing piping and instrumentation systems retain预留 expansion interfaces, allowing for direct connection of any new air‑float units at a later stage. Completely eliminate redundant investments from secondary upgrades and align with the national policy on phasing out high‑energy‑consumption, outdated equipment. 。
V. Project Summary and Industry-Scale Replicability
The Guangzhou JFE Steel Plate Wastewater Treatment Plant’s project to retrofit six air‑floatation units was implemented based on precise operational condition assessments and a comparative evaluation of multiple design options, thereby achieving… Annual comprehensive operating costs decreased by RMB 328,500, and annual CO₂ emissions were reduced by more than 220 tons. The direct economic and environmental benefits, combined with a pipeline‑pre‑installation design that eliminates the need for costly secondary retrofits when Roots blowers are phased out, make this a benchmark case for the steel and metallurgical industries as they transition their wastewater aeration systems from conventional Roots blowers to high‑efficiency air‑lift technology.
This project verifies: In metallurgical applications characterized by high electromagnetic interference and continuous 24-hour operation in wastewater aeration, air‑suspended blowers offer the best life‑cycle cost‑effectiveness compared to magnetic‑levitation and Roots blowers. It can serve as a standardized reference template for energy‑saving retrofitting of wastewater treatment plants at similar steel mills in the South China region, covering equipment selection, investment estimation, and project implementation.
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