1. Overview of Nanjing Industrial Boiler Cleaning Demand
Nanjing is a major industrial hub in the lower Yangtze River region, home to the Nanjing Chemical Industry Park (national level), Jinling Petrochemical, Yangzi Petrochemical, Nanjing Iron & Steel, Huaneng Nanjing Power Plant, Datang Nanjing Power Plant, and other large industrial enterprises, with over 3,000 industrial boilers in service. Boiler types span coal-fired steam boilers (10–220 t/h), gas-fired boilers, thermal oil boilers, waste heat boilers, and hot water boilers. The Nanjing region has a high concentration of energy-intensive industries — chemical, steel, and power — with annual boiler operating hours typically ranging from 7,000 to 8,000 hours, demanding extremely high reliability for continuous equipment operation.
Nanjing is situated in the Yangtze River water system, with raw water hardness of 90–150 mg/L (as CaCO₃), classified as moderately hard water. Additionally, the Nanjing section of the Yangtze experiences significant seasonal water quality fluctuations — during the flood season (June–September), increased turbidity brings large amounts of sediment and colloidal silica, while during the dry season (December–March), hardness increases by 20%–30%. These factors lead to rapid scaling and dense scale formation during boiler operation. Statistics show that industrial boilers in the Nanjing area require chemical cleaning after 12–18 months of operation; otherwise, annual fuel waste from scaling reaches 8%–15%, equivalent to an additional 15–25 tons of standard coal consumption per steam ton per year.
With the deepening of Jiangsu Province's "14th Five-Year Plan" industrial energy conservation and carbon reduction initiatives, the Nanjing Municipal Bureau of Ecology and Environment has implemented energy consumption limit management for in-service industrial boilers, requiring thermal efficiency to be no lower than the minimum allowable values specified in GB/T 10180, and boiler exhaust gas temperature must not exceed the design value by more than 30°C. Regular chemical cleaning and descaling is the core means of restoring boiler thermal efficiency and reducing carbon emissions, and is also a necessary measure for enterprises to pass energy conservation audits and carbon emission verification.
2. Common Boiler Scaling Issues in the Nanjing Region
2.1 Nanjing Water Quality and Scale Type Characteristics
Boiler scale samples in the Nanjing region are primarily carbonate scale (CaCO₃) and sulfate scale (CaSO₄). After softening treatment, Yangtze River water retains residual Ca²⁺ and Mg²⁺ at levels of 0.03–0.1 mmol/L, forming hard scale layers during long-term operation due to inadequate blowdown. Some chemical enterprises' captive power plant boilers also exhibit silicate scale (SiO₂ content 10%–25%), resulting from insufficient raw water pre-treatment. Thermal oil boilers commonly experience carbon deposition and coking, with pyrolysis products covering tube walls and reducing heat transfer coefficients by 40%–60%.
| Scale Type | Primary Components | Nanjing Area Proportion | Recommended Cleaning Agent |
|---|---|---|---|
| Carbonate Scale | CaCO₃, Mg(OH)₂ | ~55% | Sulfamic Acid 5%–8% |
| Sulfate Scale | CaSO₄, BaSO₄ | ~20% | NaOH Alkaline Boil-Out Conversion + Sulfamic Acid |
| Silicate Scale | SiO₂, CaSiO₃ | ~15% | NH₄HF₂ Assisted + Sulfamic Acid |
| Carbon Deposition / Coking | Carbides, Asphaltenes | ~10% | Specialized Decarbonizing Agent + Surfactant |
2.2 Typical Boiler Scaling Performance
Coal-Fired Steam Boilers: 10–75 t/h coal-fired boilers in the Nanjing Chemical Industry Park develop water-side scale thicknesses of 1.5–3 mm after 3–6 months of operation, with exhaust gas temperature rising by 30–50°C and thermal efficiency dropping by 5%–12%. Among these, the Luhe and Qixia riverside areas experience approximately 30% faster scaling rates than the Jiangning area due to higher raw water hardness. Thermal Oil Boilers: In the thermal oil systems of enterprises such as Yangzi Petrochemical and Jinling Petrochemical, carbon deposition layers on tube walls reach 2–5 mm in thickness after 12–18 months of operation, with heat transfer film coefficients declining by over 50%, accelerated thermal oil degradation, and acid values rising above 0.5 mgKOH/g. Waste Heat Boilers: The sintering waste heat boilers at Nanjing Iron & Steel have high flue gas dust content (inlet dust concentration 5–15 g/Nm³), with evaporator tube bundle ash accumulation combined with scaling, exhaust gas temperatures exceeding design values by 40–70°C, and power generation efficiency declining by 3–5 percentage points.
2.3 Impact of Nanjing Seasonal Factors on Boiler Scaling
Nanjing has a northern subtropical monsoon climate with distinct seasons and high humidity, which significantly affects boiler operation and scaling: In summer (June–September), high temperatures raise cooling water temperatures and increase boiler makeup frequency, proportionally increasing the total Ca²⁺ and Mg²⁺ introduced; simultaneously, Yangtze River flood season turbidity rises from the normal 20–50 NTU to 200–500 NTU, doubling colloidal silica and suspended solids content in raw water and increasing silicate scale risk. In winter (December–February), the dry season raises Yangtze River hardness to 120–180 mg/L, and low-temperature conditions reduce boiler blowdown frequency while increasing concentration ratios, accelerating CaCO₃ deposition on heating surfaces. It is recommended that Nanjing enterprises schedule at least one shutdown cleaning per year (preferably April–May or October–November, avoiding extreme winter and summer conditions) to balance cleaning effectiveness and production continuity.
3. Nanjing Industrial Boiler Cleaning Technical Solutions
3.1 Chemical Cleaning Formulation Systems
| Boiler Type | Primary Cleaning Agent | Corrosion Inhibitor | Passivator | Temperature / Time |
|---|---|---|---|---|
| Steam Boiler (Carbonate Scale) | Sulfamic Acid 5%–8% | Lan-826 0.3% + Urotropine 0.2% | NaNO₂ 1%–2% | 50–60°C / 6–8h |
| Steam Boiler (Sulfate Scale) | NaOH 3%–5% Boil-Out → Sulfamic Acid 6%–8% | BTA 0.1% + MBT 0.1% | Na₃PO₄ 1%–2% | Boil-Out 120–140°C / 12h → Acid 50–60°C / 6h |
| Thermal Oil Boiler | Specialized Decarbonizer + Surfactant 0.5% | Specialized High-Temperature Inhibitor | NaNO₂ 1.5% | 80–90°C / 12–24h |
| Waste Heat Boiler | Sulfamic Acid 5%–7% + EDTA 0.2% | Lan-826 0.3% | Sodium Molybdate 0.2% + NaNO₂ 1% | 45–55°C / 8–10h |
3.2 Six-Step Cleaning Process Flow
- Water Flushing and Scale Analysis: Initial high-pressure water flushing → take scale samples for XRF/XRD analysis → determine scale type and formulation ratios.
- Alkaline Boil-Out Conversion (Required for Sulfate Scale): NaOH 3%–5%, 120–140°C circulation boil-out for 12 hours, converting CaSO₄ to acid-soluble CaCO₃ and dismantling silicate network structures.
- Chemical Cleaning: Inject Sulfamic Acid cleaning solution via circulation pump, control flow rate at 0.2–0.5 m/s, sample every 30 minutes to test acid concentration and Fe³⁺ content; endpoint determined when acid concentration remains unchanged across two consecutive tests.
- Water Flush to Neutral: Extensive demineralized water flushing to pH 6–7, discharging residual acid and detached scale debris.
- Passivation Protection: NaNO₂ 1%–2% + Sodium Molybdate 0.2%, 50–60°C circulation passivation for 4–6 hours, forming a dense Fe₃O₄ protective film.
- Acceptance Testing: Visual inspection + coupon corrosion rate (≤2 g/m²·h) + borescope photography + thermal efficiency test (recovered to ≥90% of design value).
4. Service Coverage and Response
Danyang Blue Star Cleaning covers all 11 municipal districts of Nanjing: Xuanwu District, Qinhuai District, Jianye District, Gulou District, Qixia District, Yuhuatai District, Jiangning District, Pukou District, Luhe District, Lishui District, and Gaochun District. Key service areas include the Nanjing Chemical Industry Park (Luhe District, serving boiler systems of Yangzi Petrochemical, Jinling Petrochemical, Celanese, and other enterprises), Jiangning Economic and Technological Development Zone (serving manufacturing boilers at Changan Mazda, NGC, etc.), Qixia Jinling Petrochemical area, and the Yuhuatai District industrial belt around Nanjing Iron & Steel.
Response commitment: On-site inspection within 4 hours in Nanjing urban areas, technical proposal issued within 12 hours, cleaning construction completed within 3–5 working days (including waste liquid treatment). We provide pre/post boiler cleaning thermal efficiency comparison reports and a 12-month cleaning quality guarantee. Service-applicable boiler types: coal-fired steam boilers (10–220 t/h), gas/oil-fired boilers, thermal oil boilers, waste heat boilers, hot water boilers, and electric boilers.
5. Nanjing Local Cleaning Case Study
Equipment Parameters: An enterprise in the Nanjing Chemical Industry Park, model SHL20-1.6-AII coal-fired steam boiler (20 t/h, 1.6 MPa), operated continuously for 18 months without cleaning, scale thickness 2.8 mm, exhaust gas temperature rose from the design value of 160°C to 218°C, measured thermal efficiency only 72.3% (design 83.5%), consuming approximately 480 additional tons of standard coal annually.
Scale Analysis: XRF testing revealed primarily carbonate scale (CaCO₃ 72%, Mg(OH)₂ 8%), with 12% silicate and minor sulfate content. The scale layer appeared as grayish-white hard blocks with strong adhesion, difficult to remove mechanically.
Cleaning Process: NaOH 4% alkaline boil-out for 12h (120–130°C) to convert sulfate/silicate scale → Sulfamic Acid 6% + Lan-826 0.3% + Urotropine 0.2% (circulation acid cleaning for 7h, temperature controlled at 50–55°C) → demineralized water flush to pH 6.8 → NaNO₂ 2% passivation for 5h (55°C constant temperature) → borescope inspection + thermal efficiency retest.
Cleaning Results: Scale removal rate 98.5%, coupon corrosion rate 1.6 g/m²·h (superior to the standard ≤2 g/m²·h), exhaust gas temperature recovered to 163°C, boiler thermal efficiency recovered to 82.8%. Annual standard coal savings of approximately 420 tons, equivalent to fuel cost savings of approximately ¥380,000, with a cleaning investment payback period of approximately 1.5 months. Waste liquid was neutralized to pH 6–9 and entrusted to a qualified unit for disposal, providing complete HW34 hazardous waste transfer manifests.
6. Why Choose Danyang Blue Star Cleaning
- 25 Years of Boiler Cleaning Experience: Founded in 2001, member of the China Industrial Cleaning Association, with over 800 cumulative boiler cleaning projects completed, covering all boiler types including steam boilers, thermal oil boilers, waste heat boilers, and hot water boilers.
- Nanjing Localized Rapid Response: Only 80 km from Nanjing urban area (Danyang → Nanjing all-highway), 4-hour on-site inspection, eliminating scheduling delays and travel surcharges from distant construction teams. Designated service teams established for the Nanjing Chemical Industry Park and Jiangning Development Zone, with 24-hour response for major equipment failures.
- Customized Chemical Formulations: Scale samples are taken for XRF/XRD analysis before every boiler cleaning to precisely match acid type, concentration, and inhibitor system. No generic formulations — Sulfamic Acid for carbonate scale, alkaline boil-out conversion followed by acid cleaning for sulfate scale, NH₄HF₂ assistance for silicate scale — targeted treatment for every case.
- Full-Process Compliant Disposal: Cleaning waste liquid is entrusted to qualified hazardous waste treatment units (HW34 waste acid category), with complete disposal manifests provided to ensure environmental compliance.
- Data-Driven Delivery Reports: Includes pre/post cleaning borescope comparison images, coupon corrosion rates, thermal efficiency comparison, and waste liquid disposal manifests — directly usable for enterprise energy conservation audits and safety/environmental reviews.