1. Xuzhou's Industrial Landscape and Equipment Cleaning Demands
Xuzhou is situated at the junction of Jiangsu, Shandong, Henan, and Anhui provinces. It serves as the central city of the Huaihai Economic Zone, a national old industrial base, and a key energy hub in East China. The city hosts five traditional pillar industries — coal, electric power, steel, chemicals, and building materials — while also being a global leader in construction machinery: XCMG Group ranks third worldwide in the construction machinery sector. Xuzhou Economic and Technological Development Zone, Xuzhou High-Tech Industrial Development Zone, Jiawang Industrial Park, Pizhou Economic Development Zone, and others concentrate large numbers of chemical, metallurgical, and power enterprises. The city possesses the largest installed base of industrial heat exchange equipment and condensers in northern Jiangsu.
Xuzhou's industrial water supply primarily relies on groundwater and the Weishan Lake / Luoma Lake systems. Xuzhou groundwater exhibits typical high-hardness characteristics — total hardness (as CaCO₃) generally ranges from 300–500 mg/L, with some areas exceeding 600 mg/L, which is 2–4 times that of the Taihu Lake basin (120–180 mg/L). Combined with Xuzhou's location in the northern warm-temperate semi-humid monsoon climate zone, featuring large winter-summer temperature differentials and significant evaporative concentration effects, the fouling rate of heat exchangers and condensers ranks among the highest in Jiangsu Province. According to operating data from a Xuzhou chemical enterprise's heat exchangers, shell-and-tube heat exchangers running for only 8–12 months can develop tube-wall scale thicknesses of 2.0–3.5 mm, with heat transfer efficiency dropping 25%–40% — a cleaning frequency significantly higher than in southern Jiangsu. Xuzhou's installed thermal power capacity exceeds 10,000 MW. Under local high-hardness water conditions, condenser terminal temperature difference (TTD) can increase by 1.0–1.5°C annually, with corresponding coal consumption increases being substantial — a single 600 MW unit can experience an annual coal consumption increase of 5,000–8,000 tons due to condenser fouling.
2. Analysis of Major Fouling Types in Xuzhou Heat Exchangers and Condensers
2.1 Carbonate Hard Scale (CaCO₃ + Mg(OH)₂)
The high-hardness characteristics of Xuzhou groundwater determine CaCO₃ scale as the predominant fouling type. After evaporative concentration of circulating cooling water, Ca(HCO₃)₂ thermally decomposes to deposit CaCO₃ on heat exchange tube walls. Unlike scale from Taihu Lake water in southern Jiangsu, Xuzhou groundwater also has elevated magnesium ion content, and Mg(OH)₂ co-deposits with CaCO₃ to form a denser composite hard scale that is more difficult to remove by acid cleaning than pure CaCO₃ scale layers.
2.2 Silicate Scale (SiO₂ + Calcium Magnesium Silicate)
The characteristic elevated SiO₂ content in Xuzhou groundwater is relatively uncommon in southern Jiangsu. Calcium magnesium silicate scale formed by the combination of SiO₂ with Ca²⁺ and Mg²⁺ is extremely hard and chemically inert. Conventional Sulfamic Acid cleaning has limited removal efficiency for this type; NH₄HF₂ additives must be introduced into the cleaning formulation to dissolve the silicate components.
2.3 Corrosion Products and Iron Scale
Multiple steel and foundry enterprises in Xuzhou result in elevated iron ion concentrations in circulating water systems. Fe₂O₃ and Fe₃O₄ corrosion products co-deposit with carbonate scale, forming dark brown iron-calcium mixed scale with density and thickness both exceeding those of pure water scale.
2.4 Heat Exchanger Fouling Types and Cleaning Strategy Reference Table
| Scale Type | Main Components | Hardness Level | Recommended Cleaning Method |
|---|---|---|---|
| Carbonate Hard Scale | CaCO₃ 70–85%, Mg(OH)₂ 10–20% | Moderate to High | Sulfamic Acid 8–12% Chemical Cleaning |
| Calcium Magnesium Silicate Scale | SiO₂ 15–30%, CaSiO₃, MgSiO₃ | High | Sulfamic Acid + NH₄HF₂ 2% Combined Cleaning |
| Iron-Calcium Mixed Scale | Fe₂O₃ 20–40%, CaCO₃ 40–60% | High | Alkaline Wash + Acid Wash + HP Water Combination |
| Silt/Sediment Deposition | Clay, fine sand, shell fragments | Low | High-Pressure Water Jetting (50–70 MPa) |
3. Xuzhou Heat Exchanger Cleaning Technical Solutions
3.1 Shell-and-Tube Heat Exchanger Chemical Cleaning (for High-Hardness Scale)
Addressing the high-hardness, high-magnesium, and silica-containing characteristics of Xuzhou groundwater, Blue Star Cleaning has developed an enhanced chemical cleaning formulation:
| Step | Chemicals & Parameters | Mechanism | Duration |
|---|---|---|---|
| Water Flush | Industrial clean water, flow rate ≥1.5 m/s | Remove loose deposits, verify circuit patency | 30 min |
| Alkaline Wash | Na₂CO₃ 2% + NaOH 0.5% + Surfactant 0.3%, 65°C | Degreasing, conversion of Mg(OH)₂ scale layer | 4–6 h |
| Acid Wash | Sulfamic Acid 10% + NH₄HF₂ 2% + BTA 0.3% + Urotropine 0.2%, 55–60°C | Dissolve CaCO₃/MgCO₃ hard scale and silicates, corrosion inhibition protection | 6–10 h |
| Rinse | Citric Acid 0.5%, pH 3.5–4.0 | Remove residual iron ions | 2–4 h |
| Passivation | NaNO₂ 1.5% + Na₃PO₄ 0.5%, pH 9.5–10.5 | Form dense passivation film, prevent flash rust | 6–8 h |
Key Note: NH₄HF₂ (ammonium bifluoride) serves as a silicate dissolution aid and plays an irreplaceable role for the SiO₂ scale layers unique to Xuzhou groundwater. NH₄HF₂ hydrolyzes to produce HF, which reacts with SiO₂ to generate soluble SiF₄ gas that escapes, effectively stripping calcium magnesium silicate composite scale. The NH₄HF₂ dosage in the formulation is strictly controlled within 2%, combined with the BTA+Urotropine dual corrosion inhibition system to ensure corrosion rates on carbon steel and stainless steel heat exchangers remain within safe limits (carbon steel <6 g/(m²·h), stainless steel <2 g/(m²·h)).
3.2 Power Plant Condenser High-Pressure Water Jetting
Xuzhou has a dense concentration of thermal power installations — Xuzhou China Resources Power (Pengcheng Power Plant) with total installed capacity of 3,280 MW, Xuzhou Jinshanqiao Thermal Power, Jiangsu Xukuang Comprehensive Utilization Power Generation Co., Ltd. (Xukuang Thermal, 2×300 MW CFB units), Pizhou Thermal Power, Xinyi Thermal Power, etc. — with total condenser cooling area exceeding 300,000 m². For power plant condenser copper tubes / stainless steel tubes / titanium tubes, Blue Star Cleaning employs a fully automated high-pressure water jetting system: operating pressure 50–80 MPa (copper tubes 50–60 MPa, stainless steel tubes 60–80 MPa), equipped with rotating multi-orifice nozzles and automatic feed mechanisms. A single 300 MW unit condenser (approximately 15,000 tubes) can be fully cleaned within 48 hours. Post-cleaning condenser cleanliness exceeds 95%, TTD recovers to within ±0.5°C of design value, and vacuum increases by 2–4 kPa.
4. Full Xuzhou Coverage
| Area | Major Industrial Zones / Enterprise Distribution | Response Time |
|---|---|---|
| Gulou / Yunlong / Quanshan Districts | Xuzhou Economic Development Zone, urban heating pipeline networks | 4 hours |
| Jiawang / Tongshan Districts | Jiawang Industrial Park, Xuzhou High-Tech Zone, China Resources Pengcheng Power Plant | 4–5 hours |
| Pizhou / Xinyi Cities | Pizhou Economic Development Zone, Xinyi Economic Development Zone, Xinyi Chemical Cluster | 5 hours |
| Fengxian / Peixian / Suining Counties | Fengxian Economic Development Zone, Peixian Coal Chemical, Suining Economic Development Zone | 5–6 hours |
Danyang to Xuzhou is approximately 380 km, directly accessible via G2 Beijing-Shanghai Expressway or G2513 Huai-Xu Expressway. Mobile chemical cleaning pump stations and truck-mounted high-pressure water jetting equipment are deployed, with flexible allocation of 2–4 work crews operating simultaneously based on project scale. For large-scale power plant condenser cleaning projects, automated high-pressure water jetting units (single-unit daily cleaning capacity of 3,000–5,000 tubes) can be deployed to ensure all cleaning work is completed within the maintenance window.
5. Xuzhou Local Project Case Studies
Case 1: Shell-and-Tube Heat Exchanger Cleaning for a Xuzhou Chemical Enterprise
Project Background: The enterprise had one horizontal fixed-tubesheet heat exchanger (heat exchange area 450 m², tube material 20# carbon steel, shell side carrying circulating cooling water) used for distillation column overhead condensation. After 14 months of operation, heat exchange efficiency declined by approximately 35%, forcing a 40% increase in cooling water consumption to maintain process temperature. Inspection upon opening revealed 2.5–3.5 mm grayish-white hard scale adhering to the outer tube bundle surfaces, with localized brownish-yellow scale layers (containing rust). Scale sample analysis: CaCO₃ 72%, Mg(OH)₂ 15%, SiO₂ 6%, Fe₂O₃ 5%, organics 2%. This represented typical composite fouling from Xuzhou's high-hardness groundwater.
Cleaning Solution: A three-step alkaline wash – acid wash – passivation process was employed. Alkaline wash with Na₂CO₃ 2% + NaOH 0.5% converted Mg(OH)₂ and removed oil, circulating at 65°C for 5 hours. Acid wash with Sulfamic Acid 10% + NH₄HF₂ 2% + BTA 0.3% circulated for 8 hours, with enhanced dissolution targeting SiO₂ components. Fe³⁺ and Ca²⁺ concentrations were monitored online throughout; the acid wash endpoint was determined when Ca²⁺ concentration showed no further increase for 30 consecutive minutes. After rinsing, NaNO₂ passivation treatment was applied for 7 hours. Measured coupon corrosion rate: 1.3 g/(m²·h).
Cleaning Results: Post-cleaning heat transfer efficiency recovered to 91% of new equipment levels. Cooling water consumption returned to design values, yielding combined annual savings of approximately ¥230,000 in water and steam costs. After commissioning, the tube bundle surface passivation film exhibited uniform gray-black coloration. A 6-month follow-up inspection found no rust or secondary scaling.
Case 2: Condenser Chemical Cleaning + HP Water Jetting for a Xuzhou Power Enterprise
Project Background: The enterprise operated one N-20000 type two-pass condenser (cooling area 20,000 m², tube material TP316L stainless steel) paired with a 600 MW steam turbine generator unit. After 2.5 years of operation, the condenser TTD had increased from the design value of 4°C to 11.2°C, vacuum had dropped by 4.1 kPa, and the unit had to be derated to 550 MW during summer. Tube extraction inspection revealed: 0.8–2.2 mm grayish-white hard scale (primarily CaCO₃) adhering to the inner walls of stainless steel tubes, with substantial silt and shell fragment accumulation at the tube sheets (carried from Weishan Lake water source), and localized tube inlet mud blockage of approximately 18%.
Cleaning Solution: A combined chemical cleaning + HP water jetting process was adopted. Chemical cleaning phase: Sulfamic Acid 8% + NH₄HF₂ 1.5% + BTA 0.4% + Sodium Molybdate 0.1%, circulated at 55°C for 12 hours. Sodium Molybdate, as an anodic passivation-type inhibitor, provided excellent localized corrosion suppression for TP316L stainless steel. After chemical cleaning, 50 MPa high-pressure water with rotating nozzles was used for tube-by-tube precision cleaning, with emphasis on removing tube inlet silt and tube sheet deposits. Total project duration: 12 days, completed during the spring low-load window.
Cleaning Results: Post-cleaning condenser TTD recovered to 4.3°C, vacuum increased by 3.6 kPa, and the unit resumed full 600 MW load operation. Annual recovered generation was approximately 48,000 MWh. At the local grid feed-in tariff of ¥0.45/kWh, the annual economic benefit was approximately ¥21.6 million. Borescope re-inspection showed pristine, smooth stainless steel tube inner walls with intact passivation film. The client incorporated cleaning into the annual maintenance protocol, scheduling preventive cleaning every 2 years.
6. Why Choose Blue Star Cleaning for Xuzhou?
- High-Hardness Water Expertise: Xuzhou groundwater CaCO₃ hardness is 2–4 times that of southern Jiangsu and contains silicate and iron scale components that conventional cleaning formulations cannot effectively treat. Blue Star has developed an enhanced Sulfamic Acid + NH₄HF₂ formulation specifically for Xuzhou water quality characteristics, achieving >95% removal rates for calcium magnesium silicate composite scale and iron-calcium mixed scale, with stable performance verified across multiple Xuzhou local projects.
- Deep Power Industry Experience: Blue Star holds both Chemical Cleaning Grade B and High-Pressure Water Jetting dual qualifications, with over 300 completed power plant condenser cleaning projects covering all mainstream tube materials — copper HSn70-1, stainless steel TP316L/TP304, and titanium TA1/TA2. Service experience includes Xuzhou China Resources Power, Xukuang Power Plant, and others, with long-term data accumulation on the scaling patterns of Xuzhou's high-hardness circulating water.
- Qualification Assurance: Member of the China Industrial Cleaning Association. Cleaning operations strictly comply with HG/T 2387 and DL/T 957 national standards. Upon completion, comprehensive cleaning reports are delivered (including scale sample analysis, corrosion coupon data, borescope imaging, heat transfer performance recovery curves) — fully traceable and auditable.
- Rapid Northern Jiangsu Response: Danyang headquarters reaches all of Xuzhou via G2 Beijing-Shanghai Expressway in 4–6 hours; outlying areas such as Pizhou and Xinyi within 5 hours. For emergency repairs, 2 or more work crews can be deployed for parallel operations. A single 600 MW unit condenser emergency repair can be fully cleaned and returned to service within 7 days.
- Full-Process Safety Control: The cleaning process is equipped with Fe³⁺ online monitoring, standard corrosion coupons, and automated pH/temperature recording. The acid wash endpoint is determined by chemical analysis data rather than empirical estimation. All cleaning waste liquids are centrally collected and neutralized to meet Xuzhou local environmental discharge requirements. Free 6-month post-cleaning operational tracking service is provided.
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