Nanjing Industrial Equipment Cleaning: Four Industrial Foundations, Eight Equipment Types and Four Cleaning Routes

Direct answer: Nanjing is not one cleaning market but four. North of the Yangtze, continuous chemical and petrochemical plants in Jiangbei New Materials Science and Technology Park buy cleaning against shutdown windows measured in days; south of the river, Nangang and Meishan steel need tar, naphthalene and circulating-water deposits removed from gas-cooling and coking systems; Pukou and Jiangning semiconductor, display and automotive plants have sub-millimetre fouling where the real risk is what the cleaning chemistry leaves behind; and the riverside power and district-energy stations are locked to grid and heating schedules. Fouling type, permissible downtime and acceptance criteria differ on each of the four — one circulating-wash procedure is a maintenance job in the park and a contamination event in a fab.

1. Four Industrial Foundations Behind Nanjing Cleaning Demand

Applying one city-wide cleaning recipe to Nanjing is the most common mistake. The four site types differ in where the deposit comes from, how long the plant can be offline, and what counts as acceptance.

1.1 Jiangbei New Materials Science and Technology Park: deposits measured in lost production

The park grew out of the Nanjing Chemical Industry Park founded in 2001 and was formally approved in 2018 with a planned area of 31.7 km² — the only professional park in Nanjing built around modern chemicals. It hosts 146 operating enterprises and recorded an industrial output of RMB 260.17 billion in 2023, ranking near the top of the China Petroleum and Chemical Industry Federation quality-development park list. Inside the park, Jinling Petrochemical has a crude processing capacity of 18 million t/y with more than 70 units (refining, aromatics, power, alkylbenzene); Yangzi Petrochemical runs 12.5 million t/y refining, 800,000 t/y ethylene, 1.4 million t/y aromatics across 59 large units. Ethylene, aromatics and acetic acid chains, plus epoxy and derivatives, acetic acid derivatives and high-end specialty chemicals, define the equipment mix.

Cleaning on this kind of site has three characteristics. First, shutdown windows are counted in days — a unit turnaround is often 5 to 10 days and several exchangers must be worked in parallel, so crew size and equipment count are hard constraints. Second, the deposit is layered: crude preheat trains and column-bottom reboilers typically carry an organic coke layer on top of an inorganic salt layer, and removing only the top layer cleans nothing. Third, isolation requirements are severe: a leaking valve that lets cleaning liquor into the product side costs far more than the cleaning itself. New projects in the park — the Yangzi-BASF light-hydrocarbon utilisation project (new 1 million t/y ethylene and downstream new materials, about RMB 25.652 billion in total investment) and Jinling Petrochemical’s high-end daily-chemical project — keep generating demand for degreasing, cleaning and passivation before first start-up.

1.2 The metallurgical long process south of the river: gas and circulating water, not exchangers

Nangang is a full-process integrated steel works with mining, coking, sintering, ironmaking, steelmaking and rolling, producing 9.3701 million tonnes of steel products in 2025; Meishan Iron & Steel is also inside Nanjing. The cleaning problem here is unlike a chemical plant: raw coke-oven gas is cooled in primary coolers, and tar, naphthalene and dust deposit on the tube walls and baffle zones of horizontal-tube coolers, raising resistance and destabilising the final cooling temperature — in bad cases forcing a load reduction. Deposits in gas mains and ahead of the blowers bring blockage and corrosion as well. On top of that, scaling in continuous-casting secondary cooling and rolling circulating water, degradation of rolling emulsion, and fouling of sintering and coke-dry-quenching waste-heat boilers are permanent routine demand.

The process logic for gas systems is the opposite of exchanger cleaning: no strong-acid circulation. Instead the deposit is softened by hot washing or solvent soaking so that tar and naphthalene dissolve and detach, then removed with low- or medium-pressure water jetting, with off-gas and waste liquor collected throughout — this effluent is high in COD and strong in odour and cannot go straight into the plant sewer.

1.3 Pukou and Jiangning: thin scale, maximum sensitivity to what is put in

The 12-inch wafer fab in Pukou Economic Development Zone reached 16 nm volume production in 2018 and has since added 28 nm capacity; its facilities side — PCW plate heat exchangers, ultrapure-water system exchangers, clean-steam and AHU coils — is a regular cleaning client. Display-panel plants in the development zone and vehicle and parts suppliers in Jiangning concentrate injection-moulding cooling, paint pre-treatment, welding-robot cooling water and compressed-air aftercoolers.

Fouling here is often only a few tenths of a millimetre: a mixture of bio-slime, rust and trace water scale. The risk is not “can it be cleaned” but the cleaning itself. Chloride carried in by hydrochloric systems remains and initiates pitting in stainless steel; fluoride-bearing systems are prohibited on titanium and titanium-containing parts; foam, particles and rinse water entering a cleanroom or the process side can cost an entire batch. On this side of the city the acceptance criterion is therefore not removal rate but whether rinse-water conductivity, chloride residue and particle count are back to baseline.

1.4 Riverside power and district energy: condensers, heat networks and absorption chillers

Several coal- and gas-fired power stations sit along the Nanjing reach of the Yangtze, and Jiangbei New Area plus the development zones run district heating, energy stations and steam networks. On the power side the core equipment is the condenser and the oil cooler: once-through or circulating Yangtze cooling brings silt, bio-slime and carbonate hard scale, which shows up as falling vacuum and rising terminal temperature difference. On the heating side it is heat-network heaters, plate heat-exchange stations and the heat-transfer tubes of absorption chillers — thin scale but large area and many scattered points. What these projects share is that work cannot happen in the heating season or at peak load: the window is fixed by grid dispatch and the heating curve, so the plan has to be laid a quarter ahead.

2. Eight Typical Equipment Types and Their Deposits in Nanjing

The table maps the eight most common equipment types on Nanjing sites to their local cause. It is not a process list but an entry point for judgement: first identify the row, then decide the route.

3. Four Seasonal Variables Created by the Yangtze Water Source

Nanjing’s industrial water comes mainly from the Yangtze, so the cleaning window depends on the river as much as on the production plan. The same cooling loop does not form the same deposit in flood season and in dry season.

Flood season (roughly May to September) brings high turbidity and high silt load, so solids settle in low-velocity zones: shell-side bottoms, U-bends, header dead corners, cooling-tower basins. Acid washing is close to useless on this material — it has to be flushed out hydraulically. If only chemical circulation is run without mechanical cleaning, terminal temperature difference is back to its pre-clean level within one or two weeks.

Dry season (roughly November to March) raises the ionic concentration of the source water and makes the cycle of concentration easy to lose control of, so carbonate hard scale grows fast. The symptom is a terminal temperature difference that climbs a few per cent a month — invisible in a single day’s reading, obvious in a three-month trend.

Hot summer lifts cooling-water temperature and organic load, so bio-slime and algae become the dominant foulant. The slime glues scale onto the tube wall and brings under-deposit corrosion with it; biocide alone usually cannot hold it down and a penetrant and dispersant step is needed.

Cold winter slows chemical reaction rates and narrows the usable liquor temperature window. The classic old-plant mistake is to circulate at a liquor temperature in the low teens in order to hit a turnaround date: chemical consumption doubles, time stretches, and the removal rate still misses. Heating the loop or changing the chemistry is the fix, not simply circulating longer.

4. Application Boundaries of the Four Cleaning Routes

Only four routes are actually used on Nanjing sites, and choosing the wrong one usually costs more than money — it damages the equipment or stops the product line.

The order of selection is: first, whether the equipment can be looped (decides whether chemical circulation is possible); second, whether the deposit is organic or inorganic (decides whether to soften first or dissolve first); third, whether the plant can stop (decides online versus shutdown). Fixing the process first and looking for equipment to fit it almost always means rework.

5. Four Things That Most Often Go Wrong on Nanjing Projects

Beyond the technical route, four preparation items decide whether a project fails. Park management is strict and windows are short in Nanjing, so these deserve a meeting more than process selection does.

First, isolation and internal leakage. In a park turnaround the cleaning loop and the product side are often separated by a single valve, and passing valves during maintenance are common. Cleaning liquor crossing into the product line means a scrapped batch plus an environmental incident. The correct practice is a blind plate, or double valves with a drain, plus a pressure-hold check before circulation — exactly the step most often skipped in a tightly packed parallel window.

Second, sample the deposit first. Park deposits are commonly an organic layer over an inorganic layer. If the sample only scrapes the surface, the laboratory will lean towards organic fouling while the inorganic salt layer is the real thermal resistance. Sample at representative points (one at each tube-side inlet and outlet, one at the shell bottom) and record colour, thickness, hardness and odour.

Third, waste liquor and compliance. Chemical parks along the river enforce separate rainwater and sewage systems, separate clean and contaminated streams, and hazardous-waste manifests. Cleaning effluent must be collected on site, pH-adjusted and handled through the plant wastewater route; effluent with heavy metals or high COD goes out under a hazardous-waste transfer manifest and must never reach a rainwater inlet or an off-site water body. The contractor should put the estimated effluent volume, the number of collection containers and the disposal contractor into the plan before mobilising — sourcing a tanker at the last minute is the most common cause of delay.

Fourth, passivation and first start-up. Carbon-steel equipment that is not pre-filmed within 24 hours of cleaning re-rusts in humid air, and the rust then travels into downstream exchangers on restart. Stainless steel that is not passivated sees a marked rise in pitting risk in chloride-bearing service. Passivation and pre-filming are not add-ons; they belong on the same work sequence as the cleaning.

6. Three Local Anonymised Case Studies

Case 1 — Column-bottom reboiler, aromatics unit in the Jiangbei park. Shell-side process fouling combined an organic coke layer with inorganic salt scale, while the tube side (cooling water) was normal. The symptom was a column bottom that could not reach temperature and a steam consumption rising month after month. With only six days of window the sequence set was: solvent soak to soften the coke layer for 12 hours, then alkaline emulsification, then ultra-high-pressure water jetting tube by tube with a record per tube. After restart the column bottom returned to its design operating range and specific steam consumption fell clearly.

Case 2 — Primary gas cooler and gas mains at a steel plant south of the river. Tar and naphthalene had deposited on the horizontal-tube cooler walls and baffle zones, gas resistance was up and final cooling temperature out of limits. A full system shutdown was not available, so online hot washing was used: the loop was built in sections, liquor temperature was controlled inside the window in which naphthalene dissolves and is carried out with the liquid phase, and the heavily deposited sections were left for water jetting during the next planned outage. Oxygen content and outlet temperature of the gas system were monitored continuously to keep liquor out of the gas main.

Case 3 — PCW plate heat exchangers at an integrated-circuit supplier in Pukou. Thin bio-slime and rust between the plates had raised the pressure drop slowly. The scope was disassembly cleaning with chelating chemistry, chloride-free and fluoride-free throughout, rinse endpoint judged by conductivity and particle count, pressure test after re-assembly, plus a recommendation to adjust biocide dosing and sidestream filtration so that the same fouling would not return within a few months.

7. Service Coverage and Response

Danyang to Nanjing is motorway the whole way, with a normal drive of under two hours to the main city and Jiangbei New Area; the southern districts of Jiangning, Lishui and Gaochun are scheduled by arrangement. Coverage includes Xuanwu, Qinhuai, Jianye, Gulou, Pukou, Qixia, Yuhuatai, Jiangning, Luhe, Lishui and Gaochun districts plus Jiangbei New Area, with key sites in Jiangbei New Materials Science and Technology Park, Pukou Economic Development Zone, Jiangning Economic and Technological Development Zone and Nanjing Economic and Technological Development Zone.

Response: for emergency calls from park enterprises an engineer is scheduled to survey the same day the call is received; the southern districts and counties are scheduled against the turnaround window, normally the next day. Cross-city projects carry no distance surcharge — quotations are based on equipment parameters, deposit sampling and work quantity, not on mileage. Where several units share one window, several work fronts can run at once, with water jetting, chemical circulation and plate disassembly progressing in parallel.

8. Nanjing Industrial Equipment Cleaning FAQ

Q1: Does a heat exchanger in Nanjing foul faster because the cooling water comes from the Yangtze?

Speed depends mainly on the cycles of concentration and on sidestream filtration, not on the source water alone. The Yangtze carries high silt in flood season and a relatively concentrated ionic load in dry season: the first tends to deposit solids in low-velocity zones, the second grows carbonate hard scale faster. Judge by the three-month trend in terminal temperature difference and pressure drop rather than by any single day’s reading.

Q2: The park turnaround window is only one week — can several units be cleaned at the same time?

Yes, but the plan is driven by crew and equipment count, not by wish. One shell-and-tube exchanger normally needs a full day and night for chemical circulation and flushing, plus one to two more days for ultra-high-pressure water jetting of the bundle; running three work fronts at once needs three circulation pump sets, three water-jetting units and certified operators. Fix the equipment list, the number of parallel fronts and the location of utilities (water, power, steam, waste containers) at the planning stage, otherwise the window will definitely run out.

Q3: Can tar and naphthalene in coke-oven primary coolers and gas mains be handled online?

In most cases yes, provided a usable sectional loop and a waste-liquor collection point exist. The process is hot-wash softening rather than acid washing: liquor temperature is held inside the window in which naphthalene dissolves, while oxygen content and pressure of the gas system are monitored. Where deposits are heavily coked and cannot be carried out by the liquor, they still have to wait for the planned outage and water jetting.

Q4: Are there extra requirements for plate heat exchangers in a wafer fab or electronics plant?

The core issue is residue, not intensity. Such sites normally require cleaning chemistry free of chloride and free of fluoride, a rinse endpoint judged by conductivity and particle count, isolation and splash protection of the work area, separate placement of plates and gaskets, and a pressure test before re-assembly. It also helps to fold the cleaning record into the facility change-control system so that it can be traced.

Q5: How is cleaning waste liquor handled in Nanjing, and is there a compliance risk?

Follow the park procedure and there is no risk. Cleaning effluent is process wastewater that must be collected; containers are set on site, the volume generated is recorded, pH is adjusted and the stream then goes to the plant wastewater treatment system. Effluent containing heavy metals, high COD or solvents is managed as hazardous waste under a transfer manifest to a licensed contractor. Discharge into a rainwater inlet is prohibited — along the river this is a key inspection point.

Q6: What documents should be kept before and after cleaning to support acceptance?

Keep four sets: pre-cleaning deposit photographs and deposit analysis, a material verification record (especially for stainless steel, titanium, copper-nickel and lined equipment), the process record of liquor temperature and circulation time, and post-cleaning acceptance data (terminal temperature difference or pressure drop comparison, vacuum, tube-by-tube jetting record, passivation and pressure-hold results). With these four in place the acceptance meeting is usually argument-free.

9. Why Choose Danyang Blue Star Cleaning

1. 25 Years of Industrial Cleaning Experience — Founded in 2001; member of the China Industrial Cleaning Association, with chemical cleaning and high-pressure water jetting projects across chemicals, steel, power, electronics and district energy.
2. Four Routes Under One Team — Chemical circulation, ultra-high-pressure water jetting, online non-shutdown cleaning and plate disassembly are all run in-house, so the route is chosen from the deposit and the window rather than from what the crew happens to own.
3. Yangtze-Aware Window Planning — Seasonal silt, ionic load and biocide behaviour are built into the schedule, so cleaning lands in the season where the deposit can actually be removed instead of being repeated two weeks later.
4. Compliance-Ready Effluent Handling — Effluent volume estimate, container count and disposal contractor are agreed before mobilisation, with pH adjustment and manifest documentation matching park and riverside inspection requirements.
5. Data-Based Acceptance — Terminal temperature difference or pressure drop before and after, tube-by-tube jetting records, corrosion-coupon data and passivation results are reported in writing against GB/T 25146-2010.

The cleaning processes and acceptance criteria described here follow GB/T 25146-2010 Industrial Equipment Chemical Cleaning Quality Acceptance Standard.

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