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Henan Hongke Heavy Machinery Co., Ltd. ("Henan Hongke Machinery") has designed, manufactured, and commissioned a φ1.6 × 8 m rotary kiln for a steel turnings calcination project in Hebei Province, China. The kiln processes 45# steel turnings (AISI 1045 equivalent) — removing cutting oils, moisture, and contaminants to produce clean, dry material suitable for remelting in electric arc furnaces.
The Problem
Steel turnings from machining operations are contaminated with 5–15% cutting oil and 3–10% moisture. This contamination means:
Steel mills reject them or pay deeply discounted scrap prices
Fire and explosion risk during storage and transport
Environmental liability from oily waste handling
Clean turnings sell at 300–800 RMB/ton more than contaminated ones — a significant revenue difference for high-volume producers.
Equipment Specification
| Parameter | Specification |
|---|---|
| Kiln type | Indirect heating rotary kiln |
| Shell size | φ1.6 × 8 m |
| Shell material | Q345B carbon steel, 12–14 mm thick |
| Rotational speed | 1–5 rpm (VFD-controlled) |
| Capacity | 2–5 t/h |
| Feed contamination | 5–15% (oil + moisture) |
| Discharge residual | < 0.5% (oil + moisture) |
| Heat source | Natural gas / coal-fired hot air |
| Hot air temperature | 500–700 °C |
| Drive motor | 18.5 kW |
Key Design Features
Processing oily steel turnings requires specialized engineering. Standard dryers and kilns are not designed for this application.
Indirect heating — combustion gases heat through the shell wall without contacting the turnings. This is critical for three reasons: fire/explosion prevention, oil vapor recovery, and clean product quality (no combustion byproducts contaminate the output).
Heavy-duty internal flights — deep-pocket, angled flights designed for dense, tangled turnings (bulk density 1.5–2.5 t/m³) that would slide rather than cascade in standard flat flights.
Wear-resistant lining — manganese steel plates in high-impact zones protect against abrasion from sharp turnings.
Oil vapor recovery system — cyclone separator, condensation unit, and bag filter/activated carbon adsorber collect and recover evaporated cutting oil (60–70% recovery rate) while meeting VOC emission limits.
Optional nitrogen inerting — for high-oil-content turnings, maintains low-oxygen atmosphere during initial heating when fire risk is highest.
How It Works
1.Preheating (200–400 °C): Surface moisture evaporates; low-boiling fluids volatilize
2.Oil volatilization (400–600 °C): Bulk of cutting oils and lubricants vaporize and are collected
3.Final calcination (500–700 °C): Residual oil films and carbon deposits thermally decompose
4.Cooling: Calcined turnings cooled below 60 °C for safe handling and storage
Total residence time: 20–40 minutes. Continuous operation: 20+ hours/day.
Results
| Parameter | Result |
|---|---|
| Oil removal | > 97% (8–12% → < 0.5%) |
| Moisture removal | > 99% |
| Oil recovery | 60–70% recovered as liquid |
| Product quality | Accepted by local EAF steel mills at full market price |
| Energy consumption | ~80–120 Nm³ natural gas/ton |
| Payback period | ~8–14 months |
Client Feedback
"Before this kiln, we sold our oily turnings at deep discounts — sometimes half the price of clean scrap. Now our turnings are clean, dry, and accepted everywhere at full price. The oil recovery system covers a significant portion of the operating cost. One of the best investments we have made."
Applicable Steel Grades
This process works for turnings from a wide range of materials:
Low-carbon steels (10#, 20#, Q235, AISI 1010–1020)
Medium-carbon steels (45#, 50#, AISI 1045–1050)
Alloy steels (40Cr, 42CrMo, AISI 4140, 4340)
Stainless steels (304, 316, 430 — higher temperature, special atmosphere)
Cast iron chips
About Henan Hongke Machinery
Henan Hongke Heavy Machinery Co., Ltd., based in Henan Province, China, manufactures industrial rotary equipment — rotary kilns, rotary dryers, and rotary coolers — for the metallurgical, environmental, chemical, and mining industries. Complete in-house design, manufacturing, installation supervision, and after-sales support.
