Green Casting in Progress: How to Achieve Zero Wastewater in the Meltshop

As the global manufacturing industry accelerates its transition toward sustainability, the traditional foundry industry faces severe environmental challenges. As a core foundation for rail transit equipment, the foundry industry consumes an average of 30-50 tons of water per ton of castings produced, with wastewater from the melting process accounting for over 60% of the total plant wastewater. This article will delve into a breakthrough technology—the zero-wastewater meltshop system—and explain how it achieves 100% water recycling through innovative processes, injecting green momentum into rail transit equipment manufacturing.

1. Tracing the Sources of Water Pollution in the Melting Process

In rail casting production, water consumption and pollution in the meltshop exhibit three key characteristics:

2.1 High Water Consumption in the Cooling System

Core equipment, such as medium-frequency induction furnaces and cupolas, requires continuous cooling. Traditional open cooling towers consume 2-5 tons of water per hour through evaporation, generating wastewater containing suspended solids such as iron oxide and silica. Field data from a large steel foundry shows that a single 5-ton electric furnace emits over 18,000 tons of cooling wastewater annually.

1.2 Concentrated Pollution from Process Cleaning

After sand removal, castings require high-pressure water jet cleaning, generating 2-3 tons of sand-laden wastewater per ton of castings. This wastewater can contain suspended solids (SS) concentrations as high as 5,000-8,000 mg/L and carry organic pollutants such as mold release agents and lubricants.

1.3 Secondary Pollution from Flue Gas Treatment

The flue gas generated during the smelting process (containing PM2.5, SO₂, etc.) must be purified through a spray tower, consuming hundreds of tons of water per hour and generating acidic wastewater containing heavy metal ions. If improperly treated, the pH value of the water can plummet to below 3.

2. Four Technological Breakthroughs in the Zero Wastewater System

By integrating materials science, fluid dynamics, and intelligent control technologies, the new generation zero wastewater system establishes a four-level protection network:

2.1 Innovation in Dry Dust Removal Technology

This system utilizes a “ceramic multi-cyclone + pulse bag” composite dust removal process:

Flue gas first enters the ceramic cyclone separator, where 1200 rpm centrifugal force separates 95% of large particles. The remaining fine particles enter the coated fiberglass bag and are cleaned with a 0.6 MPa pulse jet. Dust removal efficiency reaches 99.9%, with dust emission concentrations below 5 mg/m³. This system completely replaces wet spraying, saving 120,000-150,000 tons of water annually.

2.2 Construction of A Closed-Loop Cooling System

Innovative “air cooling-phase change” dual-mode cooling technology:

• Intermediate frequency furnace cooling: The closed cooling tower utilizes titanium alloy coils, with indirect heat exchange via an ethylene glycol solution.

• Mold cooling: Nanofluid (Al₂O₃ particles) replaces traditional water-based coolants, increasing thermal conductivity by three times.

• Intelligent control: Deployment of 5G IoT sensors enables real-time adjustment of water temperature and flow, reducing system energy consumption by 25%.

2.3 Magnetic-Electric Sand-Water Separation

Development of a three-stage treatment process for cleaning wastewater:

• Primary separation: A cyclone generates a tangential flow velocity of 15 m/s, achieving sand-water density stratification. Fine filtration: A ceramic membrane module (pore size 0.01 μm) intercepts colloidal matter.

• Metal recovery: An electromagnetic concentrator extracts iron filings from waste sand, achieving a purity of 98%. System recovery rate >95%, effluent turbidity <0.5 NTU.

2.4 The Ultimate Line of Defense for Zero Emissions

Establishing an emergency mechanism of “qualitative reuse + evaporation and crystallization”:

• Concentrated water treatment: Mechanical vapor recompression (MVR) evaporators concentrate wastewater to 20% solids content.

• Crystallization recovery: Evaporation residue is calcined at high temperature to produce iron oxide powder that can be used in molding materials.

• Emergency reserve: Underground water reservoirs have a capacity of 72 hours’ worth of water, ensuring stable operation under extreme operating conditions.

3. The Compound Value of Green Transformation

The implementation of this technology system has brought significant comprehensive benefits:

3.1 Environmental Benefits

• Annual reduction in wastewater discharge by 150,000-200,000 tons
• COD emissions reduced by 10-15 tons, SS emissions reduced by 40-50 tons
• Hazardous waste disposal reduced by over 80%

3.2 Economic Benefits

• Water costs reduced by 60-70%
• Equipment maintenance interval extended by 40%
• Annual metal recovery revenue exceeding one million yuan

3.3 Market Benefits

• Earned EU EPD Environmental Product Declaration certification
• Meets ISO 14064 greenhouse gas verification standards
• Assisted enterprises in winning bids for high-end international rail transit projects

3.4 Industry Demonstration

• Selected for inclusion in the Ministry of Industry and Information Technology’s “National Catalogue of Industrial Water-Saving Processes, Technologies, and Equipment”
• Promoting the revision of water quota standards for the foundry industry
• Driven by upstream and downstream enterprises to implement green transformation

4. Outlook on Sustainable Development Paths

Currently, zero-wastewater technology is undergoing iterative upgrades towards intelligentization:

4.1 Digital Twin Applications

Building a virtual water plant model uses AI algorithms to predict water quality changes and dynamically optimize reagent dosage, resulting in an expected 15% reduction in treatment costs.

4.2 Exploring Hydrogen Energy Alternatives

Developing hydrogen-based direct reduction ironmaking technology eliminates flue gas generation in the smelting process at the source, eliminating the source of spray wastewater.

4.3 Industry Chain Collaboration

Establishing a standard material library for foundry wastewater treatment, promoting industry-wide sharing of key resources such as water treatment strains and adsorbent materials, and lowering the barriers to transformation for small and medium-sized enterprises.

Driven by the “dual carbon” goals, green foundry has become a core advantage for Chinese manufacturing in global competition. Through technological innovation and ecosystem collaboration, the rail transit equipment industry is writing a new paradigm for efficient water resource utilization, contributing Chinese wisdom to global sustainable development.

Railway Casting Parts Supplier

Luoyang Fonyo Heavy Industries Co., Ltd, founded in 1998,is a manufacturer in cast railway parts. Our factory covers an area of 72,600㎡, with more than 300 employees, 32 technicians, including 5 senior engineers, 11 assistant engineers, and 16 technicians. Our production capacity is 30,000 tons per year. Currently, we mainly produce casting, machining, and assembly for locomotive, railcar, high-speed trains, mining equipment, wind power, etc. Our products have been exported to Russia, the United States, Germany, Argentina, Japan, France, South Africa, Italy and other countries.
Contact: Stella Liu
Email: sales@railwaypart.com
WhatsApp: +86-152-3615-7103