I. Project Background and Equipment Specifications

This case study involves an electric resistance tilting aluminum melting furnace destined for the Yemen market, model WDL-GRQ-1500. The equipment is designed for melting non-ferrous metals and alloys with low melting points, with aluminum alloys as the typical processing material. The furnace has a rated capacity of 1,500 kilograms and adopts electric resistance heating, equipped with a hydraulic tilting system for molten aluminum discharge.

The electrical system is configured for a 380V/50Hz three-phase power supply, with control power at 220V/50Hz, using a three-phase five-wire connection. The buyer is required to provide a stable power supply with voltage fluctuation within ±10% and frequency fluctuation not exceeding ±3 Hz. This grid compatibility condition requires verification against the local industrial power supply situation in Yemen prior to installation.

II. Furnace Structure and Refractory Configuration

The furnace shell is constructed from steel plates and sectional steel welded into a cylindrical structure, with continuous full-penetration welds at all joining areas to ensure shell integrity. The lining is divided into two functionally distinct zones: side wall and furnace bottom.

The side wall lining employs a composite structure: the innermost layer consists of aluminum silicate fiber modules as insulation, with the working layer constructed from superlight refractory bricks with a density of 0.6 g/cm³. Vermiculite powder is filled into the brick joints and backing to reduce thermal conductivity. The heating elements, made of OCr27A17MO2 high-resistance alloy wire, are embedded within the side wall and controlled as a single zone – meaning the entire furnace chamber uses only one temperature control zone, suitable for scenarios where extreme temperature uniformity is not required but simplified control is preferred.

The furnace bottom is constructed from once-forming castable material. Compared to brick-laid bottoms, the monolithic cast structure offers longer service life in terms of resistance to aluminum penetration and thermal shock. An emergency drain hole is designed at the bottom of the side wall to enable emergency emptying in case of aluminum leakage, serving as a safety redundancy feature for melting furnaces.

III. Graphite Crucible and Heating System

The crucible is a Morgan brand graphite crucible, which holds strong market recognition in the non-ferrous metal melting sector. The crucible service life indicated in the proposal is 6 months or more, depending on actual operating conditions including charging method, melting temperature maintenance range, and dross removal frequency.

The heating system core element is OCr27A17MO2 resistance wire, an iron-chromium-aluminum series electric heating alloy with high resistivity and good oxidation resistance. Under single-zone control mode, the rated heating power is 200 kW, connected in star configuration with a working voltage of 380 volts. The maximum furnace temperature is designed at 850°C, with a normal working temperature range of 0 to 800°C. The empty furnace heat-up time does not exceed 3 hours, representing the time window from ambient temperature to the upper working temperature limit.

Temperature stability is specified at ±3°C, achieved by the PID regulation system under standard operating conditions.

IV. Electrical Control System Configuration

The control cabinet uses thyristors (SCRs) as the primary control elements, regulating output current by adjusting the conduction angle. The system employs an advanced phase-shift firing control circuit for continuous and smooth power regulation, rather than simple on-off control.

The temperature control system is equipped with two thermocouples: one for measuring the hearth atmosphere temperature and one for measuring the molten aluminum temperature. The thermocouple used for molten aluminum measurement is fitted with a silicon carbide protection tube to prevent chemical corrosion and physical erosion by the molten aluminum. Signals from both thermocouples are fed into two Taiwan-origin temperature controllers, one of which provides PID regulation functionality.

The control system incorporates multiple protection logics: when the furnace temperature exceeds the set upper limit or current anomalies occur due to faults, the controller automatically stops pulse output and cuts off power supply. The system also includes a soft-start function with a start delay of approximately 0.5 seconds, designed to reduce inrush current impact on both the power grid and heating elements during cold starts.

Low-voltage electrical components include air circuit breakers, contactors, and relays, sourced from CHINT or Omron as industrial-grade standard configurations.

V. Hydraulic Tilting System

The discharge method is hydraulic tilting, as opposed to a fixed furnace with manual scooping. The hydraulic system drives the furnace body to tilt around its pivot axis, enabling controlled quantitative pouring of molten aluminum from the furnace mouth. This design is suitable for scenarios where molten aluminum needs to be directly transferred to ladles or casting cavities, offering higher discharge repeatability and operational safety compared to manual scooping.

The hydraulic system comprises a hydraulic power unit, cylinders, control valve groups, and piping, interlocked with the electrical control system. Tilt angle and speed can be set via the control panel.

VI. Process Performance Parameters Summary

Rated capacity is 1,500 kilograms, with a melting rate of approximately 450 to 500 kilograms per hour – representing the average aluminum output rate from cold charging to reaching working temperature and casting readiness. With a heating power of 200 kW, the specific energy consumption is approximately 0.4 to 0.44 kWh per kilogram of aluminum, falling within the typical efficiency range for resistance-heated crucible furnaces.