I. Current Status of Waste Heat Utilization from Smelting Dry Slag

Currently, in the molybdenum iron smelting process, for enterprises using dry slag discharge technology, the heat of the dry slag is basically dissipated in the air and cannot be utilized.The initial temperature of dry slag is generally1700℃, approximately20minutes later, it drops to800℃, approximately2After a few hours, it drops to400℃, approximately. Due to rapid cooling and low temperature, it is a low-quality heat source,and the radiant heat of the dry slag also makes the operating environment temperature for slag discharging personnel higher. Heat energy recovery from smelting dry slag belongs to solid heat energy recovery, which is extremely rare in the same industry or even other industries.

We conducted an experiment at a molybdenum iron smelting enterprise in China to calculate the heat generated by smelting dry slag. The specific experimental data is as follows;

From the experimental data, it can be concluded that 1 furnace of dry slag can exchange heat into 6080.48 kg of hot water (equivalent to 95-degree hot water) within 1 hour.

II. Project Feasibility Analysis

2.1Economic Analysis

The heat recovery system uses a primary heat exchanger. Based on the experimental data and preliminary calculations,18furnace smelting dry slag can generate an equivalent of95degrees of hot water109tons. At a price of20yuan per ton of hot water, the annual profit is:109x20x330days ≈72ten thousand yuan.

2.2Reliability Analysis of Heat Recovery Project

Due to the low return on investment and complex operating conditions of the heat recovery project, during the process design, we did not aggressively choose some inapplicable processes with high cost, high technical content, and immature technology. When selecting equipment, we tried to adopt specifications and models with low failure rates and durability. The entire project does not have easily damaged or worn parts, and the equipment reliability is high.

III. Dry Slag Waste Heat Recovery Scheme

The smelting dry slag waste heat recovery is divided into four parts: transportation, coil heat exchanger, insulation, and civil construction.

3.1 Dry slag disc transportation part;

The dry slag disc transportation part adopts mine car transportation, and is manufactured and installed based on the user's existing dry slag disc. The transportation part is the power system, driving the entire disc to move within the furnace body.

3.2 Coil Part

To fully utilize heat radiation, coils with higher density are used to increase the heat exchange area. To ensure the heat exchange area while reducing the impact of scaling on the pipeline, seamless welded pipes are used. The heat exchange pipes can hold approximately6tons of water.

3.3 Insulation Part

Due to the large temperature difference between the inlet and outlet, refractory cement plus rock wool and alumina silicate magnesium are used at the top, and steel structure plus asbestos is used on both sides. The refractory cement part adopts prefabricated components made off-site and on-site connection and installation. The high-temperature zone in the front section of the insulation on both sides also adopts heat insulation first, then insulation. The heat insulation is required to have certain waterproof properties, and the insulation is required to be high-temperature resistant and have low water absorption.

3.4 Civil Construction Part

The civil engineering department adjusts according to the existing site conditions and adopts the optimal construction scheme.