Copper

Rotary Holding Furnace

The rotary holding furnace is used in combination with a TSL reactor. It is used as a buffer between the smelting reactor and the discontinuous Peirce Smith converter. The residence time in the rotary holding furnace allows for a good separation of matte and slag. Since it is closely connected to the smelting unit it is of outmost importance to reach the same refractory life time as in the smelter.

Otherwise the whole process line would be interrupted and cause a loss in production. Therefore, also high grade DBMC bricks are applied to withstand the corrosive attack of the charged matte/slag mixture during settling.

TRL Krosaki balanced lining concepts for Rotary Holding Furnace

Refining Process

Since the sulfur content is still too high for electrolytic refining, it is necessary to further oxidize it to sulfur dioxide. This reaction step and the afterwards necessary reduction of the oxygen level in the copper is done in a drum type vessel. Heat is externally added by a burner and the process gases are injected via 2-4 tuyeres from the side. The whole process kinetic can be accelerated by the use of a bottom blowing purging system.

TRL Krosaki has developed the right refractory products for the complete lining in order to achieve multi-year lifetime. The tuyere zone is offered in resistant Alumina-Chrome brick qualities. The complete purging technology can be offered together with an experienced international technology company.

TRL Krosaki balanced lining concepts for Anode Furnace

Converting Process

In the conventional Peirce Smith converter reactor, a horizontal cylindrical vessel, a two-stage process in performed.

In the first step – slag blow – the iron in the matte is oxidized and reacts with fluxes to form a fayalitic slag. For an efficient and fast reaction, the necessary oxygen is injected into the bath via a row of tuyeres that is placed below the bath level. The vessel can be rotated to follow the correct level of white metal in the bath.

Between 2 and 4 weeks the lance must be removed due to wear and maintenance needs. Therefore, the whole cylinder is regularly subject to large temperature changes in the refractory lining.

In the second step - copper blow: the remaining copper sulfide is reduced again because of injected air forming finally blister copper with a low sulfur and oxygen content.

TRL Krosaki balanced lining concepts for Converter

Slag Cleaning Process

TThe fayalitic slag coming from smelting or converting that has still a copper content too high for disposal, is further treated in a Slag Cleaning Furnace. Since heating is required, it is necessary to use an electric arc furnace that can be round or rectangular. This unit allows enough settling time for the physical separation of small matte droplets trapped in the viscous slag and allows also due to adding of reducing agents the reduction of copper oxide present in the slag.

The lower sidewall is in constant contact with corrosive slag and experiences high pre-wear especially in the interface area between bath and hot furnace atmosphere.

TRL Krosaki offers complete furnace linings for long lasting lining life. To achieve a balanced refractory wear, it can be necessary to use intensive cooling solutions in the side wall and in the tap hole area. In close cooperation with providers of cooling elements the correct refractory design and material selection was developed by TRL Krosaki.

TRL Krosaki balanced lining concepts for Slag Cleaning Furnace

TSL (Top Submerged Lance) - Technology

The TSL process is characterized using a vertical lance that is submerged in a metal/slag bath that is surrounded by a vertical fixed cylinder. The feed (concentrate, fluxes and recycling material) is charged from the top and all process gases are injected through the lance in the center. Thereby a high intensive turbulent bath movement is created leading to fast chemical reactions. In some cases, a so-called splash block that is water cooled prevents the liquid material to be lifted into the upper part of the furnace.

The high erosion caused by discontinues contact with a slag and matte suspension above the liquid bath level is creating structural stress and chemical attack to the refractory lining.

Between 2 and 4 weeks the lance must be removed due to wear and maintenance needs. Therefore, the whole cylinder is regularly subject to large temperature changes in the refractory lining.

In the bath area, the refractory material is confronted by a matte/slag mixture with changing chemical and physical properties depending on the stage of metallurgical process.

TRL Krosaki has optimized its refractory products for the different zones of the lining to resist the high demands of this metallurgical process in the best possible way. Additionally, a concept of combined copper cooling and refractory lining is now part of the portfolio of TRL Krosaki.

TRL Krosaki balanced lining concepts for TLS Furnace

Flash Smelting - Technology

A dry, fine concentrate is charged together with fluxes through the concentrate burner on the top of the reaction shaft into the furnace. Since it is mixed efficiently with oxygen enriched air the feed starts to react immediately based on the exothermic oxidation of sulfur. In the few seconds of free fall until the contact with the surface of the liquid bath in the rectangular settler zone the solid particles are melted and pre-reacted. In the bath, the slag layer is readily formed and the calm movement supports an efficient and good separation of matte and slag. At the end of the settler the gas flow is again redirected to the top into the uptake shaft to minimize losses caused by fine material escaping the furnace into the waste heat boiler.

During the last decades, more and more intensive cooling elements were introduced in the sidewall and roof design of flash smelter units. From a refractory point of view the perfect connection between refractory material and cooling elements is of outmost importance to allow a long-lasting uniform heat transfer.

TRL Krosaki has developed the matching brick and castable solution to this challenging application. Further TRL Krosaki has optimized the refractory design and heat up calculations. Therefore, a 3D thermal profile and CFD-model is essential for a correct expansion calculation.

TRL Krosaki balanced lining concepts for Flash Smelting Furnace