Submerged Arc Furnace Ferrochrome Production

Production Process of Ferrochrome by Submerged Arc Furnace 

Ferrochrome production process:  The production methods of high carbon ferrochrome include electric furnace (Submerged Arc Furnace) method, shaft furnace (blast furnace) method, plasma method and smelting reduction method. The vertical furnace method currently only produces low chromium alloys (Cr<30%), and the vertical furnace production process with higher chromium content (such as Cr>60%) is still in the research stage; The latter two methods are emerging processes that are currently being explored; Therefore, most commercial high carbon ferrochrome and reprocessed ferrochrome are produced by electric furnace (Submerged Arc Furnace) method. 

Electric furnace (Submerged Arc Furnace) smelting has the following characteristics:

(1) Electric furnaces use electricity, the cleanest energy source. Other energy sources such as coal, coke, crude oil, natural gas, etc. inevitably introduce accompanying impurity elements into the metallurgical process. Only by using an electric furnace can the cleanest alloy be produced.

(2) Electricity is the only energy source that can obtain any high temperature conditions.

(3) Electric furnaces can easily achieve thermodynamic conditions such as oxygen partial pressure and nitrogen partial pressure required for various metallurgical reactions such as reduction, refining, and nitriding.

Brief Description of the Production Process of Ferrochrome

Qualified raw materials such as chrome ore, coke, and silica are mixed according to the formula requirements for smelting alloys. The mixture is transported by a belt conveyor to a local steel platform at 27.00m in the main plant building, and then transferred to a fixed reversible belt conveyor. 

The reversible belt conveyor then sends the mixture to a rotating fabric belt conveyor, and the mixed furnace material is added to 13 furnace top silos on a 20.4m platform through hoppers and material pipes suspended on the 27.00m platform, and sent into the furnace through material pipes. Use full material tubes for feeding.

The furnace charge enters the fully enclosed ferrochrome electric furnace, and the 110KV power supply is supplied by a transformer through three-phase electrodes to introduce current into the submerged arc furnace. The electrodes generate arc heat between them and the furnace charge, which is transmitted to the submerged arc furnace filled with the furnace charge. Through the arc heat and resistance heat, the mixture of chromite, silica, and coke is heated and melted, and reduced to high carbon ferrochrome alloy. In the smelting process, the voltage level and current intensity on the electrode are set according to the smelting process parameters, and the values of voltage and current are also different at different times, that is, the power input into the furnace is different. 

The electrode is always stably inserted into the furnace material in the furnace, and the gas escapes uniformly from the entire material surface. The arc is not exposed from beginning to end, and the mixed furnace material is added to the submerged arc furnace in small batches as the material level decreases, keeping the material level in the furnace at a certain height and presenting a flat cone shape around the electrode. 

During the smelting process, the material layer has good breathability, which can expand the submerged arc furnace reaction. The high-temperature gas generated by the reaction can also pass through the material layer uniformly and slowly over a large area, heating and reducing the furnace material. Micro positive pressure operation is adopted throughout the entire smelting process.

When the molten iron generated by reduction in the submerged arc furnace reaches a certain level, use a plug opening machine and oxygen to open the furnace hole, release the molten iron and slag, and flow into the molten iron ladle and slag ladle through the iron outlet. 

After the iron production is completed, use a hole opening machine to block the furnace hole. The molten iron ladle and slag ladle are pulled to the casting room by a winch, and the molten iron ladle is lifted by a crane using a water granulation casting process. 

After water granulation casting, the granulated iron is lifted by a crane and placed in an iron container, transported to the finished product warehouse, drained, and bagged for storage. In emergency situations, mold casting can also be used to remove the slag from the ladle and cast it into ingots in the ingot mold. 

After the alloy has cooled slightly, pry it up and lift it into the iron container with a crane. The alloy ingot is then transported to the finished product warehouse by car after cooling. 

After crushing and finishing, it is bagged and stored in the warehouse. The slag package is pulled by a slag truck to the water granulation dry slag span, lifted down by a bridge crane and poured into the dry slag pit. 

After treatment, it is transported by a loader to the dry slag yard and cooled before being transported out of the factory by truck.

The submerged arc furnace is powered under the prescribed power supply system. A 30000kVA high carbon ferrochrome furnace produces iron once every 2.67 hours on average, with 9 furnaces produced per day. The amount of iron produced per furnace is about 14 tons (physical weight), and the maximum amount of iron produced is 17 tons (physical weight). Analyze the sample once for each iron tapping process, and provide the results to the furnace front within 1 hour for each sample analysis.

Smelting and pouring are both done in three shifts, with a daily annual output of about 160 tons and 340 working days.