Application of Molasses in Powder Ore Metallurgical Briquetting
Source: internal company
When smelting carbon ferrochrome and silicon-manganese alloy, there is a lot of fine ore, which makes the air permeability of burden and the furnace condition worse. And that leads to the increase of power consumption and the difficulty of recovering gas in the closed furnace. Therefore, energy utilization, economic benefits, and environmental protection will be affected. Avoiding fine ore entering the furnace has become an important part of factory smelting.
Sintering and briquetting technologies are widely used in the ferroalloy industry, but nowadays, the cold briquetting technology becomes the trend. The cold briquetting process is to mix the crushed ore, flux, reducing agent, and binder evenly, press them into briquettes at normal temperature and pressure, and dry them to have a certain strength. Of course, some of them do not need drying treatment, so that the pellets can be used as a block burden.
The selection of a binder is the key to the success or failure of cold briquetting technology. It needs to have the characteristics of the wide source and low price, and it should have certain cold strength and hot strength after forming briquettes. More importantly, it should be non-toxic and non-corrosive substances. The binders commonly used in cold briquetting are sodium silicate, pulp waste liquid, bentonite, emulsified wine residue, emulsified asphalt, molasses, and so on. Among them, the pelletizing of pulp waste liquid will gradually absorb moisture after drying, which greatly reduces the strength of pelletizing, which cannot be used. When bentonite is used as a binder, it will increase the amount of slag during smelting and increase the viscosity, which is not conducive to the smooth progress of smelting. However, molasses binder does not have the above disadvantages.
The concentration of molasses waste liquid (that is, the discharged waste liquid after distilling alcohol) is generally 8-10 Brix, and the rest is water. After three-stage evaporation, molasses waste liquid reaches 58-60 Brix, which is suitable for adding as a binder to cold briquetting process, such as chrome ore briquettes and manganese ore briquettes. Through the viscosity experiment of molasses waste liquid at different temperatures, shows that molasses waste liquid is composed of various organic compounds with different volatilization points, but there are few components with low volatilization points. The ignition point of the binder is about 600 ℃. Under the same conditions, the temperature of ignition point and volatilization point of volatile matter is quite different.
Because this binder is a by-product of the sugar industry, it is seasonal. Therefore, experiments have also been carried out on whether it can continue to be used after long-term storage and changes in external conditions. The results show that the binder does not freeze at minus 30 ℃, does not reduce its weight when stored in closed storage, and has no change in its concentration. During open storage, it will not deteriorate or ferment at any climatic temperature, but with the increase of storage temperature, the volatilization speed, loss, and concentration of binder will increase accordingly.
The chromium pellets produced with this binder can be used to smelt carbon ferrochromium in a 400KVA three-phase electric furnace, and good results have been achieved. The furnace has good air permeability, uniform flame on the material surface, stable furnace condition, and easy adjustment of alloy composition. Manganese ore powder used for making cold briquettes has the same particle size and humidity requirements as chrome ore. The composition of pellets is determined according to the composition requirements of the smelted silicon-manganese alloy, and a certain amount of flux and 8-12% molasses binder are added, mixed evenly, pressed into pellets, and then dried. The strength of dried pellets is 50-60kg/pellet.
In addition, molasses waste liquid can also be used for tungsten dust pelletizing, which is realized by disc pelletizer. The pellet strength with molasses wastes liquor as binder can be increased by 10-20 kg/pellet compared with sodium silicate. The pellet diameter is 10-15 mm.
Molasses binder and smelting experiment show that pellet can replace lump ore. Cold-briquetted pellets are superior to lump ore in terms of air permeability of the furnace, uniformity of flame on the material surface, and stability of process operation. Moreover, the dust content in the furnace gas is greatly reduced, which is more beneficial to the production of the closed furnace. After all kinds of organic matter in syrup waste liquor are volatilized and burned completely at different temperatures, less than 1% of alkali metals and alkaline earth metals remain, which has no great influence on alloy quality and slag type. Moreover, because of its low price and abundant resources, it is feasible in using as a binder for cold briquetting of fine ore.