Production process of iron oxide red pigment

Iron oxide red pigment is a very important inorganic color pigment with good pigment quality and wide application fields.

The methods of producing iron oxide red are divided into dry method and wet method. The dry method mainly includes alum calcining method, iron yellow calcining method and iron black calcining method. In addition, there are natural iron oxide mineral ultrafine grinding method with hematite as raw material.

The wet process mainly includes sulfate method, nitrate method and mixed acid method. The wet process can be divided into iron scale method and ammonia method according to the different neutralizer used in the two-step oxidation process.

About the dry process technology: the dry process is the traditional and original iron oxide red production technology in our country, which has the advantages of simple production technology, short flow and relatively less equipment investment. The disadvantage is that the quality of the product is slightly worse, and the burning process has harmful gases, which has a significant impact on the environment. For example, sideroalum calcination, the calcination process has a large amount of sulfur gas produced.

In recent years, based on the comprehensive utilization of iron waste, our country has appeared sulfuric acid cinder method, iron ore powder acid baking method and other dry process, its advantage is simple technology, less investment, the disadvantage is that the product quality level is low, can only be applied to the low-end field.

About wet process:

Wet process is based on ferrous sulfate or ferrous nitrate, iron sulfate, iron nitrate as raw materials, using the first preparation of varieties, after oxidation preparation of iron red iron oxide production method. The raw material used can be ferrous sulfate, ferrous nitrate solid raw material, can also be containing ferrous sulfate, ferrous nitrate, ferric sulfate, ferric nitrate aqueous solution. The neutralizer used can be either iron sheet, iron filings, alkali or ammonia.

The advantage of the wet process is that the obtained products have excellent quality and performance, and different types of serialized iron oxide red products can be prepared. The disadvantages are long technological process, high energy consumption in the production process, a large amount of acid wastewater, and the lack of effective comprehensive utilization of acid wastewater.

Process:

Take ferrous sulfate as raw material for example: Firstly, ferrous sulfate is dissolved and purified, and then ferrous sulfate solution is quantitatively put into intensive iron oxide red reactor and diluted with water. Then add ammonia to adjust the pH value of the solution, and then strictly control the reaction temperature, through air oxidation to obtain varieties.

After the seed preparation, water is added to dilute the seed, and then the pH value of the system is adjusted, heated, and then the air is used as the oxidant for oxidation. The oxidation process is synchronized with the addition of ferrous sulfate solution and ammonia water in a parallel flow manner. When the color light of the reaction system is close to the color light of the target product, the reaction is stopped.

The main composition of the iron oxide red mother liquor produced by the filtration process is ammonium sulfate, the mother liquor is sent to the mother liquor comprehensive utilization system, and the ammonia water is collected after treatment, and the ammonia water is returned to the oxidation process for recycling. The ammonium hydrolysis residue obtained after the decomposition of ammonium does not contain harmful substances, and is returned to the mixing and washing process for recycling.

The new process also solves the process problem of producing iron oxide red, iron oxide yellow and iron oxide black under complex working conditions. The raw material is suitable for a wide range, the product quality is stable, and it can produce a variety of iron series (iron oxide red, iron oxide yellow, iron oxide black) industrial pigment products.