Abstract: Pyrite cinder is a kind of industrial solid waste which is produced by burning pyrite ore with medium or low content of sulphur. The burning method is usually a simple and non-integrated process requiring simple equipment and low cost, which is suitable for small-scale enterprises, but the sulfur dioxide gas emitted from the burning process is large and the secondary pollution caused by the dust and fly ash generated is serious. This paper mainly expounds the physical and chemical properties, mining process and utilization of pyrite cinder, summarizes the harmfulness of pyrite cinder to the environment and introduces the main pollutant control measures of pyrite cinder.
Keywords: Pyrite cinder; Burning process; Pollutant control
Introduction
Pyrite cinder is a kind of industrial solid waste which is formed by burning pyrite ore with medium or low content of sulfur. It is mainly composed of iron-sulfur compound, mainly iron sulfide, and also contains iron oxide and silicon dioxide. It is gray-black or gray-brown in color, which is different from iron ore and iron slag.
The burning method of pyrite cinder is usually simple and non-integrated process, with simple equipment and low cost, suitable for small-scale enterprises. In the course of burning, sulfur dioxide gas is generated, and the sulfur dioxide gas emissions are large. In addition, secondary environmental pollution such as dust and fly ash is generated.
Besides, pyrite cinder also contains some useful components, so it can be utilized as raw material for building materials, cement clinker, paint raw materials, ceramic raw materials and other products, thus improving the utilization efficiency of pyrite cinder and reducing the amount of residues entering the environment.
Physical and Chemical Properties
Pyrite cinder has a blocky or earthy structure, which is porous and contains a lot of macroscopic and microscopic pores. The chemical composition of pyrite cinder mainly includes iron sulfide, iron oxide, silicon dioxide and other trace elements. Pyrite cinder will reduce the surface area, so the total air flow resistance of particles is large, which is beneficial to the absorption gas.
The average mass density of pyrite cinder is 2.62 g/cm, the bulk density is 1.44 g/cm, the porosity is 45%, and the compressive strength is below 20MPa. The closer the burning temperature is to the melting point of sulfur and sulfur dioxide is closer to the outstanding temperature, the higher the productivity of pyrite cinder and the lower the content of residual sulfur.
Mining Process
The burning method of pyrite cinder is a non-integrated process, and the main equipment includes coal stoves, racks, cyclone dust collectors and dust collectors. The burning temperature is generally about 800℃, and the burning time is about 3h-4h.
During the burning process, the coal stove is heated to a high temperature, and the pyrite ore is fed from the oxidation area to the reduction area. The sulfur dioxide generated during the burning process is discharged from the chimney. The generated ash is cooled in the cooling pool and then returned to the coal stove for burning again. Finally, the accumulated pyrite ore cinder is scraped into the ash hopper.
Utilization of Pyrite Breeze
Pyrite cinder contains a certain amount of iron sulfide and other useful elements, so the utilization value of pyrite cinder is relatively high. It can be used as raw material for building materials, cement clinker, paint raw materials, ceramic raw materials and other products.
For example, pyrite cinder can be used as raw material for building materials. Its fine particle size and high specific surface area can be used as filler material or pozzolana, which can be used to make brick, concrete, mortar and other building materials. After adding pyrite cinder to them, their workability, adhesion and wear resistance can be improved.
The harmfulness of Pyrite Cinder
The burning method of pyrite cinder has simple technology and strong adaptability, so it is widely used. However, this process will produces sulfur dioxide gas and secondary pollutants such as dust and fly ash, which are harmful to the environment.
The sulfur dioxide emission of pyrite cinder presents a peak-valley curve in loads of the process, and the emission concentration rediscovers higher concentrated at the initial stage of the process. The dust generated in the burning process of pyrite cinder has a small particle size, which is easy to suspend in the air and diffusion, causing air pollution and secondary pollution.
Pollutant Control Measures
The pollution caused by the burning process of pyrite cinder is serious, so it is necessary to take effective pollutant control measures to reduce the harm of pyrite cinder to the environment.
First of all, it is necessary to implement effective dust removal measures for the pyrite cinder burning process. Dry dust removal technology can reduce the dust content of emissions by 80%-90%, and wet dust removal technology can reduce the dust content of emissions by 80%-99%.
Secondly, it is necessary to install appropriate sulfur removal and sulfur recovery equipment, such as wet desulfurization equipment, gas washing tower, anti-pollution electrostatic precipitator, and so on. These equipment can be used to reduce the emission of sulfur and recover the sulfur resources.
Finally, it is necessary to reduce the content of sulfur and other harmful components in the burning process. When burning, the pyrite ore should be chosen carefully. When burning, the burning temperature and quality of the coal used should be controlled strictly to reduce the emission of sulfur dioxide.
Conclusion
In summary, pyrite cinder is a kind of industrial solid waste produced by burning pyrite ore with low sulfur content. It can be used as raw material for building materials, cement clinker, paint raw materials, ceramic raw materials and other products, thus improving the utilization efficiency of pyrite cinder and reducing the amount of residues entering the environment. However, the burning process of pyrite cinder will produce a lot of sulfur dioxide and other pollutant, which is harmful to the environment. Therefore, it is necessary to take effective pollutant control measures to reduce the harm of pyrite cinder to the environment.
