Industrial by-product waste salt (including organic matter) harmless and resource treatment

2018-11-09 08:13

Many enterprises produce solid waste salt in the process of fine chemical production. The solid salt is often unable to be reused in industrial production because of the organic matter. It is usually disposed in a solid waste form, which wastes resources and is also costly to process. After years of research on industrial organic waste salt, our company has completed the first set of large-scale industrial by-product waste salt (including organic matter) harmless treatment device in August 2015 through several small tests, pilot tests and industrial amplification. . It can effectively treat solid organic waste salt, and the treated waste salt can fully meet the requirements of chlor-alkali industrial salt.

First, the technical background

High-salt wastewater is often produced in industrial production. The high-salt wastewater treatment process mainly passes through pre-treatment and enters multi-effect evaporation and MVR to remove the salt. The brine is concentrated, crystallized and centrifuged to obtain solid waste salt. However, solid salt is often used because it cannot be reused in industrial production. It is usually disposed in a solid waste form, which wastes resources and is also costly to process.

At present, the most popular organic solid salt treatment technologies in China are mainly fluidized bed high temperature calcination method and pyrolysis furnace high temperature cracking method. However, these two methods are often difficult to completely remove the organic matter, and it is easy to cause some organic components to be converted into more. For complex forms of organic matter, the treated salt still cannot substantially enter the industry where ion salt and caustic soda are required.

After years of research on industrial organic waste salt, our company has completed the first set of large-scale industrial by-product waste salt (including organic matter) harmless treatment device in August 2015 through several small tests, pilot tests and industrial amplification. After testing by a third-party organization, the treated industrial salt meets the requirements of the special product of the sun-dried industrial salt in GBT5462-2003 "Industrial Salt Index", which can fully meet the salt requirement of chlor-alkali industry.

Second, the technical brief

The method of harmless treatment of industrial by-product waste salt introduced in this paper is characterized in that the industrial by-product waste salt is subjected to thorough aerobic pyrolysis of organic matter through a new pyrolysis furnace. It consists of four parts: preheating, pyrolysis, forming and packaging, waste heat and tail gas treatment.

The by-product waste salt firstly uses the waste heat generated in the industrial salt formation after pyrolysis, removes the moisture in the salt by the preheating section and preheats the salt, and then enters the special structure pyrolysis furnace at 1000-1200 °C. The high temperature pyrolysis of the organic matter in the waste salt is carried out. After pyrolysis, the gas phase enters the burner for full combustion, and the combustion heat generated by the heat enters the preheating process to preheat the original salt, removes the moisture in the original salt and preheats the original salt. The industrial salt after pyrolysis is molded into a special molding machine, and the formed salt is cooled and then enters the crushing and packaging process.

After the preheating process, the exhaust gas enters the washing and cooling tower to remove the dust and cool the exhaust gas. The cooled exhaust gas enters the photo-oxidation catalytic reactor to decompose the residual organic waste gas, and the decomposed harmless gas is discharged through the chimney. The process is highly automated and can basically achieve unmanned operation.

Third, the principle of the process

Pyrolysis is a chemical decomposition process in which an organic substance is heated in an oxygen-free or anoxic state to become a gaseous, liquid or solid combustible substance. The gaseous products are generally hydrogen, methane, carbon monoxide, the liquid product is typically methanol, tar, dissolved oil, etc., and the solid product is typically coke or carbon black. The solid waste pyrolysis process is a complex chemical process involving bond cleavage of macromolecules, isomerization and polymerization of small molecules, and the final reaction produces a variety of smaller molecules.

There are many factors affecting the pyrolysis products of organic solid waste, such as material characteristics, final temperature of pyrolysis, furnace type, material accumulation characteristics, heating method, residence time of each component, and the like.

The correlation degree of various influencing factors is: final temperature of pyrolysis> material characteristics> heating rate> docking method of materials> material heating mode. Different temperature distributions also result in different yields and characteristics of pyrolysis products. Because it is decomposed by oxygen, the amount of exhaust gas is small, which is beneficial to reduce secondary pollution to the atmospheric environment.

The main difference between the industrial waste salt treatment technology and the conventional process is how to remove the organic matter in the salt crystal nucleus. The technology conventionally used in the country generally removes the organic matter on the surface of industrial salt by hot air, and the surface organic matter is removed, but because of the special crystal structure of the salt, even by rapidly heating and cracking the salt crystal, it only becomes more Small crystal nuclei cannot completely remove organic matter inside the crystal. The special pyrolysis furnace of this project thoroughly removes the organic matter in the industrial waste salt by increasing the residence time and increasing the pyrolysis temperature (using high temperature pyrolysis >1000 degrees), changing the pyrolysis method, adjusting the heating method, etc. The organic matter in the core truly achieves the harmless treatment of industrial waste salt.

Fourth, technical advantages

Shandong Zhongtian Science and Technology Engineering Co., Ltd. has been committed to multi-effect evaporation of salty wastewater and desalination treatment of MVR for many years. Through the research on the harmless treatment of industrial solid organic waste salt in recent years, through pyrolysis method, pyrolysis furnace type, Continuous innovation of the molding method, and finally developed a set of advanced industrial waste salt harmless treatment technology, this technology has obtained the national utility model patent technology.

Taking the demonstration project that we are running as an example, after the 5-7% salt-containing wastewater produced by the project is desalted by MVR, the solid waste salt contains nearly 3% of the organic matter and the moisture content is 5%. After the operation of the process, the moisture content is 0.04%, the TOC is less than 10 mg/l, the NaCl content is 96.59%, and there is no calcium and magnesium (depending on the original salt). The heavy metal ions can meet the salt requirement of the ion-exchange membrane caustic soda, and can reach the solar industry. Salt excellent grade standard.

Economic accounting: The original waste salt is usually sent out in solid waste, and the treatment cost is 2800-3000 yuan/ton. The production process is mainly power consumption. On the basis of considering the cost of labor and equipment depreciation, the cost of harmless treatment of 1 ton of waste salt is about 300 yuan (slightly different depending on the industrial price of each place). Moreover, the quality of the waste salt after being harmlessly treated is higher than that of the sun-dried industrial salt grade, and can be directly entered into the chlor-alkali industry or other salt industry.

The process technology is advanced, the heat exchange process is optimized, and the energy consumption is low. Solving solid waste also saves the company a lot of environmental protection funds.