TWI527769B - Method for recycling calcium fluoride sludge - Google Patents

Description

Method for recycling calcium fluoride sludge

The object of the present invention is to disclose a method for recycling calcium fluoride sludge, in particular to remove calcium sulfate contained in calcium fluoride sludge produced by a wastewater treatment plant by using a sulfate removing agent to cause calcium fluoride staining. Mud no longer contains calcium sulphate, but can be used as a flux in steelmaking to achieve waste recycling.

Semiconductor manufacturing or optoelectronic materials and components manufacturing industry need to use mixed acid such as hydrofluoric acid as thinning or wafer etching in the process. The wastewater generated by the wastewater treatment facility will produce calcium fluoride sludge containing calcium sulfate. Its calcium sulfate content is often as high as 6% or more.

These fluorine-containing sludges containing calcium sulfate have been treated by landfill in the past. In recent years, some operators have dried and then entered the cement kiln as part of the substitute material for cement. Although the burial method temporarily solves the problem of treatment of calcium fluoride sludge, in the long run, due to the scouring of rainwater, it is easy to cause secondary pollution of the environment, and the fluorine resources are limited. This treatment method is nothing but a waste of resources. As for some of the alternative raw materials used in cement, although there are many related studies that have proved to be effective, but in the article about the recycling of calcium fluoride sludge in the semiconductor industry by Guan Jialun and others, the calcium fluoride sludge is pointed out. As a cement material, although there are related studies in the academic field, it is feasible, because the calcium fluoride sludge will generate fluorine and hydrogen fluoride gas at high temperature, and the addition of calcium fluoride may affect the quality of the cement, etc. Must really control the amount of sludge added to solve these The problem is that, due to the need to overcome these problems, calcium fluoride sludge has not been widely used in cement substitute raw materials, and the decalcification of calcium fluoride sludge still has great problems. Many literatures suggest calcium fluoride of calcium fluoride sludge. If the content is more than 60%, it can be recycled to the steelworks, but they have not pointed out how to recycle, and there is no specific technical description. Therefore, the application of calcium fluoride sludge in steel mills is only at the moment. The slogan phase has not really been achieved.

The reason why calcium fluoride sludge cannot be recycled to steel mills is because most of the calcium fluoride sludge contains calcium sulfate up to 6% or more. Due to the function of calcium fluoride in steelmaking, in addition to being a flux, it also has the effect of removing sulfur and dephosphorization in molten steel. For example, if the calcium content of calcium fluoride is too high, the efficiency will be greatly reduced, and even Steelmaking is difficult, so steel mills have strict specifications for the sulphur content of calcium fluoride. Recently, some companies directly feed calcium fluoride sludge into waste hydrofluoric acid, dissolve the sludge by the acidity of waste hydrogen fluoride acid, and re-manufacture calcium fluoride, because calcium fluoride and calcium sulfate are used in wastewater treatment. Or the production of calcium fluoride by waste hydrofluoric acid will cause co-sinking, so this problem still cannot solve the problem of sulfur content of calcium fluoride. Therefore, how to establish a method for recycling calcium fluoride sludge to convert calcium fluoride sludge into useful resources from waste is urgently needed and improved. In view of this, the inventor has been engaged in chemical process design for many years, with specialization and practical experience. He feels the importance of the industry in the recycling of calcium fluoride sludge, and has devoted himself to researching the calcium fluoride pollution in this case. The method of mud resource utilization.

It is an object of the present invention to provide a method of recycling calcium fluoride sludge.俾 can remove the co-precipitate calcium sulphate with calcium fluoride, so that the calcium fluoride sludge no longer contains calcium sulphate.

A second object of the present invention is to provide a method for recycling calcium fluoride sludge.俾Using calcium fluoride sludge containing calcium sulphate can be converted from fluoride-containing sludge waste into useful calcium fluoride Products can be used in the chemical industry or steel industry. In addition to avoiding the impact of calcium fluoride sludge on the environment, a wide range of economic benefits can be created.

In order to achieve the above object, the present invention first uses a pulverizer to pulverize the calcium fluoride sludge to extremely fine particles, and then adds clear water to the reaction tank to continue to reduce the calcium fluoride particles and achieve homogenization, and then add sulfate radicals. The removing agent performs a sulfate removal reaction in the calcium sulfate to remove the sulfate from the calcium sulfate and transfer it from the solid phase to the liquid phase. After the reaction solution is filtered, the filter cake no longer contains calcium sulfate precipitate. After the filter cake is pulverized and then washed, the sulfate and other ions contained in the filter cake can be washed, and then filtered to obtain a calcium fluoride product which can be used in the chemical industry or the steel industry.

M1‧‧‧First Crusher

R1‧‧‧ reaction tank

F1‧‧‧First filter

M2‧‧‧Second Crusher

C1‧‧‧Washing tank

F2‧‧‧Second filter

10‧‧‧calcium fluoride sludge feed line

20‧‧‧Pulverized calcium fluoride sludge feed line after crushing

30‧‧‧First fresh water feed line

40‧‧‧ Sulfate Remover Feed Line

50‧‧‧Reaction liquid discharge line

60‧‧‧Filter cake discharge line after reaction

70‧‧‧Crushed filter cake discharge line

80‧‧‧Second clear water feed line

90‧‧‧Clean liquid discharge line

100‧‧‧Product discharge line

Figure 1 is a flow chart of the present invention

The bulk calcium fluoride sludge is pulverized into the fine granules through the calcium sulphate sludge feed line 10 into the first pulverizer M1, and then fed to the reaction tank R1 via the pulverized calcium fluoride sludge feed line 20 while The clean water also enters the reaction tank R1 via the first clean water feed line 30 to re-crush the calcium fluoride particles, and is homogenized, wherein the weight of the clear water and the calcium fluoride sludge is between 0.5:1. Between 30:1. Thereafter, the sulfate removing agent is fed to the reaction tank R1 via the sulfate removing agent feed line 40, and the sulfate removal reaction in the calcium sulfate is performed to remove the sulfate in the solid phase from the calcium sulfate and transfer to the liquid phase. The weight ratio of the carbonate contained in the sulfate removing agent to the sulfate contained in the calcium sulfate is between 0.6:1 and 1.88:1, and the sulfate removing agent refers to sodium carbonate and sodium hydrogencarbonate. , potassium carbonate, potassium hydrogencarbonate, carbonic acid, carbon dioxide, ammonium carbonate and ammonium hydrogencarbonate; a single substance or a mixture thereof.

The reaction liquid in which the solid phase is no longer containing calcium sulfate is fed through the reaction liquid discharge line 50. The liquid is filtered out by the first filter F1, and the filter cake is pulverized through the filter cake discharge line 60 after entering the second pulverizer M2, and the pulverized filter cake is passed through the pulverized filter cake discharge line 70, and the water is also cleaned. The filter cake is washed through the second fresh water feed line 80 into the washing tank C1 to wash the sulfate and other ions in the filter cake, wherein the weight ratio of the clean water to the filter cake is between 0.5:1 and 30:1. . The cleaned solids are then filtered through the cleaning liquid discharge line 90 into the second filter F2, and the filter cake is discharged through the product discharge line 100 to obtain a calcium fluoride-free calcium fluoride product.

The actual operation result of the present invention is as follows: the calcium fluoride sludge obtained from the fab wastewater treatment facility is measured, and the sulfate content thereof is determined to be: 6.09% (corresponding to 2.03% of sulfur), and the product treated by the method of the present invention is obtained. The sulfate content has been reduced to 0.11% (corresponding to 0.036% sulfur), which is in line with the sulfur content of calcium fluoride required for steelmaking in steel plants (sulphur content less than 0.3%).

In summary, the present invention is used for the resource utilization of calcium fluoride sludge, and it has many requirements of being effective and economical, and is in conformity with the patent requirements, but the above disclosure is a preferred embodiment, and a partial change is made. It is a modification of the technical idea of the present invention, and is easily inferred by those skilled in the art without departing from the scope of the present invention.

M1‧‧‧First Crusher

R1‧‧‧ reaction tank

F1‧‧‧First filter

M2‧‧‧Second Crusher

C1‧‧‧Washing tank

F2‧‧‧Second filter

10‧‧‧calcium fluoride sludge feed line

20‧‧‧Pulverized calcium fluoride sludge feed line after crushing

30‧‧‧First fresh water feed line

40‧‧‧ Sulfate Remover Feed Line

50‧‧‧Reaction liquid discharge line

60‧‧‧Filter cake discharge line after reaction

70‧‧‧Crushed filter cake discharge line

80‧‧‧Second clear water feed line

90‧‧‧Clean liquid discharge line

100‧‧‧Product discharge line

Claims (2)

A method for recycling calcium fluoride sludge mainly comprises the following steps: from semiconductor manufacturing, photovoltaic materials and component manufacturing, and other industries using hydrofluoric acid, the bulk calcium fluoride produced by the wastewater treatment facility The sludge is first pulverized by the first pulverizer, and then, together with the clean water, the ratio of the clear water to the sludge is 0.5:1 to 30:1, and then enters the reaction tank for re-crushing and homogenization, and then the sulfate is fed. a removing agent (such as potassium carbonate, potassium hydrogencarbonate, carbonic acid, carbon dioxide, ammonium carbonate, and ammonium hydrogencarbonate; a single substance or a mixture thereof), and a sulfate in the carbonate and calcium sulfate contained in the sulfate removing agent The weight ratio is from 0.6:1 to 1.88:1, and the sulfate removal reaction in the calcium sulfate is performed in the reaction tank to remove the sulfate from the calcium sulfate and transfer from the solid phase to the liquid phase; after the reaction is completed, The first filter filters out the liquid, and the filter cake enters the second pulverizer for pulverization. The pulverized filter cake is combined with clean water, and the ratio of the water to the filter cake is 0.5:1 to 30:1 by weight. After the tank is cleaned by the filter cake, The second filter filters out the liquid and the filter cake is discharged into a product. The method for recycling calcium fluoride sludge as described in claim 1, mainly comprising: a first pulverizer for pulverizing bulk calcium fluoride sludge to extremely fine particles, a reaction tank for fluorine Re-crushing and homogenizing the calcium sludge and performing the sulfate removal reaction in the calcium sulfate, a first filter for filtering the reaction liquid, and a second pulverizer for pulverizing the filtered filter cake a water washing tank for washing the crushed filter cake and a second filter for filtering the washing liquid and obtaining the final product.