JP2003277821A - Method for recycling sludge for neutralization of waste hydrofluoric acid with calcium hydroxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recycling calcium fluoride-containing sludge as a slag forming agent by solving the problem of a heat loss by an endothermic reaction of the sludge produced by treating a waste liquid of hydrofluoric acid used in a pickling treatment for steel product surfaces with calcium hydroxide. <P>SOLUTION: The method for recycling the sludge for neutralization of the waste hydrofluoric acid with the calcium hydroxide to the slag forming agent for electric furnace steel making comprises mixing the dry sludge powder formed by subjecting the waste hydrofluoric acid produced from a waste acid treatment facility for steel production to a neutralization treatment by calcium hydroxide and regulating the moisture contained in calcium fluoride to ≤5% with oil mud containing the fine powdery or granular metal or metal oxide produced from metal working machinery and molding the mixture. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slag-forming agent used in the electric furnace steelmaking process of special steel, and more particularly to a slag-forming agent composed of sludge from waste acid treatment of steel and oil mud generated from a metal working machine. Regarding recycling.

[0002]

2. Description of the Related Art Of the acids used in the pickling treatment for surface treatment of steel materials, in the treatment of hydrofluoric acid,
Since fluorine has a wastewater standard, a method of precipitating and removing fluorine is necessary, not just a neutralization treatment of hydrofluoric acid. Therefore, a method of using calcium hydroxide that forms an insoluble calcium salt with fluorine as a base for neutralization is generally adopted. Usually, the waste acid sludge generated by the waste acid treatment is disposed of as industrial waste, such as being dehydrated and then landfilled in a managed disposal site.

The oil mud generated by a metalworking machine is a waste oil that is made into a muddy state by mixing a large amount of fine powdery or granular metal or metal oxide, and is obtained by a reprocessing treatment such as distillation. Since the amount of oil content is small, most of these materials are landfilled with ash after incineration, and the metal content and heat of oil mud have not been recycled.

Among sludges conventionally disposed as industrial wastes, sludge generated by neutralizing waste hydrofluoric acid with calcium hydroxide includes calcium fluoride which is a calcium salt of fluorine and water. It contains a large amount of calcium salts such as calcium oxide. This calcium fluoride is a substance naturally produced as fluorite, and this fluorite is a substance used as a slag forming agent in the electric furnace steelmaking process of special steel together with a substance containing calcium oxide. Therefore, sludge obtained by treating waste hydrofluoric acid generated by waste acid treatment with calcium hydroxide can be recycled as a slag-forming agent in terms of its composition. However, in the sludge, in addition to calcium fluoride, there are many precipitates of hydroxides such as calcium hydroxide and divalent or trivalent iron hydroxide. Many of these hydroxides have a large heat loss due to the endothermic reaction that loses water molecules at high temperature and becomes an oxide, and therefore the sludge containing calcium fluoride could not be reused as a sludge.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problem of heat loss due to the endothermic reaction of sludge generated by treating the waste liquid of hydrofluoric acid used in the pickling treatment of the steel surface with calcium hydroxide. And to provide a method for reusing the calcium fluoride-containing sludge as a slag-forming agent.

[0006]

As described above, among the waste acid-treated sludge, hydrofluoric acid, which is an acid used for surface treatment of steel, is neutralized with calcium hydroxide. The sludge that contains calcium fluoride, which is naturally produced as fluorspar, and hydroxides such as calcium hydroxide or iron hydroxide. The calcium fluoride and calcium oxide and iron oxide obtained by heating calcium hydroxide or iron hydroxide to about 600 ° C. are components of oxide slag in the electric furnace steelmaking process for special steel. Therefore, after the sludge is dried, if a heat source sufficient to turn the hydroxide in the sludge into an oxide is administered, the sludge can be regenerated as a slag forming agent. Therefore,
Oil mud generated from a metalworking machine is used as this heat source.

[0007] This oil mud is a waste oil that has been used as a lubricating oil or a hydraulic oil in a metal processing machine, and is mixed with fine powdery or granular metals or metal oxides in the oil mud to form a mud. Presents. By the way, this oil mud is usually recycled by incineration because the amount of oil mud that is regenerated by distillation or the like is small. However, this oil mud is mixed with calcium fluoride-containing sludge (hereinafter simply referred to as "sludge") obtained by neutralizing the hydrofluoric acid waste liquid used for the surface treatment of the steel material with calcium hydroxide. As a result, the residual organic matter in the oil mud becomes a heat source using hydroxide in the sludge as an oxide, and also serves as a carbon donor in the steelmaking process. Further, it was found that the metal or metal oxide in the oil mud can be recycled as a metal source in the steel making process, and the means of the present invention was developed.

Therefore, the means of the present invention for solving the above-mentioned problems is that, in the invention of claim 1, sludge generated from a waste acid treatment facility for steel materials is mixed with oil mud generated from a metalworking machine and molded. Is a method for regenerating waste hydrofluoric acid from calcium hydroxide-neutralized sludge into a slag forming agent for electric furnace steelmaking.

According to the second aspect of the present invention, the sludge generated from the waste acid treatment facility for steel products is obtained by neutralizing waste hydrofluoric acid generated from the surface treatment process of steel products using hydrofluoric acid with calcium hydroxide. It is a sludge containing calcium fluoride which is generated, and is a method of regenerating the sludge for use in electric furnace steelmaking of sludge neutralized with calcium hydroxide of waste hydrofluoric acid according to the means of claim 1.

In the invention of claim 3, the oil mud generated by the metalworking machine is a waste oil in the form of a mud containing fine powdery or granular metal or metal oxide. The method is a method for regenerating waste hydrofluoric acid sludge for neutralizing calcium hydroxide into a slag forming agent for electric furnace steelmaking.

In the invention of claim 4, the mixing of the sludge and the oil mud is carried out by using a sun, an air-drying or a drying device to reduce the water content to 5% or less so as to reduce the water content to such a level that the sludge can be put into the electric furnace. 4. Drying up to and then pulverizing and uniformly mixing with oil mud.
The method for regenerating the sludge for neutralization of calcium hydroxide of waste hydrofluoric acid into the slag forming agent for electric furnace steelmaking according to the method of item.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. Of the waste acids generated from the surface process of steel materials, the sludge generated by neutralizing hydrofluoric acid with calcium hydroxide is dried to a moisture content of 5% or less using sun, air drying or a drying device. Then, the lumps are crushed. The drying of the sludge is to prevent steam explosion when it is put into the electric furnace, and the crushing of the lumps is to enable uniform mixing with the oil mud. The oil mud mixed with this sludge is a mud-like waste oil consisting of a lubricating oil or a hydraulic oil containing fine metal powder or metal particles or metal oxides generated by a metal working machine for cutting, turning or forging metal. Oil mud is added to these powdery sludges that have been dried, and the mixture is uniformly mixed by a mixer. Then, it is molded into pellets of arbitrary size and shape with a molding machine such as a pelletizer. Here, the oil mud acts as a binder in forming the dried and powdered sludge, and when used as a slag-forming agent, it becomes a donor of the heat required for the dehydration reaction of the hydroxide in the sludge, Further, the carbon content and the metal content in the sludge become the carbon source and the metal source in the steelmaking process, respectively.

In the above, the metal hydroxide contained in the sludge generated by neutralizing the waste hydrofluoric acid with calcium hydroxide is mainly calcium hydroxide and iron hydroxide. Calcium hydroxide is water 1 at about 580 ℃
It releases molecules and becomes calcium oxide, a substance used as a slag forming agent. Further, iron hydroxide containing trivalent iron also releases one molecule of water at about 600 ° C. to become iron oxide. By the way, oxidized slag in the electric furnace steelmaking process for smelting special steel has a high slag basicity and a high oxygen potential of the system, that is, a large amount of calcium oxide and a large amount of iron oxide cause the dephosphorization reaction in the steelmaking process. It is a condition to promote. Therefore, the sludge containing a large amount of these hydroxides and calcium fluoride can be regenerated as a slag-forming agent used in the electric furnace steelmaking process for melting special steel. Here, it is desirable to mix the sludge with the oil mud so that more heat than is consumed by the dehydration reaction can be obtained, but the maximum value of the amount of oil mud is the upper limit of the value that can be formed by the molding machine. Although it depends on the molding machine, in a conventional pelletizer, it is desirable that the mixing ratio be approximately 10 to 20% of the oily substance in the sludge with respect to the sludge.

[0014]

[Example] Sludge in which waste hydrofluoric acid generated from a steel waste acid treatment facility is neutralized with calcium hydroxide is dehydrated with a belt press to reduce the water content to about 85%,
Then, it was dried in the sun for 2 weeks to a water content of about 25%. Further, in order to reduce the residual water content to 5% or less, it was dried by a raw material dryer installed in front of the raw material mixer. The dried sludge was mixed with oil mud in a mixer. In this case, the oil content of the oil mud used is about 20.
%, So about 20 kg of oil mud was added to 1 t of sludge. The amount of oil mud added to the sludge changes according to the properties of the oil mud. Sludge and oil mud mixed with a mixer are about 30 mm in diameter and about 50 in length by an extruder.
It was processed into a columnar shape of mm to obtain a recycled slag forming agent. After packing this recycled slag agent into a bag, 2% of the amount of the conventional slag agent and carburizing material was added as a slag agent for the production of special steel,
Electric furnace Used as a slag forming agent in steelmaking process in an electric furnace. As a result, molten steel could be smelted without causing any problems in electric furnace steelmaking even with this recycled slag-forming agent.

[0015]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, the calcium hydroxide neutralized sludge of hydrofluoric acid used for the surface treatment of steel materials, which has not been used before, is treated as industrial waste. By mixing and molding with the oil mud generated from the metal processing machine that has been discarded, it can be effectively used as a slag forming agent in electric furnace steelmaking such as special steel by utilizing the advantages of each, and further contained in them. The present invention has an excellent effect that has not been obtained in the past, such that the amount of heat of a metal or oil mud can be effectively reused.

Claims (4)

[Claims] 1. Sludge generated from a waste acid treatment facility for steel materials is mixed with oil mud generated from a metalworking machine to form the sludge for neutralizing calcium hydroxide of waste hydrofluoric acid for electric furnace steelmaking. Regeneration method for slag forming agent. 2. A sludge generated from a waste acid treatment facility for steel materials is calcium fluoride generated by neutralizing waste hydrofluoric acid generated from a surface treatment process of steel materials using hydrofluoric acid with calcium hydroxide. The method for regenerating waste calcium hydrofluoride neutralized sludge from hydrofluoric acid into an electric furnace steelmaking slag forming agent according to claim 1, wherein the sludge is contained. 3. The oil mud generated by the metalworking machine is a mud-like waste oil containing fine powdery or granular metal or metal oxide.
The method for regenerating the calcium hydroxide-neutralized sludge of waste hydrofluoric acid as described in 1 above, into a slag forming agent for electric furnace steelmaking. 4. The sludge and oil mud are mixed after drying the water content to 5% or less by a sun, an air drying or a drying device in order to reduce the water content of the sludge so that it can be put into an electric furnace. And pulverizing and uniformly mixing with oil mud, regeneration of waste hydrofluoric acid calcium hydroxide neutralized sludge as claimed in any one of claims 1 to 3 into a slag forming agent for electric furnace steelmaking. Method.