KR100957998B1 - Method for the removal of phosphorous in waste water using steelmaking slag - Google Patents

Abstract

The present invention relates to a method for removing phosphorus in wastewater using steelmaking slag,

Obtained by water-cooling steelmaking slag, yard slag containing 4.0 ~ 5.0 of basicity (CaO / SiO ₂ ) and 10-15% by weight of FeO is added to the waste water containing phosphorus in 2-10% by weight for at least 1 hour Thereafter, there is provided a method of removing phosphorus in wastewater using steelmaking slag, which includes recovering the slag from the wastewater.

According to the present invention, using the steelmaking slag, the phosphorus component contained in the wastewater can be removed without a separate additive and without causing another sludge or by-products, in particular, the slag thus recovered can be recycled as a factor. .

Steelmaking Slag, Blowing Slag, Yard Slag, Calcined Slag, Wastewater, Phosphorus

Description

Phosphorus removal from wastewater using steelmaking slag {METHOD FOR THE REMOVAL OF PHOSPHOROUS IN WASTE WATER USING STEELMAKING SLAG}

1 is a graph showing a change in phosphorus removal rate in the case of using a wind slag,

2 is a graph showing a change in phosphorus removal rate when using a yard slag,

3 is a graph showing the change in phosphorus removal rate when using the calcined slag,

Figure 4 is a microscopic observation of the recovered wind slag and component analysis results,

Figure 5 is a microscopic observation of the recovered yard slag and component analysis results,

Figure 6 is a microscopic observation of the recovered plastic slag and component analysis results, and

Figure 7 is a microscopic observation of the recovered calcined slag in detail and the results of the component analysis.

The present invention relates to a method for removing phosphorus in wastewater using steelmaking slag, and more particularly, to remove phosphorus contained in wastewater using steelmaking slag, wherein the recovered slag can be recycled as a source for other applications. The present invention relates to a method for removing phosphorus from wastewater using steelmaking slag.

Slag, which accounts for the largest proportion of steel by-products, is roughly divided into blast furnace slag generated during the manufacture of molten iron in the blast furnace and steel slag generated during the refining process to remove impurities from the molten iron. However, blast furnace slag is currently used mainly for building materials such as cement admixtures and substitutes and crushed aggregates for roadbeds. However, steel slag is crushed after cooling and partially recycled as a raw material of the steelmaking process by magnetic screening, and most of it is recycled mainly as raw material of cement or aggregate for road / port civil engineering work, but it is not used partially and is dumped for disposal. to be. The reason for the reduction of the recycling rate of steelmaking slag is that due to its high weight and weathering expandability, the treatment and recycling costs are relatively large, which makes it difficult to effectively recycle them.

On the other hand, most of the sewage treatment facilities in Korea have not been treated with phosphorus (P) properly, the eutrophication of lakes and rivers, rust, red tide occurs. In particular, the sewage generated in the apartment complex has a high concentration of phosphorus (4 ~ 6mg / L) due to the flushing toilet manure contained. Phosphorus in wastewater can be removed using anaerobic and aerobic conditions in biological removal processes. That is, phosphorus is released under anaerobic conditions, and excess phosphorus is ingested by the microorganisms under aerobic conditions at a later stage. The phosphorus is then removed by discarding the microorganisms (sludge) ingesting excess phosphorus in the reactor. As such, the biological removal process is very complex for application in a real scale treatment plant, and phosphorus release under anaerobic conditions or excess phosphorus intake conditions under aerobic conditions are easily suppressed by external conditions. In addition, in the biological removal process, phosphorus is removed by the disposal of the sludge, so that a large amount of sludge is generated compared to other processes, and the sludge treatment cost is high.

Accordingly, an object of the present invention is to provide a method for removing phosphorus components contained in wastewater by using steelmaking slag which is a by-product generated in a steel mill.

According to one aspect of the invention,

Obtained by water-cooling steelmaking slag, yard slag containing 4.0 ~ 5.0 of basicity (CaO / SiO ₂ ) and 10-15% by weight of FeO is added to the waste water containing phosphorus in 2-10% by weight for at least 1 hour Thereafter, there is provided a method of removing phosphorus in wastewater using steelmaking slag, which includes recovering the slag from the wastewater.

Hereinafter, the present invention will be described in detail.

Yard slag used in the present invention can be obtained by water-cooled steelmaking slag generated in steel mills. Steelmaking slag is made of blast slag made of spherical fine powder by blowing air into molten steel slag, yard slag which is temporarily cooled by water-cooling steelmaking slag, and calcined slag fired at high temperature under an air atmosphere. Yard slag is useful in the present invention, which is added to the waste water at 2-10% by weight. If the input amount of the yard slag is less than 2% by weight, it takes too long to remove phosphorus sufficiently, and when the amount of the yard slag is added to 10% by weight or more, the treatment effect does not increase any more, and the operation of recovering slag is inefficient due to the increased work. .

The yard slag has a basicity (CaO / SiO ₂ ) 4.0 to 4.5, preferably contains 10 to 15% by weight of FeO, and is dried and crushed prior to the addition of irregular particles. When the slag having such a condition comes into contact with the phosphorus component contained in the waste water, it was experimentally confirmed that the dephosphorization reaction occurred well. In addition, the yard slag is preferably dried and crushed before input to have an irregular particle shape. The reason is that the reaction surface and the efficiency of phosphorus removal in waste water are improved by maximizing the reaction area by maximizing the contact surface between the slag particles and the waste water. To do that.

In addition, the amount of the yard slag may vary depending on the particle size, the smaller the particle size may exhibit sufficient phosphorus removal ability even in a small amount. For example, the yard slag is preferably added at 5% by weight to waste water when using fine particles of 1mm or less, and 10% by weight when using 1-5mm of neutral.

The injected yard slag reacts with the phosphorus component contained in the waste water, where the reaction is carried out for at least 1 hour under sufficient agitation. If the reaction time is too short (less than 1 hour), phosphorus may not be sufficiently removed. Preferably, the reaction time is 1 to 4 hours.

When the yard slag is introduced into the waste water, a large amount of CaO component contained in the slag is eluted with calcium ions (Ca ²⁺ ) in the waste water, which is shown in Scheme 1 below, and the phosphate ions (PO ₄ ^{3 −} ) and hydroxyl in the waste water. ion (OH ^-) and the reaction insoluble calcium hydroxy epeo tight _{(calcium Hydroxyapatite, Ca10 (PO 4} ) 6 (OH) 2) the method crystallization precipitated in the reaction takes place.

_{^{10Ca 2+ + 6 (PO 4 3-}} ) + 2 (OH -) → Ca10 (PO 4) 6 (OH) 2

Factors that greatly affect this reaction include slag basicity, that is, CaO content and pH of the waste water. The slag basicity suitable for the reaction is 4.0 to 5.0, and the pH of the waste water is 8 to 9.5.

After completion of the reaction, the slag to which the phosphorus compound as a reaction product is bonded is recovered from the waste water. The recovered slag contains a large amount of phosphorus, which can be usefully reused as a factor in applications requiring phosphorus such as phosphate or phosphate ore. This reaction does not require a separate additive to remove the phosphorus component in the waste water and also has the advantage that no other sludge or by-products are induced after the reaction.

Further, instead of the yard slag, a firing slag of firing the yard slag may be used, which may be obtained by firing the yard slag at 700 to 800 ° C. for at least 1 hour under an air atmosphere. The calcined slag is preferably added to 2 to 10% by weight in the waste water. Such calcined slag is suitable for rapidly removing phosphorus by temporarily increasing phosphorus removal rate, but as time passes, CaCO ₃ containing Fe by Ca elution is deposited and coated on the surface of slag, so that no further contact with waste water Blocking does not cause dephosphorylation, which is inappropriate in the long run.

Hereinafter, the present invention will be described in more detail with reference to the following examples.

<Example>

Example 1 Phosphorus Removal Rate According to Type and Addition of Steelmaking Slag

The components according to the types of steelmaking slag used in this example are shown in Table 1 below.

Kinds T.Fe FeO CaO SiO ₂ Al ₂ O ₃ MgO P ₂ O ₅ basicity Blow Slag (B) Small grain (S) 20.73 0.86 42.62 11.47 2.88 8.54 2.02 3.72 Neutral (M) 17.52 3.41 43.72 13.20 2.80 10.17 1.99 3.31 Yard Slag (Y) 21.30 13.07 42.37 9.87 2.89 7.49 2.04 4.29 Plastic Slag (CY) 24.55   - 40.37 9.55 2.76 8.00 1.97 4.23

Blowing slag, Yard slag and calcined Yard slag having the components shown in Table 1 are small (S, 1 mm or less), neutral (M, 1-5 mm) and opposing (L), respectively. , 5 ~ 10mm) by 1, 2, 5, 10% by weight in each of the waste water was measured by the phosphorus removal rate by time, the results are shown in Figures 1, 2 and 3, respectively. At this time, the pH of wastewater was 8.2 ~ 9.5 before slag injection, and the pH increased after slag injection. In some cases, when the phosphorus removal rate reached 100% within 1 hour after injection, the maximum pH increased to 11.5.

As can be seen from Figures 1, 2 and 3, when the slag particle size is the same, compared to the case of using the slag slag, the excellent removal rate of phosphorus slag when using the yard slag and calcined slag. Depending on the slag particle size, phosphorus removal rate increased in the order of allele, neutral and small particle size.

Example 2 Electron Microscope (SEM) Observation and Component Analysis of Recovered Slag

On the other hand, the shape and product of the slag recovered after the end of the experiment of Example 1 was analyzed. 4, 5, 6 and 7 shows the results of microscopic observation and component analysis (method by WDS) of the recovered slag.

As shown in Fig. 4, when the air-chain slag was used, it showed beautiful circular particles, and the reaction product was also detected only at the defective part of the surface, so that the reaction surface area was the smallest, and the removal rate of phosphorus was also reduced. As a result of the component analysis of the reaction product, the slag was unsuitable for recycling as a factor source because the Ca / P value was 2.57, which is higher than the theoretical Ca / P value of the effertite, 1.67.

As shown in FIG. 5, in the case of yard slag, the shape of the slag was irregular and the reaction product was also distributed throughout the slag surface, indicating that the crystallization dephosphorization reaction was extensive, and the Ca / P value of the reaction product was 1.71. As close to the theory, it was found to be suitable for recycling it as a factor.

On the other hand, in the case of the calcined slag showing excellent phosphorus removal rate in Example 1 (c), as shown in Figure 6, the surface of the slag was finely covered with a wide range of fine reaction product, the analysis result of the reaction product Ca / P value is In addition to being very high at 11.34, it also contains a large amount of impurities, making it unsuitable for recycling as a factor.

In particular, as a result of observing the calcined slag in more detail, as shown in FIG. As a result, Ca was 40.7% by weight, Fe and O components were 28.0% and 24.8% by weight, respectively, and phosphorus (P) was not detected at all, and CaCO3 containing Fe due to a large amount of Ca eluted precipitated on the slag surface. I could see that. When CaCO 3 is deposited on the surface of the slag to form a film, dephosphorization reaction by the slag is no longer likely to occur. Therefore, it can be seen that calcined slag is suitable for rapid phosphorus removal by rapidly increasing phosphorus removal rate temporarily rather than long term.

Yard slag obtained by water cooling the steelmaking slag according to the present invention is added to waste water to dephosphorize the reaction, and then the slag which is a reaction product is recovered, without the addition of the phosphorus component contained in the waste water and without causing another sludge or by-product. Can be removed In particular, the slag recovered accordingly contains a large amount of phosphorus, which can be recycled as a printing source in applications requiring phosphorus.

Claims (3)

Obtained by water-cooling steelmaking slag, yard slag containing 4.0 ~ 5.0 of basicity (CaO / SiO ₂ ) and 10-15% by weight of FeO is added to the waste water containing phosphorus in 2-10% by weight for at least 1 hour And then recovering the slag from the wastewater, wherein the removal of phosphorus in the wastewater using steelmaking slag. 2. The method of claim 1, wherein the yard slag is crushed to have an irregular particle shape. The method of claim 1, wherein the yard slag is calcined at 700 to 800 ° C. for at least 1 hour under an air atmosphere and introduced into waste water in the form of calcined slag.

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