燃煤電廠固體廢棄物重金屬滲濾特性研究
發(fā)布時間：2018-10-05 06:45
【摘要】：我國作為世界上最大的煤炭生產國和消費國,也是世界上唯一以煤炭資源為主的大國,并且這種能源結構在今后相當長的一段時間內不會發(fā)生改變。煤作為一種不清潔的能源,燃燒時所釋放的重金屬會長期存在于環(huán)境中,很難被降解,還會在生物體內不斷蓄積。當前有關痕量重金屬污染物排放問題已經成為燃燒污染中一個重要的研究方向,引發(fā)了越來越多的關注。因此,本文以燃煤電廠的固體廢棄物(飛灰和脫硫石膏)為研究對象,首先測定了電廠固體廢棄物(飛灰和脫硫石膏)中重金屬的總量;然后在綜合考慮了影響重金屬滲濾特性因素后,研究了飛灰和脫硫石膏在不同pH值、液固比(L/S)和浸出時間這三個最為重要的因素下重金屬的滲濾特性;最后利用場發(fā)射掃描電子顯微鏡(FESEM)、X射線衍射儀(XRD)、X光電子能譜(XPS)等先進儀器,研究了飛灰和脫硫石膏重金屬滲濾機理。本文主要結論如下:(1) FA2、DG1、DG2 中的 As 以及 DG1 中的 Cd 的總量超過了 GB15618-1995的限定值,其中DG1中Cd的總量超過GB15618-1995限定值的3倍多,屬于重度污染等級,并且飛灰和脫硫石膏中大部分重金屬的含量都超過了國標中食品類的限定值,因此對于堆放電廠固體廢棄物附近區(qū)域的土壤應當謹慎利用。(2)隨著初始pH值的增加,飛灰和脫硫石膏中重金屬的浸出量整體均呈現“U”型變化趨勢。以FA1為例,在強酸環(huán)境初始pH=2時,FA1中As、Cr、Zn的浸出量達到最高,依次為0.72μg/g、1.39μg/g、0.51μg/g;而在強堿環(huán)境初始pH=12 時,FA1 中 As、Cr、Zn 的浸出量依次為 0.71μg/g、1.36μg/g、0.49μg/g,這說明樣品中的重金屬更容易在酸性環(huán)境下浸出;隨著液固比的增加,飛灰和脫硫石膏中重金屬的浸出量總體呈現上升的趨勢。在液固比30時,樣品中重金屬的浸出率依然保持上升的趨勢,這說明繼續(xù)增加液固比,重金屬的浸出量將進一步提高;利用Elovich方程對燃煤飛灰中As、Cr、Zn滲濾動力學數據進行擬合可以發(fā)現,FA1中Cr的滲濾速率最快,高達FA1中As、Zn滲濾速率的3倍之多,FA2中Cr的滲濾速率也表現出了類似的規(guī)律。(3)酸化飛灰的表面變得光滑,大量塊狀物質填充了其空隙,使空隙度明顯減少且連通性降低,結構更為緊密,這樣使重金屬的浸出變得更加困難;酸洗飛灰中正長石(KAlSi3O8)比占要比原樣飛灰高出9.1%,此外酸洗飛灰中還檢測出了夕線石(Al2(SiO4)O),這可能是在酸性環(huán)境時飛灰中某種物質和H+發(fā)生了反應,因而夕線石的特征峰值變得更加明顯;燃煤飛灰和脫硫石膏中的As3+在酸堿化過程中表現的比較穩(wěn)定,As5+的相對含量在酸堿化過程中一直在減少,而以硫化物形態(tài)存在的相對含量總是呈現上升的趨勢,因此可以推測酸堿化過程中以硫化物形態(tài)存在的As可能大部分由As5+轉變而來。
[Abstract]:As the largest producer and consumer of coal in the world, China is also the only country with coal resources in the world, and this energy structure will not change for a long time in the future. As a kind of unclean energy, coal releases heavy metals in the environment for a long time, which is difficult to be degraded and accumulates in organisms. At present, the emission of trace heavy metal pollutants has become an important research direction in combustion pollution, which has attracted more and more attention. Therefore, taking the solid waste (fly ash and desulphurized gypsum) of coal-fired power plant as the research object, the total amount of heavy metals in the solid waste (fly ash and desulphurized gypsum) of power plant is first determined. After considering the factors affecting the percolation characteristics of heavy metals, the percolation characteristics of fly ash and desulphurized gypsum under different pH values, liquid-solid ratio (L / S) and leaching time were studied. Finally, the mechanism of heavy metal percolation in fly ash and desulphurized gypsum was studied by using advanced instruments such as field emission scanning electron microscope (FESEM) X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The main conclusions of this paper are as follows: (1) the total amount of As in FA2,DG1,DG2 and Cd in DG1 exceeds the limit value of GB15618-1995, and the total amount of Cd in DG1 is more than three times of the limit value of GB15618-1995, which belongs to the serious pollution grade. And most of the heavy metals in fly ash and desulphurized gypsum exceed the limited value of food in national standard, so the soil near the solid waste of power plant should be used carefully. (2) with the increase of initial pH value, The leaching amount of heavy metals in fly ash and desulphurized gypsum all showed a "U" type change trend. Taking FA1 as an example, the leaching amount of As,Cr,Zn in FA1 was the highest in the initial pH= _ 2 of strong acid environment, which was 0.72 渭 g / g ~ (1.39) 渭 g / g ~ (-1) 渭 g 路g ~ (-1) in turn, and 0.71 渭 g / g ~ (1.36) 渭 g / g ~ (0.49) 渭 g / g ~ (-1) of As,Cr,Zn in the initial pH=12 environment, which indicated that the heavy metals in the samples were easier to be leached in acidic environment. With the increase of liquid-solid ratio, the leaching amount of heavy metals in fly ash and desulphurized gypsum increased. When the liquid-solid ratio is 30, the leaching rate of heavy metals in the sample is still increasing, which indicates that the leaching rate of heavy metals will be further increased by increasing the liquid-solid ratio. Using Elovich equation to fit the data of As,Cr,Zn percolation kinetics in coal fly ash, it can be found that Cr in FA1 has the fastest percolation rate. The percolation rate of Cr in FA2 as much as three times that of As,Zn in FA1 showed a similar regularity. (3) the surface of acidified fly ash became smooth, and a large number of bulk materials filled its voids, which significantly reduced the porosity and decreased the connectivity. The structure is closer, which makes the leaching of heavy metals more difficult; The ratio of KAlSi3O8 in fly ash is 9.1 higher than that in the original fly ash. In addition, Al2 (SiO4) O),) has been detected in the fly ash. (Al2 (SiO4) O), which may be the reaction of some substance in fly ash and H in acid environment), Therefore, the characteristic peak value of sillimanite became more obvious, and the relative content of As3 in fly ash and desulphurized gypsum decreased in the process of acid-alkalification. However, the relative content of sulfides is always on the rise, so it can be inferred that the As that exists in the form of sulphide in the process of acid-alkalification may be transformed mostly by As5.
【學位授予單位】：南京師范大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM621;X773
本文編號：2252408
[Abstract]:As the largest producer and consumer of coal in the world, China is also the only country with coal resources in the world, and this energy structure will not change for a long time in the future. As a kind of unclean energy, coal releases heavy metals in the environment for a long time, which is difficult to be degraded and accumulates in organisms. At present, the emission of trace heavy metal pollutants has become an important research direction in combustion pollution, which has attracted more and more attention. Therefore, taking the solid waste (fly ash and desulphurized gypsum) of coal-fired power plant as the research object, the total amount of heavy metals in the solid waste (fly ash and desulphurized gypsum) of power plant is first determined. After considering the factors affecting the percolation characteristics of heavy metals, the percolation characteristics of fly ash and desulphurized gypsum under different pH values, liquid-solid ratio (L / S) and leaching time were studied. Finally, the mechanism of heavy metal percolation in fly ash and desulphurized gypsum was studied by using advanced instruments such as field emission scanning electron microscope (FESEM) X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The main conclusions of this paper are as follows: (1) the total amount of As in FA2,DG1,DG2 and Cd in DG1 exceeds the limit value of GB15618-1995, and the total amount of Cd in DG1 is more than three times of the limit value of GB15618-1995, which belongs to the serious pollution grade. And most of the heavy metals in fly ash and desulphurized gypsum exceed the limited value of food in national standard, so the soil near the solid waste of power plant should be used carefully. (2) with the increase of initial pH value, The leaching amount of heavy metals in fly ash and desulphurized gypsum all showed a "U" type change trend. Taking FA1 as an example, the leaching amount of As,Cr,Zn in FA1 was the highest in the initial pH= _ 2 of strong acid environment, which was 0.72 渭 g / g ~ (1.39) 渭 g / g ~ (-1) 渭 g 路g ~ (-1) in turn, and 0.71 渭 g / g ~ (1.36) 渭 g / g ~ (0.49) 渭 g / g ~ (-1) of As,Cr,Zn in the initial pH=12 environment, which indicated that the heavy metals in the samples were easier to be leached in acidic environment. With the increase of liquid-solid ratio, the leaching amount of heavy metals in fly ash and desulphurized gypsum increased. When the liquid-solid ratio is 30, the leaching rate of heavy metals in the sample is still increasing, which indicates that the leaching rate of heavy metals will be further increased by increasing the liquid-solid ratio. Using Elovich equation to fit the data of As,Cr,Zn percolation kinetics in coal fly ash, it can be found that Cr in FA1 has the fastest percolation rate. The percolation rate of Cr in FA2 as much as three times that of As,Zn in FA1 showed a similar regularity. (3) the surface of acidified fly ash became smooth, and a large number of bulk materials filled its voids, which significantly reduced the porosity and decreased the connectivity. The structure is closer, which makes the leaching of heavy metals more difficult; The ratio of KAlSi3O8 in fly ash is 9.1 higher than that in the original fly ash. In addition, Al2 (SiO4) O),) has been detected in the fly ash. (Al2 (SiO4) O), which may be the reaction of some substance in fly ash and H in acid environment), Therefore, the characteristic peak value of sillimanite became more obvious, and the relative content of As3 in fly ash and desulphurized gypsum decreased in the process of acid-alkalification. However, the relative content of sulfides is always on the rise, so it can be inferred that the As that exists in the form of sulphide in the process of acid-alkalification may be transformed mostly by As5.
【學位授予單位】：南京師范大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM621;X773
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