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环保钢结构的设计与制造【优秀含10张CAD图纸+全套机械毕业设计】

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00-02-02-01冷却塔集气罩.dwg

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关键词：: 环保钢结构设计制造优秀优良 10 cad 图纸全套机械毕业设计

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!【详情如下】CAD图纸+word设计说明书.doc[35000字，79页]【需要咨询购买全套设计请加QQ97666224】.bat

00-01-01-01灰斗附图.dwg

00-01-01灰斗.dwg

00-01-02-01卸灰阀附图.dwg

00-01-02卸灰阀.dwg

00-01除尘器.dwg

00-02-01-01冷却塔灰斗.dwg

00-02-01冷却塔灰斗.dwg

00-02-02-01冷却塔集气罩.dwg

00-02-02冷却塔集气罩.dwg

00-02冷却塔.dwg

00总体装置图.dwg

环保钢结构的设计与制造.doc

环保钢结构设计与制造.ppt

英文翻译

设计说明书.doc[35000字，79页]

毕业设计（论文）任务书

题目环保钢结构的设计与制造——袋式除尘器

1、本论文的目的、意义随着工业的高速发展，环境污染日益严重，在人们生活水平不断提高的同时，对生活环境的质量要求也越来越高。特别在环境保护工作日益突出的今天，伴随着我国钢铁需求量的不断增加，针对冶金工业设计除尘器。对烟气进行综合治理，改善周边环境。加强对环境的保护，同时又能将从烟尘中带走的各种金属进行回收利用，特别是一些贵重的金属和稀有金属。起到了节约资源的作用。此题目的选择具的重要的意义。

2、学生应完成的任务

1）完成A0当量图纸大于3张，

2）设计说明书1份

3）英文翻译大于10000字符

4）论文日志

5）设计论文光盘一个

内容包括：1.文献综述

2.结构计算与校核

3.方案的选择与制定

4.计算结果

5.成本核算

3、论文各部分内容及时间分配：（共 15 周）

第一部分查阅文献及调研 (2周)

第二部分设计方案制定，并进行相关的计算校核 (8周)

第三部分绘制设备结构与相关制造大样图 (2周)

第四部分论文书写 (1周)

第五部分(1周)

评阅及答辩(1周)

摘要

在冶金过程中，产生大量的废气，这些废气的含尘浓度高，烟尘的危害性大，对环境造成严重的污染。同时，这些烟尘又有一定的回收和利用价值。因此，治理这些烟尘具有显著的经济效益和社会效益。

本设计针对冶炼的生产及场地等的具体情况，来设计布袋除尘器，并且使其排污情况达到国家相关的排放标准要求。而且，又要尽量满足投资少、运转费用低、操作方便、维护简单的要求。

目前，国内外除尘设备的种类和型号较多，通过对它们的原理的分析以及性能的比较等，根据实际情况，选出了对冶金炉废气控制的最佳方案。选用袋式除尘器并进行了设计计算确定了布袋的型号、尺寸、根数，对除尘器外部箱体、支架和灰斗等钢结构部件也进行了设计，并计算了其重量和面积和列出材料的数量表。然后对除尘系统进行长效防腐设计，根据现场，合理对各个部件进行了布局。

本设计选用的负压吸灰的袋式除尘器在原有除尘器的基础上，进行了一系列的改进。该除尘器节约成本，扩大了除尘的效率，同时，冷却塔的设计，降低了含尘气体的温度，保证了除尘器内布袋使用寿命，并合理地利用了空间，对除尘和清灰达到了全自动化控制。

在本设计中，不但完成了对除尘系统总体的设计，而且强化细节，做到了所设计的除尘系统可以直接进行加工、安装、调试并投入使用。并对成本进行了投资预算.对所要的材料都进行了全部的统计。

关键词：大气污染；袋式除尘器；钢结构；长效防腐

Abstract

In the process of metallurgy, a large amount of exhaust gas will be produced, which contains a high concentration of ash or dust. This kind of ash is very harmful and will pollute the environment. At the same time, the ash also has a value in reclamation and reuse. Therefore, it has a significant economic and social benefit to treat with it.

In this dpaper, according to the idiographic case of the producing and place etc. of smelting, it designs hop-pocket dust catcher and makes waste-excreting up to the relevant national standard criterion. What’s more, it should meet the requests of less investment, low running cost, conveniency for operation and easiness for maintenance as necessary as possible.

At present, there are relatively too many sorts and models of dust catcher at home and abroad, through the analyse of their theories and comparison of capability, according to the practical condition, we select the best scheme in calcium carbide furnace exhaust gas controlling. Having the hop-pocket dust catcher selected and the design calculation worked out, we fixed the model, size and root-number of the bag, and we have also designed the steel structure of the dust catcher’s several parts such as the exterior box, bracket and the ash- funnel etc. moreover, with its weight and area calculated. Then, towards the dust-removing system, we carried out the long-effective antisepticising design. According to the locale, we made a proper overall arrangement of each part, and checked on the economic and running cost at last.

This devise has a series of improvement. Compared with the original one，this hop-pocket dust catcher using a minus- pressure ash- absorbing technology. It will not only save the cost and enhance the dust-removing efficiency, because the design of cooling tower, it will also lower the temperature of the gas containing dust, in order to have the??? effective longevity of the bag guaranteed. Besides, the room can be used properly; the removing of dust and cleaning of ash are entirely automatically controlled.

In the paper, it has finished contriving the dust-removing system not only on the whole, furthermore, it has intensified the details of the device, so that it is able to carry out processing, installing, adjusting and been put in to effect directly. Moreover, the budget of investment and listed all the materials needed have worked out statistically.

keywords：air pollution, hop-pocket dust catcher, steel structure, long-effective antisepticising

第一章绪论1

1.1环境保护与可持续发展1

1.1.1环境与环境问题1

1.1.2 可持续发展2

1.2对大气的结构及组成的认识3

1.2.1大气圈及其及结构3

1.2.2 大气污染物4

1.2.3 锅炉大气污染物排放标准6

1.2.4 污染与健康7

1.2.5 大气污染的综合防治8

1.3 任务的提出与意义10

1.3.1 设计要求以及基本参数10

1.3.2 设计内容包括10

1.3.3 选题的意义10

第二章除尘设备的分类及其型号的选择11

2.1除尘设备的概述11

2.1.1 除尘器的概念11

2.1.2 除尘器的分类11

2.2 各种除尘器原理12

2.2.1 机械式除尘器12

2.2.2 静电除尘器19

2.2.3 湿式除尘器20

2.2.4袋式除尘器20

2.2.5 复合式除尘器26

2.2.6各种除尘器的性能比较及其型号的选择26

2.3 确定方案27

2.3.1滤袋速度的选择28

2.3.2 清灰方式的确定28

2.3.3 滤袋形式的确定31

2.3.4 过滤方向的确定31

2.3.5 进风口位置的选择31

2.3.7滤料的选择33

第三章除尘器的设计与计算37

3.1参数的计算37

3.1.1 计算需要的过滤面积和袋室数目37

3.2 风机的选择43

3.2.1 风机性能的比较43

3.3 冷却塔的设计45

3.3.1 冷却方式的选择45

3.3.2 冷却塔主要参数的计算48

3.4 除尘器卸灰系统设计49

3.4.1 除尘器卸灰阀的设计49

3.5 除尘器的基础的设计50

3.6钢结构部分的设计50

3.7 屋架的设计51

3.8 房子主体结构设计51

第四章.施工及其焊接要求53

4.1施工要求53

4.2 环保钢结构手工电弧焊焊接施工53

4.2.1对焊接有关人员的要求53

4.2.2开坡口53

4.2.3质量要求53

4.2.4施工准备53

4.2.5 材料的关键要求55

4.2.6 作业条件55

4.2.7 质量关键要求55

4.3 工艺流程56

4.3.1工艺流程图56

4.4 安全保护措施56

4.5 环境保护措施57

4.6 质量记录58

第五章除尘器的防腐与维护59

5.1防腐工艺的实施59

5.1.1高压空气的制备59

5.1.2工件喷砂处理59

第六章成本核算及投资63

6.1工程建设投资核算63

6.1.1 除尘器本体部分建造投资63

6.2养护、维修投资核算65

6.2.1 电耗费用65

6.2.2 维修费用65

第七章经济效益的评估66

结论67

致谢68

参考文献69

参考文献

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[4] 陈明绍,吴光兴,张大中,王长跟编著.除尘技术的基本理论与应用.北京：中国建筑工业出版社,1981.

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[9] 祝燮权主编.实用五金手册.上海：上海科学技术出版社,2001.

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[14] 张建勋编著.现代焊接生产与管理.北京：机械工业出版社,2006.

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[20] 徐世明,胡月华, 李卉, 张改芳. 反吹风布袋除尘器的应用.磷肥与复肥.

2000年第15卷第5期:P17

[21] 吴英浩. 升压风机在电厂烟气脱硫中的应用及选择. 云南电力技术.2004年11月第35期.

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2004.NO.2:49

[27] 王升,杨彦香. 环保设备用焊管的生产. 焊管,Vol25(4) 2002:33

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内容简介：: 利用静电增加对灰尘的沉积概要：这项研究的基本思想是，利用静电沉淀来减少飞尘中重金属的浓度。当重金属的浓度很高时会妨碍利用飞尘作为肥料，并且这种浓度是可变化的。飞尘分馏法实验是通过在四个发电站利用静电沉淀装置进行的。基于实验结果，第一个收集装置中重金属的浓度处于它的最低值，而最后一个装置中的浓度则是最高。镉在作为肥料的飞尘中的浓度，可以通过应用静电沉淀分馏法，使其降低 70%。对重金属的分馏情况相比之下没有对镉进行的分馏的效果明显。结果显示，静电沉淀分馏法在分馏将成为肥料飞尘或改善土壤方面是很合适的一种方法。导论：芬兰的热能工厂和发电厂每年都会产生大约 400， 000 公吨的原始生物燃料灰烬。这种灰烬的产生量在将来会随着生物燃料使用量的增加而增加。木材和泥煤燃后的灰烬能够作为肥料或土壤改良物质而被应用在林地或耕地上。并且能够达到给土壤 “ 补钙 ” 的目的。对灰烬的利用一直受到它本身含尘量和重金属浓度这些因素的局限：后者在很多情况下已经超出了芬兰在对使用土壤改良剂所规定的最高允许标准。在 2001年，燃煤灰烬的利用率（ 84%）相比泥煤和混合燃料灰烬的利用率（ 43%）高出相当多一部分。木材飞尘的利用率却相当低，在 1997 年大约是6%。从飞尘中提取出重金属能够使它更充分的被利用。通常，似乎操纵发电厂的燃料质量是达到这一目的唯一可行的方法。这就意味着我们必须知道这些易燃燃料的精确密度和性质，并且知道哪些物质提高灰尘含量中镉的浓度，进而筛选出含镉物质。 nts 少量的飞尘在农业和林产方面作为肥料已被应用。一般情况下，各种类型的灰烬在农业生产中要比化学肥料更适合作为土壤的改良物质，因为在灰烬中可溶的植物营养物质量是很低的。泥煤主要作为一种磷酸盐肥料被应用，木材燃料灰烬对于种植在含石灰的矿物质土壤中的谷类粮食作物的生长中，主要作为一种基础的营养肥料。土壤中灰烬的石灰和肥料效应取决于灰烬中钙和营养物的浓度，灰烬中营养物质的可溶性，土壤，土壤的性质，如酸度，营养浓度。表 2显示了四种类型灰烬的重金属浓度。灰烬中所含有的很多物质都是极其难溶解的。由于灰烬中的很多重金属（如镉，铅，镍）都很难溶解，可以假定灰烬肥料并不会受到重金属的显著影响。比如说，在水系中，短时期之内然后进行施肥。最后，一些有害的重金属可能就会被从灰烬中以一种可溶的形式释放出来，并且因此而转移到植被中去。灰烬中的石灰效应会降低土壤中重金属的溶解程度。灰烬最初会提高直立树木中的镉的浓度，但是一旦树木的生长提高了其中微量元素的浓度，重金属nts的浓度就会下降到甚至比最初还要低的水平。一些植物物种中的镉金属浓度的升高可以持续很长一段时间。镉被认为是所有重金属中危害最大的金属，因为它可以停留在土壤中，能够在食物链中逐渐富集，并且会使生物体中毒。图一静电除尘器静电沉淀（图一）是当前用于分离发电站废气中的固体物质最普遍的一种方法，它的优势包括高效率收集（高达 99.9%）和它在处理不同大小尺寸微粒（甚至大小小于 1流明的粒子）的适用性，以及体积不定的废气。它的更进一步的优势是它的长期有效性，很好的使用可靠性和低廉的经营维护费用。静电沉淀的机能很显著的依赖于将要收集的飞尘的性质特征。将要被分离的微粒的数量和颗粒大小的分布情况对静电沉淀的机能有很大的影响。尽管静电沉淀收集的高效性或多或少可以持续忽略微粒的量，但是它的有效迁动速度在微粒颗粒小的情况下会有所下降。由于微粒不同的专有特性，对微粒的收集效率根据微粒的大小而有变化。从分离的角度看，最难分离的颗粒大小是在 0.2到 0.5流明之间。 nts 灰烬中的重金属浓度可以通过多层静电沉淀将废气中细小灰烬颗粒分馏出的方法来降低。沉淀的分馏工具会受到比如限制或振荡电流这些方法的影响。我们的研究结果已经显示出，重金属被浓缩聚集在细小灰尘颗粒中。根据Thun 和 Korhonen（ 1999）的结果，第三层电场的静电沉淀已经停止，依赖于它的运行条件，灰尘总量的 84-95%在第一层次中， 4-15%在第二层次中，大约1%的在最后一个层次中。灰尘中镉的浓度可以通过静电沉淀的分馏法，被降低至少 15-25%。由于锅炉受到议论和怀疑，来自于以树皮为燃料和树木碎屑为燃料的发电站（大锅炉）的灰烬被划分为以下重量百分比级别，底部灰烬70-90%，气旋飞尘 10-30%，静电沉淀飞尘 2-8%和粉尘排放 0.1-0.3%。在灰尘燃烧和流化床燃烧中，产生的飞尘所占份量为 80-100%。多达75-90%的重金属存在于飞尘通过静电沉淀后的那些细颗粒中，图二展示了在底部灰尘，气旋灰尘和静电沉淀喉飞尘中锌，铅，和镉的含量（ mg/kg and m-%）。基于表二种的数据。各种灰尘类型中的重金属浓度重金属 mg/kg 煤灰泥煤灰木材燃灰树皮燃灰砷 (As) 2.3200 2200 0.260 728 镉 (Cd) 0.01250 0.058 0.440 420 铬 (Cr) 3.67400 15250 15250 4081 铜 (Cu) 303000 20400 15300 57144 nts汞 (Hg) 0.0180 0.0011 0.021 0.0120.4 镍 (Ni) 1.8800 15200 20250 3652 铅 (Pb) 3.11800 5150 151000 53140 锌 (Zn) 1413,000 10600 1510,000 11005100 表一土壤改良中允许的最大重金属浓度来自发电站 A的飞尘中的物质元素发电站 A ：飞尘（ mg/kg）允许最大值浓度（ mg/kg） 2002年 2001年 1999年汞 (Hg) 2.5 0.31 2.0 镉 (Cd) 2.69 5.05 6.3 3.0 砷 (As) 18.34 19.73 35 50 镍 (Ni ) 100 铅 (Pb) 56.59 106.5 52.7 150 铜 (Cu ) 86.7 290.1 178 600 锌 (Zn) 189.7 376.9 706 1500 可以这样确定，例如，静电沉淀飞尘含镉量要比气旋灰尘高，这是部分由于和气旋灰尘相比较，静电沉淀飞尘分离了含大部分重金属的细小颗粒。在这种情况下，一部分飞尘根据它在气旋灰尘的残余和它的浓度密度等情况适合于作为肥料。在一个机械分类器在灰尘到达沉淀器之前被连接的情况下，静电沉淀法比传统的方法更能有效地分馏飞尘。数据三显示了一个以燃烧生物燃料的发电站的基本规划设计图，并且其中在静电沉淀之前提供了多级旋风分离器装置。飞尘中所含的多达 75-90%的重金属（镉和锌）一定要通过静电沉淀法分离出并会存在于微粒的一小部分中。合适的设计规划和调整过的静电沉淀装置在原则上，是能够将那部分微粒飞尘从废气中分离出来的，而那部分飞尘含有最大量的重金属，但是却只是全部飞尘量的一个小部分。飞尘中主要部分的重金属浓度也因而能够被降低到所允许的浓度最大值以下。 2.原料和方法飞尘的分馏试验是在 4个发电站进行的（ A B C D ）。发电站的静电沉淀nts是在不同的电压水平下进行的，并且样品是来自于电压稳定程序。从静电沉淀装置中提取的所有样品都来自于在灰尘被放入筒仓之前安置在静电沉淀装置之下的灰尘进料装置中。通过石墨法分析样品中的铅，铜，锌，砷，和镉的存在情况，并且应用 Malvern装置来决定粒子颗粒大小。发电站 A使用泥煤，树木碎片和石油以及机械木材工业中的副产品作为燃料。发电站的锅炉有效燃料容量是 150兆瓦。分馏试验室利用当前发电站的 3层静电除尘装置进行的。发电站 B使用两个锅炉，一个是泡沫焦性石墨循环流化床锅炉（燃料容量 55兆瓦），另一个是单流化床锅炉（燃料容量 42兆瓦）。试验的实施是利用单流化床锅炉进行。该发电站的主要燃料是碾碎的泥煤块和木材燃料，煤烟和铝的氧化物的混合物。来自两个锅炉中的飞尘是通过 2层的静电除尘被传送到共同的灰尘筒仓之中。发电站 C 装备两个锅炉，锅炉 1 是一个单流化床，它的燃料容量是 267兆瓦。锅炉 2是一个泡沫焦性石墨循环流化床，燃料容量是 315兆瓦。试验是通过利用泡沫焦性石墨循环流化床锅炉进行的。发电站所用的燃料主要是碾碎的泥煤块和各种木材燃料。两个锅炉都被安装了 3层的静电沉淀装置，使锅炉中的飞尘能够由空气作用被吹到一个共同的灰尘筒仓。 D 发电站的流化床锅炉设备所产生的电能是 77 兆瓦，它的热容量是 246兆瓦。流化床锅炉中所使用的燃料主要是碾碎的泥煤块和木材废物。废气中的飞尘通过一个 3层的静电沉淀装置来进行分离。 3.结果在 A 发电站的静电沉淀试验中（试验 1-7），所使用的燃料是由 49%的泥nts煤和 61%的木材燃料构成。静电沉淀装置 1-3层的灰尘过滤烟窗被取样并且进行了分析。（图表 4）基于结果，静电沉淀装置第一层镉的浓度处于它的最低值，而在第三层中则是最高值。这是由于较大颗粒的飞尘微粒在第一层中积聚，而第三层中则容纳了含有最小微粒的飞尘。第一层中镉浓度的变化范围在 2.2-3.6mg/kg之间，同时第三层中的镉浓度变化范围则是在 7.2-12.4 之间。这些浓度受很多种性质情况的影响，比如电子稳定程序，燃料质量、性质，和废气的流动率。几乎在每个静电沉淀装置第一层中镉的浓度都低于为灰尘作为肥料使用所规定的允许浓度的最大值极限（ 3.0mg/kg）在试验进展过程中，静电沉淀装置层中的运转中循环周期阻滞比率被控制在 0-2之内。 0值是指被讨论的装置层所有的半循环周期在通常情况下都能正常活跃。 2 值是指只有半周期的三分之一起作用。因此运转循环周期阻滞的这个评价阐述了有多少连续的半周期已经关闭，也就是，分离器的补充电流的跳动频率是多少。 nts 在当前的研究中，运转循环周期阻滞价值由微观 kraft（牛皮纸）控制器来操控，它的主要任务就是将电压保持在靠近击穿电压值附近。最重要的就是能够影响和改变静电沉淀装置第一层中的性能。第一层能够使飞尘产物中含有的重金属的浓度水平达到适合作为肥料的标准，例如，图表 5显示了静电沉淀装置的运转循环周期阻滞比率在第一层中对飞尘中镉浓度水平的影响。在其他的情况之中，静电沉淀场的闪络数量的增加或减少则不在此控制之内。有越多的半周期场发生无效，就会导致所产生的飞尘中重金属含量越低。镉的浓度变化也是由燃料质量和性质变化引起的，除了控制本身，还存在其他因素之中。图表 6 显示了静电沉淀装置的过滤器电压是如何影响在第一层的镉浓度水平重金属浓度水平随着电压的升高而升高。这是由于较高的电压能够更加有效的分离也含有重金属的优质微粒。过滤器电压水平比运转周期阻滞比率风有nts效的显示了电场的真实情况。在其他情况中，同时也要考虑任何一种电场中发生通电击穿的情况。表 7 显示了从试验 5.6.7 种得出的结果，它的一到三层电场中微粒的大小等级在直径 10 流明到 50 流明之间的情况。直径 10 流明大小是指关于样品的90%我微粒都较大，而 10%的较小。直径 50 流明是一个二等分的微粒大小等级，或者说关于样品中的微粒大小较大的和较小的二者比例为 1： 1。根据这些数据，较小的微粒倾向于集中在静电沉淀装置的第三个电场中，而较大的微粒倾向于集中在第一个电场中。这些小微粒含有最高的重金属浓度（表 8）。数据显示可作为肥料的镉浓度水平在微粒大小种类方面超过小于 16流明的微粒。 nts镉浓度在 D发电站中处于最高值。这是由于在与其他的发电站所用燃料的比较中，该发电站的木材燃料占较大的比重。在分馏之后，静电沉淀装置第三层电场中的灰尘中镉的浓度逐渐累积，至少要为第一层电场中的浓度的 5倍。除此之外，在这些试验中，在 D发电站，有效地分馏灰尘是不可能的。根据得出的结果，铅，铜，和镍的浓度从分馏的角度看并没有什么问题。至于这些金属，飞尘不经过分馏而直接作为肥料应用是可以的。锌，砷和镉的浓度可能超过允许的最大极限时，如果将飞尘当作肥料使用就会因此引起很多的问题。对于这些金属，将飞尘作为肥料应用时，就要取决于燃料的成分和分馏的效力。表 10显示了对 B， C， D发电站各种不同大小的微粒的分析。基于这些数据，可以这样说，在静电沉淀装置的第一层电场中仍有粗糙的灰尘。 nts在发电站 BCD，静电沉淀装置是通过调节电流值来控制的。然而，静电沉淀装置的生产力容量取决于它的电压水平。电压和电流的比例并不是均衡对称的。当电流大小被降低 50%的时候，电压仅仅会降低 10-20%。而且，当电流的给定值降低时，就会有相当的更少的击穿情况。在各种实验之间，平均电压值并没有改变并达到一个足够的值是有很多原因的，以致于影响到静电沉淀装置的分离效率。这就意味着对静电沉淀装置中的电流不同的调整并没有对实验期间的重金属浓度产生很大的影响。 4.结论。燃烧后产生的灰烬，它的化学性质和物理性质，还有作为最后结果的灰烬的体积，都取决于易燃燃料的成分和性质。燃烧技术和参数（相关因素），例如温度，燃烧效率，补给空气体积，还有锅炉的燃烧环境以及以灰烬的恢复防御体系，都对最终得到的结果灰烬的性质有影响。从飞尘性质的角度来看，分离灰烬的装置尤其重要，因为在灰烬的构成上，它的废气中的细颗粒部分是至关重要的，飞尘中的微粒经常被重金属富集并浓缩强化。飞尘中重金属浓度水平的较大变化范围是飞尘在实际应用中受到质疑。飞尘中含的重金属浓度会超过可作肥料使用的法定要求局限。木材燃烧灰烬中最让人质疑的重金属就是镉。在芬兰，当前的有效法令规定的极限值是 3mg/kg。而木材灰烬则超过了这个极限值。在若干情况中，重金属的发射性可以通过科技加工方法来降低。这些包括瓦斯泻出体积的最小值，废气收集，空气流通的利用，原料和能源的有效利用，以及含有最小重金属浓度的原料和燃料的利用。并且，飞尘的性质可以通过分馏而被改变。分馏的目的是将高密度和重金属浓度的细小微粒部分从适合实际应用的那部分中分离出来。分馏实验证明了在静电沉淀装置第一层电场中重金属的浓度处于最低值，而在第三层中则是最高值。重金属在飞尘微粒中会得到富集和增多。含有最大颗粒的飞尘微粒会在第一层电场中积累，而在第三层电场中则主要更多是细小含尘微粒。由于这样，第一层中积累的灰尘含有较少的重金属。灰尘中的重金属浓度会受到如电压稳定程序，燃料性质，和废气的流动率的影响。镍，铅和铜是重金属，他们的浓度不超过对木材和泥煤燃灰作为肥料使用nts所规定的极限值。至于这些金属，在考虑到当前许可条件要求的情况下，没有必要使用分馏法。然而，分馏明显的降低了飞尘中这些金属的浓度。基于测试得到的结果，可以说，静电沉淀装置可能会增加运转循环周期阻滞的比率的特性，这样为了好的性能将会降低在分离细微颗粒方面的效果。重金属的浓度的增长是与电压的增加相联系的。这是由于高电压能够更有效的分离那些含有重金属的细微颗粒，这就意味着静电沉淀装置的分离效果可能就要受使用的最大电压值和运转循环周期阻滞的时间的影响。这些调整可能会减少电场一的分离效果，这样就使得重金属浓度的最小值能够在最终的灰烬中积累增加。相对地，重金属在细微颗粒中具有的发射性将会由于通过加强静电沉淀装置最后一层电场的效果而被减弱。对于静电沉淀法在分馏上的参数我们并不能给出全面评价和估计。使用后的燃料中的重金属浓度能够出现很大的差距和不同，并且很难决定所要求的合适分馏方法，除非使用的问题燃料已经被加以分析过。 nts11concentrations of heavy metal are at their lowest in the first collector chamber and highest in the last chamber. The concentration ofcadmium in fly ash used as fertiliser can be reduced by as much as 70% by applying electrostatic precipitation fractionation. The removalof other heavy metals is not as ecient as that of cadmium. The results show that electrostatic precipitation is an adequate method in theas increasing amounts of biofuels are used. Wood and peatash can be spread onto forest lands or arable land as fertil-ably lower, being about 6% in 1997.materials increase the ash-contained Cd concentrations,and then screen out the cadmium containing materials.ents in ash, on the solubility of nutrients in the ash and thesoil, and on soil properties, e.g. acidity and nutrient con-centrations (Orava et al., 2004; Silfverberg, 1996). Table2 shows the heavy metal concentrations of four ash types.Many substances contained in ash are in extremelypoorly soluble forms. As the heavy metals (e.g. cadmium,*Corresponding author.E-mail addresses: hanne.oravamikkeliamk.fi (O. Hanne), timo.nord-manoulu.fi (N. Timo), hannu.kuopanporttimikkeliamk.fi (K. Hannu).Minerals Engineering 19 (2006)iser or as soil improvement material, and with the purposeof adding calcium to the soil. The use of ash has been con-strained by factors such as its dust content and heavy metalconcentrations; the latter having in many cases exceededthe maximum permitted levels imposed in Finland on soilimprovement substances (Table 1).In 2001, the utilisation rate of coal ash (84%) was con-siderably higher than that of peat and mixed fuel ash(43%). Wood fly ash utilisation rates have been consider-Small amounts of fly ash are used as a fertiliser both inagriculture and in forestry. Generally, various ash types aremore suitable as a soil improvement material than fertilis-ers in agriculture because the amounts of soluble plantnutrients in ash are fairly low. Peat ash is used mainly asa phosphate fertiliser and wood ash in liming of mineralsoils and as a basic and support fertiliser in the growingof cereal crops. The liming and fertiliser eects of ash inthe soil depend on the concentrations of calcium and nutri-fractionating of fly ash to be used as a fertiliser or soil amendment.C211 2006 Elsevier Ltd. All rights reserved.Keywords: Electrostatic separation; Sizing; Classification; Flue dusts; Recycling1. IntroductionHeating-energy plants and power plants in Finland gen-erate approx. 400,000 tonnes of ash of biofuel origin peryear. The amounts of such ash will increase in the futureThe extraction of heavy metals from fly ash could enableits more ecient utilisation. Currently, it appears thatmanipulating the power plant fuel quality is the onlymethod available for this purpose. This means that we mustknow the combustible fuels exact consistency, and whichIncrease the utilisation of fly ashOrava Hannea,*, Nordman TimoaYTI Research Centre, Mikkeli Polytechnic,bUniversity of Oulu, P.O. Box 4300,Received 28 April 2006;Available onlineAbstractThe basic idea in this study is to look into the possibilities of reducingtrostatic precipitation. The utilisation of fly ash as fertiliser is hamperedvariable. Fly ash fractionation experiments were done using electrostatic0892-6875/$ - see front matter C211 2006 Elsevier Ltd. All rights reserved.doi:10.1016/j.mineng.2006.07.002with electrostatic precipitationb, Kuopanportti HannuaP.O. Box 181, FI-50101 Mikkeli, FinlandFI-90014 Oulun yliopisto, Finlandaccepted 7 July 2006September 2006the heavy metal concentrations of fly ash by means of elec-by its high concentrations of heavy metals, which are highlyprecipitators at four power plants. Based on the results, theThis article is also available online at:/locate/mineng15961602ntslead, nickel) in ash are in very poorly soluble forms, it canTable 2Heavy metal concentrations of various ash types (Palola, 1998)Heavy metals (mg/kg) Coal ash Peat ash Wood ash Bark ashArsenic (As) 2.3200 2200 0.260 728Cadmium (Cd) 0.01250 0.058 0.440 420Chrome (Cr) 3.67400 15250 15250 4081Copper (Cu) 303000 20400 15300 57144Mercury (Hg) 0.0180 0.0011 0.021 0.0120.4Nickel (Ni) 1.8800 15200 20250 3652Lead (Pb) 3.11800 5150 151000 53140Zinc (Zn) 1413,000 10600 1510,000 11005100Table 1Maximum permitted concentrations of heavy metals in soil improvementmaterials and in fly ash from power plant A (Orava, 2003)Element Power plant A: fly ash (mg/kg) Maximumpermittedconcentration(mg/kg)Year 2002 Year 2001 Year 1999Mercury (Hg) 2.5 0.31 2.0Cadmium (Cd) 2.69 5.05 6.3 3.0Arsenic (As) 18.34 19.73 35 50Nickel (Ni) 100Lead (Pb) 56.59 106.5 52.7 150Copper (Cu) 86.7 290.1 178 600Zinc (Zn) 189.7 376.9 706 1500O. Hanne et al. / Minerals Engineerinbe assumed that ash fertilisation will not result in signifi-cant heavy-metal impacts, e.g. in water systems, within ashort period of time following fertilisation. In the longrun, harmful heavy metals may, however, be released fromash in soluble forms and be thereby translocated into thevegetation (Nieminen, 2003). The liming eect of ash low-ers the solubility of heavy metals in the soil. Ash may atfirst raise the cadmium concentration in tree stands, butonce tree growth has improved the concentrations of traceelements and heavy metals may fall even below the initiallevel. The rise in the Cd concentration in some plant speciescan last for a long time (Moilanen, 2003). Cadmium is con-sidered to be the most harmful of all heavy metals becauseit remains in the soil, it becomes enriched in food chains,and it is toxic to organisms.Electrostatic precipitation (Fig. 1) is currently the mostcommon method used in separating the solid matter frompower plant flue gases. The advantages of electrostatic pre-cipitation include high collection eciency (as high as99.9%) and its suitability for dealing with particles of dier-ent sizes (even particle sizes below 1 lm) and variable fluegas volumes. Its further advantages are long service life,good operational reliability, and low operating and mainte-nance costs (Walsh, 1997; Immonen, 1987).The functioning of the electrostatic precipitator is signif-icantly dependent on the properties of the fly ash to be col-lected. The amount and size distribution of the particles tobe removed have a significant impact on the functioning ofthe electrostatic precipitator. Although the collection e-ciency of electrostatic precipitator is more or less constantirrespective of the particle mass, the eective migrationvelocity is lower in the case of small particles. Due to thedierent charging properties of the particles, the collectioneciency of the particles varies as a function of particlesize. The most dicult particle size from the point of viewof separation is 0.20.5 lm(Nykanen, 1993; Kouvo, 2003).The concentrations of heavy metal in ash can be reducedby fractionation of the finest ash particles from flue gasesby means of multi-chamber electrostatic precipitators.The fractionating properties of the precipitator can beinfluenced by actions such as restricting and pulsating thecurrent. Our research results have shown that heavy metalsFig. 1. Alstom Finland Oys electrostatic precipitator (Jalovaara et al.,2003).g 19 (2006) 15961602 1597are concentrated in fine ash particles (Orava et al., 2004;Orava, 2003). According to the results of Thun and Korho-nen (1999), the 3-field electrostatic precipitator wasstopped, depending on the operating conditions, 8495%of the overall amount of ash in the first field, 415% inthe second field, and approx. 1% in the last field. The cad-mium concentration of ash can be reduced at least by 1525% by means of fractionating the ash using electrostaticprecipitators (Orava et al., 2004; Thun and Korhonen,1999).Depending on the boiler in question, ashes from barkfuelled and wood chip fuelled power plants (grate boilers)are divided into weight percentage categories as follows:bottom ash 7090%, cyclone fly ash 1030%, electrostaticprecipitator fly ash 28% and dust emissions 0.13.0%(Agarwal and Agarwal, 1999). In dust combustion and flu-idized-bed combustion, the share of fly ash generation is80100%. As much as 7590% of the heavy metals (Cdand Zn) are contained in the fine particle fraction of thefly ash, which is separated by electrostatic precipitators(Dahl et al.). Fig. 2 sets out the zinc, lead and cadmiumcontents (mg/kg and m-%) in bottom ash, cyclone ashand electrostatic precipitator fly ash. Based on the figure,ntsash can thus be reduced to below the maximum permittedconcentrations.2. Materials and methodsThe fractionating trials with fly ash were performed atfour power plants (A, B, C and D). The electrostatic pre-cipitators were operated at the power plants at dierentvoltage levels and samples were taken from the ESPs var-ious fields. All the samples taken from the electrostatic pre-cipitators were taken from the ash feeders located underthe electrostatic precipitators before the ash was fed intothe silo. The samples were analysed for the presence ofPb, Cu, Zn, Ni, As and Cd using the graphite method1598 O. Hanne et al. / Minerals Engineering 19 (2006) 15961602it may be stated, for example, that electrostatic precipitatorfly ash has a higher Cd content than cyclone ash, which ispartly due to the fact that, compared to cyclones, electro-static precipitators separate smaller particles that containthe majority of heavy metals. In this case, the portion ofthe fly ash that is suitable for use as a fertiliser, in termsof its consistency, remains at the cyclone (Obernbergerand Biedermann, 1997).The electrostatic precipitator can more eectively frac-tionate fly ash than the traditional methods when amechanical classifier (cyclone) is connected before the ashreaches the precipitator. Fig. 3 shows a basic layout draw-ing of a power plant fired by using biofuels and which isprovided with a multi-cyclone before the electrostatic pre-cipitator. As much as 7590% of the heavy metals (Cdand Zn) contained in fly ash are bound to the fine fly ashfraction separated by the electrostatic precipitator (Dahlet al., 2002).Properly designed and adjusted electrostatic precipita-Fig. 2. Heavy metal concentrations and their division as bulk percentagefigures in bottom ash, cyclone fly ash and filter fly ash (Agarwal andAgarwal).tion is in principle, capable of separating that fraction ofthe flue gases, which contains the greatest amount of heavymetals but only a fraction of the overall amount of ash.The heavy metal concentrations in the main part of theFig. 3. The ash fractions produced by a biofuel-firedand particle size determination was done using a Malverndevice.Power plant A uses peat, forest chip and oil and the by-products of the mechanical wood processing industry as itsfuels. The boiler capacity available to the power plant is150 MW. The fractionating trials were performed withthe power plants current 3-field electrostatic precipitator.Power plant B uses two boilers, one a Pyroflow circulat-ing fluidized-bed boiler (capacity 55 MW) and the other afluidized-bed boiler (capacity 42 MW). The trials were car-ried out using the fluidized-bed boiler. The power plantsprincipal fuel is milled peat with wood fuels, soot and alu-minium oxide mixed in with it. The fly ash from both boil-ers is conveyed via 2-field electrostatic precipitators to acommon ash silo.Power plant C is equipped with two power plant boilers.Boiler 1 is a fluidized-bed boiler with a fuel capacity of267 MW. Boiler 2 is a Pyroflow circulating fluidized-bedboiler with a fuel capacity of 315 MW. The tests were per-formed using the Pyroflow circulating fluidized-bed boiler.The fuels used at the power plant were mainly milled peatand various wood fuels. Both boilers are equipped with 3-field electrostatic precipitators from which the boilers flyash is blown pneumatically to a common ash silo.The electrical power generated by power plant Ds fluid-ized-bed boiler plant is 77 MW and its heating capacity is246 MW. The fuels used in the fluidized-bed boiler arepower plant (Agarwal and Agarwal).ntsmainly milled peat and wood waste. The fly ash is sepa-rated from the flue gases by means of a 3-field electrostaticprecipitator.3. ResultsDuring trials with power plant As electrostatic precipi-tator (trials 17) the fuel used was composed 49% peat and51% wood fuels. The ash funnels of fields 13 of the elec-trostatic precipitator were sampled and analysed (Fig. 4).On the basis of the results, the Cd concentration was atits lowest in field 1 of the electrostatic precipitator and at itshighest in field 3. This is due to the bigger fly ash particlesaccumulating in field 1 and field 3 containing ash with theparticles in the first field of the electrostatic precipitator.2.833.23.4024681012CBO-ratioCd mg/kgFig. 5. The eect of the CBO ratio from electrostatic precipitator field 1on fly ash Cd concentrations (mg/kg) during trial runs with peat fuel.2.83.8425 30 35 40 45 50Voltage kVCd mg/kgFig. 6. The eect of the filter voltage level (kV) from electrostaticO. Hanne et al. / Minerals Engineering 19 (2006) 15961602 1599smallest particles. The Cd concentration in field 1 varieswithin the range of 2.23.6 mg/kg and in the last fieldwithin the range of 7.212.4 mg/kg. Concentrations areaected by properties such as the ESP voltage, fuel quality,and flue gas flow rate. In almost every electrostatic precip-itators field 1 the Cd concentration is below the permittedmaximum limit (3.0 mg/kg) set down for ash intended forfertiliser use.During trial runs, the electrostatic precipitator fieldsCBO ratio (cycle block in operation) was controlled withinthe range 012. The value 0 means that all the half-cycles ofthe field in question are currently active, and for exam-ple, the value 2 means that only a third of the half-cyclesare active. Thereby the CBO value declares how manysequential half-cycles are closed, that is, how often the sep-arators supply current is pulsated. In the present research,the CBO value was controlled by the Micro-Kraft control-ler whose main task is to keep the voltage near to thebreakdown voltage.The most important thing is to be able to influence andchange the properties of field 1 in the electrostatic precipi-tator. The first field enables the production of fly ash withheavy metal concentration levels that make it suitable as afertiliser, for example.Fig. 5 shows how the electrostatic precipitators CBOratio control for field 1 aects the fly ash Cd concentrationlevels. Among other things, the increasing or decreasing024681012141234567Cd mg/kgField 1Field 2Field 3Fig. 4. Cd concentrations (mg/kg) of the fly ash in fields (13) during trialruns (17) with peat fuel when using the electrostatic precipitator.number of electrostatic precipitator field flashovers isexcluded from this control.The more field half-cycles there are deactivated, thelower the heavy metal content of the fly ash being gener-ated. Cd concentration variations are also caused by fuelquality variations, in addition to the control itself, amongother factors.Fig. 6 shows how the electrostatic precipitators filtervoltage aects the Cd concentration level of field 1. Theheavy metal concentration level increases in accordancewith the rising voltage. This is due to the fact that highervoltages can more eectively separate fine particles thatalso contain heavy metals. The filter voltage level indicatesthe fields actual status more eectively than does the CBOratio. Among other things, it also takes into account anyelectric breakdowns that occur within the field.Fig. 7 shows the particle size classes (lm) D10 and D50of fields 13 resulting from trials 5, 6 and 7. D10 is a par-ticle size with respect to which 90% of the samples particlesare larger and 10% are smaller. D50 is a halving particlesize class, or the particle size with respect to which samplesparticles are larger and smaller in the ratio of 50/50.On the basis of this figure, the smaller-sized particlestend to be concentrated in the last field and the bigger-sizedprecipitator field 1 on fly ash Cd concentrations (mg/kg) during trial runswith peat fuel.ntsThese small particles have the highest concentrations ofheavy metals (Fig. 8). The figure shows that the permissibleCd concentration level for use as a fertiliser is exceeded inparticle size category 16 lm.The cadmium concentrations were at their highest atpower plant D (Fig. 9). This was due to the bigger shareof wood fuel in the fuel when compared to the other powerplants. Following fractionation, the cadmium concentra-tion of the ash accumulated in field 3 of the electrostaticprecipitator was at best five fold compared to field 1.051015202530D10 D50 D10 D50 D10 D50mField 1Field 2Field 3Fig. 7. The particle size classes (lm) D10 and D50 of the fly ash in theelectrostatic precipitators fields 13.1600 O. Hanne et al. / Minerals Engineerin23456786 11162126Cd mg/kgThe particle size class D50 mFig. 8. Cd concentration levels (mg/kg) and particle size (lm) D50 duringtrial runs with peat fuel.0510152025BBBCCCDDDCd mg/kgField 1Field 2Field 3SiloFig. 9. Cd concentrations of the fly ash in the various fields of theelectrostatic precipitator (limit value 3 mg/kg) at power plant B, C a

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