JPS5982953A - Treatment of waste gas from coal fired boiler - Google Patents

Abstract

PURPOSE:To improve the performance of an electrical dust precipitator by charging a calcium-contg. refining agent in a waste gas line thereby decreasing the electrical resistance of fly ash. CONSTITUTION:The waste gas from a boiler 6 is cooled in a preheater 7 and is fed to an electrical dust precipitator 8, where the gas is removed of dust and is thereafter fed to a wet type desulfurizer 8. Measuring device 13, 15 which measure soot density A or SO2 density B are provided in the outlet of the precipitator 8. Said devices input the density signals A, B to a control unit 14. An adequate amt. of a calcium-contg. refining agent is calculated in the unit 14 and is outputted to an adding device 12 for the refining agent. The device 12 adds CaSO4, CaSO3, etc. in the form of liquid or powder from a coal transfer line 2 to a mill 4 up to the high temp. part in the outlet of a boiler 6. CaSO4 and CaSO3 to be by-produced in the desulfurizer 9 are used for the Ca-contg. refining agent such as CaSO4 and CaSO3.

Description

【発明の詳細な説明】 本発明は石炭ボイラ排ガスの処理方法に関するもので、
′→く気集塵装置入口に到るまでに従来用いられなかっ
たカルシウム系調質剤（例えば０ａＳＯ４，０ａＳＯ３
等）を適正量添加投入することにより、ボイラ排ガス中
のフライアッシュの電気抵抗値を下げ、かつ電気集塵装
置におけるバックコロナ現象の発生を防止して集塵性能
の向上を図ると共に、湿式脱佃を装置の負荷増大を最小
限に抑えることができる石炭ボイラ排ガスの処理方法を
提供することを目的とする。[Detailed Description of the Invention] The present invention relates to a method for treating coal boiler exhaust gas,
'→ Calcium-based conditioning agents (e.g. 0aSO4, 0aSO3
By adding appropriate amounts of fly ash (e.g., The object of the present invention is to provide a method for treating coal boiler exhaust gas that can minimize the increase in load on the equipment.

正気奥塵朶「４の処理ガス温度の低温領域（一般に１３
０〜１５０℃）において石炭ボイラ排ガス中のフライア
ッシュの電気抵抗値（以下ρｄという。）が１０１０〜
１０１１Ω−Ｃｍ以下であれば良好な集塵性能が得られ
るが、石炭の′＄Ｊ類によってはρｄが１０　０−ａｍ
を越える高電気抵抗フライアッシュが生成してしまう。The low temperature range of the processing gas temperature of 4 (generally 13
The electrical resistance value (hereinafter referred to as ρd) of fly ash in coal boiler exhaust gas is 1010 to 150°C).
Good dust collection performance can be obtained if it is less than 1011 Ω-Cm, but depending on the type of coal, ρd may be 100-am.
fly ash with high electrical resistance exceeding .

との高電気抵抗フライアッシュの場合、石炭ボイラ排ガ
ス中の煤塵が放電極と集塵極との空間で電荷を与えられ
、電気力により該集塵極上に捕集堆積すると、堆積煤塵
層で絶縁破壊が生じ、この絶縁破壊はさらに、堆積煤塵
層上のガスの空間において気中放電を肪発するバックコ
ロナ現象が生じる。一旦バツクコロナ現象が発生すると
、排ガス中の帯電煤塵の電気的中和作用や、堆積煤塵の
排ガス中への射出により集塵性能は大巾に低下してしま
う。In the case of fly ash with high electrical resistance, the soot dust in the coal boiler exhaust gas is given an electric charge in the space between the discharge electrode and the dust collecting electrode, and when it is collected and deposited on the dust collecting electrode by electric force, it is insulated by the accumulated soot dust layer. Breakdown occurs, and this dielectric breakdown further causes a back corona phenomenon in which an air discharge occurs in the gas space above the accumulated soot and dust layer. Once the back corona phenomenon occurs, the dust collection performance is significantly reduced due to the electrical neutralization of the charged dust in the exhaust gas and the injection of accumulated dust into the exhaust gas.

そこで従来、電気集塵鵡儒、入口に到るまでに例えばＳ
Ｏ３、Ｈ２ＳＯ４、又はＮａ２５ｏ、を調質剤として添
加してフライアッシュの電気抵抗値自体を下げることに
よりバックコロナの発生を防止することが行なわれてい
る。この方法は石炭中のＳ分の大小がフライアッシュの
電気抵抗値に影響し電気集塵装置の性能を左右する現象
に着眼したものであシ、本発明もこの方法によっている
。Therefore, in the past, electrostatic precipitators were used, for example, S
The generation of back corona has been prevented by adding O3, H2SO4, or Na25o as a refining agent to lower the electrical resistance value of fly ash itself. This method focuses on the phenomenon that the magnitude of the S content in coal affects the electrical resistance value of fly ash and influences the performance of an electrostatic precipitator, and the present invention also uses this method.

しかし本発明者による最近の研究結果によれば、フライ
アッシュの電気抵抗値を下げる要因１石炭中のＳ分の他
、フライアッシュ組成中のある成分、特にｃａＯであり
、石炭中のＳ分及びフライアッシュ中のｃａＯ分を増加
する必要があることが分った。しかも、前記従来の調質
剤は高価である、取扱いが離しいなどの欠点があるが、
Ｏａ　Ｓ　ＯＣａ　Ｓ　Ｏａ等は湿式脱硫装置において
太駕°かつ安価に副生品として得られるから、このＣａ
　Ｓ　ＯＯａ　Ｓ　Ｏａ等が調４　＼ 質剤として使用できることが分った。However, according to recent research results by the present inventor, factors that lower the electrical resistance value of fly ash: In addition to the S content in coal, there are certain components in the fly ash composition, particularly caO; It was found that it was necessary to increase the caO content in fly ash. Moreover, the conventional conditioning agents have drawbacks such as being expensive and difficult to handle.
Oa S OCa S Oa etc. can be obtained as a by-product in a wet desulfurization equipment at a large scale and at low cost, so this Ca
It was found that S OOa S Oa etc. can be used as a stimulant.

そし７て本発明者による実験によれば、従来用いられな
かったカルシウム系調質剤（例えばＯａＳ　Ｏ４、Ｃａ
ＳＯ３等）を粉末状或いは液状でボイラへの石炭供給ラ
インや燃焼空気ライン或いはボイラ出口部の排ガスライ
ンに投入すると、電気集塵装置の性能を向上させること
ができることが確認できた。これは調質剤が高温条件下
で熱分解され、ボイラ排ガス中のＳ分とｃａＯ分が増加
することにより、フライラッシュのρｄが１０１０〜１
ｏ１１Ω−ｃｍ以下に低下したためと、電気的な荷電特
性（２次電圧−２次電流の関係）が改善され、バックコ
ロナ現象が発生しなくなったためである。7.According to experiments conducted by the present inventor, calcium-based conditioning agents (e.g. OaS O4, Ca
It was confirmed that the performance of the electrostatic precipitator can be improved by injecting SO3, etc., in powder or liquid form into the coal supply line, combustion air line, or exhaust gas line at the boiler outlet to the boiler. This is because the tempering agent is thermally decomposed under high-temperature conditions and the S content and CaO content in the boiler exhaust gas increase, resulting in a flylash ρd of 1010 to 1.
This is because the resistance decreased to 11 Ω-cm or less, and the electrical charging characteristics (relationship between secondary voltage and secondary current) were improved, and the back corona phenomenon no longer occurred.

第１図、第２図はいずれもオーストシリアのＡ炭につい
ての実験結果を示しておシ、第１図は燃焼石炭量（Ｋｙ
／Ｈ）に対するＷ間質剤添加！−（ｂ／ｕ　）の比（以
下調質剤添加比という。）と集塵性能（％）との関係を
示す。第２図は調質側添加比と電気集塵装置からの排ガ
ス中のＳｏ２綻度（ｐｐｍ）との関係を示す。これら第
１１（イ）、第２図から調質側添加比が増加するに従い
、集塵効率もＳＯ２濃度も上昇することが分る。今、実
機ボイラを考えた場合、ＳＯ２濃度が上昇しても電気集
塵装置の後段に設置された湿式脱硫装置により充分に対
応できる。Figures 1 and 2 both show the experimental results for Austsyrian A coal.
/H) Addition of W interstitial agent! -(b/u) ratio (hereinafter referred to as conditioning agent addition ratio) and dust collection performance (%) is shown. FIG. 2 shows the relationship between the addition ratio on the refining side and the So2 resolution (ppm) in the exhaust gas from the electrostatic precipitator. It can be seen from these Figures 11(a) and 2 that as the refining side addition ratio increases, the dust collection efficiency and SO2 concentration also increase. Now, if we consider an actual boiler, even if the SO2 concentration increases, it can be adequately addressed by a wet desulfurization device installed after the electrostatic precipitator.

しかし電気集塵装置には所定の集塵効率が得られれば良
く、それ以上に集塵効率を高めるようにλ１」質剤を添
加することは湿式脱硫装置の負荷を徒らに増大させるこ
とになり得策でない。従って所定の集塵効率が得られる
よう適正量の畢間質剤を添加すべきである。However, it is sufficient for an electrostatic precipitator to obtain a predetermined dust collection efficiency, and adding λ1'' additive to further increase the dust collection efficiency will unnecessarily increase the load on the wet desulfurization equipment. It's not a good idea. Therefore, an appropriate amount of interstitial agent should be added to obtain a predetermined dust collection efficiency.

本発明は以上の点に鑑みて創案されたもので、刀ルシウ
ム系調質剤を用いると共に該調質剤を適正量添加投入す
ることによって排ガス処理設備の高性能化を計ったもの
である。The present invention has been devised in view of the above points, and is intended to improve the performance of exhaust gas treatment equipment by using a lucium-based heat refining agent and adding an appropriate amount of the heat refining agent.

以下本発明を第３図と第４図により説明する０ ヤード１上の石炭はコンベヤ２によりバンカー３に投入
され、該バンカー３を介してミル４に移送され、そこで
破砕された後、−次通風穏５から送られる燃焼空気と共
にボイラ６に送られ、そこで燃焼される。その際発生し
たボイラ排ガスは予熱器ツにより降温されて電気集塵装
置８に送られ、そこで除廣された後、湿式脱硫装置９に
送られそこで脱硫され、昇温の上煙突工０から大気中へ
放出拡散される。湿式脱硫装置９においては、従来公知
の如くボイラ排ガス中のＳＯｘをＣａＣＯ３、又はＯａ
　（ＯＨ）２によシ吸収したものを０□により酸化し、
式らに濃縮分離、脱水してＯａ　ＳＯ４、Ｏａ　ｓｏ　
３等が製造される。The present invention will be explained below with reference to FIGS. 3 and 4. Coal on a yard 1 is fed by a conveyor 2 into a bunker 3, transferred via the bunker 3 to a mill 4, where it is crushed and then - It is sent to the boiler 6 together with the combustion air sent from the ventilator 5, and is burned there. The boiler exhaust gas generated at this time is cooled by a preheater and sent to an electrostatic precipitator 8, where it is removed and then sent to a wet desulfurization device 9 where it is desulfurized. It is released and diffused inside. In the wet desulfurization equipment 9, as is conventionally known, SOx in the boiler exhaust gas is converted to CaCO3 or Oa.
What was absorbed by (OH)2 is oxidized by 0□,
Concentrate, separate, and dehydrate to form Oa SO4 and Oa so
3rd class will be produced.

このＣａ、ＳＯ，、Ｏａ、ＳＯ３等はカルシウム系調質
剤として、ミル４への石炭移送ライン（例えばコンベヤ
２上）或いはミル４以降ボイラ６への石炭及び燃焼空気
供給ラインから該ボイラ６へ、又は、ボイラ出口の高温
部（約９００　℃以上の高温域）へ調質剤添加装置１２
にょシ液状或いは乾燥粉末状にして投入添加される。These Ca, SO, Oa, SO3, etc. are used as calcium-based refining agents and are supplied to the boiler 6 from the coal transfer line to the mill 4 (for example, on the conveyor 2) or from the coal and combustion air supply line from the mill 4 to the boiler 6. , or the tempering agent addition device 12 to the high temperature section at the boiler outlet (high temperature region of approximately 900°C or higher).
It is added in liquid or dry powder form.

他方、電気集塵装置飽１８の出口部に設ｆｊｌ　した珠
ｒＨ４濃度測定装置１３によシ煤塵濃度が測定され、そ
の値がフィードバック信号Ａとして制御コーニット１４
に入力される。との制御ユニット１４において、予め設
定しである所定集塵効率での煤塵濃度の値と前記測定値
とが比較され、その偏差に対応する調質剤添加比が算出
され、この値が制御信号ＡＩとして調質剤添加装置１２
に送られもそして調質側温加装ψ１２において、煤塵濃
度が前記集塵効率に対応した値となるよう調質剤の投入
量が制御される。On the other hand, the soot dust concentration is measured by the particle rH4 concentration measuring device 13 installed at the outlet of the electrostatic precipitator 18, and the value is sent as a feedback signal A to the control condenser 14.
is input. In the control unit 14, the value of the soot dust concentration at a predetermined dust collection efficiency, which is set in advance, is compared with the measured value, the tempering agent addition ratio corresponding to the deviation is calculated, and this value is used as the control signal. Conditioning agent addition device 12 as AI
Then, in the refining side heating device ψ12, the amount of the refining agent introduced is controlled so that the soot and dust concentration becomes a value corresponding to the dust collection efficiency.

又は、電気集塵装置８の出口部に設置した日０２濃度測
定装Ｒ１５によりＳＯ２濃度が測定され、その値がフィ
ードバック信号Ｂとして制御ユニット１４に入力される
。この制御ユニット１４にお（八て、予め設定しである
所定集塵効率でのＳＯ２濃度の値と前記測定値とが比較
され、その偏差に対応する調質剤添加比が算出され、こ
の値が制御信号Ｂ′として調質剤添加装置ｔ１２に送ら
れる。そして調質剤添加装置１２において、ＳＯ２濃度
が前記集塵効率に対応した値となるよう調質剤の投入量
が制御される。Alternatively, the SO2 concentration is measured by the day 02 concentration measuring device R15 installed at the outlet of the electrostatic precipitator 8, and the value is inputted as the feedback signal B to the control unit 14. This control unit 14 compares the SO2 concentration value at a predetermined dust collection efficiency with the measured value, calculates the conditioning agent addition ratio corresponding to the deviation, and calculates this value. is sent as a control signal B' to the conditioning agent addition device t12.The conditioning agent addition device 12 then controls the amount of conditioning agent added so that the SO2 concentration becomes a value corresponding to the dust collection efficiency.

前記した２つの１″Ａ質剤投入貴制御を併せて同時に行
なえば、制御の信頼性がそれだけ高くなる。If the above-mentioned two 1″A material injection controls are performed simultaneously, the reliability of the control will be increased accordingly.

なお、調質剤の投入箇所を異にする前記３つの添加方式
はいずれによっても充分な添加投入効果が得られ、制御
上特に問題になるものはないが、その選択に当っては次
の点が考慮されるべきである。In addition, each of the above three methods of adding the conditioning agent at different points provides a sufficient addition effect, and there are no particular problems in terms of control, but when selecting one, the following points should be considered: should be taken into account.

即ち、ミル４への石炭移送ラインでの添加方式では、他
の２つの方式に比して電気集塵装ｆｆ４４８への応答（
排ガス中のｓｏ２の憎減であられれる。）が遅くなるが
、大気榮件下で添加されることにより調質剤添加１ｉ＝
４　＠　１２が簡単かつ安価なものとなる。In other words, in the method of adding coal in the coal transfer line to mill 4, the response to the electrostatic precipitator ff448 (
This is due to the decrease in SO2 in the exhaust gas. ) is delayed, but by adding it under atmospheric conditions, the tempering agent addition 1i=
4 @ 12 is simple and inexpensive.

そして、他の２つの方式、つまりミル４以降ボイラ６へ
の石炭及び燃焼空気供給ライン貿時間が短かく数秒〜数
十秒以内であシ、応答が早い利点があるが、調質剤添加
装置１２としては前記ミル４への石炭移送ラインでの添
加方式に比較して複雑、かつ高価になる。The other two methods, that is, the coal and combustion air supply line from mill 4 to boiler 6, have the advantage of short trading times, ranging from several seconds to several tens of seconds, and quick response; 12 is more complicated and expensive than the method of adding coal to the mill 4 in the coal transfer line.

本発明は以上の構成よりなり、カルシウム系調質剤を適
正量投入できるヵ１ら、ボイラ排ガス中のフライアッシ
ュの電気抵抗値を下げることができ、かつ電気集塵装置
の電気的な荷箪特性を改善しバックコロナ現象の発生を
防止するととができ、もって集塵性能の向上を７ケ実に
図ることができると共に、湿式脱硫装置の負荷増大を最
小限に抑えることができる０ よって本発明によれば、簡単な構成をもって排ガス処理
役備の高性能化が計ることができるのである。The present invention has the above-mentioned configuration, and since it is possible to introduce an appropriate amount of calcium-based conditioning agent, it is possible to lower the electrical resistance value of fly ash in boiler exhaust gas, and it is also possible to reduce the electrical resistance of fly ash in the boiler exhaust gas, and to reduce the electrical resistance of the electrostatic precipitator. It is possible to improve the characteristics and prevent the occurrence of the back corona phenomenon, thereby making it possible to improve the dust collection performance by 7 points, and also to minimize the increase in load on the wet desulfurization equipment.Thus, the present invention According to this, it is possible to improve the performance of exhaust gas treatment equipment with a simple configuration.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は電気集塵装置醒の集塵効率と調質剤添加比との
関係を示す曲線図、牙２図は雨；気集塵装置からの排ガ
ス中の５Ｏ２ａ度と調質剤添加比との関係を示す曲線図
、第３図は調質剤投入量の制御系２示す系統図、第４図
は本発明方法の実施に使用した装置例を示す概妥図であ
る。Figure 1 is a curve diagram showing the relationship between the dust collection efficiency of the electrostatic precipitator and the addition ratio of the conditioning agent, and Figure 2 is the curve showing the relationship between the dust collection efficiency of the electrostatic precipitator and the addition ratio of the conditioning agent. FIG. 3 is a system diagram showing the control system 2 for controlling the amount of conditioning agent input, and FIG. 4 is a schematic diagram showing an example of the apparatus used to carry out the method of the present invention.

Claims (2)

【特許請求の範囲】[Claims] （１）石炭ボイラから排出される排ガスを電気集塵装置
により除塵し、次いで湿式脱硫装置により脱硫する方法
において、ボイラへ又はボ濃度を測定し、この４１１」
定される煤Ｊハ峨度が所定の集μｓ効率に対応した値と
なるよう前記カルシウム系調質剤の投入−縁を制−する
ことを特徴とする石炭ボイラ排ガスの処理方法。(1) In a method in which dust is removed from the exhaust gas discharged from a coal boiler using an electrostatic precipitator, and then desulfurization is performed using a wet desulfurization device, the concentration of sulfur in the boiler is measured.
A method for treating coal boiler exhaust gas, characterized in that the addition of the calcium-based tempering agent is controlled so that the determined soot J concentration becomes a value corresponding to a predetermined collection μs efficiency. （２）石炭ボイラから排出される排ガスを電気集塵装置
によシ除塵し、次いで湿式脱硫装置により脱硫する方法
において、ボイラへ又はボ濃兜を測定し、この測定され
るｓＯ２濃度が所定の集、哨効率に対応した値となるよ
う前記カルシウム系調質剤の投入量を制御することを特
徴とする石炭ボイラ排ガスの処理方法。(2) In a method in which dust is removed from exhaust gas discharged from a coal boiler using an electrostatic precipitator, and then desulfurization is performed using a wet desulfurization device, the concentration of sO2 in the boiler or boiler is measured, and the measured sO2 concentration is A method for treating coal boiler exhaust gas, comprising controlling the amount of the calcium-based refining agent added so that the amount corresponds to the collection efficiency.