JP4524914B2

JP4524914B2 - Wet flue gas desulfurization equipment

Info

Publication number: JP4524914B2
Application number: JP2000392845A
Authority: JP
Inventors: 哲雄河村
Original assignee: IHI Corp
Current assignee: IHI Corp
Priority date: 2000-12-25
Filing date: 2000-12-25
Publication date: 2010-08-18
Anticipated expiration: 2020-12-25
Also published as: JP2002191934A

Description

【０００１】
【発明の属する技術分野】
本発明は、湿式排煙脱硫装置に関するものである。
【０００２】
【従来の技術】
一般に、発電所等においては、石炭焚ボイラ等から排出される排ガスから硫黄酸化物（ＳＯ₂等）を吸収除去するために、吸収剤として石灰石（炭酸カルシウム（ＣａＣＯ₃））を用い、石膏を回収するようにした、いわゆる石灰・石膏法による湿式排煙脱硫装置が設けられるが、近年の湿式排煙脱硫装置においては、単位スプレー液量当りの脱硫性能を高めるために、吸収塔から石膏脱水機の間のスラリーライン途中に液体サイクロンを設け、該液体サイクロンにより石膏と吸収剤としての石灰石とを分級し、吸収液中の石灰石濃度を高めることが行われている。
【０００３】
図２は従来の湿式排煙脱硫装置の一例を表わすものであって、該湿式排煙脱硫装置は、導入される排ガスに対しスプレーノズル１から吸収液２を噴霧し脱硫を行う吸収塔３と、該吸収塔３内に噴霧された吸収液２の一部が導入され、該吸収液２中に含まれる粒径の大きな石膏と石灰石とを分級し、石灰石濃度を高めたオーバーフロー液４を前記吸収塔３へ戻すために複数段（図２の例では三段）に設けられた液体サイクロン５，６，７と、第一段目の液体サイクロン５で分級され石膏濃度を高めた液８が導入され、脱水を行って石膏９を回収する石膏脱水機１０と、最終段としての第三段目の液体サイクロン７のオーバーフロー液１１が導入され、浄化処理を行う排水処理装置１２とを備えてなる構成を有している。
【０００４】
前述の如き湿式排煙脱硫装置の場合、吸収液２がスプレーノズル１から噴霧されており、図示していない石炭焚ボイラ等から排出され吸収塔３に送り込まれた排ガスは、前記スプレーノズル１から噴霧される吸収液２と接触することにより、ＳＯ₂が吸収除去された後、吸収塔３から図示していない煙突を経て大気へ放出される。
【０００５】
一方、前記排ガスからＳＯ₂を吸収した吸収液２は、図示していない酸化空気ブロワの作動によって液溜部内へ供給される酸化空気により強制的に酸化され、石膏（硫酸カルシウム（ＣａＳＯ₄））が生成され、該石膏を含む液溜部内の吸収液２の一部は、第一段目の液体サイクロン５へ抜き出され、該第一段目の液体サイクロン５において比較的粒径の大きな石膏と石灰石とが分級され、石膏濃度を高めた液８は石膏脱水機１０へ導入され、該石膏脱水機１０において脱水され、石膏９と濾液１３に分離され、石膏９は回収され、濾液１３は吸収塔３へ戻される。
【０００６】
又、前記第一段目の液体サイクロン５において比較的粒径の大きな石膏が分級されたオーバーフロー液４は、順次、第二段目の液体サイクロン６と、最終段としての第三段目の液体サイクロン７とに導入され、各液体サイクロン６，７において石灰石が分級され、石灰石濃度が高められた液１４が吸収塔３へ戻され、前記最終段の液体サイクロン７のオーバーフロー液１１は、排水処理装置１２へ導入され、該排水処理装置１２において浄化処理され排出される。
【０００７】
【発明が解決しようとする課題】
しかしながら、前述の如き従来の湿式排煙脱硫装置の場合、煤塵等の脱硫プロセスにとって好ましくない不純物は、粒径が小さい等の理由により、液体サイクロン５，６，７において石灰石と充分に選択分離することができず、石灰石分級側に同伴されてしまい、その結果、吸収液系で不純物が濃縮し、その比率が高くなり、
▲１▼吸収液系機器の摩耗
▲２▼脱硫性能の低下
▲３▼吸収塔３内での泡の発生による液面制御不能
等のトラブル発生の要因となっていた。
【０００８】
又、最終段の液体サイクロン７のオーバーフロー液１１の固形分濃度はおよそ１〜２［％］と高く、これには微細な石膏、石灰石等が比率的に多く含まれ、これを脱硫排水処理する従来のケースでは、排水処理装置１２における固形分処理の負担が大きくなるという欠点を有していた。
【０００９】
本発明は、斯かる実情に鑑み、吸収液系で不純物が濃縮することを回避し得、吸収液系機器の摩耗、脱硫性能の低下、吸収塔内での泡の発生による液面制御不能等のトラブル発生を防止し得、且つ排水処理における固形分処理の負担を大きく軽減し得る湿式排煙脱硫装置を提供しようとするものである。
【００１０】
【課題を解決するための手段】
本発明は、吸収剤として石灰石を用い、石膏を回収するようにした湿式排煙脱硫装置であって、
導入される排ガスに吸収液を噴霧し脱硫を行う吸収塔と、
該吸収塔内に噴霧された吸収液の一部が導入され、該吸収液中に含まれる粒径の大きな石膏と石灰石とを分級する液体サイクロンと、
該液体サイクロンで分級され石灰石濃度を高めたオーバーフロー液の全部又は一部が導入され、該オーバーフロー液中に含まれる石膏及び石灰石と不純物とを分離し、石灰石濃度を高めた沈降液を前記吸収塔へ戻す沈降分離装置と、
前記液体サイクロンで分級され石膏濃度を高めた液及び前記沈降分離装置で分離された不純物含有液が導入され、脱水を行って石膏を回収する石膏脱水機と、
該石膏脱水機の濾液の一部が導入され、浄化処理を行う排水処理装置と
を備えたことを特徴とする湿式排煙脱硫装置にかかるものである。
【００１１】
上記手段によれば、以下のような作用が得られる。
【００１２】
吸収塔において、導入される排ガスに吸収液が噴霧され脱硫が行われ、該吸収塔内に噴霧された吸収液の一部が液体サイクロンへ導入され、該液体サイクロンにおいて、吸収液中に含まれる粒径の大きな石膏と石灰石とが分級され、石灰石濃度を高めたオーバーフロー液の全部又は一部が沈降分離装置へ導入され、該沈降分離装置において、前記液体サイクロンのオーバーフロー液中に含まれる石膏及び石灰石と不純物とが分離され、石灰石濃度を高めた沈降液が前記吸収塔へ戻され、前記液体サイクロンで分級され石膏濃度を高めた液及び前記沈降分離装置で分離された不純物含有液が石膏脱水機へ導入され、該石膏脱水機において脱水が行われて石膏が回収され、前記石膏脱水機の濾液の一部が排水処理装置へ導入され、該排水処理装置において浄化処理が行われる。
【００１３】
この結果、煤塵等の脱硫プロセスにとって好ましくない不純物は、沈降分離装置において石膏及び石灰石と充分に選択分離することが可能となり、石灰石分級側に同伴されてしまうことが避けられるため、吸収液系で不純物が濃縮してその比率が高くなる心配がなくなり、吸収液系機器の摩耗が防止され、脱硫性能が向上し、且つ吸収塔内での泡の発生が抑えられ液面制御が円滑に行われる。
【００１４】
更に、前記石膏脱水機の濾液の一部を排水処理装置へ導入するようにしたことにより、排水中の固形分濃度が低下し、排水処理における固形分処理の負担が大幅に軽くなる。
【００１５】
【発明の実施の形態】
以下、本発明の実施の形態を図示例と共に説明する。
【００１６】
図１は本発明を実施する形態の一例であって、図中、図２と同一の符号を付した部分は同一物を表わしており、液体サイクロン５において、吸収塔３から導入される吸収液２中に含まれる粒径の大きな石膏と石灰石とを分級すると共に、前記液体サイクロン５で石灰石濃度を高めたオーバーフロー液４の全部又は一部をシックナや沈降分離槽等の沈降分離装置１５へ導入し、該沈降分離装置１５において、前記オーバーフロー液４中に含まれる石膏及び石灰石と不純物とを分離し、石灰石濃度を高めた沈降液１６を前記吸収塔３へ戻すようにし、又、前記液体サイクロン５で分級され石膏濃度を高めた液８及び前記沈降分離装置１５で分離された不純物含有液１７を脱水機供給タンク１８を介して石膏脱水機１０へ導入し、該石膏脱水機１０において脱水を行って石膏９を回収するようにし、更に、前記石膏脱水機１０の濾液１９の一部を排水処理装置１２へ導入し、該排水処理装置１２において浄化処理を行うようにしたものである。尚、前記オーバーフロー液４の一部を沈降分離装置１５へ導入する場合、残りのオーバーフロー液４は吸収塔３へ戻すようにしてある。
【００１７】
前記沈降分離装置１５における不純物の分離は、液性状並びに運転状況に応じて、沈降分離装置１５のオーバーフロー液１７ａ、或いは固形分圧密層の上部即ち中間層における液１７ｂのうち少なくとも一方から不純物の比率が高い液を不純物含有液１７として抜き出し、該不純物含有液１７の全部又は一部を脱水機供給タンク１８へ導入するようにしてある。尚、前記不純物含有液１７の一部を脱水機供給タンク１８へ導入する場合、残りの不純物含有液１７は吸収塔３へ戻すようにしてある。
【００１８】
前記石膏脱水機１０は、所要間隔をあけて回転可能に配置されたガイドロール２０間に無端状のベルトフィルタ２１を掛け回し、該ベルトフィルタ２１をガイドロール２０の回転駆動により所要方向へ移動させ、且つ図示していない真空ポンプの作動によりベルトフィルタ２１の下面側を負圧に保持した状態で、該ベルトフィルタ２１上の上流側所要位置に脱水機供給タンク１８からの石膏濃度を高めた液８及び不純物含有液１７を流下させることにより、脱水を行い、石膏９と濾液１９に分離するようにしてあり、前記真空ポンプの作動により石膏９と分離した濾液１９は、塩素濃度が高いため、石膏脱水機濾液槽２２の区画壁２３で分割された高塩素濃度濾液貯留部２２ａへ導入し、該高塩素濃度濾液貯留部２２ａから排水処理装置１２へ導入するようにしてある。又、前記石膏脱水機１０のベルトフィルタ２１上の下流側所要位置には、工業用水等の洗浄水２４を流下させると共に、前記真空ポンプの作動によりベルトフィルタ２１の下面側を負圧に保持することにより、脱水された石膏９を洗浄し、且つ該石膏９を洗浄した後の塩素分が希釈された濾液２５を、石膏脱水機濾液槽２２の区画壁２６で分割された塩素分希釈濾液貯留部２２ｂへ導入し、該塩素分希釈濾液貯留部２２ｂから吸収塔３へ戻すようにしてある。
【００１９】
尚、前記吸収塔３から抜き出され液体サイクロン５で分級されたオーバーフロー液４は、ｐＨがおよそ５〜５．５程度であるが、該オーバーフロー液４に対し苛性ソーダ等の中和剤を添加し、そのｐＨをおよそ７程度まで上昇させ、水酸化物を形成させることにより、オーバーフロー液４に含まれる石膏及び石灰石と不純物との分離効果を高めたり、或いは、前記オーバーフロー液４に対し、例えば、アニオン系やカチオン系等の凝集剤を添加し、石膏及び石灰石を選択的に凝集させることにより、オーバーフロー液４に含まれる石膏及び石灰石と不純物との分離効果を高めたりするようにしてもよい。
【００２０】
次に、上記図示例の作動を説明する。
【００２１】
図１に示す湿式排煙脱硫装置の場合、従来と同様、吸収液２がスプレーノズル１から噴霧されており、図示していない石炭焚ボイラ等から排出され吸収塔３に送り込まれた排ガスは、前記スプレーノズル１から噴霧される吸収液２と接触することにより、ＳＯ₂が吸収除去された後、吸収塔３から図示していない煙突を経て大気へ放出される一方、前記排ガスからＳＯ₂を吸収した吸収液２は、図示していない酸化空気ブロワの作動によって液溜部内へ供給される酸化空気により強制的に酸化され、石膏（硫酸カルシウム（ＣａＳＯ₄））が生成されるが、該石膏を含む液溜部内の吸収液２の一部は、液体サイクロン５へ抜き出され、該液体サイクロン５において比較的粒径の大きな石膏と石灰石とが分級され、石灰石濃度を高めたオーバーフロー液４は吸収塔３へ戻されると共に、前記液体サイクロン５のオーバーフロー液４の一部は沈降分離装置１５へ導入され、該沈降分離装置１５において、前記オーバーフロー液４中に含まれる石膏及び石灰石と不純物とが分離され、石灰石濃度を高めた沈降液１６が前記吸収塔３へ戻される。
【００２２】
前記液体サイクロン５で分級され石膏濃度を高めた液８及び前記沈降分離装置１５で分離された不純物含有液１７の全部又は一部は、脱水機供給タンク１８を介して石膏脱水機１０へ導入され、該石膏脱水機１０において脱水が行われて石膏９が回収される。尚、回収される石膏９には不純物が含まれることとなるが、石膏９の量に対して不純物の量は微々たるものであるため、石膏９の純度に影響を及ぼす心配はない。
【００２３】
前記石膏脱水機１０の濾液１９は、石膏脱水機濾液槽２２の区画壁２３で分割された高塩素濃度濾液貯留部２２ａへ導入され、該高塩素濃度濾液貯留部２２ａから排水処理装置１２へ導入され、該排水処理装置１２において浄化処理が行われる。
【００２４】
尚、前記石膏脱水機１０で脱水された石膏９は、工業用水等の洗浄水２４によって洗浄された後、更に脱水されて回収されるが、該石膏９を洗浄した後の塩素分が希釈された濾液２５は、石膏脱水機濾液槽２２の塩素分希釈濾液貯留部２２ｂへ導入され、該塩素分希釈濾液貯留部２２ｂから吸収塔３へ戻される。
【００２５】
この結果、煤塵等の脱硫プロセスにとって好ましくない不純物は、沈降分離装置１５において石膏及び石灰石と充分に選択分離することが可能となり、石灰石分級側に同伴されてしまうことが避けられるため、吸収液系で不純物が濃縮してその比率が高くなる心配がなくなり、吸収液系機器の摩耗が防止され、脱硫性能が向上し、且つ吸収塔３内での泡の発生が抑えられ液面制御が円滑に行われる。
【００２６】
更に、前記石膏脱水機１０の濾液１９を高塩素濃度濾液貯留部２２ａを介して排水処理装置１２へ導入するようにしたことにより、排水中の固形分濃度がおよそ０．１〜０．３［％］程度に低下し、排水処理における固形分処理の負担が大幅に軽くなる。
【００２７】
こうして、吸収液系で不純物が濃縮することを回避し得、吸収液系機器の摩耗、脱硫性能の低下、吸収塔３内での泡の発生による液面制御不能等のトラブル発生を防止し得、且つ排水処理における固形分処理の負担を大きく軽減し得る。
【００２８】
尚、本発明の湿式排煙脱硫装置は、上述の図示例にのみ限定されるものではなく、本発明の要旨を逸脱しない範囲内において種々変更を加え得ることは勿論である。
【００２９】
【発明の効果】
以上、説明したように本発明の湿式排煙脱硫装置によれば、吸収液系で不純物が濃縮することを回避し得、吸収液系機器の摩耗、脱硫性能の低下、吸収塔内での泡の発生による液面制御不能等のトラブル発生を防止し得、且つ排水処理における固形分処理の負担を大きく軽減し得るという優れた効果を奏し得る。
【図面の簡単な説明】
【図１】本発明を実施する形態の一例の概要構成図である。
【図２】従来例の概要構成図である。
【符号の説明】
２吸収液
３吸収塔
４オーバーフロー液
５液体サイクロン
８石膏濃度を高めた液
９石膏
１０石膏脱水機
１２排水処理装置
１５沈降分離装置
１６沈降液
１７不純物含有液
１９濾液[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wet flue gas desulfurization apparatus.
[0002]
[Prior art]
Generally, in power plants, limestone (calcium carbonate (CaCO ₃ )) is used as an absorbent in order to absorb and remove sulfur oxides (SO ₂ etc.) from exhaust gas discharged from coal fired boilers, etc. A so-called lime / gypsum method wet flue gas desulfurization device is installed, but in recent wet flue gas desulfurization devices, in order to improve the desulfurization performance per unit spray liquid volume, gypsum dewatering is performed. A liquid cyclone is provided in the middle of a slurry line between machines, and gypsum and limestone as an absorbent are classified by the liquid cyclone to increase the concentration of limestone in the absorbent.
[0003]
FIG. 2 shows an example of a conventional wet flue gas desulfurization apparatus. The wet flue gas desulfurization apparatus includes an absorption tower 3 for performing desulfurization by spraying an absorbing liquid 2 from a spray nozzle 1 on exhaust gas to be introduced. A part of the absorption liquid 2 sprayed into the absorption tower 3 is introduced, the gypsum having a large particle size contained in the absorption liquid 2 and limestone are classified, and the overflow liquid 4 having an increased limestone concentration is obtained as described above. Liquid cyclones 5, 6, and 7 provided in a plurality of stages (three stages in the example of FIG. 2) to return to the absorption tower 3 and a liquid 8 that has been classified by the first stage liquid cyclone 5 to increase the gypsum concentration are provided. A gypsum dehydrator 10 that is introduced and collects gypsum 9 by dehydration, and a drainage treatment device 12 that introduces the overflow liquid 11 of the third-stage liquid cyclone 7 as a final stage and performs a purification process are provided. It has the composition which becomes.
[0004]
In the case of the wet flue gas desulfurization apparatus as described above, the absorbing liquid 2 is sprayed from the spray nozzle 1, and the exhaust gas discharged from a coal fired boiler or the like (not shown) and sent to the absorption tower 3 is discharged from the spray nozzle 1. The SO ₂ is absorbed and removed by contact with the sprayed absorption liquid 2, and then released from the absorption tower 3 to the atmosphere through a chimney (not shown).
[0005]
On the other hand, the absorbing liquid 2 that has absorbed SO ₂ from the exhaust gas is forcibly oxidized by the oxidizing air supplied into the liquid reservoir by the operation of an oxidizing air blower (not shown), and gypsum (calcium sulfate (CaSO ₄ )). A part of the absorbing liquid 2 in the liquid reservoir containing the gypsum is extracted to the first-stage liquid cyclone 5, and the first-stage liquid cyclone 5 has a relatively large particle size. And the limestone are classified, and the liquid 8 having an increased gypsum concentration is introduced into the gypsum dewatering machine 10, dehydrated in the gypsum dewatering machine 10, separated into gypsum 9 and the filtrate 13, the gypsum 9 is recovered, and the filtrate 13 is Returned to the absorption tower 3.
[0006]
The overflow liquid 4 obtained by classifying gypsum having a relatively large particle size in the first-stage liquid cyclone 5 is sequentially supplied to the second-stage liquid cyclone 6 and the third-stage liquid as the final stage. The liquid 14 introduced into the cyclone 7, in which the limestone is classified in each liquid cyclone 6, 7 and the concentration of limestone is increased is returned to the absorption tower 3, and the overflow liquid 11 of the liquid cyclone 7 in the final stage is treated as a wastewater treatment. It is introduced into the apparatus 12, purified and discharged in the waste water treatment apparatus 12.
[0007]
[Problems to be solved by the invention]
However, in the case of the conventional wet flue gas desulfurization apparatus as described above, impurities which are not preferable for the desulfurization process such as soot dust are sufficiently selectively separated from limestone in the liquid cyclones 5, 6 and 7 due to the small particle size and the like. Cannot be entrained on the limestone classification side, and as a result, the impurities are concentrated in the absorbent system, and the ratio increases.
(1) Wear of absorption liquid system equipment (2) Decrease in desulfurization performance (3) It was a cause of troubles such as inability to control the liquid level due to generation of bubbles in the absorption tower 3.
[0008]
In addition, the solid content concentration of the overflow liquid 11 of the last-stage hydrocyclone 7 is as high as about 1 to 2 [%], and this contains a relatively large amount of fine gypsum, limestone, etc., and this is subjected to desulfurization drainage treatment. In the conventional case, there was a disadvantage that the burden of solid content processing in the waste water treatment device 12 was increased.
[0009]
In view of such circumstances, the present invention can avoid the concentration of impurities in the absorption liquid system, wear of the absorption liquid system equipment, degradation of desulfurization performance, inability to control the liquid level due to generation of bubbles in the absorption tower, etc. It is an object of the present invention to provide a wet flue gas desulfurization apparatus that can prevent the occurrence of trouble and can greatly reduce the burden of solid content treatment in wastewater treatment.
[0010]
[Means for Solving the Problems]
The present invention is a wet flue gas desulfurization apparatus using limestone as an absorbent and recovering gypsum,
An absorption tower for performing desulfurization by spraying an absorption liquid on the introduced exhaust gas;
A liquid cyclone for classifying gypsum and limestone having a large particle size contained in the absorption liquid, wherein a part of the absorption liquid sprayed into the absorption tower is introduced;
All or part of the overflow liquid classified by the liquid cyclone and having an increased limestone concentration is introduced, gypsum and limestone contained in the overflow liquid are separated from impurities, and the sedimented liquid having an increased limestone concentration is used as the absorption tower. A settling separator to return to
A gypsum dewatering machine that introduces a liquid classified with the liquid cyclone to increase the gypsum concentration and an impurity-containing liquid separated by the sedimentation separator, collects gypsum by dehydration, and
The present invention relates to a wet flue gas desulfurization apparatus comprising a waste water treatment apparatus in which a part of the filtrate of the gypsum dehydrator is introduced and performs purification treatment.
[0011]
According to the above means, the following operation can be obtained.
[0012]
In the absorption tower, the absorption liquid is sprayed on the introduced exhaust gas and desulfurization is performed, and a part of the absorption liquid sprayed in the absorption tower is introduced into the liquid cyclone, and is contained in the absorption liquid in the liquid cyclone. Gypsum having a large particle size and limestone are classified, and all or a part of the overflow liquid having an increased limestone concentration is introduced into the sedimentation separator, and in the sedimentation separator, gypsum contained in the liquid cyclone overflow liquid and Limestone and impurities are separated, the sedimented liquid with increased limestone concentration is returned to the absorption tower, the liquid with the gypsum concentration classified by the liquid cyclone and the impurity-containing liquid separated with the sedimentation separator are gypsum dehydrated The gypsum dehydrator performs dehydration and collects gypsum, and a part of the filtrate of the gypsum dehydrator is introduced into the waste water treatment device. Oite purification process is carried out.
[0013]
As a result, impurities that are undesirable for the desulfurization process such as soot dust can be sufficiently selectively separated from gypsum and limestone in the sedimentation separator, and are not accompanied by the limestone classification side. Concentration of impurities is eliminated and there is no need to increase the ratio, wear of the absorption liquid system equipment is prevented, desulfurization performance is improved, generation of bubbles in the absorption tower is suppressed, and liquid level control is performed smoothly. .
[0014]
Furthermore, by introducing a part of the filtrate of the gypsum dewatering machine into the wastewater treatment device, the solid content concentration in the wastewater is lowered, and the burden of the solid content treatment in the wastewater treatment is greatly reduced.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is an example of an embodiment for carrying out the present invention. In the figure, the parts denoted by the same reference numerals as those in FIG. 2 represent the same thing, and an absorption liquid introduced from an absorption tower 3 in a liquid cyclone 5. 2 classifies gypsum and limestone having a large particle size, and introduces all or part of the overflow liquid 4 having a limestone concentration increased by the liquid cyclone 5 into a sedimentation separation device 15 such as a thickener or a sedimentation separation tank. In the sedimentation separation device 15, gypsum and limestone contained in the overflow liquid 4 are separated from impurities, and the sedimentation liquid 16 having an increased limestone concentration is returned to the absorption tower 3, and the liquid cyclone The liquid 8 classified at 5 and having the gypsum concentration increased and the impurity-containing liquid 17 separated by the sedimentation separator 15 are introduced into the gypsum dehydrator 10 via the dehydrator supply tank 18, and the gypsum dehydrator 10 In addition, the gypsum 9 is recovered by dehydration, and a part of the filtrate 19 of the gypsum dewatering machine 10 is introduced into the waste water treatment device 12, and the waste water treatment device 12 performs the purification treatment. It is. When a part of the overflow liquid 4 is introduced into the sedimentation separator 15, the remaining overflow liquid 4 is returned to the absorption tower 3.
[0017]
The separation of impurities in the sedimentation separator 15 is the ratio of impurities from at least one of the overflow liquid 17a of the sedimentation separator 15 or the liquid 17b in the upper part of the solid content consolidated layer, that is, the intermediate layer, depending on the liquid properties and operating conditions. Is extracted as the impurity-containing liquid 17 and all or part of the impurity-containing liquid 17 is introduced into the dehydrator supply tank 18. When a part of the impurity-containing liquid 17 is introduced into the dehydrator supply tank 18, the remaining impurity-containing liquid 17 is returned to the absorption tower 3.
[0018]
The gypsum dewatering machine 10 hangs an endless belt filter 21 between guide rolls 20 rotatably arranged at a predetermined interval, and moves the belt filter 21 in a required direction by rotational driving of the guide roll 20. And the liquid which increased the gypsum density | concentration from the dehydrator supply tank 18 to the upstream required position on this belt filter 21 in the state which kept the lower surface side of the belt filter 21 to the negative pressure by the action | operation of the vacuum pump which is not shown in figure. 8 and the impurity-containing liquid 17 are allowed to flow down to separate the gypsum 9 and the filtrate 19, and the filtrate 19 separated from the gypsum 9 by the operation of the vacuum pump has a high chlorine concentration. It introduce | transduces into the high chlorine concentration filtrate storage part 22a divided | segmented by the partition wall 23 of the gypsum dehydrator filtrate tank 22, and the waste water treatment apparatus 12 from this high chlorine concentration filtrate storage part 22a. It is to be introduced. Further, cleaning water 24 such as industrial water is allowed to flow down to a required position on the downstream side of the belt filter 21 of the gypsum dewatering machine 10, and the lower surface side of the belt filter 21 is held at a negative pressure by the operation of the vacuum pump. Thus, the dehydrated gypsum 9 is washed, and the filtrate 25 in which the chlorine content after the gypsum 9 is washed is diluted with the chlorine-diluted filtrate stored in the partition wall 26 of the gypsum dehydrator filtrate tank 22. It introduce | transduces into the part 22b, and is made to return to the absorption tower 3 from this chlorine content diluted filtrate storage part 22b.
[0019]
The overflow liquid 4 extracted from the absorption tower 3 and classified by the liquid cyclone 5 has a pH of about 5 to 5.5. A neutralizing agent such as caustic soda is added to the overflow liquid 4. , By raising the pH to about 7 and forming a hydroxide, the effect of separating the gypsum and limestone contained in the overflow liquid 4 and impurities from impurities, or the overflow liquid 4 is, for example, An anionic or cationic flocculant may be added to selectively agglomerate gypsum and limestone, thereby enhancing the separation effect between gypsum and limestone contained in the overflow liquid 4 and impurities.
[0020]
Next, the operation of the illustrated example will be described.
[0021]
In the case of the wet flue gas desulfurization apparatus shown in FIG. 1, the absorption liquid 2 is sprayed from the spray nozzle 1 as in the prior art, and the exhaust gas discharged from a coal fired boiler or the like (not shown) and sent to the absorption tower 3 is by contact with the absorption liquid 2 to be sprayed from the spray nozzle 1, after the SO ₂ is absorbed and removed, while being discharged to the atmosphere through a chimney (not shown) from the absorption tower 3, the SO ₂ from the flue gas The absorbed liquid 2 that has been absorbed is forcibly oxidized by oxidized air supplied into the liquid reservoir by the operation of an oxidized air blower (not shown) to produce gypsum (calcium sulfate (CaSO ₄ )). A part of the absorbing liquid 2 in the liquid reservoir containing water is extracted into the liquid cyclone 5 where gypsum and limestone having a relatively large particle size are classified in the liquid cyclone 5 to increase the limestone concentration. The raw liquid 4 is returned to the absorption tower 3, and a part of the overflow liquid 4 of the hydrocyclone 5 is introduced into the sedimentation separator 15, where gypsum and limestone contained in the overflow liquid 4 are introduced. And the impurities are separated, and the sediment 16 having an increased limestone concentration is returned to the absorption tower 3.
[0022]
All or a part of the liquid 8 classified by the hydrocyclone 5 and having a higher gypsum concentration and the impurity-containing liquid 17 separated by the sedimentation separator 15 are introduced into the gypsum dehydrator 10 via a dehydrator supply tank 18. The gypsum dehydrator 10 performs dehydration and collects the gypsum 9. The recovered gypsum 9 contains impurities, but since the amount of impurities is insignificant with respect to the amount of gypsum 9, there is no concern of affecting the purity of the gypsum 9.
[0023]
The filtrate 19 of the gypsum dewatering machine 10 is introduced into the high chlorine concentration filtrate storage part 22a divided by the partition wall 23 of the gypsum dewatering machine filtrate tank 22, and is introduced from the high chlorine concentration filtrate storage part 22a into the waste water treatment device 12. Then, the purification treatment is performed in the waste water treatment apparatus 12.
[0024]
The gypsum 9 dehydrated by the gypsum dewatering machine 10 is washed with washing water 24 such as industrial water, and then further dehydrated and recovered. However, the chlorine content after washing the gypsum 9 is diluted. The filtrate 25 is introduced into the chlorine-diluted filtrate storage part 22b of the gypsum dewatering machine filtrate tank 22 and returned to the absorption tower 3 from the chlorine-diluted filtrate storage part 22b.
[0025]
As a result, impurities that are undesirable for the desulfurization process such as soot dust can be sufficiently selectively separated from the gypsum and limestone in the sedimentation separator 15 and are not accompanied by the limestone classification side. Concentration of impurities and the ratio will not be increased, wear of the absorption liquid equipment will be prevented, desulfurization performance will be improved, and generation of bubbles in the absorption tower 3 will be suppressed, and liquid level control will be smooth. Done.
[0026]
Furthermore, by introducing the filtrate 19 of the gypsum dewatering machine 10 into the waste water treatment device 12 via the high chlorine concentration filtrate storage part 22a, the solid content concentration in the waste water is about 0.1 to 0.3 [ %], And the burden of solid content treatment in wastewater treatment is significantly reduced.
[0027]
In this way, it is possible to avoid the concentration of impurities in the absorption liquid system, and it is possible to prevent troubles such as wear of the absorption liquid system equipment, deterioration of the desulfurization performance, and inability to control the liquid level due to the generation of bubbles in the absorption tower 3. In addition, the burden of solid content processing in wastewater treatment can be greatly reduced.
[0028]
In addition, the wet flue gas desulfurization apparatus of the present invention is not limited to the illustrated example described above, and it is needless to say that various modifications can be made without departing from the gist of the present invention.
[0029]
【The invention's effect】
As described above, according to the wet flue gas desulfurization apparatus of the present invention, it is possible to avoid the concentration of impurities in the absorption liquid system, wear of the absorption liquid system equipment, a decrease in desulfurization performance, and bubbles in the absorption tower. It is possible to prevent the occurrence of trouble such as inability to control the liquid level due to the occurrence of water, and to achieve an excellent effect of greatly reducing the burden of solid content processing in wastewater treatment.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an example of an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of a conventional example.
[Explanation of symbols]
2 Absorption liquid 3 Absorption tower 4 Overflow liquid 5 Liquid cyclone 8 Liquid with increased gypsum concentration 9 Gypsum 10 Gypsum dewatering machine 12 Wastewater treatment device 15 Sedimentation separation device 16 Sedimentation liquid 17 Impurity-containing liquid 19 Filtrate

Claims

A wet flue gas desulfurization device that uses limestone as an absorbent and collects gypsum,
An absorption tower for performing desulfurization by spraying an absorption liquid on the introduced exhaust gas;
A liquid cyclone for classifying gypsum and limestone having a large particle size contained in the absorption liquid, wherein a part of the absorption liquid sprayed into the absorption tower is introduced;
All or part of the overflow liquid classified by the liquid cyclone and having an increased limestone concentration is introduced, gypsum and limestone contained in the overflow liquid are separated from impurities, and the sedimented liquid having an increased limestone concentration is used as the absorption tower. A settling separator to return to
A gypsum dewatering machine that introduces a liquid classified with the liquid cyclone to increase the gypsum concentration and an impurity-containing liquid separated by the sedimentation separator, collects gypsum by dehydration, and
A wet flue gas desulfurization apparatus comprising a waste water treatment apparatus in which a part of the filtrate of the gypsum dehydrator is introduced to perform purification treatment.