JP4142788B2

JP4142788B2 - Sludge treatment system

Info

Publication number: JP4142788B2
Application number: JP01081899A
Authority: JP
Inventors: 内恭三河; 手勝記井; 村恵二朗安; 藤信佐
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 1999-01-19
Filing date: 1999-01-19
Publication date: 2008-09-03
Anticipated expiration: 2019-01-19
Also published as: JP2000202495A

Description

【０００１】
【発明の属する技術分野】
本発明は下水処理施設、浄化槽施設等の排水の生物処理施設で発生する汚泥を処理する汚泥処理システムに係り、特に脱水装置と焼却炉とを有する汚泥処理システムに関する。
【０００２】
【従来の技術】
従来の汚泥処理システムの一例を図１１に示す。図１１において、生物処理施設で発生する汚泥が濃縮槽１内で沈降濃縮され、濃縮槽１の濃縮汚泥は脱水装置２で機械脱水され、その後脱水汚泥は焼却炉３で焼却される。図１１に示す汚泥処理脱水システムでは、脱水装置２からの脱水汚泥の含水率は８０％前後であり、焼却炉３で自燃することはない。このため焼却炉３において多量の補助燃料を必要とし、また焼却炉３内の温度が不安定になり排ガス処理が複雑になる。
【０００３】
【発明が解決しようとする課題】
上述のように、焼却炉３内では汚泥が自燃することはなく、このため多量の補助燃料を必要とし、かつ焼却炉３内の温度が不安定となる。
【０００４】
本発明はこのような点を考慮してなされたものであり、焼却炉において脱水汚泥を確実に自燃することができる汚泥処理システムを提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明は、汚泥を脱水する脱水装置と、脱水装置により脱水された汚泥を焼却する焼却炉と、脱水装置の入口側に設けられ、汚泥中の固形分濃度と有機物濃度を測定する検出器と、この検出器からの測定値に基づいて有機物濃度／固形分濃度の比率を求め、この比率から汚泥の自燃含水率を求める自燃含水率演算装置と、自燃含水率演算装置で求めた自燃含水率に基づいて脱水装置を制御する制御装置と、を備えたことを特徴とする汚泥処理システム、
汚泥を脱水する機械脱水装置と、機械脱水装置の出口側に設けられた加熱脱水装置と、加熱脱水装置により脱水された汚泥を焼却する焼却炉と、機械脱水装置の入口側に設けられ、汚泥中の固形分濃度と有機物濃度を測定する検出器と、この検出器からの測定値に基づいて有機物濃度／固形分濃度の比率を求め、この比率から汚泥自燃含水率を求める自燃含水率演算装置と、自燃含水率演算装置で求めた自燃含水率に基づいて機械脱水装置と加熱脱水装置の合計脱水コストを最小とする機械脱水装置出口側の中間含水率を求める中間含水率演算装置と、自燃含水率演算装置で求めた自燃含水率に基づいて加熱脱水装置を制御する第１制御装置と、中間含水率演算装置で求めた中間含水率に基づいて機械脱水装置を制御する第２制御装置と、を備えたことを特徴とする汚泥処理システム、および
汚泥を脱水する機械脱水装置と、機械脱水装置の出口側に設けられた加熱脱水装置と、加熱脱水装置により脱水された汚泥を焼却する焼却炉と、加熱脱水装置の入口側と出口側とを接続するバイパスラインと、バイパスラインへのバイパス流量を調整するバイパス調整装置と、機械脱水装置の入口側に設けられ、汚泥中の固形分濃度と有機物濃度を測定する検出器と、この検出器からの測定値に基づいて有機物濃度／固形分濃度の比率を求め、この比率から汚泥自燃含水率を求める自燃含水率演算装置と、機械脱水装置の出口側および加熱脱水装置の出口側に各々設けられた第１含水率計および第２含水率計と、自燃含水率演算装置で求めた自燃含水率と、第１含水率計で求めた機械脱水装置の出口側の含水率と、第２含水率計で求めた加熱脱水装置の出口側の含水率とに基づいてバイパスラインへバイパスするバイパス流量比を求めるとともに、このバイパス流量比に基づいてバイパス調整装置を制御するバイパス制御装置と、を備えたことを特徴とする汚泥処理システムである。
【０００６】
本発明によれば、機械脱水装置の入口側に設けられた検出器により固形分濃度と有機物濃度を測定し、この固形分濃度と有機物濃度に基づいて自燃含水率演算装置により汚泥の自燃含水率を求める。脱水装置からの脱水汚泥の含水率が自燃含水率に基づいて調整されるため、焼却炉において汚泥を適切に焼却することができる。
【０００７】
【発明の実施の形態】
第１の実施の形態
以下、図面を参照して本発明の実施の形態について説明する。図１および図２は本発明の第１の実施の形態を示す図である。
【０００８】
図１および図２において、汚泥処理システムは濃縮汚泥を貯留する貯留槽１と、貯留槽１に配管８を介して接続され貯留槽１により貯留された濃縮汚泥を脱水する脱水装置７と、脱水装置７に配管９を介して接続され脱水装置７からの脱水汚泥を焼却する焼却炉３とを備えている。
【０００９】
また脱水装置７の入口側の配管８には、汚泥中の固形物濃度（ＴＳ）と有機物濃度（ＶＳ）を測定するＴＳ・ＶＳ検出器１０が設けられている。さらにこのＴＳ・ＶＳ検出器１０には有機物比率（有機物濃度（ＶＳ）／固形物（ＴＳ））を求めるとともに、このＶＳ／ＴＳ比率から汚泥の自燃含水率（Ａｓ）を求める自燃含水率演算装置５が接続されている。
【００１０】
また自燃含水率演算装置５には、自燃含水率（Ａｓ）に基づいて脱水装置７を制御する制御装置６が接続されている。
【００１１】
なお、図１において、脱水装置７と、自燃含水率演算装置５と、制御装置６とにより脱水システム４が構成されており、脱水装置７で脱水された脱水汚泥は焼却炉３に供給されて焼却される。また配管９には含水率（Ａｐ）を測定する含水率計１１が設けられており、この含水率計１１は制御装置６に接続されている。
次にこのような構成からなる本実施の形態の作用について説明する。
【００１２】
一般に、脱水汚泥９の有機物比率（ＶＳ／ＴＳ）と自燃含水率の関係は、図２のようになる。同一の有機物比率（ＶＳ／ＴＳ）でも、自燃含水率は焼却炉３の種類、規模によっても異なるため、あらかじめ焼却炉３のＶＳ／ＴＳと自燃含水率（Ａｓ）との関係を求めておき、配管９内の脱水汚泥の含水率（Ａｐ）を自燃含水率（Ａｓ）に保つよう制御装置６で脱水装置７を制御する。
【００１３】
脱水汚泥のＶＳ／ＴＳは排水の種類、雨水混入の有無等で変化するが通常６０〜８０％の範囲であり、自燃含水率は通常５０〜７５％程度である。熱効率の良い焼却炉（焼却炉（イ））では高い含水率で自燃し、熱効率の悪い焼却炉（焼却炉（ロ））では自燃含水率は低くなる。
【００１４】
本件発明者は、通常の脱水装置、例えば遠心脱水装置、ベルトプレス脱水装置、加熱脱水装置では配管８内の濃縮汚泥のＶＳ／ＴＳと、配管９内の脱水汚泥のＶＳ／ＴＳがほぼ等しい事を見いだした。このため配管８内の濃縮汚泥を直接または採取してＴＳ・ＶＳ検出器１０により固形物濃度（ＴＳ）と有機物濃度（ＶＳ）を測定する。
【００１５】
次に自燃含水率演算装置５により濃縮汚泥のＶＳ／ＴＳを求め、これを脱水汚泥９のＶＳ／ＴＳとして使用する。配管８内の濃縮汚泥の含水率は通常９５％程度であり、配管９内の脱水汚泥に比べて採取、測定が容易であり、迅速にＶＳ／ＴＳを求めることができる。次に自燃含水率演算装置５は汚泥のＶＳ／ＴＳから図２に示すＶＳ／ＴＳと自燃含水率との関係を用いて自燃含水率（Ａｓ）を求め、制御装置６により含水率計１１からの含水率（Ａｐ）が自燃含水率（Ａｓ）となるよう脱水装置７を制御する。
【００１６】
焼却炉３は窒素酸化物発生の抑制、ダイオキシン派生の抑制、の観点から８００℃程度で運転されて、脱水汚泥を焼却する。また焼却炉３の寿命低下防止の観点から温度変化のない安定運転が必要であるが、脱水装置７からの脱水汚泥を自燃含水率（Ａｓ）に保つことで、焼却炉３の温度上昇が抑制され、かつ燃焼不良が抑制される。このため焼却炉３の安定燃焼が可能になり、運転管理が極めて容易になる。
【００１７】
本実施の形態によれば、焼却炉３の安定燃焼が可能になり、運転管理が極めて容易になる。また自燃含水率演算装置５によりＡｓを迅速に求めることができるので、制御装置６による脱水装置７の制御周期の短縮が可能になり、脱水汚泥９の含水率の安定化が可能になる。
第２の実施の形態
次に図３および図４により本発明の第２の実施の形態について説明する。図３および図４に示す第２の実施の形態において、図１および図２に示す第１の実施の形態と同一部分には同一符号を付して詳細な説明は省略する。
【００１８】
図３および図４において、貯留槽１と焼却炉３との間に、機械脱水装置２１と加熱脱水装置２２とからなる脱水装置が配置されている。
【００１９】
この場合、機械脱水装置２１の出口側に、加熱脱水装置２２が配置されており、機械脱水装置２１と加熱脱水装置２２とは配管２５により接続され、また配管２５には含水率計２６が設けられている。
【００２０】
また図３および図４に示すように、自燃含水率演算装置５には、自燃含水率（Ａｓ）に基づいて、機械脱水装置２１と加熱脱水装置２２の合計運転コストを最小にするような機械脱水装置２１の出口側汚泥の中間含水率（配管２５内の汚泥の含水率Ａｌｓ）を求める中間含水率演算装置２４が接続されている。
【００２１】
また自燃含水率演算装置５には第１制御装置６が接続され、この第１制御装置６は自燃含水率（Ａｓ）と含水率計１１からの測定値（Ａｐ）に基づいて、加熱脱水装置２２の出口側の含水率をＡｓに保つよう加熱脱水装置２２を制御するようになっている。
【００２２】
また中間含水率演算装置２４には第２制御装置２３が接続され、この第２制御装置２３は中間含水率（Ａｌｓ）と含水率計２６からの測定値（Ａｌｐ）に基づいて、機械脱水装置２１の出口側の中間含水率をＡｌｓに保つよう機械脱水装置２１を制御するようになっている。
【００２３】
図３において、機械脱水装置２１、加熱脱水装置２２、第１制御装置６ａ、第２制御装置２３、自燃含水率演算装置５、中間含水率演算装置２４により脱水システム２０が構成される。
【００２４】
図３および図４において、まずＴＳ・ＶＳ検出器１０によりＴＳおよびＶＳが測定され、自燃含水率演算装置５において有機物比率（ＶＡ／ＴＡ）と、脱水汚泥中の自燃含水率（Ａｓ）が算出される。次に第１制御装置６ａは、配管９中の脱水汚泥の含水率（Ａｐ）がＡｓとなるよう加熱脱水装置２２の運転を制御する。
【００２５】
同時に中間含水率演算装置２４には脱水汚泥の含水率目標値Ａｓと、機械脱水装置２１の運転コストパラメータと、加熱脱水装置２２の運転コストパラメータとが入力され、この中間含水率演算装置２４により、機械脱水装置２１出口側の配管２５内の汚泥の目標含水率（中間目標含水率：Ａ１ｓ）が算出される。
【００２６】
次に第２制御装置２３により、Ａ１ｓを目標値、含水率計２６による脱水汚泥の含水率（Ａ１ｐ）をプロセス値とし、機械脱水装置２１の運転を制御する。
【００２７】
ここで図４により、配管８内の濃縮汚泥を脱水し脱水汚泥（目標含水率ＡＳ）として配管９内に送る際の中間含水率Ａ１をパラメータとした機械脱水装置２１と加熱脱水装置２２の各々の脱水コストを示す。図４において、機械脱水コストは機械脱水装置２１で配管８内の汚泥を中間含水率Ａ１まで脱水する際のコストであり、内訳は凝集剤の添加量、機械エネルギー等からなる。また加熱脱水コストは加熱脱水装置２２により含水率Ａ１の配管２５内の脱水汚泥を目標含水率Ａｓまで脱水する際のコストであり、内訳は蒸気量、機械エネルギー等からなる。このため脱水システム２０の脱水コスト（Ｙ円／ｋｇ）は機械脱水コストと加熱脱水コストとの和で表せる。
【００２８】
本件発明者が脱水システム２０の脱水コストを合計脱水コストとした求めたところ、図４に示すように中間含水率がＡ１ｓのとき極小値をもつ曲線になった。このことから中間目標含水率をＡ１ｓに設定することにより合計脱水コストが最小となることが可能となる。
【００２９】
本発明はこの知見に基づくもので、中間含水率演算装置２４で配管２５内の脱水汚泥の目標値（中間含水率目標値：Ａ１ｓ）を算出し、次にこのＡ１ｓを設定値とし、含水率計２６による配管２５内の脱水汚泥の含水率（Ａ１ｐ）をプロセス値として各々第２制御装置２３に入力する。第２制御装置２３では、公知の手法で機械脱水装置２１を操作し、配管２５内の汚泥の含水率をＡ１ｓとなるよう制御する。
【００３０】
以上のように、本実施の形態によれば焼却炉３での汚泥の安定燃焼が可能になり、同時に脱水コストの最小化が可能になる。この場合、脱水コストの低減は、凝集剤、機械エネルギー、蒸気等の最小化につながるため、環境負荷の抑制に大きく寄与する。
第３の実施の形態
次に図５乃至図８により本発明の第３の実施の形態について説明する。図５乃至図８に示す第３の実施の形態は、機械脱水装置２１として遠心脱水装置３０を用い、加熱脱水装置２２として薄膜式加熱脱水装置４０を用いたものであり、他は図３および図４に示す第２の実施の形態と略同一である。図５乃至図８に示す第３の実施の形態において、図３および図４に示す第２の実施の形態と同一部分には同一符号を付して詳細な説明は省略する。
【００３１】
図５に示すように、機械脱水装置２１は遠心脱水機３０と、凝集剤タンク３１と、凝集剤演算器３２と、凝集剤ポンプ３４と、濃縮汚泥流量計３３を有し、濃縮汚泥槽１からの配管８中の濃縮汚泥を脱水し、含水率８５％前後（７８〜９０％程度）の脱水汚泥を得て配管２５へ送るものである。配管２５中の脱水汚泥の含水率は単位固形分（ｋｇ）当たりの凝集剤の注入量（ｋｇ）、すなわち凝集剤添加率Ｂに大きく依存する。このため凝集剤演算器３２では添加率Ｂ、凝集剤濃度Ｃ１、濃縮汚泥濃度Ｃ２、流量ｑ２を入力し次式で注入量ｑ１を算出し、ポンプ３４の注入量を設定する。
【００３２】
ｑ１×Ｃ１＝Ｂ×ｑ２×Ｃ２
図６に示すように、配管２５内の脱水汚泥の含水率（中間含水率：Ａ１）は凝集剤の添加率に大きく依存し、中間含水率（Ａ１）を下げるためには添加率Ｂを上げる必要がある。通常使用されている高分子凝集剤の場合、適正中間含水率（Ａ１ｓ）を得る注入率は０．５％前後である。
【００３３】
中間含水率に影響する要因としては添加率の他に遠心脱水機３０の遠心加速度、遠心脱水機内での固形物滞留時間等があるが、いずれもコストに概略比例する。
【００３４】
ところで含水率８５％前後の脱水汚泥は、自由水の一部が残存しており、スラリー状態となっている。このため配管２５内の脱水汚泥を次工程へ移送するためにはポンプ圧送方式が可能になる。ポンプ圧送は脱水汚泥の定量供給が可能になり、臭気の漏洩防止等作業環境改善効果が大きくなる。
【００３５】
次に図７により縦型薄膜式加熱脱水装置の構成を示し、図８により縦型薄膜式加熱脱水装置の脱水コストの特性を示す。加熱脱水装置２３は縦型薄膜式加熱脱水装置４０からなっている。この縦型薄膜式加熱脱水装置４０は蒸気ジャケット４０ａを持つ円筒形の伝熱胴４１と、ブレード４２を装着した回転軸４３と、モータ４４とを有し、蒸気ジャケット４０ａに蒸気４５を供給するようになっている。配管２５内の脱水汚泥はブレード４２により伝熱胴４１の内面に引延ばされて薄膜を形成し、加熱脱水後伝熱胴４１に沿って落下し、含水率６０％前後（５０〜７０％程度）の加熱脱水汚泥４６として自然排出される。薄膜式加熱脱水装置４０は短時間に多量の脱水が可能となり、脱水の能力は回転軸の回転数（厳密にはブレード４２先端の周速度）に大きく依存する。このため配管２５内の脱水汚泥の含水率（中間含水率Ａ１）が小さい場合、回転数を大きくし脱水の能力を高める必要がある。
【００３６】
中間含水率Ａ１とブレード４２の回転数との関係は、図８に示すとおりである。適正な中間含水率（Ａ１ｓ）を与えるブレード４２の先端の周速度は１０ｍ／ｓ程度であり、この際、汚泥に加わる遠心加速度は数十Ｇ（５０〜１００Ｇ程度）である。周速度は動力コストに概略比例する。
【００３７】
ところで縦型薄膜式加熱脱水装置４０において、伝熱胴４１内での汚泥の滞留時間が数分と短くなっている（薄膜方式以外の加熱脱水設備では滞留時間は数時間である）。このため制御の際の応答が早く、また縦型のため加熱脱水汚泥４６は自然排出され、装置停止の際に伝熱胴４１内に残留しない。このため装置の停止ならびにスタートが容易である。さらに高速回転のブレード４２による汚泥への遠心加速度ならびに掻き取り作用により、加熱脱水汚泥４６はチップ状もしくは粒状となり、均質な形状を持ち、かつ含水率が均質になる。このため団塊あるいは粉末が生じることはなく、次工程の焼却炉３への移送および焼却炉３への投入の際の成形が容易である。
【００３８】
本実施の形態によれば、機械脱水装置２１および加熱脱水装置２２の停止ならびにスタートが容易となる。また加熱脱水汚泥４６はチップ状もしくは粒状となり、均質な形状を持つので含水率が均質になる。このため団塊あるいは粉末が生じることはなく、次工程の焼却炉３への移送および焼却炉３への投入の際の成形が容易となる。
第４の実施の形態
次に図９および図１０により、本発明による第４の実施の形態について説明する。第４の実施の形態は、加熱脱水装置２２の入口側と出口側とをバイパスライン５０で接続し、機械脱水装置２１の出口側と加熱脱水装置２２の出口側に各々、含水率計（第１含水率計）５５と、含水率計（第２含水率計）５５ａを設けたものである。
【００３９】
また含水率計５５，５５ａはバイパス制御装置５３に接続され、このバイパス制御装置５３において自燃含水率演算装置５からの自燃含水率と含水率計５５，５５ａからの含水率に基づいてバイパスライン５０へバイパスするバイパス流量比を求められる。またバイパス制御装置５３により、バイパスライン５０に取付けられたポンプ５６と配管２５に取付けられたポンプ５７とを制御するようになっている。この場合、ポンプ５６，５７はバイパス調整装置を構成する。またバイパスライン５０の出口側には混練機５１が設けられている。
【００４０】
第４の実施の形態において、図３および図４に示す第２の実施の形態と同一部分には同一符号を付して詳細な説明は省略する。
【００４１】
図９に示すように機械脱水装置２１と、加熱脱水装置２２と、バイパスライン５０と、混練機５１と、バイパス制御装置５３とにより脱水システム５２が構成される。またバイパスライン５０中の脱水汚泥と、加熱脱水装置２２からの脱水汚泥が混練機５１で混練され、脱水汚泥９として焼却炉３に供給される。
【００４２】
ところで機械脱水装置２１の出口側に流量計５４が設けられ、この流量計５４により配管２５内の機械脱水汚泥の流量（Ｑ）が測定される。このような流量計５４としては電磁波応用の電磁流量計が用いられるが、電磁流量計では含水率７５％程度のスラリーの流量測定が可能である。また含水率計５５としては、マイクロ波の位相差を利用するマイクロ波濃度計が用いられる。マイクロ波濃度計では上記含水率範囲のスラリーの含水率を正確にかつオンラインで測定することが可能である。
【００４３】
バイパス制御装置５３に、配管２５内の機械脱水汚泥の流量（Ｑ）および含水率（Ａ１）と、配管９内の加熱脱水汚泥の含水率（Ａ２）と、自燃含水率演算装置５からの自燃目標含水率（Ａｓ）とがパラメータとして入力される。このバイパス制御装置５３において、バイパスライン５０への流量比（ｒ１）と、加熱脱水装置２２への供給比（ｒ２）と、バイパスライン５０への流量（Ｑ１）と、加熱脱水装置２２への供給量（Ｑ２）とが下式により各々演算され、ポンプ５６，５７の流量を定める。
【００４４】
Ｑ１＝Ｑ×ｒ１
Ｑ２＝Ｑ×ｒ２
ｒ１＋ｒ２＝１
配管２５内の脱水汚泥中の固形分量は、加熱脱水装置２２およびバイパスライン５０中で減少または増加することはないので、脱水汚泥中の固形分量は加熱脱水装置２２からの汚泥中の固形分量とバイパスライン５０内の汚泥中の固形分量の和である。このため配管２５内の脱水汚泥の流量（Ｑ）および含水率（Ａ１）と、加熱脱水装置２２からの汚泥の含水率（Ａ２）と、自燃含水率（ＡＳ）とをパラメータとして、バイパス制御装置５３において次式によりｒ１（バイパスライン５０への流量比）と、ｒ２（加熱脱水設備への供給比）とが算出される。
【００４５】

図１０に自燃含水率（ＡＳ：０．６０、０．６５、０．７０の３種）に対するｒ１、ｒ２の計算例を示す。簡単のため配管２５内の脱水汚泥の含水率を０．８０（８０％）、加熱脱水装置２２からの含水率を０．４０（４０％）とした。
【００４６】
加熱脱水装置２２からの汚泥の含水率（Ａ２）が焼却炉３への自燃含水率（Ａｓ）に比べて大幅に低いような場合、焼却炉３の温度上昇トラブルが生じるが、本実施の形態によれば自燃含水率の維持が可能になる。また加熱脱水装置２２の応答に比して、バイパスライン５０のポンプ５６の応答は極めて早いので、自燃含水率（Ａｓ）の制御性を向上させることができる。
【００４７】
【発明の効果】
以上説明したように、本発明によれば、脱水汚泥の含水率を広範囲に調整可能とすることができ、かつ脱水汚泥の含水率を焼却炉での燃焼に最適な値となるように効果的に制御することができる。
【図面の簡単な説明】
【図１】本発明による汚泥処理システムの第１の実施の形態を示す構成図。
【図２】ＶＳ／ＴＳと自燃含水率との関係を示す図。
【図３】本発明による汚泥処理システムの第２の実施の形態を示す構成図。
【図４】中間含水率と脱水コストとの関係を示す図。
【図５】本発明による汚泥処理システムの第３の実施の形態を示す遠心脱水装置の構成図。
【図６】遠心脱水装置の特性図。
【図７】薄膜式加熱脱水装置の構成図。
【図８】薄膜式加熱脱水装置の特性図。
【図９】本発明による汚泥処理システムの第４の実施の形態を示す構成図。
【図１０】図９に示す汚泥処理システムの特性表を示す図。
【図１１】従来の汚泥処理システムを示す図。
【符号の説明】
１貯留槽
３焼却炉
５自燃含水率演算装置
６制御装置
６ａ第１の制御装置
７脱水装置
１０ＴＳ・ＶＳ検出器
１１，２６含水率計
２１機械脱水装置
２２加熱脱水装置
２３第２の制御装置
２４中間含水率演算装置
３０遠心脱水装置
４０縦型薄膜式加熱脱水装置
５０バイパスライン
５３バイパス制御装置
５５，５５ａ含水率計
５６，５７ポンプ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sludge treatment system for treating sludge generated in biological wastewater treatment facilities such as sewage treatment facilities and septic tank facilities, and more particularly to a sludge treatment system having a dehydrator and an incinerator.
[0002]
[Prior art]
An example of a conventional sludge treatment system is shown in FIG. In FIG. 11, sludge generated in the biological treatment facility is settled and concentrated in the concentration tank 1, the concentrated sludge in the concentration tank 1 is mechanically dehydrated by the dehydrator 2, and then the dehydrated sludge is incinerated in the incinerator 3. In the sludge treatment / dehydration system shown in FIG. 11, the moisture content of the dewatered sludge from the dewatering device 2 is around 80%, and the incinerator 3 does not burn by itself. For this reason, a large amount of auxiliary fuel is required in the incinerator 3, the temperature in the incinerator 3 becomes unstable, and the exhaust gas treatment becomes complicated.
[0003]
[Problems to be solved by the invention]
As described above, the sludge does not self-combust in the incinerator 3, so that a large amount of auxiliary fuel is required, and the temperature in the incinerator 3 becomes unstable.
[0004]
The present invention has been made in view of the above points, and an object thereof is to provide a sludge treatment system capable of reliably burning dehydrated sludge in an incinerator.
[0005]
[Means for Solving the Problems]
The present invention includes a dewatering device for dewatering sludge, an incinerator for incinerating sludge dewatered by the dewatering device, a detector that is provided on the inlet side of the dewatering device and measures the solid content concentration and the organic matter concentration in the sludge. Based on the measured value from this detector, the ratio of organic matter concentration / solid content concentration is obtained, and the self-combustion moisture content calculating device for obtaining the self-combustion moisture content of sludge from this ratio, and the self-combustion moisture content obtained by the self-combustion moisture content calculating device A sludge treatment system characterized by comprising a control device for controlling the dehydrating device based on
A mechanical dehydrator for dewatering sludge, a heating dehydrator provided on the outlet side of the mechanical dehydrator, an incinerator for incinerating sludge dehydrated by the heat dehydrator, and an inlet side of the mechanical dehydrator Detector for measuring the solid content concentration and organic matter concentration in the inside, and the ratio of the organic matter concentration / solid content concentration based on the measured value from this detector, and the self-combustion moisture content calculating device for obtaining the sludge self-combustion moisture content from this ratio An intermediate moisture content calculating device for determining an intermediate moisture content on the outlet side of the mechanical dehydrator that minimizes the total dehydration cost of the mechanical dehydrator and the heating dehydrator based on the self-burning moisture content obtained by the self-burning moisture content calculating device, A first controller that controls the heating and dehydrating device based on the self-combustion moisture content determined by the moisture content calculating device; and a second control device that controls the mechanical dehydrating device based on the intermediate moisture content determined by the intermediate moisture content calculating device. The A sludge treatment system characterized by the above, a mechanical dehydration device for dewatering sludge, a heating dehydration device provided on the outlet side of the mechanical dehydration device, an incinerator for incinerating sludge dehydrated by the heating dehydration device, A bypass line that connects the inlet side and outlet side of the heating dehydrator, a bypass adjuster that adjusts the bypass flow rate to the bypass line, and a solid content concentration and organic matter concentration in the sludge provided on the inlet side of the mechanical dehydrator , A ratio of organic substance concentration / solid content concentration based on the measured value from the detector, a self-combustion moisture content calculating device for obtaining a sludge self-combustion moisture content from the ratio, and an outlet side of the mechanical dehydrator And the first moisture content meter and the second moisture content meter provided on the outlet side of the heating and dehydrating device, the self-combustion moisture content obtained by the self-combustion moisture content calculating device, and the mechanical dehydration device obtained by the first moisture content meter. The bypass flow ratio to be bypassed to the bypass line is determined based on the moisture content on the outlet side of the water and the moisture content on the outlet side of the heating and dehydrating device determined by the second moisture meter, and the bypass adjustment is performed based on the bypass flow ratio. A sludge treatment system comprising a bypass control device for controlling the device.
[0006]
According to the present invention, the solid content concentration and the organic matter concentration are measured by the detector provided on the inlet side of the mechanical dehydrator, and the self-combustion moisture content of the sludge is determined by the self-combustion moisture content calculation device based on the solid content concentration and the organic matter concentration. Ask for. Since the moisture content of the dewatered sludge from the dehydrator is adjusted based on the self-burning moisture content, the sludge can be appropriately incinerated in the incinerator.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
First Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 are views showing a first embodiment of the present invention.
[0008]
1 and 2, the sludge treatment system includes a storage tank 1 that stores concentrated sludge, a dehydrator 7 that is connected to the storage tank 1 via a pipe 8 and dehydrates the concentrated sludge stored in the storage tank 1, and a dehydration system. An incinerator 3 is connected to the apparatus 7 via a pipe 9 and incinerates the dewatered sludge from the dewatering apparatus 7.
[0009]
A pipe 8 on the inlet side of the dehydrator 7 is provided with a TS / VS detector 10 for measuring the solid matter concentration (TS) and the organic matter concentration (VS) in the sludge. Further, the TS / VS detector 10 obtains the organic matter ratio (organic concentration (VS) / solid matter (TS)) and the self-combustion moisture content calculating device for obtaining the self-combustion moisture content (As) of the sludge from the VS / TS ratio. 5 is connected.
[0010]
The self-combustion moisture content calculating device 5 is connected to a control device 6 that controls the dehydration device 7 based on the self-combustion water content (As).
[0011]
In FIG. 1, the dehydrating device 7, the self-combustion moisture content calculating device 5, and the control device 6 constitute a dehydrating system 4. The dehydrated sludge dehydrated by the dehydrating device 7 is supplied to the incinerator 3. Incinerated. The pipe 9 is provided with a moisture content meter 11 for measuring the moisture content (Ap). The moisture content meter 11 is connected to the control device 6.
Next, the operation of the present embodiment having such a configuration will be described.
[0012]
In general, the relationship between the organic matter ratio (VS / TS) of the dehydrated sludge 9 and the self-combustion moisture content is as shown in FIG. Even with the same organic matter ratio (VS / TS), the self-combustion water content varies depending on the type and scale of the incinerator 3, so the relationship between the VS / TS of the incinerator 3 and the self-combustion water content (As) is obtained in advance. The dehydrator 7 is controlled by the controller 6 so that the moisture content (Ap) of the dewatered sludge in the pipe 9 is kept at the self-burning moisture content (As).
[0013]
The VS / TS of dewatered sludge varies depending on the type of drainage, the presence or absence of rainwater, etc., but is usually in the range of 60 to 80%, and the self-combustion moisture content is usually about 50 to 75%. An incinerator with good thermal efficiency (incinerator (b)) self-combusts at a high water content, and an incinerator with low thermal efficiency (incinerator (b)) has a low self-combustion water content.
[0014]
The present inventor has found that the VS / TS of the concentrated sludge in the pipe 8 and the VS / TS of the dewatered sludge in the pipe 9 are almost equal in a normal dewatering apparatus such as a centrifugal dewatering apparatus, a belt press dewatering apparatus, or a heating dehydrating apparatus. I found. For this reason, the concentrated sludge in the pipe 8 is directly or collected and the solids concentration (TS) and the organic matter concentration (VS) are measured by the TS / VS detector 10.
[0015]
Next, the VS / TS of the concentrated sludge is obtained by the self-combustion moisture content calculating device 5 and used as the VS / TS of the dewatered sludge 9. The moisture content of the concentrated sludge in the pipe 8 is usually about 95%, and it is easier to collect and measure than the dehydrated sludge in the pipe 9, and the VS / TS can be obtained quickly. Next, the self-combustion moisture content calculating device 5 obtains the self-combustion water content (As) from the VS / TS of the sludge using the relationship between the VS / TS and the self-combustion water content shown in FIG. The dehydrator 7 is controlled so that the water content (Ap) of the fuel becomes the self-combustion water content (As).
[0016]
The incinerator 3 is operated at about 800 ° C. from the viewpoint of suppressing generation of nitrogen oxides and suppressing dioxin derivation, and incinerates dehydrated sludge. In addition, stable operation without temperature change is necessary from the viewpoint of preventing the life of the incinerator 3 from decreasing, but by keeping the dehydrated sludge from the dehydrator 7 at a self-burning moisture content (As), the temperature rise of the incinerator 3 is suppressed. And combustion failure is suppressed. For this reason, stable combustion of the incinerator 3 becomes possible, and operation management becomes extremely easy.
[0017]
According to this embodiment, stable combustion of the incinerator 3 becomes possible, and operation management becomes extremely easy. Further, As can be obtained quickly by the self-combustion moisture content calculating device 5, the control cycle of the dewatering device 7 by the control device 6 can be shortened, and the moisture content of the dewatered sludge 9 can be stabilized.
Second embodiment Next, a second embodiment of the present invention will be described with reference to Figs. In the second embodiment shown in FIG. 3 and FIG. 4, the same parts as those in the first embodiment shown in FIG. 1 and FIG.
[0018]
In FIG. 3 and FIG. 4, a dehydrating device including a mechanical dehydrating device 21 and a heating dehydrating device 22 is disposed between the storage tank 1 and the incinerator 3.
[0019]
In this case, a heating and dehydrating device 22 is disposed on the outlet side of the mechanical dehydrating device 21, the mechanical dehydrating device 21 and the heating and dehydrating device 22 are connected by a pipe 25, and a moisture content meter 26 is provided in the pipe 25. It has been.
[0020]
As shown in FIGS. 3 and 4, the self-combustion water content calculating device 5 includes a machine that minimizes the total operation cost of the mechanical dehydration device 21 and the heating dehydration device 22 based on the self-combustion water content (As). An intermediate moisture content calculating device 24 for determining the intermediate moisture content of the outlet side sludge of the dehydrator 21 (the moisture content Als of the sludge in the pipe 25) is connected.
[0021]
The first control device 6 is connected to the self-combustion moisture content calculating device 5, and the first control device 6 is based on the self-combustion water content (As) and the measured value (Ap) from the water content meter 11. The heating and dehydrating apparatus 22 is controlled so as to keep the moisture content on the outlet side of 22 at As.
[0022]
Further, a second control device 23 is connected to the intermediate moisture content calculating device 24, and the second control device 23 is a mechanical dehydrator based on the intermediate moisture content (Als) and the measured value (Alp) from the moisture content meter 26. The mechanical dehydrator 21 is controlled so as to keep the intermediate moisture content at the outlet side of 21 at Als.
[0023]
In FIG. 3, a dehydration system 20 is configured by a mechanical dehydrator 21, a heating dehydrator 22, a first controller 6 a, a second controller 23, a self-combustion moisture content calculator 5, and an intermediate moisture content calculator 24.
[0024]
3 and 4, TS and VS are first measured by the TS / VS detector 10, and the organic matter ratio (VA / TA) and the self-combustion water content (As) in the dewatered sludge are calculated by the self-combustion water content calculation device 5. Is done. Next, the first control device 6a controls the operation of the heating and dehydrating device 22 so that the moisture content (Ap) of the dewatered sludge in the pipe 9 becomes As.
[0025]
At the same time, the intermediate moisture content calculation device 24 receives the moisture content target value As of the dewatered sludge, the operation cost parameter of the mechanical dehydration device 21, and the operation cost parameter of the heating dehydration device 22. Then, the target moisture content (intermediate target moisture content: A1s) of the sludge in the pipe 25 on the outlet side of the mechanical dehydrator 21 is calculated.
[0026]
Next, the operation of the mechanical dehydrator 21 is controlled by the second controller 23 with A1s as a target value and the moisture content (A1p) of the dewatered sludge by the moisture meter 26 as a process value.
[0027]
Here, according to FIG. 4, each of the mechanical dehydrator 21 and the heating dehydrator 22 using the intermediate moisture content A1 as a parameter when dewatering the concentrated sludge in the pipe 8 and sending it to the pipe 9 as dehydrated sludge (target moisture content AS). The dehydration cost is shown. In FIG. 4, the mechanical dehydration cost is a cost when the sludge in the pipe 8 is dehydrated to the intermediate water content A1 by the mechanical dehydrator 21, and the breakdown includes the amount of flocculant added, mechanical energy, and the like. The heating and dehydrating cost is a cost when the dewatering sludge in the pipe 25 having the moisture content A1 is dehydrated to the target moisture content As by the heating and dehydrating device 22, and the breakdown includes the amount of steam, mechanical energy, and the like. Therefore, the dehydration cost (Y yen / kg) of the dehydration system 20 can be expressed as the sum of the mechanical dehydration cost and the heating dehydration cost.
[0028]
When the present inventor calculated the dehydration cost of the dehydration system 20 as the total dehydration cost, a curve having a minimum value was obtained when the intermediate water content was A1s as shown in FIG. Therefore, the total dewatering cost can be minimized by setting the intermediate target moisture content to A1s.
[0029]
The present invention is based on this knowledge, and the intermediate moisture content calculation device 24 calculates the target value of the dewatered sludge in the pipe 25 (intermediate moisture content target value: A1s), and then uses this A1s as a set value to determine the moisture content. The water content (A1p) of the dewatered sludge in the pipe 25 by the total 26 is input to the second control device 23 as a process value. In the 2nd control apparatus 23, the mechanical dehydration apparatus 21 is operated with a well-known method, and it controls so that the moisture content of the sludge in the piping 25 may be set to A1s.
[0030]
As described above, according to this embodiment, sludge can be stably burned in the incinerator 3, and at the same time, the cost of dehydration can be minimized. In this case, the reduction of the dehydration cost leads to the minimization of the flocculant, mechanical energy, steam, etc., and thus greatly contributes to the suppression of the environmental load.
Third embodiment Next, a third embodiment of the present invention will be described with reference to Figs. The third embodiment shown in FIGS. 5 to 8 uses a centrifugal dehydrator 30 as the mechanical dehydrator 21, and a thin-film heat dehydrator 40 as the heat dehydrator 22, and the others are shown in FIG. This is substantially the same as the second embodiment shown in FIG. In the third embodiment shown in FIGS. 5 to 8, the same parts as those in the second embodiment shown in FIGS. 3 and 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0031]
As shown in FIG. 5, the mechanical dehydrator 21 includes a centrifugal dehydrator 30, a flocculant tank 31, a flocculant calculator 32, a flocculant pump 34, and a concentrated sludge flow meter 33, and the concentrated sludge tank 1. The concentrated sludge in the pipe 8 is dehydrated to obtain a dehydrated sludge having a water content of about 85% (about 78 to 90%) and sent to the pipe 25. The moisture content of the dewatered sludge in the pipe 25 largely depends on the injection amount (kg) of the flocculant per unit solid content (kg), that is, the flocculant addition rate B. Therefore, the flocculant calculator 32 inputs the addition rate B, the flocculant concentration C1, the concentrated sludge concentration C2, and the flow rate q2, calculates the injection amount q1 by the following equation, and sets the injection amount of the pump 34.
[0032]
q1 * C1 = B * q2 * C2
As shown in FIG. 6, the moisture content of the dewatered sludge in the pipe 25 (intermediate moisture content: A1) greatly depends on the addition rate of the flocculant, and the addition rate B is increased to reduce the intermediate moisture content (A1). There is a need. In the case of a commonly used polymer flocculant, the injection rate for obtaining an appropriate intermediate water content (A1s) is around 0.5%.
[0033]
Factors affecting the intermediate moisture content include the centrifugal acceleration of the centrifugal dehydrator 30 and the solids residence time in the centrifugal dehydrator in addition to the addition rate, all of which are roughly proportional to the cost.
[0034]
By the way, a part of free water remains in the dewatered sludge having a water content of about 85% and is in a slurry state. For this reason, in order to transfer the dewatered sludge in the pipe 25 to the next process, a pumping system is possible. Pumping pump makes it possible to supply a fixed amount of dehydrated sludge, which increases the work environment improvement effect such as prevention of odor leakage.
[0035]
Next, FIG. 7 shows the configuration of the vertical thin film heating and dehydrating apparatus, and FIG. 8 shows the characteristics of the dehydrating cost of the vertical thin film heating and dehydrating apparatus. The heating and dehydrating device 23 includes a vertical thin film heating and dehydrating device 40. The vertical thin film heating and dehydrating apparatus 40 includes a cylindrical heat transfer drum 41 having a steam jacket 40a, a rotating shaft 43 on which a blade 42 is mounted, and a motor 44, and supplies the steam 45 to the steam jacket 40a. It is like that. The dewatered sludge in the pipe 25 is stretched on the inner surface of the heat transfer drum 41 by the blade 42 to form a thin film, falls after the heat dehydration along the heat transfer drum 41, and has a moisture content of around 60% (50 to 70%). It is naturally discharged as heated dehydrated sludge 46. The thin film heating and dehydrating apparatus 40 can perform a large amount of dehydration in a short time, and the dehydrating ability greatly depends on the rotational speed of the rotating shaft (strictly, the peripheral speed at the tip of the blade 42). For this reason, when the moisture content (intermediate moisture content A1) of the dewatered sludge in the pipe 25 is small, it is necessary to increase the rotational speed and enhance the dewatering ability.
[0036]
The relationship between the intermediate moisture content A1 and the rotational speed of the blade 42 is as shown in FIG. The peripheral speed at the tip of the blade 42 giving an appropriate intermediate water content (A1s) is about 10 m / s, and the centrifugal acceleration applied to the sludge is several tens of G (about 50 to 100 G). The peripheral speed is roughly proportional to the power cost.
[0037]
By the way, in the vertical thin film heating and dehydrating apparatus 40, the sludge residence time in the heat transfer drum 41 is as short as several minutes (the residence time is several hours in heating and dehydration equipment other than the thin film type). For this reason, the response at the time of control is quick, and because of the vertical type, the heated dehydrated sludge 46 is naturally discharged and does not remain in the heat transfer drum 41 when the apparatus is stopped. Therefore, it is easy to stop and start the apparatus. Further, due to the centrifugal acceleration and the scraping action on the sludge by the blade 42 rotating at a high speed, the heated dehydrated sludge 46 becomes chip-shaped or granular, has a uniform shape, and has a uniform moisture content. For this reason, no baby boom or powder is generated, and the molding to the transfer to the incinerator 3 and the charging to the incinerator 3 in the next step is easy.
[0038]
According to the present embodiment, the mechanical dehydrator 21 and the heating dehydrator 22 can be easily stopped and started. The heat-dehydrated sludge 46 is chip-shaped or granular and has a uniform shape, so that the water content is uniform. For this reason, no baby boom or powder is produced, and the transfer to the incinerator 3 in the next step and the molding at the time of charging into the incinerator 3 are facilitated.
Fourth embodiment Next, a fourth embodiment according to the present invention will be described with reference to Figs. 9 and 10. In the fourth embodiment, the inlet side and the outlet side of the heating and dehydrating device 22 are connected by a bypass line 50, and the moisture content meter (the first one) is respectively connected to the outlet side of the mechanical dehydrating device 21 and the outlet side of the heating and dehydrating device 22. 1 moisture content meter) 55 and a moisture content meter (second moisture content meter) 55a are provided.
[0039]
The

moisture content meters

55 and 55a are connected to the bypass control device 53. In the bypass control device 53, the bypass line 50 is based on the self-combustion moisture content from the self-combustion moisture content calculating device 5 and the moisture content from the

moisture content meters

55 and 55a. The bypass flow ratio for bypassing is required. Further, the bypass controller 53 controls the pump 56 attached to the bypass line 50 and the pump 57 attached to the pipe 25. In this case, the pumps 56 and 57 constitute a bypass adjusting device. A kneader 51 is provided on the outlet side of the bypass line 50.
[0040]
In the fourth embodiment, the same parts as those of the second embodiment shown in FIGS. 3 and 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0041]
As shown in FIG. 9, a mechanical dehydration device 21, a heating dehydration device 22, a bypass line 50, a kneader 51, and a bypass control device 53 constitute a dehydration system 52. Further, the dewatered sludge in the bypass line 50 and the dewatered sludge from the heating dehydrator 22 are kneaded by the kneader 51 and supplied to the incinerator 3 as the dewatered sludge 9.
[0042]
Incidentally, a flow meter 54 is provided on the outlet side of the mechanical dehydrator 21, and the flow rate (Q) of the mechanical dehydrated sludge in the pipe 25 is measured by the flow meter 54. As such a flow meter 54, an electromagnetic flow meter using electromagnetic waves is used, and the electromagnetic flow meter can measure the flow rate of slurry having a moisture content of about 75%. As the moisture content meter 55, a microwave densitometer using a phase difference of microwaves is used. The microwave densitometer can accurately and online measure the water content of the slurry in the above water content range.
[0043]
In the bypass control device 53, the flow rate (Q) and moisture content (A1) of the machine dehydrated sludge in the pipe 25, the moisture content (A2) of the heated dehydrated sludge in the pipe 9, and the self-combustion from the self-combustion water content calculating device 5 The target moisture content (As) is input as a parameter. In this bypass control device 53, the flow rate ratio (r 1) to the bypass line 50, the supply ratio (r 2) to the heating dehydrator 22, the flow rate (Q 1) to the bypass line 50, and the supply to the heating dehydrator 22 The amount (Q2) is calculated by the following equations to determine the flow rates of the pumps 56 and 57.
[0044]
Q1 = Q × r1
Q2 = Q × r2
r1 + r2 = 1
Since the solid content in the dewatered sludge in the pipe 25 does not decrease or increase in the heating dehydrator 22 and the bypass line 50, the solid content in the dehydrated sludge is equal to the solid content in the sludge from the heat dehydrator 22. This is the sum of the solid content in the sludge in the bypass line 50. Therefore, the bypass control device using the flow rate (Q) and water content (A1) of the dewatered sludge in the pipe 25, the water content (A2) of the sludge from the heating dehydrator 22, and the self-combustion water content (AS) as parameters. In 53, r1 (flow rate ratio to the bypass line 50) and r2 (supply ratio to the heating dehydration facility) are calculated by the following equations.
[0045]

FIG. 10 shows calculation examples of r1 and r2 with respect to the self-combustion moisture content (AS: three types of 0.60, 0.65, and 0.70). For simplicity, the moisture content of the dewatered sludge in the pipe 25 was set to 0.80 (80%), and the moisture content from the heating dehydrator 22 was set to 0.40 (40%).
[0046]
If the moisture content (A2) of the sludge from the heating and dehydrating device 22 is significantly lower than the moisture content (As) of the self-combustion to the incinerator 3, a temperature rise trouble of the incinerator 3 occurs. According to this, it is possible to maintain the self-combustion moisture content. Further, since the response of the pump 56 of the bypass line 50 is very fast compared to the response of the heating and dehydrating device 22, the controllability of the self-combustion water content (As) can be improved.
[0047]
【The invention's effect】
As described above, according to the present invention, the water content of the dewatered sludge can be adjusted over a wide range, and the water content of the dewatered sludge is effectively set to an optimum value for combustion in the incinerator. Can be controlled.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of a sludge treatment system according to the present invention.
FIG. 2 is a graph showing the relationship between VS / TS and moisture content of self-combustion.
FIG. 3 is a configuration diagram showing a second embodiment of a sludge treatment system according to the present invention.
FIG. 4 is a diagram showing the relationship between the intermediate moisture content and the dehydration cost.
FIG. 5 is a configuration diagram of a centrifugal dewatering device showing a third embodiment of a sludge treatment system according to the present invention.
FIG. 6 is a characteristic diagram of a centrifugal dehydrator.
FIG. 7 is a configuration diagram of a thin film heating and dehydrating apparatus.
FIG. 8 is a characteristic diagram of a thin film heating and dehydrating apparatus.
FIG. 9 is a configuration diagram showing a fourth embodiment of a sludge treatment system according to the present invention.
FIG. 10 is a diagram showing a characteristic table of the sludge treatment system shown in FIG. 9;
FIG. 11 is a diagram showing a conventional sludge treatment system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Storage tank 3 Incinerator 5 Self-combustion moisture content calculating apparatus 6 Control apparatus 6a 1st control apparatus 7 Dehydration apparatus 10 TS * VS detector 11, 26 Moisture content meter 21 Mechanical dehydration apparatus 22 Heating dehydration apparatus 23 2nd control apparatus 24 Intermediate moisture content calculating device 30 Centrifugal dehydrator 40 Vertical thin film heating dehydrator 50 Bypass line 53

Bypass controller

55, 55a Moisture meter 56, 57 Pump

Claims

A dehydrator for dewatering sludge;
An incinerator for incinerating sludge dehydrated by a dehydrator;
A detector that is provided on the inlet side of the dehydrator and measures the solid content concentration and the organic matter concentration in the sludge;
Based on the measured value from this detector, the ratio of organic substance concentration / solid content concentration is obtained, and the self-combustion moisture content calculating device for obtaining the self-combustion moisture content of sludge from this ratio;
A sludge treatment system comprising: a control device that controls the dehydration device based on the self-combustion water content calculated by the self-combustion water content calculation device.

A mechanical dehydrator for dewatering sludge;
A heating and dehydrating device provided on the outlet side of the mechanical dehydrating device;
An incinerator for incinerating sludge dehydrated by a heating dehydrator;
A detector that is provided on the inlet side of the mechanical dehydrator and measures the solid content concentration and the organic matter concentration in the sludge;
Based on the measured value from this detector, the ratio of organic substance concentration / solid content concentration is obtained, and the self-combustion moisture content calculating device for obtaining the sludge self-combustion moisture content from this ratio;
An intermediate moisture content calculating device for determining an intermediate moisture content at the outlet side of the mechanical dehydrator that minimizes the total dehydration cost of the mechanical dehydrator and the heating dehydrator based on the self-burning moisture content determined by the self-burning moisture content calculator;
A first control device for controlling the heating and dehydrating device based on the self-combustion water content determined by the self-combustion water content calculating device;
A sludge treatment system comprising: a second control device that controls a mechanical dehydration device based on an intermediate moisture content obtained by an intermediate moisture content calculation device.

3. The sludge treatment system according to claim 2, wherein the mechanical dehydrator has a centrifugal dehydrator, and the heat dehydrator has a thin film heat dehydrator.

A mechanical dehydrator for dewatering sludge;
A heating and dehydrating device provided on the outlet side of the mechanical dehydrating device;
An incinerator for incinerating sludge dehydrated by a heating dehydrator;
A bypass line connecting the inlet side and the outlet side of the heating dehydrator,
A bypass adjusting device for adjusting a bypass flow rate to the bypass line;
A detector that is provided on the inlet side of the mechanical dehydrator and measures the solid content concentration and the organic matter concentration in the sludge;
Based on the measured value from this detector, the ratio of organic substance concentration / solid content concentration is obtained, and the self-combustion moisture content calculating device for obtaining the sludge self-combustion moisture content from this ratio;
A first moisture content meter and a second moisture content meter respectively provided on the outlet side of the mechanical dehydrator and the outlet side of the heating dehydrator;
The self-combustion moisture content determined by the self-combustion moisture content calculation device, the moisture content on the outlet side of the mechanical dehydration device determined by the first moisture content meter, and the moisture content on the exit side of the heating dehydration device determined by the second moisture content meter A sludge treatment system comprising: a bypass control device that obtains a bypass flow ratio for bypassing to the bypass line based on the control and controls the bypass adjustment device based on the bypass flow ratio.