JP5336794B2 - Purification method of raw material crude crystals - Google Patents
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Abstract
Description
本発明は、不純物を含む原料粗結晶を高効率かつ安定に精製する方法に関する。 The present invention relates to a method for highly efficiently and stably refining raw material crude crystals containing impurities.
不純物を含む原料粗結晶を精製する方法としては、種々の型式のものがある。例えば、不純物を含む結晶性物質を、該結晶性物質の結晶成分が精製されたものを融解した融解液、あるいは他の溶媒を利用して連続的に精製を行う方法及び装置が知られている。
具体的には、精製塔の塔頂もしくは塔底に具備された加熱融解装置により結晶を融解した還流液、もしくは結晶を一旦外部に取り出して外部で加熱融解した還流液と、原料粗結晶とを向流接触させて精製する精製装置及び精製方法が示されている（例えば、特許文献１〜３）。
There are various types of methods for purifying raw material crude crystals containing impurities. For example, there is known a method and an apparatus for continuously purifying a crystalline substance containing impurities by using a melt obtained by melting a purified crystalline component of the crystalline substance or using another solvent. .
Specifically, a reflux solution obtained by melting a crystal with a heating and melting apparatus provided at the top or bottom of a purification tower, or a reflux solution obtained by temporarily taking out the crystal and heating and melting it outside, and a raw material crude crystal A purification apparatus and a purification method for purification by contacting them in countercurrent are disclosed (for example, Patent Documents 1 to 3).
特許文献１〜３のような原料粗結晶の精製には、精製塔内の向流接触中の洗浄作用、発汗作用、再結晶作用等が寄与していると考えられる。
洗浄作用とは、原料粗結晶表面に付着している不純物を、不純物が含まれていない還流液により洗い流す作用である。
発汗作用とは、強制的ないしは重力により前記還流液を液状加熱媒体として精製塔内で移動させ、原料粗結晶の温度よりも温度の高い還流液により該原料粗結晶を加温するか、または精製塔の内部に、熱媒により加熱操作が施せるような加熱室を設け、原料粗結晶を融解温度近傍で保持することにより、該原料粗結晶内部に取り込まれている不純物を溶出させる作用である。
再結晶作用とは、融点よりも低温で供給された結晶の温度が前記還流液により融点まで上昇する際の顕熱により、純度の高い還流液が粒子径の大きな結晶の近傍で一部再結晶化し高純度化が進む作用である。
ここで、塔頂もしくは塔底に備えられた加熱融解装置で結晶を融解した還流液、もしくは結晶を外部に取り出し、外部で加熱融解した還流液を外部還流液、発汗作用により精製塔内部で生成する、不純物が溶出された液を内部還流液と定義する。
It is considered that the cleaning action, the sweating action, the recrystallization action and the like during the countercurrent contact in the purification tower contribute to the purification of the raw material crude crystals as in Patent Documents 1 to 3.
The cleaning action is an action of washing out impurities adhering to the raw material crude crystal surface with a reflux liquid containing no impurities.
The sweating action is forced or gravity to move the reflux liquid as a liquid heating medium in the purification tower and heat the raw crude crystals with a reflux liquid having a temperature higher than that of the raw crude crystals, or purify the raw crystals. This is an action of eluting impurities incorporated in the raw material crude crystal by providing a heating chamber in the tower that can be heated by a heat medium and holding the raw material crude crystal in the vicinity of the melting temperature.
The recrystallization action means that the high-purity reflux liquid is partially recrystallized in the vicinity of a crystal having a large particle diameter by sensible heat when the temperature of the crystal supplied at a temperature lower than the melting point is raised to the melting point by the reflux liquid. This is the action of increasing the purity.
Here, a reflux solution obtained by melting crystals with a heating / melting device provided at the top or bottom of the column, or a reflux solution obtained by taking out the crystals outside and heating and melting outside is generated inside the purification tower by the perspiration action. The liquid from which impurities are eluted is defined as the internal reflux liquid.
洗浄作用は還流液の流量を増大させることにより効果を向上させることができ、発汗作用は還流液の温度条件もしくは加熱器に供給する熱媒の流量を制御することにより効果を向上させることができ、これらにより高い精製能力が得られる。
しかしながら、特許文献１〜３の方法では、長時間精製塔を運転する際、安定かつ高収率で精製操作を行うことは困難であった。該理由としては、夏季と冬季、昼間と夜間のような外気温の変化に伴って、精製効率が変動してしまうことが挙げられる。ここで、精製効率とは、原料粗結晶中に含まれる不純物が精製により除去される度合である。
精製により得られた製品の純度は、安定して高純度に維持される必要がある。そのため、従来は前述のような外気温による精製効率の変動が起こった場合、外部還流量を増加させることにより外気温の製品の品質への影響を低減していた。
However, in the methods of Patent Documents 1 to 3, when operating the purification tower for a long time, it is difficult to perform the purification operation in a stable and high yield. The reason for this is that the purification efficiency fluctuates with changes in the outside temperature such as summer and winter, daytime and nighttime. Here, the purification efficiency is the degree to which impurities contained in the raw material raw crystals are removed by purification.
The purity of the product obtained by purification needs to be stably maintained at high purity. For this reason, conventionally, when the refining efficiency fluctuates due to the outside temperature as described above, the influence of the outside temperature on the quality of the product is reduced by increasing the external reflux amount.
このように、外部還流量を増加させることで製品の品質が低下することを防ぐことができる。しかし、この方法では、精製塔を運転している間、常に製品の品質管理に注力しなければならず、運転員の運転負荷が高くなってしまう。また、外部還流量を増加させることは製品の減産に直結するため、外部還流量は少ない方が好ましい。外部還流量を低減して同じ効果を得る方法としては外部還流液の温度を高くすることが考えられる。しかし、この方法を用いたところ、製品の品質の向上は見られなかった。そのため、少ない外部還流量で製品の品質を向上させ、効率的かつ安定に原料粗結晶を精製する方法が求められている。 In this way, it is possible to prevent the quality of the product from deteriorating by increasing the external reflux amount. However, in this method, while operating the purification tower, it is necessary to always focus on product quality control, which increases the operating load on the operator. Moreover, since increasing the external reflux amount directly leads to a reduction in production of the product, it is preferable that the external reflux amount be small. As a method of obtaining the same effect by reducing the amount of external reflux, it is conceivable to increase the temperature of the external reflux liquid. However, when this method was used, the quality of the product was not improved. Therefore, a method for improving the quality of products with a small amount of external reflux and for efficiently and stably refining raw material crude crystals is required.
そこで本発明は、優れた品質の製品を安定して高収率で得ることのできる原料粗結晶の精製方法を目的とする。 Therefore, the present invention is directed to a method for purifying a raw material raw crystal that can stably obtain a product of excellent quality with a high yield.
本発明の原料粗結晶の精製方法は、精製塔に備えられた加熱手段により精製塔内部を加熱しながら、前記精製塔内に原料粗結晶を供給し、前記精製塔内から該原料粗結晶が精製された結晶を取り出すとともに、その一部を融解させた外部還流液を塔頂側もしくは塔底側から供給し、前記原料粗結晶から生じた不純物を前記外部還流液の供給側と逆側の塔底側もしくは塔頂側から排出して精製する方法であって、前記加熱手段により、前記精製塔内部における前記原料粗結晶が供給される位置から前記精製された結晶が取り出される位置の間の領域を少なくとも加熱し、前記加熱手段による加熱の見かけ加熱量Ｑｒを、前記精製塔の物質収支式、熱収支式、及び下式（Ｉ）を用いた計算に基づいて、精製塔内部を加熱する正味の加熱量Ｑａが、精製収率が最大になる時の最適加熱量Ｑｐとなるように制御することを特徴とする方法である。
Ｑａ＝α（Ｔ）×Ｑｒ ・・・（Ｉ）
（式（Ｉ）中、α（Ｔ）は精製塔の外気温Ｔにおける、見かけ加熱量Ｑｒの精製塔内部の加熱への寄与率である。）
The raw material crude crystal purification method of the present invention comprises supplying a raw material crude crystal into the purification tower while heating the inside of the purification tower by a heating means provided in the purification tower, and the raw material crude crystal is supplied from the purification tower. The purified crystal is taken out, and an external reflux liquid in which a part of the crystal is melted is supplied from the tower top side or the tower bottom side, and impurities generated from the raw raw crystal are separated from the external reflux liquid supply side. A method of purifying by exhausting from the tower bottom side or the tower top side , between the position where the raw crude crystals are supplied from the position where the raw crystal is supplied inside the purification tower by the heating means. At least the region is heated, and the apparent heating amount Qr of heating by the heating means is heated based on the calculation using the material balance equation, heat balance equation, and the following equation (I) of the purification tower. Net heating amount Qa is SeiOsamuritsu is a method characterized by controlling so that the optimum heating amount Qp when maximized.
Qa = α (T) × Qr (I)
(In formula (I) , α (T) is the contribution ratio of the apparent heating amount Qr to the heating inside the purification tower at the outside temperature T of the purification tower.)
また、本発明の原料粗結晶の精製方法は、任意の外気温における前記計算を予め行っておき、その計算結果に基づいて前記見かけ加熱量Ｑｒを制御することが好ましい。
また、前記見かけ加熱量Ｑｒを、前記計算を行いながら制御することも好ましい。
また、前記加熱手段による加熱を、該加熱手段に熱媒を供給することにより行い、前記見かけ加熱量Ｑｒの制御を該熱媒の流量又は温度を調節することにより行うことが好ましい。
Further, in the method for purifying raw material crude crystals of the present invention, it is preferable that the calculation at an arbitrary outside air temperature is performed in advance and the apparent heating amount Qr is controlled based on the calculation result.
It is also preferable to control the apparent heating amount Qr while performing the calculation.
Further, it is preferable that heating by the heating unit is performed by supplying a heating medium to the heating unit, and the apparent heating amount Qr is controlled by adjusting the flow rate or temperature of the heating medium.
本発明の原料粗結晶の精製方法によれば、優れた品質の製品が高収率で安定して得られる。 According to the raw material crude crystal purification method of the present invention, an excellent quality product can be stably obtained in a high yield.
以下、本発明の原料粗結晶の精製方法の一実施形態例について詳細に説明する。
（原料粗結晶）
本発明の精製方法に用いる原料粗結晶は、例えば、精製塔の上流側に設置される晶析装置により得ることができる。
晶析装置は、伝熱面を介して熱交換を行う冷却器を備え、該晶析装置に供給された被処理流体を所望の温度に冷却できるもの等の公知の晶析装置を適宜用いることができる。晶析装置の具体例としては、例えば「化学工学便覧 改訂第六版」丸善株式会社発行、１９９９年、５０５〜５２０頁に記載されている装置が挙げられる。
特に、攪拌槽と、該攪拌槽の周面に外側から冷却媒体を接触させるための冷却ジャケットとを有する冷却器を備え、該攪拌槽の周面を伝熱面として、熱交換により攪拌槽内を冷却する攪拌槽型晶析装置（以下、冷却ジャケット式攪拌槽型晶析装置という。）が好適である。
Hereinafter, an embodiment of the method for purifying raw material crude crystals of the present invention will be described in detail.
(Raw raw crystal)
The raw raw crystal used in the purification method of the present invention can be obtained, for example, by a crystallizer installed on the upstream side of the purification tower.
The crystallizer is equipped with a cooler that exchanges heat through the heat transfer surface, and appropriately uses a known crystallizer such as one that can cool the fluid to be treated supplied to the crystallizer to a desired temperature. Can do. Specific examples of the crystallizer include those described in “Chemical Engineering Handbook, Revision 6”, published by Maruzen Co., Ltd., 1999, pages 505-520.
In particular, a cooling device having a stirring tank and a cooling jacket for bringing a cooling medium into contact with the peripheral surface of the stirring tank from the outside is provided, and the peripheral surface of the stirring tank is used as a heat transfer surface to exchange heat in the stirring tank. A stirring tank type crystallizer (hereinafter referred to as a cooling jacket type stirring tank type crystallizer) is preferable.
前記被処理流体は晶析操作を施す化合物を含む流体であればよく、例えば、被処理流体が粗製（メタ）アクリル酸であり、これに晶析操作を施して（メタ）アクリル酸の原料粗結晶を得る方法に適用される。本明細書において、（メタ）アクリル酸とはアクリル酸及び／又はメタクリル酸を言い、粗製（メタ）アクリル酸とは、粗製メタクリル酸及び／又は粗製アクリル酸を言うものとする。
また、被処理流体として、ＡＣＨ（アセトンシアノヒドリン）法で副生するメタクリル酸を抽出や蒸留により分離することにより得られる粗製メタクリル酸も好適に用いることができる。
The fluid to be treated may be a fluid containing a compound that undergoes a crystallization operation. For example, the fluid to be treated is crude (meth) acrylic acid, and the raw material crude of (meth) acrylic acid is subjected to crystallization operation. Applies to the method of obtaining crystals. In this specification, (meth) acrylic acid refers to acrylic acid and / or methacrylic acid, and crude (meth) acrylic acid refers to crude methacrylic acid and / or crude acrylic acid.
Moreover, the crude methacrylic acid obtained by isolate | separating the methacrylic acid byproduced by ACH (acetone cyanohydrin) method by extraction or distillation can also be used suitably as a to-be-processed fluid.
また、被処理流体として、イソブチレン、第三級ブチルアルコール、メタクロレイン又はイソブチルアルデヒドを、一段または二段で分子状酸素と反応させる接触気相酸化によって得られる反応ガスを、水に吸収させて得られた水溶液から、有機溶剤を用いてメタクリル酸を抽出し、蒸留により有機溶剤及び不揮発分を除去して得られる粗製メタクリル酸も好適に用いることができる。この場合には、晶析操作により前記粗製メタクリル酸からアルデヒド類等の不純物を除去することができる。 In addition, the reaction fluid obtained by catalytic gas phase oxidation in which isobutylene, tertiary butyl alcohol, methacrolein, or isobutyraldehyde is reacted with molecular oxygen in one or two stages as a fluid to be treated is obtained by absorbing it in water. Crude methacrylic acid obtained by extracting methacrylic acid from the aqueous solution using an organic solvent and removing the organic solvent and non-volatile components by distillation can also be suitably used. In this case, impurities such as aldehydes can be removed from the crude methacrylic acid by a crystallization operation.
晶析操作においては、まず冷却ジャケット式攪拌槽型晶析装置に被処理流体を供給する。被処理流体の供給手段は特に限定されず、公知の供給手段を適宜用いることができる。
ついで、当該晶析装置に供給された被処理流体を冷却することにより結晶を析出させる晶析操作を行う。晶析操作は回分式であっても連続式であってもよいが、被処理流体から結晶を連続的に晶出させる操作を安定して行うことができる点から、連続式であることが特に好ましい。
In the crystallization operation, first, a fluid to be treated is supplied to a cooling jacket type stirring tank type crystallization apparatus. The supply means of the fluid to be processed is not particularly limited, and a known supply means can be appropriately used.
Next, a crystallization operation for precipitating crystals is performed by cooling the processing fluid supplied to the crystallization apparatus. The crystallization operation may be a batch type or a continuous type, but it is particularly a continuous type from the viewpoint that the operation of continuously crystallizing crystals from the fluid to be treated can be performed stably. preferable.
冷却ジャケット式攪拌槽型晶析装置において、被処理流体を冷却する冷却温度は、被処理流体中に目的とする化合物の結晶が析出し始める温度である結晶析出温度以下であればよい。例えば、被処理流体が粗製（メタ）アクリル酸である場合は、操作性の点から冷却温度を−１０〜１０℃の範囲内で設定することが好ましい。 In the cooling jacket type stirred tank crystallizer, the cooling temperature for cooling the treatment fluid may be not more than the crystal precipitation temperature which is the temperature at which the target compound crystal starts to precipitate in the treatment fluid. For example, when the fluid to be treated is crude (meth) acrylic acid, the cooling temperature is preferably set within a range of −10 to 10 ° C. from the viewpoint of operability.
また、必要に応じて、被処理流体に結晶析出温度を調整するための成分を添加してもよい。例えば、被処理流体として粗製（メタ）アクリル酸を用いる場合、第二成分として（メタ）アクリル酸と固溶体を形成しない極性有機物質を添加することにより、結晶析出温度を低下させることができる。極性有機物質の具体例としては、メタノール、エタノール、プロパノール、ブタノール等が挙げられる。 Moreover, you may add the component for adjusting crystal-crystallization temperature to a to-be-processed fluid as needed. For example, when crude (meth) acrylic acid is used as the fluid to be treated, the crystal precipitation temperature can be lowered by adding a polar organic substance that does not form a solid solution with (meth) acrylic acid as the second component. Specific examples of polar organic substances include methanol, ethanol, propanol, butanol and the like.
前記第二成分の添加量は、被処理流体及び第二成分の種類によっても異なるが、被処理流体に対して１〜３５質量％の範囲内であることが好ましい。
例えば、被処理流体として粗製メタクリル酸を用いる場合、メタクリル酸の融点が１５℃であるのに対して、結晶析出温度が−１０〜１０℃となるように、第二成分の添加量を設定することが好ましい。
Although the addition amount of said 2nd component changes with kinds of to-be-processed fluid and a 2nd component, it is preferable to exist in the range of 1-35 mass% with respect to a to-be-processed fluid.
For example, when crude methacrylic acid is used as the fluid to be treated, the amount of the second component added is set so that the crystal precipitation temperature is −10 to 10 ° C. while the melting point of methacrylic acid is 15 ° C. It is preferable.
晶析操作を経た被処理流体は、晶析装置から抜き出された後、結晶と母液とに固液分離される。結晶と母液とに分離する方法は、固体と液体とを分離できる方法であれば特に制限はなく、例えば、ろ過法、遠心分離法等の公知の固液分離方法を用いることができる。分離操作の形式は、回分式または連続式のいずれであってもよい。
以上説明した操作により、精製塔に供給する原料粗結晶を得ることができる。
The fluid to be treated that has undergone the crystallization operation is extracted from the crystallization apparatus, and then separated into a liquid and a mother liquor. The method for separating the crystal and the mother liquor is not particularly limited as long as it is a method capable of separating a solid and a liquid, and for example, a known solid-liquid separation method such as a filtration method or a centrifugal separation method can be used. The type of separation operation may be either a batch type or a continuous type.
By the operations described above, raw material crude crystals supplied to the purification tower can be obtained.
例えば、被処理流体に粗製メタクリル酸を用いる場合、原料粗結晶として母液を含んだメタクリル酸の結晶が得られる。ここで、原料粗結晶量に対する原料粗結晶中に含まれる液体量の割合を結晶含液率ｑｍと定義すると、結晶含液率ｑｍが５〜２０質量％となるような固液分離方法又は分離条件を選定することが好ましい。
母液には、被処理流体に任意に添加された第二成分と、濃縮された不純物と、析出しなかった（メタ）アクリル酸とが含まれている。
ここで、結晶含液率ｑｍの測定方法としては、原料粗結晶中に含まれる液体は前記母液とほぼ同じであることから、結晶含液率は母液に含まれる化合物で結晶には実質的に取り込まれない化合物Ｘを選定し、母液中の当該化合物Ｘの濃度（Ａ質量％）と原料粗結晶（液体を含む）を融解した液中の当該化合物Ｘの濃度（Ｂ質量％）を測定し、次式により算出する方法が例示できる。
結晶含液率ｑｍ＝Ａ／Ｂ×１００
なお、化合物Ｘとしては、被処理流体に任意に添加された第二成分、濃縮された不純物などから選ぶことができる。
For example, when crude methacrylic acid is used for the fluid to be treated, methacrylic acid crystals containing a mother liquor are obtained as raw material crude crystals. Here, when the ratio of the amount of liquid contained in the raw material crude crystals to the raw material crude crystals is defined as the crystal liquid content qm, the solid-liquid separation method or separation in which the crystal liquid content qm is 5 to 20% by mass. It is preferable to select conditions.
The mother liquor contains a second component optionally added to the fluid to be treated, concentrated impurities, and (meth) acrylic acid that did not precipitate.
Here, as a measuring method of the crystal liquid content qm, since the liquid contained in the raw material raw crystal is almost the same as the mother liquor, the crystal liquid content is a compound contained in the mother liquor and is substantially equal to the crystal. Select the compound X that is not taken in, and measure the concentration (A mass%) of the compound X in the mother liquor and the concentration (B mass%) of the compound X in the liquid obtained by melting the raw raw crystal (including liquid). A method of calculating by the following formula can be exemplified.
Crystal liquid content qm = A / B × 100
The compound X can be selected from a second component optionally added to the fluid to be treated, a concentrated impurity, and the like.
（精製塔による精製）
本発明の精製方法における精製塔としては、精製塔に備えられた加熱手段により精製塔内部を加熱しながら、精製塔内に原料粗結晶を供給し、該原料粗結晶が精製された結晶を融解させた外部還流液を塔頂側もしくは塔底側から供給し、前記原料粗結晶から生じた不純物を前記外部還流液の供給側と逆側の塔底側もしくは塔頂側から排出して精製するものを用いることができる。
すなわち、外部還流液を塔頂側から供給するものであっても塔底側から供給するものであってもよい。本発明における精製塔は、外部還流液を塔頂側から供給される場合は前記不純物を塔底側から排出する精製塔であり、外部還流液を塔底側から供給する場合は前記不純物を塔頂側から排出する精製塔である。
(Purification by purification tower)
As the purification tower in the purification method of the present invention, while heating the inside of the purification tower by the heating means provided in the purification tower, the raw raw crystal is supplied into the purification tower, and the purified raw crystal is melted. The external reflux liquid is supplied from the tower top side or the tower bottom side, and impurities generated from the raw raw crystal are discharged from the tower bottom side or the tower top side opposite to the external reflux liquid supply side for purification. Things can be used.
That is, the external reflux liquid may be supplied from the tower top side or supplied from the tower bottom side. The purification tower in the present invention is a purification tower that discharges the impurities from the tower bottom side when the external reflux liquid is supplied from the tower top side, and the impurities are removed from the tower when the external reflux liquid is supplied from the tower bottom side. This is a purification tower discharged from the top side.
精製塔内部を加熱する加熱手段としては、精製塔の外壁、すなわち精製塔缶体表面に設けられ、該精製塔缶体表面を加熱して精製塔内部を加熱する精製塔缶体表面加熱器、及び精製塔内の一部に熱媒により精製塔内部を加熱する加熱室が挙げられる。
精製塔としては、例えば、特許文献１〜３に記載の精製塔が挙げられる。
The heating means for heating the inside of the purification tower is provided on the outer wall of the purification tower, that is, the surface of the purification tower can body, and the surface of the purification tower can body is heated by heating the surface of the purification tower can body, And the heating chamber which heats the inside of a purification tower by a heat medium is mentioned in a part in a purification tower.
Examples of the purification tower include the purification towers described in Patent Documents 1 to 3.
図１は、本発明における精製塔の実施形態の一例（例えば、特許文献１の精製塔）を示した模式図である。
精製塔１は、加熱手段２として精製塔缶体表面に精製塔缶体表面加熱器が設けられている。加熱手段２により精製塔缶体表面を加熱して精製塔内部を加熱する。また、精製塔１の外部には、精製塔１から得られる精製された結晶を融解させて外部還流液とする外部加熱器３が設けられている。
FIG. 1 is a schematic diagram showing an example of an embodiment of a purification tower in the present invention (for example, a purification tower of Patent Document 1).
The purification tower 1 is provided with a purification tower body surface heater on the surface of the purification tower body as the heating means 2. The purification tower can surface is heated by the heating means 2 to heat the inside of the purification tower. In addition, an external heater 3 is provided outside the purification tower 1 to melt the purified crystal obtained from the purification tower 1 and use it as an external reflux liquid.
加熱手段２である精製塔缶体表面加熱器は、精製塔缶体表面を加熱することができるものであればよく、加熱量を高い精度で制御しやすい点から、精製塔缶体表面に加熱チューブらせん状に巻き回し、これに蒸気もしくは温水等の熱媒を流通させる加熱器であることが好ましい。加熱チューブをらせん状に巻き回す場合には、該加熱チューブを精製塔１の高さ方向に区分し、分割して巻きつけてもよい。
また、精製塔缶体表面加熱器は、熱媒の流通させるものの他、電熱ヒータ等を使用してもよい。
以下、加熱手段２が前者の熱媒を流通させる加熱器である場合について説明する。
The refining tower can body surface heater that is the heating means 2 may be any one that can heat the surface of the refining tower can body, and heats the surface of the refining tower can body from the point of easy control of the heating amount with high accuracy. It is preferably a heater that is wound in a tube spiral shape and in which a heat medium such as steam or hot water is circulated. When the heating tube is wound in a spiral shape, the heating tube may be divided in the height direction of the purification tower 1, and may be divided and wound.
Moreover, an electric heater etc. may be used for the refinement | purification tower can body surface heater other than what distribute | circulates a heat medium.
Hereinafter, the case where the heating means 2 is a heater for circulating the former heat medium will be described.
本実施形態の精製塔１では、塔底側から原料粗結晶１０が供給される。また、塔頂側から精製塔留出分１２（精製された結晶、製品）が取り出される。精製塔留出分１２の一部は外部還流液１４として精製塔１の塔頂から精製塔１に戻され、精製塔留出分１２の残りが製品１６となる。外部還流液１４には、精製塔１内部で精製された原料粗結晶１０が表面加熱器２による加熱により融解された還流液と、精製塔留出分１２に含まれる精製された結晶が外部加熱器３により融解された還流液とが含まれている。また、精製塔１の塔底からは不純物１８が濃縮された母液が排出される。
これにより、塔底側から供給された原料粗結晶１０が、塔頂側から供給された還流液と向流接触し、原料粗結晶１０の精製が行われる。
In the purification tower 1 of this embodiment, the raw material crude crystal 10 is supplied from the tower bottom side. Further, a refined column distillate 12 (purified crystals, product) is taken out from the tower top side. A part of the purification tower distillate 12 is returned to the purification tower 1 from the top of the purification tower 1 as an external reflux liquid 14, and the remainder of the purification tower distillate 12 becomes the product 16. In the external reflux liquid 14, a reflux liquid obtained by melting the raw material crude crystal 10 purified inside the purification tower 1 by heating with the surface heater 2 and a purified crystal contained in the purification tower distillate 12 are externally heated. The reflux liquid melted by the vessel 3 is contained. Further, the mother liquor enriched with the impurities 18 is discharged from the bottom of the purification tower 1.
Thereby, the raw material crude crystal 10 supplied from the tower bottom side comes into countercurrent contact with the reflux liquid supplied from the tower top side, and the raw material crude crystal 10 is purified.
本発明の精製方法における精製塔１への原料粗結晶１０の供給量（ＭＡＳＳ、単位：ｋｇ／ｈ）は、精製塔１の種類及び精製塔缶体の外径、高さ等によって適宜設定すればよい。
精製塔１に供給する原料粗結晶１０の温度ｔ０は、５〜６℃であることが好ましい。
また、精製塔１からの濃縮された不純物１８を含んだ母液の排出量（ＬＯＳＳ、単位：ｋｇ／ｈ）は、ＭＡＳＳ及び製品１６の留出量（ＰＹ、ｋｇ／ｈ）により適宜調節すればよい。
The supply amount (MASS, unit: kg / h) of the raw material crude crystal 10 to the purification tower 1 in the purification method of the present invention is appropriately set according to the type of the purification tower 1 and the outer diameter, height, etc. of the purification tower can body. That's fine.
The temperature t 0 of the raw material crude crystal 10 supplied to the purification tower 1 is preferably 5 to 6 ° C.
Further, the discharge amount (LOSS, unit: kg / h) of the mother liquor containing the concentrated impurities 18 from the purification tower 1 can be appropriately adjusted according to the distillate amount (PY, kg / h) of MASS and the product 16. Good.
精製塔１の塔頂への外部還流液１４の供給量（ＲＥＦ、単位：ｋｇ／ｈ）は、洗浄作用の効果により製品の品質を維持していく点から、最低量ＲＥＦｍｉｎ以上に設定する必要がある。
洗浄効果を充分に発揮させることのできるＲＥＦｍｉｎは、すでに本発明者らにより前記結晶含液量と等量であることが見出されている。すなわち、ＲＥＦｍｉｎは、下式（１）により算出することができる。
ＲＥＦｍｉｎ＝ＭＡＳＳ×ｑｍ／（１００−ｑｍ） ・・・（１）
（式中、ｑｍは原料粗結晶１０の結晶含液率である。）
また、外部還流液１４の供給量が多すぎると製品１６の生産性が低くなる。そのため、ＲＥＦは、ＲＥＦｍｉｎの１．０〜１．１倍にすることが好ましい。
The supply amount (REF, unit: kg / h) of the external reflux liquid 14 to the top of the purification column 1 is set to a minimum amount REF min or more in order to maintain the quality of the product by the effect of the cleaning action. There is a need.
It has already been found by the present inventors that REF min capable of sufficiently exerting the cleaning effect is equivalent to the crystal liquid content. That is, REF min can be calculated by the following equation (1).
REF min = MASS × qm / (100−qm) (1)
(In the formula, qm is the crystal liquid content of the raw material crude crystal 10.)
Further, when the supply amount of the external reflux liquid 14 is too large, the productivity of the product 16 is lowered. Therefore, REF is preferably set to 1.0 to 1.1 times REF min .
外部還流液１４の温度ｔ１は、３５〜４０℃であることが好ましい。外部還流液１４の温度ｔ１を３５℃以上とすれば、発汗作用を充分に発揮させやすい。また、外部還流液１４の温度ｔ１を４０℃以下とすれば、精製効率が低下して製品１６の品質が劣化することを抑制しやすい。外部還流液１４の温度ｔ１及び量は、外部加熱器３に供給する加熱量Ｑ１（単位：Ｗ）により調節することができる。
精製塔留出分１２の温度は、外部還流液１４の温度ｔ１と同じ温度である。
The temperature t 1 of the external reflux liquid 14 is preferably 35 to 40 ° C. If the temperature t 1 of the external reflux liquid 14 is set to 35 ° C. or higher, the sweating action can be sufficiently exerted. Moreover, if the temperature t 1 of the external reflux liquid 14 is set to 40 ° C. or less, it is easy to suppress the purification efficiency from being lowered and the quality of the product 16 from being deteriorated. The temperature t 1 and the amount of the external reflux liquid 14 can be adjusted by the heating amount Q 1 (unit: W) supplied to the external heater 3.
The temperature of the refined column distillate 12 is the same as the temperature t 1 of the external reflux liquid 14.
本実施形態の精製方法においては、精製塔１の外気温Ｔ（単位：℃）によらず、効率的かつ安定に原料粗結晶１０を精製するために、加熱手段２による加熱の見かけ加熱量Ｑｒを制御する。見かけ加熱量Ｑｒの制御には、物質収支式、熱収支式、及び見かけ加熱量Ｑｒ（単位：Ｗ）と加熱手段２が実質的に精製塔１を加熱する正味加熱量Ｑａ（単位：Ｗ）との関係式を用いる。 In the purification method of the present embodiment, the apparent heating amount Qr of heating by the heating means 2 is used to efficiently and stably purify the raw material crude crystal 10 irrespective of the outside temperature T (unit: ° C.) of the purification tower 1. To control. The apparent heating amount Qr is controlled by a material balance equation, a heat balance equation, an apparent heating amount Qr (unit: W), and a net heating amount Qa (unit: W) that the heating means 2 substantially heats the purification tower 1. The relational expression is used.
本実施形態における物質収支式は、下式（２）及び（３）で表される。
ＭＡＳＳ＝ＰＹ＋ＬＯＳＳ ・・・（２）
ＤＩＳＴ＝ＰＹ＋ＲＥＦ ・・・（３）
（式（３）中、ＤＩＳＴは、精製塔１からの精製塔留出分の排出量（ｋｇ／ｈ）である。）
The material balance equation in this embodiment is expressed by the following equations (2) and (3).
MASS = PY + LOSS (2)
DIST = PY + REF (3)
(In Formula (3), DIST is the discharge amount (kg / h) of the purification tower distillate from the purification tower 1.)
また、本実施形態における熱収支式は、下式（４）で表される。
ＭＡＳＳ×ＣＰＳ×ｔ０＋ＲＥＦ×（ＤＨ＋ＣＰＬ×ｔ１）＋Ｑａ＋Ｑ１
＝ＬＯＳＳ×（ＤＨ＋ＣＰＬ×ｔ２）＋ＤＩＳＴ×（ＤＨ＋ＣＰＬ×ｔ１） ・・・（４）
（式（４）中、ＣＰＳは結晶の比熱（単位：ｋＪ／ｋｇ／℃）、ＤＨは結晶の結晶化熱（単位：ｋＪ／ｋｇ）、ＣＰＬは製品の液比熱（単位：ｋＪ／ｋｇ／℃）、ｔ２は濃縮された不純物１８を含んだ母液の排出温度（単位：℃）である。）
ＣＰＳ、ＣＰＬ、ＤＨは精製中の各成分の物性定数であり、ＭＡＳＳ、ｔ０、ｔ１、ｔ２は実測運転データを代入する。
Further, the heat balance equation in the present embodiment is represented by the following equation (4).
MASS × CPS × t 0 + REF × (DH + CPL × t 1 ) + Qa + Q 1
= LOSS × (DH + CPL × t 2 ) + DIST × (DH + CPL × t 1 ) (4)
(In formula (4), CPS is the specific heat of the crystal (unit: kJ / kg / ° C.), DH is the heat of crystallization of the crystal (unit: kJ / kg), CPL is the liquid specific heat of the product (unit: kJ / kg / ° C.), t 2 is discharged temperature of the mother liquor containing impurities 18 enriched (unit: a ° C.)).
CPS, CPL, and DH are physical constants of each component during purification, and MASS, t 0 , t 1 , and t 2 are substituted with actually measured operation data.
加熱手段２による精製塔缶体表面の加熱は、加熱操作中に放熱現象（図１におけるＱｂ（単位：Ｗ）が起きているため、見かけ加熱量Ｑｒの全てが精製塔１の加熱に寄与するわけではなく、精製塔１の保温の形態及び外気温Ｔにより変化する。すなわち、外気温Ｔにより正味加熱量Ｑａが変化してしまう。見かけ加熱量Ｑｒと正味加熱量Ｑａとの関係は、下式（Ｉ）で表される。
Ｑａ＝α（Ｔ）×Ｑｒ ・・・（Ｉ）
（式中、α（Ｔ）は、精製塔１の外気温Ｔにおける、見かけ加熱量Ｑｒの精製塔内部の加熱への寄与率である。）
Heating of the surface of the purification tower can body by the heating means 2 causes a heat dissipation phenomenon (Qb (unit: W) in FIG. 1) during the heating operation, so that all of the apparent heating amount Qr contributes to the heating of the purification tower 1. It does not mean that it changes depending on the heat insulation mode of the purification tower 1 and the outside air temperature T. That is, the net heating amount Qa changes depending on the outside air temperature T. The relationship between the apparent heating amount Qr and the net heating amount Qa is as follows. It is represented by Formula (I).
Qa = α (T) × Qr (I)
(In the formula, α (T) is the contribution ratio of the apparent heating amount Qr to the heating inside the purification tower at the outside temperature T of the purification tower 1).
外気温Ｔ（単位：℃）は、精製塔１が設置されている環境の温度を表す。具体的には、精製塔１付近で測定した温度を用い、精製塔１にできるだけ近い位置での測定温度であることが好ましい。
α（Ｔ）は、外気温Ｔ、装置代表温度（Ｔｓ）（単位：℃）、精製塔１の缶体の外径、保温層厚み、保温材の熱伝達率、および精製塔１の缶体の熱伝導率等により変化する。α（Ｔ）は、用いる精製塔１において、任意の外気温Ｔにおけるα値を実測値から算出し、それら任意の外気温Ｔにおけるα値を少なくとも５点以上選び、外気温Ｔに対する加熱量寄与率α（Ｔ）のｎ次近似線を得ることにより求めることができる。
The outside air temperature T (unit: ° C.) represents the temperature of the environment where the purification tower 1 is installed. Specifically, it is preferable to use a temperature measured in the vicinity of the purification tower 1 and a measurement temperature at a position as close as possible to the purification tower 1.
α (T) is the outside air temperature T, the apparatus representative temperature (Ts) (unit: ° C.), the outer diameter of the can of the refining tower 1, the heat insulating layer thickness, the heat transfer coefficient of the heat insulating material, and the can of the refining tower 1. Varies depending on the thermal conductivity of the material. For α (T), the α value at an arbitrary outside temperature T in the purification tower 1 to be used is calculated from actually measured values, and at least five or more α values at any outside temperature T are selected, and the heating amount contribution to the outside temperature T It can be obtained by obtaining an n-th order approximation line of the rate α (T).
装置代表温度（Ｔｓ）とは、外気温（Ｔ）との差に基づいてα（Ｔ）を算出する際に基準となる精製塔１の代表温度である。
装置代表温度（Ｔｓ）は、厳密には精製塔１とその外側の環境との界面における精製塔１の温度であることが好ましいが、これと連動して変化する温度であればよく、装置代表温度（Ｔｓ）の測定点は使用する精製塔１によって適宜選択することができる。装置代表温度（Ｔｓ）としては、例えば、精製塔１内部の被処理液（原料粗結晶１０を含有する母液）の温度、精製塔１の表面温度等を用いることができる。
The apparatus representative temperature (Ts) is a representative temperature of the purification tower 1 that serves as a reference when α (T) is calculated based on a difference from the outside air temperature (T).
Strictly speaking, the apparatus representative temperature (Ts) is preferably the temperature of the purification tower 1 at the interface between the purification tower 1 and the environment outside thereof, but may be any temperature that changes in conjunction with this. The measurement point of temperature (Ts) can be appropriately selected depending on the purification tower 1 to be used. As the device representative temperature (Ts), for example, the temperature of the liquid to be treated (the mother liquor containing the raw material crude crystal 10) inside the purification tower 1, the surface temperature of the purification tower 1, and the like can be used.
加熱手段２に加えられる見かけ加熱量Ｑｒは、加熱手段２の運転状態から算出される。
熱媒が温水である場合は、加熱手段２の入口の温水温度と出口の温水温度との差を△ｔ（単位：℃）、加熱手段２に供給する温水流量をＭ（単位：ｋｇ／ｈ）、温水の比熱をＣｐ（単位：ｋＪ／（ｋｇ・℃））とすると、下式（５）により見かけ加熱量Ｑｒ１（単位：Ｗ）を算出することができる。
Ｑｒ１＝０．２８×Ｍ×Ｃｐ×△ｔ ・・・（５）
The apparent heating amount Qr applied to the heating unit 2 is calculated from the operating state of the heating unit 2.
When the heating medium is hot water, the difference between the hot water temperature at the inlet of the heating means 2 and the hot water temperature at the outlet is Δt (unit: ° C.), and the flow rate of hot water supplied to the heating means 2 is M (unit: kg / h). ) And the specific heat of hot water is Cp (unit: kJ / (kg · ° C.)), the apparent heating amount Qr 1 (unit: W) can be calculated by the following equation (5).
Qr 1 = 0.28 × M × Cp × Δt (5)
また、熱媒が蒸気である場合は、使用圧力での蒸気エンタルピーをＨ１（単位：ｋＪ／ｋｇ）、使用圧力での凝縮水エンタルピーをＨ２（単位：ｋＪ／ｋｇ）、加熱手段２に供給する蒸気流量をｍ（単位：ｋｇ／ｈ）とすると、下式（６）により見かけ加熱量Ｑｒ２（単位：ｋＪ／ｈ）を算出することができる。
Ｑｒ２＝０．２８×ｍ×（Ｈ１−Ｈ２） ・・・（６）
When the heat medium is steam, the steam enthalpy at the working pressure is H 1 (unit: kJ / kg), the condensed water enthalpy at the working pressure is H 2 (unit: kJ / kg), and the heating means 2 Assuming that the flow rate of steam to be supplied is m (unit: kg / h), the apparent heating amount Qr 2 (unit: kJ / h) can be calculated by the following equation (6).
Qr 2 = 0.28 × m × (H 1 −H 2 ) (6)
本発明において、正味加熱量Ｑａ、見かけ加熱量Ｑｒ（Ｑｒ１、Ｑｒ２）の値を求める方法、及び該加熱量の値を管理しつつ加熱条件を制御する方法は特に制限されない。
例えば、精製塔１の運転状態から電卓等を用いて正味加熱量Ｑａ及び見かけ加熱量Ｑｒ（Ｑｒ１、Ｑｒ２）を算出した後、手動にて精製塔１の運転条件を変更する方法であってもよく、ＤＣＳ（Ｄｉｓｔｒｉｂｕｔｅｄ Ｃｏｎｔｒｏｌ Ｓｙｓｔｅｍ）やコンピュータを用いて正味加熱量Ｑａ及び見かけ加熱量Ｑｒ（Ｑｒ１、Ｑｒ２）を自動で計算し、表示させた後、手動もしくはＰＩＤ（ｐｒｏｐｏｒｔｉｏｎａｌ−ｉｎｔｅｇｒａｌ−ｄｅｒｉｖａｔｉｖｅ）コントロール等の自動制御により、精製塔１の運転条件を変更する方法であってもよい。
In the present invention, the method for obtaining the values of the net heating amount Qa and the apparent heating amount Qr (Qr 1 , Qr 2 ) and the method for controlling the heating conditions while managing the heating amount values are not particularly limited.
For example, the net heating amount Qa and the apparent heating amount Qr (Qr 1 , Qr 2 ) are calculated from the operating state of the purification tower 1 using a calculator or the like, and then the operating conditions of the purification tower 1 are manually changed. Alternatively, the net heating amount Qa and the apparent heating amount Qr (Qr 1 , Qr 2 ) are automatically calculated and displayed using DCS (Distributed Control System) or a computer, and then manually or PID (proportional-integral- It may be a method of changing the operating conditions of the purification tower 1 by automatic control such as (derivative) control.
前記式（２）〜（４）及び前記式（Ｉ）を用い、必要な運転状態のデータを代入しながら正味加熱量Ｑａと精製収率との関係を調べることにより、精製収率が最大になる時の正味加熱量Ｑａである最適加熱量Ｑｐを得ることができる。
そして、正味加熱量Ｑａの値が最適加熱量Ｑｐの値と同等になるように見かけ加熱量Ｑｒを制御することにより、効率的かつ安定に原料粗結晶の精製を行うことができる。
Using the formulas (2) to (4) and the formula (I), the purification yield is maximized by investigating the relationship between the net heating amount Qa and the purification yield while substituting the necessary operating state data. The optimum heating amount Qp that is the net heating amount Qa at the time can be obtained.
Then, by controlling the apparent heating amount Qr so that the value of the net heating amount Qa is equal to the value of the optimum heating amount Qp, the raw material crude crystals can be purified efficiently and stably.
例えば、正味加熱量Ｑａが最適加熱量Ｑｐよりも大きい場合は、精製塔１内において発汗作用が過剰に起こることで、原料粗結晶１０の融解現象が必要以上に進行しており、精製収率が低下していると判断できる。この場合には、見かけ加熱量Ｑｒを小さくするように運転条件を変更することにより、正味加熱量Ｑａを低減させることができる。
一方、正味加熱量Ｑａが最適加熱量Ｑｐよりも小さい場合は、精製塔１内において原料粗結晶１０への加熱が不足している傾向にあるために発汗作用が抑制されており、それにより精製効率が低下してくることが予測できる。この場合には、見かけ加熱量Ｑｒを大きくするように運転条件を変更することにより、正味加熱量Ｑａを増大させることができる。
見かけ加熱量Ｑｒを調節する方法は、加熱手段２に供給する熱媒の温度（入口温度）、または供給量を調節する方法であることが好ましい。
For example, if the net heat quantity Qa is greater than the optimal pressure heat Qp is sweating in the purifying column 1 is what happens to excess, and then proceeds to more than necessary melt behavior of the raw material crude crystals 10, purification yield It can be judged that has decreased. In this case, the net heating amount Qa can be reduced by changing the operating conditions so as to reduce the apparent heating amount Qr.
On the other hand, if the net heat quantity Qa is less than the optimum pressure heat Qp is sweating suppressed to tend to heat to the raw material crude crystal 10 is insufficient in the purification column 1, whereby purified It can be predicted that the efficiency will decrease. In this case, the net heating amount Qa can be increased by changing the operating conditions so as to increase the apparent heating amount Qr.
The method of adjusting the apparent heating amount Qr is preferably a method of adjusting the temperature (inlet temperature) of the heating medium supplied to the heating means 2 or the supply amount.
また、本発明の精製方法は、任意の外気温Ｔにおいて式（２）〜（４）及び式（Ｉ）を用いた計算を予め行って最適加熱量Ｑｐを求めておき、それに基づいて見かけ加熱量Ｑｒを制御して精製塔１を運転する方法であることが好ましい。この場合には、例えば、熱媒を用いた加熱手段２を有する精製塔１では、任意の外気温Ｔにおける最適加熱量Ｑｐに対応する熱媒の温度及び供給量を算出しておくことにより、精度の高い制御を行うことができる。また、予めそれらを算出しておく場合の外気温Ｔの刻み値は、特に限定されず、例えば５℃刻みで算出しておく方法が挙げられる。
また、本発明の精製方法としては、式（２）〜（４）及び式（Ｉ）を用いた計算を行いながら見かけ加熱量Ｑｒを制御して精製塔１を運転する方法を用いてもよい。
In the purification method of the present invention, the calculation using the formulas (2) to (4) and the formula (I) is performed in advance at an arbitrary outside temperature T to obtain the optimum heating amount Qp, and the apparent heating is performed based on the calculation. A method of operating the purification tower 1 while controlling the amount Qr is preferable. In this case, for example, in the purification tower 1 having the heating means 2 using the heat medium, by calculating the temperature and supply amount of the heat medium corresponding to the optimum heating amount Qp at an arbitrary outside temperature T, Highly accurate control can be performed. Moreover, the step value of the outside air temperature T in the case of calculating them beforehand is not specifically limited, For example, the method of calculating by 5 degreeC increments is mentioned.
Further, as the purification method of the present invention, a method of operating the purification tower 1 by controlling the apparent heating amount Qr while performing calculations using the formulas (2) to (4) and the formula (I) may be used. .
以上説明した本発明の精製方法は、精製塔１の物質収支及び熱収支、並びに見かけ加熱量Ｑｒと正味加熱量Ｑａとの関係式を用い、外気温Ｔの変化に伴って精製塔１の外壁から環境中に放出される熱量の変化を加味して、正味加熱量Ｑａが最適加熱量Ｑｐとなるように見かけ加熱量Ｑｒを制御している。そのため、外部還流液の供給量を増加させることなく、外気温に左右されずに最適な条件で精製を行える。したがって、本発明の原料粗結晶の精製方法によれば、優れた品質の製品を効率的かつ安定に得ることができる。 The purification method of the present invention described above uses the mass balance and heat balance of the purification tower 1 and the relational expression between the apparent heating amount Qr and the net heating amount Qa, and the outer wall of the purification tower 1 as the outside temperature T changes. The apparent heating amount Qr is controlled so that the net heating amount Qa becomes the optimum heating amount Qp in consideration of the change in the amount of heat released from the environment into the environment. Therefore, purification can be performed under optimum conditions without being influenced by the outside air temperature without increasing the supply amount of the external reflux liquid. Therefore, according to the raw material crude crystal purification method of the present invention, an excellent quality product can be obtained efficiently and stably.
尚、本発明の精製方法は、図１に例示した精製塔１を用いる方法には限定されない。例えば、加熱手段として精製塔缶体表面加熱器が設けられた精製塔ではなく、精製塔内部に、熱媒により加熱操作が施せるような加熱室が設けられた精製塔を用いる方法であってもよい。この場合においても、前述の方法と同様に加熱室に供給する熱媒による見かけ加熱量Ｑｒを制御することで効率的かつ安定に原料粗結晶を精製することができる。
また、図２に示す精製塔４であってもよい。精製塔４において精製塔１と同じ部分については同符号を付して説明を省略する。精製塔４では、原料粗結晶１０を塔頂側から供給し、外部還流液１４を塔底側から供給し、不純物１８を塔頂側から排出する。精製塔４を用いる方法であっても、前述の精製塔１を用いる方法と同じ方法で精製を行うことができる。
The purification method of the present invention is not limited to the method using the purification tower 1 illustrated in FIG. For example, not a purification tower provided with a purification tower can surface heater as a heating means, but a method using a purification tower provided with a heating chamber that can be heated by a heat medium inside the purification tower. Good. Even in this case, the raw material crude crystals can be purified efficiently and stably by controlling the apparent heating amount Qr by the heating medium supplied to the heating chamber in the same manner as described above.
Moreover, the purification tower 4 shown in FIG. 2 may be sufficient. In the refining tower 4, the same parts as those of the refining tower 1 are denoted by the same reference numerals and description thereof is omitted. In the purification tower 4, the raw material crude crystal 10 is supplied from the tower top side, the external reflux liquid 14 is supplied from the tower bottom side, and the impurities 18 are discharged from the tower top side. Even in the method using the purification tower 4, the purification can be performed by the same method as the method using the purification tower 1 described above.
以下、実施例及び比較例を示して本発明を詳細に説明する。ただし、本発明は以下の記載によっては限定されない。
精製塔としては、図１に例示した精製塔１（特開２００１−５８１０３号公報（特許文献１）に記載）を用いた。
熱媒２０としては、３００ｋＰａＧの飽和蒸気を用いた。
また、精製塔１におけるα（Ｔ）の近似式を求めたところ、
α（Ｔ）＝９．０×１０−６×Ｔ２＋０．０００９×Ｔ＋０．１６１２ ・・・（７）
であった。
外気温Ｔは、精製塔１近辺に熱電対を設置して測定した。また、装置代表温度Ｔｓは、被処理液の融点とした。
Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited by the following description.
As the purification tower, the purification tower 1 exemplified in FIG. 1 (described in JP-A-2001-58103 (Patent Document 1)) was used.
As the heat medium 20, 300 kPaG saturated steam was used.
Further, when an approximate expression of α (T) in the purification tower 1 was obtained,
α (T) = 9.0 × 10 −6 × T 2 + 0.0009 × T + 0.1612 (7)
Met.
The outside air temperature T was measured by installing a thermocouple near the purification tower 1. The apparatus representative temperature Ts is the melting point of the liquid to be processed.
［調製例］原料粗結晶の調製
メタクロレインを分子状酸素で接触気相酸化し、得られた反応生成ガスを凝縮し、抽出した後、蒸留することにより粗製メタクリル酸を得た。得られた粗製メタクリル酸に第二成分としてメタノールを４．０質量％になるように添加し、これを冷却ジャケット式攪拌槽型晶析装置を用いて晶析操作を行い、得られたスラリーを固液分離した後、原料粗結晶についてガスクロマトグラフィーにより成分分析を行ったところ、表１に示される不純物が含まれていた。母液中のメタノールの濃度と原料粗結晶（液体を含む）を融解した液中のメタノールの濃度から算出した結晶含液率ｑｍは１５質量％であった。なお、メタノールはメタクリル酸の結晶には実質的に取り込まれない化合物である。
[Preparation example] Preparation of raw material crude crystal Methacrolein was subjected to catalytic gas phase oxidation with molecular oxygen, and the resulting reaction product gas was condensed, extracted, and then distilled to obtain crude methacrylic acid. Methanol was added to the obtained crude methacrylic acid as a second component so as to be 4.0% by mass, and this was subjected to a crystallization operation using a cooling jacket type stirring tank crystallizer, and the resulting slurry was obtained. After the solid-liquid separation, the raw material crude crystals were subjected to component analysis by gas chromatography. As a result, the impurities shown in Table 1 were contained. The crystal liquid content qm calculated from the concentration of methanol in the mother liquor and the concentration of methanol in the melted raw material crude crystal (including liquid) was 15% by mass. Methanol is a compound that is not substantially taken into the methacrylic acid crystals.
［実施例１］
精製塔１に、前記調製例で得られた原料粗結晶を供給量（ＭＡＳＳ）１５００ｋｇ／ｈで供給した。また、ｔ０は５．３℃、ｔ１は３８℃、ｔ２は１５℃、外部還流液の供給量（ＲＥＦ）は２３０ｋｇ／ｈとして、１２０時間連続運転を行った。
精製操作中、得られるデータから前記式（２）〜（３）及び前記式（Ｉ）により最適加熱量Ｑｐを算出したところ１４９３３Ｗであった。そこで、加熱手段２に供給する蒸気の流量を調節することにより、正味加熱量Ｑａが１４９３３Ｗとなるように見かけ加熱量Ｑｒを制御して精製を行った。見かけ加熱量Ｑｒは、式（６）及び（７）と式（Ｉ）を用いて算出した。蒸気流量ｍの調整、各パラメータの測定および算出は前記ＤＣＳを用いて、１分毎に連続して行った。
[Example 1]
The raw material crude crystal obtained in the preparation example was supplied to the purification tower 1 at a supply amount (MASS) of 1500 kg / h. Also, t 0 is 5.3 ° C., t 1 is 38 ° C., t 2 is 15 ° C., the supply amount of external reflux liquid (REF) as 230 kg / h, was continuously operated for 120 hours.
It was 14933W when the optimal heating amount Qp was computed by said Formula (2)-(3) and said Formula (I) from the obtained data during refinement | purification operation. Therefore, the purification was performed by adjusting the flow rate of the steam supplied to the heating means 2 so as to control the apparent heating amount Qr so that the net heating amount Qa becomes 14933W. Apparent heating amount Qr was calculated using equations (6) and (7) and equation (I). Adjustment of the steam flow rate m, measurement and calculation of each parameter were performed continuously every minute using the DCS.
［比較例１］
蒸気流量ｍを１２７ｋｇ／ｈ（見かけ加熱量Ｑｒ＝７５８３３Ｗ）に固定した以外は、実施例１と同様の方法で精製塔１の連続運転を行った。ただし、外気温Ｔが２０℃のときはＲＥＦが２３０ｋｇ／ｈでは不純物の濃度が増加したので、ＲＥＦを２６５ｋｇ／ｈに増加させて不純物の濃度をＴが３０℃のレベルに保持した。
[Comparative Example 1]
The purification tower 1 was continuously operated in the same manner as in Example 1 except that the steam flow rate m was fixed at 127 kg / h (apparent heating amount Qr = 75833 W). However, when the ambient temperature T was 20 ° C., the impurity concentration increased when the REF was 230 kg / h. Therefore, the REF was increased to 265 kg / h to maintain the impurity concentration at the level of 30 ° C.
実施例１および比較例１における精製収率を運転条件と共に表２に示す。ただし、表２の結果は、外気温Ｔが３０±０．５℃、２０±０．５℃におけるＤＣＳから得られる値の平均値を示したものである。
また、実施例１で得られた製品をガスクロマトグラフィーで成分分析した結果を表３に示す。
The purification yields in Example 1 and Comparative Example 1 are shown in Table 2 together with the operating conditions. However, the result of Table 2 shows the average value of values obtained from DCS when the outside air temperature T is 30 ± 0.5 ° C. and 20 ± 0.5 ° C.
Table 3 shows the results of component analysis of the product obtained in Example 1 by gas chromatography.
表２に示すように、実施例１では、外気温Ｔが２０℃であっても３０℃であっても精製収率が高く、安定して精製を行うことができた。また、表３に示すように、精製により得られた製品は不純物が充分に取り除かれており精製効率が高かった。
一方、見かけ加熱量Ｑｒを制御しなかった比較例１では、表２に示すように、外気温Ｔが３０℃である場合は精製収率が実施例１と同等であるものの、外気温Ｔが２０℃になると精製収率が低下し、安定に精製を行うことができなかった。該理由としては、精製塔１の熱収支上、外気温Ｔが低くなった場合に正味加熱量Ｑａが減少し、内部還流量の低下により製品中の不純物濃度が上昇することが予測されたため、正味加熱量不足分を補うように外部還流量の供給量を増加させたためと考えられる。
As shown in Table 2, in Example 1, the purification yield was high even when the outside air temperature T was 20 ° C. or 30 ° C., and the purification could be performed stably. Further, as shown in Table 3, the product obtained by purification was sufficiently free of impurities, and the purification efficiency was high.
On the other hand, in Comparative Example 1 in which the apparent heating amount Qr was not controlled, as shown in Table 2, when the outside air temperature T was 30 ° C., the purification yield was equivalent to that in Example 1, but the outside air temperature T was When the temperature reached 20 ° C., the purification yield decreased, and the purification could not be performed stably. The reason for this is that, on the heat balance of the refining tower 1, it was predicted that the net heating amount Qa would decrease when the outside air temperature T became low, and the impurity concentration in the product would increase due to a decrease in the internal reflux amount. This is probably because the supply amount of the external reflux amount was increased to compensate for the shortage of the net heating amount.
［実施例２］
精製塔１の各外気温Ｔに対応する最適加熱量Ｑｐを予め算出し、蒸気流量ｍに換算した。その結果を表４に示す。
[Example 2]
An optimum heating amount Qp corresponding to each outside air temperature T of the purification tower 1 was calculated in advance and converted into a steam flow rate m. The results are shown in Table 4.
その結果、精製収率は実施例１と同等であった。
As a result, the purification yield was equivalent to that in Example 1.
本発明の精製方法は、原料粗結晶を効率的かつ安定に精製することができるため、粗製（メタ）アクリル酸の精製方法として好適にできる。 Since the raw material crude crystals can be purified efficiently and stably, the purification method of the present invention can be suitably used as a method for purifying crude (meth) acrylic acid.
精製塔 ２ 加熱手段 ３ 外部加熱器 ４ 精製塔 １０ 原料粗結晶 １２ 精製塔留出分 １４ 外部還流液 １６ 製品 １８ 不純物 ２０ 熱媒
Purification tower 2 Heating means 3 External heater 4 Purification tower 10 Raw material crude crystal 12 Purification tower distillate 14 External reflux liquid 16 Product 18 Impurity 20 Heat medium
Claims (4)
前記精製塔内に原料粗結晶を供給し、前記精製塔内から該原料粗結晶が精製された結晶を取り出すとともに、その一部を融解させた外部還流液を塔頂側もしくは塔底側から供給し、前記原料粗結晶から生じた不純物を前記外部還流液の供給側と逆側の塔底側もしくは塔頂側から排出して精製する方法であって、
前記加熱手段により、前記精製塔内部における前記原料粗結晶が供給される位置から前記精製された結晶が取り出される位置の間の領域を少なくとも加熱し、
前記加熱手段による加熱の見かけ加熱量Ｑｒを、前記精製塔の物質収支式、熱収支式、及び下式（Ｉ）を用いた計算に基づいて、精製塔内部を加熱する正味の加熱量Ｑａが、精製収率が最大になる時の最適加熱量Ｑｐとなるように制御することを特徴とする原料粗結晶の精製方法。
Ｑａ＝α（Ｔ）×Ｑｒ ・・・（Ｉ）
（式（Ｉ）中、α（Ｔ）は精製塔の外気温Ｔにおける、見かけ加熱量Ｑｒの精製塔内部の加熱への寄与率である。） While heating the inside of the purification tower by the heating means provided in the purification tower,
The raw material crude crystals are supplied into the purification tower, the purified crystals of the raw material raw crystals are taken out from the purification tower, and an external reflux liquid obtained by melting a part thereof is supplied from the tower top side or the tower bottom side. And purifying the impurities generated from the raw material crude crystals by discharging from the column bottom side or the column top side opposite to the supply side of the external reflux liquid,
The heating means heats at least a region between a position where the raw crude crystal is supplied inside the purification tower and a position where the purified crystal is taken out,
The apparent heating amount Qr of heating by the heating means is calculated based on the calculation using the material balance equation, the heat balance equation, and the following equation (I) of the purification tower. The method for purifying the raw material crude crystal, wherein the purification is controlled so that the optimum heating amount Qp when the purification yield is maximized .
Qa = α (T) × Qr (I)
(In formula (I) , α (T) is the contribution ratio of the apparent heating amount Qr to the heating inside the purification tower at the outside temperature T of the purification tower.)
前記見かけ加熱量Ｑｒの制御を該熱媒の流量又は温度を調節することにより行う、請求項１〜３のいずれか一項に記載の原料粗結晶の精製方法。 The heating by the heating means is performed by supplying a heating medium to the heating means,
The method for purifying a raw material raw crystal according to any one of claims 1 to 3, wherein the apparent heating amount Qr is controlled by adjusting a flow rate or a temperature of the heating medium.
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