Basic knowledge of filtration
A filter is an operation in which a mixture of solids and gas is mixed with a solid body through a lot of fine holes and separates solid particles from the liquid or gas.Coffee drips and air purifiers use the principle of filtering.The film technology is used in the manufacturing process of the food, pharmaceuticals, and biotechnology fields.In this series, we will explain the basics of filtration mainly for filtration of liquids six times.This time, which is the first time, we will introduce the fields, types and characteristics of the filtration.
Lottery
1st: What is a filter?
The filter is a form of solid liquid separation operation, and is an operation in which solid particles suspended in the liquid are captured by filter material and separated from the liquid.Do you remember doing science time and filtration experiments (Fig. 1) when you were a child?Filtration is one of the oldest technology created by mankind.Even in the modern times when technology has advanced, filtering is a core technology in various industrial fields and plays an important role.
図1：ろ過の実験The characteristic of filtering is that it is simple and energy -saving, without chemical changes or thermal changes, and has less effects of secondary pollution on the environment.Recently, the development of high -performance filtering material has become a more subdivided for filtration.A wide variety of filtration technology, such as chemistry, food, pharmaceutical, bio, environment, fiber, paper / pulp, steel, batteries, glass, and ceramics.
In particular, in the environment (water treatment) field, filtration is indispensable because the filtration is high accurate, low cost and mass processing.In the water purification treatment for the manufacturing of tap water, the main separation technology uses a fast filtration with a thick sandy layer.Recently, for higher -precision separation, water purification treatment and drainage treatment using the film have been actively performed.A typical example is drainage treatment by film separation activity sludge method.The conventional active sludge method is ...
>>第1回 第2章の続きを読む（PDFダウンロード）
There are various types of filtration.Choose the method and operation correctly to make the filtration efficient.
As a basic filtration system, there are two types: constant pressure filtration that keeps the filtration pressure constant and constant filtration to keep the filtration speed constant.Industrially, a drilling method of transformation shifting, switching from constant speed to constant pressure, step -by -step rising methods, etc. may be incorporated.In addition, due to the difference in the driving method of the filter, gravity filtration that promotes the self -weight of the suspension, the pressurization of the supply fluid side, the filtration filtration, and the decompression filtration (vacuum filtration) that lowers the filter side to low pressure (vacuum).It is classified as a centrifugal filtration that promotes the centrifugal force caused by the rotation of the filter.For pressure filtration, compresser air pressure is performed with a compressor, pump is pumped with a pump, and the decompression filtration uses a vacuum pump.
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>>第1回 第3章の続きを読む（PDFダウンロード）
If the filtration device is roughly divided, it is classified into three types: a cake filter, a cakes filtration, and a Kiyosumi filter (Fig. 2).
図2：ケークろ過器、ケークレスろ過器、清澄ろ過器The cake filter is a dead end filtration system that supplies a suspension in the direction of the spill (vertical direction to the filter surface).The Cake layer grows as the filtration progresses.The pressurized device is often operated by a batch type, and when a predetermined amount of cake is formed, the filter operation is terminated and cake is exhausted.Vacuum -type devices are often operated in a continuous type, and operations such as cutting off the cake layer with a scraper while continuing filtration operations are performed.A well -known device includes a pressure bowl (filter press), leafy filter (leaf filter), and cylindrical vacuum filter (drum filter).
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>>第1回 第4章の続きを読む（PDFダウンロード）
The filter material is a porous material for solid liquid separation used in the case of filtering.The types of filters include filter, film, film, etc.
Ryokan is often used in chemical experiments and ordinary households.Generally, it is made of polymer (cellulose), and some are made of inorganic materials like glass fiber paper.
Rofu has a woven fabric and a non -woven cloth.The woven fabric is a regular woven fiber, and its weaving is basically three types: flat weaving, Aya weaving, and Suzu -wo.
図3：ろ布（織布）の織り方Hiraori is the most elaborate weave, so it has excellent particle captivity, has high durability, and is more likely to cause clogging.Suzo weaving is hard to clog and has excellent cake peeling properties.On the other hand, due to the large gaps, the particle captivity is poor and the durability is low.Aya weaving has the intermediate properties between Hiro and Suzo weaving, both good and bad, and is most commonly used.The non -woven fabric is a filtered material that is molded in a sheet, causing the fiber to be glued irregularly.
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>>第1回 第5章の続きを読む（PDFダウンロード）
In the filter, the separated liquid passes through the cake layer and the material.Let's consider the filtration model as shown in Fig. 4.
図4：ろ過モデルThe speed of the flow (flow velocity) is proportional to the pressure (propulsion) that tries to flow, and is inversely proportional to the force (resistance) to hinder the flow.That is, it is requested by flow speed = propulsion/resistance.The law of ohm in electricality (current = voltage/resistance) is exactly the case.For the flow of the film in the filter, the filtration speed = filtration pressure/filter resistance is established.This section describes the three types: filtration speed, filtration pressure, and filtration resistance.
ろ過速度q(m/s)は、単位ろ過面積当たりのろ液量v(m)（=ろ液量V(m3)÷ろ過面積A(m2)）を時間t(s)で微分したものと定義されます。
ろ過の推進力となる圧力Δp(Pa)は、供給液側の圧力p1とろ液側の圧力p2との差圧（ゲージ圧）p1-p2で与えられます。加圧ろ過ではp2が、減圧ろ過ではp1が大気圧になります。
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>>第1回 第6章の続きを読む（PDFダウンロード）
2nd: Kake filtration and closed clam filtration
Last time, I explained the type of filtration, the principle, and the basic model of the filtration.This time, I will explain the theoretical model that describes the process of changing the behavior of Kake filtration, closed clumping, and filtration.Learn how to determine the Cake filtration and the closed clam, and how to think about the actual filtration process.
Cake filtration is a filtration style in which particles are deposited on the surface of the filter material, and the closed yroll filtration is a filtration style in which particles are captured at the entrance or inside of the filter (Fig. 1).There are three basic models: a closed clam filtration: completely closed, standard closed, and intermediate closed.The model in Fig. 1 assumes that the filter material is a group of hair tubes with a uniform length and diameter.
図1：ケークろ過と閉そくろ過In the Cake filtration, as the filtration progresses, a particle sediment layer called Kake is formed on the surface of the material, which is the main factor in increasing filtration resistance.The size of the cake resistance increases in proportion to the mass of the particle group that makes up the cake.
In a completely closed claw filtration, if the particle diameter is greater than the pipe diameter, one particles are captured at one hair tube entrance and the hair tube is completely closed.At this time, as the filtration progresses, the number of untirin hair tubes decreases, and the filtration speed decreases in proportion to this.
標準閉そくろ過では、毛管径より粒子径の方が小さい場合に、...
>>第2回 第1章の続きを読む（PDFダウンロード）
前回、下記のろ過の基本モデル式が与えられることを説明しました。ろ過速度q(m/s)、ろ過圧力Δp(Pa)、ろ液粘度μ(Pa･s)、ろ過抵抗R(1/m)からなり、Rはろ材そのものの抵抗Rm、ろ材の閉そくによる抵抗Rb、ケーク層の増加による抵抗Rcの和で表されます。
The loose Cake filtration model is modeled on the process of Kake filtration in an easy -to -understand manner.With the passage of time, Cake filtration gradually increases due to the increase in filtration resistance due to the accumulation of the cake layer.Here, we will explain the filtration model of the loose.First, take a formula that does not take into account the impact of the closing, taking into account only the formation of the cake.If you ignore the closing resistance in the basic model of the filter, the following equation will be established.
ケーク抵抗Rcは、単位ろ過面積当たりのケーク内の固体分質量w(kg/m2)（ケークの成長に伴い増大）に比例します。さらに、ろ材抵抗Rmについても、ろ材をそれと等価な仮想ケークに置き換えて考えると、同様に仮想ケーク内の固体分質量wm(kg/m2)（ろ過期間中一定）に比例します。比例係数をαav(m/kg)と置くと、次式が得られます。
αavは単に比例係数ではなく、平均ろ過比抵抗と呼ばれるケークの重要な特性値です。これについては、次回に詳しく解説します。実際の操作における測定を考慮すると、ケークとして堆積する固体量の変化を追うのは難しく、流出するろ液量の変化は容易に測定できます。そこで、単位ろ過面積当たりのケーク固体質量w(kg/m2)と単位ろ過面積当たりのろ液量v(m3/m2)、ならびに仮想ケーク固体質量wm(kg/m2)と仮想ろ液量vm(m3/m2)の関係から、次式が成り立ちます。
ここで、ρ(kg/m3)はろ液密度、sは試料液の固体濃度（質量分率）、mはケークの湿乾質量比（湿潤ケークと乾燥ケークの質量比）です。この式は、試料液質量(w/s)=湿潤ケーク質量(mw)+ろ液質量(ρv)という物質収支より導かれます。以上のRc、Rm、w、wmを、式1に代入すると、次式になります。
この式はろ材の影響を加味しているので、ろ過圧力Δpはケークの圧力損失Δpcとろ材の圧力損失Δpmの和（Δp=Δpc+Δpm）を意味し、ろ液量も(v+vm)で与えられています。一方、ケークの部分だけに着目すると、次のように書き改められます。
定圧ろ過の条件下での理論を考えていきます。式2において、ろ過速度qをろ液量の時間微分q=dv/dtで表し、ろ過圧力Δpが一定の条件下で、ろ液量vを時間tで積分します。定圧条件下ではαavはろ過期間中一定と見なすことができるので、次式が容易に導かれます。
この式より、定圧ろ過ではろ液量と時間との関係が放物線で表されます。なお、tmはvmを得るのに要する仮想ろ過時間です。K(m2/s)は定圧ろ過係数と呼ばれ、ろ過速度の大きさの指標となる値です。式4を微分すると、次式が得られます。
すなわち、ろ過速度の逆数(dt/dv)とろ液量vとは直線関係を示します。なお、式5は式2の両辺を逆数で表した式でもあります。また、式4を展開してvm2=Ktmの関係を用いて整理すると、次式となります。
In the graph, the relationship between the retrospective number (T/V) and the liquid volume V of the comprehensive filtration speed can be expressed in a straight line.Figure 2 is an example of a DT/DV vs V and T/V vs. V graphs in constant pressure filtration.The two plots are obtained from the same filtration data.In each case, the linear relationship is indicated, and the inclination of DT/DV vs. V is twice the inclination of T/V vs. V.From the inclination, the value of K is 2.72×10-6(m2/s)と算出されます。このプロット法はルースプロットと呼ばれ、定圧ろ過データの整理法として有効です。異なる定圧ろ過データをルースプロットで比較するときは、縦軸がろ過速度の逆数であることに注意しなければなりません。すなわち、ろ過速度が大きいほど傾きは緩やかになり、ろ過速度が小さいほど傾きは急になります。
図2：定圧ろ過のプロット法...
>>第2回 第2章の続きを読む（PDFダウンロード）
As a model that describes the slapping process of filter material, the closed clerk filtrate model proposed by Hermance -Brady is well known.The processing process of the cake is relatively regular, but the slurber closing is often irregular, and the pole structure of the filter material is complicated, so it is not easy to theoretically capture the closed slogan process.。Therefore, it is often used to simply capture complex closed phenomena and express it in one of the three basic models described above.In the constant pressure filtration, the following is the following when describing the three basic models in the filtration speed formula.Here, the derivative process is omitted, and only the conclusion is shown.
完全閉そく：q=q0-K1v標準閉そく：q=q0(1-K2v)2中間閉そく：q=q0exp(-K3v)
In addition, the expression 5 of the Cake filtration speed is also changed in preparation for the next section, and the following is shown.
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>>第2回 第3章の続きを読む（PDFダウンロード）
In order to understand which model in the constant pressure filtration is followed by the three formulas that describe the closing woven filtration and the formula 6 that describe the Cake filtration, the data of the obtained spending speed Q -pair liquid volume VUse the following plot.Completely closed, √ q vs. Q vs V -V for standard closed, LN Q vs V -V for intermediate closed, and 1/Q vs. V for Cake filtration.Make these four types of plots and see which plot shows a linear relationship.
Figure 4 shows an example of four plots.Both are plotted the same filtration data.You can see that the most straight line of these graphs is the plot of √q vs. V.Therefore, it can be determined that this filtration process is standard closed.
図4：閉そくろ過のプロット法1In addition, the three formulas of completely closed, standard closed, and intermediate closed and Cake filtration 6 can be summarized in the following general formulas.Index I is 2 for completely closed, 2, standard closed..5. Intermediate closed 1, Cake filtration is 0.
このことから、ろ過モデルの特定は、...
>>第2回 第4章の続きを読む（PDFダウンロード）
The actual closed cloring process often indicates complicated behavior that cannot be explained by the above -mentioned closed clam, and does not always follow any of the three types of closed clam filtration.For example, the straight line in FIG. 5 does not necessarily mean either the I -value described above, and does not necessarily be a straight line.For this reason, a number of closed-filtration models have been proposed so far, including models developed based on the Hermance-Brady model and completely new type models.
また、閉そくろ過とケークろ過の両方が生じるケースも少なくありません。例えば、ごく希薄な懸濁液を長時間ろ過したときのルースプロットでは、初めは曲線的に変化し、やがて直線に移行するという挙動がしばしば見られます。これは、初めは閉そくろ過が支配的で、やがてケークろ過が支配的になったことを意味しています。このような場合、閉そくろ過過程が標準閉そくであったとして、...
>>第2回 第5章の続きを読む（PDFダウンロード）
3rd: Analysis and evaluation of Kake filtration
Last time, as a theoretical model that describes the Cake Project process, I explained each model of constant pressure and constant speed filtration.This time, I will explain in detail how to analyze the essential cake structure in understanding the Cake filtration characteristics by utilizing these models.First, let's look at the data analysis method of Kake filtration.
Before explaining the data analysis method of Cake Roit, first of all, I will review the constant pressure filtration model and the constant reputation model described earlier.
Constant pressure filtration model
Constant speed filtration model
Next, let's look at the plot method of Cake filtration data.Figure 1 shows the plot method for constant pressure and the plot of constant speed.
図1：ケークろ過のプロット法定圧ろ過では、...
>>第3回 第1章の続きを読む（PDFダウンロード）
ケーク層は一般に圧縮性を示し、その構造は均質ではありません。図2は圧縮性ケークの内部状態です。ろ液は右から左に流れています。ろ液はケーク層内の粒子間隙の抵抗を受けながら透過するため、液圧ΔpLはろ材に近づくにつれて減少します。一方、ケーク内の粒子はその抵抗に相当する圧縮圧力を受けるため、圧縮圧力Δpsはろ材に近づくにつれて増大し、ΔpL+Δps=Δpの関係が保たれます。その結果、ケーク表面付近は湿潤で、ろ材に近づくにつれて緻密化し、ケークの空隙率は減少し、ろ過比抵抗は増大します。
図2：圧縮性ケークの内部状態ろ過圧力Δpを増加させると、ケーク内の各粒子にかかる圧縮圧力は増大し、結果としてケークの総括的特性値である平均空隙率εavは減少し、平均ろ過比抵抗αavは増大します（αavの定義は第2回を参照）。このαavの圧力依存性は、...
>>第3回 第2章の続きを読む（PDFダウンロード）
ケークろ過では、ろ材面上に形成されるケークがろ過性能を本質的に支配します。従って、その特性を明らかにすることが、ろ過プロセスを設計する上で極めて重要となります。これ以降は、基本的なケーク特性値である平均ろ過比抵抗αav、平均空隙率εav、圧縮性指数nの測定・評価方法について解説していきます。
平均ろ過比抵抗αavは、ろ過の難しさの指標となる値であり、1011m/kg程度までならろ過性は高く、1012～1013m/kg程度は中程度のろ過性、1013m/kg以上は難ろ過性と判断することができます。
平均ろ過比抵抗αavは、定圧ろ過の実験データにより容易に求めることができます。式1もしくは、式2が示すように、dt/dv対vをプロットすると傾き2/Kの直線が、t/v対vをプロットすると傾き1/Kの直線がそれぞれ得られます。その傾きの値を次式に代入すれば、αavの値が算出できます。
Let's consider the constant pressure filtration in Fig. 1.As I explained last time, K = 2 from the slope of the straight line..72×10-6m2/sと算出されます。実験条件が、Δp=100kPa、m=1.60, S = 0.0100, μ = 1.00×10-3Pa･s、ρ=998kg/m3であったとします。これらの値を代入して計算すると、αavの値は、7.25×1012m/kgと求められます。この結果から、この試料のろ過性は中程度であると判断することができます。なお、試料液が希薄な場合には、1–ms≓1と近似しても差し支えありません。例えば、上記のケースでは、1–ms=0.It is 984, and it can be accepted even if it is approximated with 1.
また、次の方法でもαavの値を見積もることができます。まず、...
>>第3回 第3章の続きを読む（PDFダウンロード）
There are two ways to evaluate the gap rate: a direct measurement method for taking out and measuring the cake, and an indirect measurement method that measures without removing the cake.I will explain these two.
平均空隙率εavは、ケークの全体積に占める空隙（液体）部分の体積の割合として定義され、ケークの全量をうまく取り出すことができれば、直接的に測定することができます。先ほどから何度か出てきているmはケークの湿乾質量比で、取り出した湿潤ケークの質量Wwを測定し、これを完全に乾燥させて乾燥ケークの質量Wdを測定すれば、m=Ww/Wdが算出できます。平均空隙率εavは、湿乾質量比mと次式の関係があるので、これによりεavを求めることができます。
ここで、ρsは粒子の密度、ρはろ液の密度です。例えば、密度2,650kg/m3の粒子からなるケークの湿潤質量と乾燥質量がそれぞれ28.52g, 17.When it was 38g, m = 28.52/17.38 = 1.641と求められ、このケークの平均空隙率はεav=0.It will be guided with 630.
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>>第3回 第4章の続きを読む（PDFダウンロード）
圧縮性指数とは、ろ過圧力とケーク比抵抗の関係から求められる実験値で、ケークの圧縮性の大小を示す数値です。式4で定義される圧縮性指数nにより、ケークの圧縮性の程度が評価できます。n=0のケークは非圧縮性であり、αavは圧力に依存せず、ケーク構造は全体的に均質になります。また、nが0.If it is up to 2, low compression, 0.5程度までなら中程度の圧縮性、それ以上であれば高圧縮性と評価することができます。n=1というのは、圧力を2倍に上げると抵抗も2倍になるため、結果としてろ過速度の向上にはつながらないことを意味しています。さらに、nが1を超える場合には、圧力を上げるとそれ以上にろ過抵抗が増加するため、かえってろ過速度の低下を招く結果になります。変形能があるソフト粒子のろ過などで、このようなケースが起こり得ます。図5は、圧力Δpとαavの関係を示したグラフです。圧縮性指数nは、式4に基づき、このグラフを作成することで求められます。
図5：圧縮性指数nの求め方種々の圧力Δpで定圧ろ過実験を行い、前述の方法でαavを求め、これをΔpに対して両対数プロットして近似直線を引くと、その傾きがnとなります。例えば、...
>>第3回 第5章の続きを読む（PDFダウンロード）
4th: Colloid film by membrane
Last time, I explained the analysis and evaluation of Kake filtration.This time, the effects of the solution environment on the filtration characteristics of the film by the membrane will be explained in light of the average ratio resistance and the average gap rate.The membrane is an extremely high -performance material that separates 1 µm or less that cannot be separated with filter paper or cloth.Materials under 1 µm are called colloids.Theoretically, you can apply a loose Cake filtration model described in the second time and a Hermanth-Brady closed yusado model.Fine substances such as colloids change the micro characteristics on the particle surface depending on the solution environment such as pH and ion strength.As a result, it is greatly affected by the solution environment with a macro characteristic of filtering characteristics.
The type of membrane can be used in various ways depending on the substance that is separated.Due to the difference in separation accuracy, the membrane separation method is classified as precision, excess filtration, nan filtration, and reverse osmosis, and the separation accuracy is higher in this order (Fig. 1).It is precision and extraordinary filtration that can apply the concept of Kake filtration, which has been explained so far.Delivery of precision filtration is mainly particles (especially particle diameter 0).It is a fine particle of 01 to 1 µm) and is positioned on an extension of the conventional filtration.On the other hand, the separation target of the external filtration is mainly molecular (especially a molecular molecule with a molecular weight of 1,000 to 500,000), which is an extension of reverse ionization that separates ions.In fact, the conventional concept of Kake filtration is generally applicable.
図1：膜分離の分類と分離対象The most basic physical properties that indicate the performance of the membrane are pores, that is, the size of the sowing of the film.It is extremely important to evaluate it accurately.If the pole structure is simple, it can be measured directly from the microscope image.In fact, the pores of the membrane have a complex shape and three -dimensional structure, so it is practically determined to determine the pores of pores such as fine particles (polymer) transparency, bubble point method, mercury pressure entry method, and pure water permeability.Is used.
For precision films, the porous diameter can be identified due to the relationship between particle diameter and preventive ratio, which transmits various fine particles whose particle diameter is known.Generally, the particle diameter, which has a 90%stop rate, is defined as a pores diameter of the precision film.Bacteria such as chord monas bacteria and Ceratian bacteria are often used.On the other hand, for the out -of -limits, various polymoles with known molecular weight, such as proteins, polyethylene glycols, and dextrans, are used.The separation performance of the out -of -limited film is generally evaluated by the division of division, not a pores -diameter, and the molecular weight of 90%of the molecular weight and the stop rate is defined as a division molecular weight.
The pores of the membrane are filled with a liquid that wets the membrane such as water or alcohol, and the pressure is gradually increased by applying air pressure to one side of the membrane.The liquid in the pores is pushed out at a certain pressure P, and the occurrence of bubbles is observed on the other side.The pressure P at this time is called a bubble point pressure and can be converted to pole diameter D.
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>>第4回 第1章の続きを読む（PDFダウンロード）
Colloid particles are generally positive or negative charges, and they are diversified in the liquid due to electrostatic rebound between particles.The solution surrounding the colloid particles is electrically neutral.As a result, the opposition ion (vs Ion) is attracted to the particle surface so that the charge of the particle surface is canceled.At this time, the anti -ion, which is strongly attracted by the charge on the particle surface, is fixed around the particles to form a fixed layer.Furthermore, the ionic ion, which can move freely outside, spreads with the opposite codes and forms a diffusion layer.These two layers surrounding particles are called electric double layers.There is a potential distribution in the electric double layer, and the electrical double layer of the particles overlaps, causing an antistatic repulsion.Therefore, the thicker the electric double layer, the greater the electrostatic rebound between particles.
When an electric field is applied to the electric double layer, the colloid particles move toward the electrode of the surface charge and the opposite code.This phenomenon is called electronic swimming.At this time, the water molecule, which is strongly connected to the particles due to the fixed layer, is also accompanied by the particles, causing a relative movement with the outer liquid.This border is called a slide surface, and the potential in this aspect is called a zeta potential.The value of the potential calculated from the measurement data of the electrophoresis speed is the zeta potential.When discussing the interaction between particles, the zeta potential is commonly used instead of the surface potential.The larger the absolute value of the zeta potential, the greater the electrostatic repulsion between particles.
図2は、電気泳動速度の測定データから求めたルチル型二酸化チタン（TiO2）微粒子と、タンパク質の一種である牛血清アルブミン（BSA）分子のゼータ電位を、pHに対してプロットしたグラフです。...
>>第4回 第2章の続きを読む（PDFダウンロード）
コロイドには分散と凝集の2つの状態があります。コロイドの分散と凝集のメカニズムは、DLVO理論によって説明することができます。DLVO理論によると、粒子間には静電反発ポテンシャルVA（正の値）とロンドン-ファンデルワールス引力ポテンシャルVA（負の値）がそれぞれ作用します。コロイドが分散状態にあるか凝集状態にあるかはこれらの和、すなわち全相互作用ポテンシャルVT=VR+VAによって判定することができます。ここでは、VRやVAの具体的な理論式の記述は省きます。VRは電気二重層が厚くなるほど、あるいはゼータ電位が大きくなるほど増大する値であり、VAはこれらの影響を受けない値です。また、VRとVAは、いずれも粒子間距離hの関数形で表されます。よって、VTもhの関数であり、VTをhに対して描いた線図をポテンシャル曲線と呼びます。
図3は、ポテンシャル曲線の例です。VRが支配的となるとき、正のエリアにはポテンシャル曲線の山ができます。この山が粒子同士が接近するのを妨げる障壁となって、コロイドは分散状態を保ちます。一方、VRが小さくなってVAが支配的になると、ポテンシャル曲線は常に負の値となって障壁がなくなり、コロイドは容易に凝集します。また、分散系と凝集系の変遷の間には凝集臨界点が存在します。
図3：ポテンシャル曲線図4は、コロイドの分散と凝集の変遷の模式図です。コロイドは、疎水コロイドと親水コロイドに大別されます。疎水コロイドとは、水とコロイド粒子との親和性が弱いコロイド溶液です。電気二重層を圧縮することにより、あるいは等電点付近のpHに調整することにより、分散系から凝集系へと移行します。電気二重層は、電解質を加えてイオン強度を高めることにより圧縮されます。一方、親水コロイドとは、...
>>第4回 第3章の続きを読む（PDFダウンロード）
ここまでは、pHや電解質濃度などの溶液環境の変化によって、コロイドの表面状態や相互作用がどのように変化するかを説明してきました。ここからは、こうしたコロイド特有の変化が、ろ過特性にどのような影響を及ぼすかを具体的に説明します。まず、疎水コロイドの代表例として、TiO2懸濁液の精密ろ過で得られたケーク層の構造について説明します。
図5は、TiO2ケークの平均ろ過比抵抗αavと平均空伱率εavをpHに対してプロットしたグラフです。まず、αavとεavとは負の相関があることが分かります。すなわち、疎なケークほどろ液が流れやすく、密なケークほどろ液は流れにくいことを意味しています。この図で最も特徴的なは、αavは最小値、εavは最大値を持つところです。そのときのpHに着目すると、およそpH8であり、TiO2粒子の等電点に一致していることが分かります。
図5：TiO2のケーク特性値図6は、pHが等電点のときと、等電点からアルカリ性側に離れたときのケークの状態を模式図で示しています。左はpHが等電点のときのケークの状態を表します。ゼータ電位が0となる等電点では、粒子間に静電反発力が働かないため、粒子同士が接近してロンドン-ファンデルワールス引力により凝集します。そのため、...
>>第4回 第4章の続きを読む（PDFダウンロード）
次に、親水コロイドの代表例としてBSA溶液の限外ろ過で得られたケーク層の構造について説明します。図7は、BSAケークの平均ろ過比抵抗αavと平均空隙率εavをpHに対してプロットしたグラフです。この図でも図5と同様の特徴的な挙動を示しており、BSA分子の等電点であるpH5近傍でαavは最大、εavは最小となります。一見すると、図5と同じ傾向ですが、よく見比べると、等電点でαavが最小、εavが最大となる図5とはまったく逆の傾向であることに気が付きます。両者の結果の相違は、BSAが親水コロイドであることに着眼すると説明することができます。
図7：BSAのケーク特性値図8は、pHが等電点のときと、等電点からアルカリ性側に離れたときのケークの状態をそれぞれ模式図で示しました。左は、pHが等電点のときのケークの状態を表します。BSAは親水コロイドであるため、ゼータ電位が0となる等電点でも、BSA分子は凝集せずに分散状態を保っています。分子間に静電反発作用が働かないので...
>>第4回 第5章の続きを読む（PDFダウンロード）
5th: Cakeless filtration
Last time, I explained the film film film filtration.This time, I will explain the Cakeless filtration.Until now, we have explained the filtration operations mainly for which a cake layer is formed on the material surface.Cake is required for the purpose of collecting solids, but there is no need to form a cake when aiming to cleanse the liquid.Rather, Cake is the main factor in filtration performance, and the growth of the Cakes will decrease and increase the spilly power.So far, various types of Cakeless filtration technology have been devised and have been developed and practical.Here are some examples of the main cakes filtration method, including crossflow filtration.
This section describes the principle and features of Cakeless filtration in comparison with Kake filtration. Figure 1 schematically shows the outline of Kake filtration and Cakeless filtration (see the first one). Cake filtration is a filtration system that supplies a suspension in the direction of the spill (vertical direction to the filter surface). The Cake layer grows as the filtration progresses. Cakeless filtration is a filtering method in which the supply liquid is fluidly fluided by fluid mechanical operations on the filter surface. It is also called dynamic filtration because of its dynamic characteristics. By disturbing the cake layer and removing it, it can maintain a high filtration performance and can be used continuously. A typical one is a method of flowing the supply solution parallel to the filtration surface, and is called a crossflow filtration because the supply fluid and the fluid flow are crossed. Or, because of its dynamic characteristics, it is also called a dynamic filtration. In addition, even if the filter is rotated at high speed or a high -frequency vibration to the filter, the cake will be disturbed and swept away, and it can maintain a high filtration performance. Cakeless filtration technology is particularly effective for processing difficult -to -apply samples, especially high concentrations.
図1：ケークろ過とケークレスろ過ケークレスろ過の効果がよく分かるように、ケークろ過の結果と比較しましょう。図2は、あるケークレスろ過におけるろ過速度の逆数(1/q)対、単位ろ過面積当たりのろ液量vのデータを示しています。ケークろ過は、ろ液の流出する方向が試料液の供給方向と一致します。そのため、ろ過の進行とともにケークが成長し、ろ過速度qは急激に減少して、1/q対vのプロットは直線的に増加します。一方、ケークレスろ過は、...
>>第5回 第1章の続きを読む（PDFダウンロード）
The crossflow filtration has a relatively simple device structure, so it does not require such a large power and is easy to maintain.Therefore, it is the most commonly applied Cakeless filtration system (Fig. 3).The filter material can be used for both a flat type and a tube -shaped type.Flow and compact filter design is easy.
図3：クロスフローろ過のろ材後述する回転型ろ過や振動型ろ過と比較すると、...
>>第5回 第2章の続きを読む（PDFダウンロード）
In order to greatly improve the crossflow filtration performance, it is effective to combine other cake removal technology.The control of the supply liquid flow, the control of the pressure, and the combination of reverse wash are often used as a method of changing the flow state periodically in order to declare the regular supply liquid flow.In addition, the use of shelves, the installation of turbulent promotioners, and the use of two -phase fluids, without greatly improving the crossflow filtration device, promoting the unstable flow of fluid and promoting turbulence.This is a method to improve the filtration performance.Introducing outside (electric fields, sound fields, etc.), such as the effect of electric fields and irradiation of ultrasound, can also be an effective means.Introducing eight types: control of the supply liquid fluid, control of pressure, combination of reverse washing, use of recoil, installation of turbulence promotion, the use of two -phase streams, applying electric fields, and ultrasonic irradiation.To do.
The control of the supply liquid fluid is, for example, a method of supplying a sample solution in a pulse style (vibration flow) in order to make the indoor flow state at an definite normalization.In addition, there is also a method that periodically reverses the flow direction of the supply liquid to decompose the flow state of the filter.
Reference Li H et al., Aiche Journal, Vol.44, P.1950-1961, 1998 Hargrove S CT Al., Separation Science and Technology, Vol.38, P.3133-3144, 2003
The control of the pressure is, for example, a method of reducing the accumulation of cake by using the pulse pressure from the filter side to the supply liquid side by intermittently negative pressure on the supply liquid side.
References V G J J AND R E Sparks, Journal of Membrane Science, Vol.68, P.149-168, 1992
Use of reverse washing is a method of periodically performing reverse washing operations during cross -flow filtration and promoting cake removal.The periodic reverse -type filtration will be explained next time.
参考文献Redkar S G and R H Davis, Aiche Journal, Vol.41, p.501-508, 1995
The use of a calendar style is a method of creating a flow path that draws a supply solution.A vortex is generated, promoting fluid instability due to turbulence.
References Chung K Yet Al., Aiche Journal, Vol.42, p.347-358, 1996 KLUGE Tet Al., Aiche Journal, Vol.45, p.1913-1926, 1999
...
>>第5回 第3章の続きを読む（PDFダウンロード）
When you want to concentrate high concentration and highly viscous sampling liquid altitude, the crossflow filtration shearing force is not sufficiently obtained.In such a case, it is effective to use rotation and vibration that can generate higher shearing.In particular, Cakeless filtration using rotation and vibration is suitable for high concentration of sample solutions with strong chicksotropic.
The filtration method while rotating the filter is roughly divided into a rotary plate type and a rotating cylinder type, depending on the shape of the filter.The rotating plate type can generate a high shearing force between the rotating disc and the fixed disk, and the filtration area can be increased by linking many rotating materials on the coaxial (figure.Four).There is also a method in which the rotation plate type is fixed at high speed by fixing the rotor material by fixing the rotor (Fig. 5).In this method, the fluid state can be violently disturbed by digging a groove or protrusion on the rotating disc.On the other hand, the rotating cylinder has a structure of a co -shaft double cylinder, and strongly removes cake by using the combination effect of the shearing force, centrifugal force and whirlpool that generates between the outer cylinder and the rotating inner cylinder material.(Fig. 6).
図4：回転円板型ろ過 (ろ材回転)図5：回転円板型ろ過 (ろ材固定)図6：回転円筒型ろ過振動を利用したケークレスろ過では、ろ材表面に存在する流体が粘性と慣性により複雑に運動し、ろ材表面の粒子の移動が活発になるため、ケークの成長が抑制されます。このケークレスろ過でも、...
>>第5回 第4章の続きを読む（PDFダウンロード）
6th: Various filtration operations
Until now, we have explained the main filtration operations such as "Kake Project", "Closed Yokuro", and "Cakeless Project".In the last episode, we will pick up some other noteworthy filtration operations.Specifically, the last time I mentioned a little bit of the "period reverse -type filtration", "filtration using electric fields", "filtration using ultrasound", "filtration using filtration agentsI will explain the five items of "centrifugal filtration".
Reverse washing refers to flushing the cleaning solution from the opposite side of the filter material at a high pressure and washing off the cake accumulated on the surface of the filter (Fig. 1).A method that periodically repeats filtering and reverse washing operations is called periodic reverse filtration.This is also a broader Cakeless filtration.When processing a difficult suspension, it is extremely effective to apply a Cakeless filtration described earlier (see the 5th).On the other hand, if the cake ratio resistance is small or when a very thin suspension is processed, there is often no practical problem even in the case of Kake filtration, but it is advantageous because energy consumption is reduced.However, it is inevitable that a large or smaller cake will be generated and the filtration rate will decrease, and it is difficult to continue the filtration for a long time.
図1：周期逆洗型ろ過の概念図Figure 2 is an example of a periodic reversal filtration behavior.Since the case of the constant speed filtration has been selected, it shows a change in the filtration pressure ΔP.As the filtration progresses, the kake grows, and the filtration resistance gradually increases, and the difference between and after passing through the filter increases.Therefore, it is set so that the filtration operation is temporarily paused when the filtration force is+60 kpa increased by+60 kpa from the initial difference of each cycle, and the inverting operation that flows the cleaning solution (part of the filter) at a high voltage from the opposite side.did.As a result, each time the reverse washing operation was launched, the filtration force was reduced to the difference between the pure material, and the filtration operation was continued efficiently.
図2：周期逆洗型ろ過の挙動しかしながら、各サイクルの初期差圧に注目すると、...
>>第6回 第1章の続きを読む（PDFダウンロード）
Generally, colloid particles are charged.As described in the fourth, the colloid filtration has a significant effect on filtration characteristics of colloid particles.The filtration (electric filtration) described here (electric filtration) is a method of controlling the movement of a colloid particles with a charge by controlling the electric field and efficiently filtration (Fig.3).
Coloid particles have the property of swimming in electric fields.In other words, when a DC electric field is applied to the colloid, the particles that are generously are positive in the cathode direction, and the negative particles move in the anode direction.Using this property can reduce the growth of cake due to the accumulation of colloid particles.Figure 3 schematically shows the principle of electric filtration.In this figure, it is intended for negative colloid particles.Therefore, the anode is installed on the supply liquid side and the cathode is installed on the supply liquid side and the electric field is applied.As a result, the particles are electrically swimmed in the opposite direction of the anchor, that is, the direction of the filtrate flowing, reducing the movement of particles to the filter surface.
図3：電気ろ過過程の概略粒子は、ろ過操作によって液体と一緒にろ液流れの方向にろ過速度q(m/s)で移動します。そこに直流電場を印加すると、粒子はろ液の流れる方向と逆向きに泳動速度uE(m/s)で電気泳動します。結果として、正味の移動速度がq– uEとなり、ケークの形成が緩やかに進むことになります。ろ過速度qはケーク形成の進行に伴って減少するのに対し、...
>>第6回 第2章の続きを読む（PDFダウンロード）
Ultrasonic waves are applied in various processes such as reactions and separation, and are often attracting attention as convenient tools that can easily improve performance.One of the most popular applied examples of ultrasound is ultrasonic cleansing machine.The high -frequency -specific fine vibration peculiar to ultrasound and the occurrence and repression phenomenon of high -temperature and high -pressure bubbles called cavitation, can be effectively peeled off and removed.Many applications have been reported because the filtration process can be used to promote filtration in the filtration process.
図5は、超音波を利用したろ過(超音波ろ過)の原理を模式的に示しています。ろ過器に超音波を照射しながらろ過を行うと、...
>>第6回 第3章の続きを読む（PDFダウンロード）
A filtration agent is a powder used to improve the performance of the filter and to prevent closing of the material. By adding it to the filter solution to be filtered, the filtration is greatly improved. It generally refers to Keisou soil (diatomaceous earth), but it is also known for its perlite. Keisou soil is a type of algae, a diatom is a fossil over a long period of time. Parrite is a glass -like rock that suddenly solidified the lava erupted in volcanic activity. Both are characterized by very good drainage, and functions as an filtering agent because the filtration resistance is small and the compression is low. Beer industry is well known as an industrial field using filtration agents. In order to separate beer and yeast during the beer purification process, Keisou de filtration is mainly applied. Most of the beers in the world are draft beer (non -heated beer) because the yeast can be completely removed by Keisou Toru filtration without heat treatment. It is an excellent filtration method in addition to the high -running cost and low running costs, as well as the fact that it does not change the taste and properties of food. On the other hand, there is also a disadvantage that used Keisou soil is excreted in large quantities as industrial waste, so the burden of the processing is large.
ろ過助剤の活用法は、主にプリコート法とボディフィード法に大別されます。プリコート法とは、...
>>第6回 第4章の続きを読む（PDFダウンロード）
A centrifugal filtration is a method of performing filtration operation using centrifugal force.In addition to the propulsion of compression gas and pump pressure, and reduced pressure due to vacuum pumps, one of the main filtration operations that perform centrifugal force as propulsion.Therefore, various types of centrifugal films have been developed and are used in various industrial fields.In Chapter 5, we will focus on the basic mechanism of centrifugal filtration, and explain in comparison with normal filtration.
Figure 7 shows a typical state in the filtration during a centrifugal filtration in a part of the filtration.From this figure, you can read some points that are a characteristic of centrifugal filtration and the difference between normal filtration.
図7：遠心ろ過過程の概略A centrifugal sediment is a separate form in which particles move in the liquid in the direction of centrifugal force due to centrifugal force.Not only the cake layer due to filtering, but also the sedimentation layer due to centrifugal subsidence is formed at the same time.The cake layer in Fig. 7 is a mixture of both.It is also a major feature that the Kiyosumi liquid layer is generated as shown in FIG.
The transformation shift filtration is a filtration form that changes both the filtration pressure and the filtration speed over time.The centrifugal force, which is the propulsion force of the filter, is proportional to the own weight of the sample.Therefore, if a centrifugal filtration is performed in a format that does not add a sample solution, the sample in the filtration will decrease as the spills of the filtrate decrease, and the effectiveness will be reduced.Normal filtration is often performed in either constant pressure conditions or constant speed conditions, but in centrifugal filtration, this will result in transformation shifting conditions (both filtration and filtration speed are reduced).
...
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