JPH0645040B2 - Operation control method in sludge dewatering - Google Patents

Description

TECHNICAL FIELD The present invention relates to an operation control method for dehydration of an organic sludge by a belt press type dehydrator while adding a cationic organic polymer coagulant.

[Conventional technology]

When adding cationic organic polymer flocculants to organic sludge such as sewage sludge or night soil sludge to form flocs and mechanically dehydrating with a dehydrator such as a belt press type dehydrator, the actual treatment site In the present situation, the sludge properties are constantly changing drastically, and the dehydration efficiency is changing constantly.

Conventionally, when determining the optimum addition rate of the coagulant, the filter cloth speed, the filtration speed, etc., the condition where the sludge properties are changing drastically as described above, for example, the gravity filtration condition and the presence or absence of protrusion from the filter cloth are observed. However, it was decided by trial and error.

[Problems to be solved by the invention]

However, the above-mentioned conventional method requires a great deal of labor and time, and it is necessary to use a large amount of sludge in order to obtain the optimum addition rate, which is extremely impractical.

And the reason why I have to rely on such trial and error is
This is because the correlation between sludge properties and dewatering efficiency, and the relationship between each factor are not clearly understood.

Therefore, an object of the present invention is to quickly and easily determine operating conditions and the like without resorting to the complicated method of operating an actual machine every time the sludge property changes, and to operate with sufficient validity to determine this. It is to provide a control method.

[Means for solving problems]

In order to solve the above problems, the present invention, by adding a cationic organic polymer flocculant to organic sludge, when dehydration with a belt press type dehydrator, evaporation residue of sludge, the rate of coarse suspended matter , The anion degree, the crude protein content rate, and the organic content are used to predict the solid load per unit area that can be dehydrated by the following formula (A) using these as factors together with the filter cloth speed given as a condition, By setting the filter cloth speed obtained at a predetermined filtration speed by both the formulas (A) and (B) below to an optimum filter cloth speed, or by setting the filtration speed obtained at a predetermined filter cloth speed at the maximum filtration speed, y _{1 = a'X 1 + b'X 2 -c'X} 3 + d'X 4 + e'X 5 -f'X 8 + g '... (A) y 2 = y 1 × X 8 × 60 ... (B) , however, y _1; solids loading ^{(kg-ds / m 2)} y 2; filtration rate (kg-ds / mH) X 1; evaporation Tomebutsu (%) X _2; crude suspended solids ratio [(amount of over 100 mesh sieve in the sludge 100ml (g) / sludge 100ml
Amount of SS) × 100] (%) X ₃ ; Anion degree (meq / g-TS) X ₄ ; Crude protein amount rate (Amount of organic nitrogen in sludge × 6.25) (%) X ₅ ; Organic Min (%) X ₈ ; filter cloth speed (m / min) a ′ to g ′; a ′ = 3 or less, b ′ = 3 or less, c ′ to f ′ = − 3 to 3, g ′ = − 1
0 to 10 and the evaporation residue of the sludge, the crude suspended matter content rate, the anion degree, the coarse protein content rate, and the organic content, and the filtration rate, the filter cloth rate obtained by the formulas (A) and (B),
Furthermore, various operating conditions are determined by predicting the water content of the dehydrated cake by the following formula (C) using the pressure and the coagulant addition rate as factors.

However, y: Moisture content of dehydrated cake (%) X ₁ ; Evaporation residue (%) X ₂ ; Amount of coarse suspended solids [(Amount of 100 mesh sieve in 100 ml of sludge (g) / 100 ml of sludge)
Amount of SS) × 100] (%) X ₃ ; Anion degree (meq / g-TS) X ₄ ; Crude protein amount rate (Amount of organic nitrogen in sludge × 6.25) (%) X ₅ ; Organic Min (%) X ₆ ; Coagulant addition rate based on the amount of solids in sludge (%) X ₇ ; Filtration speed (= y ₂ ) (kg-ds / mH) X ₈ ; Filter cloth speed (m / min) ) X ₉ ; Pressure (kg / cm ² ) a to j; a = 10 or less, b = 3 or less, c = 50 or less, d = 3 or less, e = 3 or less, f = 5 or less, g = 10 or less, h = 5 or less, i = 10 or less, j = 40 to 100 [Operation] The inventors of the present invention examined the dehydration efficiency while changing a number of operating conditions for various organic sludges, and found that each factor was clear. We found that there is a correlation. Based on this correlation, it was found that the optimum filter cloth speed and the optimum filter cloth speed can be easily set, and the dehydrated cake water content can be easily predicted. Therefore, if the operating conditions are determined according to the correlation equation, efficient operation can be performed without depending on the operation of the actual machine.

Here, the coefficients of a ′ to g ′ and a to j are (A) to
It becomes a weighting coefficient of each factor in defining the equation (C), and the magnitude of this coefficient indicates the influence degree of the factor.
The coefficients a ′ to g ′ and a to j have been clarified as a result of many experiments conducted by the present inventors. The results of belt press dehydration using various sludges having different sludge components are subjected to multiple regression. This is the value obtained by analysis. Further, each of these factors is considered in principle based on the above correlation equation, but as a result of obtaining the coefficient, when the coefficient value is small and its influence can be ignored, the correlation equation In some cases, the factor term may be excluded from the calculation.

[Specific Examples of Invention]

 Hereinafter, the present invention will be described in more detail.

In general, a belt press type dehydrator is composed of three continuous mechanisms of a gravity filtration section, a wedge filtration section, and a roll compression section, and in particular, the gravity filtration section is excellent in filterability and has a low gravity filtration cake water content, It is important to set the addition rate of the cationic organic polymer flocculant. Further, the water content of the gravity filter cake changes with the addition rate of the cationic organic polymer flocculant in the same sludge, and becomes the lowest at a certain addition rate, and this addition rate is expressed as the optimum addition rate.

Considering the sludge physically, the particles of the sludge have a negative charge, and the cationic coagulant neutralizes the negative charge. Since the anion degree of sludge represents the negative charge amount of sludge, it affects the addition rate of the coagulant, and the cation degree of the coagulant represents the amount of neutralization, which also affects the optimum addition rate of the coagulant. give. Further, the coarse suspended matter becomes a nucleus of floc flocs when a flocculant is added, and has the function of maintaining the strength of floc particles and controlling the water resistance of the separated liquid. It is presumed that it affects the optimum coagulant addition rate.

Considering in this way, if a coagulant having a certain cation degree is selected, the water content of the dehydrated cake is also influenced by the addition rate, the amount of coarse suspended matter in the sludge, and the anion degree. Presumed.

In addition to factors such as the crude suspended solid content rate and anion degree, there are also evaporation residue, crude protein content rate, and organic content as factors indicating sludge properties, and these may also influence the dehydrated cake water content. Inferred from the inventors' many years of experience.

On the other hand, it is known to those skilled in the art that the operating conditions of filtration rate, filter cloth rate and operating pressure are factors that influence the dehydration case moisture.

Under such an idea, various investigations were conducted on the correlation between the water content of the dehydrated cake and each factor, and the results shown in FIGS. 3 to 12 were obtained. From this result, it was found that the above factors certainly influence the water content of the dehydrated cake. In addition, when analyzing many results of this kind, it is possible to correlate with the above-mentioned formula (C).

In the equation (C), the values of the coefficients a to j of each factor term are a =
10 or less, b = 3 or less, c = 50 or less, d = 3 or less, e = 3
Hereinafter, f = 5 or less, g = 10 or less, h = 5 or less, i = 10 or less, and j = 40 to 100.

By the way, the rate of coarse suspended solids is the ratio of the mass on the 100-mesh sieve in SS to SS and is defined by the following equation.

Amount of coarse suspended solids (%) = (amount on 100 mesh sieve in 100 ml of sludge (g) / amount of SS in 100 ml of sludge) x 100 ... Also, the crude protein amount ratio is the food analysis method "crude protein" According to the above, the amount of organic nitrogen in sludge was measured, and the value was multiplied by 6.25, which is a simple analysis value of protein. Here, the crude protein is included in the organic component, which is a superordinate concept, but since the higher the protein in the organic component, the more the dehydration performance tends to be inhibited, it should be considered separately as a single factor. It was done. Therefore, the organic content refers to proteins, fats, carbohydrates, etc. in sludge, and the crude protein refers to protein content in sludge.

On the other hand, the anion degree of sludge can be measured by a colloid titration method in which methyl glycol chitosan is added to sludge and stirred for, for example, 2 hours, and excess methyl glycol chitosan is measured by PVSK.

Referring again to FIG. 3 to FIG. 12, in the same example, when the correlation is viewed as a single correlation, it is the evaporation remaining amount and the solids load that have a strong correlation with the dehydrated cake moisture. When these 10 factors are subjected to the multiple regression analysis, the influence of the anion degree is small, and the remaining 8 factors can be used to obtain the predictive formula of the dehydrated cake water y shown in the formula (1).

The term of X ₇ / X ₈ · 60 is a solid matter loading term.

By the way, the filtration speed X ₇ and the filtration cloth speed X ₈ can be determined as follows.

The treatable solid load and each factor have a correlation shown in FIGS. 13 to 20, for example. This kind of correlation can be generally expressed by the above equation (A). In the equation (A), the coefficients a ′ to g ′ of each factor are a ′ = 3 or less,
b ′ = 3 or less, c ′ to f ′ = − 3 to 3, g ′ = − 10
It is determined in the range of 10. These a ′ to g ′ are weighting factors of each factor, and the magnitude of this factor indicates the degree of influence of the factor. These coefficients are values obtained by multiple regression analysis of the results of belt press dewatering using various sludges having different sludge components.

In the case of the illustrated example, the highest correlation is with the remaining evaporation amount. However, since the remaining evaporation amount is usually about 2 to 4%, the solid load cannot be predicted alone. The result of the influence of the term of anion degree is small among the six factors shown in the formula (B), and the prediction example formula shown in the formula (2) is obtained by the remaining five factors.

y ₁ = 2.75 + 0.379X ₁ + 0.0457X ₂ −0.057X ₄ + 0.551X ₅ −0.505X ₈ … (2) The solid load thus obtained is the optimum solid load (load from the filter cloth end of the dehydrator). It means that it is over, and a side leak occurs. On the other hand, the filtration rate, the solid load, and the filter cloth speed have the relationship (B). Therefore, if the filter cloth speed is set, the maximum filtration speed can be known. Further, if the filtration speed is set, the maximum filter cloth speed can be selected. That is, if either one is determined, the other is automatically determined.

As an example, considering the case of equation (2), (3) and (4)
The formula holds.

y ₁ = K-0.505X ₈ (3) y ₂ (X ₇ ) = y ₁ × X ₈ × 60 (4) Therefore, if the required filtration rate y ₂ is determined (3), ( By solving the equation 4), the values of X ₈ and y ₁ can be obtained, and the optimum filter cloth speed at a certain filtration speed can be set.

By the way, as the cationic organic polymer flocculant referred to in the present invention, a methacrylic acid ester polymer, a copolymer of methacrylic acid ester and acrylamide, or the like can be used.

According to the present invention described above, the optimum operating condition can be determined without operating the actual machine. And, for example, the first
As shown in FIG. 2 and FIG. 2, the predicted value and the actually measured value can be predicted with an average difference of 27 kg-ds / m-hr in the case of the dehydrated cake.

〔The invention's effect〕

As described above, according to the present invention, without operating the actual machine, based on the measured sludge properties and coagulant addition rate,
The water content of the dehydrated cake can be easily predicted with sufficient validity, and the filter cloth speed or the filtration speed can be set.

[Brief description of drawings]

Figure 1 is a diagram showing the relationship between the predicted and measured values of dehydrated cake water,
FIG. 2 is a correlation diagram between predicted values and measured values according to the present invention, and FIG.
FIG. 12 to FIG. 12 are correlation diagrams of each factor and dehydrated cake water content, and FIG. 13 to FIG. 20 are correlation diagrams of each factor and solid load.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Toshio Hamaguchi 2-17-15 Tsukushima, Chuo-ku, Tokyo Tsukishima Machinery Co., Ltd. (72) Keiichiro Miyano 2-17-15 Tsukushima, Chuo-ku, Tokyo Tsukishima Machinery (72) Inventor Noboru Morito 2-17-15 Tsukishima Machinery, Chuo-ku, Tokyo Inside Tsukishima Machinery Co., Ltd. (72) Inventor Katsunori Nishida 2-17-15 Tsukishima Machinery, Chuo-ku, Tokyo Tsukishima Machinery Co., Ltd.

Claims (1)

[Claims] 1. When sludge is dehydrated by a belt press type dehydrator by adding a cationic organic polymer flocculant to organic sludge, sludge evaporation residue, coarse suspended matter content rate, anion degree,
By knowing the crude protein content rate and the organic content, the solid load per unit area that can be dehydrated by the following formula (A) is predicted by using these as factors together with the filter cloth speed given as a condition, and the following (A) , (B) set the filter cloth speed required at the predetermined filtration speed by both equations to the optimum filter cloth speed, or set the filtration speed required at the predetermined filter cloth speed to the maximum filtration speed, and y ₁ = a ′ _{X 1 + b'X 2 -c'X 3 +} d'X 4 + e'X 5 -f'X 8 + g '... (A) y 2 = y 1 × X 8 × 60 ... (B) , however, y _1; solid Material load (kg-ds / m ² ) y ₂ ; Filtration rate (kg-ds / mH) X ₁ ; Evaporation residue (%) X ₂ ; Rate of coarse suspended solids [(on 100 mesh sieve in 100 ml of sludge Quantity (g) / sludge 100ml
Amount of SS) x 100] (%) X ₃ ; Anion degree (meq / g-TS) X ₄ ; Crude protein amount rate (Amount of organic nitrogen in sludge x 6.25) (%) X ₅ ; Organic Min (%) X ₈ ; filter cloth speed (m / min) a ′ to g ′; a ′ = 3 or less, b ′ = 3 or less, c ′ to f ′ = − 3 to 3, g ′ = − 1
0 to 10 and the evaporation residue of the sludge, the crude suspended matter amount rate, the anion degree, the crude protein amount rate, and the organic content, and the filtration rate, the filter cloth rate obtained by the formulas (A) and (B), Furthermore, the operation control method in sludge dewatering, characterized in that various operating conditions are determined by predicting the dehydrated cake water content by the following formula (C) using the pressure and the coagulant addition rate as factors. However, y: Moisture content of dehydrated cake (%) X ₁ ; Evaporation residue (%) X ₂ ; Rate of coarse suspended solids [(Amount on 100 mesh sieve in 100 ml of sludge (g) / 100 ml of sludge)
Amount of SS) x 100] (%) X ₃ ; Anion degree (meq / g-TS) X ₄ ; Crude protein amount rate (Amount of organic nitrogen in sludge x 6.25) (%) X ₅ ; Organic Minute (%) X ₆ ; Coagulant addition rate based on the amount of solids in sludge (%) X ₇ ; Filtration speed (= y ₂ ) (kg-ds / mH) X ₈ ; Filter cloth speed (m / min) ) X ₉ ; Pressure (kg / cm ² ) a to j; a = 10 or less, b = 3 or less, c = 50 or less, d = 3 or less, e = 3 or less, f
= 5 or less, g = 10 or less, h = 5 or less, i = 10 or less, j = 40 to 100