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Mu Green Reactor, static mixer for micro bubbles

Table of contents
1 General information
 1.1 What’s “MU Green Reactor”?
 1.2 How does it work?
 1.3 What are the product’s benefits?
 1.4 How is the product used for?
2 Three advantages (compared with mixing mixer)
 2.1 Motion pump free -> Running cost less than 1/10
 2.2 Motionless -> maintenance cost free
 2.3 Simple structure -> initial cost less than 1/5
3 Principles of traditional static mixer
4 Five features (compared with conventional static mixers)
 4.1 Multiple blades in a single element
 4.2 Blades with many small holes
 4.3 Two different flows: the straight and spiral flo
 4.4 Cutting air
 4.5 Circulation flow
 4.6 The above five features
5 Features of micro bubbles
 5.1 Disappearing in water
 5.2 Higher internal pressure
 5.3 Slower upward speed
6 Comparison of characteristics
7 Comparison of specifications
8 Specifications and Prices

 

General information, mu green reactor, static mixer for micro bubbles

1.1 What’s “MU Green Reactor”?
MU Green Reactor can put air into water by producing micro-bubble and circulatory strong flows, both of which greatly help enhancing the efficiency of aeration. The Reactor is combined with “MU Mixer”, a high-effective static mixer, and “MU Oscillator©”, an element of vibrating air.

ミューグリーンリアクターの外観写真 曝気装置
(MU Green Reactor)

ミューグリーンリアクターの稼働状況 曝気・エアレーションの様子ミューグリーンリアクターの稼働状況 曝気・エアレーションの様子
(Operational status #1)

MU Green ReactorMU Green ReactorMU Green Reactor
(Operational status #2 / MGR-125-10-P)

MU Green ReactorMU Green Reactor(Operational status #3)



(Operational status from youtube)

 

1.2 How does it work?
Only passing compressed air through two kinds of element, MU Oscillator and MU Mixer, can allow water to contain micro-bubble and enrich oxygen. Now let me explain the flow of air. See Figure 1. First, compressed air is injected upward at the speed of more than 10 meters per second, with MU Oscillator attached on the nozzles. The injected air changes into bubble through MU Oscillator and then the bubbles pass through MU Mixer set above the nozzles. The device and Mixer can change air into micro bubbles, by rotating, dividing, shearing, inverting the injected air. Dividing into micro bubbles make the surface area of gas-liquid contacting dramatically increase, leading to high-efficiency of oxygen provision. The Oscillators, with help from high-speed jet of air, also generate circulation flow, which enables the whole water in the vessel to provide oxygen.

 

1.3 What are the product’s benefits?
The main benefit of the product is high efficiency of aeration, together with low cost. The exhaustiveness of rational designing adds cost-competitive to this product. The combination of the principle of Kenics Motionless Mixer and our unique ideas can produce micro-bubble effectively and strong stream of circulation, causing higher-efficiency product.

Now, how much does the product keep down the cost totally? This product holds running cost down less than 1/10 and initial cost less than 1/5, both compared to the cost of motion mixer. Furthermore, free of maintenance cost and the product can deliver a significant cost saving in total.

How much does it work effective? It can produce more than six-fold micro-bubbles effectively, in terms of the content rate of micro-bubble into water, as compared to another typical Japanese static mixer. Strong circulation flows of water it produces also increase the processing speed, resulting in the efficiency of aeration.

 

1.4 How is the product used for?
The followings, for examples, are the applications of the product:
(under construction)

Now, below is the detailed explanation. First, we show the advantages of our product as compared with motion mixer. Second, before explaining our other benefits considering other static mixers, we explain the basic principles of traditional static mixers. Then, we elaborate on the features of the product and finally, for your information, refer to the characteristic of micro-bubble which is the important factors for feeding oxygen into water efficiently.

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Three advantages, mu green reactor, static mixer for micro bubbles

2.1 Motion pump free -> Running cost less than 1/10
Motion mixers for aeration need pressure pumps, air compressors and mixing pumps to produce micro bubbles. Pressure pumps are for delivering water into aeration tank, and air compressors for feeding pressurized air into water. Mixing pumps blend water with air to supply oxygen into water. MU Green Reactor, however, uses only air compressor or roots blower as power source. So its running cost can fall below less than 1/10, compared with that of motion mixer.

 

2.2 Motionless -> maintenance cost free
Motion mixers make air dissolve into water by feeding pressurized air and water in the mixing pump, rotating impeller blades to mix them together and then making them broken into millions of tiny parts. MU Green Reactor, meanwhile, provide air into water passively by increasing the complexity of flow channel. Such motionless structure can allow the Reactor to be free of maintenance cost because there are no galling and clogging of moving part, such like blades and bearings. Another superiority is the durability, which can activate it for a longer time.

 

2.3 Simple structure -> initial cost less than 1/5
MU Green Reactor can simply provide micro bubble and strong circulation flow to feed oxygen simply by passing compressed air through the Reactor. No need of any pumps or powers except air compressors or root blowers can make the price remarkably down. The price of this product is less than 1/5 as compared with motion mixers, though its average void fraction is 50-70 volume %, far greater than that of motion mixers, 4-10 volume %.

 

MU Green Reactor, in terms of cost, has advantages in every respect: running cost, maintenance cost and initial cost, though its generation efficiency and void fraction can exceed the conventional motion mixer remarkably. So its cost performance surpasses others.

Now, before I show you the feature of MU Green Reactor, let me explain the principle of the traditional static mixer invented by Kenics to clarify our characteristics.

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Principles of traditional static mixer, mu green reactor, static mixer for micro bubbles

(under construction)

スタティックミキサー
(static mixer invented by Kenics, from wikipedia)

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Five features, mu green reactor, static mixer for micro bubbles

MU Green Reactor is consisted of MU Mixer, a high-effective static mixer, and MU Oscillator, a small element of vibrating air. MU Mixer has three features and the Oscillator has also two. Now, let me explain the advantages of MU Mixer.

<Three superiorities of MU Mixer>
4.1 Multiple blades in a single element
Static mixer invented by Kenics has one blade per an element: blades are arranged in line one by one. In an element of MU Mixer are set multiple blades. The more blades are, the more fluid can be divided, which enhance the mixing efficiency per one element. For example, four elements with single blade each are in line and they can divide fluid four times and, in other words, one into 16(=2*2*2*2). Meanwhile, four elements with four blades each are to divide one into 64(=4*2*2*2*2), four times than the former, and this means the latter has more mixing efficiency than the former. Furthermore, in case of twelve blades within one element, the number of division is 192(=12*2*2*2*2), twelve times than that of one blade per an element.

 

4.2 Blades with many small holes
Any blades of conventional static mixer have no hole on it but the blade of MU Mixer has a lot of small holes. The holes help increasing the mixing efficiency since the very holes can divide and shear the flow of fluid.

 

4.3 Two different flows: the straight and spiral flow
Traditional static mixers make the fluid flow spiral along the blades. MU Mixer, on the other hands, can produce the two different flows; the fluid goes straight in the central hole in an axial direction and the other flows spirally along punching metal blades. Two have different velocities and directions, causing shearing on the boundary of the flows. The shearing also make the fluid broken up into smaller bubbles or segments, which leads to the increase of the air-water interface and, therefore, enhance the efficiency of aeration.

The above three features of MU Mixer add the more efficiency of mixing to this product than typical static mixers. Besides, the Oscillators are attached on the nozzles to enhance its performance more. The followings are two advantages of the Oscillator.


<Two features of MU Oscillator>
4.4 Cutting air

(What is “MU Oscillator”?)
MU Oscillator is a static mixer that can make air rotate, sheared and flow spiral strongly. Attached on nozzles, it can also put out air into water upward at the speed over 10 m/s. Inside the device are set two blades twisted 90 degrees and on the center is small circular room.

(Two different flows make vibration of air.)
Pressurized air injected from the nozzles is to be divided into two flows, as MU Mixer is: the spiral flow along the blades and straight flow passing through the central hole in an axis direction. The two different flows make air vibrated.

(The cause and effect of air-vibration)
The effect of air-vibration is mainly to enhance the speed of breaking up air and the following four factors cause air vibrated.

  1. Injecting compressed air into water with high speed produces turbulent flow and then the flow implodes.
  2. Injected compressed air generates sound wave with frequency of around 200-1000 Hertz by self-excited vibration. “Self-excited vibration” means that when an object or system is vibrating, the vibration itself makes the vibrated more sensitive to outer force and the force amplifies or keeps the vibration.
  3. The injected air with high speed makes the air pressure itself low, causing cavitation.
  4. MU Oscillator divides the single flow of pressurized air into two: the straight and spiral flow. The difference of velocities and direction between the two flows produces shearing force.

 

4.5 Circulation flow
One of the features for the product is to generate strong circulatory flow and to supply oxygen into the whole tank of water efficiently. Typical micro bubble generators fail to provide such strong flow as that of this product and aerate only smaller range of water. So larger or more devices would be needed to cover the whole water in tank. But only one MU Green Reactor can provide the strong stream enough to cover all the water in tank. The circulation flow can cover more water to aerate and enhances the aeration speed and energy efficiency significantly.


4.6 The above five features

Let me repeat the five advantages briefly. Three features of MU Mixer and first merit, cutting air, of the Oscillator can allow the product to have far better mixing and air-solubility efficiency. The void fraction of micro bubbles for this product is about 60 vol. %, more than six-fold than that of typical static mixer, about 10 vol. %. Second feature of MU Oscillator is the strong circulation flow and this advantage, together with efficient production of micro bubbles, can offer much better aeration efficiency.

By the way, static mixers are, in general, the devices for dissolving air into water efficiently. Micro bubbles are the very important element for feeding air into water. Micro bubbles have unique natures unlike larger bubbles and the very characteristics are the key factors. Next let me explain the features of micro bubbles.

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Charasteristics of micro bubbles, mu green reactor, static mixer for micro bubbles

How small are micro bubbles all about? Micro bubbles are defined as bubbles of tens of micrometers size when generated. Roughly speaking, the size is smaller than the breadth of hair. Micro bubbles have the following characteristics, which greatly contributes to the improvement of aeration efficiency.

5.1 Disappearing in water

マイクロバブルの特性

The most remarkable feature of micro bubbles is to vanish in water. Normal bubbles we often see in the daily life are getting bigger as they go up. As the depth is low, the water pressure is getting low and the internal pressure within bubbles also goes down. When they are going up and reach on the surface, they usually blow up.

On the other hands, the mechanism of micro bubbles is quite different from bigger bubbles and as micro bubbles goes up in water, the bubbles become smaller and then disappear. This is because surface tension has much more influenced with bubbles than buoyancy force due to its smallness. Bubbles are, in general, pressurized by surface tension created on the boundary of air-water phase and the force makes bubbles become smaller. But when bubbles are enough large to be more influenced with flotation force than surface tension, bubbles become large as they go up. Now micro bubbles are enough small to be largely subject to surface force, not buoyancy, since micro bubbles go up by far slower than the normal bubbles. So the nature of micro bubbles is different from that of bigger bubbles.

The nature of “disappearing in water” is the consequence of two physics phenomenon. One is that surface tension raises the internal pressure of bubbles and the other that bubbles go up very slowly. Now let me explain what the two factors more detailed and how the two phenomenon affect the capability of bubbles of dissolving air.

 

5.2 Higher internal pressure
The pressure of bubbles affected by surrounding water is larger when the size of bubbles becomes smaller, as shown in Young-Laplace equation. For example, the pressure of bubbles with size of 10 micrometers is about 0.3 atm and 1 micrometer around 3 atm. The dissolution of air into water is proportional to the partial pressure, as Henry’s law shows. So the higher the pressure of bubbles is, the more air in bubbles dissolve into water.


5.3 Slower upward speed
The upward speed of micro bubbles in water is proportional to the square of bubble’s diameter, as Stokes’ law indicates. (About up to 150 micrometers, the speed keeps varying proportionally as the square of the diameter.) An experiment shows that a minute take bubbles of 1 mm diameter to 6 meters upward and 10 micrometers to only 3 mm. In other words, the bubbles of 10 micrometers go up in water 2,000-fold slower than those of 1 mm. Micro bubbles move upwards very slow, which makes them stay in water longer than the bigger and enhances the dissolving efficiency of air.

Now let me compare the dissolving efficiency of bubbles of 1mm diameter with those of 10 micrometers.

The internal pressure of bubbles is inversely proportional to the diameter of bubbles, as chapter 5.2 shows, and air in 10 micrometers’ bubbles is 100-folds easier to solve in water than that in 1 mm bubbles. Plus, the upward speed of 10 micrometers’ bubbles is, chapter 5.3 says, 2000-fold slower than 1 mm bubbles and, therefore, has the 2000-fold efficiency of dissolution. Simply multiply 100 by 2000, the 10 micrometers’ bubble has the capability of dissolution to the tune of 20-millions-fold more than 1 mm.

But in fact, there are no such differences between them in terms of the capability, since other conditions affect the dissolving efficiency, such as convection flows. At all events, there are no doubts that micro bubbles have far more dissolving efficiency than normal bubbles, which greatly contribute the efficiency of aeration.

Micro bubbles are negatively charged and as micro bubbles is pressurized and shrinking, the charge gets concentrated and finally free radicals has been generated. Free radicals are subject to reaction with other materials and used for water purification.

*Reference:
"泡のエンジニアリング" (Yoshio Ishii, Techno System, 2006)
"マイクロバブルおよびナノバブルの動向" (Masayoshi Takahashi, M&E, July 2008)

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Comparison of characteristics, mu green reactor, static mixer for micro bubbles

 
MU Green Reactor
A-company's static mixer
Motion mixer
Diffusion plate
price ratio
20
100
product life
A+
A
C
C
clogging
Non Exist
Non Exist
Exist
Exist
sludge accumulation
Non Exist
Non Exist
Exist
Exist
replacement of parts
No need
Need
Need
Need
mixing pump
No need
Need
Need
No need
power consumption
Small
Medium
Large
Large
generation of micro bubbles
Yes
Yes
No
No
void fraction
50-70vol%
4-10vol%
Null
Null
circulation flow
Yes
No
No
No
install space
Small
Medium
Large
Large

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Comparison of specifications, mu green reactor, static mixer for micro bubbles

 
MU Green Reactor
(MGR-300)
A-company's static mixer
price ratio
20
100
components
Body, roots blower (or air compressor), control panel
mixing pump, line mixer, roots blower, supply pump, control panerl, steel structure for piping etc
suppling air(m3/h)
200-250
30
volume of supplied air (m3/min)
2.8
about 3
void fraction(vol%)
60
about10
dimension(mm)
D300*H900
2000*840*H950
volume of body(m3)
0.06
1.6
weight(kg)
60
400
power consumption(kWh)
2.2
11
pressure loss(kPa)
1.0-4.5
no data

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Specifications and prices, mu green reactor, static mixer for micro bubbles

Type
Blast volume
(m3/min)
depth of tank
(m)
External Diameter
(mm)
Length
(mm)
Diameter of air supply nozzle
(A)
Weight
(kg)
1
MGR-300
1.8-2.5
>2
300
900
80
55
2
MGR-500
6-8
>2.5
500
1200
100
125
3
MGR-1000
20-30
>4
1000
2000
200
650
4
MGR-1400
50-60
>4
1400
2000
250
950
5
MGR-1800
80-100
>5
1800
2200
350
1500
*Material: SUS304
(Can also be produced by other materials, such as PP, PVC, titanium, hastelloy and aluminium.)
*Pressure loss: 2.0-5.0kPa
*Prices should be asked.

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