Scrubber is a device or an equipment, which is used for cleaning gases from solubles or particulates. It is an air washer with refinements of even treating fumes on line.

Impurities which are to be removed before it is allowed to be mixed in the ambient are- 
acidic vapours like HCL, H2SO4, Chlorine, SO2, or any other foaming fumes,
alkaline vapours, which are harmful, like caustic, 
particulates- solid fines, which are defined as non solubles but of size up to .5 microns which do not get separated by filters of any kind.

In our country (India), fumes (air containing solubles in small qualities) are normally not bothered about. Fuels having sulphur presence, generate flue gases containing SO2 in hot state (Coal & Oil from certain regions have sulphur 0-1% or more). For example, in one burning furnace 20 Kg/hr of fuel having 1% sulphur presence, will be discharging SO2 of 2000 Kg/year, which will go into the atmosphere unabated.
We can use simple devices to remove or recover this.

Scrubbers are designed in various types. Some are- Packed Tower, Ventury, Dynamic, Catalytic, Multi flow, Multi tower.

Motive Power Inc. are in this field for the last 20 years. All the designs are wholly developed by us and offered based on performance and efficiency. Of course, they are recommended on specific need based. Total indigenous designs considering actual conditions and limitations are presented. Obviously cost is an important criteria for any customer.

Packed Tower Scrubber
In this design, a tower is constructed and filled with the material having large contact area. Pall rings, Rachis rings or similar items are filled in to provide large surface for contact. Coarse droplet of solute, normally wale, are sprayed from top. Water trickling down, wets the surface area. Fumes containing vapors or particulates go up through this surface area as counter flow. Due to slow motion, fumes come in contact with the fumes over surface and take up the material releasing the air and cleaning. It has larger capital cost and low power needs.
It is normally made in plastic and surface area material is similar.

Ventury Scrubber
In this design, fumes are moved through suitably designed ‘ventury’. Velocity of gas is increased. Solutes are sprayed in the stream. Due to this the gas gets fully saturated. Solubles & solids get entrenched and thus get separated.
 

Muti flow Scrubber
This is a combination of Packed tower and Ventury types. Gas velocities are changed suddenly and drops fall out separation rate is high.

Dynamic Scrubber
When fumes are moved faster, solutes are added dynamically with the aid of external air pressure. Drops are converted to the finest form. Thus fumes are made totally wet and largest liquid surface area is provided for best performance.

Catalytic Scrubber
In this design, solid catalysts are provided as surface area along with solutes sprayed over. Chemical reaction becomes easy and recovery of valuable returns is also made easy. 

Multi Tower Scrubber
When more than one vapor or particulates are to be removed from the stream, it is recommended to use multi purpose multi tower unit. Overall space, power and cost is saved.

To recommend suitable equipment following minimum details are needed-

• Gas flow in Nm3/hr 
• Gas density in kg/m3 
• Gas temp in 0C 
• Solids presents in mg/m3 
• Solid details 
• Vapor details - Names – quantity gm/m3
• Flow details – process in short
• Layout – where fume is generated 
• Location of scrubber possible.
• Material of construction – if insisted.
• Power limits 
• Water available – unlimited/recirculation
• Water quantity available – lit/hour
• Effluent treatment – necessary/not necessary
• Effluent treatment plant – existing/not existing
• If not existing, ETP needed – yes/no
• Any other information, which can help in selecting the equipment.
• Any other conditions to be fulfilled.
• Pollution control department comments, if any

Cyclones
This is a device to separate solids (in powder or granular form) from air/gases. When the material is moving as in pneumatic conveying, the solids are separated. In this device, air is made to flow at cyclonic speed and made to rotate in a cylindrical vessel of suitable design. When the solid material attains high speed, it   picks up centrifugal force and choose to cling to outer surface  while air retains high speed it gets due to its velocity factor. Suddenly in the center, air outlet is provided for air to go out while due to centrifugal force the solid material is not able to change direction but goes downwards and gets separated.
This device is capable of offering separation efficiency up to 90%, of course, depending upon, design, material, bulk density etc. There is one collecting hopper where material gets collected. Smaller the diameter, better is the efficiency. 

Multi Cyclone
When volume of air flow is large, single cyclone tends to become inefficient. Therefore it is recommended to use  multiple number of  cyclones thus called multi cyclone. It has a common body container wherein number of small cyclones are included, each handling small volumes, thus offering better efficiency. Thus, number of cyclones operating together offer far better performance for larger volume than single one. Of course dimensions are favorable  too and so the cost.

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Dryers
When solids are to be dried, hot air plays an important role. Hot air, when made to pass through material, evaporates the moisture and thus dries the material. Conventional system dryer works in this way. 
However there are some materials, which can be ideally dried only at low temperatures, as quality of material may get affected. Thus, to dry a particular material at low temperatures, new designs are evolved.
Motive Powers Inc have designed a new kind of rotary dryer in which air properties are used. Material is baked in ample quantity of air so as to remove moisture without heating. In a rotating drum, the material is tossed in low heat. Slow evaporation reduces moisture content. The air could contain smell, which is treated before discharge. Thus, odor is also contained.

This system takes care of all the problems related to dryers. Surprisingly, it is highly efficient, thus power is saved more than 50% on running cost and is easy to maintain.

Normally following information is needed to recommend a suitable device:

• Quantity of material to be dried/day
• Bulk density
• Moisture contents
• Details of material
• Smell, if any
• Restriction on power, space
• Pollution control board instructions

FUME EXTRACTION SYSTEM

When fumes (small quantity of harmful liquid vaporizes and gets mixed with ambient air, it is called fumes) are found in atmosphere, they tend to harm living and dead.

• Effect on life, be it human or animal. It affects skin from outside and lungs from inside when inhaled. Trees and leaves, vegetation get effected by losing color and life.
• Metal gets corroded and spoiled losing strength.

Hoods, Ducts &  Valves
For  handling corrosive gases ,however light, FRP,PVC or PP material are normally used. Designs of hoods and ducts are critical since they decide the efficiency of the system. Hoods are mounted on the source and its design matters for getting maximum gases out.

Scrubbers 
This device washes the gases with solvent ,which can dissolve the fumes and release free air for discharge. This is normally made suitable to gases concerned.

Fans
This device pulls gases out  by giving negative pressure in  the system. Depending upon usage, material of construction is decided.  It could be plain mild steel or coated, FRP, S.S. or any other material.

PACKAGED SYSTEM

Specially in India, where there are more than 50,000 small scale units, each unit owner is needs a sustem with following properties:

• It should be economically affordable
• It should occupy space available
• It should consume low power
• It should be easy to maintain
• It should be possible to get returns too

Some of the places where Fume Extraction Systems could be used are

• METAL TREATMENT
• GALVANIZING
• ACID TANKS AND PICKLING
• REACTORS
• FUEL ENGINES 
• REACTION VESSELS

For systems needing hoods, ducts or valves   of special corrosion proof material, FRP or PVC are normally chosen. They are otherwise made, generally by hand to meet the demand by expert workman. Materials generally used are  M.S., G.I., ALUMINUM, STAINLESS STEEL, PLASTIC, FRP ETC.
We specialize in tailor design as per clients' requirements.

Hoods
This equipment  IS NORMALLY INSTALLED ON fume generating  vessel or tank. It has to be so designed that most of the fume is channelled through hood to scrubbing device thus saving the atmosphere.

Tanks
LIQUID , CORROSIVE IN NATURE will  be suitably designed so that it can take care of the liquid it contains, fumes it generated and waste is saved from  discharge. It is no longer necessary to have overhead ducts, or complicated systems  of handling. Further, it is also possible to reduce  cost of tank by the choosing right design.

Valves
All the ductings would need valves, generally of FRP or PP for diverting or controlling the fumes.
They are not available ex stock as regular product. They are to be made to order. We can offer the same.

Ducts
For carrying the fumes  with air, ducts have to suitably designed to meet pressure drop  as minimum and cost to be on lower side. We offer expertise on the same.

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For removal of dust from air, a filter is ideal. It restricts air flow by using a suitable filter cloth.
Filter cloth should be such that it offers minimum resistance to  air flow but holds the dust particles to travel 
with air.
A suitable bag filter can be used as per the dust quality. Some details are as under:
Separation of dust follows the size of dust to be removed. Larger the size, simpler the process of separation.
Generally  larger sizes above 0.5 min are separated by sieves itself, but when the particle size goes in to micron size, filtration becomes exciting. 
Following table gives some idea on equipments which can be used depending upon the particle size.
 

• FILTER CLOTH and
• DEVICE TO CLEAN CLOTH

Filter cloth is chosen on the basis of working condition and pressure drop acceptable. It is available in cotton, nylon, polyester and Fiber glass material.

CLOTH CLEANING DEVICE are as follows
1. manual shaking by hand from time to time- most popular as it is cost free.
2. Semi auto- power pulse   manually from time to time
3. Semi auto power pulse controlled by panel
4. Auto shaking
5. Pneumatic reverse jet using compressed air

Reverse jet is expensive but more effective and  result oriented.
Depending upon the material and situation suitable unit can be designed and offered,
MOTIVE POWERS INC can guide to have correct design, size and operation. We can offer only guidance, or/and the equipment as required by the client.

Following information will be helpful in designing the equipment and selecting:
Capacity of air flow in volume
Temp of air
Material contained 
Quantity of material
Bulk density of material in air
Size of material particle.
Chemical properties of material
Type of fan used.
Collection of material methods desired.
Shaking arrangement preferred

Give us details for advice. We will help.

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