Raw recycled water enters the “KROFTA” AIR DISSOLVING TUBE tangentially at one end, pressurized
to 4-6 bar, which is discharged at
the opposite end. During the short passage the water rotates in side the tube and passes repeatedly by an
insert which is fed by compressed
air. Very thorough mixing under pressure dissolves the air in the water which is released to atmospheric pressure in the floatation cell. Suspended solids flocculated with the help of flocculants attach themselves to the air bubbles and come to the surface to form the sludge.

The patented “KROFTA” SPIRAL SCOOP takes up the floated sludge, pouring it into the stationary centre section, from where it is discharged by gravity, either for recycling or disposal.

Clarified water is removed through extraction pipes which are connected to the moving centre section. Part of the clarified water passes through the “KROFTA” AIR DISSOLVING TUBE before joining the mainstream of unclarified water. The clarified water extracted from the process normally contains less than 30 ppm of suspended solids. It can be recycled in the process or sewered.

Wiper blades attached to the moving distribution duct scrape the bottom and the sides of the tank and discharge the settled sludge into the built in sump for periodic purging.

The untreated effluent (1) is fed by gravity or pump to the center distributor (2) where it mixes with the air released from the recycled air carrier water and then enters the tank. Fine air bubbles lift the suspended, flocculated solids to the water surface (3) Heavier particles settle rapidly to the tank floor (4). The zone of clear water formed between the floated and settled solides is then discharged into the outlet annulus (5) where it overflows through an adjustable outlet weir (6). Adjustment of this weir controls the water level in the tank.

Floated matter is removed by the rotating spiral scoop (7) which discharges the sludge through the sludge pipe in the center distributor (2) to a sludge well (8) at the tank periphery.

A suspended bottom scraper (9) is supported from the structure and moved forward by the scoop drive. The settled sludge is scraped to the center of the tank and into a sludge pit (14) constructed in the foundation. From here, the sludge is removed intermittently through an automatically operated pneumatic valve (10). The scraper is so constructed as to allow it to rise and slip over any excessive obstructing sludge build-up in order to prevent any damage to the scoop drive.

The recycled air carrier water is pumped (11) at a pressure of about 80 psi into the retention tank (12). Compressed air (13) enters the retention tank directly. The air carrier water is then released into the center distributor after mixing with the raw influent. For small installations, it may be more economical to pressurize the whole of the effluent inflow.

Performance: The degree of fractionation and/ or microstraining depends on many factors; inlet consistency, spray pressure, inlet filler content, micron opening size, and particularly fines content of the fiber fraction. The following results can be expected Coarse impurities are separated out. All the water is microstrained.The fiber fraction is retained by the cloth and can be recovered. Changes in fiber content by the KROFTA Spray Filter are minimized so that subsequent clarifiers operate under a uniform load. The KROFTA Spray Filter improves the operation of clarifiers especially floatation ones, as it aerates the effluent making it more adaptable to floatation.
 

DE-INKING PLANTS : Separation of good fibers from fines and ink for a higher yield, less clay content in the stock, and reduced disposal requirements.

BOARD MILLS : Fractionation of the longer fibers from the effluent for use in the liner stock, while the fine fraction is used in the filler stock.

FINE PAPER and TISSUE MILLS :
Recovery of fiber through the fractionation of the effluent thus reducing total sludge volume. 
MICROSTRAINING of the EFFLUENT
for SHOWERS : Used to prevent the plugging of shower nozzles when either clarified or unclarified water is used.

SPRAY FILTER (SPRF)
Advantages :
 

Simple operation: few moving parts and very low rpm
Self-cleaning: built-in cleaning shower saves down-time
No fresh water required: clean ing shower nozzles are an open, non clogging type. Filtered water can be used in the shower
Easy maintenance: wide access door allows easy changing of the cloth and access to the interior
Inexpensive filter screens
Window wiper operated manually is located on inner side of the door.

Purpose : 
The KROFTA SPRAY FILTER is specifically designed for the filtration of effluents containing from 20 PPM to 5000 PPM of solids. A fine mesh cloth with openings
from 75-500 microns is used as the filter media, either to separate long fibers from clay and filler or as a safety filter for showers using clarified water. The KROFTA SPRF meets the
need for high throughput units which can handle wide variations of solids content. It is equipped with a cleaning shower which greatly reduces the need to remove the cloth for cleaning.

Belt Filter Press
Belt filter press type BFP..GR is specially designed to dewater sludge coming from clarification tank. Typically concentration of sludge is 0.5 – 1.0 % DS. The flow is up to 50 m³ / 1 m belt width. The capacity depends very much on the character of sludge and therefore the dimensioning have to ask from the manufacturer.

Typical applications are:
*  domestic sewage treatment plants
*  food processing industry
*  textile industry
*  tanneries
*  pulp and paper industry

BFP series belt press has been designed for dewatering sludge, having 3 -6 % DS.
BFP Filter Belt Press has been equipped with pneumatic belt tracking and tensioning.
BFP Filter Belt Press has separate belt tension system for both belts.
BFP Filter Belt Press has continually operating wash water system for both belts.

GT Gravitity Tables have been designed for sludges solids content from 0,1% to 1,5 % DS.
Thickened sludge concentration is typically from 5% to 7% DS.
As an optional extra GT Gravity Tables can be equipped with ploughs and pressure plate or roller.
It is possible to reach even from 10% to 12% dry solids with using extra equipment.

TECHNICAL DATA
TYPE GRB 700 GRB 1100 GRB 1600 GRB 2100 GRB 2600
Length, mm 4000 4000 4000 4000 4000
Width, mm 1100 1500 3300 2500 3000
Height, mm 1200 1200 2700 1200 1200
Belt area, m2 5.1 8.1 11.6 15.2 18.2
18.2          

Washwater GRB 700 GRB 1100 GRB 1600 GRB 2100 GRB 2600
consumption 1,3 2 2,9 3,8 4,7
Pressure, bar
5 - 6
fitting size
NS 32

Pressure air GRB 700 GRB 1100 GRB 1600 GRB 2100 GRB 2600
consumption, m3/h
0,2
required pressure, bar
8

Drive motor GRB 700 GRB 1100 GRB 1600 GRB 2100 GRB 2600
power, kW 0,37 0,37 0,37 1.1 1.1
rpm
1,8 - 8,8

Typical applications are:
* domestic sewage treatment plants
  to clients in:
* food processing industry
* textile industry
* pulp and paper industry

Our Oil Water Separators are designed as per following specifications:

Wet Scrubbing Systems is the removal of gaseous or particulate contaminants from a gas stream using a liquid. The scrubbing liquid is usually water or an aqueous solution.

Acids or alkalis are often used to control the pH to the optimum level for absorption. Oxidising agents such as hydrogen peroxide or hypochlorite can be used to react with the contaminant. 

Venturi Scrubbers:

Venturi scrubbers are an effective means of removing sub micron particulates. The contaminated gas is accelerated in the converging section before entering the throat (see left). Scrubbing liquor enters around the top of the converging section and completely flushes the wall. In addition, liquor enters through a spray to fill the throat with droplets.

In the venturi throat, the high velocity gas atomises the liquid droplets which trap the solid particles. The scrubbed gas and liquid droplets leave the venturi throat and pass through the diverging section where further agglomeration takes place to produce larger droplets. The liquor droplets are then separated from the gas stream in a cyclonic entrainment separator.

To ensure high scrubbing efficiencies, even with varying gas flows, the throat can be made adjustable, thus maintaining the required scrubber pressure drop, even at reduced throughputs.
The liquor from the separator is recycled via pumps to the venturi scrubber with a small bleed being discharged to control the build up of solids in the circulating liquor.

In 'dry scrubbing' a solid sorbent is injected into the gas stream which reacts with the contaminant and is removed on a filter, together with any other particulates. This produces a dry powder for disposal.

Alkalis such as lime or sodium bicarbonate are injected for the removal of acid gases such as SO2 and HCl. Powdered Active Carbons can be injected to remove heavy metals and trace organic compounds such as dioxin.

Thermal Oxidation

Thermal oxidation is the incineration of solvents, hydrocarbon vapours, fumes and odours, The temperature of the waste gases is heated to between 750oC and 1100oC by a gas or oil fired burner.

In the Recuperative Thermal Oxidiser, up to 60% of the energy can be recovered by using hot gases from the combustion chamber to pre-heat the incoming fume in gas/gas heat exchanger, thus reducing the amount of support fuel consumed.

The Regenerative Thermal Oxidisers can recover up to 97% of the thermal energy and offer considerable saving in the fuel used, and in many cases can reduce the fuel consumption to zero.

Where it is appropriate, further heat can be recovered in the form of hot air, heat transfer oil or steam.

Today one of the most challenging problems many industries face is the generation of dust in the plant area and its collection and disposal. The dust problem is as varied as the process machinery, the nature of material handled, availability of space & infrastructure and its maintenance requirements. We at KROFTA have endeavored to provide tailor-made solution to your dust related problems.

We offer the following range of Dust Collectors: 

INDUSTRIAL CYCLONE SYSTEMS

The Cyclone Dust Collectors are used for air having higher concentration of dust with relatively large/coarse dust particles. As the dust laden air enters the cyclone, the circular design forces the heavy dust particles to move down along its wall and creating a stream of clean air in the centre which is sucked out with the help of Blower. The heavy dust particles which move down are collected in the Bin. Depending on the air quantity, the size of Cyclone is determined.

PULSE JET DUST COLLECTORS

These dust collectors use auto purging mechanism where the dust collected on filters is dislodged by a high pressure air purging system. The purging mechanism works using a number of Solenoid valves and a timer to periodically release high pressure air pulse at designated time intervals. As a result the dust accumulated on the filters gets dislodged and is collected in the bin. This is one of the most efficient systems where minimum maintenance attention is required.

Our project managers carry out detailed programming of the works, control sub-contractors, and liaise with clients to complete the project to specification and on time.

Besides the above, various type of dust collectors are used depending upon the Filter Media chosen. We can provide more elaborate information on the type and size of filters suitable to your needs once we receive details specific to your requirement.

Please send us your enquiries to:

ACWA AIR is the air pollution control division of ACWA Services Limited which is an environmental company specialising in the design and construction of systems for the treatment of water and effluent, as well as air pollution control systems.

KROFTA in collaboration with ACWA offers a wide range of air pollution control and gas cleaning systems, individually designed for specific operating conditions and to provide the most cost-effective means of achieving increasingly more stringent emission requirements.

Capabilities:

KROFTA have the experience, expertise and resources to undertake projects ranging from the supply of equipment through to the design and construction of turnkey installations. KROFTA's process and engineering design ensures, the supply of reliable and economic systems that are fully integrated within the client's process.

Our project managers carry out detailed programming of the works, control sub-contractors, and liaise with clients to complete the project to specification and on time.
 

Quality Assurance:

KROFTA has a well deserved reputation for the quality of its products and service and its quality assurance management system is certified to BS EN ISO 9001:2000.

Process Selection:

Parameters, such as type of contaminant, temperature, humidity, etc affect the selection of the most appropriate gas cleaning system. KROFTA's specialists will be able to evaluate the application and recommend the most suitable technology to meet the required emission standards. For many applications the gas to be treated is air but KROFTA have considerable experience in the treatment of other process gas streams such as flue gases, landfill gas, biogas, nitrogen etc.