FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
TITLE OF THE INVENTION
"A PROCESS FOR CHEMICAL REGENERATION OF CERAMIC FILTERS"
APPLICANT
Essar Steel Limited, 27 KM Surat Hazira Road, Hazira 394 270 Dist. Surat, Gujarat, India
Preamble of the Description
The following specification particularly describes
the invention and the manner in which it is to be performed

Field Of Invention
This invention relates to a process for chemical regeneration of ceramic filter plates and is particularly applicable to ceramic filter plates used for dewatering iron ore slurry.
Background of Invention
Iron ore pellets are an important raw material in steel industry. Iron ore is ground to fine particle size in the presence of water to form slurry and then filtered prior to further processing like green balling, induration and pelletization. The filter cake obtained after dewatering is subjected to pelletization. The moisture content of the filter cake is an important factor in pelletization as high water content in the filter cake results in poor productivity.
Currently, vacuum filters, pressure filters, and ceramic filters are used in the industry. Ceramic filtration is found to be the most cost effective system and is widely used in mineral processing industry through out the world.
Ceramic filters are dewatering equipments which operate on the principle of "capillary action". The capillary phenomenon is based on Young-Laplace law, which states that the pores of a certain diameter cause a capillary effect due to surface tension and the contact angle of the liquid with the walls of the pores.
Ceramic filters are micro porous filter medium and are referred as ceramic plates. The iron ore slurry that is used in pelletization process is a mixture of grounded Iron Ore (70% by weight) and water (30% by weight). When a ceramic plate comes in contact with the iron ore slurry it immediately absorbs water from the slurry because of "Capillary Phenomenon". The pores of the filter plates get filled with water and the solids in the slurry are collected on the surface of the plate in the form of cake. The filter cake produced is relatively dry containing very low moisture.

Conventional ceramic filter operation in iron ore industry has five major stages such as
(a) cake forming (b) cake drying (c) cake discharge (d) back flow washing (e) plate
regeneration.
Ceramic filters in iron and steel industry have multiple discs and each disc has
multiple ceramic plates. All discs are connected to a receiver tank for receiving filtrate
and are collectively rotated along its central axis during slurry filtration. Filter cake
formed in the plates are scrapped using scrappers and are collected in chutes.
Ceramic Filtration Process
One of the most important features of ceramic filters is its ability to produce a very dry filter cake (low moisture) with an energy consumption of one tenth of the one required in conventional vacuum filtration. The capillary forces in the filter media prevent air from passing through the filter despite a high vacuum level inside the filter. Only liquid is pumped.
Moreover because of very fine nature of micropores and an additional membrane layer on ceramic plates, these plates do not allow iron ore particles to get collected with Filtrate; resultantly, the particle free filtrate is achieved.
Operating Principle
In ceramic filter operations there are "five" principle stages:
a. Cake Forming
b. Cake Drying
c. Cake Discharge
d. Backflow Washing
e. Disc Regeneration
Ceramic filters consist of a slurry boot where the slurry is stored. In one filter there are multiple discs and in each disc there are multiple ceramic plates. In case of CC-45

CERAMEC® Filters we have 18 discs and in each disc there are 12 ceramic plates. All plates are similar in all respects and are of same dimensions. All the discs are connected to a receiver tanks which collects the filtrate (the water). All discs are rotated together along the center axis at a fixed RPM. Filter cake is scrapped with the help of scrappers. Special chutes are designed in the filter boot for collection of filter cake.
Cake Forming Zone
Cake forming takes place on discs when they are rotated through the slurry. Capillary action creates an extremely high vacuum level, which draws liquid through the discs in the filtrate lines. The water is collected in the micro porous structures of the ceramic plates. The water collected inside the ceramic plates is drawn inside the filter with the help of a small vacuum pump which draws water through the disc and collects it in the receiver tank. Iron ore solids build up rapidly on the ceramic plates. Micro porous structure prevents any iron ore solids to penetrate the disc surface. The cake forming stage for a particulate ceramic plate continues till the time a plate is inside the slurry level of the filter boot.
Cake Drying Zone
Once a ceramic plate comes above the slurry level in the filter boot, it enters a cake drying zone. As the ceramic plate enters this zone the plate has already formed a layer of iron ore solids on its surface. The thickness of this layer directly decides the productivity of the ceramic filter. As the disc continues to rotate, the capillary action of the plate continues to draw water from the iron ore cake which has formed on the surface of the plate. The process continues until all free water is drawn out from the iron ore cake. The residual water (around 10%) is termed as the moisture of the filter cake and it is one of the most important process parameter in filtration technology. In

this process there is absolutely no penetration of air into the filter, which results in a
lower moisture.
Cake Discharge Zone

There are stationary scrapers installed on one side of the ceramic filters. The job of the
scrapers is to remove cake from the disc. A thin residual cake is intentionally left on
the surface to protect the ceramic plate against mechanical abrasion (because of
scrapping action).
Backflow Washing
Once the scrapping of a plate is over the plate enters a backwash zone. In this zone vacuum is released. The filtrate which is collected is pumped back into the ceramic plate with a purpose of flushing the discs. It removes the "residual cake" and cleans the microporous structure of the plate. It helps in retaining the efficiency of the filter.
Ceramic Plates Regeneration
Ceramic plate regeneration is a very critical aspect of any ceramic filter operations. The ceramic plates, act as a medium to dewater the solids out of slurry, have micro porous honeycomb type structure. Over a continuous use, the ultra fine iron ore particles in the slurry tend to clog these micro pores of the ceramic plates. This clogging of ultra fine iron ore particles in the ceramic plate dramatically impacts the efficiency of the ceramic filtration process (reduction in cake thickness and increase in moisture level in the cake).
Clogged ceramic plate tends to offer higher resistance for filtrate flow inside the ceramic plate. Cake thickness of a ceramic plate depends on the quantity of filtrate (water) collected by a plate in the cake formation zone. Higher resistance from clogged ceramic plate results in a lower filtrate collection; hence low cake thickness/low productivity. Moreover, higher resistance from a clogged ceramic plate will result in a

low filtrate collection in cake drying zone, resulting in higher moisture in filter cake. Resultantly both the filter productivity (cake thickness drops) drops and the product quality (moisture increases) deteriorates.
Hence it is extremely essential to "Regenerate" these ceramic plates on a regular interval to maintain the productivity of these filters. Regeneration is a process to unclog the pores of ceramic plates. Regeneration in a ceramic filter is generally done in two ways:
1. Ultrasonic Cleaning
Ultrasonic transducers are installed in the ceramic filtration units to generate high energy packets of waves (cavitations bubbles) which help in de-clogging the ceramic plates. There are separate transducers for each disc.
2. Chemical Wash - conventional acid wash for regeneration
Chemical regeneration is a process wherein certain chemicals (under specific conditions) are used to unclog these ceramic plates. In case of CERAMEC® Filters the original equipment supplier proposes the use of Dil. Nitric Acid and Dil. Oxalic Acid at 1.8 Bar. When a ceramic plate is in a regeneration zone, the chemical mix is pressurized from inside of a plate. These chemical tends to dissolve the iron ore particles which clog the ceramic plates. This way principally a ceramic plate can regain the original permeability and productivity.
The existing chemical process, using Dil. Nitric Acid and Dil. Oxalic Acid, has extremely poor regeneration capabilities. The rate of dissolution of Iron Ore with the existing process is very slow, resulting in poor availability and poor productivity of filters. The Ceramic plates are not able to regain their original productivity even after acid regeneration. Inspite of regular acid washes, Ceramic Plates productivity drops by atleast 30-40% in 2-3 months. Moreover, acidic systems for regeneration are difficult to handle due to the hazardous nature of the acids.

Hence, it can be concluded that in the long run the filter efficiency depends only and only on the regeneration efficiency
Object of Invention
The main objective of this invention is to develop an efficient physical and chemical process to clean the clogged pores of ceramic filters.
Summary of the Invention
This invention relates to a novel process to regenerate the clogged ceramic plates used in ceramic filters particularly in iron ore industry. An alkaline chemical process utilized to partially dissolve and wash-off the ultra-fine iron ore particles that have clogged the ceramic plates during the iron ore slurry filtration process. The invention deals with a complex chemical and physical process wherein the honeycomb ceramic plates are soaked, pressurized and washed alternatively with the chemical solution and water. Process results in an extremely high level of regeneration/cleaning. The plates regenerated with the process according to this invention have shown a dramatic increase in productivity vis-a-vis the plates regenerated with current industrial regeneration process where treatment is carried out in acidic baths.
Brief Description of Drawing
Figure 1: Is a flow chart showing backwash regeneration process Figure 2: Is a flow chart showing Suction regeneration process
Description of Invention
A novel combination of chemicals followed by physical process used to regenerate the clogged ceramic plate which is found to be much more effective than the existing

regenerating process which involves treatment with dil. oxalic acid and dil. nitric acid
in cycles.
The proposed invention is divided into two different categories;
I. Chemical Process
The Chemical Process includes chemical compositions, solution preparation
techniques, mixing ratios, and solution characteristics such as pH and Temperature.
The solution consists of three critical elements:
a. Strong reducing agents such as dithionites (S2O42-), alkali sulfites (SO32-) and
alkali bisulfites (HSO3-1) : Sodium Dithionite, Zinc Dithionite; Sodium sulfites,
Sodium Bisulfites etc.
b. Strong chelating agent (complexing agent) such as alkali Citrates, alkali Oxalates,
and alkali EDTA: Tri Sodium Citrate, Di Sodium Oxalate, Di Sodium EDTA etc.
c. pH controlling agents such as Carbonates and Bicarbonates: Sodium Carbonate,
Sodium Bi-carbonate etc.
The chemical bath according to this invention is illustrated herein after with sodium dithionite as the strong reducing agent though other reducing agent which dissociate in aqueous medium may also be used with equal efficacy. The strong reducing agent (Sodium Dithionite) is stable in dry state, but decomposes rapidly in aqueous solution because of the unstable configuration of the Dithionite ion (S2O42-). pH plays a very important role in further hydrolysis of the dithionite ion (S2O42-) The reducing power and water stability of Dithionite ion increases with pH. Hence, the "pH controlling agents", such as Carbonates, Bi-Carbonates etc, are added to create a strong reducing environment for Metal Oxide dissolution in the solution. A strong complexing/chelating agent captures the Metal ions (with strong ligand bonding) and improves the rate of reduction of Metal Oxide.
An aqueous solution of a strong reducing agent and a strong chelating agent buffered with a strong pH controlling agent to a temperature range of 60 - 100 deg C and a pH

range of about 7-10 is found to be very effective and efficient in regenerating ceramic plates - strength or concentration of dithionite and chelating agent in the solution is not very critical and largely depends on Metal Oxide characteristic, but the pH and the temperature of the resultant solution is very critical to the process. Temperature plays a very important role in the process. If the temperature is less than 60 deg C, then the rate of reduction will decrease, and if the temperature is more than 100 deg C, then the higher solution temperature in long term may crack the ceramic plates. Similarly, at lower pH the reducibility of the Dithionite ion reduces dramatically and at higher pH the efficiency of chelating agent to capture the Metal ion and thereby to facilitate the reduction process decreases.
As mentioned earlier that the strength and concentration of the chemicals are largely dependent on the oxide characteristics. However, the chemicals are generally mixed in a defined proportion (by weight of solution): Range: Based on oxide characteristics and amount of clogging.
a. Strong Reducing Agent: (such as Sodium Dithionite):- 1-4%
b. Complexing / Chelating Agent (such as Tri Sodium Citrate):- 5-10%.
c. pH Controlling Agent (such as Sodium Bicarbonate):- 0.5-2.5%
II. Physical Process
It relates the physical process of treating the ceramic plates with the above mentioned solution to efficiently regenerate the clogged ceramic plate, with minimum time and chemical consumption and maximum efficiency. The proposed process is categorized into two different processes, keeping in mind the operational requirements. a. Suction Regeneration Process
Ceramic plates to be treated with the regenerating solution are subjected to vacuum treatment for removing the aqueous solution there from. Initially regenerating solution at 80 deg is sucked into the ceramic plate with the help of vacuum-receiver system to soak the ceramic plate completely. Thereafter, the ceramic plates are treated to water

at 60 deg C. The water is sucked into ceramic plate to remove the clogged metal oxide particles. The turbidity of the residual solution collected gives an indication of the efficiency of regeneration. Initially the residual solution sucked out from the plates is coloured red, against the clear transparent colorless regenerating solution. The complete cycle is repeated until the discharge residual solution is colourless.
b. Backwash Regeneration Process:
Ceramic plates to be treated with regenerating solution are subjected to a pressurized treatment to remove the clogged particles. The regenerating solution at 80 deg C is pressurized from inside of a ceramic plate to soak the plate completely. After the soaking process, water at 60 deg C is pressurized from inside of ceramic plate to remove the clogged metal oxide particles. Pressure plays a very important role in Backwash regeneration system. A minimum pressure of 1.8 Bar (preferably in the range of 1.8-2.8 Bar) is required to efficiently regenerate the plates. As in Suction regeneration System, the turbidity of the residual solution collected gives an indication of the efficiency of regeneration. Initially the residual solution collected from the plates is coloured red, against the clear transparent colourless regenerating solution. The complete cycle is repeated until the discharge residual solution is colourless. This invention relates to a process for chemical regeneration of ceramic filter plates comprising treatment of clogged ceramic filter plates with an aqueous solution of a reducing agent, a chelating agent and a buffer of a temperature at 60°c to 100°c and at a pH range of 7 to 10 and subsequent washing with water to declogg and regenerate the same. This invention also includes regeneration and declogged ceramic filter plates obtained by the above process.
The objective of suction/backwash regeneration process is to soak the clogged ceramic plate with chemical solution. Once the plate is soaked in solution, the solution starts reacting with the iron oxide fines present inside the pores of ceramic plate. Job of

proposed chemical solution is only to reduce the size of the clogged particle so these particles can easily flow inside the pores. Objective of water wash is to carry these partially dissolved particles of iron oxide which are now free to move. Most of the cleaning is actually done by water that removes the fines along with them during suction/backwash; Thereby reducing the chemical consumption for regeneration dramatically.
The regeneration process may be carried out on line or off-line Alterations & variations known to persons skilled in the art are within the scope and ambit of this invention.

We Claim:
1. The process for chemical regeneration of ceramic filter plates comprising treatment
of clogged ceramic filter plates with an aqueous solution of a reducing agent, a
chelating agent and a buffer of a temperature at 60°c to 100°c and at a pH range of 7
to 10 and subsequent washing with water to declogg and regenerate the same.
2. The process for chemical regeneration as claimed in claim 1, wherein said reducing agent is selected from dithionite (Sodium dithionite and Zinc Dithionite), alkaline sulfites, and alkaline bisulfites, and the chelating agent is selected from alkali citrates, EDTA ( Ethylene diamine tetraacetate), and oxalates and the buffer is selected from alkali carbonates and bicarbonates.
3. The process for chemical regeneration as claimed in claims 1 & 2, wherein said aqueous solution contains 1 to 4% by wt of said reducing agent, 5 to 10 % by wt of chelating agent and 0.5 to 2.5% of said buffer.

4. The process of chemical regeneration as claimed in claims 1 to 3, wherein said aqueous solution is pressurized into said ceramic plate initially at a pressure range of 1 to 1.2 Bars and then at 1.8 to 2 Bars to initiate back wash prior to washing with water, said steps of pressurizing and water washing being repeated till the washing is clear,
5. The process of chemical regeneration as clamed in claims 1 to 3, wherein said aqueous solution is sucked into said plates by applying vacuum sucking initially and is followed by wash water sucking thereto and repeating said aqueous solution sucking and water sucking till the washings are clear.

6. The process of chemical regeneration as claimed in claims 1 to 5, wherein ceramic
filter plates of iron ore industry are regenerated either on or off line.
7. The process for chemical regeneration of ceramic plates substantially as herein
described with particular reference to the accompanying figures.
8. Ceramic filter plates regenerated and declogged by a process accordingly to claims
l to 7.