CLIAMS:We Claim:

1. A process for sintering of iron ore comprising:
blending of the desired sinter mix;
providing water source for sintering comprising biological oxidation dephenolisation (BOD) plant treated contaminated water ;
addition of said BOD plant treated contaminated water for agglomerating/granulating the sinter mix with desired moisture content.

2. A process for sintering of iron ore as claimed in claim 1 wherein said step of providing biological oxidation dephenolisation (BOD) plant treated contaminated water comprises waste water generated at coke oven by-product plant.

3. A process for sintering of iron ore as claimed in anyone of claims 1 or 2 comprising involving said biological oxidation dephenolisation (BOD) plant treated contaminated water having ammonia and phenol to suppress generation of toxic combustion by-products of the sinter process.

4. A process for sintering of iron ore as claimed in anyone of claims 1 to 3 comprising routing the (BOD plant) treated contaminated water generated from said coke oven by-product plant without subjecting to any additional treatment in RO plant enabling utilization of contaminated water without need for further purification and benefitting the sintering process and its water requirement.

5. A process for sintering of iron ore as claimed in claim 4 wherein said (BOD plant) treated contaminated water is collected from said BOD treatment plant of said coke oven plant and utilized in said sintering process via a water sump storing said contaminated water thus collected from said BOD treatment plant of said coke oven plant.

6. A process for sintering of iron ore as claimed in anyone of claims 4 or 5 wherein the BOD plant treated water from said water sump is utilized in the mixer drum and also in the nodulizer drum of said sintering of iron ore.

7. A process for sintering of iron ore as claimed in anyone of claims 1 to 6 wherein said sinter mix comprises any conventional sinter mix and addition of said BOD plant treated water is done to produce sinters with moisture content in the level of 6.5 % to 7.5% preferably 7.00 %.

8. A process for sintering of iron ore as claimed in anyone of claims 1 to 7 wherein the unsafe to dispose contaminated water from BOD treatment Plant of coke oven plant is involved in selective amounts to reduce the burden of fresh water for sintering process.

9. A process for sintering of iron ore as claimed in anyone of claims 1 to 8 wherein said BOD plant treated water comprises:
BOD plant treated water
pH 7.0 to 7.8
NH3-N mg/l 8.0 to 119.0
Phenol, mg/l 5.0 to 13.0
COD, mg/l 36.0 to 464.0
Total Cyanide, mg/l 0.5 to 3.0

10. Iron ore sinter produced according to the process as claimed in claims 1 to 9 comprising moisture content in the range of 6.00 % to 8.00 % in the blend as per the raw material characteristics and having selectively anyone or more of the following end characteristics shatter index 70% to 85% preferably 80 % and tumbler index 70 % to 85% preferably > 75% , RDI: 20% to 30% preferably 25 %; MPS: 16 mm to 20 mm preferably 18 mm; and return fines 20% to 37% (-5mm) preferably 20% to 30 %.

Dated this the 19th day of March, 2015
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

,TagSPECI:FIELD OF THE INVENTION

The present invention relates to a process for sintering iron ore using pollutant water obtained from coke oven by-product plant. More particularly, the present invention is directed to provide a process for sintering using Biological Oxidation Dephenolisation (BOD) plant treated water from coke oven by-product plant containing a significant amount of contaminants to obtain sinter products of desired quality characteristics. Importantly, in the process of sintering according to the present invention the polluted water has been used with sinter mix in the granulation of sintering process to save the water treatment cost without adversely affecting the sinter properties. During sintering the contaminants either dissociate or burn at higher temperature (~1300 0C) such that the emissions from the sinter plant suction stack conform to environmental safety standard. The process of sintering using BOD plant treated water to reduce the treatment costs and also reduces the use of fresh make up water including associated handling and storage costs and thus substantially reducing the cost of sinter production.

BACKGROUND OF THE INVENTION

It is well known in iron and steel industries that during coke making in coke oven plant, coke oven gas (COG) having a very high temperature (around 800-850 ºC). In order to bring down the temperature of the COG from ~800ºC to ~80ºC, water spraying is carried out. In the cooling process of COG, water gets contaminated. The contaminated water contains high amount of sludge, tar and ammonia liquor and is subjected to various treatment (techniques) for cleaning to comply the standards before its reuse in order to make zero liquid discharge. The ammonia liquor is passed through the distillation column to remove the ammonia and sent for further purification to Biological Oxidation Dephenolisation (BOD) plant to bring down the contaminants level within the acceptable environmental range. The major contaminants in water before BOD treatment plant are ammonia, phenol, cyanide (CN), chemical oxygen demand (COD), biological oxygen demand etc. Even after BOD plant water treatment, a significant amount of contaminants are present in water which is beyond the limit of clean water norms. The BOD plant treated water is again sent to RO plant for further purification.

It is also known that Sinter is the main feed material (60-85 % of total iron bearing burden) for most of the blast furnaces. Sintering is an agglomeration process of producing strong and porous lumps from powdered un-compacted mass of iron ore fines and other additives with the application of heat to the stage of incipient fusion. Fines generated during mining and beneficiation of iron ores cannot be charged directly into the blast furnace. Agglomeration of such fines makes a good blast furnace feed.

In conventional sintering process, the raw material mixture (iron ore fines, coke breeze, limestone, dolomite, calcined lime, sinter return fines etc.) is mixed with water in a rotary drum for specified period. The process of mixing is carried out to improve the granulometry and the process is known as granulation. During granulation, intermediate and fine particles get coated over the coarser particles through inter-particle adhesion via water bridges, whereby larger granules or quasi-particles form that are larger in size and closer in size range than the original feed. Water plays an important role during granulation in mixing and nodulizing drum forms an interface between the finer and coarser iron ore particles during granulation to form relatively bigger granules. It promotes the adhering characteristics of iron ore fines and fluxes so that the bigger granules improve the bed permeability at sinter strand which in turn enhance the productivity of process and properties of sinter. In addition to the above, the bigger granules subsequently results in homogeneous burning as well as uniform suction during sintering. It also reduces the losses of valuable fines during suction of sintering. The sinter mixes on the strand are burnt from the top. The suction of air through the bed helps sustaining the combustion of the fuel and provides the downward movement of the combustion zone through the bed up to the bottom layer to raise the temperature to 1150-1300 ºC. During the process of sintering the granulated materials undergo incipient fusion.

The present invention thus explores the use of polluted water containing harmful chemicals from by-product plant of coke oven plant for its direct utilization in sintering process during granulation without adversely affecting the sinter properties as per sinter plants and blast furnaces requirements thus saving on treatment costs.

OBJECTS OF THE INVENTION

The basic object of the present invention is directed to provide a process for sintering iron ore by utilization of highly toxic contaminated water such as BOD plant treated water from coke oven by-product plant to replace the normal water addition in granulation of sinter mix during sintering process.
Another object of the present invention is directed to provide a process for sintering iron ore by utilization of BOD plant treated water from coke oven by-product plant in granulation of sinter mix without adversely affecting the sinter properties as per sinter plants and blast furnaces requirements thus saving on water treatment costs.
A further object of the present invention is directed to provide a process for sintering iron ore by utilization of BOD plant treated water from coke oven by-product plant in granulation of sinter mix wherein the efficacy of contaminated water in granulation and sintering process as well as sinter properties is evaluated for desired industry acceptance standard when compared with results obtained using normal water.
A still further object of the present invention is directed to provide a process for sintering iron ore by utilization of BOD plant treated water from coke oven by-product plant in granulation of sinter mix which enable direct utilization of waste water generated in high quantity at coke oven by-product plant and saving of huge quantity of industrial (make up) water.
A still further object of the present invention is directed to provide a process for sintering iron ore by utilization of BOD plant treated water from coke oven by-product plant in granulation of sinter mix which ensures substantial monetary benefit with respect to the treatment cost of waste water.
A still further object of the present invention is directed to provide a process for sintering iron ore by utilization of BOD plant treated water from coke oven by-product plant in granulation of sinter mix thereby saving on account of transportation cost of water (e.g. electricity, pumping cost etc.) by using locally available water for the sinter plant requirement.
A still further object of the present invention is directed to provide a process for sintering iron ore by utilization of BOD plant treated water from coke oven by-product plant in granulation of sinter mix wherein there is no adverse effect on the sinter qualities such as productivity, Product Yield, Tumbler Index, Shatter Index and Mean Particle Size due to use of contaminated/pollutant water.
A still further object of the present invention is directed to provide a process for sintering iron ore by utilization of BOD plant treated water from coke oven by-product plant in granulation of sinter mix wherein presence of ammonia and phenol in water suppress the generation of toxic combustion by-products of the sinter process, i.e. dioxins and furans emission from the sinter plant suction stack.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to provide a process for sintering of iron ore comprising:
blending of the desired sinter mix;
providing water source for sintering comprising BOD plant treated contaminated water ;
addition of said contaminated water after BOD plant for agglomerating/granulating the sinter mix with desired moisture content.

A further aspect of the present invention is directed to provide said process for sintering of iron ore wherein said step of providing biological oxidation dephenolisation (BOD) plant treated contaminated water comprise waste water generated at coke oven by-product plant.

A still further aspect of the present invention is directed to provide said process for sintering of iron ore comprising involving said biological oxidation dephenolisation (BOD) plant treated contaminated water having ammonia and phenol to suppress generation of toxic combustion by-products of the sinter process.

A still further aspect of the present invention is directed to provide said process for sintering of iron ore comprising routing the (BOD plant treated) contaminated water generated from said coke oven by-product plant without subjecting to any additional treatment in RO plant enabling utilization of contaminated water without need for further purification and benefitting the sintering process and its water requirement.

A still further aspect of the present invention is directed to provide said process for sintering of iron ore wherein said contaminated water is collected from said BOD treatment plant of said coke oven plant and utilized in said sintering process via a water sump storing said BOD plant treated water thus collected from said BOD treatment plant of said coke oven by-product plant.

A still further aspect of the present invention is directed to provide said process for sintering of iron ore wherein the BOD plant treated water from said water sump is utilized in the mixer drum and also in the nodulizer drum of said sintering of iron ore.

A still further aspect of the present invention is directed to provide said process for sintering of iron ore wherein said sinter mix comprises any conventional sinter mix and addition of said BOD plant treated water is done to produce sinters with moisture content in the level of 6.5 % to 7.5% preferably 7.00 %.

A still further aspect of the present invention is directed to provide said process for sintering of iron ore wherein the unsafe to dispose BOD plant treated contaminated water from BOD treatment Plant of coke oven by-product plant is involved in selective amounts to reduce the burden of fresh water for sintering process.

Yet another aspect of the present invention is directed to provide said process for sintering of iron ore wherein said BOD plant treated water comprises:
BOD plant treated water
pH 7.0 to 7.8
NH3-N mg/l 8.0 to 119.0
Phenol, mg/l 5.0 to 13.0
COD, mg/l 36.0 to 464.0
Total Cyanide, mg/l 0.5 to 3.0

A further aspect of the present invention is directed to provide iron ore sinter produced according to the process described above comprising moisture content in the range of 6.0 % to 8.0 % in the blend as per the raw material characteristics and having selectively anyone or more of the following end characteristics shatter index 70% to 85% preferably 80 % and tumbler index 70 % to 85% preferably > 75% , RDI: 20% to 30% preferably 25 %; MPS: 16 mm to 20 mm preferably 18 mm; and return fines 20% to 37% (-5mm) preferably 20% to 30 %.

The above and other objectives and advantages of the present invention are described hereunder in greater details with reference to the following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: Schematic flow diagram showing the conventional steps of water usage and treatment at coke oven by-product plant.

Figure 2: is the schematic flow diagram showing the distribution of BOD plant treated contaminated water at mixing and nodulizer drum during Sintering process according to the present invention.

Figure 3(a)-(f): Comparison of sinter quality obtained using normal water vis-à-vis BOD plant treated water shown graphically as (a) shatter Index;(b) Tumbler Index; (c) product yield; (d) productivity;(e) mean particle size(MPS); & (f) sinter return fines.
Figure 4: is the bar chart showing comparison between sinter properties using normal water and BOD plant treated water based on data obtained on plant trials.
Figure 5: shows graphically the result of ESP hopper dust analysis during plant trial of the sinter process according to the present invention.
Figure 6: shows graphically the result of flue gas analysis during plant trial of the sinter process according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
The present invention is directed to provide a process for sintering iron ore by utilization of BOD plant treated contaminated water from coke oven by-product plant in granulation of sinter mix without adversely affecting the sinter properties as per sinter plants and blast furnaces requirements which enable direct utilization of waste water generated in high quantity at coke oven by-product plant and saving of huge quantity of industrial (make up) water. The process also ensures substantial monetary benefit with respect to the treatment cost of waste water and importantly also suppress the generation of toxic combustion by-products of the sinter process.
As already stated, the contaminated water produced during cooling of coke oven gas contains high amount of sludge, tar and ammonia liquor and is subjected to various treatment (techniques) for cleaning to comply the standards before its reuse in order to make zero liquid discharge. The ammonia liquor is passed through the distillation column to remove the ammonia and sent for further purification to biological oxidation dephenolisation (BOD) plant to bring down the contaminants level within the acceptable environmental range. The major contaminants in water before BOD plant are ammonia, phenol, cyanide (CN), chemical oxygen demand (COD), biological oxygen demand etc. Even after BOD plant treatment, a significant amount of contaminants are present in water which is beyond the limit of clean water norms. The BOD plant treated water is again sent to RO plant for further purification. Accompanying Figure 1 shows a process flow diagram depicting the schematic of the steps of conventional water cleaning at coke oven by-product plant to make it fit for reuse.

In the present invention, BOD plant treated polluted water containing harmful chemicals from by-product plant of coke oven plant is utilized during granulation of sinter mix in sintering process, without adversely affecting the sinter properties as per sinter plant and blast furnaces requirements. At JSW Steel Ltd., Vijayanagar Works, circulation of BOD plant treated water is: ~4000 m3/day. Water requirement at Sinter plants of JSW Steel Ltd., Vijayanagar Works, is ~1600 m3/day. The contamination level of this water is very high and hence can’t be disposed directly. This water must be treated to reduce the toxicity to comply the environmental norms before disposal. Hence the waste water from coke oven by-product plant is utilized in the granulation of sinter raw mix. Accompanying Figure 2 is the schematic flow diagram showing the distribution of BOD plant treated contaminated water at mixing and nodulizer drum during Sintering process according to the present invention.

The comparative chart between of the chemical constituent present in normal and BOD plant treated water is given in following Table 1.

Table 1: Characteristics of BOD plant treated water and Normal water
Normal Water BOD plant treated Water
pH 7.7 7.37
NH3-N mg/l 1.1 7.70
Phenol, mg/l 0.04 4.97
COD, mg/l Nil 194.05
Total Cyanide, mg/l 0.04 2.12

The process of sinter making according to the present invention wherein BOD plant treated water is used for granulation of sinter mix has been carried out as follows:
Preparation of raw materials:
(i) Raw materials were screened to obtain the desired size as given below.
Material Size
Base Mix As received
Calcined lime - 0.212 mm
Coke breeze - 3.15 mm

(ii) Base mix collected from Sinter plant weigh feeder.
(iii) Waste water after BOD plant treatment.

Steps of the process and important parameters used are as follows:
a. Approximately 85 kg of sinter mix blended using balling drum. Blending condition: mixing @ 20 rpm for 300 seconds.
b. One kg of each blended sinter mix sample was dried and analyzed for particle size distribution.
c. Agglomerated the sinter mix in presence of moisture using a drum mixer; Agglomerating condition: mixing @ 20 rpm for 480 seconds.
d. Sintered the material in pot grate with ignition conditions as under:
Ignition conditions:
Suction air flow volume before ignition 2.0 m3/min
Ignition holding time 60 sec
Suction pressure after ignition -1200 mm H2O

Efficacy of the process of sintering according to the present invention has been evaluated in terms of sinter property as per the following example I:

Example I:
Under this example, experiments were carried out involving:
(a) Waste water of coke oven by-product water (after biological oxidation dephenolisation plant) was used for replacement of normal water in sintering process.
(b) Two types of sinter mix were prepared:
(i) Sinter Mix (with normal water)
(ii) Sinter Mix (with BOD plant treated water)

(c) Sinter Bed Height: 700 mm (constant), Hearth Layer: 60 mm

Sinter Mix Composition used for the experimental trials are given in following Table 2 wherein Mix 1,3 & 5 were prepared using normal water whereas Mix 2,4 & 6 were prepared using BOD plant treated water:
Table 2:

Conditions Mix 1 Mix 2 Mix 3 Mix 4 Mix 5 Mix 6
Base Mix 97.80 97.80 97.80 97.80 97.80 97.80
Calcined Lime 1.80 1.80 1.80 1.80 1.80 1.80
Coke Breeze 0.40 0.40 0.40 0.40 0.40 0.40
Moisture, % 7.5 7.0 6.5

The Chemical Analysis of Raw Materials used under the example are as given in following Table 3:
Table 3:
Base Mix Calcined lime Coke breeze
Fe(t) 44.33 0.19 ASH 22.47
SiO2 5.90 0.74 VM 5.75
Al2O3 3.38 0.25 FC 71.78
CaO 11.16 75.41 S 0.48
MgO 2.21 1.20 --- ---
LOI 13.46 21.85 --- ---
C 5.99 --- --- ---
Moisture 5.70 --- --- ---

Results:
Pilot scale laboratory trials using normal water and BOD plant treated water have been conducted with varying moisture percentage of the raw mix. The sinter qualities, productivity and product yield using BOD plant treated water are compared with the normal water and depicted in the graphs in accompanying Figures 3(a)-(f).

Iron ore sinter results obtained after the plant trials using BOD plant treated water for a considerable period are compared with the sinter qualities obtained with the use of normal water. The comparisons are shown as a bar chart in accompanying Figure 4.
Following are the observations based on plant trials carried out:
1. No adverse effects on sinter qualities were observed during the trial period.
2. The pungent smell of BOD plant treated water has not been observed near working area of mixing and nodulising drum.

The results of ESP hopper dust analysis and Flue gas analysis at SP 2 & SP 4 during the plant trials are presented in the accompanying Figure 5 & Figure 6. Figure 5 & 6 clarifies the level of contamination in both the plants in which at one plant (sinter plant-2) normal water is used whereas at other plant (sinter plant-4) BOD plant treated water from coke oven by-product plant is used for granulation process in sinter making. Fig 5 shows the comparison of the flue gas analysis of both the sinter plants. It has been observed that alkali and chloride content (Na, K and Cl2,) of the stack emission from both the plant is almost same. In other words we can say that there is no adverse effect while using BOD plant treated water in sinter plant-4. The flue gas analysis w.r.t the toxic gas content from both the plants have also shown similar result as shown in fig-6. The NOX content is marginally increased in sinter plant-4 flue gas. The increase in NOX content may be due to the presence of NH3-N in BOD plant treated water.

It is thus possible by way of the present invention to provide a process for sintering iron ore using BOD plant treated contaminated water from coke oven by-product plant without adversely affecting sinter quality and acceptable emission standards while also saving substantially on treatment cost of waste water thus reducing the cost of production favouring wide scale application in iron and steel industry.
We Claim:

1. A process for sintering of iron ore comprising:
blending of the desired sinter mix;
providing water source for sintering comprising biological oxidation dephenolisation (BOD) plant treated contaminated water ;
addition of said BOD plant treated contaminated water for agglomerating/granulating the sinter mix with desired moisture content.

2. A process for sintering of iron ore as claimed in claim 1 wherein said step of providing biological oxidation dephenolisation (BOD) plant treated contaminated water comprises waste water generated at coke oven by-product plant.

3. A process for sintering of iron ore as claimed in anyone of claims 1 or 2 comprising involving said biological oxidation dephenolisation (BOD) plant treated contaminated water having ammonia and phenol to suppress generation of toxic combustion by-products of the sinter process.

4. A process for sintering of iron ore as claimed in anyone of claims 1 to 3 comprising routing the (BOD plant) treated contaminated water generated from said coke oven by-product plant without subjecting to any additional treatment in RO plant enabling utilization of contaminated water without need for further purification and benefitting the sintering process and its water requirement.

5. A process for sintering of iron ore as claimed in claim 4 wherein said (BOD plant) treated contaminated water is collected from said BOD treatment plant of said coke oven plant and utilized in said sintering process via a water sump storing said contaminated water thus collected from said BOD treatment plant of said coke oven plant.

6. A process for sintering of iron ore as claimed in anyone of claims 4 or 5 wherein the BOD plant treated water from said water sump is utilized in the mixer drum and also in the nodulizer drum of said sintering of iron ore.

7. A process for sintering of iron ore as claimed in anyone of claims 1 to 6 wherein said sinter mix comprises any conventional sinter mix and addition of said BOD plant treated water is done to produce sinters with moisture content in the level of 6.5 % to 7.5% preferably 7.00 %.

8. A process for sintering of iron ore as claimed in anyone of claims 1 to 7 wherein the unsafe to dispose contaminated water from BOD treatment Plant of coke oven plant is involved in selective amounts to reduce the burden of fresh water for sintering process.

9. A process for sintering of iron ore as claimed in anyone of claims 1 to 8 wherein said BOD plant treated water comprises:
BOD plant treated water
pH 7.0 to 7.8
NH3-N mg/l 8.0 to 119.0
Phenol, mg/l 5.0 to 13.0
COD, mg/l 36.0 to 464.0
Total Cyanide, mg/l 0.5 to 3.0

10. Iron ore sinter produced according to the process as claimed in claims 1 to 9 comprising moisture content in the range of 6.00 % to 8.00 % in the blend as per the raw material characteristics and having selectively anyone or more of the following end characteristics shatter index 70% to 85% preferably 80 % and tumbler index 70 % to 85% preferably > 75% , RDI: 20% to 30% preferably 25 %; MPS: 16 mm to 20 mm preferably 18 mm; and return fines 20% to 37% (-5mm) preferably 20% to 30 %.

Dated this the 19th day of March, 2015
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

ABSTRACT

TITLE: A PROCESS FOR SINTERING OF IRON ORE USING BIOLOGICAL OXIDATION DEPHENOLISATION(BOD) PLANT TREATED CONTAMINATED WATER FROM COKE OVEN BY-PRODUCT PLANT.

The present invention relates to a process for sintering iron ore using BOD plant treated water from coke oven by-product plant containing a significant amount of contaminants to obtain sinter products of desired quality characteristics. Importantly, in this process the contaminated water has been used with sinter mix in the granulation of sintering process replacing normal clean water to save the water treatment cost without adversely affecting the sinter properties. During sintering the contaminants either dissociate or burn at higher temperature (~1300 0C) such that the emissions from the sinter plant suction stack conform to environmental safety standard. The process of sintering using BOD plant treated water also reduces the use of fresh make up water including associated handling and storage costs and thus substantially reducing the cost of sinter production.