FIELD OF THE INVENTION:
The present invention discloses about a method for preparing a blast furnace gas cleaning water, which can be used for slag granulation and sinter making process, which does not create any negative corrosion effect of chloride on plant hardware and thereby improve performance efficiency and life of integrated steel plant.
BACKGROUND OF THE INVENTION:
Iron making is a very important intermittent step to produce steel from iron ore. During iron making the iron ore and metallurgical coke mix is charged in the blast furnace. The metallurgical coal is purchased from abroad and convert it to metallurgical coke near port area. Sea water is used for quenching purpose after conversion of coal to coke and thereby coke is contaminated with chloride. At high temperature coke is converted to CO and as a consequence iron oxide is reduced to iron. This iron with high amount of C, Si and P called pig iron. Waste gas is being generated as a by product during iron making process. As this waste gas is contaminated with different pollutants (Cl2, CO, CO2, solid oxides and coke particles) and cannot be exposed directly to the atmosphere. Thereby the waste gas is being passed in water medium to separate out the contaminants from the waste. After this process water is contaminated with the pollutants and contaminated water is treated in a thickener using surfactant for separation of contaminant from water. A thickener is a piece of equipment in which sedimentation is carried out as a continues process. A slurry of solid particles suspended in water is separated by passage through a thickener. A thickener is a vessel or stage in which gravity brings together suspended solids. Different flocculating agents (long chain of hydrocarbon like sucrose) are added in the medium in ppm level to allow the formation of an agglomerate of fine particles and subsequently separate out from the medium.
Solid contaminants like different oxide particles and coke are separated but chloride remains in water. This chloride contaminated water is being discarded

as waste. Corten and SS grade of steels are being used for plant hardware at sinter plant. The corrosion of mild steel in wet gas and multi-phase gas environment is responsible for frequent maintenance, lower life cycle and production loss. The corrosion loss of metals is undoubtedly influenced by the nature of the atmosphere in which they are exposed. The sinter plant pipe line corrosion study was done when raw petroleum coke was used as trimming fuel [1]. Raw petroleum coke contains high level of sulfur and sulfur is converted to SO2 during sintering process. It was established sinter plant pipe line may not under go any sulfuric acid corrosion due to uses of high sulfur containing trimming fuel in place of anthracite coal. Stainless steel is generally passive and corrosion resistant in aqueous solutions except for pitting corrosion due to some reactive species, such as chloride [2-4]. The pitting tendency abruptly disappears at all potentials for a drop in temperature of only about 10C [5]. A recently theory of the CPT is developed [6–10]. The definition for passivation in the pit solution [6], via under an anodic salt film [7], that retains the pit contents [9–12].
USPTO 4,137,166 describes a process for the purification of ammonia or ammonium salt containing waste waters using alkali metal or alkaline earth metal hypochlorites comprising adjusting the waste water to an initial pH of 8-10.5 with an alkaline material and then treating the waste water with an alkali metal or alkaline earth metal hypochlorite in an amount practically equivalent to the ammonia or ammonium salt, in a given case while lowering the pH during the evolution of nitrogen.
USPTO elaborates the process for the purification of waste water produced in hydrazine production by the oxidation of ammonia or an amine with an oxidizing agent in the presence of an aldehyde or ketone, comprising intensively mixing the waste water with chlorine or a hypochlorite at a temperature of about 10.degree. C to 110 degree C and a pH of about 5 to 10 until the treated waste water reaches a redox potential to platinum, relative to Ag/AgCl, of about -400 mV to +800 mV.

USPTO explains an automatic system for controlling the chlorine feed in the breakpoint chlorination process at the optimum dose level, under the conditions of varying ammonia concentration and process flow rates as well as other fluctuations in process chlorine demand.
USPTO 4,366,064 explains how to the wastewater, particularly blowdown from a recycle gas-scrubbing and gas-cooling system of a blast furnace, is treated in a two-stage chlorination unit.
Hence, there is always a long felt need to prepare blast furnace gas cleaning water, which can maintain optimum chloride level yet produce no discharge from integrated steel plant.
The present invention meets the long felt need.
SUMMARY OF THE INVENTION:
A method for zero discharge of blast furnace gas cleaning water, the method comprising: Subjecting the gas cleaning water to a thickener to separate fine particles; Adjusting pH of water from step 1 by addition of different alkali compounds; and Reusing the pH adjusted water in slag granulation and sinter making process.
OBJECTS OF THE INVENTION:
It is therefore, the primary object of the present invention to prepare the blast furnace gas cleaning water, which substantially control the negative corrosion effect of chloride on plant hardware and thereby enhance the performance efficiency and life of integrated steel plant.
Another object of the present invention is to prepare blast furnace gas cleaning water, which can be useful in slag granulation and sinter making process.
Yet another object of the present invention is to prepare blast furnace gas cleaning water, which ensures less water consumption for per ton of steel production and ensures no discharge from integrated steel plant.

Further object of the present invention is to prepare blast furnace gas cleaning water, which is eco-friendly and makes environment more clean and green.
Another object of the present invention is to prepare blast furnace gas cleaning water, which is simple yet effective.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING:
It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. Some embodiments of system or methods in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
Fig. 1 illustrates pictorial view of all the samples exposed in different environments immediately after exposure.
Fig 2 illustrates the pictorial view of all the samples after exposure for 27days. It evident from Fig. 65 that MS is under gone oxidation process in all three environments whereas SS does not under gone oxidation process in any environment.
Fig 3 illustrates SEM morphology and EDS results of reaction product obtained on grate bar surface after cycle (a) 1st and (b) 4th when GBF 1700 ppm chloride was used for preparation of green mix.
Fig 4 illustrates XRD results of reaction product obtained on grate bar surface after cycle (a) 1st and (b) 4th when service water was used for preparation of green mix.
Fig 5 illustrates the X-ray diffraction results of reaction product obtained on grate bar surface when blow down water with chloride content 1700 ppm was used for preparation of green mix.

Fig 6 illustrates SEM depth morphology and EDS depth analysis of reaction product obtained on grate bar surface for exposure in sintering atmosphere after different cycles when service water was used for preparation of green mix.
Fig 7 illustrates SEM depth morphology and EDS depth analysis of reaction product obtained on grate bar surface after cycle (a) 1st and (b) 4th when GCW 4 was used for preparation of green mix.
Fig 8a illustrates of the flow diagram of the conventional process.
Fig 8b illustrates the flow diagram of the novel process as claimed hereinafter.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
The present subject matter relates to process of preparing a blast furnace gas cleaning water by adjusting the pH of the water, so that an optimum chloride content can be achieved.
The gas cleaning water can be subjected to use in slag granulation and sinter making process which does not create any negative corrosion effect of chloride on plant hardware and thereby improve the performance efficiency and life of the integrated steel plant.
The process of preparing the gas cleaning water comprises:
Subjecting the gas cleaning water to a thickener to separate fine particles;
Adjusting pH of water from step 1 by addition of different alkali compounds; and
Reusing the pH adjusted water in slag granulation and sinter making process.
Different corrosion tests were performed in different chloride containing blast furnace gas cleaning water mediums under different temperatures of different steel grades used in plant hard. Table 1 and 2 show the different steel grades and water mediums used for the corrosion test. The different water grades will be used as abbreviated form (service water: SW, service water with 400 ppm chloride: SW 400, service water with 800 ppm chloride: SW 800, service water

with 1250 ppm chloride: SW 1250, service water with 1600 ppm chloride: SW 1600, service water with 1700 ppm chloride: SW 1700, blast furnace gas cleaning water with 434 ppm chloride: GCW 1, blast furnace gas cleaning water with 585 ppm chloride: GCW 2, blast furnace gas cleaning water with 1250 ppm chloride: GCW 3 and blast furnace gas cleaning water with 1700 ppm chloride: GCW 4) in subsequent section.
Table 1 Different steel grades used in slag granulation and sinter plant

Steel grade C
0.22
0.16
0.08
1.15 Mn Si Cr Ni Mo
MS 2062
1.5 0.4 ---- --- ----
MS
0.94 0.213 0.012 0.004 0.011
SS plate
2 -- 16 10 2.00
Grate bar
0.80 2.1 26.5 3.9 0.035
Table 2 Different chloride containing water mediums used for corrosion test

Water grade Cl (ppm) S (ppm) TDS(ppm) pH Electrical conductivity
SW traces 3.3 111 7.53 0.354 mS/cm
SW 400 400 3.3 111 7.45 2.623 mS/cm
SW 800 800 3.3 111 7.43 4.534 mS/cm
SW 1250 1250 3.3 111 7.35 6.23 mS/cm
SW 1600 1600 3.3 111 7.32 7.55 mS/cm
SW 1700 1700 3.3 111 7.30 8.02 mS/cm
GCW 1 434 33.4 1458 7.36 3.03 mS/cm
GCW 2 585 22.5 2139 8.46 4.34 mS/cm
GCW 3 1250 138.35 2419 7.84 8.46 mS/cm
GCW 4 1700 135.12 2496 8.32 10.05 mS/cm
SW 1250 1250 3.3 111 9.00 6.67 mS/cm
SW 1700 1700 3.3 111 9.00 8.85 mS/cm

Corrosion test also performed under different temperatures (25, 80 and 1250 degree C) to simulate plant conditions. Then comparative corrosion rates were evaluated for different steels in different chloride containing water mediums by different techniques like exposed in water mediums (weight loss calculation after exposure), tafel (corrosion current, potential and rate calculation) electrochemical impedance (charge transfer resistivity at the interface between steel and medium), potentiodynamic polarization (Pitting current and potential), high temperature cyclic pot sintering test.
Electrochemical tests were conducted at 30 and 80 degree C using Gamry make potentiostate. Tafel, normal weight loss measurement, EIS and Cyclic polarization tests were conducted for evaluation of material behavior under different environmental conditions. Tafel test provides thermodynamic and kinetic aspect of the material in a particular environment. Thermodynamic information will tell that material will go for oxidation or not? Tafel test consists of first cathodic polarization followed by anodic polarization.
The corrosion rate of material in a particular environment can be calculated by Farady law using Icorr value. The free energy change for the oxidation process of the material in a particular environment can be calculated by the formula as mentioned in equation i using Ecorr value.
ΔG= -nFEcorr (i)
ΔG: free energy change for oxidation
n: number of electron donated for the oxidation
F: Faraday constant
Ecorr: it is measured by tafel test
If material is thermodynamically favourable for oxidation then kinetic data will tell under what rate material will be oxidized. Tafel test may be good enough for MS but corrosion behavior of SS is quite different as SS is passive in nature. Measurement of passivation and pitting potential of SS is very important to

know the behaviour of the material in a particular environment. Fig 4 shows the cyclic polarization curve of typical active passive material. This curve provides Epass (Epp) and Epit (Ep) values. Epass indicates passivation potential whereas Epit indicates pitting potential. The area under the Ep and Epp is called the passive zone of the material in a particular environment. More area indicates better resistance against pitting can be expected whereas very close to zero or no such area indicates material may not able to provide protection against pitting corrosion. EIS provides resistivity against charge transfer at the interface between steel and water medium. This data indicates comparative oxidation of the material.
All the steel samples were cut into small pieces as per requirement for the corrosion test. All samples were mirror polished before corrosion test to avoid any non-uniform surface effect on corrosion.
Grate bar experiences the sintering atmosphere. Pot sinter tests were conducted to simulate sintering atmosphere which faces the grate bar. Different level of chloride containing water samples were used to prepare green mix to check the effect of chlorine in water on corrosion of grate bar. Pot tests were conducted in a cyclic manner to evaluate the effect of time on grate bar corrosion. One cycle consists of heating at around 1250 0C for around a hour and after that stop the firing and kept as it for one day. The pot tests were conducted upto four cycles. Initially eight samples were exposed just below the green mix and after each cycle two samples were removed. One used for weight loss measurement and other one used for characterization of reaction products by different equipment like scanning electron microscopy with elemental analysis (SEM-EDS) and X-ray diffraction (XRD). SEM gives the morphology of the reaction product and EDS result indicates the elements present in the reaction product. SEM-EDS technique used for analysis of top surface morphology as well as depth of reaction product XRD techniques used to identify the all the compounds present in the reaction product. Grate bar samples were treated in acid solution as per standard to separate out the

reaction product from the grate bar surface. Then weight loss was calculated and based on weight loss corrosion rate for all samples were identified. Also experimental was conducted by varying chloride and pH of the solution to check the effect of pH and chloride level of the solution on corrosion of mild steel. The chloride content of service water is 15 ppm and this water was used for test as base case. The specific level of 1250 and 1700 ppm chloride containing solutions were prepared by addition of measured amount of sodium chloride in specific volume of service water. The pH of all the solutions was recorded. The pH of both the 1250 and 1700 ppm chloride containing solutions were raised to 9 by cautiously addition of sodium hydroxide. Tafel test was conducted in all solutions to check the effect of pH and chloride on mild steel corrosion.
Corrosion test results in different environments
Table 3 shows the thermodynamic and kinetic aspect of two grades of steel samples in different environments. It is evident that Ecorr values for MS are negative in all environments whereas Ecorr values may not be negative in all environments.
Table 3 Corrosion rate and Ecorr values calculated from Tafel tests conducted at room temperature (300 C) for MS and SS and at high temperature (800 C) fro SS.

Water grade Steel grade Temperature Ecorr (mV) Icorr (µA) Corr rate (mpy)
Service water MS 300 C - 554 4.35 2.12
SW 400 MS 300 C - 677 4.78 2.18
SW 800 MS 300 C - 608 5.46 2.49
SW 1250 MS 300 C - 650 6.25 2.66
SW 1600 MS 300 C - 666 5.82 3.09
SW 1700 MS 300 C - 686 7.15 3.51
GCW 1 MS 300 C - 679 5.39 2.46
GCW 2 MS 300 C - 688 5.32 2.43
GCW 3 MS 300 C - 742 6.22 3.05

GCW 4 MS 300 C - 686 6.65 3.22
SW 1250 MS 300 C - 600 4.02 1.95
SW 1700 MS 300 C - 620 4.95 2.46
SW SS 300 C - 154 0.06 0.03
GCW 1 SS 300 C - 247 0.22 0.10
GCW 2 SS 300 C - 262 0.17 0.08
GCW 3 SS 300 C - 255 0.40 0.18
GCW 4 SS 300 C - 242 0.24 0.11
SW SS 800 C - 121 0.10 0.05
GCW 1 SS 800 C - 156 0.22 0.10
GCW 2 SS 800 C - 176 0.19 0.09
Hence oxidation potential of MS in all environments must be positive whereas oxidation potential of SS may not be positive as corrosion potential was measured vs standard calomel electrode. Thereby free energy changes for MS in all the environments used for testing should be negative and free energy changes for SS may not be negative which indicates MS has a tendency for oxidation or corrosion whereas SS may not have oxidation or corrosion tendency in all environments. MS corrodes spontaneously in the range of 1.8 to 2.8 mpy in different environments whereas SS may not corrode in any environment tested. Orange symbol indicates MS can be used in all environments with precaution whereas green symbol indicates SS can be used without any concerned.
Normal Exposure test
Normal exposure test was conducted for MS & SS in SW, GCW 2 and GCW 3 mediums. Fig. 1 shows the pictorial view of the samples in beaker immediately after exposure in different environments. Test was conducted for 27 days.
Fig. 1 Pictorial view of all the samples exposed in different environments immediately after exposure.
Fig. 2 shows the pictorial view of all the samples after exposure for 27days. It evident from Fig. 65 that MS is under gone oxidation process in all three

environment whereas SS does not under gone oxidation process in any environment.
Fig. 2 pictorial view of all the samples exposed in different environments after exposure for 27 days.
The details about initial weight, surface area, exposed environmental conditions, final weight and corrosion rate of all the samples are shown in Table 4. Corrosion rates were calculated for all the samples based on weight loss measurement. MS corrodes in all three environments but SS not. Corrosion rate of MS is maximum in GC 3. Corrosion rate may not be so high even in GCW 3 where chloride level is around 1250 ppm.
Table 4 results of normal exposure test

Water grade Steel grade Intial wt Surf area Final wt Corr rate gm cm2 gm
SW MS 103.3328 46.025 103.2007 2.11
GC 2 MS 106.2958 46.40 106.1139 2.57
GC 3 MS 100.8762 45.075 100.6943 2.86
SW SS 95.4175 46.08 95.4180 ~ zero
GC 2 SS 89.7995 46.28 89.7994 ~ zero
GC 3 SS 75.9453 40.73 75.9454 ~ zero
Table 5 shows the corrosion rate of grate bar samples after different sintering cycles for both cases where service and blow down water used to prepare green mix. It is evident that the corrosion rate is high initially but corrosion rate drop down significantly after onwards. This can be explained by the formation of first reaction product acts as passive film to retard the further reaction. It is also evident that the corrosion rate of grate bar samples was comparable under exposure in green with different chloride level. From this result it can be concluded that such level of chloride in blow down water which used to prepare

green mix may not strongly participating for formation of reaction product on grate bar surface.
Table 5. The characterization of grate bar samples after exposure for different cyclic pot sintering tests.

Cycle
1
2
3
4
1
2
3
4 Water grade Initial wt Final wt Wt loss Area Corr rate

SW 45.66 gm 45.48 gm 0.18 gm 30.2 cm2 77.3 mpy

SW 57.63 gm 57.40 gm 0.23 gm 38.1 cm2 39.2 mpy

SW 60.52 gm 60.22 gm 0.30 gm 40.3 cm2 32.0 mpy

SW 69.69 gm 69.60 gm 0.39 gm 46.1 cm2 27.5 mpy

GCW 4 80.85 gm 80.54 gm 0.31 gm 53.4 cm2 76.7 mpy

GCW 4 53.44 gm 53.33 gm 0.21 gm 36.1 cm2 38.5 mpy

GCW 4 57.41 gm 57.14 gm 0.27 gm 38.3 cm2 32.1 mpy

GCW 4 59.75 gm 59.38 gm 0.37 gm 39.7 cm2 30.2 mpy

Characterization of reaction product on grate bar surface after pot test
Figure 2 shows the SEM morphology and EDS results of reaction product obtained on grate bar surface for exposure in sintering atmosphere after different cycles. Here service water was used for preparation of green mix before the pot test. From EDS results it is clear that reaction product consist of oxides of different elements such as Fe, Cr, Ca, Si and Al. It is also evident from the EDS results that no chloride peak was detected and can be say absence of chloride in the reaction product.
Figure 2 illustrates SEM morphology and EDS results of reaction product obtained on grate bar surface after cycle (a) 1st and (b) 4th when service water was used for preparation of green mix.
Figure 3 illustrates SEM morphology and EDS results of reaction product obtained on grate bar surface after cycle (a) 1st and (b) 4th when GBF 1700 ppm chloride was used for preparation of green mix
Figure 3 represent the SEM morphology and EDS results of reaction product formed on the surface of grate bar samples after exposure in simulated pot sintering atmosphere for different cycles. Specially prepared blow down water with 1700 chloride content was used to prepare green mix and subsequent pot test. EDS results indicates reaction product consist of oxides of different elements such as Fe, Cr, Ca, Si and Al. It is also clear from the EDS results that no chloride peak was identified and it can be concluded absence of chloride in the reaction product.
1.1.2.2.2. Characterization of reaction product by XRD
Figure 4 illustrates XRD results of reaction product obtained on grate bar surface after cycle (a) 1st and (b) 4th when service water was used for preparation of green mix.
Figure 4 and table 6 shows the X-ray diffraction results of reaction product formed on grate bar surface for exposure in simulated pot sintering atmosphere

for different cycles when service water was used for preparation of green mix. It is evident from the figure that the reaction product consists of different oxides of iron and chromium. The predominant oxide formed on the grate bar surface was identified as hematite. Even after cycle number four the reaction product is almost identical in nature with reaction product formed on the grate bar surface after 1st cycle. It is also evident that no chloride compound was detected in the reaction product irrespective of number of cycles.
Table 7: The presence of different compounds in reaction product when service water used for green mix

Cycle No Compounds in the reaction product
Cycle 1 Hematite: Fe2O3, Magnetite: Fe3O4, Weistite: FeO, Eskolaite: Cr2O3
Cycle 4 Hematite: Fe2O3, Magnetite: Fe3O4, Weistite: FeO, Eskolaite: Cr2O3
Figure 5 illustrates XRD results of reaction product obtained on grate bar surface after cycle (a) 1st and (b) 4th when GBF 1700 ppm chloride was used for preparation of green mix.
Figure 5 shows the X-ray diffraction results of reaction product obtained on grate bar surface when blow down water with chloride content 1700 ppm was used for preparation of green mix. Here also, the reaction product analyzed as oxides of iron and chromium. The main oxide component on the grate bar surface was identified as hematite. The reaction product is almost identical in nature even after cycle number four with the reaction product which was obtained on grate bar surface after 1st cycle. As like earlier, no chloride compound was detected here as well in the reaction product irrespective of number of cycles when blow down water was used in place of service water to prepare green mix.

Figure 6 illustrates SEM depth morphology and EDS depth analysis of reaction product obtained on grate bar surface after cycle (a) 1st and (b) 4th when SW was used for preparation of green mix.
Figure 6 depicts SEM depth morphology and EDS depth analysis of reaction product obtained on grate bar surface for exposure in sintering atmosphere after different cycles when service water was used for preparation of green mix. The results indicate the thickness of reaction products obtained on the grate bar surfaces were around 4 and around 8 µm for exposure in simulated sintering atmosphere after 1st and 4th cycles respectively. Hence the formation of reaction product may not follow the linear relationship with time rather it follows parabolic. This can be explained by the fact that the initial oxide scale formed on the grate bar surface acts as a passive layer and hinder further oxidation of the base metal. Depth EDS analysis indicates presence of O, Fe, Cr, Ca, Si, Ni and Al in the reaction product. It is evident from the EDS results that trace of chloride was detected in the reaction product after 4th cycle and it might be appeared in the analysis due to contamination.
Figure 7 illustrates SEM depth morphology and EDS depth analysis of reaction product obtained on grate bar surface after cycle (a) 1st and (b) 4th when GCW 4 was used for preparation of green mix.
Figure 7 represent SEM-EDS depth analysis of reaction product obtained on grate bar surface for exposure in sintering atmosphere after different cycles when specially prepared blow down water with chloride level of 1700 ppm was used for preparation of green mix. The analysis infers the thickness of reaction products formed on the grate bar surfaces were around 4 and around 8 µm for exposure in simulated sintering atmosphere after 1st and 4th cycles respectively. Here as well like earlier, the formation of reaction product may not follow the linear relationship with time and 1st reaction product retard further oxidation of base metal. Depth EDS analysis indicates presence of mainly O, Fe, Cr, Ca, Si, Ni and Al in the reaction product. At some location trace of

chloride here also detected in the reaction product after 4th cycle and it might be appeared in the analysis due to some contamination.
The earlier practice and new innovative process developed have been mentioned below as a flow diagram. This innovative process leads to not only saving of natural resource (water) but also controlling environmental pollution up to a great extent.
The chloride concentration varies in the range of 1700 ppm to 3000 ppm chloride; however, the preferred chloride concentration is 1600 ppm to 1700 ppm.
The evaluation of different tests was performed at temperature range such as low as room temperature to high as 1250°C.
The pH has been increased from 7 to 9.8 but an optimum level is pH 8.5 to 9.5 to combat up to 2000ppm chloride, so that the performance of the plant hardware material against chloride corrosion does not deteriorate.
The Alkali compounds were used in single or in combination, but single alkali compound and sodium hydroxide is used as preferable pH modifier.
Further, the material used for thus purpose are different grades of mild steel, stainless steel and high chromium containing grate bard materials.
The performance against corrosion of different materials is provided in different chloride containing mediums under different temperature to simulate plant condition of slag granulation plant and sintering plant.
Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the method of the present invention will be apparent to those skilled in the art, and thus it is

intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.

WE CLAIM:
1. A method for zero discharge of blast furnace gas cleaning water, the method
comprising:
Subjecting the gas cleaning water to a thickener to separate fine particles;
Adjusting pH of water from step 1 by addition of different alkali compounds; and
Reusing the pH adjusted water in slag granulation and sinter making process.
2. The method as claimed in claim 1, wherein the optimum pH varies in the
range of 8.5 to 9.5.
3. The method as claimed in claim 1, wherein chloride concentration in the gas cleaning water varies in the range of 400 ppm to 3000 ppm.
4. The method as claimed in claim 1, wherein chloride concentration in the gas cleaning water is preferably maintained in the range of 1700 ppm to 3000 ppm.
5. The method as claimed in claim 1, wherein the alkali compounds are
selected from a group consisting of sodium hydroxide, potassium hydroxide,
calcium hydroxide and combinations thereof.
5. The method as claimed in claim 1, wherein the treated gas cleaning water does not have negative corrosion impact on steel.
6. The method as claimed in claim 1, wherein the treated gas cleaning water was tested for corrosion impact in the temperature range varying from room temperature to 1250°C.