FIELD OF INVENTION:
This invention relates to a process for removing colour bodies from coke oven
wastewater constituting a typical refractory organic wastewater, containing toxic
cyanides and other objectionable complex organic compounds. More
particularly, the invention relates to a process for removing color from BOT
water of coke oven effluents.
BACKGROUND OF THE INVENTION
Coke is a major component in manufacturing of steel, which is produced by
pyrolysis of coal. During pyrolysis, coke oven gases are produced and cooled for
further steel-making purposes. The condensed water from the coke-oven gases
consists of many pollutants that contain refractory compounds, such as tar,
ammonia, phenols, naphthalene, light oil, and sulfuric compounds. Tar and
ammonia can be recovered in a decanter for use in other processes. The liquid
remaining after recovery, called coke-oven wastewater, is ready for treatment
and discharge into a body of water. The conventional processes used to treat
coke-oven wastewater include chemical neutralization, activated sludge process,
and sand filtration Due to the difficulty in removing refractory organic matter, the
treated wastewater released in conventional processes can not effectively be
treated meet to the current effluent standards. The discharged effluent therefore
becomes the subject of complaints from the local communities. Although some
treatment processes, for example, chemical coagulation, ion exchange, and
active carbon adsorption, may achieve high removal efficiencies of organic
matter and color, they are accompanied by high cost of sludge treatment,
disposal, and activated carbon regeneration. Ozone having a high oxidation

capability, has been successfully applied in water and wastewater treatment to
remove applied in the textile, leather tanning, and petrochemical industries.
Prior art teaches different methods to remove compounds such as NH3, HCN and
the like from coke oven gas. However, the prior art methods are mostly designed
to wash coke oven gas with waste pickle liquor to remove ammonia, H2S and
HCN from the coke oven gases. In contrast, the ferrous sulfide and ammonium-
ferro-cyanide formed being insoluble, are disposed of by burning in a blast
furnace. The prior art processes are complex, expensive and utilize high speed
centrifuges or a filter apparatus to remove the cyanide sludges from the
ammonium sulfate containing liquid. While the processes may remove some of
the complex organic compounds, they are not capable of removing neither the
cyanides nor sufficient amounts of the complex organic compounds. Accordingly
prior art processes are disabled to reduce the discoloration of the wastewater
sufficiently enough to allow disposal of coke oven waste water in environmental
surface waters. The prior art further teaches processes for removing waste pickle
liquor, acid mine drainage from coke oven waste water. While these systems
have proven relatively effective in reducing the acidity and removing iron from
acid wastewaters, they are generally not effective in treating non-acid liquors,
such as benzol wastes and waste liquor from ammonia stills in coke oven by-
product plant recovery systems.
OBJECTS OF THE INVENTION:
It is therefore an object of the invention to propose a process for removing
colour compounds from coke oven waste water.
Another object of this invention is to propose a process for removing colour
compounds from coke oven waste water reutilization of solid waste without
chemicals.
A Still another object of this invention is to propose a process for removing
colour compounds from coke oven waste water which is cost effective.
SUMMARY OF THE INVENTION:
Broadly, this invention is an improved absorbent process for treating
wastewaters containing cyanides and complex organic compounds, which
complex organic compounds discolor the wastewaters. The inventive process
enables an effective separation of cyanides and complex color producing organic
compounds from the wastewaters without adding any flocculent. Finally, coke
bye products materials are used in the process as an absorbent. Further, the left
over materials in the process are fed back to sinter making process.
The present invention provides a process to remove colour bodies from BOT
water. According, to the invention, colour from coke oven waste water is
removed by using coke oven by- product material acting as a catalyst. The
process has single stage i.e. column absorber or mix reactor cum mixing and the
final left over is used as sinter making processing.
The invention is based on a thorough investigation of the effects of absorbent on
the degradation of target pollutants in coke-oven wastewater under various pH
conditions and the effect on subsequent biological treatment. The experiments
were performed in a bench-scale bubble column so that they could be easily
controlled. The results of the chemical and biological tests in this study can serve
as a reference for evaluating the effectiveness of coke-oven wastewater and the
combination of treatment systems for practical applications. The chemical oxygen
demand (COD) and total organic carbon (TOC) of wastewater as well as the
effect of cyanide (CN-), thiocycanate (SCN-) and phenolic compounds for
removal of color have been experimental before implementation of the inventive
process in the industry.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 is a block diagram illustrating the flow chart of the present invention.
Figure 2 is a mix reactor according to the invention.
Figure 3 slows an UV absorption spectra of organic pollutants removed by
absorbent treatment.
DETAILED DESCRIPTION OF THE INVENTION
The inventors have recognized that a substantial portion of cyanides, and
complex organic compounds which discolor wastewaters, such as waste liquor
from ammonia stills, benzol wastes, bio-effluent from an activated sludge plant
and the like, can be re-moved from said wastewaters by the use of a surface
modified coke by-product material in a column adsorbent or a mix reactor
process.
According to the inventive process, in a first aspect, as shown in figure 2,
the coke and color water are stirred in reactor A for a time, for example,
about 1 minute to about 25 minutes, to produce a uniform mix and to cause
intimate contact between the particles in the materials.
After thorough mixing, the mixed materials either flow under the influence
of gravity or are pumped to a second reactor B. It has been found that as
much as 99 per-cent of complex organic compounds responsible for the
discoloration of the wastewaters are removed, thereby reducing the color of
the wastewaters to less than about 50 APHA units.
In a second aspect, the process comprises the steps of:
removing the Color by passing water through a Pack bed column
(PBC), as shown in figure 1, which is packed by coke breeze (CB). This
is very standard equipment & easy to implement. Some results are
mentioned below to have a better perception.
a.1 kg of coke is able to remove near about 8 litre of water
(1:8 ratio).
b.-3.15 mm - 0.25 mm size coke by-product is found
satisfactory to remove color bodies.
mixing the Coke breeze (CB) and color water (CW) thoroughly in a
mixture (M) with stirrer arrangement as shown in figure 2. After
providing some residence time in the mixer (M), the slurry (SL) is
separated through a pressure filter or vacuum belt filter (F) to treated
water (TW) and coke (CK). Some results having that kind of treatment
is explained below.
a.Raw Coke by-product without any size fraction can be used
with 1:7 ratio. That implies 1 kg coke is able to remove 7
litre of water.
b.Stirring speed is maintained at 600 r.p.m.
c.Normal filtration technique is able to separate coke from
clean water.
The color can be removed completely by implying both the method. The analysis
of results is as follows.
1.The color constituents are developed due to phenyl thiocyanate complex
with cyanide & other phenolic compounds linkage with sulphur.
2. >99% color is removed which is analysed by UV-visible spectro-
photometer
3. >=97% Phenolic compound is removed from treated water.
4. >=99% cyanide compound is removed from treated water.
5. >96% thiocyanate compound is removed from treated water.
6. 1 ton of coke breeze adsorbed 50 gm of color bodies which implies 150
gm of CO2 & NO2 can be generated.
REFERENCES
1. U.S. Pat. No. 2,584,280 issued Feb. 5, 1952 to Herman P. Meissner et al.
and U.S. Pat. No. 2,712,980 issued July 12,1950 to Richard D. Hoak.
2. U.S. Pat. No. 3,617,559 issued Nov. 2,1971 to Allen Cywin
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WE CLAIM:
1. A process for removing colour from BOT water of coke oven effluents
comprising the steps of:
- adding of coke by-product materials at pH 8-9 at normal temperature;
to cokeoven waste water for absorption of color compounds; and
- subjecting the soluble compounds to a step of removing and followed
by a Colum separation or filtration in a mix reactor.
2.The process as claimed in claim 1, wherein the step of column absorption and
mix reactor are carried out for a period of 2 hour and 3 minutes respectively with
sequential sampling for checking colour.
3.The process as claimed in claim 1, wherein the coke by product material acting
as an absorbent is selected form carbon materials or rejects coke materials.
4.The process as claimed in claim 1, wherein the particle size of absorbent is -
3.15 mm-0.25 mm.
5.The process as claimed in claim 1, wherein the concentration of absorbent 1:7
by weight.
6.The process as claimed in claim 1, wherein 99% of colour compounds are
removed.
7.The process as claimed in claim 1, wherein 100 % of the absorbent is
reusable.
8. A process for removing colour from BOT water of coke oven effluents,
comprising the steps of :
- preparing a slurry of absorbant using coke by-product dissolved in
coke oven effluent in a ration between 1:5 and 1:20 in a reactor at a
reaction speed of 800 to 900 rpm for a period of 120 minutes to form
color precipitant; and
- subjecting the formed color precipitant to a step of filtration in a mixer.

The invention relates to a process for removing colour from BOT water of coke
oven effluents comprising the steps of adding of coke by-product materials at pH
8-9 at normal temperature; to cokeoven waste water for absorption of color
compounds; and subjecting the soluble compounds to a step of removing and
followed by a Colum separation or filtration in a mix reactor.