The present invention relates to a continuous reactor system for handling high
throughput in an Ultra High Lime Aluminium (UHLA) process for optimum
reduction of chloride level in the waste water. The invention further relates to an
improved process for optimum removal of chloride-content in coke-quenching
water maintaining using a continuous reactor system.
BACKGROUND OF THE INVENTION
Chloride is a deleterious ionic species in coke quenching water because it is
important in promoting corrosion in blast furnace. Chloride can be removed from
cooling water by precipitation as calcium chloroaluminate using the ultra-high
lime with aluminum (UHLA) process.
The current trend in industrial wastewater management focuses on pollution
prevention by source reduction and by maintaining water systems with no in
which water recycling plays a major role. Discharge from blast furnace water is a
major environmental concern because of the presence of toxic chemicals, and
organic and inorganic materials .Among these contaminations chloride is a
deleterious ionic species because it promotes corrosion in pipelines. At very high
temperature in blast furnace (~11000c) chloride vapors are formed, which
originates from the coke and start corroding on equipment. After an intense
investigation it was found that this chloride contamination was owing to the
quenching of hot coke with water. As quenching water contains more than 2000
ppm chloride concentration, this high concentration of chloride results into
corrosion in gas cleaning pipelines, pumps etc. and hence those are subjected to
change very frequently, even twice in a year. Chloride can be removed from
water by precipitation as calcium chloro aluminate using the ultra-high lime with
aluminum process (UHLA).

OBJECTS OF THE INVENTION
It is therefore an object of this invention to propose a continuous reactor system
for handling high throughput in an Ultra High Lime Aluminium (UHLA) process for
optimum reduction of chloride level in the waste water, which is enabled to
remove chloride level from coke quenching water by >80%.
Another object of this invention is to propose an improved process for optimum
removal of chloride-content in coke-quenching water maintaining using a
continuous reactor system.
SUMMARY OF THE INVENTION
Accordingly, in a first aspect of the invention, there is provided a continuous
reactor system for handling high throughput in an Ultra High Lime Aluminium
(UHLA) process for optimum reduction of chloride level in the waste water. In a
second aspect of the invention, there is provided an improved process for
optimum removal of chloride-content in coke-quenching water maintaining using
a continuous reactor system.
As disclosed the continuous reactor of the invention having higher handling
capacity of say, 5 m3/hr pilot plant setup for optimization of UHLA process for
desalination of coke quenching water. As the improved process is continuous
one a continuous reactor has been designed and constructed for the treatment of
at least 5 m3 of water per hour. All the ancillary equipment starting from reagent
preparation, transporting of chemical and finally solid liquid separation system
was also developed for maintaining inlet and outlet of the reactor at steady state
level to deliver at least 5m3/hr desalination rate of process water. A continuous
system having the of capacity of 5 m3/hr is constructed by optimizing the design

parameters of dosing, dosing sequence, pH and the kinetics of the system. A
high quality of process water along with the solid residue has been obtained
during the experimentation of the inventive system.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 – shows a process flow diagram implemented in the continuous reactor
of the invention.
Figure 2 – shows a general arrangement showing the Reactor of the invention.
DETAILED DESCRIPTION OF THE INVENTION
As shown in figure 1, the process consists of several unit operations. At first,
reagents are prepared in reagent preparation unit which consist of four tanks T01,
T02, T03 and T04. T01 is the feed water storage tank, T02 is the slacker tank,
T03 is the sodium aluminate preparation tank and T04 is the acetic acid tank.
The next unit is the dosing unit which comprises of several pumps which
transported the reagents from all four reagent tanks to the main reactor V01. The
mixing time of the reactor set by the kinetics of the process, which is
approximately equal to 1 hour. The treated slurry is then sent to solid liquid
separation unit. The first tanks is the settlingtank1 (V02) in solid liquid separation
unit which receives slurry from the reactor (VO1) directly. From the bottom of V02
solid is collected in pit. From the top of the V02 liquid with marginal solid loading
is pumped into another settling tank V03. From the bottom of the V03 solid is
again collected in a pit and from the top almost clear water is the sent into gravel
and cartridge filter. To maintain the discharge water quality a cartridge filter is
attached at final discharge point. The discharge water quality is reported in table
below.

The key equipment of the process is the continuous stir tank reactor for handling
5m3/hr throughput as described in figure 2. It is a continuous stirred tank reactor
having baffle at 1800 angle which ensure better mixing phenomena. The material
of construction is fire reinforcement plastic (FRP). An epoxy coating is done both
inside and outside of the reactor to withstand salinity of the process and weather.
As shown in Figure 2, the Reactor system comprises three agitated tank, three
storage tank, two settling tank, two centrifugal pump and four number of dosing
pump. A plurality of pH sensor are introduced at the mixing vessel and at the final
settling tank to measure the pH of the process. Two agitated tanks are used for
reagent preparation, one is used for slacker and another one is for sodium
aluminate solution preparation. Firstly, in a lime solution is prepared in tank T02.
Slack lime is then pumped into a reactor V01 where the main reaction is taking
place.
The general arrangement drawing of the rector is shown in figure 2. The reactor
is a top open reactor as the process involves aqueous mixing of some non
hazardous chemical. As the chemicals involves in the process has high degree of
corrosion efficiency, instead of steel tank, a FRP tank is designed. FRP tank is
insensitive to the chemicals used in the process. Mixing is one of the key things
to get the desired efficiency level. An agitator is attached for starring the whole
slurry. The type of agitator is propeller type and having a speed of 50 to 100
RPM. A double propeller type system is designed for better mixing. In this
arrangement, the bottom propeller is positioned at the bottom of the moving shaft
having clearance of 0.7 meter from the bottom. Another propeller is also attached
at a height of 2 meter from the bottom. This positioning of the propellers ensures
high level of mixing from top to bottom. At least three baffles are attached in the
inner periphery of the reactor to attain a vigorous mixing phenomena. In this way,
a stable uniform slurry density is maintained inside the reactor. The reactor is
about 2.5 meter long and 1.8 meter in diameter where the main reaction takes

place. The coating of the rector from both sides was done by epoxy resin. The
purpose of the epoxy coating is to sustain the reactor from both salinity and other
chemical corrosion. The reactor volume is around 8 m3 and it is able to deliver 1
at least one hour residence time for a continuous high feed flow for example, 5
m3/hr. The reactor is equipped with online pH sensor and level sensor to track
the pH and the level of the process. The reactor for quick releasing material is
designed with conical bottom having an angle of 300. After having a residence
time of about 1 hour, the entire slurry is transferred continuously to the first
settling tank V02, where first settling of the solid sludge is taking place. The MOC
is also FRP and it allows a residence time of the slurry for the 5 minute to get
accumulated the solid at the bottom. From the bottom of the tank, the solid
sludge is transferred to a pit. The liquid from the V02 is discharged out through
an overflow line. Liquid from the V02 is pumped from the overflow line to a
second settling tank V03. V03 is exactly the identical tank like V02. It also allows
most of the remaining solid to get accumulated at the bottom. From the bottom,
the solid is transferred to the pit. Acetic acid is added at the second tank (VO3) to
control the pH around 8. A flocculent is also added here to the precipitate out all
the solid material from its very fine suspension from. From the overflow line, clear
water is pumped to a filter F01.This whole operation is accomplished in
continuous fashion. Proper dosing rate and the input water flow rate are set
corresponding the residence time maintained inside the reactor V01. Second
settling tank V03 is able to eliminate almost 99.5% slurry. All the slurry is sent to
the pit from both the settling tanks. To maintain a suspended solid level < 50
NTU, a pressure filter followed by said cartridge filter (F01) is attached in
downstream of the second settling tank V03. Those filters can manage to trap the
particle having size of 5 to 10 micron level. Discharge water from the filter is
crystal clear and can be connected with the quenching pond. pH is adjusted in
the main reactor and in the second settling tank by an acetic acid dosing pump.
Thus a continuous process is executed without any interruption.

Quality parameters- (Liquid):
Table 1 shows the feed water quality being tabulated together with treated water
quality. Based on the level of separation, it can be observed that desiliconization
happens almost at the level of 100%. Hardness is removed almost by 90% as Ca
and Mg ions are removed from the water. Iron is also removed from the water by
60%. Most importantly Cl-1 and SO4-2 irons removed from the water by greater
than 80%. Table 2 shows that the different level of separation as mentioned
above. A significant amount of TDS is enhanced in the process due to the
contribution of Na ion in the form of sodium aluminate. This increase in TDS will
not be affecting the coke quality as solubility of Na+ is very high in any solution.



Solid Analysis:
Result of chemical analysis of solid is depicted in Table 3. Solid contains mainly
AL, Ca and chloride elements being formed as a complex compound. The result
of chemical analysis shows some indication that it could be used in other process
industries. Based on the chemical analysis a structure is proposed for the solid
generated which is very close to the structure of hydrocalumite (Table 4).

ADVANTAGES
An innovative design of a reactor and ancillary equipment’s to continuously and
effectively execute the UHLA process for desalination. The reactor is able to
remove about 80% chloride from the quenching water. Further, the reactor
system allows reduction of sulfate silicon, Ca+2, Mg+2, and iron from the process
water by 95%, 100%, 90%, 88%, and 60% respectively. The cleaned quenching
water is used in blast furnace for good quality coke generation without causing
erosion problems. The solid generated as the reject is hydrocalcumite which
finds application in cement industries.

WE CLAIM
1. A continuous reactor system for handling high throughput in an Ultra High
Lime Aluminium (UHLA) process for optimum reduction of chloride level in
the waste water, the system comprising:-
- at least one reagent preparation unit;
- at least two centrifugal pumps;
- at least one dosing unit;
- a continuous stir tank reactor; and
- a solid-liquid separation unit,
wherein the reagent preparation unit comprises four tanks
(T01,T02,T03,T04) each for storage of feed water, slacker, sodium,
aluminate, and acetic acid respectively, wherein the dosing unit consists of
a plurality of pumps corresponding to the number of units in the reagent
preparation unit for transporting the reagents to said tank reactor (V01),
wherein the mixing time in the reactor is determine by the kinetics of the
process and the treated slurry transferred to the separation unit, wherein
the separation unit consists of an upper setting tank (V02) receiving the
slurry directly from the reactor (V01), and a bottom settling tank (V03)
receiving liquid with marginal solid from said upper settling tank (V02),m
the settled solid at the upper settling tank (V02) including the bottom
settling tank (V03) collected in a pet, wherein a cartridge filter (F01)
disposed at the final discharge point of the system to maintain the quality
of the clear water transferred into the gravel from the top portion of the
second settling tank (V03),
characterized in that the reactor (V01) is top –open and formed of fibre-
reinforced polymer (FRP) with a conical bottom of 300 angle, in that at

least one each on-line pH and level sensor is provided in the tank to track
the pH and the level of the process, in that a double propeller type high-
speed agitator is provided inside the tank to achieve optimum mixing of
the slurry, and in that a plurality of baffles are attached in the inner
periphery of the tank to attain a high level of mixing including maintenance
of the slurry density at uniform level.
2. The system as claimed in claim 1, wherein the reactor is internally and
externally coated with epoxy resin to prevent damage from salinity and
chemical erosion.
3. The system as claimed in claim 1, wherein a first of the double propeller
agitator is disposed at the bottom of the tank with a clearance, and
wherein a second propeller is located at a height of about 2-metas from
the first propeller.
4. An improved process for optimum removal of chloride-content in coke-
quenching water maintaining using a continuous reactor system, the
process comprising the steps of:-
- supplying feed water to the feed-water storage tank (01),

- preparing reagent in the sodium aluminate storage tank (T03)
preceded by preparing lime solution in the slacker tank (T02);
- transferring the feed water and the reagent into the reactor (V01)
for a high-level mixing for about an hour in a continuous stirring
activity based on the pH and the process level being monitored in
real time by pH and level sensors disposed in the reactor (V01);

- transferring the highly-mixed slurry from the reactor (V01) to the
first settling tank (V02) in which the first settling of the solid sludge
takes place which sludge being transferred to a pit;
- pumping-out the liquid portion from the first settling tank (V02) to
the second settling tank (V03) through an overflow line, the second
settling tank (V03) allowing settling of the remaining solid;
- adding the acetic acid from the third storage tank (T04) including a
flocculent into the second settling tank (V03) to respectively control
the pH value and allow precipitation of all solid material;
- transferring the substantially clear water from the top portion of the
second settling tank (V03) to the gravel via a cartridge filter (F01),
the remaining slurry from the second settling tank (V03) being
diverted to said pit,
wherein the dosing rate and input feed water flow rate are set in
corresponding with the residence time of the slurry inside the reactor
(V01).