FORM 2
THE PATENT ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION
An apparatus for drying of wet staple fibre and a method thereof.
APPLICANTS
Aditya Birla Science and Technology Company Pvt Ltd, Plot number 1 and 1-A/1, Taloja, MIDC, Taluka- Panvel, District- Raigad- 410208, Maharashtra, India.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes this invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
[001] The present invention relates to an apparatus for drying of wet staple fibre and a method thereof. More particularly, it relates to an apparatus for drying of wet staple fibre using a fluidized bed dryer. The present invention also relates to a method for drying of wet staple fibre in a minimum residence time by expense of low thermal energy along with low output moisture variability.
BACKGROUND OF THE INVENTION
[002] During the process of manufacturing of staple fibre, the fibres are treated by washing, bleaching, oil-treatment to get the desired quality. Post the treatment processes, the fibre is wet and needs to be dried before going for final packing. Conventionally, two types of dryers are used for drying of the wet staple fibre – conveyor dryer and drum dryer. The mechanical design of both types of dryers is quite complex due to more number of rotating parts involved. In both the cases, hot air is blown through circulation manner in multiple zones where fibre to air direction is counter current.
[003] To enhance the production in a specific conveyor or drum dryer, circulation fan capacity and temperature can be increased up to a certain limit, post which, in order to maintain desired residence time, length of the conveyor dryer or additional drum is required, which has space limitation in existing unit. A main drawback in conveyor dryer is the moisture variation of outlet fibre. Due to high mat thickness, the hot air does not uniformly come in contact with the top and bottom of the fibre mat which leads to moisture variation. Further, due to a moving conveyor and a number of circulation / exhaust fan, frequent maintenance of the dryer is required which leads to operational / production downtime. Lastly, due to the process and the design limitation, it is difficult to enhance the production beyond a certain limit in such types of dryers.

[004] During drying of wet fibre using drum dryers, the production can be increased by using an additional drum in the overall apparatus. Additionally, in this type of drying, surface renewal takes place which ensures less moisture variation. However, a major drawback is fibre dropping/damage which happens when staple fibre is transferred from one drum to another. Further, since the drum is moving, the fibre is likely to get contaminated with lubricant as well. Lastly, more time is required for the completion of drying as there is heat and mass transfer limitation.
[005] In the recent past, another type of technology has been used in the staple fibre industry. In this method, both hot air and wet staple fibre are blown through a pipe by a booster fan. Due to high air velocity and sufficient contact between hot air and fibre, moisture gets easily flashed out from the fibre surface. Also, the mass and heat transfer is increased enormously and drying happens faster as compared to processes using drum and conveyor dryers respectively. The main drawback of this technology is that if there is high moisture variation at the inlet then it is difficult to follow narrow moisture band at dryer outlet, at same residence time and temperature. Also, it has been observed that during blowing of hot air on wet staple fibre, the wet staple fibre comes in contact with the fan blades thereby generating short fibre. Such generation of short fibre is increased as wet fibre has low mechanical strength.
[006] Additionally, the conventionally used technology shows a standard deviation of 6 at the dryer outlet with respect to moisture which is very high depicting a non-uniform drying of the wet staple fibre.
[007] Therefore, there is a need for a simple apparatus and an effective method for drying of wet staple fibre that solves some of the problems present in the prior art.

SUMMARY OF THE INVENTION
[008] According to an embodiment of the present invention, there is provided apparatus for drying wet staple fibre (1), comprising:
- a wet opener (3) connected to a first fluidized bed dryer (5) wherein hot air is blown at high
pressure;
- a first separation unit (9), connected to the top portion of the first fluidized bed dryer (5) through
a first duct (7), said first separation unit (9) separating warm moist air (12) from partially dried fibre, further connected to
- a suction device (10) placed at its one end to suck the warm moist air out (12);
- a first fibre opener (11), placed at its other end, to further tease the partially dried fibre;
- a second fluidized bed dryer (14) connected to the first fibre opener (11) through an intermediate
channel, and hot air being blown through the second fluidized bed dryer (14) at high pressure;
- a second separation unit (18) connected to the second fluidized bed dryer (14) through a second
duct (16), said second separation unit (18) further connected to
- a first conduit (19), to recycle the hot air back into the first blower (6), said first conduit (19) having a first heater (8) placed inside it;
- a second fibre opener (20) to further open dried fibre; and
- an ultimate channel connected to the second fibre opener (20) comprising a booster fan (30)
through which the dried fibre is blown into a venturi duct (31) to a bailing section through an
outlet (32). [009] According to another embodiment of the present invention, there is provided method of drying wet staple fibre (1), comprising the steps of: a) opening the wet fibre using a wet opener (3);

b) drying the wet opened fibre using a first fluidized bed dryer (5), connected to the wet opener (3), wherein partially dried fibre exits through a first duct (7) along with warm moist air (12);
c) separating the partially dried fibre from the warm moist air (12) in a first separation unit (9) connected to the first fluidized bed dryer (5) through the first duct (7);
d) opening the partially dried fibre of step b) in a first fibre opener (9);
e) drying the partially dried fibre using a second fluidized bed dryer (14), connected to the first fibre opener (9) through an intermediate channel wherein the dried fibre exits through a second duct (16);
f) separating the dried fibre from the air in a second separation unit (18) connected to the second fluidized bed dryer (14) through the second duct (16);
g) opening the dried fibre of step e) using a second fibre opener (20), and
h) collecting the opened dried fibre through an ultimate channel comprising a booster fan (30) through which the dried fibre is blown into a venturi duct (31) to a bailing section through an outlet (32), wherein the air from the second separation unit (18) at step f) is recirculated in the system to dry the wet fibre of step a) and wherein the second conduit (33) connected to the second fluidized bed dryer (14) of step e) receives fresh air (2).
BRIEF DESCRIPTION OF THE DRAWINGS
[010] Fig. 1 illustrates the apparatus used for drying the wet staple fibre, according to an embodiment of the present invention;
[011] Fig. 2 depicts the apparatus used for drying the wet staple fibre with an additional drying stage, according to an embodiment of the present invention; and

[012] Fig. 3 is a graphical representation comparing the standard deviation in moisture content at the outlet of two types of drying methods, according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[013] As set out in the claims, the present invention eliminates or reduces the aforementioned problems of the prior art by providing an apparatus for drying of wet staple fibre that requires less space and does not require frequent maintenance thereby ensuring less operational downtime. Additionally, the present invention relates to a method for drying of wet staple fibre wherein there is no fibre damage due to contact with fan blades. The main purpose of the present invention is to dry the wet staple fibre in a minimum residence time by expense of low thermal energy along with low output moisture variability.
[014] According to an embodiment of the present invention, there is provided an apparatus for drying of wet staple fibre. Figure 1 depicts a schematic representation of the apparatus that comprises a wet opener (3) to which the wet staple fibre (1) is fed wherein said wet opener (3) disintegrates the wet fibre mat into small fibre bunch. Depending upon the non-uniformity of fibre moisture, each small fibre bunch has different minimum fluidization velocity. The small wet fibre bunches are then fed to a first fluidized bed dryer (5). Preferably, said first fluidized bed dryer (5) has a first blower (6) placed below a perforated plate (4) to blow hot air on the wet fibre (1). The said perforated plate (4) helps to restrict the wet fibre (1) from coming in contact with the first blower (6) thereby avoiding generation of short fibre and also for determining the air flow distribution pattern in the first fluidized bed dryer (5).
[015] Moreover, a first separation unit (9) is connected to the top portion of the first fluidized bed dryer (5) through a first duct (7) which leads the partially dried fibre to first separator unit (9) wherein,

due to the density difference, when a mixture of hot air and fibre (1) hits an obstacle, the fibre (1) falls down and the warm moist air (12) goes out with the help of a suction device (10). Further, the first separator unit (9) is connected to a first fibre opener (11) that further teases the partially dried fibre. The opened partially dried fibre is fed into a second fluidized bed dryer (14) connected to the first fibre opener (11) through an intermediate channel. In the second fluidized bed dryer (14), hot air is blown by a second blower (15) placed below a perforated plate (13) such that the second blower (15) is placed in a second conduit (33) that has a heater (26) placed inside it.
[016] The dried fibre from the second fluidised bed dryer (14) is blown out through a second duct (16) to second separator unit (18) where the dried fibre gets separated from the warm moist air. The said warm moist air travels through a first conduit (19) fixed at one end of said second separator unit (18) through the first heater (8), placed inside the first conduit (19), to be blown in the first fluidized bed dryer (5) by the first blower (6). The said dried fibre then travels to a second fibre opener (20) that further opens the dried fibre. The said second fibre opener (20) is connected to an ultimate channel comprising a booster fan (30) through which dried fibre is blown into a venturi duct (31) to a bailing section through an outlet (32).
[017] In a preferred embodiment, the said suction device (10) is an exhaust fan that releases the warm moist air (12) to the atmosphere and helps to create pressure gradient across the apparatus. In another embodiment, the second conduit (33) receives ambient fresh air (2) at a counter current direction to the feed flow. The fresh air (2) is heated by a second heater (26) before being blown into the second fluidized bed dryer (14) by said second blower (15). Preferably, the air and fibre flows in counter current direction whereas inside the fluidized bed dryers, air and fibre flows in co-current direction.

[018] In an embodiment, the first heater (8) is at a higher temperature than the second heater (26) and wherein the temperature of hot air in the first fluidized bed dryer (5) is in the range of 70°C - 110°C and the temperature of hot air in the second fluidized bed dryer (14) is in the range of 60°C - 85°C.
[019] In a preferred embodiment, as more clearly depicted in Figure 2, the apparatus comprises of at least one additional fluidized bed dryer (22) and at least one additional separation unit (27) similar in structure to the second fluidized bed dryer (14) and the second separation unit (18) respectively, provided that each additional fluidized bed dryer is connected to the preceding intermediate channel receiving partially dried fibre from the preceding fibre opener and further provided that each additional separation unit (27) is connected to the next fluidized bed dryer through an intermediate channel, wherein the last fibre opener of the series is connected to the ultimate channel. In a yet another preferred embodiment, the said second blower (15) fitted at the bottom of the second fluidized bed dryer (14), draws the second stage humid air which is pre-heated by a third heater (17) and is fed to the second fluidized bed dryer (14) by said second blower (15). This said pre-heated humid air is mixed with the fibre (1) and flushes out the moisture up to a certain level from the said fibre (1).
[020] In another embodiment, the last fibre opener of the series that is connected to the ultimate channel is a fine opener having spikes to finely open the dried fibre. Preferably, a maximum of six such fluidised bed dryers and separator units can be added to the entire apparatus in order to increase the production capacity.
[021] In an embodiment, hot air blown from the bottom of the first and second fluidized bed dryers (5, 14) helps in reducing the inlet moisture variability by fluidization and in transporting the fibre to the next section. In a preferred embodiment, the volume of the pre-heater and fluidised bed dryer is in the range of 0.1 to 0.2 m3 and the total residence time of fibres inside dryers is in the range of 90 to

150 seconds. In an embodiment, the residence time is dependant on the volume of the fluidised bed dryer.
[022] In another embodiment of the present invention, there is provided a method for drying of wet staple fibre. The said method comprises the steps of (Step 1) opening the wet fibre using a wet opener (3). (Step 2) Drying the wet opened fibre using a first fluidized bed dryer (5), connected to the wet opener (3), wherein partially dried fibre exits through a first duct (7) along with warm moist air. (Step 3) Separating the partially dried fibre from the warm moist air in a first separation unit (9) connected to the first fluidized bed dryer (5) through the first duct (7). (Step 4) Opening the partially dried fibre of step 2 in a first fibre opener (11). (Step 5) Drying the partially dried fibre using a second fluidized bed dryer (14), connected to the first fibre opener (11) through an intermediate channel wherein the dried fibre exits through a second duct (16). (Step 6) Separating the dried fibre from the air in a second separation unit (18) connected to the second fluidized bed dryer (14) through the second duct (16). (Step 7) Opening the dried fibre of step 5 using a second fibre opener (20). (Step 8) Collecting the opened dried fibre through an ultimate channel comprising a booster fan (30) through which the dried fibre is blown into a venturi duct (31) to a bailing section through an outlet (32).
[023] In a preferred embodiment, the air from the second separation unit (18) at step 6 is recirculated in the apparatus to dry the wet fibre of step 1 and wherein the second conduit (33) connected to the second fluidized bed dryer (14) of step 5 receives fresh air.
[024] In a preferred embodiment of the present invention, the air to fibre ratio is maintained at each stage of the method for optimum results. Preferably, the air to fibre ratio is 65 to 90 m3 per kg.
[025] In an embodiment, the drying of step 2 is carried out at 70°C - 110°C and the drying of step 5 is carried out at 60°C - 85°C. In another embodiment, the warm moist air in step 3 is expelled through a

suction device. Preferably, the temperature of exhaust warm moist air is in the range of 50 to 75 °C and absolute humidity at the suction device is in the range of 0.025 to 0.04.
[026] In an embodiment, at least one additional drying step and at least one additional separation step similar to steps 5 and 6 respectively provided that each additional fluidized bed dryer is connected to the preceding intermediate channel receiving partially dried fibre from the preceding fibre opener and further provided that each additional separation unit is connected to the next fluidized bed dryer through an intermediate channel, wherein the last separation unit of the series is connected to the ultimate channel.
[027] Figure 3 illustrates a graphical representation of standard deviation in moisture content at the outlet of two types of dryers during fibre drying. According to the figure, the standard deviation of moisture content at the inlet is 10-30 for both the dryers. The standard deviation of outlet moisture content is 0.6-1 in case of the present invention whereas the conventional dryer has a higher standard deviation of 0.8-2. Therefore, the standard deviation of moisture content at the outlet of the present invention is lower than that in the conventional conveyor dryer.
[028] Advantages and benefits of the apparatus for drying of wet staple fibre and a method thereof, according to the embodiments of the present invention, would become more apparent from the below experimental details to a person skilled in the art.
Example 1:
[029] During experimentation, three stages were used where 1st stage was pre-heating stage along with two stage fluidized bed dryers. Mass flow rate of wet fibre was 20 kg/hr with inlet fibre moisture 100% (dry basis) with standard deviation at. For drying, ambient air was taken having absolute

humidity in a range of 0.015 to 0.03 kg moisture/ kg dry air. The air to fibre ratio was maintained at 80 m3 dry air/ kg of dry fibre. Different air temperature was maintained in the three stages, for instance, 75°C in first pre-heating stage, 83°C in second fluidized bed dryer and 80°C in third fluidized bed dryer. Post first stage pre-heating, fibre moisture was reduced up to 65% and this partially dried fibre was fed to the second fluidized bed dryer where at the end, the moisture reduces up to 25%. After final stage, dried fibre having 10% (dry basis) moisture was obtained. Standard deviation of moisture at dried fibre was noted as 0.8 in the present invention whereas in case of conveyor dryer it was 1.2. Exhaust air temperature at the initial stage of the fluidized bed dryer was 70°C with 0.028 absolute humidity which is used for heat recovery. Projected area required for drying in case a fluidized bed is used is reduced by up to 30% - 50% in comparison to a conveyor dryer.
[030] Further, mass transfer coefficient is a crucial parameter for drying process. At the preheating stage or the 1st stage of conveyor dryer, the mass transfer coefficient was similar as the moisture of fibre was high. However, the value of mass transfer coefficient was 20% - 45% higher in case of fluidized bed dryer due to the efficient fibre to fibre and air to fibre mixing. This helps in reducing the drying time and moisture variation within the fibre.

Parameters Conveyor Dryer Fluidized bed dryer
Number of dryers 2 stage 2 stage
Fibre intake 20 Kg /hr 20 Kg /hr
Initial Moisture 100% (dry basis) 100% (dry basis)
Standard Deviation at Inlet 28 28
Air to fibre ratio 17 m3/ kg 80 m3/ kg
Air Temperature 80-120 °C 70-110 °C
Fresh air intake 375 kg/hr with absolute humidity 0.02 kg moisture/ kg dry air 1800 kg/hr with absolute humidity 0.02 kg moisture/ kg dry air
Dryer volume 0.1 – 0.2 m3 0.12-.20 m3
Total residence time in dryer 125 sec 100 sec

Outlet moisture 10% (dry basis) 10% (dry basis)
Standard Deviation at outlet 1.2 0.8
Exhaust Air Temperature 45-70 °C 50-75 °C
Absolute Humidity at Exhaust 0.09-0.12 0.028
Figure 1
[031] The foregoing description of specific embodiments of the present invention has been presented for purposes of description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obvious modifications and variations are possible in light of the above teaching.

We Claim:
1. An apparatus for drying wet staple fibre (1), comprising:
- a wet opener (3) connected to a first fluidized bed dryer (5) wherein hot air is blown at high
pressure;
- a first separation unit (9), connected to the top portion of the first fluidized bed dryer (5) through
a first duct (7), said first separation unit (9) separating warm moist air (12) from partially dried fibre, further connected to
- a suction device (10) placed at its one end to suck the warm moist air out (12);
- a first fibre opener (11), placed at its other end, to further tease the partially dried fibre;
- a second fluidized bed dryer (14) connected to the first fibre opener (11) through an intermediate
channel, and hot air being blown through the second fluidized bed dryer (14) at high pressure;
- a second separation unit (18) connected to the second fluidized bed dryer (14) through a second
duct (16), said second separation unit (18) further connected to
- a first conduit (19), to recycle the hot air back into the first blower (6), said first conduit (19) having a first heater (8) placed inside it;
- a second fibre opener (20) to further open dried fibre; and
- an ultimate channel connected to the second fibre opener (20) comprising a booster fan (30)
through which the dried fibre is blown into a venturi duct (31) to a bailing section through an outlet (32).
2. The apparatus claimed in claim 1, wherein hot air is blown in the first fluidized bed dryer (5) by a first blower (6) placed below a perforated plate (4) of the said first fluidized bed dryer (5).
3. The apparatus claimed in claim 1, wherein hot air is blown in the second fluidized bed dryer (14) by a second blower (15) placed below a perforated plate (13) such that the second blower (15) is placed

in a second conduit (33) that has a second heater (26) and receives fresh air (2) in a direction counter current to the movement of the fibre.
4. The apparatus claimed in claim 1, wherein the first heater (8) is at a higher temperature than the second heater (26) and wherein the temperature of hot air in the first fluidized bed dryer (5) is in the range of 70°C - 110°C and the temperature of hot air in the second fluidized bed dryer (14) is in the range of 60°C - 85°C.
5. The apparatus claimed in claim 1, comprising at least one additional fluidized bed dryer and at least one additional separation unit similar in structure to the second fluidized bed dryer and the second separation unit respectively, provided that each additional fluidized bed dryer is connected to the preceding intermediate channel receiving partially dried fibre from the preceding fibre opener and further provided that each additional separation unit is connected to the next fluidized bed dryer through an intermediate channel, wherein the last fibre opener of the series is connected to the ultimate channel.
6. A method of drying wet staple fibre, comprising the steps of:

a) opening the wet fibre using a wet opener (3);
b) drying the wet opened fibre using a first fluidized bed dryer (5), connected to the wet opener (3),
wherein partially dried fibre exits through a first duct (7) along with warm moist air (12);
c) separating the partially dried fibre from the warm moist air (12) in a first separation unit (9)
connected to the first fluidized bed dryer (5) through the first duct (7);
d) opening the partially dried fibre of step b) in a first fibre opener (9);
e) drying the partially dried fibre using a second fluidized bed dryer (14), connected to the first fibre
opener (9) through an intermediate channel wherein the dried fibre exits through a second duct (16);

f) separating the dried fibre from the air in a second separation unit (18) connected to the second
fluidized bed dryer (14) through the second duct (16);
g) opening the dried fibre of step e) using a second fibre opener (20), and
h) collecting the opened dried fibre through an ultimate channel comprising a booster fan (30)
through which the dried fibre is blown into a venturi duct (31) to a bailing section through an
outlet (32),
wherein the air from the second separation unit (18) at step f) is recirculated in the system to dry the
wet fibre of step a) and wherein the second conduit (33) connected to the second fluidized bed dryer
(14) of step e) receives fresh air (2).
7. The method claimed in claim 6, wherein the drying of step b) is carried out at 70°C - 110°C and the drying of step e) is carried out at 60°C - 85°C.
8. The method as claimed in claim 6, wherein the warm moist air in step c) is expelled through a suction device (10).
9. The method as claimed in claim 6, comprising at least one additional drying step and at least one additional separation step similar to steps (e) and (f) respectively provided that each additional fluidized bed dryer is connected to the preceding intermediate channel receiving partially dried fibre from the preceding fibre opener and further provided that each additional separation unit is connected to the next fluidized bed dryer through an intermediate channel, wherein the last separation unit of the series is connected to the ultimate channel.