FIELD OF INVENTION
The invention relates to a device and the methodologies to maintain the dryness of hollow fiber membrane used in capturing carbon dioxide from flue gas/synthesis gas generated in power plants or integrated gasification combined cycle plant in a continuous process.
BACKGROUND OF THE INVENTION & PRIOR ARTS
CO2 capture from flue gas/syngas from power plants or IGCC plant is necessary to reduce greenhouse gas emissions. One of the method to CO2 capture is employing hollow fiber membrane with amine solutions. The Hollow fiber membrane (HFM) based absorber provides 10 times more specific surface area than conventional packed column which reduce the CO2 absorber size to 1/10th. One of the drawback of the HFM based absorber is membrane wetting. After few hours of operations, the hollow fiber membranes get wetted by diluted amine solutions (Yuexia Lv, Xinhai Yu, Shan-Tung Tu, Jinyue Yan, Erik Dahlquist, Wetting of polypropylene hollow fibe membrane contactors, Journal of Membrane science, 362 (2010) 444-452) and hence reduces the CO2 capture efficiency drastically. The study of the polypropylene membrane wetting in

water, Monoethanolamine (MEA) and Methyldiethanolamine (MDEA) solutions were carried out and confirmed that the membrane wetting can deteriorate CO2 capture efficiency and membrane structure.
Kurashina et al (WO/2012/004865) developed the specific device to dry HFM module with hot air to de-wet the membranes, in such specific invention, membranes has to be removed from absorber and dismantle to put into device which consumes the time and interrupt the operations. Mcdonald et al. (US3842515) developed the method for drying hollow fiber membrane sheet by immersing the membrane in alcohol solutions. The method of drying provided by the above patents necessitates that the CO2 capture System have to be shut down. Then membrane system have to be dismantled and dried in separate chamber. They have to be assembled again before operation. This makes the CO2 Capture process discontinuous.
OBJECTS OF THE INVENTION
The object of the invention is to develop a device and a system, operative to continuous capture of carbon dioxide in power plant and IGCC plant to reduce green house gas emission.

Another object of the invention is to reduce the down time by using alternate membrane between the two, one for absorbing carbon dioxide while the other for drying and vice versa without any shutdown.
Further object of the invention is to develop a process for drying the membrane for CO2 absorption at minimum time by circulating hot flue gas/synthesis gas/CO2 gas/hot air simultaneously with the process of CO2 absorption.
SUMMARY OF THE INVENTION
Two trains of membrane assembly have been used in the present invention to operate in continuous carbon dioxide capture operation. At any point of time one set will be in capture mode while the other will be in drying mode and vice versa. In the capture mode, CO2 will be removed from the gas by amine or equivalent solution in the membrane absorber. In the drying mode, the moisture present in the membrane wall of the absorber will be removed by external air/gas. De wetting of membrane assembly can be achieved by any of the schemes as detailed in the description below. The de-wetting method for hollow fiber membrane as absorber of co2 can be adapted for pre combustion (Integrated gasification combined cycle) and post combustion (Thermal power plant) plants.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1- Shows the de-wetting system and arrangement Hollow fiber membrane CO2 absorber. This scheme employs flue gas/syngas for drying the membrane. Fig.2 - shows the arrangement of CO2 Capture system using Hollow fiber membrane. This scheme employs hot CO2 gas liberated from the Stripper for drying the membrane. Rg.3 - shows the arrangement of C(h Capture system using Hollow fiber membrane. This scheme employs hot air for drying the membrane. Fig.4 - shows the typical membrane absorber assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
The CO2 absorption in HFM takes place by contacting flue gas/ syngas containing CO2 with Amine solution. The typical membrane absorber assembly is shown in Figure 4. The de-wetting can be achieved by anyone of the three schemes provided in Figure 1, Figure 2 and Figure 3.

As shown in Figure 1, Figure 2 and Figure 3, the Amine solution is circulated into absorber by pump (4) through regenerative heat exchanger (3), Trim Cooler(13) and the control valve (6). Amine solution is passed through membrane lumens and flue gas passes through shell side as shown in Figure 4. The HFM modules are made generally hydrophobic Polypropylene or PVDF (8). The CO2 from the gas gets absorbed into amine solution. The amine solution contains CO2 sent back to Stripper (2) via regenerative heat exchanger (3). In Stripper, amine was heated above 100°C by re-boiler to release the CO2 from the amine solution.
The differential pressure measurement transducer is placed to measure the differential pressure across the gas and amine solution. This measurement used for maintaining the pressure drop of 100-1000mm H2O across the amine and the gas contains CO2 using differential pressure controller by adjusting differential pressure control valve (6). This increases the membrane wetting time. Due to Appropriate dP controller action, Membrane wetting time will be increased by enhancing efficient CO2 capture.
This approach cannot avoid membrane wetting due to disturbance in gas an liquid flow and other external factors. However, this approach can reduce

rate of wetting. The Drying of membrane will re-set the HFM module CO2 Capture efficiency and hence continuous operation can be achieved.
Any one of the following drying scheme can be adapted to dry the membrane completely. In this approach, two trains of absorbers (la & lb) is provided. In these scheme at any point of time only one set of membrane will be in capture mode and other in the drying mode.
Scheme 1 (Fig. 1)
Gas contains CO2 will be passed through the both set of absorber serially, however the Monoethanolamine (MEA) solution will be sent parallel, a. Mode-1: Vessel la in Dry and lb in capture
The C02 Rich gas will be passing through both the vessels.
In vessel lb, which is in capture mode, the valve V3, V4 will be opened
and 10b will be closed. The Monoethanolamine (MEA) solution will pass
through only lb assembly.
In vessel la, which is in dry mode, the valves V1, V2 will be closed and
valve 10a will be opened. Since the gas pressure is slightly higher than the
liquid pressure, the liquid present in the vessel la will be pushed inside
the lumen and collected at the bottom and top of the membrane

assembly. They will flow through the valve 10a to Knockout drum (KOD) (9). The KOD will separate the gas and liquid. The gas is sent to the gas stream or vent. The liquid trap (7b) which is similar to steam trap separates liquid and send it into amine. The small quantity of gas will be moved into gas line as shown in fig 1 b. Mode-2: Vessel la in Capture and lb in dry
In this mode the valve V3, V4,10a will be closed and V1, V2 and 10b will be opened. The operation is same as above.
Scheme 2 (Fig. 2)
Hot C02 gas liberated from the stripper is used as drying gas for drying
the membrane.
a. Mode-1: Vessel la in Dry and lb in capture
in Vessel 1a, which is in dry mode, the valve V1, V2, & 11 will be closed and 10a will be opened to admit hot C02 gas, which is liberated from the stripper to dry the membrane. The gas temperature should be in the range of 70-80 °C. The gas will flow inside membrane and push the moisture to either bottom of the vessel or to the outside the membrane to be collected at the bottom of the gas chamber. The collected amines are sent to KOD (9). There, the liquid is separated from the gas for recycling.

In Vessel lb, which is in capture mode, the valve V3, V4, 12 will be opened to admit Syngas and amine solution for C02 absorption. The valve 10b will be dosed to stop the drying gas. b, Mode-2: Vessel la in Capture and lb in dry
In this mode the valve VI, V2, 10b & 11 will be opened and V3, V4, 10a,
12 will be closed. The operation is same as above, Scheme 3 (Fig. 3)
This scheme is same as above except hot air is used as drying gas instead of CO2 gas. The drying air temperature should be in the range of 70-80 °C.

WE CLAIM
1) A method of continuous absorption of green house gas (CO2), contained in the flue gas/synthesis gas, emitted from thermal power/integrated gasification combined cycle plant, characterized by, uninterrupted operation through dual type hollow fiber membrane (HFM) module (la, lb) absorber.
2) The method as claimed in claim 1, wherein the dual unit module (la, lb), used alternately, one absorbing CO2 in absorbing mode and the other in drying mode and vice versa.
3) The method as claimed in the preceding claims, wherein in an alternate
operation of the membranes, the set of valves (V1, V2 & 10b) & (V3,V4 & 10a) operate alternately, while one set opened and the other closed and vice versa in the process of absorption of CO2 and drying of the membrane.
4) The method as claimed in the preceding claims, wherein the knockout drums (9) separate the unabsorbed gas and the absorbing agent Monoethanolamine (MEA) for recycling.

5) A method of drying the membrane (8) alternately in dual type HFM module absorber (4) by the hot CO2 liberated from the stripper (2) and the flue gas/Synthesis gas coming out of thermal power plant or IGCC plant, wherein, one of the modules is in drying mode (la) and the other (lb) in absorbing mode and one set of valves (V1, V2, 10a & 11) being closed and the other (V3, V4,10b, 12) opened.
6) The method as claimed in claim (5), wherein the modules (la, lb) interchange operation of drying along with respective valves.
7) The method as claimed in claims (5) & (6), wherein hot air can be used in drying the membranes in de-wetting mode.
8) The method as claimed in the preceding claims, wherein liquid and gas flow rate is such that the pressure drop between gas side and amine solution is maintained at (100-1000)mm of H2O, reducing the time taken to get membrane wetting.

9) A device for uninterrupted absorption of green house gas (CO2) and drying of hollow fiber membrane comprising the following,
a) Membrane absorber assembly (14), (la, lb)
b) Pump (4) for circulating amine solution in to the absorber
c) Regenerative heat exchanger (3) for exchange of heat through flue gas
d) Valves/Control valves (V1, V2, V3, V4, 6,10a, 10b, 11,12)
e) Stripper (2)
f) Controller (15) maintaining the pressure difference
g) Knockout drums (9) separating amine from the gas h) Liquid trap (7a, 7b)