Studies on the Reducing Method of Co2

8/6/2019 Studies on the Reducing Method of Co2

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STUDIES ON THE METHOD OF

REDUCING CARON DIOXIDE

EMISSION IN THERMAL POWER

PLANT


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A BRIEF INTRODUCTION

One of the biggest problems faced by mankind today is

global warming.

Major contributers are : carbon dioxide, water vapour,

methane, nitrous oxide and ozone. Carbon dioxide concentration in atmosphere has

increased from 315 ppm in 1955 to 393.18 ppm in April

2011.

Power sector contributes to about 30% of total production. Emission control mechanisms easier to install on power

plants.


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THE POSSIBLE METHODS OF CO2

CAPTURE:

1. PRE-COMBUSTION CAPTURE METHODS

2. OXY-FUEL FIRING

3. POST COMBUSTION CAPTURE METHODS

Carbon capturing is done by five possiblemethods :1. Absorption

2. Adsorption3. Liquefaction (Cryogenic Separation)

4. Membrane based separation

5. Biologically (Algae process)


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OBJECTIVE

Main objective is to capture CO2 in alkanolamine.

The steps are:

1. Generating flue gas at par with thermal power station using minicoal fire boiler.

2. Removal of particulate matters using hepacartridge filter.3. Water scrubbing for removal of VOC and residual particulate matter

from flue gas.

4. Absorption of CO2 from flue gas using conventional packed columnusing different alkanolamines.

5. Regeneration of loaded alkanolamines by stripping under vacuumas well as steam stripping.

6. Amine degradation studies and purification of amines.

7. Purification of generated CO2 for its commercial production


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BRIEF HISTORY OF ALKANOLAMINES

Credit for the development of alkanolamines as absorbents for acidic gasesgoes to R.R. Bottoms (1930),

Triethanolamine (TEA): first alkanolamine to become commercially available.

Amines of principal commercial interest for gas purification aremonoethanolamine (MEA), diethanolamine (DEA) and methyldiethanolamine(MDEA)

proprietary formulations comprising mixtures of the amines with variousadditives are widely used. Example: Dows GAYSPEC, UOPs Amine Guard.

Newest development: tailored amine mixtures. These are usually based onMDEA, but contain other amines as well as corrosion inhibitors, foam

depressants, buffers, and promoters blended for specific applications A different class of acid gas absorbents, the sterically hindered amines, has

been disclosed by EXXON Research and Engineering Company


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REACTION MECHANISM

For primary and secondary amines :

Carbamate formation takes place according to following reaction

CO2+2RRNH = RRNH2+ + RRNCOO-

Where R is alkyl and R is H for primary amine and alkyl for secondary amines.

The Zwitterion mechanism is taken as the mechanism for the above reaction.

CO2 + RRNH = RRNH+COO-

RRNH+COO- + B = RRNCOO- + BH+

B is a base which could be amine, OH-

or water.


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REACTION MECHANISM - II

For sterically hindered amines :

In sterically hindered amines, the carbamate is unstable, undergoingcarbamate reversion reaction. This leads to

RRNCOO- + H2O = RRNH + HCO3-

For tertiary amines :

In tertiary amines, bicarbonate ions are formed according to followingmechanism:

CO2 + R1R2R3N + H2O = R1R2R3NH+ + HCO3

-

CO2 + OH- = HCO3

-

HCO3- + OH- = CO32-

R1R2R3NH- + OH- = R1R2R3N + H2O

2H2O = OH- + H3O


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EXPERIMENTAL SETUP


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BOILER

Fire-tube boiler is used

The boiler has three parts:

Pre-heater Economizer

Steam generator

It can generate pressures upto 5kg/cm2


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ABSORPTION COLUMN

Length of the column is

1.63 m.

Diameter of column is

1.425 inch.

Helical packing is used.

Volume is 1.25 litre.

Void fraction of packingis 0.8.


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STRIPPING SECTION

Stripping column hassame dimensions as thatof absorption column.

Transformer oil is used tocool the amine vapors.

Oil temperature iscontrolled by using a

thermostated bath.


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CARBON DIOXIDE STORAGE

Carbon dioxide from

stripping section is sent

to the pressure vessel by

using a water ringvacuum pump.

The volume of the

storage tank is 100 litre


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WORK DONE

Boiler firing has been standardised and can be fired

with consistent results.

Hepacartridge filter and scrubber have been installed.

The flue gas is free of particulate matter.

Absorption column has been installed and initial runs

with MDEA and MEA have been carried out.

Stripper section has been installed and initial runshave been taken.


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GAS FLOW RATE : 1 LITRE/MIN.


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GAS FLOW RATE : 2 LITRE/MIN.


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RESULTS AND DISCUSSION

Initial investigation with MDEA revealed that CO2 emmision

could be reduced effectively by absorption purification

route.

The quality of flue gas is dependent on the quality of coal,

low ash content is required for the high CO2 content in flue

gas.

We could achieve 93% reduction of CO2 emission withMDEA alone & the increased percentage ofCO2 in the

pressure vessel (storage) means the success of amine

regeneration .


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CONCLUSION

Up until now we have not been able to

standardize the coal combustion.

As some of the runs are taken and the fluegas are analyzed.

Due to unavailability of instrument we could

not perform the further work of our project.


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THE END

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Studies on the Reducing Method of Co2