Carbon Sequestration by Rocks and Minerals

8/8/2019 Carbon Sequestration by Rocks and Minerals

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DEPARTMENT OF MINING

ENGINEERING

I N S T I T U T E O F T E C H N O L O G Y ,

B A N A R A S H I N D U U N I V E R S I T Y ,

V A R A N A S I .

2005


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BHUMINERS Nelanuthula Srikanth

Nikhil Ninad Sirdesai

MENTORED BY:

Dr. Aarif Jamal

Reader, Institute of TechnologyBanaras Hindu University,

Varanasi


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CARBON DIOXIDE SEQUESTRATION

BY ROCKS AND MINERALS


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INDEX:INDEX: INTRODUCTIONINTRODUCTION

CO2 Emission, Consequences,

Strategies for Control, Global Scenario

MINERAL CO2 SEQUESTRATIONMINERAL CO2 SEQUESTRATIONChemistry, Selection Of Minerals,

Thermodynamics, Kinetics , Mechanism,

Optimisation

PROPOSED TECHNIQUEPROPOSED TECHNIQUEConstruction and Working

CONCLUSIONCONCLUSION


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INTRODUCTION:

We have reached the pinnacle of

industrial and technological development,

on the expense of CO2 concentration in

the atmosphere.

The level of CO2 in the atmosphere has increased by 36.07% i.e.

280-381ppm since the industrial revolution which has led to:

The Greenhouse Effect.

Acidification of the surface of the ocean.

Fertilization of Eco-system

YEAR 1990 2000 2007 2025

CO2 (MMT)

EMISSION

21563 23899 27715 37124


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INTRODUCTION:

Consequences of excess CO2 emission:

Global surface temperature increased by

0.74 0.18C (1.33 0.32F) during the

last 100 years.

Surveys indicate that the surface temperature

will rise a further by 1.1 to 6.4C ( 2 to 11.5F).

Other effects include: Ozone Layer Depletion,

Melting of Ice Caps and Glaciers leading to increase in sea-level. Main Strategies use for reducing the level of CO2 in atmosphere:

Improvement of energy efficiency

Use of renewable energy

Carbon Dioxide Sequestration


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INTRODUCTIONINTRODUCTION:

OPTION Estimated Global

Capacity (GtC)

Mineral

Sequestration

Very large

Sea-Bottom 1000

Geological

Repositories

345

Biological

Sequestration

50-100

CARBON SEQUESTRATION:

It refers to the capture and the storage of CO2 in repositories in such a way that

it remains stored and will not release into the atmosphere. All CO2 sequestration

technologies consist of two steps. First, the carbon dioxide is captured and

separated from the flue gas or the air. Second, the CO2

is stored.


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MI

NERAL CO2 SEQUESTRATI

ON Mineral CO2 sequestration refers to a technology whereby carbon

dioxide is reacted with metal (Ca-Mg) cations to form solid

carbonate minerals.

In nature such a reaction is called silicate weathering and takesplace on a geological time scale.

Metal cations are mainly obtained

from silicates of Ca-Mg bearing

rocks such as:

Olivine (MgSiO4)

Serpentine ((Mg,Fe)3 Si2O5 )

Wollastonite (CaSiO3 )

Others


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CHEMISTRY OF MINERAL CO2 SEQUESTRATION.GENERAL EQUATION:

MO + CO2

OLI

VI

NE:Mg2SiO4 + 2CO2 2MgCO3 + SiO2 + 89 kJmol

-1CO2

SERPENTINE:

Mg3Si2O5(OH)4 + 3CO2 3MgCO3 + 2SiO2+ 2H2O +

64 kJmol-1

CO2

WOLLASTONITE:

CaSiO3 + CO2 CaCO3 + SiO2 + 90 kJmol-1CO2

MCO3 + heat


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MINERAL CO2 SEQUESTRAT

ION

Mineral Carbon Dioxide Sequestration technique can

be discussed under the following four heads:

1. SELECTION OF MINERALS :

Alkaline Earth Metal Oxides are considered over alkali

metal oxides as alkali metal carbonates are very soluble in water.

As oxides are more reactive, silicates from Mafic and Ultramafic rocks

are preferred.

Alkaline solid waste materials ( pulverized fuel ash, bottom ash, fly

ash, de-inking ash) from industries are also used.MINERAL STORAGE CAPACITY

Serpentine (50% MgO) 0.507 kg/kg of rock

Olivine (50% MgO) 0.398 kg/kg of rock

Wollastonite (10% Cao) 0.080 kg/kg of rock

MINERAL CO2 SEQUESTRAT

ION


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2. THERMODYNAMI

CS

The Carbon Dioxide Sequestration reactions are exothermic in

nature. Formation of carbonates is favored at low temperature and

low partial pressure. Whereas at high temperature (above 900C for calcium carbonate

and above 300C for magnesium carbonate, at CO2 partial pressure

of 1bar) the reverse reaction, i.e. calcinations is favoured.

Even at low partial pressure of atmospheric CO2 and at ambient

temperature carbonation of minerals occur spontaneously. In aqueous systems temperature is typically kept below 200C,

since high temperature favours gaseous CO2 over precipitated

carbonates.


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3. KI

NETI

CS: Simplest approach to mineral carbonation is the reaction of gaseous CO2 andparticulate metal oxide bearing material at suitable temperature and pressure.

As the above mentioned process is slow, the alternative requires the

extraction of metal from the solid. This is done by suspending the solids

material in an aqueous solution. The metal oxide dissolution is the rate-limiting

step. Ways to speed up the extraction of the metal include:

Activation:

Heat treatment at 650 C for serpentine.

Ultrafine (attrition) grinding for olivine and wollastonite.

Additives And Catalysts: Catalysts eliminates of interference between

metal oxide dissolution and carbonate precipitation.

Important catalyst include: Carbonic acid(H2CO3),

Hydrochloric acid (HCl), Ammonium Chloride(NH4Cl),

EDTA, Sodium Bicarbonate (NaHCO3).


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4. MECHANISM : Process routes comprises of the following methods:

Mineral pre-treatment:

Mineral pre-treatment, excluding the chemical processing steps,

involves crushing, grinding and milling, as well as some mechanical

separation, for example magnetic extraction of magnetite (Fe3O4).

CO2 pre-processing:

Carbon dioxide should be used at a pressure similar to pipeline

pressure, requiring minimal or no compression.

Purity demands in carbonation are minimal as acidic components of the

flue gas are neutralized by the base and disposed.

Most carbonation processes would preheat CO2 ,100-150C for aqueousprocesses whereas in gas-solid reactions it is 300-500C.


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Sequestration Routes:

The pre-treatment is followed by sequestration routes. Two main types ofroutes can be distinguished.

1. Direct Routes (One Step)

2. Indirect Routes (More than one step)

Direct Route:

Direct route of a mineral can be conducted in two ways:Direct Gas-Solid Carbonation with CO2 : Its direct gas-solid carbonation.

As an example, the direct gas-solid reaction of olivine is given:

Mg2SiO4(s)+ 2CO2 (g) 2MgCO3 (s)+ SiO2(s)

High CO2 pressures obtain reasonable reaction rates. The rates can be

enhances by the use of supercritical CO2 which dissolves the produced

water. The reaction can be expressed as:

Mg3Si2O5(OH)4 (s)+ 3CO2(sc) 3MgCO3(s) + 2SiO2(s)+ 2H2O(l/g)

Aqueous Scheme:

In this method CO2 reacts at high pressure in aqueous suspension of

serpentine. Carbonic acid is used in this method.


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Aqueous Scheme:

CO2 , NaHCO3 dissolves in water to form H+ and HCO3- ion whichconsequently react with silicate mineral forming respective carbonate

Mg2SiO4 (s) + 4NaHCO3 (aq) 2MgCO3 (s) + 2Na2CO3 (aq) +

SiO2 (s) + 2H2O (l)

2Na2CO3 (aq) + 2H2CO3 (aq) 4NaHCO3 (aq)

NaHCO3 is regenerated in this process and NaCl acts as catalyst toincrease Mg2+ ions.

Indirect Route:

In this method reactive components are first extracted from the mineral

matrix and then carbonated in a separate step. It includes :

HCl extraction route:

This process is used for serpentine. To extract Mg from the mineral matrix

HCl is used. HCl is recovered by heating solution from 100 to 250C.

MgCl(OH) is formed as intermediate which converts to Mg(OH)2 which on

carbonation gives MgCO3. Changing the extraction medium can lower

energy consumption, so molten salt MgCl2 3.5 H2O is used as medium.


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Method via Calcium Hydroxide from Calcium-rich silicate rock

This method is HCl extraction route used with CaSiO3 .CaSiO3 + 2HCl CaCl2 (aq) + SiO2 (s) + H2O (l)

CaCl2 obtained is converted and precipitated as Ca(OH)2 for easy separation

of HCl, which inturn gets converted to carbonate.

Wollastonite Carbonation using carbonic acid:

It uses acetic acid and wollastonite as reactants. First step consists of

wollastonite reaction with acetic acid.CaSiO3 + 2CH3COOH Ca

2+ (aq) + 2CH3COO- (aq) + H2O+ SiO2

Next step includes carbonation of calcium and recovery of acetic acid.

Ca2+ (aq) + 2CH3COO- (aq) + CO2 + H2O CaCO3 + 2CH3COOH (l)


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OPTIMISATIONS:OPTIMISATIONS:Surface AreaSulphuric acid ( 1.5M,51C ) can be used

for increase of surface area of serpentine.

There was change of surface area from

8m2/

g to 172m2

/g in the first 3 hours ,further no notable change is observed.

Pressure

Raising the partial pressure of CO2,increasesthe extent of reaction in one hour due to

increased activity of CO2 .It also completes

the reaction due to volume change desiring

products of reaction


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Temperature

The rate of reaction increased until particular

temperature and then decreased as CO2Solubility decreases. The temperature is

185C for olivine and 155C for pre-treated

serpentine


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PROPOSED TECHNIQUEPROPOSED TECHNIQUE Thermal Power Plants (coal based) are one of the leading CO2 emitters of

the world, considering this fact we proposed a design which could

sequestrate CO2 and store it for future needs

On the basis of the literature discusses above, it is suggested that Ca-Mg

silicate rich minerals may be used as liner in duct ,which is to be fitted on

chimneys of coal based Thermal Power Plants or any plants using coal asfuel

The proposed design is given below in steps:

Hot Flue Gases Serpentine/Olivine Duct

Cooled Flue Gas Ca-Mg carbonates CO2 get adsorbed

Water Methanol (CH3OH)


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Outlet

Acids and Methanol are

collected

Water Chamber Concrete

Brick wall

Coolant

Pre-treated Serpentine /

Olivine Layering

Air Filter

Heat Regulator

Inlet for Flue Gases

PROPOSED

DESIGN


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CONCLUSI

ON:CONCLUSI

ON: The sources of Carbon dioxide emission are mostly non-point and aerial in

nature. The CO2 absorbing properties of the above mentioned minerals can

be used to design the roofs of houses in such a way that they absorb

maximum amount of CO2 as possible.

Mineral carbon sequestration has advantages such as formation ofthermodynamically stable solid carbonates which can be permanently

stored, large sequestration capacity due to large volumes of suitable

feedstock deposits of Ca-Mg bearing rocks worldwide. Finally the

carbonation reactions are exothermic and occur spontaneous in nature

It may be concluded from the above survey that minerals are most suitable,

logical and play an active role in sequestration of CO2 on a large scaleamong the available Carbon Sequestration techniques.

The experimental setup at laboratories stage will further conform the

application of technique for CO2 sequestration.


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AndPleasemake an attemptto

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Carbon Sequestration by Rocks and Minerals