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Steam production at a Power generation Plant is possible by coal combustion process, which produces bottom and fly ash, their quality depends on milling and combustion efficiency. Ash quality is mainly measure by its unburned carbon content, thus it is required ash with low unburned carbon content for using it as a supplementary cementing material. For this reason, the aim of this project is to produce high quality ash (low unburned carbon content and a specific granulometric size) for putting on the Construction Industry market as high value added product.


Fly ash is the non-combustible mineral portion of coal mixed with unburned carbon that are produced by coal combustion. Fly ash is mostly generated as molten particles rich in silica, alumina and calcium

Unburned carbon content depends on milling and combustion technology, This value can be until 30 weight percent of coal. There are a lot of combustion technology that generates different types of ash,

Different types of coal can be burned, thus Fly ash generated can be categorized as Type F or Type C according to ASTM C-618 for using it as a supplementary cementing material.

Fly ash characterization has shown that Fly Ash handle in this project bellows to Type F (ASTM C-618), so it has a high content of silica, alumina and a low content of Calcium.


MOIS TURE

UNBURNED CARBON

%

%

20

18,4

DENSITY g/cm3 0,85

GRANULOMETRIC ANALYSIS-ACCUMULATED MASS RETAINED IN THE SIEVE (%) MESH No. 4

No. 8

No. 30

No. 50

No. 100

No. 170

No. 200

No 325

BO TTO M

0,08

0,3

15,47

25,37

37,41

52,2

56,02

70,94

29,06

CHEMICAL COMPOSITION OF FLY ASH SiO 2

Al 2O 3

Fe 2O 3

CaO

MgO

K2O

Na2O

Mn2O 3

SO 3

64,5

20,5

9,1

0,5

0,85

1,9

0,32

0,03

0,07


Fly ash has been consider a pozzolan that can form cementitious compounds. It becomes concrete stronger, more resistant to chemical attack and more durable. Size particle of fly ash allows them to effectively fill voids, what enhances concrete workability and durability. Fly ash with high unburned carbon have been mostly dispose as a residue because it has been difficult to put them in any market. Thus, It has appeared a lot of ash beneficiation technologies that make possible to utilize them in construction industry as a supplementary cementing material.


There are a lot of patent processes around the world, which main characteristics make possible to produce fly ash with low unburned carbon content. These technologies can cost about 12 millions. Technologies such as Carbon Burn-out (CBO) have been installed in the United States and have gotten carbon credits as a Voluntary Emissions Reduction (VERs) Project. This mechanism create 137,884 verified Carbon Credits for emission reductions that occurred in 2007 and 2008 from fly ash manufactured at the Chesapeake Energy Center (CEC) CBO facility. This technology makes possible to use fly ash as pozzolanic material and recovers residual carbon's valuable heat. More information at: http://www.pmiash.com/docs/inthenew20090728a.pdf


COMPARATIVE CHART OF ASH BENEFICIATION TECHNOLOGIES

TECHNOLOGY

ST

PMI

TORFTECH

MTU

SV

NAME

Triboelectrostatic

CBO (Combustion Burn Out)

Torbed Reactor

Flotation

High Voltage separation

Chemical and Physical(toroidal Separation principle Physical (magnetic forces) Chemical (combustion) bed motion and combustion)

Physical

physical

PRODUCTS

Ash with low Unburned carbon content (2-4%) and fly ash with much coal (50% of ash and 50% coal, without volatile matter).

Ash with low Unburned carbon content (2-4%) and flue gas(300째C)

Ash with low Ash with low Ash with low Unburned Unburned carbon Unburned carbon content content (2-4%) and carbon content and fly ash with heat. (<2%) much coal .

Unburned Unburned carbon Unburned carbon Unburned PRODUCT CONTROL Unburned carbon content carbon content content and FOAM content and FOAM carbon content PROPERTIES and FOAM index. and FOAM index. index. and FOAM index. index.


COMPARATIVE CHART OF ASH BENEFICIATION TECHNOLOGIES

TECHNOLOGY

ST

PMI

TORFTECH

MTU

SV

NAME

Triboelectrostatic

CBO (Combustion Burn Out)

Torbed Reactor

Flotation

High Voltage separation

Testing Period

There is not restriction about moisture or particle size. Desirable unburned carbon content between 3% to 23%.

Dry

MATERIAL FEEDING

There is not restriction about moisture or Dry and small particle size particle size. Desirable (unable for bottom ash). unburned carbon Ash unburned carbon content between 8% to content until 35%. 30%.

MASS BALANCE (100 TON fly ash with much coal= 30 CENIZA CON 10% DE ton y INQUEMADOS) Beneficiated ash= 70 ton.

PRODUCT CHARACTERISTICS

Unburned carbon content (2-4%), low FOAM index, low product variability

Beneficiated ash= 90 ton. .

Beneficiated Beneficiated ash= 90 ash= 90 ton. ton. Coal= 30 ton . Cenospheres= 1 ton

fly ash with much coal= 40 ton y Beneficiated ash= 60 ton.

Unburned carbon Unburned Unburned carbon Unburned carbon content (2%), low carbon content content (2-4%), low content (2-4%), low FOAM index, low (5%), low FOAM FOAM index, low FOAM index, low product index, low product variability product variability variability product High fineness product High fineness product . variability


Nox emissions reductions of Power Generation Plants do not have direct relation with ash beneficiation, even though they can mean combustion process enhancement. So, we propose the following questions: If a Power generation Plant switch its combustion technology to another one that makes possible Nox emissions reduction to atmosphere, Will it be possible to propose a CDM project? Which is theCO2-equivalency factor for NOx ?


The main phases of the Project are: • •

Ash Collection and transportation to the Plant Beneficiation. Ash Beneficiation, material with unburned carbon content below 5 %. Ash selling as raw material in precast- concrete, cement and concrete production process. The aim of the project is to beneficiate and sells high quality ash as raw material in precast- concrete, cement and concrete production process. A US$5,000,000 investment is required to put in operation the beneficiation plant needed.


According to the commercial project, we propose a CDM project:

• • •

Project Proposal: Ash Collector and Ash Beneficiation maker. Base Line Scenario: The base line scenario computed on the CDM proposed by Cement Company Colombian. Greehouse Gas emissions reductions: Each time that high quality ash is sold would make possible to avoid using about 50% of clinker (or cement) by each blending and to reduce 0,80 ton of CO2 per ton of clinker replaced. Additionality Criterion: A high investment is required to put in operation the beneficiation plant needed.

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