Petrology and Ultimite Proximite analysis

Petrology

Petrology is scientific study of rocks that deals with their composition, texture, and structure;

their occurrence and distribution; and their origin in relation to physicochemical conditions and

geologic processes. It is concerned with all three major types of rocks—igneous, metamorphic,

and sedimentary. Petrology includes the subdisciplines of experimental

petrology and petrography. Experimental petrology involves the laboratory synthesis of rocks for

the purpose of ascertaining the physical and chemical conditions under which rock formation

occurs. Petrography is the study of rocks in thin section by means of a petrographic

microscope (i.e., an instrument that employs polarized light that vibrates in a single plane).

Petrography is primarily concerned with the systematic classification and precise description of

rocks.

Petrology relies heavily on the principles and methods of mineralogy because most rocks consist

of minerals and are formed under the same conditions. Also essential to petrological research is

the careful mapping and sampling of rock units, which provide data on regional gradations of

rock types and on associations unavailable by other means.

Origin Of Coal

Accumulated, compacted and altered plants form a sedimentary rock called coal. It is not only a

resource of great economic importance, but a rock of intense fascination to the student of earth

history. Although coal forms less than one percent of the sedimentary rock record, it is of foremost

importance to the Bible-believing geologist. Here is where he finds one of his strongest geological

arguments for the reality of the great Noachian Flood.

Two theories have been proposed to explain the formation of coal. The popular theory held by many

uninformitarian geologists is that the plants which compose the coal were accumulated in large

freshwater swamps or peat bogs during many thousands of years. This first theory which supposes

growth-in-place of vegetable material is called the autochthonous theory.

The second theory suggests that coal strata accumulated from plants which had been rapidly

transported and deposited under flood conditions. This second theory which claims transportation of

vegetable debris is called the allochthonous theory.

Coal Classification

There are many classification of coal that we know. Coal classified by their maturity calor value

and material matters. The classification is defined by Rank, Grade, Type. In CBM, the most

important classification that we should know is the rank of coal. Rank provides a measure of

how far sedimentary organic matter has advanced along the maturation pathway. A wide variety

of physical and chemical parameters can be used to determine rank: fixed carbon yield or

vitrinite reflectance

a. Peat – a dark brown and black residuum produced by the partial decomposition and

disintegration of mosses, sedges, trees and other plants that grow in marshes and swamps.

b. Brown coal – a low rank coal, intermediate between peat and bituminous rank; +/-

synonymous with lignite.

c. Bituminous coal – a term commonly applied to certain varieties of soft (medium rank)

coal which burn freely with a flame and which yield volatile bituminous matter on

heating.

d. Anthracite – a hard, black lustrous coal containing a low %-age of volatile matter,

commonly referred to as “hard coal” and mined mostly in eastern Pennsylvania. A coal

yielding < 8% volatile matter. 22 Significance of Rank Rank

Proximite system

The proximate analysis is a routine coal analysis to derive the mineral mattercontent, moisture

content, volatile matter, and fixed carbon content of the coal.Mineral matter, often called ash content,

is residue after thecoal sample has been burned. Of primary interest to the CBM project development

are the mineral matter and moisture content. When compared, one notices a good correlation between

mineral matter content and bulk-density measurement from wireline logs. It is possible to derive the

proximate analysis using the correlationsbetween the wireline log measurement of bulk density and

the constituents of theproximate analysis. Because each coal is unique, the modeling between

coremeasurements and wireline log measurements provides essential information that should be

obtained early in the lifecycle of the project.

The proximate analysis of coal is presented as a group of test methods (ASTM D-3172; ASTM D-

3173; ASTM D-3174; ASTM D-3175; ASTM D-5142; ISO 1171) that has been used widely as the basis

for coal characterization in connection with coal utilization. These analyses are in contrast to the ultimate

analysis of coal, which provides information about the elemental composition.Some objectives that will

be measured in proximite analysis.

Moisture (ASTM D3173, ISO 11722, AS1038.3)

Moisture is the water that exists in the coal at the site, time, and under the conditions it is sampled.

Determine the amount of moisture in your samples by measuring the loss in mass between an as-mined

sample and a sample that has been heated under controlled conditions to drive off the water that is not

contained within the chemical structure of the coal. 

Calorific Value (ASTM D5865, ISO 1928, AS1038.5)

The calorific value of coal or coke is the heat liberated when the solid fuel undergoes complete combustion

in oxygen.  In order to obtain accurate results, burns your fuel sample in a bomb calorimeter and measures

the total heat energy.

Volatile Matter (ASTM D3175, ISO 562, AS1038.3)

Volatile matter includes the components of coal, except for water, which are liberated at high temperature

in the absence of oxygen. Volatile matter is a key health and safety concern as coals high in volatiles have

an increased risk of spontaneous combustion.

Fixed Carbon (ASTM D5142, ISO 17246)

The fixed carbon content of coal is determined by subtracting the percentages of moisture, volatile matter

and ash from the original mass of the coal sample: the solid combustible residue that remains after a coal

has had the volatiles driven off. .

ASH 

The residual material of coal after burning the coal.

By definition, coal must contain at least 50% of its weight, or 70% of its volumeas organic,

carbonaceous matter. A proximate analysis is a common laboratoryprocedure to provide fundamental

composition of the coal. Proximate analyses of coal provide the percentage composition in coal of

the following:

• Ash.

• Fixed carbon.

• Volatile matter.

• Moisture.

The tests are specified by procedure D-3172, ASTM Standards. Each of the four measured

parameters has significance to the CBM process.

The ash measured in the proximate analysis represents that part of the mineral matter left

after thermal degradation of the sample by combustion (ASTM D-3174). A small (1–2 gram) sample

of the coal is completely burned in air at 725 ±25°C. The residue is the ash content. It has a value

near that of the percentage of mineral matter. An increasing ash content, from a proximate analysis

indicating mineral matter, proportionately lowers the amount of methane that can be adsorbed.

Mineral matter also has a deleterious effect on fracturing in the coal. Being a determinant in limiting

cleat formation and gas content, mineral matter thus impacts two of the most important parameters in

the commercial CBM—permeability and adsorbed methane capacity. The inorganic particles that

comprise the ash of the analysis are distributed throughout the coal as clayminerals, carbonate

minerals, sulfide minerals (pyrite), and silica minerals (quartz).

Fixed carbon is the material remaining after the determination of moisture, volatile matter, and

ash. It is, in fact, a measure of the solid combustible material in coal after the expulsion of volatile matter,

and like determination of the carbon residue of petroleum and petroleum products (Speight, 1999, 2001)

represents the approximate yield of thermal coke from coal (Zimmerman, 1979). The fixed-carbon value

is one of the values used in determining the efficiency of coal-burning equipment. It is a measure of the

solid combustible material that remains after the volatile matter in coal has been removed. For this reason,

it is also used as an indication of the yield of coke in a coking process.

Fixed carbon plus ash essentially represents the yield of coke. Fixed-carbon values, corrected to a

dry, mineral-matter-free basis, are used as parameters in the coal classification system (ASTM D-388).

Data reporting (i.e., the statement of the results of the proximate analysis test methods) usually includes

(in some countries but not in all countries) descriptions of the color of the ash and of the coke button. As

an interesting comparison, the test for determining the carbon residue (Conradson), the coke-forming

propensity of petroleum fractions and petroleum products (ASTM D-189; ASTM D-2416), advocates the

use of more than one crucible. A porcelain crucible is used to contain the sample, and this is contained

within two outer iron crucibles. This corresponds to the thermal decomposition of the sample in a limited

supply of air (oxygen) and the measurement of the carbonaceous residue left at the termination of the test.

Moisture content affects methane adsorption capacity. There are several sources of the water

found in coal. The vegetation from which coal was formed had a high percentage of water that was both

physically and chemically bound, and varying amounts of this water were still present at various stages of

the coalification process. But the overall result of the continuation of the coalification process was to

eliminate much of the water, particularly in the later stages of the process, as is evident from a

comparison of the moisture contents of different ranks of coal, from lignite to anthracite Moisture

contents are determined (ASTM D-3173) by heating a small coal sample for 1 hour in a vacuum or in

a nitrogen atmosphere to 107 ±4°C. The weight loss as a percentage of the original sample is

reported as moisture content. Before beginning the analysis, the sample is crushed to <60 mesh.

Volatile matter is determined from the thermal decomposition, without oxidation, of a 1-gm

crushed sample (<60 mesh) at 950 ±20°C for 7 minutes in a muffle furnace (ASTM D-3175). Volatile

matter, as determined by the standard test methods (i.e., ASTM D-3175; ISO 562), is the percentage of

volatile products, exclusive of moisture vapor, released during the heating of coal or coke under rigidly

controlled conditions. The measured weight loss of the sample corrected for moisture establishes the

amount of material (volatile matter) evolved from the coal under the conditions of the test.

However, the method, being empirical, requires close adherence to detailed specifications, and

since the test is essentially an assay of the sample of coal on a small scale rather than a purely chemical

test, it is necessary in order that results may be comparable among laboratories that the conditions

prescribed be followed rigidly. The type of heating equipment and the size and shape of the sample

holders as well as the material from which they are made (platinum crucibles specified) all have some

influence on the rate of heating of the sample and the range of temperatures to which it is exposed. The

crucibles used are 10 to 20 mL in capacity, of specified size, with deep-fitting lids, and there are two

procedures for determination of volatile matte Volatile matter and fixed carbon of the proximate

analysis are used to specify higher coal ranks above hvAb in the United States. Carbon content

increases with maturation until graphite of 100% carbon would be reached ultimately. Fixed carbon

from the preceding three tests is calculated using Eq:

where:

FC = calculated fixed carbon of the coal

%Ash = measured by ASTM D-3174

%H2O = measured by ASTM D-3173

%VM = measured by ASTM D-3175

The percentages of ash, fixed carbon, volatile matter, and moisture of the proximate analysis may be

presented on the following bases:

• As received—Percentages based on all four measured components, which represent the coal as received

in the laboratory, approximating the conditions in

the seam.

• Ash-free (AF)—Percentages based on three measured components without inclusion of ash.

• Dry—Percentages based on the three components of volatile matter, fixed carbon, and ash.

• Dry, ash-free (DAF)—Percentages based on the two components of volatile matter and fixed

carbon.

Table 2.3 gives a proximate analysis for an hvAb coal presented on an as-received, dry, and dry ash-

free basis for comparison. Note that volatile matter and fixed carbon percentages appear regardless of

the basis on which the analysis is made.

Ash content of coals can vary significantly from seam to seam in the same CBM or over several

vertical feet of a single seam. The inhomogeneity affects gas content estimates and physical

properties, although the inhomogeneities are seldom compensated for in gas content estimates

because such extensive coring and analysis would be impractical. In an effort to circumvent the

difficulty and estimate fixed carbon and volatile matter from well logs, Hawkins, Schraufnagel,

Table 2.3—Example Proximate Analysis

As received (%) Dry (%) DAF (%)

Moisture 1.4 - -

Volatile

Matter

36.33 36.8 41.3

Fixed

carbon

51.6 52.3 58.7

Ash 10.7 10.9 -

Total 100.0 100.0 100.0

and Olszewski noted that the volatile matter and

fixed carbon content of proximate analyses are

linearly related to the ash content. If the proximate

analysis parameters of a formation could be

evaluated from well logs, a more continuous

analysis would result to account for

inhomogeneities. For example, if density from

geophysical logs could be correlated with ash

content, the proximate analysis could be estimated from calculated ash content to give a practical

solution without numerous cores and proximate analyses. Their correlations from core data of

moisture, volatiles, and fixed carbon content with percentage of ash are given in Fig. 2.10 for the San

Juan basin, where the linear relationship holds even though data were taken from three wells over a

40-sq mi area.

Fig. 2.11 shows the wide variation of ash content from 10 seams over 1,235 vertical ft of a single

well in the Appalachian basin. Again, the linear relationships hold for moisture, ash, and volatiles

with ash content.

A problem to be resolved with the technique is the

correlation of the density with

ash content. Core analysis provides the standardization

of the logs, but the standardization remains site-

specific. Technical advancements, such as the use of

well logs to characterize a coal reservoir, are needed to

make the CBM process more economical in the future,

especially prospective properties that might be

marginally profitable.

Ultimite analysis

Ultimate analysis tests produce more comprehensive results than the proximate analyses. Lab

usually uses the results from ultimate analysis tests to determine the elemental composition of

the coal including moisture, ash, carbon, hydrogen, nitrogen, sulfur, and oxygen (by difference).

We determine each element through chemical analysis and express it as a percentage of the total

mass of the original coal or coke sample. Ultimate analysis provides the elemental composition

of oxygen, carbon, hydrogen, sulfur, and nitrogen.

The annual book of ASTM standards presents the standard method for ultimate analysis as

procedure D-3176. It specifies that carbon and hydrogen of the coal will be determined from the

gaseous products of the material’s complete combustion (D-3178). The total sulfur (D-3177),

nitrogen (D-3179), and ash (D-3174) are to be determined from the entire material in separate

calculations.

The standard method for the ultimate analysis of coal and coke (ASTM D- 3176) includes the

determination of elemental carbon, hydrogen, sulfur, and nitrogen, together with the ash in the material as

a whole. Oxygen is usually calculated by difference. The test methods recommended for elemental

analysis include the determination of carbon and hydrogen (ASTM D-3178), nitrogen (ASTM D-3179),

and sulfur (ASTM D-3177; ISO 334; ISO 351), with associated determination of moisture (ASTM D-

3173) and ash (ASTM D-3174) to convert the data to a moisture-ash-free basis.

For lack of a suitable test for oxygen, its percentage content in the coal is determined by

subtracting from 100 the sum of the percentages of the other components. A small error is taken

for granted but cannot be compensated for in the procedure because some hydrogen and oxygen

will be derived from the bound water of clay, shale, or carbonate impurities in the coal. The

elemental analysis of coal obtained by this procedure, when converted from a weight basis to a

mole basis, provides the ratios of O/C and H/C used in the van Krevelen diagram7 to define the

maturation state of coal. The following ultimate analysis applies to a mvb coal of the Blue Creek

seam of the Warrior basin that contains 4.82% ash: (1) carbon, 83.46%; (2) hydrogen, 4.39%; (3)

nitrogen, 1.81%; (4) sulfur, 0.47%; and (5) oxygen, 5.05%.

Carbon and hydrogen, which, respectively, account for 70 to 95% and 2 to 6% by weight (dry, ash-free)

of the organic substance of coal, are thought by some to be the most important constituents of coal.

Almost all of the carbon and hydrogen in coal occurs in combined form in the complex organic

compounds that make up coal. But carbon also occurs in the mineral carbonates, with calcite being the

principal component, and hydrogen is also present in the various forms of moisture found in coal.

Nitrogen occurs almost exclusively in the organic matter of coal. Very little information is available

concerning the nitrogen-containing compounds present in coal, but they do appear to be stable and are

thought to be primarily heterocyclic. The original source of nitrogen in coal may have been both plant and

animal protein. Plant alkaloids, chlorophyll, and other porphyrins contain nitrogen in cyclic structures

stable enough to have withstood changes during the coalification process and thus to have contributed to

the nitrogen content of coal.

Sulfur is an important consideration in coal utilization, and hence, there is a considerable amount of

published work relating to the development of methods to improve the efficiency of the techniques as

well as improve the accuracy and precision of the sulfur determination (Ahmed and Whalley, 1978;

Chakrabarti, 1978a; Attar, 1979; Raymond, 1982; Gorbaty et al., 1992). Total sulfur data (ASTM D-

3177; ASTM D-4239) are necessary for the effective control of the emissions of oxides of sulfur

whenever coal is used as a fuel. The emission of sulfur oxides leads to the corrosion of equipment and

slagging of combustion or boiler equipment, as well as contributing to atmospheric pollution and

environmental damage. Sulfur data are therefore necessary for the evaluation of coals to be used for

combustion purposes.

Oxygen occurs in both the organic and inorganic portions of coal. In the organic portion, oxygen is

present in hydroxyl (–OH), usually phenol groups, carboxyl groups (CO2H), methoxyl groups (–OCH3),

and carbonyl groups (=C=O). In low-rank coal, the hydroxyl oxygen averages about 6 to 9%, whereas

high-rank coals contain less than 1%. The percentages of oxygen in carbonyl, methoxyl, and carboxyl

groups average from a few percent in low rank and brown coal to almost no measurable value in high-

rank coal. The inorganic materials in coal that contain oxygen are the various forms of moisture, silicates,

carbonates, oxides, and sulfates. The silicates are primarily aluminum silicates found in the shalelike

portions. Most of the carbonate is calcium carbonate (CaCO3), the oxides are mainly iron oxides (FeO

and Fe2O3), and the sulfates are calcium and iron (CaSO4 and FeSO4).

Chlorine occurs in coal (Chakrabarti, 1978, 1982; Hower et al., 1992) and is believed to be a factor not

only in fouling problems but also in corrosion problems (Canfield et al., 1979; Slack, 1981). The chlorine

content of coal is normally low, usually only a few tenths of a percent or less. It occurs predominantly as

sodium, potassium, and calcium chlorides, with magnesium and iron chlorides present in some coals.

There is evidence that chlorine may also be combined with the organic matter in coal.

Mercury has been identified as a very dangerous environmental contaminant, largely by reason of the

process of concentration in the food chain. Thus, the presence of mercury in coal is an extremely sensitive

issue. The possible emission of mercury that may be found in coal is an environmental concern. The test

for total mercury (ASTM D-3684; ISO 15237) involves combusting a weighed sample in an oxygen

bomb with dilute nitric acid absorbing the mercury vapors. The bomb is rinsed into a reduction vessel

with dilute nitric acid, and the mercury is determined by the flameless cold vapor atomic absorption

technique. Mercury and mercury salts can be volatilized at low temperatures. Precautions against

inadvertent mercury loss should be taken when using this method. When coal samples are burned

according to this procedure, provided that sample preparation in is accord with the standard procedure

(ASTM D-2013), the total mercury is quantitatively retained and is representative of concentrations in the

whole coal. Caution is also advised in use of the bomb, considering the chemicals required for the test

method.

Carbon dioxide, Most coals contain small amounts of mineral carbonates made up primarily of calcium

carbonate and to a lesser extent ferrous and other metal carbonates. Some coals contain a comparatively

large amount of the inorganic carbonates, and the determination of carbon dioxide content is required in

estimating the mineral matter content of these high-carbonate coals. Indeed, it is necessary to have a

knowledge of the carbonate content of coal to correct the carbon figure and since, without resorting to

very elaborate analyses, it would be impossible to express the carbonate content as definite quantities of

calcium carbonate, magnesium carbonate, and so on, it is customary, and sufficient for all analytical

purposes, to express it simply in terms of carbon dioxide

Sources:

http://www.sgs.com/en/Mining/Analytical-Services/Coal-and-Coke/Proximate-and-Ultimate-

Analysis.aspx

http://www.britannica.com/science/petrology

file:///C:/Users/compaq/Downloads/Handbook_of_coal_Analysis.pdf

Coal Bed methane principles practice