Pulverising of Coal

General Description:
The function of the pulverising mills is to dry the coal, to reduce the coal from stockpile size to pulverised fuel size, typically 70% passing 75 micrometres (200 mesh), and to transport the pulverised fuel (PF) to the boiler. Coal is continuously fed to the pulverisers from the power station bunkers. Hot air enters the pulverisers and continuously conveys the PF to the boilers.

This transport air is generally known as "primary air". Figure 12 shows a general schematic of a mill. Hot primary air is blown through the mill by the primary air fan while coal is fed in at the required rate by a feeder. The temperature of the air/coal mixture exiting the mill is normally controlled (typical temperature 70 °C) by adjusting the temperature of the inlet air. This is done by balancing the mix of air from the air-heater and ambient air. The wetter the coal fed to the mill, the higher must be the inlet temperature.


Figure 12: General Schematic of a Pulverising Mill


Figure 13: Schematic Layout of a High-Speed Attrition Mill


Figure 14: Schematic Layout of a Medium Speed Vertical Spindle Mill


Figure 15: Schematic Layout of a Low Speed Ball or Tube Mill

Pulveriser Performance
Poor performance of mills can have the following forms:
* Capacity problems because coal is too difficult to grind.
* Capacity problems because coal has low energy content.
* PF fineness problems.
* Mill temperature problems, which could lead to capacity problems or mill fires.
* High maintenance requirements because of abrasive nature of mineral matter in the coal.

Relevant Coal Properties:
The coal properties that have the most impact on pulverising performance are:

Surface Moisture Content
Power stations typically operate pulverisers to achieve a target mill outlet temperature, normally of 70-80˚C. High surface moisture levels cause mill inlet temperatures to rise, so as to maintain the desired mill outlet temperature. Increases in mill inlet temperatures may impose limitations on primary air fan capacity, which in turn impose limitations on achievable boiler load. Additionally, increases in mill inlet temperatures also enhance the risk of fires inside the pulverisers.

Specific Energy
The specific energy of the coal governs the rate (t/h) at which coal must be pulverised to achieve a required boiler load. Low specific energy coals are more likely to cause boiler load limitations to be imposed because maximum pulveriser capacity has been exceeded.

Hardgrove Grindability Index
The Hardgrove Grindability Index (HGI) test is a laboratory procedure designed to predict mill power consumption and/or product fineness. Coals that have lower values of HGI are generally more difficult to grind than coals which have higher HGI values ie. more mill power is required and the PF product is coarser. HGI does not always produce reliable predictions. Coals of different rank having the same value of HGI do
not behave in the same way in the pulveriser. Generally, lower rank coals require less pulveriser power to grind, than higher rank coals of the same HGI, however they generally produce a coarser PF product.

Nature and Concentration of Hard Minerals
The nature and concentration of hard minerals (especially quartz and pyrite) affect the potential of the coal to cause wear of pulveriser components. Estimates of the wear potential of coal are made by the Abrasion Index test, using the apparatus of Yancey, Geer and Price, however Abrasion Index values do no necessarily correlate well with actual mill wear results. The wear potential of a coal is primarily governed by the nature and concentration of hard minerals in the coal, with increases in the angularity, the coarseness and concentration of hard minerals causing a corresponding increase in mill wear potential.

Tendency of Coal to Ignite in Pulveriser
It is generally felt in the utility industry that the tendency of a coal to ignite in pulverisers is governed by the volatile content of the coal. Although studies of mill fires and mill explosions do no necessarily support this association, pulveriser manufacturers generally specify mill air outlet temperature limits based on coal volatile content, with 80-90˚C being specified for medium-volatile coals, and 60-70˚C being specified for high-volatile coals. A more plausible factor that would influence the tendency of a coal to ignite in the pulveriser is the surface moisture content, which influences air inlet temperatures as previously discussed.

Pilot-Scale Results versus Coal Properties
From pilot-scale measurements, an evaluation of a particular coal's performance can be made against the performance of a range of reference coals. Figures 16 and 17 show correlations between HGI and mill performance (fineness and specific power consumption respectively)for a range of coals. These correlations are somewhat scattered, indicating that factors other than HGI play an important part in the grinding process. When power consumption is adjusted for PF fineness (kW.h per tonne of the PF fraction less than 75 mm) the scatter is reduced (Figure 18).

Abrasion Index is designed to predict mill wear but, as Figure 19 shows, the correlation is not strong when the Abrasion Index is high. The explanation may lie in the fact that the Abrasion Index mill is a batch process, whereas the vertical spindle mill has continuous throughput, allowing hard but fine mineral particles to be swept out of the mill.


Figure 16: PF Fineness versus HGI for Pilot-Scale Mill Tests


Figure 17: Mill Power Consumption (kW.h/t coal) versus HGI for Pilot-Scale Mill Tests


Figure 18: Mill Power Consumption (kW.h/t coal) versus HGI for Pilot-Scale Mill Tests after adjusting for the Fraction passing 75 mm


Figure 19: Mill Roll Wear versus Abrasion Index for Pilot-Scale Mill

Coal Heat Release: Flame Behaviour
The primary purpose of the coal/air path is to produce heat from the coal. The ease with which the heat available from the coal is released may be termed “combustion reactivity”; a coal that is easy to burn may be described as “free burning”. One aspect of combustion reactivity is the coal’s ability to produce a flame that is strong, stable, free of pulsation and situated close to the burners. In this way, there is no danger of flame extinction and the rapid heating of the coal provides the maximum time for the coal to burnout in the boiler furnace. A related aspect of flame stability is flame behaviour at part-load: the inherent instability of flames at part-load determines the limits of turn-down capability.

Relevant Coal Properties
The coal properties that have the most impact on boiler performance are:

Moisture Content
Moisture content affects combustion temperatures, with higher moisture contents resulting in lower temperatures.

Volatile Matter (VM) Content
Flame ignition and stability are to a large degree maintained by combustion of the VM, since these gaseous products are able to burn much faster than the residual char. Therefore high VM coals may be expected to display superior flame behaviour.

Pilot-Scale Results versus Coal Properties
When VM is considered to be a significant factor, an alternative index, Fuel Ratio, is often utilised. This is defined as follows:

                               Fixed Carbon
Fuel Ratio (FR)= ----------------------
                             Volatile Matter

A low Fuel Ratio corresponds to a high VM content.

In the pilot-scale Boiler Simulation Furnace, burner turn-down capability is measured by operating the burner at full-load (150 kW) as well as a number of part-loads. At each load the required swirl setting to achieve a stable flame is recorded. If a high swirl setting is required this signifies poor turn-down capability. In the limiting case there is simply not enough swirl available and the flame cannot be stabilised. In Figure 20, the coals that required the highest swirl settings tended to have the highest Fuel Ratios (lowest VM contents) as expected, but the correlation is not perfect. The VM determined by proximate analysis is therefore an imperfect predictor of flame stability.

This may be partly because Figure 20 did not take into account moisture content which is also a factor. Another explanation is that the VM released under PF combustion conditions can be much different, usually higher, than the VM yield determined by the proximate analysis. In addition, the calorific value of the volatile matter is more relevant than the quantity released.

* Some coal technologists use VM (% daf) to correlate with coal reactivity data. It is easily shown that there is a one-to-one correspondence between VM (% daf) and FR. For example, a VM of 40% daf corresponds to a Fixed Carbon of 60% daf, which gives a FR of 1.5.


Figure 20: Burner Turndown Capability (from the required swirl to stabilise the flame as firing rate is reduced)

Coal Heat Release: Char Burnout Efficiency
The second aspect of coal combustion reactivity is the burnout efficiency, defined as:

                                          Total Mass of Combustibles Burnt
Burnout Efficiency (%)= ------------------------------------------------ x 100
                                          Total Mass of Combustibles inCoal

The unburnt combustibles (100 – Burnout Efficiency) represent a waste of coal. In addition, the unburnt combustibles remain in the fly ash; too much in the ash renders it unsuitable for use in concrete. The ability to use fly ash in concrete is a convenient way of avoiding disposal costs and environmental effects.

Relevant Coal Properties
The coal properties that have the most impact on boiler performance are:

Volatile Matter (VM) Content
A high VM yield during combustion leaves a smaller percentage of char to be burnt, which is a good start to achieving favourable burnout. In addition, fundamental experimentation has shown that char remaining from high volatile coals tends to be more reactive than char from low volatile coals.

Maceral Analysis and Vitrinite Reflectance
In an effort to remedy to imperfect predictions provided by VM content, researchers have undertaken studies to correlate petrographic characteristics of coal with burnout efficiency.

PF Fineness
Finer PF burns more quickly than coarser PF. Fineness is very much a result of a coal’s inherent milling behaviour.

Pilot-Scale Results versus Coal Properties
Figure 21 shows the correlation between burnout of coals in ht pilot-scale BSF and FR. Though the coals had all been pulverised to the same nominal fineness of 70% passing 75 mm and furnace conditions were the same, there was considerable scatter in the trend. Efforts to include data from the petrographic analysis in a correlation have brought only partial success.

From this we must conclude:
· Char properties (size, shape, porosity, chemical reactivity, variability) may to too complex to be predicted or characterised by petrographics and VM determinations,
· The full size distribution of the PF is never the same for two coals, even though the percentage passing 75 mm may be the same.


Figure 21: Burnout versus Fuel Ratio for Coal Burnt in Pilot-Scale Boiler Simulation Furnace

Thermal Coal Use In Pulverised Fuel Fired Boilers

Power Generation Technology

What is a Boiler?
The basic concept of coal based power generation is the conversion of coal energy to electrical energy. This is achieved by the combustion of the coal in a boiler to generate steam which is used to drive turbine alternators. Typical conversion efficiencies of coal energy to electrical energy, for modern coal-fired power plant, are 36-39%, a limitation largely imposed by properties of the steam cycle. The major coal-related components of power generation equipment are as follows:

* Coal handling plant
* Pulveriser plant
* Boiler
* Airheater
* Electrostatic precipitator/Fabric filter
* Atmospheric emissions control
* Ash disposal systems

To understand the operation of a PF fired boiler, the three basic fluid flow processes must be understood, as follows:

* Water and steam path
* Coal and air path
* Flue gas path

Water and Steam Path
In the steam circuit of a boiler, illustrated in Figure 1, water enters the economiser at the correct pressure where it picks up heat to raise its temperature close to saturation temperature. From the economiser, the water enters the boiler steam drum, from which it circulates through the downcomers, outside the boiler, and up through the water wall tubes of the furnace, and returning to the drum. Heat transfer in the furnace is essentially by radiation from the

In the following sections, the different items of plant are discussed, along with the impact of coal properties on individual aspects of behaviour. It must be stressed however that the way in which coal or ash behaves in the various parts of a power plant is governed as much by the features of the plant and how it is operated, as it is coal and ash properties. Some coals may have problematic behaviour in some installations, yet not cause any difficulties in other installations.

Coal and Air Path
The coal and air path is shown schematically in Figure 2. As shown, clean air at ambient temperature is drawn through the forced draft (FD) fans and pumped through the air pre-heater, which recovers heat from the outgoing flue gas and heats the air to a temperature of approximately 300C. On leaving the air heater, the hot air is divided into two streams, viz. primary and secondary air. The secondary (or combustion) air goes to the boiler windbox from where it enters the combustion zone of the furnace.

The primary air goes through the primary air (PA) fans and controlled to give the mill inlet air temperature required to maintain the desired mill outlet air temperature. The pulverised coal produced in the mill is entrained in the primary air and pneumatically conveyed to the burners mounted in the walls of the boiler furnace. Typically, boilers are equipped with a number of mills, each mill supplying pulverised coal to one level of burners.

Flue Gas Path
As shown in Figure 3, the mixture of coal and air issuing from the burners is burnt in the boiler furnace, and the products of combustion pass from the furnace, across the superheaters, reheaters and economisers. A small amount of ash drops out in both the furnace hopper and the economiser hoppers (approximately 5% of the total ash produced, in each). The flue gas enters the air heater at a temperature of approximately 500C and, after heat is transferred to the clean incoming air, leaves the air heater at approximately 130 C, and enters the electrostatic precipitator (ESP). The bulk of the ash produced is removed from the flue gas in the ESP as fine fly ash, and disposed of into ash dams or dry storage silos for subsequent use in other industries.

Boiler Configurations
The essential features of a boiler are:
* Type of burner - swirl, diffusion, slot, multi-fuel (ie. coal/oil/gas), low NOx
* Arrangement of burners - opposed, front/rear wall, corner-fired
* Amount and disposition of heat transfer surfaces
* Number and location of soot-blowers1
* Size of convective (rear) pass - affects velocity of flue gas

Measures of Generating Plant Performance
In general terms, there are several ways in which plant performance can be expressed. Coal properties may impact on any of the following performance aspects. Also contributing to these performance criteria are plant design and the way the plant is operated.

Thermal Efficiency
The overall efficiency of a generating unit is expressed as:

                                             Electrical Energy
Thermal Efficiency (%) = ------------------------ x 100
                                               Coal Energy
It is desirable to maximise thermal efficiency in order to minimise coal costs. It is also a way of minimising the production of greenhouse carbon dioxide.

Availability
Availability is the percentage of time that the plant is able to be operated. Any operating problems that require the plant to be stopped will detract from availability.

Capacity
Capacity is the possible electrical output as a percentage of the rated output. A 500 MWe plant that is able to produce only 400 MWe would have a capacity of 80%. Turn-Down Capability At times of low electricity demand it is necessary for some generating units to run at part-load. Below a certain percentage of full-load the plant may not operate satisfactorily. This load, expressed as a percentage of full-load, is termed the turn-down capability.

* Soot-blowers are devices which are used to clean the ash deposits off the heat transfer surfaces inside the boiler. Typically, soot-blowers consist of lances which, when activated by the operating staff, direct high velocity steam (or in some cases, compressed air) onto the heat transfer surfaces, thus removing the ash deposits.

Operating Costs
These are the costs of keeping the plant operating satisfactorily.

Environmental
Environmental impacts may incur extra operating costs to control them. If they are not controlled the plant owner will be seen as operating irresponsibly, and fines may be imposed.



Figure 1: Schematic Layout of Boiler/Turbo Steam Circuit



Figure 2: Schematic Layout of Coal and Air Circuits in a Boiler



Figure 3: Layout of Flue Gas Path in a Boiler

Processes Occurring During Combustion
Gross Chemical Reactions
The gross combustion of coal involves the chemical reaction of the combustible components of coal, mainly carbon and hydrogen, with oxygen.

C + O2 ---> CO2
(1 mole) + (1 mole) ---> (1 mole)

2H2 + 02 ---> 2H2O
(2 mole) + (1 mole) ---> (2 mole)

S + O2 ---> SO2
(1 mole) + (1 mole) ---> (1 mole)

From these simple chemical equations, the air requirements for combustion can be calculated along with the flue gas quantity and composition. The chemical reactions above are highly exothermic ie. significant heat energy is liberated during the reactions, which is then available for conversion to electricity. The most common
means of achieving this conversion being through the generation of steam in a boiler which is used to drive a steam turbine and electric generator.

Combustion Processes
Coal goes through a number of processes to achieve complete combustion. Some of these are illustrated in Figure 4.

* Release and combustion of volatile matter
* Residual char combustion
* Release of coal mineral matter
* Production of gaseous pollutants.
* Release of trace elements

The first two steps above are necessary to heat production, while the last three are unavoidable side-effects of using coal and these must be managed.

Devolatilisation:

In this process, the coal decomposes as heating takes place, releasing volatile matter. The gaseous volatiles are mixed with the surrounding air and rapidly burned if the prevailing temperature is above the ignition temperature of the volatile species. The rate at which volatiles are released, and the concentration of gaseous species is dependent on:
* The final temperature to which the coal is heated.
* The final temperature to which the coal is heated.
* The nature of the coal (chemical composition, rank etc)

Figure 5 shows the effect of heating rate and final temperature on the total quantity of volatile matter liberated from a high and a low rank coal. As shown, the yield of volatile matter increases with the rate of heating, and the final temperature to which the coal is heated.

The yield of volatile matter during combustion can be significantly higher than the volatile yield as determined by the Proximate Analysis of the coal. Figure 6 shows that some coals have volatile yields up to two times the proximate volatile yield.

Char Burnout:
After devolatilisation, a solid char particle remains which reacts with oxygen on the surface and burns at a much slower rate than the release and combustion of the coal volatile matter.

The process of combustion of the solid char is illustrated in Figure 7 where oxygen diffuses through the boundary layer surrounding the coal particle and reacts with carbon at the exposed coal surface to form carbon dioxide and/or carbon monoxide, which then diffuses back through the boundary layer to the free gas surrounding the particle. The carbon monoxide which is generated is oxidised to carbon dioxide in the free gas stream. There are two competing and limiting processes which determine the rate at which the char burns:

* The rate at which oxygen can diffuse to the char surface,
* The rate at which carbon at the char surface can chemically react with oxygen.

Based on mathematical models of idealised spherical and homogeneous char particles, reaction rates can be calculated over a range of temperatures for representative particles sizes(Figure 8), and the combined effects of diffusion and chemical control calculated.

The theoretical approach can be used to show that the factors which affect the reaction rates of char particles are:

* Char type, density, reactivity, porosity
* Particle diameter, for smaller particles, burning time reduces
* Availability of oxygen, as oxygen concentration increases, burning time reduces.
* Temperature, as temperature increases, burning time reduces.

In real life char particles come in a whole range of sizes, structures and shapes and the distribution of particle types differs for every coal. During devolatilisation, some coal macerals soften and individual particles form various types of chars. Based on shape, wall thickness, and porosity, these chars may be classified into three major groups - "cenosphere", "network/honeycomb", and "solids", as illustrated in Figure 9. The char types have different burning times according to the surface area available for chemical reaction.

The cenosphere type chars are associated with vitrinite, while the network/honeycomb and solid chars are derived from medium to high reflectance inertinite. In general, chars which have thin wall thickness (< 5 m) and are highly porous, more reactive and have shorter burning times than chars with thicker walls and denser textures. Nevertheless, some unfused chars can also be reactive under high temperature and high heating rate conditions. Generally, the ranking of burnout reactivity of these char types, from highest to lowest is network/honeycomb, cenospheres and solids. Release of Mineral Matter: During combustion, the ash contained in the coal is liberated and flies through the boiler with the combustion gas (thus "fly ash"). The fly ash causes problems in boilers by:

* Impinging and sticking on heat transfer surfaces causing ash deposition and subsequent reduction in heat transfer.
* Eroding boiler tubes by impingement.
* Polluting the atmosphere. This requires boilers to be fitted with dust collection equipment such as electrostatic precipitators or fabric collectors.

Fly ash has a wide range of particle sizes, shapes, compositions and structure:
* Larger mineral inclusions in the coal are separated from the coal substance during pulverising of the coal. These large ash particles are of primary importance in wear of pulveriser components and erosion of boiler tubes.

* Finer mineral inclusions, which are initially dispersed through the coal material, enter the boiler in mixed particles of coal and mineral matter. As the particle burns away these inclusions tend to merge to produce a composite residual particle but substantially smaller than the original coal particle. Particles formed this way are often enriched in fluxing elements and are therefore active in the formation of ash deposits.

* Fly ash also contains a proportion of sub-micron particles. These may be due to disintegration of larger ash particles, or from elements in the ash which are vaporised at high temperature and reducing conditions experienced during combustion. These may condense to form fume in the lower temperature parts of the boiler. These sub-micron particles and fumes are difficult to remove from the flue gas steam and pose a pollution problem.

Production of Gaseous Pollutants
Carbon dioxide would once have been considered a harmless consequence of burning a carbonaceous fuel. It is now a high-priority pollutant due to the Greenhouse Effect. Carbon dioxide production is minimised by using fuels that are high in hydrogen as against carbon, and by maximising the thermal efficiency of the power plant process. A more radical approach is the proposed sequestration, whereby the carbon dioxide would be stored to prevent it mixing with the atmosphere.

All coals contain some sulphur and this burns to produce Sulphur dioxide (SO 2). This oxidises in the atmosphere to make sulphur trioxide which causes acid rain. Before the flue gas exits the boiler a small amount of acid is already formed and this impacts on corrosion of duct-work and electrostatic precipitators. Where high sulphur coals are utilised or environmental regulations are stringent, boilers are fitted with flue gas desulphurisation(FGD).

Oxides of nitrogen (NOx) are produced mainly from the nitrogen in the coal. NO x may cause acid rain and brown haze in the atmosphere. NO x emissions may be reduced by a combination of combustion modifications to oxygen availability and flame temperature, and/or a post-combustion Selective Catalytic Reduction (SCR) to remove NO x after it has been produced.

Release of Trace Elements
Given sensitive enough detection equipment, most elements can be found in coal, as they can also be found in garden soil. Some of these trace elements are potentially toxic if they are released in certain forms in high enough concentrations. Of importance is not just the concentrations in the coal, but also whether these elements (i) report to the collected ash and (ii) then to water supplies, or (iii) are emitted from the stack into the atmosphere.


Figure 4: Processes Occurring during Combustion


Figure 5: Volatile Matter Yield as a Function of Final Temperature and Heating Rate


Figure 6: Relative Volatile Yield: Actual Yield over Proximate Yield


Figure 7: Ideal Model of the Combustion of Solid Char


Figure 8: Theoretical Reaction Rates of Char with Diffusion and Chemical Control


Figure 9: Types of Chars formed during Combustion

Performance Prediction
The need for testing and evaluation of coals for combustion arises for a number of reasons:
· To provide technical knowledge of a new coal deposit, so that the quality of the resource can be evaluated.
· To demonstrate that a coal satisfies contractual specifications.
· To identify potential problems of coals before boiler designs are produced, or coal supplies are committed.
· To provide design data for boilers and other combustion equipment.
· To evaluate options for coal beneficiation, blending or the use of coal additives.
· To provide technical support for marketing of export coals.

The quality of the coal affects most of the costs associated with coal-fired power plants, and inadequacies in power station design, poor maintenance, and inconsistent coal quality within specified boiler design limits have a large impact on these costs. Proper evaluation of the combustion performance of the coal to ensure optimum utilisation costs is therefore essential.

Scales of Testing
There is a wide range of testing and evaluation procedures used to evaluate the performance of coals for pulverised coal combustion. These procedures range in scale from:

* Standard laboratory analyses of coal,
* Bench-scale testing to simulate some aspect(s) of the coal’s impact on power plant processes,
* Pilot-scale simulation of power plant,
* Testing in full-scale boilers.

The aim of these procedures is to determine the performance of coals in operating plant, and identify and alleviate potential problems in the use of particular coals. When the scale of testing is being chosen, the trade-offs need to be considered:

* Smaller-scale tests tend to be cheaper, require smaller sample masses and are experimentally more precise,
* Larger-scale tests provide a more realistic simulation of the power plant processes.

To illustrate the above points, a laboratory determination of Volatile Matter (VM) content costs a few dollars, requires a about two grams of coal and the test can be performed with excellent repeatability and reproducibility. As such, the VM determination is ideal for borecore programs and for satisfying contractual requirements. However, the intended function of the VM test is as an indicator of the combustibility of a coal; in this respect the test is sometimes found wanting because it sometimes gives erroneous indications. Figure 10 illustrates the stages at which the different coal scales of evaluation may be employed.
Figure 10: Stages and Scales of Coal Evaluation

Use of Laboratory Analysis
Standard chemical analyses of coal and ash are often unreliable predictors of power plant performance. Nevertheless this type of data is generally available during borecore exploration programs before there have been opportunities for more sophisticated investigations. The laboratory data may be valuable for the following applications:

* As a pointer to the sort of reaction that potential coal buyers might display to a new product,
* As an indicator of areas of the coal’s performance that may be suspect, requiring investigation by a larger-scale form of testing,
* As a measure of the variability of the coal’s quality over the mine. It is difficult to justify the cost of pilot-scale tests on samples that represent every quality. For these reasons extensive use is made of laboratory analysis is a preliminary predictor.

Their effectiveness can be improved by the use of standard or in-house indices derived from these analytical parameters. Such an index may be useful for specific applications, such as by “calibrating” the index against pilot-scale or full-scale data for a given mine; the variability in the value of the index over that mine area may then have real meaning, whereas an attempt to use the index the same way for coal from a different region may not work.

Pilot Scale Testing
Pilot-scale testing and evaluation is generally adequate to establish the boiler design parameters and operational characteristics of a coal. The level of confidence achieved in the style of evaluation is sufficient to predict the coal's performance, and to select coals for use in specific power plants.

Pilot scale testing and evaluation is generally undertaken on combustion test facilities which closely simulate the important aspects of the combustion processes occurring in full-scale boilers. Pilot-scale testing requires coal samples of about three tons for a coal input rate of 20-40 kg/h (150 to 300 kW thermal heat input), and is therefore an economical means of testing for new coal deposits.

A typical pilot scale evaluation furnace, the ACIRL Boiler Simulation Furnace, is illustrated in Figure 11. At this scale, successful evaluation of the coal depends upon comparisons between the sample coal and known reference coals tested in the same facilities, the experience of the testing personnel, and the methods used in the evaluations to extrapolate the test results to full-scale performance.

Pilot Scale Evaluation Procedures
The Australian Combustion Technology Centre, operated by ACIRL, has a range of pilot scale combustion test facilities with which to evaluate the pulverised coal combustion performance of coals. These facilities simulate all the coal-related processes which occur in a power station and have the capability to investigate aspects of combustion, including:

· Pulverising performance, including mill wear.
· Combustion characteristics and performance in power station burners.
· Ash deposition (fouling and slagging).
· Electrostatic precipitation and fabric filter fly ash collection.
· Gaseous emissions of NOx and SOx.
· Fly ash disposal and utilisation.

Pulverising Performance:
Investigations are carried out in a Raymond bowl type vertical spindle mill with a nominal capacity of 500 kg/h, to assess the performance of particular coals with respect to pulverising.
Measurements are carried out to assess:
· Mill roll pressure versus grinding performance.
· Feedrate versus grinding performance.
· Mill power consumption.
· Pressure drop through the mill.
· Mill wear, including the performance of different mill materials.

Combustion Performance:
Testing for combustion performance is carried out in the Boiler Simulation Furnace (BSF). The coal is fired through a variable swirl burner mounted at the top of the down-fired combustion chamber, at a nominal thermal input of 150 kW, equivalent to approximately 20-25 kg/h of bituminous coal.

Testing for combustion performance is carried out over a range of burner swirl settings and primary to secondary air ratios to determine the regimes of flame stability and turn-down ratios. Relative ignitability is determined by measuring the flame stand-off distance from the burner under conditions of zero swirl. At a standard firing rate, samples of solid particulate are sampled along the flame axis and subjected to proximate and ultimate analyses to determine volatile release and carbon burnout along the flame axis.

Evaluations based on the combustion performance procedures provide positive conclusions about a particular coal's performance with regard to burner stability, ignitability and completeness of combustion. The evaluations are related to the known performance of reference coals in power plants.

Ash Deposition:
Test procedures to evaluate a coal's propensity to cause ash deposition problems are carried out in the BSF. The combustion chamber is fitted with three slagging panels that simulate the water walls of a utility boiler. Also, hot gas and suspended ash particles enter a tunnel with incorporates fouling probes which simulate super heater tubes in the convective pass of a utility boiler.

Measurements are made on the rate of build up and strength of deposits, and variations in heat transfer are monitored over time. Operating conditions such as temperature and gas velocity are chosen to simulate real operating conditions in utility boilers, and testing is carried out over a range of gas temperatures to identify the gas temperature at which troublesome deposits may form.

Electrostatic Precipitation:
The time/temperature history of ash particles in the BSF closely simulate that in a utility boiler, and hence the fly ash structure closely resembles that produced in full-scale plant.

The gas leaving the Boiler Simulation Furnace is fed to a pilot scale electrostatic precipitator(ESP), and testing is carried out to measure the collection efficiency of the fly ash over a range of specific collecting areas. The ESP can be operated over a wide range of operating conditions including intermittent energisation and flue gas conditioning.

The evaluation procedure enables the performance of the fly ash to be predicted in existing plant where the size of precipitators is known, as well as the size of precipitator necessary to meet clean air requirements for plants which are being designed for the test coals.

Gaseous Emissions:
Measurement of NOx and SOx generation during combustion are determined under standard combustion conditions in the BSF using on-line flue gas sampling and analysis. Testing is also carried out in the NOx Evaluation Furnace, which has a nominal thermal input of 20kW. NOx levels generated under conditions of excess air and staged combustion are measured.

Measurements are also carried out in a nitrogen free environment to determine the proportion of NOx generated from the nitrogen in the fuel.

Other Testing:
Other pilot scale evaluation procedures include:
· Flame radiation characteristics.
· Fly ash disposal and utilisation.

The pilot scale test procedures, along with a range of bench scale testing can be performed at ACTC to demonstrate the suitability of a coal properties on the performance of power plant, and the range of power plant parameters under which it will perform satisfactorily

Figure 11: ACIRL Boiler Simulation Furnace

Impact on Power Plant Processes
Introduction
This Section covers those power plant processes for which coal quality may impact on the performance. For each process will be detailed:
* The principal of operation,
* Coal quality parameters and indices that may be associated with the process,
* A demonstration of the correlation between these parameters/indices and performance measured in pilot-scale plant.

Self-Heating & Spontaneous Combustion at the Stockpile
Description of the Phenomenon
Self-heating is caused by the adsorption of water (vapour or liquid) and oxygen onto the coal surfaces. These are exothermic reactions and, if the rate of heat generation is greater than the rate at which it is removed (by conduction, ventilation and evaporation) the coal will progressively increase in temperature and may eventually ignite. If an equilibrium condition can be maintained by limiting the chemical reaction rates and/or removing heat at a sufficient rate, then ignition may never occur. In such cases it is possible that the coal’s reactivity to these low temperature reactions may decline over time and the temperature may in fact drop. In these cases the term “self-heating” is more appropriate than “spontaneous combustion”.

Spontaneous combustion occurs because the rates of the reactions increase with higher temperature. A gradual temperature increase reaches a stage where the reaction rate accelerates, thus upsetting the approximate equilibrium between heat generation and heat removal. After the stockpile temperature reaches about 75˚C, acceleration of heating is likely to occur, leading eventually to ignition, though this temperature may be lower for low-rank coals.

Physical Factors
The physical factors associated with spontaneous combustion provide the clues to optimising stockpile management practices for a given coal. These factors include:

(a) Rate of heat generation
· Smaller particle size allows a larger surface area for reaction
· More humid air increases the water/coal reaction
· Flow rate of air into the coal bed increases the reaction rate. This is increased by:
· High permeability of coal bed (uniformly large lumps of coal)
· High stockpiles assisting the chimney effect
· High prevailing winds

(b) Rate of heat dissipation
· Flow rate of air into the coal bed (same factors as under (a))
· Thermal conductivity of coal

(c) Rate of heat accumulation
· Balance of (a) and (b)
· Heat capacity of coal (including moisture)

Clearly, some of the above physical factors are associated with competing mechanisms (eg, air flow into the bed helps to increase the rates of both heat generation and heat dissipation). On the balance, the following factors are generally considered undesirable:

· Segregation causing localised areas of uniformly coarse coal and other areas of fine coal,
· Loosely packed coal,
· Exposure to high prevailing winds,
· High ambient temperature and humidity,
· Exposure to heavy rain ,
· Long residence time on stockpile

Factors Relating to Coal Quality
All coals are capable of self-heating and spontaneous combustion under certain conditions. It is not always possible to say why one coal has a greater propensity for self-heating than another. The most general observation that can be made is that lower rank coals have a greater propensity. Definitions of lower rank include:

· High volatile matter content (% daf),
· Low carbon content (% daf) reported with the Ultimate Analysis,
· Low Fuel Ratio (defined as the ratio of Fixed Carbon to Volatile Matter content),
· Low Calorific Value (basis defined by the ASTM)
· Low reflectance of vitrinite.

ACIRL performs two laboratory-scale tests to determine a coal’s propensity to spontaneous combustion. When these test results are not available, the coal property that seems to predict the results is the Air-Dried Moisture.

* These tests, the Relative Ignition Temperature and the Adiabatic Oxidation Test (R70), are small-scale tests of coal properties and do not account for site factors.

Thermal Coal Quality Determination

Introduction

The supply of quality coal products to the customer is the culmination of a chain of events that begins in the earliest geological assessments of a lease area, to mine planning, to mine operations and finally, shipment of products to contract specification.

Testing and analysis of exploration samples is critical to the development of new projects and the prediction of product quality and quantity for existing producing mines. It is vitally important that exploration sample programs include appropriate testing and analysis work.

Analysis and Testing

This section describes briefly the most common laboratory tests for coal quality determination and discusses their importance. These tests are shown in the attached table, along with the reference to the relevant standard method. Many of these tests are routinely performed on borecore samples from the exploration phase of a project, on production samples from the process for technical information and finally on shipping samples to establish the qualities of the coal in relation to the specification of a contract.

Total Moisture

Representative samples of a shipment or consignment, generally crushed to minus 6 mm, are heated in special ovens at 105oC for up to five hours. The mass loss on drying as a percentage of the original sample mass is taken as the total moisture content.

Relevance

This is one of the most important contractual parameters in a coal supply contract. The total moisture identifies that part of a consignment or cargo that is dead weight. It does not take long to calculate that for a shipment of 100,000 tonnes of coal at 10% total moisture, transportation costs of 10,000 tonnes of water must be paid by the customer.

Often the price of shipments of high moisture coal are adjusted to a contracted figure of say 8%, and a penalty paid by the coal producer for excess moisture. The "moisture penalty" can be determined by two factors. Firstly the "freight cost" penalty and secondly, the "nuisance" penalty.

High moisture levels can cause operational problems for the producer (hang up in bunkers, bins or chutes that create loading delays in train loading or delays in plant operation) and for the consumer (mill capacities are reduced due to the inability of system to dry the ground product or add to process inefficiencies as heat is wasted in evaporating the water in the coal).

Proximate Analysis

This is the term given to a group of three tests on the air dried sample that are commonly used to provide basic data that can identify the coal type.
The three tests are:
1) Moisture (sometimes still referred to as inherent moisture)
2) Ash
3) Volatile Matter



All these tests are performed on an "air dried" sample and are reported on an "as analysed" basis. The term "proximate" means "first" or "immediate". It does not mean, "approximate".

A brief description of each test is now detailed.
1) Moisture (or "air dried moisture" or “as-analysed moisture”)

This is the moisture remaining in the coal after air drying at room temperature. The moisture level is determined by heating the air dried sample of coal in a nitrogen atmosphere (to eliminate oxidation) at 105oC for 2 hours.

Application

It is essential to know the moisture level at which the Proximate Analysis was determined so that Ash, Volatile Matter and Fixed Carbon can be converted to other bases. It is sometimes called “inherent moisture” but this term dose not strictly apply because the drying conditions are not rigidly controlled.

2) Ash

Rapid testing of ash content has been developed at large mine laboratories over the past 20 years to give access to a result in a shorter time than that spelt out in the Standards. Rapid entry of the coal sample directly into the hot zone of an oven together with injection of nitrogen and then oxygen over a period of 15 minutes gives fairly accurate results.

A one-gram sample of the air-dried coal, after grinding to minus 212 micron is incinerated in a special furnace at 815oC for over one hour. The sample is introduced into the furnace at room temperature and increased to 800 C over 1 hour.

Application

Ash is one the most common parameters used in coal quality evaluation, from early exploratory work, to final shipment certification. It is one of the main parameters of any coal contract and does attract bonus or penalty payments for particular consignments or shipments. Coal ash level is the main control parameter in the coal preparation plant.

Changes to the separation density of the process can increase or decrease the ash content of the product at any time. The trend in the market is towards lower ash coals for particular end uses. From the customer’s point of view, a lower ash level means less waste material that has to be handled or disposed of.

3) Volatile Matter
A one-gram sample of fine coal (minus 0.212mm) is heated, out of contact with air, for seven minutes at 900oC. The mass loss percentage corrected for the moisture % is the volatile matter %. The volatiles, which are driven from the coal during the test, are primarily combustible gases such as hydrogen, carbon monoxide and methane and condensable vapours such as tars.

Application

The volatile matter content is often used as a measure of the rank of the coal by geologists. Volatile matter is also important to combustion engineers. The higher volatile coals give off a greater proportion of their weight as combustible gases allowing easier ignition, superior flame stability, higher flame temperatures and thus faster burnout of carbon residues. Low volatile coals contain a lesser proportion of these combustibles making ignition and flame stability more difficult.

In coking coals, the volatile matter content is important to the estimation of the yields of coke and "by-products". Fixed Carbon is also reported in the Proximate analysis. There is no test for fixed carbon. It is arrived at by subtracting the summation of the ash, moisture and volatile results from 100 percent.

Calorific Value
For the test a one gram sample of the air dried coal is burnt in the presence of excess oxygen in a bomb calorimeter. The gross specific energy, or "calorific value", is then calculated in MJ/kg from the measured heat output.

Application

This is the test that quantifies the amount of heat released by the complete combustion of coal. It represents the true value of the coal as a fuel, so it follows that this test quantifies a very important contractual requirement for a customer. Selection of a coal with a high specific energy for a power station can allow reduction in the design capacity of coal receiving, handling, grinding and ash disposal facilities with savings to the customer in capital and operating costs.

Total Sulfur

Sulfur occurs in coal in three forms. As organic sulfur, as pyritic sulfur, and as sulfate sulfur. The usual test is to determine the total of the three types i.e. total sulfur. A small sample (0.5 gram) of fine air-dried coal is combusted in the presence of excess oxygen in a tube furnace operating of 1350oC. The acid gases given off are absorbed or measured to give the sulfur content of the coal.

Application

Total sulfur is a parameter used in all coal contracts because of the environmental importance of acidic sulfur oxide emissions when coal is burnt. Australia is fortunately endowed with low sulfur coals in comparison with some other countries. This fact encourages the utilisation of Australian coals to meet emission standards for sulfur oxides in flue gases. Evaluation of the sulfur levels of raw coal in an exploration program gives important information as to the eventual saleability of the coal.

A knowledge of the forms of sulfur gives an indication whether total sulfur content can be reduced because the pyritic sulfur can be removed by special operations in the preparation plant. Pyritic sulfur in coal may signify the presence of iron pyrite which is associated with spontaneous combustion, acid drainage from stockpiles and slagging.

Hardgrove Grindability Index

The Hardgrove Grindability Index (HGI) is a widely used test for measuring the ease of size reduction of a particular coal. The HGI test involves crushing 50 gram of sized coal (1.18 mm x 0.6 mm) in a small ball in track mill for 60 revolutions at 20 rpm. The grindability index is derived from a sieve analysis of the ground product and by reference to a calibration prepared from Australian certified reference coals.

Application

The HGI value is used to estimate the grinding capacity of mills and to select the type of mill best suited to the coal. It is a fairly common contractual parameter because grinding capacity is of major concern to a power station customer. The higher the HGI figure the more easily crushed is the coal. HGI is not suitable for predicting pulveriser wear rates.

Abrasion Index

The test involves milling 2 kg of -6.7 mm coal in a small hammer mill for a fixed number of revolutions. The mill has removable blades that are weighed before and after. The Abrasion Index is defined as the milligrams of metal removed per kilogram of coal.

Application

The Abrasion Index is used to determine the abrasiveness of coals. This is particularly relevant to abrasive wear of pulverising mill components, but also applies also to the wear of materials handling equipment. It is commonly used for high ash coals or those that have high levels of hard minerals.

Ultimate Analysis

This is the term given to the group of tests that determine the elemental composition of the organic part of the coal. These tests determine the levels of Carbon, Hydrogen, Sulfur, Nitrogen and Oxygen in a coal. Generally C, H, S and N are derived directly and O by difference. This test does not appear as a contractual parameter, but does play an important role in determining the suitability of coals for various uses.

Application

Carbon content is another means of determining the rank of the coal. C, H, N, S and O are used by engineers to calculate the products of combustion Hydrogen and oxygen are necessary for calculating nett specific energy of a coal. Nitrogen and sulfur contents may be limited by coal contracts for environmental reasons related to the emission of the gaseous oxides.

Ash Fusion Properties

Slipcase cones of coal ash are heated to high temperatures in either a reducing or oxidising atmosphere. Photographic or video records are kept of the changing shape of the ash cone as the minerals in the ash begin to soften, fuse and melt.

Temperatures at which specific states occur are noted:
1) Initial deformation temperature oC
2) Spherical temperature oC
3) Hemispherical temperature oC
4) Flow temperature oC

Temperatures of up to 1600 C are reached in this test. Reducing atmospheres in the furnace are achieved by introduction of a hydrogen/carbon dioxide gas mixture during the test. Samples of ash subjected to oxidising conditions tend to produce higher ash fusion temperatures.

Application

The test was designed to characterise the fusion properties of the ash to predict the formation of sticky ash deposits in combustion processes. The deformation temperature is usually included in tender or contract specifications, even though it is the least reproducible of all the coal laboratory tests.

Ash Analysis

In this test the elemental composition of the ash from the combustion of the coal is determined by x-ray fluorescence or atomic absorption spectrometry or inductively coupled plasma. The elements usually reported are Silicon, Aluminium and Iron, Calcium, Magnesium, Sodium, Potassium, Titanium, Manganese, Sodium and Phosphorus. The above elements are reported as the most commonly occurring oxides.

Application

Coal contracts often specify limits for silicon, iron, calcium and sodium. In cement manufacture, the coal ash ends up in the cement product and therefore must be known to control the cement composition.

Trace Elements

Coal samples have been analysed for more than 50 elements using, predominantly, atomic absorption spectrometry and neutron activation analysis. The elements usually tested for are barium, beryllium, cadmium, chromium, copper, lithium, nickel, lead, strontium, vanadium, fluorine, boron, zinc, mercury and selenium. A standard method for determination of trace elements is given in AS 1038.10.1. Methods for determination of boron and fluorine are given in AS 1038.10.3 and AS 1038.10.4 respectively.

Application

Trace element content is becoming an increasingly important environmental consideration in many countries.

Moisture Holding Capacity

In this test a sample of coal is allowed to come to equilibrium with an atmosphere saturated with moisture vapour (in practice 96% humidity) at 30C. The equilibrium moisture content is determined.

Application

This gives a good indication of the moisture that the coal can carry without being visibly wet (i.e.without any surface moisture), sometimes equated to the "in-situ" or "bed" moisture content of the coal. A similar test is covered by ASTM standards where it is sometimes referred to as “inherent” moisture (not to be confused with air-dried moisture). The Moisture Holding Capacity is sometimes used as a basis for trying to estimate a reasonable “as-received” moisture for coal sales.


Maceral Analyses

Maceral analysis involves the microscopic examination of the coal to determine its constituents. Macerals are the microscopically recognisable organic constituents of coal, analogous to the minerals of inorganic rocks, but differing from the latter in that macerals have no characteristic crystal form.

The macerals are named with words ending with "-inite" and are distinguished from one another microscopically on the basis of their differences in such properties as reflectance, colour, morphology, anisotropy and hardness. They originate from the remains of different organs and tissues of plants and have acquired their present properties during peat accretion and coalification.

For reporting, the macerals are arranged into the three groups vitrinite, exinite (also called liptinite) and inertinite. Minerals, form the fourth group reported. The reflectance (i.e. brightness) of the vitrinite maceral is an accurate indicator of the rank of the coal.

Application

The main application is to coking coals, where vitrinite content and vitrinite reflectance are key components of a specification. Maceral analysis has been the subject of many research projects to try to predict the combustion performance of thermal coals.

Standard Methods

Consistency is an important attribute of a commodity like coal. A prerequisite for consistency of a coal product is that the analysis which defines the quality should be repeatable and reproducible within close tolerances.

For any test, there must be a specified procedure to follow in order to minimise differences between personnel in one laboratory, or between two different laboratories. In Australia, all the tests associated with coal sampling and analysis are documented in the following Australian Standard Methods; published by the Standards Association of Australia:

a. AS 4264.1, covers all aspects of sampling and sample preparation.
b. AS 1038, covers the general analysis and testing methods.

These Australian standards spell out in detail:

a. The type of equipment to be used for the test
b. The operating conditions for the test, and
c. The procedure required to complete the test.

Other countries have similar organisations to the Standards Association of Australia, for example:

a. USA has the ASTM - American Society for Testing Materials
b. Japan has the JIS - Japanese Industrial Standards.
c. U.K. has the BS - British Standards
d. European Countries have the ISO - International Standards Organisation.

Close examination of the various standard methods from each organisation shows that the procedures and methods are very similar. Generally, robust standard methods developed in one country are adopted by other countries with little modification.

There are however a few standard methods where there are major differences in equipment that can produce different results when comparing with other standards. The most significant of these are the ASTM tests for Volatile Matter and Ash Fusion Temperatures.

In Australia the Standards Association of Australia has permanent committees established that continually review and update Standard Methods as and when necessary. These committees are made up of (in the case of coal) specialist coal technologists, or engineers from major organisations that participate in the Australian Coal Industry. These people meet on a regular basis to discuss any changes or reviews of the Standard Methods. A list showing a cross-reference to the most commonly used coal standards is provided in Table 1.


Reporting of Results

Precision and Reproducibility of a Laboratory Test Generally all analyses in a laboratory are performed in duplicate. The average of the two results is reported as the best estimate of the true value of the test result for the sample.

When the difference between the duplicate results of a test falls outside a specified range, called the "tolerance", the test will be repeated. Even in the most carefully conducted test, differences occur between the results of two tests on two sub-samples of the same coal.

The standard methods spell out precisely the equipment and procedures so that the differences between tests within a laboratory or between laboratories are as small as possible. The repeatability to be expected for each of the common coal tests performed according to Australian Standard methods, is shown below:

Repeatability
Ash Content
< 10 percent 0.10% 10-20 percent 0.20% 20-40 percent 0.25% Volatile Matter % 0.20% Specific Energy (MJ/kg) 0.12 Total Sulfur £ 1.5% 0.03% > 1.5% 2% of Mean

The reproducibility to be expected between different laboratories on the same coal sample for tests conducted according to Australian Standards, are shown in Table 2.

Reporting Basis

All analyses in the laboratory are determined on an "air-dried" basis. However, parameters are reported to different bases for contractual requirements e.g. thermal coal consignments sometimes report the specific energy (Kcal/Kg) to an 'as received' basis.

This takes into account the moisture that is present in the consignment and thus its actual energy value. Sometimes results are reported to "dry", "dry and ash-free" or "dry, mineral matter-free" bases so that true comparisons between different coals can be made.

Australian Standard AS 1038 Part 16 "Reporting of Test Results" gives all the information on reporting terms, abbreviations, changes of bases, interpretation of results and the repeatability and reproducibility tolerances for all coal analyses.

Traditional Mineworker Pickings of Diamond

This is rest of traditional mineworker of diamond which still flipping up to look for hope. This mining activity is including region Sebamban VI Kecamatan Kuranji Kabupaten Tanah Bumbu and there [are] around year of 1995. and this is mineworker pickings which still staying to get secuil hope. Most this mineworker comes from region Kalimantan south like martapura, new town, go abroad, pagatan or people local x'self. There is thing funny from this traditional mineworker, said them usually the mineworkers coming from far it is said has known location which will be mined from paranormal (" bright people") to get result larger ones.

It is they which still draping lives by mining of diamond traditionally. Only with machine capital dongfeng assembled x'self with pump to suck and a few creative modifications to accommodate material which in the form of wood and board and carpet applied to precipitated material and equipments applied tray to which wooden rengas they are to searching portion for and on behalf of family.



Simply this traditional mining activity can be described as following :

1. Water pump machine placed periphery basin to suck water coming from pool to be used sprays material taken and or material which has entered in precipitation board.

2. Water inhaled from the pool is flown [by] towards link pump having some tubing's applied to spray material which will be sipped and or material which has stepped into precipitation board.

3. Pump machine sucks applied to inhale material in the form of sand and gravel from within dig pool. By assisted water from link pump, the material in dig pool sipped by after sipping towards precipitation board of through (via paralon pipe).

4. The mineworkers usually cleans former of dig pool from the king sized wood or root or stones in pool. Commissioned in dig pool usually there are 3 people where 1 people holds machine gas string dongfeng to control rising or alights from every attraction of material, usually is adapted for condition of material. 1 people again undertook holds water tubing spray pool material and 1 people again undertakes cleans material from wood, king sized root or stones in dig pool. Whereas 1 people undertakes in precipitation board to spray material so that clean and 1 people again undertakes takes care of the pump machine or assists cleans material in precipitation board.

5. mixed Sand material and gravel of the water is admission in to precipitation board and cleaned continually with water sprayer. Before precipitation board admission of the material through carpet unfolded by concurrent with modification design of accurate board under exhaust tubing which in the form of paralon pipe. So if there is smooth fairish diamond, beforehand patch in carpet patching in precipitation board.

6. After material in the form of sand and gravel in precipitation board of cleanness (there is no mud), the material is input by sack for mobilization to tray pool. So from here activity of tray done to dissociate between materials which in the form of sand and gravel to get diamond.

7. Diamond got mostly fairish smooth like sand sugar, once in a while if chance again lucky they can get measure larger ones usually size pentol match or about 3 fiat ( term people local calls). The result usually is sold to collector which there are in village to be sold to martapura banjarmasin. sometime mineworker sells x'self to martapura if result gotten is fair to middling bigness to get higher level price.

In flow diagram can be described as following :

Pump Sucks Basin ---> Link Water Pump (to Pond Excavation & Precipitation Board) ---> Pump Sucks Dig Pool ---> Precipitation Board (in the form of material ready for washed raw-gold) ---> Tray Pool

Coal Mining Sebamban

Indonesia earth simply to save so much once natural resources is including coal energy resource. Kalimantan and Sumatra is island with the biggest coal producer in Indonesia. From strarting small industry (ceramics, tile, textile) until big industry like PLTU and cement factory applies coal as component of burning.

Sebamban is part of region Kecamatan Kuranji Kabupaten Tanah Bumbu Kalimantan Selatan, from banjarmasin is gone through with journey of land toward smooth stone ± 5 hour. This area topography hill and dale by cultivated trees of acacia which is including Hutan Tanaman Industri. So do with plantation of oil palm which almost flattens all this region.



Activity of coal mining included in region Sebamban VI Kecamatan Kuranji Blok B, started with making of road(street hauling towards base camp mine along the length of 2,3 kms. Making activity of this hauling road(street covers making of drainage through the street, Bridge from acacia wood and accumulation of road(street with material claystone and laterite. Making of road hauling is done by means of ... excavator PC 200-7 and Dozer D85-ESS and requires time ± 4 month of considering weather with high rainfall and condition of equipment where its Mechanical Availability under 75%.

Phase hereinafter is making of base camp mines for mess, office, warehouse, workshop which required time ± 3 month. After construction work completed equipment excavator PC 200-7 and Dozer D85-ESS does making activity of stockpile mine with a width of 3/4 Ha and making of road(street hauling from mine to stockpile and preparation disposal. Making activity of this hauling road(street covers making of drainage through the street, Bridge from acacia wood and accumulation of road with material clay stone and laterite.

Phase hereinafter is land clearing for areal which would in mine is continued with work of O/B Removal covering dig, loading and

Rainbow in the sky Sebamban

This is appearance rainbow an evening in the sky sebamban, it is said he/she said the houris alights from fairyland to take a bath and its(the shawl is outspread is celestial to forms variegation bunch (red, yellow and green) which so beautiful. And this rainbow appearance inspires to all musicians to create a song following the sample :


" Rainbow Rainbow what a respect you

Red turned yellow blue sky green

You paint is who is the bloody hell classiness

creation rainbow rainbow of The infinite"

The Rareness Ulin Wood

Ulin Wood is wood that is famous and strong and good is earth by "urang banua", this rose colored wood of brick if abrading its skin. This wood many applied by people for construction work like house, office, and or bridge create. Formerly this wood so much and easy to be got by has not tightened it permit from forest usage rights. However the existing of this wood after rareness because forest which has started pot is clean is cut away.