Experimental studies on coals of different metamorphic grades and
various fractional states were conducted in 2000 by the Institute of
Thermal Physics of the Russian Academy of Sciences, at experimental
thermal energy facilities. These showed that fine-ground coal, milled to
a particle size of 15-30 microns, develops a highly reactive property
that is analogous to fuel oil - to which it can become an alternative.
The experimental facility was rated at up to 1000 kW, and equipped for
use with ultra-fine ground coal (produced with an ultra-fine ball mill);
burning (pre-furnace and furnace equipment); a plasma system and gas
starter for ignition and supplementary firing; combustion control (an
automated post for combustion control) and cleaning (a vortex scrubber).
The results produced in these experiments can be used to establish the
parameters needed in technological facilities for ignition systems and
supplementary burning using coal-dust boilers - a replacement fuel for
gas and fuel-oil boilers.
The conclusions from these theoretical
and experimental studies pointed to the technical and economic viability
of using ultra-fine ground coal as a new oil-free technology for the
ignition and stabilisation of combustion in coil-fired boilers at power
plants, in addition to the ability to replace liquid fuels in boilers.
The
primary technological facilities for making use of this new technology
are: equipment for ultra-fine milling (ball mills), and the
supplementary equipment for supplying and combustion of coal. Technical
designs for the supplementary equipment have been developed, which are
essential for wheeling-out the new technology (muffle furnace apparatus,
input nozzles for the coal dust, accelerating devices for igniting the
primary fuel mixtures, feeders for fuel discharge, hoppers for storage,
and so forth). Factories able to manufacture the new supplementary
equipment already exist in Russia. The last-mentioned also produces
milling equipment, and specifically ball mills for ultra-fine milling
processes.
This new technology is low-cost, with a short
return-on-investment cycle which will hit break-even in no more than 2
to 3 years. The additional financing costs are in producing the
ultra-fine ground coal (the purchase of ball mill machinery) - the
additional machinery also has a short investment payback cycle due to
the economics of the fuel supply industry.
The new Plasma-fuel
technology has now passed the final stages of certification - for pilot
industrial use. This allows assessment of the risks of the new
technology - and if required, it can be further honed to optimise its
operation prior to finalising the business case which can be put to
potential investors.
Converting oil-fired boilers to run on ultra-fine ground coal
The
primary task is moving to rejecting the use of fuel oil by the facility
in future. Of course, in places where it is available, it makes sense
to change to using natural gas. However, where this is not an available
option, then such facilities can be converted to run on ultra-fine
ground coal. The economic result of making the change from fuel oil to
ultra-fine ground coal will be in the greatly reduced cost of fuel. Over
and above this, there is an environmental gain to be made - since there
will be a marked reduction in the emission of sulphurous oxides into
the atmosphere. This has a further economic benefit, in terms of
decreased payments to be made for such emissions.
When making the
changeover to using ultra-fine coal, the issue of disposal of the ash
waste which it produces needs to be addressed. For facilities currently
using fuel oil, this can be problematic. In the first instance, this
issue could be resolved by making agreements to remove the ash and slag
waste from the boiler room to nearby ash dumps or industrial sites. This
process could lead to a loss of some of the cost benefits of making the
changeover. But in a more positive light, the ash and slag waste can be
recycled as a component in the manufacture of construction industry
materials, mineral components, and similar by-products. Installing a
production line for the recycling of slag and ash is not only a
responsible way of negating environmental pollution - but can similarly
cull in economic benefits.
This means that the issue of converting
oil-fired power stations to run on ultra-fine ground coal can be easily
resolved both technically and administratively. Each individual case
for conversion should properly be put through a business plan, including
a technical survey of the boiler equipment, and the prevailing economic
situation.
Evaluating the efficiency
Energy
efficiency can be determined by making a comparison with the costs of
fuel oil operation (i.e. the current costs), against the projected costs
of transferring the facility's operation to ultra-fine coal (the
current costs, plus the cost of additional equipment). To make these
estimates for the current costs, it follows that the costs of the
current in-purchasing of fuel oil should be compared against the costs
of purchasing coal, plus the additional electricity costs incurred in
the grinding process. Particularly concerned with this latter cost, it
pays to consider the choice of grinding machinery in the light of its
electrical consumption costs. It makes obvious sense to purchase
machinery with the lowest energy operating costs. Furthermore, when
weighing up the decision to switch from fuel oil to ultra-fine coal, the
operation of installing the additional equipment needed for ignition of
the ultra-fine coal must be carefully considered.
Essential equipment:
The
ball mill for grinding ultra-fine coal is essential. This kind of
coal-grinding apparatus to create combustible fuel is traditionally
divided into several categories. Quiet-Operation Slow Ball Mills operate
with a rotation speed of 16-23 revs per minute. Fast-Action Tangential
Mallet Mills have an operational speed of 590 to 980 revs per minute;
and there are also Medium Roller Mills which rotate at 40 to 78 revs per
minute. The table of ultra-fine coal dust obtained is below, depending
upon the type of machinery chosen.
- Ball drum mills are used for grinding anthracite and bituminous coal
with a milling operational range of ≤ 1.1 and low volatility required
fine grinding (6... 7 %). If the raw source material to be milled
includes some presence of pyrite sulfur fuel ( up to SP > 6 % ) then
only ball mills can be used.
- Hammer mills are used for brown and black coal of relatively high volatility (Vg > 30 % ).
- Medium Roller Mills are used for grinding coals with a milling
operational range of at least 1.1 Wp and humidity of no more than 16 %,
with an ash content of no more than Ar 30 %
Additional Equipment required for producing the ultra-fine coal fuel:
- crusher
- crushed coal bunker
- coal feeder
- high-pressure fan
- coil-dust burner
- muffle furnace extension
- blowing fan
- milling shelf
- cyclone dust collector
The primary rationale for undertaking the technical
changeover is to replace expensive and increasingly-scarce fuel oil -
traditionally used for the ignition and stabilisation of combustion in
coal-fired thermal plant boilers - and also to replace liquid fuel oil
in boilers. Issues of economic efficiency in tandem with environmental
responsibility should underlie decisions for making the changeover. Coal
combustion can make up part or the whole of the combustion process in
combination with other resources, and offers enhanced productivity for
boiler equipment along with reductions in fuel consumption when
producing energy through combustion processes, along with an improved
level of cleanliness and purification in the resulting flue gases.
The Strommashina plant in Samara produces and installs all of the above-mentioned and recommended kinds of
ballmill and mill machinery - as well as dryers, crushers, feeders, cyclones and separators.
Strommashina has been producing reliable
power generating machinery
since 1942. Over that time, the corporation has been continuously
honing its technology and quality control - thus resulting in
Strommashina's appearance on the world market for industrial equipment.
The company's specialist staff are on hand to offer their advice in
designing and purchasing equipment, as well as providing expert
technical advice and support at every stage of the design, set-up,
inception and operation of the equipment they produce.
Strommashina's Strong Points
- Geographical
convenience - Samara is a big transportation hub located in the middle
of Eurasia. The railway sidings are part of Strommashina's Plant
infrastructure. River port accessibility provides ease of connectivity
to Europe and Central Asia.
- Installation supervision (comprehensive control over how equipment and production lines are installed and commissioned)
- 1 + year warranty
Have a question or need a quote? Please, feel free to Contact us!
Strommashina Corp.
22 Partsyezda st., 10a, Samara, Samara Oblast, Russia, 443022
Tel: +7 (846) 374-1741
