Cyclic-and-continuous technology (CCT) based on steeply inclined conveyor (SIC)
Far into the CCT for ore based on high-capacity steeply inclined (370)
conveyor with capacity of 3500t/hour with lifting height of 270 meters
(see photo and video) was first implemented on a quarry "Muruntau" (Navoi MMC, Republic of Uzbekistan).
1. Composition of the CCT-ore.
In CCT-ore envisaged:
CRS — crushing-reloading station;
SIC — steeply inclined (high-angle) conveyor;
LCS — loading-storage complex;
ACS "CCT-ore" — computerized control, management and monitoring system.
Each of these objects, or unique, or has its original solutions. Special attention at development was paid to selection of SIC route and
determination of main process values of CCT — technical capacity of 3,500 t/h (2,000 m3/h) and working capacity of 16 million t/year.
2. SIC -270 steeply inclined conveyor.
Becoming a single flight of SIC-270 combines high-angle and low-angle parts. The tilt angle of high-angle part was determined by steady
configuration of the side. Size of sections was determined by height of benches. Section props are located on bench bottom. The high-angle part of SIC-270 is made with pressure belt. Cargo lifting
height by such SIC is determined by total strength of two belts. Changing speed, belt parameters and technical capacity one can receive lifting height, which is necessary in specific mining-technical
conditions. For Muruntau quarry the lifting height by one flight is accepted as equal to 270 m. There is a possibility of further lowering by extra 180 m at SIC-180 installation. Thus, the total lifting
height can reach up to 450 m.
The Length of SIC high-angle part is 480 m and consists of 12 sections. Mounting of these sections up to 51 m long and weighing up to 84 t was
performed by successive lowering of sections assembled at section installation site using truck-mounted cranes. Maintenance of the high-angle part's linear sections is provided to be performed using repair
trolley, which moves along SIC metal structures by a radio control device. Rope haulage is provided for inspection of SIC high-angle part and people delivery to the CRS.
Both belts SIC are actuated independently by group electric drives, which have the following scheme: two drums of load-carrying belt 4*630+2*630
and one drum of pressure belt 2*630 kW. Eight electric motors with total power of 5,000 kW in total. Presser belt drive located at a distance more than 300 m from the load-carrying belt drive. Technical
solutions to provide for the following: the joint smooth start and operation of the two belts, redistribution of load between all engines, discrete and smooth adjustment of the pressure belt speed to synchronize
the movement of the joint belt. In the process of setup the relative speed of two belts was at a level of up to 3 mm/sec, i.e. sliding is less than 0.1%.
3. The main components of LCS.
The main components of the LCS are storage conveyor, self-propelled loader-stacker for the rocky LSR, buffer conveyor and standby motor
vehicle storages.
Irregularity of ore delivery to the surface and its shipment to the plant is compensated by buffer conveyor storage. In case of dump cars absence
ore is delivered to the buffer conveyor storage. Continuous direct loading of ore to dump cars or conveyor storage is provided by LSR with trolley, which is built organically into the storage conveyor,
which allows unloading ore along railway tracks and buffer storage. Reverse conveyor LSR allows loading ore into railway dump cars or storage.
To implement the direct flow of shipment by placing two railway
tracks were laid and train of 11 dump cars is formed at the station near the storage, they are delivered to these tracks each 20-25 minutes in succession. As a result, ore is delivered continuously from
the quarry bottom to the plant without unnecessary reloading on the surface.
Shipments from storages are bucket excavator with extended boom. The volume of shipments from the warehouse conveyor expected 20-30%,
and automotive (backup) storage 5-6% of the total shipment. . It is planned that shipment volume from the conveyor storage is to be 20-30% and that from the motor vehicle (standby) storage 5-6% of
the total shipment volume. The LSC scheme allows using CCT both for ore and overburden, which has been implemented as of today.
4. Crushing-reloading station (CRS).
A screw-tooth crusher STC, which can be referred to energy-saving equipment, is installed at the CRS. Its mechanism provides for impact
split-up of oversized lumps, but not their squeezing by compression in operating cone and jaw crushers. Horizontally mounted auger-toothed crusher shafts allows to reduce its height, and the
counter-rotating balancing shafts disturbing forces, which eliminates the need for building a strong foundation for the perception of the reaction.
In order to load the crusher, a traditional scheme with receiving hopper and feeder has been accepted. Besides, instead of plate feeder
belt feeder is used, which is recognized to be better solution and is recommended for all new CRS. Grizzly screen is installed between the belt feeder and STC; it screens fines and increases
the service life of more complex crusher components.
The solution on keeping the buffer storage near the receiving site of the CRS has been maintained. The original solution of the CRS layout was
proposed and implemented. It provides for using bearing capacity of the massif-pillar in the area of the receiving site. As a result, the height of the retaining wall was reduced considerably,
up to 9.5 m. NMMC specialists developed a solution, at which pressure of dump trucks is taken up not by the reinforced concrete retaining wall, but by prefabricated metal structures.
Such solution allows removing the retaining wall and moving it to a new place of operation, which will provide faster movement of the CRS to a deeper horizon.
Control System ACS "CCT-ore" is completely computerized from the bottom to the top level. It has a plentyof diagnostic functions,
which help both at process modes of operation and at the complex start to find faults in case of emergency shutdown, give much material for equipment operation recording and analysis and for staff.
Monitoring of the technological process status and progress, as well as management, down to start of a separate drive on machines of the complex,
is performed from computer screen in the central control room (CCR) and operator's panels with graphic display in the CRS and LSR cabs. A new type of the line shutdown has been provided — direct,
program, i.e. not up the flow, but from the place of its formation to full unloading of each conveyor. As a result, rock is unloaded from the whole line facilitating next start, which is especially
important for SIC with its drives with capacity of 5,000 kW. Emergency counter-current shutdown is also maintained for those cases when direct-current software shut-down is not allowed
(for example, from emergency rope switch).
All operations are recorded in log of programmable logic controllers PLC and computers of the central control room (CCR), which allows restoring
history of previous events In case of failure of ACS components its self-diagnostics is fulfilled; according to its results a specific element to be restored is indicated. A service bench provides for staff
training, software and hardware testing, setup of new functions and changes in programs. Maintenance staff has restrictions in access to available functions according to its qualification and functions.
Trends, which reflect graphically in scale the most important current processes and processes for previous shifts during more than a month appeared
to be very illustrative and useful for optimization of electric drives of 8 engines.
6. The main advantages of the CCT with a steeply inclined conveyor.
Total length of conveyor belts (load-bearing and pressure) of high-angle part is almost not reduced as compared to standard inclined
conveyors. However, the benefits of CCT-based SIC are available, and they are shown in the accompanying costs:
1) SIC installed almost without additional mining and development works in a narrow strip of this side, which does not restrict development of mining operations throughout the quarry contour, does not require making of special trenches or shaft sinking;
2) less overloads and no need in creation of haulage benches for maintenance, which reduce general angle of the side by 7-8 degrees, what requires either suspension of mining operations or expansion of sides in this zone;
3) wider opportunities on layout of conveyor transport routes, which configuration can combine areas with different tilt angles;
4) necessity of primary ore crushing is excluded at its transportation;
5) possibility of further buildup of conveyor lowering depth (option of one more SIC-180 installation has been prepared);
6) it should be noted specifically that at the average service life of dump trucks of 6-7 years it will be necessary to renew the park of dump trucks, which is emptied by CCT-ore, thrice during the de-sign resource service life of CCT-ore being 20 years.
7. Main Areas of CCT-Ore Creation
1) Working project CCT-ore was developed by Institute "UkrNIIproekt" (Kiev) according to the Technical Assignment of Navoi Mining and Metallurgical Combine. Implementation of design documentation on CCT-ore for Uzbekistan was performed by the General Designer of Muruntau quarry — Institute "UZGEORANGMETLITI" (Tashkent).
2) Development and production of individual process equipment, including SIC and LSR were performed by Novokramatorsky Mashinostroitelny zavod.
3) Computer control system ACS "CCT-ore" was created by
"Constar" (Ukraine, Kharkov),
"SC Krona" (Latvia, Riga) and Institute
"UkrNIIproekt" (Kiev).
4) Equipment was delivered by
ALTEKO ACTION TRADE during 2 years from the date of the Technical Assignment approval. Construction and assembly works were performed by Navoi MMC during one year; startup-and-commissioning works with involvement of suppliers and designers were completed within 100 days.
8. Conclusion.
1) Based on height of rock transportation by high-angle conveyor (270m, 370), capacity (3,500 t/h) and reloading on the surface directly to railway transport without additional transshipment, CCT-ore of Muruntau quarry is considered to be the largest engineering facility and has no analogues in the world practice in open cast mining.
2)
The first trial start of CCT-ore was on the December 28, 2010
and transfer to run-in and trial operation
was on the 17th of March, 2011. Commercial operation started on the 21st of June, 2011. , during which of July 31, 2012:
shipped about 12.5 5 million t of mountain mass;
the burst performance of 1,040 million t/month is attained., and 46300 t/ch or 3860 t/h is shipped in one of 12 h of changing (i.e. the project monthly and removable operating productivity already exceeded);
for the first half-year of 2012 technological outages were 30,7%, i.e. there is substantial reserve for the further increase of the productivity;
for the first half-year of 2012 emergency outages were 11,5%: mechanical - 7,0%; electric - 3,0%; computerized control system - 1,5%;
at transportations of mining mass on the average distance is brief a motor transport on 3,5км, run on 30,4%, amount of drivers and repairers - on 27,2%, expense of fuels and lubricants materials - on 37%;
running expenses are reduce on 2,7 million $ in a year.
3) CCT introduction to SIC gives an opportunity to continue the field quarrying to a depth around 1000 m.
4) Cyclic-and-continuous technology based on steeply inclined conveyor for quarrying can be used in underground mining, in particular when opening new horizons.
