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Technical Paper October 2015
Pipe Conveyor; New Start to Solve Urea Handling Problems
Alireza Orooji
S.Sajjad Hosseininia
Pardis Petrochemical Company, Process Engineering Department
Assaluyeh,Bushehr,Iran [email protected]
Introduction
New developments in the pipe conveyor and belt are advanced to address the growth in the capacity, length and complexity of pipe conveyor systems. These modern day conveyors in various configurations offer unique solutions to the everyday problems of belt conveyors and are accepted by the modern plant design engineers.
The selected pipe conveyor eliminated the need for multiple transfer points and conditioned galleries. Urea product is reclaimed from the bulk halls and transferred to the pipe conveyor, which envelops the product, thus protecting it from dust and humidity.
Improved belt construction can offer better stability during horizontal curves and resistance to twist. Low rolling resistance rubber compound can significantly lower the power consumption and belt tension, producing capital and operation cost savings. Dynamic analysis, when used to analyze the conveyor’s starting and stopping behavior, can improve the design and reliability Urea handling pipe conveyor systems.
Pipe Conveyor; New Start to Solve Urea Handling Problems
Alireza Orooji
S.Sajjad Hosseininia
Pardis Petrochemical Company, Process Engineering Department
Assaluyeh,Bushehr,Iran [email protected]
Introduction
New developments in the pipe conveyor and belt are advanced to address the growth in the capacity, length and complexity of pipe conveyor systems. These modern day conveyors in various configurations offer unique solutions to the everyday problems of belt conveyors and are accepted by the modern plant design engineers.
The selected pipe conveyor eliminated the need for multiple transfer points and conditioned galleries. Urea product is reclaimed from the bulk halls and transferred to the pipe conveyor, which envelops the product, thus protecting it from dust and humidity.
Improved belt construction can offer better stability during horizontal curves and resistance to twist. Low rolling resistance rubber compound can significantly lower the power consumption and belt tension, producing capital and operation cost savings. Dynamic analysis, when used to analyze the conveyor’s starting and stopping behavior, can improve the design and reliability Urea handling pipe conveyor systems.
1. Pipe Conveyor History
The first pipe conveyor concept was introduced in 1978 by Japanese Pipe Conveyor (JPC), who proceeded to obtain worldwide patents. The basis for the patent was the ability to form a trough belt conveyor into a pipe shape using a unique belt construction and special pipe forming idlers.
Bateman (South Africa) were the first License Partner worldwide successful in marketing the system outside Japan. With other successful JPC Agents Internationally being Koch (Germany), Noyes (France), Nova (Italy), Dosco (UK), Simplicity (India), Krupp Robins (USA), Young Poony (Korea) and Sistemas (S. America).
Worldwide there are approximately 700 pipe conveyors in operation; they have a combined length of 160km with the longest being 5 km pulley centers.
Fig.1: Piping the Urea Product from Plant to Port by Pipe Conveyor System
When the pipe conveyor was first started in 1980s in Japan the principle benefits of using pipe conveyor was its ability to handle sharp curves and seal the transporting material. Rolling the belt into the pipe shape separates the material from the environment. It also reduces the area moment of inertia, which facilitates the bending of the pipe belt over horizontal and vertical curves. Over the last fifteen years, pipe conveyor saw not only increased number of installations and growth in the size and complexity of the system, but also better recognition by the general material handling sector as a feasible material handling system. India and China now represent the biggest market for pipe conveyors. In south-‐east Asia, Australia and South America, several major pipe conveyor installations are either operating, being erected or under planning.
If these initial high profile systems are perceived to be successful, it is reasonable to expect that more pipe conveyors will be planned and installed during the next decade in these areas.
In urea industry, Qatar Fertilizer Company (QAFCO) has currently in operation one of the largest urea handling capacity pipe conveyors.
Fig.2: Eliminate Multiple Transfer Points and Galleries
2. Future Potential of Pipe Conveyors
Krupp Robins of the USA try to take the Pipe Conveyor to new levels of performance after Bridgestone took over the JPC Company in the early 1990’s. It was only at this time that efforts were made to take the conveyor towards its true potential.
From this combined Krupp Robins / Bridgestone effort, the JPC pipe conveyor was taken over the 5km long barrier in 1994 in Venezuela. Today, numerous pipe conveyor projects of 10 km in length and more are being considered, with capacities exceeding 2500 tons per hour.
Fig. 3: Two parallel 300mm diameter heat resistant Confine fabric pipe belts and a 400mm
diameter Confine fabric pipe belt.
Fig.4: 400mm diameter ST1100 Low Rolling Resistance Pipe Belt.
3. Limitations of Current Belt Conveyor Systems
Belt conveyors have been widely applied in the urea plants for several decades. The main benefit of belt conveyors compared to other material handling machines like trucks, trains and barges is the higher efficiency in the mechanical system, energy consumption and total cost over the long term, especially when conveyor system is design optimized.
Fig.5: Conventional Belt Conveyor in Urea Handling
3.1 Some limitations of a belt conveyor are:
a) The loading and transfer points need to be properly designed. b) Dust making during urea handling in transfer points. c) The effect of galleries air condition on urea quality. d) Numbers of protective devices have to be incorporated to save the belt from getting damaged by operational problems.
e) The belt needs higher initial tension (40-‐200% of useful pull). f) Conveying of sticky urea is associated with problems of cleaning and discharge causing poor productivity.
g) Higher elongation of the belt (4% elongation may take place at the working load).
h) Belt slips when conveyor is started.
i) Belt slips while running. j) The covers are hardening and/or cracking.
k) A certain section of the belt runs to one side regardless of the location on the conveyor.
l) The belt runs to one side only in a certain section or portion of the conveyor. m) Belt runs fine when it's empty but wont track right when it's loaded.
n) You are experiencing excessive belt stretch.
Fig.6: protecting Urea from dust and humidity
4. Application of Pipe Conveyors
Pipe conveyors find their application in virtually every industry for the transport of bulk solids. These include cement, fertilizer, coal, power, steel, pulp and paper, food grains etc. Pipe conveyors overcome several of the problems commonly associated with conventional conveyors, e.g. spillage of materials, belt training, limited angles of conveyance, horizontal curves and multiple flights. Pipe conveyors have also developed as an alternative and significant energy saving device to pneumatic means of conveying of fine material.
Fig.7: Comparison of a 400mm ST1250 Confine pipe belt with a FEA model of the same belt. FEA simulation of Confine (left) and conventional (right) pipe belt during horizontal curves.
Fig.8: Multi Layer Rubber Used in Pipe Conveyor Belts
5. Advantages Material Transport by Pipe Conveyors
The pipe conveyor resembles a troughed belt conveyor at its tail end where the material is loaded. Thereupon the belt is made to pass over a series of transition idlers of varying trough angles to form the pipe shape. Prior to the discharge pulley the belt is made to open to effect material discharge over the head pulley drum. Largely due to reasons of engineering geometry as well as with a view to keeping the dirty side of material with the pipe shape, the return belt is also made to form the pipe shape.
F Fig.9: Non Stop Urea Handling and Vessel Loading During Rainy Weathers
5.1 Environmental protection and totally enclosed conveying
In the last few years environmental policy has played a primary role vis-‐a-‐vis the complex problems of pollution. Industry must supply all technical solutions it has available.
One of the big advantages of a pipe conveyor is that material transported is contained within the rolled tubular shape of the belt for the majority of its conveying distance. This has the following benefits:
a) Environmental pollution is minimized as urea spillage is eliminated. b) The urea conveyed is protected from wind losses, spillage, contamination and rain.
5.2 High angle conveying
The increased friction between material and the pipe shape of conveyors due to packing makes generally a 50 % higher angle of conveyance possible by pipe conveyors as compared with conventional troughed belt conveyors to angles of inclination as high as 29 degrees. Therefore:
a) Smaller space requirements are required for installation making pipe conveyors viable solutions if there are space restrictions within the plant.
b) With the steeper angle of inclination the overall length of the conveyor system can be reduced.
5.3 Complex 3D profiles
The flexibility of the pipe shape permits the belt to be curved both horizontally as well as vertically. In many instances this is a big advantage as it eliminates transfer points where there is a relatively sharp change in conveyor direction. A single conveyor can thus replace several conventional belt conveyors reducing:
a) The need of multiple transfer points, drives, dust collection systems, structures etc all prone to operation and maintenance.
b) Reducing urea dust formation resulting from transfer points.
Fig.10: Twist and Turns which eliminate Urea Granule Degradation and Dust Production
5.4 Return belt conveying
The basic design feature of the pipe conveyor belt enables using the return side of the belt for conveying materials in the opposite direction. The conveying in of materials and conveying out of materials in a single belt possible in longer belt conveyor installations especially for plants in the vicinity of ports offer distinct cost advantages.
5.5 Same volume of material transported
A pipe conveyor transports the same volume of material as a conventional troughed belt conveyor that 2.5 to 3 times its pipe diameter. This means that pipe conveyor requires support structures of narrower widths and often lesser weights.
5.6 Power saving
When a single pipe conveyor replaces several conveyors in a system, the total power consumed is considerably lower. A series of several conventional belt conveyors also require additional power to lift material at each transfer point. When the pipe conveyor replaces a pneumatic mode of conveyance, energy savings pay for the pipe conveyor themselves.
6. QAFCO 5 & 6 Urea Plants Pipe Conveyor System Experience
Urea product from Qatar Fertilizer Company (QAFCO) Urea 5 and 6 plants is stored in two bulk halls E and F with capacities of 100000 and 175000 MT respectively. Bulk urea export from QAFCO is being done via two Jetties. A network of enclosed trough conveyors allows urea 5 and 6 plants to send their product to either of the bulk halls E and F. Pipe conveyor system was selected as the obvious solution to move granular urea in a single go from the bulk halls E and F to the Jetties. Two pipe conveyors are used to send urea products from QAFCO 5/6 to either Jetty 1 or 2. The conveyors length is about 2.8 km.
7. Key Elements of a pipe conveyor
Like a conventional belt conveyor, a pipe conveyor comprises of the belt, a feed section, the intermediate sections, the head or discharge section and the drive. Each of these sections is described below:
7.1 The pipe conveyor belt
As in a conventional troughed conveyor and dependent on the belt tensions the construction of a pipe conveyor belt could be fabric or steel cord. However as the belt is required to form the pipe shape, several important features are employed in its design.
A special carcass construction is employed as the belt requires adequate stiffness as it is made to form the pipe passing through the idler rolls. Flexibility for transition from the flat to pipe shape at the feed end and pipe to flat at the discharge end is also essential. A layer of special rubber compound is usually placed between each fabric ply to achieve this.
7.2 The loading section
The feeding or loading section of a pipe conveyor is similar to that of a conventional belt conveyor. To eliminate the problem of material spillage as associated with troughed belt conveyors, the FFE – CKIT company pipe conveyor feed zone incorporates a specially designed skirt board for effective sealing with low friction impact slider pads. A quick release mechanism enables impact rollers to be lowered for removal even with a moving belt and facilitates ease of maintenance. Uniform feed to the pipe conveyor is important in a pipe conveyor for its stability and tracking.
7.3 The intermediate and tubular section
The intermediate section of the pipe conveyor is the part where the belt is made to roll into a tubular shape. This is achieved by causing the belt to pass through a set of six idlers arranged in a circle each for the carrying and return run. To prevent “squeezing” of the belt, the FFE – CKIT company design incorporates offsetting of idlers alternatively on either side of the panel. The construction of the panel which is supported the idlers is very simple and can be fabricated from rolled steel sections / plates or pressed from sheet metal plates.
Fig.11: Pipe Making Stage on the Conveyor Route
Fig.12: Qatalum Handling System,Qatar. Partner: ThyssenKrupp. A pipe belt conveyor with a 2100 mm wide CONTI® PIPE 1600/5 G-‐K2 carries up to 2200 t/h of alumina and petroleum coke from the ship unloading facility to the Qatalum smelter.
Mounting holes are jig drilled to maintain idler mounting accuracy. With the pipe conveyor belt guided by idlers surrounding the belt on all sides, the conveyor is able to negotiate curves and centerline misalignments. To ensure that the belt overlap is located as near the top of the belt on the carrying side, a few set of training idlers are provided with adjustable bottom rollers. Assisting most in belt stability and also keeping the overlap near the center position is of course the weight of material conveyed in the pipe and its heavy center of gravity on the lower cross section of the belt.
On the return side where the overlap is on the bottom of the pipe shape, the extra weight of the overlap maintains dynamic stability of the belt.
7.4 The discharge end and drive
The discharge of the pipe conveyor is similar to that of conventional belt conveyors. The belt in the tubular form is allowed to gradually take the trough shape by a series of idlers of varying trough the angles. Material as discharged over the head pulley. Modern drives are used by FFE –CKIT in all their pipe conveyors which include high efficiency, compact space saving bevel helical gear unit shaft mounted to respective pulleys using shrink discs.
7.5 Triangular gantry and maintenance trolley
Overland pipe conveying systems offered can incorporate the FFE – CKIT triangular gantry. This eliminates access walkways and platforms along the length of the conveyor, providing a cost effective solution. Installed first by CKIT at their Richards Bay Pipe Conveyor installation in South Africa, these conventional facilities have been replaced by a self propelled traveling maintenance trolley, which is mounted onto the triangular gantry structure and travels along the full length of the conveyor with man carrying maintenance trolley.
Fig.13: 350mm diameter ST2000 EPDM heat resistant pipe belt, with material temperature 180°C.
8. ADVANTAGES
The pipe conveyor has the following generic advantages:
a) The belt encloses the material on the carry-‐side. This eliminates spillage and protects the environment and product conveyed.
b) Minimize the dust production during handling process. c) On the return-‐side the belt encloses the dirty side and eliminates spillage along the
conveyor. This is advantageous environmentally and reduces on-‐going clean-‐up costs. d) The pipe conveyor can handle tight horizontal and vertical curves thereby eliminating
transfer points and multiple troughed conveyors to perform the same duty of one pipe conveyor.
e) Material can be conveyed along the top and bottom strands simultaneously, along the same route, without spillage or contamination of the product.
f) The pipe conveyor is cost-‐effective. In some instances the pipe conveyor has a lower total capital cost than multiple troughed conveyors.
g) Pollution-‐free transport h) Formation of belt into pipe shape encloses the material during travelling on carrying side
and prevents leakage and dropping of materials on return run i) Easy lay-‐out designing j) Curved transport in horizontal plane k) More slope in inclined transport l) Reduced dimensions of the sectional area m) More compact supporting structures n) Easy cleaning and maintenance o) Particular attention to Safety
Fig.14: A Hypocrite snake, which decides to bite Urea Handling Problems
9. Some Points about Pipe Conveyors
a) The longest pipe conveyor installed is approximately 5.2 km in length and conveys petroleum coke at approximately 300 tons per hour in a 12” diameter pipe. Krupp Robius, Inc. in the USA supplied this conveyor. Conveyor Kit’s longest pipe conveyor is a 450 mm diameter pipe with a conveying capacity of 1800 tons per hour. The transport distance is 3.2 km. This conveyor is at Indo Gulf in India. Current technology is making pipe conveyors of up to 10 km in length feasible.
b) Currently technology enables to engineer pipe conveyors to deflect through a horizontal angle of 90°. An example of this is the Indo Gulf pipe conveyor designed by Conveyor Kit. The layout of each specific installation must be checked to ensure that a sharp bend can be accommodated.
c) The rule-‐of-‐thumb is that the pipe diameter should be four times the maximum lump size. Depending on the percentage of larger lumps however, this can be reduced to three times maximum lump size. The largest diameter pipe conveyor supplied by Conveyor Kit has been 450 mm. Pipe diameters of 500 mm and larger are theoretically feasible.
d) The required flexibility in a pipe conveyor belt to form and maintain the tubular shape is partially dependent on the belt design. The pipe conveyor belt is thus different to the troughed conveyor belting.
e) There are approximately six major suppliers of pipe conveyors worldwide, with substantial reference installations.
f) The greatest belt speed on a Conveyor Lit pipe is 4.2 m/s on a 900 m long, 2500 tons per hour installation at Richards Bay, South Africa. Belt speeds of 6 m/s and more are possible but may not be practical.
g) Multiple loading points can be used on a pipe conveyor. Provided these loading points are not located on a curve and there is adequate room to open and re-‐close the belt.
Conclusions
The invention of the pipe conveyor is one of the greatest inventions in the bulk materials handling industry.
It comes now clear that the pipe conveyor will be more cost effective, friendlier to the environment and a safer installation in comparison to almost all other conveying types in urea handling industries.
Resulting from the ability of pipe conveyors to handle urea product, the relative ease in accommodating single conveyors within layouts of existing plants, reduction in dust production during handling and subsequently reduction in caking problems, ease of operation and maintenance and export to ships during rainy or high humidity weather, pipe conveyors shall continue to find its main application within the urea industry as has been brought out statistically worldwide.
REFERENCES
1. Pipe Conveyor and Belt: Belt Construction, Low Rolling Resistance and Dynamic Analysis, Y. Zhang, Conveyor Dynamics Inc., Bellingham, Wa. , R. Steven, Veyance Tech., Inc., Marysville, OH. , SME Annual Meeting, Feb. 19 -‐ 22, 2012, Seattle, WA.
2. Staples, P. (2002), "The History of Pipe Conveyors", Bulk Solids Handling, 22(3).
3. Imai, A. (2011), "Pipe Conveyor Development, Benchmark and Future Trend", in Bulk
Solids India 2011, India.
4. Urea Handling at QAFCO, © ThyssenKrupp Fördertechnik GmbH / BulkInside