Re: Optimum Design Of Slurry Pipelines
You are doing excellent work in a discipline which sorely needs it.
Regarding HDPE pipes. Thirteen years ago I was presented with the celerity examinations for a composite pipe & although the results were eventually satisfactory the poisson's ratio selected had to be justified. Is there a table of poissons ratios/elastic moduli for polymer pipes available somewhere, even within your available published papers, or in the program, or anywhere else that you can suggest? ■
Re: Optimum Design Of Slurry Pipelines
My software considers different values of modulus of elasticity at different temperatures for HDPE pipe. I am giving here 2 values:
1530 MPa at 10 deg C & 1300 MPa at 23 deg C.
HDPE pipe was ruled out in both my consultancy projects of 18 km and 220 km long slurry pipelines. Operating pressures in these pipelines considering the surface roughness similar to that of HDPE (i.e. 5 micron) were 2.7 MPa and 16.5 MPa which is larger than the maximum operating pressures permissible in HDPE pipelines (1.8 MPa). ■
Re: Optimum Design Of Slurry Pipelines
Dear Dr. D. R. Kaushal,
Criteria 1, also applies in pneumatic conveying.
My pneumatic conveying computer program shows the same phenomena as your slurry conveying calculation describes.
In pneumatic conveying, of course, the compressibility of the used carrying gas is an extra parameter to consider.
Other parameters, such as water hammer, do not pose a problem in pneumatic conveying.
Sometimes, pressure waves in a pneumatic conveying pipeline do cause problems, as those pressure waves cause fluctuating velocities along the pipeline.
Very interesting.
Best regards
Teus ■
Teus
Re: Optimum Design Of Slurry Pipelines
My particular interest in 'pulp hammer' stems from a recent awareness that the pump casings are not NDT'd by most reputable manufacturers. Their excuse is, universally, that the test fluid is not available. Only water performance curves are established.
In slurry pumping the pressures are quite high & I am interested to hear opinions about the safety of pump casings, which may carry inherent undetected manufacturing flaws to an operator's grave, when hit by any overpressures.
Until very recently I was under the delusion that slurry pumps were manufactured in a quality regime that could support the rated casing pressures. With some major manufacturers this is not the case & it worries me. Should consultants specify API's or similar & let the customer carry the expense? ■
Re: Optimum Design Of Slurry Pipelines
During design calculations, i came to know that 3 mm of Carbon Steel API 5 L X65 Steel was able to sustain a pressure of 9 MPa. The worst case water hammer pressures in 18 Km and 220 Km slurry pipelines which I designed was found to be around 9 MPa without rupture disc and 25 MPa with rupture disc arrangement at terminal valve facility, respectively. ■
Re: Optimum Design Of Slurry Pipelines
Thanks for the reassurance.
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Re: Optimum Design Of Slurry Pipelines
yes, it is absolutely safe. There are slurry pipelines of more than 300 km lenghts having pumps of larger capacities operating successfully for last many years. These pipelines are transporting many types of minerals simultaneously in batch mode by seperating two batches with water. Advanced technologies sends signals at terminal facility about arrival of a particular batch so that different minerals may be collected in different containers. ■
Physical State Of Iron Ore Slurry- Large Volume Stored
Ladies and Gentlemen,
Could I kindly ask those of you with iron ore experience what the probable physical state (solid, slurry, mixed) of iron of slurry (salt water) may be that is in a closed tank in 60 meters of water, and after 25 years in the tank - warm water conditions? The iron ore slurry was used as heavy ballast instead of water. We need to decomission the tank and do not know if such material would normally oxidize and form a solid material that cannot be pumped out. The volume is over 500 tons.
Thank you in advance for any input or references that may help us make a preliminary determination of the probable state of the iron ore slurry today.
Mark ■
Iron Ore Ballast Sedimentation
Originally Posted by mneillamb
Could I kindly ask those of you with iron ore experience what the probable physical state (solid, slurry, mixed) of iron of slurry (salt water) may be that is in a closed tank in 60 meters of water, and after 25 years in the tank - warm water conditions? The iron ore slurry was used as heavy ballast instead of water. We need to decomission the tank and do not know if such material would normally oxidize and form a solid material that cannot be pumped out. The volume is over 500 tons.
Thank you in advance for any input or references that may help us make a preliminary determination of the probable state of the iron ore slurry today.
Mark
Hello Mark and welcome to the forum.
The iron ore will have to be dewatered to the level of the settled ore and then the fun begins.
The ballast tank will need to be ventilated continually and a determination made with poison gas monitoring equipment whether it is safe to enter with out SCBA equipment.The use of a hand held gas monitor need to be used while in the ballast tank.
You might get lucky using a fire hose to break it loose and pump it out with a large double diaphram mud pump if you have sand piper with large diameter hose to use.
If not the standard method of digging and filling a shaft sinking bucket using a hoist will have to do. but if you have room for a skid loader to be lowered in the ballast tank it will go faster using a small digging bucket and a back hoe attachment but the ballast tank must be continually ventilated at all times even when empty as many gasses harmful to life are heavier than air especially carbon dioxide and hydrogen sulfide.
The other option is a the "guzzler mud pump" which is used to dewater mud pits for drilling sites- all hydraulic drive, high volumes and fast delivery of solids- rentals are available I think the mud puppy screener removes the water out of the product stream and give a very dry product to handle.
High pressure water from a deluge gun or fire hose could be used to essentially wash it out to the pump and as the pump sinks it will be pulling any and all loose material as it works and it will behave just like a suction dredge.
The Guzzler can run dry safely as well.
lzaharis ■
Re: Optimum Design Of Slurry Pipelines
Originally Posted by lzaharisThe iron ore will have to be dewatered to the level of the settled ore and then the fun begins.
The ballast tank will need to be ventilated continually and a determination made with poison gas monitoring equipment whether it is safe to enter with out SCBA equipment.The use of a hand held gas monitor need to be used while in the ballast tank.
You might get lucky using a fire hose to break it loose and pump it out with a large double diaphram mud pump if you have sand piper with large diameter hose to use.
If not the standard method of digging and filling a shaft sinking bucket using a hoist will have to do. but if you have room for a skid loader to be lowered in the ballast tank it will go faster using a small digging bucket and a back hoe attachment but the ballast tank must be continually ventilated at all times even when empty as many gasses harmful to life are heavier than air especially carbon dioxide and hydrogen sulfide.
The other option is a the "guzzler mud pump" which is used to dewater mud pits for drilling sites- all hydraulic drive, high volumes and fast delivery of solids- rentals are available I think the mud puppy screener removes the water out of the product stream and give a very dry product to handle.
High pressure water from a deluge gun or fire hose could be used to essentially wash it out to the pump and as the pump sinks it will be pulling any and all loose material as it works and it will behave just like a suction dredge.
The Guzzler can run dry safely as well.
lzaharis
Dear sir
MAY I ASK FOLLOWING BASIC QUIRIES
1) What si significance of transition velocity (velocity transit from laminar to turbulant)
2) Why the high concentrated throughput requires more pressure than lean slurry ■
Re: Optimum Design Of Slurry Pipelines
Dear guddu
Transition velocity is the flow velocity below which flow becomes laminar. Particles have a tendancy to settle down at pipe bottom in laminar flow. That is why operating flow velocity is always kept larger than both the transition and critical deposition velocity in slurry pipeline.
Pressure drop in pipeline for flow of highly concentrated slurry will obviously be more than the flow of dilute suspensions due to increased particulate interactions and their collisions with pipe wall & bottom.
D.R. Kaushal
http://web.iitd.ac.in/~kaushal ■
Re: Optimum Design Of Slurry Pipelines
Originally Posted by D.R. KaushalTransition velocity is the flow velocity below which flow becomes laminar. Particles have a tendancy to settle down at pipe bottom in laminar flow. That is why operating flow velocity is always kept larger than both the transition and critical deposition velocity in slurry pipeline.
Pressure drop in pipeline for flow of highly concentrated slurry will obviously be more than the flow of dilute suspensions due to increased particulate interactions and their collisions with pipe wall & bottom.
D.R. Kaushal
http://web.iitd.ac.in/~kaushal
Dear Dr Kaushal
You stated o in previous thread " concentration at which critical deposition velocity and laminar/turbulent flow transition velocity coincides will correspond to the optimum design concentration.". Can you elaborate and explain the same . The reason iam asking , you also stated that the flow velocity shall be higher that the critical deposition and transition in order to avoid any choking in pipeline , than how is it possible to coincides the critical deposition and transition velocity ■
Problem With Iron Tailing Pumping
hello
first i beg your pardon because i am not fluent in writing english.
I am working as a process engineer in an iron processing plant (tailing recovery not iron ore from mine).
in this plant clogging of tailing pipeline causes some problems. the pipelines comes from underflow of thickener. properties of this stream is :
120 tph solid iron ore tailing
80 m3 water
density of solid 4 gr/cm3
maximum solid percent 60
pipeline length 900 meter
top size 1.5 mm
d80 900 micron
static head 20 meter
i remark that the plant is not working with its full capacity and rate and solid percent above is ones of design. the solid percent of tailing now is about 30%.
would you mind give some suggestion about what kind of pump and with what characteristics is needed.
i asked help from a consulting company but i tend to have the basic view.
thanks regards. ■
Re: Optimum Design Of Slurry Pipelines
Dear m.qaredaqi,
You have not mentioned the pipe diameter and flow velocity in your post. Before making any comment, I would like to see the design and testing reports. Slurry pipeline transportation of Iron ore tailings with specific gravity of 4, top size of 1.5 mm and d80 of 0.9 mm needs a very careful design. However, if I presume that design is OK, concentration of 30% which is half of the design concentration (60%) may be a cause for clogging of pipeline. At lower concentrations, interference effect due to surrounding particles reduces, and particles start settling down. You can run your pipeline in batch mode at design concentration to stop the clogging of pipeline.
D.R. Kaushal ■
Re: Optimum Design Of Slurry Pipelines
diameter of designed pipe is 6 inch (with SDR of 11) and it's made of polyethylene. average velocity of pulp is 2 m/s. I want to replace the pipe with a narrower one. but because of increasing friction due to this change, i am worry about pressure drop (head of pump is 52 m). i want to mention that most of this pipeline path is horizontal. unfortunately i could not find reports about the pipeline so far.
thanks for attention D.R. Kaushal. ■
Re: Optimum Design Of Slurry Pipelines
Flow velocity of 2 m/s is not sufficient enough to keep the iron ore tailings (with specific gravity of 4, top size of 1.5 mm and d80 of 0.9 mm) in suspension. Your pipeline is bound to have clogging problems. I have experimental experience for flow behaviour of such tailing slurries in my laboratory. I will suggest you to get your pipeline redesigned by some expert.
D.R. Kaushal
http://web.iitd.ac.in/~kaushal ■
Re: Optimum Design Of Slurry Pipelines
Slurry pipelines are also considered to de-silt or remove silts from deposits behind dams in man-made lakes. After the Hurricane Katrina disaster there have been proposals to pump silt to the shore and remedy the environment. Proposals have also been made to de-silt Lake Nubia-Nasser in Egypt and Sudan by slurry pipelines as Egypt is now deprived of 95% of its alluvium that used to come every year. These projects to remedy the environment will be very beneficial to the damage caused by large dams and man-made lakes. ■
Problem With Iron Tailing Pumping By M.qaredaqi
i have been involved periodically with solids transport in pipelines and launders for 20+ years and have taken a greater interest over the past 2+ years. i am working on methods to arrive at carry velocities and hydraulic gradients for slurries and came across this thread in the forum. d.r. kaushal, because of your level of knowledge and research in the field i would like to see your comments on my solution for the problem stated by m. qaredaqi above, specifically pumping iron tailings under the conditions:
120 tph solid iron ore tailing
80 m3 water
density of solid 4 gr/cm3
maximum solid percent 60, current 30% solids
pipeline length 900 meter
top size 1.5 mm
d80 900 micron
static head 20 meter
through a 6" dr11 hdpe pipe
by using plitt's equation with ß = 2.75 to determine a PSD based on d80=900 micron, and 1500 micron max particle size, i arrive at a d50 of 660 micron. this is a very tight PSD for a slurry. by applying the conditions to the durand, wilson and mti holland models for carry velocity at Cw=60%, i arrive at Vsm = 2.78, 2.74 m/s for the durand and wilson models; and 2.86 m/s for a 944 micron particle size and 3.02 m/s for a 1500 micron particle size from the mti holland model.
using a four component model for calculating the hydraulic gradient with Cw<45µm = 0%, Cw<200µm = 2.6% and Cw<0.015D = 100%, where 'D' is the pipe i.d., the water gradient 'im' = 0.416 m water/m and slurry gradient 'if' = 0.229 m slurry/m. the minimum hydraulic gradient is at a velocity 'v' = 5.0 m/s. the pipeline should operate at a velocity 10% higher than the minimum gradient velocity, therefore, v = 5.5 m/s.
for the case Cw=30% the carry velocities are 2.44 m/s, 2.74 m/s and 2.68 m/s respectively; and the hydraulic gradient is 'im' = 0.206 m water/m and 'if' = 0.160 m slurry/m.
i estimate the 6" pipe will operate with 35mm stationary bed, that is not recommended for a pumped slurry system.
i am surprised at two of the results. first, the hydaulic gradient is lower at a higher velocity than the critical deposition velocity. second, the critical deposition velocity is lower for 30% solids than for 60% solids; i agree with your earlier comments that with higher concentrations the increased particle to particle contact should result in a lower critical deposition velocity. one factor that may contribute to the results from the durand, wilson and mti holland models is the lack of particles in the -200µm range that does not provide a psuedo-viscosity modification for the carrier fluid, water.
i am interested to see your comments. ■
Re: Optimum Design Of Slurry Pipelines
Components in slurry come from the coal and the chemicals used in processing it. The washing or purifying process reduces pollution-causing contaminants in the coal, but these impurities then become part of the slurry. ■
Optimum Design of Slurry Pipelines
Optimum design methodology for ore concentrate and tailings pipeline
Optimum design of slurry pipeline for a particular throughput (tones per hour of solids) requirement can be carried out using my software based on following steps:
Step I: Calculations are made for concentration, flow velocity, laminar/turbulent flow transition velocity, critical deposition velocity, corrosion & erosion wear allowance and water hammer pressure allowance at different inner diameters for each commercially available CS, HDPE and rubber-lined pipelines.
Step II: Various pipe sizes are tested computationally as described in step I. The optimum pipe size will be the size which satisfies following criterions considering the system life as 30 years:
Criteria 1. Both the critical deposition velocity and laminar/turbulent flow transition velocity are less than the flow velocity. Obviously, concentration at which critical deposition velocity and laminar/turbulent flow transition velocity coincides will correspond to the optimum design concentration. In addition to the reduced steel tonnage and lesser water volume, this design point will have smaller pumping requirement as it falls in the transition flow regime. Solids can be transported overcoming the frictional losses considering the least friction factor corresponding to the laminar flow in Moody’s diagram.
Criteria 2. The outer diameter (OD) calculated by adding up the corrosion & erosion wear allowance and water hammer pressure allowance into the inner diameter (ID) of pipeline is less than the pipe OD for which the calculations are made.
Criteria 3. The capital cost of slurry pump and pipeline system is the least.
For iron ore concentrate and tailings slurry pipeline, an optimum concentration of 65% by weight at flow velocity of 1.5 m/s gives optimum design. Following design calculations I performed recently for iron ore concentrate will give you an idea of importance of optimized design:
Pumping requirement based on optimum design: 23 MPa (Pipe length = 220 Km, Concentration of 63% by weight, Flow velocity of 1.5 m/s).
Pumping requirement based on optimum design for fixed concentration of 50% by weight: 4 MPa (Pipe length = 18 Km, Concentration of 50% by weight, Flow velocity of 1.67 m/s).
For queries, please write here or email me at:
drkaushal.iitd@gmail.com
Dr. D. R. Kaushal
IIT Delhi
INDIA ■