Print page

Experts

Powder Handling

Powder Handling by Lee Dudley, Diamondback Technology

Lee Dudley is president of Diamondback Technology, Atascadero, Calif., a company that focuses on bulk solids’ handling. He has more than 35 years of experience, dealing with a wide variety of materials including plastics and rubber and with continuous and batch operations. Previously, he worked for Free-Flow Packaging, where he won the President’s Award for improving the process capabilities of three plants. He also has worked for Raychem and General Electric.

For powder handling, is there a system that ensures total protection of the product/environment?
We fill barrels from a dryer. The environment is a classic, non-protected chemical workshop -- a closed room where one production is in progress at a time.

Is there a system that ensures total protection of the product/environment and vice-versa? So that to control the particle and bio contamination of the product and ensure a safe handling for the workers. We're look for total closing and if possible an isolator.
Category: Powder Handling

How Can We Prevent Ratholing?
Working in a powder plant an investigation led us to define the problem of coreflow/ratholing causing weight fluctuations and segregation problems during emptying of the bin/silo. Designing a new bin we think about a conical bin with steep angles and short volume to try to avoid the coreflow. The powder characteristics are several small size particles and sticky characteristics so we fear polishing walls of the bin will not be effective in time. Placing a conveyor system for bin outlet will cause dramatic changes. A few hints for perfect bin angles and design would be appreciated.
Category: Powder Handling

Using Wood Dust as Feedstock
I am designing a pilot plant that will use wood dust as its feedstock. I am having difficultly finding a method for moving the wood dust from a hopper into a reactor that is operating at 25-40 psig. My initial idea was to pressurize the hopper at 25-40 psig and use a screw feeder that would meter the flow rate, but all the manufactures are telling me that the feeder cannot operate with an internal pressure. I have also looked at using an airlock after the screw feeder and operating the hopper at atm. Has feeding wood dust into a 40 psig vessel been done before? If so, how was it accomplished?
Category: Powder Handling

The best method for loading the hopper
We are setting up a polyester and alkyds resins manufacturing plant, having two production lines each consisting of a 12.5 m3 reactor and a 25 m3 blender. To manufacture alkyd and polyester resins, we have to charge the reactors, as per formulations, with chemicals (solid powder materials) like phthalic anhydried in flakes form, maleic anhydride in pellets form — size 1/2 inch by 1 inch — and isophthalic acid in powder form. The top of the hopper is attached to the reactor will be at a height of 25 Mts. What is the most practical and least costly method for loading the hopper?
Category: Powder Handling

Rotary valve capacity, power
How does one determine the capacity of a rotary valve and the power needed by a rotary valve for a given capacity?
Category: Powder Handling

Funnel flow
In our powder feed hoppers, funnel flow is experienced. The smaller the product particle size the more outspoken the problem is. Due to space and other limitations, it is not possible to change the configuration dramatically. The powder product has a wall friction angle between 12.6 and 16.7 degrees (measured with Jenicke shear test). Hopper wall inclination at outlet is 30 degrees (vertical to wall). Based on these numbers, mass flow should normally occur. What could we improve to get mass flow? The options that we’ve thought of are: the wall surface roughness could be improved by a grinding operation; to increase the particle size, but this also means a dramatic change in the whole process; or to increase outlet diameter and/or install another feeding system. What is the best option in your mind, and are there other options?
Category: Powder Handling

Overcoming slow, horizontal powder runs
We have a customer blowing our barite with SG 4.3 and ground to -75 micron, with around 16% -6 micron. While this material blows more quickly from truck to silo than Moroccan Barite with an SG of 4.18, ground to -75 micron, but with 25-30% -6 micron, on long horizontal runs it blows much slower on a horizontal run of approximately 100 feet from the silo to the boat. Is it possible that the higher SG and larger paticle size of our barite lets it settle out? What is normally the solution? Will using a smaller transport pipe raise the pipe velocity and overcome this problem, or can one just use a bigger blower?
Category: Powder Handling

Separating an air-blown waste stream
I'm looking for an appropriate technology to separate an air-blown waste stream that contains sub 100 micron powder and water. A 20% moisture product is passed through a piece of equipment that splits the water from the base material and reduces it to a fine powder. I need to then remove the moisture from the air stream before it is re-absorbed into the powder. This is so that the powdered component of the stream can be reintroduced into a dry milling facility. This needs to operate at up to 20tph (i.e., 4tph of moisture is stripped out). Can you help or point me in the right direction?
Category: Powder Handling

Transporting fine powders
With a given pneumatic conveying system (6-in diameter), transport of 11 ton/h of powder (150 micron D50) is possible. Material that is finer (125 micron D50) transports much more difficult. It seems that as the powder settles somewhere along the first part of the transport line and is then (due to pressure increase) blown as a package through the line, the pressure spikes and causes the safety valve of the blower to go off. This causes the line to block and transport capacity is therefore limited to 2/3 of normal transport rate. (Velocity in the line is high enough. Mass to air ratio -3.5.) What is the powder property that relates to this behavior? What can we to increase transport capacity of this "fine" powder?
Category: Powder Handling

Airlift incline blower specificiations
I have a question about material handling by airlift to hebht of 80m. If a portion of piping route at begining at top of airlift be inclined, what is its effect on assumed capacity and blower specifications? What are the restrictions in pipng route for material handling by airlift?
Category: Powder Handling

Material handling by airlift
I have a question about material handling by airlift to height of 80m. If a portion of piping route at begining at top of airlift be inclined, what is its effect on assumed capacity and blower specifications? What are the restrictions in pipng route for material handling by airlift?
Category: Powder Handling

Determining the cause of a variation in analyzer readings
We are experiencing variations in both our raw materials and finished product. We chemically analyze the raw materials using an online vertical analyzer, but the data from the raw materials do not correspond to those for the finished product. We have experienced hang-ups and segregation in our feed silos, which might be exacerbated when the raw materials are mixed and then transported on a belt conveyor. We suspect the variation in analyzer readings could be due to increased moisture in the raw materials after leaving the feed silos, but we don't know why. Is the difference in readings due to segregation or to moisture?
Category: Powder Handling