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Will thermal dispersion units separate the 'stickies'?

Q: I am working in a paper mill. My co-worker wants to know about thermal dispersion units and how he can use it there to separate stickies from wood.

A:

This is a rather difficult problem that has been made worse by the use of recycled fiber stock.  The "stickies" are usually resins or other organic materials that agglomerate to form small holes in the final product or coat the equipment, resulting in excessive downtime or poor product quality. 

The thermal dispersion units attempt to limit the problem by keeping these organics from agglomerating.  Normally, a surfactant is used to prevent the agglomeration, but this may alter the product properties.  I'm only familiar with one type of thermal dispersion unit and it uses an electrically heated wire that is placed just after the sheet forming device.  The floating pulp is consolidated by a series of wires and the extra heat prevents the organics from coming out of solution as the sheet dries.  This only works for small amounts of organics.  It is better to remove these stickies in the front end of the process, such as de-inking of the recycled materials.  This can be done by steam injection and/or heating of the recycled material followed by floatation of the pulp using screens.  However, bleaching chemicals are usually still required to destroy the stickies.  Inks, which are often fine carbon particles, are more difficult to separate by thermal means because of their poor solubility.

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I am working in a paper mill. My co-worker wants to know about thermal dispersion units and how he can use it there to separate stickies from wood.

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See the data below:

Product to be handled: Sodium sulphate (salt)

Chemical formula: Na₂SO₄

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Bulk density: 1500 kg/M³

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Average particle size: 0.18 mm

Specific particle surface area: 68 M2/kg

Total throughput: 6000 kg/hrs dry salt, 6250 kg/hrs wet salt

Temperature: 40 degree C

Residual moisture: 3% - 4% by weight

Material of construction:
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- all non wetted parts: SS 316L

Speed of screw conveyor: Fixed 36 rpm

Electrical data: 380/680 V, 50 Hz, IEC standard, IP 53, non explosion proof, F insulation class

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Our plant is currently investigating methods to decrease filtration time for one of our products. The process involves a neutralization reaction in which Calcium Salt of Dodecylbebzene Sulfonic Acid is formed. Sulfuric acid also exists in the raw materials, which leads to a secondary reaction that yields calcium sulfate. It is the calcium sulfate that is removed during filtration. Currently, a filter press is employed for the removal of the CaSO4. We are hoping to employ some type of agglomeration technique to improve the filtration rate.

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