White functional additives derived from filtration spent cake containing diatomite
This disclosure concerns flux-calcined products manufactured from filtration waste streams, and methods for manufacturing the same. In particular, it concerns functional additives produced from spent cake comprising diatomite filtration media which are suitable for use in paints, plastic films and elastomers for control of optical and surface properties, and processes which are suitable for manufacture of such products. It further concerns the recovery of energy from spent cakes during the regeneration process.
1. A product comprising diatom frustules reclaimed from a filtration waste stream comprising a spent cake, wherein the product has a d90 of 25 μm to 50 μm, and an L* brightness value of at least 91, wherein the product is produced by a method comprising:
(1) selecting the spent cake such that it includes the diatom frustules; and
(2) thermally treating the spent cake to produce reclaimed diatom frustules; and wherein the product is free of diatom frustules that have not been reclaimed from a filtration waste stream.
2. The product of claim 1 , in which the L* brightness value of the product is at least 94.3.
3. The product of claim 1 , wherein the product also has a b* value of no more than 6.2.
4. The product of claim 1 , wherein the product also has a b* value of 2.3 to 3.4.
5. The product of claim 1 , wherein the d90 is from 25 μm to 45.2 μm.
6. The product of claim 1 , wherein the product also has a Hegman value of 0.5 to 4.
7. The product of claim 1 , wherein the product also has a centrifuged wet density of 0.3 g/ml to 0.5 g/ml.
8. A coating, plastic film, or elastomer comprising the product of claim 1 .
9. A method for manufacturing a product, the method comprising:
selecting spent cake that includes diatom frustules;
drying the spent cake;
thermally treating the spent cake to produce reclaimed diatom frustules, the thermal treatment free of gasification or pyrolysis; and
optionally, classifying the reclaimed diatom frustules, to form a product,
wherein the product comprises at least a portion of the reclaimed diatom frustules, wherein the product has a d90 of 25 μm to 50 μm and an L* brightness value of at least 91, wherein the product is free of diatom frustules that have not been reclaimed from a filtration waste stream.
10. The method of claim 9 , wherein, during the thermally treating, the heat contact time for the spent cake is 10 minutes to 40 minutes.
11. The method of claim 9 further comprising adding, during or prior to the thermally treating, a chemical to the spent cake.
12. The method of claim 11 , wherein the chemical comprises potassium hydroxide.
13. A method for manufacturing a product, the method comprising:
selecting spent cake that includes diatom frustules;
recovering energy from the spent cake through gasification to obtain a spent cake ash;
thermally treating spent cake ash that results from the recovering to produce reclaimed diatom frustules; and
classifying the reclaimed diatom frustules, wherein the product comprises least a portion of the reclaimed diatom frustules to form a product, wherein the product has a d90 of 25 μm to 50 μm and an L* brightness value of at least 91, wherein the product is free of diatom frustules that have not been reclaimed from a filtration waste stream.
14. The method of claim 13 , wherein the thermally treating is conducted at a temperature range of 900° C. to 1100° C.
15. The method of claim 13 , wherein, during the thermally treating, the heat contact time for the spent cake is 1 minute to 40 minutes.
16. The method of claim 13 further comprising: adding, during or prior to the thermally treating, a chemical to the spent cake.
17. The method of claim 16 , wherein the chemical comprises potassium hydroxide.