Amine-aldehyde resins and uses thereof in separation processes
View Patent ↗Amine-aldehyde resins are disclosed for removing a wide variety of solids and/or ionic species from the liquids in which they are suspended and/or dissolved. These resins are especially useful as froth flotation depressants, for example in the beneficiation of value materials (e.g., bitumen, coal, or kaolin clay) to remove impurities such as sand. The resins are also useful for treating aqueous liquid suspensions to remove solid particulates, as well as for removing metallic ions in the purification of water.
1. A method for purifying a coal ore, comprising:
a. providing a coal ore comprising coal and one or more soluble or insoluble impurities;
b. prior to or during a size or a density classification operation, contacting an aqueous slurry of the coal ore with an amine-aldehyde resin, and
c. separating the purified coal from the aqueous slurry;
wherein the purified coal has, relative to the coal ore, a reduced amount of mercury, nitrogen, sulfur, silicon, ash, or pyrite, as measured on a volatile free weight basis; and
wherein the amine-aldehyde resin comprises a urea-formaldehyde resin prepared by:
mixing formaldehyde, urea, triethanolamine and optionally ammonia reactants at an alkaline pH, heating the mixture to an elevated temperature for a time sufficient to obtain complete metholylation of the urea, the reactants being present in an amount of about 1.50 to 4.0 moles of formaldehyde, about 0.001 to 0.1 mole of triethanolamine, and about 0.0 to 0.5 mole ammonia, per mole of urea; and
adding acid to lower the pH to within the range of about 4.9 to about 5.2 and adding urea until the molar formaldehyde to urea ratio is within the range of about 1.5:1 to about 2.5:1 and reacting for a time sufficient to reduce free formaldehyde to less than 2%.
2. The method of claim 1 , wherein the purified coal has, relative to the coal ore, a reduced amount of mercury, cadmium, lead, arsenic, or any compound thereof, as measured on a volatile free weight basis.
3. The method of claim 1 , wherein the purified coal has an amount of mercury, nitrogen, sulfur, silicon, ash, or pyrite, as measured on a volatile free weight basis, that is less than the corresponding amounts in a purified reference coal recovered in the size or density classification operation, in which the aqueous slurry of the reference coal ore has not been contacted with the amine-aldehyde resin.
4. The method of claim 1 , wherein the purified coal has, relative to the coal ore, a reduced amount of moisture, an increased BTU value, or both.
5. The method of claim 1 , wherein the contacting step further comprises contacting the aqueous slurry of the coal ore in step b. with silica, a silicate, a polysiloxane, a polysaccharide, a polyvinyl alcohol, a polyacrylamide, a flocculant, or any combination thereof.
6. The method of claim 1 , wherein the reaction mixture of formaldehyde, urea, triethanolamine and ammonia is heated to a temperature of about 95° C. over a period of 30 minutes and maintained at a temperature of 95° C. for 15 to 20 minutes.
7. The method of claim 1 , wherein the amine-aldehyde resin comprises a urea-formaldehyde resin having a number average molecular weight (M n ) of greater than about 300 grams/mole.
8. The method of claim 1 , wherein the amine-aldehyde resin is further modified with an anionic functional group.