Issued Patents All Time
Showing 1–11 of 11 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4936513 | Ball mills | — | 1990-06-26 |
| 4461625 | Methods of cleaning coal | Douglas V. Keller, Jr. | 1984-07-24 |
| 4447245 | Methods of cleaning coal | Douglas V. Keller, Jr. | 1984-05-08 |
| 4294695 | Multi-phase separation methods and apparatus | Douglas V. Keller, Jr. | 1981-10-13 |
| 4274946 | Agglomeration type coal recovery processes | Douglas V. Keller, Jr. | 1981-06-23 |
| 4265737 | Methods and apparatus for transporting and processing solids | Douglas V. Keller, Jr. | 1981-05-05 |
| 4252639 | Coal beneficiation processes | Douglas V. Keller, Jr. | 1981-02-24 |
| 4249699 | Coal recovery processes utilizing agglomeration and density differential separations | Douglas V. Keller, Jr. | 1981-02-10 |
| 4244699 | Treating and cleaning coal methods | Douglas V. Keller, Jr. | 1981-01-13 |
| 4234232 | Methods of and apparatus for mining and processing tar sands and the like | Douglas V. Keller, Jr. | 1980-11-18 |
| 4224039 | Coal briquetting methods | Douglas V. Keller, Jr. | 1980-09-23 |