Evaluation of filtering efficiency of walnut granules as deep-bed filter media

Rahman, S.S., 1992. Evaluation of filtering efficiency of walnut granules as deep-bed filter media. J. Pet. Sci. Eng., 7:239-246. For many years the oil industry has been using surface and deep-bed filters in cleaning oilfield brines and injection water. With the use of surface filters, mainly cartridge filters, an influent with 50-100 ppm solids can be cleaned to 2-5 ppm. They pose several operational limitations, however, including low dirt capacity, low flow density, and problems of by-passing. These limitations are overcome with deep-bed filters consisting of sand, graphite, and diatomaceous material, but the water quality is poor. With the introduction of walnut shell granules for use as deep-bed media, it is now possible to attain a water quality of 5 ppm at high flow density. In this paper, different filter systems currently in use are reviewed. Finally, the concept of walnut shell granules as a deep-bed filter media is described, and some test results are presented to demonstrate its filtering efficiency over conventional bed filters.