Characterization of the Gas and Liquid Conductivity of an Aboveground, Commercial-Scale Sulfur Block

Elemental sulfur (S-0) is commonly stored in aboveground blocks formed by pouring molten S-0 in thin lifts. The long-term storage of S-0 blocks is a potential source of high acidity effluent as a result of the oxidation of S-0 to H2SO4, resulting in effluent waters with low pH and elevated SO42- concentrations. These blocks are currently managed during operations within a secure, engineered, containment facility. Characterization of the accessibility of the S-0 block to O-2 and water ingress is required to fully understand the generation of H2SO4 within the block. The O-2 and water ingress are defined by the gas (K-g) and liquid (K-l) conductivity of the S-0 block. We present the results of in situ gas pumping tests in vertical and angled boreholes conducted on an aboveground S-0 block to determine K-g within the block and to indirectly determine Kl. The K-g test results showed that the block is highly conductive in both the horizontal (geometric mean = 2.3 x 10(-4) m s(-1)) and vertical (geometric mean = 1.7 x 10(-5) m s(-1)) directions and heterogeneous with respect to K-g. Results of the cross-hole tests were considered to yield more representative estimates of bulk K-g than single-well tests because cross-hole tests are relatively insensitive to high head loss associated with turbulent flow conditions that develop near the borehole. In addition, numerical modeling of cross-hole test data provided insight into the anisotropic nature of K-g of the S0 block. Corresponding values of anisotropic Kl computed from K-g were 2.6 x 10(-3) m s(-1) (horizontal) and 1.9 x 10(-4) m s(-1) (vertical). Given that S-0 blocks are constructed in a similar manner throughout the world, the results of this study should be generally applicable to other S-0 blocks.