Challenges in High-Temperature Filtration at the Integrated Waste Treatment Unit - 21160

An integrated test of the Integrated Waste Treatment Unit (IWTU) facility steam reforming process was conducted from July 21, 2018 to August 21, 2018. The primary objective of the test was to evaluate performance of a new fluidized-bed distributor in the denitration mineralization reformer (DMR). The test was the longest demonstration run up to that time and successfully demonstrated modifications made to the DMR to improve fluidization behavior. However, the differential pressure across the high temperature (550 deg. C) process gas filter (PGF) began increasing more rapidly than during previous shorter tests. The rate of change began increasing exponentially after the pressure drop exceeded about 10.2 kPa (41 inches of water column (in. WC)) and the plant was eventually shut down due to high filter pressure drop. Inspection of the filters showed they were extensively bridged with solids and the pressure drop could not be reduced by vacuuming the solids from the filters or by rinsing them with hot water and steam. This report describes the process of identifying and resolving the PGF issues through a combination of laboratory studies, bench-scale experiments, modeling, industry and national laboratory collaboration, and pilot plant studies over a period of two years. It was found that oxidative corrosion of the sintered metal filter elements constructed of the high nickel alloy (INCONEL^R alloy 625) had caused nearly pure nickel to be exuded from the base metal, plugging the pores in the filter elements. The filter elements are being replaced with the same number of silicon carbide ceramic elements with the same external dimensions and particulate filtration rating (99% for particles 2 μm and larger). (authors)