The scope of work at KRW Energy Systems, Inc. (KRW) under the current contract consists, in part, of designing and installing an external hot gas cleanup system for testing in the Process Development Unit (PDU) at Waltz Mill, PA. This system comprises an external fixed-bed desulfurizer of zinc ferrite sorbent with a sintered metal filter system and associated hot piping and instrumentation. Document FE-21063-40 reports progress on PDU modifications completed on the external hot gas cleanup system (HGCU), and it specifically discusses the safety reviews and safety issues completed for this system. Zinc ferrite sorbent was procured, received and loaded into the fixed-bed desulfurizer. The sintered metal filter was successfully tested in the PDU for 230 hours with no operational upsets during in-bed desulfurization test, TP-036-5. These test results are reported herein, along with metallographic analyses from the Argonne National Laboratory on the failed filter elements retrieved from PDU test TP-036-4. PDU modifications, a test summary, test accomplishments, and set point data for test TP-036-5 are reported as part of the Advanced In-Bed Gas Cleanup Program under the contract. Process analyses continued on analyzing existing data for inclusion in the mechanistic gasifier model to enable improved prediction of gasifier performance. Fines recycle analyses also continued to better understand fines loss and fines elutriation and enable evaluation of cyclone performance. Advanced system design work was completed on regenerated sulfur dioxide, external sulfation, and advanced instrumentation for the External Hot Gas Cleanup Program.