JEPCO helped a mine to increase their bottom line, by enabling their low sulfur ore for an additional source of gold recovery. They needed a highly reliable sulfur system to achieve this. The client’s roasting facility had an older sulfur storage and injection system that was plagued by corrosion, plugging and leaks. That sulfur system had been shut down for approximately 20 years as their concentration was on the higher sulfur ore, as it yielded more gold recovery.
About the project
The facility processes a “refractory” gold ore. Such ore is characterized by submicroscopic gold, finely disseminated within a silica or sulfide mineral matrix, which also contains some organic carbon. The roasters at this facility heat and oxidize the ore, releasing the encapsulated gold, making it more leachable in subsequent steps. Oxygen is injected into the roasters to supply the chemical oxidation of pyrite, and organic carbon at high temperature. For ore feeds low in natural sulfide, injecting a bit of sulfur into the roasters is the preferred way to increase roasting temperature.
Solution
The client chose JEPCO because of our extensive knowledge of sulfur. We chose one of our senior staff process engineers to head the project. In fact, he presents at Brimstone Sulfur Symposium.
Engineering Scope
1. Re-design/Rebuild of the Sulfur storage pit.
a. Special corrosion-resistant concrete was used for all surfaces in contact with liquid sulfur or the vapor space.
b. In high corrosion areas, certain metal parts were made of Alloy 20 and 316L SS.
c. Natural draft venting was designed to significantly heat the vapor space, and to maintain extremely low H2S concentrations. Such venting also minimizes corrosion.
2. Installation of new packaged boilers and steam controls.
3. The sulfur truck unloading area was relocated and re-designed.
4. The liquid sulfur piping network is considerably more complex than typical for JEPCO’s petroleum refinery sulfur facilities. Contra Trace and Contra Heat by Controls Southeast are used extensively for heating of liquid sulfur piping. Jacketed piping is only used for the vent system, sulfur piping in the truck unloading area, and for a short distance on the sulfur pump discharges. Wedge meters are used for sulfur flow measurement. Seals using alloy C-276 diaphragms are used for sulfur pressure measurement and for flow meter sensing.
5. JEPCO also provided unit checkout near the end of construction and provided startup assistance.
Outcome
This sulfur injection system had a successful start-up, and we look forward to the benefits our client will receive and the possibility of working on more projects with them in the future. For us, this is what partnership with clients is all about — our clients’ success is our success.
