Sr./Staff Process Engineer - Detailed Engineering and Plant Design

Mariana Minerals is a software-first, vertically integrated minerals company on a mission to supply the critical minerals powering modern energy, AI, and defense technologies. We are hiring a Senior / Staff Process Engineer to execute detailed engineering deliverables such as P&IDs, line and instrument and valve lists, control narratives, hydraulic models, equipment and bulk specifications, and the procurement packages behind them. Mariana executes process engineering in-house, and the role owns these deliverables' technical content and revision history, carrying them through procurement, construction, and commissioning.

Responsibilities

Own the process design basis for assigned areas, including design cases and margins, turndown, utility and reagent demands, and first principles and assumptions; Develop PFDs, heat and material balances, and P&IDs from concept through IFC, and manage metadata behind smart drafting and modeling software such as Plant 3D; Manage and develop automated workflows for line, instrument, and valve list process data; Build and maintain hydraulic models for line sizing, pressure drop, pump and blower curves, NPSH margin, control valve and orifice sizing, slurry and two-phase lines, and gravity, launder, and vent flow; Size and specify process equipment such as pumps, control valves, relief devices, heat exchangers, tanks and agitators, filters, thickeners, mixer-settlers, crystallizers, and solid-liquid separation; Write control narratives and functional descriptions with support from the controls engineering team; Represent process in PHAs and HAZOP; Coordinate across detailed engineering disciplines including mechanical, electrical, controls, piping, and civil-structural; Support construction and commissioning, including RFI and field change resolution, P&ID walkdowns, loop checks, functional testing, water and first-feed startup, and as-built closeout

Requirements

8+ years of process engineering delivering detailed design for industrial process facilities in an EPC/EPCM, owner's engineer, or in-house capital projects environment; Detailed-engineering cycle on at least one greenfield or major brownfield project; BS in Chemical, Metallurgical, or Process Engineering

Nice to have

PE (Professional Engineer) preferred; Lithium: direct lithium extraction, spodumene leaching, crystallization, and battery-grade product specifications; Copper: heap and tank leaching, solvent extraction and electrowinning, tankhouse and electrolyte circuits; Slurry and solids handling: thickeners, filters, pulp and tailings piping, and settling and erosion design; Data-centric P&ID platforms such as SmartPlant P&ID, AVEVA P&ID, or Plant 3D P&ID