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

About Mariana Minerals 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’re reimagining the minerals supply chain by combining deep industry expertise with advanced software, automation, and data-driven decision-making. The Role 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, you will produce these deliverables yourself, own their technical content and revision history, and carry them through procurement, construction, and commissioning. What You’ll Do

• Own the process design basis for your assigned areas. Design cases and margins, turndown, utility and reagent demands, and the first principles and assumptions basis behind them

• Develop PFDs, heat and material balances, and P&IDs. Manage the metadata behind smart drafting and modeling software such as Plant 3D

• Develop P&IDs from concept through IFC. Including, but not limited to, equipment, instrumentation and control loops, isolation and relief philosophy, drains and vents, sample and utility stations, sloping and tracing notes, and tie-ins

• Manage and develop automated workflows for the process data behind the line, instrument, and valve lists. E.g. line numbers and sizes, service conditions, design and test pressures and temperatures, pipe class selection, insulation and heat tracing, and instrument process data

• Build and maintain the hydraulic models. Line sizing and pressure drop, pump and blower curves and duty points, NPSH margin, control valve and orifice sizing, slurry and two-phase lines, and gravity, launder, and vent flow. Evaluate automation opportunities to link this to heat and material balances and Plant 3D datamanger

• 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 the control narratives and functional descriptions with support from the controls engineering team

• Represent process in PHAs and HAZOP.

• Coordinate across detailed engineering disciplines. Such as equipment lists and loads to mechanical, motor and instrument lists to electrical and controls, and layout, access, and maintenance clearances with piping and civil-structural

• Support construction and commissioning. RFI and field change resolution, P&ID walkdowns and field verification, loop checks and functional testing, water and first-feed startup, and as-built closeout

Desired Qualifications

• 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. PE preferred

Preferred, but not required

• 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 — SmartPlant P&ID, AVEVA P&ID, or Plant 3D P&ID — where the drawing is a database, not a picture

Our culture is built on four principles:

Everyone Gets Home Safe. We never put speed or cost ahead of people. Extreme Ownership. We take full responsibility for outcomes, relentlessly driving toward solutions. Engineer Out Requirements, then Automate. We simplify, optimize, and then automate for scale. Share Your Legos. We collaborate openly, share knowledge, and empower each other to build bigger, better solutions.

Join us as we build the future of responsible mineral sourcing and supply!