Sr. Process Engineer

Doist; San Francisco (CA); On-site; USD 140,000 - 210,000; Full time

Job summary

Mariana Minerals in San Francisco seeks a Sr. Process Engineer to lead the design, deployment, and operation of pilot-scale refining processes for critical minerals, while supporting software-driven plant optimization.

You will bridge R&D and Operations, collaborate with cross-functional teams, and ensure safe, cost-effective, scalable processes from lab to production. This hands-on role requires hands-on leadership, documentation discipline, and a strong commitment to health, safety, and

Qualifications

• B.S., M.S., or PhD in Chemical Engineering or related field.
• 5+ years of experience supporting R&D scale up, pilot plant operation, and/or commercial production in minerals processing, chemicals, or related industries.
• Strong understanding of reaction engineering, solid-liquid separation, leaching, ion exchange, solvent extraction, or similar unit operations.
• Hands-on experience designing, commissioning, and operating pilot or commercial-scale process equipment.
• Ability to design experiments, problem-solve, and analyze complex datasets.
• Strong commitment to Health & Safety and experience with risk management and hazard assessment.

Responsibilities

• Operate and improve pilot-scale processing equipment with technicians.
• Design experiments to evaluate process performance, recovery, throughput, and product quality.
• Create and maintain PFDs, HMBs, P&IDs, Operating Procedures, and Process Control Narratives.

Skills

Process engineering

Experiment design

Data analysis

Technical writing

Education

B.S./M.S./PhD in Chemical Engineering

Job description

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.

Role Overview

Mariana Minerals is looking for a highly motivated Sr. Process Engineer to join our San Francisco Pilot Plant team. You will lead the design, deployment, and operation of first-of-its-kind refining processes for critical minerals, while also supporting development of software for automated plant optimization. This position is highly hands-on and will play a critical role in bridging R&D and Operations, ensuring processes are robust, safe, cost-effective, and suitable for commercial production.

What You’ll Do

• Work closely with Pilot Plant Technicians to operate, maintain, troubleshoot, and improve pilot-scale processing equipment.
• Design experiments to evaluate process performance, recovery, throughput, and product quality.
• Create and maintain key engineering and operational documentation such as PFDs, HMBs, P&IDs, Operating Procedures, and Process Control Narratives.
• Lead equipment design scopes from concept, through procurement, fabrication, installation, commissioning, and handover to Operations.
• Work closely with cross-functional teams including R&D, commercial plant design engineers, project execution teams, and more to scale designs from lab to the pilot to production scale.
• Work closely with the software and machine learning teams to develop and implement reactor and plant optimization algorithms.
• Travel to pilot and commercial sites to drive commissioning, startup, and ramp-up alongside operations & plant design teams.

What You’ll Bring

• B.S., M.S., or PhD in Chemical Engineering or related field.
• Minimum of 5 years of experience supporting R&D scale up, pilot plant operation, and/or commercial production in minerals processing, chemicals, specialty materials, oil & gas, or similar industry.
• Strong understanding of reaction engineering, solid-liquid separation, leaching, ion exchange, solvent extraction, and/or similar unit operations.
• Hands-on experience designing, commissioning, and operating pilot or commercial-scale process equipment.
• Ability to design experiments, problem-solve, and analyze complex datasets.
• Strong commitment to Health & Safety and experience with risk management, management of change, and hazard assessment.
• Excellent technical writing, communication, and teamwork skills.
• Comfort working in fast-paced, cross-functional environments.

Our culture is built on three principles:

• 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.