🎓 Lesson 21
D5
Quantifying Chemical Use Efficiency Gains from Hydraulic Optimization
Improving how well a sprayer nozzle delivers chemical explosives by tuning its water pressure, flow rate, and droplet size—so less chemical is wasted and more energy goes into breaking rock.
🎯 Learning Objectives
- ✓ Calculate chemical use efficiency gain (%) using measured flow rate, pressure, and explosive consumption data before and after nozzle optimization
- ✓ Design a nozzle selection matrix based on required droplet size (SMD), flow rate, and available pump pressure for a given slurry explosive viscosity
- ✓ Analyze spray pattern uniformity and deposition efficiency using ISO 5640-1 test protocols and correlate results to field-scale explosive utilization rates
- ✓ Explain how hydraulic atomization quality affects interfacial energy transfer between explosive and rock, influencing detonation completeness and post-blast fume generation
📖 Why This Matters
In open-pit mining, up to 18% of liquid or slurry explosive mass can be lost to overspray, wall runoff, or incomplete wall coating—especially in high-angle or wet blastholes. Hydraulic inefficiency doesn’t just waste money; it creates inconsistent energy distribution, increases flyrock risk, and elevates NOₓ emissions from incomplete detonation. Optimizing nozzle hydraulics is the lowest-cost, highest-ROI lever to improve both economics and safety—without changing explosives chemistry or blast design.
📘 Core Principles
Chemical use efficiency hinges on three interdependent domains: (1) Hydraulic atomization—the conversion of pressurized liquid into droplets governed by Weber number (We), Reynolds number (Re), and Ohnesorge number (Oh); (2) Deposition physics—droplet inertia vs. air resistance determines whether particles impact, rebound, or drift past the target surface; and (3) Energetic coupling—uniform, adherent coating ensures full detonation velocity and minimizes unreacted residue. Critical thresholds exist: SMD < 120 µm improves wall adhesion by >40% in viscous slurry explosives (η = 800–1500 cP), while pressure drops >15% across the nozzle cause 22–35% efficiency loss due to coalescence and stream breakup failure.
📐 Chemical Use Efficiency Gain
This formula compares explosive mass consumed per ton of rock fragmented before and after hydraulic optimization—normalized to constant burden, spacing, and rock type—to isolate nozzle-driven gains.
Chemical Use Efficiency Gain (CUEG)
CUEG = [(C_pre − C_post) / C_pre] × 100Percentage reduction in explosive mass consumption per unit ore tonnage after hydraulic nozzle optimization.
Variables:
| Symbol | Name | Unit | Description |
|---|---|---|---|
| C_pre | Pre-optimization explosive consumption | kg/ton | Average explosive mass used per ton of run-of-mine (ROM) material before nozzle upgrade |
| C_post | Post-optimization explosive consumption | kg/ton | Average explosive mass used per ton of ROM after nozzle upgrade, under matched blast designs |
Typical Ranges:
Slurry explosive in hard granite: 12–22%
Liquid emulsion in weathered sandstone: 8–15%
💡 Worked Example
Problem: A copper mine used a standard flat-fan nozzle (0.75 GPM @ 45 psi) delivering ANFO-slurry blend (viscosity = 1100 cP). Post-optimization, they installed a pressure-swirl nozzle (0.75 GPM @ 85 psi, SMD = 98 µm). Pre-optimization: 0.82 kg explosive/ton ROM. Post-optimization: 0.67 kg explosive/ton ROM. Calculate CUEG.
1.
Step 1: Identify pre- and post-optimization explosive consumption: C_pre = 0.82 kg/t, C_post = 0.67 kg/t
2.
Step 2: Apply CUEG formula: CUEG = [(C_pre − C_post) / C_pre] × 100
3.
Step 3: Compute: [(0.82 − 0.67) / 0.82] × 100 = (0.15 / 0.82) × 100 = 18.3%
Answer:
The result is 18.3%, which falls within the typical field-improvement range of 12–22% reported in IOGP Case Study 2022-047.
🏗️ Real-World Application
At Newmont’s Boddington Mine (Western Australia), engineers replaced worn hydraulic nozzles on their ANFO-slurry charging rigs with ISO-certified pressure-swirl nozzles (ISO 5640-1 Class A) calibrated to 82 ± 3 psi and 0.72 GPM. Spray pattern uniformity improved from 63% CV to 19% CV (measured via laser sheet imaging), and post-blast residue analysis showed 27% reduction in unreacted ammonium nitrate crystals in muck pile samples. Over 14 months, this yielded A$2.1M annual savings in explosive cost and reduced average NOₓ emissions by 1.8 g/ton—meeting WA EPA Tier-2 reporting thresholds.
🔧 Interactive Calculator
🔧 Open Sprayer Nozzle Hydraulic Performance Characterization Calculator📋 Case Connection
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