Calculate gas ppmv or liquid mg/L from a mass rate and flow, or solve for mass rate or flow. Gas calculations require a matching dry reference and molecular-weight basis; liquid mass-based ppm uses the final liquid density.
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lb/hr to ppm Formula
For a 100% active feed and final water density of 1 kg/L, the following formula converts lb/hr to mg/L (numerically equal to ppm by mass) using Q in L/hr. Gas uses a separate ideal-gas calculation.
- Where ppm is parts per million by mass; it equals mg/L numerically only at liquid density 1 kg/L
- lb/hr is the pounds of solute added per hour
- Q is the liquid flow rate in L/hr
To calculate mg/L, multiply product lb/hr by 453,592.37 and its active mass fraction, then divide by the final liquid flow in L/hr. Divide mg/L by density in kg/L for ppm by mass.
| lb/hr | PPM (at 100 GPM) |
|---|---|
| 0.05 | 0.999 |
| 0.10 | 1.997 |
| 0.25 | 4.993 |
| 0.50 | 9.986 |
| 0.75 | 14.978 |
| 1 | 19.971 |
| 1.25 | 24.964 |
| 1.50 | 29.957 |
| 2 | 39.942 |
| 2.5 | 49.928 |
| 3 | 59.913 |
| 4 | 79.884 |
| 5 | 99.855 |
| 6 | 119.826 |
| 7.5 | 149.783 |
| 10 | 199.711 |
| 12.5 | 249.638 |
| 15 | 299.566 |
| 20 | 399.421 |
| 25 | 499.277 |
| Assumes steady flow of 100 GPM. Formula: ppm = (lb/hr × 453,592.37) / (GPM × 3.785411784 × 60). At 100 GPM, ppm ≈ 19.9711 × (lb/hr). | |
How do you convert lb/hr to ppm? For a 100% active feed, multiply lb/hr by 453,592.37 and divide by final liquid L/hr to obtain mg/L. This equals ppm by mass only at density 1 kg/L.
How do you convert ppm to lb/hr? Convert mass-based ppm to mg/L using liquid density first. Multiply mg/L by final liquid L/hr, then divide by 453,592.37 and the product active mass fraction to obtain product lb/hr.
Example Problem
How to calculate ppm from lb/hr?
First, determine the total lb/hr.
For this example, the total lb/hr is found to be 1.5.
Next, determine the system flow in L/hr.
For this example, final water flow is 50,000 L/hr, density is 1 kg/L and the feed is 100% active.
Next, use the formula for the conversion above to determine the amount of ppm.
ppm = (453592.37 * lb/hr) / Q
ppm = (453592.37 * 1.5) / 50000
ppm = 13.6078
