Cost Reduction in Quench and Tempering of OCTG Pipe
- Gas vs Induction
- Houston Texas
- Feb, 2019
Energy Costs for Feb 2019
- Gas - Henry Hub pricing $2.60 per million BTU
- Industrial User - $3.10 per million BTU
- Electric - National industrial user 6.7 cents per KW.
- 293 KW = 1 million BTU
- $19.63 per million BTU 600% over gas
- Natural gas pricing is expected to remain low due to extensive drilling west Texas Supply excess is anticipated for next 20+ years.
- Electric pricing is dictated by demand. As economy heats up demand will go up. Time is required to put on more capacity.
- Beware of electrical "Demand Charge" Once established you are entitled to pay for even in low usage times.
Heat Conversion Efficiency - Induction
Induction has four losses associated with it
- Step down transformer, if on customer side – Loss equals 1 to 2%
- Power conversion to the high frequency voltage – Loss on best systems 5%, 10% not uncommon.
- Coil efficiency Loss
- The first is called coupling efficiency. It relates to the distance between the coil and the pipe, there is an optimum distance. As the gap gets wider the efficiency drops off rapidly. Loss 15% but can go up rapidly with size change Use 18%.
- The second issue is the curie point of the metal. Steel loses its magnetic properties above 1300° F. This is the curie point. For induction, efficiency is better below 1300°F and then drops significantly above 1300 F. Loss- additional 15% above curie
- Loss overall appr. 3%.
- Loss to the surrounding environment – Loss equals 1%.
- Loss = 1.5% + 7.5% + 18% +3% + 0% = 30%
Induction
- Overall efficiency can be estimated for the entire heating range of the pipe at about 30% loss or 70% energy available for use.
Gas Fired Furnace Energy Usage
- Austenitizing loss to flue gas 55% @ 1950 F
- Temper loss to flue gas 37% @ 1100 F
- Loss to air: insulated furnace 2%
- Loss to water cooled shafts 5%
- 60% of the heating is used in Aust. Fce
- 40% of the heating is used in Temper Fce
- Combined Loss to flue gas = .60 x 55% + .40 x 37% = 48%
- Total Loss = 48% + 2% + 5% = 55%
Gas
- Overall efficiency can be estimated for the entire heating range of the pipe at 55% loss or 45% energy available for use.
The Numbers
- Gas - $3.10 per million BTU - energy loss 55%
- Electric – $19.63 per million BTU - energy loss 30%
- Austentizing - Btu required for on e ton of steel to heat to 1650 F
2000 lbs x 1580 F x .122 Btu/lb F = 385,500 BTU
- Temper - Btu required for one ton of steel to heat to 1200 F
2000 lbs x 1130 F x .122 Btu/lb F = 275,720 BTU
Savings for one ton
- Gas 661,220 Btu / .45 = 1,469,400 Btu x $3.10 = $4.55
- Elect 661,220 Btu / 70 = 944,600 Btu x $19.63 = $18.54
- Savings per ton $14.00
Bottom Line
Annual Savings - Gas vs Induction
- 10 ton per hour
- $14.00 per ton x 10 ton per hour x 7884 hours = $1,104,000
- 20 ton per hour
- $14.00 per ton x 20 ton per hour x 7884 hours = $2,208,000
- 90% On line is 7884 hours.