Let’s discuss how waste heat recovery works in our company
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Overview: Our company produces 30 tons of steam per day, which is used to heat ovens. . . Most of it is used for ovens at 120–130°C, while a smaller portion is used for heating in ovens at 70°C. . . The condensate that passes through the steam trap is collected in a small tank provided by the waste heat recovery supplier, and then it is pumped every 5 minutes or so into the hot water tank used to feed water to the boiler. . . So here’s the question: the temperature of the condensate water at 130°C, after passing through the super-hygroscopic valve, is still not below 130°C; this inevitably leads to flashing, thereby increasing the pressure in the drainage pipeline (the pressure gauge shows 0.2–0.3 MPa). Meanwhile, the temperature control in the oven heated at 70°C works normally. What’s going on? Their condensate water is connected together as soon as it passes through the hydrophobic valve; why can a oven at 70°C still function properly for water drainage? Why is its temperature control still working properly?
Why is the temperature of the condensate water not lower than 130 degrees Celsius?
Using steam of the same quality, drainage can be achieved as long as the back pressure of the drain valve meets the requirements specified by the valve manufacturer; the driving force for drainage in both approaches is the same.
A furnace temperature set at 70°C does not mean that the temperature of the heating steam is also 70°C; it’s possible that the temperature of the heating steam is 130°C – there is simply a large difference between the two temperatures.
It’s just that the amounts of steam used are different; the steam pressure and temperature remain the same, as does the back pressure of the steam trap, so there’s no problem.
The oven is set to a temperature of 70 degrees; the heating medium used must be at a temperature higher than 70 degrees. It’s fine for the condensate water after the hydrophobic valve to be at 130 degrees as well – as long as the flow rate is controlled properly, the temperature can be maintained at 70 degrees.
The pressure of the steam entering the oven at 70°C may not be 120°C, as the temperature is controlled by regulating the flow rate of the steam; this is how the pressure of the heating steam is controlled. Therefore, the steam that enters the oven’s coil may not be at 120°C. As for the pressure behind the drain valve being 0.2–0.3 MPa, this is somewhat confusing