The terms live steam and flash steam are only used to differentiate their origin. Whether steam is produced in a boiler or from the natural process of flashing, it has exactly the same potential for giving up heat, and each is used successfully for this purpose. The flash steam generated from condensate can contain up to half of the total energy of the condensate.
An efficient steam system will recover and use flash steam. Condensate and flash steam discharged to waste means more make-up water, more fuel, and increased running costs. This Module will look at two essential areas — condensate management and flash steam recovery. Some of the apparent problem areas will be outlined and practical solutions proposed. The ability of any trap to pass condensate relies upon the pressure difference across it, whereas a pumping trap or a pump-trap combination will be able to pass condensate irrespective of operational pressure differences subject to design pressure ratings.
An effective condensate recovery system, collecting the hot condensate from the steam using equipment and returning it to the boiler feed system, can pay for itself in a remarkably short period of time.
Figure Condensate is a valuable resource and even the recovery of small quantities is often economically justifiable. The discharge from a single steam trap is often worth recovering. Un-recovered condensate must be replaced in the boiler house by cold make-up water with additional costs of water treatment and fuel to heat the water from a lower temperature.
Any condensate not returned needs to be replaced by make-up water, incurring further water charges from the local water supplier. Condensate above thistemperature must be cooled before it is discharged, which may incur extra energy costs. Similar restrictions apply in most countries, and effluent charges and fines may be imposed by water suppliers for non-compliance. Colder boiler feedwater will reduce the steaming rate of the boiler. The lower the feedwater temperature, the more heat, and thus fuel needed to heat the water, thereby leaving less heat to raise steam.
Valves above the water line can introduce oxygen as the velocity of the water lowers the pressure at the Valve stem. Flanges can have the same problem as Valves. Oxygen is dissolved in makeup water that was added to the boiler because of condensate leaks. Pumps with built in repellers that create a negative pressure in the pump stuffing box. How do you get rid of the dissolved oxygen..
Add chemicals to convert it. Hydrazine is an example. You are adding hydrogen that will combine with the oxygen to form water. In nuclear applications it is common to add hydrogen to the system for the same reason. Hydrogen and oxygen will combine to form water in a neutron flux. Deaerate the condensate. This is normally done by heating the condensate with steam in a deaerating tank that is located close to the suction of the boiler feed pump.
Convert to balanced, o-ring mechanical seals that will prevent air from coming into the stuffing boxes of condensate pumps through packing. Seal Valves above the water line and pipe flanges to prevent air from entering the system. Why are we concerned about carbon dioxide in condenste systems.. Where does the CO 2 come from.. Mammals exhale CO 2 it enters condensate and feed water: Through the packing in condnsate pumps that take a suction on hot wells Valves above the water line Gaskets Why do we have to use so much "Make Up" water in our boiler..
Because we lose so much of it. Background Molecules, which make up everything around us—including air—are in a constant state of motion. The hotter water molecules become, the faster they move, turning from water their liquid phase to steam their gas phase.
When liquid water turns to gas, not only do the molecules move much faster, they also are spaced much farther apart. They spread out so much that they generate pressure by pushing on each other and everything else they come into contact with. What happens when we take the heat source away from that steam? The molecules form liquid water again. This is called condensation. The air in our atmosphere is also a gas that exerts a fairly strong pressure of its own.
This experiment will illustrate what can happen when the changing pressure of condensing steam goes up against the pressure of air, which remains relatively constant. Use caution with thinner plastic containers—hot water can cause them to melt; and avoid glass—boiling water can cause glass to break. It should be too large to slip through the neck of the bottle via gravity alone but not so large that it would burst were it to get pushed through.
Knowing what we know now about water and steam pressure, why do you think this happens? In a heating process, condensate is the result of steam transferring a portion of its heat energy, known as latent heat, to the product, line, or equipment being heated.
In steam-using industries, Latent Heat refers to the energy required to transform water into steam, also known as the Enthalpy or Heat of Vaporization. By absorbing this Latent Heat, water becomes steam, and by releasing it, steam reverts to high temperature water condensate. When steam condenses, at the threshold or instant of phase change, the condensate temperature is the same as steam because only the latent heat has been lost, and the full amount of sensible heat remains.
Not wasting, but rather recovering and reusing as much of this sensible heat as possible is one of the main reasons behind condensate recovery. Condensate recovery is a process to reuse the water and sensible heat contained in the discharged condensate. Recovering condensate instead of throwing it away can lead to significant savings of energy, chemical treatment and make-up water.
Reusing hot condensate can lead to considerable savings in terms of energy and water resources, as well as improve working conditions and reduce your plant's carbon footprint. Feeding the boiler with high-temperature condensate can maximize boiler output because less heat energy is required to turn water into steam.
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