Flash Steam Systems

FLASH STEAM SYSTEM

Flash Steam is the form of steam formed when the condensate under high pressure is reduced to a lower pressure, throwing out the energy it contains. Because this steam is low pressure, it can be used in applications such as processes that do not require high pressure, preheating of boiler feed water, and degasser steam feeding.

In the condensate system, one of the simplest and  most efficient methods to make use of the resulting flash steam is the use of a flash vessel. Inside the flash vessel, the condensate and the emergent flash steam have enough space to separate from each other. The steam rising to the top can be fed into a steam line for a technical application, therefore reducing the steam generation burden on the boiler. Additional savings are obtained through reduced expenditure on water purification. The successful application of flash vessel systems depends on the size of the flash vessel, the stability of the pressure control, and the effective draining of condensate.

Steam Plus FVS Compact Flash Steam Recovery System is an innovative heat recovery system that delivers major energy savings by recovering waste heat from a condensate return system and using it to pre-heat boiler feedwater.

Thanks to the tangential condensate inlet the flash vessel works like a cyclone separator, forcing the incoming condensate to flow in a spiral pattern. The Steam Plus Flash Steam Tank has a tangential condensate inlet design Pre-assembled unit minimises design and installation time. Using condensate returned from the steam distribution system to heat boiler feedwater is an extremely effective energy saving method. For every 6°C rise in boiler feedwater, 1% is typically knocked off the boiler energy bill.

CALCULATION

The amount of blowdown can be calculated with the following formula.

Q=BxS/(T-B)

B: Feedwater TDS Value μs/cm

T: Desired TDS value in the boiler μs/cm

S: Boiler capacity (kg/h)

Q: Blowdown amount (kg/h)

For example;

Boiler capacity 14.000 kg/h - 7 bar operating pressure, feed water TDS value 300 μs/cm

In case the desired TDS value in the boiler is accepted as 6,000 μs/cm;

Amount of blowdown required hourly in the steam boiler =Q=300*14,000/(6,000–300)=737 kg/h

mflash= (h’-h”) / r x Q(kg/h)

*h' = Enthalpy of condensate at operating pressure (kJ/kg)

*h”=Enthalpy of Condensate at atmospheric pressure and 100°C (kJ/kg)

*r=1 is the enthalpy of evaporation at atm (kJ/kg)

According to the values ​​you have designed;

Flash: ((722-417)/2258) = 13.3% flash vapor will be produced.

Amount of Flash Steam that can be produced from the blowdown = 737 kg/h * 0.133 = *98 kg/h we can obtain steam at 0.5 bar.

Condensate Amount from the flash steam system = 737 – 98 = **639 kg/h.

* With 98 kg/h 0.5 bar steam, approximately 8 m³ natural gas is saved per hour by feeding the degasser system, if available.

The temperature of the 638 kg/h 90-95°C waste water separated from the flash steam, which will normally be sent to the drainage, will be reduced to 30°C and approximately Q= 638*1*(95-30°C) = 41.470 kcal/h energy will be obtained.

With this energy, for example, it is possible to raise 2 tons of water by 20°C using a plate heat exchanger.