At a minimum, boiler feedwater must
be softened water for low pressure boilers
and demineralized water for high pressure boilers. It must be free of oxygen and essentially free of hardness constituents and suspended solids.
Which water is used as boiler feed water?
The steam or hot fluid is then recirculated out of the boiler for use in various processes in heating applications. The boiler receives the feed water, which consists of
varying proportion of recovered condensed water (return water)
and fresh water, which has been purified in varying degrees (make up water).
Is standard for boiler feed water?
5 to 2.0 MN/ma and above
, the boiler feed water used should be completely demineralized and the characteristics of the boiler feed water and boiler drum water should also be main- tained as stringent as for high pressure boilers operated at 59 MN/m* pressure and above, since recovery boilers cannot tolerate even a …
What is necessity of feed water treatment?
In order to prevent corrosion,
oxygen that is present in the pure water to be used in the production of saturated steam must be eliminated through the use of chemicals and de-aeration towers
. This is what feedwater treatment does.
Can we use tap water to feed boiler?
The reason why
industrial boilers cannot use tap water
Impurities
in tap water are divided into suspended impurities, colloidal impurities, and soluble impurities, which can cause certain harm to the boiler.
What means boiler feed water?
Feedwater is
water that undergoes purification or preheating and is then supplied to boilers
for hot water and steam production, or it can remain still. It is typically found in thermal power plants where it is stored and conditioned in tanks, known as boiler feedwater.
What are the parameters of boiler feed water testing?
The HI-3827 boiler and feedwater chemical test kit measures 6 main parameters;
alkalinity, chloride, hardness, pH, phosphate and sulphite
. All the tests are performed with a titration method except for the pH test.
Which of the following should not be a requirement of boiler feed water?
2. Which of the following should not be a composition of boiler-feed water? … Explanation:
Excess of impurities in boiler-feed results
in scale and sludge formation, corrosion, priming, foaming and caustic embrittlement. It does not contribute to the decomposition process.
What is the recommended hardness of boiler feed water?
In boilers the hardness of the water can cause the formation of scale and sludge or mud. The hardness must be removed in the makeup water to the return system. Total hardness should
not exceed 50 PPM
.
What should be the pH of boiler feed water?
The consensus is that feedwater oxygen, iron, and copper content should be very low (e.g., less than 7 ppb oxygen, 20 ppb iron, and 15 ppb copper for a 900 psig boiler) and that pH should be maintained
between 8.5 and 9.5
for system corrosion protection.
Why is boiler water treatment required?
Why is boiler treatment required? Boiler corrosion: water contains oxygen which will eventually lead to the thinning and pitting of the metal pipes. … Suitable boiler water treatments
will eliminate oxygen from the water
and help prevent corrosion.
What are the 5 control of boiler carryover?
As discussed earlier, the principle chemical factors causing carryover are the
dissolved solids, suspended solids, alkalinity, silica (vaporous carryover), and oil contents of boiler water
. In many cases, limiting the concentration of these components will satisfactorily control carryover.
What are the quality requirements of boiler and cooling waters?
The most important parameters are:
conductivity, pH, sodium and silica concentration
and as the primary corrosion parameter, oxygen content.
How do you make boiler feed water?
The feed water is put
into the steam drum from a feed pump
. In the steam drum the feed water is then turned into steam from the heat. After the steam is used it is then dumped to the main condenser. From the condenser it is then pumped to the deaerated feed tank.
Why the fresh water is not recommended as boiler feed water?
Water for boilers. All natural waters contain varying amounts of suspended and dissolved matter as well as dissolved gases. The type and amount of impurities in fresh water vary with the source (lake, river, well) and with the area of location. …
Poor quality water gives poor quality steam
.
What is the standard value of hydrazine in boiler water?
The normal level of hydrazine reserve to be maintained in the boiler water is
between 0.1 and 0.3 ppm N2H4
. As the products of reaction are harmless – nitrogen as and water, hydrazine treatment does not increase the dissolved solids content of the boiler water.
How does a boiler water feeder work?
On a signal (normally from the low water cutoff valve) the water feed valve
will open to send additional makeup water into the steam boiler
. The McDonnell & Miller float operated water feed valve will automatically send water into the steam boiler if water falls sufficiently to activate its float.
What is the chlorine test?
The test for chlorine can use either type of
litmus paper
, but blue litmus paper is used most commonly. The litmus paper must be damp – the water dissolves some of the chlorine so that it can react with the indicator on the litmus paper. Test for chlorine. Result. Place damp blue litmus paper in a test tube of the gas.
What is meant by pH in boiler water test?
A PH test indicates how alkaline or acidic your boiler water is. Ideally, the water should be maintained
between 9.5-11.5 PH
inside the boiler (alkaline environment). Engineers perform this test to prevent acidic corrosion from the water (low PH) as well as scale formation (high PH).
What is P and M alkalinity in boiler?
p alkalinity is
the measurement of alkalinity given by hydroxide ions and half of the carbonate alkalinity
. m alkalinity is the measurement of alkalinity given by hydroxide ions and total carbonate alkalinity. Indicator. Phenolphthalein indicator is used to determine p alkalinity.
What is scale and sludge?
If the precipitation takes place in the form of loose and slimy precipitate, it is called sludge. On the other hand, if
the precipitated matter forms a hard, adhering crust/coating on the inner walls of the boiler
, it is called scale.
What is scale formation in boiler?
Boiler scale is caused by impurities being precipitated out of the water directly on heat transfer surfaces or by suspended matter in water settling out on the metal and becoming hard and adherent. Scale is
formed by salts that have limited solubility but are not totally insoluble in boiler
water. …
What is mechanical deaeration?
Several principles apply to the mechanical deaeration of feedwater:
The solubility of any gas in a liquid is directly proportional to the partial pressure of the gas at the liquid surface
.
The solubility of a gas in a liquid decreases with increasing liquid temperature
(see Figure 10-2)
Why is the pH in my boiler water high?
In order to minimize corrosion of boiler hardware, the pH of feedwater must be controlled within a narrow range. Too low a pH will result in excessive corrosion of iron components, while too
high a pH will result in attack on copper containing parts
.
What is priming and carryover?
Boiler water carry-over is the contamination of the steam with boiler-water solids. … Priming is the
carryover of varying amounts of droplets of water in the steam
(foam and mist), which lowers the energy efficiency of the steam and leads to the deposit of salt crystals on the super heaters and in the turbines.
What is water carryover?
Introduction to carryover
Carryover results
from incomplete separation of water from mixture of steam and water
. Carryover, a commonly faced problem in many boiler systems results in many other issues like corrosion and water hammer. In common situations, drum water passes in to the steam system along with the steam.
How do you prevent carryover?
Prevention of Carryover
The prime means of preventing carryover is to have
good mechanical steam separation devices
. For low/medium pressure fire tube boilers where steam purity is not stringent, gravity separation is normally satisfactory.
