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EngineeringMechanical Engineeringhe tank of a leaky air compressor originally holds 90 L of air at 33deg C and 225 kPa.
Intermittent manual blowdown is designed to remove suspended solids, including any sludge formed in the boiler water.
The manual blowdown take-off is normally located in underneath of the lowest boiler drum, where any sludge formed would tend to settle.
The maximum levels easy for each specific system could be determined only from experience.
The result of water characteristics on steam quality can be verified with steam purity testing.

The line must also be located in order that boiler feedwater or chemical feed solution will not flow straight into it.
The size of the lines and control valves depends on the amount of blowdown required.
The tank of a leaky air compressor originally holds 90 L of air at 33deg C and 225 kPa.
During a compression process, 4 grams of air is lost; the rest of the air occupies 42 L at 550 kPa.

In certain cases, you’ll be able to exceed standard total solids , silica, or alkalinity limits.
Antifoam agents have already been applied successfully to allow higher-than-normal solids limits, as shown in Figure 13-1.
Chelating and effective dispersant programs also may allow certain water criteria to be exceeded.
Heat recovery is used frequently to lessen energy losses that derive from boiler water blowdown.
Figure 13-2 illustrates an average boiler blowdown heat recovery system using a flash tank and heat exchanger.
Properly controlled intermittent manual blowdown removes suspended solids, allowing satisfactory boiler operation.

Generally in most units, the take-off line is several inches below the low water level.
Equipment for manual blowdown, considered a part of the boiler and installed with the unit, usually consists of a take-off line, a quick-opening valve, and a shut-off valve.
The take-off line is definitely located in the cheapest part of the lowest boiler drum, where

Figure 13-4 Typical Steam Drum Showing Continuous Blowdown Location

[newline]With the use of a competent heat exchange unit, the only real heat loss may be the terminal temperature difference between the incoming makeup water and the blowdown water to the sewer.
In plants with sodium zeolite softened makeup water, automatic control systems can maintain boiler water conductivity within 5% of the set-point.
Plant operating records have verified that with manual adjustment, continuous blowdown is within this 5% range no more than 20% of the time.

• Because chlorides usually do not precipitate in the boiler water, the relative chloride concentrations in feedwater and boiler water offer an accurate basis for calculating the rate of blowdown.
• Other boiler water constituents such as for example chlorides, sodium, and silica are also used as a means of controlling blowdown.
• It offers several benefits not provided by the use of bottom blowdown alone.
• Through improved control methods, including automatic boiler blowdown equipment, boiler water blowdown could be reduced to maintain the solids close to but not above the maximum level permissible.

Through improved control methods, including automatic boiler blowdown equipment, boiler water blowdown can be reduced to keep up the solids close to but not above the maximum level permissible.
Another major benefit of continuous blowdown may be the recovery of a great deal of its heat content by using blowdown flash tanks and heat exchangers.
Control valve settings should be adjusted regularly to improve or decrease the blowdown in accordance with control test results also to maintain close control of boiler water concentrations all the time.

Deg Gig Timeline

In general, the average plant saves approximately 20% of boiler blowdown when changing from manually adjusted continuous blowdown to automatically controlled continuous blowdown.
This reduction is gained without threat of scale or carryover due to high boiler water solids.
The rate of blowdown required depends on feedwater characteristics, load on the boiler, and mechanical limitations.

• manually controlled boiler blowdown are often quite wide, with the lower limits below 70% of the maximum safe value.
• When an excess way to obtain exhaust or low-pressure steam has already been available, there is little justification for installing heat recovery equipment.
• The rate of blowdown required depends on feedwater characteristics, load on the boiler, and mechanical limitations.
• Scale reduction through proper pretreatment and internal chemical treatment results in cleaner internal surfaces for more efficient heat transfer and resultant energy savings.

Quantity feedwaterThe blowdown can range from significantly less than 1% when an exceptionally high-quality feedwater is available to higher than 20% in a crucial system with poor-quality feedwater.
In plants with sodium zeolite softened makeup water, the percentage is often determined by method of a chloride test.

In this case, a high blowdown rate must get rid of the contaminants as rapidly as possible.
Usually, continuous blowdown equipment is installed by the boiler manufacturer.
The exact located area of the continuous blowdown take-off line depends primarily on the water circulation pattern.

Continuous blowdown, because the term implies, may be the continuous removal of water from the boiler.
It offers many advantages not provided by the application of bottom blowdown alone.
For instance, water may be removed from the location of the highest dissolved solids in the boiler water.
Also, a maximum of dissolved solids could be removed with minimal lack of water and heat from the boiler.
Its purpose is to control boiler water parameters within prescribed limits to minimize scale, corrosion, carryover, and other specific problems.
These solids are due to feedwater contamination, by internal chemical treatment precipitates, or by exceeding the solubility limits of otherwise soluble salts.