【Daily Question】Chemical Engineering Principles 320: Scale (February 16)
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This post was last edited by “Back to Cambridge” on February 27, 2016, at 11:24. Starting today, the Chemical Engineering Theory section is launching the “Question of the Day” activity, aimed at helping everyone reinforce their basic knowledge of chemical engineering. Subsequently, series such as “Fundamentals of Chemical Engineering”, “Mass Transfer and Separation”, “Chemical Thermodynamics”, and “Chemical Process Technology” will be introduced. We hope for your active participation! Wishing you all a Merry Christmas~~ For replies to the “Question of the Day” activity, answers can be viewed directly; however, the thread will be closed after one day! ! To encourage continued participation from everyone this year! Participation earns 3 wealth points, with an additional 4 wealth points for correct answers~~~ Short answer question: What are the hazards of scale on the operation of thermal equipment? Answer: The harms of scale to boilers: 1) Wasting fuel. 2) Affects safe operation. Due to the poor thermal conductivity of scale, heat from the metal surface cannot be transferred quickly, which leads to an **increase in the temperature of the heated metal surface. This results in a significant reduction in strength, causing the pipe wall in the area affected by scaling to overheat, deform, bulge, crack, and even burst, posing a threat to safe production. 3) Affect the water cycle. If scaling occurs inside the water wall, it reduces the flow cross-sectional area and increases the flow resistance; in severe cases, it can block the tubes and disrupt the water circulation. 4) Shortens the service life of the boiler. The accumulation of scale causes corrosion of the boiler’s metal, necessitating shutdowns for regular descaling, which reduces the boiler’s operating time and results in significant waste of manpower and resources. When mechanical and chemical methods are used for descaling, the heating surfaces are damaged, thereby shortening the boiler’s service life.
1) Wasting fuel. 2) Affects safe operation. Due to the poor thermal conductivity of scale, heat from the metal surface cannot be transferred quickly, which leads to an **increase in the temperature of the heated metal surface. This results in a significant reduction in strength, causing the pipe wall in the area affected by scaling to overheat, deform, bulge, crack, and even burst, posing a threat to safe production. 3) Affect the water cycle. If scaling occurs inside the water wall, it reduces the flow cross-sectional area and increases the flow resistance; in severe cases, it can block the tubes and disrupt the water circulation. 4) Shorten the service life of the boiler. The accumulation of scale causes corrosion of the boiler’s metal, necessitating shutdowns for regular descaling, which reduces the boiler’s operating time and results in significant waste of manpower and resources. When mechanical and chemical methods are used for descaling, the heating surfaces are damaged, thereby shortening the boiler’s service life.
What are the hazards of scale to the operation of thermal equipment? 1) Wasting fuel. 2) Affects safe operation. Due to the poor thermal conductivity of scale, heat from the metal surface cannot be transferred quickly, which leads to an **increase in the temperature of the heated metal surface. This results in a significant reduction in strength, causing the pipe wall in the area affected by scaling to overheat, deform, bulge, crack, and even burst, posing a threat to safe production. 3) Affect the water cycle. If scaling occurs inside the water wall, it reduces the flow cross-sectional area and increases the flow resistance; in severe cases, it can block the tubes and disrupt the water circulation. 4) Shorten the service life of the boiler. The accumulation of scale causes corrosion of the boiler’s metal, necessitating shutdowns for regular descaling, which reduces the boiler’s operating time and results in significant waste of manpower and resources. When mechanical and chemical methods are used for descaling, the heating surfaces are damaged, thereby shortening the boiler’s service life.
The harms of scale to boilers: 1) Waste of fuel. 2) Affects safe operation. Due to the poor thermal conductivity of scale, heat from the metal surface cannot be transferred quickly, which leads to an **increase in the temperature of the heated metal surface. This results in a significant reduction in strength, causing the pipe wall in the area affected by scaling to overheat, deform, bulge, crack, and even burst, posing a threat to safe production. 3) Affect the water cycle. If scaling occurs inside the water wall, it reduces the flow cross-sectional area and increases the flow resistance; in severe cases, it can block the tubes and disrupt the water circulation. 4) Shortens the service life of the boiler. The accumulation of scale causes corrosion of the boiler’s metal, necessitating shutdowns for regular descaling, which reduces the boiler’s operating time and results in significant waste of manpower and resources. When mechanical and chemical methods are used for descaling, the heating surfaces are damaged, thereby shortening the boiler’s service life.
The harms of scale to boilers: 1) Waste of fuel. 2) Affects safe operation. Due to the poor thermal conductivity of scale, heat from the metal surface cannot be transferred quickly, which leads to an **increase in the temperature of the heated metal surface. This results in a significant reduction in strength, causing the pipe wall in the area affected by scaling to overheat, deform, bulge, crack, and even burst, posing a threat to safe production. 3) Affect the water cycle. If scaling occurs inside the water wall, it reduces the flow cross-sectional area and increases the flow resistance; in severe cases, it can block the tubes and disrupt the water circulation. 4) Shortens the service life of the boiler. The accumulation of scale causes corrosion of the boiler’s metal, necessitating shutdowns for regular descaling, which reduces the boiler’s operating time and results in significant waste of manpower and resources. When mechanical and chemical methods are used for descaling, the heating surfaces are damaged, thereby shortening the boiler’s service life.
It increases the heat transfer resistance; in severe cases, it can lead to blockages, changes in the flow rate of hot/cold fluids, and localized overheating and cracking of the equipment. Contaminating the fluid medium will, over time, shorten the service life of the equipment.
Consumes fuel. 2) Affects safe operation. Due to the poor thermal conductivity of scale, heat from the metal surface cannot be transferred quickly, which leads to an **increase in the temperature of the heated metal surface. This results in a significant reduction in strength, causing the pipe wall in the area affected by scaling to overheat, deform, bulge, crack, and even burst, posing a threat to safe production. 3) Affect the water cycle. If scaling occurs inside the water wall, it reduces the flow cross-sectional area and increases the flow resistance; in severe cases, it can block the tubes and disrupt the water circulation. 4) Shorten the service life of the boiler.
1. Scale blocks heat exchange, reducing the heat transfer efficiency； 2. If the water wall tubes of a boiler become scaled, the scale prevents the tube metal from being effectively cooled by water, which can lead to tube rupture ； 3. Scale can also cause under-scale corrosion in metals ； 4. Severe scale can block pipes.
The main reason is the poor thermal conductivity of scale, which is only one-tenth to one-thousandth that of steel plates. The formation of scale poses the following hazards to thermal equipment: 1) Fuel waste. It has been determined that when the scale thickness reaches 1.5 millimeters, 6% more fuel is required ； When the scale thickness is 5 millimeters, 15% more fuel is required ； When the scale thickness is 8 millimeters, 34% more fuel is required ； 2) Affects safe operation. Due to the poor thermal conductivity of scale, heat from the metal surface cannot be transferred quickly, which causes the temperature of the heated metal surface to rise significantly. This leads to a marked decrease in strength, and results in overheating, deformation, bulging, cracking, and even bursting of the pipe wall at the scaled areas, posing a threat to safe production. 3) Affect the water cycle. If scaling occurs inside the water wall, it reduces the flow cross-sectional area and increases the flow resistance; in severe cases, it can block the tubes and disrupt the water circulation. 4) Shortens the service life of the boiler. The accumulation of scale causes corrosion of the boiler’s metal, necessitating regular shutdowns for descaling, which reduces the boiler’s operating time and consumes a great deal of labor and resources. When mechanical and chemical methods are used for descaling, the heating surfaces are damaged, thereby shortening the boiler’s service life.
What are the hazards of scale to the operation of thermal equipment? Answer: The harms of scale to boilers: 1) Wasting fuel. 2) Affects safe operation. Due to the poor thermal conductivity of scale, heat from the metal surface cannot be transferred quickly, which leads to an **increase in the temperature of the heated metal surface. This results in a significant reduction in strength, causing the pipe wall in the area affected by scaling to overheat, deform, bulge, crack, and even burst, posing a threat to safe production. 3) Affect the water cycle. If scaling occurs inside the water wall, it reduces the flow cross-sectional area and increases the flow resistance; in severe cases, it can block the tubes and disrupt the water circulation. 4) Shortens the service life of the boiler. The accumulation of scale causes corrosion of the boiler’s metal, necessitating shutdowns for regular descaling, which reduces the boiler’s operating time and results in significant waste of manpower and resources. When mechanical and chemical methods are used for descaling, the heating surfaces are damaged, thereby shortening the boiler’s service life.
1) Wasting fuel. 2) Affects safe operation. Due to the poor thermal conductivity of scale, heat from the metal surface cannot be transferred quickly, which leads to an **increase in the temperature of the heated metal surface. This results in a significant reduction in strength, causing the pipe wall in the area affected by scaling to overheat, deform, bulge, crack, and even burst, posing a threat to safe production. 3) Affect the water cycle. If scaling occurs inside the water wall, it reduces the flow cross-sectional area and increases the flow resistance; in severe cases, it can block the tubes and disrupt the water circulation. 4) Shorten the service life of the boiler. The accumulation of scale causes corrosion of the boiler’s metal, necessitating shutdowns for regular descaling, which reduces the boiler’s operating time and results in significant waste of manpower and resources. When mechanical and chemical methods are used for descaling, the heating surfaces are damaged, thereby shortening the boiler’s service life.