Here load means, amount of steam drawn from the boiler. So when the load increases, the specific volume of the steam in the boiler increases reducing the pressure. This inturn demands for more feed water and more amount of fuel to be burnt. So, for any boiler there will be a feed water level control system put in place to measure the water level in drum. As and when the level of water in the drum reduces, the controller sends a signal to the feed water pump to start and stops when the desired water level is reached. This way the steam generation continues to maintain the desired pressure.
A water level sensor fail on a steam boiler is extremely dangerous. The low water cut of should be tested daily. If the sensor fails the boiler could turn all the water into steam, leaving the boiler dry. Without water in the boiler the flame from the burner would heat up the heating surface to extreme temperatures and would crack and damage the inside of the boiler. But that’s not the dangerous part. If water added to boiler while it is extremely hot. Once water touches the extremely hot heating service, water would immediately start to evaporate into steam. When water evaporates it expands 18x it’s original size. The boiler would explode from the sudden increase in pressure from the inside. Some in some cases, boilers that have exploded out of a building and have landed 100s of feet away.
Missing insulation reduces the system’s efficiency. Insulation helps hold heat in the system, and when the heat can dissipate, more fuel is needed to maintain proper temperature and pressure.
Since missing insulation may not be visible, the best way to detect it is with a thermal imager. If you don’t have a thermal imager as a part of your building’s operations, a plumber or other professional likely will carry one. If your energy costs have increased without a rise in the amount you use the boiler, suspect missing insulation and call to have the system inspected with a thermal imager.
Soot on the heating surfaces. Even a thin layer of soot will reduce the boiler efficiency. Not the right fuel for the burner. For instance, diesel oil to a rotary cup burner wouldn't do. Too low feed water temperature.
There are many opinions on the best way to clean a steam boiler. One of the oldest ways is to dissolve a pound of tri-sodium phosphate (TSP) and a pound of caustic soda (lye) in water and pour it into the boiler. Let it cook for a few hours and then drain the boiler. If you can't buy TSP in your town, try a commercial soap called MEX. It works well and will not damage the rubber gaskets found in some boilers. However, before you clean any boiler, check the manufacturer's instructions for their recommendations.
The causes of coal erosion as distinct from all the other types of erosion are many but from a theoretical point of view are simply high velocity particles impacting and rubbing along the surface of the tubes.
The boiler designer minimises this by providing a volume in the furnace and a direction of travel of the coal such that it is burned before it can touch the tubes. This can be defeated by increasing the velocity reducing the combustibility or increasing the mass flow. All of these parameters occur if you reduce the calorific value of the fuel or overload the boiler. If you had no erosion before changing your fuel that is the cause. If you have never had design fuel you dont know if it would have eroded anyway. If it would the cause will be a different reason such as arodynamic flows and aiming of the burner or size of the tartget fireball centre. This is a serious problem and should be dealt with by an experienced expert.
It could also say, how much heat is required to rais the water temperature from 60 ℃ to 90 ℃.
To calculate heat required follow below steps
Q= mCp dt
Where
m - water flow rate (kg/hr)
Cp- specific heat of water
dt- temperature differences ( 90–60)
You will get heat required in kcal/ hr.
dividing to Q by fuel GCV and system efficiency you will come to know how much fuel (either it is coal or oil) required to raise the temperature of water from 60 ℃ to 90℃.
1.Primary air is used for transportation of fine coal particle from coal mill to boiler floor at different elevations as per requirement.
2.Primary air is used for preheating of moisturised coal in to the coal mill so that minimum energy is required for combustion of the same.
3.As we all know that only 23% oxygen is available in the air by weight. For combustion of huge quantity of coal inside the boiler very high quantity of oxygen is required. This oxygen requirement will be completed by secondary air which is supplied by FORCED DRAFT fans through ducts.
This secondary air is coming via air preheater hence its outlet temperature increases this will help in combustion and low heat input is required for combustion of coal.
