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.
Few parameters critical to health of the Boiler are
(4)Heat rate of the Boiler. This is a composite index of many performance indicators. Most of them will appear below.
(5)Unburnt fuel in flue gas and at boiler bottom .
(6)Flue gas furnace exit temperature.
(7)Boiler tube metal temperatures.
(8)Oxygen in flue gas.
(9)Imbalances in flue gas temperature over a cross section.
(10)Spray water consumption in Super heater and Reheater.
(11)Heat radiation from insulation.
The above all affects the performance of the boiler.
Boiler efficiency is mainly depended on the amount of losses in the system. In high capacity pulverized coal fired boilers the total losses account to about 12 to 14%. Roughly 50% of the losses are governed by fuel properties like hydrogen in fuel, moisture in fuel and ambient air conditions. The other 50% losses are carbon loss and dry gas loss. The best efficiency in the boiler can be achieved if the losses are kept to the minimum. Since 50% of the losses are dependent on the fuel and ambient condition, the best efficiency can be achieved by properly tuning the other 50%, i.e. mainly carbon loss and dry gas loss.
The following conditions will occur when a gas-fired boiler is leaking:
The working pressure of natural gas changes.
There is a strong airflow sound near the source of the leak.
The hand-held alarm makes an abnormal sound.
If the boiler has a serious leakage, the fixed alarm will issue an automatic alarm and the exhaust fan will be opened automatically.
