Efficiency of a boiler is the result of its basic heat transfer design. Boiler designs that use all possible heat transfer surfaces to their fullest advantage consistently produce the most efficient source of steam or hot water with the lowest total lifetime costs.
SOFTWARE FOR FIRE-TUBE & WATER-TUBE BOILERS
Softwares are based on new theoretical findings on heat transfer in boilers. It delivers unprecedented proven +/-2% uncertainty. It can be used to carry out tasks like:
• heat transfer analysis in boilers
• boiler design optimization
• retrofit of installed boilers.
Software calculates heat transfer in fossil fuel fired fire-tube and water-tube steam, hot water and waste heat boilers of arbitrary geometry and for arbitrary operating conditions (excess air, pressure up to 99bar/1435psi). Boiler can consist of multiple segments such as furnace, channels, chambers and tubes, with or without front or/and rear cooled door. The boiler segments can be combined, which makes calculation of next to every known boiler design possible.
Water-tube boilers are in essence of relatively simple basic design consisting of a large rectangular combustion chamber while fire-tube ones come in various designs. Following fire-boiler designs can be calculated with the software:
1. Tubular boiler
• single pass or double pass
• horizontal or vertical
• tubes can have coiled-wire turbulators or dents.
2. Furnace (combustion chamber)
• circular or rectangular
• horizontal or vertical
• with or without rectangular fins
• wetback or dryback
• with or without front cooled door.
3. Channel after furnace (if any)
• one or more
• circular or rectangular
• horizontal or vertical
• with or without rectangular fins
• with or without baffles.
4. Boiler with 1, 2 or 3 tube assemblies after furnace (2-pass, 2-pass reverse flue, 3-pass, 4-pass)
• horizontal or vertical
• tubes can have coiled-wire turbulators or dents.
5. Redirection channel between two tube sets (one in 3-pass and two in 4-pass boilers)
• circular or rectangular
• horizontal or vertical.
6. Channel before boiler exit (if any)
• one or more
• circular or rectangular
• horizontal or vertical.
7. Boiler with cooled rear door.
8. Waste heat boiler or exhaust gas boiler (such as hybrid biomass system) without or with supplemental firing .
9. Tubular economizer with or without fins (circular or rectangular). Can also be calculated separately as can stoichiometry of combustion.
Boiler can be made of following materials:
• boiler steel
• cast iron.
Economizer tubes can be made of following materials:
• steel
• copper.
Boiler liquid can be following:
• water
• Rankine cycle liquid
• thermal oil.
Input and output values can be either in Metric or English units.
Order of calculations
1. A stoichiometry of the combustion, adiabatic combustion temperature, flue-gas enthalpy at that temperature, and a first estimation for the furnace exit temperature are calculated.
2. Convective and radiant parts of the heat transfer are considered to be simultaneously coexistent. For convection, the relevant temperature is mean logarithmic, for radiation the mean radiant temperature that is calculated by proprietary procedure.
3. The impact of the turbulators or tube dents is taken into account according to the proprietary developed procedure.
4. The convective and radiant parts of the heat transfer in the furnace are summed-up and deducted from the flue gas enthalpy at the adiabatic combustion temperature. The result is a temperature at the furnace exit.
5. The calculated flue-gas exit temperature is compared to the estimated one in step 1. If they do not meet the preset difference (0.1°C) a new estimation is calculated as the average of assumed one in step 1 and just calculated one. The procedure is then repeated.
6. This same procedure is applied to every boiler segment using the exit temperature of flue gas from one segment as being the initial temperature in the next section. Thus, the initial temperature in next boiler section is equivalent to the exit temperature from preceding section.
7. The sum of the heat transferred in all boiler sections represents its heat output which, when divided by heat released from fuel, yields the boiler efficiency.
Discrepancy sources between measured and calculated values
There are always differences between calculated and actual values. The discrepancies are of an operational (fouling, scaling on gas and water side) and of mathematical nature (heat transfer equations are always derived from experiments). In general, for new and well maintained boilers the discrepancy to actual values is as low as 2% (boiler output, steam capacity, efficiency).
Heat balance for a boiler
Fuel fed to a burner is converted to heat. The heat is absorbed by the water in the boiler, but not all the heat released from the fuel is used to heat the water. Some of the heat is wasted in the process. The heat balance of a boiler consists of accounting for all the heat units in the fuel used or wasted. It is a balance because it is the sum of all the heat consumed. Heat balance of a boiler is found by using the following equation:
A = B + C
A= heat energy available in the fuel
B= heat energy absorbed any the water in the boiler
C= heat losses
Therefore: Efficiency of the unit = B divided by A
Energy losses in a boiler
Gases of combustion to atmosphere (about 9%)
Incomplete combustion (about 1%)
Moisture in fuel (less than 1%)
Moisture in air used for combustion (less than 1%)
Water vapor produced from the burning of hydrogen (about 2%)
Unburned combustibles (about 2%)
Radiation (about3%)
Total heat losses in this examples equal 18-19% While some of these losses are preventable losses over which the boiler operator has control, such as:
Heat carried away in the dry chimney gases
Incomplete combustion of the fuel
Unburned combustibles (about 2%)
SOFTWARE FOR FIRE-TUBE & WATER-TUBE BOILERS
Softwares are based on new theoretical findings on heat transfer in boilers. It delivers unprecedented proven +/-2% uncertainty. It can be used to carry out tasks like:
• heat transfer analysis in boilers
• boiler design optimization
• retrofit of installed boilers.
Software calculates heat transfer in fossil fuel fired fire-tube and water-tube steam, hot water and waste heat boilers of arbitrary geometry and for arbitrary operating conditions (excess air, pressure up to 99bar/1435psi). Boiler can consist of multiple segments such as furnace, channels, chambers and tubes, with or without front or/and rear cooled door. The boiler segments can be combined, which makes calculation of next to every known boiler design possible.
Water-tube boilers are in essence of relatively simple basic design consisting of a large rectangular combustion chamber while fire-tube ones come in various designs. Following fire-boiler designs can be calculated with the software:
1. Tubular boiler
• single pass or double pass
• horizontal or vertical
• tubes can have coiled-wire turbulators or dents.
2. Furnace (combustion chamber)
• circular or rectangular
• horizontal or vertical
• with or without rectangular fins
• wetback or dryback
• with or without front cooled door.
3. Channel after furnace (if any)
• one or more
• circular or rectangular
• horizontal or vertical
• with or without rectangular fins
• with or without baffles.
4. Boiler with 1, 2 or 3 tube assemblies after furnace (2-pass, 2-pass reverse flue, 3-pass, 4-pass)
• horizontal or vertical
• tubes can have coiled-wire turbulators or dents.
5. Redirection channel between two tube sets (one in 3-pass and two in 4-pass boilers)
• circular or rectangular
• horizontal or vertical.
6. Channel before boiler exit (if any)
• one or more
• circular or rectangular
• horizontal or vertical.
7. Boiler with cooled rear door.
8. Waste heat boiler or exhaust gas boiler (such as hybrid biomass system) without or with supplemental firing .
9. Tubular economizer with or without fins (circular or rectangular). Can also be calculated separately as can stoichiometry of combustion.
Boiler can be made of following materials:
• boiler steel
• cast iron.
Economizer tubes can be made of following materials:
• steel
• copper.
Boiler liquid can be following:
• water
• Rankine cycle liquid
• thermal oil.
Input and output values can be either in Metric or English units.
Order of calculations
1. A stoichiometry of the combustion, adiabatic combustion temperature, flue-gas enthalpy at that temperature, and a first estimation for the furnace exit temperature are calculated.
2. Convective and radiant parts of the heat transfer are considered to be simultaneously coexistent. For convection, the relevant temperature is mean logarithmic, for radiation the mean radiant temperature that is calculated by proprietary procedure.
3. The impact of the turbulators or tube dents is taken into account according to the proprietary developed procedure.
4. The convective and radiant parts of the heat transfer in the furnace are summed-up and deducted from the flue gas enthalpy at the adiabatic combustion temperature. The result is a temperature at the furnace exit.
5. The calculated flue-gas exit temperature is compared to the estimated one in step 1. If they do not meet the preset difference (0.1°C) a new estimation is calculated as the average of assumed one in step 1 and just calculated one. The procedure is then repeated.
6. This same procedure is applied to every boiler segment using the exit temperature of flue gas from one segment as being the initial temperature in the next section. Thus, the initial temperature in next boiler section is equivalent to the exit temperature from preceding section.
7. The sum of the heat transferred in all boiler sections represents its heat output which, when divided by heat released from fuel, yields the boiler efficiency.
Discrepancy sources between measured and calculated values
There are always differences between calculated and actual values. The discrepancies are of an operational (fouling, scaling on gas and water side) and of mathematical nature (heat transfer equations are always derived from experiments). In general, for new and well maintained boilers the discrepancy to actual values is as low as 2% (boiler output, steam capacity, efficiency).
Heat balance for a boiler
Fuel fed to a burner is converted to heat. The heat is absorbed by the water in the boiler, but not all the heat released from the fuel is used to heat the water. Some of the heat is wasted in the process. The heat balance of a boiler consists of accounting for all the heat units in the fuel used or wasted. It is a balance because it is the sum of all the heat consumed. Heat balance of a boiler is found by using the following equation:
A = B + C
A= heat energy available in the fuel
B= heat energy absorbed any the water in the boiler
C= heat losses
Therefore: Efficiency of the unit = B divided by A
Energy losses in a boiler
Gases of combustion to atmosphere (about 9%)
Incomplete combustion (about 1%)
Moisture in fuel (less than 1%)
Moisture in air used for combustion (less than 1%)
Water vapor produced from the burning of hydrogen (about 2%)
Unburned combustibles (about 2%)
Radiation (about3%)
Total heat losses in this examples equal 18-19% While some of these losses are preventable losses over which the boiler operator has control, such as:
Heat carried away in the dry chimney gases
Incomplete combustion of the fuel
Unburned combustibles (about 2%)
No comments:
Post a Comment