Stack losses for natural gas _ natural resources canada

Calculating stack losses for boilers using natural gas involves six steps and is based on the following:

Ultimate Analysis values for natural gas‚ lb/ lb fuel Carbon (C)

• Loss due to CO in the flue gas is negligible. How to work out fuel cost for a trip CO concentrations in the flue gas should normally be under 50 ppm by volume. Average price for gas and electric per month A concentration of about 350 ppm CO is on the brink of violation of CCME emissions guidelines‚ and represents a loss of efficiency of about 0.11 % of fuel input.

• Loss due to unburned hydrocarbons in the flue gas is negligible.


Costco gas vacaville ca These should normally be under 50 ppm by volume. Price of gasoline in canada 2013 100 ppm would represent a loss of efficiency of about 0.1 % of fuel input.

Obtain the maximum capacity rating (MCR) of the boiler unit. Gas prices merced ca This is nameplate information.

• For high temperature water generators the units are millions of Btu/ h. Gas cost trip planner 1 lb of steam = 1000 Btu is an approximation sufficiently accurate for this analysis.

It is important that measurements of flue gas temperature and composition be representative. Current cost of natural gas per cubic foot There may be stratification in the gas duct‚ particularly at low loads. How much gas would it take to drive 2000 miles Sampling at a few different locations in the gas duct is desirable.

Permanently installed (on-line) flue gas analyzers almost always have a moisture trap to condense water vapor and remove it from the sample upstream from the analyzer cell. Trip gas cost calculator canada The sample is therefore analyzed on a dry gas basis. Trip cost gas calculator canada Sometimes portable flue gas analyzers are used to obtain a spot measurement without employing a moisture trap. Costco gas prices merced ca Then the sample is analyzed on a wet gas basis‚ and the result must be converted to the dry gas basis.

Convert to a dry gas basis using the following formula for natural gas:

Obtain the CO 2 ‚ % by volume‚ dry gas basis. Average cost of electricity and gas per month 2012 When firing any given fuel the amount of CO 2 in the flue gas is related to the amount of O 2 in the flue gas. Gas cost calculator ontario For natural gas‚ the relationship is defined by the following equation:

Some portable analyzers will print out a value for CO 2 in the flue gas‚ perhaps based on a calculation using the oxygen measurement. Figure my gas cost trip It is important to ensure that the O 2 and CO 2 values used in subsequent calculations are dry-basis values.

Determine the actual unit output at the time of test. Average natural gas prices by state This is usually available from the control panel display. How many gallons of gas to travel 1000 miles It may be displayed in lb/ h of steam or millions of Btu/ h. Calculate gas cost per mile Convert it to a percentage of the maximum capacity rating. How much gas would it cost Step 2. Average gas prices by month 2008 Calculate dry flue gas (DG)‚ lb/ lb fuel

For natural gas containing 0 % sulphur and fired with negligible C O and hydrocarbons‚ the ASME formula for DG simplifies to: DG‚ lb/ lb fuel‚ = ( 11 C O 2dry + 8 O 2dry + 7 N 2 ) x C

The value of excess air is not needed for calculation of stack losses‚ but it is the most common parameter of burner performance‚ so it is useful to calculate it for the likely range of O 2 in the flue gas.

The ASME formula for excess air (EA)‚ % by volume‚ when C O is negligible‚ is: EA‚ % by volume‚ =

For natural gas of the given composition‚ the table below gives the relationship of excess air to flue gas composition. Gas heating cost calculator O 2dry‚ %

The ASME formula for L DG‚ % of fuel input‚ is: L DG‚ % of fuel input‚ = [ DG x C p x ( FGT – CAT)] x

= 0.00105 x DG x ( FGT – CAT) Commentary on dry flue gas loss

The dry flue gas loss (L DG ) can be reduced by reducing the amount of dry flue gas (DG) and by reducing the difference between flue gas temperature (FGT) and combustion air temperature (CAT).

DG can be reduced by reducing the excess air‚ but only up to a point; insufficient excess air leads to increased emissions of C O and hydrocarbons‚ even a risk of furnace explosion. Calculate gasoline cost per mile The lower limits of excess air are determined by the ability of the burner to mix the fuel and air‚ and by the accuracy of the burner controls in metering the two fluids. Average cost of gasoline per year Good burners with good controls should be able to operate with about 10 % excess air at full load‚ perhaps 30 % excess air at 20 % of full load.

Reducing excess air has a moderate effect on reducing the value of DG. How much does a gallon of gas cost in brazil This can be explored by substituting different values for CO 2 ‚ O 2 and N 2 into the formula for DG. Estimate gas cost for trip canada It is necessary to maintain the correct relationship in composition‚ so use the values from the table in Step 3‚ or interpolate between them.

While reducing excess air only moderately reduces DG‚ the effect on reducing L DG is greater‚ because reducing DG also reduces the flue gas temperature ( FGT). Calculate total gas cost trip The reduced volume of flue gas passing over the same heat exchange surface results in a lower end temperature‚ but the reduction in FGT is not easy to predict‚ and is best determined by experiment.

FGT can also be reduced by exposing more heat exchange surface to the flue gas‚ such as an economizer‚ which heats the feedwater‚ or an air heater which heats the combustion air. Costco gasoline timings One can assume a lower value for FGT‚ calculate its effect on L DG ‚ and then determine whether the improvement in efficiency‚ and corresponding fuel savings‚ justify the cost of the additional heat exchanger.

It should be noted that when an air heater is employed‚ the combustion air temperature (CAT) is measured where the air enters the air heater‚ not at the burners.

When adding heat exchange surface it is important that the final FGT be kept above the dewpoint‚ to avoid condensation‚ unless the heat exchanger is designed to accommodate it. Gastric band surgery cost south africa Condensing flue heat exchangers can offer substantial gains in efficiency‚ but are beyond the scope of this discussion. Average cost of gas in us When firing natural gas‚ a minimum temperature of the heat exchanger surface to avoid condensation is about 105 °C (220 °F) Step 5. Gas chromatography mass spectrometry theory Calculate loss due to moisture from combustion of hydrogen (L H )‚ % of fuel input

The ASME formula for L H‚ % of fuel input is: L H‚ % of fuel input

Enthalpy of liquid at CAT (h f ‚ Btu/ lb) vapor at 1 psia & FGT (h g‚ Btu/ lb)

h g can be calculated as follows: h g ‚ Btu/ lb = 1055 + (0.467 x FGT)

L H ‚ % of fuel input = 0.00935 x (h g – h f ) Commentary on loss due to moisture from combustion of hydrogen

In the process of combustion the hydrogen content of the fuel is converted to H 2 O‚ which normally leaves the stack as water vapor‚ carrying with it the heat required to convert it from liquid to vapor. Gas price for trip calculator With fuels high in hydrogen‚ such as natural gas‚ this is a significant loss‚ upwards of 10 % of the energy in the fuel‚ depending on flue gas temperature.

Much of this loss can be recovered by employing condensing flue heat exchangers‚ but as already stated‚ these are outside the scope of this discussion.

In conventional systems‚ minimizing L H is a matter of reducing FGT but staying above the dewpoint to avoid condensation. Estimate gas cost for trip As already stated‚ safe minimum temperatures for heat exchanger surfaces handling flue gas from natural gas are about 105 °C or 220 °F. Calculate gas costs for my trip Step 6. The cost of gasoline Calculate stack losses (L S )‚ % of fuel input

Stack losses can be minimized by reducing excess air‚ which reduces the quantity of flue gas that is heated to exhaust temperature (FGT)‚ and by reducing the exhaust temperature. Average gas cost 2014 The latter can be accomplished by adding heat exchange surface‚ such as economizers and air heaters‚ within the constraints already discussed. Gas cost travel The former can be accomplished by improving burner performance‚ through burner design or precise combustion controls. Average cost of diesel fuel in california In heating plants with more than one generating unit‚ gains can also be made by adjusting the number of units in operation so those operating are close to peak efficiency‚ which is usually at about 75 % of capacity rating.

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