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Fuels

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fuels

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LIQUID AND GAS BOILER FUEL OPTIONS

The selection of the correct fuel for your boiler can either represent a large cost savings or expense (normally a sum greater than the cost of the actual boiler).

The availability and price of different fuel options can vary significantly by region or country so Calderas Powermaster recommends doing a thorough analysis of available fuels and their true costs before taking delivery of your boiler.

Below is a review of the most commonly used fuels and their general characteristics:

Natural Gas

Natural gas is a mix of gases that are normally taken from the earth at the same time that oil is extracted. Because it is affordable, easy to use, and relatively clean, natural gas is one of the most commonly used gases in the industry.

State: Gaseous.

Required Conditioning: Pressure regulation, filtered.

Supply type: Piped

Average Chemical Composition (PEMEX): Methane (85 to 90%); Ethane (up to 9%); other gases such as Carbon Dioxide and Nitrogen.

Net Calorific Value (Hi) (PEMEX): 8,205 kcal/m3 (922 BTU/ft3).

Gross Calorific Value (Hs) (PEMEX): 9,104 kcal/m3 (1,024 BTU/ft3).

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Natural gas is a mix of gases that are normally taken from the earth at the same time that oil is extracted. Because it is affordable, easy to use, and relatively clean, natural gas is one of the most commonly used gases in the industry.

State: Liquid.

Required Conditioning: Evaporation, pressure regulation, filtered.

Supply type: Piped.

Average Chemical Composition (PEMEX): Propane (30%) and Butane (70%).

Net Calorific Value (Hi) (PEMEX): 11,000 kcal/kg.

Gross Calorific Value (Hs) (PEMEX): 10,680 kcal/kg.

Fuel Oil #2 is a product of oil distillation and has become a widely used fuel in the boiler industry because it is safe, easy to transport, and inexpensive. Industrial Fuel Oil #2 is not the same as automotive diesel, with the latter containing additives which make it explosive and therefore inappropriate for boilers.

State: Liquid.

Required Conditioning: Pressure regulation, air elimination, filtered.

Supply type: Piped.

Average Chemical Composition (PEMEX): Carbon (84.6%), Hydrogen (9.7%), Sulphur (2.7%), Nitrogen (1%), Water (1.5%), and Ash (0.5%).

Net Calorific Value (Hi) (PEMEX): 10,000 kcal/kg.

Gross Calorific Value (Hs) (PEMEX): 10,680 kcal/kg (19,224 BTU/lb).

Density (PEMEX): 0.865 kg/l.

Fuel Oil #6, also known as Bunker C Oil or Heavy Oil #6, is a remnant of the oil distillation process and has been a popular fuel choice in the boiler industry because of its attractive price tag. It requires, however, a high level of conditioning and generates undesirable emissions. Environmental concerns have in fact led to the prohibition of the use of Fuel Oil #6 in many states throughout both Mexico and the US.

In Mexico, this fuel does not comply with specifications published by the manufacturers and as such cannot be burned with mechanical atomization as is the practice in Europe. Given that Fuel Oil #6 may freeze and solidify if there are interruptions in the steam demand, it is recommended that this fuel option be used only if continuous 24 hour steam demand exists over prolonged periods.



State: Solid at room temperature; liquid at or above 90°F.

Required Conditioning: 2-stage pre-heating, pressure regulation, air elimination, filtered, atomizing medium (compressed air or steam), gas pilot.

Supply type: Piped.

Average Chemical Composition (PEMEX): Carbon (83.04%), Hydrogen (11.3%), Sulphur (4.2%), Nitrogen (0.4%), Oxygen (0.46%), Ash (0.6%), Vanadium (246 ppm), Sodium (70 ppm) and Nickel (37 ppm).

Net Calorific Value (Hi) (PEMEX): 9,583 kcal/kg.

Gross Calorific Value (Hs) (PEMEX): 10,111 kcal/kg.

Density (PEMEX): 0.982 kg/l.

Biogas or Digester Gas is a product of the digestion of organic matter, typically sewage or the residual fecal matter of livestock. The chemical composition of Digester Gas depends on the organic material from which it is produced and varies from digestive entity to digestive entity. All biogas contains hydrogen sulfide (H2S), which is highly toxic and corrosive and necessitates that the fuel undergo additional conditioning to be burned safely.

State: Gaseous.

Required Conditioning: Scrubbing of H2S, drying, pressure regulation, filtered.

Supply type: Organic Digester.

Chemical composition average: Variable.

Power lower heating value (Hi): Variable.

Calorific value (Hs): Variable.

FUEL COST ANALYSIS – CALCULATING THE REAL COST PER KILOCALORIE

Boiler fuel consumption depends on the quantity of energy that the fuel contains and the specifications of the boiler stipulated by the client.

Independent of the boiler size, fuel cost is a determining factor in whether large expenses or savings are realized over the operational life of the boiler. Conducting a fuel cost analysis, however, can be confusing as the various fuels are sold in different units of measurement (gallons, pounds, cubed feet, etc.) and contain varying quantities of energy.

The easiest way to select the appropriate fuel for your boiler is to derive the real cost per unit of energy (kilocalorie) of all available fuel options and compare these directly.



The real cost per kilocalorie is obtained as follows:

$kal = $UM x 1,000 / Hi

Terms Defined:
•$kcal is the actual cost per kilocalorie.
•$UM is the cost per unit of measurement (supplier cost).
•Hi is the net calorific value of the fuel (per the same unit of measurement).

Ejemplo: In this example, we are determining whether it is cheaper to use L.P. Gas or Diesel (Fuel Oil #2) in the boiler. The L.P. Gas supplier sells at $12.42 per kg and the Fuel Oil #2 supplier at $12.05 per liter.



Using the net calorific values of the respective fuels (see section above), we obtain the real cost per kilocalorie of each of the fuel options:

For LP Gas:
$kcal - Gas LP = 12.42 $/kg x 1,000 / 11,000 kcal/kg = 1.12 $/1,000 kcal

For Fuel Oil #2:
12.05 $/l / 0.865 kg/l = 13.93 $/kg
12.05 $/l / 0.865 kg/l = 13.93 $/kg
$kcal - Diesel = 13.93 $/kg x 1,000 / 10,000 kcal/kg = 1.39 $/1,000 kcal

Comparing the two real costs per kilocalorie, it is easy to see that in this example, Fuel Oil #2 is 85% cheaper than L.P. Gas.

Any Powermaster salesman will be happy to work out your real fuel costs with you based on pricing in your area.