It is not possible to understand whether a steam boiler is economical or not just by looking at its hourly fuel consumption. The pressure of the steam produced, the temperature of the feed water, the boiler efficiency, the condensate return rate, the amount of blowdown and how the burner operates under load should be evaluated together. Therefore, "How many cubic meters of natural gas are needed for 1 ton of steam?" There is no single answer to the question valid for every facility.
The correct approach is to find the net heat required to convert one ton of feed water into steam at the desired pressure and divide this value by the actual boiler efficiency. When the result is divided by the lower calorific value of the fuel, approximate fuel consumption is obtained.
Key variables that determine the cost of steam production
Vapor pressure
As the vapor pressure increases, the saturated vapor temperature and energy content change. In the calculation, not only "boiling a ton of water" but also the enthalpy difference required to turn the feed water from its current temperature into steam at the desired pressure should be used.
Feed water temperature
Giving 20 °C water to the boiler is not the same as giving water in the range of 90–105 °C with hot condensate and deaerator support. The boiler consumes less energy for hotter feed water. For this reason, condensate tank and deaerator tank are not only auxiliary equipment, but system parts that affect the operating cost.
Actual boiler efficiency
Catalog yield may indicate ideal or defined test conditions. Actual operating efficiency is affected by load ratio, excess air, flue gas temperature, cleanliness of heat transfer surfaces, fuel quality and number of stops and starts. Measured fuel flow rate and steam production should be taken as basis in accurate cost calculation.
Condensate return rate
Hot condensate returning from the process returns both the water and the heat it contains. As the condensate return increases, the need for make-up water, water preparation chemicals and fuel may decrease. However, condensate with the risk of oil or process chemical contamination should not be sent directly to the boiler; It must be subjected to quality control.
Bluffing and line losses
High blowdown rate means loss of hot water and energy. Steam leaks, inadequate insulation, faulty traps and flash steam released into the atmosphere also cause the energy produced in the boiler to be lost before it reaches the process.
Fuel consumption calculation formula
An approximate calculation can be made with the following energy balance:
Required fuel amount = [Steam flow rate × (Steam enthalpy − Feed water enthalpy)] / [Boiler efficiency × Fuel lower calorific value]
Here:
- Steam flow rate kg/h,
- Enthalpy values kJ/kg,
- Boiler efficiency as decimal value,
- Fuel lower calorific value is taken as kJ/Nm³ or kJ/kg.
The actual lower calorific value of the fuel should be obtained from the supplier analysis. Using a fixed internet value for natural gas only gives a preliminary estimate, as gas composition and billing conditions can change.
Example: Natural gas calculation for 1 ton/hour steam
For example, let's assume that saturated steam is produced at around 10 bars, the feed water is 80 °C and the boiler efficiency is accepted as 90 percent. The exact enthalpy values to be used should be taken from the current steam table. Approximately:
- The enthalpy of the desired steam is determined.
- The enthalpy of the 80 °C feed water is extracted.
- The difference is multiplied by the steam flow rate of 1,000 kg/h.
- The result is divided by 90 percent efficiency.
- The obtained fuel energy is divided by the lower calorific value of natural gas, which is the basis for billing.
This method clearly shows the assumptions and not only the theoretical consumption of the boiler body. In the actual facility, fans, pumps, water preparation, chemical consumption, electricity, personnel, maintenance and unplanned downtime costs should also be added to the ton steam cost.
How to find the actual cost of a ton of steam?
The most reliable method is to use data measured over a specific period:
| Value to be measured | Why is it necessary? |
|---|---|
| Total steam production | Denominator of unit product cost |
| Fuel consumption and unit price | Shows the largest variable cost |
| Make-up water and condensate return | Indicates water, chemical and heat loss |
| Blowdown amount | Indicates hot water and energy loss |
| Electricity consumption | Includes fans, pumps and auxiliary systems |
| Maintenance and chemical expense | Complements the total cost of ownership |
| Operating hours and load rate | Reveals partial load losses |
Ton steam cost = Total steam system expense for the period / Net steam ton produced in the period
It is important that the meters are read at the same time interval. If fuel is measured monthly and steam daily, the comparison can be misleading.
Where should we start to reduce fuel consumption?
The first step is not to buy a new boiler, but to measure the location of the loss. High flue gas temperature indicates dirty heat transfer surfaces or heat recovery opportunity; High oxygen value means more air; Low condensate return may indicate losses on the process side.
The main areas for improvement are:
- Burner air-fuel adjustment and load modulation,
- Regular cleaning of heat transfer surfaces,
- Evaluation of flue gas heat with economizer,
- Condensate and flash steam recovery,
- Correct insulation of steam and condensate lines,
- Removing defective traps and leaks,
- Preventing production at unnecessary high pressure,
- Controlled management of water quality and blowdown rate.
What consumption information should be requested when comparing offers?
Two boilers should not be compared solely on nominal efficiency percentage. In the offers, it should be clearly asked under what conditions steam capacity, working pressure, feed water temperature, fuel lower calorific value, test standard, minimum load, burner modulation range and auxiliary electricity consumption are given.
Hisarmak's steam boiler models are evaluated according to the capacity, pressure and fuel structure of the facility. Process data can be shared in the steam boiler request form for pre-selection.
Frequently asked questions
Is there an exact amount of natural gas for 1 ton of steam?
No. Pressure, feed water temperature, boiler efficiency, lower calorific value of the gas, blowdown and system losses change the result.
Is the catalog efficiency sufficient for cost calculation?
Can be used for preliminary calculation; Fuel, steam and flue gas values measured in the field are more reliable for budget and savings decisions.
Why is condensate return so important?
Condensate is hot and purified water. Recycling it in appropriate quality can reduce fuel, as well as water, chemical and wastewater costs.
Does the economizer provide the same savings in every facility?
No. The exact ratio should not be given without examining the flue gas temperature, operating hours, load profile, feed water temperature and condensation-corrosion limits.
Technical resources
- T.R. Ministry of Energy and Natural Resources, Optimization in Industrial Systems — Steam Systems.
- T.R. Ministry of Energy and Natural Resources, Energy Efficient Technologies in Industry.
