Energy amount conversion method of steam / sludge drying, slurry drying, waste drying

Heat source of KENKI DRYER, which is a drying apparatus, is saturated steam. To convert the amount of steam consumed for its drying process into energy amount, “Conversion method of steam” issued by METI (Ministry of Economy, Trade and Industry) is a good reference.

Specific enthalpy of steam is used for the calculation of amount of steam consumed.


The enthalpy of a system suggests internal heat energy that the system has, and is equal to the system’s internal energy plus energy of expansion and contraction.

Specific enthalpy

Enthalpy per unit of mass

Calorific value

Amount of energy released to outside, or taken in from outside


Saturated steam is in saturated state, which is a state that both liquid and gas phases exit together at the same time. On the “Steam tables”, values of both saturated water (liquid part) and saturated gas (gas part) are described. The steam tables have single quotation mark (‘) for values of saturated water, and double quotation mark (“) for saturated gas.
The “Steam table” here suggests JSME (Japan Society of Mechanical Engineers) Steam Tables.


1. Steam energy , Saturated steam
The following is extracted from the steam tables and calculated.

steam pressuresteam temperatureh”:Specific enthalpy (Saturated steam)r:Specific enthalpy (Latent heat of vaporization)(1)
0.199.632.6750.7430.639 2.2580.6270.539
0.4143.622.7380.7610.6542.133 0.5930.509
(1)h”(Saturated steam Specific enthalpy)-h’(Saturated water Specific enthalpy)=r(Latent heat of vaporization Specific enthalpy)


2. Conversion formula


Amount of steam energy =[ h”(Specific enthalpy / Saturated steam)   
 ( 1- Dryness of steam )×r( Specific enthalpy /Latent heat of vaporization )]
 ×Steam amount    



Steam energy amount=h”( Specific enthalpy / Saturated steam )×steam amount


3. Caluculation example

Steam pressure0.4Mpa
Dryness of steam0.8 
Steam amount308kg/h









Comparison between heat pump type KENKI DRYER and previous KENKI DRYER


Comparison between heat pump type KENKI DRYER and the previous type which uses steam generated by boiler (saturated steam) is the following. Values are not actually proofed values but estimated values.


Amount of carbon dioxide emission from boiler
 Petroleum hydrocarbon
gas consmption
 Heating value per unit × emission factor × 44/12
 Amount of CO2 emission (tCO2/h)
Boiler fuel58×0.0023380.1356
Amount of carbon dioxide emission from compressor
 Electricity consumption (kwh) 

Emission factor after adjustment

 Amount of CO2 emission (tCO2/h)
Compressor input power125×0.0003470.0434



running cost ,CO2 emission reduction heat pump sludge dryer 11/07/2020


Heat pump dryers


■ Heat source, Saturated steam


Even KENKI DRYER uses only saturated steam as its heat source, it is outstanding in safety and hygiene point of view with its unique drying mechanism based on combined use of conductive heat transfer method and heated air method. Since steam is a stable heat source, quality of discharged material after drying is also stable and equable. Maximum allowed steam pressure is 0.7Mpa and adjustment of steam pressure, adjustment of drying temperature in other words, can be easily done. Saturated steam is commonly used in many factories so that it can be said as a familiar and handy heat source. In comparison with drying methods using burner or hot blasts, saturated steam method is an indirect drying applying heat exchange via pipes that steam is passing through, therefore, it hardly burns the materials and is outstanding in safety and hygiene point of view.
Saturated heat has specific characteristics. Steam temperature changes according to steam pressure, so that adjustment of drying temperature can be done easily. Also, because condensation heat and latent heat can be used, its quantity of heat is 2 to 5 times larger than sensible heat of hot water, oils etc. and it can be said as one of the most suitable heat source for drying. Saturated steam turns to drain after being used for drying and running cost can be kept low by collecting and re-using it as hot feedwater for steam generating boilers.


Heat source, Steam



Please consider KENKI DRYER for drying of sticky materials, adhesive materials and materials in liquid state that no other dryer can deal with.
Initial, running and maintenance costs are low because of its simple structure based on internationally patented technology.
For sludge drying, costs of our dryers are estimated to be retrieved within 2, 3 years by reducing industrial waste disposal cost.
For raw material slurry drying, laborious works of manual operation will be decreased significantly by replacing box shaped compartment tray dryer with our dryer
In case of organic wastes drying, the waste can be recycled as fuel, fertilizer, soil conditioner and feedstuff after being dried.



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