Introduction to Electric Steam-generators That Offer High Energy Efficiency and High Steam Temperatures.

Modern Steam Generators are easy to operate. Set the flow and temperature on the touchscreen HMI, then press start. It’s that simple. Electric methods permit clean steam generation.

Video:  OAB Unit 360 view (download).

What is Steam? In engineering, steam is vaporized water, a chemically pure, invisible gas that exceeds 100 degrees Celsius at standard atmospheric pressure. It occupies about 1,600 times the volume of the same mass of liquid water and can reach even higher temperatures as pressure increases, forming high-temperature or superheated steam.

Recent innovations in steam technologies include electric, decarbonized steam systems that enable rapid production and adjustments without pressurization, allowing steam temperatures up to 1200°C at a variable set rate within the performance limits of a steam generator.  Electrical steam generator systems generally feature touchscreen automation to control steam flow rate, temperature, and power settings, with programmable operation for high-energy-efficient clean steam generation.

MHI systems maintain a set temperature regardless of pressure or back pressure.

Steam (clean) Generator Applications and Industries – use of high-temperature steam

• Biomass (for electricity generation), Waste Conversion: Treatment of Sawdust, wood fiber, pulverized coal, wood chips. Fuel from Waste, and Municipal and plant waste.
• Chemical Industry: Use – catalysts, regeneration (chemical), carbon activation, vulcanization,…
• Food Industry: Drying, flash drying, heating, processing, curing, cooking, cleaning, shrink wrapping, for various food and pharmaceutical production environments
• Paper & Pulp, Wood: Paper, fiber/fiber sludge from wastewater treatment, drying
• Metal Finishing: For antimicrobial and other cleaning/finishing metals, semiconductors, silicone/plastics, rubber, composites, and ceramics.
• Cleaning, Sterilizing: Laundry, dry cleaning, cleaning (several levels including microbial). Clean bio-implants and textiles.

Steam is a valuable energy source because water has a high heat of vaporization. At sea level and one atmosphere of pressure (101 kPa or 1 bar), steam boils at about 100°C (212°F). The boiling point varies with pressure and, therefore, with location. Unlike pressure-typical boilers, the temperature of the steam gas from a steam generator is independent of pressure, allowing steam production at any temperature. Water’s boiling point increases with pressure, and beyond 647.096K and 22.064 MPa, it exists in a supercritical state. Steam can be either saturated or superheated. Saturated steam boilers produce steam at the pressure-dependent boiling temperature.

Dry steam is typically required for antimicrobial, chemical, and power applications.

Switching from fuel-based boilers to electric boilers can significantly reduce CO2 emissions. For example, replacing steam turbines with electric drivers in chemical and petrochemical plants can substantially reduce CO2 emissions, further enhanced by the energy efficiencies and other control features of electric steam generators.  The output from old-style pressure boilers often contains water droplets mixed with steam-gas, a condition called wet steam, which is not the steam condition required for steam processes.  Electric steam generators easily produce dry steam, or properly superheated steam, at temperatures above the boiling point with no water droplets (also known as high-quality steam).

A 25-10,000 Kg/hr. Instant Steam Generator for 24/7 Industrial Use

Choose temperatures between Saturated and 1000C.

For high back-pressure requests

Steam Calculator,

Steam generators are flexible. One can set the required steam flow rate, output temperature, and back pressure. They also provide pulsing and power settings for energy efficiency. Infinite flow variation is available across a wide range. Some typical variable flow ranges are listed below; however, other requested parameters will influence this range.  Please request a quote for your specific requirements.

Cost Savings of Ancillary Steam Equipment by using Electric Heating (does not include any tax penalty for emissions, which today could exceed $283/ton of CO2 (eq) emitted).  Electric systems do not have to factor in these costs, plus the space and installation of this extra equipment.  Emissions Control Equipment generally includes:

Steam and Water Vapor Terminology: 

What is humidity? Humidity is a measure of the amount of water vapor present in the air.  There are several ways to understand Humidity (generally used only below 100°C, at 1 atmosphere). Water vapor has limited solubility in air below 100 °C (and 1 bar pressure).

What is dew point? The dew point is the temperature at which air becomes saturated with water vapor and can no longer hold more water in its gaseous form. Some water vapor condenses into liquid water when the air is cooled below its dew point. The dew point temperature measures humidity.  The dew point is the temperature the air must be cooled to (at constant pressure) to reach a relative humidity (RH) of 100%.

What is Relative Humidity? The Relative Humidity (RH) compares the amount of water vapor in the air-steam mix to the amount in the air if the air were fully saturated. It is a ratio comparing the amount of water vapor in the air with the amount present at saturation. Relative Humidity is a percentage of water vapor expressed as a percent of saturation. The saturation amount increases with temperature.  Humidity is a contextual property.   Below the saturation temperature, Relative Humidity (RH) is used when Steam is mixed with air. Relative Humidity is a ratio that compares the amount of water vapor in the air with the amount of water vapor present at saturation for equivalent conditions. It is a percentage: water vapor is expressed as a percent of saturation. At 30 °C (86 °F), air volume can contain up to ~4 percent water vapor. However, at -40 °C (-40 °F), it can hold no more than 0.2 percent. The adjacent column gives equations for water content, partial pressure, and the enthalpy of moist air.

What is Specific Humidity?   At high temperatures above the boiling point, it is more appropriate to talk about Specific Humidity (also called the humidity ratio), which is the mass of water vapor present in a unit mass of dry air; that is, it is the ratio of the mass of water vapor to the mass of dry air.   This can range from 0 to 1.   For example, at 25°C and one atmosphere of pressure, if the Specific Humidity is 0.02 (it means two grams of water vapor in 100 grams of dry air).  Note that the corresponding Relative Humidity (RH) is ~10%.

Brief History of Steam Generation

Modern steam generators deliver instant, high-quality superheated Steam that can overcome backpressure. They also offer variable steam rates.

Modern, high-quality superheated Steam is employed for several critical applications. High-temperature Steam is helpful for pharmaceutical, biopharmaceutical, comfort, utility, and chemical uses because it lacks water droplets. Noncondensing superheated Steam is the most energy-efficient method of steam use. Using dry superheated Steam above the inversion temperature of steam provides the best antimicrobial action and the fastest drying for steam applications. The wicking properties and oxygen control of this type of Steam are attractive features of high-temperature steam. High-temperature steam availability leads to high-productivity applications. Steam generator products are classified into two types, namely:

• MightySteam® Pure Steam Products (Industrial and R&D Use)
• MigthySteam® Controlled Humidity Products  (Commercial Use)
• The average molecular weight of air is approximately 29g, heavier than the molecular weight of steam (H2O), which has a molecular weight of 18g. However, the actual densities of air and steam vary greatly based on steam-to-air ratio, temperature, and pressure. For example, at 10 bar, air is heavier than steam below 162 °C (~325 ºF) but lighter than steam above it.  This is sometimes called the density inversion temperature, which is vital for drying. The relationship flips again at 20 bar. Electric steam generators do not need high pressure, making process development much easier.

What is superheated Steam? Steam can be saturated or superheated. At the boiling temperature (which depends on the pressure), the steam is called saturated steam. Saturated Steam is often a mixture of water and gas. Above the boiling temperature, it is called superheated Steam, especially when no water droplets are present (i.e., dry or high-quality Steam). At sea level and one-atmosphere pressure (101 kPa), Steam boils at ~100°C (~212°F), and the saturated steam temperature at 1 bar is ~100°C—the boiling point changes with pressure and geographical location.  The steam can be superheated (called steam-gas).   Steam generators make superheated Steam-gas.  Unlike boilers, steam-gas temperature is unrelated to pressure.  Steam at any temperature and any unrelated pressure to Tsat can thus be requested from a steam generator.

Modern steam generators use sophisticated electric and computer controls that permit flow rate and temperature variations. This versatility makes them suitable for applications ranging from chemical reactions, dry cleaning, and antimicrobial use to drying ores and wet materials, including food. Modern steam generators offer significant benefits in downstream efficiencies and dryness.  Pressurizing steam to reach a higher temperature and then using it at room pressure causes a considerable loss in energy efficiency.

What is Supercritical Steam: There’s a unique mix of temperature and pressure – called the critical point – where the difference between liquid and gas ceases to exist. For water, this happens at 374 °C (705 °F) and 218 bar. This type of steam forms beyond the critical point (> 647.096 K and> 22.064 MPa). About ~30% of free monomeric H2O molecules exist at the critical point. The rest contain different types of H2 bonds. Supercritical water has very low surface tension with its gas or liquid phase; therefore, no interfaces can delineate the liquid/gas interface. Above 647.096K, increasing the pressure cannot liquefy supercritical Steam.  There is no difference in the energy content between supercritical steam at 460◦C and 250 bar and medium-pressure steam at 280°C and 10 bar, i.e.,  3.0 GJ/ton.  But their entropies are different.  Steam at 280 °C and 10 bar has an entropy of 7.0 kJ/kg-K. Supercritical steam at 460 °C and 250 bar has an entropy of 5.7 kJ/kg-K.  Now, it is clear why supercritical steam is used to generate power. However, this has little bearing on the thermal use of steam for reactions or cleaning purposes.    Electric steam generators prevent such energy losses.  Supercritical steam can capture CO2.

Another example of a supercritical material is Supercritical CO2 (above 304.13 K and 7.38 M a). CO2 in this state is used to decaffeinate coffee beans. Its viscosity and diffusivity are like a gas, so it penetrates the beans quickly. However, its density is like that of a liquid. It binds to caffeine (this property is much more critical than its supercritical fluid properties). Supercritical CO2 is also used in dry cleaning.

 The properties of superheated Steam and types of steam kinetics are shown on the  Steam Calculator page.

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A pound of water x 0.016 = cubic feet at 62.2 °F.
A pound of water x 0.12 = gallons of water
1 gallon of H2O liquid = 8.33 lb. @ 62.2 degrees Fahrenheit.  The mineral content of calcium and magnesium determines the hardness of water.
The freezing temperature of water at one Bar is 32 Fahrenheit (°F) = 0 Celsius (°C) (this phase change temperature is only mildly pressure dependent)

Water specifications pertinent to Boilers and Steam Generators.

Soft and Hard Water:

Any boiler feedwater treatment system usually incorporates the following water purification methods:

• Filtration.
• Softening.
• Reverse osmosis (RO). This water is generally recommended for modern steam generators.  In 2025, the average operating cost for a 100 kg/h (~100 LPH) reverse osmosis machine typically ranged from $150 to $300 per year for light-to-moderate usage (approximately 10 hours per day).  The capital cost for a 100 LPH unit was about $500.  Please contact the various manufacturers for current information.
• Primary ion exchange.
• Deaeration or Degasification.

Feedwater is piped to a steam generator to form continuous high-temperature dry steam. The condensate may be combined with treated makeup water and re-fed.

Water treatment plants today are very cost-efficient and inexpensive.

Softening. Water softening removes hardness due to calcium and magnesium in the water. A softening resin accomplishes this, typically using a strong acidic resin to capture and remove hardness ions from the stream.

Makeup Water Intake. Replacement or make-up water is drawn from treated city supplies or raw water treatment systems. Steam generators can use the condensate return.  Water supplied to a steam generator must meet RO and DI water specifications.

Filtration: Water is typically filtered to remove sediment, turbidity, and organic material. Membrane filtration units may be the most cost-effective pretreatment option.

Deaeration or Degasification: After all other treatment steps, the makeup water and condensate from the boiler system are combined, removed, and degassed to prevent corrosion.

• Water Hardness Ratings:
  The water’s calcium and magnesium content determines its hardness. Water softness is measured in grains/gallon or parts per million (ppm). 
• Less than 1 GPG or less than 17.1 ppm is soft
  1.0 to 3.5 GPG  or 17.2 to 60 ppm is slightly hard
  3.6 to 7.0 GPG  or 61 to 120 ppm is moderately hard
  7.1 to 10.5GPG  or 121 to 180 ppm is hard
  10.6 GPG & over 181 ppm & over is very hard

What is the conductivity in comparison to RO and RO/DI water?

Reverse Osmosis (RO) cleans tap water to about 90% to 99% purity. Deionization (DI) filters exchange positive hydrogen and negative hydroxyl ions for positive and negative contaminant ions in water. DI filtering and other processes are sometimes called “water polishing.” RO can remove bacteria, salts, organics, silica, and hardness. RO and nanofiltration both employ membrane filtration to capture contaminants. RO systems for industrial purposes typically provide a 65 to 75 percent recovery rate (or much higher in combined recirculating RO water systems), which is very efficient water use.  RO results in exceptionally pure water.  The conductivity is typically 5-25 micro-mho/cm.

DI water. DI-grade water is purified by removing almost all mineral ions, including cations like sodium, calcium, iron, and copper, and anions like chloride and sulfate. The DI process uses specially manufactured ion-exchange resins that exchange hydrogen (H+) and hydroxyl (OH-) ions for dissolved minerals, then recombine to form water (H2O). Primary Ion Exchange – Deionizers may be used instead of membrane filtration for large volumes of water or high-pressure boilers. Ion exchange typically produces water of comparatively higher quality and resistivity and provides better yields. The conductivity is about 1 to 5 micro-mho/cm.

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Typical water feed requirements for ultraclean steam generation.

• RO and DI water or highly purified water.  0.1 – 50 micro-mho/com.  RO filters and RO/DI filters often recycle and may achieve 95% recovery. They remove chlorine and chloramines, bad taste and odors, Volatile Organic Compounds (VOCs), PFAS/ PFOS (also called forever chemicals), radon, and H2S.  Sometimes other filters are added to soften water and remove  amines, Chlorine, and Chlorides
• Total suspended solids (TDS)  – low.   Total dissolved solids (TDS) combine the sum of all ion particles smaller than about 2 microns. Silica is less than one ppm.   This includes all dissociated electrolytes that make up salinity concentrations, plus other compounds such as dissolved organic matter.  Total dissolved solids are reported in mg/L or ppm.  An empirical TDS “constant” relates TDS (ppm) and water conductivity in micro-mho/cm’.  The conductivity of a water sample can be multiplied by the TDS constant for an approximate TDS. A TDS constant of 0.55-0.7 is reasonable for typically clean (i.e., free of urea and organic waste) RO, DI, or tap water.   However, if the water source is known to be high in calcium or sulfate ions, you may use a constant of 0.8.
• Total hardness less than 1ppm
• For conductivity, it depends on the use (see the table above).

High-quality superheated Steam has applications in drying, cooking, proper and complete bacterial inactivation, fracking, chemical processes engineering, comfort heating, chemical processes, fuel production, tablet making, mixing, and materials processing  High-temperature Steam in one atmosphere packs the proper punch required for these applications while minimizing the dangers of using high-pressure boilers  This type of superheated Steam is used in applications requiring a critical need to reduce the processing time  Superheated Steam often offers a higher heat transfer coefficient and high enthalpy content, enabling many unique applications  When at a high temperature, significantly above the inversion temperature, such Steam is often considered a non-toxic antimicrobial agent  Superheated Steam at high temperatures also offers superior reactions, for example, in energy reactions such as bio-fuels, reforming, hydrogen production, ammonia production, and denaturing, all with rapid heat transfer kinetics  In the US, more than 90% of electric power is produced using Steam as a working fluid, mainly by steam turbines  Condensation of Steam to water occurs downstream, but such wet-steam conditions must be carefully controlled to avoid excessive blade erosion and preserve energy efficiency  Oxidation and erosion tests can be done with Steam Generators  There is no moisture from the start-up in many modern steam generators  The HGAs and OAB produce high-quality pure Steam The HGA-M is for applications requiring steam-gas(air) mixtures  The Mightysteam® and SaniZap® models are helpful for steam cleaning at several levels of cleaning  The OAB® and GHGA models are used for industrial and R&D purposes  The high-temperature Steam also tends to be useful for pharmaceutical, biopharmaceutical, comfort industry, utility, and chemical uses because of a lack of droplets and rapid antimicrobial action for several orders of log reductions in a short duration.

Do you want to know? Does high pressure enable the outcome of steam for drying or a chemical reaction involving steam? The short answer is seldom significantly above 10 °C.   For the long answer, click here.

The standard steam diagrams for process design are below.

Atmospheric gases exert a certain amount of pressure (about 1013 millibars at sea level). Vapor pressure measures the air’s water vapor content using the partial pressure of the water vapor in the air  (Pressure may be expressed using a variety of units: pascals, millibars, pounds per square inch (psi), among others). Since water vapor is one of the gases in the air, it contributes to the total air pressure. Water vapor’s contribution is relatively small because it makes up only a few percent of the total mass of a parcel of air. The vapor pressure of water in the air at sea level, at 20 °C, is ~24 mbar at saturation (about 3% by volume).

Does the saturation pressure of H2O in the air depend on the total pressure? Yes, as the total pressure of a system decreases, the Relative Humidity will decrease.   Likewise, as the total pressure of a system increases, relative humidity increases until saturation is reached.

HGA-M:  High Specific Humidity High-Temperature Device.

Air Steam Mixture Generator

HGA-M-04

HGA-M-01

For larger devices, please contact MHI.

Example of RH: Suppose 10 grams of water vapor were present in each kilogram of dry air, and should the air at that temperature be saturated at 30 grams of water vapor per kilogram of dry air, the Relative Humidity is 10/30=33 3%. A parcel of air at sea level, at a temperature of 25^oC, would be completely saturated if there were ~20 grams of water vapor in every kilogram of dry air. For one-atmosphere conditions above 100C, use the term specific humidity, which is the mass of water vapor (i.e., Steam) per unit mass of dry air.

Another, more technical term is the ratio of actual vapor pressure to saturation vapor pressure. You will note below that the HGA-M produces a lot of steam, and very high specific humidity is possible because, above 100C in one atmosphere, air and steam mix well, as any other “ideal gasses could. Below 100C, RH is a key limit on how much water vapor can mix with air.

The enthalpy of vaporization and molar volume change decrease as pressure increases from 1 Bar to 10 Bar.

Power Steam Jet

SaniZap-600-4-240.   A must for cleaning. (Mobile Platform)

Discover Steam Tunnels for Continuous use

Sometimes you need a steam-gas mixture instead of pure steam. The HGA-M-01 and HGA-M-04   can enable this.

Calculating your parameters.

Endotoxins, microbes, and bacteria are known to be inactivated by heat and H₂O. All MHI superheated steam production produces high-temperature Steam that, during protection, reaches temperatures over 50 °C.  Several models’ steam output temperature and humidity conditions are controllable, as discussed below.  Refer to the HGA-M manual to see how your HGA-M is configured/rated. The mass fraction of Steam in the final flow is about 18% for a valve setting, which gives, for example, 200ml/15.5 minutes (i.e., specific humidity is about 2%). We assume the water vapor is ideal and that its enthalpy can be taken as that of saturated vapor at the same temperature (~2501.3 + 1.82T (kJ/kg)). Temperature, T, is in degrees centigrade.    Of course, after a specific temperature and pressure, ~374 °C and 22.06 MPa, called the critical temperature Tc and critical pressure Pc, respectively, no amount of pressure can cause condensation. The superheated steam generator can produce steam at temperatures above this point, but the output is not at critical conditions because the pressure is lower.

The HGA and OAB operate at close to 100% power efficiency, from which the steam temperature can be calculated  by the equation below for the efficiency of HGA-M; h is enthalpy, and T, the temperature, is given in Kelvin (Kelvin=273+Centigrade):

Obtain h (enthalpy per kg) of steam from the figures above, steam tables, or the Mollier diagram. Or, you can measure the temperature from the exit thermocouple.

GENERAL INSTRUCTIONS FOR HGA-M

Instructions for using and protecting the HGA-M are enclosed with the product. It’s a uniquely designed device that’s easy to use. Turn on the air and monitor with a flow meter so the SCFM does not fall below  .4. Higher airflows give lower temperatures, or you may control power with a separately obtained controller.   Then turn on the heater and finally open the water metering valve.   Steam-air will be the product.   Remember to read the manual for the shutdown procedure.

  Q:  When do you dry with Steam instead of hot air? Answer: Steam has many benefits. The main one is that steam is a gas with a lot of stored enthalpy at a lower temperature than the corresponding dry air with the same enthalpy. So, suppose you are interested in drying paper with an ignition temperature of 450F. In that case, using superheated steam at a much lower temperature may produce the same drying efficiency as hot air at a higher temperature, which could be above the paper’s ignition temperature.

Follow all safety procedures. NOTE: STEAM IS AN ODORLESS GAS AT VERY HIGH TEMPERATURES. STEAM, LIKE OTHER HOT GASES, WILL BURN OUT. STEAM PACKS A LARGE AMOUNT OF ENTHALPY SO THAT THE BURN COULD BE SEVERE; DO NOT ALLOW THE STEAM TO FALL ON THE SKIN.   WEAR GOGGLES AND GLOVES AND PROTECTION FOR YOUR CLOTHES,   ALWAYS.

A selection of steam tables is given below. It is best to use a standard text or the International Association for the Properties of Water and Steam (IAPWS)

If you want superheated, high-quality Steam, you should now search for the HGA or OAB models that address your needs. The information below refers to the HGA-M models only where an air or gas-steam mixture is required. You may e co. Humidity is a design term or property used when using air or gas mixtures with steam.

IT IS EASY TO BE CONFUSED BETWEEN RELATIVE AND SPECIFIC HUMIDITY.   RELATIVE HUMIDITY DEPENDS ON TEMPERATURE; SPECIFIC HUMIDITY IS ONLY RELATED TO THE MASS FRACTION.

See below from the public site http://www.pals.iastate.edu/mteor/mt206/lectures/feb7/tsld020.htm.

Potential uses: For layering, epoxy drying, and other film use, superheated Steam is required at one atmospheric pressure. This makes it ideal for steam drying or steam oxidation. It can also be used to precipitate crystals of several small sizes, including nanocrystals, from solutions. You can control precipitation droplet sizes by adjusting the cooling rate, impingement conditions, and surface type. 

The steam temperature depends on the water valve setting and air inflow setting.

HGA-M (typical settings at Full Power):

• Air 1.45 CFM (inlet at ~30C) and water 330ml in 45 mins (inlet at ~30C) yield a steam-air temperature of about 350°C.
• Air 1.4CFM (inlet at ~30C) and water 200ml in 20 mins (inlet at ~30C) yield a steam-air temperature of about 250°C.
• Air 1.8CFM (inlet at ~30C) and water 200ml in 20 mins (inlet at ~30C) yield a steam-air temperature of about 150°C.

The graph below gives a fair idea of how to adjust the HGA750-1 for different specific humidity levels. As specific humidity increases, overall temperature decreases as total energy is consumed. The gas thermocouple is correct as the exit for the graph below the steam. If you reduce the steam gas temperature too much, you may not get superheated steam; instead, the output may be a heated mist. The red line graph requires a power controller.

Your results may vary. The values above are approximate because of thermocouple placement, flow restrictions, and other random errors common in multivariate measurements. The user must optimize all valve settings to get the best results for specific applications.

SUPERHEATED STEAM IS AN ODORLESS GAS (not to be confused with mist). Output: constant steam air (superheated steam). Take safety precautions when dealing with hot gases.

DO NOT USE UNITS WITH COMBUSTIBLE LIQUIDS; THE DANGER OF SUPERHEATED STEAM SHOULD BE WELL UNDERSTOOD.   PLEASE WEAR GLOVES, GLASSES, AND A HARD  HAT. PROTECTIVE CLOTHING IS REQUIRED; STEAM CAN PENETRATE CLOTHES.

The product uses cleaning, drying, curing, and nanotechnology.

Patents have been issued, applied for, and are pending for the HGA.

A control thermocouple is included for the hot air generator part. Steam output temperature thermocouples and brackets are sold separately, or users may provide their own. This unit requires an electrical 110-120V 50/60Hz supply. The 1KW system requires compressed air input.

RELATIVE HUMIDITY DEPENDS ON TEMPERATURE; SPECIFIC HUMIDITY IS RELATED TO THE MASS OF WATER. IT IS EASY TO BE CONFUSED BETWEEN RELATIVE AND SPECIFIC HUMID TY. See below from http://www.pals.iastate.edu/mteor/mt206/lectures/feb7/tsld020.htm.