Steam is one of the most efficient and widely used energy sources for heating, drying, sterilizing, power generation, etc. As energy cost continues to rise, precise measurement and optimised steam usage becomes an important factor for industrial operators to improve energy efficiency, minimise wastage, and reduce operation cost.
Advantages of Steam
- Economical: Steam is gaseous form of water. Water is an inexpensive, and readily available resource. It can be reused and offers sustainable resource utilization.
- Energy Holding Capacity: When water is heated in a boiler to create steam, it absorbs energy. Steam can hold 5 or 6 times as much energy as an equivalent mass of water. It is easier to transport for direct or indirect heating purposes in process operations.
- Easy to transfer: Steam has high heat transfer properties, and smaller required heat transfer surface area
- Safe to Use: Steam is non-hazardous and environmentally friendly.
- Multipurpose: Steam can be used for heating, drying, and sterilizing that are performed in the various of industrial operations.
Dry Steam (Saturated)
Dry steam is the results from water being heated to its boiling point (100°C). Dry steam has a very high dryness fraction, with almost no moisture. Steam produced in a boiler typically contains approximately 5% water by mass.
Dryness fraction can be expressed: ζ = ws / (ww + ws)
ζ = dryness fraction; ww = mass of water (kg, lb); ws = mass of steam (kg, lb)
If the water content of the steam is 5% by mass, then the steam is said to be 95% dry and has a dryness fraction of 0.95.
Dry steam is an excellent source for heating. It is used as the heating source for process fluid heat exchangers, reboilers, reactors, and other types of heat transfer equipment.
Wet Steam (Unsaturated)
Wet steam occurs when dry steam and condensate water molecules are mixed. Dry steam leaving the boiler and heat loss in piping causes dry steam to condense. Condensate will lead to problems like:
- Temperature drop: Water is a heat barrier. Temperature drop can lead to reduced efficiency and increased energy costs, as more steam is needed for the processes. Lower heat transfer coefficient will affect heating processes (ie sterilization and distillation).
- Water hammer: Steam-induced water hammer can occur if condensate is trapped and accumulates in the bottom of steam pipe. As steam flows over the condensate, it creates ripples. Under pressure, and with high-speed steam pushes it along, the ripples can transform into a dangerous slug that grows larger. Water hammer occurs when the slug hits an obstruction or restriction (ie pipe fittings, regulating valves, elbow, tees). Unmanaged water hammer can cause mechanical damage, leakage, catastrophic failure that causes downtime and even endangering safety of the operators.
- Corrosion: Water can cause corrosion. For example, formation of rust can weaken metal piping and leading to damage to piping structure and pipe thinning. Corrosion by-products are transported through pipes can also contaminate the fluid.
Superheated Steam
Superheated steam is created by continually heating saturated steam beyond the boiling point, thus increasing the steam temperature without increasing the pressure. Superheated steam does not contain any moisture. This makes it a good approach for processes that do not allow any moisture. Superheated steam is ideal for power generation.
Steam for Process Heating: Steam is mostly used for process heating. In direct heating, steam is directly injected in the substance which is to be heated. Indirect heating uses steam to heat the product with the help of heat exchangers, so the product(s) is not physically in contact with steam.
Steam for Power Generation: For decades, steam is being used for the purpose of power generation in form of electricity. Rankine Cycle is the process by which steam engines commonly found in thermal power generation plants. Superheated steam is generated and then taken to steam turbine. The steam drives the turbine which in turn generates the electricity. The used steam is again converted into water using a condenser. This recovered water is again fed back to the boiler to generate steam.
Steam for Sterilization and Disinfection: High-temperature steam are used in industries such as pharmaceutical, healthcare, chemicals, distilleries, etc. For example in healthcare, steam sterilization is achieved by exposing products to saturated steam in a device (autoclave) and heated through pressurized steam (high temperature of 121°C to 134°C) to kill all spore and microorganisms.
Steam for Humidification: Steam can be used for humidification. Maintaining humidity is a crucial aspect of HVAC (Heating, Ventilation, and Air Conditioning) systems. Many environments such as automotive manufacturing facilities, data centres and national defence properties depend on consistently regulated electrostatic discharge (ESD) control. Low humidity leads to increased static electricity problems which might damage the sensitive electronic equipment.
Steam for Moisturization: Steam can be used to add moisture to a process while at the same time supplying heat. For example, steam is used for moisturization in the production of paper, so that paper moving over rolls at high speed does not break or tear.
Steam for Atomization: The process of atomization (a process where steam is used to mechanically separate a fluid) ensures a better combustion of fuels. In burners, steam is used for the purpose of atomizing the fuel. This ensures a larger surface area of the fuel available for the combustion.
COMATE VFM60 Vortex Flow Meter is a powerful flow meter utilizing “Karman vortex” theory, which can meet the requirement of measuring the flow rate of various fluids such as gas, steam and liquid. The product has an excellent signal processing capability, with lower measuring limit, better stability and accuracy. The digital transmitter support communication via bluetooth and APP which allows users to access and diagnose the meter remotely, on a smart device. The unique dual-sensor design and special signal processing method eliminates vibration signals to provide a reliable performance. The VFM60 series is a highly customisable product, allowing upgrades and customisation according to specific requirements.
Process fluids: Liquid, natural gas, biogas, saturated steam, superheated steam applications, etc. Fluids must be homogeneous and single-phase.
Measurable parameter:
- Standard version: Volume flow rate in pipe, velocity (Can measure mass flow rate, temperature and pressure if wired to separate RTD and pressure transmitter.)
- Multi-variable version: Mass flow rate, volume flow rate in standard condition, temperature, pressure, volume flow rate in pipe, velocity.
