Steam is used on a grand scale for heating or power generation in turbines, for sterilisation or for cleaning purposes in many industrial sectors. Today, steam management covers far more than checking water levels, conductivity, pH value, temperature and pressure in the boiler. Steam systems offer numerous options for saving, re-using and reclaiming energy, whether in generation, distribution, accurate billing or boiler efficiency.
Endress+Hauser provides all the measuring instruments required for optimum improvement. The company’s product range also includes water analysis devices for seamlessly monitoring the quality of feed, boiler or condensate water for dissolved oxygen, limescale content or electrical conductivity. Generating, transporting and distributing steam requires a huge amount of energy. The goal therefore is to run and control these processes as efficiently as possible.
How do you reduce your energy costs?
You can only control what you measure. The right device installed correctly at the right place permits the accurate metering of flow, pressure, temperature and other important process values. The Prowirl vortex meter for steam flow applications is a good example. This highly robust flowmeter has been developed for steam applications and offers a broad scope of multi-variable solutions for steam mass and energy measurement. A new optional feature designed to detect wet steam on a continuous basis is an innovation that helps to increase safety and improve the efficiency of steam systems.
What is wet steam and why is it important?
When dry saturated steam passes on its energy to a process, its latent energy is released. This energy can be found in steam tables as enthalpy. As this energy is released the steam becomes wetter and its dryness fraction is reduced from 1 down to 0. What does not change, however, is the combination of pressure and temperature during this process. This means that ideally steam enters a heat exchanger at 3 bar g and 144°C and condensate can be found at the exit at exactly the same pressure and temperature – but the steam has lost 2138 kJ/kg of latent heat. The problem now is that if both liquid and steam, and any state in between, can exist at the same pressure and temperature, it is impossible to determine the dryness fraction by just measuring pressure and temperature.
Wet steam is generated mainly during the distribution of steam. Heat losses in steam piping will lead to a reduced dryness fraction because of lack of isolation. This wet steam can lead to water hammers (slug flow caused by water entering the steam line) and will reduce the efficiency of the steam system because wet steam has less energy than dry saturated steam. If the wet steam is a result of carry-over from the boiler itself, stress corrosion cracking may result. Until the launch of the innovative Prowirl with wet steam detection, there was no solution available to determine the presence of water in the steam line. Wet steam detection makes it possible to monitor the steam quality. A warning is issued when the steam quality drops below the limit value for steam quality in the range between 80 to 100%. The Prowirl is the preferred measuring principle for wet/saturated/superheated steam applications. The integrated temperature measurement allows for easy calculation of mass/energy flow of the saturated steam. In addition to the Prowirls’ robustness and resistance to vibrations, temperature shocks and water hammer, the meter is calibrated for life.
Another challenge is the constant monitoring of a steam boiler and steam system in order to improve the system’s performance and detect changes at an early stage. The solution is to define the right KPIs, which help to evaluate steam boiler efficiency, system balancing and leakage, as well as specific energy consumption. This is the precondition for energy management and cost reduction. Endress+Hauser’s RSG45 energy and data manager collects, stores and displays all the required data. Very often the target values, such as steam boiler efficiency, fuel consumption or pressure loss, need to be registered, read and verified onsite. Endress+Hauser’s Memograph is able to visualise, register and analyse energy data, as well as calculate characteristic values such as specific energy consumption, boiler efficiency and fuel and steam consumption, as well as leakage loss. The web-based energy monitoring software permits access to the entire monitoring system on the plant from anywhere. In addition, this software can be used to analyse measurement data and serve as the basis for creating energy reports.
For more information contact Natlee Chetty, Endress+Hauser, +27 (0)11 262 8000, [email protected], www.za.endress.com
| Tel: | +27 11 262 8000 |
| Fax: | +27 11 262 8062 |
| Email: | [email protected] |
| www: | www.endress.com |
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