Undercurrent: The Alden Blog


Industrial fluid dynamics insights

Preventing Ice Build-Up on Wet Stacks
Preventing Ice Build-Up on Wet Stacks
Ice chunks the size of Volkswagens falling from the sky! Sounds like a Hollywood special effects scene in an action movie, right? Unfortunately, this is a real-life danger that can occur just about anywhere, but especially on wet stacks running in cold weather. It should go without saying that ice falling from a tall stack can have damaging, even catastrophic effects on process equipment and personal safety. But with some situational knowledge and attention to design details, you can prevent ice build-up on wet-stacks before it becomes a problem.  Icing and the Downwash Effect Essentially, to operate an ice-free wet stack system, you need to properly handle the discharge of wet flue gas during prolonged exposure to cold temperatures. Units running at low loads on cold, windy days can see a dangerous icing develop from an effect called plume downwash. Plume downwash occurs when a cross-wind at the top of the stack deflects the plume from its vertical path. This phenomenon is more likely to happen when flue gas exits at a lower velocity—like, for example, when units aren’t running ...

The Changing Energy Climate - Part II
In the last installment of this series, we discussed energy demand, energy supply, and the impact of the rapid growth of solar power on changing energy sources.  Today, we continue with the effects of power prices, the importance of power storage, and offer some conclusions. Price of Power A significant portion of the United States electricity markets is split into hubs.  Each hub is an independent energy market in which supply and demand set the price of electricity on a real time basis.   A map of United States hub zones is shown in the following figure. Daily electricity demand is primarily based upon the time of day and climate.  As shown in Part I, more electricity is used during daylight and evening hours than night time.  Very cold or very warm weather can add demand due to heating and cooling.  Additional constraints on fuel costs and available supply add an extra layer of complexity.  The cost of environmental mitigations for coal fired power plants, the lack of sufficient natural gas supply in certain markets like New England, and the recent addition ...

The Changing Energy Climate - Part I
As we discussed in our first blog post, there are many challenges facing the nuclear industry. One of the greatest is the current energy climate.  There are many contributing factors to the general state of flux in energy production, which we would like to explore today.  These challenges don’t just impact the nuclear industry, but also affect energy producers across generation types. Energy Demand It may surprise you, but US energy consumption has effectively plateaued over the last 15 years.  Below is a plot generated with the US Energy Information Administration Open Data Embedded Visualization Library.  The EIA provides a wide range of information and data products covering energy production, stocks, demand, imports, exports, and prices; and prepares analyses and special reports on topics of current interest. There are four sectors that are included when looking at total energy consumption.  These include Residential, Commercial, Industrial, and Transportation, all of which are shown in the figure.  As you can see, starting around the year 2000 the Total Energy Consumption has plateaued.  The largest changes in trends  have been experienced by the Industrial Sector, ...