Environmental emissions air dispersion calculation / air pollution from combustion
Suppose you want to estimate the combustion products from heaters, boilers, etc. Based on my experience, the environmental specialist doing the Gaussian distribution calculation needs the following needs the four pieces of information about the combustion equipment. Below, I list them, and suggest where you might find them:
- Amount of exhaust gas/complete combustion products: get by vendor quote, or by combustion equation (see below), or Combustion rules of thumb
- Amount of contaminates/incomplete combustion products: get by vendor quote or by the US EPA’s guideline AP 42
- Gas Discharge velocity: exhaust gas volume ÷ stack area (using stack diameter from vendor quote)
- Likely site location and weather conditions: from plot plan & site climate data. (Wind modeling / testing may be required in some cases)
You’ll notice I said “vendor quote” a lot – that’s the best source if you’ve got it. If not, time to look up similar results and ask around and do some digging.
Combustion Equation
Suppose you have a fuel source made up of some mixture of hydrocarbons and other molecules. You want to calculate the amount of exhaust gas your heater will exhaust by burning it. For simple fuels, you can do this manually.
But what's coming out the stack? (Photo credit: William Warby)
First, look up the chemical composition of the fuel you are combusting. Then, knowing your composition and the LHV of each chemical in your composition, determine the overall lower heating value per amount of fuel you combust. Then, look at your heater’s duty ÷ heater efficiency, and calculate the amount of fuel you will be burning in the heater. If you don’t know the heater efficiency yet, look into industry literature for an estimate.
Then, knowing the chemical composition of your fuel and how much fuel you must burn overall, figure out how many moles of each chemical species you will be burning.
For any mole of hydrocarbon of chemical formula CxHy, with e excess air (where 1 is 100% excess air and 0.03 is 3% excess air), using air which we will approximate as 79% N2 / 21% O2, and assuming 100% complete combustion as a first approximation, we have this reaction formula:
CxHy + (1+e)(x+y/4)O2 + (1+e)(79/21)(x+y/4)N2 –> xCO2 + (y/2)H2O + eO2 + (1+e)(79/21)(x+y/4)N2
So for example ethane is C2H6, so substitute x=2 and y = 6 above. You are providing the perfect amount of oxygen for the combustion, and e% extra on top to help ensure complete combustion. The N2 is from the air and just goes along for the ride. read more…
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The Economist has a MBA series, including what and where to study MBAs, how to write your MBA application, and how to write the perfect MBA essay. I think the latter two links are worth saving, even if you’re just considering an MBA.
Of course, if you prefer to take the self-study route, you could try this list of the 99 best business books ever.
Lastly, you might forget the whole thing and build your startup company on your own.
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Hi everyone,
I updated the articles Salary Comparison & Prediction Tools and Assign Control Valve Pressure Drops with new resources. So you don’t have to re-read, here they are:
- I found a spot in the U.S. Bureau of Labour Statistics providing older mean (average) wages. But as a nice benefit, the data broken down by professionals and states. Check it out: Occupational Employment Statistics. Example: 2009 Chemical Engineers.
- A reader sent me this article, check it out if you have a Chemical Engineering Magazine subscription: Realistic Control Valve Pressure Drops
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Hey everyone, just a quick update on the website.
I previously had a small unit conversion program installed on the site, where you could hold your mouse over numbers expressed in Metric and a pop-up would convert them into Imperial, and vice/versa. I was glad to do this because we have readers whose unit preference varies.
Unfortunately, I have recently determined that this was interfering with some of the other coding the site, including some web links and the “print or pdf” buttons. I’m going to have to deactivate the unit auto-conversion until further notice. This should resolve the website problems a few of you have been experiencing.
Remember, you still have the conversion tool at the bottom of the “sidebar” on the right side of the page, and some previous posts suggest options for easy unit conversion. If you have another web-browser tab open to Wolfram Alpha or even Google you should be able to manage.
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Need to get stream data from a Sim-Sci Pro/II simulation (also known as Provsion or PRO-2) into another format; say Microsoft Excel? It could be for a heat and material balance table, an equipment datasheet, or just data for a calculation. Try one of the following approaches to copy out the PRO-II data:
- For small amounts of data you can copy from a stream or unit operation’s window directly. For example, for streams, right-click on the stream and select the data review window. At the bottom-left of the window is a drop-box listing the different Property Lists which you can request. In this context, Property Lists function like report formats. Pick the Property List with the data you want, and then click the “copy” button to copy all of the data on the screen. Then paste into other programs. By the way, from the main Pro-II screen, you can go to Option>Stream Property Lists to configure new lists in exactly the format you like. Similarly, under the Options menu you can create and view Unit Operation lists for equipment.
- You can also right-click on a stream and pick “View Results” to get a text report. For simple printing purposes just paste the report using a monospaced font like courier new. If you need to get the data into something like Excel, paste the data in Excel and try to use the Data>Text to columns option and play with the “delimited” settings to try to extract the numbers from the data as cleanly as possible. You may have to do a little manual work to get the data as a delimited data import will not be perfect
- Use the Output commands such as Output>Report Format and Output>Generate Text Report to get a text report. These text reports let you get a lot of data in one go: it’s a super-sized version of Option #2. Use the tactics of Option #2 to extract data from the report.
- Select Tools>Spreadsheet to access a variety of built-in spreadsheet reports. You can only get the default reports out with this approach. The results are attractively formatted and don’t have to fight with the data so this is a great option if the report covers your needs. Note: I find this tool is very slow and it often crashes. Save all your work beforehand, especially your PRO/II AND Excel work, in case these programs crash.
- Open your PFD Palette (the sidebar that has streams and unit operations that you can drop into a simulation). Near the bottom you of the Palette should see Stream Property and Unit Op Property tables. You can drop these tables onto the PFD and configure them to show your desired Property List, the same lists discussed in Option #1. You can copy these tables and paste them directly into Excel. This is a good method if you want to get the same property list for several streams or equipment items at once. A warning: for large tables it becomes difficult for PRO/II to display the data and it may slow down your simulation, as PRO-II will constantly fight to keep the numbers up to date. I suggest you add a “Block Diagram” from your PFD palette and build the stream table inside the “subflowsheet” which is accessed by double-clicking on the block diagram. That way, the table is hidden inside the subflowsheet and PRO-II will only create the table when you need to look at it
Personally, I find Option #5 the most flexible, although it takes work to set up the Property List just how you want it and it can slow down your simulation if you don’t hide the tables inside Block Diagrams. Option #4 is a really great option if the default report has the information you need, probably the best. Sometimes Option #4 can be extended with Option #2, if you just need to add a tiny bit of information to the otherwise fine default reports.
P.S. The techniques in this entry have been used with PRO/II V7.1-V8.3 and may not work with older or newer versions.
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