Incinerator Stack Design Issues

[pvcguy]

Does anyone have experience designing incinerator stacks for the incineration of VCM trace gases? I apologize in advance for the length of my question.
At our plant (PVC) we use a Brule designed incinerator to burn off inert gases which vent from processes containing nitrogen and very low levels of vinyl chloride monomer (VCM). The chemical is destroyed in the Incinerator at temperature above 1600 degrees F. before being released to the atmosphere. Incineration is carried out in a fire brick refractory lined chamber . The high temperature needed to completely burn
VCM is maintained by natural gas. The Vinyl Chloride Monomer, during combustion, is connected to Hydrogen chloride (HCl), Carbon dioxide (CO2) and water vapour, which is dispersed to the
atmosphere.
The incinerator was installed in the early 1980’s. Since that time we have replaced the entire 190’ high, 3’ - 10” OD stack once and the top 3 (of 10) sections a number of times. The original design, which we have followed to fabricate replacement sections, is of carbon steel shell with a FRP (Derekane) liner and a 2 ½” refractory layer over that. I should say that we originally purchased replacement stack sections from Brule but stopped doing that after they arrived on site requiring major refractory repairs from the distanced traveled. The local contractors have done a great job of replicating what Brule fabricated for us.
Now the problem. The failure of the stack sections appears to occur when the refractory breaks down allowing the high temperatures to degrade the FRP allowing the HCL to attack the CS shell. Usually the top section sees the most damage and it has been replaced 3 or 4 times the latest being Nov 03. When the section was removed to replace the refractory on the section below was disturbed and now that section is failing. What is the latest design on a stack like this? We could go with an exotic type of metal but $ are on issue. My other question would be, is there something better than Derekane we should be using? There is no technical back up with Brule out of business.

Any comments on this would be appreciated.

 

[Compositepro]

Where are you located where you can vent HCl without scrubbing it? I worked in a PVC and VCM plant in Calif. in 1980 where we installed an incinerator and an FRP scrubber. As I recall there was lots of maintainence required. The engineer in charge is retired now but may be interested in consulting.

 

[pvcguy]

We are located north of the US and are regulated on what can go out the stack. If your former employer scrubbed the stack effluent they may not have had the same issues with HCL corrosion in the stack.

 

[dan21703]

This is not a difficult problem to figure out. The key is to know the composition of the gas stream that is the percentage of the CL in the stream water vapor percentage and the stack temperature at the base of the stack.

It is likely a liner can be installed that would completely eliminate the problems you have. The liner costs is typically much lower than the original stack costs. In order to design a liner it would be necessary to have lots of details of your stack.

It seems that you have an acid brick stack which by the way is at traditional solution that if installed and operated correctly should last a lifetime. You may not want to hear the information that your operations may be as much to blame for the failure as the stack or liner itself.

Be glad to help, but you have a project here that requires someone with some experience and capability to integrate the process and structural aspects.

 

[abcmex]

PVCGUY,
there are many Incinerator suppliers (

http://www.johnzink.com,

http://www.anguil.com,

http://www.duerrenvironmental.com)

which may have seen your trouble already and can help you (my be paying a small consultancy fee) or stack companies like (

http://www.schicks.com

or

http://www.steelcom.com)

 

[MedicineEng]

We would need some more information but maybe you can consider these suggestions:

Instead of touching in the stack, isn't a possiblity to low down the gases temperature to the allowable range of the FRP?
1-Install a recovery boiler (and you will have free steam) and then wash the gases with a venturi and scrubber;
2-Mix the gas stream with outside air at the entrance of the stack to low down the temperature (be careful because this will increase the possibility of plume, if this is an issue, I don't recomend it);

I don't know you % of HCL but I can tell you that in our plant (completely different process) we can have % of HCL as high as 10% and the system that we use is the one that I descrived on point 1 (burning at 1100C+recovery boiler+venturi+FRP scrubber+FRP stack). The only issue that you have is in the venturi. You should consider Hastelloy C-276. Then the scrubber can be FRP and the stack also. I believe that it is cheaper than to replace the all stack by Hastelloy C-276 and your gas stream will be much more environmental friendly.

Hope that helps.

 

[dagur777]

Does any of you have knowledge and experience for analyzers on EDC and VCM purification sections? Please check my question in the Forums in measurement and control instrumentation engineering.

I wnat to know if you know any analyzer available for Heads Column top (to measure CCl4, EDC) and VCM column top (to measure MtCl, EtCl, EDC, 1,1,2-TCE).

I checked website, Siemens has vent gas analyzer for Oxychlorination section, ABB and AppliTek have analyzer for water. I would like to know any analyzer available for by-products in EDC peuification and VCM purification section as described.

Thanks

 

[meca]

I have a totally off the wall comment/suggestion. I design a lot of stacks, but I'm more specialized on the structural aspects rather than the chemical design. When you get a stack this tall, 190', often wind induced vibration can be an issue. There may be a wind speed, and it may not necessarliy be high, where the stack will vibrate. If the stack is not equiped with a damper or vortex disruption device (i.e. helical strakes) it is possible that the vibration could be quite high.

I only mention this because it is common with tall stacks, and could explain refractory failure. Although, I would have expected someone in the plant to notice excessive swaying of the stack.