Air Pollution Control Innovations

Wet Scrubber Ductwork using Rolled Alloy's 253MA

Posted by Andy Olds on Thu, Feb 28, 2013 @ 06:00 AM

Authors: Zach Schulz and Andy Olds


Recently, Envitech was tasked by a leading waste oil refiner in Southern California to supply and install a wet scrubber on a process gas afterburner.  The goal of the project was to reduce the sulfur emissions from the facility to avoid the SOx (sulfur oxides) reclaim program in the Southern California Air Quality Management District.  The SOx reclaim program is a cap and trade program that requires emitters to secure or purchase the right to emit sulfur into the atmosphere.  Details of the project can be found in the article "High Efficiency SO2 Scrubber Case Study for a Waste Oil Re-Refiner" which outlines the incredibly stringent SO2 emissions standards that Envitech's wet scrubber successfully met.

SO2 Scrubber resized 600

Envitech; holding a general contractor's license in California; has the capability to not only supply the wet scrubber but to also supply and install the support equipment for the project.  As the project developed, the waste oil supplier expanded Envitech's scope to include nearly all of the work required for the wet scrubber, including the supply, installation, and warranty for the ductwork from the existing afterburner to the wet scrubber system.

Envitech faced some unusual challenges with the ductwork for the existing afterburner.  The afterburner itself is composed of refractory lined carbon steel, with an average exit temperature of 1600°F and with excursions to 2000°F.  Exhaust gas from the afterburner can also contain 1000ppm sulfur dioxide (SO2) with the potential of some sulfur trioxides (SO3).  Further, 90% of the time the gas passes through a heat exchanger that reduces the temperature to as low as 600F, with outages on the heat exchanger once a week.  Thus, Envitech had to provide an exhaust duct that could handle temperatures from 600F to 2000F with an elevated concentration of sulfur compounds, cope with thermal cycling, and operate near the acid dew point.

Envitech consulted with Rolled Alloys to determine the best alloy for the design conditions.  Separately, Envitech evaluated the cost and expected lifetime of refractory lined duct.

RA 253 MA was chosen for this application for its great resistance to high temperatures up to 2000°F. It also has a very lean nickel content (11%) which is beneficial for sulfur bearing environments at high temperatures. After working with Rolled Alloys and its subcontractors, Envitech found that the cost of a refractory lined duct, including installation, was slightly higher than that of the RA 253 MA material suggested by Rolled Alloys.  Further, Envitech found that insulated RA 253 MA material would have a longer expected lifetime than the refractory lining especially due to the thermal stress created by the temperature cycling and the aggressive nature of the sulfur in the gas.

SO2 Ductwork 

With this information, Envitech presented the RA 253 MA option to the waste oil refiner and jointly agreed that the RA 253 MA material was the best option for the ductwork.  Envitech's subcontractors built the ductwork out of Rolled Alloys RA 253 MA material on-time and on-budget, with startup occurring in May, 2012.  The ductwork is still in service with no reported issues.

With the help of Rolled Alloys, Envitech was able to provide ductwork that was easy to install, cost-effective, and within budget, contributing to success on the project that has enabled the waste oil refiner to avoid the SOx reclaim program by lowering its emissions. 

The project was considered a success by all parties and Envitech is currently working with the waste oil refiner on a second wet scrubber project with similar design conditions and intends to use the RA 253 MA material.

The above article was jointly written by Zach Schultz of Rolled Alloys and Andy Olds of Envitech.  The article was co-published on the Rolled Alloys Technology blog and Envitech's Air Pollution Control Innovations blog.

Envitech is an air pollution control equipment supplier serving industrial, medical, refinery and utility customers since 1993.  Their website is  You can contact Andy Olds directly at

For more information on this project, please read our white paper.

Download Paper

Topics: SO2 Scrubber, Guests, Acid Gas

CFD in Air Pollution Control Systems

Posted by Andy Olds on Tue, Oct 27, 2009 @ 06:00 AM

By Mike Simon
Director of Simulation Products, Digital Dimensions

Understanding how simple design changes affect the airflow inside of Envitech's products is critical in designing efficient industrial gas cleaning systems.  Engineers who design this equipment need to analyze and understand the behavior of the components if they want to improve performance.  Computational Fluid Dynamics (CFD) is a good tool for studying the effects of different design changes on these systems.  CFD provides a way to save time and money in obtaining the necessary information, and assists engineers in designing better quality air pollution control systems.    The use of CFD makes it possible to minimize the use of physical prototypes and find serious flaws much earlier in the design process. 

SolidWorks is the 3D CAD system used by Envitech to design their industrial gas cleaning systems.  SolidWorks has a number of complementary features to its mechanical CAD system including CFD capabilities that are fully integrated within the main CAD interface.  SolidWorks Flow Simulation is the name of the CFD program inside of SolidWorks that allows engineers to take their 3D CAD models and perform virtual prototyping on their designs without having to fabricate any parts.  To perform a simulation, the following steps are needed:

  • 1. Create solid model in the SolidWorks CAD system
  • 2. Specify the working fluid ( air was used in this case)
  • 3. Specify the flow rate at the duct inlet
  • 4. Specify the outlet opening of the duct
  • 5. Specify the pressure drop or resistance properties of the filter material (properties taken from filter manufacturer specifications)
  • 6. Run the simulation inside of the SolidWorks interface

Flow Simulation


Envitech's products were particularly challenging since Envitech's products utilized very thin fins and packing materials within a large ducting area.  Thin fins are used to direct the airflow and also to collect water from entering the system.  SolidWorks Flow Simulation was able to capture the geometry of these thin fins and create a corresponding CFD model for the simulations.  Packing material is used to help distribute airflow and trap particulates from being released into the environment.  The porous media feature inside of SolidWorks Flow Simulation was used to simulate the packing material and create the additional resistance to the airflow.  After performing the simulations, the Envitech engineers had the ability see the effectiveness of the scrubber fins in directing the airflow and to understand the pressure drops caused by the packing material.  The simulations helped the Envitech engineers validate their designs and gave them additional insight into how to improve future product performance.

For additional information on SolidWorks CAD or SolidWorks Flow Simulation software, go to or contact Mike Simon, Director of Simulation Products, at

For a case study on the impact of CFD analysis, click on the link below.

Download  Case Study

Topics: Venturi scrubbers, Scrubbers, wet electrostatic precipitators, Guests

Guest Blog: CFD Analysis

Posted by Andy Olds on Mon, Oct 26, 2009 @ 10:48 AM

Digital DimensionsI am very excited to announce that we will be publishing our first special guest blog post tomorrow, Tuesday, October 27.  The topic of the blog will be CFD analysis in air pollution control systems.

Our guest blog author is Mike Simon, Director of Simulation Products at Digital Dimensions.  Mike is a former SolidWorks/Cosmos Technical Manager and he has 10 years of FEA/CFD experience at companies such as General Atomics and General Dynamics.  Mike earned a BSME from UCSD, a MSME from Stanford, and a MBA from USD.  I am sure you will find his article very interesting.

A little more background Digital Dimensions...In addition to being an authorized reseller of Solidworks, Digital Dimensions hosts a variety of Solidworks training sessions, including topics such as structural analysis, flow simulation, and heat transfer - all tools available in the Solidworks design package.  I personally have benefited tremendously from the training sessions, and would recommend it to anyone interested in CFD or structural analysis using 3D models.  I use the CFD analysis on many of our Venturi scrubber designs as well as for our wet electrostatic precipitators.

Topics: Guests