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Wet Scrubber Not Working Properly?

Posted by Anthony DeLoach, President on Sep 12, 2022 8:47:33 AM

When it comes to Odor Control and Air Emission scrubbers, you're either pleased with how yours works or highly frustrated with how it isn't.

Image of Wet Scrubber Tower in Water Treatment

While wet scrubbers are powerful devices that can reduce harmful air pollutants and exhaust gases, not all are created equal. An operator's most common problem with a scrubber is a lack of performance. The following are some main reasons why your scrubber may not work correctly.

When it comes to designing a wet scrubber, different manufacturers have different design standards. Creating a device that can handle high throughput with reduced cleaning cycles. Others will develop a scrubber concentrating on the maximum removal of pollutants.

The wet scrubber that you purchase should be based on your specific needs. If you buy a scrubber not designed for your particular application, you're setting yourself up for problems.

Some factors will determine how well your scrubber will perform, including the gas flow rate, gas pressure, the type of media used, and the design of the scrubber itself. If your wet scrubber design cannot handle your application's specific requirements, you'll experience reduced performance and increased downtime. Faulty installation of the scrubber

If your scrubber is not installed correctly, it will not perform properly. A poorly executed installation can cause a wide variety of issues.

The most common problem is channeling, which causes a low-pressure drop across the scrubber. The most common cause of this issue immediately after an installation is an out-of-level scrubber tower, followed by the improper placement of the media bed. A poor installation will cause reduced performance and allow odor or chemical breakthrough from the exhaust of the scrubber. The incorrect type of media in a scrubber can also cause a reduction in performance. Upon discovering a low-pressure drop, the scrubber should be inspected to ensure the installation was done properly and that the media bed is correctly sized and placed within the scrubber for its specific application. Remember, one size does not fit all regarding odor control and air emissions scrubbers!

First, hire a reputable engineering firm or work directly with a manufacturing company with professional engineers who have experience and specialize in wet scrubber design and installation. Reviewing the manufacturer's installation manual and following the instructions is also essential.

Suppose your wet scrubber is the final device on an exhaust stream laden with particulate matter. In that case, it is recommended that the particulate be removed through a roughing filter or a water scrubber first to safeguard the more expensive media in the wet scrubber to prevent the media from becoming fouled. When a media bed becomes fouled, the hydraulic load conditions change within the scrubber impacting the scrubber's performance and eventually will cause a complete scrubber failure. 

Another problem while operating a wet scrubber is the raw air feed entering the scrubber. Suppose you experience excessive foaming, high steam flow rates, or liquid carryover. In that case, you may need to inspect upstream of your scrubber to determine if there has been a change in the process or a potential failure in a valve or instrument. If your installation includes an inlet feed damper, inspect it to ensure the settings have not changed. If your process has changed, creating different concentrations or even new emissions, contact your manufacturer to ensure you have the correct type of scrubber for your application.

The wrong type/product of media was used in your scrubber.

The media you use will significantly impact how well the scrubber performs. When purchasing a wet scrubber, it should be sized and designed to utilize a specific media type. Be aware that during a media replacement cycle, if you replace the media with a less efficient type, you'll experience reduced performance.

Review the wet scrubber product datasheet to ensure you purchase the best media type for your application. The product data sheet will contain everything you need about the scrubber, including the optimal media type, recommended media amount, and regeneration requirements.

Excess accumulation of solids in your scrubber.

As your scrubber removes pollutant-laden from the source, it also produces solids as a byproduct of the internal reaction or oxidation occurring internally or from particulate that may be entering the scrubber from the raw feed source. If not adequately managed within the scrubber and the blow-down components, the solids will eventually build up in the bed until they reach a level that impacts the scrubber's performance. Care should also be taken to analyze and review the makeup water feed for the scrubber. Utilizing hard water can cause calcification inside certain types of wet chemical scrubbers. Making up water containing chlorine, often found in potable water supplies, harms biological wet scrubbers and their performance.

The best way to avoid excessive buildup of solids in your scrubber is to properly size the scrubber, recirculation system, and blow down controls. A properly designed system and proper installation and setup of the scrubber controls will allow the scrubber to perform to its specified design and remove excessive solids in the blow-down control device to prevent build-up.   

Exhaust gas temperature is out of range for your wet scrubber's efficiency.

The exhaust gas temperature will significantly impact your scrubber's efficiency if the exhaust gas temperature is too cold or hot. From the original design parameters, the efficiency of the wet scrubber can suffer depending on the application type and the wet scrubber being utilized.

If the exhaust gas temperature is too hot, your scrubber may not be able to perform correctly. You must monitor the exhaust gas temperature and make necessary adjustments to ensure it operates in the original design's optimal range. The specific scrubber type and application will determine the optimal exhaust gas temperature range. You can find the recommended exhaust temperature range on the product datasheet.

Most modern larger industrial wet scrubbers have an SCR to reduce Nitric Oxide emissions from the wet scrubber bed. If the SCR is operating below optimal efficiency, it may cause issues for your scrubber.

Issues with an inefficient SCR include:

  • Excessive foaming in the wet scrubber bed
  • Issues with the wet scrubber regeneration
  • Reduced throughput

If your scrubber isn't working correctly, it may be due to the performance of the SCR.

Ensure the wet scrubber bed conditions are correct and check the SCR if the problem persists. If your wet scrubber isn't working correctly, it may be due to the performance of the SCR. Ensure the scrubber bed conditions are correct and check the SCR if the problem persists. You should check with your SCR vendor to ensure their machine meets the correct efficiency criteria.

Wet scrubbers are one of the most powerful air pollution reduction devices, but only if properly designed, installed, and operated. The reasons listed above are some of the most common reasons a scrubber may not work correctly. The best way to avoid problems is to hire a reputable design and manufacturing company like DeLoach Industries Inc., which has been manufacturing odor control and air emission scrubbers for decades and has trained professionals to assist with every application.

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Topics: the type of media, gas flow rate, wet scrubber, wet scrubber design, media type, gas pressure, gas flows, pressure drops

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