Air Pollution Control Innovations

Ceramic Tile Kiln Acid Gas Scrubber: HF, HCl, SO2

Posted by Andy Bartocci on Thu, Oct 15, 2015 @ 04:38 PM

SO2 Scrubber Ceramic Tile Kiln

PROBLEM:

A Midwestern ceramic tile manufacturer needed an acid gas scrubber to treat the off gas from 3 kilns being installed at a new manufacturing plant. Each kiln was equal in size and emits HF, HCl, and SO2. The scrubber needed to remove > 98.5% of acid gases. The scope of supply included an ID Fan, interconnect duct, stack, control system, and pump skid. The facility was faced with the additional challenge of less than 22 ft of overhead space inside the building. A tight schedule required receipt of equipment in 16 weeks, including engineering. The customer operated other scrubbers at different facilities and reported difficulty in controlling the spray quenchers to cool and saturate the gas.

SOLUTION:

The customer selected an Envitech quencher/packed bed scrubber to meet their requirements. To eliminate difficulty in controlling gas cooling the scrubber used a proprietary, low pressure drop Venturi quencher. This provided a means to saturate the gas over a wide range of operating conditions and flow rates. The scrubber used a proprietary internal duct design with an outlet and entrainment separator at the bottom of the scrubber. This allowed the scrubber to fit in the low overhead space with no roof penetrations to minimize installation cost and time. Other equipment features included:

  •  Quencher design to capture > 90% of particulate > 3 microns.
  • Skid mounted dual pumps (1 opr/1 spare) with pre-piped and valved instruments.
  • Hydro-testing of piping assemblies.
  • Instruments pre-wired to a junction box.
  • Control System Factory Acceptance Test (FAT).
  • High efficiency, low pressure drop packing with high void spaces to prevent material accumulation and fouling.

 RESULTS:

The customer placed the order in June, 2015. The equipment shipped on time in October 2015 and arrived on site one week early, 15 weeks from order placement. The system will be operational in early 2016. Stack testing will confirm compliance with the performance guarantee summarized in the table below.

DESIGN

VALUE

Flow Rate, acfm

70,000

Inlet Temp, oF

482

HF Removal

> 98.5%

HCl Removal

> 97%

SO2 Removal

> 53%

 To download a Free Case Study, please click on the icon below.

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Topics: Scrubbers, SO2 Scrubber, Acid Gas, quenchers

Sulfite Pulping Mill Recovery Boiler Scrubber System

Posted by Andy Bartocci on Tue, Oct 30, 2012 @ 11:55 AM

Envitech has received an order from Tembec to supply an ammonia based red liquor recovery boiler scrubber for the Temiscaming sulfite pulping mill in Québec, Canada.   The scrubber system will treat the off-gas from an upstream sulfite power boiler supplied by Andritz and will meet stringent emission standards for particulate and SO2.sulfit pulp mill scrubber, recovery boiler scrubber, red liquor boilerr

This system is part of a $190-million power generation project that will upgrade Tembec’s existing specialty cellulose manufacturing facility.  The upgrade will increase annual green energy production by up to 40-megawatts, reduce sulfur dioxide emissions by 70%, and increase annual production capacity of specialty cellulose by 5,000 metric tonnes.  The upgrade will make Temiscaming one of the lowest-cost specialty cellulose manufacturing facilities in the world.

The scrubber system is engineered to Tembec’s requirements and is the result of close collaboration with the customer over several months and their engineering firm Pöyry.   The design leverages experience from several other large volumetric flow rate applications including a coal dryer scrubber, secondary lead smelter wet electrostatic precipitator (WESP) system, and a hazardous waste incinerator scrubber.  The scope of supply includes an inlet duct from the boiler exhaust fan, quencher, ammonia scrubber, condenser, WESP, caustic scrubber, heat exchangers, structural steel, access platforms, and stack.  Primary vessels will be shop fabricated and shipped to the site for assembly and installation.  This provides a lower total installed cost, greater quality control over manufacturing, and shorter delivery and installation time.  System start-up will occur in the fall of 2013.

To read more about this system, download the case study below.

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Topics: particulate control, Scrubbers, SO2 Scrubber, wet electrostatic precipitators, quenchers

Pharmaceutical Scrubber

Posted by Andy Olds on Tue, Oct 13, 2009 @ 04:50 PM

pharmaceutical scrubberAs the EPA continues to tighten the emissions belt, I am seeing new industries with air emissions issues. One such industry is pharmaceuticals, who are now more commonly regulated for acid gases on post-combustion devices.

Pharmaceutical air emissions are typically a result of an organic fume from a solvent. The fume, containing vaporized solvent, is captured either within a fume hood or central ventilation system. When regulated, the most effective way of removing a fume is to combust it in a regenerative thermal oxidizer (RTO) or some other combustion device.

The combustion of a solvent such as methyl chloride in an RTO leaves three compounds: carbon dioxide, water vapor, and hydrochloric acid. The last of the three - hydrochloric acid - is often treated as an emission and if so must be removed from the outlet exhaust.

Pharmaceutical Scrubber 

The most best method for removing hydrochloric acid from a gas is the use of a pharmaceutical scrubber. A scrubber offers extremely high efficiencies (greater than 99%, or as required) at a low pressure drop. Recirculating neutralized water across a packed tower, the capital and operating cost of a scrubber is minimal. Further, the effluent from a HCl scrubber contains only sodium chloride - table salt - and can easily be disposed of through a wastewater sewer with little to no further treatment. Using FRP for the scrubber provides a low cost building material highly resistant to acid attack.

Hydrochloric Acid Corrosion

The removal of hydrochloric acid from a combustion exhaust does offer one particular difficulty over other common acid gases, of which designers and operators in the pharmaceutical industry need to be wary. Hydrochloric acid and neutralized chlorides are very aggressive towards most metals, especially so at elevated temperatures typically seen on the outlet of a combustion process. Since the HCl is contained in the exhaust of a combustion process, the inlet gas temperature to the scrubber is high. In turn, the recirculation water temperature is also high, usually well above 100F. Standard metallic materials such as stainless steel will quickly corrode in this environment.

In the past, I have used both AL6XN and hastelloy for metallic materials in HCl scrubber systems. Common metallic items in a pharmaceutical scrubber include the quencher, instrumentation, and downstream devices.  AL6XN is a duplex material that provides very good corrosion resistance to around 1000F. It also has about an order of magnitude greater chloride pitting resistance than stainless steel at neutral pH, and over two magnitudes resistance at low pH.  AL6XN is ideal for quenchers on the exhaust of an RTO, where the outlet temperature is usually around 500F. Hastelloy is more expensive, but it offers heat resistance to 2500F as well as a further order of magnitude resistance to chlorides over AL6XN.

Hydrochloric Acid Mist

The other issue provided by hydrochloric acid in a gas stream is the formation of hydrochloric acid mist, which I have previously touched upon in my acid gas dewpoint post.

Hydrochloric acid mist usually requires a high efficiency mesh pad for removal of any HCl aerosols that may form in the scrubber.  A mesh pad is more expensive than a standard wave form mist eliminator, and is also much more prone to particulate plugging.  If hydrochloric acid is in your gas stream, make sure you consider a mesh pad and beware of particulate!

If you would like to learn more about corrosive acid gas scrubbers, download the free case study below.

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Topics: Scrubbers, Acid Gas, quenchers

Quenchers: Spray Lances

Posted by Andy Olds on Fri, Aug 07, 2009 @ 09:00 AM

Quenchers are used in air pollution control equipment to rapidly cool a high temperature gas stream.  Rapid cooling prevents gas phase reactions that may occur at intermediate temperatures, such as dioxin and furan formation.  Rapid cooling also relaxes the material requirements of downstream equipment, allowing the use of materials such as FRP, CPVC, and duplex steels.

In the video above, we take a look at a rectangular quencher.  We have used the rectangular quencher for regenerative thermal oxidizers.  A rectangular quencher provides sufficient quenching for relatively low temperature gas streams (200F to 600F).  Water is sprayed directly on to the gas, away from the upstream process.  Water drains from the quencher into the basin for recirculation.

spray lanceIn the picture to the right, the spray headers are installed using a double flange approach.  The two flange approach improves the accessibility of the nozzles in the quencher, which can be susceptible to plugging in some applications.  Water is connected to the first (header) flange.  The second flange connects to the quencher.  The spray header can then be removed like a lance.

 

 

 

 

gas quencherThe picture to the left shows an example of a rectangular quencher.  A rectangular quencher in low flow, low temperature quench applications are typically more cost-effective than round quenchers, especially if they are attaching to rectangular or horizontal ducts.

 

 

 

 

Download a 3D video of the spray lances using the link below.

Free Video

Topics: quenchers