Air Pollution Control Innovations

Merrill Crowe Refining Furnace SO2 Scrubber

Posted by Andy Bartocci on Thu, Oct 25, 2018 @ 06:02 PM

There are many applications that require packed bed absorbers for scrubbing SO2. Some applications Refining furnace SO2 Scrubberpreviously blogged about include refinery sulfur recovery unit tail gas treatment units (SRU/TGTU), geothermal power generation, and waste oil re-refining to name a few.  Another SO2 scrubber example is gas cleaning equipment for a mineral processing application to recover gold and silver from mine sites with low grade ore.   Discovered and patented in the early 1900 by Charles Merrill and later refined by Thomas Crowe, the Merrill-Crowe process is a common separation technique for removing gold and silver from a cyanide solution using zinc dust.  Gold and silver precipitate (concentrate) is the product of the Merrill-Crowe process.  Furnaces are then used to recover ingots from smelting Merrill-Crowe precipitate.  Fluxes are mixed with the precipitate to bring impurities to the surface. The precious metals settles down and can then be easily removed.

Envitech is currently building an SO2 scrubber to treat the exhaust gases from a melting furnace for a South American precious metals refinery mining project.  Furnace off-gases are in the 300oF to 500oF range and contain particulate and SO2.  A bag-house removes particulate from the gas before passing downstream to the packed bed absorber for SO2 removal.  Gas is first cooled to saturation in an evaporative quencher using re-circulated water. In the case of a pump failure, an emergency spray nozzle provides an independent source of water controlled by a thermocouple.  Water that has not evaporated flows from the quencher into the packed bed absorber sump. Gas from the quencher enters the bottom of the absorber and travels vertically upward through a packed bed.  Recirculated water is sprayed over the packed bed and mixes with the counter current gas.  A dilute solution of plant-supplied sodium hydroxide is metered into the scrubber recirculation line to neutralize acid gases and is controlled by pH of the absorber sump liquid.  The scrubbing water is collected in the sump and is re-circulated to the top of the packed bed and to the quencher. A blowdown stream is taken from the recirculation line to purge the system of reaction products. After the packed bed, the gas passes through an entrainment separator to remove water droplets entrained in the gas during scrubbing. The gas then exits the scrubber and is exhausted to atmosphere through an ID fan and stack.

The scrubber scope of supply includes a quencher, packed bed absorber, instruments, control system, recirculation pump, piping, valves, and fittings, ID fan, and metering pump. The unit will be pre-assembled to the fullest extent possible with pre-mounted instruments pre-wired to a control panel.  The assembly will be broken down as necessary for shipment and packaged for export to South America.  Bilingual submittals are provided for the O&M manuals and engineering submittals.  The scrubber will be delivered and started up in Q1 of 2019.

Click on the link below for a case study on the Merrill-Crowe Refining Furnace SO2 Scrubber and a packed bed absorber cut sheet.

 Download Literature

Topics: Scrubbers, SO2 Scrubber, Acid Gas

Envitech Lab Scrubbers for Gaseous Emissions and/or Particulate Control

Posted by Andy Bartocci on Tue, May 22, 2018 @ 02:31 PM

Packed bed absorbers are often used to treat gaseous emissions for reasonably large gas flow rates ranging from a few thousand cfm to greater than 70,000 cfm. Common emissions include SOx, HCl, HF, and NOx. The absorbers are often custom engineered for a specific plants and have been used for secondary lead smelters, geothermal power plants, waste oil-re-refiners, ceramic tile manufacturing, waste incinerators, and ethanol plants. The types of emission sources range from thermal oxidizers, regenerative thermal oxidizers (RTO’s), furnaces, kilns, direct fired heaters, incinerators, fermenters, vent tanks, and batch mixers.

Lab Scrub Mktg 1-1Envitech developed a lab scrubber to provide an economic solution for smaller gas flow rate applications.  The lab scrubber is a packaged unit designed for high efficiency of water soluble contaminants and can handle up to 2,000 cfm of gas at a maximum temperature of 180°F. The system is engineered for reduced footprint at 4 ft x 4 ft and includes a pre-wired control panel and pre-piped service utility connections requiring minimal installation and maintenance costs. Scrubber units are configurable to different levels of automation and treatment applications.  

A recent lab scrubber is for a manufacturer of pharmaceutical products in Southern, California. The scrubber is designed to remove HCl from the exhaust of several small laboratory process vent streams. The vent streams includes low organic concentrations which are incompatible with many common plastic materials. Special resin was selected for the fiber reinforced plastic (FRP) vessel and ductwork.  Piping and valves were assembled using PVDF.  The scrubber is designed for a classified area with explosion proof motors and instruments and is provided as a turn-key installation.

 

 

Lab Scrub Mktg 3Another example  is a process vent scrubber for a blending facility in South Carolina that produces crop protection products for agricultural markets.  The vent stream is 1,500 cfm and includes HCl and water soluble particulate greater than 3 micron in size. The Envitech lab scrubber was configured to include a low pressure drop Venturi for particulate control combined with a packed bed absorber for HCl control.  The system includes instruments, control system, recirculation pump, pre-assembled piping, valves, and fittings, interconnect duct, ID fan, and stack. 

Vent ScrubberA different use for a lab scrubber includes an ethylenediamine (EDA) scrubber installed in the South Eastern United States.  The storage of this precursor chemical requires extra handling than is typical with other common industrial chemicals.  With a relatively low exposure limit of 10 ppm, storage tanks must be properly engineered and scrubbed to remove excess vapors.  The Envitech lab scrubber is an ideal, low cost solution for this type of storage system.

Please click on the link below to download a brochure and case studies for the lab scrubber.

 Download Literature

Topics: particulate control, Scrubbers, SO2 Scrubber, Acid Gas, NOx, Vent

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

Rectangular Acid Gas Scrubber Lowers Installation Cost and Improves Maintenance

Posted by Andy Bartocci on Thu, Jul 09, 2015 @ 03:29 PM

Acid gas scrubbers are one of the most common types of air pollution control systems found in industry.  They are often used to treat exhaust gases from combustion sources such as incinerators, hazardous waste combustors, thermal oxidizers, regenerative thermal oxidizers (RTO), furnaces, and direct fired heaters.   Acid gas scrubbers are found on a wide range of facilities including, geothermal plants, secondary lead smelters, waste oil re-refiners, refineries, chemical and pharmaceutical plants, and mineral and metal processing facilities.  The most common types of acid gas emissions are HCl and SO2, but can also include Cl2, HBr, HF, and NOx.

Most acid gas scrubbers are wet scrubbers using vertical packed bed absorbers.   In the case of combustion sources, the scrubber is coupled to an evaporative quencher to cool the gas to saturation before it passes to the packed bed. This arrangement is shown in the adjacent figure for a medical waste WSU_Vertical_Scrubberincinerator.  The incinerator exhaust is ducted to a metal quencher (shown in the foreground). The hot gas enters the top of the quencher and flows vertically downward. The gas then elbows into the bottom of a vertical packed bed scrubber (shown in the background). The gas passes upward through the packed bed as re-circulated water flows downward, counter-current to the gas from the top of the packed bed.  Water from the quencher and packed bed is collected in the sump and re-circulated back to the quencher and packed bed.  An entrainment separator at the top of the scrubber removes entrained water droplets.  After exiting the scrubber vessel, an interconnect duct transports the gas to a induced draft fan located at grade.

The scrubber above is one of the earliest Envitech medical waste incinerator scrubbers.  These types of scrubbers are often installed in hospitals where critical design considerations include limited space, low ceilings, and difficult to reach locations through elevators and narrow corridors.  To help minimize installation costs Envitech developed a rectangular scrubber which is shown in the figure below. 

UTMB_Scrubber_Skid_Pic

 

 

 

 

 

 

 

 

 

 

 

This configuration provides several advantages over a vertical scrubber, including:

Greater integration and pre-assembly of ancillary equipment and pumps, piping, valves, and fittings.

  • Ground level access manways for safer, easier maintenance.
  • Simplified ductwork connection to the fan and stack.
  • Elimination of caged ladders and platforms for nozzle and mist eliminator access.
  • Ability to fit in locations with low head space.
  • Simplified requirements for setting and integrating equipment which lowers installation costs.

The rectangular scrubber has been used on over 60 installations.  Envitech has found that facilities tend to prefer a rectangular design over a vertical scrubber for the advantages noted above.  In some cases, total installed cost is reduced by 40% to  50%.  Weather a scrubber is purchased from an EPC contractor, upstream equipment supplier, or architectural & engineering firm, it is recommended that facility preferences be taken into consideration in the final selection process.

The video link below shows a few recently installed rectangular scrubbers at waste oil re-refiners as well as several examples of other rectangular scrubber installations.

 

 

Click the link below for a free case study on  a rectangular acid gas scrubber for a direct fired heater at a waste oil re-refiner.

Download Case Study

Click the link below for a free case study on a rectangular medical waste incinerator scrubber for the control of acid gases, particulate, and heavy metals.

Download Case Study

Topics: Scrubbers, SO2 Scrubber, Acid Gas, HMIWI Scrubber

Refinery Sulfur Recovery Unit (SRU) SO2 Scrubber for Startup, Shutdown, and Malfunctions

Posted by Andy Bartocci on Wed, Jun 24, 2015 @ 05:55 PM

For years, many states have exempted industrial facilities from rules prohibiting the release of toxic pollution during startup, shutdown, and malfunctions. That could all soon change.  On May 22, 2015, the U.S. Environmental Protection Agency (EPA) finalized a rule which will force state regulators to limit industrial upset emissions. The EPA issued a state implementation plan (SIP) call action to 36 states directing them to correct specific startup, shutdown, and malfunction provisions in their SIPs to ensure they are fully consistent with the Clean Air Act (CAA).  The ruling will affect a wide range of facilities including refineries, chemical manufacturers, and natural gas producers.  This will create challenges for state regulators and industrial facilities and opportunities for technology providers and environmental consulting and engineering firms.
A common industrial application which may be impacted by the new rule is found in refineries for sulfur recovery units (SRU).  Most SRU’s are based on a multi-step Claus process which recovers sulfur from gaseous hydrogen sulfide. The hydrogen sulfide is found in by-product gases from refining crude oil and other industrial processes.  A Tail Gas Treatment Unit (TGTU) follows the SRU to recover sulfur and return it to the SRU.  A TGTU can yield 99.9% sulfur recovery for a typical oil refining plant.  An inRefinery SO2 Scrubbercinerator and waste heat boiler treats the TGTU off-gas before it is exhausted to atmosphere. During normal operations, there is very little SO2 emissions due to the high sulfur recovery. However, TGTU upsets can occur several times per year which sends unrecovered sulfur to the incinerator.  During these upsets, SO2 emissions can be as high as 1 tph  or more for a period of 8 to 12 hours.Envtech is designing a refinery standby SRU tail gas caustic scrubber which will eliminate SO2 emissions during upset conditions.  The scrubber uses Envitech’s proprietary quencher which acts as a low pressure drop Venturi. The quencher is  followed by a packed bed absorber for SO2 removal.  The overall pressure drop is less than 10 inches and has lower power consumption than other types of SRU scrubbers installed in refineries.   Special design considerations enable the exhaust gas to pass through the scrubber at both elevated and cool temperatures.  During normal operation, hot gas from the TGTU passes through the scrubber in standby mode with the re-circulation pumps turned off.  In this mode, the gas is at elevated temperatures of 500oF to 600oF.  During a trip event, the TGTU is bypassed and the recirculation pumps turn on automatically.  The gases are then cooled to saturation and SO2 is absorbed and removed in the packed bed.  Implementation will enable the facility to reduce SO2 emission by 40 to 80 tpy and to meet the new EPA compliance standards for start-up, shutdown, & malfunction.    The scrubber is a good example of how an innovative solution can help a facility meet the new emission requirements during upset conditions with significant benefit to the environment.

 

To read more about the use of Envitech's scrubbers in difficult refinery applications, please download the white paper below on the topic of meeting ultra-low SO2 emissions.

Download Paper

Topics: Scrubbers, SO2 Scrubber, Acid Gas

Marine Diesel Scrubber Passes CARB Testing

Posted by Andy Bartocci on Mon, Jan 13, 2014 @ 07:04 PM

Marine ScrubberIn 2012 Envitech designed and built a marine diesel scrubber to remove SO2 from the engine exhaust of ocean going vessels.  The scrubber was integrated into the Advanced Maritime Emissions Control System (AMECS) used at the Port of Long Beach.  AMECS is a stationary system that uses a bonnet to capture the exhaust gas from the ships stack while at port. The exhaust gases are conveyed to AMECS to clean the gases of particulate (PM), NOx and SOx before exhausting to atmosphere. This allows the ship to operate its auxiliary engines and boiler system while at port to provide power to the ship.  AMECS provides a cost effective way for ships and port operators to reduce emissions and to meet tougher regulatory standards. 

The AMECS team recently announced that the California Air Resource Board (CARB) has approved AMECS as an alternative technology for the At-Berth Regulation.  This approval follows more than 1500 hours of validation testing on 40+ vessels during 2012 and 2013.  The most recent testing occurred in October of 2013 and was attended by representative of CARB and SCAQMD as well as representatives from the Ports of Long Beach and Los Angeles.  The test yielded impressive results, including:

    • PM                                                                  94.5%
    • NOx (@1.6ppm ammonia slip)                       99+%
    • SO2                                                                 98.5%
    • VOCs                                                              99.5%

In a parallel track, the maritime industry is looking for ways to meet tougher standards not only at port but while operating at sea based on the IMO Annex VI MARIPOL Tier III requirements. Envitech continues to develop De-SOx technology options for ship based marine diesel engines.  The recent CARB approval is a milestone achievement for demonstrating the Envitech scrubbers ability to achieve high SO2 removal efficiency over a wide range of diesel exhaust and operating conditions.

Click on the link below to download a case study on the marine scrubber.

Download  Case Study

Topics: Scrubbers, SO2 Scrubber, Marine Scrubber

Geothermal Plant SO2 Scrubber

Posted by Andy Bartocci on Fri, Sep 13, 2013 @ 11:56 AM

A geothermal plant produces a sustainable source of energy by converting super heated fluidsGeothermal Plant SO2 scrubber from the earth’s geothermal resources into electrical energy.  The fluids are recovered in the
process and re-injected back into the earth. The following YouTube video from CalEnergy provides a good overview of how a typical geothermal plant works.  California currently obtains about 4.5% of its electricity from geothermal plants. Most of these plants are sized at 50 MW but some plants can be larger in the 150MW range.  There is an estimated 2,300 megawatts of undeveloped energy in an area in Imperial County California near the Salton Sea just outside of San Diego.

SO2 Scrubber Geothermal Plant

 

The geothermal energy conversion process generates a sulfur containing off-gas which passes through a thermal oxidizer to destroy volatile organic compounds (VOC’s).   The sulfur compounds are oxidized to sulfur dioxide (SO2) and must be removed before exhausting to atmosphere.  A packed bed absorber treats the thermal oxidizer exhaust to remove SO2.  Often times geothermal plants are located in an extreme desert environment with summer  temperatures reaching > 120oF.  The scrubber equipment must be designed to achieve high removal efficiency, continuous operation and withstand the extreme environment.    

 

Click the link below to download a case study for an SO2 scrubber installed at an ORMAT geothermal plant near the Salton Sea in Southern California.

Download  Case Study

Topics: Scrubbers, SO2 Scrubber, Acid Gas

Wet Scrubber Technology for Reducing China’s Air Pollution

Posted by Andy Bartocci on Wed, Jun 26, 2013 @ 03:01 PM

Envitech recently got noticed in a local news story by Michael Chen of KGTV Channel 10 News, “San Diego Companies Could Help Clean China’s Air”.  The story is about how California’s Governor Jerry Brown’s diplomatic trip to China could lead to opportunities for local San Diego companies like Envitech.  During his visit, Gov. Brown signed a pact that will pave the way for California companies to help China measure and improve its air quality.   As a leader in industrial air pollution control equipment, Envitech has process technology that can be used in China for reducing hazardous air pollutants (HAPs) and pollutants that contribute to regional haze like sulfur dioxide (SO2). These technologies have been applied to many processes in North America including a coal gasification plant, hazardous waste incinerators, lead smelters, sulfite pulping mills, waste oil re-refiners, geothermal plants, and mining and mineral processing to name a few.  Envitech has pursued several opportunities in China through 3rd party customers and will have one installation starting up later this year.

For more information on Envitech's capabilities, please download our product brochure.

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Topics: particulate control, Venturi scrubbers, gasification, Scrubbers, SO2 Scrubber, wet electrostatic precipitators, cleaning systems

Wet Scrubber Ductwork using Rolled Alloy's 253MA

Posted by Andy Olds on Thu, Feb 28, 2013 @ 09:00 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 www.envitechinc.com.  You can contact Andy Olds directly at aolds@envitechinc.com.

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

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Topics: SO2 Scrubber, Guests, Acid Gas

Secondary Lead Smelter Wet Electrostatic Precipitator Case Study

Posted by Andy Bartocci on Mon, Dec 03, 2012 @ 12:30 PM

A secondary lead smelter in Southern California recovers leadlead scrubber, lead smelter scrubber from used automobile batteries. The process uses a combination of combustion processes including kilns and furnaces. Despite extensive control equipment including bag-houses, HEPA filters, and wet scrubbers, low concentrations of heavy metals were being emitted from various stack sources.  Cancer risk index standards were being exceeded due to the close proximity of residents to the plant.  To be compliant with state regulations a solution was needed to reduce these emissions. The special circumstances of nearby residents and a stringent cancer risk index required the facility to meet emission limits well below any other secondary lead smelter in the country.

A case study is now available to describe how an Envitech high performance Wet Electrostatic Precipitator was used to solve this problem.

Please click on the icon below to download the case study.

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