Air Pollution Control Innovations

Wet Scrubber Basics

Posted by Andy Bartocci on Tue, Sep 10, 2019 @ 12:02 PM

 

As an equipment supplier of custom engineered wet scrubber equipment, Envitech frequently provides lunch and learns (L&L’s) to engineering companies to help educate engineers about the basics of available technology.

Figure 1 below is a summary chart of predominant wet scrubber technology options. The main product categories include packed bed absorbers, Venturi scrubbers, and wet electrostatic precipitators (WESPs). Each wet scrubber type serves a different purpose and is used in different circumstances. For instance, packed bed absorbers are primarily used to remove gaseous emissions like SO2, HCl, or HF. We often receive packed bed absorber inquiries for particulate removal, however, this would be a misuse of technology. Packed bed absorbers remove some particulate but they are not nearly as efficient as other options.

Figure 1: Wet scrubber technology summaryEnv wet scrubber technologies

Venturi scrubbers are used for particulate removal. Just like we sometimes receive packed bed absorber inquiries for particulate removal, we’ll occasionally get Venturi scrubber inquiries for acid gas removal. This would also be a misuse of technology. Venturi scrubbers achieve some acid gas removal, but they have poor mass transfer compared to a packed bed absorbers.  

Venturi scrubbers use mechanical forces to remove particulate. Particles are captured through a process of impaction between particles in the gas and water droplets in the Venturi throat. A high differential velocity is created between particles and droplets by accelerating the gas in the throat. A pressure drop in the throat provides energy to capture the particles. Smaller particles less than 1 micron in size avoid capture by behaving like gas molecules and finding slip streams around the water droplets. Venturi scrubber performance drops offs exponentially for submicron particulate. Overall removal efficiency may be limited for a gas stream with a high concentration of submicron particulate. Venturi scrubbers are a good choice for industrial dryers or other applications with large size particulate.

Wet electrostatic precipitator (WESP) are the third type of wet scrubber summarized in the table. Like Venturi scrubbers, they are also particulate removal devices. They differ from Venturi scrubbers in a couple of ways, 1.) electrical, not mechanical forces are used to capture particulate, and 2,) they are efficient at capturing submicron particulate. Figure 2 shows a performance comparison between a WESP and Venturi scrubber. It can be seen that performance drops off dramatically for Venturi scrubbers for particles less than 1 micron in size. WESP’s on the other hand remove particles regardless of particle size.

Figure 2: WESP, Venturi scrubber performance comparison versus particle size.

Envitech WESP Venturi Performance

The summary in Figure 1 also shows how each wet scrubber technology differs in regulatory control. A packed bed absorber is typically controlled for recirculation flow rate and liquid pH. A Venturi scrubber is controlled by recirculation rate and pressure drop. A WESP is controlled by voltage. Control limits are typically spelled out in the operating permit.

Finally, some examples of applications are given for each type of wet scrubber. It should be noted that there are many applications that have multiple types of pollutants. A hazardous waste incinerator, for instance, contains particulate, acid gases, and specific heavy metals like cadmium and lead. A fraction of particulate is submicron in size and difficult for a Venturi scrubber to remove. It is common for different types of wet scrubbers to be combined into a multi-pollutant device. Figure 3 shows a common arrangement for an incinerator scrubber. The gas is first cooled in a quencher. A packed bed absorber removes acid gases. A Venturi scrubber removes particulate and a WESP removes the submicron particulate and heavy metals.

Figure 3: Incinerator wet scrubber arrangement

Env wet scrubber arrangement

Wet scrubbers can also be combined with dry scrubbers in certain circumstances. An upstream bag-house can remove particulate followed by a packed bed absorber for acid gas removal. A cyclone can be used to knock out large particulate before using a Venturi scrubber for the remaining particulate. A cyclone helps to minimize blowdown and water consumption. In some cases, a dry filter or carbon bed absorber can be integrated downstream of a wet scrubber for mercury and/or dioxin/furan. Click here to read a blog piece about an example of a wet scrubber combined with a carbon bed.

This about covers wet scrubber basics. If you’re with an engineering company and want to discuss scheduling a lunch an learn, please give Envitech a call. You can click on the icon below for a set of Envitech brochures.

Click on the icon below to download an Envitech brochure.

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Topics: particulate control, Venturi scrubbers, Scrubbers, SO2 Scrubber, wet electrostatic precipitators, Acid Gas, Packed Bed Absorbers, Packed Bed Scrubbers, Wet Scrubbers

International Conference on Thermal Treatment Technologies and Hazardous Waste Combustors (IT3/HWC)

Posted by Andy Bartocci on Mon, Aug 26, 2019 @ 01:55 PM

IT3 Logo

Envitech will be attending and exhibiting at the 37th International Conference on Thermal Treatment Technologies and Hazardous Waste Combustors (IT3/HWC) in League City, TX on October 2nd and 3rd, 2019. If you happen to be attending the conference, please stop by the Envitech booth or find me at the conference to say hello.

Three keynote panels will include high level experts and cover hot topics in the industry:

  • PFAS Overview, Regulatory Approach, Testing and Destruction
  • Emerging Air Quality Monitoring
  • Lessons Learned from the United Kingdom's 2018 Novichok Nerve Agent Incident

Papers presented in technical sessions cover:

  • Technologies and Trends in Incineration
  • Plastics Recycle and Reuse
  • Emission Monitoring
  • Waste-to-energy, Emission Monitoring, Pyrolysis 

Envitech will present papers on the following two topics.

Technology Solutions for Sulfuric Acid Formation and Removal in Liquid Waste and Waste Gas Thermal Oxidizers

Petrochemical plants, refineries, and waste-oil re-refiners operate liquid waste or waste gas thermal oxidizers.Candle filter The thermal oxidizers need a wet scrubber to neutralize and remove SO2. Flue gas entering the scrubber contain some sulfur trioxide (SO3) which is converted to sulfuric acid (H2SO4) in the quencher. Sulfuric acid is a submicron liquid aerosol that passes through the downstream packed bed absorber. Some facilities are now being regulated for H2SO4. This paper evaluates and compares candle filters versus wet electrostatic precipitators (WESP’s) for H2SO4 removal in these applications.

Sewage Sludge Incinerator (SSI) Mercury Control Technologies

Mercury Control ScrubberWaste water treatment facilities operating sewage sludge incinerators (SSI) can reduce sludge volume and disposal costs by combusting dewatered sewage sludge. Emissions are regulated by the US EPA Maximum Available Control Technology (MACT) standard 40 CFR Part 60 and 62 to control particulate, lead (Pb), cadmium (Cd), SO2, HCl, dioxins/furans, and mercury (Hg). Many SSI’s need a control device specifically for mercury. This paper evaluates two mercury control technologies: sulfur‐impregnated activated carbon and Gore sorbent polymer catalyst (SPC) modules. Several facilities have used sulfur-impregnated activated carbon but safety issues have arisen due to fires which have shut down some systems. The Gore SPC modules are a relatively new technology with at least seven installations. A comparison is made of capital cost, operating cost, mercury removal efficiency, fire and performance risks based on incineration of 3,000 lbs/hr of sewage sludge. Finally, an overview is provided for an Envitech SPC mercury control scrubber operating at one facility.

Click on the icon below to download an Envitech brochure.

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Topics: particulate control, Scrubbers, SO2 Scrubber, wet electrostatic precipitators, Acid Gas, Incinerator Scrubber, SO3 Aerosol

Technology Solutions for Sulfuric Acid Formation and Removal in Thermal Oxidizers

Posted by Andy Bartocci on Fri, Aug 23, 2019 @ 05:56 PM

Enivtech will be attending the 2019 International Conference on Thermal Treatment Technologies andCandle filter Hazardous Waste Combustors  (IT3/HWC)  October 2-3 in Houston, TX. A paper will be given on “Technology Solutions for Sulfuric Acid Formation and Removal in Liquid Waste and Waste Gas Thermal Oxidizers”. The paper is available for download by clicking the button at the bottom of this blog piece.

Petrochemical plants, refineries, and waste-oil re-refiners operate liquid waste or waste gas thermal oxidizers. The thermal oxidizers need a wet scrubber to neutralize and remove SO2. Flue gas entering the scrubber contains some sulfur trioxide (SO3) which is converted to sulfuric acid (H2SO4) in the presence of water vapor. Sulfuric acid is a submicron liquid aerosol that can pass through downstream equipment, such as a packed bed absorber or a baghouse. Some facilities are now being regulated for H2SO4.

WESPOver the last decade, Envitech has supplied SO2 scrubbers for thermal oxidizers burning sulfur containing compounds in refining applications. Most of these do not have add-on controls for capturing sulfuric acid mist. More recently, however, Envitech has supplied two systems with candle filters for the capture of sulfuric acid mist. Another known system used a wet electrostatic precipitator for the capture of sulfuric acid mist. A potential fourth system with a large gas flow rate with expected SO3 emissions was evaluated for a wet electrostatic precipitator.

A thermal oxidizer converts sulfur containing liquid or gaseous waste in the presence of excess oxygen to sulfur dioxide (SO2). A fraction of SO2 is further converted to SO3. The reaction is:

SO2 + 1/2O2 => SO3

The conversion amount is influenced by many factors including the thermal oxidizer operating temperature, residence time, sulfur concentration, amount of excess air, and the presence of catalytic oxides and metal catalysts in the fuel. Literature suggests that even a well-performing thermal oxidizer still converts 1 to 5% of SO2 into SO3. Given the numerous factors influencing the formation of SO3¬, most designers select a conservative estimate of SO3 conversion, even when actual SO3 emissions have been measured, as variations in operation can generate substantially higher conversion.

Once formed in the thermal oxidizer, SO3 reacts with water in the downstream quencher to form sulfuric acid (H2SO4) by the reaction:

SO3(g) + H2O(l) => H2SO4(l)

At temperatures below 350°F, H2SO4 condenses into submicron liquid droplets which are difficult to remove because of their small size. Aerosol droplets pass through a quencher and packed bed absorber. A separate control device is needed for sulfuric acid removal that is suitable for submicron droplets.

Click on the link below to download the IT3/HWC conference paper to learn about “Technology Solutions for Sulfuric Acid Formation and Removal in Liquid Waste and Waste Gas Thermal Oxidizers”. The paper evaluates and compares candle filters versus wet electrostatic precipitators (WESPs) for H2SO4 removal in these types of applications.

Download Literature

Topics: particulate control, Scrubbers, SO2 Scrubber, wet electrostatic precipitators, Acid Gas, Incinerator Scrubber, SO3 Aerosol

Ozone Injection for NOx Control on Medical Waste Incinerators

Posted by Andy Bartocci on Tue, Oct 30, 2018 @ 12:39 PM

Early this year I posted about achieving ultra-low emission limits for medical waste incinerator scrubbers.Med waste incinerator scrubber Front  An example was given for a captive incinerator at the University of Texas Medical Branch (UTMB) in Galveston, TX. It’s one of the only systems in the United States permitted as a “new” medical waste incinerator according to the EPA HMIWI (hospital, medical, and infectious waste incinerator) MACT standard. This standard has the most challenging emission limits found in industry today. That is because in 2009 the EPA completed a source review and revised the standard based on a MACT-on-MACT analysis.  Data used to set limits for each pollutant was individually based on waste feed and not incinerator/scrubber technology performance.  This resulted in emission limit reductions for lead (Pb), cadmium (Cd), and dioxins/furans (D/F) that were orders of magnitude below the previous standard and below the capability of installed equipment.  The impact of the new standard is discussed in greater detail in a 2013 blog post and corresponding paper from the Air & Waste Management Association (AWMA) International Conference on Thermal Treatment Technologies and Hazardous Waste Combustors (IT3/HWC)..
Medical waste incinerator Scrubber add-on controlsExisting incinerators needed to be upgraded with add-on controls to meet the new standard.  New incinerators need air pollution control equipment capable of extraordinarily high removal efficiency for particulate, Pb, Cd, and D/F.  A new medium sized incinerator between 200 to 500 lb/hr capacity, has the additional challenge of meeting NOx.  A medical waste incinerator can be tuned to a NOx limit of about 130 ppmv.  The MACT standard limit for a new medium sized medical waste incinerator was set at 67 ppmv which means NOx abatement is required to guarantee compliance.

Envitech is building two scrubber systems to treat exhaust gases from two new medical waste incinerators that will treat captive waste at a research facility.  The incinerators are permitted as new medium size incinerators which must meet the 67 ppmv NOx limit. The scrubbers have an equipment arrangement for meeting emission standards for PM, HCl, SO2, Pb, Cd, Hg, D/F, and opacity.  The schematic below shows the components of the gas cleaning system. The quencher is used to cool the gas to saturation and remove large particulate. The packed bed condenser/absorber sub-cools the gas and removes acid gases with caustic injection. The Venturi scrubber removes particulate and the majority of heavy metals. The gas then passes through additional polishing controls to meet the ultra-low emission limits for Pd, Cd, Hg, and D/F. The polishing equipment includes a re-heat duct followed by a filter and carbon bed adsorber.Med waste scrubber PFD

NOx removal is achieved by injecting ozone injection into the quencher outlet. The sizIMG_1032 Backside 1e of the condenser/absorber is increased to provide sufficient residence time for ozone-NOx reactions to occur.  Ozone is highly selective for NOx relative to other combustion products.   The NOx is rapidly converted to water soluble species. NO and O3 react to form NO2 and O2.  NO2 and O2 react to form N2O5 and O2. N2O5 and water react to form 2HNO3 which is readily absorbed with caustic solution.

Envitech used it’s rectangular scrubber design for the condenser absorber. To maintain a modular design and make it shippable.  The vessel was flanged connected and shipped in two pieces. The scrubber system otherwise looks like a typical medical waste incinerator scrubber except the condenser/absorber is double the height compared to systems that do not require NOx control.

The system has been built and shipped to the site. The major components are installed at the facility.  Envitech will deliver a water treatment system in 2019 to treat the scrubber effluent before it is discharged to the facilities main water treatment system.  System Start-up is scheduled for 2020.

Click on the link below to download a case study and other medical waste incinerator scrubbing literature.

 Download Literature

Topics: Scrubbers, Acid Gas, MACT Standards, Medical Waste Incinerator Scrubber, Incinerator Scrubber, NOx

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

Emergency Vent Lab Scrubber

Posted by Andy Bartocci on Tue, Apr 19, 2016 @ 01:28 PM

Lab_Scrubber.jpgA common application for small scrubber systems is an emergency vent scrubber for laboratories. Envitech's lab scrubber is a packaged packed bed absorber designed for high efficiency removal of water soluble contaminants (e.g. HCl, HF, HBr, SO2, NO2, etc.) from the gas stream and can handle up to 500 acfm of gas at a maximum temperature of 180oF.  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 typical application might be a facility with a gas cylinder filling stations laboratory hood vent.  The scrubber comes with a fan, pump, instrumentation, and control panel and is shop fabricated and assembled.

Click on the button below to download a free Envitech Lab Scrubber Brochure.

Download Brochure

Topics: Scrubbers, cleaning systems, Acid Gas, Product Information

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.

Download  Case Study

 

 

 

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