Air Pollution Control Innovations

I posted previous blogs discussing the South Coast Air Quality Management District (SCAQMD) Regional Clean Air Incentives Market   RECLAIM program and the A&WMA/AQMD SO_x Control Technology Conference held at Diamond Bar, CA on March 17^th.  During the conference I participated as a panel member to present Envitech’s Ultra-Low SO₂ scrubber design.  I will also be giving this presentation at the upcoming International Conference on Thermal Treatment Technologies (IT3) in Jacksonville, FL, May 10-13, 2011 and again at the Annual Air & Waste Management Conference in Orlando, FL June 21-24, 2011.  Envitech will have a booth at the IT3 conference.

Below is an abstact for discussing the Ultra-Low SO₂ scrubber design.  You can click the icon below to download the paper.

High Efficiency SO₂ Scrubber Design to Reduce Caustic Consumption

ABSTRACT 

An industrial facility located in Southern California operates a thermal oxidizer to treat vapor recovery and waste gas streams containing sulfur compounds.  The facility has an available source of alkali waste water which could be a potential scrubbing solution.  Several technologies were evaluated to replace the existing control equipment for reducing SO₂ emissions.  Incentives exist for similar facilities with the South Coast Air Quality Management District (SCAQMD) Regional Clean Air Incentives Program (RECLAIM) to reduce SO_x emissions below the facilities operating permit limits.  The RECLAIM program is requiring plants to achieve less than 5 ppm_v SO₂ stack emissions and greater than 99% SO₂ removal.

Plans are currently underway to replace the existing control equipment with a two stage packed bed scrubber system.  This arrangement enables the plant to achieve very low emission limits and reduce caustic consumption by as much as 28% compared to a single stage scrubber.  It also provides flexibility for future use of available alkali waste water to reduce caustic consumption by as much as 75% compared to a single stage caustic scrubber.  This reduction will save an estimated $165,000 per year in operating cost. This paper will discuss the system design and how it achieves low outlet emissions while reducing overall chemical consumption.  It will also discuss several other design considerations and benefits.  The design approach provides a viable alternative for other Southern California facilities impacted by the SO_x RECLAIM program as well as facilities in other regions.

Click on below icon to download whitepaper.

This is a follow-up to my blog post last week on SO_x scrubbers and the AQMD RECLAIM program.  I was a panel member duringone of the conference sessions for the SOx Control Technologies & Emissions Monitoring for Stationary Sources hosted by AQMD and the Air & Waste management Association (A&WMA).  The conference was held on March 17^th at the South Coast AQMD facility in Diamond Bar, CA.  There were about 90 attendees at the conference and my understanding is that all but one of the 11 major facilities impacted by the AQMD RECLAIM program had someone in attendance.

There were interesting presentations given in the morning sessions focused primarily on refinery applications. These included presentations by both INTERCAT and GRACE on additives that can be used in Fluid Catalytic Cracking Units (FCCU’s) to reduce SO_x emissions without add-on controls.  This type of approach will likely be used by most of the local refineries to meet shorter term requirements. However, the speakers noted limitations for achieving lower outlet emissions in the 5 ppm_v range.  These can include higher chemical consumption and impacts on opacity.  This suggests there may still be a need for back end controls to meet longer term requirements to achieve limits below 5 ppm_v.

PRAXAIR gave an informative presentation introducing their Refinery Gas Processor (RGP) technology.  This technology is targeted at treating non-H₂S sulfur compounds (Mercaptans, COS/Sulfides, Disulfides, Thiophenes) for use in conjunction with existing amine H₂S removal systems.  The RGP technology can enable a 90% reduction of non-H₂S sulfur  from refinery fuel gas.

Another issue discussed during the conference was the ability accurately measure and report outlet emissions as low as 5 ppm_v.  This will present a challenge for many facilities because most existing monitoring equipment are designed for measuring outlet emissions at higher concentrations.  However, several panel members from the afternoon session on emissions measurements provided useful information on how to address these challenges. These include presentations from:

• AMETEK
• HORIBA
• THERMO FISHER SCIENTIFIC
• PERMA PURE

I gave a talk during the afternoon session on control technologies. This session was dedicated to wet scrubber technology for achieving ultra-low SO_x emissions.  Ultra-low is loosely understood to be less than 5 ppm_v.  This is generally a longer term target for the AQMD RECLAIM program.  Most the technologies focused on wet gas scrubbers for refinery FCCU units.   I presented an innovative SO_x scrubber design to remove SO₂ from a thermal oxidizer exhaust at an industrial facility located in Southern California. The exhaust contains more than 1,000 ppm of SO₂ and the facility is required to achieve less than 5 ppm_v with greater than 99% removal efficiency.  There are several advantages of the scrubber design for applications requiring ultra-low SO₂ emissions.  The scrubber design may be a viable option for some of the facilities impacted by the AQMD RECLAIM program including FCCU units and glass manufacturers.  I’ll provide a future blog post that gives more information about the ultra-low SO₂ scrubber design.

If you would like to download the white paper on an ultra-low SO₂ scrubber design, click the link below.

A hot topic right now in California is the South Coast Air Quality Management District (SCAQMD) Regional Clean Air Incentives Market (RECLAIM), adopted in October 1993.  The purpose of the RECLAIM program is to reduce NO_x and SO_x emissions through a market-based program.  Reduction of these pollutants helps reduce smog and improve visibility.  Recent proposed amendments will affect eleven major facilities which emit and estimated 93% of the total emissions from the SO_x RECLAIM facilities.  These amendments will require many facilities to reduce SO_x emissions below the level of control they currently have in place.  Financial incentives exist for other facilities to reduce emissions below existing permit limits. 

The West Coast Section of the Air & Waste Management Association (A&WMA) is hosting a technical conference on innovative SO_x control strategies and technologies for stationary sources on March 17-18, in Diamond Bar, CA.  Part of the conference is dedicated to providing an overview of the regulatory landscape including new federal rules related to SO_x and the recently amended SO_x RECLAIM program.  I will be giving a presentation on an innovative SO₂ scrubber design used at an industrial facility in Southern California to remove SO₂ from a thermal oxidizer. The SO₂ scrubber is designed to achieve low outlet emissions below 5 ppmv and greater than 99% removal efficiency.  The presentation will discuss the advantages and benefits of the design, including reduction in caustic consumption. Continued efforts to deploy better technology and reduce emissions will enable clearer skies in the face of growing populations.

To learn more about achieving ultra low SO₂ emissions, please download our white paper.

Photo Credit, LA Smog - Recursive_1

Photo Credit, LA Clear Day - Nomadlovebird 

I gave recent presentations at the International Thermal Treatment (IT3) Conference in San Francisco, CA and the AWMA Conference in Calgary, Canada.  The paper is co-authored with Liran Dor, CTO of EER - Environmental Energy Resources Ltd.  The paper discusses an environmentally friendly way of converting medical waste to energy using EER’s Plasma Gasification Melting (PGM) and Envitech’s wet scrubbing technology. 

ABSTRACT 

A plasma gasification melting (PGM) technology has been developed to transform waste into synthesis gas and products suitable for construction materials.   The core of the technology was developed at the Kurchatov Institute in Russia and has been used for more than a decade for the treatment of low- and intermediate-level radioactive waste in Russia. It is applicable to municipal solid waste (MSW), municipal effluent sludge, industrial waste and medical waste.

Plans are currently underway to build a plant in the US to recycle medical waste using the PGM technology into a high calorific Syngas and a benign residue.  Both output materials may be considered secondary materials since they have commercial use in other processes.  Current plans include the production of steam which will be sold as a commodity to nearby industrial users. 

The Syngas is fed into a Heat Recovery Steam Generator (HRSG) to produce superheated steam for use as heat or electricity generation using a steam generator. The Syngas leaving the HRSG will enter an Air Pollution control (APC) system for post process gas cleaning.  The APC system will use a wet scrubber system that has successfully achieved low emission standards on other typical combustion processes.  This paper will discuss how these technologies are combined to create an economically viable and environmentally friendly solution for converting medical waste into energy.

Please click on the below icon to download the AWMA and IT3 conference white paper. 

I gave recent presentations at the International Biomass Conference in Minneapolis, MN and the International Thermal Treatment (IT3) Conference in San Francisco, CA on wet scrubbers for gasification.  Below is the paper abstract. A free download of the paper and presentation is available by clicking the links below. The paper discusses two common tar management approaches regarding syngas cleaning:

1. Thermal Tar Destruction Systems 
2. Tar Removal Systems

ABSTRACT

Concern for global climate change coupled with high oil prices has generated new interest in renewable energy sources.  Many innovative companies are working to commercialize these sources using gasification to convert waste to energy and fuels.  Gasification is a thermal conversion process which produces synthetic gas (syngas).  With proper cleaning, syngas can be used to fuel an internal combustion engine (ICE) to drive a generator, and produce electricity.  Waste heat is recovered from the system to improve the overall plant efficiency. 

During gasification, various pollutants may be produced depending on the type of gasification process and the make-up of the waste feedstock.  The feedstock can vary from biomass, municipal solid waste (MSW), to even medical or hazardous waste.  The pollutants involved can include large to sub-micron particulate matter, tars, and acid gases.  A key challenge to commercializing gasification is designing a syngas cleaning system that removes pollutants to a level that is tolerated by the ICE (or fuels and chemical production system) and also meets emission standards. This paper will discuss different approaches to tar removal and control strategies for the various pollutants. 

Please click on the icon below to download the IT3 conference white paper and the International Biomass Conference presentation. 

I gave recent presentations at the International Thermal Treatment (IT3) Conference in San Francisco and the Annual AWMA conference in Calgary, Canada that discusses the new hospital/medical/infectious waste incineration (HMIWI) MACT standard and implications for existing systems.  Below is the abstract.  A free download is available by clicking on the link below.  The paper presents emissions data on several scrubber systems and discusses how these relate to the new rules.  I also discuss cost effective strategies to comply with the new rules using add-on controls. 

ABSTRACT

On October 6th, 2009, proposed revisions to the New Source Performance Standards (NSPS) and Emission guidelines (EGs) for the Hospital/Medical/Infectious Waste Incinerators (HMIWI) Standards became final. These regulations, originally promulgated in 1997, were established under Section 129 of the Clean Air Act (CAA) and serve as the maximum achievable control technology (MACT) standards for hospital, medical, and infectious waste incinerators.

Wet scrubbers are currently used on many hospital, medical, and infectious waste incinerators in the United States.  The new emission limits exceed the design capability of most of these systems, primarily with respect to particulate matter (PM), lead (Pd), cadmium (Cd), and mercury (Hg). As a consequence, new control strategies are needed to meet the more stringent standards. 

This paper presents a cost effective control strategy for meeting the new limits and discusses how the strategy has been implemented on similar hazardous waste incinerator scrubbers.

Please click on the below icon to download a white paper on this topic: "Wet Scrubber Control Strategy to Meet the New Hospital/Medical/Infectious Waste Incinerator Standard"  

Photo Credit: bravosixninerdelta

The US Department of Energy (DOE) has funded R&D in coal gasification in recent years as part of a strategy to reduce green house gases.  One aspect of this technology is the use of coal dryers to dry the coal before feeding it into the gasifier.  This requires a coal dryer scrubber which can be comprised of a Venturi scrubber followed by a condenser tower shown in the sketch.

The exhaust gas from the dryer passes through a Venturi scrubber for particulate removal then through a condenser tower to condense water vapor in the gas stream.  The gas passes through a mist eliminator at the top of the condenser tower to remove water droplets in the gas stream.  Re-circulated water in the Venturi throat is collected in the sump of the condensertower.  Gas flow rates for these processes are relatively large and can exceed 300,000 acfm.  Because of the large gas flows, the condenser tower can be as large as 20 feet in diameter or larger.  The Venturi scrubber (shown in the image on the left) must have a special throat design to account for the large gas flow rate. The Venturi throat design is discussed in  in the previous blog post for Venturi Scrubber Throat Design for Large Gas Flow Processes.

To learn more about this application, please download our case study.

In previous blog posts, I have discussed how a key to particle collection in a Venturi scrubber is maintaining uniform water distribution across the Venturi throat to collide with particles.  This presents a Venturi scrubber design challenge for large volumetric gas flow rate processes.  The difficulty becomes getting water across a large cross sectional area  without any void spaces for particles to escape through.  Often times, the solution may be to simply split the gas flow into multiple trains.  However, this increases capital costs for additional ductwork and piping and takes up more real estate. It is always desirable to minimize the equipment footprint and maintain the gas flow in one train.

To achieve this objective, Envitech uses a proprietary Venturi throat design that has been used on large gas flow rates processes, including foundries and purified teraphthalic acid (PTA) plants. The proprietary design has an internal construction that ensures uniform water distribution throughout the Venturi throat cross sectional.

The adjacent image shows a picture of an Envitech Venturi/Quencher constructed from Hastelloy C276 used for a PTA plant with a gas flow rate of 530,000 acfm.  This type of Venturi design may be used on other large gas flow rate processes like a coal dryer system for a coal gasification plant which can have a gas flow rate as large as 300,000 to 400,000 acfm. 

For another large flow Venturi application, read our case study on particulate removal for a coal dryer.

On March 18^th, 2010 I participated on a panel discussion for the Cruise Lines International Association's Inc. (CLIA) Exhaust Gas Scrubber (EGS) Workshop in Miami, Fl. The workshop was professionally managed by BMT Designers & Planners, a navy architecture and marine engineering firm.   The panel was comprised of potential marine exhaust gas scrubber vendors.  The intent of the workshop was to provide information to cruise line participants to assess the maturity of the industry and the likelihood that exhaust gas cleaning systems will be a feasible response to the challenges of changes in regulations.

The industry is evaluating alternatives for meeting upcoming SOx emission limits under Annex VI of Marpol 73/78.  The SOx emission limits will require ships to achieve at least a SOx reduction equivalent to 0.1% sulfur fuel by 2015.  This requirement can be met by using more expensive, low sulfur fuel, or by scrubbing the exhaust gas stream.  The rules essentially require > 97% SOx removal assuming 3.5% sulfur fuel.   The International Maritime Organization (IMO) has issued Guidelines for Exhaust Gas Cleaning Systems, Annex 4, Resolution MEPC.170(57), adopted April 4^th, 2008 to specify the requirements for testing, survey certification, and verification of exhaust gas cleaning (EGS) systems to ensure compliance with Annex VI.   

Envitech first started evaluating the marine scrubber application in early 2008 at the request of one of the major cruise lines.  The cruise line was interested in working with a company that could apply industrial air pollution control equipment experience to marine diesel exhaust streams on board a ship.   Envitech has deployed many particulate and acid gas scrubbers on a wide range of combustion processes including a seawater scrubber for an industrial waste incinerator at a pharmaceutical plant.  Many of these systems are similar process requirements for a diesel engine exhaust.   As a result of our evaluation Envitech developed, and recently filed a patent application for, the Hysea Marine Scrubber which is a hybrid seawater scrubber system.  We introduced this technology to the industry during the CLIA EGS workshop.

The Hysea Marine Scrubber uses available seawater alkalinity to scrub SOx.  The system is chemically assisted with caustic solution (NaOH) to achieve high SOx removal and reduced water flow rates.  The chemical consumption is minimal and estimated to be less than 7% of the usage of a closed loop, recirculation system.  The system is designed to provide flexibility to operate in two modes:

• Open Loop/Caustic Reduced Mode - Continuous, once-though liquid discharge.
• Closed loop/bunkering Mode - Re-circulated seawater with a small discharge stream that can be temporarily bunkered on board the ship.

The discharge liquid in both operating modes is treated to meet regulatory requirements.  Because chemical assistance with caustic substantially reduces the water flow rate, the water treatment system becomes more manageable on board a ship.  The water treatment system also re-oxygenates the water to meet chemical oxygen demand (COD) standards.

The table below shows a comparison of three different marine scrubber configurations, including:

• Open Loop - Using once through seawater
• Closed Loop - Using re-circulated water
• HySea Marine Scrubber - Using chemically assisted Seawater

A comparison of the operating parameters highlights the reduced water and power consumption of the hybrid system compared to an open loop system.  It also shows the substantial caustic reduction compared to a closed loop system.  The main advantages of the Hysea Marine scrubber include:

• Reduced seawater flow rates - 75% - 80% Reduction
• Reduced power consumption - 70% - 75% Reduction
• Smaller piping - Simplified installation
• Smaller water treatment system - Simplified installation
• High removal efficiency -  0.1% sulfur fuel equivalent
• Including low alkalinity seawater conditions
• Operating flexibility to bunker a low flow discharge stream
• Reliance on reliable and proven process technology
• Water discharge that exceeds  discharge requirements
• Water treated for chemical oxygen demand (COD)

Although the Hysea scrubber was designed for ship board use for a diesel engine exhaust, the same design principals also apply to acid gas scrubbing for land based industrial processes that have access to seawater.

A lot of interest in Marine exhaust gas cleaning systems was expressed during the EGS workshop. However, the cruise line industry is still evaluating the full range of options for complying with Annex VI of Marpol 73/78.  The general consensus of the panel participants is that exhaust gas cleaning is not only technically feasible, but provides a compelling financial case as a means for meeting the new regulations.

Please read our case study on reducing SO2 emissions for ships docked at ports by clicking the link below.

Photo Credit: Saint Seminole

Last November I made a blog post describing the use of a wet electrostatic precipitator (WESP) for meeting metals emisssions.  This topic will be discussed in greater detail in an Envitech paper being presented at the 2010 A&WMA 103rd annual conference in Calgary, Canada.  

The metals of concern can include mercury, arsenic, lead, cadmium, nickel and others, depending on the process.  A control strategy using a wet electrostatic precipitator (WESP) in conjunction with sub-cooling was used on a secondary lead smelter to meet more stringent emission standards.  This approach achieved > 98% removal of arsenic and > 92% removal of lead and other condensed metals downstream of a bag-house.  This substantially reduced the plant's cancer risk index and helped to meet reduced fence line lead emission limits.   

The table below provides a summary of other processes facing similar challenges including the additional removal efficiencies that can be required downstream of existing air pollution controls.  Most of the processes are from combustion sources and use a range of air pollution controls including bag-houses, packed bed absorbers, and Venturi scrubbers.  In some cases a combination of controls are used. Despite existing controls, very low concentrations of heavy metals can be emitted.  In the case of bag-houses for instance, the operating temperature may be in a range that some of the metals are in a gas phase.  In such case they will not be collected by particulate control devices. In other cases, the concentrations of submicron, condensed phase heavy metals may exceed the removal capability of controls like packed bed absorbers or Venturi scrubbers.

*Refers to additional removal efficiency after the upstream controls. 

The performances achieved on a secondary lead smelter using a WESP, suggest the approach can be used on these other processes to remove residual concentrations of condensed metals.  In the case of mercury, the ability to remove it with a WESP depends on whether it is in a condensed form. This requires reliable speciation data to make that determination.  More specifically, the mercury must be in a particulate or oxidized form for it to be removed by a WESP.

Please click on the below icon to download a white paper on this topic from the 2010 A&WMA's 103 Annual Converence in Calgary, Canada: "Wet Electrostatic Precipitator (WESP) Control for Meeting Metals Emission Standards".