Air Pollution Control Innovations

Envitech will be attending the International Biomass Conference & Expo in Minneapolis, MN April 8-10, 2013.  We will exhibit at Booth 807.  During the conference I will be presenting in the Pellets & Densified Biomass track between 8:30 am and 10:00 on Wednesday, April 10^th. The topic will be "High Performance Wet Electrostatic Precipitator (WESP) for Pellet Mills".   

ABSTRACT

A large portion of wood pellets produced in North America are exported to Europe to support aggressive low-carbon fuel incentives.  Growth of the export market has lead to large scale pellet mills with production capacities ranging from 500,000 to 750,000 tons of pellets per year.

These mills use wood dryers to remove moisture from incoming feed material.  A wet electrostatic precipitator (WESP) collects particulate (PM) and condensed volatile organic compounds (VOC) from the dryer exhaust. This is required to protect a downstream regenerative thermal oxidizer (RTO) from fouling. The RTO destroys volatile organic compounds (VOCs) before exhausting to the atmosphere.  The process flow conditions are large and typically several hundred thousand cubic feet per minute.

This presentation will discuss a high performance WESP design to treat the pellet mill dryer exhaust.   The design leverages experience from several large flow rate applications including a coal dryer scrubber, secondary lead smelter WESP, and sulfite pulp mill recovery boiler WESP.  The presentation will focus on how the design achieves high performance.

A copy of the presentation is available by clicking the link below.

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 SO_x (sulfur oxides) reclaim program in the Southern California Air Quality Management District.  The SO_x 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.

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.

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 SO_x 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.

Mississippi Power Company recently released a Youtube video providing an update on the Kemper County Coal Gasificaton Integrated Combined Cycle (IGCC) Project.  The project is a 582-megawatt power plant currently under construction.  The facility will convert locally mined lignite coal into energy using a state of the art coal gasification process call Transport Integrated Gasification, or TRIG^TM.  The process enables a 65% CO₂ reduction making green house gas emissions equivalent to similar size natural gas combined cycle power plant

The lignite coal is very wet and needs to be dried before it is gasified.  An Envitech wet scrubber-condenser system is used in the material handling/drying train.  The system is comprised of a Venturi scrubber and packed bed condenser.  The wet scrubber equipment treats 2.1 MM cfm of dryer exhaust and can be seen in the lower left corner of the screen 28 seconds into the video.

Part of the CO₂ reduction comes from CO₂ capture using 200 ft solvent absorbers.  The CO₂ will be piped to another location in MS and used for enhanced oil recovery. This will allow an increase in oil production of approximately 2M barrels per year. Some milestones/features of the plant include:

• Installation is 70% complete
• Start-up planned during the summer of 2013
• The plant will be a zero liquid discharge facility
• Approximately 2,500 workers are currently on site
• Over 12,000 construction jobs will be created during the course of onstruction
• About 1,000 permanent positions will be created once the facility is open.

Click on the icon below to download a free presentation from the 2012 Coal-Gen conference on the coal dryer wet scrubber system.

Emissions from marine vessels contribute to global smog forming pollutants.  In response, the International Maritime Organization (IMO) has adopted new regulations in MARPOL  Annex VI for progressive reduction of NOx, SOx, and Particulate.  The new regulations require ships to achieve 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   using a marine diesel scrubber. The scrubbers must achieve greater than 97% SOx removal with 3.5% sulfur fuel.  A cost effective scrubber is needed to help ship operators comply with these rules and avoid high cost ultra-low sulfur fuel.

The Envitech HYSEA DeSOx scrubber combines 30 years of experience achieving low emissions on stationary sources with patent pending technology.  Scrubber  features include:

• Innovative inlet design allowing a vertical bottom direct connect to minimize space.
• Proprietary quencher to cool the gas to saturation and remove particulate.
• Flow works modeling to ensure uniform gas distribution for maximum performance.
• Flexibility for open loop operation to minimize operating cost and closed loop operation for navigation in inland water ways and SECA zones.
• High performance, foul-resistant mass transfer media to minimize pressure drop and parasitic load.
• Skid mounted pump skid with integrated control panel.

Please click on the icon below to download a case study on the Envitech HYSEA DeSOx scrubber.

A secondary lead smelter in Southern California recovers lead 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.

A waste oil re-refiner in the Western United States will increase production to nearly 20 MM gpy.  The state requires a direct fired heater to reduce SO₂ emissions by 95%.  Although packed bed scrubbers are common for this type of process, a vertical scrubber design can be expensive to retrofit into an existing facility. The facility was looking for a solution to meet or exceed emission standards and be relatively simple to install and maintain.

A case study is now available to describe how an Envitech high efficiency SO2 scrubber was used to solve this problem.

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

A 582-megawatt (MW) electric generating plant in Kemper County Mississippi is being built. The process uses locally mined lignite coal for fuel which contains 40% moisture.  The coal must be dried before it is converted to syngas in the gasifier.

Six (6) fluidized bed dryers dry the coal with a combined exhaust gas flow rate of 2.1 MM cfm.  A cost effective means was needed to remove particulate and moisture from the exhaust gas before it is recycled back to the dryers.

A case study is now available to describe how an Envitech Venturi scrubber-condenser solves this problem.

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

Follow the link to a previous blog post to download a presentation on this project from the 2012 Coal-Gen Conference.

A specialty cellulose provider, Tembec, is upgrading a sulfite pulping mill in Eastern Canada to incorporate a new red liquor recovery boiler for power generation.  The boiler system increases annual green energy production by up to 40-megawatts, reduces sulfur dioxide emissions by 70%, and increases annual production capacity of specialty cellulose by 5,000 metric tonnes.  The off-gas from the recovery boiler contains a high concentration of SO2 which needs to be recovered for re-use in the production process. 

A cost effective solution was needed to recover sulfur and clean the stack gases to meet stringent particulate and SO2 emission limits.  The plant is located in a high labor rate area, which makes a field erected system very expensive due to lengthy installation time.

A case study is now available to describe how an Envitech scrubber/wet electrostatic precipitator (WESP) system solves this problem.

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

A waste oil re-refiner in Southern California, Demenno Kerdoon, needed to retrofit an SO₂ scrubber downstream of a thermal oxidizer. The oxidizer treats vapor recovery and waste gas streams containing sulfur compounds.  California has some of the toughest standards in the country and required the facility to meet a permit limit of 2.7 ppmv. This limit exempts the facility from the SCAQMD SOx Reclaim program saving reporting and administrative costs.

A case study is now available to describe how an Envitech ultra low SO₂ scrubber solved this problem.

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

 Follow the link to a previous blog post on this project to download a white paper from the international conference on thermal treatment technologies and hazardous waste combustors (IT3/HWC).

I previously posted a blog post about a new project for lead removal using a wet electrostatic precipitator (WESP). A Midwestern manufacturer heat treats metal materials in a furnace that generates low concentrations of lead fumes.  The fumes are sub-micron in size, making them difficult to remove.  The facility is compliant with their existing permit, but wants to be pro-active to control emissions further. They investigated several technologies including HEPA and cartridge filters, Venturi scrubbers, and wet electrostatic precipitators (WESPs). Because of the small particle size, low concentration, and high removal efficiency, they had difficulty finding technologies or vendors willing to guarantee the requested performance limit.

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

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