Our mission is to make the world a safer place to breathe and live by removing harmful contaminants, particulates and greenhouse gases from industrial processes (Coal, Natural Gas, Biomass). Our goal is to help our customers reduce their environmental footprint by providing long lasting reliable pollution control equipments such asa Particulate Control, VOC Control, NOx Control, Odor Control, Opacity Control, CO Control, PM 2.5, HF, HCl, SO2 & SO3 Control.
Electrostatic Precipitation (ESP) - Dry ESP
How It Works
Particulate control begins when the dust laden gases enter into the unit. Inside, high voltage electrodes impart a charge to the particles entrained in the gas. These charged particles are then attracted the grounded collecting surfaces. The gas then leaves the unit up to 99.9% cleaner than when it entered.
The negatively charged rigid type discharge electrodes are accurately centered between the collecting surfaces and supported from high voltage insulators located in insulator compartments on the ESP.
The particulate control process inside the box does not end with the initial collection. The particles from the continuous dirty gas flow build up on the collecting plates and need to be removed. At periodic intervals, the collecting plates are rapped or vibrated causing the particles to fall into the hoppers. The collected particles are then removed from the hoppers by a screw conveyor or rotary airlock or a combination thereof.
Precipitator Service
One of the most important considerations in design and operation of the dry electrostatic precipitator (ESP) is the removal of the collected material from the collecting surfaces without re-entraining it in the gas stream, this ensures compliance with Federal Standards (MACT), State SIPS (State Implementation Plans) and local regulations. On PPC dry electrostatic precipitators (ESP), material removal from the plates is accomplished by electromagnetic rappers or sonic horns installed on the roof section. Rappers deliver hammer blows of preset intensity at preset intervals to the plate headers creating a vertical shock wave while sonic horns deliver a system wide sonic wave that simultaneously vibrates all surfaces at once. A shock wave, however it is created, causes the collected material to shear off and fall into the hopper. The wave intensity and interval is dictated by the characteristics of the deposited material. These adjustments are made to the particulate removal system to suit the requirements of each installation and are a part of the dry electrostatic precipitator (ESP) start up service provided by PPC.
As opposed to conventional hoppers, the PPC dry electrostatic precipitator (ESP) hoppers have integral, support members which simplifies support steel fabrication and structural steel erection. Additionally this allows shop installation of insulation and heaters at substantial savings. PPC dry electrostatic precipitator hopper openings are a minimum of 18" wide to allow free flow of ash and eliminate bridging. Hopper depth is kept to a minimum to reduce cooling of ash and subsequent caking.
Maximum effectiveness of the dry electrostatic precipitator particulate control system occurs when the voltage supply output reaches the sparking threshold. Variation in gas volume, dust loading and other factors, however affect the sparking threshold level. Employing an advanced electrical control system, an automatic control circuit regulates each high voltage power supply output for maximum dry electrostatic precipitator (ESP) efficiency regardless of process variation. Sparking causes the power supply to "notch down" slightly with the automatic controls bringing it right back up to sparking potential. Modern digital electronic controls automate this process and assure the ESP particulate control device operates at peak performance levels at all times, ensuring compliance with MACT guidelines as set forth by the EPA.
Electrostatic Precipitation (ESP) - Wet ESP
How It Works
The PPC Industries Wet electrostatic precipitator (WESP) is used for particulate control, opacity control, and MACT Compliance. The WESP can operate either downflow, or upflow depending upon the gas stream characteristics. Pre or post treatment scrubbers can be incorporated into the design to accomplish acid neutralization or VOC removal.
The design to the left illustrates a down flow WESP. Gas enters the roof of the electrostatic precipitator where perforated plates and turning vanes evenly distribute the gas before entering the collection tubes. The collection tubes are bundled in a honeycomb arrangement to provide the necessary particle residence time, velocity, and collection plate area. Two sets of spray headers are installed above the collection tubes. The first spray header provides a fine mist where the water droplets become immediately charged and flow down the sidewall of the collection tube, co-current with the gas flow. This continually wets the tubes to prevent sticky particulate from adhering to the tubes during the collection process. The second spray header is a flushing system which periodically sprays a larger amount of water to flush the collected precipitate out of the collection tubes and into the lower plenum. The misting and flushing occur simultaneously with the particulate collection process. Particulate control is accomplished by charging the particles, collecting the precipitate on the tubes which operate at ground potential while simultaneously misting and flushing.
Centered in each collection tube is a rigid electrode with corona generating pins. Each electrode is suspended from an adjustable support rack. The support rack is suspended from high voltage insulators located out of the gas flow. The insulators are blanketed with a continuous flow of heated purge air. A 65 to 80 KV transformer rectifier energizes the electrode rack using an automatic T/R controller.
As the dust and condensed aerosol particles enter the wet electrostatic precipitator collection tubes, they become charged from a bombardment of negatively charged electrons. The negatively charged particles adhere to the wetted collection tubes and are periodically flushed into the lower plenum of the electrostatic precipitator (ESP).
The lower plenum is designed to demist the gas and drain the collected precipitate out of the particulate control equipment. Ancillary water treatment can be incorporated into the design. Each PPC air quality control system including the wet electrostatic precipitator (WESP), the dry electrostatic precipitator (ESP), the biofilter, SCR, and the dry acid gas scrubbing system is designed to meet the customer objectives for EPA and corresponding MACT Compliance.
Reduction & Oxidation Catalysts
NOx + NH3 N2 + H3O
The most effective method of post-combustion control of NOx is Selective Catalytic Reduction (SCR). This technology routinely removes up to 85% of NOx and can be pushed to a higher removal efficiency. The gas velocity is reduced in an expanded section of ductwork, ammonia carefully metered into the gas stream and balanced to match the distribution of NOx across the duct. The gas stream then passes across a special catalyst designed to cause a reaction between the NOx and ammonia, resulting in their conversion to nitrogen and water vapor.
CO Reduction
Because high NOx reduction requirements are often accompanied by CO abatement regulations, PPC offers optional CO catalyst combined into the SCR system. CO reduction catalyst can be integrated into the SCR with very little space requirement.
- CO Reduction - Oxidation Catalyst
- Integration with Precipitator
- Modular Design
- Removal of Some VOC's
- NOx Reduction
- Small Footprint
- Simple Installation
- Flexible Choice of Reagent
Combination systems
PPC provides SCR and CO catalyst beds that are integrated into the dry electrostatic precipitator (ESP) design. This provides several advantages:
- Separate support steel is often not required.
- The hot side electrostatic precipitator (ESP) removes up to 95% of the particulate matter allowing the same reduction with less catalyst and a longer catalyst life.
- The ESP removes metallic salts that can poison the catalyst.
- The precipitator conditions flow and distribution of the flue gas for the NOx and CO catalyst chamber.
- Single point responsibility for the system.
- Economical design that incorporates particulate control in combination with CO and NOx control.
Dry Acid Gas Scrubbing
DRY ACID GAS SCRUBBING: SO2, SO3, HF, HCI CONTROL
Up to 85% Control of SO2
Up to 95% control of SO3, HCL & HF
- Easily installs ahead of existing particulate controls (e.g. dry electrostatic precipitator or baghouse)
- Minimal footprint
- Lower installed capital cost than limestone slurry scrubber or spray dryer.
- Possible to use existing duct work with minimal modifications
- No water discharge requirements
- Used reagent and reaction products are handled with existing ash handling equipment and disposed of with the ash.
- Pre Wired
- PLC Controlled
General
PPC’s dry powder injection (DPI) system, is designed to control acid gas emissions from boilers and other combustion sources by injecting sodium reagents such as sodium bicarbonate (NaHCO3) or trona (sodium sesquicarbonate – Na3(HCO3)(CO3)•2H2O) directly into the flue gas, to neutralize acid gases.
Sodium reagents are used instead of calcium reagents (i.e. limestone – CaCO3) because they are more reactive. This results in less reagent and less time required to neutralize acid the gases. An added benefit is improved precipitator performance.
Principle of Operation
The DPI system relies on gas/solid reaction and the efficiency and effectiveness of the reaction depends on the surface area of the solid injected into the flue gas. To maximize the reagent surface area, PPC designs a self contained injection system which includes reagent milling, feed rate regulation, a classifying mill and an injection blower to deliver the milled reagent into the exhaust gas.
The milled reagent is delivered to the exhaust gas duct work where it mixes with the exhaust gas and reacts with the acid gases, forming solid sodium salts. These salts are then collected in existing particulate control devices, and removed using existing ash handling systems.
System Design
PPC designs the DPI system to deliver the necessary amount of milled reagent to achieve the desired removal efficiency. The system is self contained and skid mounted and includes the reagent feed control, classifying milling system and the injection blower.
The system includes a raw material storage silo, power distribution panel, motor starters and variable frequency drives as well as a pre-programmed PLC control system. The DPI system is shipped with all motors and instrumentation mounted.
Biofiltration
What is Biofiltration?
Biofiltration is a process to purify air and water biologically with the aid of micro-organisms, specifically bacteria.
What is Industrial Biofiltration?
An Industrial Biofilter is a housing that contains and encourages the growth of vast numbers of bacteria through regulated temperature, humidity and pH for the destruction of volatile organic compounds (VOC's) and odor causing compounds (including NH3, CS2, H2S), in a way that can be quantified and measured, often for compliance purposes. Industrial biofilters utilize a group of aerobic organisms that are classified as chemotropic, meaning they derive the energy needed to live and degrade compounds from the reaction itself. As a point of fact organisms that derive their required energy from sunlight are classified as phototropic. Two sub-groups of the chemotrophs are the hetero-organotrophs and auto-lithotrophs. The sub group mainly utilized in biofilters are the hetero-organotrophs which have the ability to utilize the carbon in carbon compounds (i.e. methanol) as an energy source as well as the creation of cell components. As a point of fact auto-lithotrophs gain their energy through the degradation of non-organic compounds (NH3, H2S, S2O3, etc..).
What is the history of Industrial Biofiltration?
One of the earliest known uses of biofiltration in the Industrial Era was in World War I (1914 to 1918). Stagnant air was sucked out of tunnels and trenches, blown through earth where it would permeate and re-enter the tunnels and trenches. The air would be "cleaned" through the actions of bacteria naturally present in the soil. In 1923 the concept of treating off gases from sewage treatment plants was developed. In 1953 R.D. Pomeroy received a patent (#2,793,096) for "De-Odoring of Gas Streams by the use of Microbiological Growths" that arose out of a successful commercial application in California.
A high pressure blower (#12) is used to pull polluted gases (#11) through a pipe and inject it into a vertical header (#14) before it turns and becomes a horizontal header (#15) buried under a biologically active medium (#17) that is suspended above the header by a layer of permeable medium (#16) such as gravel or aggregate. The header is composed of perforated sections (#18) and non-perforated sections and couplings (#19). The basic design developed then is still used in many commercial applications today with the exception that the medium, or media, has changed. Since that patent, the major innovations in biofiltration have been in two areas: bacteria enhancement and media development.
Source: PPC Industries
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