GEA Emission Control Technology GEA Electrostatic Precipitator´s (Dry & Wet)

GEA electrostatic precipitators deliver exceptional performance for various industrial process applications.

GEA has been building electrostatic precipitators for cleaning industrial process for over many years. Well over 12.000 units have been supplied to firms all over the world. Being the air pollution control technology supplier of choice, GEA offers innovative system designs, state-of-the-art microprocessor controls and constantly upgrades and rebuild enhancement strategies for your specific situation. Various technologies are suggested to ensure the precipitation of particles and aerosols. GEA has the capacity to resort to all proven filtration technologies and will select the most effective and cost-efficient one in dependence of the respective application to meet the customer needs.

 

One of the most common applications for the separation of dust at temperatures up to 450°C in several process industries.

In the case of a high solid content, built-in atomizing nozzles can be used to spray water continuously into the precipitator to prevent formation of sludge deposits on the collecting electrodes. The spray increases the liquid film on the collecting electrodes and reduces its solids content.

General

Dust particles or drops contained in the gas flow collect a negative electrical charge from discharge electrodes connected to a high voltage (T/R) block. Under the influence of a strong electrical field the particles migrate to the grounded collecting electrodes where they adhere to the surface and get discharged. Regular cleaning of the electrodes is ensured by appropriate cleaning devices. Accumulated deposit layers fall or flow into bunkers or trays arranged beneath the collecting chamber. From this place, discharge and further transportation is carried out by mechanical or pneumatic devices and pumps respectively. The raw gas flows through the gas distribution internals arranged within the conical inlet hood and is routed into the active separation section. In accordance with the required collection efficiency of the electrostatic precipitator the dust-laden gas flows through several sequentially arranged collection zones.

Collection Principle

The dust particles suspended in the gas are electrically charged and migrate under the influence of a strong electric field towards the collection electrodes  where they are deposited. The collecting electrodes are connected to earth via the precipitator casing. The discharge electrodes are suspended from insulators and have negative polarity.

Frame Design

Dry ESP horizontal

The precipitator carry a d.c. voltage ranging from 20 kV to more than 80 kV depending on the precipitator design and the application. In the immediate vicinity of the discharge electrodes corona discharges are produced due to the high field strength and electrons are set free. The negative gas ions produced charge the dust particles which migrate under the influence of the electric field towards the collecting electrodes, where they release part of their charge and are captured. Horizontal dry type precipitators are equipped with collecting electrodes consisting of parallel vertical plates. The form passages, in the center of which the discharge electrodes are suspended from insulators. The plates are shaped to provide quiescent zones to prevent the collected dust from being dislodged up and re-entrained by the gas stream. The construction of the precipitator casing varies according to the application and the precipitator dimensions. The structure design calculations  are mainly performed with the aid of specially developed computer programs.

Casing of frame-type design are a proven, reliable and economical solution for horizontal precipitators. The discharge and collecting electrodes are supported from box-type roof beams. The loads are transmitted via stanchions from the roof beam ends to the precipitator support structure. The roof and side walls are only designed to withstand the internal precipitator pressure and the wind forces.

An essential factor in achieving maximum collection efficiency is an even distribution of the gases over the entire cross section of the precipitator. This is ensured by correct design of the precipitator. This is ensured by correct design of the precipitator inlet transition duct and the installation of specially designed gas deflection and distribution plates. The experience gained from an extensive series of tests on two- and three-dimensional models in our laboratory and from measurements in operational industrial plants were used to establish design standards that guarantee a very even gas distribution with a low pressure loss and minimum expenditure on material. This is achieved by means of perforated plates with round or square openings, X-type distribution plates. The flap-type plate immediately deflects the gas flow through 90 degree before it enters the precipitator, thus reducing precipitator over-all length.

 

Features

  • Even flow distribution achieved by specially designed gas distribution walls that are proven by CFD-modelling.
  • Use of optimized discharge electrode type ZT24
  • Electrode rapping with reliable and robust tumbling hammer system superior to magnetic/top rapping
  • Reliable Insulator design for long-term operation
  • High Voltage supply with T/R-sets and Controllers
  • No Ammonia injection needed
  • Comprehensive experience in ESP design and project execution for FCC units

Wet ESP brings the additional kind of cleanliness

Wet-type electrostatic precipitators are employed in saturated gas atmospheres and ensure precipitation of aerosols to reach minimum pollutant levels in the cleaned gas. SO3, TiO2 and tar can be reliably removed. For cleaning purposes, the mass flow is horizontally routed through wet-type electrostatic precipitators which are manufactured from high-quality corrosion-resistant materials.

General

wet gas cleaning plant with wet esp

Image description:
1. Wet Electrostatic Precipitator
2. Star tube cooler
3. Radial flow scrubber with venturi head

Wet electrostatic precipitator (WESP) particulate control systems designs can either up flow or down flow relative to where polluted air enters the WESP during the particulates control process. Turing canes and perforated plate evenly distribute the gas glow inside of the wet electrostatic precipitator.

GEA´s wet electrostatic precipitator (WESP) use electrostatic force to remove particulate. It is used treat gas streams with sub-micron particulate, aerosol, or fumes. These can include heavy metals such as lead, arsenic or cadmium, condensed acid aerosols like sulfur trioxide (SO3), or condensed volatile organic compounds (VOC´s). The use of electrostatic forces minimizes energy costs compared to other technologies, which require large amounts of energy to overcome resistance to air low.

Wet electrostatic precipitators are used in a wide range of applications including, hazardous and medical waste incinerators, metals refining, sulfite pulp mill recovery boilers, copper roasters, sulfuric acid plants, and wood dryers including oriented stand board, medium density fiber board, or pellet mill dryers.

The GEA WESP is a proprietary, robust design. It has a unique alignment mechanism to hold electrodes rigidly in place. This reduces installation and maintenance time and proves performance. The field strength is consistently maintained at high levels with minimal sparking, resulting in the highest available efficiency. The greater the electrostatic fields strength, the greater the particle migration velocity (velocity component towards the collection tube). Increase migration velocity achieves higher particle collection efficiency with lower specific collection area  (SCA) than conventional precipitators. Lower SCA means a smaller, less expensive unit.

GEA´s wet electrostatic precipitators may also be designed with a integrated packed bed scrubber section for acid gas removal. This makes the unit a versatile, multi-pollution system which has demonstrated proven performance for meeting the most stringent emission limits encountered in industrial today with smallest available footprint.

Frame Design

GEA wet electrostatic precipitator are of the vertical type with the gas inlet either at the top or at the bottom. Gas distribution devices are installed ahead the electrical field.

The vertical precipitator are normally cylindrical. Rectangular precipitators are possible in exceptional cases.

In the case of 2 precipitators in series the gas normally passes through the first stage from bottom to the top, in the second stage from top to bottom. The off-gas is routed through the precipitator tubes with discharge electrodes suspended down each vertical axis. By applying high-voltage, an electric field will be produced which will electrically charge the aerosol and dust particles, which in turn, migrate to the collection tubes.

All parts coming into contact with the gas are either lead coated, plastic or rubber lined. The materials are selected in order to accommodate the stresses and temperatures to which the plant is subjected.

Collection Principle

The collecting surface is formed by round tubes to a length of 6 m maximum. Material section is either Polypropylene (PP) or Polyvinylchloride (PVC).

The surface of both materials is given a special surface treatment. This permits the formation of a continuous liquid film on the surface.

In the case of a precipitator design with single tubes, these are suspended from a upper tube plate and sealed by means of o-rings. The lower tube ends are fitter into a grid allowing unrestricted expansion.

The latest design of GEA wet type precipitator incorporates a tube bundle consisting of prefabricated PP segments. For large precipitators several separate bundles are used.

The bundle is assembled in the workshop and erected into the precipitator casing on site.

 

Features of GEA Wet Electrostatic Precipitator

wet electrostatic precipitator features

  • The application of plastic tubes permit operation at maximum voltage within the spark range. Sparks do not cause damage to the PVC or PP tubes. The higher voltage allows a considerably higher efficiency.
  • The casing which can be rubberlined steel, resin coated steel, homogeneously lead lined steel or FRP can be built for any negative pressure required.
  • The high voltage support frame, which is built into the upper part of the precipitator and to which the discharge electrodes are fastened, is normally homogeneously lead lined, as is the associated support. The frame is suspended from air-purged insulators.
  • The lower frame which guides the discharge electrodes is not connected to the upper guide frame; it is supported by separate air-purged insulators. This frame is also homogeneously lead-lined.
  • An even gas distribution is achieved by means of a central inlet with built-in gas distribution grids.
  • Each precipitator is equipped with a separate transformer / rectifier set.
  • Unlike lead precipitators the GEA design allows for a large portion of the unit to be shop assembled. This reduces site erection costs and time.
  • Maintenance and repair costs for plastic tubes precipitators are significantly lower than those for lead precipitators.
  • The location of the precipitator is flexible. It can be flanged on a scrubber, supported on a steel structure system or built with a cylindrical support on a ring foundation.