Process Engineering Equipment Handbook Episode 1 Part 3 pdf

A-82 Air Filtration; Air Inlet Filtration for Gas Turbines FIG. A-74 Filter with water eliminator. (Source: Altair Filters International Limited.) FIG. A-75 Pressure loss versus volume flow rate filter characteristic. (Source: Altair Filters International Limited.) semirigid construction, together with the fact that each pocket is divided into smaller segments by means of a semipermeable “shelving” system, ensures the best possible profile throughout all operating conditions. This produces an extremely uniform flow distribution, leading to improved dust-holding capacity and eliminating the likelihood of localized dust breakthrough. Air Pollution Control A-83 Dynamic water eliminator This feature conducts water and salt removal. The vanes, which are constructed from corrosion-resistant marine grade aluminum (other materials are available), are produced with a profile that allows the maximum removal of salt and water, yet produces an extremely low pressure loss. This optimal profile has been achieved by the very latest design methods, and in particular by utilizing a Computational Fluid Dynamics (CFD) flow modeling system. Hydra also incorporates a unique and novel method of separating water droplets from the air stream, and this has led to improvements in bulk water removal compared with conventional methods. Reference and Additional Reading 1. Tatge, R. B., Gordon, C. R., and Conkey, R. S., “Gas Turbine Inlet Filtration in Marine Environments,” ASME Report 80-GT-174. Typical Specifications for Range of Air Filters This range includes panels and bags as well as high-efficiency, high-velocity systems and air/water separators. Filter holding frames are constructed in mild or stainless steel, designed to provide quick and easy removal from upstream, downstream, or sides of ducting, without the use of springs or clips of any kind. Filter housings, ducting, louvres, dampers, and silencers can also be designed and fabricated, providing a total system capability. Air Pollution Control* The main methods of combating and controlling air pollution include: ᭿ Electrostatic precipitators (for particulates) ᭿ Fabric filters (for dust and particulates) ᭿ Flue gas desulfurization (for SO x removal) ᭿ SCR DeNO x (for NO x removal) ᭿ Absorbers (for environmental toxins) ᭿ End-product–handling systems (for solid and liquid wastes) ᭿ Combined unit systems (for some or all of the previous items) FIG. A-76 Efficiency versus pressure loss filter characteristic. (Source: Altair Filters International Limited.) * Source: Alstom. Adapted with permission. Air Pollution Control A-83 Dynamic water eliminator This feature conducts water and salt removal. The vanes, which are constructed from corrosion-resistant marine grade aluminum (other materials are available), are produced with a profile that allows the maximum removal of salt and water, yet produces an extremely low pressure loss. This optimal profile has been achieved by the very latest design methods, and in particular by utilizing a Computational Fluid Dynamics (CFD) flow modeling system. Hydra also incorporates a unique and novel method of separating water droplets from the air stream, and this has led to improvements in bulk water removal compared with conventional methods. Reference and Additional Reading 1. Tatge, R. B., Gordon, C. R., and Conkey, R. S., “Gas Turbine Inlet Filtration in Marine Environments,” ASME Report 80-GT-174. Typical Specifications for Range of Air Filters This range includes panels and bags as well as high-efficiency, high-velocity systems and air/water separators. Filter holding frames are constructed in mild or stainless steel, designed to provide quick and easy removal from upstream, downstream, or sides of ducting, without the use of springs or clips of any kind. Filter housings, ducting, louvres, dampers, and silencers can also be designed and fabricated, providing a total system capability. Air Pollution Control* The main methods of combating and controlling air pollution include: ᭿ Electrostatic precipitators (for particulates) ᭿ Fabric filters (for dust and particulates) ᭿ Flue gas desulfurization (for SO x removal) ᭿ SCR DeNO x (for NO x removal) ᭿ Absorbers (for environmental toxins) ᭿ End-product–handling systems (for solid and liquid wastes) ᭿ Combined unit systems (for some or all of the previous items) FIG. A-76 Efficiency versus pressure loss filter characteristic. (Source: Altair Filters International Limited.) * Source: Alstom. Adapted with permission. A-84 Air Pollution Control Electrostatic Precipitators In combustion processes, the largest quantities of heavy metals and dioxins are found in the fly ash, or can be contained there by technical means. It is therefore essential to increase even further the very high precipitation efficiencies that are already being achieved. There are two types of ESPs, wet and dry, for collecting particles. (See Fig. A-77.) New and retrofit systems are used. Retrofitting with new spiral electrodes, a rapping system, and pulsed energization pay immediate dividends in the form of improved abatement efficiency and lower power consumption. Semipulse ® and Multipulse ® for enhanced separation and energy efficiency The rather uncomplicated process of charging dust by means of a high-voltage DC system, which makes dust stick against collector plates, has undergone high-tech refinement. Several of the improvements have been implemented to minimize energy consumption. Originally, it took about 1 MW of power to operate an ESP in a large coal-fired power station. Pulsed energization is a means to cut energy consumption substantially while simultaneously improving separation efficiency. Two systems for this purpose have been developed: the Semipulse Concept (SPC) with millisecond pulses, and the Multipulse Concept (MPC) with microsecond pulses. (See Fig. A-78.) Since their introduction in 1983, more than 3500 SPC and MPC units have been supplied. SPC can be easily installed in existing plants, while MPC involves a higher investment and is generally considered for retrofits and new plants. The savings for high-resistivity dust can be substantial. Energy consumption after installation of SPC or MPC is typically between 10 and 20% of the original. At the same time, dust emissions are reduced to 25–50%. Upgrading or retrofitting with pulsed energization is often the solution when a utility wants to switch to low-sulfur coals, which often produce dust of higher FIG. A-77 A typical electrostatic precipitator. (Source: Alstom.) resistivity. It also gives a utility a wider choice of coals that can easily be valued in money terms. Semipulse and Multipulse offer an inexpensive route not only by improving energy and separation efficiency, but also by requiring a minimum of supervision and maintenance. Fabric Filters Fabric filters are used for cleaning large flows of flue gases from coal-fired power plants and municipal waste incinerators. (See Fig. A-79.) The fabric filter has gained a wide market, due to its versatility for a large number of dust and process types and its ability to capture all particles, not only those that can be charged electrically (as in ESPs). (See Fig. A-80.) Another reason for the recent success of fabric filters is that they operate by passing the dust-laden gas through a dust cake that is constantly being built up with the support of the fabric. This enables the removal of a large portion of the finest particles, a feature that is becoming increasingly important as more stringent emission controls are required. (See Fig. A-81.) With the fine particles, several heavy metals can be trapped in the dust cake, together with sulfur dioxide, if lime is introduced in the flue gas. This manufacturer/information source supplies two different kinds of fabric filters: the high-ratio and low-ratio type, denominated by the air-to-cloth ratio. A major difference between the two filter types is the cleaning system. The high-ratio fabric filter is cleaned by the Optipulse ® cleaning system (see following text). Air Pollution Control A-85 In the Semipulse system, pulsing is achieved by controlling the conventional T/R set of the precipitator. In the Multipulse system, special T/R equipment produces intensive bursts of short pulses. FIG. A-78 Pulse systems in precipitators. (Source: Alstom.) In the low-ratio filter, gas enters the filter bags from the inside, then outward. The filter bags are cleaned “off-line” using either the reverse gas flow, reverse gas with high-energy sound horns, or a cleaning system of the deflate or shake mechanism type. (See Fig. A-82.) The Optipulse ® cleaning concept (Optipulse is a trademark for a proprietary design of this information source.) Pulse-jet fabric filters operate with dust-laden gas approaching the filter elements from the outside, depositing the particles on the fibers of a depth-filtering medium. The clean gas leaves the open end of the filter element, which is typically of tubular design with a diameter of 120–150 mm (5–6 in). An internal wire cage supports the filter element against the pressure caused by the gas flow. (See Fig. A-83.) Periodically, the dust cake is cleaned off by expanding the filter element with a rapid pulse of air. The removed dust cake is transported by gravity toward the dust hopper. The effectiveness of the cleaning depends on the character of the pressure pulse. Optipulse produces a forceful pulse by an optimized geometry of the pneumatic system delivering the pulse (see Fig. A-84): ᭿ The pulse air is injected in the filter element, without dissipation of energy in a large volume of flue gas, through injection nozzles optimally selected in relation to filter element size. ᭿ The area of all nozzles on the header serving one row of filter elements is matched to the area of a large, pilot-operated, fast-opening supply valve. Flue Gas Desulfurization (FGD) Today, flue gas desulfurization is a well-established method to fight global environmental impairment such as acid rain. Most industrial countries have set standards for SO 2 emissions and committed themselves to large reductions of national emissions in international agreements. There are several different types of FGD technologies for a wide range of applications. A-86 Air Pollution Control FIG. A-79 Fabric filter installation in a metallurgical plant, Höganäs, Sweden (left). (Source: Alstom.) FIG. A-80 Typical filter product range. (Source: Altair Filters International Limited.) A-87 A-88 Air Pollution Control FIG. A-81 Air filter elements. (Source: Alstom.) FIG. A-82 Low-ratio fabric filter installation at Nevada Power, United States. (Source: Alstom.) FIG. A-83 Installation of filter elements in an Optipulse fabric filter. (Source: Alstom.) Air Pollution Control A-89 FIG. A-84 Operating principles of the Optipulse pulse cleaning system. (Source: Alstom.) FIG. A-85 Wet/dry flue gas FGD plant, including fabric filters, after two coal-fired boilers at TWS Dampfkraftwerk, Stuttgart, Germany. (Source: Alstom.) Three common technologies for FGD 1. The wet/dry lime spray drying process offers low capital costs and an easily disposable/reusable end product for small and medium-sized plants. (See Figs. A-85 and A-86.) [...]... be worked out with equipment vendors, but basically it involves: A -10 2 Air Purification; Air Sterilization FIG A -10 3 Unit for separating submicron particles, heavy metals, and toxic hydrocarbons (Source: Alstom.) 1 Filtration (the end process may require removal down to 0 .1 mm; 1 to 5 mm is common) 2 Electrostatic precipitation (can remove up to 90% plus of the particles in the air) 3 Air washing (can... used in magnetic bearing control for over 30 years, but are rapidly being displaced by digital control systems, suitable for low load applications (Fig B -10 A) and high load (Fig B -10 B) Low load control systems provide as much as 1 kW of power for applications such as turbomolecular pumps in an enclosure about the size of a shoe box Higher load B -10 Bearings FIG B -11 Open-loop control system (Source: Revolve.)... bearings can be used in processes that will not withstand the presence of any lubricant—such as refrigeration compression, pure gas processing, and vacuum processes such as those used in semiconductor manufacturing 3 Higher rotational speeds Noncontacting also means that higher rotational speeds are possible, as friction and surface galling are no longer factors to be Brakes B -11 concerned with Speeds... (Fig B -14 ) the working fluid is fed to the brake from a tank by means of a pump The required amount of fluid in the brake is maintained by a control element in the feed line The heated working fluid flows back to the tank through the return line and a second circuit provides for cooling the fluid in the storage tank Brakes B - 13 FIG B - 13 Closed-circuit hydrodynamic brake (Source: J.M Voith GmbH.) FIG B -14 Open-circuit... in the plant, if their readings with their vibration analysis equipment confirm that this is what needs to be done For more critical items, such as process compressors, this process is best done in the overhaul facility of the original equipment manufacturer (OEM) The exception to this would be if the end user had his or her own balance equipment and had trained staff that was capable of handling the... solutions for true eco -engineering Reference and Additional Reading 1 Soares, C M., Environmental Technology and Economics: Sustainable Development in Industry, Butterworth-Heinemann, 19 99 Air Purification; Air Sterilization Certain specialized processes require air that is a great deal cleaner than outlined in the previous section on air pollution control Examples include food processing and pharmaceuticals... at sea FIG A-90 Basic operation of seawater FGD (Source: Alstom.) A-92 Æ FIG A- 91 The reduction of nitrogen oxides with ammonia is achieved at a manageable temperature by the use of a catalyst (Source: Alstom.) FIG A-92 Flow diagrams for different DeNOx process systems (Source: Alstom.) A- 93 A-94 Air Pollution Control 1 High dust system The reactor is placed before the air preheater, and operates directly... toxic hydrocarbons by a combination of filtering, “sorption,” and chemical reaction The Wetpac® process is an absorption stage collecting the acid gas components and producing recyclable products, such as hydrochloric acid, chloride, and sulfate compounds Air Purification; Air Sterilization FIG A -10 2 A -10 1 Combined NOx and FGD units (Source: Alstom.) Catpac is used to reduce nitrogen oxides but may... are control schemes that use actively changing external signals, as well as the reference and sensor signals used in closed-loop systems (See Fig B -11 .) Control algorithm Advantages and benefits 1 Noncontacting Separation of the rotating and stationary parts means that the only friction is that provided by the air or other gas present This is negligible compared to conventional oil or grease lubricants... the wet phase The process is regulated in such a way that the reaction product becomes dry and can be collected in a conventional dust collector FIG A-86 Basic principles of wet/dry FGD installation (Source: Alstom.) 2 The open spray tower lime/limestone wet FGD process offers low operating costs and proven production of commercial grade gypsum (See Figs A-87 and A-88.) 3 The seawater process offers low . Multipulse Concept (MPC) with microsecond pulses. (See Fig. A-78.) Since their introduction in 19 83, more than 35 00 SPC and MPC units have been supplied. SPC can be easily installed in existing plants,. large portion of the finest particles, a feature that is becoming increasingly important as more stringent emission controls are required. (See Fig. A- 81. ) With the fine particles, several heavy. depositing the particles on the fibers of a depth-filtering medium. The clean gas leaves the open end of the filter element, which is typically of tubular design with a diameter of 12 0 15 0 mm (5–6