Process for separating particulate solids from a gas stream (UOP)

CATEGORY: FLUE GAS
PATENT
Process for separating particulate solids from a gas stream (UOP)
Publication number US20130263735 A1
Publication type Application
Application number US 13/899,763
Publication date Oct 10, 2013
Also published as CN103328106A, 4 More »
Inventors
Sathit Kulprathipanja, Paolo Palmas, A. Johnson II Richard
Original Assignee
Uop Llc
Abstract
One exemplary embodiment can be a process for separating particulate solids from a gas stream. The process can include regenerating a catalyst in a regenerator, separating particulate solids in first and second cyclone stages, passing the gas stream from the second cyclone stage to an external third stage separator, and passing the gas stream from the external third stage separator to a cyclone recirculator to obtain a clean gas stream.
FIELD OF THE INVENTION
This invention generally relates to a process for separating particulate solids from a gas stream.
DESCRIPTION OF THE RELATED ART
Industry standards have been reducing the amount of particulates emitted to the environment. Often, emitted gas streams such as flue gases contain particulates. The standards are requiring lower amounts of particulates in released streams to enhance environmental quality.
Often, a cyclonic system is used to reduce particle emissions. In a cyclonic system, the particulates collection efficiency can be a function of the particle velocity and particle size distribution (hereinafter may be abbreviated as “PSD”). The greater the average particle size of the solids in a flue gas stream, the better the collection efficiency of the cyclonic system. Generally, a flue gas stream can contain solids in the range of about 30-about 40 microns with an average particle size of less than about 10 microns. Generally, smaller particles can be more difficult to capture by using existing technologies, such as an external third stage separator that is often used with one or more cyclonic stages. Hence, these systems may not meet new environmental standards and regulations requiring less particle emissions. As a consequence, there is a desire to improve these systems to provide a gas effluent that has low levels of particles, particularly those particles that are smaller and more difficult to separate from the gases.
SUMMARY OF THE INVENTION
One exemplary embodiment can be a process for separating particulate solids from a gas stream. The process can include regenerating a catalyst in a regenerator, separating particulate solids in first and second cyclone stages, passing the gas stream from the second cyclone stage to an external third stage separator, and passing the gas stream from the external third stage separator to a cyclone recirculator to obtain a clean gas stream.
Another exemplary embodiment may be a process for separating particulate solids from a gas stream. The process can include regenerating a catalyst in a regenerator, separating particulate solids in a first and/or second cyclone stage, and passing the gas stream from the first and/or second cyclone stage to an external stage separator. The external stage separator can include a vessel, in turn, including an inlet for receiving the gas stream, and a first outlet for providing a clean gas stream and a second outlet for providing collected particulate solids. Typically, the vessel contains an electrical field positioned between the inlet and at least one cyclone.
A further exemplary embodiment can be a process for separating particulate solids from a gas stream. The process can include regenerating a catalyst in a regenerator, separating particulate solids in a first and/or second cyclone stage, passing the gas stream from the first and/or second cyclone stage to an external stage separator, and passing the gas stream from the external stage separator to a cyclone recirculator. The cyclone recirculator can originate a current density below about 0.1 mA/m2 to obtain a clean gas stream and a further gas stream including particulate solids. The further gas stream can be sent to the external stage separator.
The embodiments provided herein can remove smaller particles that may be difficult to separate in conventional third stage separation systems. Particularly, the embodiments herein can utilize a device that electrostatically charges the particles while using centrifugal force to separate the particles into a collection point. Particularly, the device can clump the particles and separate them in a single vessel to enhance collection efficiency and reduce the costs of the system. Generally, such a device is particularly useful for removing particles of less than about 10 microns in size. In one exemplary embodiment, a cyclone recirculator using a combination of electrostatic charges and centrifugal force can agglomerate and collect particles in a gas stream. The collected particles can then be provided to an external third stage separator. In such an instance, a clean flue gas can be obtained from the cyclone recirculator and sent to a waste gas recovery system, such as a heat exchanger, to recover the heat energy, and exhaust to a stack. In another exemplary embodiment, a third-stage separator can have multiple small electrical wires across the vessel to generate electrostatic charges to agglomerate particles. As the charged particles flow downward, the particles can agglomerate into larger particle clusters and then be collected and removed.
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