lDtmaspheric Pollution ~
N e w catalytic muffler cleans exhaust gases from in-plant materials handling equipment by louis C. McCabe
XY-CATALYST,Inc., of Wayne, 0 Pa., has announced the availability of a new catalytic muffler for use on industrial vehicles using leaded gasoline. The Oxy-Muffler (Figure 1) uses a pellet-type catalyst that resists lead contamination and is reported to eliminate as much as 90% of exhaust carbon monoxide, aldehydes, and hydrocarbons. Gases from the engine exhaust manifold enter the muffler through the Venturi section containing the air-inlet filter and flow down through beds of catalytic pellets where contaminants are burned. The cleaned exhaust gases leave through an outlet pipe a t the right. The catalyst pellets may be replaced when necessary through removable ports. The units now being produced are designed for fork-lift trucks, power sweepers, and various in-plant materials handling equipment, but OxyCatalyst is now working with automotive specialists on specific designs for practical catalytic mufflers for automobiles, commercial trucks, and buses. It is reported that shortcomings in design and structural strength of the muffler, pointed up in recent road tests, have been overcome. Operation of the engine under load or a t high speed idling for 3 or 5 minutes is sufficient to bring the catalyst up to operating temperature. The company’s tests indicate that the muffler will provide a t least 90% clean-up for a t least 600 operating hours, the equivalent of 5 months of lift truck performance in some plants. All parts of the muffler that come in contact with exhaust gases are made of stainless steel.
in the waste gases. These installations show a 2- to 3-year pay-off. The gas stream leaving the catalytic cracker regenerator and the products of combustion of the coke deposited on the cracking cataIyst are fuel already superheated, but low grade fuel that is not ignitable under the usual conditions of the mixture of regenerator gas plus the air required to effect oxidation. The catalytic units can ignite and sustain the practically complete oxidation of this stream without the use of extraneous heat (Figure 2). The quantities of recoverable energy in question are considerable: they consist of the sensible heat (between the temperature of the regenerator gas as it leaves the regenerator and that of the gas stream leaving the heat recovery unit-steam boiler or heat exchanger) together with the heat of combustion of the carbon monoxide and hydrocarbons or their derivatives formed by partial oxidation in the regenerator. As a rough guide, the recoverable heat for 1000 barrels of daily charge to the reactor of the catalytic cracker is from 1,200,000 to 3,000,000 B.t.u. per hour.
The figure varies widely because of differences in the charging stocks, the operation of the catalytic cracker, and the regenerator. The content of carbon monoxide is usually from 2.5 to 7.5% by volume. The oil plus derivatives vary from small quantities to 10 barrels per day and water vapor in the hot stream from 10 to 25% by volume.
Figure 2. Oxidizing catalytic unit with one end p l a t e removed
Catalytic cracker regenerator
The original oxycatalyst (Oxycat) units, developed 5 or 6 years ago, recently have been installed on several commercial catalyst regenerators a t petroleum refineries to complete the combustion of carbon monoxide, hydrocarbons, and oxidized hydrocarbons December 1955
Figure 1.
Catalytic exhaust cleaner
INDUSTRIAL AND ENGINEERING CHEMISTRY
83 A
Inside-Outside Topside!
MULTI=WASH ____
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DUST COLLECTORS
n e e d no productive floor space
How Multi-Wash collectors can be installed, up off the floor, inside t h e b u i l d i n g.
Battery of MultiWash units installed on the roof of a large production factory.
Schneible Multi-Wash Collectors were designed to save money in many ways. Not the least, is the variety of methods of installation. In a majority of instances Schneible installations are operating without taking away any valuable production space. This means profit from every foot of floor space, plus cleaner, more healthful working conditions that increase productive effort. Specify Schneible Dust Control for simplicity and efficiency.
See you in Philadelphia at the Chemical Exposition BOOTH 900
C L A U D E B. S C H N E I B L E C O . P.O. Box 81, North End Station Detroit 2, Michigan Circle
a4 A
No.
84 A on Readers' Service Card, page 111 A
Atmospheric PolIut ion The oxygen content is usually low (below the theoretical percentage for oxidation), since the air supplied to the catalytic cracker regenerator is for economical reasons kept at a low rate. This condition requires that air be added to the regenerator gas before it is sent to the Oxycat chamber; the requirement is that the gas leaving the Oxycat units contain a minimum of 2% of oxygen before condensation of the water vapor. The dust loading of the regenerated gas varies widely depending on the type of catalytic cracker and on the dust collector used in or after the regenerator. An Oxycat boiler can operate successfully with any reasonable dust loading on any of the current types of catalytic cracker. I n fact, a commercial boiler has operated successfully for a period of several weeks of extremely high dust loading. The operation and equipment of the Oxycat section of a heat recovery unit, advantageously a steam boiler, are simple. It is necessary to admix the regenerator gas thoroughly with the required quantity of air and to apportion the stream through the bed of catalytic units. Admixing ensures uniformity of temperature, composition, apportioning, and the equality of flow rate to uniformly complete combustion. The temperature of the gas leaving the catalytic cracker regenerator is usually between 850" and 1150O F. If the mixture temperature of the regenerator gas and required air is i 5 0 ° F. or higher, the gas stream can be sent directly to the Oxycat units; if lower than 750' F., the temperature is normally raised to this value by a line burner or other combustion chamber. Alternately, a modification of the usual design of the Oxycat chamber permits sending the gas stream to the units a t temperatures below 750' F. A choice between the two methods can be made in such cases. The gas pressure of the stream leaving the catalytic cracker regenerator usually varies between 2 and 15 pounds per square inch gage. The boiler (or heat exchanger) is normally designed so as not to offer much back pressurefor example, up to 6 inches of water. The usual loss through the bed itself is about 1 inch of water and through the whole chamber, 4 inches of water. The temperature of the bed is controlled through the composition of the entering gas stream by increasing the excess air, if necessary, so that the maximum temperature is l6OO0 F. I n these conditions, the life of the catalyst is guaranteed for one year (for 90% oxidation of the carbon monoxide) and a life of 2 years, a t least, is expected.
Automatic control of the operation is provided. For example, a continuous oxygen analyzer below the bed provides for additional air when the oxygen content falls to a chosen value. If this additional air lowers the inlet temperature of the stream too much, a temperature controller a t the inlet of the bed provides for more fuel to the preheat burner. A temperature controller at the outlet of the bed is set for the maximum permissible temperature of operation. If this temperature is reached, a warning signal is actuated or a by-pass valve to the stack is opened. The boiler is preferably provided with oil and gas burners, so that the steam raising can be realized when the regenerator gas is not available. It is, of course, possible to design the boiler for the production of any desired quantity of steam above that raised by the regenerator gas alone. The economics of a typical commercial catalytic unit boiler is as follon-s: The erected cost of the complete boiler was $450,000. Regenerator gas sent to the boiler is 216,000 pounds per hour, entering a t 850' F. KOadditional air is required in this case, as the average analysis of the gas shows:
C Oa
co
Per Cent b y Volume 8.5 3.8
5.3 67.7 i4.7
0 2
NZ H20
With no supplementary firing, the boiler absorbs 55,200,000 B.t:u. per hour, making steam a t 450 pounds per square inch gage and 550" F. total temperature (feed-water temperature, 250' F.) A partial breakdown of the costs affecting the catalytic section of the boiler is as follows: Catalytic unit chamber Units (9600) Spacers (for laying u p the bed) Building the bed Freight, miscellaneous Annual coat of catalytic section: Amortization t o 10% Labor to replace units once a year (conservatively expected to be once in 2 years) Reprocessing of units Interest on investment, 6% Operator, 1/1 man per shift (actually not used in refinery in question) Overhead for above item
S 30,000
96,000 1,000 1,800 1,000 1129,000 B 12.900
3,500 33, GOO
7,740
4,500
4,500 $ 66,740
The net saving per year is $133 260 since t h e full saving by these units is 020d,000 per year. Correspondence concerning this column will be forwarded if addressed to the author, c/o Editor, INDUBTRIAL AND ENGINEERINQ CHEMISTRY, 1155--16th St., N.W., Washington, 6, D. C.
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 47, No. 12
