HE ACTIVATED C A R B O N I N D U S T R Y PRODUCTION
~
I
was used to pun> liquids, an area
1
which represented by f a r the bulk of the market Now, large@ because of handling
problems, the trend is toward the granular
JOHN J. SCHANZ, JR. R I C H A R D H. P A R R Y
I
24
INDUSTRIAL AND ENGINEERING CHEMISTRY
he growing demand for higher quality prcducts and T improved purification methods has created laiger markets for activated carbon. Before World War 11, domestic productionwas only about 17,000 short tons 'per year. BTuf by 1961, this figure had reached 60,000 tons, and for 1962 it is estimated at 62,000 tons. More growth is predicted, particularly for white sidewall tires, fats and oils, pharmaceuticals, dry cleaning, and air purification. However, the activated carbon industry is still relatively young. Commercial development has occurred only within the last half century, and growth has been fairly steady-about 5% per year. The first comprehensive study. (7). in 1951, coven . . . published . properties, preparation, and uses; a second edition is scheduled for the near future. This article covers economic trends and structure of the industry.
Definition and Types
Activated carbon is any form of carbon capable of adsorption. Its properties are determined primarily by its source, and activation is accomplished by driving off volatile products with heat. This leaves a porous carbonaceous residue ( 2 ) with a vast network of interconnecting capillary passages which provides a tremendous surface area for adsorption. Activated carbon can be divided into two broad categories : that suitable for decolorizing or purifying liquids, and that suitable for gas adsorption. T h e two groups are not interchangeable. Further, powdered and granular carbons differ, and even different lots of the same grade may differ. Therefore it has become common practice to use end-use tests for determining the effectiveness of periodic shipments of the same grade. Unlike the granular form, the powder is used only for liquids where it is mixed with the liquid and then filtered out. Impurities adsorbed on the carbon surface remain on the filter cake. Therefore, the powder must be a light, filterable material with a high bulk density. Granular carbon, used as a fixed bed in adsorption columns through which liquids or gases percolate, must be a dense, abrasion-resistant material which can be regenerated. Such a material is obtainable by mixing a hard, dense carbon with a resinous binder prior to activation. This binding plus longer activation time
are two important factors contributing to the higher price of the granular form. Granular carbons are used in all gas-phase adsorption, and within the last decade, they have been used for liquids as well. They can be regenerated, and therefore have become acceptable where lowpriced powdered carbons, usually discarded after use, have been dominant. However, most liquid applications have been restricted to volume consumers who can justify investment in expensive reactivation equipment, Sources
Most carbonaceous materials are potential sources of activated carbon and hundreds have been investigated. However, quality, cost, and availability in large quantities are prime requisites. As a result, only six sources are used a t the present time: bituminous coal, coconut shells, lignite, petroleum residues, pulp mill residues, and wood charcoal (see tabulation below). Bituminous coal is used exclusively by Pittsburgh Chemical, and to a lesser extent by Barnehey-Cheney. I t is rather expensive, and must be purchased according to rigid specifications for carbon and ash content, especially soluble ash content. However, two factors compensate for the higher cost. the granular carbon it yields can be produced in the heart of the mining region,
SOURCES OF ACTIVATED CARBON AND COMPANIES I N PRODUCTION Company
1
Plant Source Material
LOCQtiOn
Type of Carbon
Markets M o s t Prevalent
I
: ;%:
American N o rit
Jacksonville, Fla.
W o o d charcoal (Florida pine)
Powdered"
Fats and oils Pharmaceuticals
Atlas Chemical Industries
Marshall, Tex.
Lignite
Powdered"
Sugar (corn, cane, beet), d r y cleaning, industrial water purification, electroplating
Da r c o
BarnebeyCheney
Columbus, Ohio
Coconut and pecan shells, bituminous coal, w o o d charcoal
Granularb
Gas-adsorption specialties, air purification
Adsorbite
Cliffs-Dow Chemical
M a rque tte, Mich.
W o o d charcoal (birch, maple)
Granular
Industrial water purification
Cliffchar
National Carbon
Fostoria, Ohio
Petroleum base residues
Granular
Solvent recovery, gas purification, catalyst, catalyst carriers
Columbia
Pittsburgh Chemical
Pittsburgh,
Bituminous c o a l
Granularb
Sugar (corn, cane), various gas adsorption applications
Pittsburgh
W e s t Virginia Pulp & Paper
Covington,
Pulp mill residues (black ash)
Powdered"
Municipal water purification, reclaimed rubber
Nuchar
Norit
~
~~~
a
Special granular carbons also available.
b
Special powdered carbons also available. VOL. 5 4
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DECEMBER
1962
25
thus reducing shipping charges for the raw material; and the product brings a higher price because it can be regenerated repeatedly. Therefore, bituminous coal carbons can compete with powdered carbons far liquid decalorizatiOn. &a, they are used widely in g a p applications. Coconut shells used by Bamebey-Cheney, are among the oldest source materials used for making gas-adsarption carbons and yield pahaps the best granular carbons available. This supaiority results from the hardness, high basic carbon density, tiecdom from iron and sulfur, and the pore size distribution the shells pmvide. Coconut shells unfortunately, are imported and the supply is limited. The carbons produced are expensive and are therefore resewed primarily for specialty applications. Similar carbon is provided by pecan shells, but only small amauntS are used domestically. Lignite, used primarily far making powdered carbon, is the major source for Atlas Chemical Indusuies. It is mined in Taras, and the company’s carbon plant is located nearby. Petroleum residues are used by National Carbon. The granular carbon produced is used solely for gas adsorption.
PRICES OF ACTIVATED CARBON T E N D TO BE STABLE
ITvpical delivered prices as quoted early in 19611 AppIk&’m
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I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
Municipal w t e r purification Industrial water purification Beet sugar Cane sugar Corn sugar Dry cleaning Electroplating Fats and oils Pharmaceuticals Reclaimed rubber Air conditioning and purification Catalyst and catalyst carriers Gas mash Gas purification Gas separation Solvent recovery
7-9
13 11-17 11
40 18 11-30 15-40 IC45
I
25-50
30 28
33 30 Mwo 40-100 45 75 4360 M)
.
Pulp mill residue is used exclusively by West Virginia Pulp & Paper. The carbonaceous d u e from large scale chemical pulping provides raw material well in excess of f a s a s t demand. The residue is a byproduct, and therefam it has a decided advantage in terms of raw material cost. Also, carbon pmduction solves in part a waste disposal problem. Wood charcoal is the sole material far American Narit and Cliffs-Dow Chemical. American Norit uta Florida pine charcoal from pine stumps purdmsed from a nearby wood chemical producer. Hard woods yield good granular c a ~ and b soft w a d s usually give powdered carbon. Although present carbon p d c t i a n is limited to eix sau~ces,new soumes may be utilized in the future. For aample, anthracite can be activated, probably far granular carbon, a l h g h powdered carbon can be made (?). It is cancavable that activated carbon frinn antbracite may have properties not found in other carbons. Also, it may be economical because the preactivation binder may be eliminated. MarlaHw FmcHC.I
About 75% of the market is supplied by two powder producers (West V i Pulp & Paper and Atlas Chemical Industries), and another 15% by Pittsburgh -Chemical and American Narit. The remaining 10% is shared by three companies; National Carbon and Barnebey-Cheney hold mast ofthe gas-absorption American Narit sells through two d e s agents, but the others supply most consamem M y . Distributors arc used for specialty mark- where the carbon bdcomes an actual component of the end product, or where wnsumers are small and widely separated. specially trained d e s and technical personnel service consumem. Mostly they W e activated carbon adusively, but one company use8 salesmen who handle other chemicalsalso. Most of the producers are suppliers of basic carbon. One furnishes custom installations and complete engineering service for spsciaity consumers. Another in the gas phase area once offered similar service, but now it has given this to an engineering firm. Each prcducer markets its carbon under a brand name, but one, a specialty pmducw, has s e v d brand names which may change with the application. This company also m e s private label distributam who in turn sell the carbon as specialty purifiers. Activated carbon can be bought by the pound or in carload lots. Some 90 grad& arc available, but about 10 account for 90yoof the market. Prices tend to be stablt-7 to 40 cents per pound far the powder and 21 cents to $1.25 far the granular (see table at the right). However, price is seldom the sole de-t in consumed selection among eompetetive brands.
PRODUCTS AND PROCESSES USING ACTIVATED CARBON
Liquid Phase Municipal and industrial water treatment Cane, corn, and beet sugar
Dry cleaning Reclaimed rubber Pharmaceuticals Fats and oils Electroplating
-
Miserllanoour Llqqid Phase Alcoholic beveroges Alginates Alum
Caffeine Dyestuffs Monosodium glutamate Nylon salts Plasticizers Soda ash Upgrading local sugars
Oa. a&dswptkn
Air conditioning and purification
Catalysts and carriers Cigarette filters Gas masks Gas purification, and separation Solvent recovery
ConawnpHon
About 105 to 110 million pounds arc consumed annually far liquid purificrttion and 10 million pounds for gas adsorption. Powdered carbons account far VOL 54
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27
MUNICIPAL WATER PURIFICATION AND SUGAR REF I N I N G PROVIDE T H E T W O LARGEST MARKETS FOR ACT I VATED CARBON
(Listed in descending order according to volume in pounds) Volume
A.b.blzcotion
Municipal water purification Corn sugar Cane sugar Gas adsorption Dry cleaning Reclaimed rubber Pharmaceuticals Fats and oils Beet sugar Plasticizers Industrial water purification Electroplating Alcoholic beverages
Pounds
1
1 2 3 4 5
2 1
7 3 4
8
6 7
8 9 10 11 12 13
Dollars
5 6
,
11 10 9 12 13
about 85% of the market on a weight basis and on a dollar basis. Municipal water purification and sugar refining account for about 60% of total granular consumption. Each of the last five uses listed in the above table accounts for 2 million pounds or less per year. Market location
Over 50% of the activated carbon used for municipal Tvater treatment is consumed in the East North Central States. Except for small quantities, all carbon used for decolorizing corn sugars and sirups is consumed in the corn belt, primarily Iowa, Illinois, and Indiana. Cane sugar refineries are concentrated in Gulf Coast ports and major ports in the Northeast. Performance
In selecting an activated carbon, most consumers attach primary importance to performance. I n water purification, taste- and odor-producing substances must be adsorbed, and in sugar refining, color bodies and color precursors are adsorbed. Color removal is also involved for dry cleaning fluids, fats and oils, dyestuffs, and plasticizers. In electroplatinq solutions, dissoh7ed organic impurities are removed. Selective adsorption is of prime importance in pharmaceutical purification and all gas-phase purification. For the sugar, electroplating, fats and oils, and dry cleaning industries, good filterability is important. For fats and oils, howeirer, rather severe oil retention in the carbon filters precludes greater usage of activated carbon. Consequently bleaching clays are used, together with smaller amounts of carbon. Competition
Except for the sugar, fats and oils, and alcoholic beverage markets, activated carbon does not compete AUTHORS John J . Schanz, J r . , is Professor o j Mineral Economics at T h e Pennsylvania State University, and Richard H. Parry is a Graduate Assistant in Mineral Economics 28
INDUSTRIAL A N D ENGINEERING CHEMISTRY
with other adsorbents or purifying chemicals. To a large extent, it has replaced bone char, and et-entually may replace it completely, for removing colors from corn and cane liquors. For decolorizing various sugars, ion exchange resins are used on a small scale, and through improvements in technology and price reduction, they may compete with activated carbon Historically, certain markets have been considered suitable for powdered carbon only, and others for granular carbon. But in the past decade, fixed-bed granular systems have replaced powdered carbon. particularly in corn and cane sugar refining. This trend is expected to continue-handling problems connected with powdered carbon are a major factor. Handling difficulties and consequent losses and process contamination because of dusting have restricted carbon consumption in other applications, especially electroplating. Packaging has been modified, and special handling techniques are advocated, but powdered carbon is still black and it is still light and fluffy. Powder producers seem faced with two alternatives: either make a carbon that is much easier to handle or produce qranular carbon. Easier-handled powdered carbon seems more feasible because it is difficult to make granular carbon from a povder. Most producers have available only a single source. The Future
Adsorption by activated carbon has gained recopition as an important chemical unit process, and it is in \ arious chemical applications that this superior adsorbent will find its market expansion. For the most part, small volume markets will be the fastest growing, but a large increase in over-all consumption is not expected, although growth will be sufficient to ensure continued prosperity for the activated carbon industry. Large percentage increases cannot be expected in the two major markets-water purification and sugar refining. Beet and sugar cane will not require much more carbon, but corn sugars and sirups should provide somewhat more growth Increasing demand for palatable water accompanying population growth makes the municipal water treatment market attractive for poll dered active carbon producers. Rubber manufacturers will probably consume more increased production of kvhite sidewall tires is predicted Air pollution control will account for more The dry cleaning trade will probably use more, especially if coinoperated machines using an activated carbon purification package gain widespread acceptance Increases for fats and oils and pharmaceuticals will be moderate SUGGESTED READING
(1) Hassler, John M’., “Active Carbons,” Tudor Publishing Co. (order from Harlem Book Co.), New York, 1951. (2) Helbig, M‘.A., “Colloid Chemistry, Theoretical and Applied,” (J. Alexander, ed.), Vol. 6,p. 834, Reinhold, New York. 1946. (3) Kawahata, M., “Activated Carbon from Anthracite,” P1i.D. dissertation, Dept. of Fuel Technology, The Pennsylvania State University, 1960.
