Richard F. Toro and Norman J. Weinstein
Princeton Chemical Research, Inc., Princeton, N.J. 08540
Air pollution control needs snur catalyst sales I
Billion-dollar-per-year market beckons in such areas as exhaust controls, incinerator systems, and new refining processes
control equipment and techniques, and to lower capital and operating costs. Catalysts have real and potential outlets in four general areas of air pollution abatement: Incineration of waste gases containing combustibles. Removal of other noxious pollutants from industrial waste gases. Control of automotive exhaust gases. Changes in petroleum refining required to produce modified fuels to meet new air pollution abatement standards. Catalytic incineration
1 here is no question that air pollution has become a national concern, is a real problem, and is likely to become a multibillion dollar business in a few years. Probably more than $300 billion will be spent on this problem in the next 30 years; even conservative estimates put the figure at $1.0 billion per year, Those companies working to establish themselves now in the pollution control field are likely beneficiaries of these vast expenditures, along with the public. Generally, technology is available to solve most air pollution problems. However, since pollution control equipment usually is not an income producing investment, there has been little incentive for industry to install such equipment. The automobile industry, for example, has been reluctant to add as standard items anything that increases costs without making the car more salable. Seat belts are a case in point. However, this conservative industrial attitude is changing, for two reasons: Governmental pressures, statutory and otherwise, are increasing rapidly. Public relations has become more important, particularly to large consumer-oriented companies, because of the great publicity the air pollution problem is receiving. There are, then, tremendous incentives to develop more efficient pollution 30 Environmental Science & Technology
Incineration in the context of this article is the combining of oxygen with noxious material to form harmless compounds, usually carbon dioxide and water. It can be carried out by two methods: thermal incinerationwhereby a flame is maintained-and catalytic incineration-whereby the combustion is carried out in the presence of a solid catalyst without a flame. Thermal or direct-flame incinerators are in widespread use in solid waste disposal and, in some cases, are the proper choice for air pollution applications. However, there are many situations where catalytic incineration offers a much better system for air pollution control. Some of the advantages of a catalytic system include: Significantly lower capital costs. Lower temperatures allow less expensive construction materials and require less heat exchange equipment. Fuel economies. These economies result from the lower operating temperatures and from the elimination of the requirement of maintaining a combustible mixture. Safer installation. Combustible mixtures need not be maintained, and the solid catalyst tends to suppress any explosive mixtures. Catalytic incineration, in spite of its resulting savings, has very often been bypassed in favor of the flame system because of a lack of confidence in the ability to achieve favorable results.
There is little literature concerning the use of catalytic incineration, and few commercially available systems. This deficiency is partly because, in the past, problems have often been treated on a custom basis. Each problem is analyzed by itself, and pilot tests are run before equipment is specified. Thus, there is a real need for off-theshelf systems. Possible applications for catalytic incineration are numerous. Any industry emitting hydrocarbons, solvent vapors, or any combustible vapors is a potential customer-for example, paint, varnish, and lacquer manufacturers; dry cleaning plants; printing plants; chemical plants; oil refineries. The potential size of this market is indicated by the following: probably some 3000 tons per day of organic materials are emitted in the United States. A typical catalytic incinerator may contain 1000 pounds of catalyst for every ton per day of organic material passed through it. If one half of all the organic emissions (1500 tons per day) were catalytically incinerated, the potential initial market for catalysts in this field is 1.5 million pounds. At an average catalyst price of $2 i e r pound. this market corresponds to about $3 million. Nickel and platinum catalysts have been the most widely used combustion catalysts, but their high cost may spur the development of less expensive replacements. Assuming a catalyst life of about two years, the replacement market would be about $1.5 million per year. The potential initial market for selling the catalytic incineration system is $30-60 million since the catalyst cost runs between 5-10% of the total cost of the system. Other waste gas pollutants
There are various sources of industrial air pollution where incineration is not possible or not recommended. For example, the pollutants may not be combustible, or the combustion products may give rise to secondary pollutants. The most important examples of
feature these difficult cases are inorganic smoke and dust, hydrogen sulfide, sulfur oxides, nitrogen oxides, and gaseous organic materials containing sulfur or chloride. Solid pollutants generally can be removed by electrostatic precipitation, filtration, or liquid washing, but the gaseous materials require more complicated procedures. Sulfur oxides have been called the next major air pollution problem after auto exhausts, and are emitted in large quantities during the burning of fossil fuel. Electric utilities are the prime source of sulfur oxides, although other fuel users, chemical plants, and mineral processing plants also contribute major quantities. Nitrogen oxides, generally found in much lower concentrations, have not received as much attention as sulfur oxides; but, since nitrogen oxides are very dangerous, both in themselves and as promoters of smog, they will probably become the next target of special control legislation. Nitrogen oxides generally are emitted by the same industries as those emitting sulfur oxides, but also are found in automotive exhausts and other combustion processes which use sulfur-free fuels. Various methods for removal of sulfur oxides are being considered, but an economically attractive and technicallp feasible method has not yet been developed. Development of removal techniques is a prime concern of the National Air Pollution Control Administration, which is attacking the problem on many fronts: Absorption in aqueous solutions, inorganic liquids, or organic liquids. Adsorption onto inorganic or organic solids. Chemical conversion to easily recoverable and valuable byproducts. The chemical conversion route is likely to involve one or more catalytic steps. For example, one method of removing sulfur dioxide is by reacting it with oxygen to form sulfur trioxide, which, with water, forms sulfuric acid. Other methods involve catalytic reduction of SO2to elemental sulfur. The potential of removal by conversion as opposed to absorption or adsorption is difficult to assess. However, this method has at least as much chance of success and ultimate use as
the other two. Possibly, the final choice will depend on local conditions, and all three routes will be used. The size of this potential catalyst market can be delineated. Consider: If all the electrical utility companies which burn fossil fuels utilized a catalytic SO, control method, the initial catalyst market might be in the range of 30-300 million pounds of catalysts, with a probable replacement market of 15-150 million pounds per year. At catalyst prices of $0.25-2.00 per pound, this market becomes very large, Even if only one third of the utilities makes use of such methods, the initial market might be 10-100 million pounds of catalyst, with a replacement of 5-50 million pounds of catalysts per year. In addition, about as much fossil fuel is burned in other applications as by utilities. These other applications would likely require similar sulfur dioxide control systems. For example, if the effluent gases from all the coal burned in the U S . were to be cleaned up catalytically, an initial market for catalysts might approach 60-600 million pounds. If one considers systems and hardware in addition, a multibillion-dollar industry could be formed. Vanadium, alumina, and bauxite catalysts, widely used in chemical petroleum processing, are leading contenders for this potential market. Several long-term solutions to sulfur oxide pollution eliminate the need for after-combustion cleanup, but it is difficult to predict whether they will be utilized extensively. A switch to nuclear generating plants has already begun. However, the extent and timing of this development is difficult to predict. Furthermore, the switch depends on the successful development of breeder reactors. In any case, a complete switchover to nuclear power probably will not take place for decades. (Nuclear reactors have pollution problems of their own: thermal pollution of waters, and less widely discussed problems associated with nuclear fuel processing plants.) Another alternative solution to the SO2 problem is the use of naturally occurring low sulfur fuels, which are rare and in great demand. Reducing the sulfur content of residual fuels to a low level is very expensive; complete sulfur
removal may be next to impossible. Work is proceeding in this area, but no short-term answer is at hand. Extensive sulfur removal from fuel oil would open an entirely new catalyst market. The most likely short-range solution, then, is SO, removal by catalytic methods after fuel combustion. Research to this end should be process oriented, since many of the fundamentals are known or are being studied. The development risks entailed in this area are not as great as in the automotive after-burner field. Automotive pollution
Automotive vehicles in the US. are the biggest source of air pollutants. Vehicle exhaust gases account for more than 60% of the country’s air-borne wastes: in the cities, this figure reaches as high as 90%. Control of these emissions represents possibly the largest potential market for catalysts outside the petroleum refining industry. The devices proposed usually are known as catalytic mufflers or afterburners, used for internal combustion engine exhausts. They generally operate under the same principles as incinerators, in that unwanted exhaust pollutantscarbon monoxide and unburned hydrocarbons-are oxidized to carbon dioxide and water. The sheer size of the automobile industry, with a current production rate of 9 million new cars per year, has made this potential market one of almost unbelievable proportions. The potential market for catalytic mufflersat about $20 each-for new cars alone, is nearly $200 million per year. Catalyst life probably would not exceed one year, and the replacement market could exceed $1.0 billion per year, based on 50 million U.S. registrations. This tremendous potential understandably has drawn many companies into the field with extensive research programs. A few years ago, there were between 25-50 companies working on catalytic mufflers: because of the tremendous problems involved, interest waned until recently. In May 1967, Ford Motor Co. and Mobil Oil announced a joint research project to attack the problem anew, and others have since joined them in this project. Chrysler and Esso Research and EngiVolume 3, Number 1, January 1969 31
neering Co. also have announced similar efforts. An examination of the Ford-Mobil program is enlightening in that it points up the risks involved in this field. The project has been budgeted for $7 million for three years and will attack the problem from several aspects: Elements of basic engine design. Exhaust systems with catalytic afterburners for leaded and unleaded gasoline, and noncatalytic afterburners for leaded gasoline. Control of fuel tank and carburetor vaporization losses. Dual-fuel systems for reducing octane requirements and gasoline production costs. New fuel and lubricant compositions. This program illustrates three characteristics of this field. First, the research costs involved are likely to be very high, particularly in the testing phases. Second, the technical problems to be overcome are very difficult because of the presence of lead and other catalyst poisons in the gasoline. Third, basic changes or improvements in engines could eliminate completely the need for the catalytic muffler, There are other important factors involved in developing this market. These include the intense competition in the development of the muffler in contrast to the apparent lack of success in the past. New types of auto engines are proffered, utilizing nonpolluting fuels -nuclear engines, gas turbines, fuelcell or battery-driven electric motors, or the Wankel engine. Unless a clearly superior catalytic muffler were developed, marketing could be a problem. We see, then, that the potential market for automotive catalytic mufflers is extremely large-in fact, big enough to support a medium-to-large size corporation. However. entry into this field would require extensive research efforts with the attendant risks of failure. Even moderate technical success may meet with severe marketing difficulties. Total success may be short-lived because engine modifications, new types of engines, or improved fuels may eliminate the need altogether. Petroleum refining
Major changes in the patterns of fuel utilization are underway which will have dramatic effects on the character of petroleum refining. The net effect will be a rapid growth of catalyst consumption in this industry, which already consumes more than $100 mil32 Environmental Science & Technology
SO2 Removal processes Alkalized Alumina (AA) R u M / n e s process utilizes Claus type catalyst as final step 57- -
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