Page images



On the other hand, Mr. Vernon MacKenzie, of the Public Health Service, has stated that he feels a need to reduce this limit to 0.1 part per million. This is an extremely wide discrepancy, and this committee should be as concerned with the degree of control required as with the methods of reduction.

No purpose is served in adding an economic burden that is not needed to safeguard public health.

My purpose in being here is to discuss the current status of methods for control of emission of oxides of sulfur from coal-burning powerplants. We welcome this opportunity because we feel that through such discussions a better understanding of the complexity of sulfur dioxide control measures will result.

Our organization, representing the bituminous coal industry, and with financial assistance and technical guidance of the electric utility industry, through the Edison Electric Institute and the Association of Edison Illuminating Companies, has been engaged in research on sulfur dioxide control for the past 8 years.

We believe substantial progress has been made, as it has by other groups, including the Bureau of Mines and the Department of Health, Education, and Welfare, both of which have worked extensively on this subject. However, while several technically possible solutions have been developed, none is currently available which can be considered economically practical.

We feel that the time for coordination of the activity of all groups concerned has arrived, and that through such coordination we will be able to develop a better understanding of this gap between technical feasibility and economic practicality, and perhaps such coordination will enable closing the gap in the near future.

Accordingly, we support the idea proposed in S. 306, calling for the establishment of a technical committee, with membership representing the Department of Health, Education, and Welfare, the Bureau of Mines of the Department of Interior, and the coal, petroleum, and electric power industries.

We have omitted the Federal Power Commission because it is closely confined to strictly regulatory powers established by statute and probably should not be expected to expand its field of activity into problems of this nature.

As I stated, some research progress has been made toward a solution of control of sulfur dioxide emissions from coal-burning powerplants. With the permission of the committee, I would like to review briefly the state of the art and outline some of the work which is currently underway.

Senator Muskie. Can you submit copies of the charts for the use in the record, so the verbal references will be clear?

Mr. GARVEY. Yes, sir. When we are talking about the control of sulfur dioxide emission primarily from powerplants, for this is the area in which the greatest quantity of coal is used, we must keep in mind the means by which the energy of coal is converted to electricity in the conventional powerplant.

[ocr errors][ocr errors]
[merged small][merged small][merged small][graphic][subsumed][subsumed][ocr errors][subsumed][subsumed][subsumed][merged small]
[ocr errors]
[ocr errors]
[ocr errors]

Here, in such a plant, coal, usually of the order of 2 inches by zero in size, a size which is suitable for rail shipment, is delivered to the powerplant where it is stored. Such a coal might contain 3.4 percent sulfur.

At the plant the coal passes to a mill where it is crushed to a fineness about equivalent of talcum powder. The fine coal is mixed with air and burned in a boiler. Most of the heat of the gases at temperature of 2,500° is transferred to water to make steam which then goes

to the turbines for production of electricity.

The gases from combustion, still at about 880°, pass through an air heater where more heat is extracted by incoming cold combustion air. The gases, then at 325o go to a very efficient ash collector where upward of 99 percent of the ash is removed.

On the average, this ash removed takes out with it about 10 percent of the original sulfur. The essentially fly-ash-free gases then pass to the stack and, if we used 3.4 percent sulfur coal, there will be emitted to the atmosphere approximately 3,000 parts per million sulfur dioxide and 30 parts per million sulfur trioxide.

These concentrations are diluted after they leave the top of the stack, stacks of several hundred feet in height, and mix with the air of the outside atmosphere. By the time the ground level is reached several miles away, the concentrations are with rare exception of the order of 0.1 parts per million.

While concentrations of sulfur dioxide of this low level are well below the limits accepted for continuous 8-hour exposure for persons working in industries where such gases are part of their everyday. environment, it has nevertheless been arbitrarily decided that the stack emission concentrations shall not exceed 2,000 parts per million SO:

To achieve such a concentration in the conventional powerplant will require the combustion of a coal having about 2.2 percent sulfur if we assume that 10 percent of it will be retained in the ash. Because coal for steam purposes containing sulfur contents of this level, and at reasonable prices, is not available in many areas, the research has been directed at determining a method for utilizing the higher sulfur coal

and still achieving the stack emission concentrations which have been indicated to be satisfactory.

Senator MUSKIE. May I ask a question at this point? On the average, you say, coal contains three parts per million sulfur?

Mr. Garvey. No; coal contains on the average somewhere between five-tenths and 5 percent sulfur. I have taken for my example a typical coal of 3.4 percent sulfur.

Senator MUSKIE. By weight?

Mr. GARVEY. Yes. That is, if we assume that is typical that 10 percent of sulfur will stay in the ash we will get 2,000 parts per million by volume out of the stack.

Senator MUSKIE. You suggested that percentage is almost translatable to parts per million translated by a thousand.

Mr. Garvey. That is right.

Senator MUSKIE. So if you had a half percent sulfur in coal this would translate to about 500 parts per million sulfur dioxide. But the 3.4 percent you think is a typical figure.

Mr. Garvey. It is a typical one of many areas. There are lower and higher coals.

What is available now and what is conceivable for the future to enable achievement of this goal? Control of sulfur oxide emissions from & powerplant can be achieved in three areas, namely: (1) reduction of the sulfur content of the fuel prior to firing, (2) the development of a new concept of conversion of the heat energy of coal to electricity, and (3) the recovery of sulfur oxides after combusion but prior to the passage of gases to the stack.

Let us look at each of these and review its status. Because we have some cost data available, let us start with the processes for recovering sulfur dioxide and sulfur trioxide from the flue gases.

Since they produce a recoverable and potentially salable byproduct, the three processes listed in the following chart show the most promise for application in electric utility plants.


[ocr errors][ocr errors][ocr errors][ocr errors][ocr errors]
[merged small][merged small][ocr errors][ocr errors][merged small][merged small][ocr errors]
[ocr errors]


GERMANY ABSORPTION The work on all of these processes has passed the laboratory bench scale stage and is now entering the pilot stage. While some additional technical problems must be solved before technical feasibility can be assured, it is possible at this time to determine the approximate cost of such recovery processes.


We don't have time now to go into detail but all of these could be added to a powerplant so the sulfur dioxide and the sulfur trioxide in the flue gas could be reduced to the levels apparently desirable in light of 2,000 parts per million.


[blocks in formation]


7.8 S 2.8 1.0 5.0T0 8.8 But these processes cost something. In order to do this, these prices have been developed by others and with no credit for the product producer. The additional cost to the coal in the case of the catalytic gas phase is 8.3; the Reinluft 10.2; and the Bureau of Mines process

is 7.8. These include the operating cost and capital investment in order to change the plant. However, these processes have an advantage in that they do produce a salable product. The first two produce acid and the Bureau of Mines produces sulfur that can be sold.

The first two have a possible credit of 3.9 and the Bureau of Mines is 2.8. However, in certain areas of the country they might not be able to be sold so they would have to be disposed of. So we have to take into conisderation a possible disposal cost.

One point nine for the first two and one cent per B.t.u. for the selond one. The variation of 10 or 15 percent at this stage is not sig, nificant. We can't really pin it down that close. So we have a range of prices from 4.4 cents per B.t.u. to 12.1 cents per million B.t.u., depending on conditions and processes.

Twelve point one cents per million B.t.u. is about $3.15 per ton of coal and 4.4 cents per million B.t.u. is about $1.14 per ton. In other words to install these processes, if the problems are overcome and if the economics turn out the way we think they will, you have to add 15 to 50 percent to the cost of burning coal in a powerplant.

This, I think, would put a good many companies out of business. Nevertheless these processes have reached the stage where they appear to be technically feasible from the laboratory standpoint. So much for the recovery of the sulfur dioxide.

Senator MUSKIE. May I ask a question on these three processes? Do these seem to hold the best prospect for the development of an economical way of dealing with the sulfur problem even though they do not now seem to be economically feasible?

Mr. Garvey. Yes, sir; some versions of these right now, because of the fact that you do produce a salable product. There have been a number of other ideas tried primarily in England but because they

don't produce a salable product, you can't get back this product here, they are almost hopeless.

The second approach to better control of sulfur oxide emissions is through pretreatment of the coal prior to combustion so as to reduce the sulfur content of the fuel entering the boiler. Sulfur occurs in coal in two primary forms, organic and as a mineral called pyrite.

The organic sulfur is chemically combined with the coal and cannot be removed except by chemical processing. Pyrite can be removed mechanically, but because of the extremely small size of the pyrite particles in many bituminous coals, not all of them are amenable to cleaning to the low level required.

[merged small][ocr errors][merged small][merged small][merged small]


This is a microphotograph which shows a piece of coal taken under a microscope. The greenish material is coal, the yellowish and whitish specks are pyrite. That particle is two-hundredths of an inch across. So you can appreciate that the pyrite particles are extremely small.

We measure them in what are called microns. A micron is about for one-hundred-thousandths of an inch. I have a photographic reproduction of this micron. Here is a 116-inch particle. Here is a 64-micron particle. This is the talcum powder size. Many of the sulfur particles you are looking at on that slide are 5 microns or less in

You can see the extremely fine pulverization that would be required so it could be extracted. Therefore, the conclusion is it is not a simple thing to do. You cannot do it at the plant where the coal is produced. It will have to be done, if feasible, at the powerplant.

What we are suggesting is that a process be developed to remove to this at the powerplant where the coal is already cruslied. We have

done a considerable amount of this in the last few years and we think there is hope of removing some of the pyrite.

We also think we have to move to the pilot stage. How about this organic material! The organic material can only be recovered by a chemical conversion process of some kind. Here the coal is coming again into a mill, but instead of going to the miller it would go to a gasifier where this energy would be converted to a gas.

« PreviousContinue »