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Salt as a By Product

( Originally Published Early 1900's )



THIS economic age prescribes that, for the continuing commercial success of any business, that business shall be con-ducted without waste. The management which fails to realize all its possibilities of thrift invites competition that will undersell its market; and this competition, continuing to make lower prices, will ultimately occupy the market to the exclusion of the wasteful producer.

Not only by the adoption of economical processes of manufacture, but by the utilization of all by-products, must the manufacturer of today keep down his production cost. In some cases he has apparently the choice between economical manufacture of his chief product without a by-product, and a less economical process which leaves as residue a valuable by-product. A correct choice between these two alternatives requires commercial instinct as well as technical knowledge.

Our friends, the gas companies, have long ago let the public know that their profits are in their by-products. Many of them have modified their gas-producing processes toward lower efficiency in order to increase the value of the by-products. Our other friend, The Standard Oil Company, is somewhat secretive. Nevertheless, we know that the commercial success of that corporation has to no little extent resulted from the utilization of all the contents of the crude oil, whereof in the beginning only illuminating oil was marketed.

Increasing the Load Factor of the Electric Plant

In our business—the production and sale of electric light and power—our greatest waste has been time—18 or 20 hours out of each 24. We have had, and still have, at best only work enough fully to employ our investment 20 to 25 per cent of the time. Our interest, insurance and depreciation—and our taxes—accumulate during every one of the 8,760 hours of the year. No improved efficiency of generation, no reduction of the losses in distribution, can possibly help us so much as would the discovery of profitable work to which our investment might be set during its hours of idleness. This is not a new theory; it is a long established and well recognized condition, and the suggested ameliorations of the condition have been very many.

The Salt Industry

This paper presents the latest of these suggestions, as adopted by The Detroit Edison Company, to wit : The combination with the electric light and power industry of the manufacture of common salt by the evaporation of saturated brine. Obviously, this combination can be made only within well defined geographical limits. The first requisite is the existence of a sufficient deposit of salt. The greatest store of salt is in the water of the oceans, which contains approximately 3 per cent by weight of sodium chloride. To recover this percentage involves the evaporation of 97 per cent of water; which is unprofitable excepting in a limited way, and in warm climates where the sun furnishes the requisite heat. In the United States, salt is produced from four principal deposits of rock salt, located as follows:

1. In western New York.

2. In Ohio and Michigan, running from southeastern Ohio northwest through Cleveland, under Lake Erie to Detroit and across the State of Michigan to Lake Michigan at Manistee and Ludington.

3. In south central Kansas.

4. In Louisiana.

A limited amount of salt is obtained by mining; running shafts and tunnels directly into the rock salt. There is an excellent demand for this class of salt, which, taken with the cost of production, maintains it at a good price. The more common method, and the method that is used exclusively in the Ohio and Michigan field, is to pump water down to the salt vein, where it dissolves about one pound of salt to each three pounds of water, forming a 25 per cent brine; this brine, returned by the pressure of the pumps through a separate pipe, is evaporated in open vats or vacuum pans by contact with steam pipes or steam jackets. The building, equipped with vats (called grainers) and vacuum pans, together with the pumps and other machinery required, is in common parlance called a salt block.

Salt as a Sawmill By-Product

It is customary to use exhaust steam, when such is available, to heat the brine. This practice has led to the combination with the production of salt of other industries using steam power. In the State of Michigan the most frequent combination with the salt block is a sawmill, this particular combination being so common that it is almost standard. A sawmill raises steam by burning its own refuse strips and sawdust; that is to say, fuel is produced in sufficient and sometimes in excessive quantities by the operations of the mill. Old lumbermen said, therefore, that their fuel cost them nothing, and when they, moreover, utilized their exhaust steam in a salt block the commercial result was exceedingly good, and many Michigan fortunes have been earned thereby. These saw-mill salt blocks have had possession of the salt market of the upper lakes for years, and they virtually still control it.

In more than one instance an electric light plant has been operated in combination with a salt block and sawmill. I could name a dozen such electric light plants in the State of Michigan. The electric lighting load comes on at dark, when many sawmills shut down either partly or altogether. Salt evaporation is preferably, though not necessarily, a continuous process, and the addition of the electric lighting load is a step toward continuity.

The pine, which was the beginning and the strength of the Michigan lumber industry, has nearly disappeared, and with it will go the control of this salt market by the Michigan salt blocks. At Manistee, and in that vicinity, the supply of pine still holds out and the sawmills and salt blocks are as busy as ever; but on the east shore of the State, the pine has been worked out, and the original combination is there no longer possible. Around Detroit, where the greatest salt beds in Michigan have been explored and developed within the last ten years, there is no pine nor available lumber of any kind, and salt is produced only with fuel bought and burned expressly for the purpose. This leaves but a narrow margin of profit, and if it were not for the lower cost of distribution, the industry in the vicinity of Detroit could not exist in competition with that at Manistee. The cost of distribution is a controlling element in the salt business. The material is heavy, and the freight from the salt block to the point of use is frequently greater than the first cost of the salt. In this respect salt and coal are on a similar basis. Each salt field, like each coal field, has a certain area which is its natural area of distribution, and beyond which it comes into competition with the product of some other district. Special qualities of coal, such as the anthracite coal of Pennsylvania, are shipped for special purposes all over the United States; similarly, table salt and other special grades are shipped all over the country; but bulk salt, such as is used by packing houses and in manufacturing and chemical processes, has a well defined radius of distribution from each producing district. Low first cost will, in some cases, offset high freight rates; and special freight rates (which are not unknown to the salt industry) will extend the radius of some producer who is favored with the same; but these are exceptions not affecting the general rule.

The Detroit Salt Industry

The Detroit salt bed is worked to a very great extent by companies producing the salt products—the alkalies—carbonate of soda, soda ash, etc. The Solvay Process Company, whose main works are at Syracuse, N. Y., has established works at Detroit, which were the first on a large scale in that district. Other makers of salt products have followed the lead of the Solvay Company until the alkali industry has become one of the most important in Michigan. These chemicals have a very much wider radius of distribution than has common salt, and the immense salt beds at Detroit, in combination with good water, cheap coal and limestone, and excellent lake and rail transportation facilities, now give Detroit an advantage that it is likely to retain for many years.

Creating a Detroit Manufacturing Industry

As I have already said, it is not new to turn the exhaust steam of an electric light plant into a salt block. What is new about the Detroit proposition is the recognition of the possible reaction of salt production on the electric light and power business. Economically, it would be just as profitless to operate a salt block during the few hours when an ordinary electric light system would give it a liberal supply of steam as it is to operate that same electric system only during those hours. To work the electric light investment to good purpose, requires a better load factor than is usually obtained. To work the investment in a salt block to the best purpose, requires continuous operation. A salt block that takes and utilizes the exhaust steam of a lighting plant at its peak load and is idle or using live steam at times when the electric light plant is lightly loaded, can not be made to pay. But if a continuous load can be obtained for the electric light machinery, a continuous and profitable operation can be assured to the salt block. The converse is true; namely, that if all the exhaust steam of the continuously running electric plant is profitably used in the salt block, the reduced or extinguished cost of fuel will make the electric lighting business profitable. To obtain this very desirable state of affairs, it is necessary to find the continuous electric load. The use of electric light has physical limitations. People are not going to turn on lights in the daytime merely to be kind to the electric light companies. Differential rates will improve your electric light daily load curve and will bring you business that would otherwise go to kerosene or gas; but, after all, it is essentially a night business—I may even say an evening business, because all-night lighting is a comparatively small portion of the maximum demand. Electric power is a different proposition. Industries that use power 24 hours a day have always existed, and their number is increasing. To these must be added the industries—mostly chemical —that use electricity for heating or for electrolysis. To these may yet be added—if the inducements are sufficient—industries that now use power only 8 or 10 hours per day, but that, if power be cheap enough, can profitably work a night shift or even establish continuous 24-hour operation.

The possibility of creating a manufacturing district of such industries has been demonstrated at Niagara Falls. Cheap power, cheap and convenient transportation, and cheap land, are the essentials. With these it is desirable to have an existing population which takes kindly to factory work. All the conditions except the cheap power are existent in Detroit, and our proposition is to furnish the missing essential. We believe that among the industries already established in the City of Detroit, and among those which can be brought to locate in the City or in its vicinity, we can find such a demand for our electric product as will enable us to operate with a good load factor 24 hours a day and 365 days a year. Under these conditions the exhaust steam from our engines can be profitably utilized in the evaporation of brine—that is to say, in the production of salt; the sale of the salt will reduce or extinguish our cost for fuel; and it will be practicable for us to sell electric energy—the fuel cost being reduced or extinguished—at such figures as will secure the stability of our economic combination.

Exhaust Steam for Process Work and Central Heating

You will observe that I do not say that salt as a by-product will in itself make the difference between profitless and profitable operation. It is good to utilize your exhaust steam; but because you don't utilize it you are not necessarily throwing away your dividends, nor sending them out of the chimney, according to advertisement. If the proposition merely afforded a use for our exhaust we should run condensing. Indeed, we are providing condensers for use under certain conditions, of which more hereafter. What we see in the plan, and what I am trying to show to you, is the possibility of utilizing the idle hours of our electric investment. The business we expect to get during these idle hours can only be obtained at low prices—virtually at cost of production. The profit lies in the fact that the salt business will reduce or extinguish the fuel cost. Where-fore it is hard to say whether, during these hours of sometime idleness, the electric supply will be our business and the salt will be our by-product, or whether we shall be truly in the salt business with electricity as the sideshow.

About those condensers: We don't expect to do away with the peak of our electric load. That will be always with us, like the poor and the tax collector. We shall have to put up with it, more or less, as with them. But we can provide for the peak in either of two ways. We can have spare engines and boilers, continue to run noncondensing, and crowd the salt block to use the excess steam, or turn it into the atmosphere. Or we can shut down part or all of the salt block for the hour or two and run some or all of our engines condensing. The latter plan suits us best, and requires less investment. It does not pay to crowd a salt block—it affects the quality of the salt. And it does not hurt to shut it down, except to the extent of the loss due to the investment being idle. That latter loss is less if the block is idle during the few hours of winter peak and the condensers idle the rest of the year, than if spare engines and boilers, and land and building to accommodate them, were idle all the year and busy only during the peak.

I have just indicated one aspect in which the salt block as a user of exhaust steam is preferable to a steam heating system. I can shut down my block the week before Christmas and no one will complain. The men who work in the block will probably even be happy to take a holiday just then. But please shut your eyes and imagine the lovely row there would be if I undertook to shut off my steam heat distribution that same week. Then I can run my salt block all summer and ship my summer product up lake till navigation closes. I wish I could sell steam heat all summer. Also, the salt block will use what steam I give it at the times I give it, and will not want to be specially warmed up at six o'clock each winter morning; neither to have the heat turned on again for a Fourth of July celebration that has failed to make seasonable arrangements with the weather bureau.

Collateral Engineering Problems

There are many interesting engineering problems connected with our proposed combination of industries. For instance, the question of the economical limit of the back pressure on our engines (which are to be turbines), is exceedingly complex. We can make that pressure just about what we please by proper design of the salt pans; but the first cost of the pans, the rate at which they can be worked, and the quality of the salt produced, are all varied by variation of the back pressure. Again, although we run noncondensing, we shall have an ample supply of distilled water for our boiler feed in return from the pans; but the economical temperature of this feed water is a matter of discussion. Still more interesting is the question of how to utilize the waste heat of flue gases—whether in heating brine or in heating feed water.

These matters, although interesting, are secondary. Moreover, this paper is already long enough. Like the cowboy who was chased by Indians through the Bad Lands, I have hit only the high places of the trail. If you want to hear from me of what lies between, I must make another trip at another time. When that time comes I shall know more about the subject.



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