benches, as the tar can readily be taken direct from the hydraulic main to the burner by the installation of a simple tank separator provided with suitable overflow connected back into the main leading to the tar well.

A sketch showing a simple arrangement devised by Mr. F. C. Slade is shown on page 610, American Gas Light Journal of April 17, 1905, and though differing considerably from the one we are using will serve to convey the idea and will undoubtedly work as well.

DISCUSSION.

Chairman-Tar burning seems to resolve itself into whether you can get more out of it as fuel, or as a sale product. Mr. Barthold: The whole secret of burning coal tar is getting a smooth flow, and most attention must be paid to that end of it, getting it to go to the tar burner well strained and at the proper temperature. The next, it must be sprayed into the furnace at the proper temperature. In the benches you have the burners surrounded by incandescent fire brick. In most boilers you do not get this condition, but you do in the Stirling boiler, where we have an incandescent arch above and it is an ideal boiler to

burn tar on. Any Dutch oven would answer the same purpose, but you must have the boiler surrounded by incandescent fire brick, as it must be at a very high temperature. We tried, I think, three patent burners for coal tar, and none were successful. We had to make up a burner of piping and fitting. I noticed that the amount of tar that we used replaced fuel at $3, at about 2c per gallon. The best you can do is to burn the tar, and taking the greatest pains possible, it destroys the benches very rapidly, and it is safe to say that it cuts its life in one-half, and that and the attention required, and extra expense about half a cent a gallon. We burned 500 barrels one year, and obtained about 3c a gallon for it. We deducted 5c from that for extra wear and tear on the benches and expenses. We always use coke with ours. Mr. Whalen at Jackson burned some tar, and the way he was burning it, I think he was getting the best results as far as wear and tear on benches is concerned. As far as I saw, it was not any harder on the benches than coke or coal, and he has had considerable experience on this subject; and also Mr. Traver, I think has had a good deal of exper-. ience in burning in boilers.

Chairman-What kind of a strainer did you use, Mr. Bar

thold?

Mr. Barthold-We had a measuring tank that held about

eight barrels, and it flowed from that to an ordinary barrel. This barrel had a float in it that regulated the inlet cock, keeping it a certain height, and that gave a constant head on the burner. This tar coming into the barrel went through several screens, and the barrel had a coil in it to keep the tar at the proper temperature. We use a wire screen. We first tried gunny sack, but it clogged up too quickly. I think we had several layers of ordinary window screen.

Chairman--You found no difficulty with tar going through ordinary window screen?

Mr. Barthold--Not with the home made burner. We use six or eight thicknesses of screen.

Chairman-You figure 2c a gallon, with fuel at $3 a ton. That is a fairly high price for fuel.

Mr. Barthold-$3 replacing coke or coal; that is a fair price. Mr. Whalen-We used a tank that held about 300 gallons, I believe, and we have a two-inch pipe leading from that to four benches, and through that 2-inch pipe I had a quarter inch pipe that carried a small amount of steam through the two inches, and the feeders were taken off the benches, and this steam pipe inside kept the tar about the same temperature all the time. Then we had a strainer on the inlet tube from the pump. This tar fed into barrels upstairs where the operator could see it, and we had strainers, brass, regular wire screens on the top of those barrels where the tar went through. This prevented dust from getting down and plugging up the burner. We tried all sorts of schemes to keep that tar from plugging up. We had trouble in the fire box, that it would stop it at the end of the burner and clog up and not run, when we got it too hot or too cold; but by a small amount of steam going through the quarter inch pipe, it kept the tar at the same temperature all the time, and fed all right. Our trouble then was in the fire boxes. If you got the pipe too far in the fire box, the pipe would get hot, and the tar would pitch up on the end of the burner and clog up. I cut that off entirely and I used an open piece of ordinary pipe, and I put that right underneath the fire pot of the door, just extended the tar pipe through the wall, and it never got into the fire box far enough to get hot. We used no fuel at all but the tar. We used a little breeze, probably 100 pounds a day in each bench. This tar was scattered inside of the wall all along on top and in the arch box, but the pipe was out, and we had no white heat at all in the fire box; we had nothing more than a cherry red in the fire box; and I gave it a large amount of secondary air from the bench. This tar went through from the fire box, a regular smoke, and the secondary air took care of it after that. It did not affect the settings any, and we used

about 135 gallons for a day of 24 hours-that is about 100 pounds of solid fuel-but we could not do as well with the tar as we could with the coal fuel. The tar would not run as constantly and give the steady heats; we could not decarbonize as much coal. We would run about 2150 pounds on six benches for four hours, and sometimes the heats would be up and sometimes down. We could not run as uniformly with tar as with coal. I figured that coal at $3 a ton took about 300 pounds to the ton carbonizing the coal, and took a great deal more coal out of the coal box than the tar fire box, and I figured tar is not worth a great deal. To decarbonize a ton of coal we used 45c worth of coal per ton, and 37 gallons of tar. You would only have 45c of fire if you used 37 gallons of tar per ton of coal carbonized; and to use 45c worth of coal to carbonize, you have only 45c for 37 gallons. And we have extra labor attached to that, and there is some more cost to the bench. The bench won't last as long. I figured in all that your extra labor will cost you a cent more. Take the way he is using it four and a half tons of coal to five tons per day of 24 hours and compare that. Compare five tons of coal for 24 hours, with the 13,500 pounds of coal for the 24 in the coal fire box, your labor costing a cent and a half more, end add that on to the 37 gallons, and I don't think you will have much left, if you can decarbonize that coal for 45c.

Chairman-Mr. Whalen has gotten unusual fuel results, and he has carbonized six and a half to eight tons on a bench of six every day. Three quarter tube?

Mr. Whalen-Yes. That is comparing with tar fuel.

Chairman-That is certainly getting good results, Mr.

Traver?

Mr. Owens-I found the greatest trouble entirely with tar burning was to get it to run constantly. If we can get something that will keep the tar running freely all the time, then we can get down the cost of it; we can use a great deal less if we can keep it going all the time. If running too fast, and you run it slower, the heats will go down, and you have to lower the charge and get them up again. If we can get something that will make the tar run constantly, a great deal less can be used, because when the tar stops running, the steam keeps going and clears the bench off. It is a matter of getting the tar to flow with a very small stream of steam. I believe 90 or 100 gallons of tar will decarbonize six tons of coal if we keep it going all the time. It is a matter of getting the tar to go all the time, where you get good results.

Mr. Schwarm-How long did you use tar?

Mr. Owens-About four months, I guess.

Mr. Schwarm-What effect did it have upon the benches?

Mr. Owens-None whatever on three, but it seemed to affect one, and I don't know whether I can lay it to the tar or not. It didn't hurt the bench, it never got around to the recuperators.

Chairman-Nobody else seems to have attempted to burn tar with the use of secondary air. This paper contemplates cutting out the arch and directing the flame up and making a plain setting out of it.

Mr. Owens-That was the same principle that I had; it went through those large openings in the arch.

Mr. Owens-Went through the ordinary nozzles from the fire box, and then we used my secondary air. My fire box was not over a cherry red. The heat went up through there, and it went right underneath the fire box and extended up, so that it pointed towards the center of the arch and went in a kind of half moon shape going in, and it all went up. There was no white heat in my fire box and in the arch.

Chairman-That seems to be different.

Mr. Douglas-We burned tar in two benches for about three months with very good satisfaction. They were not exactly the type of bench that Mr. Whalen used his on, but they were a bridge wall setting, and we used our secondary air all of the time. We cut out all our underdraft, and had everything plugged up tight, and while it was considerably harder on the bench than a coal fire would be, the result was not very bad, and they were in pretty good shape. We kept our heat very constantly. We did not have any trouble in carbonizing fully as much coal, about 315 pounds in four hours in the retort, about the same as we are doing with coal. We took our tar from the hydraulic main into the separator, but found that was not quite sufficient for the tar we required. We erected a steam pump from the tar well and pumped a constant stream and let it overflow. This kept it stirred up in the separator, and we used what was required from that, screening it through two or three screens. We tried several of those pipe burners, and one with fair success. They seemed to centralize the heat too much in one spot, and we finally went back to the old burner which my father designed some 15 or 20 years ago for burning oil. They used to burn crude oil in their benches. It consisted of two castings of conical shape, and turned up on the points, so that the inner cone screwed up to the outer cone, leaving only about a % inch aperture. This formed more of a whirling spray, and seemed to spread the tar. We tried all the pipe burners which have been described in the journals, but none seemed to work so well as this old burner.

The way I burned the tar, and I guess the most of us, we

would get a white hot furnace and spray the tar in there, and the instant the tar got in there, it exploded and gassified, and burned instantly, right at that point. It was a different way that Mr. Whalen burned it. It shot in this fire box with just enough heat to vaporize it, and the tar went through the fire arch in the form of vapor and a thick smudge, and the secondary air came over and burned that air and vapor, and it is the only proper way to burn tar because you can burn it in that way without any detriment to your bench.

Chairman-Through the use of secondary air?

Mr. Whalen-I found I had no trouble at all. I do not believe there is any particular damage done to the bench with tar. I believe it will make good bench fuel, if we can get some arrangement that will keep that thing going constanly all the time. I had no trouble keeping the heats up. I had no heat when it went through into the recuperators except when the burner was stopped up and turned on too much tar, and then we would throw it free. There would not be too much for the secondary to take care of, and it would not burn. I had one bench that I experimented upon, and worked on entirely for several days. I have decarbonized 13,000 pounds in 24 hours on that bench with four gallons per hour, and just about 100 pounds of fuel; but that was a case where I kept it constantly going all the time. On the other benches, where I didn't do so well, I took over five gallons per hour, but it wasn't able to keep the heats up-a waste of tar.

Chairman-That is a low quantity per ton.

Mr. Tippey-I have not had any experience recently with burning coal tar; but we had a relief holder partly filled up with water gas, oil and tar mixture, and we burned that under our boilers, and fed the tar by gravity. This was used under horizontal tubular boilers, with latterly, the grate bars within six or eight inches of the bottom of the ashpit, and kept a coke fire on top of the grate, so that if for any reason the tar stopped coming for a minute it would be sure and light when it came again. I used the Snell burners most sucessfully. They were made in the city here, a brass burner, and very good for burning tar. At the bridge wall we built two four-inch walls, on each side of the bridge wall, with a space of a foot between them, and that was built like checker brick in water gas works, so that the combustion would pass through the checkered brick in the first wall and whirl around in behind and strike against the solid face of the second wall and deflect and go through the opening. By that means we were able to get smokeless combustion and had very good success, and only quit when the tar was all burned up.