Low-Temperature Carbonization of Coal

Design of Plant for Low Temperature Carbonization
of Utah Coal by Karrick Process

by  William Larsen & Clifford Stutz

Thesis, University of Utah, B. Sci., Civil Engineering (May 14, 1932)


1.   History of Utah Coal [Not included here]
2.   Smoke Menace [Not included here]
3.   History Low Temperature Carbonization
4.   Process for Continuous Method
5.   Process for Batch Method
6.   Products Obtained from LTC (Smokeless Fuel, Oils, Gas)
7.   Sample Calculations of Heat Balance
8.   Design of Unit Plant (Location, Building Requirements, Gas Distribution)
9. Cost Estimates of Unit Plant
10. Value of Products per Ton of Coal Treated
11. Conclusions

1.  History of Utah Coal ~ [Not included here]

2.  Smoke Menace ~ [Not included here]

3. History Low Temperature Carbonization

Low Temperature Carbonization (LTC) of coal is not new. A great deal of scientific and technological work has been done on this form of coal processing in Germany, England, and USA. It is closely allied with the principles embodied in the industries which produce oil shale in Scotland and Australia. The subject began to receive governmental aid about 1906 and since then a great number and variety of processes have been developed, and patents issued. The most promising processes of treating coal have been developed to meet the needs of certain localities, viz., types of coals and economic factors.

The principle products of LTC are smokeless fuel, tar-oils and gas. From Utah coals particularly there may be produced tar acids, resins, and ammonia products. The quantities and characteristics of each of these products obtained from carbonization varies more with the type of coal used than with the method of heating. However, the temperature and time of heating greatly influence the yield and character of all the products. Hence the problem lies in developing a method of heating the coal which will best suit the particular needs.

There are two general methods of supplying heat, viz., external and internal heating. In the external heating method the coal to be treated is placed in an airtight cylinder of small diameter and heat applied to the outside. The volatile matters that are expelled are generally let off at one end if the cylinder is horizontal or at the top if vertical; although one important process was a perforated vapor takeoff centrally placed in which the vapors pass, and from which they are conducted out of either end of the retort.

In the internal method of heating coal, some inert gas that will not react with the coal when heated, and preferably will not dilute the gases, is passed through the charge to transmit heat to it. In a number of process, producer gas is used as the internal heating agent but this obviously gives a resulting gas of low fuel value.

Several of the processes that are developed by Mr Karrick from his studies of treating Utah coals differs from former processes in the type of heating medium used and the method of its application and the type of equipment. In one of the Karrick Processes superheated steam is used to transmit the heat to the sized, dust-free coal. Vertical metal cylinders insulated on the outside are used for retorts. The treating of Utah coal is easily accomplished by this method because (1) its highly volatile content of oils and gases are rapidly carried away with the steam into zones of low temperature; (2) Utah coal does not fuse nor disintegrate ion heating and hence allows the steam to distribute itself evenly throughout the charge during the entire process; (3) the rate and temperature of the heat applied controls the density of the treated coal product; (4) the oils and gas given off can be separated easily from the steam by use of fractionating condensers.

Mr Karrick worked on two general methods of treating Utah coals by this type of processing, viz., continuous and batch method. Figure 1 [Not included] is a sketch of the setup used in the continuous method at Pittsburg. The drawings in the back show the setup used in the batch method.

4. Process for Continuous Method

Magazine "e" delivers the sized and dust-free coal to be carbonized to the retort. The upper part of the vertical metal carbonizing chamber "g" is 10 feet high and 5 inches inside diameter increasing to 7 inches at "h" where superheated steam from the generator "a" is introduced through a manifold. Lower section "i" of the carbonizing chamber is 3.5 ft long and is externally heated electrically; "j" is the feeding mechanism used to discharge the devolatilized coal. "K" is a condenser for the heaviest oils, "l" is an air-cooled condenser which removes the tar and the steam; "n" is a scrubber and "o" is a gas meter.

The carbonizing chamber and supply bin was filled with sized coal and superheated steam was run upwardly through the charge until the temperature of the coal had reached the value for normal operation. The feeding mechanism was then started and all the charge passed through the retort. A quantity of coal was placed in the bin sufficient to occupy 3 hours of continuous carbonization was usually used.

In a commercial plant the retorts would be about 3 feet in diameter and 20 feet high. The superheated steam would enter at a temperature of 1200° degrees F under a pressure sufficiently high to overcome the friction of passage through the charge. Approximately one-half to one pound of superheated steam would be used for each pound of coal treated. Before discharging the product into cars or onto a conveyer belt below the retort saturated steam would be passed into the bottom of the lower bin and up through the charge in "p" so as to re-use this heat and reduce the temperature of the devolatilized smokeless coal.

5. Process for the Batch Method

In this method the retorts are metal cylinders 3 feet in diameter and 20 feet high with a capacity of 2-1/2 tons each, insulated on the outside with diatomaceous earth. The steam enters the charge through a manifold at the top of the retort and is led off at the bottom. In the batch method the coal is dried and preheated to 300°-600° F in the bunkers with flue gases. Superheated steam at a temperature 1000°-1400° F and under a pressure of several lb/sq inch blows through the charge from 2-3 hours depending upon the preheat of the coal and the size of the lumps. During this period the upper 2/3 of the charge is carbonized. Then the superheated steam is shut off and switched over into another retort and saturated steam is blown in for a period of 2-3 hours. Also oil may be vaporized or sprayed into the top of the retort at the end of the carbonizing period. The heat contained in the upper 2/3 of the charge is sufficient to superheat the entering saturated steam so that the lower third of the charge is carbonized by this reclaimed heat, while the oil vapors may also be cracked into gasoline. Either water or very wet steam is then passed into the charge to cool it down to 400 F or below before discharging.

In the batch process the coal is charged into the retorts in several graded sizes varying in the case of Utah slack coal from 1-5/8" to 3/8" diameter. The coarsest material is placed on the bottom with the finest on top. Large sizes of crushed power plant coal may also be treated by this method or by the continuous process.

The product at the end of the carbonization period is emptied into cars or onto a conveyer and is taken to the storage bins where it may be further screened into its different marketable sizes ready for shipment. The gas and oils are carried out with the steam and are separated in the condenser and separator units.

This type of crude oil produces a large quantity of carbon when it is cracked so that by passing the crude through the hot coke, causes a large part of the carbon to be released to be precipitated on the treated coal. The crude oils therefore are topped and the heavier portion is then passed down over the hot coke and the light vapors produced are condensed and run into storage tanks. The gas is separated and stored in a gas holder  ready for purification and distribution.

In a commercial the steam will be generated from the coal which is under 3/8" in diameter comprising part of the shipments of coal delivered to plant for treatment. The superheater will be fired either with the gas that comes from the process or with the fine coal, either stoker fired or with pulverized coal burners.

A small demonstration unit of the batch type is being used at the University of Utah for the purpose of producing test samples of smokeless fuels from the principal coal mines of the state. Representative samples of coal form Wyoming and Idaho also have been treated, the smokeless fuel product from each having been used in domestic heating appliances and were found to have the desirable kindling and burning properties.

His plant comprises a vertical steel cylinder into which sized, dust-free coal is charged, the coal being introduced so that the small lumps form the upper layers and the large lumps the base of the charge. The heating is accomplished by an atmosphere of superheated steam which flows down through the coal and in contact with the lumps.

Steam is supplied from the power plant and is superheated for use in the coal-treating unit by passing it through a spiral coil of 50 feet of 1/2" stainless steel pipe. The coil is set vertically in the annular space between a central core and an outer insulating wall. The steam flows downwardly through the coil while the heating gases pass upwardly around the coil counter-flow to the steam. The heating gases are derived from burning gas in a combustion chamber in communication with the superheater chamber. The flow of the steam is controlled by a regulating valve and pressure gauge at the inlet of the superheater while the burning of varying amounts of gas makes possible the heating of the steam to temperatures as high as 1600° F if desired.

In about 40 test runs recently made, the rate of oxidation of the hottest portion of the superheater tubing indicated that replacement of the hot end of the coil would not be required for possibly 200-250 hours. A new section of the coil recently installed was coated with an aluminum preparation which is claimed to resist oxidation at 1100° F. In larger units now being contemplated the hottest elements will be of calorized (aluminum impregnated) steel tubing which resists oxidation exceptionally well at 1600° F over long periods.

The steam passes out of the bottom of the retorting chamber mixed with the lubricated gases and oil vapors from the coal. It then passes into a "hot" condenser which permits the condesation only of the oils and resins that are heavier than water, and also prevents condensation of any of the steam. This condenser consists of two 7-feet lengths of 2" pipe set vertically and connected together at the bottom and having an oil drain at the lowest point. Inside the 2" pipes are twisted metal ribbons which fill the pipes giving a whirling motion to the stream of vapors and gases, thus causing efficient contacting of the fluids with the condenser walls. Outside of these pipes are 3" steam jackets 6-1/2 ft long with inlet and outlet control valves and a pressure gauge. By adjusting the steam pressure in the jacket the temperature of the condenser surface is readily controlled to condense out any portion desired of the heavy (high-boiling) oil. The steam enters the top of one branch of this condenser, then passes down and up the other branch and out at its top.

Following the "hot" condenser is a "cold" condenser consisting of a vertical water tank 10" diameter and 20' long in which is a double copper coil taken from a gas water-heater. The vapors pass down through this coil which is surrounded by a flow of cold water.  The condensed oil and water flow out of the condenser at its lowest point and thereby effects condensation by concurrent flow of the condensing vapors and condensed products which effects more efficient condensation of the lightest volatiles. The cooling water is coldest at the outlet portion of the condenser.

The condensed products pass form the "cold" condenser into an oil-water separator. This device is designed to permit long aquescent flow of the oil and water so as to enable then to separate well by difference in specific gravity. The device is a cylindrical tank set vertically, 12" diameter, and 6' high, and contains a spiral vertical wall starting at the center and passing 6 times around, thereby forming a continuous channel 1" wide by 6" deep and about 10 ft long. The oil and water enter by a drop-pipe at the center of the lid and pass through the spiral channel and are decanted through two goose-neck outlet pipes at the top and bottom of the outer wall of the tank, the water flowing out at the lower opening and the oil at the top opening. Receivers are provided for these products, also for the "hot" oil condensate.

The incondensable oil is burned at the top of a gas off-tube, or chimney, in the lid of the separator.

In normal operation of this LTC unit, a charge of about 15 lb of coal, sized to minus 1/5" plus 3/8", is placed in the retort with the fine coal on top and the coarse coal at the bottom. The lid is fastened down with a gasket and bolts making it gas-tight. The gas fire is started and within 10 minutes the steam attains a temperature of 1100° F, which temperature usually is used, this being below the temperature (1200° F) at which water gas begins to form from the reaction of the steam and the active low-temperature coke, also the temperature at which vapor-phase cracking of the oil vapors begins to occur. Higher temperatures are used when either of the above reactions are desired.

With 15 lb of coal in the retort, and a flow of approximately ½ lb of steam per minute at 1000° F to 1150° F, the charge of coal is distilled to a smokeless condition in 60-90 minutes. The treated coal, now rendered smokeless, is then dry-quenched by passing saturated steam through the charge.

If the coal is preheated, the distillation time and the quantity of steam is reduced. Also, the heat lost from the retort walls, trough insufficient insulation, is excessive and can be cut down greatly. With cooling water entering the "cold" condenser at 700° F and leaving at 120° F, there is required 14 lb of cooling water per minute or 1.7 gallons. Usually the superheated steam flow is continued until the distillation zone has passed 2/3 the way down the retort and then saturated steam is substituted. The latter steam becomes superheated in the top part of the treated coal and thence carries on the distilling to the bottom of the retort. This technic has the advantage of dry-quenching the treated coal while simultaneously completing the distillation.

6. Products Obtained From LTC Karrick Process

The desiderata of LTC are:

(1) The production of a popular smokeless fuel suitable for domestic and other purposes and at attractive prices.

(2) The maximum production of oil of low specific gravity which can be easily refined into suitable products for local markets.

(3) The maximum production of gas of high calorific value.

Smokeless Fuel: The smoke from fuel is due to soot which is unburned carbon and heavy tars that come mainly from incomplete burning of the oils and tars formed in the heating of the coal. When the volatile matter in Utah coal is reduced so that the coke contains 1% or less by weight, the resulting product is a smokeless fuel. The combustible nature of the carbon in the coal is not affected by LTC where the carbon is changed to a graphitic form which is difficult to ignite and burn in household types of heating equipment.

The ignition point of low temperature coke is practically the same as the coal from which it was made. The product resembles anthracite coal very much in its burning properties, although it ignites somewhat more readily and is freer burning. It burns with a shnort blue flame with no smoke and gives off a great deal of heat in the form of radiation. It has a much higher efficiency in burning than ordinary coal. The product looks very much like the coal from which it was made, but only weighs 60-75% as much.

Oils: When LTC of Utah coal is carried on until the product has less than 18% volatile matter remaining the yield of crude oils obtained will be approximately 30 gal per ton of coal treated. When this oil is cracked it yields 10 gal gasoline, 800 cu ft of 1300 Btu gas and 90-100 lb oil coke. The gasoline obtained resembles the present form of the best ethyl or other high anti-knock gasoline; "The chemical properties of oils arising out of the high olefinic content fit them for use in high compression motors" -- (Composition of Light Oils of LTC, by R.L. Brown and R.V. Cooper in Industrial & Engineering Chemistry). The oil coke is a very high quality product which can be mixed with low-temperature coke and sold for domestic fuel.

Gas: The analysis of the gases obtained in the LTC studies of Utah’s coals by Mr Karrick in the large-scale experiments conducted at the Pittsburgh experimental Station and were reported by F.E. Frey and W.P. Yent are given in Table 1. From the inspection of the last two items in each column it can be seen that as the temperature of the steam is raised the volume of gas produced is increased with a corresponding decrease in the Btu value. The calculated Btu given for temperature of 1115° F seems to be in error. If this is the case, then with a temperature of 1115° F a gas with a Btu value of 1000 Btu per cu ft could be obtained. Also, at 1200° F the fuel value should be about 9800 Btu/cu ft.

If the product is not heated to a temperature above 1200° F the gas formed is a truly low-temperature gas, but if 1200° F is exceeded steam and coal react with each other and form water gas. This gas has theoretically a Btu value of from 217-324 Btu per cu ft depending on the amounts of H2, CO and CO2 formed, hence it is a diluent and may be undesirable. Also when this gas is produced the quantity of low-temperature coke obtainable is diminished. This gas is very good for household use having a calorific value comparable with natural gas and burns with an inoffensive odor.

Table 1: Gas Analysis (Unscrubbed Gas)

Constituent %     @ 935° F %     @ 1115° F %     @ 1290° F %     @ 1560° F

CO2                   22.3                  18.6                  15.0                  13.1
Nitrogen               1.2                     1.0                    0.4                    0.6
Oxygen                 0.2                     0.0                    0.0                    0.2
Hydrogen              3.2                   10.1                  12.8                  21.9
CO                       9.8                    11.5                  10.4                  10.0
Methane              35.7                   40.3                   41.6                  38.5
Ethylene                 2.7                     1.9                    2.0                    1.8
Ethane                  10.8                    7.4                    8.3                    6.6
Propylene               2.6                    1.8                    1.75                   1.65
Propane                 4.5                     2.7                    2.9                     2.6
Butylene                 2.0                     1.4                   1.45                   0.96
Butone                   1.5                     0.95                  1.0                     0.61
Liq. HCs               0.18                    0.12                  0.13                   0.10
Total HC             24.1                    16.15                  17.4                  14.22
H-Sulfide 2.7        ---                       1.8                     ---
Total %                 93.5                  97.8                     97.6                  98.5
Btu Calc’d.           992                    856                      896                  822
Btu Actual 1065    880                    915                      835
Cu Ft/Ton 960      1325                  1711                   2954

Industrial & Engineering Chemistry, vol 19 (1927)

7. Sample Calculations of Heat Balance

Heat Exchange: There are several methods of regulating the transfer of heat, to the coal for carbonization, and away from it after the process sis completed. Among some of the methods that have been investigated are the following:

Assumptions --
(1) Coal dried and preheated to 300° F in bunkers
(2) Superheated steam (1400° F)
(3) Period of superheating: 2 hours
(4) Coal carbonized 2/3 of way down at end of 2 hours
(5) Steam leaves at average temperature of 800° F
(6) Each retort holds 5000 lb coal
(7) Coal cooled with saturated steam.

Heat lost per lb of superheated steam = ( 1400 - 800 ) / 0.5 = 300 Btu.
Heat taken up by coal that is carbonized in upper 2/3 of retort =
2/3 x 500 x 2/3 (*a) x 0.20 (*b) [ 1200 - 933 (*c) / 2 ] - 300 ] = 340,000 Btu.
Heat taken up by coal in lower 1/3 of retort =
5000 x 1/3 x 0.31 (d) [ 866 (*e) – 300 ] = 292,000 Btu
Total heat taken up by coal = 632,000 Btu.
(*a) Spec. weight of the coke = 2/3 sp wt of coal; (*b) sp heat of coke = 0.20; (*c) temperature at 2/3 point is 933 F; (*d) sp heat of coal = 0.31; (*e) average temperature in lower 1/3 of retort.

Number of lb superheated steam required = 632,000 / 300 = 2106 lb.
Heat given off by coke in upper 2/3 when cooled to 400° F =
3333.3 x 0.75 ( 1066 - 400 ) / 0.2 = 334000 Btu
Heat given off by coal in lower 1/3 when cooled to 400° F =
1667 x 0.3 (866 - 400 ) = 233,000
Total heat given off = 567,000 Btu

Heat taken up per lb of saturated steam when heated from 225° F to 400° F =
175 x 0.5 = 87.5 Btu.

Number taken up per lb of saturated steam required =
567,000 / 87.5 = 6430 lb

Total weight of water required in the form of steam = 8536 lb

Heat given up per lb by the steam when cooled and condensed from 800° F to 190° F =
[ ( 800 - 220 ) x 0.5 / ( 1100 - 190 ) ] = 1100 Btu/lb.

Heat given up by a superheated steam = 1100 x 2106 = 2,320,000 Btu

Heat given up by saturated steam if cooled and condensed from 400° F to 190° F =

[ ( 400 - 220 ) x 0.5 / ( 1100 - 190 ) ] x 6430 = 5,787,000

Total heat to be taken up by cooling water when 70° F to 190° F = 120 Btu/lb.

/\ Number of lb water required =
8,107,000 / 120 = 62,500 lb

/\ Total water needed = 71,036 lb per lb

Rate = 71,036 / 2 x 62.5 x 3600 = 0.158 cu ft/sec.

Assumptions --
(1) Coal dried and preheated to 300° F in bunkers.
(2) Superheated steam at 1400° F is passed into charge for 2 hours.
(3) Heat is transferred from one retort to another by passing the gases out of the bottom of the hot charge up through the bottom of the cold charge.

Temperature gradient in charge before the superheated steam is turned will vary from 500° F at bottom to 400° F at top.

Heat given up by superheated steam when cooled from 1400° F to 800° F =
( 1400 - 800 ) x 0.5 = 300 Btu/lb.

Number of lb steam required =
825,000 / 300 = 2750 lb

Heat taken up by cold charge from hot gases =
( 450 - 300 0 x 0.3 x 500 = 225,000 Btu.

The remaining heat above 400° F will have to be removed by water or saturated steam.

Heat given up by steam when cooled and condensed from 800° F to 190° F =
( 800 - 220 ) x 0.5 / 970 / 30 = 1290 Btu per lb steam.

Heat taken up per lb of condensing water used when it is heated from 70° F to 190° F = 120 Btu.

/\ Number of lb of condensing water required = 1290 x 2750 / 120 = 29,800 lb.

Assumptions --
(1) Coal dried and preheated in bunkers with flue gases to 300° F.
(2) Heat supplied by superheated steam running for 2 hours at same rate as the superheated steam and finished cooling with water.
(3) Charge cooled with saturated steam running for two hours at same rate as the superheated steam and finished cooling with water.
(4) Temperature at 2/3 point when superheat is shut off is 900° F. The amount of heat required to carbonize upper 2/3 =
( 1050 - 300 ) x 0.2 = 150 Btu/lb of coke

Amount of heat taken up in upper 2/3 =
5000 x 2/3 x 2/3 x 150 = 333,330 Btu

Amount of heat taken up in lower 1/3 =
5000 x 1/3 x 0.3 ( 650 - 300 ) = 275,000 Btu

/\ Total heat supplied = 608,333 Btu.

Heat taken out of superheated steam when it is cooled from 1400° F to 800° F =
( 1400 - 800 ) x 0.5 = 300 Btu/lb

Number of lb superheated steam required to carbonize the coal =
608,333 / 300 = 2026. 67 lb.

Heat given up by coal in lower 1/3 of retort when cooled to 400° F =
5000 x 1/3 x 0.31 ( 850 - 400 ) = 225,000 Btu

/\ Total heat given up by coal = 514,000 Btu

Heat taken up by saturated steam when it is heated from 225° F to 400° F =
175 x 0.5 = 87.5 Btu

If 2026.67 lb saturated steam are introduced, heat taken up =
2026.67 x 87.5 = 177,000 Btu.

Amount of heat left in charge to be removed =
514,000 - 177,000 = 337,000 Btu.

Latent heat of water = 1000 Btu/lb.

/\ Amount of water needed to finish the quenching =
337,000 / 1000 = 337 lb.

Total water needed in form of steam and water = 4390.34 lb.

Heat given up per lb of steam when cooled and condensed from 800° F to 190° F = 1290 Btu per lb of steam.

/\ Number of lb of condensing water required =
1290 / 120 x 2026.67 x 2 = 43,500 lb.

In the first method of heat transfer, no additional apparatus is needed to extract the heat from the charge before taking it from the retorts. However, a great deal of water will be necessary for the procedure.

The second method makes the most economical use of heat possible. It requires the least amount of steam and water but does require the installation of additional apparatus in the form of pumps and insulated piping.

The third method is similar to the first except that water is used for part of the quenching. The main objection to this method over the first method is the additional piping required and also the inexact method of determining the quantity of water needed to just quench the product and not leave it wet. In a small plant such as the one designed for a test plant, the first or third methods of heat transfer would be used. But in a large installation the second method would be justified and most economical.

8. Design of Unit Plant

Since Mr Karrick’s return from Pittsburgh, where he carried on extensive research work on Utah coals for the production of a smokeless fuel, he has been advocating the building of a commercial plant. In a discussion of the possibilities of producing smokeless fuel, at one of the Smoke Abatement Committee’s meetings, it was decided that without plans, specifications, and estimates of construction and operating costs being drawn up, no accurate knowledge of the economics of Mr Karrick’s project could be obtained. The Committee finally agreed to instruct the Research Department of the University of Utah to prepare plans for the smallest sized unit of a treating plant that could use commercial sized retorts and other equipment. $50,000 was suggested as the appropriate cost of such a plant.

Under the direction of Mr Karrick, Mr Wardrop and Dean Ketchum, a unit plant has been designed to be presented to the Smoke Abatement Committee.

Location of Plant: From economic considerations as well as convenience and desirability, a location for the test plant has been selected at Spring Glen, Utah…. [ etails not included here ].

Building Requirements: In building a unit plant for demonstration purposes it is very desirable to construct it as a large commercial plant would be constructed only smaller in size. Or, in other words, the handling of the coal, the oil, the smokeless fuel, and the gas will be handled in the same manner as in a commercial plant. The coal will come in car loads lots, unloaded, stored and charged into the retorts with mechanical equipment. The products will be led off, separated, and refined ready for market. Everything will be run in a systematic orderly manner so that information regarding any part of the process can be obtained and experimental work done to improve the processing or the products produced.

This grouping of the entire process together is very important on a test plant of this sort because:

(1) It is very difficult to get cost data where the processing is scattered out.

(2) It is very difficult to keep account of all products produced, such as the gas, tar acid, resins, etc., that are produced when the crude oil is cracked and refined.

(3) The cost of shipping crude oil great distances prohibits its refining.

(4) It makes possible the study of the byproducts and methods of processing.

The plant is designed for minimum operation cost, hence all materials will be handled mechanically to do away with hand operations as much as possible. In deciding on the capacity of the plant, an arbitrary figure was chosen at about one carload per day. This gives 30 tons to be treated and 10 tons to be used as fuel under the boilers every 24 hours.

In buying the coal to be treated, it will be specified that the slack shall not have over 25% that will pass through a 3/8” screen. It will be necessary to make these specifications because in ordinary 1-5/8” slack over 68% will pass through a 3/8” screen, as shown on the screen data curves. This, however, will not place any rigid requirements on the mining interests, but will keep the mine sweepings out of the coal purchased.

The accompanying flow sheet shows what products go into the process and what products come out. Drawings of the plant arrangement and of the apparatus used are included in the back. [Not available]

The track hopper is of the standard Jeffery type, with a capacity of 80 tons or two carloads. This capacity will, with the bunkers full, provide for a 3-day run without replenishment. A standard Jeffery elevator is used to raise the coal from the hopper to the screens, 65 feet above the tracks. It has a capacity of 5 tons per hour so that the bunkers can be filled in 8 hours or during one shift.

The screens are of the shaker type and with the same capacity as the elevator. They divide the coal into 4 sizes: one below 3/8” diameter and three over 3/8”.

The four bunkers each have a capacity of 10 tons so that a car of coal can be screened into them at one time. The three bunkers that feed the retorts are equipped with hot gas heaters that allow the hot flue gases from the superheater to blow up through the coal to dry and partly heat it before it is charged into the retorts. The bunkers are made of steel plates with sloping bottoms that direct the coal to the spouts.

A steel monorail larry car of about one ton capacity is used to load the retorts. It is operated by hand from the loading platform. There are three steel retorts with accommodations provided for one more. They are 3 feet in diameter and 15 feet 9 inches high with a capacity of 2-1/2 tons each. The retorts are made of ½”steel plate and insulated on the outside with 12” of diatomaceous earth, that is held in position by another metal cylinder. In order to take care of the thermal expansion, the retorts are hung from the top and rest on a ball bearing with side supports and a spring arrangement, as shown in the detailed sketch, to keep them straight. The coves for the top and bottom openings are designed to allow for no leakage of steam during expansion by having a knife edge around the lid press against a ring of asbestos packing. The bottom of the retort had to be contracted so that the bottom door would not be too heavy. A door the same size as the cross-section of the retort would weigh 1000 lb, and hence would be too heavy to manage by hand. A chain with crossbars on is hung down through the center of the charge. When the charge is ready to be taken out, the chain is jerked up, with a hoist, which loosens the charge so that it will fall out.

The steam is led in at the top through a specially designed connection and valve to take care of the thermal expansion, as shown in detailed drawing. The steam and gas are led through a hot condenser where the heavy oils are taken out. The gases then go to the cold condenser where the steam and oils are condensed and the gas led off. The condensed liquid then goes to the separator where the crude oil and waste water are separated. The gas is first scrubbed and then stored in a gas holder. The crude oil is taken to the crude storage tanks before being cracked and refined

The hot condenser reduces the temperature of the steam and gases from 800° F to 240° F and is designed to handle 2000 lb of steam per hour. In this condenser about 630,000 Btu are removed per hour. The cold condenser is designed to reduce the temperature of the gases to 120° F. Its capacity is for 2000 lb per hour. The condensing water used enters at 70° F and leaves at 120° F. About 18 gal per minute of condensing water will be required.

The smokeless fuel is dropped into cars beneath the retorts and then hoisted to the storage bins where it is screened into 3 marketable sizes before going into covered bins ready for shipment. Each of the 3 bins will have a capacity of about 30 tons.

The superheated steam supplied to the retorts comes from a gas-heated superheater. The superheater is 6’8" x 5’11" x 15’ 6" and is made of refractory brick. The pipes have a heating surface of 880 sq. ft and a capacity of 1500 cu ft per hour and a steam velocity of 240 ft/sec. In the lower 3-1/2 feet 1-1/2" calorized pipe which is good for 1600° F without corroding is used. In the upper 8-1/2 feet standard 1-1/2" steam pipe is used. Arrangement of the tubing, as shown in the detailed drawings, is made so tha the pipes can be repaired when they become corroded, by having valve arrangements at the bottom to shut off any section independent of the rest of the superheater. The pipes have RR unions on the bends with loose bricks opposite them in the walls so that the pipes can be removed.

A 50 kw turbine generator set will be used to supply light and power to the plant.

In the test plant a large quantity of gas (3000 cu ft/ton) is produced during the treatment.

As a supplementary source of revenue we have planned to distribute this gas [locally -- section not included here]

It would be wise to consider a distributing system for gas when a plant is built.

9. Cost Estimate of Unit Plant

[ 1932 $$ not included except examples for comparison to modern costs ]

4     Retorts   @ $653 = $2612
2     Condensers  @ $1500 = $3000
1     Separator
1     Feed Pump & Motor (12 gpm)
1     Condenser Pump & Motor
1     Boiler Stoker & Air Pump, &c
1     Boiler (Locomotive type)
1     Superheater
1     Elevator (70 ft Jeffrey type) & Motor
4     Bunkers
1     Screen & Shaker ( 5 tons/hr) & Motor
1     Steel Stack erected
1     Larry
       Steam Piping
       Gas Piping
       Flue Gas Piping & Fan
1     Track Hopper complete
       Retort House
       50 kw Electric Power
       Relief Gas Holder (30,000 cu ft)
2     Oil Tanks 500 Bbl
       Spur Tracks
       Coke Storage
Total Cost Estimate [ 1932 $$ ] = $ 44,193

Coke Storage Bins & Car Equipment:
Screen ~ Column & Beams ~ Sides, steel ~ Track ~ Car ~ Hoist.
Total Cost Estimate [ 1932 $$ ] = $ 4117

2    8" T-Beam Trolleys
1    3’6" x 7’6" x 30" x 1/8" Plate (40 sq ft 1/8" Plate)
1    Discharge Gate 1/2 x ½ x 1/8 x 14 ft

Unit Plant Estimate

Steel Coal Bins:
2    Chanels, 6" x 15 ft long, 240 lb)
12  I-Beams 6" (1215 lb)
3    Angles 3 x 3 x Ό x 8-1/4’ long (122 lb)
6    Angles 3 x 3 x Ό x 10 ft long (300 lb)
3    Chanels 6" x 33 ft (792 lb)
3    Chanels 6" x 15 ft (550 lb)

3/16" x 14’ x 18’ Bottom 3 Bins (252 sq ft)
3/16 x 10 x 9 Bottom 1 Bin (90 lb)
3/16 x 24 x 6 Front 4 Bins (144 lb)
4 x 3/16 x 10 x 4 Sides 4 Bins (40 lb)
1/8 x 24 x 6 Front 4 Bins (144 lb)
4 x 1/8 x 10 x 4 Sides 4 Bins (40 lb)
Total 184 sq ft
Erecting Labor: $ ---

Retort Discharge Piping to Condensers:
4     Valves 3"
7     Screwed elbows 3"
3     Tees 3"
4     Pipes 3" x 3’10" ( = 12’ 0")
2     Pipes 3" x 5’ 0" ( = 10’ 00")
1     Pipe 3" x 4’ 00" ( = 4’ 00")
1     Pipe 3" x 4’ 6" ( = 4’ 6")
1     Pipe 3" x 1’ 8" ( = 1’ 8")
1     Pipe 3" x 5’ 6" ( = 5’ 6")
1     Pipe 3" x 1’ 9" ( = 1’ 9")
1     Pipe 3" x 2’ 0" ( = 2’ 0")
Total Pipe: 3" x 43’ 5"
1     Pipe 1" x 20’ 0"
9   &nb"p; Elbows 1"
1     Pipe 12" x 20’ 0"
2     Flanges 12"
2     Flanges 12” Blend
Installation Labor: $ ---

Hot Piping Top of Retorts:
4     Flanged Elbows 5"
4     Screwed Elbows 5"
10   Expansion Bellows
2     Pipes 5" x 5’ 6" ( = 11’ 0")
2     Pipes 5" x 1’ 3" ( = 2’ 6")
2     Pipes 5" x 3’ 0" ( = 6’ 0")
2     Pipes 5" x 2’ 0" ( = 4’ 0")
1     Pipe 5" x 6’ 0" ( = 6’ 0")
4     Pipes 5" x 5" ( = 1’ 8")
Total Pipe 5" x 29’ 2"
4     High Temperature Valves 4"
7      Pipe Flanges 5"
Installation Labor: $ ---

Steel Bill -- Retort House: [Not included here ]

Retort Estimate:
1     Top Door Cr-Steel  95 lb
1     Top Ring --  70 lb
1     Bottom Ring “  170 lb
1     Bottom Door  --  120 lb
1     Inner Shell, steel plate  2900 lb
7     Rings, 3/4"    332 lb
8     Castings, 38 lb   304 lb
1     Outside Shell   269
253 Rims
Pipe 5"
Diatomaceous Earth   100 cu ft

Superheater Estimate:
155   Pipe 1-1/2" x 5’ 0" ( =… 775’ 0")
65     Pipe 1-1/2" x 5’ 0" calorized ( = 325’ 0")
5       Pipe 1-1/2" x 6’ 4" ( = 32’ 0")
5       Pipe 1-1/2" x 6’ 4" calorized ( = 32’ 0")
5       Pipe 1-1/2" x 7’ 0" ( = 35’ 0")
5       Pipe 1-1/2" x 7’ 0" ( = 35’ 0")
240   Elbow Union RR 1-1/2"
240   Elbows, Mal. St. 1-1/2"
10     Gate Valves 1-1/2"
10     Plug Cocks, spec. alloy, 1-1/"
1      Pipe 5" x 6’ 9" std.
1      Pipe Flanges 5", pair (2)
1      Pipe 5" x 6’ 9" Ex .Hy.
1      Pipe Flange F.S. 5"
3000  Fire Brick
3000  Common Brick
115’   Special  Lining 3"
Bricklayer labor
Fire Brick Doors
Installation Labor: $ ---

10. Value of Products per Ton of Coal Treated

[1932 Prices, not included here]

Smokeless Fuel, 1200 lb.
Assume coal to be screened into 3 sizes (Large, Medium, Small).
Freight = $ ---
Wholesale Price of smokeless fuel = $ ---
Therefore value of 1200 lb of smokeless fuel = @ ---
Tar Oil, 30 gal per ton of coal. This will crack into 10 gal gasoline (value: $ ---), 800 cu ft 1300 Btu gas (value: $ ---), 5 gal kerosene (value: $ ---), & 89 lb coke (value: $ ---).

Gas: 2200 cu ft of 950 Btu gas are produced per ton of coal treated. Value: $ ---. Gas will have no actual value unless sold.

Total Value of Products: $ ---

Cost of Producing per Ton of Coal Treated

Cost of Coal:
Cost of  4/3 x 2000 lb @ $ --- per ton = $ ---
Cost of Labor @ $ ---/hr & 2 men/shift = $ ---
Cost of Water @ $ --- per 100 cu ft & using 0.13 cu ft per second = $ ---
Interest on Investment ($ 44,193)/ton
Total Cost per Ton = $ ---
Income per Ton = $ ---
Cost per Ton = $ ---
Profit & Depreciation = $ ---

11. Conclusions:

Utah has a natural resource, coal, which in its dormant state means little but if developed will give to Utah a gigantic industry.

Although Utah has a huge supply of coal, its present method of use is undesirable. The burning of coal by hand-fired burners has created the smoke menace. To surmount this problem, a plan has been presented, namely the Karrick process of low-temperature carbonization. In this process, valuable oil, gasoline, and gas are obtained from the coal, leaving a desirable low-priced smokeless fuel.

From the figures given, it is seen that the process is justifiable, economical, and scientifical. A commercial test plant can be built which will, without a doubt, pay dividends.

As a sideline a distributing system of the gas obtained from the treating of the coal can be constructed to a benefit.

It is our sincere recommendation that such a plant as herein shown should be given a fair trial.


Parker, E.W.: "Coal"; USGS Min. Res. # 110
Industrial Commission Report Bulletin # 4
Spieker, E.M.: Geology of Utah Coal Fields
Parr: Univ. Illinois Bulletin: "Low Temperature Distillation of Coal"
London: Low Temperature Carbonization
Lander & McNary: Low Temperature Carbonization
Bell, H.S.: American Petroleum Refining
Brown, R.L.: Composition of Light Oils from LTC of Utah Coal
Ind. & Engg Chem., vol 19 (1927)
Frey, F.E. & Yant, W.: Fractional Analysis of Gas from LTC of Coal