Low-Temperature Carbonization of Coal

Feasibility of a Pilot Plant for Treating Coal by the Karrick Plant

by Richard Ketchum

Report to the Joint Smoke Abatement Committee

October 28, 1932

As per your verbal request at your meeting March 30, 1932, we are submitting the following report relative to plans and estimates for a pilot plant to treat coal by the Karrick Process.

You will recall that under our instructions we were to make a study of the possibility of building a pilot treating plant for the sum of $50,000 mentioned at the meeting as an approximate total cost of said plant. With this figure in mind we proceeded with the work, Mr Grover Wardrop doing the designing with the close supervision of Mr Karrick and with such assistance as I could render. Also Mr C. N. Stutz and Mr Wm. Larson, senior civil engineering students assisted materially in compiling data and in computations, and their thesis now in the Engineering Library at the University of Utah is a valuable treatise on this subject. We also refer you to the thesis by Mr Schmutz of the School of Business on the oil reserves and oil shales of Utah, which is now in the University library. During the time that Mr Wardrop worked on this project, Mr Karrick carried on further coal tests in the laboratory at the University, and was assisted by Dr C.R. Kinney of the Chemistry Department, verifying and demonstrating the various steps of the process of various Utah coals. Arrangements were thus made for Mr Karrick and Mr Wardrop to have close contact throughout the work.

This report includes the following drawings: [Drawings not included here; they were too pale to photocopy (at the University of Utah Special Collections)] Location Plan ~ General Layout of Plant ~ Flow Sheet of Refinery ~ Flow Sheet of Retort Process ~ Retort Detail -- Structural Setting ~ Superheater ~ Retort House -- Elevations -- Section Plan-Steel Framing ~ Storage Bins for Finished Coke ~ Oil Refinery Outline ~ General Plat.

Smoke Elimination for Salt Lake City ~

No arguments need be given relative to the economic importance of smoke elimination for Salt Lake City. The exodus of many of our best citizens from Salt Lake in recent years because of the intolerable smoke condition in the minter months makes it imperative that a complete solution of this problem be effected at once if we are to maintain even normal growth for our city. We have gas for those who can afford it, we have stokers for some residences and apartment houses, but we still have smoke produced by kitchen ranges, heating stoves and hand-fired furnaces to such an extent that already in 1932 the familiar black blanket of dense smoke has appeared, much to the disgust of everyone. No one who can afford to move out will live here under such conditions.

Present Heating & Cooking Equipment in SLC ~ [ Table not included here ]

The obvious conclusion from the above data is that a suitable solid smokeless fuel must be provided if the smoke cloud is to be eliminated.

To build a pilot plant for the treatment of Utah coals, and to run such a plant for a year or two, we believe, would contribute largely to the solution of SLC’s smoke problem and add valuable information toward the development of Utah’s greatest resource. A slight change in the market favoring better prices for coal, oil and gasoline would at once make this type of development very attractive. The cost per ton capacity for this small pilot plant is high and the labor cost is high, but the capacity could be doubled at comparatively small cost and we believe the operation would then be more economical. However, we have confined this report to a pilot plant of smallest practical capacity to represent commercial operations. This was done in order to keep within your instructions as nearly as possible, and to determine facts that might guide us later in the design of a large commercial plant. We do not believe it practicable to design a large commercial plant until a pilot plant is run long enough to ascertain all the facts. We know of no other way to get these facts.

It is likely that Utah coal fields will eventually be large users of power, and this power could be a by-product of this process of treating coal in Carbon County. The large amount of gas thus produced could be converted into power and the gas also used in the mining towns and for future industries.

In view of the importance of the experiment to the State of Utah, we recommend that steps be taken to finance such a plant as is herewith described.

In conclusion we wish to state that this report could not have been prepared without the help of Mr Karrick, who has furnished practically all the data relative to the process.

This is the first attempt to make plans and specifications for a commercial sized coal plant using the Karrick process.

Location of Plant ~

After preliminary studied of the possible sites for the plant it soon became apparent to us that the proper place to build such a plant is in Carbon County near the mines.

[Freight] rates on coal from the mines to the plant and on the treated coal from the plant to SLC were the basis for selecting the Carbon county site.

Type of Plant ~

We propose to build a plant to treat one carload of coal per day. The coal is to be dumped into track hoppers on plant spur as shown in plant layout, then elevated to screen, sized and thence taken to bins over retorts. The retorts to be charged by weigh-lorry on weigh. Retorts will drop treated coal into car which is drawn up incline over screen where coal is sized and delivered into finished bins from which it falls by gravity to railroad cars for shipping.

The building is a steel frame with corrugated iron roof and siding housing elevator, bins, retorts, boiler, generator, superheater, and condensers.

Process ~

The treating process in this pilot plant contemplates the treatment of 2" slack. This must be purchased with the understanding that it will contain the normal distribution of sizes with not over 25% below 3/8". In this plant we will use the fines for boiler fuel. The superheater will be fired by gas formed by the distillation of the coal. The combustion chamber of this superheater is designed to burn either gas or fine coal fed by a stoker. The above percentage of fines is ore than sufficient to take care of the plant fuel requirements.

The screens divide the dust free coal into three sizes of approximately equal amounts.

5,000 pounds of sized coal is charged into each of the retorts with the largest size forming the bottom third of the charge, the second size forming the middle portion, and the smallest size forming the top third of retort charge. The retort is closed and the coal is then ready for treatment by low temperature carbonization.

The carbonization is affected by internal application of heat, superheated steam being the distilling medium. The superheated steam is derived from the boiler. After expanding the steam through the 50 kw turbo-generator it is passed through a separately fired superheater and thence into the top of the retort. From the top of the retort the steam passes down through the charge thereby surrounding the coal and heating all the lumps uniformly. The steam is delivered into the retort at temperatures between 900 degrees and 1400 degrees F, the temperature depending upon the yield and character of products desired. The steam is generated at 200 pounds pressure in the boiler and expands to 35 lbs pressure in passing through the turbine, and further expands to 10 lbs pressure in the superheater and enters retort at this pressure.

The steam on passing through the charge distills the oil and gas from the coal, beginning at top of charge and passes continuously down to the bottom of the retort. The released gas and oil vapors mix with the steam and pass down and out of the retort through bottom connections to the condensers. When the distillation zone has passed approximately 2/3 the way down from the top of the charge, the flow of superheated steam is diverted into another retort, and saturated steam becomes superheated on entering the highly heated toper of the charge and on passing down serves to transfer the heat down through the charge and complete the distillation of the lower portion of the charge, thus effecting economy in the use of superheated steam.

The hot volatiles and steam coming from the first retort, as the distillation zone approached the bottom, are diverted into the base of a third retort containing a new charge of coal, thus serving to preheat the fresh charge. The saturated steam passing into the top of the first retort simultaneously serves to cool the distilled coal. The flow of this steam is continued, however, after the distillation has been completed and until most of the sensible heat has been transferred into the charge of fresh coal in the adjacent retort. The cooled charge of treated coal is now dumped from the first retort and a fresh charge introduced. The superheated steam is now diverted from the second to the third retort whereupon saturated steam is introduced into the second retort and the issuing hot volatiles pass into the first retort to preheat the fresh charge. Thus the cycle of preheating, distilling, and dry-quenching is continuous and with minimum consumption of fuel and superheated steam.

The above is a description of the ideal heat cycle but in the design and proposed operation of the pilot plant we propose to simplify the plant by omitting a part of the cycle. Since we will have an excess of fuel under the above plan of operation of the pilot plant, there is no immediate necessity of extreme steam economy. Therefore we propose to cool the charge solely by the use of wet steam which will be obtained largely from one of the condensers which operates on the evaporator principle. That is, as one charge is being distilled, the previous charge will be undergoing dry-quenching as indicated above. Under this plan water may be atomized and carried with the steam into the charge being cooled. When the treated coal has been cooled to below 400 degrees F it will not ignite on exposure to air. After the charge is cooled it is dropped into car and taken to bins as described.

Equipment ~

All equipment is described in the rough draft of specifications hereto attached. These specifications give sizes and general information but owing to limitation of funds for this work they are not in sufficient detail to use in present form to request bids.

Basis of Design

Superheater ~

This unit was designed for a capacity of 1,500 lb of steam per hour superheating same from the temperature of turbine exhaust at 35 lb to 1400 degrees F and 10 lb  pressure.

Retorts ~

The estimate includes one spare retort, a total of four, but three only are used simultaneously. Assume 40 tons slack coal received. Ten tons of fines less than 3/8" to be used for fuel for process; 30 tons to be treated, each retort being charged four times in 24 hours. Retort capacity of untreated coal 5000 lb each; weight of treated charge 3333 lb.

Time of Cycle ~

(a) Superheated steam flows through charge for 3 hours (distilling)
(b) Cooling steam flows through charge about 2 hours (preheating and dry-quenching)
(c) Discharging and charging, one hour.

Total time of cycle, 6 hours.

The retorts to be of 1/2" steel and not lined in this pilot plant. The retorts are provided with a flexible top and bottom support so as to allow for vertical and lateral movement.

The design and estimate also provides for corrosion resisting metals in the superheated steam lines and valves.

Apparatus has bee provided for supporting charge in retort during distillation to regulate compression of charge and to assist in discharge of treated coal.

Condensers ~

A steam-jacketed hot condenser receives the evolved gases and vapors directly from the retort and serves to condense the high boiling oil which are heavier than water. This condenser also functions as an evaporator and produces a part of the cooling steam.

A second cold condenser containing water completes the condensation of the oils lighter than water and the remaining steam.

The two condensers function together as a means of readily separating the oil and water, the total crude oil having a specific gravity approximately the same as water.

These two crude oil condensates may be combined or stored separately, depending on the products desired.

Power ~

We contemplate using a 50 kw, 3600 rpm AC generator unit. The coiler steam at 200 lb pressure will be expanded through the steam turbine and exhaust at 35 lb pressure. This steam then enters the superheater and becomes the process steam for the coal treating operation. This 50 kw unit will thus utilize the steam required in processing the coal and will supply ample power for all of the pilot plant requirements.

Water ~

[Not include here ~ local information, not pertinent]

Fire Protection ~

[Not include here ~ local information, not pertinent]

Refinery ~

If the building of this pilot is to obtain results, we recommend that it include a refinery to produce the finished oil products that can be marketed in Carbon County. Laboratory results in the State and Federal investigation have proved conclusively that good quality products can be obtained from the oil. A large part of the revenue must come from the refinery products and the main justification for this report and further consideration of the subject is the fact that the Utah coal fields are in reality one of the largest proven oil fields in the United States. A slight change in our economic conditions affecting oil markets favorably might easily make the results that may be obtained from this complete pilot plant of immense importance to the future of Utah. Further we believe that by placing the refinery at the plant the operation of this small pilot plant will be self-sustaining as shown by the estimates, and may therefore be prolonged to any desired length of time, thus making it possible to study the various phases of the problem, quality of products, markets, reaction of the public to the use of the smokeless fuel and other products, or community needs.

Our estimate therefore includes the necessary equipment for a 20 bbl per day refinery. The yield of oil is about 30 gal per ton of coal treated. The operation of this refinery will coordinate well with the operation of the treating plant, requiring very little additional labor.

Note the only products for revenue considered in the estimates are treated coal, gasoline and kerosene. There are other products that will be produced in the refinery: One ton per day oil carbon; 15,000 cu ft of 1300 Btu gas; and about one bbl of cresols. Ammonia gas or ammonium sulfate may also be obtained.

Gas ~

When the details of the pilot plant operation have been perfected sufficiently, then steps should be taken to connect the plant by gas lines to [towns]. This pilot plant will provide adequate 1000 Btu gas.

Quality of Fuel Product ~

According to work done at Pittsburgh the following is a comparison of quality of raw and treated King Coal No. 1 mine:

Quality    Raw Coal  Treated Coal
BTU        12750   12500  Loss 2%
Volatiles   43%   10%
Ash    6.5%   10%
Combustion Efficiency 45%   60%  Increase 33%

Actual househeating studies made at Pittsburgh with the raw coal and with the treated coal from Utah, showed under a wide range of firing conditions an increased heating efficiency from 10% to 30%. In other words, the treated coal will in no case give as low heating efficiency (heat delivered to the house) as with raw coal and on an average, will give 20% more actual delivered heat.

The treat coal burns very much like anthracite but it is easily ignited and nis very satisfactory for kitchen ovens. It is an ideal fuel for fireplaces.

Estimate of Cost ~

[$ amounts are not included here; they are outdated and must be recalculated for modern values]


Total Cost of Retorting Plant
Total Cost of Refinery
50 kw Generator Unit

Engineering & Supervision
Testing Laboratory Equipment
Instruments for Control of Plant
Real Estate Lease
Water Rights
Emergency Funds

Retort Process: Retort Building ~ Coal Lorry ~ Elevator ~ Screen ~ Retorts (4) ~ 100 hp Boiler ~ Stoker ~ Boiler Feed Pump ~ Superheater ~ Hot Condenser ~ Cold Condenser ~ Oil & Water Separator ~ Crude Oil Pumps ~ Water Circualting Pump ~ Bunker Heating ~ Hot Piping Supersteam to Retorts ~ Retort Discharge Piping ~ Miscellaneous Water/Steam Piping ~ Railroad Siding ~  Finished Product Storage Bins (Steeel, w/ Discharge Gates, Screen, Motor, belt Feeder) ~ Track & Trestle ~ Hoist 4000 lb capacity ~ Hoist House ~ Wiring Power & Lights ~ High Temperature Valves ~ Finished Product Car ~ 5000 Cu Ft Relief Gas Holder ~ 240 Bbl Crude Storage Tanks ~ Water Mains & Fire Hydrants ~ Water Pump & Spray Pond.

Total Cost (1932): $41,766

Refinery Unit: 1 x Cracking Still, 25 Bbl capacity ~ 1 x Steam Still ~ 7 x 50 Bbl Vertical Tanks ~ 1 x 200 Bbl Tank, horizontal ~ 3 x 25 Bbl Tanks, lead-lined
2 x Condensers ~ 1 x Pump House & Storage ~ 5 x Pumps ~ Foundations, Pipes, Fittings & Valves, &c. ~ Labor

Total Cost of Refinery [1932 ]: $13,120

Operation Estimates

Estimated Income Per Day: [1932 Prices]

20 tons of treated coal @ 5.75                                    $ 115.00
    6-2/3 tons @ $8.50 retail ($7.50 wholesale)
     “              @ $7.25 “      ($5.75 “ )
     “      @ $6.00 “       ($4.50 “ )
     Treated coal can be sold at plant for $3.65/ton

180 gal gasoline @ $0.145 cents/gal                             $  26.10
180 gal kerosene @ $0.14/gal                                      $  25.60

Total Income per day      $ 166.30

Other valuable products not included in the above: 15 gal of cresylic acid per day and 74,000 cu ft of gas per day
 Resins could be saved if price justifies

Estimated Expenses Per Day:

40 tons of coal @ $0.70                                               $  28.00
Freight: 20 tons @ $2.10 / 20 tons @ $0.30                 $  28.00
Labor                                                                           $  24.00
Supervision                                                                   $    7.00
Water                                                                           $    1.12
Supplies & Lubricants                                                   $    0.50
Refining Reagents & Supplies                                        $    7.38
Maintenance & Depreciation                                         $  19.00
Taxes & Insurance                                                        $    4.40

Total Expenses per day                                                 $ 139.40

Operation Estimates for One Year:

On the basis of the above, the following is an estimate of Income & Expense for operating the plant for one year of 305 working days and 60 idle days.

Income for 305 working days                                         $ 50,721.50
Expenses for 305 working days (60 Idle Days @ $42)   $ 45,037.00
Profit                                                                             $   5,684.00

This estimated profit on one year’s operation amounts to $7.5% on $75,186.

Production for One Year:

Total production for one year’s operation of 305 days: Treated coal 6100 tons ~ Gasoline 54,900 gal ~ Kerosine 54,900 gal. It is estimated that the gasoline and kerosene can all be sold to local dealers.

Gas Distribution [ Not included here ]


General ~ Due to the incompleteness of the plans drawn, specifications are descriptive of the general material and fabrication of the components for one complete 30 ton per day low temperature coal carbonization plant and associated tar oil refinery.

[ NOTE: Parts of this section are nearly illegible in the library original and are not included here. ]

Retorting Plant: Operating floor, superheater subass [sic], and 4 coal bins each of 10 ton capacity. Steel stairway to retort operating floor. Track hopper & Feeder, &c…

Elevator: Bucket type with steel casing approx. 70 ft total height. Capacity 6.5 tons/hr. Supplier to furnish all setting drawings and power requirements.

Screen: Horizontal shaker type, with screens of such size as to grade coal into 3 sizes from 2" to 3/8" and one size smaller than 3/8". Capacity 200 lb/minute required.

Lorry: This unit to be of steel to general dimensions shown in drawings; shall be equipped with 2 x 8" I-beam trolleys and 9" x 9" double cutoff gates for discharge.

Retorts: Four are required in accordance with drawings. Fabricated of coiler steel plate 1/2" thick; all seams welded and tested for gas-tight. All castings shown to be of cast steel of the following analysis: [blank in text],  and are to be hot-riveted to the shell with 3/4" diameter rivets and caulked where required to make a gas-tight joint.

Each retort will be placed in position and will be supported by the top bracket castings in a manner so that limited horizontal motion can be secured.

The sheet metal covering will be put in position and the intervening space will be filled with diatomaceous earth for heat insulation.

At top and bottom of doors a packing groove is provided which will require a gas-tight seal.

Boiler ~ A 100 hp boiler is specified of locomotive or portable type. This unit shall be complete with stack, boiler feed pump equipment, gauges, blowoff valve, etc., and the stoker of appropriate size to guarantee continuous operation of the plant to loads as high as 150%. Boiler shall be covered with 2" of heat-insulating material.

Superheater ~ This unit must pass test at 1400 degrees F/2 hr. All pipes and fittings are calorized. Special tube supports are to be constructed of equivalent material.

Condensers ~ The hot condenser shall be of such size that an outlet temperature of [blank] degrees F can be obtained at all times with an inlet temperature of {blank] degrees F when passing [blank} cu ft of gas, [blank} lb of water vapor and {blank] lb of oil vapor per hour. A water temperature inlet of [blank] degrees F is specified with an outlet temperature of [blank] degrees F.

The cold condenser shall be of sufficient size to give a final outlet temperature of [blank] degrees F from an inlet temperature of [blank] degrees F. When passing [blank] cu ft of gas, [blank] lb of water, and [blank] lb of oil vapor per hour, using a cooling water temperature of [blank] degrees F initial temperature and a [blank] degree F temperature.

Separator ~ This unit to consist of one piece of 12" standard pipe, closed both ends with welded on inlet for [blank] pipe and [blank] pipe outlet for gas, [blank] pipe outlet for oil, and [blank] pipe outlet for water.

Pumps ~ Provide one gas pump and motor drive capable of compressing 75 cu ft gas per minute at 100 degrees F to 6" water pressure continuous service. Provide one hot oil pump and motor drive capable of pumping [blank] gal of hot oil at [blank] degrees F per minute at 251 lb pressure. Also one hot oil pump for [blank] gal/minute [blank] degrees F to 25 lb. Provide a centrifugal water pump for 50 gal/min 180 degrees F water at 50 lb pressure.

Bunker Heating System ~ To preheat coal in bunkers and to dry the moist coal, there is required one [blank] cu ft capacity motor unit for operation on 500 degrees F flue gas continuously. Piping of this unit from superheater stack to coal bunker takeoff shall be 16 gauge black iron covered with insulating material.

Piping ~ All piping carrying superheated steam from superheater to retorts shall be "calorized pipe. All fittings calorized. Expansion units to be constructed of 10 gauge chrome-nickel iron sheets welded throughout with 5" nipple connections. Valves 4" of special high temperature construction. The unit of piping shall all be covered with a minimum heat insulation of 6" diatomaceous earth.

Pipes carrying saturated steam shall be insulated with valves placed so that the failure of one unit will not interrupt the functioning of other apparatus. Live steam will be required at retorts, superheater, generator unit, and a main header to supply all refinery requirements. All pipe and fittings shall be covered with 1" heat insulation and all pipes exposed to the weather, further protected with weatherproof covering.

Water pipes are required as follows: A 2" main supply line of galvanized pipe shall be installed from the pipe line and run to the retort house. General water piping is required at Boiler, Condensers and the Refinery Condensers. All water will be recirculated by means of a 100 gal/minute centrifugal pump through a spray pond and thence back to the system again.

Gas will be piped from the separator in the Retort house through a blower to the storage tank. Line will be run from tank to superheater and a relief outlet for surplus gas installed at a point well in the clear of all buildings so surplus gas may be burned.

Outside Structures ~ [Some details not included here] Railroad siding, narrow gauge, trestle. Finished product bins: steel frame and plate construction. Each of 3 compartments having a capacity of 1600 cu ft for a 20 ton storage.

A screen will be located over the bins to size the product into each bin. This unit will be substantially the same as that shown for the bins in the retort house. This screen receives its material from a 14" wide belt conveyer acting as a feeder from the track hopper.

To transport the finished product from the retort house to bins a 100 cu ft car is required. Weight of charge 3500 lb. Car to be of dumping bottom type.

As a means of traction a double-acting hoist of 4000 lb capacity will be required. Location to be in a special enclosure under the product bins, arranged so that car will be under the control of the operator at all times when making the trip out or back to the retort house.


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