US1886350A - Method of distilling solid carbonizable material - Google Patents

Description

Nov. 1, 1932.. NlELSEN ET AL 1,886,354)

METHOD OF DISTILLING SOLID QARBONIZABLE MATERIAL Filed Feb. 17. 1927 Patented Nov. 1, 1932 UNITED STATES PATENT OFFICE HAEALD NIELSEN", OF MUSWELL HILL, AND BRYAN LAING; OF HATFIELD, ENG-LAND METHOD OF DISTILLING SOLID GAEIBONIZABLE MATERIAL Application filed February 17, 1927, Serial No.

This invention relates to processes for the distillation of raw solid carbonaceous materials such as coal, lignite, brown coal, peat, wood, and shale' (hereinafter called raw solid carbonaceous materials) involving the use of a non-oxidizing gas such as producer or water gas, said gas as it is generated in the producer being withdrawn therefrom and after, if necessary being superheated, being passed through a contiguous revolving retort in direct contact with carbonaceous materials such as raw coal so as to utilize the socalled sensible heat of the producer or water gas for the purpose of distilling off at low 1:, or moderate temperatures from therawcarbonaceous materials passing through the retort the volatilizable and condensable oils contained therein, the inert heating gas containing the volatilized oils being subsequently passed through condensers, scrubbers, oil washer, etc., for the purpose of condensing and recovering in liquid form the said condensable oils. The aforesaid low temperature process also results in the production of a semi-coke which is readily combustible and which can, therefore, be employed in domestic fire grates in lieu of ordinary raw coal, and a portion of this semi-coke is usually fed into the producer and employed in I conjunction with air or with air and steam,

for the purpose of producing either the proi ducer or the water gas whose sensible heat is employed as the distilling medium within the retort. The combined retort and water or producer gas which remains after the oils have been condensed therefrom is a rich gas suitable forilluminating purposes.

The semi-coke, however, which is obtained from the retort contains a considerable volume of permanent gases, which gases, if the material is burnt in a fire grate are wasted so far as heating purposes are concerned, while furthermore, a smaller and less rich volume of combined retort and producer gases is obtained by the retorting process than 169,123,and in Great Britain March 6, 1926.

'of condensable oils in their so-called primary or uncracked state, also to distil 01f from the raw coal or like carbonaceous material the maximum volume of permanent gases contained therein, so as both to increase the volume of and also to enrich the gases which remain after the oils have been condensed therefrom and thus to produce a high grade and high calorific gas suitable for use as socalled town or illuminating gas.

According to the present invention the dis tillation of the solid carbonaceous" materials is effected'by means of a combustible as, such as water or producer gas, which, a ter being superheated if necessary, is passed through an apparatus such as a retort or a two-stage retort, in contact with the raw carbonaceous materials so that the so-called sensible heat of the distilling medium is employed first to distil off the volatilizable and condensable oils contained therein and thereafter to drive off the so-called' permanent gases, the temperature zones, throughout the length of the retort, being graduated so that the said oils are distilled off at the temperatures at which they volatilize and are then withdrawn from the apparatus either at one end or preferably at different points along the length thereof and at temperatures at which no cracking can occur, while the volume of combustible gas whose sensible heat is employed as thedistilling medium is so controlled as to lower the vapor pressure of a contlnuous manner first to a process of distillation at low or moderate temperature so as to drive off the volatilizable oils and then to a process of high temperature distillation so as to drive off the permanent gases and we have found that it is essential in order to ob tain a freely burning solid carbonaceous residuum that the volatilizable oils should be withdrawn from theretort without cracking as otherwisegraphitic carbon is deposited on the solid material which coats the microscopic and sub-microscopic cells and cell walls w th a highly impervious carbonfilm which is difficult to oxidize and whichv reduces to a marked degree the readiness to combustibllity as well as to reactivity of the resultant fuel. It is also essential that the oil yieldlng and volatilizable constituents should be expelled from the solid material at as. low a temperature as possible, that is to say, attemperatures ranging from 185 to 580 C. while the expelling of the so-called permanent gases from the solid material should then \take place at from 580 up to approximately 1200 C. A suitable temperature range from the inlet to the outlet end of the retort can be maintained so as to efi'ect the aforesaid result in the same retort. In order that the said invention may be clearly understood and readily carried into efiect, the same'will now be described more fully with reference to the ac companying drawing which illustrates diagrammatically the layout of a plant constructed according to the present invention and in which:

A is a hopper or container for the raw material B, which is fed into the retort or rotary drum C. a is a pipe by means of which the raw material is fed from the hopper A into the retort C, the pipe a also serving to conduct the mixed producer gas and retort gases away from the retort C. c is a fixed annular casing surrounding one end of the retort and wherein the coked fuel which is treated in the retort is collected after falling through the opening 0. 0 is the coke offtake which is controlled by a discharge valve, not shown, from the retortC. E is a gas producer, the producer gas from which is employed for treating the material undergoing distillation in the retort C. -e is a pipe through which the producer gas is drawn from the producer on its way to the retortC. The producer gas may be fed through regen erators (not shown) so't'hat its temperature is raised from 1000 C. to 1200- C. so that it enters unburnt into the retort C. or the gas may beburnt in a combustion chamber 6 after it leaves the producer and before passing the valve 6 The valve 6 controls the quantity of producer gas supplied to the retort C. F is a condenser for the mixed gases which leave the retort C, and G is an absorption apparatus for therecovery from the said mixed gases of condensable and absorbable hydrocarbon products contained therein.

The pipe 71 conducts the stripped gases from the absorption apparatus G to an ammoma absorber I.

The raw solid carbonaceous material WlllCh is to be distilled enters the retort from the hopper A, while the hot gas from the producer which may be burnt in the combustion chamber 6 enters the retort in the form of a continuously flowing stream at a temperature of from 1000 C. to 1200 C. Consequently, the solid carbonaceous mater1al which is to be distilled and the hot distilling medium pass in contrafiow to one another. The controlled volume of the hot gas first meets the solid carbonaceous residue from which the oil Vapors have been driven ofi further along the retort at temperatures ranging from 185 to 580 C. The hot gas,

therefore, after entering the retort first dis-' tils off from the material which it encounters and at high temperatures the so-called 'permanent gases are cooled down to a temperature of approximately 580 C. Thereafter it drives off from the carbonaceous material the oil bearing constituents and is cooled down t9 approximately 185 C. Asthe heating medium flows in countercurrent to the raw carbonaceous materials, the oil bearing constituents are prevented from passing into hotter zones and are carried away from the retort through, the pipe a to the condenser F, the absorption apparatus G and the ammonia absorber I. If desired two retorts may be employed and placed in communication with one another in any suitable manner, the volatilizable'oils being distilled oif in a retort having a progressive temperature range of from 185 to 580 C. and thereafter the solid material being passed into a second retort, where the gaseous hydrocarbons are ClI'lVGILOfi at temperatures from 580 up to 1200 C. The inert heating gas can, if neces: sary, or desired, be superheated before being passed into the second high temperature retort or before entering the high temperature zones of the single long retort; or the distilling gaseous medium at suitable high temperatures can be by-passed and admitted at different points along the length of the retort. By carrying on the process in the aforesaid manner we have found that tempera- .tures up to and exceeding 1100 C. may be employed after the condensable 7 oils have been driven ofi' by an inert heating medium and removed in unifiow with the heating medium so as to drive off the residual gaseous volatile matters, and reduce the volatile matter in the solid residuum to about 1%, this result being obtained without in any way interfering with the easy ignitibility, combustibility or reactivity of the solid residue. 7 The solid resdue can, as aforesaid be burnt in open domestic grates; and is more read ly ignltible than the ordinary semi-coke obta ned by any of the usual processes of low temperature distillation and far more readily combustible than ordinary gas coke or coke oven coke. This property of the solid carbonaceous material obtained by the aforesaid process apof raw material at this temperature were zpears to be due to the fact that the original cell structure of the raw material is left intact, and the depositing of a carbon film on the residual fuel is avoided, while the thinness of the cell walls is maintained so that a very large superficial surface is made available for attack by oxygen either combined or in a free state.

Wehave also found, that a fusible or cok ing coal, which on distillation passes through a so-called plastic state, can be given the same degree of reactivity, etc. as a so-called noncaking or non-coking coal, that is to say, be made to retain its original cell structure by being subjected to a preliminary heat treatmentby gases containing suflicient oxidizing constituents, free oxygen and the like and to an extent which will stop fusing and ag-- glomeration.

For example a bituminous coal was distilled by means of an inert gaseous heating medium in a rotary retort, the raw coal having a volatile content of 30%. It wasv observed that oil began to distill oil at 210 C. together with a small volume of gas and at 570 C. all the oil yielding constituents or condensable hydrocarbons were removed from the material under distillation.

The quantity of products obtained per ton (570 C.)

20 gallons of oil.

15 gallons of ammoniacal liquor,

2,500 cubic feet of gas. The volatile matter still present in the solid material was reduced to 10%.

When this material passed into the next zone and was subjected to a temperature of 950 C. the volatile matters were expelled in the form of gas, and a volume of about 5000 cubic feet was obtained, the gas consisting mainly of hydrogen, methane and carbon monoxide. Only 1.5% to 2% of volatile matter was left in the resultant fuel or coke after being subjected to this. second treatment at temperatures upto 950 (1, and it was found possible to ignite the coke by means of paper only in an ordinary open domestic grate.

Microscopical research showed that no deposit of graphitic carbon was present.

It was also found that on account of the fact that cracking did not take place owing to the oil yielding volatilizable constituents being carried off in unifiow with the heating gases a primary oil was obtained containing a large percentage of the more valuable high boiling fractions or lubricating oils rich in hydrogen.

By the present method it is possible therefore to produce from solid carbonaceous ma way interfering with the reactivity or combustibility of the solid residue, or in other words, to produce so-called high temperature coke with a reactivity, v ignitibility, equal to, if not superior to, socalled low temperature coke, together with the largest possible yield of liquid and gaseous hydrocarbons in their most valuable state.

As the resultant fuel is exceedingly reactive and easily oxidized, either by free oxygen or combined oxygen such" as is present in metallic ores, such as iron or copper oxides, and the like, or in steam, it is of greater value for domestic use or industrial processes than the comparatively speaking non-reactive carbon. material hitherto used with scant success only.

The resultant coke is friable and after crushing is eminently suitable for use as a powdered fuel owing to its high degree of reactivity and free burning properties.

What We do claim as our invention anddesire to secure by Letters Patent is 1. A method of distilling raw, solid, distillcombustibility and able and carbonizable material, which comprises passing the raw material to be distilled in a continuous manner through a retort, admitting to the retort, at a temperature of approximately 1200 C., a controlled volume of a heated non-oxidizing gas, and passing the heated gas in the form of a continuously flowing stream through the retort in counter flow to the carbonizable material passing therethrough, so that the sensible heat of the heating gas is utilized both for the purpose of expelling from the material, at low temperatures, in vapor form, the oil yielding constituents and carrying the same into cooler zones in uniflow with the heating gas, and also for expelling at a higher temperature, gaseous hydi'ocarbons contained'in the solid residue remaining after the oils have been expelled, whereby the coke formed contains from 1.5% to 2% volatile matter.

2. A method of distilling raw, solid, distillable and carbonizable material with byproduct recovery, which comprises passing the material in thin, continuously moving, layers in contraflow to and in contact with a heated non-oxidizing gas, the volume of heated gas employed as the distilling medium being so controlled as to lower the partial pressure of the volatilizable oils as much as possible, the material being first subjected toa process of low temperature distillation, at a temperature not exceeding approximately 580 6., whereby oil in vapor form will be obtainedat temperatures at which no cracking can occur, said oil vapors being carried in suspension in the heating gas into cooler zones, and subjecting to high temperature distillation by direct contact with the heating gas at temperatures ranging from approximately 580 C. to approximately 1200 C. the solid residue that has been freed from oil to drive off gaseous hydrocarbons contained in said residue, the same heating gas being employed for both the high and low temperature distillation processes, whereby the coke formed contains 1.5 to 2% volatile matter.

HA-RALD NIELSEN.

BRYAN LAING.

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