US2642387A - Low-temperature carbonization of carbonaceous material - Google Patents

Description

June 16, 1953 M. STEINSCHLAEGER 2,642,387

LOW-TEMPERATURE CARBONIZATION 0F cmsomcsous; MATERIAL Filed March 10, 1949 INVENTOR. Ma /051. Smwsa/mvm f BYM'ZMW Patented June 16, 1953 LOW-TEMPERATURE oARnoivIzATIoN F CARBONACEOUS MATERIAL Michael Steinschlaeger, London, England Application March 10, 1949, Serial No. 80,663 In Great Britain March 22, 1948 2 Claims.

This invention relates to the low temperature carbonisation of coal and other carbonaceous materials, including such fuels as cannel, torbanite, shale, peat, lignite, bituminous coal and mixtures of the same.

According to a known process the carbonisation is carried out in an apparatus consisting of several chambers arranged vertically on a central steel shaft which is rotated by means of a gearing at the base of the shaft.

The material to be carbonised may be in the form of lumps or may be in crushed or pulverised form. v

In operation, the carbonaceous material .enters each chamber at the centre and falls upon a horizontal plate or table and is caused to travel over the surface of the table by means of ploughs which depend from the roof of the chamber.

The carbonaceous material falls from the periphery of the table to the floor of the chamber and is carried to the centre of that chamber by means of ploughs which are fixed on the underside of the table. ,The carbonaceous material rotates back and forth in each chamber in the same manner until it reaches the last chamber where the treated carbonaceous material is ejected.

The chambers are heated by a plurality of radial burners arranged in sections, each burner entering a space in a section between two of the chambers.

The combustion gases pass along one side of a vertical dividing plate to the centre and back again to the flue at the circumference. Heat is, therefore, transferred through the floor of the upper chamber and the roof of the one below.

It is the usual practice to use one or two top chambers for removing moisture from the carbonaceous material and the next four or five chambers to complete the distillation in stages while the remaining chambers serve as cooling chambers. I

- The vapours and gases resulting from the carbonisation are removed from each chamber separately by means of off-takes and passed to washers and coolers.

The pressure or vacuum in each chamber is so regulated as to prevent the mixing of the gases and vapours from onechamber with those of another.

In the practical operation of the process described above a number of difiiculties are encountered.

Thus, to allow of complete carbonisation it is essential that the carbonaceous material be crushed very small which allows a large percentage of extremely fine dust to become entrained in the vapours and gases leaving the chambers. As the vapours and gases are transferred to the washersv and coolers the vapours condense and with the entrained dust choke the off-take pipes and coolers with a solid hard mass composed of wax, pitch, dust, oil and tar. Within a matter of a few hours the plant ceases to be operative.

Furthermore, if the carbonaceous material is coarsely crushed so that a large proportion of the dust is eliminated with, of course, a sacrifice of carbonisation efiiciency, there will still be the difiiculty arising from the entrainment of pitch and some dust in the gases and vapours leaving the chamber.

Moreover, as the chambers are constructed of high-grade cast iron (e. g. the material known under the Registered Trade-Mark Meehanite) or other'alloys or similar materials, the carbonisation temperature has to be limited to about 1000 F. to 1400 F. Consequently the flame temperature of the combustion gases must be kept low and this is achieved by using excessive air or combustion gases resulting in heavy losses in waste gases.

It is an object of this inventionto overcome these difficulties and, at the same time, improve the quality of the resultant oil and gases by increasing the olefinic and wax content of the oil and unsaturated hydrocarbons in the gases such as ethylene, propylene and butylene, while decreasing the pitch and acid content of the oil, and also increasing the throughput of carbonaceous material and thermal eificiency of the process, using a smaller excess of air and achieving a substantially uniform temperature over the whole of the plant. I

It has been found according to this'invention that this object can be achieved if the gases and I chambers must be at at least 0., preferably.

vapours are removed at such a temperature and at such a position in the carbonisation unit as will prevent the vapours condensing until they reach a point where condensation will not be harmful to the operation of the process. If so required, additional heat may be applied to the gases and vapours to maintain or increase their temperature.

In order to prevent the condensation the temperature of the gases and vapours leaving the at least 400 C. or in any case above the condensation or precipitation point of the compo-' nents of the mixture.

In practical operation it was found that this method prevented the condensation of the vapours and precipitation of the dust.

Accordingly, the present invention provides a process for the low temperature carbonisation of coal and other carbonaceous materials such as cannel, torbanite, shale, peat and lignite in which the carbonaceous material is carbonised by heating whilst passing through a plurality of vertically disposed chambers in succession, at least one of said chambers being provided with an offtake for the removal of gases and vapours produced wherein the temperature of the gases and vapours in the off-take is maintained at a temperature above the condensation or precipitation point of the components of the mixture.

This will in general be at least 100 C. and preferably at least 400 C.

The removal of the oil or vapours or gases is preferably effected in the middle of the appa- A ratus (the third or fourth chambers) since this enables the oil to be removed before any substantial cracking thereof occurs. If the fuel is pre-heated, the removal is effected from the third chamber or from the chamber where the highest amount of oil or vapour is formed.

The prevention of condensation in the offtakes is usually effected by heating the off-takes in any convenient manner, e. g. by superheated steam, hot gases or by electrical heating elements but in some cases it may be sufiicient to lag the off-takes.

To overcome the drawback arising from the limitation of the flame temperature of the combustion gases it was found advantageous to use a gas containing dust and other foreign matter as opposed to cleaned gas. The dust becomes deposited on the plate to which heat is being applied and forms a protective layer against the effect of the high temperature of the combustion gases.

Furthermore, to reduce the amount of excess air during combustion, preferably a refractory or metal pipe or structure drilled with a number of small holes is used around the combustion gases when they are at their maximum temperature. 1 In this way the high temperature flame is prevented from coming into direct contact with the metal which would otherwise be dama ed.

The temperature of the last heating chambers is so high as will cause cracking of the vapours and gases as they pass through these chambers, and it has been found essential to take off a major proportion of the vapours at a temperature at which they have not been subjected to the maximum temperature in the apparatus.

The same applies in the case of the gases to obtain the highest percentage of unsaturated hydrocarbons such as ethylene, propylene and butylene. I

The temperature and position or positions at which gases containing unsaturated hydrocarbons are removed may be different from the temperature and positions at which the oil or vapours are removed, as the temperatureand positions at which the best quality of oil is obtained do not coincide with the maximum amount of unsaturated hydrocarbon obtained. For example. oil or vapours can be removed at around 300 C. from the third chamber and gases at around 400 C. from the fourth and fifth chambers.

The separation of the vapours from the gases is accomplished in stages.

The process of the invention will now be further described with reference to the accompanying drawings, in which:

Fig. 1 shows diagrammatically a part sectional view of an apparatus suitable for carrying the invention into effect, and

Fig. 2 is a sectional view of a detail of the apparatus.

Referring to Fig. 1 of the drawings, the apparatus is disposed in a building I and comprises eight vertically disposed chambers 2, 3, 4, 5, 6, "i, 3 and 9. A central shaft l0 driven through gearing l i by a motor 12 drives a plurality of revolving tables [3, one in each of the chambers. Each of these revolving tables carries a plurality of movable ploughs 14 whilst a plurality of fixed ploughs l5 depend from the roof of each of the chambers. The chambers are surrounded by heat-insulating material l6 and this is encased in brickwork 11. The chambers are heated by gas burners l8, vents i9 being provided for the admisison of air to the gas burners. Fuel is supplied to the apparatus from a storage hopper 28, an agitator 2| disposed in the bottom of the hopper being carried at the top of the shaft 2. Off-takes 22 are provided in chamber 4 and off-takes 23 in chamber 5 each leading to a box 24 having a seal 25 and leading in turn to conduits 26. The off- takes 22 and 23, the boxes 24 and the conduits 26 are each provided with a heating jacket 2'! through which a heating fluid such as a hot gas may be passed. The conduit 26 leads to a blower 28 which is connected by a conduit 29 having a heating jacket 36 to a condenser 3i, which in turn is connected by a further conduit 32 to a further condenser 33, which is connected by a conduit 34 to a washer or activated carbon plant 35 having an outlet 36. A chute 3'! is provided at the bottom of the chamber 9 to remove solid residue.

The process is carried out as follows:

The solid. fuel in finely divided form is fed from the hopper 2E5 to the chamber 2 where it falls upon the revolving table l3 and is caused to travel over the surface thereof by the ploughs l5 and thence over the periphery of the table to the bottom of the chamber where the ploughs M cause it to proceed to the centre and thence to the chamber 3. The fuel proceeds in a similar manner through each of the chambers and finally the solid residue leaves through the chute 31. In chamber 2 drying is effected, in chamber 3 drying and some carbonisation, whilst in chambers 4 to l carbonisation proceeds, and chambers 8 and 9 act as cooling chambers. The oil, vapour and gases produced leave through off-takes 22 and 23, being sucked out by the blower 28 and after passing through the boxes 24 proceed down the jacketted conduits 26, the heated fluid in the jackets 2T preventing condensation. Heavy oil is condensed in the condenser 31 which may be cooled by air or water and light oil is condensed in the condenser 33. Benzene or petrol is removed by the washer or activated carbon plant 35 and residual gas leaves through conduit 3'6.

Referring now to Fig. 2 of the drawings, this shows diagrammatically further details of the gas burners 18. The combustion gases from the burner is are surrounded by a pipe 30 which may be of refractory material or of metal such as mild steel and is provided with a number of small holes 39. By this means the high temperature flame from the burner I8 is prevented from coming into direct contact with the walls of the vertically disposed chambers.

I claim:

1. A process for the low temperature carbonization of coal and other carbonaceous material including cannel, torbanite, shale, peat and lignite, comprising carbonizing the material by heat- 5 ing while passing through a plurality of ver- 7 .tically disposed chambers in succession, heating each of said chambers from below by burning fluid fuel and passing the products of combustion of the fuel while at their maximum temperature through an elongated zone and drawing into and mixing with the products of combustion while in said zone a plurality of spaced, separate small streams of air before entering between the chambers, removing gases and vapors from at least one of said chambers and maintaining the temperature of the removed mixture of gases and vapors above the condensation and precipitation points of the components of the mixture by heating the off-takes by' means of a heating fluid, but below the temperature at which substantial cracking occurs. l

6 2. A process as claimed in claim 1 wherein oil produced by the carbonization is removed before any substantial cracking thereof has occurred.

MICHAEL STEINSCHLAEGER.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain July 9, .1937

Claims (1)

1. A PROCESS FOR THE LOW TEMPERATURE CARBONIZATION OF COAL AND OTHER CARBONACEOUS MATERIAL INCLUDING CANNEL, TORBANITE, SHALE, PEAT AND LIGNITE, COMPRISING CARBONIZING THE MATERIAL BY HEATING WHILE PASSING THROUGH A PLURALITY OF VERTICALLY DISPOED CHAMBERS IN SUCCESSION, HEATING EACH OF SAID CHAMBERS FROM BELOW BY BURNING FLUID FUEL AND PASSING THE PRODUCTS OF COMBUSTION OF THE FUEL WHILE AT THEIR MAXIMUM TEMPERATURE THROUGH AN ELONGATED ZONE AND DRAWING INTO AND MIXING WITH TH EPRODUCTS OF COMBUSTION WHILE IN SAID ZONE AND A PLURALITY OF SPACED, SEPARATE SMALL STREAMS FO AIR BEFORE ENTERING BETWEEN THE CHAMBERS, REMOVING GASES AND VAPORS FROM AT LEAST ONE OF SAID CHAMBERS AND MAINTAINING THE TEMPERATURE OF THE REMOVED MIXTURE OF GASES AND VAPORS ABOVE THE CONDENSATION AND PRECIPITATION POINTS OF THE COMPONENTS OF THE MIXTURE BY HEAT-

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