US2227951A

US2227951A - Process for carbonizing coal

Info

Publication number: US2227951A
Application number: US191910A
Authority: US
Inventors: George W Wallace
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-02-23
Filing date: 1938-02-23
Publication date: 1941-01-07
Anticipated expiration: 1958-01-07

Description

Jan. 7, 1941. G. w. WALLACE PROCESS FOR CARBONIZING COAL Filed Feb. 25, 1958 3 Sheets-Sheet 3 Flc, 9.

INVENTOR Patented Jan. 7, 1941 UNITED f srA'rEs 4 claims.

This invention relates to the carbonization of coal and similar solid carbonaceous substances and its principal object is to provide an improved process of and apparatus for effecting the carbonization of coking or semi-coking coal' and it is primarily adapted to carbonizing slackcoal or screenings and more particularly adapted to carbonizing the ne coal and dust resulting from the preparation of so called stoker fuel where the product is often as fxneas a minusten mesh material. A

Another object of the invention is the production of smokeless fuel by low temperature car' bonization. A further object of the invention is the tion of a smokeless fuel under conditions wherein the volatile content of the resultant product may be controlled within close limits to that desired. And still another object isthe production of a low temperature smokeless fuel vof improved structure and denseness.

Other objects and desirable features of the invention will be hereinafter pointed out.

In the present invention the process of carbonizing coal consists in'causing the coal to pass Athrough a carbonization chamber supported on a moving or movable pan or apron conveyor, regulating the depth of coal in the pans or thickness of layer on the apron to that desired and covering the coal in the pans or layer on the aprons with a series of covers of sufficient weight to affect the structure and compactness of the resultant fuel product and heating the coal undergoing carbonization from beneath the supporting medium and above the covers with hot gaseous products of combustion in direct contact with a. bustion are controlled by using an excess of gasl where gases are burnedwith air to produce said hot gaseous products of combustion.

Figure 1 of the drawings is a vertical sectional view of one form of apparatus that can be vused in practicing the present process. The sectionI (Cl. 2oz-26) 3-3 and illustrates the manner in which thalinks support the pans.

I Figure 4 is a vertical cross sectioni,v of the ap`- "paratus on line 4-4 Fig. 1 and illustrates the manner in which the hot combustion gases are admitted to the carbonization chamber.

Figure 5' is a vertical cross section of the apparatus on line 5 5 Fig. 1 and illustrates the manner in which the hotl combustion gases leave the chamber. L*

Figure 6 is a broken vertical sectional view of another form oi appar tus which can be used in practicing the presen 'invention and illustrates one type of apron conveyorwhich may be used.

Figure 7 is a vertical section in part onl line 1-1Fig. 6. No

Figure 8 is an enlarged view of the driving sprocket illustrating the manner in which the covers may be brought into position and` placed on top of the coal.

.Figure 9 is a cross sectionthrough line 9-9 Fig. 6 and illustrates a damper'control of'the hot gaseous products of combustion.

sist either of shallow pans or an apron conveyor,l

a series of more or less loosely riding covers C which are arranged to cover the coal in'the pans or on the apron conveyor. and which are of sufllcient weight to affect` the structure of the carbonized residue or smokeless fuel. The rsaid supporting medium and covers may be constructed of steel, cast steel, cast ironor a special alloy of iron having heat resisting properties, usually two or more of such metals will be used in assembling the apparatus; A coal hopper D is provided from which the coal to be carbonized is fed onto thepans or onto the apron conveyorat the desired depth or thickness. In the apparatus sprocket wheels E actuate the conveyor and sprocket wheels E which are synchronized with sprockets E actuate the covers, tail sprockets F and F' reverse the direction of the conveyor and covers to the point of loading. Links G carry the weight of thepans or aprons and in turn are supported by rods H which are connected with wheelsI' which travel on rails J, links G carry the covers excepting when they are resting on the coal and are supported by rods H' and wheels I which travel'on rails J. A driving gear K, preferably of variable speed is provided to actuate the sprocket wheels Eand E' said driving gear may be powered in any suitable manner for instance by an electric motor K'. In the apparatus as illustrated means are provided for admitting hot products of combustion beneath the coal supporting medium and above the covers at L through a series of ilues M below the supporting medium and through a series of flues M' above the covers. 'Ihe hot gaseous products of combustion after passing through the ues M and M' leave the carbonization chamber at N from which they are conducted to the desired condensing and scrubbing apparatus not shown. 'I'he product of the carbonization or smokeless fuel is discharged from the conveyor or supporting medium into the hopper O from which it is removed from the carbonization chamber by means of star feeder P which serves also to prevent any airI entering the chamber at this point. It is to be understood that the hopper O may be of any desired size. With certain coals it may be desirable to use the apron conveyor or supporting medium B Fig. 6 which provides means X for assisting in the removal of the carbonized residue from the supporting medium. In the apparatus R Fig. 1 is a refractory top and bottom for flues M and M which if desired may be dispensed with. In Figs. 1 and 2 the ilues M and M' are shown as cross flues which conduct the hot combustion gases backand forth across and beneaththe supporting medium and above the covers from the inlet L as shown in Figs. 2 and# to the outlet N as shown in Figs. 2 and 5.

' Fig: 6 illustrates a single longitudinal open flue S beneath they supporting medium and S above the covers, in this illustration the top and bottom refractory lining R as shown in Figs. 1, 4 and 5 is omitted. In order to control the hot combustion gases entering and leaving the open ues S and S' bailies T and T' may be provided at the inlet and outlet of said iiues the bailles having a series of ports which may be adjusted by partially opening' or closing dampers U and`U' as shown in Fig. 9, By the use of these dampers the hot combustion gases entering the carbonization chamber beneath the supporting medium and above the covers at inlet L and leaving the chamber at outlet N may be distributed uniformly below and above the coal being carbonized.

While two different systems of ilues have been illustrated other arrangements of passing the hot combustion gases used toeiect the carbonization into and through the carbonization chamber,

may be used and in some cases it may be desirable Ato effect the carbonization by passing the hot combustion gases beneath the supporting medium only, this would apply particularly to cal having unusual swelling and plastic characteristics. The hot gaseous products of combustion used to effect the carbonization are preferably admitted to the carbonization chamber at the discharge end of the coal supporting medium, and caused to pass in countercurrent to the direction of movement of the coal through the chamber, and removed from the end where the coal is fed onto the supporting medium.

In synchronising the placing of the covers on the coal short rails V Fig. 3 may be used to guide the covers as they leave sprockets E' and position them properly on the coal after which the full weight of the covers, links, rods and wheels 'will be on the .coal body during the carbonization period until short guide rails Vv pick the weight up as the covers reach sprocket wheels F', or the modification shown in Figs. 6 and 8 may be used ln which case the covers are positioned over the coal either on the pans or aprons of the conveyor directly from sprocket wheels E' which are synchronized with sprocket wheels E and as the supporting medium and covers move forward into the carbonization chamber the weight of the covers is transferred to the coal due to the slots W shown in Figs. 6, 7 and 8 moving up on rods H' freeing the covers from any support until they are lifted from the carbonized residue by sprocket wheels F'.

Other means of placing the covers on the body of coal being carbonized and properly synchronising the same with the body of coal on the supporting medium may be used, the drawings illustrating two practical methods.

The primary object of the covers is to compress the coal during carbonization particularly while it is passing through the plastic stage so as to produce as dense and compact a product as possible.

The coal or material to be carbonized may be passed through the carbonization chamber either continuously or intermittently, it may be advanced through the chamber for short distances at frequent intervals or through substantial distances with correspondingly long stationary periods between the intervals of movement. While the continuous movement of the material through the chamber is preferable the intermittent movement is entirely practical.

The hot gaseous products of combustion used to effect the carbonization are preferably produced entirely outside the carbonization chamber by burning gases with air the gases being in excess of the amount of air required for the theoretical complete combustion of the same. The temperature of the hot gaseous products of combustion is controlled by the amount of excess gas used, i. e., 60 parts of a 120 B. t. u. gas and 40 parts air will furnish products of combustion having a lower temperature than when using 50 parts gas and 50 parts air, by using this method of regulating the carbonization and controlling the temperature `of the gaseous products of combustion used to effect the carbonization temperatures of 550C. to 800 C. may be maintained uniformlly, and higher or lower temperatures may be secured and controlled if desired, the greater the amount of excess gas used the lower is the temperature of the products of combustion. The -hot gaseous products of combustion are preferably of a reducing nature as this condition serves to protect the mental portions of the apparatus. While a less desirable result would be secured it is possible to have the combustion of the gases take .place partially within the carbonization chamber.

The gases resulting from the operation of the process are usually sucient in amount and quality to furnish the hot gaseous products of combustion used to effect the carbonization. If for any reason it is not desirable to use the gases resulting from the operation of -the process producer gas may be used or any other combustible gas or fuel or a furnace may be installed to furnish the hot gaseous products of combustion. If de`- sired instead of using an excess of gas to control the temperature of Vthe hot gaseous products of combustion the same may be controlled by admixing or diluting with inert gas and/or steam or the temperature may be controlled in any other 1 and 6, the gate Y shown in Fig. 1 may if desired be arranged so as to bring thelevel of the coal in the pans to a point level with or just below the top of the pans, the gate Y as shown in Fig. 6 may be adjusted so as to control the thickness of the layer or body of coal to that desired.

The thickness of the layer or body of coal may Vary considerably with different coals however a thickness of from three to four inches should meet any usual requirements as relatively thin layers will carbonize more eiciently.

In practicing the process of the present invention a layer of coal of the desired thickness is fed from hopper D on to the moving or movable conveyor or supporting medium B which enters the carbonization chamber within A where the coal is covered and compressed by covers C. Hot gaseous products of combustion are passed beneath the supporting medium and above the covers to eiect the carbonization of the coal at a temperature of from 550 C. to 650 C. for low temperature carbonization where around 8 to 12% volatile matter is desired in the resultant fuel and at higher temperatures where a lower amount of volatile matter is wanted. The rate at which the coal travels through the chamber is adjusted so that the carbonization is complete when the residue is discharged into hopper O from which it is removed through sealing device and feeder P and, from which point it is cooled and taken to storage.

The gases, oils and liquids distilled from.the coal during carbonization escape around or through the covers which may be perforated if desired and between the sections of the supporting medium and they are removed from the carbonization chamber entrained with the hot gaseous products of combustion. The combined gases may be cooled and washed in any manner desired to remove such of the coal tar and other byproducts as it may be found protable or desirable to recover. An exhauster may be used to remove the gases and vapors from the carbonization chamber under a partial vacuum and deliver them under pressure to the condensers or place oi use. The amount of gas required to eect the carbonization may if desired be returned to a combustion chamber which may form a part of the carbonizing apparatus where it is burned with air to produce the hot gaseous products o cornbustion, the temperature of said products being controlled and regulated in the manner described. The excess gas produced in the operation of the process and not used for carbonization purposes may beused otherwise or may be wasted.

T. claim:

1. The process of carbonizdng csr coal to produce a substantially smokeless fuel which consists in confining the coal in shallow pans, and continuously passing the panned coal in a substantially horizontal direction through a hot carbonizing chamber, the coal being confined across its upper .surfaces by loosely riding covers of suincient Weight to produce a relatively small-pored dense coke while permitting escape of the gaseous products of such carbonization.

2. The process of carbonizing coking coal to produce a substantially smokeless fuel which consists in conning the coal in shallow pans, and continuously passing the panned coal in a substantially horizontal direction through a hot carbonizing chamber, having a temperature range from 550 C. to 800 C., the coal being conned across its upper surfaces by loosely riding covers of sumcient weight to produce a relatively smallpored dense coke while permitting escape of the gaseous products of such carbonization.

3. The process of carbonizing coking coal to produce a substantially smokeless fuel which consists in confining the coal in shallow pans, continuously passing the panned coal in a substantially horizontal direction through a carbonzing chamber, the coal being coniined across its upper surfaces by loosely riding covers of suicient weight to produce a relatively small-pored dense coke while permitting escape of the gaseous products of such carbonization, and passing hot gaseous products of combustion through the chamber in a direction opposite to the direction of movement of the coal, said products of combustion being produced by burning combustible gases with air in an amount insulcient for their complete combustion.

4.. The process of carbonizing coking coal to produce a substantially smokeless fuel which consists in conning the coal in shallow pans, continuously passing the panned coal in a substantially horizontal direction through a carbonizing chamber, the coal being conned across its upper surfaces by loosely riding covers of sufficient weight to produce a relatively smallwpored dense coke whiie permitting escape of the gaseous prod1 ucts of such carbonization in a serpentine path generally counter-current to the movement of the coal, and passing hot gaseous products of come bustion through the chamber in a direction oppo site to the direction oi movement of the coal, said products of combustion being produced by burnn ing combustible gases with air in an amount inB sumcient for "their complete combustion.

GEORGE W. WALLACE.