US2074881A - Apparatus for preheating coal before coking - Google Patents

Description

March 23, 1937. 'A, G. WITTING APPARATUS FOR PREHEATING COAL BEFORE COKING Filed Sept. 21, 1934 2 Sheets-Sheet 1 N% m m Q R an .U. WWH 1- .38

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March 23, 1937. A. G. WITTING 2,074,381

APPARATUS FOR PREHEATING COAL BEFORE COKING 2 Sheets-Sheet 2 Filed Sept. 21 1934 V Int/29%;; JYZQZ W G Patented Mar. 23, 1937;

APPARATUS FOR PREHEATING com.

. arons come Albin Gottlieb Witting, Gary, Ind.

Application September 21, 1934, Serial No. 745,002

7 Claims.

The invention relates to improved apparatus for drying and preheating finely crushed solid material. Although the present apparatus has been designed for processing coal to prepare it 5 for the coke ovens, it is also applicable to other materials having excess moisture or occluded gases as a detriment to further processing.

It has long been recognized by the trade that if coal is dried so as to remove substantially all '10 the moisture present in the coal and is then heated to a temperature slightly below that at which it' begins to soften to drive oil? the carbon oxide gases, a better quality of coke will result and the coking time will bematerially shortened. 15 The primary object of the invention is to provide improved apparatus for drying and preheating finely crushed solid material which will overcome the defects present in previousdesigns and which will operate economically and on a thermally self-sustaining basis.

A further object of the invention is to provide novel means for recirculating the hot gases through the apparatus which will supply the deflciency in the volume of hot gases received from the coke ovens.

With these and various other objects in view, the invention may consist of certain novel features of construction and operation, as will be more fully described and particularly pointed out 30 in the specification, drawings and claims appended hereto.

In the drawings which illustrate an embodiment of the invention and wherein like reference characters are used to designate like parts 35 Figure 1 is a plan view of the preheating apparatus of the invention with parts in section to more clearly illustrate the novel features;

Figure 2 is an elevational view of the apparatus shown in Figure 1; and

' Figure 3 is a vertical sectional view taken substantially along line 3-3 of Figure 2, and showing the structure for recirculating the hot gases.

The process of drying and preheating coal is performed in two stages. In the first stage the 45 raw coal is delivered to a drier designated in its entirety by I supported upon foundation II and which indirectly heats the coal and also subjects the same to direct contact with the hot gases to remove the moisture and some of the con- 50 tained gases such as carbon dioxide. In the second stage the coal is indirectly heated in a heater designated in its entirety by 12 to a temperature just short of that where the coal becomes viscous to drive off the carbon oxide gases, but which 5 is not high enough todistill off the valuable hydrocarbon compounds. The coal leaving the drier should have a temperature of approximately 250 degrees Fahrenheit which is raised to approximately 600 degrees Fahrenheit by the heater. The exact temperature of the coal, on 5 leaving the heater will depend on the temperature of the heating gasesand to a large extent on the grade of coal.

The drier is mounted, for rotation on spaced supports. l3 and is driven by the power unit it through the chain drive 115, pinion l6 and gear ll encircling the drier and meshing with the pinion. The raw coal is admitted to the right hand end of the drier, Figure 2, through the chute i8 connecting with the coal hopper i9 having the feeder 26 which also prevents air from entering the drier, it being understood that the drying and heating of the coal must take place without the presence of oxygen which at the high temperatures would cause combustion of the coal. The drier has its highest end where the raw coal is admitted and gradually slopes to cause progression of the coal toward the left, which after the proper interval of time necessary to complete the drying operation will be delivered to the enclosure 2i; which seals the left end of the drier from the' atmosphere and connects through passage 22 with the hoisting mechanism 23. The coal in the drier is subjected to direct contact with the heating gases which enter the drier at the left and travel toward the right in opposition to the travel of the raw coal, said gases being drawn oil through conduit 24 by the fan 25 and allowed to escape to the atmosphere.

The heater I2 is mounted for rotation on suprespect to the drier. The heater receives thecoal from the hoisting mechanism 23 and slopes from left to right to cause progression of the coal 4() in the same direction, which is eventually discharged to enclosure 28, sealing the right hand end of the drier, and which delivers the coal to a carrier 30. x r

The drier and heater are in the form of cylinders which as shown in Figure 3 are provided on their interior surfaces with ducts 3| and 32, respectively, which form longitudinal passageways for conducting the hot gases. By this arrangement the maximum heating surface is provided for efliciently transferring the heat from the hot gases to. the coal while at the same time the gases are prevented from direct contact with the coal. The right hand end of the drier and heater are enclosed within 'a chamber formed 5 by the rectangular brick housing 33 which is suitably supported upon the foundation II and divided into two compartments by the partition 34 extending between and separating the drier and heater. Said partition 34 has an opening 35 equipped with valve head 36 having handle 31 projecting through the rear wall of the chamber to permit-the operator to open and close the valve as desired. The hot flue gases are conducted from the coke ovens through the conduit 38 and enter compartment 48 through conduit 4| having a burner 42. The gases from the coke ovens, which are-inert as it is necessary to prevent oxidation, are at a temperature varying between 500 degrees and 800 degrees Fahrenheit, which is not sufllcient to heat the coal in the heater l2 to the required temperature, namely, 600 degrees Fahrenheit. Therefore, live gas must be used to give the necessary excess heat, which for practical reasons can not exceed 1100 degrees Fahrenheit. The live gas delivered to burner 42 heats the flue gases in compartment 40, giving thereto the necessary heat, whereupon the hot gases enter openings 43 in the heater leading to the longitudinal passageways formed by ducts 32. The gases travel the length of the heater and indirectly heat the coal within the heater.

The left end of the heater is enclosed and sealed from the atmosphere by the housing 44 which has communication with openings 45 leading from the longitudinal passageways and connect with the fan casing 46. The hotgases are withdrawn from the heater and housing 44 by the fan within casing 46 and discharged to conduit 41. Said conduit enters the base of compartment 48, and delivers the gases through openings 68 to said compartment. The conduit, however, continues through to the opposite side of the brick chamber 33, being equipped at a point outside the chamber with valve 5|, whereby when the volume of heating gases exceeds the requirements, the excess can be dischargedto the atmosphere. Within the compartment 48 the drier is provided with a plurality of openings 52 leading to the longitudinal passageways formed by ducts 3| which terminate at the left end of the drier just short of enclosure 2| and communicate with the interior of said drier, said gases being thus delivered to the interior of the drier for direct contact with the coal; These gases travel counterin compartment 48- and therefore when valve 36 is opened the direction of gas flow will be from compartment 48 to compartment 48 to effect a recirculation of said gases.

The heat or number of heat units required for the evaporation of the moisture and the heating of a given quantity of coal in a stated time to approximately 600 degrees Fahrenheit depends on several factors, namely, the volume of the gases, the heating surface of the cylinders or drums and the heat head, that is, the temperature difl'erence between the gases and the coal.

While the variables of these factors may permit many combinations practical operating rules and economical considerations necessitate a limitation on each of these factors. The volume of gases required in the preheating apparatus is considerably in excess of the volume produced by the combustion of the live gases at the coke ovens for coking the same amount of coal. Also the temperature of these flue or waste gases is low and requires additional heating in order to raise the coal in the heater to the required temperature. Particularly important is the heat head which with the limitations of the other factors determines the volume required. To obtain the maximum heat head it must be nearly as constant as'possible throughout the length of the drums and therefore it is important that the heating gases are hottest at the end where the coal is hottest. With the established conditions it can be calculated that the heater will require approximately twice as much gas to transfer the necessary amount of heat than the drier will require, which is a much greater volume than that produced in coking the coal. The invention accordingly provides means for recirculating the heating gases through the heater, introducing into the drier only the volume needed for the operation performed in this drum. In this way the volume of gases taken from the coke oven fiues is reduced to about one-half of the volume heretofore required. The cost of operation of the preheating apparatus is therefore reduced to a point where its installation is practical.

As previously explained, the heating gases enter compartment 48 through conduit 4| and are at this point raised to a higher temperature by the live gas burned in burner 42. The hot gases enter the heater and by the construction of the ducts the heat is indirectly transferred to the coal. The fan within casing 46 withdraws the gases from the heater and delivers them to compartment 48, enclosing the drier. From this compartment the gases are again delivered to compartment 40, the proportion of the gases being recirculated, depending upon the extent of opening of valve 36. It is necessary that some of the gases be delivered to the drier which enter through openings 52 and initially heat the coal as described. In chamber 48 the recirculated gases mingle with those gases from the coke oven which have been heated by burner 42,

whereupon they are again delivered to the heater as described.

I claim:

1. In apparatus of the character described, in combination, a drying cylinder and a heating cylinder, means mounting said cylinders for rotation to cause progression of the material delivered thereto through the cylinders, a housing enclosing a portion of the heating and. drying cylinder respectively and providing a separate compartment for each cylinder, means supplying high temperature gases to the compartment for the heating cylinder and a burner at the entrance of said compartment for heating the gases to raise their temperature before they are delivered to said compartment.

2. In apparatus of the character described, in combination, a drying cylinder and a heating cylinder, means mounting said cylinders for rotation to cause progression of the material delivered thereto through the cylinders, each of said cylinders having longitudinal ducts for conducting the heating gases, a housing providing compartments enclosing a portion of the cylinders respectively and communicating with the entrance to said ducts, means supplying hot gasesto each compartment, a burner for heating the gases delivered to the compartment for the heating cylinder for raising the temperature of said gases, and valved means between the compartments for permitting the gases to flow from one to the other.

3. In apparatus of the character described, in combination, a drying cylinder and a heating cylinder, means mounting said cylinders for rotation to cause progression of the material delivered thereto through the cylinders, each of said cylinders having longitudinal ducts for conducting the heating gases, a housing providing compartments enclosing a portion of the cylin-' ders respectively and communicating with the entrance to said ducts, means supplying hot gases to the compartment for the heating cylinder, and means withdrawing the gases from the ducts at the opposite end of the heating cylinder and delivering them to the compartment for the drying cylinder.

4. In a drying apparatus of the character described, in combination, a pair of cylinders comprising a drier and a heater, means mounting said cylinders for rotation to cause progression of the material delivered thereto through the cylinders, a housing providing compartments en-,

closing a portion of the cylinders respectively, means delivering hot gases to each of said compartments, and valve means for permitting the gases to flow from one compartment to the other.

5. In a drying apparatus of the character described, in combination, a pair of cylinders comprising a drier and a heater, means mounting said cylinders for rotation to cause progression of the material delivered thereto through the cylinders, a housing providing compartments enclosing aportion of the cylinders respectively, ducts extending longitudinally of each cylinder and having an opening within their respective compartments, means delivering hot gases to the compartment for the heater, a burner associated with said compartment for the heater for raising the temperature of the hot gases delivered thereto, means withdrawing the gases from the exit of the heater ducts and delivering them to the compartment for the drier, and a valved opening connecting said compartments.

6. The method of drying solid material by means of hot gases which consists in raising the temperature of said gases to that desired and immediately subjecting the solid material to the drying action of said heated gases, withdrawing the gases, returning a portion of said gases for reheating by said temperature raising means and for recirculation, and utilizing the remainder to initially dry the solid material and condition the same for said first mentioned drying operation.

7. The method of drying solid material by means of hot gases which consists in raising the temperature of said gases'to that desired and immediately but indirectly subjecting the solid material to the drying action of said gases with the solid material travelling counter to the flow of said heated gases, withdrawing the gases, returning a portion of the same for reheating by said temperature raising means and for re-l circulation, and utilizing the remainder to initially heat and condition the solid material by bringing the gases and solid material into direct contact with each other.

ALBIN GOI'ILIEB WI'I'IING.

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