Pollution Control System

Abstract

A system for controlling pollutants from the quenching station of a coke oven is provided. The system includes a coke breeze sump that is divided into two zones, a coke breeze settling zone and a clean liquid zone. A first pumping means withdraws a thickened sludge of coke breeze, either continuously or intermittently, from the coke breeze settling zone and a second pumping means flows clean liquid from the clean liquid zone to a spray means. The spray means directs the clean liquid onto hot incandescent coke in a quenching car thereby producing quenched coke and a slurry of coke breeze and of liquid. This slurry drains into the coke breeze settling zone of the sump where the coke breeze settles by gravitational force to form a thickened sludge of coke breeze in the coke breeze settling zone so that clean supernatant liquid collects above the thickened sludge of coke breeze in the clean liquid zone of the sump.

Parent Case Text

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation (Rule 60) of application Ser. No. 27,487, filed Apr. 13, 1970, now abandoned.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a system for preventing pollution of the environment surrounding a coke making facility when hot, incandescent coke is quenched.

Heretofore, the manufacture of coke has been considered to be an inherently dirty operation which has tended to contribute significantly to air and water pollution. The coke making industry, realizing its responsibility to provide cleaner operating systems, has provided cleaner systems, such as, for example, improved gas collecting hoods, improved gas cleaning systems, and the like; but, an area of pollution which has not been well handled has been that involved with the quenching of coke.

One essential operation in the manufacture of coke is the quenching of hot, incandescent coke to stop the coke from burning after it has been removed from an oxygen-poor atmosphere in the coke oven to an oxygen-rich atmosphere of the air. This quenching is best and most economically accomplished by dousing the coke with water. The water, after quenching the hot, incandescent coke, becomes a spent quenching liquid comprising a slurry containing a liquor of water including various organic chemicals, such as, for example, phenols, cyanides, and of a suspension in the water of coke particles, commonly referred to as "coke breeze."

The problem that has resulted is that there is no practical method of disposing of the spent quenching liquid without a consequential severe contamination of our streams. Therefore, coke plants generally recirculate the waters used for the quenching until eventually the water evaporates into the atmosphere.

2. Description of the Prior Art

Hence, in conventional quenching, a quenching car containing hot, incandescent coke travels to a quenching station where sprays of quenching liquid are directed onto hot, incandescent coke for a predetermined interval of time to quench the coke. As would be expected the spent quenching liquid, being a slurry, contains large amounts of fine coke, called "coke breeze" and other solid materials. This spent quenching liquid drains from the quenching car to the floor of the quenching station and thence, as a slurry, flows to a conventional deep sump below the level of the floor of the quenching station. A portion of the coke breeze in the spent quenching liquid settles by gravity to the bottom of the sump so that the spent quenching liquid becomes relatively clean to form a supernatant liquid above the settled sludge of coke breeze. The time required for this separation is naturally dependent upon the particle size of the coke breeze. Liquid pumps recirculate the relatively clean supernatant liquid to a storage and surge tank for reuse to quench another quantity of hot, incandescent coke. When the sump becomes full with the sludge of settled coke breeze, the operation of the quenching sump is discontinued and a "clam shell crane" or the like is used to remove the sludge of settled coke breeze therefrom. The sludge of coke breeze, containing about 15 percent to 40 percent liquid, is usually dumped onto the ground in piles and dried. The contaminated water in the sludge of coke breeze drains from the coke breeze to the ground and from there into sewers and streams. In this dried form the coke breeze has various industrial uses, such as, for example, a sintering fuel. In some instances the sludge of coke breeze is dumped onto the quenching wharf and processed along with the quenched coke in a conventional manner.

The difficulties of the existing systems for quenching coke and the handling of spent quenching liquid are numerous. Heretofore, quenching sumps have been rectangular in cross-sectional configuration from top to bottom. The spent quenching liquid or slurry has entered the sump at its top and has been held in the sump for relatively long periods of time so that the coke breeze may separate by gravity to the bottom of the sump. To compensate for the long periods of time required for adequate separation, it has been necessary to provide sumps having relatively large cross sectional areas and a clear well to receive the supernatant liquid. Nevertheless, only a portion of the coke breeze and other solids have settled to the bottom of the sump within any given time period. This is especially true when the settling capacity of the sump has been exceeded or when the sump has been improperly cleaned. When the quenching liquid was then recirculated to the quenching storage and surge tank, unsettled coke breeze remaining in the quenching liquid has abraded the pumping equipment causing premature failure of that equipment.

Moreover, as coke breeze accumulated in the sump, the efficiency in separating coke breeze from spent quenching liquid has necessarily decreased. Eventually, the entire operation has had to be temporarily suspended so that the accumulated coke breeze and other solids or sludge could be withdrawn by conventional means from the bottom of the sump.

Another feature of the prior systems is that to avoid the carry over of breeze to the quenching pumps it has been necessary to have a plurality of settling sumps and baffles in association with the quenching stations.

Hence, the toll exacted for providing clean water for coke manufacturing operations has been a heavy one. For example, in wet coke quenching unsettled coke breeze remaining in the supernatant liquid has abraded the liquid pumping equipment causing premature failure of the equipment. The numerous quenching sumps has been expensive in capital investment, in maintenance, and in operational efficiency, thus emphasizing the need for an improved system that is not costly yet achieves desirable pollution control.

The pollution control system of this invention requires less capital investment; is easier to maintain; and, has a much improved operational efficiency than known systems. The system of this invention extends the operating life of currently used pumping equipment much beyond that of prior systems and provides a much higher efficiency in the separation of the coke breeze from the spent quenching liquid than heretofore known. The time for separating coke breeze from spent quenching liquid is substantially reduced in this invention. It is no longer necessary to use men, trucks, cranes and the like to remove accumulated coke breeze from the sump nor is it necessary to provide several sumps in association with quenching stations. This invention provides a breeze removal system that is compact and yet assures a satisfactory separation of coke breeze and other solids from the quenching liquid.

SUMMARY OF THE INVENTION

In accordance with the invention a pollution control system for use at the quenching station of a coke oven battery wherein hot, incandescent coke in a car is quenched with water to produce quenched coke and a slurry of coke breeze and of water is provided. The system includes a sump for receiving the slurry of coke breeze and of water which sump is divided into two zones, a coke breeze settling zone and a clean liquid zone. The coke breeze settling zone in the preferred embodiment of the invention is adjacent to but at a lower elevation than the clean liquid zone. In another embodiment the coke breeze settling zone is laterally adjacent to the clean liquid zone.

A means is provided for directing the slurry of coke breeze and of water into the coke breeze settling zone so that coke breeze separates by gravitational force from the water of the slurry to form a thickened sludge of coke breeze in the coke breeze settling zone. The water forms a supernatant liquid above the thickened sludge of coke breeze in the clean liquid zone.

A first pumping means withdraws periodically or continuously the thickened sludge of coke breeze from the coke breeze settling zone and a second pumping means flows the supernatant liquid from the clean liquid zone to a sprayer means. The sprayer means directs the supernatant liquid onto a car containing a new quantity of hot, incandescent coke.

In accordance with the invention, the sump has a continuous liquid retaining surface comprised of an upper portion and a lower portion. The lower portion slopes downwardly and converges inwardly of the sump to terminate at a terminus for providing a confined volume in which the coke breeze settles by gravity.

GENERAL DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a plan view illustrating an embodiment of the pollution control system of the invention;

FIG. 2 is a side elevation view of the pollution control system of FIG. 1;

FIG. 3 is a side elevation view illustrating another embodiment of the sump of the pollution control system of the invention; and

FIG. 4 is a side elevation view illustrating another embodiment of the sump of the pollution control system of the invention.

DETAILED DESCRIPTION

FIGS. 1 and 2 show a quenching car 11 in a quenching station generally indicated at 13. The quenching station 13 includes a quenching hood 15 having associated therewith a quenching storage and surge tank 17. In accordance with the invention, the quenching station includes a quenching sump 21 that has two zones, denoted as A and B. The zone B has a first pumping means 25 and the zone A has a second pumping means 23.

The quenching car 11 is conventional. Such a car has a sloping floor or apron therein (not shown) on which hot, incandescent coke 29 lies in a uniform layer. The car 11 travels over rails 31 into the quenching station 13 from a coke oven battery (not shown) from which hot, incandescent coke has been discharged into the quenching car 11.

The quenching hood 15 illustrated in FIGS. 1 and 2 is conventional and rests on a concrete foundation 33. The purpose of the quenching hood is to prevent air pollution when hot, incandescent coke is quenched. Gas collecting equipment (not shown) cleans and removes dust particles that are produced when the hot, incandescent coke is quenched with water.

A concrete floor 35 conventionally slopes along the length of the rail 31 (as illustrated herein from the left to the right of FIG. 2) and from both sides of the quenching hood 15 thereof to form a trough or funnel for channeling spent quenching liquid into a spent quenching liquid outlet 37.

In accordance with the invention, the quenching sump 21, as illustrated in FIGS. 1 and 2, is a receptacle having at the top a rectangular cross sectional configuration that, as the sump 21 is viewed in a vertical relationship, becomes a generally truncated, inverted pyramid and that terminates at the bottom in a smaller rectangular cross sectional configuration. The sump 21 is situated below the rails 31 over which the quenching car 11 travels and is disposed adjacent to the quenching hood 15 as illustrated in FIGS. 1 and 2.

To provide for this configuration of the top, the quenching sump 21 has opposite end walls 51a and 51b and opposite side walls 53a and 53b that are joined to define a upper portion of a continuous liquid retaining surface. Forming a lower portion of the continuous liquid retaining surface of different cross sectional dimensions, each of the opposite end walls 51a and 51b of FIG. 2 have depending therefrom lower downwardly sloping surface portions 55a and 55b that converge inwardly of the sump 21 and, each of the side walls 53a and 53b have depending therefrom lower downwardly sloping surface portions 57a and 57b that also converge inwardly of the sump 21. As illustrated herein, the sloping portions 55a, 55b, 57a, and 57b are joined by a bottom surface 59. The lower sloping portions define a confined volume in the sump 21 in which the separation of coke breeze takes place. Restricting the volume in which separation of coke breeze occurs improves the efficiency of coke breeze separation and reduces the time required for efficient separation of coke breeze from the slurry of coke breeze and of water.

In accordance with the invention, sump 21 in FIGS. 1 and 2 includes a flume 49 which is a simple conduct that extends from the top of sump 21 to a location near the bottom 59 of sump 21. Flume 49 has a barscreen 61 or the like for preventing large solid particles from entering the sump 21. The screen 61 may be of any size as desired, but it is preferred to have a screen size such that solids having a diameter larger than two inches are retained on the screen and solids having a diameter less than two inches pass through the screen. The flume 49 is connected with the quenching liquid outlet 37 and is arranged so that spent quenching liquid is discharged at the bottom surface 59 of the sump 21. This arrangement has the advantages of preventing the bridging of coke breeze and solids around the first pumping means 23 during periods of inoperation and, moreover, of aiding the settling of the coke breeze and solids as they have less distance to travel in settling to the bottom surface 59 of the sump 21.

It should be noted that in FIG. 2 sump 21 has two zones, a coke breeze settling zone, identified as A, and a clean quenching liquid zone, identified as B. Upon the quenching of a quantity of hot, incandescent coke a slurry of coke breeze and of water is formed, which slurry flows through outlet 37 into flume 49 to the bottom of sump 21. As the coke breeze in the slurry settles a sludge of coke breeze is formed in zone A, the coke breeze settling zone, whereby the liquid is rendered relatively clean to form a supernatant liquid above the sludge of coke breeze in zone B, the clean quenching liquid zone.

The sludge of coke breeze is removed from zone A by a first pumping means 23 in FIGS. 1 and 2. This means 23 may be a conventional sludge pump that is capable of continuously withdrawing solid materials in the form of sludge from the bottom of the sump 21. The pump 23 removes the coke breeze and other solids continuously or intermittently so that little or no accumulation of breeze and other solids occurs in and around the breeze removal pump 23 at its bottom.

The first pumping means 23 in FIG. 2 includes a motor 63 situated on platform 64 that has a drive shaft 65 which extends to drive an impeller 71. A housing 69 is connected to the shell of motor 63 and encloses drive shaft 65 to protect it from corrosion and the like. Near the bottom of housing 69 is a suction bell 67 within which impeller 71 rotates to pump the sludge of coke breeze through discharge conduit 73 that extends from a side of the suction bell 67. By rotating the impeller 71 at a high velocity a vacuum is created in the suction bell 67 causing the sludge of coke breeze and other solids to pass from the bottom of the sump 21 through the suction bell 67 into discharge conduit 73 and through a conduit 75 to a breeze collecting tank 77.

Breeze collecting tank 77 has a plurality of apertures 79 through which excess water of the recirculated sludge of coke breeze may pass but through which the coke breeze and other solids do not pass. Alternatively, the breeze collecting tank 77 may use screens or the like for the separation of any water from the sludge of coke breeze. Quenching liquid or water is thereby conveniently separated from the sludge in the breeze collecting tank 77.

The breeze collecting tank 77 has an operable gate 81, FIG. 1, or a dumping means, which may be opened to discharge the collected coke breeze and other solids from the breeze collecting tank 77 to the coke quenching car or to a suitable conveying device or the like (not shown). Breeze collecting tank 77 is therefore discharged periodically to receive more coke breeze and other solids from the sump 21. Connected with the breeze collecting tank 77 is a quenching liquid conduit 83 that drains the excess water from the breeze tank 77 into flume 49.

By opening valve 75a and closing valve 73a in conduit 73 the sludge of breeze and other solids that are pumped by pumping means 23 flow into coke breeze collecting tank 77 and are deposited therein. Discharge conduit 73 also leads to coke breeze discharge headers 85 which empty into quenching car 11. Hence, by closing valve 75a and opening valve 73a coke breeze and solids may pass into coke breeze discharge header 85 and onto the quenching car 11 containing quenched coke, if desired. This feature may be desirable when breeze collecting tank 77 is being discharged; hence, the operation of the system of this invention never need be discontinued.

The supernatant, relatively clean liquid is to be handled by a second pumping means 25 which includes a motor 87 on platform 64, a suction line 89, a suction bell 91, and a discharge conduit 93 which empties the water into quenching tank 17. The tank 17 is optional and by-pass conduit 94 may alternatively be used to divert the liquid from tank 17 directly to spray header 45. In operation, when the motor 87 of the second pumping means 25 is actuated clean quenching liquid or water passes through suction line 89 into conduit 93 and is discharged into the quenching storage and surge tank 17.

The quenching storage or surge tank 17 may be equipped with pressure or float devices that automatically cut off the second pumping means 25 when a predetermined level is obtained in the tank 17 and automatically turns the pump on when the liquid in the tank falls below the predetermined level. A quenching liquid conduit 39 with a valve 43 leads into the spray header 45 having a plurality of sprays 47 that are directly over the quenching car 11.

The storage and surge tank 17 has a breeze removal conduit 101 with valve 103 which leads into coke breeze discharge header 85. This optional feature is used when coke breeze and other solids for some reason should collect in the bottom of the quenching storage or surge tank 17. By opening the breeze removal valve 103, coke breeze and solids pass into the coke breeze discharge conduit 73 onto the quenched coke contained in the quenching car 11.

In operation, clean liquid flows from the quenching liquid storage or surge tank 17 through conduits 39, and quenching valve 43, and, thereafter, through a quenching liquid distributor 45 where the liquid is distributed through a plurality of sprays 47 onto the hot incandescent coke 29 in the quenching car 11. The quenching valve 43 is conventionally opened for a predetermined time during a quenching period and closed during a non-quenching period when the quenching car 11 is removed from under the quenching hood 15 and replaced with a new quenching car (not shown), if desired. The quenching valve 43 may be actuated by any conventional means, such as, for example, hand, electrical, hydraulic or pneumatic means.

Spent quenching liquid comprising a slurry of coke breeze and of liquid flows from the quenching car 11 to the floor 35 of the quenching hood 15 to the quenching liquid outlet 41 and thence into quenching liquid flume 49. The spent quenching liquid or the slurry enters sump 21 at the bottom thereof wherein coke breeze and other solids settle by gravity to the bottom 59 of the sump 21 to form a sludge. As desired, pump 23 is operated continuously or intermittently to withdraw the sludge from the bottom of the sump 21 to either the breeze collecting tank 77 or to breeze header 85. Pump 25 withdraws supernatant liquid from sump 21 to quenching storage and surge tank 17 to be used in quenching a new quantity of hot, incandescent coke.

In FIG. 3, another embodiment of quenching sump 21 is illustrated which has the same general cross sectional configuration as that of FIGS. 1 and 2 except that the lower downwardly sloping surface portions 55a, 55b, 57a, and 57b meet at a point. Sump 21 of FIG. 3 has a dividing wall 105 extending from the top of sump 21 to adjacent the downwardly sloping surface portions 105 and extending across the cross section of the sump 21. Thus, in the sump 21 of FIG. 3 the coke breeze settling zone; A, is laterally adjacent to the clean liquid zone B, both of which communicate with each other at the bottom of the sump 21. The first pumping means 23 in the coke breeze settling zone, A, similarly removes the sludge of coke breeze therefrom. The second pumping means 25 in the clean liquid zone B similarly withdraws clean liquid therefrom. The water return conduit 83 from the coke breeze collecting tank in FIG. 3 is disposed towards one side of the sump 21 and comprises a simple trough to catch excess liquid from the breeze collecting tank 77.

In operation, spent quenching liquid comprising a slurry of coke breeze and water enters sump 21 of FIG. 3 at the top thereof. Coke breeze and other solids settle by gravity to the bottom of the sump to be withdrawn by pumping means 23. Clean liquid accumulates in zone B, and is withdrawn by pumping means 25.

In FIG. 4, another embodiment of quenching sump 21 is illustrated. The general cross sectional configuration is similar to that of the embodiments of FIGS. 1 and 2 of this invention. The sump 21 of FIG. 4 has lower sloping downwardly surface portions 55a, 55b, 57a, and 57b similar to those same portions of FIGS. 1 and 2, which portions terminate at a bottom surface 59.

Sump 21 of FIG. 4 has two zones where the upper zone, B is the clean quenching liquid region and where the lower zone A, is the coke breeze settling region. The sump includes a dividing wall 105 that extends from the top of sump 21 to adjacent the downward sloping wall portions and extends across the cross section of sump 21 of FIG. 4 to channel spent quenching liquid that enters the sump 21 at the top thereof to the bottom of the sump 21.

A first pumping means 23 in zone A includes a motor 63 and its associated parts of a driving shaft (not shown) and an impeller (not shown). A housing 69 surrounds the impeller and is connected to suction conduit 67 and discharge conduit 73. The motor 63 and its associated parts are situated to the side of sump 21 of FIG. 4. Such an arrangement is referred to as a horizontal pump as contrasted to the vertical pump in the embodiments of FIGS. 1 and 2. The suction conduit 67 extends into the coke breeze settling region A of sump 21 and leads from the bottom of the sump 21 to the housing 69 of pump 23. In operation, when motor 63 is actuated sludge at the bottom of the sump is withdrawn through conduit 67 into housing 69 and thence into discharge conduit 73.

The second pumping means (not shown) in zone B is also a horizontal pump that recirculates clean quenching liquid to the quenching liquid storage and surge tank. Suction conduit 89 extends into zone B horizontally, passing through side 51b of sump 21. The operation of the second pumping means, is similar to the same second pumping means in the embodiment of FIGS. 1 and 2.

It should be noted that the embodiments of my invention illustrated in the drawings show sumps 21 that have generally rectangular cross-sectional configurations. Yet, other cross-sectional configurations may be used in accordance with the invention such as, for example, a circular cross-sectional configuration. Thus, the upper portion of the continuous liquid retaining surface would comprise a cylindrical surface and the lower portion of the continuous liquid retaining surface would comprise an inverted frusto-conical surface.

Thus the pollution control system of this invention quite surprisingly controls pollution without the disadvantages of the prior art systems. Coke breeze and other solids are more efficiently separated from spent quenching liquid than heretofore known. The system may be operated automatically, thus requiring less personnel and less supervision to maintain its efficiency. The system may be operated continuously without interruption thereby avoiding the use of contaminated water when the sump is shut down for cleaning.

The time required for the settling of coke breeze from the spent quenching liquid is substantially reduced by virtue of the design of the quenching sump of the invention. The size of the quenching sump is now smaller as compared with the sumps of the prior art; hence, a capital cost savings is realizable. Also, only one quenching sump need be constructed in association with a quenching station.

Because the pumping means and their motors are situated above or beside the quenching sump they may easily be inspected and maintained. The quenching sump of my pollution control system may have a permanent covering placed over its top and thus the sump may be placed below ground level without posing any danger to workman who might fall into quenching sumps.

The sludge of coke breeze is periodically discharged on the coke quenching car or periodically or continuously collected in the breeze collecting tank and thus confined. The collected coke breeze may be drained and discharged on the coke wharf and further processed along with the quenched coke, if desired. The coke breeze may then be used for its intended industrial uses.

Because the efficiency of separating coke breeze and the like from spent quenching liquid is improved the problems of periodic replacement of various valves and moving parts of the system is substantially reduced. Thus the operating life and efficiency of the moving parts of my system is thereby extended and improved. Consequently my pollution control system represents substantial maintenance and capital cost savings.

Hence the combination of all of these favorable factors represents to the coke making industry an advancement in the art of controlling pollution without heavy outlays of money as compared to the expense of the prior art systems. The system of my invention is so much more efficient than prior art systems, and the costs of maintenance are substantially reduced with my invention.

Claims

1. In a system wherein coke breeze is recovered from a quenching station, the improvement in said system comprising:

a. sump-type receptacle for receiving and holding liquid containing coke breeze, said receptacle including:

i. first walls defining an upper portion that merge into converging second walls of a lower settling zone portion with the smaller end of said second walls being connected to

ii. a bottom, with

iii. third walls disposed adjacent said first and said second walls and forming thereby a flume that terminates adjacent said bottom;

b. a channel communicating with said flume for carrying said liquid thereinto;

c. a first pumping means having a suction in said settling zone portion adjacent said bottom for picking up and conveying said liquid to

d. a second receptacle wherein there are perforations whereby said coke breeze is retained therein, but said liquid passes through said perforations;

e. conduit means for conveying said liquid from said receptacle to said flume;

f. second pumping means having a suction in the upper portion of said sump-type receptacle for removing clear liquid therefrom; and

g. conduit means conducting said liquid to apparatus for quenching coke at

2. The invention of claim 1 including:

a. a third receptacle adapted to receive and hold liquid;

b. means for conducting said clear liquid from said sump-type receptacle to said third receptacle; and

c. conduit means for conducting said clear liquid from said third

3. The invention of claim 2 including:

a. conduit and flow control means connected to said third receptacle for conveying coke breeze therefrom.