US1516314A - Flash evaporator - Google Patents

Description

Nov. 18, 1924. 1,516,314

L. E. SEBALD FLASH EVAPORAT O R Filed Jan. 27. 1921 FLASH ANUJHAH/H'INQ CHAMBEK C/wuzAT/A/s PUMP (Jvwmxfoz 3% d How 1 QV 5 Patented Nov. 18, 1924.

UNITED STATES 1,516,314 PATENT OFFICE,

LESLIE EARL SEBALD, OF NEW YORK. N. Y., ASSIGNOR TO THE GRISCO'M RUSSELL COMPANY; OF NEW YORK, N. Y., A CORPORATION OF DELAWARE- FLASH EVAPORATOR.

Application filed January 27, 1921. Serial No. 440,327.

To all whom it may concern:

Be it known that I, LnsLrE E. SEBALD, a

A citizen of the'United States, residing at New York, in the county of Bronx, State of New York, have invented certain new and useful Improvements in Flash Evaporators; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to evaporators, particularly to the type employed for producing distilled water from brine or other impure water for boiler feed or similar purposes.

Such evaporators as now constructed consist usually of a shell containing the raw water with heating tubes or coils in the shell and immersed in the raw water, live steam being circulated through the tubes or coils to evaporate the water in the shell. One serious defect in evaporators of this kind is the formation of scale on the heat-transferring surface of the tubes or coils, due to the precipitation, as the water vaporizes, of the scaleforming salts or other impurities in the wa ter on the tube surface, and also due to the fact that the water velocity around the tubes is very low. This scale forming on the tubes lowers the heat-transferring efliciency of the surface and necessitates frequent cleaning of the tube surface to maintain the evaporator operative.

My invention has for its principal object to provide an evaporator in which there is no vaporization of the water at the heating surface whereby there will be no scale-fo mation and the heat-transferring capacity of the surface will be constant and higher than the capacity of the surface of the ordinary evaporator heating coil.

A further object of the invention is to provide an evaporator in which the raw water may be concentrated to a greater degree of salinity than heretofore practical, thereby lessening the heat loss due to the discharge or blow-down of the concentrated brine at com paratively hi h temperature.

A further 0 ject of the invention is to provide an evaporator in which variations in the water level and steam pressure have little effect on the operation of the evaporator whereby the plant requires little attention and with a suitable automatic feed pump will be virtually self-regulating.

In the drawing, which is largely diagrammatic, I have illustrated my improved evap orator in vertical section with the auxiliary apparatus shown in side elevation.

In said drawing, 1 indicates the heating chamber of the evaporator into which live steam is fed through the line 2, the steam condensing on the tubes 3 which extend across the chamber 1 and fill. the lower cylindrical portion of the chamber, with the ends of the tubes supported in suitable tube sheets forming the end walls of the chamber 1.

The shell 1 of the main heater has a discharge line 18 and will be provided with the usual trap, not shown, for preventing the discharge of steam from the main heater but allowing the water of condensation to pass into the fresh water line.

The tube sheet at one end is enclosed by a drum 5 forming a chamber 6 into which the raw water is fed through a line 7 connected to the discharge side of a circulating pump 8. The tube sheet at the other end is similarly enclosed by a drum 9 having its discharge pipe 10 extending upwardly and communicating with a horizontal branch 11leading into what may be termed the flash and separating chamber 12 which, as shown, consists of a suitable shell supported on the upper wall of the main heater but entirely disconnected from the heating chamber. The horizontal branch 11 of the discharge pipe is perforated on its under side throughout its length in the manner shown and extends just above the surface of the water in the flash chamber, the level of which will be maintained by any suitable feed at about that shown in the drawing. Above the pipe 11 the chamber 12 is provided with a series of staggered baflies 13 arranged in the manner shown in the drawing or in some other equivalent manner, to provide a circuitous passage for the vapor to separate from the vapor any entrained liquid which would otherwise carry impurities into the vapor line 14,

I The other side of the circulating pump is connected to the flash 'chamberthrougll a line 15 leading from the chamber below the water' level, whereby the pump will maintain a constant circulation of the water through the tubes of the heater, thence through the perforated discharge pipe 10 into the flash chamber, and thence back through the circulating pump. The discharge pipe 10 is preferably provided with a regulating valve 4 whereby the discharge of water from the pipe may be regulated and the load imposed on the pump increased or decreased to maintain the pressure on the liquid just above the pressure corresponding to the temperature to which the water is raised in the heating chamber.

The water circuit may be provided with any desired arrangement of feed and blowdown connections for maintaining the water .level at the desired point and-discharging the concentrated liquor at the desired degree of concentration. I have shown for the purpose a suction feed pump 20 and a blowmanner shown, although the point of con:

their capacities of a amount of feed with a the heater,

nection of neither the feed pump nor. the blow-down pump is material.

The blow-down and feed pumps have proper ratio to determine the degree of concentration to be produced in the evaporator, for instance, if the feed pump has a capacity of three times that of the blow-down pump the raw water will be concentrated to three times its normal salinity and the volume of blow-down Wlll be but half the volume of distillate produced from the vapor. For varying'the ratio between the feed and the blow-down a bypass 23'containing an ordinary regulating valve may be employed, whereby more or less water, as desired, may be short-circuited directly from the delivery side of the the suction side of the blow down pump, of blow-down in greater proportion than the correspondingly greater concentration of the brine. Also this injection of cold water will prevent flash in the blow-pump suction.

- In operating my improved evaporator the circulating pump will be maintained at a speed such as to impress on the water at the delivery side of the pump a pressure greater thanthe vaporizing pressure of the water to the temperature to which the water is heated in the heating chamber, so that there.

will be no vapor formed in the tubes of but instead, the heat will be absorbed by the liquid under pressure. When the liquid is discharged from the pipe 11 it will be at a temperature in excess of the pressure maintained in the flash chamber, which may be a sub-atmospheric pressure, and the excess heat will be instantaneously converted or flashed into vapor which will rise through the bafiles in the separating I chamber to be discharged "into the va or line. The water from the flash cham er withits temperature thus reduced by the own pump 21 connected tothe same shaft 'pump on one side and thereby decreasing the amount.

chamber as well as th My improved evaporator is particularly advantageous for operating at low temperatures. In an ordinary evaporator the tendency to foam and prime is so increased by loweringthe pressure in the vapor space as to make it diflicult of operation except at comparatively high pressures in the vapor space and hence at small temperature differences; In my improved evaporator the tendency to prime will be decreased. No

"scale will be formed on the tubes at any temperature and the vapor space may .be kept at a sub-atmospher1o pressure with a correspondingly high efliciency of the heattransferringsurface. The tubes may be arranged in a more compact and condensed space than in an ordinary evaporator in which the vapor is formed at the tubesurface, as willbe obvious. sure is substantially the same on both sides of the tube, that is, the high pressure of the on the steam on the other, the tubes may be made of light material withoutdanger of destruction. t

Instead of the above described arrangement of feed and blow-down pumps I may employ a separate float feed controlled suction pump and blow-down regulator such as is ordinarily employed for" evaporators. Also, ifdesired, I may employ an automatic regulator for the feed and blow-down pump motor, such for instance, as a float controlled rheo'stat,'but ifthe steam supply is fairly uniformno automatic control will be necessary for the heat transferring surface of the tubes remains cleanand at its maximum efficiency at all times and the vapor output will beconstant. a I e term pump circuit. asemployed in the appended claimsis intended toinclude the entire circuit of'the apparatus, including the separating chamber and the heating e pumps and pipes, and it is to be understood that the raw water will be introduced anywhere in the pump circuit and not necessarily at the location pump maintained in the the vapor pressure and the heating fluid as- Also, as the presand arrangement of the parts shown in the drawing is by way of exampleonly and various changes. may be made therein, within the scope of the appended claims.

I claim: V I

1. In a 'fiash evaporator the combination of a heating chamber having spaces for the heating medium, passages through said chamber for the circulation of the liquid to be evaporated, said passages being separated from said spaces by heat transferring surfaces, a vaporizing chamber separate from said heating chamber, connections between said passages and said vaporizing chamber, a pump for'circulating the liquid through said passages and discharging it into said vaporizingchamber, a return connection from said vaporizing chamber to said pump whereby said pump maintains the liquid to be evaporated in continuous circulae tion, means for addin to the liquid being evaporated a controlle amount of raw feed water to replenish the liquid being vaporized and regulating means cooperating therewith for discharging concentrated liquid from the apparatus to maintain a substantially constant liquid density therein.

2. In a flash evaporator, the combination of a heating chamber to receive the heating fluid, heating tubes extending across said chamber, a separate vaporizing chamber, connections for the passage of liquid from said tubes to said chamber, a pump for forcing the liquid to be evaporated through said tubes and into said vaporizing chamber, a

return connection from said vaporizing "fluid, heating tubes extending across said chamber,- a separate vaporizing chamber,

connections for the passage of liquid from said tubes to said chamber, a pump for forcing the liquid to be evaporated through said tubes and into said vaporizing chamber, a return connection from said vaporizing chamber to the suction side of said pump, a feed pump for pumping into said circuit the raw l quid to be evaporated, a separate blowdown pumphaving its suction side connected to said circuit, and means for regulating the relative capacities of said pumps to maintain the blowdown capacity at a definite fraction of the feed capacity.

In testimony whereof I affix my signature.

LESLIE EARL SEBALD.

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