Continuous production of boiler feed water

BESCHRANKTEN HAFTUNG ESSEN DE (72) Inventor REINHOLD COHN AND PARTNERS 21

AHAD HA'AM ST., P.O.B. 4060, TEL AVIV 61040 IL 03-7109333 03-5606405

This PDF First Page has been artificially created from the Israelian Abstracts

ייצור רציף של מים להזנת דוודים

Continuous production of boiler feed water

Fried. Krupp Gesellschaft mit beschrankter Haftung

C:_ 66996

BACKGROUND OF THE INVENTION

The present invention relates to a process for the continuous production of pure water for boiler feed from waters containing-salt, hydrocarbons and Fe⁺⁺.

Waters of this kind containing salt, hydrocarbons and Fe⁺⁺are obtained, for example, as process waters in the petroleum extracting industry and in this case, particularly, as surplus waters from steam flood installations. These waters are difficult to reprocess and reuse. Recovery of petroleum extracted from meager deposits requires a high expenditure of energy. The petroleum extracting industry produces high pressure steam in its own boilers. Steam generators require pure water as boiler feed water.

Desalination devices for waters are known in many forms. Separating hydrocarbons from water is also known. For boiler feed water, salts and hydrocarbons must especially be removed. In doing so, the twice positively charged Fe ions (Fe⁺⁺) must be prevented from oxidizing and depositing.

SUMMARY OF THE INVENTION

A primary object of the present invention is to create a process by which waters containing salt, hydrocarbon and Fe⁺⁺ can be converted into boiler feed water without Fe⁺⁺ precipitation, and therefore without depositing Fe⁺⁺ on heating surfaces and other installation parts.

Additional objects and advantages of the present invention will be set forth in part in the description which follows and in part will be obvious from the description or can be learned by practice of the invention. The objects and advantages are achieved by means of the processes, instrumentalities and combinations particularly pointed out in the appended claims.

To achieve the foregoing objects and in accordance with its purpose, the present invention provides a process for the continuous production of pure water for boiler feed from waste waters containing salt, hydrocarbon and Fe⁺⁺, comprising: subjecting mechanically purified water to a thermal degassing under vacuum in the absence of air in a degasser, subjecting the resulting thermally degassed water to an open-surface evaporation in an open-surface evaporator to produce a vapor, subjecting the so produced vapor to a mechanical vapor compression, passing the so produced compressed vapor through the heating surfaces of the open-surface evaporator to condense the vapor inside the heating surfaces and form purified water, the passing being conducted in such a manner that the open-surface evaporation is conducted at a lower temperature, compared to the condensation process inside the heating surfaces, feeding the condensed water from the heating surfaces of the open-surface evaporator under a gas vapor- and hydrocarbon vapor-atmosphere to a separator to separate the condensed purified water from non-condensable hydrocarbons, removing the purified water from the separator, and drawing off the non-condensable hydrocarbons from the separator.

In the process of the present invention, the heavy hydrocarbons are separated out of the water to be purified by the mechanical purification. The volatile hydrocarbons are separated out of the water to be purified by the thermal degassing. The remaining low boiling hydrocarbons still present in the water after the thermal degassing are separated by an open-surface evaporation conducted under vacuum. The vapors formed by the evaporation are then compressed, and the compressed vapors are subjected to a condensation process in the heating surfaces of the open-surface evaporator, by which a purified distillate condenses out. The purified distillate can be expanded in a separator, and some non-condensable hydrocarbons still present in the distillate and expanded vapors of the distillate can conseguently be drawn off from the separator, so that a desalinated pure water, free of oxygen, can be removed.

The evaporation/separation process works especially advantageously if the temperature difference between the evaporation process and the condensation process amounts to about 3 to 5°c.

In the process according to the present invention, the waters do not come in contact with oxygen during the entire treatment, so that no Fe⁺⁺⁺ can precipitate. A further advantage of this measure is that no deposits result anywhere in the entire process, which deposits would lead to contamination of the installation parts and consequently to problems in the process.

Preferably, the mechanically purified waters are stabilized before the thermal degassing.

The thermal degassing preferably is carried out by means of vapor from the expanded distillate and associated non-condensable gases. 4

In one preferred embodiment of the present invention, the thermal degassing is carried out in a joint step, that is, the heating of the water and the degassing of the water are performed in a common step.

The vapors resulting from the open-surface evaporation preferably are passed through a demister with a coalescense effect before the condensation.

Preferably, the volatile hydrocarbons from the degassing step are removed from the degasser by means of a vacuum pump or a 10 jet compressor.

' It is also preferred that waste liquor from the open-surface evaporation is passed through a cyclone, from which the solid components are drawn off.

It is to be understood that both the foregoing general description and the following detailed description are exemplary’, and explanatory, but are not restrictive of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a flow chart of one embodiment of the process according to the present invention ²־ Figure 2 shows a further embodiment of the thermal degassing which can be employed in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The waters to be treated are fed by a supply line 2 to a mechanical purifier 1 in which the waters are subjected to a 25 mechanical purification step. Mechanical purifier 1 can be a conventional purifier such as a mechanically functioning filter and removes solid materials, sAch as, for example salts, solid impurities, such as sand, or the like.- ־

Heavy hydrocarbons contained in the waters are drawn off from purifier 1 over a supply line 3.

The mechanically purified water from purifier 1 is introduced by a pipe 4 into a stabilizer 5 where it is subjected to a stabilization step. »

Stabilized water from stabilizer 5 is conducted through a pipe 6 to a preheater 6a and from there via a pipe 6b to a final preheater 7 having heating surfaces 7a to effect preheating of the water. The preheated water reaches a degasser 9 by means of a pipe 8 and a spray device 10. Volatile hydrocarbons are drawn off from degasser 9 by means of a pipe 11 and a jet pump 12. Moreover, volatile components are drawn off from final preheater 7 in the same way, that is, by means of a pipe 11a which is connected to jet pump 12. >

The thermally degassed water leaving degasser 9 is fed by a pipe 13 to a spr^y system 15 inside an open-surface evaporator 14 containing a heat exchanger 16 and is distributed evenly as a thin film on the outside of the evaporation pipe of heat exchanger 16. The vapor formed by the evaporation passes through a demister 17 in evaporator 14 and is drawn off from evaporator 14 by a pipe 18 Which feeds the vapor to a compressor 19. The vapor is compressed in compressor 19, and in that way brought to a higher temperature level. The compressed vapor leaving compressor 19 is passed in a pipe '20 to the inside of the heating

6־ surfaces of heat exchanger 16 and condenses in the heating surfaces of heat exchanger 16. The condensate resulting thereby reaches a separator 22 by a pipe 21. In this separator 22, the condensate is released by a controlled partial expansion from the remaining hydrocarbons, so that a purified distillate results that is fed to preheater 6a by a condensate pump 23 and a pipe 24 and is drawn off from preheater 6a by a pipe 28. During the controlled partial expansion there is produced a vapor from the expanded distillate.

The oils still found within the vapors are not condensed with it in heat exchanger 16, so that the non-condensable hydrocarbons released in separator 22 together with vapor from the expanded distillate are drawn off from separator 22 by a pipe 25 and led to preheater 7. The vapor from the expanded distillate condenses in preheater 7 and this condensate is drawn off from preheater 7 by a pipe 27.

During the open-surface evaporation, the easily low boiling remaining hydrocarbons evaporate as well as the water. A part of the waste liquor is led out of evaporator 14 to a cyclone 30 by a pipe 29 by means of a circulating pump 26. The solid materials are removed from the waste liquor by cyclone 30 and are removed from the cyclone by a pipe 31. The remaining waste liquor, that is, the waste liquor which is not led to the cycle 30, is rejected by means of a pump 33 and a pipe 34 through preheater 6a with a pipe 35.

In the embodiment according to Figure 1, the thermal degassing consists of preheater 7 and degasser 9. According to

Figure 2, the thermal degassing is conducted in a common step. For this purpose the heating surfaces 7a are provided in degasser 9 and are connected to feed pipe 27 and a drain pipe 27a. As in the embodiment according to Figure 1, the water here is also delivered to degasser 9 by pipe 8 and a distributor or spray device 10 and the thermally degassed water is drawn off by pipe 13. The volatile hydrocarbons are again drawn off by pipe 11 and jet pump 12.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the 5 appended claims.