Distillation: apparatus – Apparatus – Systems
Reexamination Certificate
2000-02-10
2002-08-20
Manoharan, Virginia (Department: 1764)
Distillation: apparatus
Apparatus
Systems
C202S172000, C202S205000, C159S024100, C159S044000, C159SDIG001, C203S001000, C203S011000, C203S026000, C203SDIG001, C203SDIG002
Reexamination Certificate
active
06436242
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and device for distilling water, for example to desalinate or remove contaminants from water.
2. Background Information
Distillation of seawater or contaminated water occurs through boiling water to produce water vapor. The vapor, which largely is free of salt and other contaminants, is then extracted to provide pure distilled water.
In prior art desalinating devices, it has been known to boil seawater at sub-atmospheric pressures, so that the boiling point of the seawater is lowered. For example, pure water will boil at 1 atmosphere (760 mm Hg) at about 100 degrees Celsius. At a pressure of 0.5 atmospheres, pure water will boil at about 81 degrees Celsius. Salt content however raises the boiling point of water due to boiling point elevation, also known as molecular elevation of the boiling point. For example, one extra gram of salt in a liter of water at atmospheric pressure will raise the boiling point approximately 0.5 degrees Celsius. The boiling point elevation effect is reduced at lower pressures however, so that an extra gram of salt will raise the boiling point temperature by less that the amount at atmospheric pressure. As a result, the boiling point of salt water or brine can be adjusted by controlling the pressure, temperature and salinity of the salt water to be boiled.
Once water has been boiled to form vapor or steam, it is possible to raise the temperature of the steam by compressing the steam, since steam generally follows the perfect or ideal gas law, i.e. PV=RT, where P is pressure, V is volume, R is a constant and T is temperature.
The firm Alfa Laval sells a vacuum vapor compression distiller which functions as follows.
Seawater is fed through a the Alfa Laval distiller so that a distillate stream and a brine stream are output, the brine stream having approximately twice the salinity of the seawater and the distillate stream containing substantially pure water. The seawater first is fed through a filter, is split into two input substreams, one of the substreams being preheated in a heat exchanger by the brine output stream and one by the distillate output stream. The input substreams are then recombined, and the seawater is vented to remove air and NC gases. The seawater then passes into an evaporation chamber of an evaporation condenser, which is a large horizontal cylindrical structure. A vacuum has lowered the atmospheric pressure of the evaporation chamber to a sub-atmospheric pressure. By virtue of the temperature and the pressure in the evaporation chamber, a recirculating brine stream (taken from the seawater and the remains of evaporated brine) evaporates, i.e. boils. The evaporated water vapor then is sent through a vapor compressor, which raises its temperature. The water vapor is then sent back through heat exchanger plates, which reheats recirculating brine and at the same time condenses to form the distillate, i.e. pure water. The reheated brine evaporates due to its increased temperature, thereby forming more water vapor to be sent through the compressor. The brine which is not re-circulated is output from the evaporator condensor by a discharge pump.
The Alfa Laval distiller thus produces a continuous process which outputs a distillate stream and a brine stream having approximately twice the salinity of the incoming seawater.
However, the Alfa Laval distiller has several disadvantages: (1) the brine in the evaporator distiller is split into two substreams: one which is output and one which recirculates to be reheated and evaporated in a plate-type system. This brine has a high salt and/or contaminant content which can foul the piping or plate-type system. Thus an anti-scalant dosing unit is provided to the recirculating brine stream, which can be expensive and complicated. Moreover, even with anti-scalant the plate-type system may fail; (2) an extra filter and an electrical heater also added to the recirculating brine stream. These elements are expensive and also prone to expensive maintenance; (3) the vapor and brine streams must be split into several substreams to be fed through the plate-type system, which thus becomes complicated, expensive and more prone to failure; and (4) the brine output stream has approximately twice the salinity of the seawater, which is too low a concentration for further processing and generally must be considered waste brine. The waste brine stream must generally be returned to a large body of seawater, so as not to environmentally disturb the body of water by increasing its salinity greatly, or be processed in costly and expensive ways such as being deposited in a deep well. Moreover, the distiller cannot be used for decontamination of water with pollutants, as the remaining contaminants are still in a dissolved form.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a low maintenance device and method for distilling water. An additional or alternative method of the present invention is to provide a device and method for distilling water which can produce a high concentration brine or contaminated water stream to permit extraction of salt or contaminants. Another additional or alternative object of the present invention is to provide a low cost device and method for distilling water.
The present invention provides a water distiller comprising a sub-atmospheric boiler having a non-recirculating brine section, an input, a brine output and a vapor output, the input for water to be distilled, the brine output for brine, and the vapor output for water vapor. A compressor or other vapor heater is connected to the vapor output and heats the water vapor. An heated vapor line then heats the brine section of the boiler, the heated vapor line eventually outputting the water vapor in condensed form as distillate.
Because the brine section does not need to re-circulate through a heat exchanger, the distiller of the present invention can provide for much more concentrated brines, which can be output through the brine output. “Brine” as defined herein is water having a high salt or contaminant concentration. The concentrated brines provided by the present device can be easily centrifuged to provide salable salt or to provide solid and easily disposable contaminants.
Moreover, with the present device no anti-scalant need be used and a plate-type system is not necessary.
For example, some seawater contains approximately 30 grams of salt per liter. The present device can produce an output brine with a concentration of salt of over 200 grams per liter, or more preferably of a concentration of 250 to 350 grams per liter. At this concentration, the brine can be centrifuged to provide salt which can be resold. The distiller of the present invention thus preferably further includes a centrifuge connected to the brine output for producing solid salt or waste. The water removed from the centrifuge preferably is returned through the input to the boiler, so that a closed system results, the only outputs being the salt or waste and the distilled water.
The brine section preferably is at the bottom of the boiler. The boiler preferably includes a filter, most preferably made of titanium wool, over brine section. The filter permits vapor to escape but helps retain contaminants and/or salt in the brine. In order to provide for continuous cleaning of the filter, the input may be located above the filter, so that the input water flows over the filter. A second filter may also be provided above the first filter for additional filtering, and may be cleaned periodically.
The heated vapor line may wrap around the outside of the brine section or may pass through the brine section, preferably in coiled form. After condensation, the heated vapor line forms a heated distillate line. Preferably, the heated distillate line passes though a heat exchanger to heat water entering in through the input line to the input of the boiler.
The input line preferably includes an initial silica filter and a venting device, and the heated vapor
Davidson Davidson & Kappel LLC
Manoharan Virginia
Sanchez Belmar Pedro Joaquin
LandOfFree
Device and method for distilling water does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device and method for distilling water, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device and method for distilling water will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2918053