CA2676730A1 - System and process for producing fresh water - Google Patents

Abstract

A method relates to the combustion of Hydrogen and Oxygen under high pressure to produce fresh water. The pressurized hydrogen and oxygen are then combusted in a high pressure high temperature combustor to generate high pressure high temperature superheated steam. The heat from the superheated steam is then removed by a high temperature heat exchanger system to be used in industrial process or generate electricity. The high pressure high temperature superheated steam is condensed, as a result of the heat extraction by the heat exchanger system, to produce fresh water.

Description

System and Process for Producing Fresh Water The present invention relates to the production of fresh water.
BACKGROUND

Water is one of the most vital natural resources for a!l life on Earth. The availability and quality of water has always played an important part in determining not only where people can live, but also their quality of life. Domestic use includes water that is used in the home every day such as for drinking, food preparation, bathing, washing clothes and dishes, flushing toilets, and watering lawns and gardens.
Commercial water use includes fresh water for motels, hotels, restaurants, office buildings, other commercial facilities, and civilian and military institutions. Industrial water use is a valuable resource to a nation's industries for such purposes as processing, cleaning, transportation, dilution, and cooling in manufacturing facilities.
Major water-using industries include steel, chemical, paper, and petroleum refining.
Water is used in the production of electricity in thermoelectric power plants that are fueled by fossil fuels, nuclear fission, or geothermal. Irrigation water use is water artificially applied to farm, orchard, pasture, and horticultural crops, as well as water used to irrigate pastures, for frost and freeze protection, chemical application, crop cooling, and harvesting. Livestock water use includes water for stock animals, feed lots, dairies, fish farms, and other nonfarm needs. Water is needed for the production of red meat, poultry, eggs, milk, and wool, and for horses, rabbits, and pets.

The planet's water reserves are estimated at 1,304,100 teratons (1 teraton is 1012 tons) of which freshwater reserves only account for 2.82% of this figure.
Page l Agriculture consumes 70% of the world's freshwater, industry 20% and households 10%. Between 1900 and 1995, drinking water demand grew twice as fast as the world population. By 2025, this demand should grow another 40%. In fifty years, the Canadian Agency for International Development has predicted that some forty countries could lack adequate drinking water. This will inevitably lead to conflict, even wars, as local areas, provinces and countries will go to any length to defend their fresh water resources.

Almost all conventional power plants, including coal, oil, natural gas, and nuclear facilities, employ water cycles in the generation of electricity.
Recently available data from the U.S. Geologic Survey shows that thermoelectric power plants, in the U.S.A., use more than 195 billion gallons of water per day. Such immense water needs produce equally immense concerns given the likelihood of future droughts and shortages, especially during the summer months. The addition of new conventional power plants therefore, has inherent water-related risks that may result in electric utilities no longer able to construct them.

In Canada, there are vast oil sand resources estimate at 1.7 trillion barrels (270x109 m) of bitumen. Water is required to convert bitumen into synthetic crude oil.
A recent report by the Pembina Institute shows that it requires about 2-4.5 m3 of water to produce one cubic metre (m) of synthetic crude. The need for industrial water use will increase with population growth and global warming as the demand for fuel and electricity increases.

DESCRIPTION OF PRIOR ART

Hydrogen is commonly produced by extraction from hydrocarbon fossil fuels via a chemical path. Hydrogen may also be extracted from water via biological production in an algae bioreactor, or using electricity (by electrolysis), chemicals (by chemical reduction) or heat (by thermolysis). Commercial bulk hydrogen is usually produced by the steam reforming of fossil fuels such as natural gas, gasoline. At high temperatures (700-1100 C), steam (H20) reacts with methane (CH4) to yield syngas.
The heat required to drive the process is generally supplied by burning some portion of the methane. There are other processes that can be used to recover hydrogen and these are well known and established processes.

Oxygen is present in air and there are two main methods to extract oxygen from air. The most common method is to fractionally distill liquefied air into its various components with nitrogen distilling as a vapor while oxygen is left as a liquid. The other major method of producing oxygen gas involves passing a stream of clean, dry air through one bed of a pair of identical zeolite molecular sieves, which absorbs the nitrogen and delivers a gas stream that is 90% to 93% oxygen. Simultaneously, nitrogen gas is released from the other nitrogen-saturated zeolite bed, by reducing the chamber operating pressure and diverting part of the oxygen gas from the producer bed through it, in the reverse direction of flow. After a set cycle time the operation of the two beds is interchanged, thereby allowing for a continuous supply of gaseous oxygen to be pumped through a pipeline. This is known as pressure swing adsorption.
There are other processes that can be used to recover hydrogen and these are well known and established processes.

The combustion of hydrogen and oxygen is well known. The combustion of hydrogen and oxygen yields extreme heat and water vapour in the form of steam.
The combustion temperature of hydrogen and oxygen is around 3200 C.
Conventional industrial boilers or gas turbines are not designed to handle such extreme temperatures and they would experience metal fatigue and melting if exposed to such temperature.

At ambient temperatures, the oxygen and nitrogen gases in air will not react with each other. In an internal combustion engine, combustion of a mixture of air and fuel produces combustion temperatures high enough to drive endothermic reactions between atmospheric nitrogen and oxygen in the flame, yielding various oxides of nitrogen (NOX). Nox can penetrate deeply into sensitive lung tissue and damage it causing premature death in extreme cases. Inhalation of such particies may cause or worsen respiratory diseases such as emphysema, bronchitis it may also aggravate existing heart disease.

As NOX moves to the atmosphere it eventually forms nitric acid which contributes to acid rain consequently NOX emissions are regulated by the various Environmental Protection Agencies. Consequently, it is extremely critical to ensure that the no air is present in the combustor that is combusting hydrogen and oxygen as the extreme combustion temperature will result in NOXs that will exceed the environmental standards.

Today the only place where pure hydrogen is combusted with pure oxygen is in the fueling of rockets. Hydrogen, which is the propellant, is used because it is the lightest in weight and oxygen is required for the combustion.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to combusting hydrogen and oxygen under high pressure to produce superheated steam and heat. The heat generated through the combustion of hydrogen and oxygen is then extracted and can be used as an energy input in another process, such as in the generation of electricity.
The extraction of the heat condenses the superheated steam to produce fresh water.

The generated electricity can be used internally in a plant using a process embodying the principles of the invention (thereby reducing the amount of external electricity that needs to be purchased), or be sold to an external source resulting in a revenue stream.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates processes according to an embodiment of the present invention where the hydrogen and oxygen are provided from other source(s) and/or process(es) to be combusted under high pressure to produce fresh water. The heat extracted from the superheated steam is used to generate electricity according to one embodiment of the present invention.

FIG. 2 illustrates one embodiment of a hydrogen and oxygen combustor according to the present invention.

FIG. 3 illustrates one embodiment of a heat exchanger used for extracting heat from the combustion of hydrogen and oxygen to produce superheated steam according to the present invention.

FIG. 4 illustrates one embodiment of the present process where part of the heat extracted from the superheated steam is used to generate electricity and the balance of the heat extracted is used in a industrial/chemical process according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 1, in one embodiment, of the present invention a process where all of the hydrogen and oxygen are provided from external sources and/or process. Hydrogen can be produced by extraction from hydrocarbon fossil fuels via a chemical path. Hydrogen may also be extracted from water via biological production in an algae bio-reactor, Similarly, oxygen can be obtained by fractional distillation of liquid air. The imported hydrogen and oxygen are then combusted under high pressure to produce superheated steam and heat. The heat generated through the combustion of hydrogen and oxygen is then extracted by the heat exchanger system is used to generate electricity. The extraction of the heat by the heat exchanger system condenses the superheated steam to produce fresh water. The generated electricity can be used internally (thereby reducing the plant's external electrical purchase) or be sold to an external source resulting in a revenue stream.
Once hydrogen and oxygen are obtained, they are separated into different storage tanks under high pressure. Pressure is used so as to minimize the amount of the required storage. In addition, high pressure gas is required for the combustion is the combustor in a later stage of the process. A compression pressure of 2 atmospheres can be used for example. A compressor 1a is used to compress hydrogen and store it in a storage tank 2a, and a compressor 1b is used to compress oxygen and store it in a storage tank 2b. . The hydrogen and oxygen gases will be cooled by their respective compressor la, lb operating at elevated pressure (i.e greater than 1 atmosphere). A compression pressure of 2 atmospheres can be used for example.

As shown in FIG. 2, pressurized hydrogen 31 and pressurized oxygen 32 are then injected into a combustor 3 to generate high pressure high temperature superheated steam 33. The pressurized hydrogen and oxygen ensures that the combustion will occur under high pressure thus preventing air from entering the combustor thereby preventing the creation of nitrous oxide ("NOX"). The combustion pressure will exceed 1 atmosphere so as to exclude the air from entering the combustor. A combustion pressure of 2 atmospheres can be used for example. The combustion chamber is designed to withstand high combustion temperatures without significant heat loss. The combustion chamber is preferably constructed of refractory materials or has high temperature ceramic surface coatings 34. Another means for carrying out high temperature combustion is described in U.S. Patent No.
7,128,005, details of which are incorporated herein by reference. The combustion process produces superheated steam at high temperatures. The heat from the superheated steam is extracted through a heat exchanger S. The material in the system is chosen from material that is suitable for high temperature operation. Current technology has the capacity to deal with heat in excess of 3200 C. For example, there are ceramics that can withstand the heat and thus could line the surface of the combustor, the appropriate selection of which is within the knowledge of a person of ordinary skill in the art.

As shown in FIG 3, the superheated steam 41 so produced is at a combustion temperature of about 3200 C. This high temperature superheated steam then flows through a water pipe 4, transferring heat to a high temperature heat exchanger system 5. The returned heat exchanger fluid from loop 1 enters the heat exchanger system at 43. The heat energy extracted by the heat exchanger system from the high temperature superheated steam is then returned to water boiler 42 to heat the water used in the electrical generating process through loop 1. The superheated steam produced by the combustion process is cooled by the extraction of the heat by the heat exchanger system to produce fresh water 10. The water pipe 44 serves the purpose of containing the superheated steam isolated so that no impurities are introduced into the process of fresh water creation. The water pipe and the combustor are hermetically sealed thereby ensuring that no air or contaminants will enter the process. The superheated steam exiting from the combustor to the water pipe is also under pressure thus ensuring that no air will enter the water pipe. It will be understood by those skilled in the art that any number of suitable types of collection vessels (referred to generally as a "collector") can be used in place of a water pipe for condensing steam and the present invention is not limited to the use of a water pipe.

The wall thickness of the water pipe can be tapered as the temperature gradient reduces along the water pipe due to heat extraction. The tapered wall reduces the cost of the water pipe. Heat is extracted from the water pipe by way of suitable heat exchangers. The combustor and the water pipe containing high temperature superheated steam and are made of material that can stand high temperatures, such as refractory material. The heat exchanger fluid is not in direct contact with the super saturated steam. Many known industries such as nuclear plants, foundries, rockets etc. operate at very high temperatures and consequently, the selection of appropriate heat exchanger and heat exchanger fluids suitable for the process is within the knowledge of a person of ordinary skill in the art.

Preferably, the combustor 3 and the high temperature heat exchanger 5 are insulated so as to minimize heat loss and maximize their efficiencies. The selection of insulating materials is within the knowledge of a person of ordinary skill in the art.

Another embodiment of the present invention as shown in FIG. 4 illustrates a process where part of the heat extracted from the superheated steam is used to generate electricity and the balance is used in an industrial/chemical process. The generated electricity can be used internally (thereby reducing the plant's external electrical purchase) or be sold to an external source resulting in a revenue stream.

It will be further understood by those skilled in the art that the system of the present invention can be configured in a number of ways. For example, in certain embodiments, multiple units can be used such as two combustors, and four heat exchangers.

While preferred processes are described, various modifications, alterations, and changes may be made without departing from the spirit and scope of the process according to the present invention as defined in the appended claims. Many other configurations of the described processes may be useable by one skilled in the art.

Claims (24)

1- A method of producing fresh water, comprising the steps of:

(a) combusting hydrogen gas and oxygen gas in a chamber at elevated pressure to produce superheated steam at high temperature;

(b) collecting superheated steam produced by the combustion; and (c) recovering heat from the superheated steam whereby at least some of the superheated steam condenses to produce fresh water.

2- The method of claim 1 wherein the elevated pressure is a pressure sufficient to prevent ambient air from entering the chamber.

3- The method of claim 2 further comprising providing hydrogen gas and oxygen gas, compressing and separately storing the hydrogen gas and oxygen gas at elevated pressure prior to step (a).;

4- The method of claim 1, wherein the recovery of heat in step (c) uses a high temperature heat exchange process.

5- The method of claim 4, further including the step of using at least some of the recovered heat of step (c).

6- The method of claim 3, further including the step of supplying energy for the compression at least partially from an external source.

7- The method of claim 6, wherein the external source of energy is selected from group consisting of solar energy, wind energy, nuclear energy, fossil fuel energy, and geothermal energy.

8- A system for producing fresh water comprising:

a hydrogen and oxygen combustor operable at elevated temperature and elevated pressure for producing superheated steam under high temperature and pressure;

a collector connected to the combustor for collecting superheated steam produced by the combustor; and wherein the collector is hermetically sealed to the combustor; and, a high temperature heat exchanging unit for recovering heat from the superheated steam in the collector.

9- The system of claim 8 further comprising a first compressor unit for compressing hydrogen gas and a second compressor unit for compressing oxygen gas used in the combustor.

10-The system of claim 9, further comprising first and second storage tanks for separately storing the compressed hydrogen and oxygen under pressure.

11-The system of claim 9, wherein the first and second compressors are adapted to operate under elevated pressure and elevated temperature.

12-The system of claim 11, further including means for transferring hydrogen gas and oxygen gas from the first and second storage tanks to the combustor.

13-The system of claim 8, wherein the combustor comprises refractory material.

14-The system of claim 8, further including means for insulating the combustor so as to minimize heat loss.

15-The system of claim 8, further including means for insulating the high temperature heat exchanger system so as to minimize heat loss.

16-The system of claim 8, wherein the collector is wall thickness is tapered along its length.

17-The system of claim 8, wherein the collector is adapted to operate under elevated pressure and elevated temperature.

18-The system of claim 8 further comprising a storage unit for fresh water produced in the collector.

19-The method of claim 1, further comprising using some of the recovered heat as an energy input for another process.

20-The method of claim 19, wherein the other process is the production of electricity.

21-The method of claim 20, wherein the production of electricity comprises using the recovered heat to heat water to create steam to run a steam turbine.

22-The method of claim 21, further comprising a step selected from the group consisting of selling and using at least some of the electricity produced by the electricity generation process.

23-The system of claim 8, further comprising means for removing part of the heat recovered from the collector to an industrial process.

24-The system according to claim 23, wherein the industrial process is an electricity generating unit.