Patent Application
20200039841
The following is a tabulation of some prior art that presently appear relevant:
Freshwater is becoming a major constraint on global development. Water supplies could run out in the next century if water consumption continues to exceed the available fresh water. In the past few decades, clean water has become an emerging controversial issue in the world. People who have the privilege of having clean water from their tap often take it for granted. But those who have to fight for that privilege understand well that how water is important in every aspect of their lives. Neither people, nor ecosystem can survive without clean water. Water is crucial for the survival of humans and the planet. Water is vital for reducing the global burden of disease and improving the health, welfare, and productivity of populations. It is also a critical part of preventing and adapting to climate change, and an essential part of infrastructure. While nearly 70 percent of the world is covered by water, only 2.5 percent of it is fresh. The rest is saline and ocean-based. Even then, just 1 percent of our freshwater is easily accessible, with much of it trapped in glaciers and snowfields. The average person will need 5 liters of water to drink daily to survive in a moderate climate with little activity. Water scarcity has affected more than 40% of the world's population and more than 1.2 billion people globally lack access to clean drinking water. World consumes around 4 trillion cubic meters of fresh water a year. Water is a key factor in managing risks such as famine, migration, epidemics, inequalities, and political instability. Countries which are currently facing extreme water shortage are listed as Yemen, Libya, Jordan, Western Sahara, Djibouti, Mozambique, Rwanda, Haiti, Ethiopia, and Uganda.
At least three principle methods of desalination exist namely; thermal, electrical, and pressure. The oldest method is the thermal distillation which has been around for thousands of years. In thermal distillation, the water is boiled and then the steam is collected, leaving the salt behind. The most common desalination methods employ membrane reverse-osmosis (RO) in which salt water is pumped at high pressure and forced through a membrane (or a series of semi-permeable membranes) that allows water molecules to pass but blocks the molecules of salt and other minerals. Unfortunately, many existing desalination technologies require excessive amounts of energy to operate, making the process costly. Depending on the local energy prices, 1,000 gallons of desalinated seawater can cost around $3 or $4. The installed cost of desalination plants has been reported to be approximately S1 million for every 1,000 cubic meters per day of installed capacity. Therefore, a large scale desalination plant serving 300,000 people typically costs in the region of $100 million. The costs of infrastructure to distribute water must be added to this. Equivalent electrical energy (kWh/m3) consumed by different methods has been reported about 13.5-25.5 for Multi-stage Flash MSF, about 6.5-11 for Multi-Effect Distillation MED, about 7-12 for Mechanical Vapor Compression MVC, and about 3-5.5 for Reverse Osmosis (RO). The suggested method here would take only a fraction of kWh in theory to produce one cubic meter of potable/drinkable water. Desalination plants operate in more than 120 countries in the world, including Saudi Arabia, Oman, United Arab Emirates, Spain, Cyprus, Malta, Gibraltar, Cape Verde, Portugal, Greece, Italy, India, China, Japan, and Australia. Current methods may require about 14 kilowatt-hours of energy to produce 1,000 gallons of desalinated seawater. The cost of distillation is high because we need notable large amount of electricity to heat water in thermal plant and generate high pressure. The desalination plant typically uses three kilograms of seawater to produce 1 kilogram of fresh water. The extracted salt dissolves in the excess sea water used in the process to form so-called brine. The brine is returned to the sea where it is diluted again in its natural medium. The first step in most common water treatments is generally filtering such as sand filters which removes large particulate matter from the water. Utilization of wells for the intake water supply from sea or ocean bed may decrease the need for that kind of treatment.
A new approach for desalination and purification of sea water using compression refrigeration (also called “Reverse of Rankine Cycle”) is suggested (components 1-9, 1a-9b, claims 1-12), which seems promising to provide high volume of potable/drinkable water with reasonable cost. The apparatus uses compression refrigeration system (claims 1-4) to provide heat at the condenser (component 2, claims 1-4 and 11) to partially evaporate the intake sea water and uses the evaporator (component 3, claims 1-4 and 12) at the other side to condense the produced water vapor back to clean drinkable water. A heat recovery heat exchanger (9) captures the heat left in the returning sea water (2b) and delivers it to the fresh intake sea water (2a) to improve the efficiency. The system can be designed using many refrigerants with some providing higher efficiencies and coefficients of performance. An ideal Reverse Carnot cycle working between 240° F. and 70° F. indicates a maximum Coefficient of Performance (COP) of about 3.12. A typical actual refrigeration cycle working under the same temperature condition shows a possible COP value of about 2.49 with selected refrigerants. A typical desalination system using this approach shows in theory a production of about 700 billion gallons of drinkable water per year with only about 100 MW electric power installed. Refrigeration unit can be designed to work under different pressures, different temperatures, different refrigerant flows, different capacities, and different powers. This purification system/apparatus can be utilized to purify sea/ocean water as well as any other type of water with dissolved and/or undissolved impurities. This purification system/apparatus can be designed to include optional processes, equipment and parts. Compressors (1) utilized in the system can be of any type including reciprocating, scroll, screw type, rotary, and centrifugal; condensers (2) utilized in the system also can be any type including air-cooled, water-cooled, and evaporative types; and finally, evaporators (3) utilized in the system can be of any type including the bare-tube, plate-type, finned, and finally shell and tube type. All types of refrigerants can be utilized with the suggested systems.
The advantages are:
(e) Better economy
(f) Lower kWh to produce one cubic meter of potable/drinkable water
(g) Easier operation, maintenance and repair
One embodiment of this patent application is presented in
Compression refrigeration units are mainly comprised of four components, compressor (1), condenser (2), evaporator (3), and expansion valve (4). The pipeline between compressor and condenser is called “hot gas line” (1a), the pipeline between condenser and expansion valve is called “liquid line” (1b), and the pipe line between evaporator and compressor is called “suction line” (1e). In the second embodiment, the condenser and evaporator are open heat exchangers which let crude/saline water in and out. Condenser (2) heats the intake crude/saline water (2a) and brings it to the boiling temperature but provides only about ⅓ of latent heat for the evaporation of water. This way the quality (x) of saturated crude/saline water will be about % 33.0 which means about ⅔ of crude/saline water/vapor mixture could be returned (2b) to the heat recovery heat exchanger (9) and eventually to the sea/ocean to avoid heavy deposits in the condenser. In this embodiment, both condenser (2) and evaporator (3) are located in a “closed air-tight container” under different possible arrangements and orders, which allows the generated water vapor inside of the condenser (2) to move to the evaporator (3) and get condensed on the cool evaporator tubes and provide the desired potable/drinkable fresh water (3b).
In the first embodiment, condenser (2) and evaporator (3) are closed heat exchangers. So the flow of crude/saline water in and out through them should be brought to a different tank (i.e. a separation tank (5)) to facilitate the separation of water vapor from the water liquid. Pressures are adjusted in this tank using pressure reducing valves to assure proper operation of the process. Due to a separate separation tank, the control of the process should be easier with the use of automated valves (8).
In the second embodiment, condenser (2) and evaporator (3) are open heat exchangers. So the flow of crude/saline water in and out through them would not need a separate tank. But both condenser and evaporator would be located in a “closed air-tight container” (7) under different possible arrangements to facilitate the transfer of water vapor from condenser into evaporator. This type of design would probably need less equipment but it may have limitations with operational modes. The design would similarly use automated valves (8) to control the flows, mode of operation and the process output.
Additional ramifications may include applications with other refrigerants, applications for purposes other than water treatment, and applications to process other liquids and fluids.
In general, the suggested system may couple with current technologies in different fields to bring up more effective processes and technologies.
