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EP-4735389-A1 - WATER ADSORPTION DESALINATION PROCESS WITH PRESSURE SWING

EP4735389A1EP 4735389 A1EP4735389 A1EP 4735389A1EP-4735389-A1

Abstract

A method of purifying water comprises: • (i) evaporating feed water in an evaporator 220 to produce water vapour, wherein the evaporator 220 is set at an evaporator temperature T ey ; • (ii) allowing the water vapour from the evaporator 220 to an adsorption chamber 230 comprising an adsorption apparatus 231, wherein the adsorption apparatus 231 is set at a temperature T SB , wherein T SB is greater than T ey ; and • (iii) allowing the water vapour from the adsorption chamber 230 to a condenser 240, wherein the condenser 240 is set at a condensation temperature T cond , wherein T cond is less than T SB . • the method is based on actuating adsorption and desorption in the sorption chamber via a pressure swing, rather than a temperature swing.

Inventors

  • SANTORI, Giulio
  • BRANDANI, Stefano
  • OLKIS, Christopher
  • HASNI, Shihab

Assignees

  • The University Court Of The University of Edinburgh

Dates

Publication Date
20260506
Application Date
20240626

Claims (15)

  1. 1 . A method of purifying water, the method comprising: (i) evaporating feed water in an evaporator to produce water vapour, wherein the evaporator is set at an evaporator temperature T ev ; (ii) allowing the water vapour from the evaporator to an adsorption chamber comprising an adsorption apparatus, wherein the adsorption apparatus is set at a temperature TSB, wherein TSB is greater than T ev ; and (iii) allowing the water vapour from the adsorption chamber to a condenser, wherein the condenser is set at a condensation temperature T CO nd, wherein T CO nd is less than TSB.
  2. 2. A method according to claim 1 , comprising repeating steps (i)-(iii).
  3. 3. A method according to claim 1 or claim 2, wherein TSB is set to be constant or substantially constant.
  4. 4. A method according to any preceding claim, wherein T CO nd is less than T ev .
  5. 5. A method according to any preceding claim, wherein T ev is between about 30°C and about 50°C, optionally between about 35°C and about 45°C.
  6. 6. A method according to any preceding claim, wherein TSB is between about 40°C and about 60°C, optionally between about 45°C and about 55°C.
  7. 7. A method according to any preceding claim, wherein TSB is between 0.5°C and 15°C greater than T ev , optionally between 1 °C and 10°C greater than T ev .
  8. 8. A method according to any preceding claim, wherein the method comprises supplying heat to the evaporator and/or to the adsorption apparatus, from a source of energy comprising or consisting of a low grade heat source.
  9. 9. A method according to any preceding claim, comprising performing step (i)-(iii) sequentially.
  10. 10. A method according to any of claims 1 to 9, wherein steps (i) and (ii) are performed concomitantly, and step (iii) subsequently.
  11. 11. A method according to any preceding claim, further comprising: (iv) ceasing fluid communication between the adsorption chamber and the condenser; and (v) recovering water from the condenser.
  12. 12. A method according to any preceding claim, wherein desorption of water vapour from the adsorption apparatus occurs via a pressure swing in the adsorption chamber during steps (ii) and (iii).
  13. 13. A method of purifying feed water, the method comprising: (i) evaporating feed water in an evaporator to produce water vapour, wherein the feed water is set at an evaporation temperature T ev ; (ii) providing fluid communication between the evaporator and a first adsorption chamber comprising a first adsorption apparatus, thereby allowing the water vapor from the evaporator to the first adsorption chamber, wherein the first adsorption apparatus is set at a first adsorption temperature TSB 1 , wherein TSB 1 is greater than T ev ; (ii-a) ceasing fluid communication between the evaporator and the first adsorption chamber; (iii) providing fluid communication between the first adsorption chamber and a condenser, thereby allowing the water vapor from the first adsorption chamber to the condenser, wherein the condenser is set at a condenser temperature T CO nd, wherein Tcond is less than TSB 1 ; (iv) providing fluid communication between the evaporator and a second adsorption chamber comprising a second adsorption apparatus, thereby allowing the water vapor from the evaporator to the second adsorption chamber, wherein the second adsorption apparatus is set at a second adsorption temperature TSB 2 , wherein TSB 2 is greater than T ev ; (iv-a) ceasing fluid communication between the first adsorption chamber and the condenser; (iv-b) ceasing fluid communication between the evaporator and the second adsorption chamber; and (v) providing fluid communication between the second adsorption chamber and the condenser, thereby allowing the water vapor from the second adsorption chamber to the condenser, wherein T CO nd is less than TsB 2 .
  14. 14. A system for purifying water, the system comprising; an evaporator configured to produce water vapour, wherein the evaporator is configured to be set at an evaporator temperature T ev ; an adsorption chamber comprising an adsorption apparatus, wherein the adsorption apparatus is configured to be set at an adsorption temperature TSB, wherein TSB is greater than T ev ; and a condenser, wherein the condenser is configured to be set at a condenser temperature T CO nd, wherein T CO nd is less than TsB.
  15. 15. A system for purifying water, the system comprising: an evaporator configured to produce water vapour, wherein the evaporator is configured to be set at an evaporator temperature T ev ; a first adsorption chamber comprising a first adsorption apparatus, wherein the first adsorption apparatus is configured to be set at a first adsorption temperature TSB 1 , wherein TSB 1 is greater than T ev ; a second adsorption chamber comprising a second adsorption apparatus, wherein the second adsorption apparatus is configured to be set at a second adsorption temperature TSB 2 , wherein TSB 2 is greater than T ev ; and a condenser, wherein the condenser is configured to be set at a condenser temperature T CO nd, wherein T CO nd is less than TsB 1 and TSB 2 .

Description

WATER ADSORPTION DESALINATION PROCESS WITH PRESSURE SWING Field of the Invention The present invention relates to systems and methods for controlling an Adsorption Purification device. In particular, but not exclusively, the invention relates to systems and methods for controlling a heat-powered Adsorption Desalination apparatus, for example to produce purified water. Background The generation of clean and/or drinking water is a growing concern throughout the world for various reasons, which include, amongst others, pollution, climate change, industrialisation, and increasing population. Many water purification systems exist in order to provide a solution when access to clean and/or drinkable water is insufficient. Water desalination is one such available solution, which is particularly attractive in regions of the world where rainfall is low and/or where population density is high. Adsorption Desalination (AD) is a heat-driven evaporative technology for the purification of feed water from substances having lower saturation pressure (e.g. salts in seawater). Typically, in its simplest configuration, an AD system is composed of an evaporator to evaporate water from feed water, an adsorption chamber in the form of a Sorption Bed (SB) on which water vapour is adsorbed, and a condenser to condense and collect purified, liquid, water that is released from the SB. The Sorption Bed (SB) typically comprises a nanoporous material in contact with a heat transfer surface such as the external surface of a heat exchanger. Examples of AD systems are disclosed in US8535486B2 (Kim Choon Ng et al), US8603223B2 (Bidyut Baran Saha), US20210107807 (Qasem et al), US11311818B1 (Amaltrafi et al), and Olkis et al. (A small-scale adsorption desalinator, Vol 158, 2019, p1425-1430). However, conventional operation of adsorption-based water desalination facilities are associated with a number of disadvantages: The adsorption/desorption cycle in the adsorption chamber is typically driven by temperature swings, where the chamber is heated to a high temperature, typically around 70-80°C, and cooled down to around 30-40°C. This an energy inefficient step due to the heating/cooling cycles. This is also time inefficient, particularly when no additional energy is used to accelerate heating and cooling. The low energy efficiency of these systems contributes to a high carbon footprint for this technology, estimated to be 76 million tons (Mt) of CO2 per year as of 2018 (Muhammad W. Shahzad et a/; Adsorption desalination - Principles, process design, and its hybrids for future sustainable desalination; 2018; King Abdullah University of Science & Technology (KAUST), Thuwal, Saudi Arabia). The heating/cooling temperature cycle tends to hinder the vacuum tightness of the adsorption chamber, which then requires maintenance. Muhammad Wakil Shahzad et al (Pressure driven adsorption cycle integrated with thermal desalination; Case Studies in Thermal Engineering 41 (2023) 102608) describes a pressure-driven adsorption cycle in a water desalination system. However, this system relies on the active regulation of the pressure in the adsorption chamber using a vacuum ejector. It is an object of the invention to address and/or mitigate one or more problems associated with the prior art. It is an object of the invention to improve the efficiency of Adsorption Desalination systems and methods. Summary The present invention is based on the finding that it is possible to effectively operate an Adsorption Desalination system by actuating adsorption and desorption in the sorption chamber via a pressure swing, rather than a temperature swing. Advantageously, because the sorption chamber is not subjected to repeated cycles of high and low temperatures, the main source of heat needed to operate the system does not require the same power levels as in a conventional facility, and the system can use “low grade” heat in order to power the desalination water purification system. Low grade heat is typically considered a source of heat supplying a temperature less than about 60°C, e.g. about 50°C. This is advantageous as it enables the AD facility to be associated with and/or combined with existing activities that typically generate this source of low grade heat, which in most cases is discarded or released into the environment. For example, in colder climates, such as in the UK, traditional industries such as whisky distilleries or power stations generate waste heat (<60°C). It was discovered that such waste heat may be sufficient to operate an AD system according to the present methodology. Traditionally, certain distilleries may shut down in the summer, because of the lack of water of sufficiently high quality. The current technology can sustainably extend their operational time since rivers or sea water can be purified up to drinkable quality using the low grade heat generated on site. In water climates, for example central and southern Europe, solar radiation is