Multi -Effect Adsorption Distillation with Cooling
The present invention relates to a multi-effect adsorption distillation system combined with cooling Combined Desalination and Cooling - (CoDeCo) .
The invention relates to the field of solutions for water desalination.
Known multi-stage distillation systems - Multi Effect Desalination (MED) are highly efficient installations for desalination of water and production of a distillate suitable for consumption. This solution is particularly attractive due to the high efficiency of desalinated water production, using supplied to the system thermal energy in a very effective way. The principle of the MED system operation is based on condensing the distillate vapors generated in the "n" effect with the simultaneous release of the condensation heat in the "n + 1" effect. This heat is used to evaporate another portion of the distillate from the "n + 1" effect, and then its condensation in the next effect ("n + 2") . The cascade is repeated until the effect at a temperature close to the ambient temperature is obtained. In conventional systems, the minimum temperature is at the level of 45°C, which is determined by the temperature of the water used to cool the condenser - the condensing element of vapor coming from the last effect of the MED system. Due to the limitations imposed by the wear of the installation, the temperature of the first effect is about 70°C. According to this principle, MED systems operate in the temperature range 70-45°C, which results in the final product (distillate) with a temperature of about 45°C. Implementation of three-bed adsorption chiller to the MED system allows to
reduce the minimum working temperature of the system to about 22°C, and so enabling the increase of the number of the effects by the temperature range of 45-22°C, thanks to which there is a significant increase in distillate production from the MED solution and production of additional quantities of distillate from the AD solution and with the temperature significantly lower than in the conventional solution. The consequence is an increase in distillate production from the same amount of energy delivered to the first effect. The adsorbent bed can be compared to a condenser, characterized by an additional advantage - it allows for a significant reduction of pressure in the last effect allowing the evaporation of water at a temperature of about 22°C. Sorbent, with which beds of three- bed adsorption device are filled, sucks and condenses vapor from the last effect of Multi Effect Desalination and Adsorption Desalination (MEDAD) . MEDAD technology allows to increase the temperature difference from, for example, 35 K to 58 K by lowering the pressure by using AD, which results in a significant increase in the distillate production and lowering the temperature of subsequent effects below the ambient temperature .
The specificity of this system is the significant energy consumption for the supply of the three-bed adsorption device with water at a temperature of about 90 ° C in order to prepare the bed to adsorb the next portion of the distillate.
The solution described in application SG193372 "Regenerative adsorption distillation system", presents the characteristics and possible configurations of the "MED-AD" system with a two-bed adsorption chiller.
The invention as referred to in the application
US2017072336 "A method and apparatus for multi-effect adsorption distillation" presents possible configurations of the MED-AD system with multi-bed adsorption chiller.
In turn, in the application SG11201605976S "Adsorption/distillation in a single column design" - presents adsorption through a light fractions bed (e.g., alcohols or hydrocarbons) . This solution is used in petrochemical distillation columns.
The invention CN105441101 - "Method for refining pyroligneous solution through combination of enzymolysis, distillation and adsorption " - presents a method of purifying chemical compounds by means of a combination of various processes including adsorption.
Japanese invention, application no JP2017040387 describes an absorption heat pump with a reduced number of exchangers.
In turn, the application JP2017032218 "Heat exchanger using geothermal heat" is referring to an absorption heat pump used as a geothermal exchanger.
The solution described in CN205307834 "Absorbent heat pump for waste water desalination" presents the use of an absorption heat pump in desalination of seawater feeding the classic MED system. This solution does not use a three-bed adsorption chiller thus an absorption heat pump supplies the generator of the first effect of the MED system and not the process of regeneration of adsorbent beds. Both the configuration of the system as well as the techno-economic working conditions fundamentally distinguish the discussed solution from the invention being the subject of the application .
In the application for utility model no. CN205279513 titled " Low temperature heat source system is united to drive absorption formula seawater desalination ' s solar energy and geothermal energy " - a heat pump supplying the MED desalination system was disclosed, where geothermal heat is the energy that supplies the absorption heat pump and the solar collectors are the sources of waste heat. This solution is
different from the one proposed in the scope of heat utilization (for feeding the MED system generator and not regeneration of the adsorbent bed) and waste heat recovery (in this solution the useful heat from the geothermal system is used, not the waste heat from the system) .
Solution with application number CN204675851 pt . "Open heat pump low-temperature multi-effect evaporation sea water desalination device of water and electricity coproduction" contains an absorption heat pump supplying the MED desalination plant where waste heat comes from the steam condensation system behind the steam turbine and the upper source is a high parameter heat from the turbine extraction. Similarly, to the utility model no. CN205279513, both waste heat and useful heat come from a different system, and the energy produced by the absorption heat pump is used to power the MED generator and not regenerate the AD bed.
In turn, application CN204625229 pt . "Preheat open heat pump MED sea water desalination device of feeding sea water" refers to a seawater desalination solution using an absorption heat pump combined with a MED system. In this case, the heat produced by the absorption heat pump is used to heat the brine feeding of the MED system, and thus in a different way than the proposed one.
From the above results, that in known state of the art, both absorption heat pumps, MED desalination systems, two- and three-bed chillers and a combination of a MED system with an Absorption Heat Pump, or a MED with an adsorption chiller are known. However, the system that combines a three-bed chiller, the MED system and an absorption heat pump is not known. In the disclosed solutions, knowledge of the operating parameters limits of both the MED system, Adsorption Chiller and Absorption Heat Pump systems, enabling failure-free operation of the entire system, hasn't been used so far.
The use of the proposed system configuration, by avoiding the risk of crystallization of the absorption heat pump through the use of three sorbent beds, will effectively combine the heat recovery from the MED condenser with the supply of the adsorption chiller. The above results from the intermittent nature of the adsorption chillers, having an even number of beds, operation leading to an increase in the temperature of the hot feedwater returning to the absorption heat pump exchanger. The above leads to its serious failure and system stoppage. By using the three-bed chiller, allowing switching flow between beds, the temperature of the heating water returning from the system to be heated in the absorption heat pump is constantly low, guaranteeing trouble-free operation.
The objective of the presented invention is to develop a new multi-stage combined desalination and cooling (CoDeCo) system equipped with three-bed adsorption chiller, ensuring the efficiency increase of distillate production in the system and saving fuel consumption and reducing emissions and water consumption .
Because the specificity of the heat pump's operation consists in the recovery of low parameter heat, which in MED / MEDAD systems is a waste heat, the main benefit from the use of absorption heat pumps is a significant increase in the distillate production efficiency in the system due to the recovery of the heat, which would be dissipated in the atmosphere and its use for the three-bed adsorption device power supply, hence the lower energy consumption for producing unit of the condensate in comparison to the conventional system. The described advantage leads directly to an increase in the production of distillate, savings in fuel consumption and reduction of emissions, and reduction of water consumption.
Due to the fact that the absorption heat pump has the function of producing hot water at a temperature of about 90°C,
while recovering heat from water or steam at a low temperature of about 30-50°C, using as a driving energy burning of any fuel, hot water or steam with a temperature > 100°C and the amount of heat at 90°C is equal to the sum of energy supplied in a high parameter form (burning fuel, hot water, steam) and low parameter (water or steam at a temperature of about 30- 50°C) and that in MED systems the last effect is cooled with water at a temperature of about 30°C receiving heat of vapor condensation at a temperature of about 40°C, and a three-bed adsorption chiller uses heat in the form of hot water at about 90°C as feed energy, it is possible to use an absorption heat pump in a multi-stage distillation system together with a three-bed adsorption chiller, leading to the improvement of the energy efficiency of the entire process. The system should be located behind a conventional part of the MED system producing hot water supplying the adsorbent bed. In the case of such a preferred configuration of the system, the amount of useful energy necessary to power the adsorption system (fuel) will be less by the amount of energy recovered from the condenser of the MED system. Taking into account, that the COP of absorption heat pumps available on the market is at a level of 2, this means reducing the fuel consumption for regeneration of the adsorption bed by 50%.
A multi-stage adsorption distillation system comprising of at least two distillate-production effects connected to each other by liquid channels and vapor channels characterized in that the absorption heat pump is connected to distillate production effects via a liquid channel or a vapor channel and with hot water pipeline with an adsorption chiller, and an adsorption chiller is connected with the last distillate- production effect via vapor channel.
Preferably, the adsorption device is a three-bed device.
Preferably, the absorption heat pump is connected to the distillate production effects via a liquid channel using a heat exchanger located between the absorption heat pump and the liquid channel.
Preferably, the absorption heat pump is connected to the distillate production effects via a steam channel using a heat exchanger located between the absorption heat pump and the steam channel.
Preferably, the absorption heat pump is steam-powered. Preferably, the absorption heat pump is hot water- powered .
Preferably, the absorption heat pump is powered by the combustion of any fuel in the built-in burner.
The subject of the invention in a preferred embodiment is shown in the drawing, in which fig. 1 shows a multi-effect adsorption distillation system according to the invention.
A system according to the invention comprises of six effects for the production of distillate 2 connected to each other with liquid channels 3 and vapor channels 8 where the absorption heat pump 1 is connected to distillate production effects 2 through liquid channel 3 and heating water pipeline 9 with a three-bed adsorption device 5. The three-bed adsorption device 5 is connected with the last distillate production effect 6 via a vapor channel 4. The steam-powered absorption heat pump 1 is connected to the distillate production effects 2 via the liquid channel 3 using a heat exchanger 7 located between the heat pump 1 and the liquid channel 3.