Subject of the invention is combined desalinated water production system CoDeCo (Combined Desalination and Cooling) .

The invention relates to the field of solutions for water desalination .

Known from the prior art multi-stage distillation systems

Multi Effect Desalination (MED) - are using directly externally produced heat for the supply of the first effect and condenser cooled by air or water to cool the last effect.

Cogeneration systems have a very wide application, mainly producing electricity and heat directly at the place of its use. Combined energy production has a number of advantages over separated systems, guaranteeing at the same time a number of ecological advantages (primary energy saving and reduction of CO2 emissions by 33% for solutions based on hard coal and 66% for gas-based solutions) as well as economic ones.

In separated systems, electricity and heat are produced in separate installations and delivered to the final customer via the power and heating networks. Both the production of electricity and heat and their transfer over longer distances generates losses, some of which can be avoided by combining the process of producing electricity with heat close to the recipient. The energy efficiency of the combination of generating electricity and heat in relation to a separate system producing electricity and heat in separate devices is 40% higher, meaning 30% less fuel consumption to produce the same amount of electricity and heat. It is the combined production of electricity and heat that enables the highest values of media production efficiency and thus the reduction of primary energy consumption and emissions to the atmosphere. There are a number of technologies associated with the combined production of electricity and heat, however, in the trigeneration applications, systems based on reciprocating piston engines and lithium bromide absorption chillers are the most popular. The popularity of such a set is confirmed in particular by installations operated for many years in Poland and abroad, based on spark-ignition piston engines and lithium bromide absorption chillers, producing energy for the needs of all types of customers.

The absorption chiller works on the basis of the absorption effect (absorption of the refrigerant in the entire volume) and the desorption (separation of the refrigerant from the solution) . Boiling of the refrigerant absorbs heat, providing a useful cooling effect. The absorber and desorber system in absorption chiller is called a chemical compressor and corresponds to the functionality of an electrically powered compressor in conventional chillers. Absorption chillers are very well-recognized technology. Yoon (Yoon J-I, Kwon O-K., Cycle analysis of air-cooled absorption chiller using a new working solution. Energy 24, 1999, 795 - 809) and others concentrated in their work on absorption chillers using the mixture of H ₂ 0/LiBr, H ₂ 0/LiBr + HO(CH ₂ )30H and NH3/H2O and NH3/L1NO3, while Sun (Sun D.W. Comparison of Performance of NH3-H20, NH3-L1NO3 and NH3-NASCN absorption refrigerant systems, Energy Conversion and Management 39, 1998, 357 - 68) on NH3/NaSCN. Their work was aimed at determining optimal working conditions for individual solutions. The absorption systems available on the market use, depending on the required evaporation temperature of the refrigerant, a mixture of water / lithium bromide (H2O / LiBr) or ammonia / water (NH3 / H2O) . The choice of a particular solution depends on the required evaporation temperature of the refrigerant and the available heat temperature. Wherever a refrigerant with a temperature of not less than 5°C is needed, an aqueous solution of lithium bromide is used. For a lower temperature range (down to -50°C) the ammonia / water solution is used. The mentioned authors also analyzed the range of possible to use temperatures of the heating medium, enabling the effective operation of the absorption cycle, exceeding the possibilities of heat recovery from cogeneration systems, but which have an impact on their efficiency. For absorption systems, the efficiency of cold production is defined by COP - Coefficient of Performance - which is the ratio of a useful cooling effect to the useful energy supplying the device. The higher the COP value, the less useful energy is need to produce the same amount of cold. Devices currently available on the market produce cooling capacity with COP 0.7 - 2.7 at the currently defined maximum at a level of 3. In order to ensure proper operation of the absorption system, the heat supplied - both in the form of heating and chilled water - must be discharged to the external cooling system. Discharge require significant amount of energy coming from refrigerant condensation and heat absorption - if the unit produces cold at COP = 1 to produce 1 unit of chilled water, 1 unit of heating water should be fed, and thus 2 medium temperature heat units should be discharged to the cooling system. Cooling towers or dry-coolers are operated in the solutions used, but in any case, the heat discharged is waste, the utilization of which involves energy costs (electricity in the case of dry-coolers) and environmental cost (evaporating water from towers in open circuit systems) . The lack of heat dissipation leads to an immediate stop of the system, often connected with a failure. For systems operating in dry climates, the key cost factor is the water consumption of the cooling system - the lower the use of evaporated water, the more economically reasonable the system is.

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. In the case of providing a lower cooling temperature of the last condenser effect, there is the possibility of extending or shifting the MED system operating range towards a lower condensing temperature. Raising the temperature of the first effect is not recommended due to the significant acceleration of material wear processes at temperatures higher than 70°C.

The closest prior art is included in the literature items and applications below.

Hassan K. Abdulrahim, Abdelnasser A. Mabrouk, Mohamed A. Darwish, Ashraf S. Hassan in HYBRID MULTI EFFECT DISTILLATION SYSTEM AND GAX CYCLE: A NOVEL PROCESS INTEGRATION The International Desalination Association World Congress on Desalination and Water Reuse 2015/San Diego, CA, USA REF: IDA15WC_Abdulrahim_51539 presented the combination of absorption chiller with MED, which uses steam condensate, which previously fed the absorption system as a heat source for one MED installation and the distillate from the last effect of one MED installation for absorber cooling and feeding the first effect of the second MED installation. In our solution, the heating circuit of the generator is separated from the MED circuit, all heat from the absorption chiller is fed to the MED and all of the cooling capacity from the absorption chiller is cooling the MED condenser.

Kiyan Parham, Mortaza Yari Ugur Atikol, Alternative absorption heat transformer configurations integrated with water desalination system, Desalination 328 (2013) 74-82, presented the use of an absorption heat transformer (device other than an absorption chiller) in many configurations for feeding the MED system. The system is supplied with medium- temperature heat, which is separated by the absorption heat transformer system to supply the MED system. In the solution according to the claimed invention, the system is supplied with high temperature heat which in the diaphragm system feeds the first MED effect and ensures cooling of the last MED effect.

C. Chiranjeevi, T. Srinivas, Augmented desalination with cooling integration, International Journal of Refrigeration 80 (2017) 106-119 presented a solution in which the first MED effect is powered by solar collectors and the condenser is cooled by an absorption chiller also supplied with solar heat. In this solution, the absorption chiller has only the function of allowing the condensation temperature to drop.

Kiyan Parham, Mehrdad Khamooshi, Sanahd Daneshvar, Mohsen Assadi, Mortaza Yari, Comparative assessment of different categories of absorption heat transformers in water desalination process, Desalination 396 (2016) 17-29, analyzed the possible configurations of the use of an absorption heat transformer (device other than an absorption chiller) for cooperation with the MED system. Each configuration assumes supplying the system with medium-temperature heat and distribution to high and low temperature as well as direct system operation (direct absorption of refrigerant vapors) . The solution according to the claimed invention uses an absorption chiller powered by high temperature heat, using the cool and heat produced by the absorption chiller in full, which leads to minimization of the operating time and load of the cooling tower.

Muhammad Shu a Azhar, Ghaus Rizvi, Ibrahim Dincer, Integration of renewable energy based multigeneration system with desalination, Desalination 404 (2017) 72-78, proposed integration of the combined system with the MED system. However, the MED system and absorption chiller are separated (the absorption chiller system is supplied with heat after the MED system has reduced its temperature) .

Sami M. Alelyani, Nicholas W. Fette, Ellen B. Stechel, Pinchas Doron, Patrick E. Phelan, Techno-economic analysis of combined ammonia-water absorption refrigeration and desalination, Energy Conversion and Management 143 (2017) 493- 504, presented the use of condenser and ammonia refrigerant rectifier for supplying the first MED effect. The rectifier does not appear in the lithium bromide chillers. The last effect of MED is also cooled by sea water, not cold from the ammonia system.

GCC Patent no. 2017-32908 & GCC Patent no. 2016-31325 presents a solution in which the absorption chiller generator is supplied from an external boiler, the refrigerant evaporated in the generator during the condensation feeds directly the first MED effect and the absorber directly absorbs the distillate vapors produced in the last MED effect. In our solution, the absorption chiller is supplied from the combined system, all heat from the absorption chiller in the form of absorber and condenser cooling water using the diaphragm supplies the first MED effect and the cooling produced by the absorption chiller cools the MED system condenser in a diaphragm manner. The solution presented by the authors is basically a small modification of the existing MEDAD system available on the market.

Application CN205653194 presents the use of an absorption device alternately fed with solar and geothermal heat. The proposed solution prevents the use of low and medium parameter heat from the absorption chiller as it is in the invention proposed by us.

The solution presented in the application CN205640840 discloses an invention where vacuum tubes of solar collectors are used to improve the vacuum quality in the desalination systems .

The solution according to the invention CN105923676 uses solar energy for desalination and cold production for air conditioning purposes. The system is not a fully integrated desalination system in which the heat from the absorption chiller is fully utilized.

The invention described in CN105841395 describes a power production and desalination system based on the recovery of LNG gas expansion energy. It is not a system integrated with the combined system in the field of the desalination system but a system feeding various production systems (cooling, desalination, etc.) .

The invention reported in US2017190597 presents the use of cooling in desalination installations as a method of direct freezing of desalinated water vapor as a method of separating it from salt.

The solution presented in the CN106698563 application presents the use of an electrically powered compressor cooperating with a membrane filtration system: a system other than the desalination using the MED method.

The application no WO2017066534 presents the use of a heat pump for heat recovery from the "gray water" installation and its use to supply the desalination system. In contrast to the present solution, the invention according to the present application relates to a fully integrated system where the use of heat from the condenser and the absorber reduces the cooling water demand from the tower, allowing balancing of the combined electricity, cold and desalinated water production.

The aim of the present invention is to develop a combined system for desalinated water production enabling operation of a combined system without participation or with significant limitation of the external cooling system, i.e. cooling tower or dry-cooler, leading to significant (at least 50%) reduction of water evaporation from the cooling system.

The essence of the invention is the combination of an absorption chiller fed from a combined system with the MED system, allowing its first effect to be supplied with heat necessary to be discharged from the absorption system and cooling the MED condenser with chilled water produced by the absorption chiller. This will be accomplished by supplying the absorption chiller with recovered heat that can be obtained from the combined system, supplying the first effect of the MED installation with heat from the absorption chiller cooling system and cooling the MED condenser with chilled water produced by the absorption chiller. This configuration of the system will enable maximum efficiency of the combined system due to full use of heat while significantly reducing the evaporation from the medium-parameter heat exhaust to atmosphere system (cooling tower system) .

The essence of the invention is a desalinated water production system comprising of a heat source, an absorption chiller, a block of effects for distillate producing MED characterized in that, the absorption chiller is supplied with heat recovered from the heat source via a heating medium pipeline connecting the absorption chiller to the cogeneration system. The first distillate producing effect of the MED block is supplied with heat received from the absorption chiller's cooling system through the pipeline connecting the absorption chiller to the first distillate production effect. The pipeline consists of a supply pipeline and a return pipeline. The condenser of the last distillate production effect is cooled using the chilled water produced by the absorption chiller. The chilled water is supplied by a cold water pipeline that connects the last effect of distillate production with an absorption chiller. The pipeline consists of a supply pipeline and a return pipeline. The brine is fed to the first distillate production effect through a pipeline, and concentrated brine is extracted from the last distillate production effect through a pipeline. The desalinated water is derived from the last distillate production effect through the pipeline.

Preferably, the heat source is a cogeneration system producing electricity and heat.

Preferably, the heating medium supplying the absorption chiller is the flue gas from the heat source being the cogeneration system.

Preferably, the heating medium supplying the absorption chiller is water or a mixture thereof circulating in a closed system between the absorption chiller and the cogeneration heat source, where the water or mixture thereof is supplied to the absorption chiller via a pipeline and extracted via a pipeline.

Preferably, when the heating medium feeding the absorption chiller is steam supplied from a heat source being a cogeneration system, to an absorption chiller via a pipeline and from an absorption chiller by means of a pipeline, the condensate collected is supplied to a heat source being a cogeneration system.

Preferably, the system according to the invention comprises a cooling tower connected to the absorption chiller by means of a pipeline. Preferably, the system according to the invention comprises a heat exchanger which is connected with a pipeline to a pipeline connecting the absorption chiller to the MED system and via a brine pipeline to any effect or any distillate production effects. The brine is fed to the heat exchanger through the pipeline.

Heat recovered from a cogeneration system, e.g. a cooling system for the engine body and exhaust gases as a whole, or part, can be used for purposes other than feeding an absorption chiller. The medium parameter heat produced by the absorption chiller is used to supply the first stage of the MED installation and to heat the brine to be desalinated, and the chilled water produced by the chiller is used to cool the condenser after the last MED stage. The heat from the combined system (in the form of hot water, steam or flue gas) can be partly or entirely used for heating or technological purposes. Cold water from the absorption system can be used in whole or in part for cooling or air conditioning purposes.

The invention in a preferred embodiment is shown in Fig. 1 presenting a combined desalinated water production system.

The system according to the invention, in a preferred embodiment, consists of a heat source 1 being a cogeneration system, based on a reciprocating piston engine fueled with natural gas connected to a generator. The cogeneration system produces 417 kW of hot water at 90/80°C (supply and return) and 362 kW of electricity. The mechanical energy produced by the engine is converted into electricity by means of a built- in generator. The heat is recovered from the engine's cooling system and flue gas and transferred to water, which is a heating medium supplying the lithium bromide absorption chiller 2. The heating medium - water - circulates in a closed circuit between the absorption chiller 2 and the heat source 1 being a cogeneration system. The chiller 2 in the embodiment is a lithium bromide absorption chiller producing 300 kW of chilled water at a temperature of 6/ll°C (supply and return) . Water is supplied to the absorption chiller 2 via pipeline 5a and received via pipeline 5b. The heat of absorption and condensation at 32/39°C (supply and return) is collected via an open type cooling tower 4 with a capacity of 717 kW connected to the absorption chiller 2 by means of a pipeline 9 connecting to the pipeline 6. Cooling Tower 4 during full load consumes 0.88 t/h of water and during the reduced due to the invention load 0,29 t/h. The first distillate production effect 3a of the MED block 3 (operating in the 31.1°C-15°C temperature range) producing 95,67 t/d of desalinated water, which includes seven effects, is supplied with heat received from the cooling system of the absorption chiller 2 (water) via a pipeline 6 connecting the absorption chiller to the first distillate production effect 3a. The pipeline 6 consists of a supply pipeline 6a and a return pipeline 6b. The condenser of the last (seventh) distillate production effect 3n is cooled using the chilled water produced by the absorption chiller 2. The chilled water is supplied by a cold water pipeline 7 connecting the last - seventh effect of distillate production 3n with an absorption chiller 2. The pipeline 7 consists of a supply pipeline 7a and a return pipeline 7b. The brine is fed to the first distillate production effect 3a via pipeline 11, and concentrated brine is derived from the last distillate production effect via the pipeline 12 and the desalinated water via the pipeline 14.

The system according to an embodiment of the invention produces 95.67 tons of desalinated water per day and allows reducing the evaporation of water from the cooling tower from 21.21 tons of water per day to 6.85 tons of water per day (reduction of evaporation by 67.7%), increasing the production of a useful distillate from 75.45 t/d to 88.81 t/d (increase in distillate production by 19.3%) .