WO2019083416A1

WO2019083416A1 - Water desalination system

Info

Publication number: WO2019083416A1
Application number: PCT/SA2018/050027
Authority: WO
Inventors: Yousef AL YOUSEF; Filip HERMAN; Michał CHABER; Fahad
Original assignee: King Abdulaziz City For Science And Technology; New Energy Transfer Spółka Z Ograniczoną
Priority date: 2017-10-23
Filing date: 2018-10-09
Publication date: 2019-05-02
Also published as: PL423244A1; PL234747B1

Abstract

Desalination system comprising of a heat source (1), absorption heat pump (2), block of effects (3), absorption chiller (16) specific by that the system comprises of at least one heat exchanger and the heat source (1) is connected to the absorption heat pump (2) through the heat-transfer medium pipeline comprising the supply pipeline (4a) and the return pipeline (4b) which connects the absorption chiller (16) with the heat source (1). The absorption chiller (16) is connected to the heat source (1) through the heat-transfer medium pipeline consisting of the supply pipeline (7a) and the return pipeline (7b). The absorption heat pump (2) is connected through the heating water pipeline consisting of the supply pipeline (5a) and the return pipeline (5b) to the first effect from the block of distillate production effects (3) and the absorption chiller (16) through the chilled water pipeline consisting of the supply pipeline (8a) and the return pipeline (8b) is connected with the last effect from the block of distillate production effects (3) and with the absorption heat pump (1) through the pipeline consisting of the supply pipeline (6a) and return pipeline (6b). The brine supply pipeline (11) is connected to the first effect from the block of distillate production effects (3). Desalinated water discharge pipeline (12) is connected with the last effect from the block of distillate production effects (3). Brine reject pipeline (13) is connected to the second to last effect from the block of distillate production effects (3).

Description

Water desalination system

The subject of the invention is a desalinated water production system CoDeCo (Combined Desalination and Cooling) .

The invention belongs to the field of water desalination techniques .

Solutions, including those used for water desalination, comprising of distillate production effects, heat pumps and absorption chillers are known from the prior art.

Patent application No. CN205653194 demonstrates a usage of absorption unit alternately supplied by solar and geothermal heat. The proposed solution precludes a utilization of low and medium grade heat from an absorption chiller as it is in the case of present invention.

The solution presented in patent application No. CN205640840 represents an invention in which vacuum collector tubes are used to improve vacuum quality in desalination systems.

The solution disclosed in invention CN105923676 utilizes a 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 absorption chiller is fully utilized.

The invention disclosed in application No. CN105841395 represents a system of energy generation and water desalination based on the LNG regasification energy recovery. It is not a system integrated with a combined system when it comes to desalination but rather a powering system for different production systems (refrigeration, desalination etc . ) The invention disclosed in the application No. US2017190597 represents a usage of refrigeration in desalination for a joint membrane- less freezing of desalinated water vapors as a method of its separation from salt.

The solution disclosed in the application No. CN106698563 represents a usage of electrically powered compressor cooperating with membrane filtration system, which is a different system from MED desalination method.

The application No. WO2017066534 presents a usage of heat pump for heat recovery from "gray water" and utilizing it to power a desalination system. Unlike this solution, the present invention represents a fully integrated system where a utilization of heat from condenser and absorber reduces a demand for a chilled water from a cooling tower, thus enabling balancing of the solution of combined cold and desalinated water production .

The objective of the present invention is to provide a combined system for the production of desalinated water enabling its operation without an external cooling system, i.e. a cooling tower.

The energy source for the system according to the present invention is a heat in a form of a hot water or a saturated steam which is distributed by a circuit to Absorption Heat Pump and by a circuit to Absorption Chiller. Absorption Chiller produces a stream of refrigerated water delivered by a circuit to a condenser of a Multi Effect Desalination (MED) system. The purpose of the condenser supplied with chilled water is to condense vapors produced at the last effect of a Multi Effect Desalination (MED) system. During the chilled water production cycle, the Absorption Chiller produces absorption heat generated in the process of vapor absorption by a lithium bromide solution and condensation heat resulting from a condensation of vapors generated in a refrigerant production process.

It is therefore necessary to provide a stream of cooling water to the Absorption Chiller in order to reject both absorption heat and condensation heat of desorbed vapor. Cooling water is distributed by a circuit to the evaporator of Absorption Heat Pump in order to lower its temperature through reception of heat needed to evaporate the refrigerant circulating in the Absorption Heat Pump. In conventional systems cooling water circuit of absorption chillers cooperates with cooling towers which receive the heat generated in a process of absorption and condensation of desorbed vapors. In the solution of the present invention a cooling tower has been eliminated completely, thus preventing water losses resulting from evaporation associated with cooling tower operation. For example, in case of a multi effect desalination system operated away from a sea as a cooling water source, with 500kW power requirement for condensation of generated vapors, the emission of water vapor to the atmosphere is as high as 0,72m³ per hour while a production of desalinated water would be 10,8m³ per hour. In case of cooling with the evaporator of Adsorption Heat Pump emission of water vapor to the atmosphere does not occur. Due to a necessity of maintaining the energy balance and the fact that Absorption Heat Pump is capable of cooling 75% of a circulated cooling water, the remaining part is cooled in a Heat exchanger which preheats a brine supplied to MED effects block. A part of returning cooling water from the circuit is directed by the circuit to the heat exchanger which preheats the brine directed to the block of MED effects in order to reject its heat for the purpose of preheating a stream of brine subjected to desalination process and distributed by the circuit, which results in improved energy balance and eventually higher volume of desalinated water production. There is also a possibility to cool down the cooling water return in a heat exchanger used for heat rejection to a brine reject as well as in a heat exchanger used for heat rejection to distillate. This can be done by directing a part of cooling water by the circuit to heat exchangers and rejecting a part of its heat to desalinated water and brine reject, which temperatures allow such a procedure. The Absorption Heat Pump after receiving of a low-grade heat from the circuit as well as supplying driving heat by a circuit, produces the useful heat distributed by the circuit and used as a heat source for the process of evaporating the brine directed to the first evaporator of MED system. The Absorption Chiller supplied with a heat through a circuit generates a stream of chilled water distributed by the circuit, allowing condensation of water vapors in the last effect of MED system to the form of desalinated water. Since the evaporation temperatures of last effects of the system are significantly reduced, the circuit delivers to them the brine which does not take part in heating through a heat exchanger .

The essence of the invention is a desalination system comprising of a heat source, an absorption heat pump, a block of effects, absorption chiller, characterized by a presence of at least one heat exchanger in the system. A heat source is connected with an absorption heat pump by a heat-transfer medium pipeline consisting of a supply pipeline and return pipeline which connects the absorption chiller with the heat source. The absorption chiller is connected with the heat source by a heat-transfer medium pipeline consisting of a supply pipeline and return pipeline. Absorption heat pump is connected with the first effect from the set of distillate production effects by a heating water pipeline consisting of a supply pipeline and return pipeline. Absorption chiller is connected with the last effect from the set of distillate production effects by a chilled water pipeline consisting of a supply pipeline and return pipeline and to an absorption heat pump by a pipeline consisting of supply pipeline and return pipeline. Brine feeding pipeline is connected to the first effect from the block of distillate production effects. Desalinated water discharge pipeline is connected to the last effect from the block of distillate production effects. Brine reject pipeline is connected to the one before last effect from the block of distillate production effects.

It is preferred when the brine supply pipeline to the first effect from the block of distillate production effects is connected through a brine preheating heat exchanger which is additionally connected through supply and return pipelines with a supply pipeline and return pipeline connecting absorption chiller with absorption heat pump.

It is preferred when a desalinated water discharge pipeline is connected through a heat exchanger and a brine reject pipeline is connected through a heat exchanger and both heat exchangers are connected to a connecting pipeline which is connected to the supply pipeline on one side and to the return pipeline on the other side.

It is preferred when a heat source is a cogeneration system or steam generator or water boiler or solar collectors.

A preferred embodiment of the invention has been depicted in the drawing which presents a block diagram of the system.

The preferred embodiment of the system comprises the heat source 1 being an oil powered boiler with maximum power of 875 kW providing 10% overcapacity, generating a saturated steam at the pressure of 8 bar, connected with the absorption heat pump 2 with COP at the level of 236% and usable heat (55/50 ^°C) nominal power of 1050 kW for the flow rate of 181 t/h through the heat-transfer medium pipeline consisting of the supply pipeline 4a and return pipeline 4b, connecting the absorption chiller 16 with the heat source 1. The absorption chiller 16 has a COP at the level of 142% and nominal cooling power of 500 kW for the chilled water parameters 12/7 ^°C at the flow rate of 86 t/h. The absorption chiller 16 is connected to the heat source 1 through the heat-transfer medium pipeline consisting of the supply pipeline 7a and the return pipeline 7b. The absorption heat pump 2 is connected through the heating water pipeline consisting of the supply pipeline 5a and the return pipeline 5b to the first effect from the block of distillate production effects 3 and the absorption chiller 16 is connected through the chilled water pipeline consisting of the supply pipeline 8a and the return pipeline 8b to the last effect from the block of distillate production effects 3 and the absorption heat pump 1 through the pipeline consisting of supply pipeline 6a and return pipeline 6b. The first effect from the block of distillate production effects 3 through the 200 kW brine heating heat exchanger 14 the brine supply pipeline 11 is connected. To last effect from the block of distillate production effects 3 the desalinated water discharge pipeline 12 is connected. Moreover, the brine heating heat exchanger 14 is connected to the supply pipeline 9a and return pipeline 9b. The brine reject pipeline 13 is connected to the second to last effect from the block of distillate production effects 3. Each of the fluid pipelines 5,8,6 is equipped with pump sets 17,18,19.

Claims

Desalination system comprising of a heat source (1) , absorption heat pump (2), block of effects (3), absorption chiller (16) characterized by that the system comprises of at least one heat exchanger, and the heat source (1) is connected to absorption heat pump (2) through the heat-transfer medium pipeline consisting of a supply pipeline (4a) and return pipeline (4b), connecting the absorption chiller (16) with the heat source (1); the absorption chiller (16) is connected to the heat source (1) through the heat- transfer medium pipeline consisting of the supply pipeline (7a) and return pipeline ( 7b); the absorption heat pump (2) is connected through the heating water pipeline consisting of the supply pipeline (5a) and the return pipeline (5b) with the first effect from the block of distillate production effects (3) , and the absorption chiller (16) is connected through the chilled water pipeline consisting of the supply pipeline (8a) and the return pipeline (8b) to the last effect from the block of distillate production effects (3) and through the pipeline consisting of the supply pipeline (6a) and the return pipeline (6b) to the absorption heat pump (1); the brine supply pipeline (11) is connected to the first effect from the block of distillate production effects (3) ; the desalinated water discharge pipeline (12) is connected to the last effect from the block of distillate production effects (3); the brine reject pipeline (13) is connected to the second to last effect from the block of distillate production effects (3) .

Desalination system according to claim 1 specific by that, the pipeline (11) which supplies the brine to the first effect from the block of distillate production effects (3) is connected through the brine heating heat exchanger (14) which is additionally connected through the supply pipeline (9a) and return pipeline (9b) to the supply pipeline (6a) and return pipeline (6b) .

Desalination system according to claim 1 or 2 specific by that, the desalinated water discharge pipeline (12) is connected through the heat exchanger (15b) and the brine reject pipeline (13) is connected through the heat exchanger (15a) and heat exchangers (15a) and (15b) are connected to the pipeline (10) connecting the supply pipeline (6a) with the return pipeline (6b) .

Desalination system according to claims 1, 2, 3, specific by that, the heat source (1) is a cogeneration system or steam generator or water boiler or solar collectors.