Device for the efficient separation of a liquid from the foreign substances dissolved in it by means of humidification and dehumidification of a carrier gas

Abstract

Device (100) with a condensation module (1) in which an evaporative cooling medium is placed as a condensation medium instead of a heat exchanger in a carrier gas stream (2), wherein the condensation medium is traversed by a liquid stream (3) which thus comes into direct contact with the carrier gas (2), the temperature of this liquid being at a value below the dew point temperature of the carrier gas.

Description

background

[0001] There are many applications in which liquids contaminated with dissolved foreign substances need to be separated from these contaminants. This is particularly true for drinking water production through desalination. For years, the demand for drinking water production has been increasing dramatically worldwide, due on the one hand to population growth and on the other hand to the contamination of existing freshwater reserves or sources by foreign substances.

[0002] The leading technology for separating liquids, typically water, from dissolved contaminants, especially salts, is reverse osmosis. The disadvantages of this technology are the high electrical (or mechanical) energy consumption and the requirements regarding liquid purity to avoid membrane fouling.

[0003] A somewhat older form of separation is thermal desalination, which, however, requires a very high supply of high-temperature heat. This heat typically comes from fossil fuels at high temperatures, which is currently being avoided. Furthermore, the residues from the evaporation of the liquid reduce the efficiency and service life of the equipment, especially the heat exchangers.

[0004] For this reason, the process of humidification and dehumidification of a carrier gas (HDH process) has been gaining importance in recent years. This process works well even when the fluid contains a certain amount of solid impurities and can utilize heat at low temperatures, typically well below 100°C—i.e., below the evaporation temperature of water. This allows the use of solar heat and inexpensive, non-temperature-resistant materials such as plastics in the fluid circuit. State of the art

[0005] The evaporation of liquid at temperatures significantly below the evaporation temperature has been state-of-the-art for decades, for example, in so-called evaporative cooling. In this process, the carrier gas is passed through a labyrinth-like medium filled with plastics or cellulose fibers. This medium is humidified by a crossflow of liquid. The gas stream is also humidified as it passes through the moist medium. Simultaneous heat and mass transfer takes place.

[0006] The heat for evaporation can be supplied via the carrier gas, the liquid or both.

[0007] The direct contact that occurs between the gas and the liquid results in high efficiency of mass and heat transfer.

[0008] Metal heat exchangers (e.g., tube-and-fin heat exchangers) are typically used for condensation. These are expensive, prone to corrosion, and lose efficiency due to fouling.

[0009] Devices for cleaning and / or concentrating contaminated liquids by means of humidification and dehumidification of a carrier gas are known from DE102004005689A1, EP000001770068A2 and US020150047963A1.

[0010] These devices use, as described above, a module or medium for evaporation, and a heat exchanger for condensation.

[0011] Furthermore, several stages can be interconnected to recover the condensation waste heat and thus increase efficiency. invention

[0012] The present invention is a device (sketch 1, pos. 100) consisting of a condenser module (1) composed of an evaporation medium as described above. A liquid stream (3) flows through this medium. The liquid can be distributed over the condenser module by means of a distributor (8) and collected in a container (6).

[0013] At the same time, a carrier gas stream (2) flows through the condenser module. The carrier gas contains a proportion of liquid vapor, as is the case, for example, with humid air: the gas (air) contains water vapor.

[0014] The liquid (3) can be pumped by a pump (5) and connected to a cooling source by means of a liquid-liquid heat exchanger (4), in particular a plate heat exchanger, in order to keep the temperature of the liquid flow below the dew point temperature of the carrier gas.

[0015] This creates a large condensation surface that brings both mass flows, liquid (3) and carrier gas (2), into contact with each other highly efficiently. This surface can be made of any material (not metal), which saves weight and costs compared to metallic air-liquid heat exchangers. It is also not susceptible to corrosion. Furthermore, potential fouling has little impact on efficiency, unlike condensation heat exchangers. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 102004005689A1

[0009] EP 000001770068A2

[0009] US 020150047963A1

[0009]

Claims

[1] Device (100) comprising a condensation module (1) in which an evaporative cooling medium is placed as a condensation medium instead of a heat exchanger in a carrier gas stream (2), wherein the condensation medium is crossed by a liquid stream (3) which thus comes into direct contact with the carrier gas (2), the temperature of this liquid being at a value below the dew point temperature of the carrier gas. [2] The liquid flow can be passed through a container (6), the liquid level of which can rise due to the condensed liquid and the excess amount can be discharged or recovered by means of an overflow (7). [3] The temperature of this liquid can be kept at a value below the dew point temperature of the carrier gas, for example by means of a heat exchanger (4). [4] A pump (5) can be used for circulation. [5] For even distribution of the liquid flow in the condensation medium, a liquid distributor (8) can be used [6] Device as in claims 1-5 in an arrangement (200) as described in sketch 2, in which the condensation module (1) is coupled to an evaporation module (11) via a heat exchanger (4), wherein the condensation heat from a moist carrier gas stream (2) can be used for evaporation in a carrier gas stream (12) to be humidified.

Images