System and method for freezing and desalting seawater / saline water and making brine by using air cold energy in winter

Abstract

The invention discloses a system and method for seawater / saline water freezing desalination and brine making by using winter air cold energy, the system comprises a brine making pool, a desalting pool, a water diversion and drainage system and an artificial freezing system, and the water diversion and drainage system comprises a pump station, a water diversion ditch and a brine drainage ditch; the artificial freezing system comprises an air pump and a heat absorbing plate group, the double-sided heat absorbing plate group consists of a plurality of double-sided heat absorbing plates which are connected in series, the double-sided heat absorbing plates are vertically mounted in the marinating pool, the single-sided heat absorbing plate group consists of a plurality of single-sided heat absorbing plates which are connected in series, and the single-sided heat absorbing plates are laid at the bottom and on the side slope of the marinating pool. Compared with the prior art, the system can simultaneously generate a large amount of fresh water and brine, realizes comprehensive utilization of seawater / salty water resources, can provide a large amount of low-cost fresh water for saline-alkali soil improvement, desert greening and resident life, can also provide a large amount of brine for a salt field, and greatly reduces the occupied area of brine production of the salt field. By applying the method, huge economic benefits and ecological benefits can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of seawater / brackish water desalination and also to the technical field of bittern production in salt pans, and particularly relates to a system and method for seawater / brackish water freezing desalination and bittern production by using the cold energy of winter air. Background Art

[0002] 1) The per capita fresh water resource in China is only 1 / 4 of the world average, and the per capita fresh water resource in the Bohai Rim region is less than 1 / 5 of the national per capita. The Bohai Rim region is one of the most economically developed regions in China, with a GDP accounting for more than 1 / 4 of the country. The limited fresh water resources in the Bohai Rim region are mainly used for urban domestic and industrial water, and it is impossible to be used for agricultural irrigation for the improvement of coastal saline-alkali land with low added value. Seawater desalination is an inevitable choice to solve the shortage of fresh water resources in the Bohai Rim region. However, at present, the cost per ton of seawater desalination is 4 - 6 yuan, and the high-cost desalinated seawater is also impossible to be used for the irrigation water for the improvement of coastal saline-alkali land with low added value. The high cost of seawater desalination is the primary factor restricting the improvement of coastal saline-alkali land in the Bohai Rim region, which makes a large area of coastal saline-alkali land in the Bohai Rim region not be developed and utilized. Reducing the cost of seawater desalination is an urgent problem to be solved for the improvement of coastal saline-alkali land in the Bohai Rim region at present.

[0003] 2) It is cold in winter in the Bohai Rim region, and seawater freezing phenomenon will occur. In the 1990s, the Bohai Sea ice was regarded as a fresh water resource, which attracted the attention of scholars. The relevant research results show that after temperature-controlled solid desalination of the Bohai Sea ice, it can meet the requirements of agricultural irrigation water, and there is a broad application prospect for using desalinated sea ice water to irrigate the coastal saline-alkali land in the Bohai Rim region. However, due to the energy consumption costs, labor costs of workers, and the depreciation and maintenance costs of equipment generated in the processes of ice harvesting and transportation, etc., the cost of desalinated sea ice water is very high, and it cannot be commercially produced and utilized at present.

[0004] 3) Sufficient bittern source is a prerequisite for high-quality and high-yield sea salt production. At present, sea salt production mainly relies on bittern production by solar evaporation in salt pans, and more than 80% of the area of a salt field is used for bittern production by solar evaporation. The salt pans occupy a large area of land in the coastal plain, which will inevitably affect the social and economic development of coastal cities. For example, the Nanpu Salt Field in Tangshan City covers an area of about more than 300 square kilometers, and the salt pan area reaches more than 240 square kilometers. Such a huge salt pan area has had a serious impact on the economic development of Caofeidian, and it is urgent to adjust a part of the salt pan area for the economic development of Caofeidian.

[0005] 4) In the improvement of saline-alkali land in the western inland of China, the main method is the "flood irrigation or drip irrigation for desalination - drainage through ditches - sewage reception in the flood detention area" model. Discharging the desalination sewage downstream or into the flood detention area exacerbates the salinization of the soil in the downstream area and damages the ecology of the flood detention area. The construction of large-scale drainage ditches requires huge capital investment, and the discharge of desalination sewage also causes a huge waste of fresh water resources. How to eliminate the saline-alkali pollution of the desalination sewage to the downstream area or the flood detention area, reduce the cost of building drainage ditches, realize the recycling of fresh water resources, and thus reduce the water diversion from the transit river is an urgent problem to be solved in the improvement of inland saline-alkali land.

[0006] 5) The agricultural development, desert greening, and residents' livelihoods in the arid inland areas with saline-alkali land and other wastelands far from surface water sources are restricted by the lack of fresh water resources, but the underground saline water resources are abundant. How to obtain low-cost desalinated water from underground saline water for agricultural irrigation, desert greening, and residents' livelihoods is an urgent problem to be solved in the economic development of arid inland areas.

[0007] In view of the above problems, Patent CN102139932A discloses an experimental device for desalinating seawater using the cold energy of liquefied natural gas. The device is composed of a cold energy regulation subsystem of liquefied natural gas and a seawater desalination device system connected in parallel or in series. Liquefied natural gas is used as a refrigerant for heating and cooling to provide the energy required for the evaporation of seawater. Patent CN101671058B discloses a semi-automatic production method for desalinating seawater by using natural energy to make ice. The method designs an ice-making pool similar to terraced fields, fills seawater below 0 °C, drains the seawater at the bottom after freezing, and realizes the purpose of desalination through repeated freezing and thawing of the ice. These two invention patents only involve the field of seawater freezing desalination and do not involve the field of seawater freezing to produce bittern. The production cost of desalinated water from sea ice is very high and is not suitable for large-scale commercial production. In addition, both of these methods will produce a large amount of high-salt wastewater, and the discharge of high-salt wastewater will also have a certain impact on the marine ecology. Summary of the Invention

[0008] In order to solve the above technical problems, the present invention provides a system and method for freezing desalination and bittern production of seawater / brine using the cold energy of winter air. Through the implementation of this technology, a huge amount of fresh water and bittern can be generated simultaneously, realizing the comprehensive utilization of seawater / brine resources. It can not only provide a large amount of low-cost irrigation water or domestic water for the improvement of saline-alkali land, desert greening, and residents' livelihoods, but also provide a large amount of bittern for salt fields. At the same time, it can also greatly reduce the land occupation for bittern production in salt fields, thus generating huge economic and ecological benefits.

[0009] To achieve this technical purpose, the present invention adopts the following scheme: In a first aspect, the present invention provides a system for seawater / brackish water freezing desalination and brine production using the cold energy of winter air, which includes a brine production pond, a desalination pond, a water intake and drainage system, and an artificial freezing system. There is a water intake on one side of the brine production pond; there is a drainage outlet on one side of the desalination pond; the water intake and drainage system includes a first pumping station, a water diversion channel, a brine drainage channel, and a second pumping station. The first pumping station is arranged at the water intake, and both the water diversion channel and the brine drainage channel are connected to the water intake. The second pumping station is arranged at the drainage outlet, and the drainage outlet is connected to the farmland irrigation system; the artificial freezing system includes a first air pump, a second air pump, a double-sided heat absorption plate group, and a single-sided heat absorption plate group. The first air pump is connected to the double-sided heat absorption plate group, and the double-sided heat absorption plate group is composed of a number of double-sided heat absorption plates connected in series. The double-sided heat absorption plates are vertically installed at the bottom of the brine production pond. The second air pump is connected to the single-sided heat absorption plate group, and the single-sided heat absorption plate group is composed of a number of single-sided heat absorption plates connected in series. The single-sided heat absorption plates are laid on the bottom and slopes of the brine production pond.

[0010] Further, the cross-section of the brine production pond body is an inverted trapezoid, and the horizontal shape is a rectangle. The length-width ratio can be set arbitrarily according to specific circumstances. The depth of the brine production pond is designed according to the maximum thickness of the ice layer that can be mined in the brine production pond, the net evaporation amount, and the depth of the generated brine. In order to reduce the cost of earthwork excavation for the brine production pond, it is advisable for the brine production pond to be semi-submerged, or a brine production pond can also be constructed by building a dike directly in the salt field of a coastal saltworks or other low-lying areas.

[0011] Further, a filter screen is arranged at the water intake of the brine production pond to filter out larger particulate matters and organisms in the seawater / brackish water; the water diversion channel is connected to the seawater / brackish water source, and the brine drainage channel is connected to the salt evaporation pond or crystallization pond of the saltworks. Gates are arranged on both the water diversion channel and the brine drainage channel.

[0012] Further, composite geomembranes are laid on the bottom and around the brine drainage channel, the brine production pond, and the desalination pond for anti-seepage treatment.

[0013] Further, a water collection trough is built on the middle line parallel to the long side at the bottom of the brine production pond and the desalination pond. A water collection well is built on one side of the water collection trough. The water collection well in the brine production pond is arranged on the side close to the water intake, and the water collection well in the desalination pond is arranged on the side close to the drainage outlet; the width and depth of the water collection trough are 1m×0.5m; the inner diameter of the water collection well is 0.8m - 1m, and the depth is 1m - 1.5m; the water collection trough and the water collection well are covered with iron gratings, and the mesh size of the iron grating is 5cm×5cm - 10cm×10cm.

[0014] Furthermore, the heat absorbing plate is made of stainless steel with high thermal conductivity and corrosion resistance. The heat absorbing plate is a hollow structure welded from stainless steel plates. A guide plate is provided inside the heat absorbing plate, and the material of the guide plate is the same as that of the heat absorbing plate. The function of the guide plate is, on the one hand, to increase the length and flow time of the flow path of the cold air in the heat absorbing plate, so that the cold air can fully pass through the heat absorbing plate to absorb heat from the seawater / salt water in the brine pool; on the other hand, it can play a supporting role, so that the heat absorbing plate can withstand the huge water pressure in the brine pool. The thickness of the heat absorbing plate steel plate is determined according to the maximum water pressure in the brine pool, so that the heat absorbing plate can withstand the maximum water pressure in the brine pool without deformation.

[0015] Furthermore, the thickness of the double-sided heat absorbing plate is 20-30cm, the height of the double-sided heat absorbing plate is not less than 2 / 3 of the depth of the brine making pool, the double-sided heat absorbing plate is vertically installed on the bottom of the brine making pool through the base, the interval between two adjacent double-sided heat absorbing plates in the horizontal direction is 3-5m, and the interval between two adjacent double-sided heat absorbing plates in the vertical direction is 6-8m, and insulation baffles are installed at the outer corners of the double-sided heat absorbing plate; the thickness of the single-sided heat absorbing plate is about 10cm, and insulation baffles are arranged between adjacent single-sided heat absorbing plates. The function of the insulation baffle is to separate the heat absorbing plate into independent ice surfaces, so that when harvesting ice, the sea ice / salt water ice attached to each heat absorbing surface can be separated in blocks independently.

[0016] Furthermore, the positions of the air inlet and outlet of the heat absorbing plate can be selected according to the specific conditions of the connection or splicing of the heat absorbing plate. In this application, in order to facilitate the assembly of the heat absorbing plate, the air inlet and outlet of the double-sided heat absorbing plate are arranged on both sides of the bottom of the heat absorbing plate; the air inlet of the first heat absorbing plate of the double-sided heat absorbing plate group is connected to the first air pump, and the air outlet of the last heat absorbing plate is arranged on the bank of the adjacent brine-making pool. The air outlet of any other double-sided heat absorbing plate is connected to the air inlet of the next double-sided heat absorbing plate, so that all double-sided heat absorbing plates form a series structure; the positions of the air inlet and outlet of the single-sided heat absorbing plate can be arranged on any corner of the single-sided heat absorbing plate according to the specific splicing needs. All single-sided heat absorbing plates are connected by ventilation pipes to form a series structure.

[0017] Furthermore, the shape and anti-seepage treatment of the desalination pool are the same as those of the brine production pool. The long side of the desalination pool is adjacent to the long side of the brine production pool, separated by a cement road that is passable for ice harvesting and transportation. The desalination pool is divided into several ice storage rooms in the longitudinal direction, which are used to stack sea ice collected at different times. The water collection ditches of each ice storage room are connected through a culvert, and each culvert is provided with a gate so that the sea ice / salt water ice desalinated water in the first desalinated ice storage room can be discharged into the farmland irrigation system first. An aeration pipe is laid at the bottom of the desalination pool, and the aeration pipe is connected to the third air pump. The material density of the aeration pipe is less than the density of seawater / salt water, so that when water accumulates in the desalination pool, the aeration pipe can float on the water surface for aeration.

[0018] In a second aspect, the present invention provides a method for utilizing winter air cold energy to freeze and desalinate seawater / salt water and produce brine, comprising the following steps: S1, water storage in the brine making pool, introducing seawater / salt water into the brine making pool through natural drainage or pumping from the first pumping station; S2, the brine pool is air-cooled and frozen. The low-temperature cold air is input into the double-sided heat absorbing plate group and the single-sided heat absorbing plate group through the first air pump and the second air pump, and the cold air in the heat absorbing plate absorbs heat from the seawater through the heat absorbing plate. The first air pump and the second air pump are provided with automatic opening and closing switches. When the temperature difference between the air temperature and the seawater / salt water temperature reaches a certain threshold, the first air pump and the second air pump are automatically turned on or off. For example, when the temperature difference between the air temperature and the seawater / salt water in the brine pool is ≧5°C, the first air pump and the second air pump are automatically turned on, and when the temperature difference is less than 5°C, the first air pump and the second air pump are automatically turned off. Through the long-term heat absorption of the seawater / salt water in the brine pool by the artificial freezing system, the temperature of the seawater / salt water in the brine pool is basically consistent with the air temperature. When the air temperature drops to the freezing point of the seawater / salt water, the temperature of all the seawater / salt water in the brine pool also reaches the freezing point. This greatly reduces the cold energy required for subsequent seawater / salt water freezing, thereby greatly accelerating the freezing speed of seawater / salt water in the brine pool and the thickness of the harvestable ice layer. The continued input of cold energy causes the surface seawater in the brine pool to freeze through natural freezing, and the middle and lower layers of seawater freeze on the outer surface of the heat absorbing plate; S3, ice harvesting in the brine pool. When the surface sea ice / salt water ice in the brine pool reaches 10cm~20cm, ice harvesting begins, together with the sea ice / salt water ice attached to the heat absorbing plate. When harvesting the sea ice / salt water ice attached to the heat absorbing plate, first input hot air into the heat absorbing plate (it can be air when the temperature is high that day, or other heat source gases) to melt the sea ice / salt water ice in direct contact with the surface of the heat absorbing plate, and the sea ice / salt water ice will detach from the various surfaces of the heat absorbing plate in blocks. Under the action of buoyancy, the sea ice / salt water ice will float to the surface of the water and then be harvested. According to the time sequence of ice harvesting, the collected block sea ice / salt water ice is stacked in the ice storage room of the desalination pool in sequence. The salt content of brine cells contained in the sea ice / salt water ice collected at different times is different, and the duration of desalination is different, so they must be stacked separately. In order to prevent evaporation loss and facilitate temperature control and desalination, the surface of the ice pile is covered with an insulation layer; S4. Evaporation for brine production: After ice harvesting, the unfrozen concentrated seawater / brackish water in the brine production pond is further concentrated into brine through evaporation, and then transported to the salt evaporation pond or crystallization pond of the salt field through the brine drainage ditch for further processing by the salt field. If the brine drainage ditch is not built, tank trucks can be used to transport the brine to the salt field. During evaporation for brine production, to accelerate the evaporation rate, when the temperature difference between the air temperature and the concentrated seawater / brackish water in the brine production pond reaches a certain threshold, for example, the temperature difference threshold can be set at 5°C, hot air is input into the single-sided heat absorption plate group through the second air pump to increase the temperature of the brine, accelerate the evaporation rate, and shorten the time for brine production. During evaporation for brine production, if a certain ice storage chamber or some ice storage chambers in the desalination pond have been emptied, part of the concentrated seawater / brackish water in the brine production pond can be pumped into these ice storage chambers for evaporation for brine production, increasing the evaporation area of the concentrated seawater / brackish water, thereby increasing the total evaporation volume and accelerating the speed of concentrated seawater / brackish water becoming brine.

[0019] S5. Temperature-controlled solid desalination: The sea ice / brackish water ice is stacked statically in the desalination pond, and the brine cells wrapped in the ice body will gradually connect with each other to form brine channels, and the brine will flow out of the ice body under the action of gravity. To accelerate the desalination rate of the sea ice / brackish water ice, when the air temperature fluctuates near the melting point of the sea ice / brackish water ice, the aeration pipe at the bottom of the desalination pond is used to aerate the ice pile, so that the sea ice / brackish water ice crystals melt to a limited extent, promoting the formation or expansion of brine channels in the ice body, and accelerating the speed of brine seeping out of the ice body; the brine collected in the sump of the desalination pond is pumped into the brine production pond through the second pumping station for refreezing or evaporation for brine production; when the salt content of the melt water of the sea ice / brackish water ice reaches 2‰, or when the air temperature rises and the ice blocks begin to melt in large quantities, desalination is stopped; S6. Ice melting for irrigation: After desalination is stopped, the melt water of the sea ice / brackish water ice in the desalination pond is the desalinated water of the sea ice / brackish water ice that can be used for farmland irrigation, and the desalinated water of the sea ice / brackish water ice generated in the desalination pond is transported to the farmland irrigation system through the second pumping station. If the salinity of the desalinated water of the sea ice / brackish water ice is higher than 2‰, it can be mixed with river water, underground fresh water or collected rainwater and then used for farmland irrigation. To ensure the demand for farmland irrigation water during spring plowing, the sea ice / brackish water ice stacked in the desalination pond must be completely melted before spring plowing. When the air temperature reaches a certain threshold temperature, for example, when the air temperature ≥ 5°C, hot air is aerated into the ice pile through the aeration pipe at the bottom of the desalination pond to quickly melt the sea ice / brackish water ice to ensure the demand for farmland irrigation water during spring plowing.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) When the system and method of the present invention are used for seawater freezing desalination and bittern production in cold coastal areas in winter, by combining artificial freezing method and natural freezing method, the ice-forming surface area of the bittern production pond and the thickness of the exploitable ice layer are greatly increased, and the bittern output per unit area of the bittern production pond is also greatly increased. In the natural state, when the air temperature reaches the freezing point temperature of seawater, only the surface seawater temperature reaches the freezing point temperature, while the seawater temperature below the surface remains at about 4°C. To freeze the seawater below the surface, a large amount of cold energy is required to reduce the seawater temperature from 4°C to the freezing point temperature (about -2°C), which makes the natural freezing speed of seawater in winter slow and the thickness of the frozen seawater small. Since an artificial freezing system is installed in the bittern production pond of this system, on the one hand, through the long-term heat absorption of the artificial freezing system for the seawater in the bittern production pond, the seawater temperature in the bittern production pond is basically the same as the air temperature. When the air temperature drops to the freezing point temperature of seawater, the temperatures of all the seawater in the bittern production pond also reach the freezing point temperature, which greatly reduces the cold energy required for the seawater in the bittern production pond to freeze, thus accelerating the freezing speed of the seawater in the bittern production pond and the thickness of the exploitable ice layer. On the other hand, since both single-sided and double-sided heat absorption plates are ice-forming surfaces, the ice-forming surface area in the bittern production pond is increased by 3-4 times compared with the natural ice-forming surface area. Due to these two reasons, the sea ice output in the bittern production pond is greatly increased, and thus the output of desalinated water from sea ice is also greatly increased. At the same time, since a large amount of fresh water is removed from the bittern production pond, the bittern output in the bittern production pond is also greatly increased. For example, the natural freezing thickness of the Bohai Sea ice along the coast of Tangshan City is about 30 cm. If the ice is harvested every time the ice thickness reaches 10 cm, the exploitable ice layer thickness per year can reach about 1.3-1.5 m. If seawater is introduced into the bittern production pond of the system of the present invention for freezing desalination and bittern production, since when the air temperature drops to the freezing point temperature of seawater, the temperatures of all the seawater in the bittern production pond have reached the freezing point temperature, and the ice-forming surface area in the bittern production pond is increased by 3-4 times, the exploitable ice layer thickness of the entire winter bittern production pond can reach about 7 m. In addition, the evaporation volume of the concentrated seawater in the bittern production pond in spring and autumn can be converted to more than 2 m (the annual net evaporation volume of Nanpu Salt Field is about 1200 mm, the evaporation volume of the concentrated seawater in the bittern production pond is about 1200 mm, and the evaporation volume of the concentrated seawater pumped to the desalination pond is also about 1200 mm). In this way, about 9 m deep of fresh water will be removed from the bittern production pond throughout the year. Theoretically, if the salt pans in Nanpu Salt Field are transformed into 10 m deep bittern production ponds, 7 m thick sea ice can be formed through freezing. Even at a 60% sea ice fresh water production rate, 4.2 m deep of fresh water can be produced. Adding the 2 m deep net evaporation volume, about 1 m deep of bittern with a salt content of 30% can be produced in the bittern production pond. 1 km 2A 10-meter-deep brine production pond will produce 4.2 million tons of fresh water and 1.2 million tons of brine with a salt content of 30% annually. If the water consumption for drip irrigation required for coastal saline-alkali land improvement is calculated at 200 mm, the fresh water produced can provide irrigation water for nearly 21 km 2 (31,500 mu) of coastal saline-alkali land. If the brine with a salt content of 30% is priced at 80 yuan / ton, 1.2 million tons of brine with a 30% salt content can generate an economic benefit of 96 million yuan. After 1.2 million tons of brine with a 30% salt content is input into the salt field, about 360,000 tons of crude salt can be produced. Therefore, when the system and method of the present invention are used for seawater freezing desalination and brine production in cold coastal areas in winter, huge economic benefits can be obtained. If the system and method of the present invention are used for seawater / saltwater desalination and brine production in higher-latitude or high-altitude areas that are colder in winter, the thickness of the exploitable ice layer in the brine production pond will be greater, more brine will be produced, and the economic benefits will be better.

[0021] 2) When the system and method of the present invention are applied to brine production in salt fields in cold coastal areas in winter, without changing the area of the salt pans, the brine production of the salt pans can be greatly increased; without changing the total target of brine production, the land area for brine production in the salt pans can be greatly reduced, which can provide a large area of land for the social and economic development of coastal cities. For example, the brine production in Nanpu Salt Field in Tangshan City depends entirely on natural evaporation. The designed annual production of crude salt is 1.88 million tons with a sun-drying area of 240 km 2 , and the actual annual production of crude salt is about 1.7 million tons. Theoretically, if half (120 km 2 ) of the 240 km 2 salt pans in Nanpu Salt Field are transformed into 10-meter-deep brine production ponds and the other half into desalination ponds, the crude salt production in Nanpu Salt Field will be increased to 43.2 million tons (120 km 2 × 360,000 tons / km 2 ). The fresh water from sea ice desalination produced by the 120 km 2 desalination ponds can provide irrigation water for 2,520 km 2 (3.78 million mu) of coastal saline-alkali land. If the designed annual production of 1.88 million tons is to be maintained, only 6 km 2 of brine production ponds are needed, and together with the supporting 6 km 2 of desalination ponds, more than 200 square kilometers of land can be saved for the urban development of Caofeidian.

[0022] 3) The application of the system and method of the present invention has greatly reduced the production cost of desalinated water from sea ice / brackish ice and brine, enabling the large-scale commercial production of desalinated water from sea ice / brackish ice and brine. ① Using low-temperature cold air as the refrigerant saves the cost of refrigerant generation and operation. ② Combining the brine production pool and the desalination pool greatly reduces the costs of ice collection, ice transportation, etc. ③ There is no need for special land acquisition and plant construction, nor the purchase of special seawater desalination equipment, saving the costs of land acquisition for the construction of seawater / desalination plants, plant construction, the purchase cost of seawater / desalination equipment, and equipment maintenance costs.

[0023] 4) When the system and method of the present invention are used to treat the salt-washing sewage of inland saline-alkali land, good economic and ecological benefits can be achieved. Matching a certain area of saline-alkali land improvement project with this system, using the salt-washing sewage of saline-alkali land as the raw water for freezing desalination and brine production eliminates the saline-alkali pollution of the salt-washing sewage to downstream areas or receiving areas, reduces the cost of building drainage ditches for saline-alkali land improvement to drain alkali, and the desalinated water from brackish ice produced enables the recycling of fresh water resources, thus reducing the water diversion volume from the passing river. At the same time, it can also provide a large amount of brine for inland salt fields.

[0024] 5) When the system and method of the present invention are used for desalination of underground brackish water in arid inland areas, it can provide fresh water for agricultural irrigation, desert greening, and residents' lives in arid inland areas, and can also provide a large amount of brine for inland salt fields. Therefore, good economic and ecological benefits can also be achieved.

[0025] 6) The system and method of the present invention combine the brine production pool and the desalination pool, artificial freezing method and natural freezing method, and freezing and evaporation, and can simultaneously obtain a huge amount of low-cost desalinated water from sea ice / brackish ice and high-salt brine. The desalinated water from sea ice / brackish ice can provide fresh water resources for saline-alkali land improvement, wasteland reclamation, desert greening, and residents' lives, etc., and the brine can be used for salt production in salt fields. Therefore, the application of this system and method can form a multi-functional system integrating seawater / desalination, seawater / desalination brine production, saline-alkali land improvement, wasteland reclamation, desert greening, etc. This technical system has the characteristics of being green, environmentally friendly, and low-cost, can form a new industrial chain without waste and pollutant emissions, which conforms to the principles of ecological economics, and can generate great economic and ecological benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a plan view of the seawater / desalination and brine production system according to the embodiment of the present invention; Figure 2 It is a cross-sectional view of the brine production pool according to the embodiment of the present invention; Figure 3 It is an internal structure diagram of the double-sided heat-absorbing plate according to the embodiment of the present invention; Figure 4Internal structure diagram of the single-sided heat absorption plate in the embodiment of the present invention; Figure 5 Technical route diagram of the seawater / brackish water freezing desalination and brine production system in the embodiment of the present invention.

[0027] The markings in the figure are: 1. Brine production pond; 2. Desalination pond; 3. Water intake; 4. Drainage outlet; 5. Double-sided heat absorption plate; 6. Single-sided heat absorption plate; 7. Flow guide plate; 8. Water collecting trough; 9. Water collecting well; 10. Iron grate; 11. First pumping station; 12. Second pumping station. Detailed implementation manners

[0028] To fully understand the purpose, features and effects of the present invention, the present invention will be described in detail through the following specific implementation manners, but the present invention is not limited thereto.

[0029] See Figures 1 to 4 , the present invention provides a system for seawater / brackish water freezing desalination and brine production using winter air cold energy, including a brine production pond 1, a desalination pond 2, a water intake and drainage system and an artificial freezing system. The water intake and drainage system includes water pumps, water intake ditches and brine drainage ditches. The artificial freezing system includes air pumps, double-sided heat absorption plate groups and single-sided heat absorption plate groups.

[0030] The cross-section of the brine production pond 1 is an inverted trapezoid, and the horizontal shape is a rectangle. The length-width ratio can be set arbitrarily according to specific circumstances. The depth of the brine production pond is designed according to the maximum thickness of the ice layer that can be mined in the brine production pond, the net evaporation amount and the depth of the brine that can be generated. In order to reduce the cost of earthwork excavation of the brine production pond 1, it is advisable that the brine production pond 1 be semi-submerged, or the salt pans of the salt field or other low-lying places can be directly constructed into brine production ponds by building dikes. A water intake 3 is built on one side of the brine production pond 1. The water intake 3 is also the brine drainage port. A filter screen is provided at the water intake 3 of the brine production pond 1 to filter out larger particles and organisms in the seawater / brackish water. A first pumping station 11 is built at the water intake 3. The first pumping station 11 includes a first water pump, a first air pump and a second air pump. The water intake ditch and the brine drainage ditch are both connected to the brine production pond 1 through the water intake 3. The other end of the water intake ditch is connected to the seawater / brackish water source, and the other end of the brine drainage ditch is connected to the salt drying pond or crystallization pond of the salt field. Gates are provided in both the water intake ditch and the brine drainage ditch.

[0031] A drainage outlet 4 is provided on one side of the desalination pond 2. A second pumping station 12 is built at the drainage outlet 4. The second pumping station 12 includes a second water pump and a third air pump.

[0032] The bottoms and peripheries of the brine drainage ditch, the brine production pond 1 and the desalination pond 2 are all laid with composite geomembranes for anti-seepage treatment.

[0033] A water collecting trough 8 is built on the middle line parallel to the long side at the bottom of the brine production pool 1 and the desalination pool 2, and a water collecting well 9 is built on one side of the water collecting trough 8. The water collecting well 9 in the brine production pool 1 is arranged on the side close to the water inlet 3, and the water collecting well 9 in the desalination pool 2 is arranged on the side close to the drain outlet 4; the width and depth of the water collecting trough 8 are 1m×0.5m; the inner diameter of the water collecting well 9 is 0.8m~1m, and the depth is 1m~1.5m; the upper part of the water collecting trough 8 and the water collecting well 9 is covered with an iron grate 10, and the mesh size of the iron grate 10 is 5cm×5cm~10cm×10cm.

[0034] The double-sided heat absorbing plate group is connected to the first air pump. The double-sided heat absorbing plate group is composed of a plurality of double-sided heat absorbing plates 5 connected in series. The double-sided heat absorbing plates 5 are vertically installed at the bottom of the brine making pool 1 through a base. The thickness of the double-sided heat absorbing plates 5 is 20-30 cm, and the height of the double-sided heat absorbing plates 5 is not less than 2 / 3 of the depth of the brine making pool. Figure 1 The distance between two adjacent double-sided heat absorbing plates 5 is 3~5m, and the longitudinal direction ( Figure 1 The distance between two adjacent double-sided heat absorbing plates (in the vertical direction) is 6-8m. Insulating baffles are installed at the outer corners of the double-sided heat absorbing plates 5 to separate the outer surfaces of the double-sided heat absorbing plates 5 into independent heat absorbing surfaces, so that when harvesting ice, the sea ice / saltwater ice attached to each heat absorbing surface can be separated in blocks independently.

[0035] The single-sided heat absorbing plate group is laid on the bottom and slope of the brine making pool 1, and the laying height of the single-sided heat absorbing plate on the slope is consistent with the height of the double-sided heat absorbing plate. The single-sided heat absorbing plate group is connected to the second air pump group, and the single-sided heat absorbing plate group is composed of a plurality of single-sided heat absorbing plates 6 connected in series. The thickness of the single-sided heat absorbing plate 6 is about 10 cm. The size and shape of the single-sided heat absorbing plate 6 can be designed according to the specific conditions of the bottom and slope of the brine making pool 1. An insulating baffle is provided between adjacent single-sided heat absorbing plates 6, so that when harvesting ice, the sea ice / saltwater ice attached to each single-sided heat absorbing plate 6 can be separated in blocks independently.

[0036] The heat-absorbing plate is made of stainless steel with high thermal conductivity and corrosion resistance. The heat-absorbing plate has a hollow structure and is welded by stainless steel plates. A flow guide plate 7 is arranged inside the heat-absorbing plate, and the material of the flow guide plate is the same as that of the heat-absorbing plate. The function of the flow guide plate is, on the one hand, to increase the length of the flow path and the flow time of the cold air in the heat-absorbing plate, so that the cold air can fully absorb heat from the seawater / brackish water in the brine-making pond through the heat-absorbing plate; on the other hand, it plays a supporting role, enabling the heat-absorbing plate to withstand the huge water pressure in the brine-making pond. The thickness of the steel plate of the heat-absorbing plate is determined according to the maximum water pressure borne by the bottom of the brine-making pond, so that the heat-absorbing plate can withstand the maximum water pressure at the bottom of the brine-making pond without deformation. For example, if the salt field in Tangshan Nanpu Saltworks is transformed into a brine-making pond with a depth of 10 m, with the support of the flow guide plate, the thickness of the steel plate of the heat-absorbing plate should be able to withstand the water pressure of 10 m deep seawater without deformation. The positions of the air inlet and outlet of the heat-absorbing plate can be selected according to the actual situation of the connection or splicing of the heat-absorbing plate. In this embodiment, for the convenience of installing the heat-absorbing plate, the air inlet and outlet of the double-sided heat-absorbing plate 5 are arranged on both sides of the bottom of the heat-absorbing plate; the air inlet and outlet of the single-sided heat-absorbing plate 6 can be arranged at any corner of the single-sided heat-absorbing plate according to the need for splicing of the single-sided heat-absorbing plate. As Figure 4 shown, for the single-sided heat-absorbing plate, one of the two air inlets at the lower left corner and one of the two air outlets at the upper right corner can be arbitrarily selected according to the specific splicing situation of the single-sided heat-absorbing plate.

[0037] The shape, anti-seepage treatment, etc. of the desalination pond 2 are the same as those of the brine-making pond 1. The long side of the desalination pond 2 is adjacent to the long side of the brine-making pond 1, with a passable cement road in between, which is used for ice collection and transportation. The desalination pond 2 is provided with a drain outlet 4, and a second pumping station 12 is arranged at the drain outlet 4. The second pumping station 12 includes a second water pump and a third air pump, and the desalinated water of the sea ice / brackish water ice generated in the desalination pond 2 is transported to the farmland irrigation system through the second water pump. The desalination pond 2 is longitudinally divided into several ice storage chambers, which are respectively used for stacking sea ice collected at different times. The catch basins of each ice storage chamber are connected by culverts, and each culvert is provided with a gate, so that the desalinated water of the sea ice / brackish water ice in the ice storage chamber that is desalinated first can be discharged into the farmland irrigation system first. An aeration pipe is laid at the bottom of the desalination pond 2, and the aeration pipe is connected to the third air pump. The material density of the aeration pipe is less than the density of seawater / brackish water, so that when there is accumulated water in the desalination pond 2, the aeration pipe can float on the water surface for aeration.

[0038] See Figure 5 , a method for seawater / brackish water freezing desalination and brine making using winter air cold energy provided by the present invention includes the following steps: S1. The brine-making pond 1 stores water. Seawater / brackish water is introduced into the brine-making pond 1 through natural drainage or pumping by the first pumping station 11.

[0039] S2, air cooling and freezing of the brine pool 1. The low-temperature cold air is respectively input into the double-sided heat absorbing plate group and the single-sided heat absorbing plate group through the first air pump and the second air pump, and the cold air in the heat absorbing plate absorbs heat from the seawater through the heat absorbing plate. The first air pump and the second air pump are provided with automatic opening and closing switches. When the temperature difference between the air temperature and the seawater temperature reaches a certain threshold, the first air pump and the second air pump are automatically turned on or off. For example, when the temperature difference between the air temperature and the seawater / salt water in the brine pool 1 is ≧5°C, the first air pump and the second air pump are automatically turned on, and when the temperature difference is less than 5°C, the first air pump and the second air pump are automatically turned off. Through the long-term heat absorption of the seawater / salt water in the brine pool 1 by the artificial freezing system, the temperature of the seawater / salt water in the brine pool 1 is basically consistent with the air temperature. When the air temperature drops to the freezing point of the seawater / salt water, the temperature of all the seawater / salt water in the brine pool 1 also reaches the freezing point. This greatly reduces the cold energy required for subsequent freezing of seawater / salt water, thereby greatly accelerating the freezing speed of seawater / salt water in the brine pool 1. The continued input of cold energy causes the surface seawater in the brine pool 1 to freeze through natural freezing, and the middle and lower layers of seawater freeze on the outer surface of the heat absorbing plate.

[0040] S3, ice harvesting in brine pool 1. When the surface sea ice / salt water ice in brine pool 1 reaches 10cm~20cm, ice harvesting begins, together with the sea ice / salt water ice attached to the heat absorbing plate. When harvesting sea ice / salt water ice attached to the heat absorbing plate, first input hot air into the heat absorbing plate (it can be air when the temperature is high that day, or other heat source gas) to melt the sea ice / salt water ice in direct contact with the surface of the heat absorbing plate, and the sea ice / salt water ice will be detached from the various surfaces of the heat absorbing plate in the form of blocks. Under the action of buoyancy, the sea ice / salt water ice will float to the surface of the water and then be harvested. According to the time sequence of ice harvesting, the collected block sea ice / salt water ice is stacked in the ice storage room of desalination pool 2 in sequence. The salt content of brine cells contained in sea ice / salt water ice collected at different times is different, and the duration of desalination is different, so they should be stacked separately. In order to prevent evaporation loss and facilitate temperature control and desalination, the surface of the ice pile is covered with an insulation layer.

[0041] S4. Evaporation for bittern production. After ice harvesting, the unfrozen concentrated seawater / brackish water in the bittern production pond 1 is further concentrated into bittern by evaporation, and then transported to the salt evaporation pond or crystallization pond in the salt field through the bittern drainage ditch for further treatment by the salt field. If there is no bittern drainage ditch built, tank trucks can be used to transport the bittern to the salt field. During evaporation for bittern production, to accelerate the evaporation rate, when the temperature difference between the air temperature and the concentrated seawater / brackish water in the bittern production pond 1 reaches a certain threshold value, for example, the temperature difference threshold can be set at 5°C, hot air is input into the single-sided heat absorption plate group through the second air pump to increase the temperature of the bittern, accelerate the evaporation rate, and shorten the time for bittern production. During evaporation for bittern production, if a certain or some ice storage chambers in the desalination pond 2 have been emptied, part of the concentrated seawater / brackish water in the bittern production pond can be introduced into these ice storage chambers for evaporation and bittern production, increasing the evaporation area of the concentrated seawater / brackish water, and thus accelerating the rate of concentrated seawater / brackish water becoming bittern. After the bittern production pond is drained, seawater is reintroduced for evaporation. After entering winter, the next round of freezing desalination and bittern production is carried out.

[0042] S5. Temperature-controlled solid desalination. The sea ice / brackish ice is stacked statically in the desalination pond, and the brine cells wrapped in the ice body will gradually communicate with each other to form brine channels, and the brine will flow out of the ice body under the action of gravity. To accelerate the desalination rate of the sea ice / brackish ice, when the air temperature fluctuates near the melting point of the sea ice / brackish ice, the aeration pipe at the bottom of the desalination pond 2 is used to aerate the ice pile, so that the sea ice / brackish ice crystals melt to a limited extent, promoting the formation or expansion of brine channels in the ice body, and accelerating the rate of brine seeping out of the ice body; the brine collected in the sump 9 of the desalination pond 2 is pumped to the bittern production pond 1 through the second pumping station 12 for refreezing or evaporation and bittern production again; when the salt content of the melt water of the sea ice / brackish ice meets the standard of farmland irrigation water (≤2‰), or when the air temperature rises to the point where the sea ice / brackish ice begins to melt on a large scale, desalination is stopped.

[0043] S6. Ice melting for irrigation. After desalination is stopped, the melt water of the sea ice / brackish ice in the desalination pond 2 is the desalinated water of sea ice / brackish ice that can be used for farmland irrigation, and is transported to the farmland irrigation system through the second pumping station 12. If the salinity of the desalinated water of sea ice / brackish ice is higher than the standard of farmland irrigation water, it can be mixed with other fresh water such as river water, underground fresh water or collected rain and snow water and then used for farmland irrigation. To ensure the demand for farmland irrigation water during spring plowing, all the sea ice / brackish ice stacked in the desalination pond 2 must have melted before spring plowing. When the air temperature reaches a certain threshold temperature, for example, when the air temperature ≥5°C, hot air is aerated into the ice pile through the aeration pipe at the bottom of the desalination pond 2 to quickly melt the sea ice / brackish ice to ensure the demand for farmland irrigation water during spring plowing.

[0044] Finally, it should be noted that: The above-listed are only the preferred embodiments of the present invention. Of course, those skilled in the art can make changes and modifications to the present invention. If these modifications and variations fall within the scope of the claims of the present invention and its equivalent technologies, they should all be considered as the protection scope of the present invention.

Claims

1. A system for freezing and desalinating seawater / salt water and making brine by using cold energy of winter air, comprising a brine making pool, a desalination pool, a drainage system and an artificial freezing system, characterized in that: A water inlet is arranged on one side of the brine making pool; a drainage outlet is arranged on one side of the desalination pool; the drainage system comprises a first pump station, a water inlet ditch, a brine drainage ditch and a second pump station, the first pump station is arranged at the water inlet, the water inlet ditch and the brine drainage ditch are both connected with the water inlet, the second pump station is arranged at the drainage outlet, and the drainage outlet is connected with the farmland irrigation system; the artificial freezing system comprises a first air pump, a second air pump, a double-sided heat absorbing plate group and a single-sided heat absorbing plate group, the first air pump is connected with the double-sided heat absorbing plate group, the double-sided heat absorbing plate group is composed of a plurality of double-sided heat absorbing plates connected in series, the double-sided heat absorbing plates are vertically installed in the brine making pool, the second air pump is connected with the single-sided heat absorbing plate group, the single-sided heat absorbing plate group is composed of a plurality of single-sided heat absorbing plates connected in series, the single-sided heat absorbing plates are laid on the bottom and slope of the brine making pool.

2. The system for freezing and desalinating seawater / salt water and producing brine by utilizing cold energy of winter air according to claim 1, characterized in that: The cross-section of the brine-making pool is an inverted trapezoid, and the horizontal shape is a rectangle.

3. The system for freezing and desalinating seawater / salt water and producing brine by utilizing cold energy of winter air according to claim 1, characterized in that: A filter is installed at the water inlet of the brine production pool, the water diversion ditch is connected to the seawater / salt water source, the brine discharge ditch is connected to the salt drying pool or crystallization pool of the salt field, and gates are installed in both the water diversion ditch and the brine discharge ditch.

4. The system for freezing and desalinating seawater / salt water and producing brine by utilizing cold energy of winter air according to claim 1, characterized in that: Composite geomembranes are laid on the bottom and around the brine drainage ditches, brine production pools and desalination pools for anti-seepage treatment.

5. The system for freezing and desalinating seawater / salt water and producing brine by utilizing cold energy of winter air according to claim 1, characterized in that: A water collection trough is built on the middle line parallel to the long side at the bottom of the brine making pool and the desalination pool, and a water collection well is built on one side of the water collection trough. The water collection well in the brine making pool is set on the side close to the water inlet, and the water collection well in the desalination pool is set on the side close to the drainage outlet; the width and depth of the water collection trough are 1m×0.5m; the inner diameter of the water collection well is 0.8m~1m, and the depth is 1m~1.5m; the top of the water collection trough and the water collection well is covered with iron grates, and the mesh size of the iron grate is 5cm×5cm~10cm×10cm.

6. The system for freezing and desalinating seawater / salt water and producing brine by utilizing cold energy of winter air according to claim 1, characterized in that: The heat absorbing plate is made of stainless steel with high thermal conductivity and corrosion resistance. The heat absorbing plate is a hollow structure, and a guide plate is arranged inside the heat absorbing plate.

7. The system for freezing and desalinating seawater / salt water and producing brine by utilizing cold energy of winter air according to claim 1, characterized in that: The thickness of the double-sided heat absorbing plate is 20~30cm, and the height of the double-sided heat absorbing plate is not less than 2 / 3 of the depth of the brine making pool. The double-sided heat absorbing plate is vertically installed on the bottom of the brine making pool through a base. There are gaps between adjacent double-sided heat absorbing plates, and insulating baffles are installed at the external corners of the double-sided heat absorbing plates; the thickness of the single-sided heat absorbing plate is 10cm, and insulating baffles are provided between adjacent single-sided heat absorbing plates.

8. The system for freezing and desalinating seawater / salt water and producing brine by utilizing cold energy of winter air according to claim 7, characterized in that: The air inlet and the air outlet of the double-sided heat absorbing plate are arranged on the same side of the heat absorbing plate; the air inlet and the air outlet of the single-sided heat absorbing plate are arranged on the diagonal sides of the heat absorbing plate.

9. The system for freezing and desalinating seawater / salt water and producing brine by utilizing cold energy of winter air according to claim 1, characterized in that: An aeration pipe is laid at the bottom of the desalination tank, and the aeration pipe is connected to a third air pump. The density of the aeration pipe material is less than the density of seawater / salt water.

10. A method for freezing and desalinating seawater / salt water and producing brine by utilizing cold energy of winter air, characterized in that: The following steps are involved: S1, water storage in the brine making pool, introducing seawater / salt water into the brine making pool through natural drainage or pumping from the first pumping station; S2, air cooling and freezing of the brine pool, the low-temperature cold air is respectively input into the double-sided heat absorbing plate group and the single-sided heat absorbing plate group through the first air pump and the second air pump, and the cold air in the heat absorbing plate absorbs heat from the seawater through the heat absorbing plate, the surface seawater / salt water in the brine pool is naturally frozen and frozen, and the middle and lower layers of the seawater are frozen on the surface of the heat absorbing plate; S3, ice harvesting in the brine pool: when the surface sea ice / saltwater ice in the brine pool reaches 10cm~20cm, ice harvesting begins; according to the order of ice harvesting, the collected block sea ice / saltwater ice is stacked in the desalination pool in sequence; S4, evaporation brine production. After ice harvesting is completed, the unfrozen concentrated seawater / salt water in the brine production pool is further concentrated into brine through evaporation, and then transported to the salt drying pool or crystallization pool of the salt factory through the brine drainage ditch for further processing; S5, temperature-controlled solid-state desalination, sea ice / salt water ice is stacked in a desalination tank, and the brine cells wrapped in the ice body will gradually connect with each other to form brine channels. The brine will flow out of the ice body under the action of gravity. The aeration pipe at the bottom of the desalination tank is used to aerate the ice pile, so that the sea ice / salt water ice crystals are melted to a limited extent, promoting the formation or expansion of brine channels in the ice body, and accelerating the speed of brine in the ice body seeping out of the ice body; the brine collected in the water collection well of the desalination tank is pumped to the brine production tank through the second pumping station to be frozen again or evaporated to produce brine; when the salt content of the melted water of the sea ice / salt water ice reaches the standard for farmland irrigation, or when the temperature rises and the ice blocks begin to melt in large quantities, the desalination is stopped; S6, ice melting irrigation. After desalination is stopped, the melted water of sea ice / brackish ice in the desalination tank is sea ice / brackish ice desalinated water that can be used for farmland irrigation. The sea ice / brackish ice desalinated water generated in the desalination tank is transported to the farmland irrigation system through the second pump station.

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