RU2494787C1 - Method of waste fluids evaporation - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to physical-chemical treatment of aqueous solutions of mineral salts, particularly, to evaporation of fluid wastes. proposed method comprises evaporation of mineral salts by direct fire caused by combustion of fuel pulsating at resonance frequency, solid phase crystallisation and separation from evaporated solution with withdrawal of clean water from gas-vapor mix heating the solution fed for evaporation.

EFFECT: higher efficiency of evaporation.

3 cl, 1 dwg

Description

1. The technical field

The invention relates to industrial energy, and in particular to methods for evaporating liquid waste and can be used in various industries, in particular, to obtain mineral salts from their aqueous solutions.

2. The level of technology

Known methods for concentrating solutions of mineral salts by evaporators using superheated steam as a heating agent. Such installations are associated with the creation of steam power facilities and the corresponding pollution of the environment (waste water treatment, the emission of flue gases into the atmosphere containing up to 400 mg / m ³ nitrogen oxides, etc.). In evaporators, 1 ton of heating steam evaporates approximately 2.5 tons of water.

The more modern heat-using equipment is submersible combustion apparatus (APG), characterized by bubble processes that occur between the combustion products formed during the combustion of gaseous or liquid fuels in an immersion burner located so that its open nozzle is placed at a certain depth in the liquid. Due to this, the combustion products, sparging in liquids, are broken into gas bubbles, which form a large interfacial surface of heat and mass transfer upon surfacing.

Intensive evaporation of the solution is achieved due to the complete saturation of gas bubbles with water vapor due to the heat given off by the liquid in direct contact with fire, and intensive evaporation of the liquid occurs at a temperature of 15-16 ° C below the boiling point.

It is characteristic that, at equilibrium temperature, gas bubbles are completely saturated with water vapor and leave aqueous solutions in the form of a gas-vapor mixture with a temperature of 1-2 ° C above the evaporation temperature. Therefore, with direct contact of the combustion products with a liquid, the processes of heat and mass transfer proceed with a sharp decrease in heat loss. The efficiency of the calorific value of fuel is about 95%. In this case, combustion of fuel (gas, fuel oil, etc.) occurs in the burner tunnel and emissions of nitrogen oxides remain at the level of the chimney of the boiler house, in the amount of 300 mg / m ³ .

A known method of operation of an apparatus for evaporating liquid waste containing a container with liquid waste, a pulsating combustion chamber having a perforated resonant tube mounted coaxially to the vessel, and a separation device installed in the annular space between the walls of the vessel and the resonant pipe under the water part of the combustion chamber (USSR AS No. 937893. M.C. ³ : F23G 7/04, 06/23/82).

The disadvantage of this analogue is the increased drop entrainment, due to which the efficiency of the evaporation process is reduced.

Known accepted for the prototype of the claimed proposal is the method of evaporation of liquid waste, implemented by the plant as. USSR No. 1709154. M.cl. ³ : F23G 7/04, 1980, including evaporation by direct exposure to a flame obtained by pulsating combustion, crystallization and separation of the solid phase from the evaporated solution with the release of pure water from the vapor-gas mixture.

The disadvantage of the prototype is the limited operational efficiency due to the high fuel consumption (0.15 ÷ 0.2 kg of equivalent fuel / kg of one stripped off solution) and limited reliability of operation.

3. Presentation of the invention

The objective of the invention is to increase the efficiency of the process of evaporation of liquid waste.

The task is ensured by the fact that the method of evaporation of liquid waste includes evaporation of an aqueous solution of mineral salts by direct exposure to a flame obtained as a result of fuel pulsating with a resonant frequency of combustion, crystallization and separation of the solid phase from the evaporated solution with the release of pure water from the vapor-gas mixture heating the solution to the park.

A pulsating flame frequency of 60-80 Hz is used.

The process is carried out in continuous or batch mode.

4. Brief description of the drawing

The attached figure shows a flow chart of the production of mineral salts from their aqueous solutions using pulsating combustion of fuel, where it is indicated: 1 - consumable capacity; 2 - a pulsating combustion chamber; 3 - resonance tube, lowered in evaporable liquid onto _^1/2 -1.0 diameter; 4 - a bubble chamber, which is a container with a conical bottom, along the longitudinal axis of which there is a resonance tube 3 with a pulsating combustion chamber 2 located in the upper part of the resonance tube 3 outside the bubble chamber 4; 5 - circulation capacity; 6 - centrifugal pump; 7 - node cleaning from kapleunos; 8 - heat exchanger; 9 - mixer.

The installation works as follows.

The initial solution of mineral salts, as sea or other water, in the form, for example, of a waste from a chemical enterprise, is fed to a heat exchanger 8, in which it is heated with a vapor-gas mixture supplied through the purification unit from droplet-dropping vessel 7 from the bubble chamber 4. The heated initial solution is fed into supply tank 1, from where it enters the bubble chamber 4, into the lower part of which through the resonant pipe 3 the fuel combustion products from the pulsating combustion chamber 2 are supplied. The liquid fraction of the bubbler enters the circulation tank 5, de is stirred by the stirrer 9 for the uniformity of density and temperature of the layers, where the product is pumped to filter 6 and simultaneously - in the storage container 1 for more advanced processing.

Use the resonant frequency of a pulsating flame of 60-80 Hz.

Depending on the conditions of receipt of raw materials and other technological reasons, the process is conducted in continuous or batch mode.

5. Examples of the invention

Example 5.1.

98 l / h of distillation liquid (liquid waste from the production of soda) with a content of NaCl and CaCl _{2 of} 10% (the rest water) at a specific gravity of 1.159 g / cm ^{3 was} supplied to the pilot plant. Specific fuel consumption of 0.09 kg of fuel equivalent / kg of distillation liquid. The air flow coefficient of 1.05, the content of CO in the flue gases of 0.02% vol., Nitrogen oxides 82 mg / m ³ . The process is completed with a content of 39% CaCl ₂ in the mother liquor (specific gravity 1.396 g / cm ³ ) and complete precipitation of NaCl.

The resulting table salt (after a single wash) corresponds to the table salt in chemical and fractional composition.

Calcium chloride can be used immediately as an anti-icing agent or, when redistributed, to obtain a crystalline product.

Obtaining calcium chloride by the described method turned out to be 50% or more more profitable than the known chemical process, and the production of table salt is 2 times more economical than the processes of its production in case evaporators.

Example 5.2.

96 l / h of the mother liquor from the condensed portion of the extraction phosphoric acid neutralized with ammonia was supplied to the experimental setup at a specific gravity of the mother liquor of 1.22 g / cm ³ . The air flow rate of 1.1, the content of CO in the flue gases of 0.015% vol., Nitrogen oxides 85 mg / m ³ . Specific fuel consumption of 0.09 kg of fuel equivalent / kg of waste. The process is completed at a specific gravity of 1.48 g / cm. Deposition of large crystals of ammonium monophosphate is observed. When examined under a microscope, the crystals were 1.4-1.5 times larger than the crystals obtained during the chemical process of producing ammonium monophosphate.

Example 5.3

98 l / h of copper sulfate solution with a specific gravity of 1.22 g / cm ^{3 was} supplied to the pilot plant. The air flow coefficient of 1.05, the content of CO in the flue gases of 0.02% vol., Nitrogen oxides 82 mg / m ³ . Specific fuel consumption of 0.09 kg equivalent / kg. The process is completed upon reaching a specific gravity of 1.41 g / cm ³ . Deposition of large crystals of copper sulfate is observed. The sedimentation rate of sediment more than 15 m / h. It is easily separated from the mother liquor, without suspension.

The formation of large crystals during the concentration process on a submersible pulsating installation indicates the ability of this process to sharply reduce the Z-potential of the molecules of the target product, which contributes to the adsorption of molecules and the appearance of large crystal formations.

Example 5.4.

96 l / h of a purified solution of sodium chloride extracted from an underground well in the area of the city of Novomoskovsk (Tula region) was supplied to the pilot plant. The content of NaCl is 308 g / l. The coefficient of air consumption is 1.05-1.07, the CO content in flue gases is 0.015% vol., Nitrogen oxides 80 mg / m. Specific fuel consumption of 0.09 kg of equivalent fuel / kg of evaporated medium. When the specific gravity of more than 1.4 g / cm ^{3 is} reached, the active precipitation of NaCl begins. The resulting table salt reaches nutritional conditions. An analysis of the mother liquor and the table salt obtained after evaporation did not reveal the presence of carbon, which indicates the completeness of fuel combustion in pulsating mode.

6. Technical Results

The proposed method of evaporation of liquid waste is 1.5 or more times more efficient in terms of technical and economic indicators of traditional methods of evaporation by known evaporators with higher product quality and process reliability. This result provides the claimed combination of features, one of the important elements of which is the use in the claimed proposal of a gas-vapor mixture heated by a combustion chamber supplied from a bubbler chamber to a heat exchanger, from which a heated initial solution goes to all technological stages of the process. In this case, the formation of condensate (pure water) proceeds with the release of heat equal to the amount of heat expended in the evaporation of the initial solution, which, in turn, increases the efficiency of subsequent processes in which, in particular, pure water is obtained, which is expedient to use to obtain solutions necessary concentrations directly during evaporation.

Claims (3)

1. The method of evaporation of liquid waste, including evaporation of aqueous solutions of mineral salts by direct exposure to a flame, resulting from a pulsating fuel with a resonant frequency of combustion, crystallization and separation of the solid phase from the evaporated solution with the release of pure water from the vapor-gas mixture that heats the solution supplied to the evaporator. 2. The method according to claim 1, characterized in that use the resonant frequency of the pulsating flame of 60-80 Hz. 3. The method according to claim 1 or 2, characterized in that the process is carried out in continuous or batch mode.

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