RU2013410C1 - Method of manufacturing microspheres of aqueous suspension of volatile ash of heat power stations - Google Patents

Abstract

FIELD: production of plastics. SUBSTANCE: method involves hydroseparation of aqueous suspension (rate of descending stream being 5-7 m/h), removing emersed microspheres and their dehydration. Solid phase content in aqueous suspension is 8-25 mass % . With the help of proposed method degree of removing microspheres is 83% , no flocculants being used. EFFECT: improves efficiency of the method. 2 cl, 3 dwg

Description

 The invention relates to the production of hollow microspheres from fly ash of thermal power plants used as fillers, for example, in the manufacture of plastics and in some products operating in aggressive environments.

 A known method of producing microspheres from fly ash, including obtaining an aqueous suspension with the addition of kerosene, mixing in successively installed mixers with the addition of a blowing agent in the last stage of mixing, double flotation with the maximum removal of unburned carbon, settling and thickening the remainder of the fly ash with a concentration of microspheres in discharge, eat and dehydrate them [1].

 The disadvantage of this method is the high cost and complexity of obtaining microspheres, since the technology of producing microspheres from fly ash includes a large number of mixing operations, flotation to remove unburned carbon using a foaming agent.

 There is also a method of producing microspheres from an aqueous suspension of fly ash of thermal power plants, including hydroseparation, removal of surfaced microspheres and their dehydration [2].

 An aqueous suspension of fly ash is sent to hydroseparation (precipitation), while in the presence of a flocculant, microspheres float, they are removed and sent for dehydration. The remaining ash residue is sent for processing to obtain a magnetic concentrate. The known method of producing microspheres in comparison with the analogue is simpler by eliminating flotation operations and reducing the number of mixing operations. However, the need to use a flocculant for hydroseparation increases the cost of producing microspheres.

 The aim of the invention is to reduce costs.

 The goal is achieved in that in the known method of producing microspheres from an aqueous suspension of fly ash of thermal power plants, including hydroseparation, removal of the emerging microspheres and their dehydration, the suspension is hydroseparated in a downward flow at a speed of 5-7 m / h, in addition, the solid content in the suspension makes up 8-25%.

No technical solutions having features similar to the distinguishing features of the proposed method were found. Studies have established that at a downward flow velocity of a suspension of 5-7 m / h, hydroseparation in it occurs most effectively: there is a maximum yield of microspheres without the use of a flocculant; microspheres, the ascent rate of which is greater than the speed of the downward flow, are concentrated in the upper layer of the suspension, their extraction is more than 80%. Impurities polluting microspheres include unburned coal particles, ash particles and microspheres with a density of more than 1000 kg / m ³ , the quality of materials in which microspheres are used depends on their content. It is known from practice that the permissible content of impurities polluting microspheres should not exceed 2%. The best results in hydroseparation in a downward flow of a suspension are achieved with a solids content of 8-25%, since the maximum release of impurities. The maximum concentration of solids in suspension (25%) was determined experimentally (Fig. 2). As can be seen from the graph, when the solid content in the suspension is above 25%, the content of impurities in the emerging microspheres increases.

= 1.25-1.75 т/ч·м² и
q_т=

= 0,4-0,56 т/ч·м ²
При заданных значениях показателей удельной производительности по жидкому и содержания твердого в суспензии удельная производительность аппарата по микросферам определяется по формуле:
q_м.сф=

т/ч·м²,
где α - содержание микросфер в летучей золе, % ;
ε - извлечение микросфер в готовую продукцию, % .Experimentally established and the dependence of the indicators of extraction of the microspheres, the specific productivity of the liquid apparatus for hydroseparation and its relative productivity in the allocation of microspheres from the speed of the downward flow of the suspension (Fig. 3). As can be seen from the graph, the optimal values of these indicators were obtained at a downward flow velocity of the suspension of 5-7 m / h - the extraction of microspheres is more than 80%, the relative productivity of the apparatus for hydroseparation for the isolation of microspheres is close to unity, its specific liquid productivity is q _w = 5-7 m ³ / h˙ m ² . The specific productivity of the apparatus in terms of solid can vary widely depending on the specified solid content in the suspension (C), while the maximum specific productivity is achieved at C = 25%, and the minimum allowable at C = 8%, which respectively make:
q _t =

= 1.25-1.75 t / h · m ² and
q _t =

= 0.4-0.56 t / h · m ²
For given values of the indicators of specific productivity in liquid and solid content in suspension, the specific productivity of the apparatus in microspheres is determined by the formula:
q _m.sf =

t / h · m ² ,
where α is the content of microspheres in fly ash,%;
ε is the extraction of microspheres in the finished product,%.

 The maximum specific productivity in microspheres is achieved at a downward flow rate of 5-7 m / h and a solids content of 25% in suspension, while the extraction of microspheres from ash is 83%.

 With a decrease in the downward flow velocity of the suspension of less than 5 m / h, the relative productivity in microspheres sharply decreases with a slight increase in the extraction rate. With an increase in the downward flow velocity of more than 7 m / h, there is a decrease in the extraction and relative performance of the hydroseparator in the microspheres, and consequently, costs increase.

 In FIG. 1 shows an installation that implements the proposed method; in FIG. 2, 3 are graphs explaining the proposed method.

 The method is implemented using an installation comprising a number of pyramidal containers 1 installed in series, a belt vacuum filter 2 and a dryer 3. The pyramidal containers 1 are installed at the same level, which allows the suspension to move freely in the horizontal direction without swirls. In the lower part, they have outlet openings 4 with valves 5 for the adjustable output of the spent suspension. The last pyramidal tank 1 has a threshold of 6 to limit the level of suspension in the tank system and is equipped with a scraper 7 for picking up the emerged microspheres.

The method includes the following operations:
- feeding an aqueous suspension of fly ash into pyramidal containers;
- hydroseparation of the suspension in a downward flow at a speed of 5-7 m / h and a solid content of 8-25% with extraction into the upper layer of microspheres and the withdrawal of the spent suspension through an adjustable outlet of the pyramidal containers;
- eat pop-up microspheres;
- dehydration of microspheres by filtration and drying;
- packaging of microspheres ready for use.

 Example of the method with average values of operating parameters.

An aqueous suspension of fly ash is fed to the hydroseparation in the amount of Q _W = 650 m ³ / h with a solid content of 15.0% and a microsphere content of solid 0.3%. Hydroseparation is carried out in three sequentially installed pyramidal containers with a cross section of 6x6 m ² each with a total area of S = 108 m ² .

=

= 6 м/ч
При этом производительность линии пирамидальных емкостей составляет: по твердому Q_т=

= 97,5 т/ч ; по микросферам Q_м.с.=

= 0,24 т/ч .These parameters provide the extraction of microspheres of 83% at an optimal downstream speed:
V _nis =

=

= 6 m / h
In this case, the productivity of the line of pyramidal containers is: for solid Q _t =

= 97.5 t / h; on microspheres Q _m.s. =

= 0.24 t / h.

 The process of hydroseparation is carried out in the following order.

An aqueous suspension of fly ash enters the first pyramidal tank 1 and from there the second and third tanks move in a horizontal stream. In each of the containers, the spent suspension in the amount of approximately 33% of the initial suspension per line is unloaded by gravity through the discharge opening 4 and is removed into the ash dump. Harmful impurities, regardless of their size, are completely discharged by the downward flow of the suspension into the waste, and microspheres, the ascent rate of which is greater than the speed of the downward flow, float and are transferred by a horizontal fluid flow to the last pyramidal tank, where they are removed using a scraper 7. The removed microspheres are sent to dewatering in vacuum filter 2, where dehydrated to a moisture content of not more than 40%. After vauum filter 2 receives the microspheres in the dryer 3, the drying is performed at a temperature up to 300 ° ^C. After drying, the microspheres are packaged for shipment to the consumer.

 This method in relation to the conditions of Reftinskaya TPP can be implemented as follows. Every year, Reftinskaya GRES receives about 6 million tons of fly ash during coal combustion, which, after four-stage deposition in electrostatic precipitators, is mixed with water and transported as a suspension into an ash dump.

= 2,6-3,6 кг/ч·м²
В результате предварительного опробования по определению количества и качества микросфер в летучей золе можно ориентировочно утверждать, что сырьевых ресурсов достаточно для организации производства микросфер из водной суспензии в объеме 5000 т/год. Для выполнения гидросепарации рекомендуется установить на площадке перед запроектированной насосной станцией второго подъема суспензии пирамидальные емкости, которые просты и надежны в эксплуатации и обеспечивают высокую производительность по микросферам. Суспензия по имеющимся трубопроводам будет направляться в пирамидальные емкости и через регулируемые выходные отверстия самотеком поступать в приемные емкости насосной станции, оттуда насосами откачиваться в золоотвальный водоем. Всплывшие микросферы из одной пирамидальной емкости в другую перемещаются горизонтальным потоком и в конце линии собираются механическим скребком. Затем микросферы подвергают фильтрации, сушке и упаковке.For the fly ash of Reftinskaya GRES, the average content of microspheres in which is 0.25%, the maximum specific productivity of the pyramidal capacity for microspheres is achieved when the solids content in the suspension is 25%, recovery is 83% and is:
q _m.s. =

= 2.6-3.6 kg / h · m ²
As a result of preliminary testing to determine the quantity and quality of microspheres in fly ash, it can be tentatively stated that raw materials are sufficient to organize the production of microspheres from an aqueous suspension in the amount of 5000 tons / year. To perform hydroseparation, it is recommended to install pyramidal tanks on the site in front of the designed pumping station for the second suspension lift, which are simple and reliable in operation and provide high microsphere performance. Suspension through existing pipelines will be routed to the pyramidal tanks and through regulated outlet openings will flow by gravity to the receiving tanks of the pumping station, from there it will be pumped to the ash dump pond. Surfaced microspheres from one pyramidal tank to another are moved in a horizontal stream and are collected by a mechanical scraper at the end of the line. Then the microspheres are subjected to filtration, drying and packaging.

 Thus, the use of this method allows to reduce costs by eliminating the use of a flocculant, which under the specific conditions of the Reftinskaya TPP reduces costs not only due to the flocculant, but also on the installation and operation of the installation for its supply to the process.

Claims (2)

 1. METHOD FOR PRODUCING MICROSPHERES FROM AQUEOUS SUSPENSION OF FLYING ASH OF HEAT POWER PLANTS, including hydroseparation of an aqueous suspension, removal of surfaced microspheres and their dehydration, characterized in that the hydroseparation of the suspension is carried out at a flow speed of 5-7 m / h.  2. The method according to p. 1, characterized in that the hydroseparation is carried out when the solids content in the suspension is 8 to 25 wt. %

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