CN218755033U

CN218755033U - Collection and transfer device of simple substance phosphorus among phosphorus sludge recovery process

Info

Publication number: CN218755033U
Application number: CN202223449933.8U
Authority: CN
Inventors: 张汉雄; 暴学云; 杨增荣
Original assignee: Yunnan Chengjiang Zhicheng Phosphorus Chemical Co ltd
Current assignee: Yunnan Chengjiang Zhicheng Phosphorus Chemical Co ltd
Priority date: 2022-12-23
Filing date: 2022-12-23
Publication date: 2023-03-28
Anticipated expiration: 2032-12-23

Abstract

The utility model discloses a device for collecting and transferring simple substance phosphorus in the process of recovering mud phosphorus, which relates to the technical field of mud phosphorus recovery and comprises a simple substance phosphorus collecting mechanism and a simple substance phosphorus transferring mechanism; the elemental phosphorus collecting mechanism comprises a phosphorus steam condensing and collecting mechanism and a phosphorus steam conveying mechanism, and the elemental phosphorus transferring mechanism is communicated with the phosphorus steam condensing and collecting mechanism and a subsequent refining mechanism. In the simple substance phosphorus collecting mechanism, a composite phosphorus steam pipeline is provided with a plurality of branch pipes which are connected in parallel, the branch pipes are provided with a scouring cleaning structure, and a washing tower and a phosphorus receiving groove are provided with double-layer structures, so that the blockage caused by phosphorus steam adhesion is avoided; secondly, arranging drain pipes and phosphorus discharge pipes with different overflow heights, and effectively controlling the water level of cooling water in a phosphorus receiving tank and the liquid level of the collected elemental phosphorus; in addition, a flushing pipe and a one-way valve for preventing backflow are respectively arranged on the phosphorus discharging pipe, so that the phosphorus discharging pipe is effectively prevented from being adhered to the pipe wall due to cold in the phosphorus discharging process.

Description

Collection and transfer device of simple substance phosphorus among phosphorus sludge recovery process

Technical Field

The utility model relates to a technical field is retrieved to the phosphorus mud, concretely relates to collection and transfer device of simple substance phosphorus among phosphorus mud recovery process.

Background

Yellow phosphorus is a simple substance of phosphorus and is white or light yellow translucent solid in appearance. Soft, brittle and deep in color when cold. The exposure to air produces green phosphorescence and white smoke in the dark. The fire was about 40 ℃ in humid air and slightly higher in dry air.

Yellow phosphorus is produced in various and large quantities of toxic and harmful substances in the production process, such as phosphorus sludge, yellow phosphorus tail gas and the like, and the substances are useful byproducts from the viewpoint of recycling economy. The recovery of the phosphorus sludge can realize energy conservation and emission reduction, save resources and reduce the pollution of the phosphorus sludge to the environment, so the recovery of the phosphorus sludge has great significance.

In the production of yellow phosphorus by an electric heating method, phosphorus furnace gas contains CO, phosphorus, siF4, H2S, fine phosphorus ore powder, coke powder and other impurities, the impurities and the phosphorus furnace gas enter a cold phosphorus system together, and are washed by water and condensed in a phosphorus receiving groove to form a large amount of emulsion-shaped mixture, namely phosphorus sludge. One part of the formed sludge phosphorus is put into a refining tank along with the crude phosphorus for refining, and the other part of the formed sludge phosphorus enters a sewage treatment and purification system along with the overflow water of the phosphorus receiving tank. The phosphorus content of the sludge phosphorus is very high, the phosphorus content of the sludge phosphorus generated in the refining tank can reach 90 percent at most, the phosphorus content of the sludge phosphorus entering the sewage system is lower, generally 35 to 60 percent, and the phosphorus content of the sand-grain sludge phosphorus entering ditches and the like is 3 to 35 percent. Therefore, the treatment of the sludge phosphorus is an important component of the production of the yellow phosphorus, which not only affects the yield and the production cost of the yellow phosphorus, but also pollutes the surrounding environment. The phosphorus content of the sludge phosphorus can be divided into three types: the phosphorus content in the phosphorus sludge is more than 70 percent, which is called rich phosphorus, and most of the phosphorus sludge is blocky, for example, the phosphorus sludge discharged from a refining tank is condensed to be grey black solid, the phosphorus sludge is less than 20 percent, which is called poor phosphorus sludge, which is generally sandy and light, for example, the phosphorus sludge is precipitated in an advection ground and a trench in a sewage treatment system, and the solid blocky is not easy to form after cooling: phosphorus contents of between 20% and 70% are generally referred to as phosphorus sludge.

The recycle of phosphorus sludge, not only will eliminate the pollution of phosphorus sludge to the environment, will turn waste into wealth again, for the enterprise creates wealth, and is the most important, must guarantee the security in the equipment operation, current phosphorus sludge recovery technology, basically all follows the thinking that the heating is evaporated futilely, the condensation is retrieved, disposes two or even a plurality of converters and collects after the phosphorus sludge heating, exists the problem in two aspects:

1. the tail gas emission problem, phosphorus steam rely on the hot water rinsing condensation recovery in the collection phosphorus crucible alone, and the gas and liquid mixing degree is low, and this has just led to hot water to the rinsing condensation of phosphorus steam incomplete, and the gas of final emission is great to the environmental impact.

2. The equipment safety problem, when phosphorus-containing gas generated after heating sludge phosphorus enters a condensation recovery system, if the temperature is improperly controlled, the pipeline is easily blocked by solid yellow phosphorus, the sludge phosphorus recovery efficiency is influenced by light people, and serious accidents such as pipeline explosion occur when the sludge phosphorus is serious.

Disclosure of Invention

In order to solve the problem, the utility model provides a collection and transfer device of simple substance phosphorus among difficult jam pipeline, the recovery rate is high, the little mud phosphorus recovery process of potential safety hazard.

In order to achieve the above purpose, the utility model adopts the following technical scheme: a device for collecting and transferring simple substance phosphorus in the mud phosphorus recovery process is connected with a mud phosphorus heating device consisting of a mud phosphorus rotary pot and supporting facilities, and comprises a simple substance phosphorus collecting mechanism and a simple substance phosphorus transferring mechanism;

the simple substance phosphorus collecting mechanism comprises a phosphorus steam condensing and collecting mechanism consisting of a phosphorus receiving groove and a washing tower, and a phosphorus steam conveying mechanism, wherein the phosphorus steam conveying mechanism is used for communicating the sludge phosphorus heating device with the phosphorus steam condensing and collecting mechanism; and the elemental phosphorus transfer mechanism is communicated with the phosphorus steam condensation and collection mechanism and the subsequent refining mechanism.

Wherein, the phosphorus steam conveying mechanism comprises a composite phosphorus steam pipeline and a pipeline washing mechanism; the gas inlet end of the composite phosphorus steam pipeline is connected with a phosphorus steam outlet of the mud phosphorus rotary pot, and the gas outlet end of the composite phosphorus steam pipeline extends into the phosphorus receiving groove and is submerged below the level of condensed water in the groove; the composite phosphorus steam pipeline guides yellow phosphorus steam generated in the phosphorus mud rotary pot into the phosphorus receiving groove, the composite phosphorus steam pipeline is divided into a main gas inlet end pipe and two parallel branch pipes, the main gas inlet end pipe is connected with a gas outlet pipe of the phosphorus mud rotary pot, each branch pipe is provided with an independent opening and cutting mechanism, valves are respectively arranged at the starting end and the tail end of each branch pipe, meanwhile, a pipeline washing mechanism is arranged between the front valve and the rear valve, the concrete structure is that gas nozzles are respectively communicated with pipe bodies on the inner sides of the valves of the branch pipes, the gas nozzles are connected with a high-temperature high-pressure gas source, and stop valves are respectively arranged on the front gas nozzle and the rear gas nozzle; in addition, the main body part of the phosphorus receiving groove is of a hollow double-layer structure, and the hollow part is filled with flowing constant-temperature hot water so as to maintain the temperature stability of the inner layer of the composite phosphorus receiving groove and prevent simple substance phosphorus condensed in the phosphorus receiving groove from being condensed into a solid state and accumulated in the phosphorus receiving groove after the temperature is reduced.

The washing tower is arranged on the top surface of the phosphorus receiving groove and is communicated with the inside of the phosphorus receiving groove, and the condensed water sprayed in the washing tower condenses the phosphorus steam led in by the composite phosphorus steam pipeline into elemental phosphorus which is sunk into the phosphorus receiving groove; the washing tower is divided into three vertical hollow cylinders, one side close to the phosphorus mud converter is taken as a starting point, and a first-stage washing tower, a second-stage washing tower and a third-stage washing tower are sequentially arranged, wherein the top of the first-stage washing tower is communicated with the top of the second-stage washing tower, the bottom of the first-stage washing tower is arranged above the level of condensed water in the phosphorus receiving tank, the bottom of the second-stage condensing tower is kept below the level of the condensed water, and the bottoms of the first-stage washing tower and the second-stage washing tower are mutually blocked to prevent gas from flowing; the bottom of the third-stage washing tower is arranged above the water level of the condensed water in the phosphorus receiving tank; the washing tower also adopts a hollow double-layer structure, and the hollow part is filled with flowing constant-temperature hot water so as to maintain the temperature of the inner layer of the washing tower to be stable.

The simple substance phosphorus treatment transfer mechanism is arranged on the main body part of the phosphorus receiving groove and comprises a drain pipe and a phosphorus discharge pipe; the water outlet of the water drainage pipe is higher than the outlet of the composite phosphorus steam pipeline and the lower port of the secondary washing tower, so that the water outlet of the water drainage pipe and the outlet of the composite phosphorus steam pipeline are always submerged below the water level of cooling water; the phosphorus discharge pipe is obliquely arranged at the lower part of the phosphorus receiving groove and is also communicated with the inside of the phosphorus receiving groove, a phosphorus outlet of the phosphorus discharge pipe is preset with a proper height, liquid elemental phosphorus deposited at the bottom of the phosphorus receiving groove overflows into the phosphorus discharge pipe when the height of the liquid elemental phosphorus exceeds the height of the phosphorus outlet, the phosphorus discharge pipe is provided with a one-way valve at the position extending out of the phosphorus receiving groove, a pipe body outside the one-way valve by a specific distance is connected with a flushing pipe with a downward outlet, hot water is filled in the flushing pipe, and the liquid elemental phosphorus overflowing into the pipe is transferred into a temporary storage groove and is sent to a refining system; during the process of flushing hot water, the one-way valve arranged in the phosphorus discharge pipe can prevent the situation that the hot water flows back to the phosphorus receiving groove due to the excessive water pressure. The time point of flushing water of the flushing pipe can be determined according to the time of outflow of simple substance phosphorus in the phosphorus discharge pipe, the control of the part belongs to the prior art, and the control can be realized by arranging a corresponding valve and a detector, which does not belong to the content claimed by the application and is not repeated

The method comprises the following steps that (1) because yellow phosphorus recovered from sludge phosphorus inevitably contains some organic impurities, the impurities have certain differences in components with the yellow phosphorus normally prepared by an electric furnace and are not completely suitable for a yellow phosphorus refining system matched with the electric furnace, in order to reduce the treatment pressure of the yellow phosphorus refining system in a normal process, a flushing and impurity removing mechanism for the organic impurities in elemental phosphorus is arranged in a temporary storage tank, and specifically comprises a flushing mechanism and an active carbon impurity removing mechanism, wherein the flushing mechanism is arranged at the bottom of the temporary storage tank, and is simultaneously provided with a hot water pipe connected with a hot water source and a flushing pipe arranged at the bottom of the temporary storage tank, and the flushing mechanism and the flushing pipe are communicated; the flushing pipe is horizontally arranged, water outlet holes with downward openings are uniformly formed in the pipe wall of the flushing pipe, and the yellow phosphorus deposited at the bottom of the temporary storage tank is flushed; the opposite side at the temporary storage tank bottom is provided with the gentle slope structure, it has the entry of active carbon edulcoration mechanism to open on the gentle slope, the back of gentle slope sets up the active carbon adsorption bed of a plurality of layers of vertical drawable settings, the discharge gate is seted up to the temporary storage tank bottom at active carbon adsorption bed rear, yellow phosphorus after the active carbon adsorption bed treatment is led away from the discharge gate, get into yellow phosphorus refining system, the upside in temporary storage tank is provided with the overflow pipe of cooling water, the water that will wash is discharged, the active carbon adsorption bed regularly takes out the washing.

Has the advantages that:

firstly, in the simple substance phosphorus collection mechanism, a compound phosphorus steam pipeline is provided with a plurality of branch pipes which are connected in parallel, any branch pipe can work independently, and structural conditions are created for other single pipes to be closed, purified and cleaned; in addition, according to the characteristics of the phosphorus steam, the branch pipe is provided with a structure for washing and cleaning by high-temperature and high-pressure gas, the washing tower and the phosphorus receiving tank are both arranged to be hollow double-layer structures, and the hollow part is filled with flowing constant-temperature hot water, so that the inner wall is kept at a stable high temperature, and the blockage caused by the adhesion of the phosphorus steam is avoided; secondly, a drain pipe and a phosphorus discharge pipe with different overflow heights are respectively arranged in the elemental phosphorus transfer mechanism, so that the water level of cooling water in a phosphorus receiving tank and the liquid level of the collected elemental phosphorus are effectively controlled, and no extra power equipment is needed for extraction; in addition, a flushing pipe and a backflow-proof check valve are respectively arranged on the phosphorus discharging pipe, hot water is introduced into the flushing pipe, and the phosphorus discharging pipe can be effectively prevented from being cooled and adhering to the pipe wall in the phosphorus discharging process; in addition, a flushing device and an adsorption device for organic impurities are arranged in the temporary storage tank for the elemental phosphorus, so that pretreatment can be carried out in advance, and the condition that the working pressure of a refining system is increased because the elemental phosphorus recovered from the phosphorus sludge contains organic impurities inconsistent with yellow phosphorus obtained by a normal process is avoided.

Drawings

Fig. 1 is a schematic view of the top view structure of the present invention.

FIG. 2 is a schematic structural diagram of the phosphorus receiving tank and the washing tower.

FIG. 3 is a schematic structural diagram of a flushing mechanism and an activated carbon impurity removal mechanism in the temporary storage tank.

In the figure: the device comprises a mud phosphorus rotary pot 1, a phosphorus receiving groove 2, a main pipe 3, branch pipes 4, an air tap 5, a stop valve 6, a first-stage washing tower 7, a second-stage washing tower 8, a third-stage washing tower 9, a drain pipe 10, a phosphorus discharge pipe 11, a one-way valve 12, a flushing pipe 13, a temporary storage groove 14, a hot water pipe 15, a flushing pipe 16, a water outlet hole 17, an inlet 18, an activated carbon adsorption bed 19, a discharge hole 20 and an overflow pipe 21.

Detailed Description

The present invention will be further explained with reference to the drawings and examples.

Referring to fig. 1, the basic structure of the device for collecting and transferring elemental phosphorus during the phosphorous sludge recovery process in this embodiment includes a phosphorous sludge heating device, and includes an elemental phosphorus collecting mechanism and an elemental phosphorus transferring mechanism.

Firstly, the elemental phosphorus collecting mechanism comprises a phosphorus steam condensing and collecting mechanism and a phosphorus steam conveying mechanism, and the phosphorus steam conveying mechanism is used for communicating the sludge phosphorus heating device with the phosphorus steam condensing and collecting mechanism; and the elemental phosphorus transfer mechanism is communicated with the phosphorus steam condensation and collection mechanism and the subsequent refining mechanism.

The key improvement is that the composite phosphorus steam pipeline is divided into a main gas inlet end pipe 3 and two parallel branch pipes 4, the main gas inlet end pipe 3 is connected with a gas outlet pipe of the phosphorus mud rotary pot 1, each branch pipe 4 is provided with an independent opening and cutting mechanism, valves are respectively arranged at the starting end and the tail end of each branch pipe 4, meanwhile, a pipeline washing mechanism is arranged between the front valve and the rear valve, the concrete structure is that gas nozzles 5 are respectively communicated with the inner side pipe bodies of the valves of the branch pipes 4, the gas nozzles 5 are connected with a high-temperature high-pressure gas source, and stop valves 6 are respectively arranged on the front gas nozzle 5 and the rear gas nozzle 5; when the device works, one branch pipe 4 is closed, the other branch pipe 4 is communicated to convey phosphorus steam, the branch pipes on the pipe walls at two ends open the stop valves on the air nozzles 5, high-temperature and high-pressure gas, which can be steam or inert gas, is introduced to wash and remove impurities from the inner walls of the branch pipes 4, impurity particles brought by the phosphorus steam or phosphorus simple substances attached to the pipe walls are blown away, blockage caused by accumulation in the day and the month is prevented, and the blown gas containing the impurities can be led into a yellow phosphorus electric furnace tail gas treatment system or a slag steam treatment system to be treated.

In order to maintain the temperature of the phosphorus steam in the walking process and prevent the phosphorus steam from being cooled and attached to the pipe wall, the phosphorus receiving tank 2 and the washing tower are both arranged into a double-layer structure, flowing constant-temperature hot water is filled in an interlayer, and the phosphorus receiving tank 2 can also maintain the higher temperature in the tank body by adopting the structure, so that the phosphorus steam is prevented from being directly converted into a solid state from a gaseous state after being cooled by condensed water and being accumulated below the outlet of the composite phosphorus steam pipeline to cause blockage; in addition, referring to fig. 2, the washing tower is divided into three vertical hollow cylinders, and a first-stage washing tower 7, a second-stage washing tower 8 and a third-stage washing tower 9 are sequentially arranged from one side close to the phosphorus pan 1, wherein the top of the first-stage washing tower 7 is communicated with the top of the second-stage washing tower 8, the bottom of the first-stage washing tower 7 is arranged above the level of condensed water in the phosphorus receiving tank 2, the bottom of the second-stage condensing tower is kept below the level of the condensed water, and the bottoms of the two are blocked from each other, so that gas is prevented from flowing; the bottom of the third-stage washing tower 9 is arranged above the level of the condensed water in the phosphorus-receiving tank 2.

Referring again to fig. 1, the elemental phosphorus treatment transfer mechanism is installed in the main body part of the phosphorus receiving tank 2 and comprises a drain pipe 10 and a phosphorus discharge pipe 11; wherein the drain pipe 10 is connected with the upper part of the phosphorus receiving tank 2 and communicated with the inside of the phosphorus receiving tank, the cooling discharge collected in the phosphorus receiving tank 2 after cooling phosphorus steam is subjected to water purification treatment, and the water outlet of the drain pipe 10 is higher than the outlet of the composite phosphorus steam pipeline and the lower port of the secondary washing tower 8, so that the two are always submerged below the water level of cooling water; the phosphorus discharge pipe 11 is obliquely arranged at the lower part of the phosphorus receiving groove 2 and is also communicated with the inside of the phosphorus receiving groove, a phosphorus outlet of the phosphorus discharge pipe is preset with a proper height, liquid elemental phosphorus deposited at the bottom of the phosphorus receiving groove 2 exceeds the height of the phosphorus outlet and then overflows into the phosphorus discharge pipe 11, the phosphorus discharge pipe 11 is provided with a one-way valve 12 at the position extending out of the phosphorus receiving groove 2, a pipe body outside the one-way valve 12 at a specific distance is connected with a flushing pipe 13 with a downward outlet, hot water is introduced into the flushing pipe 13, the liquid elemental phosphorus overflowing into the pipe is transferred into a temporary storage groove 14 and is sent to a refining system; the check valve 12 disposed in the phosphorus discharge pipe 11 prevents the hot water from flowing back to the phosphorus receiving tank 2 due to excessive water pressure during the hot water flushing process.

Referring to fig. 3, in order to remove organic impurities in yellow phosphorus recovered from phosphorus sludge, a flushing and impurity removing mechanism for organic impurities in elemental phosphorus is arranged in the temporary storage tank 14, and specifically comprises a flushing mechanism and an activated carbon impurity removing mechanism, wherein the flushing mechanism is arranged at the bottom of the temporary storage tank 14, and is simultaneously provided with a hot water pipe 15 connected with a hot water source and a flushing pipe 16 arranged at the bottom of the temporary storage tank 14, and the flushing pipe and the hot water pipe are communicated; the flushing pipe 16 is horizontally arranged, and the pipe wall of the flushing pipe is uniformly provided with water outlet holes 17 with downward openings, so that the yellow phosphorus deposited at the bottom of the temporary storage tank 14 is flushed; the other side of the bottom of the temporary storage tank 14 is provided with a gentle slope structure, an inlet 18 of an active carbon impurity removal mechanism is arranged on the gentle slope, the back of the gentle slope is provided with a plurality of layers of vertical active carbon adsorption beds 19 which can be drawn and arranged, a discharge port 20 is arranged at the bottom of the temporary storage tank 14 behind the active carbon adsorption beds 19, yellow phosphorus treated by the active carbon adsorption beds 19 is guided away from the discharge port 20 and enters a yellow phosphorus refining system, an overflow pipe 21 of cooling water is arranged at the upper side of the temporary storage tank 14, the washed water is discharged, and the active carbon adsorption beds 19 are taken out and cleaned periodically.

Claims

1. A device for collecting and transferring simple substance phosphorus in the mud phosphorus recovery process is combined with a mud phosphorus heating device consisting of a mud phosphorus transfer pot and supporting facilities, and is characterized by comprising a simple substance phosphorus collecting mechanism and a simple substance phosphorus transferring mechanism; the simple substance phosphorus collecting mechanism comprises a phosphorus steam condensing and collecting mechanism consisting of a phosphorus receiving tank and a washing tower, and a phosphorus steam conveying mechanism; the phosphorus steam conveying mechanism comprises a composite phosphorus steam pipeline and a pipeline washing mechanism; the gas inlet end of the composite phosphorus steam pipeline is connected with a phosphorus steam outlet of the phosphorus slurry converter, and the gas outlet end of the composite phosphorus steam pipeline extends into the phosphorus receiving groove and is submerged below the level of condensed water in the groove; the composite phosphorus steam pipeline is divided into an air inlet end main pipe and two parallel branch pipes, the air inlet end main pipe is connected with an air outlet pipe of the phosphorus rotary pot, each branch pipe is provided with an independent opening and cutting mechanism, valves are respectively arranged at the starting end and the tail end of each branch pipe, meanwhile, a pipeline washing mechanism is arranged between the front valve and the rear valve, namely, air nozzles are respectively communicated with the inner pipe bodies of the valves of the branch pipes, are connected with a high-temperature high-pressure air source, and are respectively provided with stop valves on the front air nozzle and the rear air nozzle; the phosphorus vapor conveying mechanism is used for communicating the phosphorus sludge heating device with the phosphorus vapor condensing and collecting mechanism; and the elemental phosphorus transfer mechanism is communicated with the phosphorus steam condensation and collection mechanism and the subsequent refining mechanism.

2. The apparatus for collecting and transferring elemental phosphorus in a phosphorus sludge recovery process as claimed in claim 1, wherein the main body of the phosphorus receiving tank is a hollow double-layer structure.

3. The device for collecting and transferring the elemental phosphorus in the phosphorus sludge recovery process according to any one of claims 1 or 2, wherein the washing tower is arranged on the top surface of the phosphorus receiving tank and is communicated with the inside of the phosphorus receiving tank, the washing tower is divided into three vertical hollow cylinders, and a primary washing tower, a secondary washing tower and a tertiary washing tower are sequentially arranged from one side close to the phosphorus sludge rotating pot, wherein the top of the primary washing tower is communicated with the top of the secondary washing tower, the bottom of the primary washing tower is arranged above the level of condensed water in the phosphorus receiving tank, the bottom of the secondary condensing tower is kept below the level of the condensed water, and the bottoms of the primary washing tower and the secondary condensing tower are mutually blocked; the bottom of the third-stage washing tower is arranged above the water level of the condensed water in the phosphorus receiving tank; the washing tower also adopts a hollow double-layer structure.

4. The device for collecting and transferring the elemental phosphorus in the sludge phosphorus recovery process as claimed in claim 1, wherein the elemental phosphorus treatment and transfer mechanism is arranged on the main body part of the phosphorus receiving tank and comprises a drain pipe and a phosphorus discharge pipe; the water outlet of the water drain pipe is higher than the outlet of the composite phosphorus steam pipeline and the lower port of the secondary washing tower; the phosphorus discharge pipe is obliquely arranged at the lower part of the phosphorus receiving groove and is also communicated with the inside of the phosphorus receiving groove, a phosphorus outlet of the phosphorus discharge pipe is preset with a proper height, liquid simple substance phosphorus deposited at the bottom of the phosphorus receiving groove overflows into the phosphorus discharge pipe when the height of the liquid simple substance phosphorus exceeds the height of the phosphorus outlet, a check valve is arranged at the position of the phosphorus discharge pipe extending out of the phosphorus receiving groove, and a flushing pipe with a downward outlet is connected to a pipe body outside the check valve by a specific distance.