KR100263819B1 - The method of producing pulverized gravels and grinded sand for building materials and a apparatus for proceeding the same - Google Patents

Abstract

In the production of coarse aggregate and crushed sand by crushing rock collected from mines or quarries, etc., by improving the productivity by producing coarse aggregate and crushed sand in a single process, the coarse aggregate manufacturing device and the crushed sand manufacturing device are unified The present invention relates to a method and apparatus for manufacturing coarse aggregate and crushed sand for construction that can reduce the production cost of the aggregate and the plant production cost by preventing the installation.

Crushing the rock supplied through the hopper with a first crusher and recovering the soil powder; First crushing the crushed recovered rock and passing it through an aggregate raw material storage tank and a vibration feeder for storing aggregate raw materials; Crushing the rock that passed through the vibration feeder with a second crusher and then supplying the rock to the first vibration screen; Crushing the rock remaining on the first vibrating screen with a third crusher and then putting it back on the first vibrating screen; Passing the rock through a first vibrating screen having a first mesh; Passing the rock that passed through the first vibrating screen through a second vibrating screen having a second mesh; Crushing the rock remaining on the second vibrating screen with a fourth crusher; Passing the rock crushed by the fourth crusher through a third vibrating screen having a third mesh; Outputting the rock remaining on the third vibrating screen as coarse aggregate; Passing the rock that has passed through the third vibrating screen through a fourth vibrating screen having a fourth mesh; Crushing the rock remaining on the fourth vibrating screen with the fourth crusher and passing it back through the fourth vibrating screen; Passing the rock passing through the fourth vibrating screen through a fifth vibrating screen having a fifth mesh; Outputting the rock remaining on the fifth vibrating screen as crushed sand; And spraying water on the rock passing through the first to fifth vibrating screens;

Hoppers and first shredders, aggregate raw material reservoirs, vibration feeders; A second crusher for crushing the rock that has passed through the vibration feeder; A third crusher for crushing rock remaining on the first vibrating screen; A first vibrating screen for filtering a rock having a first size from the input rock; A second vibrating screen for filtering the second size of the rock passing through the first vibrating screen; A fourth crusher for crushing rock remaining on the second vibrating screen; A third vibrating screen for filtering the rock having a third size among the rocks crushed by the fourth crusher and outputting the rock as coarse aggregate; A fourth vibrating screen for filtering the rock having a fourth size among the rocks passing through the third vibrating screen and feeding it back to the fourth crusher; A fifth vibration screen for filtering out the rock having the fifth size from the rock passing through the fourth vibration screen and outputting it as sand; And water jetting means for sprinkling water on the rock passing through the first to fifth vibrating screens.

Description

The method of producing pulverized gravels and grinded sand for building materials, and An apparatus for proceeding the same

The present invention relates to a method and apparatus for manufacturing coarse aggregate and crushed sand for building, in particular, in the production of coarse aggregate and crushed sand by crushing rock collected from mines or quarries, by producing coarse aggregate and crushed sand in a single process. The present invention relates to a method and apparatus for manufacturing coarse aggregate and crushed sand for improving aggregate productivity and lowering aggregate manufacturing cost and plant production cost by preventing the installation of overlapping devices by unifying the coarse aggregate manufacturing device and the crushed sand production device.

Generally, aggregates obtained by crushing rock collected from mines or quarries are called crushed aggregates (hereinafter referred to as crude aggregates), and sands obtained by crushing the rocks are called crushed sands (hereinafter referred to as crushed sands).

Therefore, the manufacturing process for crushing the rock collected from mines or quarries is usually divided into a manufacturing process for producing coarse aggregate and a manufacturing process for producing crushed aggregate, and coarse aggregate and crushed sand are produced separately.

Thus, Figure 4 is a schematic diagram showing the structure of the device for producing a building aggregate according to the prior art,

According to the prior art there is provided a method for producing architectural aggregates:

The method comprises the steps of: sorting out the soil waste from the rock supplied through the hopper (51); Crushing the rock through a first crusher (52), a second crusher (53) and a third crusher (54); Supplying the rock that has passed through the third crusher (54) to the first vibrating screen (56); Crushing the rock remaining on the first vibrating screen (56) using a fourth crusher (55) and then feeding it back onto the third vibrating screen (58); Passing the rock through a first vibrating screen 56 having a first mesh; Passing the rock passing through the first vibrating screen (56) through a second vibrating screen (57) having a second mesh smaller than the first mesh; Outputting the rock remaining on the second vibrating screen (57) as coarse aggregate; Crushing the rock remaining on the third vibrating screen (58) by using a fourth crusher (55) and passing it back to the third vibrating screen (58); Passing the rock passing through the third vibrating screen (58) through a fourth vibrating screen (59) having a fourth mesh smaller than the third mesh; Outputting the rock remaining on the fourth vibrating screen (59) as coarse aggregate; And outputting the rock passing through the second and fourth vibrating screens 57 and 59 as a rock for sand production.

In the method, the first to fourth meshes are each sized to pass a rock having a diameter of 25 mm or less, 8 mm or less, 25 mm or less and 8 mm or less, respectively.

Thus, according to the above method there is provided a device for manufacturing building aggregate;

The apparatus includes: a soil discharge vibrating screen (52) for sorting soil waste disposed in the rock supplied to the hopper (51); First, second, and third crushers 52, 53, and 54 for crushing the rock introduced through the hopper and then crushing the rock; A first vibrating screen (56) for filtering out rocks having a first size from the input rock; A second vibrating screen (57) for filtering the second sized rock out of the rock passing through the first vibrating screen (56) and outputting the coarse aggregate; A fourth crusher 55 for crushing the rock remaining on the first vibrating screen 56 and putting it on the third vibrating screen 58; A third vibrating screen (58) for filtering the rock having a third size among the rocks crushed by the fourth crusher (55) and outputting the rock which is passed to or passed through the fourth crusher (55) as coarse aggregate; A fourth vibrating screen (59) for filtering the rock having the fourth size among the rocks passing through the third vibrating screen (58) and outputting the coarse aggregate; It characterized by having a.

In the apparatus, the first to fourth sizes are each 25 mm or more, 8 mm or more, 25 mm or more and 8 mm or more in diameter.

5 is a schematic diagram showing the structure of an apparatus for manufacturing crushed stone sand for construction according to the prior art,

According to the prior art there is provided a method for producing building crushed sand;

The method includes the steps of supplying the sand powder (hereinafter referred to as stone powder) obtained through the crude aggregate manufacturing process to the first vibrating screen 62; Crushing the stone powder remaining on the first vibrating screen by using a first crusher (61) and then inputting it on the second vibrating screen (63); Crushing the stone powder remaining on the second vibrating screen (63) by using the first crusher (61) and feeding it back onto the second vibrating screen (63); Outputting the crushed sand passed through the first and second vibrating screens (62,63) having the first and second meshes to the spiral classifier (64); Sprinkling water on the crushed sand passing through the first and second vibrating screens (62, 63); Feeding the crushed sand containing water passing through the first and second vibration screens (62, 63) to the spiral classifier (64); Bringing the crushed sand classified by the spiral classifier (64) into the sand; Flowing water containing fine powder classified by the classifier into a settling tank (65); Flowing the sludge discharged from the settling tank 65 to the concentration tank 66; And supplying and discharging the sludge concentrated in the concentration tank 66 to a filter press.

In the method, the first and second meshes are each sized to pass crushed sand, each having a diameter of 4.75 mm or less.

Thus, according to the above method there is provided a device for manufacturing building crushed sand;

The apparatus comprises: a first vibrating screen (62) for filtering stone powder having a first size to which stone powder is supplied; A first crusher (61) for crushing the stone powder remaining on the first vibrating screen (62) and putting it on the second vibrating screen (63); A second vibrating screen (63) for filtering out the second sized stone powder among the stone powders broken through the first crusher; A spiral classifier 64 for outputting crushed sand passed through the first and second vibration screens 62 and 63; Water spraying means (68) for sprinkling water on the crushed sand passing through the first and second vibrating screens (62, 63); A settling tank (65) for storing water classified by the classifier and containing fine powder; A concentration tank 66 for storing the sludge discharged from the settling tank 65; And a filter press 67 for molding and discharging the sludge concentrated in the concentration tank 66 into a cake.

In the apparatus, the first and second sizes are each 4,75 mm or more in diameter.

However, in the production of coarse aggregate and crushed sand as described above, as the process proceeds separately when manufacturing coarse aggregate and crushed sand, the production efficiency is reduced, overlapping apparatus (crusher, vibration screen) in coarse aggregate manufacturing device and crushed sand production device Etc.) had a problem that the manufacturing cost of the aggregate and the manufacturing cost of the plant is increased.

In addition, in the production process of coarse aggregates, resources are wasted by disposing of the soil produced without using the initial soil powder. Also, since the fine powder remaining on the surface of the crushed coarse aggregates is not removed, the strength of concrete is reduced due to the poor adhesion to cement. Has become a declining factor overall.

In the manufacturing process of crushed sand, when sand and water are separated through a classifier that has passed through the first and second vibration screens, sand is mixed with water and introduced into the settling tank by using a spiral shaft. I had.

In addition, in the manufacturing process of the crushed sand, as the sedimentation tank and the concentration tank are separated, the manufacturing cost of the water treatment means is increased, and the precipitation and concentration efficiency is lowered as the chemical (sedimentation material) is manually added.

The present invention has been invented to solve the problems according to the prior art as described above, in the production of coarse aggregates and crushed aggregates by crushing rock collected from mines or quarries, by producing coarse aggregates and crushed sand in a single process, It improves the productivity of coarse aggregate and crushed sand, and lowers the production cost of the plant by unifying the overlapping devices (crusher, vibrating screen, etc.) in the conventional coarse aggregate manufacturing device and crushed sand manufacturing device. It is an object of the present invention to provide a method and apparatus for manufacturing low-grade building aggregate and crushed sand.

In addition, by using the soil generated from the rock introduced through the initial hopper, waste of resources can be prevented, and fine fine aggregate and crushed sand are removed by removing fine powder remaining on the surface through water during the screening process of coarse aggregate and crushed sand. There is also a purpose to get.

In addition, in separating the crushed sand and water, it is also equipped with a classifier consisting of a cyclone and a dewatering vibrating screen to maximize the classification efficiency of sand and water.

In addition, by providing a precipitation and concentration means to perform the precipitation and concentration of the sludge discharged from the classifier at the same time can reduce the manufacturing cost of the water treatment equipment, and also automatically put chemicals (sedimentation material) according to the precipitation rate As a result, the purpose of preventing the waste of drugs is to have.

The present invention for achieving the above object, the step of crushing the rock supplied through the hopper with a first crusher and recovering the soil; Passing the crushed recovered rock through an aggregate raw material reservoir and a vibration feeder; Crushing the rock passing through the vibration feeder with a second crusher and then supplying the rock to the first vibration screen; Crushing the rock remaining on the first vibrating screen with a third crusher and then putting it back on the first vibrating screen; Passing the rock through a first vibrating screen having a first mesh; Passing the rock that passed through the first vibrating screen through a second vibrating screen having a second mesh; Crushing the rock remaining on the second vibrating screen with a fourth crusher; Passing the rock crushed by the fourth crusher through a third vibrating screen having a third mesh; Outputting the rock remaining on the third vibrating screen as coarse aggregate; Passing the rock that has passed through the third vibrating screen through a fourth vibrating screen having a fourth mesh; Crushing the rock remaining on the fourth vibrating screen with the fourth crusher and passing it back through the fourth vibrating screen; Passing the rock passing through the fourth vibrating screen through a fifth vibrating screen having a fifth mesh; Outputting the rock remaining on the fifth vibrating screen as crushed sand; And sprinkling water on the rock passing through the first to fifth vibrating screens.

In addition, the hopper and the first crusher, aggregate raw material storage tank, vibration feeder; A second crusher for crushing the rock that has passed through the vibration feeder; A third crusher for crushing rock remaining on the first vibrating screen; A first vibrating screen for filtering out rocks having a first size from the input rock; A second vibrating screen for filtering the second size of the rock passing through the first vibrating screen; A fourth crusher for crushing rock remaining on the second vibrating screen; A third vibrating screen for filtering the rock having a third size among the rocks crushed by the fourth crusher and outputting the rock as coarse aggregate; A fourth vibrating screen for filtering the rock having a fourth size among the rocks passing through the third vibrating screen and feeding it back to the fourth crusher; A fifth vibration screen for filtering out the rock having the fifth size from the rock passing through the fourth vibration screen and outputting it as sand; And water jetting means for sprinkling water on the rock passing through the first to fifth vibrating screens.

1 is a system diagram showing the overall structure of a device for producing aggregate and sand for building according to the present invention.

2 is a view showing a classifier according to the present invention.

3 is a view showing the precipitation and concentration means according to the present invention.

Figure 4 is a system diagram showing the structure of a device for producing a building aggregate according to the prior art.

Figure 5 is a system diagram showing the structure of a device for manufacturing building crushed stone sand according to the prior art.

Explanation of symbols for main parts of the drawings

11: hopper 12: first shredder

13: aggregate raw material storage tank 14: vibration feeder

15: second shredder 16: third shredder

17: fourth shredder 18: the first vibration screen

19: second vibration screen 20: third vibration screen

21: fourth vibration screen 22: fifth vibration screen

23: water injection means 24: classifier

25: sedimentation and concentration means

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 is a system diagram showing the overall structure of the apparatus for manufacturing coarse aggregate for construction and crushed sand according to the present invention.

According to the present invention there is provided a method for producing coarse aggregate and crushed sand for construction:

The method comprises the steps of: crushing the rock supplied through the hopper (11) using a first crusher (12) and recovering the soil; Passing the crushed recovered rock through an aggregate raw material reservoir (13) and a vibration feeder (14); Crushing the rock that has passed through the vibration feeder (14) using the second crusher (15) and then supplying the rock to the first vibration screen (18); Crushing the rock remaining on the first vibrating screen (18) using a third crusher (16) and then feeding it back onto the first vibrating screen (18); Passing the rock through a first vibrating screen (18) having a first mesh; Passing the rock passing through the first vibrating screen (18) through a second vibrating screen (19) having a second mesh smaller than the first mesh; Crushing the rock remaining on the second vibrating screen (19) using a fourth crusher (17); Passing the rock crushed by the fourth crusher (17) through a third vibrating screen (20) having a third mesh larger than the second mesh; Outputting the rock remaining on the third vibrating screen 20 as coarse aggregate; Passing the rock passing through the third vibrating screen (20) through a fourth vibrating screen (21) having a fourth mesh smaller than the third mesh; Crushing the rock remaining on the fourth vibrating screen (21) using the fourth crusher (17) and then passing it back through the fourth vibrating screen (21); Passing a rock passed through the fourth vibrating screen (21) through a fifth vibrating screen (22) having a fifth mesh smaller than the fourth mesh; Outputting the rock remaining on the fifth vibrating screen (22) as crushed sand; And spraying water through the water jetting means 23 on the rock passing through the first to fifth vibrating screens 18, 19, 20, 21, and 22.

In the method, the first to fifth meshes are each sized to pass a rock having a diameter of less than 28mm, less than 2mm, less than 8mm, less than 5mm and less than 2mm, respectively.

The method comprises the steps of: supplying a crusher sand comprising water passed through the second and fifth vibrating screens (18, 19, 20, 21, 22) to a classifier (24); Flowing water including the fine powder classified by the classifier (24) to the precipitation / concentration means (25); Bringing the crushed sand classified by the classifier 24 into the crushed sand; Supplying sludge precipitated and concentrated in the sedimentation / concentration means (25) to the filter press (26); And discharging the cake produced by the filter press 26.

Thus, there is provided an apparatus for producing building aggregate and sand according to the above method:

The apparatus includes a first crusher 12, an aggregate raw material storage 13, and a vibration feeder 14 for crushing the rock supplied through the hopper and collecting and passing the soil powder; A second crusher 15 for crushing the rock that has passed through the vibration feeder 14 before entering the first vibrating screen 18; A third crusher (16) for crushing the rock remaining on the first vibrating screen and putting it back on the first vibrating screen (18); A first vibrating screen (18) for filtering out rocks having a first size in the input rock; A second vibrating screen (19) for filtering the second size of the rock that has passed through the first vibrating screen (18); A fourth crusher (17) for crushing rock remaining on the second vibrating screen; A third vibrating screen (20) for filtering the rock having a third size among the rocks crushed by the fourth crusher (17) and outputting the filtered rock as coarse aggregate; A fourth vibrating screen (21) for filtering the rock having a fourth size among the rocks passing through the third vibrating screen (20) and feeding it back to the fourth crusher (17); A fifth vibration screen (22) for filtering out the rock having the fifth size from the rock passing through the fourth vibration screen (21) and outputting it as sand; And water spraying means 23 for spraying water on the rock passing through the first to fifth vibrating screens.

In the apparatus, the first to fifth sizes are respectively 28 mm or more, 2 mm or more, 8 mm or more, 5 mm or more and 2 mm or more in diameter.

The apparatus comprises a classifier 24 for separating crushed sand containing water passing through the second and fifth vibrating screens 18, 19, 20, 21, 22 and matching the separated crushed sand with the crushed sand. ); Sedimentation / concentrating means (25) for storing water containing fine powder classified by the classifier (24); And a filter press 26 for molding and discharging the sludge discharged through the precipitation and concentration means 25 as a cake.

As shown in FIG. 2, the classifier 24 includes a hopper 241 and a hopper 241 which receive crushed sand mixed with water including fine powder passing through the second and fifth screens 19 and 22. The front is inclined downward to dehydrate the sand discharged through the cyclone 242, the cyclone 242 to classify the water and sand by pulling up the crushed sand mixed with the water flowing into the pump 245 and the hopper ( Dewatering vibrating screen (243) provided on the upper side of the 241, and the water (sludge) containing the fine powder to the upper side of the hopper 241 and the water separated from the cyclone 242 is collected and precipitated means Characterized by consisting of a sludge box 244 provided to be sent to (25).

As shown in FIG. 3, the sedimentation / concentration means 25 is a storage tank 251 into which sludge flows from the sludge box 244, and is installed and rotated in the storage tank 251, depending on the concentration of sludge. The amount of sedimentant is adjusted according to the instructions of the chemical control 253 and the chemical control 253 which periodically measure the state in which the sludge and the sediment reacts on the center upper part in the storage tank 251 to be elevated. The first and second pumps 255 and 256 positioned at the lower side of the chemical injection tank 254 to be introduced and the storage tank 251 and selectively operated according to the concentration of the sludge and supplying the sludge to the filter press 26 are provided. will be.

As described above, in the production of coarse aggregate and crushed sand by crushing the rock collected from mines or quarries, etc., by improving the productivity by producing coarse aggregate and crushed sand in a single process, unifying the coarse aggregate manufacturing apparatus and crushed sand manufacturing apparatus It is possible to reduce the manufacturing cost of the aggregate and the production cost of the plant by preventing the installation of overlapping devices.

In addition, it is possible to prevent the waste of resources by using soil powder introduced into the initial hopper, and fine fine aggregate and crushed sand can be obtained by removing fine powder remaining on the surface during the screening process of coarse aggregate and crushed sand. The effect is to increase the adhesive strength.

In addition, in the separation of crushed sand and fine water, fine quality sand and fine sand completely removed are introduced into the sedimentation and concentrating means by using a classifier consisting of a cyclone and a dehydration vibrating screen. It can be prevented.

In addition, the sedimentation and concentration of the sludge discharged from the classifier can be made at the same time to reduce the manufacturing cost of the water treatment equipment, while detecting the sedimentation rate of the sludge to automatically inject the chemical (sedimentation material) waste of chemicals There is also an effect that can be minimized.

While the present invention has been illustrated and described with reference to certain preferred embodiments, the invention is not limited thereto but may vary without departing from the spirit or scope of the invention as set forth in the claims below. It will be readily apparent to those skilled in the art that such modifications and variations can be made in the art.

Claims (7)

Crushing the rock supplied through the hopper 11 using the first crusher 12 and recovering the soil powder; Passing the crushed recovered rock through a rock reservoir (13) and a vibration feeder (14); Crushing the rock that has passed through the vibration feeder (14) using the second crusher (15) and then supplying the rock to the first vibration screen (18); Crushing the rock remaining on the first vibrating screen (18) using a third crusher (16) and then feeding it back onto the first vibrating screen (18); Passing the rock through a first vibrating screen (18) having a first mesh; Passing the rock passing through the first vibrating screen (18) through a second vibrating screen (19) having a second mesh smaller than the first mesh; Crushing the rock remaining on the second vibrating screen (19) using a fourth crusher (17); Passing the rock crushed by the fourth crusher (17) through a third vibrating screen (20) having a third mesh larger than the second mesh; Outputting the rock remaining on the third vibrating screen 20 as coarse aggregate; Passing the rock passing through the third vibrating screen (20) through a fourth vibrating screen (21) having a fourth mesh smaller than the third mesh; Crushing the rock remaining on the fourth vibrating screen (21) using the fourth crusher (17) and then passing it back through the fourth vibrating screen (21); Passing a rock passed through the fourth vibrating screen (21) through a fifth vibrating screen (22) having a fifth mesh smaller than the fourth mesh; Outputting the rock remaining on the fifth vibrating screen (22) as crushed sand; And coarse aggregate and crushed sand for building, characterized in that the step of spraying water through the water injection means 23 to the rock passing through the first to fifth vibrating screen (18, 19, 20, 21, 22). Method for preparing the same. According to claim 1, wherein the first to fifth mesh is a construction aggregate, characterized in that each having a size to pass through the rock having a diameter of less than 28mm, less than 2mm, less than 8mm, less than 5mm and less than 2mm, respectively; Method for preparing crushed sand. 2. The method of claim 1, further comprising: feeding crushed sand comprising water passed through the second and fifth vibrating screens (18, 19, 20, 21, 22) to a classifier (24); Flowing the water classified by the classifier (24) to the precipitation / concentration means (25); Bringing the crushed sand classified by the classifier 24 into the crushed sand; Supplying sludge precipitated and concentrated in the sedimentation / concentration means (25) to the filter press (26); And discharging the cake produced by the filter press (26). A first crusher 12, an aggregate raw material storage 13, and a vibration feeder 14 for crushing the rock supplied through the hopper 11 and collecting and passing the soil powder; A second crusher 15 for crushing the rock that has passed through the vibration feeder 14 before entering the first vibrating screen 18; A third crusher (16) for crushing the rock remaining on the first vibrating screen and putting it back on the first vibrating screen (18); A first vibrating screen (18) for filtering out rocks having a first size in the input rock; A second vibrating screen (19) for filtering the second size of the rock that has passed through the first vibrating screen (18); A fourth crusher (17) for crushing rock remaining on the second vibrating screen; A third vibrating screen (20) for filtering the rock having a third size among the rocks crushed by the fourth crusher (17) and outputting the filtered rock as coarse aggregate; A fourth vibrating screen (21) for filtering the rock having a fourth size among the rocks passing through the third vibrating screen (20) and feeding it back to the fourth crusher (17); A fifth vibration screen (22) for filtering out the rock having the fifth size from the rock passing through the fourth vibration screen (21) and outputting it as sand; And water spraying means (23) for sprinkling water on the rock passing through the first to fifth vibrating screens. 5. The classifier of claim 4, wherein the rock comprising water passing through the second and fifth vibrating screens (18, 19, 20, 21, 22) is separated to conform the separated crushed sand to the crushed sand. (24); Precipitation and concentration means (25) for storing water containing fine powder classified by the classifier (24); And a filter press (26) for molding and discharging the sludge discharged through the precipitation and concentration means (25) as a cake. 5. The fine powder of claim 4, wherein the classifier 24 is introduced into the hopper 241 or the hopper 241 which receives the crushed sand mixed with the water passing through the second and fifth screens 19 and 22. The front is inclined downward to dehydrate the sand discharged through the cyclone 242, the cyclone 242 to pull up the crushed sand mixed with water containing the water and sand is provided on the upper side of the hopper 241 The dewatering vibrating screen 243, and the water containing the fine powder (sludge) to be filled in the upper side of the hopper 241 and the water separated from the cyclone 242 to be collected and sent to the precipitation and concentration means (25) Apparatus for manufacturing coarse aggregate and crushed sand for building, characterized in that consisting of a sludge box (244) provided. The storage tank 251 in which the sludge flows in the sludge box 244, which is installed and rotated in the storage tank 251, is elevated according to the concentration of sludge. The amount of the sedimentation agent is adjusted according to the instructions of the chemical control 253, the chemical control 253 to measure the state in which the sludge and the sediment reacts in the center upper portion in the storage tank 251 It is characterized by consisting of the first and second pumps (255, 256), which is located in the lower side of the input tank 254, and the storage tank 251 is selectively operated according to the concentration of the sludge, and supplies the sludge to the filter press 26 Apparatus for manufacturing coarse aggregate and crushed sand.