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The Classifications of EB Tungsten Filament

Details: Category: Tungsten Information; Published on Wednesday, 13 April 2016 18:25; Written by xuejiao; Hits: 300

All EB (electron beam) tungsten filaments are made of tungsten which is also known as wolfram. The EB tungsten filament has a good discharge performance and an excellent anti-sag performance. The two characteristic can ensure that the filament is not deformed during working. The following classifications are the main types of EB tungsten filament.

Classification	Specification	Picture
Mosquito Coil: the shape of the EB tungsten filament is similar to the mosquito coil, therefore, it can be named as Mosquito Coil. And the Mosquito Coil can be divided into the following specifications.	0.55mm
	0.65mm
	0.80mm
Pull-type: Pull-type is also known as the cavity type of Mosquito Coil.	0.80mm
Classification	Specification	Picture
U-shaped: this kind of EB tungsten filament is similar to the shape of the letter U.	0.80mm
U-shaped with folding legs: the feet of the EB tungsten filament has a curved.	0.80mm
Half Moon: the shape of this type is the shape of a half moon.	0.80mm
Straight shape	0.80mm

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Low-NOx Combustion Unit Uses Tungsten Trioxide SCR Denitration Catalyst

Details: Category: Tungsten Information; Published on Wednesday, 13 April 2016 18:24; Written by chunyan; Hits: 240

The two major mechanisms of NOx formation in low-NOx combustion unit are while reducing combustion temperature, the concentration of oxygen in the fire zone also be reduced, in order to suppress the formation of nitrogen oxides in the furnace. The concentration of NOx emissions can be reduced by 30% to 60% by using low-NOx combustion furnace technology. Nowadays, the widely used low-NOx combustion technology is mainly through low-nitrogen furnace transformation, for achieving the goals of low-oxygen, hierarchical partitioning combustion in the furnace, thus to achieve the reduction of NOx emission.

Due to the limitations of the furnace low NOx combustion technology, the NOx emissions can’t meet environmental requirements, so denitration process should be carried out in order to further reduce NOx emissions. Dry, semi-dry and wet method ate the prevailing flue gas denitration processes. Wherein, dry SCR denitration process is of high commercial value and being widely used with its nice properties, such as simple structure, easy operation, high reliability, high denitration efficiency, relatively low initial Investment.

SCR device consists of denitration reaction preparation system and the composition of the reactor body, reducing NOx into nitrogen and water vapor by injecting into denitration reaction agents--NH₃ into the reactor. SCR denitration catalysts are generally taking titanium dioxide as a carrier, vanadium pentoxide and tungsten trioxide as the main active ingredients, its activation temperature is generally between 300~400 ℃. Tungsten trioxide plays the role of anti-curing, anti-poisoning in the catalyst, thus to enhance the activity of the catalyst. SCR denitration reactor can be divided into high and low dust categories according to installation location of precipitator. However, due to low dust device needs to install a steam heater and flue gas heat exchanger (GGH), which makes the system complex, investment increased, so the generally chosen is the high dust process.

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Tungsten Bronze (TB) Crystal Structure

Details: Category: Tungsten Information; Published on Wednesday, 13 April 2016 17:58; Written by xinyi; Hits: 323

The tungsten bronze (TB) crystal material, due to good optical effects, electrical properties and blastic phase boundary and so on, has been widely used in the technical field of laser frequency doubling, optical modulator, optical information processing, superconducting, humidity sensors, fuel cells and other solids. Molecular design of TB crystal material is to design on the atomic level, explore and synthetic crystalline material of the target structure based on the understanding of its structure. In recent years, this area has made a lot of new results, which becomes an effective means of research and development and improved performance of this type of crystal material.

Tetragonal tungsten bronze (TTB) crystal is relative common of tungsten bronze type crystals, (many rhombic TB structure is a superstructure of TTB structure), which is widely used. So the commonly known TB crystal mainly refers to the TTB crystals. the structure projection of C-axis shown in FIG. B-O octahedra corner-top connection formed pentagonal, square and triangular pores. They are called A1, A2 and C positions. The thick solid line drawn is a unit cell, wherein: the number of void ratio down to A1: A2: C = 4: 2: 4, ie there are10 positions of A totally; and 10 positions of B and 30 of O^{2 -}.

B position can be divided into two B1 position (cell edges midpoint) and eight B2 position (cell interior) based on symmetric types. C axis translation period equals to the height of a B-O octahedron . In the structure: coordination number of A2 and O^2-may be 9,10,11,15, ligand effect of A2, C, B and O2- respectively are 12,9 and 6.

Therefore, the formula of TB structure is (A1) 1 (A 2) 2C4 (B1) 2 (B2) 8O30. When six A1, A2 positions are not filled with cation and C position is completely empty, it is called not filled structure; when six A1, A2 positions are all filled with cation and C position is completely empty, it is called full structure; When six A1, A2 positions and C position are all filled with cation, it is called completely filled structure.

TB structure

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CaO Effects Designing WO3 Denitration Catalyst

Details: Category: Tungsten Information; Published on Wednesday, 13 April 2016 18:19; Written by chunyan; Hits: 250

Calcium oxide (CaO), the so-called quicklime, is an inorganic compound powder with white, hygroscopic and corrosive. The plaster (Calcium sulfate) in thermal power plant is generated by sulfur dioxide reacting with desulfurization and then oxidized, and then discharged with the flue gas exhaust system. When it comes into being that calcium sulfate contacts with tungsten trioxide SCR denitration catalyst, large number of calcium sulfate will be deposited on the surface of the catalyst, which can cause the catalyst surface shielding, and then the catalyst activity decreased.

By the time the content of calcium oxide in the flue gas is less than 5%, little effect has occurred on catalyst design. However, when the content of calcium oxide is more than 5%, its effect on the catalyst design generates becomes very large. With the calcium oxide content increasing, the amount of tungsten trioxide SCR denitration catalyst turns to linearly increasing trend, especially when the calcium oxide content is about 30%, the consumed catalyst required will increase about 25% compared with low calcium conditions. In this condition, catalyst activity and aging speed can’t overestimate when design catalyst; in order to ensure the chemical catalyst lifetime (24,000 hours), we need to leave enough adequate catalyst, thus will result in a larger number of design volume and costs increased.

Therefore, in the high calcium conditions, the blind pursuit of a minimum amount of tungsten trioxide SCR denitration catalyst will result in a short life of the catalyst, reduction denitration efficiency decreased and other adverse consequences. Besides, if we ignore the impact of calcium on the running of catalyst, reduce design margins unprincipled, overestimated the catalyst activity, the risk of high operating costs will present although it bring cost savings to some extent. It is worth mentioning that, the presence of tungsten trioxide can effectively inhibit the sintering of the catalyst particles, delaying the degree of sintering, therefore, tungsten trioxide SCR denitration catalyst is particularly suitable for high calcium conditions.

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Tungsten Carbide Ball for Universal Joint (2/2)

Details: Category: Tungsten Information; Published on Wednesday, 13 April 2016 16:16; Written by xiaobin; Hits: 247

Tungsten carbide ball is composed of hard phase WC and binder phase Co. It has higher hardness, strength, excellent wear resistance and chemical stability, which is the ideal material for universal joint. In the arc type universal joint, the active fork ball and do some carbide groove driven fork mounted four synthetic carbide ball raceway can accommodate four carbide balls. Besides, there is a spherical ball mounted in the center of the groove as centering ball. Straight groove raceway-type universal joint in the two fork ball with carbide straight grooves, straight grooves and each axis is inclined relative to the center line and the same tilt angle and symmetrical to each other. Built in the raceway between the two fork ball has four tungsten carbide balls.

Velocity joint cage can be divided into stationary and scalability ball basket universal joints according to the movement of the universal joint axial direction. Viewed from the structure, fixed cage universal joints are composed of spline, star sets, curved groove. Star spherical shell fitted jacket and synthesized six races, each mounted in each race a carbide ball and keep cage carbide ball inside in the same plane. It powered by a drive shaft through a spherical shell and tungsten carbide ball. The structural feature of scalability ball basket universal joints is the inner wall of the cylindrical shell of the star and the external cylindrical sleeve made straight slot, built-in two raceways fitted together after the formation of cemented carbide ball. Star set bore splined for connection with the input shaft, which allows relative movement of the tubular sleeve in the axial direction. Overall, due to high hardness, high strength, wear and corrosive resistance, tungsten carbide ball has a broad application prospect in universal joints.

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