月: 2023年1月

What Is a Jet Heater?

Jet heaters, particularly used in commercial settings, warm large areas like warehouses and factories using kerosene as fuel. The air, heated by combustion, is circulated by a large fan to efficiently heat the space.

Although these heaters can deliver warm air over long distances, caution is advised due to the high temperatures they can reach, which pose burn risks. It’s also crucial to keep hazardous or flammable materials away to prevent explosions.

Uses of Jet Heaters

Jet heaters are utilized in various large spaces, including school gymnasiums, logistics warehouses, factories, and event venues. The direct-fired types, which blow heat from the burner directly with a fan, are particularly effective for drying applications, such as paint drying or concrete curing at construction sites.

They are also employed for heating in plastic greenhouses and drying food, making them versatile for numerous fields.

Principle of Jet Heaters

Jet heaters are primarily categorized into three types:

1. Infrared Type

Known as “bright heaters,” these provide spot heating similar to residential heaters, offering quiet operation ideal for school events and venues.

2. Hot-Air Open-Flame Type

This method uses a burner to generate hot air, which is then blown by a fan, effectively heating and drying spaces. It’s highly suitable for construction site applications.

3. Hot-Air Indirect Type

The heat from the burner is split into clean hot air and combustion gas via a heat exchanger, with only the clean air being circulated. This method, venting combustion gases externally, is perfect for food drying, heating greenhouses, and temporary tents.

Types of Jet Heaters

Jet heaters come in ducted and bright models:

1. Duct Type

Ideal for drying food, paint, and concrete, or thawing frozen areas. Available in direct-fired and indirect types, allowing for selection based on specific needs.

The direct-fired type is powerful, and ideal for quick drying at construction sites, while the indirect type, suitable for environments where cleanliness is paramount, is used in greenhouses and food drying.

2. Bright Type

Using infrared rays, this type efficiently heats large indoor or outdoor spaces, beneficial for events and gymnasium gatherings. Its widespread heating capability ensures even remote areas are warmed.

How to Choose Jet Heaters

Selection criteria include:

1. Size

Consider the heater’s capacity and size relative to the intended area of use.

2. Fuel Consumption

Check the fuel consumption rate (L/h) to assess efficiency and operating costs.

3. Quietness

For events requiring low noise, select a model with reduced operational sound, typically measured in decibels (dB).

4. Output Adjustment

Adjustable heat output ensures comfort and fuel efficiency.

5. Safety Function

Opt for heaters with safety features, such as automatic shut-off, to prevent accidents in sensitive environments like schools.

What Is L-Threonine?

Figure 1. Basic Information on L-Threonine

L-threonine, an essential amino acid, plays a critical role in protein synthesis in humans. It is a vital nutrient, sourced from dietary intake of eggs, chicken, skim milk, and gelatin, among others.

Uses of L-Threonine

Beneficial for preventing fatty liver and regulating gastric acid, L-threonine supports skin moisture and hair health through collagen and keratin production. It is also crucial in animal feed to ensure nutritional balance.

Properties of L-Threonine

Water-soluble, with a melting point of 256°C and notable for its biochemical roles, L-threonine’s solubility and acid dissociation constants underline its biological significance.

Structure of L-Threonine

Figure 2. Isomers of L-Threonine

Characterized by its polar, uncharged side chain and presence in human proteins, L-threonine’s structural isomerism and optical activity are highlighted by its four possible isomers.

Other Information on L-Threonine

1. Biosynthesis of L-Threonine

Figure 3. Biosynthesis of L-Threonine

While humans must obtain L-threonine through diet, plants, and microorganisms synthesize it from aspartic acid, following a multi-step biochemical pathway involving several enzymes.

2. Metabolism of L-Threonine

L-threonine’s metabolic pathways vary across species, contributing to vital processes such as glycine and acetyl CoA production in animals and playing a role in the biosynthesis of essential biomolecules like vitamin B12 in bacteria.

What Is a Jib Crane?

A jib crane is a crane with a jib.

The arm fittings protruding diagonally from the crane are called a jib. A jib crane is designed so that the jib can be swung and retracted. A jib crane is capable of moving a suspended load in three dimensions by means of jib motion and wire hoisting.

A jib crane with a lifting load of 0.5t or more is likely regulated by local laws. Specific details are stipulated, and periodic performance inspections and voluntary inspections must be conducted for jib cranes.

Uses of Jib Cranes

Jib cranes are widely used in industrial applications and heavy industries. The following are some examples of jib crane applications:

• For unloading raw materials or shipping products in steel mills and smelters.
• Container loading and unloading on container ships.
• For maintenance of large vessels.
• For loading and unloading materials at construction sites.
• For loading/unloading raw materials to/from warehouses.

In most cases, quay unloading cranes are rigidly fixed to the quay. This is because they are stronger and can carry a higher lifting load.

Jib cranes with traveling movements are also used for loading and unloading and for ship maintenance. In the case of cranes with traveling functions, electric power is supplied by robot cables or other means.

Principle of Jib Cranes

Jib cranes consist of a mounting base, jib, drive unit, and wire rope.

The mounting base is the foundation on which the jib cranes are installed. The jib crane itself is heavy and carries a load of several tons or more, so the strength of the foundation is important. The foundation is made by pouring concrete, and in the case of a self-propelled type, strong rails are laid on top of it.

The jib is the arming portion of the crane and must be both sturdy and lightweight. Therefore, it is usually reinforced by a box structure or pipe truss structure.

The drive unit drives the crane and consists of a reduction gear and motor. In the case of the hoisting equipment, a wire rope is wound around a wire drum to raise or lower a suspended load.

Types of Jib Cranes

Jib cranes are classified into several types according to their structures. The following are some of the types of jib cranes:

1. Low Floor Jib Cranes

These are jib cranes with the crane mounted on a fixed slewing rail. These cranes are often used for loading and unloading at wharves, and in the case of traveling type, the slewing rail is mounted on a cart. 

2. Vertical Jib Cranes

Jib cranes are cranes with a horizontal jib mounted on a post installed on the ground. Since the jib is horizontal, rails may be installed and a hoist may be attached. These cranes are used in a wide range of situations, such as construction sites and wharves.

3. Tower Jib Cranes

Tower jib cranes are jib cranes with a jib attached to a tower-shaped structure. It is characterized by its ability to transport suspended loads from high places. They are mainly used in shipyards. 

4. Retractable Jib Cranes

General jib cranes are operated by lifting the jib, which causes the load to move up and down during retrieval. Retractable jib cranes have a structure that allows the crane to retract the load horizontally. They are mainly used at docks to unload powder loads.

Other Information About Jib Cranes

1. Operation of a Jib Crane

Jib cranes are characterized by their ability to perform three movements: slewing, retracting, and hoisting.

The slewing motion is a 360° rotation of the jib about the crane’s central axis. When used for unloading cargo at the wharf, the crane is swung while the cargo is suspended to transport the cargo from the ship to land. The turning motion is mainly powered by a motor with a reduction gear or a hydraulic pump and is performed gently to avoid excessive impact due to the heavy loads being handled.

The retracting motion moves the load closer to or further away from the center axis of the crane. Typical jib cranes perform the retracting action by lifting or pulling down the jib.

The hoisting operation raises or lowers the load by hoisting or lowering the wire. Because it actually raises and lowers the load, it requires the most power of all jib cranes.

What Is Nickel Sulfamate?

Nickel sulfamate, an odorless blue or green solid, serves as an ionic compound of sulfamic acid and nickel. With the formula Ni(SO₂NH₂)₂, a molecular weight of 250.85, and CAS No. 13770-89-3, it is utilized in sulfamic acid baths for metal surface treatments.

Uses of Nickel Sulfamate

This compound is pivotal in nickel plating for its corrosion resistance, employed in various methods including matte nickel plating via sulfamic acid baths. These baths, differing from the common Watts baths, are utilized for corrosion resistance, decoration, and electroforming. Electroforming is crucial for precision machinery and aerospace components, offering high-accuracy metal replication.

Properties of Nickel Sulfamate

With a melting point of 125°C (trihydrate) and solubility in water, nickel sulfamate is available as both an aqueous solution and tetrahydrate powder. Its plating baths, characterized by minimal electrodeposition stress and high ductility, allow for high current density and easy control, significantly differing from the stresses of Watts and nickel chloride baths.

Other Information on Nickel Sulfamate

1. Manufacturing Process

Produced by reacting nickel powder or nickel(II) carbonate with sulfamic acid under acidic conditions, nickel sulfamate is formed through a direct combination or carbonate reaction, resulting in its sulfamate form along with by-products.

2. Regulatory Information

While not designated under certain laws, it requires careful handling due to its designation under various environmental and safety regulations.

3. Handling and Storage Precautions

• Store sealed in a cool, dark place and use in well-ventilated areas or outdoors.
• Wear appropriate protective gear, avoid inhalation, and manage exposure promptly with medical advice or treatment.
• Follow thorough hygiene practices post-handling, with specific measures for skin and eye contact.

What Is Sulfamic Acid?

Figure 1. Basic Information on Sulfamic Acid

Sulfamic acid, known also as amidosulfuric acid, is a water-soluble chemical formed by substituting the hydroxyl group in sulfuric acid with an amino group. This white solid decomposes at 205°C and is insoluble in ethanol, not hygroscopic, facilitating the production of a pure form. Its synthesis involves urea and fuming sulfuric acid.

Reacting with nitrous acid yields nitrogen gas, and nitric acid, acts as a reducing agent, producing nitrous oxide.

Uses of Sulfamic Acid

As a precursor to the artificial sweeteners Cyclamate and acesulfame potassium, sulfamic acid finds extensive use. It also reacts with 2-ethyl hexanol to form 2-ethylhexyl sulfate, used in cotton silketing and as a standard in acid-base titrations for determining sodium hydroxide concentrations. Moreover, it serves as a cleaning agent and rust remover, offering an odorless alternative to hydrochloric acid-based cleaners.

Properties of Sulfamic Acid

In aqueous solutions, sulfamic acid exhibits strong acidity (K_a = 1.01×10⁻¹), dissolving metal salts without corroding metals. It hydrolyzes to ammonium hydrogen sulfate above 80°C and releases ammonia when heated in water.

Structure of Sulfamic Acid

Figure 2. Structure of Sulfamic Acid

The chemical structure of sulfamic acid (H₃NSO₃), featuring a molar mass of 97.10 g/mol and a density of 2.15 g/cm³, includes a tautomeric zwitterionic form, as determined by neutron diffraction studies.

Other Information on Sulfamic Acid

1. Chemical Reactions

It acts as a scavenger of hypochlorite ions in various chemical oxidations and forms sulfate esters when reacted with alcohols under mild conditions, facilitated by urea as a catalyst.

2. Synthesis of Cyclo

Figure 3. Synthesis of Cyclo from Sulfamic Acid

The reaction between sulfamic acid and cyclohexylamine, in the presence of sodium hydroxide, produces Cyclo, a sodium cyclamate sweetener, demonstrating a sweetness significantly greater than sugar but with a bitter aftertaste at high concentrations.

What Is Styrene?

Styrene is an aromatic hydrocarbon with the formula C₆H₅CH=CH₂.

It is also known as styrene, phenylethylene, styrene, and cinnamene. It is highly flammable and toxic and should be handled with care.

Uses of Styrene

Styrene is mainly used as a raw material for synthetic resins. It is used in the production of synthetic resins such as polystyrene (PS), ABS resin, AS resin, and unsaturated polyester. Styrene can also be used as a monomer for polymerization, as it easily polymerizes into polystyrene in the presence of heat and catalysts.

In particular, polystyrene resin has a very wide range of applications, including packaging materials for electrical appliances, kitchenware, containers, plastic models, automobiles, various parts of household appliances, and food trays, due to its low cost and good moldability. Depending on the application, polystyrene may be used by itself or in expanded polystyrene (styrene foam).

In addition, styrene is used not only as a raw material for manufacturing styrene butadiene rubber, polystyrene, synthetic resin paints, and FRP, but also for building materials such as adhesives, glues, and heat insulators, as well as dry oils, polyester resins, and ion exchange resins.

Properties of Styrene

A colorless liquid with aromatic properties, it is lighter than water with a specific gravity of 0.9044 and floats on water because it is insoluble in water. It has a flash point of 32°C, a melting point of -30.63°C, a boiling point of 145.2°C, and a refractive index of 1.5439. It is soluble in alcohols and ethers.

Styrene has a structure in which one hydrogen atom of benzene is replaced by a vinyl group. Because of the vinyl group, it is extremely reactive and easily polymerized by heating, light, peroxides, etc. to form polystyrene, which gradually increases in viscosity from a liquid state to a colorless solid state.

The vapor density is 3.6, which is heavier than that of air, and it easily stays in low places to form explosive gas mixtures. When temperatures rise due to sunlight or other factors, it can polymerize, posing a fire or explosion hazard. Therefore, it is recommended to store in a cool and dark place with good ventilation.

Other Information on Styrene

1. Production Method of Styrene

Dehydrogenation Method
Styrene is synthesized by dehydrogenating the raw material ethylbenzene at high temperature. The process is carried out under reduced pressure at 550°C or higher using a catalyst consisting mainly of iron oxide. Since this reaction is reversible, Styrene is synthesized by removing the hydrogen produced by the oxidation of ethylbenzene to allow the reaction to proceed.

Another method to synthesize Styrene is to oxidize the hydrogen produced in the reaction, thereby lowering the partial pressure of hydrogen and increasing the temperature in the system due to the heat of reaction, thereby allowing the reaction to proceed.

Halcon Method
This method was developed by Halcon International, Inc. in the U.S. and can synthesize Styrene and propylene oxide from ethylbenzene and propylene. In this method, ethylbenzene is air-oxidized to ethylbenzene hydroperoxide, which reacts with propylene under reaction conditions of 2 to 7 MPa and 100 to 130°C to produce propylene oxide and methylbenzyl alcohol.

Styrene is obtained by catalytic dehydration of the resulting methylbenzyl alcohol using a titanium oxide catalyst. The yield of propylene oxide and Styrene is high, and it is considered an advantageous method for simultaneous synthesis of these two substances.

2. Safety of Styrene

Styrene is a flammable liquid and has been reported to be a self-reactive chemical. It is also a fire and explosion hazard that can polymerize under the influence of heat, light, oxidants, oxygen, and peroxides.

Harmful by inhalation and may cause skin and eye irritation. Caution should also be exercised with regard to permissible concentrations in the work environment, as long-term or repeated exposure may cause central nervous system and liver damage.

The Ministry of the Environment’s Initial Environmental Risk Assessment suggests that there may be health effects if Styrene is inhaled through respiration. When handling, it is recommended that appropriate protective equipment such as protective gloves, impervious protective front coverings, safety glasses or safety goggles, and gas masks for organic gases be used.

What Is Dimethyl Disulfide?

Dimethyl disulfide, an organic compound with the formula C₂H₆S₂, is a notable organosulfur compound. It is known by various names, including methyl disulfide, 1,2-dimethyldisulfan, and 2,3-dithiabutane, characterized by its S-S (disulfide) bond. Its CAS registration number is 624-92-0.

Uses of Dimethyl Disulfide

Primarily, dimethyl disulfide serves as a sulfidizing agent for hydrogenated desulfurization catalysts in fuel oil refining. It is also utilized as an intermediate in agricultural chemicals, a solvent in synthetic resin production, and a thiomethylating agent. Additionally, it finds use in instrumental analysis and solution preparation at the research level. Despite its pungent sulfur odor, reminiscent of garlic, it is employed as a flavoring agent in foods like onions and cabbage, where it can contribute to the unwanted odor during cooking.

Properties of Dimethyl Disulfide

This compound has a molecular weight of 94.19, melts at -85°C, and boils at 110°C. It appears as a clear yellow liquid at room temperature, with a distinctive sulfur-garlic odor. Its density is 1.06 g/mL, and it dissolves well in organic solvents like ethanol and ether while being slightly soluble in water.

Types of Dimethyl Disulfide

Available primarily for research and development, dimethyl disulfide is marketed in various volumes, including 5mL, 25mL, 250mL, and 1L. It is intended for use in organic synthesis and standard solution preparation for instrumental analysis, not beyond research purposes.

Other Information on Dimethyl Disulfide

1. Synthesis of Dimethyl Disulfide

The synthesis of dimethyl disulfide can be achieved through the reaction of methyl iodide with potassium disulfide or by methanethiol oxidation with iodine. Naturally, it is present in certain fishes, cruciferous plants, and garlic, and is produced during the decomposition of organic waste, including garbage and sewage.

2. Reactivity of Dimethyl Disulfide

As a flammable substance with a flash point of 15°C, dimethyl disulfide can ignite from heat, sparks, or flames. It reacts violently with strong oxidizers, bases, and reducing agents, producing hazardous combustion by-products such as carbon monoxide, dioxide, and sulfur oxides. Its chlorination and oxidation processes yield various sulfur-containing compounds.

3. Safety and Regulatory Information on Dimethyl Disulfide

Given its flammability and potential health hazards, dimethyl disulfide is regulated under various safety laws. It poses risks of acute toxicity, skin and eye irritation, and potential long-term health effects. Proper handling, per occupational health and safety regulations, is essential to mitigate these risks.

What Is Dicyandiamide?

Dicyandiamide is an organic compound with the chemical formula C₂H₄N₄. It is known in IUPAC nomenclature as 2-cyanoguanidine. Other common names include dicyanodiamide and DCD, with a CAS registration number of 461-58-5.

Uses of Dicyandiamide

1. Main Applications

Dicyandiamide is primarily utilized as a curing agent for epoxy resins, an additive for starch paste, a raw material for both organic synthesis and dicyandiamide resin, a stabilizer for synthetic detergents, and in the production of dyes, fertilizers, and agricultural chemicals including insecticides and fungicides. As a curing agent, it requires the addition of a tertiary amine, such as an imidazole adduct, as a catalyst to manage the high curing temperature (180°C or higher) and the heat generated during curing.

2. Synthetic Applications

Upon heating above its melting point, dicyandiamide decomposes into melamine and ammonia, making it a valuable raw material for the organic synthesis of cyanamide derivatives such as guanidine, dicyandiamidine, diguanide, and melamine.

3. Use as Fertilizer

Dicyandiamide also serves as a component in slow-release fertilizers, applied as basal fertilizers at planting. Soluble in water, it inhibits soil microorganisms like nitrite bacteria, slowing the conversion of ammonia nitrogen to nitrate nitrogen, thereby retaining nutrients in the soil. Its effectiveness is influenced by the water temperature, affecting its solubility.

Properties of Dicyandiamide

Dicyandiamide, with a molecular weight of 84.08, melts at 210°C and appears as a white crystalline powder at room temperature. It forms orthorhombic or plate-like crystals in its crystalline state and is easily soluble in hot water, slightly soluble in cold water and ethanol, and insoluble in acetone. Aqueous solutions of dicyandiamide are nearly neutral.

Types of Dicyandiamide

Dicyandiamide is marketed both as a reagent for research and development and as an industrial chemical, available in various sizes including 25g, 500g, 1kg, and 3kg for R&D, and typically in 25 kg bags for industrial use. Its applications vary, so usage should be checked depending on whether it is intended as an epoxy resin hardener, starch glue additive, synthetic detergent stabilizer, or dye.

Other Information on Dicyandiamide

1. Synthesis of Dicyandiamide

The synthesis of dicyandiamide commonly involves reacting lime nitrogen with water and acid to form a cyanamide solution, which is then heated to induce polymerization. This method benefits from the tautomerism of cyanamide, with the process potentially yielding dicyandiamide through the reaction of cyanamide and carbodiimide in a basic solution.

2. Tautomerism of Dicyandiamide

Dicyandiamide exhibits tautomerism similar to cyanamide, with the nitrogen atom attached to the nitrile group being in equilibrium between bonding and protonation states, possibly existing as zwitterionic ions.

What Is Dichloroethylene?

Dichloroethylene (DCE) is an organochlorine compound with the chemical formula C₂H₂Cl₂, featuring a double bond within its molecule.

It exists as two structural isomers, “1,1-dichloroethylene” and “1,2-dichloroethylene,” differentiated by the positions of the chlorine atoms, and two geometric isomers, E– and Z-isomers of 1,2-dichloroethylene. Their respective CAS numbers are 75-35-4 (1,1-dichloroethylene), 156-59-2 (1,2-dichloroethylene, Z-isomer), 156-60-5 (1,2-dichloroethylene, E-isomer), and 540-59-0 (1,2-dichloroethylene, mixed isomers).

Uses of Dichloroethylene

1. 1,1-Dichloroethylene Applications

1,1-dichloroethylene (1,1-DCE) is used as a comonomer in synthesizing polymers, including polyvinyl chloride and polyacrylonitrile. It serves as a raw material in producing household wraps, packaging films, artificial turf, fishing nets, vinylidene chloride latex, and flame-retardant fibers, and in semiconductor engineering to create pure silicon dioxide films.

2. 1,2-Dichloroethylene Applications

1,2-dichloroethylene (1,2-DCE) is mainly utilized as a synthetic feedstock for producing other chlorinated solvents. It also finds use as a low-temperature solvent for extracting resins, fragrances, and dyes, and as a cleaning agent.

Properties of Dichloroethylene

1. 1,1-Dichloroethylene Properties

1,1-dichloroethylene (1,1-DCE) is a colorless liquid with a chloroform-like odor, having a molecular weight of 96.94, a melting point of -122°C, and a boiling point of 32°C. Its density is 1.221 g/mL at 20°C, and it is soluble in alcohols, hydrocarbons, and ethers but insoluble in water, with a solubility of 2,420 mg/L.

2. 1,2-Dichloroethylene Properties

The E (trans) and Z (cis) geometric isomers of 1,2-dichloroethylene are colorless liquids with pungent odors. Their melting points are -81.5°C for the Z-isomer and -49.4°C for the E-isomer, with boiling points of 60°C and 47.2°C, respectively. The densities are 1.28 g/mL for the Z-isomer and 1.26 g/mL for the E-isomer.

Types of Dichloroethylene

Dichloroethylene is marketed primarily as a reagent for research and development, including the isomers 1,1-dichloroethylene and 1,2-dichloroethylene, available in volumes of 5 g, 25 g, 100 g, and 500 mL. Deuterium-labeled 1,1-dichloroethylene-d2 is also offered for use as a solvent in NMR analysis.

Regulatory Information on Dichloroethylene

1. 1,1-Dichloroethylene Regulations

1,1-dichloroethylene, with a low flash point of -28°C, is extremely flammable and toxic, affecting the central nervous system upon inhalation. High concentrations can lead to sedation, intoxication, convulsions, and coma. It is regulated under various safety laws.

2. 1,2-Dichloroethylene Regulations

1,2-dichloroethylene, flammable with a flash point of 6°C, can have anesthetic effects on the human body, causing vomiting and affecting the central nervous system at high concentrations. It is classified under various safety and environmental laws.

What Is Diethylene Glycol?

Diethylene glycol, a glycol derivative formed by the dehydration and condensation of two ethylene glycol molecules, is known by various names including diethyl glycol and 2,2′-oxydiethanol. Recognized under various safety laws, it poses significant toxicity risks to the liver, central nervous system, and kidneys upon oral ingestion, with a history of causing fatal poisonings due to its sweet taste.

Uses of Diethylene Glycol

Its applications are diverse, including use in brake fluid, antifreeze, lubricants, inks, cosmetics, and more, due to its chemical properties. However, following regulation changes, its use in toothpaste is banned, and only glycerin containing 0.1% or less diethylene glycol is permissible in cosmetics.

Properties of Diethylene Glycol

As a colorless, syrupy liquid, diethylene glycol has a melting point of -10.45°C and a boiling point of 244.3°C, dissolving readily in polar solvents like water. Its molecular details include a formula of C₄H₁₀O₃, a molecular weight of 106.12, and a density of 1.1160 g/cm³ at 20°C.

Other Information on Diethylene Glycol

1. Synthesis of Diethylene Glycol

Produced as a byproduct in ethylene glycol manufacturing, it results from the reaction of ethylene glycol molecules with water. It is part of a family of compounds derived from ethylene oxide, varying by the number of ethylene oxide units (n), leading to various glycols being more hydrophilic due to their ether bonds.

2. Related Compounds and Synthesis

From ethylene glycol to polyethylene glycol, these compounds are synthesized through reactions with ethylene oxide, influenced by factors like temperature, catalysts, and reactants such as water or alcohol. The synthesis conditions determine the specific glycol produced, with diethylene glycol forming under certain conditions alongside other glycols like triethylene and tetraethylene glycol.