US researchers have made Molecular

Sieve fibers that open up new possibilities for large scale chemical

separations that use much less energy than conventional distillation methods. Sankar

Nair and his Georgia Institute of Technology team have shown their metal–organic

framework (MOF)-lined fibers can perform similarly to distillation in separating

propylene and propane. That’s the same post-cracking raw mixture that the majority

of the 77 million tons of propylene produced in 2011 was distilled from. ‘The degree

of separation by the membrane is comparable, but uses vastly less energy,’ Nair

says.

Though scientists recognize MOF membranes’ separation potential, they’ve mostly

been fabricated on large tubes, whose surface area-to-volume ratio is too low for

producing cheap separation modules. Micron-scale fibers would be better, but inside

them conditions for successful membrane formation change significantly, Nair

explains. ‘The amount of reactant present in the fiber is miniscule, and molecular

transport and reaction processes are quite different,’ he says.

The Georgia Tech team’s new approach uses two solutions – one containing zinc

ions and another containing methyl imidazole. With one solution inside 250μm

diameter hollow poly(amide-imide) porous fibers and another outside them, they start

forming a zeolitic imidazolite framework (ZIF) where the two meet. They initially

explored conditions where the solution inside the fiber didn’t move, but got patchy

coatings. When they realized this setup wasn’t supplying enough reactant, they

pumped the inner solution through the fiber, getting better coatings but struggling

to control thickness and quality. Finally, they devised an intermittent approach,

allowing the membrane to grow under static conditions, then periodically replenishing

the reactant supply.

This lets Nair’s team direct film growth inside the fiber or on its inner or

outer surfaces through different reagent and solvent permutations. Using tiny pores

in MOF films inside the bore of the fibers as selective Carbon Molecular Sieves they

then separated hydrogen or propylene from propane. ‘We have a demonstrated path to

“scale down” MOF membranes to hollow fibers, in a manner that we can now look to “

scale up” by an in-parallel replication of the process to many fibers bundled

together into a module,’ Nair explains.

What are Pneumatic Solenoid Valves?

Pneumatic solenoid valves are electromechanical devices that control the flow of

air or process gas. They are mostly used for controlling pneumatic actuators such as

cylinders, turbines (pneumatic motors), diaphragms, and tubes. Pneumatic Valve and actuators form auxiliary air

circuits. These devices are used to control plant equipment.

Other pneumatic solenoid valves are used as an integral part of some pieces of

equipment or processes. Examples are compressed air systems, vacuum systems,

ventilation systems, and air-operated equipment.

Pneumatic solenoid valves are commonly seen in many industrial and manufacturing

plants. One of their main benefits is being remote controlled by sending low-power

electric signals over large distances. These electric signals are easily handled by

the plant‘s control system. A control panel or unit distributes signals that

manipulate the valve at unattended locations in the process area. Pneumatic solenoid

valves are employed in a wide range of industries such as oil and gas, power

generation, chemical, and plastics.

Angle Seat Valve

in the fields of medicine, pharmaceuticals, food, and beverage are preferred

because of their clean operation. They are much cleaner than hydraulic solenoid

valves which mainly use oil. They can be sealed to prevent any product from being

trapped within its internal cavities. This, in turn, lessens the risk of product

contamination.

Working Principle

The heart of a Shuttle

Valve is the solenoid. A solenoid is an electromagnetic actuator that converts

electrical energy into mechanical action. It consists of a coiled wire tightly

wrapped around an iron core, and a ferromagnetic plug or plunger. As an electrical

current passes through the coil, a magnetic field is generated. The magnetic field

lines can be imagined as a series of circles with the direction of their current

axis. In the case of a current flowing through a looped coil, the circles combine

forming the magnetic field.

The magnetic field around the coil causes the ferromagnetic plunger to become

attracted. The electromagnetic force generated can be increased using two ways. The

first is by adding more loops or windings in the coil. This increases the number of

magnetic field lines or flux emanating from the coil.

The second method is by increasing the amount of current flowing through the

coil. This increases the supply voltage into the solenoid. Solenoid Valves operate with either DC or AC voltages.

The other main part of a pneumatic solenoid valve is the valve. The valve is the

part in contact with air or gas. It is made up of components designed to withstand

the pressure of the system. It also resists corrosion and erosion brought by

contaminants entrained into the pneumatic system.

Parts of a Pneumatic Solenoid Valve

The previous chapter generally describes the two main parts of a pneumatic

solenoid valve, the solenoid, and the valve. To further understand its operation, it

is useful to note its detailed components. Below are the parts of a

2 Way Solenoid

Valve common to almost every design.

The core, also referred to as the armature or plunger, is the moving part of a

solenoid. This is a soft magnetic metal (soft, meaning a ferromagnetic metal that can

easily be magnetized and demagnetized at low magnetic fields). When the coil is

energized generating a magnetic field, the core is attracted which opens or closes

the valve.