Acetylene Plant And Generator
Our Acetylene plants are manufactured with complete in-house know how. Every part has been carefully designed by experienced engineers. These parts are made of the best material. Every part has been accurately made and carefully inspected before assembly. Each unit, after assembly, is charged and worked continuously to check its performance. You are, therefore, assured of an efficient and dependable D.A. Plant.
Our Acetylene Gas Plant is of an advanced design, incorporating several features not ordinarily found in other generators enabling them to attain the highest efficiency in the world — that is 98%. They are fully automatic plants with twin hopers and needs an operator's attention for only ten minutes in an hour.
All operations are performed by pneumatically controlled valves, assisted by highly sensitive sensors, integrated with the temperature control instruments. These in turn open the water inlet valve or residue drain valve .Two pneumatic operated cylinders help to open and close the feed of calcium carbide which is fed into the
Acetylene generator by screw feed conveyors. The screw feed mechanism and the agitator are operated by flame-proof motors and fittings. The entire operation is perfectly synchronized to give maximum efficiency and simplicity in operation of the Acetylene plant . Any failure, whether it is of power supply, water, instruments, air is signaled visually as well as audibly when an alarm bell rings to alert the operator of the acetylene plant.
The design of the entire acetylene plant has been made keeping the utmost safety in mind. Auto controls, flash back arrestors, high pressure reverse flow check valves, safety valves and complete visual gauging helps to protect both equipment and personnel.
Acetylene Plant Process Description.
In a stationary carbide to water type automatic acetylene generator, acetylene gas is produced by the reaction of calcium carbide with water. Adequate quantity of water is held in the generator shell to which calcium carbide is fed from the top, whereupon the following reaction takes place:
CaC2 + 2H2O = C2H2 + CA(OH)2 + 27000 CALORIES.
THE GENERATED ACETYLENE GAS occupies the free volume inside the generator shell over the water level and the pressure of this gas is allowed to rise till it reaches the preset pressure level. At this point the carbide feed motor is cut off by action of the pressure controller.
If the acetylene gas is removed from the acetylene generator shell the pressure inside the generator shell is reduced whereby the pressure controller reactivates the carbide feed motor and further carbide is fed by the screw feed mechanism from the hopper into the shell and more acetylene is generated. This process continues till the carbide in the hopper under operation is exhausted. This operation can be made continuous by using a second hopper which comes into operation as soon as the carbide in the first is exhausted. While the second hopper is being utilized to supply carbide to the acetylene generator shell, the first can be replenished and kept ready for replacement. Passage of acetylene gas from the acetylene generator to the carbide chamber (hopper) under filling is kept shut off by pneumatically operated shut off device which operates automatically when the carbide in the hopper is exhausted and screw feed motor is stopped.
Since the process of acetylene generation is exothermic, there is a temperature rise in the acetylene generator. This temperature rise cannot be allowed to go unchecked as acetylene is inflammable. Moreover, the optimum generation of acetylene takes place around 60ºC. Hence it is necessary to maintain the acetylene generator temperature around 60ºC. This is achieved automatically by the temperature controller which is preset to 60ºC. As the temperature inside the acetylene generator rises beyond 60ºC, the temperature controller activates the water inlet valve which lets in fresh process water and thereby reduces the temperature of the acetylene generator to the desired level .
As fresh water is introduced to lower generator temperature, the water level inside the generator rises and a slurry discharge valve opens automatically to discharge some slurry and thus lower the level of water to an acceptable level when the slurry discharge valve closes automatically. This slurry discharge valve is operated by a pneumatically operated water level controller which is preset for minimum and maximum water levels inside the generator. Its operation, in conjunction with that of the discharge valve ensures that only a small quantity of slurry is discharged at a time. The advantage of such action is that the water inside the generator, which dissolves a certain quantity of the acetylene generated, is not discharged continuously, or in large quantities, so that the dissolved acetylene is not discharged with the slurry.
The acetylene generator also incorporates an agitator which is continuously driven during the operation of the carbide feed motor to keep the carbide and water intimately mixed for complete reaction and thus prevents loss of carbide in the form of solids with the slurry.
When the acetylene generator is dormant there is a tendency of the slurry to settle down and jam the agitator so a timer controlled electric motor keeps the agitator running even when there is no carbide feed to the generator.
The acetylene generated is passed from the acetylene generator chamber through wet type flashback arresters into a low pressure condenser where the temperature of the gas is lowered by water cooling. This also removes part of the moisture in the acetylene in the form of condensed water. The gas is then passed through a low pressure dryer filled with anhydrous calcium chloride to remove further quantities of moisture before the gas enters the purifying chamber with an optimum quantity of moisture.
The purifying chamber is filled with chemicals which removes phosphorus and sulphur compounds and any acidic fumes. Thereafter the gas passes through a water scrubber so that the particles of the purifying chemicals which may have been carried over with the gas from the purifying chamber are removed.
The wet gas then enters the acetylene compressor where it is compressed and passed to the high pressure dryer where mechanical devices and chemicals remove moisture and any lube oil vapour from the gas. After passing through this dryer, the gas is arrested by a back pressure valve on the pipeline leading to the manifold. This also ensures efficient drying of the gas in the high pressure dryer. Thereafter, the gas is passed through a dry type flashback arrester to the cylinders hooked onto the manifold by means of static free uniflow valves (optional).
Prior to hooking the cylinders to the manifold, they have to be made ready by ascertaining that the quantities of acetone contained in them are as per requirement.
This is done by simple weighing on a balance.
During the filling of cylinders they are cooled by water spray so that any temperature rise due to the filling operations and the absorption of gas into the acetone is maintained at an optimum level. There may be some drop in pressure after filling the cylinders for the first time which may necessitate a second or third filling. After disconnection the cylinder are weighed and the quantity of acetylene in them is ascertained. Cylinders are also tested for leaks before storage.
Water meters are provided with the generators to check the quantity of water consumed to determine that the ratio of carbide and water is correct for proper utilisation of the generator. Hoist with skip and chain pulley block is provided to lift carbide from the ground to the generator hopper for filling of hopper.
Instrument air compressor is provided for operating the pneumatic instruments and valves. Apart from the instruments mounted on the generator, some of the control instruments are located on a panel which is installed at a safe distance along with MCC.
It is recommended that the customer keeps a small bank of 4 to 6 numbers of 6M³ Nitrogen cylinders and pipe nitrogen gas to various points of the plant to be able to purge the plant with nitrogen before startup or maintenance .
Electrical lines are to be provided by customer from MCC located at a safe distance to feed carbide screw feed motors, compressor motor controls and instrumentation. Water requirements are also to be noted and catered for.
Special precautions when making the Acetylene Plant building (As per PESO guidelines):
- A safety zone of 15 m. all around the Acetylene Plant from any other building should be provided and a minimum of 9 m. from any slurry pit.
- A separate acetone godown should be constructed and must be provided with a 9 m. safety zone all around.
- A distance of 90 m. must be maintained from any Oxygen Plant in the vicinity.
- All non-flame and explosion proof switches must be provided separately in an enclosure away from the Acetylene Plant building.
- No flammable material should be used for construction of the Acetylene Plant building.
- Both the acetone godown and calcium carbide store as well as the Acetylene Plant building should be wellventilated with ventilators on the roof as well as ground level. All ventilators must be protected with noncorrosive, galvanised mesh, with a minimum gauge of 11 mesh to the linear cm. Covers should be provided on the ventilators so that rain water may not enter through these openings.
- All electrical wiring should be of low voltage in the Acetylene Plant premises. Electrical lines must not cross or run in same trench used for conveying water or steam or acetylene.