Acetylene plant: how it works
Acetylene plants are manufactured with complete in-house know-how to produce acetylene gas. Every part has been carefully designed and inspected by experienced engineers. Each unit, after assembly, is charged and worked continuously to check its performance. You are, therefore, assured of an efficient and dependable Acetylene Plant.
Acetylene 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 acetylene plants with twin hopers and need an operator’s attention for only ten minutes in an hour.
The Production Process of acetylene GAS
STEP 1: ACETYLENE GENERATOR
In a stationary Carbide to Water type Automatic Acetylene Generator, acetylene gas is produced by the reaction of calcium carbide with water.
The the following reaction takes place:
Acetylene Gas Generation
The generated acetylene gas occupies the free volume inside the generator shell over the water level. The pressure of this gas rises till it reaches the pre-set 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 generator shell, the pressure inside the generator shell reduces. The pressure controller reactivates the carbide feed motor and adds more calcium carbide through screw feed mechanism to generate more acetylene. This process continues till the carbide in the hopper under operation is exhausted.
Passage of acetylene gas from the generator to the carbide chamber (hopper) under filling is kept shut off by pneumatically operated shut off device. This device 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 generator. This temperature rise cannot be allowed to go unchecked as acetylene is inflammable. Moreover, the optimum generation of acetylene takes place around 60°C. Thus, it is necessary to maintain the generator temperature around 60°C. This is achieved automatically by the temperature controller which is pre-set to 60°C. As the temperature inside the generator rises beyond 60°C, the temperature controller activates the water inlet valve which lets in fresh process water and reduces the temperature of the generator to the desired level.
Discharge of Slurry Lime
As fresh water is introduced to lower generator temperature, the water level inside the generator rises. A slurry discharge valve opens and closes automatically to discharge some slurry and lower the water level to an acceptable.
The generator also incorporates an agitator that is operating along with the carbide feed motor to keep the carbide and water well mixed for complete reaction. This prevents loss of carbide in the form of solids with the slurry.
Step 2: COOLING Chamber
The acetylene generated is passed from the generator chamber through wet type flashback arresters into a low pressure condenser. Here, 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.
Step 3: Low Pressure Drier
The gas is then passed through a low pressure dryer filled with anhydrous calcium chloride. This step is done to remove further quantities of moisture before the gas enters the purifying chamber with an optimum quantity of moisture.
Step 4: Purifying Chamber
The purifying chamber is filled with chemicals which removes phosphorus and Sulphur compounds and any acidic fumes.
Step 5: Scrubber
Thereafter, the gas passes through a water scrubber. Here, additional particles of the purifying chemical that might have been carried over with the gas, are removed.
Step 6: Acetylene compressor
The wet gas then enters the acetylene compressor where it is compressed. Cooling coils and condensate traps are located at every stage. The entire assembly of the compressor is submerged in water for maximum cooling of the acetylene gas.
Step 7: High Pressure Drier
The compressed gas is passed to the high pressure dryer. The mechanical devices and chemicals remove moisture and any lube oil vapor from the gas.
Step 8: Cylinder Charging Manifold
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
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, the gas is cooled by water spray to reduce the temperature to an optimal level.
Safety check for acetylene gas leakage
There may be a drop in pressure after filling the cylinders for the first time. This may necessitate a second or third filling. After disconnection the cylinders are weighed and the quantity of acetylene 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. 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 these instruments, some of the control instruments and MMC are located on a panel installed at a safe distance.
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 start-up 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.