Self-sealing devices in gypsum production

One of the most famous units of gypsum production, which has been used for many decades, is a vertical stationary self-sealing device that makes it possible to process gypsum crushed stone with a grain size of 10-50 mm into high-strength gypsum. Over the long life of the device, many changes were made to its design, which increased its efficiency, reduced production costs or simplified its maintenance.

As a rule, a vertical self-sealing device includes:

• metal cylinder 1800x3000x8 mm;
• upper and lower pipe walls and manholes and pipes welded into them that allow hot gases to pass through;
• gas-conducting metal pipes, manholes and covers adjacent to them, which are hermetically sealed by means of folding bolts;
• a glass with a perforated hemisphere inserted into the opening of the lower hatch and designed to prevent gypsum rubble from entering the neck of the lower hatch;
• a metal truncated cone of 1800x470 mm that protects gypsum rubble from burnout and guides it into the opening of the lower manhole;
• cylindrical steel mesh 510x8 mm, which protects the air supply pipes (fittings) from being blocked by gypsum rubble;
• 76 mm air supply pipe and 25 mm fittings;
• connection for steam, water and air removal;
• two gas collectors, one of which is designed to supply hot gases to the pipes, and the second, on the contrary, to take hot gases out of the pipes. Both manifolds have flanges for connecting to flues and 4 manholes for cleaning;
• four metal brackets for hanging the devices;
• the device is equipped with a pressure gauge with a scale of up to 2 at, a safety valve and two thermometers with a scale of up to 360° and up to 600-700°.

The outside of the device is covered with a protective thermal insulation based on the calculation that the temperature on the surface of the device will not exceed + 35°.

The device operates under the vacuum created by the smoke extraction fan, so it is necessary that the cleaning hatches available on the gas collectors are hermetically sealed; otherwise, cold air may be sucked in and, in addition, the useful operation of the fan is reduced. Usually, one medium-pressure fan is installed on four devices. Each unit has two slide gates; one on the gas supply pipe and one on the gas discharge pipe. These valves regulate the gas supply to the device, and also provide the ability to disconnect the device from the gas network in case of its repair. The temperature of the exhaust gases varies between 250-360° C; therefore, the exhaust pipe is made of metal with a thickness of 2-3 mm. Attempts to use waste gases to mix them with hot gases supplied to the device (by recirculation), and thereby regulate the temperature constancy of 600-700° C, practically did not lead to positive results. Since maintenance personnel usually do not pay due attention to this and do not monitor the constancy of the temperature of incoming gases, therefore, the newly designed plants do not provide for the use of exhaust gases, and they are released into the atmosphere. According to the author, such a provision is permissible only in the case where the fuel is waste from local industries, for example, sawdust and shavings; in other cases, some of the exhaust gases should be used. First of all, the heat of the exhaust gases should be used to heat the steam collected from the apparatuses and the air supplied to the apparatus during the heating and drying of gypsum crushed stone. These measures are easily implemented, and the effect is significant, since the heating and drying process is accelerated, and therefore the entire cycle of processing gypsum crushed stone in apparatuses. Air is supplied to the devices by pumping it with a fan.

In cases where steam is generated from the heat of gases coming from the apparatus, the gypsum rubble should be heated by steam; in this case, the heating process is sharply reduced, and after 30-40 minutes the required pressure is created in the apparatus.

You can get 200-250 kg of steam from each samozaparnik and collect it in a special steam collector. The amount of steam pressure in the steam collector is not significant, since steam coming from the steam collector to the device through special (air) fittings immediately comes into contact with hot pipes, overheats and washes gypsum rubble, already being in an overheated state. This method of heating should be arranged in factories where there are four or more devices. In the end, it is also possible to supply ordinary water to the air supply pipe, which, when it enters the nozzle ring, also turns into steam, and this accelerates the process of heating the crushed stone.

No additional devices are required to remove the water produced by condensation of steam during the heating of gypsum rubble. The resulting condensate is discharged through a special pipe located at the lower hatch.

Specially instructed workers, so-called "apparatchiki" or, as they are sometimes called, "zaparschiki", are allowed to operate the apparatuses. Instructing these apparatchiks is mandatory, since the devices operate under high pressure.