Improvement of vacuum carbonate desulfurization process

In the production of coke for ironmaking and the production of city gas by coke oven method, a large amount of highly toxic hydrogen sulfide and hydrogen cyanide are generated, and carbon dioxide, a combustion product of hydrogen sulfide, is one of the sources of environmental pollution. In order to remove harmful substances such as hydrogen sulfide and hydrogen cyanide from coke oven gas and improve the air quality and ecological environment in the surrounding area, a coking plant of a company introduced a vacuumcarbonate desulfurization and de-cyanide process technology from Japan .

vacuum coating machine,pvd coating machine,pvd vacuum machine,vacuum ion coating machine,multi-arc ion coating machine

The process is as follows: the hydrogen sulfide in the coke oven gas is removed by the carbonate, and the rich liquid is analyzed under vacuum; the analyzed acid gas is produced by the Claus process, and the process is s* in China. . Since the process is analyzed under vacuum and the sensible heat of circulating ammonia is used as the distillation heat source, the main component of the absorption liquid, sodium carbonate, can be regenerated, and can be decomposed by the sea component, thereby having less steam consumption, less process gas, and low operating cost. The utility model has the advantages of small occupied area and good environmental protection, but the process also has some problems after being put into operation, mainly because the pipeline equipment is easy to be blocked, and the problem of plugging of the desulfurization device is particularly prominent.

First, the principle of the desulfurization device

The function of the desulfurization device is to remove hydrogen sulfide and hydrogen cyanide in the coke oven gas to obtain a net gas, and simultaneously recover the hydrogen sulfide and the hydrogen cyanide acid gas to the SCL process. The main component of the absorption liquid used to remove the coke oven gas is sodium carbonate, the temperature is about 35 ° C, and the main reaction of the absorption tower is as follows:

Na2CO3+H2S-NaHCO3+NaHS

NaCO3+HCN-2NaCN+ NaHCO3

Na2CO3+CO2+H2O-2NaHCO3

The desulfurization rich liquid is produced by the reaction, and in the regeneration tower which maintains the vacuum state, the absolute pressure of the top of the tower is 85/Hg, the absolute pressure of the bottom of the tower is 100/Hg, the liquid at the top of the tower is about 51.7 ° C boiling, and the generated steam and the top of the tower The rich liquid is reversely contacted on the surface of the filler to precipitate acid gas, and the reaction is as follows:

vacuum coating machine,pvd coating machine,pvd vacuum machine,vacuum ion coating machine,multi-arc ion coating machine

NaHCO3+NaHS-Na2CO3+H2S

2NaCN+ NaHCO3―NaCO3+HCN

2NaHCO3―Na2CO3+CO2+H2O

The precipitated acid was cooled to 27 deg.] C through the gas by the vacuum pump is pressurized to an absolute pressure of 150 KPa, and then cooled after the separation step taken SCL. Due to the generation of acid vapor, some other substances entrained in the gas, such as naphthalene and polymers reacted under high temperature and high pressure, are generated, and these substances have an influence on the equipment.Therefore, when absorbing gas, how to eliminate the influence of these substances on the equipment; and try to get rid of these substances, it becomes a key factor for the normal operation of the desulfurization equipment.

Second, the desulfurization device process improvement

1. Desulfurization device process

The coke oven gas from the benzene washing is fed into the bottom of the desulfurization absorption tower, and is in reverse contact with the absorption liquid from the liquid distributor at the top of the tower, and the purified gas is sent out through the mist trap. The absorption liquid is boosted by the rich liquid pump, and the lean and rich liquid heat exchanger is heated to the top of the regeneration tower, and the rich liquid is analyzed in the regeneration tower to extract acid vapor, and the absorption liquid is regenerated. The absorption liquid is analyzed to release acid gas such as hydrogen sulfide, hydrogen cyanide or carbon dioxide from the top of the regeneration tower together with water vapor, cooled to 42 ° C by steam divider, steam cooled to 25 ° C, and then passed through the gas-liquid separator. The jacket steam heating is increased by about 2 ° C, pressurized by the vacuum pump, sent to the acid vapor cooler, and the acid vapor is cooled to 40 ° C. It is sent to the SCL process via an acid vapor separator. The condensed water separated in the steam divider, the steam cooler, and the gas-liquid separator is collected into a condensation tank. Most of the condensed water is pressurized by the condensate pump and sent to the lean pump inlet. The condensate from the acid vapor cooler, the acid vapor separator, and a small amount of lubricating oil leaked from the vacuum pump are filled through the water seal tank. Cool the sink. The oil-containing condensate in the coolant tank is pumped once a day through the condensate to the mechanized tar ammonia clarification tank.

2. Problems and improvements

During the operation of the desulfurization and dehydrogenation unit, the desulfurization and dehydrogenation effect is good. However, since the acid vapor contains more naphthalene and oil, in the process of acid vapor cooling, naphthalene is easily crystallized in the cooling equipment acid vapor cooler, which increases the system resistance. Large, the cooling effect is deteriorated, and the amount of entrainment in the gas is increased, which causes inconvenience to subsequent processes.

vacuum coating machine,pvd coating machine,pvd vacuum machine,vacuum ion coating machine,multi-arc ion coating machine

In order to solve the existing problems, that is, the analysis and demonstration, we have made some improvements to the desulfurization device:

1) Add a new mist eliminator to the desulfurization unit after washing the benzene tower to reduce the naphthalene and washing oil entrained in the gas;

2) Control the final cooling temperature, ranging from 21 to 23 °C, to reduce the entrainment of naphthalene in the gas;

3) Renovate the acid vapor cooler, from horizontal to vertical cooler, install a mist trap at the outlet, and add irregular acid vapor condensate at the bottom of the acid vapor separator for flushing.

3. Improved effect

After a period of operation, after analysis and comparison, the following advantages are achieved after the transformation:

1) The clogging phenomenon of the desulfurization device is reduced, the running time is increased, and the clogging phenomenon is basically eliminated from the original 25 days;

2) Due to the increased running time, the number of inspections is reduced and the consumption is saved;

3) Reduce the impurities in the acid vapor, provide a strong guarantee for the operation of the SCL parts, and reduce the probability of blockage in the subsequent process.

Third, further consolidation measures

In order to further stabilize the operation of the desulfurization unit, we have also developed a regular purge of the acid vapor cooler and the new mist trap to ensure the normal operation of the fan and stabilize the desulfurization operation.