SU912263A1 - Zeolyte regeneration method - Google Patents

Description

one

This invention relates to a regenerant.

zeolites during the deep drying of pyrogas in ethylene production and can be used in the regeneration of sorbents in other processes of fine drying of gases, as well as in the oil, petrochemical and gas industries.

In modern ethylene plants, pyrogas undergoes fine drying on zeolites before entering the low-temperature, fractionation system. The regeneration of the adsorbent from moisture, as in most adsorption processes, is carried out by heating the layer with a hot gas.

A known method for the regeneration of zeolite KA-3M 1 by regeneration gas with a humidity corresponding to the dew point () at 220 or, with this time, the sorbent is kept at the temperature of the gas at the outlet of the adsorber 220 or

is respectively 35 and O h pi.

The disadvantage of this method is the required long exposure time of the sorbent at the reached limiting temperature; as a result, it is not possible to withstand the cyclical switching of the adsorbent to drying and regeneration if there are three adsorbents in the circuit, as is the case with existing ethylene plants. A long exposure time of the sorbent at elevated temperatures also leads to a drop in the moisture capacity of the sorbent and a significant expenditure of energy.

There is also a known method of regeneration, which consists in the fact that the litter; bent is blown at BSO-iOOC with atmospheric air with a concentration of water vapor of 2.8 10 - 50 sub-temperatures of ° C per minute C21. 391 The closest in technical essence to the proposed regeneration method is that the sorbent is heated and purged with a hot methane – hydrogen fraction at a pressure of atm heated in a tube furnace, and as a result, the temperature in the sorbent layer is gradually brought to. The duration of the sorbent heating and aging at 21 h 3J. The disadvantages of these regeneration methods are that the method does not allow maintaining the stable moisture capacity of zeolites for a long time of operation, following the violation of their structure and lack of moisture in the process of regeneration at high temperature. The last factor is especially manifested during the drying of gas pyrolysis, when unsaturated hydrocarbons present in gases are sorbed at the adsorption stage, at the regeneration stage they turn into polymers and coke, which plug the pore openings. During multi-cycle operation (after 80 cycles of adsorption .- desorption), a significant decrease in the adsorption capacity and drying quality is noted. The coke content is 3 .. Therefore, the service life of zeolites for drying pyrogas in ethylene plants is about 8000 h, me; This method is characterized by high energy consumption. The purpose of the invention is to increase the lifetime of the adsorbent and reduce the energy intensity of the process. This goal is achieved by the fact that, according to the method of regeneration, the heating of the zeolite layer is carried out up to 10-200 C, then purge the layer at the same temperature with a lawn with a moisture content corresponding to the dew point (-70) - (). An inert gas, individual saturated hydrocarbons or their mixtures with or without hydrogen are used for purging; the gas feed rate is 1000–2000 h at a pressure of 1–6 at. The difference is the indicated 1 | e parameters of heating and purging of the zeolite layer and the gases used. Note E.P. 1. Moisture-saturated pyrogas during deep drying, zeolites KA, NaA without a binder, with a volume of 6 O ml and a bed height of 20 cm are heated with continuous nitrogen purge with a flow rate of 1000 h, to 1 0200 C for 2 hours and kept at this temperature for another hour. The dew point of nitrogen is (-70) - () C, the pressure is atmospheric. The results characterizing the effect of regeneration temperature on the drying properties of zeolites are given in Table. 1. Table 1

KA KA

-75

200 -70 200 -70

NaA without -75 200 per

-71

200 -70

200

-7 -70 -55 -73

-72 -72 59 In the last experiment, regeneration is carried out with methane. As can be seen from the above results, at a regeneration temperature of 200, the degree of drying achieved corresponds to the dew point (-70) (-7), which satisfies the moisture requirements of pyrogas used in low-temperature separation systems. By reducing the regeneration temperature to the dry gas point, the moisture content decreases by 3. However, in those industries where the moisture content requirements are limited to the specified moisture content, the zeolite can be regenerated with more moderate heating.

According to the proposed method, a mild temperature (–200 ° C) and a slight warm-up and holding time (total hours) allow us to avoid the polymerization of unsaturated hydrocarbons sorbed by the zeolite at the drying stage, and consistently preserve the drying properties. So, at the indicated temperature regime of regeneration, the carbon content on the zeolite KA-3M after 50 cyclones of drying — regeneration is 0, which does not affect the moisture capacity of the zeolite. The use of this method in industrial conditions increases the service life of zeolite up to 2-3 years, i.e. up to 16000 h, while existing installations overload

the sorbent is carried out every year. The energy consumption is reduced due to the fact that the regeneration gas is heated to lower temperatures and its consumption will be less due to the insignificant regeneration time.

Claims (3)

The use of moderate temperatures simplifies the regeneration process, allows you to replace the heating of the purge gas in the furnaces with the heating in heat exchangers, where heat of water vapor is used, which is cheaper. At the same time, capital costs are reduced. At the same time, the proposed regeneration mode ensures the restoration of the adsorption properties at the drying stage: point 200C, i.e. regeneration temperature can be reduced to. Example 2. Saturated in the process of deep drying of pyrogas (ethylene, air, nitrogen) KA zeolite in an amount of 200 CM, a layer height of 35 cm is heated to 200 C for 3 hours and at this temperature it is maintained for another hour while continuously supplying the methane-hydrogen fraction at a rate of 2000 hours, the moisture content of the menat-hydrogen fraction corresponds to the dew point of –70, the pressure is 6 at. After a certain number of cycles has been carried out, the dew point of the dried pyrogas does not change and is equal to -70 ° C, the water-holding capacity remains at the same level. The results are shown in Table. 2. Table2 7912 dew of the dried stream at a regeneration temperature (-70) - (- 7), which satisfies the tpe6oBaHMHM presented to pyrogas in relation to the content of water vapor in the process of deep drying for further use in installations of low-temperature fractionation of pyrogas Claims 1. Method for regenerating zeolites for drying gases, including heating and blowing a layer of gas at elevated temperature and pressure, characterized in that, in order to increase the service life of the adsorbent and reduce the energy intensity of the process in zeolites, it is carried out up to IO200®S, and the purging is carried out with gas with agogenic content corresponding to the dew point (-701 (- (- 75). 2. The method of claim 1, characterized in that an inert gas is used for purging hydrocarbons or their mixtures with hydrogen with a feed rate of tOOO-2000 h at a pressure of 1-6 at. Sources of information taken into account in the examination 1. Kravtsova EA, Talisman LV,, Kadatska VF Refining and petrochemistry. Sat, 1972, No. 8, 2. USSR author's certificate “66211, cl. B 01 D 15-06.15.05.79. 3. Bobrova LA, Leontyev A.S., Solkov A.S. Oil refining and petrochemistry. Sci. Sat, 1972, If 10, p. 25-30 (prototype).