CS254627B1 - A method of preprinting a generator gas obtained by gasification of petroleum and tar residues - Google Patents

Abstract

A method of pre-purification of producer gas obtained by gasification of oil and tar residues by partial oxidation with oxygen and steam, in which, during catalytic hydrolysis of carbonyl sulfide on a first catalytic bed containing a Co/Mo/AlgOg type catalyst and on a second catalytic bed containing A12O3, the contained iron and nickel carbonyls are simultaneously removed to a residual value of less than 3 or 1 to 2 mg Fe and Ni per mn of producer gas, consisting in that the hydrolysis of carbonyl sulfide and the removal of iron and nickel carbonyls take place at a temperature of 170 to 250 °C, while simultaneously increasing the steam content in the producer gas to a value of 15 to 20 g H2O per mn, while deposits from the decomposition of both carbonyls are removed from the first catalytic bed during operation of other parts of the pre-purification technological unit

Description

(54) Method for prepressing producer gas obtained by gasification of oil and tar residues

A method for pre-purifying producer gas obtained by gasification of oil and tar residues by partial oxidation with oxygen and steam, in which, during catalytic hydrolysis of carbonyl sulfide on a first catalytic bed containing a Co/Mo/AlgOg type catalyst and on a second catalytic bed containing Al ₂ O _3, the contained iron and nickel carbonyls are simultaneously removed to a residual value of less than 1 to 2 mg Fe and Ni per m _n of producer gas, consisting in the hydrolysis of carbonyl sulfide and the removal of iron and nickel carbonyls taking place at a temperature of 170 to

250 °C, while simultaneously increasing the steam content in the generator gas to a value of 15 to 20 g H ₂ O per m _n , while the deposits from the decomposition of both carbonyls are removed from the first catalyst bed while the other parts of the pre-treatment technological unit are operating

The invention relates to a method for pre-purifying producer gas obtained by gasification of oil and tar residues by partial oxidation with oxygen and water vapor from nickel and iron carbonyls.

The gasification of oil and tar residues by partial oxidation with oxygen and steam produces raw producer gas, which is the starting material for the production of hydrogen and for the production of synthesis gases intended for the synthesis of ammonia, methanol, oxonation of olefins, etc.

Raw generator gas emerging from pressure generators operating at e.g. 3.5 MPa is first freed from the soot contained by pressure washing with water and in subsequent stages the contained hydrogen cyanide, hydrogen sulfide and carbonyl sulfide are removed. It is usual that the generator gas pre-cleaned in this way is freed from sulfur compounds to a value lower than 25 mg/m^.

Raw producer gas also contains iron and nickel carbonyls as impurities. Their formation during the gasification itself and during the treatment of producer gas cannot be prevented. When gasifying petroleum residues, the producer gas produced contains, for example, 3 to 10 mg Fe/m as ^iron pentacarbonyl and 1 to 5 mg Ni/ _m as nickel tetracarbonyl. Both carbonyls pass with the producer gas during its cleaning, such as washing soot with pressurized water, washing hydrogen cyanide with pressurized cold water, during selective washing of hydrogen sulfide and partly also during hydrolysis of carbonyl sulfide on a catalyst packing formed of alumina. It has so far been customary for pre-cleaned producer gas intended for hydrogen production to be fed to the section of high-temperature and low-temperature conversion of carbon monoxide.

In the high-temperature conversion plant, the incoming producer gas is heated to 300 to 350 °C and enters the Fe-Cr conversion catalyst. In the upper layers of this catalytic charge, not only does the conversion of carbon monoxide with the contained water vapor take place, but the complete decomposition of the contained iron and nickel carbonyls also occurs. The products of this decomposition of both carbonyls settle in the catalytic charge, clog it and gradually increase the pressure loss of the production plant. This means that the amount of producer gas fed through must be reduced and that the conversion catalyst charge must be replaced more frequently, which is undesirable.

It has now been found that these problems can be eliminated if the content of iron and nickel carbonyls in the producer gas entering the high-temperature conversion of carbon monoxide is substantially reduced to a value below 1 to 2 mg Fe and Ni/m _n of the producer gas entering. It has been found that this reduction can be achieved in an installed plant intended for the hydrolysis of carbonyl sulfide, whereby the reaction conditions are changed so that in addition to the hydrolysis of carbonyl sulfide by steam, thermal decomposition of the contained nickel and iron carbonyls also occurs.

A method for pre-purifying producer gas obtained by gasification of oil and tar residues by partial oxidation with oxygen and steam, in which, during catalytic hydrolysis of carbonyl sulfide on a first catalytic bed containing a catalyst of the Co, Mo/Al2O3 type and on a second catalytic bed containing _Al2O3 , the contained iron and nickel carbonyls are simultaneously removed to a residual value of less than 1 to 2 mg Fe and Ni per _m2 of producer gas, according to the invention, the hydrolysis of carbonyl sulfide and the removal of iron and nickel carbonyls take place at 170 to 250 °C, preferably at 190 to 220 °C with a simultaneous increase in the steam content in the producer gas to a value of 15 to 20 g _H2O per m2, and deposits from the decomposition of both carbonyls are removed from the first catalytic bed during operation of other parts of the pre-purification technological unit, whereby the producer gas passes outside the catalyst bed for a maximum of 72 hours in 3 to 5 months.

Up to now, the hydrolysis of carbonyl sulfide has been carried out in such a way that the generator gas, which has passed through the first stage of selective washing of hydrogen sulfide using alkazide liquor DIK, whereby the hydrogen sulfide content is reduced from 8 g/m^ to 250 mg/rn^, is saturated with water vapor at about 70 °C and, after preheating, is first passed to the 1st bed of the Co/Mo/Al^O-^ type catalyst and then to the 2nd bed of the catalyst filled with shaped Al ₂ O _3<. The hydrogen sulfide contained is then washed in the second stage of washing with alkazide liquor DIK to a residual value of 25 mg/m\

Ί.

According to the new technological arrangement, the hydrolysis of carbonyl sulfide is now carried out at 170 to 250 °C, preferably at 190 to 220 °C. Increasing the reaction temperature will allow a significant reduction in the content of iron and nickel carbonyls. The decrease in the content of carbonyls can also be inferred from the value of the equilibrium constant as a function of temperature:

„ ^P Ni ^(C0, 4 °C p P ⁴ WHAT - 1.91 x 10 ^-3 150 3.98 x 10~ ⁵ 200 1.78 x 10 ^-6 250 The course of hydrolysis of carbonyl sulfide, according to the procedure established so far and according to the newly proposed a process in which the carbonyls contained are mostly removed iron and nickel are following: Composition of the input producer gas CO2 content 4% mol. content CO 48 contents 46.5 inert 1.5 content I^S 8 years/year>year for the 1st stage of washing 250 mg/ ^m3 /day for the 2nd washing stage 23 mg/ ^m3 carbonyl sulfide content input 3,520 mg/ ^m2 current arrangement new arrangement amount of generator gas m^/h 72,000 72,000 working pressure, MPa 3.15 3.15 water vapor saturation g H^O/m^ 10 19 - COS hydrolysis temperature °C 150 200 amount of catalyst in 1. . v. 3 lodge m 3.15 3.5 in the 2nd bed 16 20 residual COS content ppm vol. 7 7 carbonyl content as Fe/m^ 3.5 0.15 3 as Ni/m _n 1.5 0.1 replacement of the catalyst in the 1st bed at the stop as needed for operation e.g. after • 4 months From the above data it is clear that the majority of carbonyls are removed by the specified

to the hydrolysis of carbonyl sulfide. To prevent the resulting deposits from increasing the pressure loss of the device and from forcing a reduction in the amount of producer gas being pushed through, the following measures were taken:

- both catalyst beds pre-cleaned with producer gas and hydrolysis of carbonyl sulfide were connected in such a way that the first bed filled with the Co/Mo/A^O-^ type catalyst can be separated from operation as needed and the clogged filling can be replaced with a fresh one without shutting down the entire production. When replacing the catalyst in the first reactor, i.e. when replacing 3.J5 m ³ of catalyst, which is carried out as needed, e.g. once every 4 months and which lasts 3 days, i.e. 72 h, the producer gas is only cleaned on the catalyst filling in the second reactor. Compared to the previous state _w 3 3 , however, the catalyst filling in the second reactor was increased from 16 m 3 to 20 m 3 . The total volume

The catalyst loading is therefore 20 m , even with the first reactor removed, which is slightly larger than in the previous arrangement, when the loading in both reactors was 19.5 m . The main amount of deposits from the decomposition of iron and nickel carbonyls is deposited in the first reactor. When the catalyst is replaced in the first reactor three times a year (i.e. 3x3x24= 216 hours), the second reactor is therefore loaded with raw producer gas for 216 hours. During this time, 72,000/m _n x 216, i.e. 15.552 mil/m _n of gas passes through the second reactor, and deposits corresponding to about 73.87 kg Fe + Ni (4.75 mg x 15.552 mil/m^) are captured in the second reactor. With an operating time of 8,000 hours, this is only 2.7% of the total operating time when only the second reactor is loaded, and this is not essential for the smooth operation of the production plant. If the content of iron and nickel carbonyls at the output of the producer gas from the device intended for hydrolysis of carbonyl sulfide increases from 0.25 mg/m _^ to 0.5 mg/m^ when the first reactor is shut down, then this means that the pre-cleaned gas will contain more deposits corresponding to 1 kg of Fe + Ni when 72,000/m^ of the producer quantity is passed through per hour. This increased amount cannot be significantly reflected in the subsequent stages of producer gas processing, especially in the high-temperature conversion section. In order to prevent the residual content of carbonyls in the producer gas from increasing, it is technologically realistic to increase the reaction temperature within the specified range and thus prevent an increase in the residual content of Fe + Ni even when the first reactor is shut down. The removed catalyst can be freed from deposits and reused for the most part.

- The 1st catalyst bed was modified so that it can operate with radial flow of the producer gas. The catalyst filling was replaced, for example, after 4 months. Satisfactory results were also achieved when the producer gas entered axially as before.

During the time of exchange of the catalyst charge in the first catalyst bed, the producer gas enters directly into the second catalyst bed of the reactor and the decomposition products of both carbonyls are deposited on the alumina charge. Since the exchange period of the catalyst charge in the first catalyst bed lasts about 3 days, there is no significant deterioration of the function of this second catalyst bed during this short time, not even when the operating cycle of the entire production line, which lasts 1.5 years, ends;

- 2. the catalyst bed can optionally be modified so that at least part of the filling has radial flow;

- for better heat utilization, the operating unit was equipped with a heat exchanger, in which the heat of the outgoing gas is used to heat the incoming gas with a heat exchange area _ 2 e.g. 160 m ?

- to maintain the hydrolysis of carbonyl sulfide at a value of around 7 ppm vol. when the temperature is increased, the saturation of the gas with water vapor in the installed choke is increased as necessary. For example, the temperature is increased from 70 °C to 90 °C.

The increase in the partial pressure of water vapor in the producer gas has a positive effect not only on the hydrolysis of carbonyl sulfide, but also on the decomposition of both carbonyls. The advantage of the new arrangement is that the amount of deposits in the first high-temperature conversion reactor is significantly reduced and that the conversion section can be fully exploited throughout the entire operating cycle, e.g.

1.5 years.

The proposed modifications to the production equipment are easily feasible and do not require large investment costs.

In the production plant, where two lines for selective hydrogen sulfide scrubbing and carbonyl sulfide hydrolysis are installed, the new operating mode can be introduced gradually.

Claims (1)

SUBJECT OF THE INVENTION Process for pretreatment of a gasifier gas obtained by gasification of petroleum and tar residues by partial oxidation with oxygen and steam, wherein the catalytic hydrolysis of carbonyl sulphide on a first catalytic bed containing a Co / Mo / A ^ O ^ catalyst and a second catalytic bed containing Αΐ2θ3 ^{simultaneously} iron and nickel carbonyls to a residual value of less than 1 to 2 mg of Fe and Ni per m 2 of the generator gas, characterized in that the hydrolysis of the carbonyl sulfide and the removal of the iron and nickel carbonyl takes place at 170 to 250, preferably 190 to 220 ° C the vapor content of the generator gas to a value of 15 to 20 g I 2 O and decomposition deposits of both carbonyl are removed from the first catalyst bed while the other parts of the pretreatment process are operated, the generator gas passing outside the first catalyst bed for a maximum of 72 h within 3 to 5 months.