JP2617608B2 - High-temperature reducing gas purification equipment - Google Patents

Description

The present invention relates to a high-temperature reducing gas, for example, a method for removing sulfur compounds such as hydrogen sulfide and carbonyl sulfide contained in a product gas of a coal gasification process. It relates to a purification device.

(Prior Art) In recent years, diversification of fuels or raw materials has been demanded due to depletion of petroleum resources and soaring prices, and coal and heavy oil (tar sand oil,
The development of utilization technologies for oil surreal oil, Daqing crude oil, maya oil, or vacuum residua is being pursued. However, this gasification product gas contains sulfur compounds such as hydrogen sulfide (H ₂ S) and carbonyl sulfide (COS) of several hundreds to several thousand ppm, depending on the raw material coal and heavy oil, and is used to prevent pollution. Alternatively, it must be removed to prevent corrosion of downstream equipment. As a method for this removal, the dry method is thermoeconomically advantageous and the process configuration is simple, so that a method of absorbing and removing an absorbent mainly composed of a metal oxide at a high temperature into a sulfide at a high temperature is generally used. Has become.

As the absorbent, metal oxides such as Fe, Zn, Cu, Mo and W are used, and reacted with hydrogen sulfide and carbonyl sulfide at 250 to 500 ° C.

Hereinafter, a case where H ₂ S is removed by using an Fe ₃ O ₄ absorbent will be described as an example. The absorption reaction proceeds as shown in equations (1) and (2).

Fe ₃ O ₄ + H ₂ + 3H ₂ S → SFeS + 4H ₂ O (1) Fe ₃ O ₄ + CO + 3H ₂ S → SFeS + 3H ₂ O + CO ₂ (2) Next, the absorbent after the absorption reaction is an oxygen-containing gas. Then, the metal oxide (Fe ₂ O ₃ ) is regenerated by reacting as shown in equation (3), and the sulfur compound in the high-temperature reducing gas is recovered and removed as SO ₂ gas.

4FeS + 7O ₂ → 2Fe ₂ O ₃ + SO ₂ (3) Further, after the regenerating reaction, by passing a reducing gas such as H ₂ , CO, etc., the absorbent becomes as shown in equations (4) and (5). To the original Fe ₃ O ₄ . Thus, by repeating the absorption reaction, the regeneration reaction, and the reduction reaction, the metal oxide (Fe ₃ O
_The sulfide can be removed from the high-temperature reducing gas by effectively utilizing ₄ ).

3Fe ₂ O ₃ + H ₂ → 2Fe ₃ O ₄ + H ₂ O (4) 3Fe ₂ O ₃ + CO → 2Fe ₃ O ₄ + CO (5) The absorbent used in this process is the above metal An oxide alone or a support made of a heat-resistant porous substance, which is formed into a spherical, cylindrical, or honeycomb shape, is usually used.

Next, a conventional apparatus will be described with reference to FIGS. FIG. 2 is a diagram showing a process flow of a high-temperature reducing gas purifying apparatus at a stage where the reaction tower 1 is placed in an absorption step, the reaction tower 2 is placed in a reduction step, and the reaction tower 3 is placed in a regeneration step. FIG. 3 is a diagram showing the relationship between all the pipes and valves of the reaction tower 1.2.3, in which the white valves indicate the open state and the black valves indicate the closed state, and correspond to FIG. It shows the state. FIG. 4 is a diagram showing a time chart of a cycle in which three reaction columns are switched to an absorption step, a regeneration step, and a reduction step, and FIG. 5 shows the open / closed state of all valves in FIG. 3 over time. FIG.

The high-temperature reducing gas subjected to the treatment flows into the reaction tower 1 in the absorption step via the pipe 10 and the pipe 44, and comes into contact with the absorbent (Fe ₃ O ₄ ) 100 filled in the reaction tower to make the (1) By the reactions of the formulas (2) and (2), the sulfide in the gas to be treated is absorbed and removed, and the purified gas is recovered through the pipe 45 and the pipe 11, and is sent as a fuel or the like to a turbine or the like of a subsequent device, for example. Further, a part of the purified gas is introduced into the reaction tower 2 in the reduction step through the pipe 13 branched from the pipe 45, and the reducing component (H ₂ , CO) in the purified gas and the absorbent after the regeneration step (Fe ₂
O ₃ ) and by the reaction of formulas (4) and (5),
The absorbent is reduced to Fe ₃ O ₄ . At this time, by installing the flow rate detection controller 30 and the valve 31 in the pipe 13 connected to the reaction tower 2, the flow rate of the purified gas supplied to the reaction tower 2 can be controlled to a predetermined fixed amount. On the other hand, an oxygen-containing gas is introduced into the reaction tower 3 in the regeneration step via pipes 23, 24, 25, and 15, and the sulfur component (FeS) and oxygen absorbed by the absorbent according to the equation (3). To generate SO ₂ gas, and the absorbent is regenerated from FeS to Fe ₂ O ₃ . The regenerated absorbent is transferred to the above-described reduction step, where Fe ₃ O
Reduced to ₄ . Exhaust gases from the reaction tower 2 in the reduction step and the reaction tower 3 in the regeneration step are integrated via pipes 12, 14, and 16, and the exhaust gas heated by the heat of oxidation reaction in the regeneration step is supplied to a heat exchanger. At 4, the gas is cooled by heat exchange with the oxygen-containing gas, and further sent to the cooler 5 via the pipe 17.
At this time, a pipe 27 branched from the inflow pipe 10 for the gas to be treated is connected to the pipe 17 and a part of the gas to be treated is added to the exhaust gas. The addition amount of the gas to be treated is controlled by operating the valve 33 by the gas flow rate detection controller 32. Then, the external exhaust gas is cooled by the refrigerant supplied to the pipe 28 in the cooler 5, further introduced into the reduction reactor 6 through the pipe 18, and comes into contact with the reduction catalyst 101 (6) and (7). It reacts according to the formula to produce the carrier sulfur Sx. The temperature in the reduction reactor is a temperature at which the reactions of equations (6) and (7) can easily proceed (for example,
250 ° C) and the temperature detection controller 34 and the cooler 5
Is controlled by a valve 35 that operates the refrigerant flow rate.

SO ₂ + 2H ₂ → (1 / x) Sx + 2H ₂ O (x = 2-8) (6) SO ₂ + 2CO → (1 / x) Sx + 2CO ₂ (x = 2-8) (7) The gas containing elemental sulfur vapor flowing out of the reduction reactor 6 is cooled by the refrigerant supplied by the pipe 29 in the cooler 7, introduced into the condenser 8 through the pipe 20, and supplied as liquid elemental sulfur from the pipe 77 through the pipe 77. Collected. At this time, the temperature in the condenser 8 is controlled by the temperature detection controller 36 and the valve 37 for controlling the flow rate of the refrigerant in the cooler 7 so as to be lower than the condensation temperature of sulfur. On the other hand, the inert gas (main component N ₂ ) from which sulfur has been removed by the condenser 8 enters the circulating blower 9 via the pipe 21, and the circulating flow is kept constant by the valve 39 and the flow rate detection controller 38 installed in the pipe 21. Is controlled. This inert gas is integrated with the air or oxygen from the pipe 23 through the pipes 22 and 24 from the circulation blower 9 and enters the heat exchanger 4 to be heated. The oxygen concentration in the pipe 24 is controlled to a predetermined value by the oxygen concentration detection controller 40 and the valve 41. The oxygen-containing gas is heated by the heat exchanger 4 and enters the reactor 3 in the regeneration step via the pipes 25 and 15. In addition, a part of the inert gas in the pipe 22 is connected to the pipe 10 for introducing the gas to be treated via the pipe 26, and merges. A valve 43 is provided in the pipe 26 and is controlled by a pressure detection controller 42 so that the pressure of the circulation blower 9 becomes constant.

If the absorption process is continued for a certain time, the total amount of Fe ₃ O ₄
Since it changes to eS, the sulfide flows out of the reactor 1. Therefore, before the sulfide flows out, the valves 61, 64, 68, 70, 75 shown in FIG. 3 are closed and the valves 62, 63, 69, 7
By opening 1,73, the reactor 1 is shifted from the absorption step to the regeneration step, the reactor 2 is shifted from the reduction step to the absorption step, and the reactor 3 is shifted from the regeneration step to the reduction step. FIG. 4 shows the switching situation of each reactor with the duration of each step being 4 hours, and FIG. 5 corresponds to FIG.
It shows the open / closed state of the valves 61 to 75 in the figure. By sequentially switching the three reactors in this way, the desulfurization purification of the reducing gas is continuously performed.

(Problem to be Solved by the Invention) In the above-described purification apparatus, a part of the purified high-temperature reducing gas is introduced into the reactor 2 in the reduction step at a constant flow rate (4).
Although the absorbent is reduced from Fe ₂ O ₃ to Fe ₃ O ₄ by the reaction of the formula (5), there is no means for confirming the completion of the reaction. Even after the completion, high-temperature reducing gas was often introduced, wasting valuable purified gas.

Therefore, the present invention has solved the above-mentioned disadvantages of the purification apparatus,
An object of the present invention is to provide an apparatus for purifying a high-temperature reducing gas that can surely perform a reduction treatment of an absorbent without wasting purified high-temperature reducing gas.

(Means for Solving the Problems) The present invention provides a reaction tower filled with an absorbent for absorbing a sulfur compound in a high-temperature reducing gas, a gas to be treated, an oxygen-containing regeneration gas, and a high-purity gas. A pipe for supplying and discharging the reducing gas is connected via a valve, and by opening and closing the valve, the reaction tower can be sequentially changed to an absorption step, a regeneration step, and a reduction step. In a high-temperature reducing gas purifying apparatus provided with a gas flow detection controller and a gas flow control valve operated by an output signal of the controller in a pipe for supplying a reducing gas, a discharge pipe of a reaction tower in a reduction step is provided. Is provided with a reducing gas concentration detector, a function generator for inputting a detection signal of the detector and outputting a set value is provided, and an output signal from the function generator is input to the gas flow rate detection controller. Gas flow control A high-temperature reducing gas purifying apparatus characterized in that a supply of a high-purity reducing gas to a reaction tower in a reduction step can be controlled by adjusting a node valve.

(Operation) The present invention limits the supply of a high-purity reducing gas supplied to the reaction tower in the reduction step, for example, a purified gas discharged from the reaction tower in the absorption step, to a minimum supply necessary for reducing the absorbent. By doing so, waste of the purified gas is suppressed. That is, since an increase in the reducing gas component in the gas discharged from the reaction tower in the reduction step means the end of the reduction reaction, the reduction gas concentration in the exhaust gas is detected to reduce the reduction gas component. The purpose is to stop the supply of the high-purity reducing gas to the reaction tower in the process and eliminate waste of the high-purity reducing gas that does not contribute to the reduction reaction.

Specifically, a reducing gas concentration detector is installed in a discharge pipe of a reaction tower in a reduction step, a detection signal of the detector is input to a function generator, a set value is output, and a set value is output. A signal is input to a gas flow rate detection controller provided at a reaction tower inlet pipe in a reduction step, and a gas flow rate control valve of the input pipe is operated to control supply of a high-purity reducing gas.

(Example) An example of the present invention will be described with reference to FIG. The apparatus shown in FIG. 1 is different from the conventional apparatus shown in FIG. 2 in that a reducing gas concentration detector 79 is installed at an outlet pipe 12 of a reaction tower 2 in a reduction step, and a detection signal of the detector 79 is transmitted to a function generator 80. To output a set value. The output signal is input to a gas flow rate detection controller 30 provided at the inlet pipe 13 of the reaction tower 2, and the gas flow rate control valve 31 of the inlet pipe 13 is adjusted to perform a reduction process. Reaction tower 2
The flow rate of the reducing gas supplied to the device is controlled, and there is no difference in other device configurations. Therefore, as for the other device configurations, the same members as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 6 shows an example of a function set in the function generator 80 described above. Immediately after switching from the regeneration step to the reduction step, the entire amount of the absorbent 100 in the reaction tower 2 is in the state of Fe ₂ O ₃ , and the amount of H ₂ and CO contained in the purified gasification product gas and the above (4)
It reacts as shown in equation (5). For this reason, H ₂
And CO are all consumed in the reaction. As a result, H ₂ and CO do not flow out of the outlet of the reaction tower 2. When the supply of the gasification product gas to the reaction tower 2 is continued, Fe ₂ O ₃ in the absorbent is reduced from the inlet and is successively reduced to Fe ₃ O ₄ . When all are reduced, H ₂ and CO flow out of the outlet of the reaction tower 2. Therefore, a reducing gas concentration detector installed at the outlet pipe 12 of the reaction tower 2
The reducing gas concentration is detected at 79,
If the ratio of the content of H ₂ and CO is constant, it is possible to control by detecting either. Although FIGS. 1 and 6 describe the case where the H ₂ concentration is detected and controlled, the control may be performed based on the CO concentration. In FIG. 6, while the H ₂ concentration measured by the detector is 1.0%, the flow rate F of the gasification product gas to the reaction tower in the reduction step is kept constant, and as the H ₂ concentration increases, the flow rate F is reduced. When the H ₂ concentration reached 2.0%, the supply of the gasification product gas was stopped. FIG. 4 and FIG.
In order to perform each operation in the cycle shown in the figure, it is necessary to secure a sufficient supply of H ₂ and CO so that the above reduction operation can be completed within 4 hours.

(Effect of the Invention) By adopting the above configuration, the present invention can detect the end of the reduction reaction in the reduction step, and suppress the supply of the purified reducing gas to the reaction tower to the minimum necessary. As a result, the purified gasified purified gas, which is a valuable fuel gas, is not wasted.

[Brief description of the drawings]

FIG. 1 is a view showing a process flow of a purification apparatus according to one embodiment of the present invention, FIG. 2 is a view showing a process flow of a conventional apparatus, and FIG. 3 is a relation between all pipes and valves of a reaction tower. FIG. 4 is a diagram showing a time chart of a cycle in which three reaction towers are switched to each step. FIG. 5 is a diagram showing the open / closed state of all valves in FIG. 3 over time. FIG. 6 is a diagram showing one specific example of a function set in the function generator in the embodiment.

Claims (1)

(57) [Claims] 1. A reaction tower filled with an absorbent for absorbing a sulfur compound in a high-temperature reducing gas, and a gas to be treated, an oxygen-containing regeneration gas, and a high-purity reducing gas are supplied to and discharged from the reaction tower. A pipe is connected via a valve, and the reaction tower can be sequentially changed to an absorption step, a regeneration step, and a reduction step by opening and closing the valve, and a pipe for supplying a high-purity reducing gas to the reaction tower in the reduction step. In a high-temperature reducing gas purifying apparatus provided with a gas flow rate detection controller and a gas flow rate control valve operated by an output signal of the controller, a reducing gas concentration detector is provided in a discharge pipe of a reaction tower in a reduction step. A function generator for inputting a detection signal of the detector and outputting a set value, and inputting an output signal from the function generator to the gas flow rate detection controller to adjust a gas flow rate control valve. , Reduction process That the supply of high-purity reducing gas into the reaction tower was controllable apparatus for purifying high-temperature reducing gas which is characterized in.