JPS60202202A - Combustion method with low sulfur oxide - Google Patents

Abstract

PURPOSE:To inhibit the formation of sulfur trioxide in combustion gas by adding hydrocarbon group fuel when burning combustion gas containing sulfur component. CONSTITUTION:When burning combustion gas containing sulfur component, hydrocarbon group fuel is added, and the formation of sulfur trioxide in combustion gas is inhibited. That is, when fuel gas rich in carbon and CO is burnt while aiming at a fact that lowering as much as possible of the partial pressure of CO in a combustion zone has an effect on the inhibition of SO3, hydrocarbon fuel is used as a combustion assist. Accordingly, the generation of sulfur trioxide at a time when fuel gas containing S component is burnt is suppressed, and trouble, such as the deterioration of the performance of a catalyst in a denitrifier on the rear flow side and the corrosion, blocking, etc. of an air heater can be prevented.

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention relates to a low sulfur oxide combustion method, and in particular to a method for reducing sulfur dioxide in the exhaust gas of a waste heat recovery boiler using fuel gas from a regeneration tower in a fluidized catalytic cracking method. The present invention relates to a combustion method suitable for reducing <s' o 3).

(Background of the invention) Since the oil crisis, fuel diversification has been promoted, and even in the field of gasoline production using fluid catalytic cracking (FCC), the feedstock oil has changed to conventional naphtha and diesel oil, and the sulfur content (8
Heavy oil containing a large amount of

The catalytic cracking method is a method for producing high-octane gasoline by decomposing the high-boiling heat content of petroleum oil, which is higher than that of kerosene, at high temperatures in the presence of a catalyst. Although it cannot be said that all reactions in catalytic cracking have been elucidated, they are roughly as follows. That is,
It is characterized by a first-order decomposition of the raw material hydrocarbons and a second-order reaction of the olefins produced. The integral reaction is the production of olefins through the decomposition of nonorahin and the dealkylation of naphthenes and aromatic compounds, and among these, the decomposition of paraffins is the fastest. The olefin thus produced subsequently undergoes secondary reactions such as decomposition, hydrogen isomerization rearrangement, polymerization, cyclization, and alkylation. in this case,
When a fluidized bed system is used, the decomposition reaction occurs in the reaction tower riser, which originally plays the role of feeding the catalyst and feedstock oil into the reaction tower.
Since the contact time with the catalyst is short, undesirable secondary reactions do not occur. Therefore, it is known that the amount of coke produced is small compared to the reaction inside the reaction tower, and more gasoline is produced.

FIG. 1 shows an overview of the fluid catalytic cracking (FCC) method. Feedstock oil passes through a pipe 12 and enters the reaction tower riser 1 together with circulating oil from a pipe 15, where it is transferred to the regeneration tower 2.
The high-temperature catalyst from provides the necessary amount of heat for the decomposition reaction. The catalyst is carried upward along with the evaporated oil gas, is partially decomposed, and enters the reaction column 3. The remaining reaction is completed here, and the oil gas is separated from the catalyst by the cyclone 4 at the top of the reaction tower 3 and enters the rectification tower 5. Further, a certain amount of catalyst is continuously extracted from the reaction tower 3 and returns to the regeneration tower 2 through the waste catalyst U-bend 6 and the waste catalyst riser 7. In the regeneration tower 2, air burns the carbon deposited on the catalyst to perform regeneration. The regenerated catalyst is again circulated to the reaction column 3 via the overflow well 8 and the regenerated catalyst U bend 9. On the other hand, the generated combustion gas is separated from the catalyst by a cyclone 10 at the top of the regeneration tower 2, and is discharged to the outside of the system through a flue 11. In the figure, 6 is a waste catalyst U-bend, 7 is a waste catalyst riser, 13 is a combustion air pipe, 14 is a regulating air pipe, 1
6 is a steam pipe.

Here, in the process of burning the coke deposited on the catalyst surface to recover the reaction heat and regenerate the catalyst, for example, zeolite is used as the catalyst, but the temperature inside the regenerator 2 is kept below 700°C to prevent deterioration of the catalyst. must be suppressed. In addition, as mentioned above, since heavy oil is used as the feedstock, the combustion gas contains CO1f(2, H2S, etc.).Furthermore, due to environmental issues, the combustion zone is It is necessary to implement measures such as two-stage combustion, which creates a state of excess fuel and injects the insufficient amount of air from its wake.As a result, compared to the combustion of normal hydrocarbon fuels, SO3 is produced during the combustion process. The problem is that it occurs in large quantities.

Even if a denitrification device or a desulfurization device is installed in the flue as an environmental measure against combustion exhaust gas, the following problems will occur if the gas contains a large amount of SO3.

First, in denitrification equipment, when using the NH3 selective reduction method, ammonium is injected into the system at approximately 350°C, resulting in deterioration of catalyst performance due to the formation of NH4H3O4 and blockage of the air heater (A/H) on the downstream side. This may cause problems such as corrosion and corrosion. In addition, in desulfurization equipment, when processing gas containing a large amount of 303, if a wet method such as alkaline cleaning is used, the SO3 is rapidly cooled and becomes fog.
, and the performance is not sufficient. Therefore, if a dry activated carbon adsorption method were to be used, it would be necessary to reduce the space velocity (SV), and in order to prevent corrosion in relation to the dew point of H2SO4, it would be necessary to maintain a high exhaust gas temperature. Issues such as increased energy loss remain.

For the reasons described above, when processing gas containing a large amount of sulfur (S) in a waste heat recovery boiler, it is desirable to suppress the amount of SO3 generated at the combustion stage as much as possible.

(Objective of the Invention) The object of the present invention is to eliminate the drawbacks of the prior art described above, and to reduce sulfur trioxide from the sulfur contained in the fuel gas containing sulfur, especially the fuel gas from the regeneration tower in the FCC. The object of the present invention is to provide a low sulfur oxide combustion method that can reduce the amount of sulfur oxides generated.

(Summary of the invention) In short, the present invention focuses on the fact that reducing the 00 partial pressure in the combustion zone as much as possible is effective in suppressing SO3, and when burning carbon and GOIJ lunch fuel, The system uses hydrocarbon fuel as the fuel. That is, the present invention is characterized in that when combusting fuel gas containing sulfur, hydrocarbon fuel is added to suppress the generation of sulfur trioxide in the combustion gas.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 2 is for explaining the present invention in detail, and shows the conversion rate of SO2 to SO3 produced by combustion of various fuel gases. Here, Co, H2 and C are used as fuel.
H, and the concentration of SO□ added to the combustion gas is 0.
It was varied from 1% to 3.0%. The results show that in all flames, the conversion rate from SO□ to SO+ decreases as the concentration of SO2 added to the combustion gas increases. Furthermore, when CO gas is used as a fuel, the conversion rate to SO3 is the highest, followed by H2 gas and CH4 gas, decreasing sequentially. , it can be seen that it has increased from 5 to 7 times.

Next, FIG. 3 shows a similar experiment in which the amount of 803 generated was investigated when a S-containing twisted material containing CO3, H2S and CH3SH was burned. from this result,
It can be seen that the amount of S03 generated in the CO8 flame is extremely large. In this way, when CO exists in the fuel gas,
It was found that a large amount of 803 was generated. Therefore, CO
A combustion product gas from a regenerator in a fluid catalytic cracking (FCC) process when heavy oil is typically used as a feedstock (a large amount of CO1H2, H).

In a waste heat recovery boiler that uses S03), a large amount of S03 is generated.

The present invention focuses on the fact that the amount of 803 generated is small when using hydrocarbon fuel (CH4, etc.), and supplies the hydrocarbon fuel into a combustion device, such as a waste heat recovery boiler, to reduce the partial pressure of CO. This is intended to reduce the amount of S03 generated.

(Embodiment of the Invention) FIG. 4 is an explanatory diagram of a combustion test apparatus showing an embodiment of the method of the present invention. The reaction tube 51 is made of quartz tube with an inner diameter of 109 mm, and from the burner 52 at the bottom, C01H
Fuel gas containing 2S is supplied in a premixed state with air, and hydrocarbon fuel (C3H in this test) is supplied from the downstream supply hole 53.

etc.) is injected as a combustion improver. A sampling probe 54 is installed near the outlet of the reaction tube to measure the SO3 concentration. In the figure, 55 is an electric furnace, 56 is a compressor, 57 is a flue, 58 is a fuel gas pipe, 59 is a fuel air pipe, 60 is a combustion improver air pipe, and 61 is a combustion improver pipe. C in the fuel gas supplied from the burner 62
The concentrations of O and H2S simulated the combustion gas from an actual FCC regeneration tower, with C0 = 9% and H2S = 700 ppm (
fixed). The amount of combustion improver (C3H8, etc.) injected was varied from 0 to 3 Qwt% of the amount of gas from the burner 52. The combustion improver was supplied in two ways: one was to supply a predetermined amount together with air through the supply hole 53, and the other was to supply it in a premixed state together with the fuel gas from the burner 52.

The above test results are shown in FIG. 5, and it can be seen that the amount of S03 generated is significantly reduced in cases B and C when a combustion improver is added, compared to case A when it is not added.

In addition, it has been found that it is sufficient to supply the combustion improver at 5~lQwt% or more of the fuel gas containing CO, etc.
・I did. Furthermore, as for the supply method, B is better when the fuel gas is supplied in a premixed state with the fuel gas from the burner 52.
It was also found that when a combustion improver was added, the amount of SO3 generated could be slightly reduced compared to C. In addition, in this test, C3H was used as a combustion improver.

was used.

Next, the results of experiments similar to those described above using various hydrocarbon fuels as combustion improvers will be described. Here, the combustion improver used was CH, which is representative of hydrocarbon fuel.
4, C3H8, kerosene and light oil. Further, the supply amount was kept constant at 1Qwt% of the fuel gas, and the fuel gas was supplied in a premixed state with the fuel gas containing CO and the like. The results are shown in Table 1.

Table 1: From the above results, it was found that all the hydrocarbon fuels used in this test had a large effect on reducing S03.

(Embodiment of the Invention) FIG. 6 is a diagram showing an apparatus system that uses low-calorie combustion gas from a catalyst regeneration tower of an FCC plant as fuel for a waste heat recovery boiler. The regeneration tower of the FCC plan 41 is equipped with a waste heat recovery boiler 42 having a combustion improver pipe 43 according to the present invention. The exhaust gas from the waste heat recovery boiler 42 is processed by a denitrification device 44, an air heater 45, a desulfurization device 46, and a wet electrostatic precipitator 47, which are provided downstream, and then sent to the chimney 4.
It is discharged from 7. A part of the gas generated from the reaction tower can be used as a supply source of the combustion improver. 7th
The figure shows an example in which gas generated from a reaction tower of an FCC plant is introduced into a waste heat recovery boiler 42 through a line 71 as a combustion improver.

According to the embodiment described above, in the fluid catalytic cracking (FCC) process using heavy oil containing a large amount of 8 min as feedstock, low-calorie fuel gas discharged from the regeneration tower is sent to the waste heat recovery boiler 42. When used, various adverse effects caused by S03 in the denitrification bag w44, air heater 45, etc. in the downstream can be prevented. Moreover, this expands the range of feedstock oils used in FCC, and inexpensive heavy oil can also be easily used, making extremely economical operation of FCC possible.

The present invention is applicable not only to FCC cracking processes, but also to sulfur-containing fuel gases produced from other similar fossil fuel cracking or combustion processes.

(Effects of the Invention) As described above, according to the present invention, the generation of sulfur dioxide when burning fuel gas containing 8 minutes can be suppressed, and the catalyst performance in the downstream denitrification device can be reduced, and the air heater can be corroded and blocked. It is possible to prevent such troubles.

[Brief explanation of the drawing]

Figure 1 shows an overview of fluid catalytic cracking (FCC), and Figure 2 shows the S02 to 8 generated by combustion of each M fuel gas.
Figure 3 is a diagram showing the conversion rate to SO3, Figure 3 is a diagram showing the amount of SO3 generated when fuel containing 8% is burned, Figure 4 is
FIG. 5 is a diagram showing the test results conducted using the test device shown in FIG. 4, and FIG. 6 is a diagram showing a combustion test apparatus according to an embodiment of the present invention. FIG. 7 is a partial diagram showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Reaction tower riser, 2... Regeneration tower, 3... Reaction tower, 4... Reaction tower cyclone, 5... Rectification column, 6
... Waste catalyst U Hair 1', 7 ... Waste catalyst riser,
8... Overflow well, 9... Regenerated catalyst U hand, 1o... Regeneration tower cyclone, 11... Flue,
12... Raw oil piping, 13... Combustion air piping, 1
4... Conditioned air piping, 41... FCC plant, 4
2... Waste heat recovery boiler, 43... Combustion aid piping, 44
...Denitration equipment, 45...Air heater, 46...
Desulfurization equipment, 47... Wet EP, 48... Chimney. Agent Patent Attorney Takeshi Kawakita Fig. 2 Fig. 3 Barb Kaunoyu JfL (mm) There is a stealth attack - 1 (wt'/,)

Claims (1)

[Claims] (1) Low sulfur oxide combustion characterized by adding hydrocarbon fuel when burning fuel gas containing sulfur to suppress the generation of sulfur dioxide in the combustion gas. Law. (2. The low sulfur oxide combustion method as set forth in claim 1, characterized in that the amount of hydrocarbon fuel is 5 wt% or more of the amount of fuel gas. (3) Claim 1 The low sulfur oxide combustion method according to item 1 or 2, wherein the fuel gas is a fuel gas generated from a catalyst regeneration tower in a fluidized catalytic cracking method.