JPS61204023A - Desulfurizing method using pressurized water - Google Patents

Abstract

PURPOSE:To remove H2S and SO2 in the simple treatment by sending both a gas contg. H2S and a gas contg. SO2 simultaneously and continuously into the pressurized water free form an additive and allowing both to perform the Claus reaction. CONSTITUTION:Both a gas contg. H2S and a gas contg. SO2 are sent into a reactor 1 charged with water free from an additive through the lines 2, 3 and the soln. in bubbled in the pressurization. The Claus reaction is made active together with passage of time and elemental sulfur is produced and made slurry. The slurry of sulfur is sent to a separator 5 through a line 4 to separate it into water and sulfur and sulfur is discharged through a line 6 and water after the separation is circulated to the reactor 1 through a line 7. After the desulfu rized gas removed with the large parts of H2S and SO2 is sent to a cooler 11 via a line 10 to condense and separate the accompanied steam, it is washed with water in a purification tower 13 to remove the nonreacted H2S and SO2 and discharged or recovered through a line 14.

Description

Detailed Description of the Invention This invention provides hydrogen sulfide (H2S) or sulfur dioxide gas (SO2
).

The Claus reaction, in which H2S and 302 are reacted to produce elemental sulfur, is widely used as a desulfurization method for gases containing H2S or SO2.

A method of conducting the Claus reaction underwater has also been attempted, but in this case, even if H2s and S02 are simultaneously introduced into the water,
It is said that they do not react effectively because their dissolution rates in water are different.

In additional tests conducted by the present inventors, S02 was 2,500 ppm in an absorption reactor filled only with water.

H2S:5. When a gas containing OOppm (the rest is nitrogen) is fed and maintained at 40 kg/cm2G, H2S in the reactor outlet gas reaches 4,000 ppm, with almost no absorption or reaction. (Due to the fast absorption rate of S02 into water, only a trace amount is initially detected in the reactor outlet gas.) Therefore, suitable absorption enhancers such as boron oxyacid, phosphorus oxyacid, citrate, etc. Using a dissolved aqueous medium, the aqueous medium first absorbs S02 (absorption step), and the absorbed water is fed with H2S-containing gas under pressure to perform the Claus reaction (reaction step) in two stages. Law (
(Special Publication No. 52-28113, Japanese Patent Publication No. 59-207808)
is proposed.

In addition, as the reaction continues, 820 s' in the aqueous medium,
There are also problems in that ions such as 5406' and SOa' are produced, the pH is lowered, the solubility of 502 is reduced, the reaction rate is lowered, and equipment materials are corroded.

Problems to be Solved by the Invention The present invention solves the problems associated with the liquid phase Claus method and provides a method for effectively desulfurizing gas containing H2S or 502 by simple means. The purpose is to

Composition of the Invention Means for Solving the Problems When researching a desulfurization method using the liquid-phase Claus method, the present inventors investigated the most basic reaction mechanism when only water is used without adding any additives. When we conducted tests on the reaction rate and reaction rate, we surprisingly found that even if H2S and 502 were simultaneously introduced into water, they did not react sufficiently and H2S It has been found that the phenomenon of outflow occurs for a while after the start of the reaction, and if the reaction is continued despite such conditions, the desulfurization rate gradually decreases.

To explain the situation using Figure 2, an absorption reactor filled with only water contains SO2: 2,500 ppm, H2S25
．． When a gas containing OOOppm (the rest is nitrogen) is fed and maintained at 40Kg/cm2G, H in the reactor outlet gas
2S was initially 4.000 PPm, but after 10 hours it became 370 ppm, and that level was maintained thereafter.

Even after continuing for 200 hours, no decrease in the reaction rate was observed.

The desulfurization method of the present invention was completed based on such new knowledge, and involves simultaneously immersing H2S-containing gas and 502-containing gas in pressurized water that does not substantially contain additives.
That is, it is characterized in that it is continuously fed into the same aqueous phase and the Claus reaction is carried out in water.

An example of a process for carrying out the invention is shown in FIG.

A H2S-containing gas and a S02-containing gas are fed from lines 2 and 3 to a reactor l filled with water (not containing additives) and bubbled under pressure.

As can be seen from the test results shown in FIG. 2, as time passes, the Claus reaction becomes more active and elemental sulfur is produced, which accumulates in the reactor I and becomes slurry. The sulfur slurry is sent via line 4 to separator 5 where water and sulfur are separated. Sulfur becomes liquid at about 120'0, so if the separator is maintained above this temperature, the sulfur will be discharged in liquid form from line 6 at the bottom of the separator. The water from which sulfur has been separated is circulated to the reactor 1 via line 7, and since the water generated by the Claus reaction and the water added to the system for gas cleaning are excessive, they are sent to the neutralization tank 8 for neutralization. and discharge from line 9.

The desulfurized gas from which most of H2S and SO2 have been removed is sent via line 10 to a cooler 11, where the accompanying water vapor is condensed and separated, and then sent via line 12 to a purification tower 13, where it is washed with wood supplied from line 15. to remove unreacted H2S and SO2, which are then discharged or recovered via line 14.

Also, in the condenser li, H2S and SO2 are present in the condensed water.
The Claus reaction proceeds and increases the desulfurization efficiency.

The water separated by the cooler 11 passes through the line 16 to the line 1.
Together with the water supplied from 5, it is used as wash water and is further fed via line 17 into the circulating water line 7 to the reactor 1.

In order to demonstrate the effects of the present invention, a stainless steel (inner diameter 27 mm) bubble column reactor with a 2-hole diameter sintered metal dispersion plate was filled with a predetermined amount of water, and then a predetermined amount of H2s-N2
and 5O2-N2 mixed scum was supplied through a flow meter, and the change in gas composition at the outlet of the reactor over time was analyzed and tracked by gas chromatography (detection tube for 100 ppm or less) until the composition became constant.

Example 1 The effect of pressure on H2S and SO2 conversion was tested. The results are shown in Table 1.

Table 1 As is clear from Example 1 of the low-force saw, a desulfurization rate of about 60% can be obtained even when the pressure of the reaction water is 0.5 Kg/cm2; however, when the pressure of the reaction water is 5 Kg/cm2 The above is about 9
A desulfurization rate of 0% can be achieved.

At a gauge pressure of 40Kg/cm2, both the H2S conversion rate and S02 conversion rate are 98% or more, and the gauge pressure is 60-80Kg/cm2.
At cm2, both are 99% or more. There is no need to use pressures further north than those possessed by the raw material waste, as higher pressures are not harmful but do not have any particularly significant effect.

If the upper limit of 10,000 pressure is to keep the desulfurization rate constant,
The higher the H2S and SO2e content in the process gas, the lower it tends to be, but from Table 1, the pressure effect becomes more pronounced5.
K g /CDI of 2 or more is preferred.

Example 2 The effect of the S02/H2S molar ratio on the conversion of H2S and SO2 was tested. The results are shown in Table 2.

The supply molar ratio of SO2/H2S is the theoretical value of Claus reaction 0.
．． Almost complete reaction rate can be achieved at around 5, so it is usually 0.
．． The range of 4 to 1 is preferable. However, depending on the combination process, it is also possible to consciously remove 502/H2S from the theoretical value, leaving one to remain and the other to be removed more reliably.

The effect of contact time on the conversion of H2S and S02 was tested. The results are shown in Table 3.

0.003 hours (10.8 seconds) is enough.

If the pressure and SO2/H2S molar ratio are optimal, it will take 0.0017 hours (6.1 seconds) as is clear from Tables 1 and 2.
However, good desulfurization efficiency can be achieved.

Example 4 The effect of reaction temperature on the conversion of H2S and 502 was tested. The results are shown in Table 4.

According to Table 4, the reaction temperature has little effect on the desulfurization rate, but it is preferable to operate at room temperature to 160°C. 160
If the temperature is above ℃, handling of the produced f&yellow becomes difficult.

Furthermore, if the temperature of the reactor is maintained at 120° C. or higher, the produced sulfur is in a liquid state, so sulfur can be produced and separated in the reactor without installing a separate separator.

As is clear from Example 3, the present invention is effective in reducing the amount of 0.0% in the raw material gas.
Low concentration (7) H2S of 3% (3,000 ppm)
, or even at a low concentration of 502 of 0.18% (1,800 ppm), a high conversion rate of nearly 100% can be achieved. However, it is appropriate to target a gas in which the concentrations of SO2 and H2S in the raw material gas are each 100 ppnn or more. At concentrations lower than this, the amounts of both dissolved are small and a sufficient desulfurization rate cannot be expected.

The present invention is applicable to, for example, natural gas containing H2S, partially oxidized gas of heavy oil and coal, off-gas containing H2S during petroleum refining,
It is suitable for refining Claus process tail gas or combustion exhaust gas containing SO2. In addition to these, C
Even gases containing O2 can be selectively desulfurized. In particular, it is suitable for removing H2S to generate methanol synthesis gas from natural gas containing H2S and CO2.

The present invention can be carried out in a highly acidic region where the pH of the absorption liquid is 6 or less and about 1. As shown in Figure 1, washing water in the purification tower and by-product water from the Claus reaction are constantly added to the absorption liquid, and excess water is discharged from the neutralization tank, so that acidity in the absorption liquid increases. The accumulation of ions is suppressed to a certain limit, and the pH is maintained within the above-mentioned optimum pH range even without adding a neutralizing agent or a pH regulator.

Effects of the invention a) H2S and SO2 can be easily removed by in-cylinder treatment.
It can be removed in less than pp.

b) Since only water is used as the absorption liquid, there is no need for PH buffers or other chemicals to promote absorption as in conventional methods, and a reduction in operating costs can be expected.

C) Unlike the gas phase catalytic oxidation method, it does not require a catalyst, so there is no need to consider troubles related to the catalyst.

d) Since the Claus reaction is carried out at low temperature, H into the produced sulfur is
The amount of 2SX by-product is small, and the H2SX removal process can be expected to be simplified.

[Brief explanation of the drawing]

Figure 1 shows an example of a process flow sheet for carrying out the present invention, and Figure 2 shows the basic principle of the present invention that the desulfurization rate improves over time and stabilizes at a high level after a certain period of time. FIG. Applicant JGC Co., Ltd. Company Agent
Patent Attorney Masa Ao Asa No. 2 711

Claims (1)

[Claims] 1 H_2S-containing gas and SO_2-containing gas are simultaneously and continuously fed into pressurized water that does not substantially contain additives,
A desulfurization method using pressurized water, which involves carrying out a Claus reaction in water. 2. The method according to claim 1, wherein water is used under pressure of 5 kg/cm^2 or more gauge pressure.