CN1168526C - Improved complex iron method for removing sulfide from gas - Google Patents

Abstract

The present invention relates to an improved complexing iron method for eliminating sulphide in gas, which belongs to the technical field of gas purification. The present invention is characterized in that complexing iron desulfurizing agents mainly contain molysite, complexing agents, absorbing agents, stabilizing agents, sulfur modifying agents and corrosion inhibitors, and the pH value of doctor solution is from 6.5 to 8.5 preferably. The composition and the proportion of desulfurizing agents are different according to different kinds of gas containing sulphur raw materials. The present invention has the advantages of stable performance, no corrosion to carbon steel, easy sulfur recovery, elimination of most of organic sulfur, etc. The desulfurizing agent of the present invention eliminates inorganic sulfur and can eliminate organic sulfur as required simultaneously.

Description

Complex iron method for removing sulfide from gas

The technical field is as follows: a method for removing sulfide in gas by an improved complex iron method belongs to the technical field of gas purification, and particularly belongs to the field of wet type oxidation reduction method desulfurization.

Background art: techniques related to the present invention:

removal of H from gas streams by US 4,374,104₂S method and composition, the patent proposes that a complex iron solution containing high valence state and H₂S, gas contact is carried out, hydrogen sulfide in the gas is removed and reduced into elemental sulfur, and meanwhile, the complexing iron solution at least contains a nonionic surfactant to prevent the formation of sulfur foam;

US 4,421,733 method for removing hydrogen sulfide from gas by using stabilized complexing iron solution, in which unique hydrosulfite is added to complexing iron solution to prolong service life of complexing agent, NaHSO is added to solution₃Then, the degradation amount of the sulfur complexing agent is less than 0.07 g per 1g of generated sulfur complexing agent;

removal of H from gases by US 4,774,071₂S, the patent proposes that the hydrogen sulfide in the gas is removed by adopting an absorption liquid with the content of low-valence metal ions being 5 times of that of high-valence metal ions, so as to reduce the degradation of a complexing agent;

US4,871,520 composition and method for removing hydrogen sulfide, which patent proposes the use of a novel complex iron solution containing unique Fe³⁺/Fe²⁺The solution contains ammonia and other inorganic salts, and the adopted complexing agent has very high solubility in water, so that the high-concentration complexing iron solution can be prepared. And the solution is stable and does not generate precipitate;

5. the study on the desulfurization of TEA complex iron by Vol.22, No.11, P11, university of east China's university, describes TEA and citric acid as complexing agents for iron, with a total iron concentration of 1g/L and an iron ratio of Fe³⁺The total Fe is more than 70 percent. The PH value is more than 8.5, and the method mainly considers the economy of solution cost ratio ADA, FD and the like;

6. chemical fertilizer industry 1984, 65(5), 17-22, CN complex iron desulfurization experiment. The article describes the use of FeSO₄To catalyzeThe desulfurizer takes alkali or ammonia as a desulfurizer of an absorption medium, and the desulfurization efficiency is 97-99%;

CN93112429.8 describes an improved process for removing sulfide from gas by complexing iron, the desulfurization solution is composed of iron salt complexing agent, hydrosulfide absorbent, desulfurization solution stabilizer, synergist and corrosion inhibitor, wherein the desulfurization stabilizer is polyhydroxy sugar, the corrosion inhibitor is tungsten corrosion inhibitor, and the concentration of iron is 0.0001-0.054 mol/L;

the patent application CN1227135 describes a technique for decarbonizing, desulfurizing and decyanating gas by iron-alkali solvent catalysis, in which the alkaline saline solution containing iron ions is used to remove organic sulfur and inorganic sulfur, hydrogen cyanide and carbon dioxide from gas, and the ferricalkali solution can produce by-product sulfur when it is regenerated by air under the catalysis of hydroquinone and iron ions.

The invention content is as follows: compared with the prior art, the absorption solvent of the invention is added with the organic sulfur hydrolysis catalyst, so that most of organic sulfides can be removed while inorganic sulfur is removed; secondly, the unique antimony compound corrosion inhibitor is added into the solvent in the formula, so that the corrosion of high-concentration complex iron solution to carbon steel can be effectively prevented; in addition, the invention adopts the cooperation of reducing salt and special biochemical bactericide to maintain the stability of the complexing agent.

The desulfurizer containing high valence state iron contacts with gas containing sulfide, so that the sulfide in the gas phase is absorbed by the complex iron desulfurizer and is oxidized into sulfur at the same time, the desulfurizer is characterized in that the complex iron desulfurizer mainly contains ferric salt, a complexing agent, an absorbent, a stabilizer, a sulfur modifier and a corrosion inhibitor, and the pH value of the desulfurization solution is preferably 6.5-8.5; the composition and the proportion of the desulfurizer are different according to different raw gases containing sulfur.

Wherein the iron salt complexing agent is one or more than one carboxylic acid, amino carboxylic acid, such as: EDTA, NTA, HEDTA, citric acid, tartaric acid; the stabilizer is reducing salt and bactericide; the absorbent is inorganic alkali and heterocyclic amine organic matters; said corrosion inhibitionThe agent is an antimony corrosion inhibitor which mainly contains benzotriazole, sodium antimonate, sodium p-toluenesulfonate, sodium phosphate, HF, bismuth nitrate and selenium oxide; the iron salt may be FeSO₄·7H₂O、FeCl₃、FeCO₃。

The desulfurization process of the invention is carried out in an absorption tower in a complex state of Fe³⁺As an oxidizing agent, H in a liquid₂S is oxidized to sulphur, which is itself reduced to Fe²⁺Complexing Fe in the regeneration column²⁺Oxidized to complex Fe in contact with oxygen³⁺Recovering the oxidation performance, and then returning to the absorption tower to absorb sulfide, wherein the main reaction is as follows:

and (3) total reaction:

in order to adapt to the removal of different sulfur-containing raw material gases, the invention designs three desulfurization process flows. The first process flow is that the packing absorption tower absorbs sulfide in gas under normal pressure and normal temperature, and air is introduced to oxidize and regenerate under normal pressure and normal temperature. The second process flow adopts jet absorption or empty tower coarse desulfurization and packed tower fine desulfurization. Normal pressure and normal temperature regeneration process. The third process flow adopts the absorption of sulfide and the oxidation regeneration of low-valence metal ions in the same tower.

The first procedure is suitable for the sulfur compound content<0.5%, CO₂The removal of sulfur-containing raw gas with the content of less than 30 percent, such as semi-water gas and conversion gas. The iron ion concentration is 0.01-0.05 mol/L, the alkali concentration is 2-20 g/L, the stabilizer/Fe is 0.5-1.2, the bactericide is 10ppm, and the antimony corrosion inhibitor is 5 mg/L. By fillingThe material tower absorbs sulfide in the gas source, the air is oxidized to regenerate the complex iron solution, the complex iron solution is in countercurrent contact with the sulfur-containing feed gas in the absorption tower, and Fe in the complex iron solution³⁺Is reduced to Fe²⁺The sulphide is removed from the gas and the sulphide ions are reduced to elemental sulphur. The pregnant solution absorbing the sulfide contacts with air in a regeneration tower, and ferrous iron ions are oxidized into ferric iron ions; the sulfur concentrated in the regeneration tower is removed by centrifugal separation in a centrifugal machine, the desulfurizer is returned to the circulating tank, and the gas H treated by the method₂S content less than 5mg/m³The organic sulfur removal rate is more than 80 percent.

The second process is suitable for occasions with high sulfur content, such as refinery gas, the total sulfur content is 1-10%, and CO is₂Less than 10 percent, adopts an empty tower coarse depacking absorption tower for fine dehydration, and specially designs a high-efficiency gas distributor in the tower in order to improve the removal efficiency of the empty tower, thereby improving the gas-liquid mass transfer efficiency. The absorption sulfur of the complex iron in the coarse desulfurization process is as high as 0.8-2.0 g/L. 0.2-0.6 mol/L Fe exists in the coarse desulfurization process³⁺Conversion to Fe²⁺The content of sulfide in raw material gas after coarse removal is less than 10g/m³The gas after coarse removal enters an absorption tower of a filler to be in countercurrent contact with a high-concentration complex iron solution, and Fe in the solution³⁺Conversion to Fe²⁺The sulfide in the gas is reduced into sulfur, and the pregnant solution absorbing the sulfide enters an oxidation regeneration tank and is emptiedGas contact, so that Fe in the solution is obtained²⁺Conversion to Fe³⁺Recovering oxidation performance, and purifying gas H treated by the method₂The S content is less than 10ppm, and the organic sulfur removal rate is more than 80 percent.

The third flow path, absorption and regeneration, is carried out in the same device, and the flow path is suitable for treating sulfur-containing raw gas or acid waste gas with higher oxygen content. The method adopts the iron concentration of 0.005-0.2 mol/L and the alkali concentration of 2-25 g/L; 0.8-1.5% of stabilizer/iron; 10-30 ppm of bactericide and 5-10 ppm of defoaming agent; the concentration of the sulfur modifier is 10-100 ppm. Fe of the complex iron solution when absorbing sulfide in the device³⁺Conversion to Fe²⁺While Fe in solution²⁺Is oxidized into Fe by oxygen in the gas³⁺Recovery of oxidation energyForce. Under the quick drive of the air flow, sulfide in the gas is circularly absorbed, sulfur generated in the absorption process is polymerized and settled under the action of a sulfur particle modifier and is concentrated at the bottom of the device, concentrated sulfur particles are discharged into a centrifugal machine from a liquid discharge port to centrifugally separate solid sulfur, and clear liquid returns to a system. H in tail gas treated by the method₂The content of S can reach the exhaust emission standard.

The desulfurizer of the invention can remove inorganic sulfur and organic sulfur at the same time according to requirements. The invention has the advantages of stable performance, basically no corrosion to carbon steel, easy recovery of sulfur, capability of removing most organic sulfur and the like.

Description of the drawings:

FIG. 1 is a schematic process flow diagram of example 1 of the present invention; FIG. 2 is a schematic process flow diagram of example 2 of the present invention; FIG. 3 is a schematic process flow diagram of example 3 of the present invention.

The specific implementation mode is as follows: the invention is described in detail below with reference to the figures and examples.

The example is shown in FIG. 1 and is suitable for the first process flow. The raw material gas (1) enters a gas distribution tank (2) to be configured into a sulfide concentration of 1-5 g/m³The experimental gas enters the bottom of the absorption tower (3) and is in countercurrent contact with the desulfurization solution from top to bottom, the sulfide of the gas is absorbed by the complex iron solution (4), and the purified gas (5) after desulfurization enters a gas-liquid separator (6) to remove entrained desulfurization agent and then enters a subsequent working section. The pregnant solution (7) absorbing the sulfide is discharged from the bottom of the absorption tower (2) and enters an oxidation regeneration tank (8) to be contacted with air (9), and Fe in the pregnant solution²⁺Is oxidized into Fe³⁺Air used and CO released from the solution₂The resulting mixture (10) is drained from the regeneration column. Sulfur particles settle at the bottom of the regeneration tower during the regeneration process. The concentrated sulfur (11) enters a centrifuge (12) for liquid-solid separation, the sulfur is taken out, the recovered liquid (13)is sent into a regeneration tank (8), the regenerated complex iron liquid enters a circulating tank (14) from the top of a regeneration tower,then is pumped into an absorption tower through a pump (15)And (5) circulating absorption.

Second embodiment referring to FIG. 2, regarding the second flow, the gas (1) is fed into the buffer tank (2) and the concentration of sulfide is set to be 0-100 g/m³The gas enters from the bottom of an absorption tower 1(3) and is fully mixed with the complex iron solution in the tower, most of sulfide in the gas is absorbed by the complex iron solution, the treated gas (4) enters into the bottom of an absorption tower 2(5) through the absorption tower 1(3) and is in countercurrent contact with the desulfurization solution from top to bottom, and the gas (6) from which the sulfide is removed enters into the subsequent working section through a gas-liquid separator (7). The rich liquid (8) from the absorption tower 1(3) and the rich liquid (9) from the absorption tower 2(5) are mixed and enter an oxidation regeneration tank (10) to be mixed and contacted with air (11), and the Fe in a reduction state in the oxidation regeneration tank (10)²⁺Is oxidized into Fe³⁺The sulfur ions in the solution are oxidized into elemental sulfur, and the air is regenerated and reacts with CO released from the solution₂The mixed gas is discharged into the atmosphere (12), and the lean solution (13) which is regenerated by oxidation enters a circulating tank (15) to be mixed with the added fresh solution (14) and is pumped into the absorption tower 1 and the absorption tower 2 by a solution pump (16) for circulating absorption. The sulfur formed in the regeneration tank is polymerized and settled at the bottom of the regeneration tank under the action of the sulfur particle modifier, the concentrated sulfur solution (17) is sent to a centrifuge (18) to separate the sulfur, and the clear liquid (19) is sentto a circulating tank.

In the third embodiment, as shown in fig. 3, corresponding to the third process flow, it is especially suitable for the treatment of acidic waste gas, in this scheme, acidic gas (1) is introduced into the bottom of the device (2) and uniformly dispersed in the absorption liquid through the gas distributor (3), the bottom of the air (4) input device (2) is sprayed into the solution through the gas distributor, after the acidic gas and the complexing iron solution are fully contacted and reacted, the purified gas and the regenerated air are discharged from the device through the vent (6), sulfur is deposited on the bottom of the device (2) and discharged into a centrifuge (8) through a drain outlet to remove sulfur, and the desulfurization liquid is returned to the system.

Claims (1)

1. A process for removing sulfide from gas by complex iron method features that the desulfurizing agent containing high-valence iron is contacted with the gas containing sulfide to make the sulfide in gas phase be absorbed by the desulfurizing agent and oxidizedThe sulfur is prepared, and the complex iron desulfurizer is characterized by containing iron salt, complexing agent, absorbent, stabilizer, sulfur modifier and corrosion inhibitor, and the pH value of the desulfurization solution is 6.5-8.5; composition range for gas is CO₂When the volume content is less than 30 percent and the sulfide content is less than 0.5 percent, the process flow of normal temperature and normal pressure absorption is adopted, and the prepared complex iron comprises the following components: 0.01-0.05 mo1/L of total iron concentration, 2-20 g/L of alkali concentration, 0.5-1.2 mol ratio of stabilizer/total Fe, 10ppm of bactericide and 5-50 mg/L of antimony corrosion inhibitor; composition range for gas is CO₂When the volume content is less than 10 percent and the volume of the total sulfur content is 1-10 percent, adopting a process flow of empty tower or jet absorption rough removal and fine removal in a series packed tower to prepare a stabilizer/total Fe (0.8-1.5 mol ratio), a bactericide of 10-50 ppm, a sulfur modifier of 50-100 ppm and a corrosion inhibitor of 0.05-5 g/L, wherein the iron concentration is 0.1-0.6 mol/L, the alkali concentration is 2-20 g/L; composition range for gas is CO₂% of the acid waste gas with the volume content of 10-80% and the total sulfur with the volume content of 0.5-30% is absorbed and regenerated in the same tower, so that the power consumption is saved, and the complex iron solvent consists of the following components; the iron-containing composite material is characterized by comprising 0.005-0 mol/L of total iron, 2-25 g/L of alkali, 0.8-1.5 mol ratio of stabilizer/total Fe, 10-30 ppm of bactericide, 5-10 ppm of defoaming agent, 10-100 ppm of sulfur modifier and 0.05-5 g/L of corrosion inhibitor.

Images