JPH03250091A - Method for removing mercury from liquid hydrocarbon - Google Patents

Abstract

PURPOSE:To realize the removal of mercury (compound) contained in a liquid hydrocarbon by a simple process at a high rate of removal, by bringing a liquid hydrocarbon into contact with an aqueous solution containing a specified sulfur compound. CONSTITUTION:A liquid hydrocarbon (e.g natural gas condensate) is brought into contact with an aqueous solution containing a sulfur compound of the formula MM'Sx (wherein M is an alkali metal or ammonium; M' is H or M; (x) is 1 to 6), preferably an aqueous solution of a mixture of Na2S4 with Na2S, at 40 deg.C or higher.

Description

[Detailed Description of the Invention] 10 Objects of the Invention [Field of Industrial Application] Natural gas condensate, which is a liquid hydrocarbon, has recently begun to be used as a raw material for ethylene. Natural gas condensate can contain up to several ppm of mercury, depending on the region of production. Mercury must be removed because it causes corrosion of low-temperature heat exchangers, poisoning of catalysts, and deterioration of the working environment.

[Conventional technology] Natural gas condensate contains elemental mercury, ionic mercury,
It contains organic mercury (refractory mercury), and the amount varies depending on the production area. Elemental mercury can be removed using an adsorbent, ionic mercury can be removed using a NazS aqueous solution, and organic mercury can be removed using a solid acid. The amount of adsorption was small (there were some practical problems).

[Problems to be Solved by the Invention] The present invention improves the removal rate of not only elemental mercury and ionic mercury but also organic mercury, and in particular, provides an economical liquid hydrocarbon solution that can simultaneously remove these mercury and consumes less chemicals. The purpose is to provide a mercury removal method.

8. Constitution of the invention [Means for solving the problem] The method for removing mercury and mercury compounds contained in a liquid hydrocarbon of the present invention is based on a method for removing mercury and mercury compounds contained in a liquid hydrocarbon. Aqueous solutions containing sulfur compounds, especially NaaS4 and N
It is characterized in that it is brought into contact with a mixed aqueous solution of a and S at a temperature of 40°C or higher.

As the sulfur compound represented by 2MM'Sx, for example, Na
aS, NaH3,K, S, NH3, (NH4)2S
, NH4HS, Na2S4, K, S4, etc.
In the case of a polysulfide in which X is 2 or more, it is often a mixture of sulfides in which X is different. Among these, NaaS,
Particularly preferred are Na2S4, K, S, K, S4, and the like.

The removal rate of mercury and mercury compounds can be increased by bringing a liquid hydrocarbon into contact with an aqueous solution of these compounds at a temperature higher than room temperature, usually from 40 to 200°C.

According to the present invention, mercury and mercury compounds in various liquid hydrocarbons, particularly liquid hydrocarbons obtained from natural gas condensate or petroleum-associated gas, can be removed.

In carrying out the present invention, when removing mercury from natural gas fundensate, it is desirable to wash the natural gas condensate with water in advance. Some natural gas condensates contain ethylene glycol and surfactants used in the production process, and these can be mixed with an aqueous solution containing a sulfur compound represented by 2MLl'Sx and heated to form an emulsion. Post-processing becomes troublesome. The purpose of water washing is to remove the above compounds.

For example, natural gas condensate containing elemental mercury, ionic mercury, organic mercury (refractory mercury), etc.
When mixed with 1S4 aqueous solution and heated, all mercury components become H
The HgS is converted into gS, and the HgS is further dissolved in the Na, S4 aqueous solution. Heating is necessary to remove organic mercury (refractory mercury). At low temperatures, the reaction rate is slow, while at high temperatures, a high-pressure device is required due to the vapor pressure;
Preferably, heating to 0°C. Note that in an aqueous solution of Na1S < alone, there is a problem that the solubility of the generated HgS is low, but this can be solved by using Na and S together.

The concentration of the aqueous solution of the sulfur compound represented by the formula MM'S is not particularly limited, but is usually 1% to 10%. 1
A decrease in reactivity was observed at concentrations below 10%.
Above, no particularly remarkable increase in reactivity was observed.

The use of a monosulfide represented by the formula MM'S in combination with a polysulfide represented by the formula MM'Sxfx (where MM'Sxfx is a number from 2 to 6) increases the solubility of HgS generated as described above. It's for a reason.

In this case, the ratio of monosulfide to polysulfide is not particularly limited, but for example, the mixing (weight) ratio of Na2S< and NatS is preferably about 10/l - 1/10.

It is desirable to wash the liquid hydrocarbon which has been mixed with an aqueous solution of a sulfur compound represented by MM'Sx and heated to remove all mercury components. The purpose of this is to remove these sulfur compounds entrained in liquid hydrocarbons.

Note that the organic mercury (refractory mercury) referred to herein refers to a mercury compound that cannot be removed even if condensate is stirred and mixed with an Na*S4 aqueous solution at room temperature for 60 minutes. Since organic mercury (diethylmercury) does not react with the NazSn aqueous solution at room temperature, it is assumed that the refractory mercury in the condensate is organic mercury.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

[Example 1] A test was conducted to remove mercury from two types of natural gas condensates, A and B shown in Table 1 below, which were produced in different regions, as raw materials.

Table 1 The mercury content in the raw materials was measured by gold amalgam flameless atomic absorption spectrometry. In the data in Table 1, the amount of organic mercury is 60% when the raw material is mixed with a 5% Na*Sa aqueous solution at room temperature (20°C).
The mercury remaining in the raw materials was determined by analysis after stirring and mixing for a minute.

5% Na2S<50ml of aqueous solution and 50ml of raw material washed with water
After heating and stirring ρ in a glass autoclave for one hour at a predetermined temperature, the oil and water phases were separated and the mercury remaining in the oil phase was analyzed. The results are shown in Table 2.

Table 2 also shows the results of a similar treatment using a 5% Na, S aqueous solution. From the results shown in Table 2, it was found that the higher the temperature, the more effective the results. Also, under all temperature conditions tested, N
a, NazS4 was more effective than S.

[Example 2] Regarding natural gas condensate A shown in Table 1, 5
An experiment was conducted in the same manner as in Example 1 except that a mixed aqueous solution of %Na□S4 and 3% Na, S was used. As a result of treatment at 100° C., the residual mercury concentration was 9 ppb, which was no different from that of the Na2S4 alone aqueous solution.

However, the solubility of mercury is different from that of Na2S4 alone aqueous solution and N
When azS< was compared with a mixed aqueous solution of Na and S, 5
%NatS<11000pp in single aqueous solution, 5%Na
In a mixed aqueous solution of 25n, 3% Na, and S, the solubility of mercury in the mixed solution was 3%, which was about 30 times higher.

C1 Effects of the invention l) The removal rate of mercury and mercury compounds can be improved.

2) Organic mercury can be removed simultaneously with elemental mercury and ionic mercury.

3) The process is simple.

4) The processing liquid has a long service life and can be operated continuously for a long period of time.

5) Since no solid (HgS) is generated, operation management of the device is easy.

Claims (1)

[Claims] 1. A liquid hydrocarbon is represented by the formula MM'S_x (M represents an alkali metal or an ammonium group, M' represents hydrogen, an alkali metal or an ammonium group, and x represents a number from 1 to 6). A method for removing mercury and mercury compounds contained in liquid hydrocarbons, which comprises contacting with an aqueous solution containing sulfur compounds at a temperature of 40° C. or higher. 2. The method for removing mercury and mercury compounds contained in liquid hydrocarbons according to claim 1, wherein the aqueous solution containing the sulfur compound represented by the formula MM'S_x is a mixed aqueous solution of Na_2S_4 and Na_2S.