Method of preparing carbon-based sulfur-loading iron-containing adsorbent for mercury removal

Abstract

This invention introduces a method of preparing a carbon-based sulfur-loading iron-containing adsorbent for mercury removal, which can solve the problems in the prior art that sulfur-rich heavy organic materials have low-value utilization and the elemental mercury in atmosphere is hard to be efficiently and economically removed by the existing mercury removal agents. A carbon-based sulfur-loading iron-containing adsorbent for mercury removal is prepared in this invention. The adsorbent with a porous structure is prepared in situ by performing steps such as chemical activation of sulfur-rich heavy organic materials that are rich in iron. The adsorbent prepared herein has good mercury removal performance in simulated coal-fired flue gas. This invention not only improves the utilization value of sulfur-rich heavy organic materials, but also prevents SO.sub.X pollution caused by the combustion of sulfur-rich heavy organic materials and controls mercury pollution in the coal-fired flue gas.

Claims

1. A method for preparing a carbon-based sulfur-loading iron-containing adsorbent for mercury removal, comprising: (1) drying, grinding and sieving a sulfur-rich iron-containing heavy organic matter with a sulfur content more than 1% to obtain a sulfur-rich iron-containing heavy organic material; (2) mixing the KOH and the sulfur-rich iron-containing heavy organic material obtained in step (1) uniformly according to a mass ratio of 0.5-1:1 to obtain a mixture and dropwise adding an aqueous ethanol to the mixture for infiltration; (3) placing the infiltrated mixture obtained in step (3) in a tubular furnace to perform the calcination and activation under the protection of N.sub.2, thereby obtaining an activated product; and (4) washing and filtering the activated product with hot water repeatedly until a pH of a filtrate is 7, and drying the product to obtain the carbon-based sulfur-loading iron-containing adsorbent for mercury removal.

2. The method of claim 1, wherein the sulfur-rich iron-containing heavy organic matter in step (1) is high sulfur coal or coal liquefaction residue.

3. The method of claim 1, wherein a drying temperature in step (1) is 60-110° C.

4. The method of claim 1, wherein a mesh number of a sieve used during the sieving in step (1) is 20 mesh or less.

5. The method of claim 1, wherein the aqueous ethanol in step (3) is a solution of absolute ethanol and water mixed in a volume ratio of 2:8, and a ratio of a volume of the aqueous ethanol to a mass of the sulfur-rich iron-containing heavy organic material is 0.4-1.5 mL/g.

6. The method of claim 1, wherein the calcination and activation in step (4) are performed at 400-1000° C. for 1-5 h.

7. The method of claim 1, wherein a temperature of the hot water in step (5) is 50-100° C., and a drying temperature is 110° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph showing an effect of an alkali-carbon ratio on the efficiency of mercury removal.

(2) FIG. 2 is a graph showing an effect of an activation temperature on the capacity of mercury removal.

(3) FIG. 3 is a graph showing an effect of atmosphere on the mercury removal performance.

(4) FIG. 4 is a graph showing an effect of a temperature of a fixed-bed experimental device on the efficiency of mercury removal.

DETAILED DESCRIPTION OF EMBODIMENTS

Example 1

(5) ZunYi (ZY) high-sulfur coal, which contained 6.4% by weight of sulfur and 3.5% by weight of iron, was selected as an experimental raw material. The ZY high-sulfur coal was dried in a drying oven at 110° C. for 8 h, then ground and sieved by a 40-60 mesh sieve to obtain ZY coal particles for use.

(6) Five solid mixtures were prepared by uniformly mixing the components as follows:

(7) Solid mixture 1: 10 g ZY coal particles;

(8) Solid mixture 2: 10 g ZY coal particles and 5 g KOH;

(9) Solid mixture 3: 10 g ZY coal particles and 7.5 g KOH;

(10) Solid mixture 4: 10 g ZY coal particles and 10 g KOH;

(11) Solid mixture 5: 10 g ZY coal particles and 30 g KOH.

(12) A mixed solution of absolute ethanol and water in a volume ratio of 2:8 was dropwise added into the five solid mixtures by a pipette, respectively, to produce five infiltrated solid mixtures (R0-1, R0.5-1, R0.75-1, R1-1, R3-1).

(13) The five infiltrated solid mixtures were placed in a programmed tubular furnace for the calcination and activation at 800° C. for 2 h to produce resulting samples.

(14) The resulting samples were washed by 50° C. hot water followed by filtering repeatedly until a pH of filtrate was 7, and then the filtered samples were dried to obtain carbon-based sulfur-loading iron-containing adsorbents for mercury removal.

Example 2

(15) ShenHua (SH) coal liquefaction residue, which contained 1.22% by weight of sulfur and 2.24% by weight of iron, was selected as an experimental raw material. The SH coal liquefaction residue was dried in a drying oven at 60° C. for 12 h, then was ground and then was sieved by a 60-80 mesh sieve to obtain coal liquefaction residue particles for use.

(16) Five solid mixtures each were prepared by mixing 5 g coal liquefaction residue particles and 10 g KOH uniformly, where the coal liquefaction residue particles and KOH were weighted using a balance.

(17) A mixed solution of absolute ethanol and water in a volume ratio of 2:8 was dropwise added into the four solid mixtures by a pipette, respectively, to produce five infiltrated solid mixtures.

(18) The five infiltrated solid mixtures were respectively placed in a programmed tubular furnace for the calcination and activation at 400° C., 500° C., 600° C., 700° C. and 800° C. for 2 h to produce five resulting samples (T400, T500, T600, T700, T800).

(19) The resulting samples were washed by 100° C. hot water followed by filtering repeatedly until a pH of filtrate was 7, and then the filtered samples were dried to obtain carbon-based sulfur-loading iron-containing adsorbents for mercury removal.

Example 3

(20) The carbon-based sulfur-loading iron-containing adsorbents for mercury removal prepared in Examples 1 and 2 were separately placed in a fixed-bed experimental device to continuously perform a mercury removal test for 2 h at a temperature of 120, 150 or 180° C. under N.sub.2+O.sub.2+Hg.sup.0 (40 μg/m.sup.3) or simulated coal-fired flue gas which included N.sub.2, O.sub.2, SO.sub.X, NO.sub.X, Hg.sup.0 (40 μg/m.sup.3) with a total gas volume of 1 L/min (N.sub.2 was used as balance gas). The simulated coal-fired flue gas was introduced into a reaction tube to contact with the adsorbents. The loading amount of the adsorbents was 1.5±0.1 mL and the particle size of the adsorbents after sieving by a 40-60 mesh sieve was 0.25-0.42 mm.

(21) The mercury removal test was carried out on a fixed-bed reactor through the following steps.

(22) Quartz wool was laid in the reaction tube, and a blank value was calibrated as a concentration value of mercury at an inlet of the fixed-bed reactor; 1.5 mL adsorbents was measured and filled into the fixed-bed reactor. After a temperature in the fixed-bed reactor was stable, the mercury removal test of the adsorbents was performed under the simulated coal-fired flue gas.

(23) The mercury removal performance of carbon-based sulfur-loading iron-containing adsorbents was evaluated and defined by a mercury removal efficiency of elemental mercury, that was, η (%)=(1−C.sub.1/C.sub.0)×100%, where η was the mercury removal efficiency of the adsorbents, and C.sub.1 and C.sub.0 were mercury concentrations at the inlet and the outlet of the fixed-bed reactor, respectively, and the units of C.sub.1 and C.sub.0 were μg/m.sup.3 or ppm.

(24) The concentration of Hg.sup.0 was measured by a LUMEX 915M mercury analyzer which could record one data every 1 minute. A plurality of average values were calculated by using data every 5 minutes to create a dot-line graph. FIGS. 1-4 showed the mercury removal performance of samples under different test conditions.

(25) Test conditions of FIGS. 1, 2 and 4 were 150° C., 40±2 μg/m.sup.3 Hg.sup.0, N.sub.2+4% O.sub.2, a space velocity of 40000 h.sup.−1.

(26) FIG. 3 is a graph showing the test results of the sample T800 under a test condition of 40±2 μg/m.sup.3 Hg.sup.0, a space velocity of 40,000 h.sup.−1.

(27) FIG. 4 is a graph showing the test results of the sample R0.5-1.

Example 4

(28) SH coal liquefaction residue, which contained 1.22% by weight of sulfur and 2.24% by weight of iron, was selected as an experimental raw material. The SH coal liquefaction residue was dried in a drying oven at 90° C. for 12 h, then was ground and then was sieved by a 200-400 mesh sieve to obtain SH coal liquefaction residue particles for use.

(29) Three solid mixtures each were prepared by mixing 10 g SH coal liquefaction residue particles and 5 g KOH uniformly, where the SH coal liquefaction residue particles and KOH were weighted using a balance.

(30) A mixed solution of absolute ethanol and water in a volume ratio of 2:8 was dropwise added into the three solid mixtures by a pipette to produce three infiltrated solid mixtures.

(31) The three infiltrated solid mixtures were placed in a programmed tubular furnace for the calcination and activation at 1000° C. for 1 h, 3 h and 5 h respectively to produce three resulting samples (SH1, SH2 and SH3).

(32) The resulting samples were washed by 60° C. hot water followed by filtering repeatedly until a pH of filtrate was 7, and then the filtered samples were dried to obtain carbon-based sulfur-loading iron-containing adsorbents for mercury removal.

(33) The mercury removal adsorbents prepared above were subjected to a mercury removal experiment on an eject mercury removal device at 120° C. for 2 s, wherein a carbon/mercury ratio was 100,000 and the mercury removal efficiency of the three adsorbents was above 70%.

(34) The experimental results showed that the adsorbents prepared herein had the high mercury removal activity at 120-180° C. under various atmospheres, where the adsorbent R0.5-1 prepared in Example 1 and the adsorbent T800 prepared in Example 2 had high mercury removal activity in N.sub.2 and O.sub.2 atmosphere, and the average mercury removal efficiency in 2 h was above 90%. Although the adsorbents R3-1 and T500 had a relatively low mercury removal activity, their mercury removal performance had been significantly improved compared to ZY coal without KOH activation. Predictably, an adsorbent with better mercury removal performance could be prepared by adjusting the amount of KOH, types of sulfur-rich heavy organic materials and conditions during activation. Thus, it could be concluded that the carbon-based sulfur-loading iron-containing adsorbent for mercury removal prepared in this invention had good mercury removal effect under the coal-fired flue gas, indicating that the carbon-based sulfur-loading iron-containing adsorbent for mercury removal could be prepared using the sulfur-rich heavy organic material and had immeasurable industrial application prospects in the mercury removal for the coal-fired flue gas.