Process for preparing sulfur from reduction of sulfate/ nitrate by iron-carbon and recovering desulfurization/ denitration agents

Patent metadata

Field	Value
Publication number	US-11292718-B2
Application number	US-201816618937-A
Country	US
Kind code	B2
Filing date	Dec 27, 2018
Priority date	Dec 17, 2018
Publication date	Apr 5, 2022
Grant date	Apr 5, 2022

Abstract

The present invention discloses a process for preparing sulfur from reduction of sulfate/nitrate by iron-carbon and recovering desulfurization/denitration agents. High-concentration SO2 flue gas produced by calcination of a sulfate and NOx produced by heating decomposition of a nitrate can be directly reduced to elemental sulfur vapor and N2 through reaction with an iron-carbon material at a high temperature. Then, after dust removal, cooling and fine dust removal, sulfur is recovered by a sulfur recovery device, and metal oxides can replace alkaline mineral resources such as limestone as raw materials of desulfurization (denitration) agents. This process can recycle the desulfurization and denitration agents.

First claim

The invention claimed is:

1. A system for preparing sulfur from reduction of sulfate/nitrate by iron-carbon and recovering desulfurization/denitration agents, the system comprising:
a desulfurization tower, a denitration tower, a chimney, a drying device, a roaster for reduction, a first separator, a second separator, a thermal reduction tower using carbon, a third separator, a reheater, a fine dust removing device, a sulfur recovery device, a sulfur storage bin, a concentration device, a pneumatic transporting device, and a nitrate decomposition tower,
wherein a flue gas inlet of the desulfurization tower is connected to a flue gas supply source, a flue gas outlet of the desulfurization tower is connected to a flue gas inlet of the denitration tower, a flue gas outlet of the denitration tower is connected to an inlet of a wet electrostatic precipitator, and an outlet of the wet electrostatic precipitator is connected to an inlet of the chimney;
a tower kettle of the desulfurization tower is connected to an inlet of the drying device, an outlet of the drying device is connected to an inlet of a sulfate bin, the sulfate bin is connected to the roaster for reduction, and the roaster for reduction is also connected to an iron powder supply source and a carbon powder supply source;
a tower kettle of the denitration tower is connected to an inlet of the concentration device, an outlet of the concentration device is connected to an inlet of the nitrate decomposition tower through the pneumatic transporting device, and an outlet of the nitrate decomposition tower is connected to an inlet of the thermal reduction tower using carbon;
an outlet of the roaster for reduction is connected to the first separator, a solid outlet of the first separator is in communication with an interior of the roaster for reduction, a gas outlet of the first separator is connected to an inlet of the second separator, and a solid outlet of the second separator is connected to a filtering device;
a gas outlet of the second separator is connected to the inlet of the thermal reduction tower using carbon, an outlet of the thermal reduction tower using carbon is connected to an inlet of the third separator, a gas outlet of the third separator is connected to the reheater, and the reheater, the fine dust removing device, the sulfur recovery device and the sulfur storage bin are connected in sequence; and
a solid outlet of the third separator is connected to the thermal reduction tower using carbon.

2. The system according to claim 1 , wherein the filtering device is provided with a chamber therein, a filter screen is disposed across the cross section of the chamber, a first outlet is disposed at the upper end of the filter screen, and a second outlet is disposed at the lower end of the filter screen.

3. The system according to claim 1 , wherein a first dust collector is connected to the flue gas inlet of the desulfurization tower, and a flue between the first dust collector and the desulfurization tower is connected to an ozone generator.

4. The system according to claim 1 , wherein the concentration device comprises a membrane concentration device and an MVR evaporation concentration device, an inlet of the membrane concentration device is connected to the tower kettle of the denitration tower, an outlet of the membrane concentration device is connected to an inlet of the MVR evaporation concentration device, and the pneumatic transporting device is disposed at the outlet of the MVR evaporating concentration device.

5. The system according to claim 1 , wherein a feeder is disposed between the drying device and the roaster for reduction.

6. The system according to claim 1 , wherein the fine dust removing device is a metal mesh filter or a ceramic filter.

7. A process for preparing sulfur from reduction of sulfate/nitrate by iron-carbon and recovering desulfurization/denitration agents, comprising:
subjecting a flue gas to dust removal, ozone oxidation, alkali washing desulfurization, and alkali washing denitration, and then discharging;
drying a sulfate precipitate produced in the alkali washing desulfurization and then transporting the dried sulfate precipitate together with carbon powder and iron powder at a set ratio to a roaster for reduction and conducting roasting reduction at a roasting temperature of 800° C. to 1100° C. for a roasting time of 4 to 200 s;
concentrating and crystallizing a nitrate solution produced in the alkali washing denitration to produce a nitrate powder, decomposing the nitrate powder at a high temperature into a solid metal oxide and a mixed gas, and delivering the mixed gas to the roaster for reduction such that the mixed gas is reduced to nitrogen by roasting;
separating an unroasted sulfate carried in the gas flowing out from an outlet of the roaster for reduction by a first separator, and then returning the separated unroasted sulfate to the roaster for reduction for further reaction;
separating a metal oxide and carbon powder in a gas flow from the first separator by a second separator and feeding into a filtering device, wherein the metal oxide is dissolved in water of the filtering device to form an alkali liquid, and the carbon powder is intercepted by the filtering device and dried for reuse;
subjecting remaining gas from the roaster for reduction to a dust removal by condensing and to a sulfur recovery, and then sequentially introducing the remaining gas back into the alkali washing desulfurization and the alkali washing denitration for treatment, and finally discharging.

8. The process according to claim 7 , wherein the sulfate precipitate transported to the roaster for reduction has a particle diameter of 60 μm to 3 mm, the nitrate has a particle diameter of 60 μm to 3 mm, the carbon powder has a particle diameter of 60 μm to 3 mm, and the iron powder has a particle diameter of 60 μm to 500 μm.

9. The process according to claim 8 , wherein a mass ratio of the sulfate, the carbon powder, and the iron powder in the roaster for reduction is (8-11):(1-2):(1-2).

10. The process according to claim 7 , wherein the temperature for high-temperature decomposition of the nitrate powder is 400 to 600° C., and the reaction time is 10 to 200 s.

Assignees

• Univ Shandong

Inventors

• Ma Chunyuan
• Xia Xiao
• Cui Lin
• Zhang Liqiang
• Zhao Xiqiang
• Li Jun
• Feng Tai
• Zhang Shizhen

Classifications

• C01B17/05 Primary

  by wet processes · CPC title

• B01D2251/402

  of magnesium · CPC title

• B01D39/2068

  Other inorganic materials, e.g. ceramics · CPC title

• B03C3/16

  wet type · CPC title

• B01D2258/0283

  Flue gases · CPC title