WO2018223546A1 - System and method for desulfurizing coal and recovering elemental sulfur - Google Patents

Abstract

A system and a method for desulfurizing coal and recovering elemental sulfur. The system comprises a microwave desulfurization unit, and further comprises a raw coal drying unit, an exhaust gas collecting unit, and an elemental sulfur reaction unit, a discharge port of the raw coal drying unit being connected to a feed port of the microwave desulfurization unit, the exhaust gas collecting unit being disposed at an air outlet of the microwave desulfurization unit, and an air inlet of the elemental sulfur reaction unit being respectively connected to an air outlet of the raw coal drying unit and an air outlet of the exhaust gas collecting unit. The system and method can simultaneously remove and recover sulfur from coal, producing treated coal with a total sulfur content of less than 2.0%, and a total recovery rate of elemental sulfur of not less than 40%. The system and the method are safe and energy-saving and are suitable for desulfurization and sulfur recovery of medium- and high-sulfur coals of varying quality.

Description

System and method for desulfurizing coal and recovering elemental sulfur Technical field

The invention belongs to the technical field of coal cleaning, and relates to a system and a method for desulfurizing coal and recovering and producing elemental sulfur.

Background technique

China's coal resources are abundant, and the sulfur content in coal is 1.72% on average. Among them, high-sulfur coal (S content ≥2.0%, including high-sulfur coal and medium-sulfur coal) has about 1/3 of the total reserves of coal, accounting for the production of raw coal. 16.67% has great potential application value.

There are huge sulfur resources in high-sulfur coal. In 2016, China's raw coal production totaled 33.64 tons. According to the S content of coal, which is 2.0%, the high-sulfur coal contains S 11.1 million tons. In 2016, China's sulfur production is only 5.16 million tons, imported sulfur is 11.961 million tons, and the external dependence is more than 50%. However, the use of high-sulfur coal and low sulfur recovery in China is low, and the amount of sulfur recovered from coal is very small. In addition, high-sulfur coal directly burned without any treatment will cause a large amount of SO ₂ emissions and cause serious pollution to the environment. Therefore, it is urgent to develop an economically viable technology and method for high-sulfur coal desulfurization and sulfur resource recovery.

The use of microwave desulfurization is a new method for desulfurization of high-sulfur coal in recent years. The microwave is an electromagnetic wave with a frequency of 0.3-300 GHz and a wavelength of 1 mm-100 cm. The inorganic sulfur such as pyrite in the coal is decomposed under microwave, mainly releasing H ₂ S. H ₂ S and a small amount of SO ₂ form elemental sulfur on the coal surface, and pyrite is converted into magnetic pyrite under the action of high temperature. This method can remove about 50% of sulfur in coal. US4076607 first proposed this method, CN206051972A (a microwave pretreatment device for high sulfur coal desulfurization), CN102816623A (a microwave upgrading device for microwave low temperature dehydration and desulfurization) and CN105623775A (a microwave thermal desorption method) In addition to mercury, sulfur, and nitrogen in coal gangue, microwaves are used to remove sulfur from coal/gangue. However, the above method only considers the release method of sulfur in coal, and generally ignores the reaction after the reaction. The collection of gas and the recovery of sulfur are limited by the type of reactor, existing patents or failure to achieve continuous production, or safety issues such as microwave processing temperature and microwave leakage are not considered.

Summary of the invention

In view of the problems existing in the prior art, the present invention aims to provide a system and method for desulfurizing coal and recovering elemental sulfur, which can simultaneously remove and recover sulfur in coal to make total sulfur in coal. The quantity control is below 2.0%, the total recovery rate of sulfur element is not less than 40%, safe and energy saving, suitable for desulfurization and sulfur recovery of various coal high-sulfur coal.

To this end, the present invention employs the following technical solutions:

One of the objects of the present invention is to provide a system for desulfurizing coal and recovering elemental sulfur, including a microwave desulfurization unit, and further comprising:

Coal drying unit, for containing SO ₂ from flue gas for coal drying, the resulting dried coal and flue gas discharged after heat exchange;

An exhaust gas collecting unit for collecting the H ₂ S-containing gas generated by the microwave desulfurization unit;

An elemental sulfur reaction unit for reacting between the H ₂ S-containing gas and the heat-exchanged coal-fired flue gas to produce elemental sulfur;

Wherein, the discharge port of the raw coal drying unit is connected to the feed port of the microwave desulfurization unit, the exhaust gas collection unit is disposed at the air outlet of the microwave desulfurization unit, and the air inlet of the elemental sulfur reaction unit is respectively separated from the raw coal The air outlet of the drying unit is connected to the air outlet of the exhaust gas collection unit.

The raw coal drying unit is dried by the waste heat of coal-fired flue gas (high-temperature flue gas generated by coal combustion). Under normal circumstances, the temperature of the coal-fired flue gas is 160-340 ° C, and the use of the heat to dry the raw coal can reduce the energy consumption. Moreover, the energy consumption of the microwave in the microwave desulfurization unit is not consumed, and the energy saving effect is achieved.

The system for desulfurizing and recovering elemental sulfur of the coal can not only remove the sulfur in the raw coal, but also recover the elemental sulfur product, and simultaneously desulfurize the coal-fired flue gas.

The system further includes a raw coal crushing unit connected to the feed port of the raw coal drying unit, or the raw coal drying unit is connected to the microwave desulfurization unit through the raw coal crushing unit.

Preferably, the raw coal crushing unit comprises a crusher, preferably a ring hammer crusher and/or a hammer crusher.

Preferably, the raw coal drying unit comprises a dryer. Coal-fired flue gas can be introduced into the dryer through a first induced draft fan.

The pulverization and drying of raw coal and then microwave desulfurization can greatly reduce the energy loss of the microwave and the temperature of the raw coal.

Preferably, the microwave reaction unit comprises a microwave reactor, wherein the microwave reactor is provided with an infrared temperature probe, a humidity sensor and a pressure sensor respectively connected to the centralized control system to control the temperature of the raw coal in the microwave reactor to prevent The coal is burned in a microwave reactor.

Preferably, the microwave desulfurization unit further includes a microwave leakage suppression device disposed at a bottom and/or both sides of the microwave desulfurization unit; the microwave leakage suppression device is disposed at a microwave leakable position of the microwave desulfurization unit To prevent microwave leakage.

Preferably, the microwave leakage suppression device is made of graphite and/or an alloy. The microwave leakage suppressing device may also be made of other absorbing materials as long as it can prevent leakage of microwaves in the microwave desulfurization unit.

The system further includes a dust removing unit, wherein an air outlet of the exhaust gas collecting unit is connected to an air inlet of the elemental sulfur reaction unit through the dust removing unit; the dust removing unit is capable of collecting dust in the H2S-containing gas collected by the air collecting cover Remove 70-90%.

Preferably, the dust removing unit comprises any one or a combination of at least two of a cyclone, an electrostatic precipitator or a bag filter. Typical but non-limiting combinations are cyclones and electrostatic precipitators, electrostatic precipitators and bag filters.

Preferably, the exhaust gas collecting unit comprises a gas collecting hood, and the top of the gas collecting hood is provided with a flow regulating valve and a gas component sensor.

Preferably, the gas collecting hood is a closed gas collecting hood or a semi-closed gas collecting hood, and collects the dissipated gas by side suction or suction, in order to avoid the influence of the air flow on the feeding and discharging, the set The movable side baffle is arranged at the connection between the hood and the microwave desulfurization unit, and the bottom baffle is designed with an oblique airflow distribution hole, which is favorable for the upward lifting of the airflow.

Preferably, the elemental sulfur reaction unit comprises a sulfur reactor, in which a catalyst layer is provided, the catalyst layer comprising a pretreated Al ₂ O ₃ -based catalyst catalyst and/or a pretreated TiO ₂ group Catalyst catalyst, pretreatment method includes redox treatment and/or roasting treatment, the pretreatment time is 1-5h, such as 1.5h, 2h, 2.5h, 3h, 3.5h, 4h or 4.5h, etc., the pretreatment temperature is 300- 600 ° C, such as 320 ° C, 330 ° C, 350 ° C, 380 ° C, 400 ° C, 420 ° C, 450 ° C, 500 ° C, 550 ° C or 580 ° C, etc., in order to increase the porosity and catalytic activity of the catalyst. The redox treatment may be such that the catalyst can undergo a redox reaction.

The H ₂ S-containing gas reacts with the coal-fired flue gas under the action of a catalyst, and the Claus reaction occurs in SO ₂ and H ₂ S in the flue gas (SO ₂ +2H ₂ S→3S+2H ₂ O+615kJ/mol ), the formation of elemental sulfur vapour, the elemental sulfur vapour after multi-stage condensation finally forms a sulfur by-product to achieve efficient recovery of elemental sulfur.

Preferably, the elemental sulfur reaction unit further comprises a preheating device, and an air outlet of the exhaust gas collecting unit and an air outlet of the raw coal drying unit are connected to an air inlet of the sulfur reactor through the preheating device; The thermal unit is used to heat the reaction gas to bring the temperature to the reaction temperature. The temperature at which the H ₂ S-containing gas reacts with SO ₂ in the coal-fired flue gas is 200-400 ° C.

Preferably, the preheating device comprises a heat exchanger.

The system further includes a condensing unit, the feeding port of the condensing unit is connected to the discharge port of the elemental sulfur reaction unit; and the condensing unit is used for cooling the elemental sulfur produced by the elemental sulfur reaction unit for storage.

Preferably, the condensing unit comprises a multi-stage synergistic condenser, and a spiking thread structure is arranged in the condenser pipeline to promote condensation of low concentration sulfur vapor;

Preferably, the system further includes a draft unit connected to an outlet of the elemental sulfur reaction unit; the lead unit is capable of withdrawing residual gas in the elemental sulfur reaction unit and discharging it into the atmosphere Or discharged into the atmosphere through the chimney.

Preferably, the air guiding unit comprises a second induced draft fan.

Another object of the present invention is to provide a method for desulfurizing coal and recovering elemental sulfur, the method comprising the following steps:

(1) drying the raw coal with coal-fired flue gas containing SO ₂ to obtain dried raw coal and coal-fired flue gas after heat exchange; the dried raw coal is subjected to microwave desulfurization to obtain a gas containing H ₂ S;

(2) The gas containing H2S reacts with the coal-fired flue gas after heat exchange to form elemental sulfur.

The raw coal in the step (1) is crushed and then dried or dried, and then first broken and then subjected to microwave desulfurization.

Preferably, the crushed raw coal has a particle diameter of 0.1 to 50 cm, such as 0.5 cm, 1 cm, 5 cm, 10 cm, 20 cm, 30 cm, 35 cm, 40 cm or 45 cm.

Preferably, the mass percentage of water in the dried raw coal in the step (1) is 5% or less, such as 1%, 2%, 3%, 4% or 4.5%.

After the raw coal is crushed and dried, microwave desulfurization can greatly reduce the energy loss of the microwave.

Preferably, the microwave frequency used in the microwave desulfurization in step (1) is 2500-2600 MHz, such as 2510 MHz, 2530 MHz, 2560 MHz, 2570 MHz or 2590 MHz, etc., and the microwave power is 300-500 W, such as 320 W, 350 W, 380 W, 400 W, 430 W, 450W or 480W, etc., microwave desulfurization time is 1-5min, such as 2min, 3min, 4min or 4.5min.

The gas containing H ₂ S in the step (2) is first dedusted and then reacted with the coal-fired flue gas after the heat exchange.

Preferably, the dust removal efficiency is not less than 95%, such as 96%, 97%, 98% or 99%, and the like.

The temperature of the reaction in the step (2) is 200 to 400 ° C, such as 220 ° C, 250 ° C, 280 ° C, 300 ° C, 320 ° C, 350 ° C or 380 ° C.

Preferably, the reaction in the step (2) is carried out under the catalysis of a pretreated Al ₂ O ₃ -based catalyst and/or a pretreated TiO ₂ -based catalyst, and the pretreatment method comprises redox treatment and/or calcination. Treatment, pretreatment time is 1-5h, such as 1.5h, 2h, 2.5h, 3h, 3.5h, 4h or 4.5h, etc., the pretreatment temperature is 300-600 ° C, such as 320 ° C, 330 ° C, 350 ° C, 380 ° C, 400 ° C, 420 ° C, 450 ° C, 500 ° C, 550 ° C or 580 ° C, etc., to increase the porosity and catalytic activity of the catalyst. The redox treatment may be such that the catalyst can undergo a redox reaction.

As a preferred technical solution, the method for desulfurizing coal and recovering elemental sulfur includes the following steps:

(1) After the raw coal is crushed to 0.1-50cm, the coal-fired flue gas containing SO ₂ is exchanged with the recovered raw coal to obtain dry raw coal with a water content of 5% or less and coal after heat exchange. Flue gas; dry raw coal for microwave desulfurization, microwave frequency is 2500-2600MHz, microwave power is 300-500W, microwave desulfurization time is 1-5min, and gas containing H ₂ S is obtained;

(2) The coal-fired flue gas after heat exchange and the gas containing H ₂ S are catalytically reacted at 200-400 ° C. The catalyst is a pretreated Al ₂ O ₃ -based catalyst and/or pretreated TiO ₂ based catalyst catalyst, redox treatment comprising a pretreatment and / or calcination treatment, pretreatment time is 1-5h, pretreatment temperature of 300-600 deg.] C, to give elemental sulfur product.

The method for desulfurizing coal and producing elemental sulfur provided by the invention not only saves energy consumption, but also can simultaneously treat exhaust gas and coal-fired flue gas generated by coal desulfurization, and has broad industrial application prospect.

Compared with the prior art, the beneficial effects of the present invention are:

1. The system and method for desulfurizing and recovering elemental sulfur provided by the invention have reasonable process design, strong operability, wide application range, safe and stable system, and can simultaneously remove and recover sulfur in coal. The total sulfur content of coal is below 2.0%, and the total recovery rate of sulfur is not less than 40%.

2. The system and method for desulfurizing and recovering elemental sulfur provided by the invention have the advantages of compact process flow and small occupied area, and can be applied to coal desulfurization before combustion of coal-fired power plants, and utilizing waste heat of coal-fired boiler flue gas to pre-predetermine moisture in raw coal. Removal, reducing the consumption of microwave energy by moisture, achieving system-wide optimization and energy saving.

3. The system and method for desulfurizing coal and recovering elemental sulfur provided by the invention, and arranging the H ₂ S of the high sulfur coal heat by the catalyst to catalyze the release of the SO ₂ in the coal combustion flue gas, thereby eliminating the H ₂ in the traditional sulfur recovery process. In the partial oxidation combustion process of S, the generated sulfur element can be sold as a by-product after purification, and has good environmental and economic benefits.

4. System and method for desulfurizing and recovering elemental sulfur provided by the invention The microwave desulfurization process adopts infrared temperature measurement and installs a microwave leakage suppression device to ensure the safety of the system operation, and the microwave reactor operates under a negative pressure to avoid pollutants from escaping. .

DRAWINGS

1 is a schematic view showing the structure of a system for desulfurizing coal and recovering elemental sulfur provided in Example 1.

Among them, 1-crusher; 2-dryer; 3-first induced draft fan; 4-infrared temperature probe; 5-microwave reactor; 6-microwave leakage suppression device; 7-collector cover; 8-dust collector 9-heat exchanger; 10-sulfur reactor; 11-condenser; 12-second induced draft fan; 13-chimney.

In addition, the solid line in Fig. 1 indicates the flow direction of the material, and the broken line indicates the flow direction of the gas.

detailed description

The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

Example 1

A system for desulfurizing high sulfur coal and recovering elemental sulfur, as shown in Figure 1, the system comprising:

a raw coal crushing unit for crushing raw coal, including a crusher 1, preferably a crusher 1 and/or a hammer crusher 1;

Raw coal drying unit for drying raw coal, including dryer 2;

a microwave desulfurization unit for microwave desulfurization of coal, comprising a microwave reactor 5, wherein the microwave reactor 5 is provided with an infrared temperature probe 4, a humidity sensor and a pressure sensor connected to the control system; the microwave desulfurization unit further comprises a microwave leakage suppression device 6, which is made of graphite and/or an alloy, and the microwave leakage suppression device 6 is disposed at the bottom and/or both sides of the microwave desulfurization unit;

The exhaust gas collecting unit is configured to collect the H ₂ S-containing gas generated by the microwave desulfurization unit, and includes a gas collecting cover 7 . The gas collecting cover 7 is provided with a flow regulating valve and a gas component sensor at the top, and the gas collecting cover 7 is sealed. a gas collecting hood or a semi-closed gas collecting hood; a movable side baffle is arranged at a joint of the gas collecting hood 7 and the microwave reactor 5, and a bottom air flow distribution hole is arranged at the bottom of the side baffle;

a dust removing unit for dedusting a gas containing H ₂ S, including any one or a combination of at least two of a cyclone 8, an electrostatic precipitator 8 or a baghouse 8;

An elemental sulfur reaction unit for reacting the H ₂ S-containing gas with the SO ₂ -containing coal-fired flue gas to produce elemental sulfur, including a sulfur reactor 10 and a heat exchanger 9, the sulfur reaction The catalyst layer 10 is provided in the catalyst 10, the catalyst layer comprises a pretreated Al ₂ O ₃ -based catalyst catalyst and/or a pretreated TiO ₂ -based catalyst catalyst, and the pretreatment method comprises a redox treatment and/or a roasting treatment, The treatment time is 1-5h, such as 1.5h, 2h, 2.5h, 3h, 3.5h, 4h or 4.5h, etc., the pretreatment temperature is 300-600 °C, such as 320 °C, 330 °C, 350 °C, 380 °C, 400 °C, 420 ° C, 450 ° C, 500 ° C, 550 ° C or 580 ° C, etc.;

a condensing unit for condensing high-temperature elemental sulfur produced by the sulfur elemental sulfur reaction unit, comprising a condenser 11, the condenser 11 being a multi-stage condenser, such as a 2-stage condenser, a 3-stage condenser, a 5-stage condenser or 10 Stage condenser, etc., a spiked thread structure is arranged in the condenser line;

a draft unit for extracting unreacted gas in the elemental sulfur reaction unit, comprising a second induced draft fan 12;

The coal-fired flue gas is introduced into the dryer 2 through the first induced draft fan 3;

The crusher 1, the dryer 2 and the microwave reactor 5 are connected in sequence, and the gas collecting cover 7 is disposed at the gas outlet of the microwave reactor 5, and the gas outlet of the gas collecting cover 7 passes through the dust remover 8 and the heat exchanger. 9 is connected to the inlet of the sulfur reactor 10, and the outlet of the coal-fired furnace is connected to the inlet of the sulfur reactor 10 through the dryer 2 and the heat exchanger 9, and the inlet of the condenser 11 and the sulfur reactor The discharge port of 10 is connected; the second induced draft fan 12 is disposed between the sulfur reactor 10 and the chimney 13.

A process for desulfurizing high-sulfur coal and producing elemental sulfur is as follows: the raw coal conveyed by the coal storage bin enters the crusher 1, and the raw coal is broken into a particle size of 0.1-50 cm, and the crushed raw coal enters the dryer 2 by heat The coal-fired flue gas is dried and dehydrated to reduce the moisture in the raw coal to less than 5%. The dried raw coal is transported to the microwave reactor 5 by a continuous conveyor belt, and irradiated in a microwave of 2500-2600 MHz and a power of 300-500 W. 5 min, the raw coal after desulfurization is ground to the coal mill for grinding and then injected into the boiler for combustion;

The dust, H ₂ S, SO ₂ flue gas generated by the microwave pyrolysis of the raw coal is collected by the gas collecting hood 7 and then enters the dust collector 8 , and the dust collector 8 collects the dust, and the dust collecting efficiency is not less than 95%. The captured dust ash is transported to the pulverized coal bin for reuse; the flue gas after dust removal is mixed with the hot flue gas after the dryer 2, and is heated by the heat exchanger 9 to enter the sulfur reactor 10, and the catalyst is catalyzed by the catalyst. Sulfur elemental vapor is produced under the reaction temperature of 200-400 ° C, and the elemental sulfur vapor is condensed by multiple stages to form a sulfur by-product, thereby achieving efficient recovery of elemental sulfur.

Example 2

Using the system described in Example 1, the high sulfur coal desulfurization test was carried out by the method of desulfurizing high sulfur coal of Example 1 and producing elemental sulfur. The details are as follows: in the 1000MW coal-fired power plant, the coal consumption is 360t/h, the sulfur content in the high-sulfur raw coal is 3.56%, the moisture content is 6.11%, and the particle size is 20-35cm after crushing, and the induced draft fan will be 240. °C boiler flue gas is introduced into the front end of the dryer. The SO ₂ content in the flue gas is 2000mg/Nm ³ , the O ₂ content is 6%, the flue gas flow rate is 15×10 ⁴ Nm ³ /h, and the moisture content of the raw coal after drying is reduced. At 4.23%, the outlet flue gas temperature drops to 180 °C, the raw coal after drying enters the conveyor belt, the conveyor belt conveys 50t/h, the raw coal enters the microwave reactor, and is irradiated for 3min in 2540MHz, 300W microwave, desulfurization The sulfur content in the post coal was reduced to 1.44%, and the total desulfurization efficiency (the total desulfurization efficiency in the present invention is the ratio of the reduction before and after the sulfur content unless otherwise specified) was 59.5%.

The dust and H ₂ S pollutants generated by microwave irradiation and raw coal transportation are collected by the gas collecting hood. The gas flow rate of the gas collecting hood is 8m/s, the gas flow rate is 15×10 ⁴ m ³ /h, and the O ₂ content is 20. %, H2S concentration is 708mg/m ³ , gas temperature is 120 ° C, the flue gas and boiler flue gas are mixed and heat-treated to 340 ° C, reacted under the action of catalyst, sulfur elemental conversion rate is 95%, total The sulfur recovery rate was 56.5%, and the sulfur element was 2.85 t/h.

Example 3

Using the system described in Example 1, the high sulfur coal desulfurization test was carried out by the method of desulfurizing high sulfur coal of Example 1 and producing elemental sulfur. The details are as follows: in the 500MW coal-fired power plant, the coal consumption is 200t/h, the sulfur content in the high-sulfur raw coal is 6.24%, the moisture content is 7.21%, and the crusher is crushed to a particle size of 15-30cm, and the induced draft fan will be 280. °C boiler flue gas is introduced into the front end of the dryer. The SO ₂ content in the flue gas is 4000mg/Nm ³ , the O ₂ content is 6%, the flue gas flow rate is 10×10 ⁴ Nm ³ /h, and the moisture content of the raw coal after drying is reduced. 4.61%, the outlet flue gas temperature drops to 160 ° C, the raw coal after drying enters the conveyor belt, the conveyor belt transport volume is 30t / h, the raw coal enters the microwave reactor, irradiated in the microwave at 2540MHz, power 500W for 5min, desulfurization The sulfur content in the post coal was reduced to 1.52%, and the total desulfurization efficiency was 75.6%.

The dust and H ₂ S pollutants generated by microwave irradiation and raw coal transportation are collected by the gas collecting hood. The gas flow rate of the gas collecting hood is 10m/s, the gas flow rate is 8×10 ⁴ m ³ /h, and the O ₂ content is 18 %, H ₂ S concentration is 17708mg / m ³ , gas temperature is 130 ° C, the flue gas and boiler flue gas mixed after heat exchange, the temperature is raised to 400 ° C, the reaction under the action of the catalyst, the sulfur elemental conversion rate is 96% The total sulfur recovery rate was 72.6%, and the sulfur production was 3.84t/h.

Example 4

Using the system described in Example 1, the high sulfur coal desulfurization test was carried out by the method of desulfurizing high sulfur coal of Example 1 and producing elemental sulfur. The details are as follows: in the 300MW coal-fired power plant, the coal consumption is 150t/h, the sulfur content in the high-sulfur raw coal is 3.15%, the moisture content is 5.12%, and the particle size is 40-50cm after crushing, and the induced draft fan will be 260. °C boiler flue gas is introduced into the front end of the dryer. The SO ₂ content in the flue gas is 1500mg/Nm ³ , the O ₂ content is 6%, the flue gas flow rate is 5×10 ⁴ Nm ³ /h, and the moisture content of the raw coal after drying is reduced. At 2.58%, the outlet flue gas temperature drops to 160 °C, the raw coal after drying enters the conveyor belt, the conveyor belt conveys 30t/h, the raw coal enters the microwave reactor, and is irradiated for 2min in 2500MHz, 300W microwave, desulfurization The sulfur content in the post coal was reduced to 1.38%, and the total desulfurization efficiency was 56.2%.

The dust and H ₂ S pollutants generated by microwave irradiation and raw coal transportation are collected by the gas collecting hood. The gas flow rate of the gas collecting hood is 10m/s, the gas flow rate is 5×10 ⁴ m ³ /h, and the O ₂ content is 18 %, H ₂ S concentration is 5312mg / m ³ , gas temperature is 140 ° C, the flue gas and boiler flue gas mixed heat exchange and then heated to 200 ° C, the reaction under the action of the catalyst, sulfur elemental conversion rate of 92% The total sulfur recovery rate was 51.7%, and the sulfur production was 0.69 t/h.

Example 5

Using the system described in Example 1, the high sulfur coal desulfurization test was carried out by the method of desulfurizing high sulfur coal of Example 1 and producing elemental sulfur. The details are as follows: in the 600MW coal-fired power plant, the coal consumption is 250t/h, the sulfur content in the high-sulfur raw coal is 2.65%, the moisture content is 5.17%, and the particle size is 10-50mm after crushing, and the induced draft fan will be 300. °C boiler flue gas is introduced into the front end of the dryer. The SO ₂ content in the flue gas is 1000mg/Nm ³ , the O ₂ content is 6%, the flue gas flow rate is 8×10 ⁴ Nm ³ /h, and the moisture content of the raw coal after drying is reduced. 2.80%, the outlet flue gas temperature drops to 150 ° C, the raw coal after drying enters the conveyor belt, the conveyor belt transport volume is 30t / h, the raw coal enters the microwave reactor, irradiated in the microwave at 2600MHz, power 400W for 2min, desulfurization The sulfur content in the post coal was reduced to 1.51%, and the total desulfurization efficiency was 43.0%.

The dust and H ₂ S pollutants generated by microwave irradiation and raw coal transportation are collected by the gas collecting hood. The gas flow rate of the gas collecting hood is 10m/s, the gas flow rate is 5×10 ⁴ m ³ /h, and the O ₂ content is 18 %, H ₂ S concentration is 5666mg / m ³ , gas temperature is 120 ° C, the flue gas and boiler flue gas mixed after heat exchange, the temperature is raised to 300 ° C, the reaction under the action of the catalyst, the sulfur elemental conversion rate is 95% The total sulfur recovery rate is 40.85%, and the sulfur production is 0.76t/h.

The catalysts of Examples 2-5 were selected from the pretreated Al ₂ O ₃ -based catalysts, which were calcined at a calcination time of 3 h and a calcination temperature of 500 °C.

The catalyst of Examples 2-5 may also be selected from a pretreated Al ₂ O ₃ -based catalyst catalyst and/or a pretreated TiO ₂ -based catalyst catalyst other than the above catalysts, the pretreatment method including redox treatment and/or Or roasting treatment, the pretreatment time is 1-5h, such as 1.5h, 2h, 2.5h, 3.5h, 4h or 4.5h, etc., the pretreatment temperature is 300-600 ° C, such as 320 ° C, 330 ° C, 350 ° C, 380 ° C, 400 ° C, 420 ° C, 450 ° C, 550 ° C or 580 ° C and so on.

The Applicant claims that the above description is only the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and those skilled in the art should understand that any person skilled in the art disclosed in the present invention Variations or substitutions that are conceivable within the scope of the invention are within the scope of the invention and the scope of the disclosure.

Claims (12)

1. A system for desulfurizing coal and recovering elemental sulfur, comprising a microwave desulfurization unit, wherein the system for desulfurizing and recovering elemental sulfur of the coal further comprises:

   The raw coal drying unit is used for drying the coal by the coal-fired flue gas containing SO ₂ , obtaining the dried coal and discharging the coal-fired flue gas after the heat exchange;

   An exhaust gas collecting unit for collecting the H ₂ S-containing gas generated by the microwave desulfurization unit;

   An elemental sulfur reaction unit for reacting between the H ₂ S-containing gas and the heat-exchanged coal-fired flue gas to produce elemental sulfur;

   Wherein, the discharge port of the raw coal drying unit is connected to the feed port of the microwave desulfurization unit, the exhaust gas collection unit is disposed at the air outlet of the microwave desulfurization unit, and the air inlet of the elemental sulfur reaction unit is respectively separated from the raw coal The air outlet of the drying unit is connected to the air outlet of the exhaust gas collection unit.
2. The system for desulfurizing and recovering elemental sulfur according to claim 1, wherein the system further comprises a raw coal crushing unit, the raw coal crushing unit is connected to a feed port of the raw coal drying unit, or the raw coal is baked. The dry unit is connected to the microwave desulfurization unit through a raw coal crushing unit.
3. The system for desulfurizing and recovering elemental sulfur according to claim 2, wherein the raw coal crushing unit comprises a crusher, and the crusher is preferably a ring hammer crusher and/or a hammer crusher.
4. The system for desulfurizing and recovering elemental sulfur in coal according to claim 1, wherein the raw coal drying unit comprises a dryer;

   Preferably, the microwave reaction unit comprises a microwave reactor, wherein the microwave reactor is provided with an infrared temperature probe, a humidity sensor and a pressure sensor respectively connected to the centralized control system;

   Preferably, the microwave desulfurization unit further includes a microwave leakage suppression device disposed at a bottom and/or both sides of the microwave desulfurization unit;

   Preferably, the microwave leakage suppression device is made of graphite and/or an alloy.
5. The system for desulfurizing and recovering elemental sulfur in coal according to claim 1 or 2, wherein the system further comprises a dust removing unit, and an air outlet of the exhaust gas collecting unit passes through the dust removing unit and the elemental sulfur reaction unit. Air port connection;

   Preferably, the dust removing unit comprises any one or a combination of at least two of a cyclone, an electrostatic precipitator or a bag filter.
6. The system for desulfurizing and recovering elemental sulfur according to any one of claims 1 to 5, wherein the exhaust gas collecting unit comprises a gas collecting hood, and a flow regulating valve and a gas component sensor are disposed at the top of the gas collecting hood;

   Preferably, the gas collecting hood is a closed gas collecting hood or a semi-closed gas collecting hood, a movable side baffle is arranged at a joint of the gas collecting hood and the microwave desulfurization unit, and a diagonal air flow distribution hole is arranged at the bottom of the side baffle ;

   Preferably, the elemental sulfur reaction unit comprises a sulfur reactor, in which a catalyst layer is provided, the catalyst layer comprising a pretreated Al ₂ O ₃ -based catalyst catalyst and/or a pretreated TiO ₂ group Catalyst catalyst, the pretreatment method comprises redox treatment and/or roasting treatment, the pretreatment time is 1-5 h, and the pretreatment temperature is 300-600 ° C;

   Preferably, the elemental sulfur reaction unit further comprises a preheating device, and an air outlet of the exhaust gas collecting unit and an air outlet of the raw coal drying unit are connected to an air inlet of the sulfur reactor through the preheating device;

   Preferably, the preheating device comprises a heat exchanger.
7. A system for desulfurizing and recovering elemental sulfur in coal according to any one of claims 1 to 6, characterized in that the system further comprises a condensing unit, the feed port of the condensing unit being connected to the discharge port of the elemental sulfur reaction unit ;

   Preferably, the condensing unit comprises a multi-stage condenser, and a spiking thread is arranged in the condenser line;

   Preferably, the system further includes a draft unit connected to an air outlet of the elemental sulfur reaction unit;

   Preferably, the air guiding unit comprises a second induced draft fan.
8. A method for desulfurizing coal and recovering elemental sulfur by using the system for desulfurizing coal and recovering elemental sulfur according to any one of claims 1-7, wherein the method comprises the following steps:

   (1) drying the raw coal with coal-fired flue gas containing SO ₂ to obtain dried raw coal and coal-fired flue gas after heat exchange; the dried raw coal is subjected to microwave desulfurization to obtain a gas containing H ₂ S;

   (2) The gas containing H ₂ S reacts with the coal-fired flue gas after heat exchange to form elemental sulfur.
9. The method according to claim 8, wherein the raw coal in the step (1) is crushed, dried or dried, and then first broken and then subjected to microwave desulfurization;

   Preferably, the crushed raw coal has a particle size of 0.1-50 cm;

   Preferably, the mass percentage of water in the dried raw coal in step (1) is 5% or less;

   Preferably, the microwave desulfurization used in the step (1) uses a microwave frequency of 2500-2600 MHz, a microwave power of 300-500 W, and a microwave desulfurization time of 1-5 min.
10. The method according to claim 8 or 9, wherein the gas containing H ₂ S in the step (2) is first dedusted and then reacted with the coal-fired flue gas after the heat exchange;

    Preferably, the dust removal efficiency is not less than 95%.
11. The method according to any one of claims 8 to 10, wherein the temperature of the reaction in the step (2) is 200-400 ° C;

    Preferably, the reaction in the step (2) is carried out under the catalysis of a pretreated Al ₂ O ₃ -based catalyst and/or a pretreated TiO ₂ -based catalyst, and the pretreatment method comprises redox treatment and/or calcination. Treatment, pretreatment time is 1-5h, pretreatment temperature is 300-600 °C.
12. Method according to one of the claims 8-11, characterized in that the method comprises the following steps:

    (1) After the raw coal is crushed to 0.1-50cm, the coal-fired flue gas containing SO ₂ is exchanged with the recovered raw coal to obtain dry raw coal with a water content of 5% or less and coal after heat exchange. Flue gas; dry raw coal for microwave desulfurization, microwave frequency is 2500-2600MHz, microwave power is 300-500W, microwave desulfurization time is 1-5min, and gas containing H ₂ S is obtained;

    (2) The coal-fired flue gas after heat exchange and the gas containing H ₂ S are catalytically reacted at 200-400 ° C. The catalyst is a pretreated Al ₂ O ₃ -based catalyst and/or pretreated TiO ₂ based catalyst catalyst, redox treatment comprising a pretreatment and / or calcination treatment, pretreatment time is 1-5h, pretreatment temperature of 300-600 deg.] C, to give elemental sulfur product.

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