CN101126035B - Phenol water closed operation high-conversion coal gasification production technique - Google Patents

Abstract

A phenolic water closed operation high-conversion coal gasification production process, including a gasification agent, is characterized in that the temperature of the gasification agent is 65-350°C, and the water content is 55-60°C when the same weight of saturated air is water volume. The gasification agent is formed by fully mixing the phenol-containing waste water with the hot air in the mixing box under the action of the pressure pump, and enters the gasification furnace to participate in the reaction under the action of the fan. The phenol-containing waste water of the present invention refers to the aqueous solution containing benzene, phenol, etc. that is separated out during the cooling process of the coal gas. It is transported mechanically to the oxide layer of the furnace body to be cracked and incinerated in a completely closed environment of the gasification process system. No external discharge, completely solve the problem of phenol water pollution and secondary pollution; part of the heat is returned to the furnace for use, saving the amount of coal participating in the oxidation reaction, thus increasing the gasification efficiency by 3% to 5%, and the gasification intensity by more than 10%. .

Description

A high-conversion coal gasification production process with closed operation of phenol water

technical field

The invention belongs to the technical field of coal gasification technology, and in particular relates to a coal gasification production technology with high conversion rate in closed operation of phenol water.

Background technique

As shown in Figure 1, the traditional two-stage furnace refrigerant gas production process is as follows: through the conveying mechanism, coal blocks of appropriate quality and size are sent to the coal bunker, and the coal feeding mechanism is continuously and evenly added to the gas furnace. In the furnace, there are the following three main chemical reactions: 1. The reaction between the carbon in the coal and the oxygen and water vapor in the air of the gasification agent; 2. The reaction between the oxygen, water vapor in the gasification agent, and various generated gases 3. Coal pyrolysis reaction, these three reactions are carried out at different levels in the furnace.

The oxide layer becomes the fire layer again, and the thickness is 100-200mm under normal circumstances. The main function of the oxide layer is to make the oxygen in the air meet with carbon to undergo a rapid thermochemical reaction, generate a large amount of carbon dioxide, and release heat at the same time. The heat required for the thermochemical reaction of the gas is maintained by this. The temperature of the fire layer is generally maintained at 1100-1250°C, which depends on the melting point of the raw coal ash.

The reduction layer is the area where the main combustible gas is generated, and is divided into the first reduction layer and the second reduction layer (or the main reduction layer and the second reduction layer) according to the progress of the reaction formula. Under normal circumstances, the thickness of the reduction layer is 200-400mm. The role of the reduction layer is: ① carbon dioxide and hot charcoal act together to perform a thermochemical reaction to generate combustible carbon monoxide; ② water vapor and hot charcoal undergo an endothermic chemical reaction to generate combustible carbon monoxide and hydrogen; ③ except for the above two types In addition to the reaction, carbon monoxide reacts with excess water vapor to produce carbon dioxide and hydrogen, while releasing heat.

The gas in the two-stage generator is divided into upper and lower stages. The gas in the upper stage leaves from the top outlet of the generator and enters the electric tar catcher to remove tar, and the tar flows into the tar tank. The cooling water in the jacket enters the steam drum through the steam pipe. The generated gas enters the intercooler and leaves from the bottom after being cooled. After the gas is cooled, it condenses and precipitates toxic phenol water, which flows into the phenol pool through the water pipe; the gas enters the electric detarter to remove light oil, and the light oil flows into the oil storage tank. After purification The gas is sent to the user by the gas delivery machine.

Mixed producer gas uses the mixture of air and steam as the gasification agent, and reacts with carbon in the producer to generate combustible gas. The effect of water vapor is as follows:

(1) Since the water vapor decomposes and absorbs heat, the temperature in the furnace can be reduced. The amount of water is controlled by controlling the saturation temperature of the gasifying agent.

(2) Since water vapor can lower the furnace temperature, the reaction rate of reducing carbon dioxide to carbon monoxide when it encounters carbon is weakened, so that the ratio of carbon monoxide to carbon dioxide is reduced.

(3) Since most of the water vapor can be decomposed to generate hydrogen and carbon monoxide under appropriate furnace temperature conditions, the quality of the gas is improved and the calorific value of the gas is increased.

(4) Water vapor cannot be completely decomposed, and the decomposition rate is related to factors such as the temperature in the furnace, the nature of the coal, and the amount of water vapor. Undecomposed water vapor is mixed into the gas and flows out of the generator. In this way, due to the high temperature of the gas furnace, the heat loss increases. At the same time, when there is a lot of water in the gas, it needs to be purified and cooled, otherwise it will affect the life of the pipeline and the use of users. Air supply is normal, and the thermal efficiency of the user's heating equipment is reduced.

Due to the above reasons, water vapor has an impact on the normality of gas production, the ease of operation, the quality of gas and the economy of the production process. At present, the amount of water vapor in the gasification agent is controlled by the saturation temperature of the mixed gas. For example, the gasification agent of a mixed gas station uses a mixture of air and water vapor. The water volume is controlled by transporting air and water vapor into the mixing box at the same time, and using the temperature control sensor to automatically adjust the water vapor intake by controlling the temperature of the mixed steam. "Professional Technology" No. 10, 2006, page 152 "Analysis of Gasification Process of Coal Gasifier" (Yang Lisen, Wang Diwen) discloses that the general blast temperature ranges from 50 to 65°C, and the disclosed content is quoted here.

This method of using saturated steam has many advantages, low technical content requirements, using the steam generated by circulating cooling water to enter the furnace, easy to operate, easy to control, and relatively few monitoring points.

Causes of sewage generated during gas production:

The phenol-containing sewage of the gas station mainly contains five kinds of pollutants such as tar, light oil, crude phenol, ammonia and sulfur (the composition of gas water is slightly different in different devices), among which the phenols are mainly monohydric phenols, and the content of phenol is the highest , followed by m-p-cresol, which comes from the washing water and phenol-containing condensate in the process of cooling and purifying the gas. The amount of phenol-containing condensate depends on the gasification coal quality and the gasification process used. Taking the gasification of Datong bituminous coal in the two-stage furnace gas station as an example, the gas in the upper stage is finally cooled by the indirect cooler, and the condensed water produced is about 100kg/t coal, and the phenol content in the condensed water is about 8500-10000mg/L; the gas in the lower stage The phenol content of the washing water is 10mg/L, and the phenol content of the condensed water increases continuously with the increase of the cycle time. After increasing to a certain extent, it will affect the mass transfer and heat exchange in the washing and cooling equipment, thus bring a series of adverse effects.

For decades, how to thoroughly treat phenol-containing sewage has been an environmental problem that plagues gas stations. After long-term research and discussion, experts engaged in industrial gas design and research have found some effective treatment methods and achieved certain results. effect, but there are still many shortcomings.

Several conventional treatment methods for phenolic sewage:

The treatment of phenol-containing sewage in gas stations is generally divided into two stages: first, the pretreatment stage, which aims to remove most of the suspended solids and tar in the sewage; second, the dephenol treatment stage, whose purpose is to remove Most of the phenolic substances and some organic substances in the pretreated sewage are removed.

1.1 Pretreatment methods: The pretreatment methods that have been applied in gas stations generally include the following:

1) natural sedimentation separation method; 2) mechanical filtration method; 3) chemical coagulation precipitation method; 4) electrolytic flotation method; 5) centrifugal separation method; Air flotation method; 8) jet air flotation method

Among them, the natural sedimentation separation method can be directly installed in the circulating water process system of the gas station. Although the effect is not very ideal, but the operation cost is low, and it has been adopted by most gas stations as a pretreatment method for phenolic sewage. The other seven methods must be processed in additional equipment, and the relative processing costs will be much higher.

1.2 Dephenolization treatment method: The dephenolization treatment method can be divided into physical chemical method and biochemical method.

1.2.1 Physicochemical method

1.2.1.1 Steam chemical dephenolization method

Use strong high-temperature steam to heat phenol-containing sewage, so that the phenol in the sewage evaporates and escapes with the steam, and then passes through the lye to absorb and become phenol sodium salt, so as to achieve the purpose of dephenolization. This method is simple to operate and requires less investment, but the steam consumption is relatively large, and the dephenolization efficiency is not ideal, and the purpose of thorough treatment is generally not achieved.

1.2.1.2 Steam dephenolization method

Heat the phenol-containing sewage to volatilize the phenol with the water vapor, and then pass this part of the phenol-containing steam into the bottom of the generator furnace and mix it with air as a gasification agent. In the furnace, the phenol is burned and decomposed into _CO2 and H ₂ O finally achieves the purpose of dephenolization. The disadvantage is that this method can only remove low-boiling point phenols, and the energy consumption is relatively large. It takes about 180 kilograms of fuel equivalent to standard coal to evaporate 1 ton of sewage. The saturation temperature of the bottom of the gas furnace is not easy to control.

1.2.1.3 Incineration method

The phenolic sewage is sprayed into the incinerator, so that the phenolic organic matter will undergo oxidation reaction at a high temperature of about 1100 ° C, and finally generate CO ₂ and H ₂ O emissions. This method has a simple process and is easy to operate, but it consumes a lot of energy. The cost of incinerating 1 ton of phenolic wastewater is about 200 yuan. In the early 1990s, the two-stage gasifiers imported from abroad and domestically supported were basically equipped with phenol water incinerator facilities, but they were basically idle due to energy consumption problems. Another key disadvantage of using incineration to treat phenol-containing sewage is that once the operation is careless, the furnace temperature will drop, which will often cause incomplete combustion and easily form secondary pollution.

1.2.1.4 Solvent extraction dephenolization method

The main process of this method is divided into two parts: extraction and desorption. The extraction process is a material redistribution process. The phenol is extracted from the sewage by using the extractant; A reaction occurs to generate sodium phenolate, which is a desorption process. The effluent treated by this kind of phenol removal method still contains 100-200mg/l phenol, which cannot be discharged directly, and the loss of the extractant will cause the emulsification of sewage and form secondary pollution. In addition, this method must use high-efficiency extractant and alkali, and the operating cost is relatively high.

1.2.1.5 Resin dephenolization method

The main process of this method includes adsorption and desorption. The phenol in the wastewater is adsorbed by resin, and then desorbed by lye to generate sodium phenate. The process of this method is relatively complicated, and there are many factors affecting the efficiency of phenol removal, and the operating cost is relatively high. high.

1.2.1.6 Sulfonated coal adsorption method

In this method, phenol is adsorbed by sulfonated coal polar groups, and then absorbed by lye to form phenol sodium salt for dephenolation. The adsorption of sulfonated coal is carried out intermittently, and one cycle includes two links of adsorption and regeneration. The main disadvantage of this method is that the amount of phenol absorbed by sulfonated coal is too low, the adsorption period is too short, and it is difficult to analyze and regenerate.

1.2.1.7 Biochemical method

Biochemical treatment of phenolic sewage is a process of cultivating microorganisms and using microorganisms to digest, absorb and decompose phenolic organic matter in sewage into H ₂ O and CO ₂ . This method can be divided into aeration method, contact oxidation method, biological turntable method and biological filter method according to the different ways of carrying microorganisms and oxygen supply. The biochemical method has strict requirements on the quality of the sewage entering the biochemical pool. The concentration of organic matter such as tar and phenol in the sewage should not exceed the concentration that microorganisms can withstand. Otherwise, the sewage needs to be diluted before entering the biochemical pool, which limits the amount of treated water. At the same time, it is difficult for microorganisms to domesticate. The concentration of influent water exceeds the standard and the ambient temperature is not suitable, which can easily limit the survival of microorganisms. A factory in Northeast China used biochemical methods to treat phenolic wastewater, but the cost of treatment was quite high due to strict requirements.

As mentioned above, whether it is incineration or biochemical method, either the cost is high or secondary pollution is caused. Among the many gas stations at present, there are very few users who are very ideal for phenol water treatment.

The Chinese patent with the publication number CN1162624A discloses a two-stage furnace water gas plant process flow and the treatment of phenol-containing water, including gasification, cooling and purification, and phenol-containing water treatment processes, wherein the phenol-containing water treatment part is provided by a phenol-containing water pump. , combustion regenerator, and two-stage furnace. The phenol-containing water uses the energy of air blowing to burn the checker bricks in the combustion regenerator to a high temperature of 800-900°C, and then sprays the phenol-containing water into the In the heat accumulator, it is gasified by heat exchange with checker bricks, and then enters the two-stage furnace as a gasification agent to produce water gas with hot coke to dispose of the phenolic water.

Contents of the invention

The present invention aims at the deficiencies in the prior art, starting from the heat balance required for the oxidation and reduction reactions of the gas, and adopts the method of incinerating the phenol water in the furnace without discharging it, so that the gas phenol water operates under a completely closed condition, effectively avoiding the Environmental pollution problems, and, due to the effective use of gas waste heat and the heat generated by phenol combustion, the gasification rate of coal into gas and the gasification intensity per unit area of the gas furnace body have been improved.

The present invention specifically adopts the following technical solutions:

A phenol water closed operation high-conversion coal gasification production process, including a gasification agent, characterized in that the temperature of the gasification agent is greater than 65°C, and the water content is the same weight of saturated air when the water content is 55-60°C .

The temperature of the gasifying agent is 65-80°C, 80-150°C or 150-250°C.

The gasifying agent is made by atomizing phenol-containing water in a mixing box and mixing it with hot air, and then enters the two-stage furnace in the next step; The air with a temperature of 300-500°C after heat exchange in the middle enters the mixing box in the next step.

The beneficial effects of the present invention are: compared with the traditional gas furnace gas production process, the air entering the bottom of the furnace undergoes heat exchange with high-temperature gas in the heat exchange equipment, becomes high-temperature air, and is sent into the In the mixing tank, the phenol water is transported into the mixing tank by the phenol water pump. There is an atomizing device in the mixing tank. After the atomizing device atomizes the phenol water, flash evaporation occurs in the high-temperature air, and it is rapidly vaporized. The agent is unsaturated hot air, and the relative humidity entering the bottom of the furnace is small. In the traditional process, hot steam is added to the air at room temperature, and it becomes supersaturated air before entering the furnace, and part of the water changes from gaseous state to liquid state. , After entering the bottom of the furnace, it needs to absorb a large amount of heat to gasify again, which will cause a certain degree of adverse effects on the ash layer and combustion layer at the bottom of the furnace, and reduce the calorific value of the gas.

In this process, the phenol-containing wastewater operates in a completely closed environment, and is cracked and incinerated in the oxide layer of the furnace body without pollution; part of the heat is returned to the furnace for use, which saves the amount of coal participating in the oxidation reaction and ensures that more coal participates in the reduction reaction, the gasification efficiency is increased by 3% to 5%, and the gasification intensity is increased by more than 10%. Solved the problems of phenol water pollution and secondary pollution.

The coal conversion rate of the present invention is high: taking Jincheng coal with a calorific value of 27000kJ/Kg as an example, the gasification efficiency is 76%, and the heat wasted by one kilogram of coal is 6480kJ. Income into the furnace, the heat value is about 1200kJ, accounting for 4.4% of the total heat of one kilogram of coal, accounting for 18.5% of the heat wasted by one kilogram of coal, because the process is continuous, the gasification intensity is improved in the process of continuous energy recovery and utilization , the improved value can reach 76 ^(1+0.04) %=92% theoretically.

Description of drawings

Fig. 1 is a prior art coal gasification production process flow chart;

Fig. 2 is a flow chart of the coal gasification production process of the present invention;

Fig. 3 is the equipment flowchart of embodiment 1;

Fig. 4 is the equipment flowchart of embodiment 2

Fig. 5 is the equipment flowchart of embodiment 3

In the figure, 1-gas furnace; 2-upper gas; 3-lower gas; 4-cyclone dust collector; 5-electric tar catcher; 6-intercooler; 7-electric light oil catcher; 8-gas output 9-phenol pool; 10-heat exchanger; 11-waste heat boiler; 12-hot air blower; 13-mixing box; 14-spray device; 15-steam drum; 16-air cooler; 17 is heat exchanger.

Example 1: The air enters the mixing box after heat exchange in the air cooler.

The gas 3 in the lower section is discharged from the outlet of the middle and upper part of the generator body 1. First, most of the dust in it is removed by the cyclone dust collector 4, and enters the waste heat boiler 11. The water performs heat exchange, and part of the water is vaporized and sent to the steam drum 15. The steam in the steam drum 15 can be used for flushing the system, and can be raised outward for other uses by the user. After the initial cooling of the waste heat boiler 11, the gas enters the Air cooling system heat exchanger 10, in the heat exchanger 10, a suitable number of tubes are arranged in the heat exchanger 10, the hot gas travels in the tubes, and under the action of the fan 12, the air between the inlet and outlet of the heat exchanger 10 A pressure difference is generated. Under the action of pressure, the air travels between the tubes, and through the tube wall conduction and radiation, the gas is cooled and the air is heated. The cooled hot gas joins with the upper stage gas and enters the intercooler 6 for further cooling, and then enters the electric light oil capture device, and after purification, it is sent to the user by the gas discharge machine 8.

As the gasification agent necessary for the gasifier—air, under the suction of the blower fan 12, when it comes out from the outlet of the heat exchanger 10, it becomes a high-temperature gas (300-500° C.). The toxic phenolic water discharged from the intercooler 6 is transported into the mixing tank 13 through the phenolic water pump, and under the action of the atomizer 14 in the mixing tank 13, the phenolic water is atomized into small mist droplets. The amount of water required in the gasification agent is generally controlled to be the amount of water saturated with air at 55-60°C, and the amount of phenolic water added to the mixing tank is controlled to be less than this value, and the missing part is made up by the steam in the steam drum 15 . Under the action of high-temperature air, the mist droplets are quickly evaporated in a short period of time, and are transported to the gas generator through the hot air steam pipe, and the temperature of the air entering the gas generator is controlled to be higher than 65°C. Then, the air entering the gas generator becomes Unsaturated air, water is in the state of complete monomolecular gas, and there is no gasification process when entering the furnace and passing through the ash layer at the bottom of the furnace, which will not cause a large decrease in the temperature of the ash layer and damage such as partial furnace.

Example 2: The waste heat boiler performs a heat exchange process.

The gas 3 in the lower section is discharged from the upper outlet of the raw furnace body 1. First, most of the dust is removed through the cyclone dust collector 4, and then enters the modified waste heat boiler 11. High temperature (550-600°C) gas passes through the waste heat boiler 11 , an appropriate number of tubes are arranged inside, the hot gas travels in the tubes, the air enters the waste heat boiler 11 from the inlet, and can pass through the outer gap of the tubes, the air outlet is connected to the bottom of the furnace, and the air is sucked by the fan 12. There is a pressure difference between the inlet and outlet. Under the action of the pressure, the air passes through the pipe, and the gas is cooled and the air is heated through the conduction and radiation of the pipe wall. The cooled hot gas joins with the upper stage gas and enters the intercooler for further cooling, and then enters the electric light oil capture device, and after purification, it is sent to the user by the gas discharge machine 8.

The air from the waste heat boiler 11 becomes a high-temperature gas (300-500° C.), and the hot air is delivered to the mixing box 13 through the hot air pipe and the fan 12. Under the action of the atomizer 14 in the mixing box 13, the phenol The water gets atomized into small mist droplets. Under the action of high-temperature air, the fog droplets are quickly evaporated in a short period of time, and are transported to the gas generator through the hot air steam pipe.

Embodiment 3: The heat exchange process is carried out on the conveying pipe.

The gas delivery pipe is properly transformed into a heat exchanger 17, and the gas 3 in the lower section is discharged from the middle outlet of the generator 1. When passing through the gas delivery pipe, heat is transferred to the air that is traveling against it, and it is heated. The air outlet is connected to the fan 28, under the action of the fan, a pressure difference is generated between the air inlet and outlet, under the action of the pressure, the air and the gas flow in reverse, through the conduction and radiation of the pipe wall, the gas is cooled and the air is heated. The cooled hot gas joins with the upper stage gas and enters the intercooler for further cooling, and then enters the electric light oil trap, and after purification, it is sent to the user by the gas discharge machine 13. The air from the waste heat boiler becomes high-temperature gas (300-500°C), and the hot air is transported into the mixing box through the hot air pipe 29 and the fan 28. Under the action of the atomizer in the mixing box, the phenol water is mist into small mist droplets. Under the action of high-temperature air, the fog droplets are quickly evaporated in a short period of time, and are transported to the gas generator through the hot air steam pipe.

In the traditional process, the high-temperature gas from the waste heat boiler is wasted by dissipating excess heat into the air through the air cooler. In this process, this part of the heat is returned to the furnace for utilization. Compared with reducing the amount of coal involved in the oxidation reaction, more coal participates in the reduction reaction to generate useful gas, and the gasification rate can be increased by 3% to 5%. Since the gasification agent uses hot air instead of room temperature air, the gasification intensity of the gas can be increased by more than 10%. The phenol water condensed from the intercooler is mechanically returned to the furnace for incineration in a completely closed environment. Solved the problem of phenol water pollution and secondary pollution.

Claims (4)

1. A phenolic water closed operation high-conversion coal gasification production process, including a gasification agent, is characterized in that the temperature of the gasification agent is 65 to 250 ° C, and the water content is 55 to 60 ° C when the same weight is saturated Moisture content of the air; the gasification agent is made by atomizing phenol-containing water in a mixing box and mixing with hot air, and the hot air is made by air in an air cooler, waste heat boiler or gas pipeline Hot air with a temperature of 300-500°C after heat exchange. 2. The phenol water closed operation high-conversion coal gasification production process according to claim 1, characterized in that the temperature of the gasification agent is 65-80°C. 3. The phenol water closed operation high-conversion coal gasification production process according to claim 1, characterized in that the temperature of the gasification agent is 80-150°C. 4. The phenol water closed operation high-conversion coal gasification production process according to claim 1, characterized in that the temperature of the gasification agent is 150-250°C.

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