A device and method for grading utilization of residual energy from coal gasification

Abstract

The present invention discloses a device for graded utilization of waste energy of a coal gasification device, comprising a waste pressure energy recovery and utilization unit, a spiral waste heat recovery and utilization unit, a positive pressure flash evaporation waste heat power generation unit, a negative pressure flash evaporation waste heat power generation unit, a gasification ash water circulation utilization unit and an organic medium power generation unit; a method for graded utilization of waste energy of coal gasification using the device is also disclosed. The device of the present invention converts the waste heat energy and waste pressure energy carried by the high-temperature crude synthesis gas and high-pressure black water of the coal gasification product into heat energy and electrical energy respectively by arranging a waste pressure energy and spiral waste heat recovery and utilization unit, a positive pressure flash evaporation and negative pressure flash evaporation waste heat power generation unit, thereby realizing the recovery and utilization of waste heat energy and waste pressure energy. At the same time, the waste heat power generation group is used instead of the heat exchanger to recover waste heat energy, and the waste pressure energy recovery device is used instead of the pressure reducing valve to recover waste pressure energy, thereby effectively reducing the power capacity expansion cost of the entire gasification device and the heat exchange circulating water consumption of the device; the method of the present invention improves energy utilization efficiency and is suitable for the field of coal gasification.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy and chemical industry, and in particular relates to a device and method for graded utilization of residual energy from coal gasification. Background Art

[0002] Coal gasification technology is the leader of the modern coal chemical industry. Based on the synthesis gas cooling method, coal gasification technology can be divided into two types: the quenching process and the waste boiler process. The quenching process is mature in technology, with low equipment investment and simple operation. It is the coal gasification technology with the most application achievements at home and abroad. The raw coal and oxygen undergo combustion and partial oxidation reaction in the gasifier reaction chamber to generate high-temperature, high-pressure crude synthesis gas and liquid slag. After the crude synthesis gas and slag come out of the reaction chamber, they enter the quenching chamber. A large amount of quenching water is used to rapidly cool the crude synthesis gas from a high temperature of 1300℃ to 1400℃ to 240℃ to 260℃, obtaining crude synthesis gas with a high steam-gas ratio and quenching black water that absorbs a large amount of sensible heat. The crude synthesis gas and quenching black water leaving the quenching chamber carry a large amount of waste heat. Due to the low energy grade of the waste heat and the fact that the crude synthesis gas easily carries water and ash, the pH value of the quenching black water fluctuates greatly, the solid content is high, and it contains soluble gases and Ca. 2+ Mg 2+ 、Cl - 、S 2- The presence of harmful elements such as chlorinated carbon dioxide (CO2) and chlorinated ether (CO2) makes waste heat recovery and utilization in the gasification unit difficult, leading to significant energy waste in the gasification system, an energy utilization rate of less than 70%, and irrational energy utilization. Furthermore, the black water exiting the quenching chamber is at a high pressure and contains pressure energy. Currently, pressure reduction valves are the primary method for reducing the pressure. However, due to the high solids content in the black water, this not only causes severe erosion of the valves but also wastes valuable residual pressure energy. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide a device for the graded utilization of waste energy from coal gasification. The device is provided with a waste pressure energy recovery and utilization unit, a spiral waste heat recovery and utilization unit, a positive pressure flash waste heat power generation unit, and a negative pressure flash waste heat power generation unit, respectively converting the waste pressure energy and waste heat energy carried by the high-temperature crude synthesis gas and high-pressure black water from the coal gasification product into heat energy and electrical energy, thereby realizing the component utilization of waste heat energy and waste pressure energy. At the same time, the waste heat power generation unit is used instead of the heat exchanger to recover waste heat energy, and the waste pressure energy recovery device is used instead of the pressure reducing valve to recover waste pressure energy, effectively reducing the cost of increasing the power capacity of the entire gasification device and the amount of heat exchange circulating water used in the device, and solving the problems of severe wear of the pressure reducing valve, high consumption of circulating water cooling water, and low energy utilization efficiency of the device in the traditional gasification black water system.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is: a coal gasification waste energy graded utilization device, characterized by comprising a waste pressure energy recovery and utilization unit, a spiral waste heat recovery and utilization unit, a positive pressure flash evaporation waste heat power generation unit, a negative pressure flash evaporation waste heat power generation unit, a gasification ash water recycling unit and an organic medium power generation unit;

[0005] The residual pressure energy recovery unit includes a gasification black water concentrator, a black water filter, a residual pressure energy recovery device, and a residual pressure generator set connected in sequence. The inlet of the gasification black water concentrator is connected to the gasifier and the water washing dust removal tower respectively, the top outlet is connected to the inlet of the black water filter, and the bottom outlet is connected to the positive pressure flash evaporation waste heat power generation unit. The outlet of the black water filter is connected to the inlet of the residual pressure energy recovery device, and the outlet of the residual pressure energy recovery device is connected to the booster pump, the residual pressure generator set, and the spiral waste heat recovery unit respectively.

[0006] The spiral waste heat recovery unit includes a first-level spiral heat recovery device and a second-level spiral heat recovery device connected in parallel. The inlet of the first-level spiral heat recovery device is connected to the gasification furnace, and the outlet is connected to the water washing dust removal tower. The inlet of the second-level spiral heat recovery device is connected to the residual pressure energy recovery device, and the outlet is connected to the positive pressure flash waste heat power generation unit.

[0007] The positive pressure flash waste heat power generation unit includes a positive pressure flash evaporator, the inlet of the positive pressure flash evaporator is connected to the gasification black water concentrator and the secondary spiral heat energy recovery device, and the outlet is respectively connected to the medium heater, the primary waste heat generator set, and the negative pressure flash evaporator, and the outlet of the medium heater and the outlet of the primary waste heat generator set are connected to the flash steam gas-liquid separator;

[0008] The negative pressure flash waste heat power generation unit includes a negative pressure flash evaporator, a secondary waste heat generator set, a gas-water separator, and a condensate pump connected in sequence. The inlet of the negative pressure flash evaporator is connected to the positive pressure flash evaporator, the flash steam outlet is connected to the secondary waste heat generator set, the black water outlet is connected to the concentrator feed pump, the inlet of the gas-water separator is connected to the outlet of the secondary waste heat generator set, the non-condensable gas outlet is connected to the negative pressure generator, and the condensate outlet is connected to the condensate pump.

[0009] The gasification grey water recycling unit comprises a flash black water concentrator, a filter, an grey water tank and a grey water pump, and a heat recovery device connected in sequence. The black water inlet of the flash black water concentrator is connected to the concentrator feed pump, the clear liquid outlet is connected to the inlet of the grey water tank, the concentrated black water outlet is connected to the filter, the outlet of the filter is connected to the inlet of the grey water tank, the water outlet of the grey water tank is connected to the grey water pump, the inlet of the heat recovery device is respectively connected to the outlet of the positive pressure flash evaporator of the positive pressure flash waste heat power generation unit, the water outlet of the flash steam gas-liquid separator, and the water outlet of the condensate pump, the vent air outlet is connected to the three-stage medium heater, and the circulating water outlet is connected to the underflow pump of the heat recovery device;

[0010] The organic medium power generation unit includes a medium mixer, an organic medium generator set, a medium cooler, a medium collecting tank, and a medium circulation pump, which are connected in sequence. The feed port of the medium mixer is connected to the outlet of the medium heater of the positive pressure flash waste heat power generation unit and the outlet of the three-stage medium heater, and the outlet is connected to the organic medium generator set. The feed port of the medium cooler is connected to the organic medium generator set, and the outlet is connected to the medium collecting tank. The feed port of the medium circulation pump is connected to the medium collecting tank, and the outlet is respectively connected to the medium heater and the three-stage medium heater of the positive pressure flash waste heat power generation unit.

[0011] The above-mentioned coal gasification waste energy graded utilization device is characterized in that a wear-resistant layer is provided in the gasification black water concentrator.

[0012] The above-mentioned coal gasification waste energy graded utilization device is characterized in that the bottom outlet of the first-stage spiral heat energy recovery device is connected to the lower quenching chamber of the gasifier.

[0013] The above-mentioned coal gasification waste energy graded utilization device is characterized in that the positive pressure flash evaporation waste heat power generation unit is a first-level positive pressure flash evaporation unit, including a first-level positive pressure flash evaporator, the inlet of the first-level positive pressure flash evaporator is connected to the gasification black water concentrator and the second-level spiral heat energy recovery device, the flash steam outlet is respectively connected to the first-level medium heater and the first-level waste heat power generation unit, the black water outlet is connected to the negative pressure flash evaporator, the outlet of the first-level medium heater and the outlet of the first-level waste heat power generation unit are both connected to the flash steam gas-liquid separator; correspondingly, the inlet of the heat recovery device in the gasification ash water recycling unit is connected to the lower section flash steam outlet of the first-level positive pressure flash evaporator, the feed port of the medium mixer in the organic medium power generation unit is connected to the outlet of the first-level medium heater, and the outlet of the medium circulation pump is connected to the inlet of the first-level medium heater;

[0014] Alternatively, the positive-pressure flash waste heat power generation unit is a two-stage positive-pressure flash unit, comprising a first-stage positive-pressure flash evaporator and a second-stage positive-pressure flash evaporator connected in sequence, the inlet of the first-stage positive-pressure flash evaporator being connected to the gasification black water concentrator and the second-stage spiral heat energy recovery device, the flash steam outlet being respectively connected to the first-stage medium heater and the first-stage waste heat power generation unit, the black water outlet being connected to the second-stage positive-pressure flash evaporator, the outlet of the first-stage medium heater and the outlet of the first-stage waste heat power generation unit being both connected to the flash steam gas-liquid separator, the outlet of the second-stage positive-pressure flash evaporator being respectively connected to the second-stage medium heater and the negative-pressure flash evaporator; correspondingly, the inlet of the heat recovery device in the gasification ash water recycling unit is connected to the lower flash steam outlet of the first-stage positive-pressure flash evaporator and the flash steam outlet of the second-stage medium heater, the feed port of the medium mixer in the organic medium power generation unit is connected to the outlet of the first-stage medium heater and the outlet of the second-stage medium heater, and the outlet of the medium circulation pump is connected to the inlet of the first-stage medium heater and the inlet of the second-stage medium heater.

[0015] The above-mentioned coal gasification waste energy graded utilization device is characterized in that the first-stage positive pressure flash evaporator adopts an upper and lower two-stage flash evaporation structure, and the upper flash steam outlet is connected to the first-stage medium heater, and the lower flash steam outlet is connected to the first-stage waste heat generator set and heat recovery device.

[0016] The above-mentioned coal gasification waste energy graded utilization device is characterized in that the negative pressure generator is a water ring vacuum pump or a dry screw vacuum pump.

[0017] The above-mentioned coal gasification waste energy graded utilization device is characterized in that the first-level waste heat generator set, the second-level waste heat generator set and the organic medium generator set are composed of a screw expander combined with a generator, or a turbine combined with a generator.

[0018] At the same time, the present invention also discloses a method for graded utilization of residual energy from coal gasification using the above-mentioned device, characterized in that the method comprises the following steps:

[0019] Step 1, recycling of residual pressure energy: the high-pressure black water from the gasifier and the water-washing dust removal tower is sent to the gasification black water concentrator for solid-liquid separation. The concentrated black water after separation is discharged from the bottom of the gasification black water concentrator and sent to the positive pressure flash evaporator, while the high-pressure gasification gray water with low solid content overflows from the top of the gasification black water concentrator, is filtered and removed by the black water filter, and then sent to the residual pressure energy recovery device. At the same time, the low-pressure circulating gray water returned by the gasification gray water recycling unit also enters the residual pressure energy recovery device. The high-pressure gasification gray water after impurities removal in the residual pressure energy recovery device completes the pressure increase of the low-pressure circulating gray water and is sent to the secondary spiral heat energy recovery device. The pressurized circulating gray water is either pressurized by a booster pump and sent out as high-pressure gray water for direct use, or sent to the residual pressure generator set to complete power generation and then sent out as low-pressure gray water for use;

[0020] Step 2: Spiral waste heat recovery and utilization: The high-temperature crude synthesis gas prepared from the gasified raw materials from the gasifier is fed into the first-stage spiral heat recovery device, undergoes countercurrent heat exchange with the boiler feed water fed into the first-stage spiral heat recovery device, and produces low-pressure steam as a by-product. The by-product low-pressure steam is sent to the pipeline network for use. The quenching water and fine ash entrained in the high-temperature crude synthesis gas are separated from the liquid in the countercurrent heat exchange process and returned to the quenching chamber of the gasifier, thereby reducing the liquid level fluctuation in the quenching chamber and the ash in the subsequent conversion system. The high-temperature crude synthesis gas that has completed the countercurrent heat exchange and gas-liquid separation is sent to the water washing and dust removal tower for water washing and dust removal, and then sent to the subsequent conversion system.

[0021] The high-pressure gasified ash water after the pressure increase in step 1 is sent to the secondary spiral heat energy recovery device, and is subjected to countercurrent heat exchange with the boiler feed water sent to the secondary spiral heat energy recovery device to produce low-pressure steam as a by-product. The by-product low-pressure steam is sent to the pipeline network for use, and the high-pressure gasified ash water that has completed the countercurrent heat exchange is sent to the positive pressure flash evaporator;

[0022] Step 3, positive pressure flash evaporation waste heat power generation: the concentrated black water discharged from the bottom of the gasification black water concentrator in step 1 and sent to the positive pressure flash evaporator and the high-pressure gasification ash that completes countercurrent heat exchange and is sent to the positive pressure flash evaporator in step 2 are flash evaporated to obtain flash steam and positive pressure flash evaporation concentrated black water, part of the flash steam is sent to the medium heater to heat the circulating medium and then sent to the flash steam gas-liquid separator for gas-liquid separation to obtain condensate and non-condensable gas, part of the first-level lower section flash steam is sent to the first-level waste heat generator set to generate electricity, and the generated electricity is sent to the power grid, the flash steam that has completed power generation is sent to the flash steam gas-liquid separator for gas-liquid separation to obtain condensate and non-condensable gas, the non-condensable gas in the flash steam gas-liquid separator is sent for treatment, the condensate is sent to the heat recovery device, the remaining first-level lower section flash steam is sent to the heat recovery device, and the positive pressure flash evaporation concentrated black water is sent to the negative pressure flash evaporator;

[0023] Step 4, negative pressure flash waste heat power generation: After the positive pressure flash concentrated black water generated in the positive pressure flash evaporator in step 3 is sent to the negative pressure flash evaporator, it is flash vaporized under the negative pressure conditions provided by the negative pressure generator to obtain flash steam and negative pressure flash concentrated black water, and the flash steam is sent to the secondary waste heat generator set to generate electricity, and the generated electricity is sent to the power grid. The flash steam that has completed power generation enters the gas-water separator for gas-liquid separation to obtain non-condensable gas and condensate, and the non-condensable gas is emptied through the negative pressure generator, and the condensate is sent to the heat recovery device under the action of the condensate pump. The negative pressure flash concentrated black water is pressurized by the concentrator feed pump and sent to the flash black water concentrator;

[0024] Step 5: Recycling of Gasified Grey Water: The black water pressurized by the concentrator feed pump in Step 4 is fed into the flash black water concentrator for negative pressure flash evaporation and concentration, where it undergoes liquid-solid separation to obtain clean grey water and bottom concentrated black water. The clean grey water is fed from the top of the flash black water concentrator to the grey water tank and pumped out for recycling. The bottom concentrated black water is fed into a filter for further liquid-solid separation to obtain dehydrated fine residue and filtrate. The fine residue is sent to the slag yard, and the filtrate is sent to the grey water tank for recycling as make-up water.

[0025] At the same time, the condensate obtained by gas-liquid separation in the flash steam gas-liquid separator in step 3, the remaining first-stage lower flash steam sent to the heat recovery device, and the condensed water sent by the condensate pump in step 4 enter the heat recovery device together to obtain vent air and degassed gray water. The vent air is discharged from the top of the heat recovery device, then enters the three-stage medium heater to heat the circulating medium and then emptied. The degassed gray water is discharged from the bottom of the heat recovery device and recycled under the action of the underflow pump of the heat recovery device;

[0026] Step 6, organic medium power generation: the circulating medium heated in the medium heater in step 3 and the circulating medium heated in the tertiary medium heater in step 5 are sent to the medium mixer for thorough mixing, and then sent to the organic medium generator set for power generation, and the generated electricity is sent to the power grid. The circulating medium that has completed power generation is sent to the medium cooler for cooling, and then sent to the medium collection tank, and then sent again to the medium heater and the tertiary medium heater of the positive pressure flash waste heat power generation unit through the medium circulation pump for recycling.

[0027] The above method is characterized in that, in step three, a first-stage positive pressure flash evaporation unit including a first-stage positive pressure flash evaporator is used to perform positive pressure flash evaporation waste heat power generation, and the first-stage positive pressure flash evaporator has an upper and lower two-stage flash evaporation structure: the concentrated black water discharged from the bottom of the gasified black water concentrator in step one and sent to the first-stage positive pressure flash evaporator and the high-pressure gasified gray water that completes countercurrent heat exchange in step two and is sent to the first-stage positive pressure flash evaporator are flash evaporated to obtain first-stage upper flash steam, first-stage lower flash steam and first-stage positive pressure flash evaporation concentrated black water, the first-stage upper flash steam is sent to the first-stage medium heater to heat the circulating medium and then sent to the flash steam gas-liquid separator for gas-liquid separation to obtain condensate and non-condensable gas, part of the flash steam is sent to the first-stage waste heat generator set to generate electricity, and the generated electricity is sent to the power grid, and the flash steam that has completed power generation enters the flash steam gas-liquid separator for gas-liquid separation Separate to obtain condensate and non-condensable gas, send the non-condensable gas in the flash steam gas-liquid separator for treatment, send the condensate to the heat recovery device, send the remaining flash steam to the heat recovery device, and send the positive pressure flash concentrated black water to the negative pressure flash evaporator; correspondingly, in the gasification ash water recycling process described in step five, the condensate obtained by gas-liquid separation in the flash steam gas-liquid separator in step three, the remaining flash steam and the condensed water sent in by the condensate pump in step four enter the heat recovery device together; in the organic medium power generation process described in step six, the circulating medium after heating in the first-level medium heater in step three and the circulating medium after heating in the third-level medium heater in step five are sent to the medium mixer for sufficient mixing, and are sent to the medium collection tank after power generation and cooling, and are sent to the first-level medium heater and the third-level medium heater again for recycling through the medium circulation pump.

[0028] Alternatively, in step three, a two-stage positive pressure flash evaporator unit including a first-stage positive pressure flash evaporator and a second-stage positive pressure flash evaporator is used to perform positive pressure flash evaporation waste heat power generation, and the first-stage positive pressure flash evaporator has an upper and lower two-stage flash evaporation structure: the concentrated black water discharged from the bottom of the gasified black water concentrator in step one and sent to the first-stage positive pressure flash evaporator and the high-pressure gasified ash in step two that completes countercurrent heat exchange and is sent to the first-stage positive pressure flash evaporator are flash evaporated to obtain a first-stage upper flash steam, a first-stage lower flash steam and a first-stage positive pressure flash concentrated black water, and the first-stage upper flash steam is sent to a second stage positive pressure flash evaporator. After the circulating medium is heated in the secondary medium heater, it is sent to the flash steam gas-liquid separator for gas-liquid separation to obtain condensate and non-condensable gas. Part of the flash steam in the lower section of the first stage is sent to the first stage waste heat generator set to generate electricity, and the generated electricity is sent to the power grid. The flash steam that has completed power generation enters the flash steam gas-liquid separator for gas-liquid separation to obtain condensate and non-condensable gas. The non-condensable gas in the flash steam gas-liquid separator is sent out for treatment, the condensate is sent to the heat recovery device, and the remaining flash steam in the lower section of the first stage is sent to the heat recovery device to condense the first stage positive pressure flash steam. The black water is sent to the secondary positive pressure flash evaporator for further flash evaporation to obtain secondary flash steam and secondary positive pressure flash concentrated black water. The secondary flash steam is sent to the secondary medium heater to heat the circulating medium and then sent to the heat recovery device. The secondary positive pressure flash concentrated black water is sent to the negative pressure flash evaporator; correspondingly, in the gasification ash water recycling process described in step five, the condensate obtained by gas-liquid separation in the flash steam gas-liquid separator in step three, the remaining first-level lower flash steam, and the second-level flash steam sent after heating the circulating medium in the secondary medium heater, together with the condensed water sent through the condensate pump in step four, enter the heat recovery device for degassing and heat exchange; in the organic medium power generation process described in step six, the heated circulating medium in the first-level medium heater in step three, the heated circulating medium in the second-level medium heater, and the heated circulating medium in the tertiary medium heater in step five are sent to the medium mixer for full mixing, and are sent to the medium collection tank after power generation and cooling, and are sent to the first-level medium heater, the second-level medium heater and the tertiary medium heater again through the medium circulation pump for recycling.

[0029] The above method is characterized in that the negative pressure condition in step three is 4kPa to 38.6kPa.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] 1. The device of the present invention is provided with a residual pressure energy recovery and utilization unit, a spiral residual heat recovery and utilization unit, a positive pressure flash evaporation residual heat power generation unit, and a negative pressure flash evaporation residual heat power generation unit, which respectively convert the residual heat energy and residual pressure energy carried by the high-temperature crude synthesis gas and high-pressure black water of the coal gasification product into heat energy and electrical energy, and produce steam. At the same time, a gasification ash water recycling unit and an organic medium power generation unit are provided to recycle the by-product gasification ash water and organic medium, and convert them into electrical energy at the same time, thereby converting the residual heat energy and residual pressure energy generated by the coal gasification device into heat energy and electrical energy in a graded manner, completing the cooling and pressure reduction treatment of the high-temperature and high-pressure fluid, and realizing the full utilization of the residual pressure energy and residual heat energy of the coal gasification.

[0032] 2. In the device of the present invention, by setting a waste pressure energy recovery and utilization unit and a spiral waste heat recovery and utilization unit, higher-grade waste heat energy such as waste heat energy carried by high-temperature crude synthesis gas and high-pressure gasification ash water is recovered, and high-value low-pressure steam is produced as a by-product. By setting a positive-pressure flash evaporation waste heat power generation unit and a negative-pressure flash evaporation waste heat power generation unit, medium-grade waste heat energy such as waste heat energy carried by flash steam obtained by positive-pressure flash evaporation and negative-pressure flash evaporation is used to generate electricity through waste heat power generation groups at various levels to achieve electrical energy conversion. By setting an organic medium power generation unit, lower-grade waste heat energy such as waste heat energy carried by flash steam and vented air is recovered through a circulating medium, and the circulating medium is used to generate electricity, thereby achieving graded utilization of waste heat energy, maximizing the recovery of waste heat energy from the previous coal gasification device, and improving the energy utilization efficiency of the coal gasification device by more than 3%.

[0033] 3. In the device of the present invention, a two-stage waste heat generator set is set in the positive pressure flash evaporation waste heat power generation unit and the negative pressure flash evaporation waste heat power generation unit, which replaces the traditional heat exchange equipment to recover the waste heat of the gas flash steam, greatly reducing the consumption of circulating cooling water and reducing the operating costs of the device. In addition, the electricity generated by the two-stage waste heat generator set further increases the economic efficiency.

[0034] 4. The device of the present invention is equipped with a residual pressure energy recovery unit, and the residual pressure energy recoverer is used instead of the traditional pressure reducing valve, thereby effectively recovering the residual energy of high-pressure black water, improving the energy utilization efficiency of the device, and solving the problems of severe wear of the pressure reducing valve, large consumption of circulating water and cooling water, and low energy utilization efficiency of the device in the traditional gasification black water system.

[0035] 5. In the device of the present invention, a first-stage spiral heat recovery device is connected to the outlet of the gasifier quenching chamber, which not only recovers the sensible heat carried by the high-temperature crude synthesis gas leaving the gasifier, but also separates the liquid water and fine ash entrained in the crude synthesis gas in the first-stage spiral heat recovery device, and returns the entrained water and ash to the quenching chamber, thereby reducing the ash carried by the crude synthesis gas into the subsequent system and reducing the impact of the liquid carried by the crude synthesis gas on the liquid level fluctuation in the quenching chamber.

[0036] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the unit connection structure of the device for graded utilization of surplus energy of a coal gasification device according to the present invention.

[0038] Description of the accompanying drawings:

[0039] 1—Gasification furnace; 2—First-stage spiral heat recovery device; 3—Water washing dust removal tower;

[0040] 4—Gasification black water concentrator; 5—Black water filter; 6—Excess pressure energy recovery device;

[0041] 7—Second-stage spiral heat recovery device; 8—Booster pump; 9—Excess pressure generator set;

[0042] 10—first-stage positive-pressure flash evaporator; 11—second-stage positive-pressure flash evaporator; 12—negative-pressure flash evaporator;

[0043] 13—concentrator feed pump; 14—first-stage waste heat generator set; 15—second-stage waste heat generator set;

[0044] 16—first-stage medium heater; 17—second-stage medium heater; 18—third-stage medium heater;

[0045] 19—Flash steam gas-liquid separator; 20—Gas-water separator; 21—Negative pressure generator;

[0046] 22—Condensate pump; 23—Heat recovery device; 24—Heat recovery device underflow pump;

[0047] 25—medium mixer; 26—organic medium generator set; 27—medium cooler;

[0048] 28—Medium collection tank; 29—Medium circulation pump; 30—Flash black water concentrator;

[0049] 31—Filter; 32—Gray water tank; 33—Gray water pump. DETAILED DESCRIPTION

[0050] The device for graded utilization of residual energy from coal gasification of the present invention is described in detail through Example 1.

[0051] Example 1

[0052] like Figure 1 As shown, the coal gasification waste energy graded utilization device of this embodiment includes a waste pressure energy recovery and utilization unit, a spiral waste heat recovery and utilization unit, a positive pressure flash evaporation waste heat power generation unit, a negative pressure flash evaporation waste heat power generation unit, a gasification ash water recycling unit and an organic medium power generation unit;

[0053] The coal gasification residual energy graded utilization device of this embodiment is provided with a residual pressure energy recovery and utilization unit,

[0054] The spiral waste heat recovery and utilization unit, the positive pressure flash evaporation waste heat power generation unit, and the negative pressure flash evaporation waste heat power generation unit respectively convert the waste pressure energy and waste heat energy carried by the high-pressure crude synthesis gas and high-pressure black water of the coal gasification product into thermal energy and electrical energy. At the same time, the gasification ash water recycling unit and the organic medium power generation unit are set up to recycle the by-product gasification ash water and organic medium, and convert them into electrical energy.

[0055] The residual pressure energy recovery and utilization unit of this embodiment includes a gasification black water concentrator 4,

[0056] Black water filter 5, residual pressure energy recovery device 6, residual pressure generator set 9, the inlet of the gasification black water concentrator 4 is respectively connected to the gasification furnace 1 and the water washing dust removal tower 3, the top outlet is connected to the inlet of the black water filter 5, and the bottom outlet is connected to the positive pressure flash waste heat power generation unit. The outlet of the black water filter 5 is connected to the inlet of the residual pressure energy recovery device 6, and the outlet of the residual pressure energy recovery device 6 is respectively connected to the booster pump 8, the residual pressure generator set 9, and the spiral waste heat recovery unit;

[0057] In the residual pressure energy recovery and utilization unit of this embodiment, a gasification black water concentrator 4 is set to perform liquid-solid separation on the high-pressure gasification black water from the gasifier 1 and the high-pressure washing black water from the water washing dust removal tower 3. The concentrated black water with a higher solid content is discharged from the bottom of the gasification black water concentrator 4 and enters the positive pressure flash evaporation waste heat power generation unit for waste heat utilization. The high-pressure gasification gray water with a lower solid content overflows from the top of the gasification black water concentrator 4 and is then sent to the residual pressure energy recovery device 6 for residual pressure energy utilization. It is usually used to increase the pressure of the low-pressure circulating gray water returned from the gasification gray water recycling unit for sending it out for use, thereby realizing the transfer and utilization of residual pressure energy, and passing through the pipe before it enters the inlet of the residual pressure energy recovery device 6. A black water filter 5 is set on the road to filter out impurities to prevent impurities from clogging the residual pressure energy recovery device 6, thereby ensuring that the residual pressure energy recovery device 6 fully utilizes the residual pressure energy in the high-pressure gasified ash water; at the same time, by setting a booster pump 8 at the outlet of the residual pressure energy recovery device 6, the circulating ash water after pressure increase is pressurized to a suitable pressure and then sent out for use, or further, by setting a residual pressure generator set 9 at the outlet of the residual pressure energy recovery device 6, the circulating ash water after pressure increase is directly subjected to residual pressure power generation to realize the recovery and utilization of residual pressure energy, and by setting the residual pressure energy recovery device 6 to be connected to the spiral waste heat recovery unit, the high-pressure gasified ash water after pressure reduction is sent to the spiral waste heat recovery unit for further utilization of residual heat. In summary, this embodiment sets up a residual pressure energy recovery and utilization unit to separate the high-pressure gasified black water generated by gasification and the high-pressure washing black water generated by water washing and dust removal through liquid-solid separation, and transfers the residual pressure energy and generates residual pressure electricity according to the physical and chemical properties of the separated products, concentrated black water and high-pressure gasified gray water, and sends them to subsequent units for utilization with the heat they carry, that is, converting the residual pressure energy into electrical energy, thereby realizing the full utilization of the residual pressure energy carried by the high-pressure black water.

[0058] Typically, the residual pressure energy recovery device 6 is a piston type residual energy recovery device, a rotor type residual energy recovery device or a diaphragm type residual energy recovery device.

[0059] The spiral waste heat recovery unit of this embodiment includes a primary spiral heat recovery device 2 and a secondary spiral heat recovery device 7 connected in parallel. The inlet of the primary spiral heat recovery device 2 is connected to the gasification furnace 1, and the outlet is connected to the water washing dust removal tower 3. The inlet of the secondary spiral heat recovery device 7 is connected to the residual pressure energy recovery device 6, and the outlet is connected to the positive pressure flash waste heat power generation unit.

[0060] In the spiral waste heat recovery unit of this embodiment, a first-stage spiral heat recovery device 2 and a second-stage spiral heat recovery device 7 are set in parallel, and a two-stage heat recovery process is adopted. The heat recovery device with a spiral structure is used to increase the heat recovery area, thereby improving the heat recovery efficiency and recovery amount. First, the inlet of the first-stage spiral heat recovery device 2 is connected to the gasifier 1, so that the main product of coal gasification in the gasifier, high-temperature crude synthesis gas, that is, high-temperature crude coal gas, directly enters the first-stage spiral heat recovery device 2, and undergoes countercurrent heat exchange with the boiler feed water sent in by the external pipeline and produces low-pressure steam as a by-product, so that the waste heat in the high-temperature crude coal gas is transferred to the low-pressure steam and sent out for utilization, and the quenching water and fine ash entrained in the high-temperature crude coal gas are separated in the countercurrent heat exchange process. By setting the outlet of the first-stage spiral heat energy recovery device 2 to be connected to the water-washing dust removal tower 3, the raw coal gas that has completed countercurrent heat exchange and separation is sent to the water-washing dust removal tower 3 for water washing and dust removal, and then sent out for utilization, thereby realizing the transfer and recovery of waste heat in the high-temperature raw synthesis gas; secondly, by setting the inlet of the second-stage spiral heat energy recovery device 7 to be connected to the residual pressure energy recovery device 6, and the outlet to be connected to the positive pressure flash waste heat power generation unit, the high-pressure gasified ash water after the residual pressure energy transfer in the residual pressure energy recovery and utilization unit enters the second-stage spiral heat energy recovery device 7, and undergoes countercurrent heat exchange with the boiler feed water sent in by the external pipeline and produces low-pressure steam as a by-product, that is, the waste heat in the high-pressure gasified ash water after the residual pressure energy transfer is transferred to the low-pressure steam, thereby realizing the transfer and recovery of the remaining heat carried by it. In summary, this embodiment sets up a spiral waste heat recovery unit and adopts a multi-stage spiral heat energy recovery device to form a two-stage heat energy recovery process, which respectively recovers the heat energy carried by the high-temperature crude synthesis gas, the main product of coal gasification, and the waste heat energy of the gasified ash water in the residual pressure energy recovery unit, thereby avoiding waste of heat energy, improving the heat energy recovery efficiency, and sending the gasified ash water carrying the remaining heat energy to the lower-level unit for utilization.

[0061] The positive pressure flash waste heat power generation unit includes a positive pressure flash evaporator, the inlet of the positive pressure flash evaporator is connected to the gasification black water concentrator 4 and the secondary spiral heat energy recovery device 7, and the outlet is respectively connected to the medium heater, the primary waste heat generator set 14, and the negative pressure flash evaporator 12, and the outlet of the medium heater and the outlet of the primary waste heat generator set 14 are connected to the flash steam gas-liquid separator 19;

[0062] In the positive pressure flash waste heat power generation unit of this embodiment, a positive pressure flash evaporator is provided, and the inlet of the positive pressure flash evaporator is connected to the gasification black water concentrator 4 and the secondary spiral heat energy recovery device 7, which is used to flash the concentrated black water with a high solid content in the waste pressure energy recovery unit and the high-pressure gasification gray water after heat energy recovery sent from the secondary spiral heat energy recovery device 7, so as to realize the recovery and transfer of heat energy in the concentrated black water, obtain flash steam and positive pressure flash concentrated black water; by setting the outlet of the positive pressure flash evaporator to be connected to the medium heater, the first level waste heat power generation unit 14, and the negative pressure flash evaporator 12 respectively, the positive pressure flash concentrated black water is flashed. The heat is sent to the negative pressure flash evaporator 12 for further heat recovery, and part of the flash steam is used to heat the circulating medium in the medium heater to realize the transfer and utilization of heat energy. Part of the flash steam is sent to the first-level waste heat generator set 14 for power generation, and the heat energy is converted into electrical energy. By setting the outlet of the medium heater and the outlet of the first-level waste heat generator set 14 to be connected with the flash steam gas-liquid separator 19, part of the flash steam after heating and discharge is sent to the flash steam gas-liquid separator 19 for gas-liquid separation to obtain condensate and non-condensable gas, and the condensate is sent to the gasification ash water recycling unit for residual heat recovery. In summary, this embodiment flashes the concentrated black water generated in the waste pressure energy recovery unit and the low-pressure gasification ash water generated in the spiral waste heat recovery unit by setting a positive pressure flash evaporation waste heat power generation unit, transfers the heat energy for utilization, or converts the heat energy into electrical energy, realizes different conversion and utilization of heat energy, or sends it to the lower unit for further recovery and utilization.

[0063] The negative pressure flash waste heat power generation unit includes a negative pressure flash evaporator 12, a secondary waste heat generator set 15, a gas-water separator 20, and a condensate pump 22 connected in sequence. The inlet of the negative pressure flash evaporator 12 is connected to the positive pressure flash evaporator, the flash steam outlet is connected to the secondary waste heat generator set 15, the black water outlet is connected to the concentrator feed pump 13, the inlet of the gas-water separator 20 is connected to the outlet of the secondary waste heat generator set 15, the non-condensable gas outlet is connected to the negative pressure generator 21, and the condensate outlet is connected to the condensate pump 22.

[0064] In the negative pressure flash waste heat power generation unit of this embodiment, a negative pressure flash evaporator 12 is provided, and the inlet is connected to the positive pressure flash evaporator, and a negative pressure generator 21 is provided on the connecting pipe thereof. The negative pressure generator 21 is used to provide negative pressure conditions to flash the positive pressure flash concentrated black water sent from the positive pressure flash evaporation waste heat power generation unit to the negative pressure flash evaporator 12 to obtain flash steam and negative pressure flash concentrated black water, thereby further separating and recovering the heat carried by them, meeting the requirements of the subsequent gasification ash water recycling unit and maximizing the recovery of waste heat energy; the outlet of the negative pressure flash evaporator 12 is provided to be connected to the secondary waste heat power generation unit 15, so as to generate electricity from the flash steam obtained by flash evaporation, thereby converting heat energy into electricity The inlet of the gas-water separator 20 is connected to the outlet of the secondary waste heat power generation unit 15, the non-condensable gas outlet is connected to the negative pressure generator 21, and the condensate outlet is connected to the condensate pump 22. The gas-water separator 20 is used to separate the flash steam that has completed power generation into gas and liquid to obtain non-condensable gas and condensate, and the non-condensable gas is discharged through the negative pressure generator 21, and the condensate is sent to the gasification ash water recycling unit for further recovery through the condensate pump 22. At the same time, by setting the black water outlet of the negative pressure flash evaporator 12 to be connected to the concentrator feed pump 13, the concentrator feed pump 13 is used to pressurize the negative pressure flash evaporation concentrated black water and send it to the gasification ash water recycling unit for liquid-solid separation, thereby realizing gasification ash water recovery. In summary, this embodiment recovers the waste heat energy of the positive pressure flash evaporation concentrated black water generated by the positive pressure flash evaporation waste heat power generation unit by setting a negative pressure flash evaporation waste heat power generation unit, converts the heat energy into electrical energy, or sends it to the lower unit for further recycling.

[0065] The gasification gray water recycling unit includes a flash black water concentrator 30, a filter 31, a gray water tank 32 and a gray water pump 33, and a heat recovery device 23 connected in sequence. The black water inlet of the flash black water concentrator 30 is connected to the concentrator feed pump 13, the clear liquid outlet is connected to the inlet of the gray water tank 32, the concentrated black water outlet is connected to the filter 31, the outlet of the filter 31 is connected to the inlet of the gray water tank 32, the water outlet of the gray water tank 32 is connected to the gray water pump 33, the inlet of the heat recovery device 23 is respectively connected to the outlet of the positive pressure flash evaporator of the positive pressure flash waste heat power generation unit, the water outlet of the flash steam gas-liquid separator 19, and the water outlet of the condensate pump 22, the vent air outlet is connected to the tertiary medium heater 18, and the circulating water outlet is connected to the heat recovery device underflow pump 24.

[0066] The gasification grey water recycling unit of this embodiment is provided with a flash black water concentrator 30, a filter 31, an grey water tank 32 and a grey water pump 33 connected in sequence, and the black water inlet of the flash black water concentrator 30 is connected to the concentrator feed pump 13. The flash black water concentrator 30 is used to perform liquid-solid separation on the negative pressure flash concentrated black water pressurized and fed into the negative pressure flash waste heat power generation unit by the concentrator feed pump 13. The obtained clean grey water is directly sent from the top of the flash black water concentrator 30 to the grey water tank 32 for storage, and is pumped out for recycling by the grey water pump 33. It can be sent to the residual pressure energy recovery device 6 in the residual pressure energy recovery unit as a pressure-raising object for high-pressure gasification grey water, thereby assisting in the transfer and utilization of residual pressure energy and realizing the recycling of gasification grey water. At the same time, a filter 31 is provided to perform liquid-solid separation on the bottom concentrated black water obtained again to obtain filter residue and filtrate, and the filtrate is sent to the grey water tank 32 through a pipeline for recycling as make-up water.

[0067] At the same time, by setting up a heat recovery device 23, and the inlet of the heat recovery device 23 is respectively connected to the outlet of the positive pressure flash evaporator of the positive pressure flash waste heat power generation unit, the outlet of the flash steam gas-liquid separator 19, and the outlet of the condensate pump 22, the heat recovery device 23 is used to make the condensate obtained by gas-liquid separation in the flash steam gas-liquid separator 19 and the condensate water sent by the condensate pump 22 deaerated and heat-exchanged under the action of the remaining flash steam sent by the positive pressure flash evaporator to obtain vent air and deaerated gray water. The vent air outlet of the heat recovery device 23 is connected to the tertiary medium heater 18 to discharge the vent air and enter the tertiary medium heater 18 for further heat exchange with the circulating medium, and then vented, thereby achieving full utilization of the heat carried in the vent air. The circulating water outlet of the heat recovery device 23 is connected to the heat recovery device underflow pump 24 to pump out the deaerated gray water for recycling. In summary, this embodiment sets up a gasification ash water recycling unit to recycle the negative pressure flash evaporation concentrated black water generated in the positive pressure flash evaporation waste heat power generation unit, and uses it for the waste pressure energy utilization of the waste pressure energy recovery and utilization unit. At the same time, the condensate generated in the positive pressure flash evaporation waste heat power generation unit and the condensate generated in the negative pressure flash evaporation waste heat power generation unit are heat recovered, and the recovered heat is utilized.

[0068] The organic medium power generation unit includes a medium mixer 25, an organic medium generator set 26, a medium cooler 27, a medium collecting tank 28, and a medium circulation pump 29, which are connected in sequence. The feed port of the medium mixer 25 is connected to the outlet of the medium heater of the positive pressure flash waste heat power generation unit and the outlet of the three-stage medium heater 18, and the outlet is connected to the organic medium generator set 26. The feed port of the medium cooler 27 is connected to the organic medium generator set 26, and the outlet is connected to the medium collecting tank 28. The feed port of the medium circulation pump 29 is connected to the medium collecting tank 28, and the outlet is respectively connected to the medium heater and the three-stage medium heater 18 of the positive pressure flash waste heat power generation unit.

[0069] In the organic medium power generation unit of this embodiment, a medium mixer 25 is provided, and the feed port is connected to the outlet of the medium heater of the positive pressure flash waste heat power generation unit and the outlet of the three-stage medium heater 18, and the outlet is connected to the organic medium generator set 26, so as to transport and collect the heated circulating medium in each medium heater to the medium mixer 25, and generate electricity through the organic medium generator set 26, thereby converting thermal energy into electrical energy; by providing a medium cooler 27 with a feed port connected to the organic medium generator set 26 and an outlet connected to the medium collecting tank 28, the feed port of the medium circulation pump 29 is connected to the medium collecting tank 28, the circulating medium that has completed power generation is sent to the medium cooler 27 for cooling, then collected and stored in the medium collecting tank 28, and returned to the original medium heaters for recycling and heating under the action of the medium circulation pump 29, thereby realizing the use of circulating medium for heat recovery and electrical energy conversion.

[0070] Preferably, a wear-resistant layer is provided in the gasified black water concentrator 4. By providing the wear-resistant layer in the gasified black water concentrator 4, the abrasion of the gasified black water concentrator 4 by the high-pressure black water is reduced, and the service life of the gasified black water concentrator 4 is extended.

[0071] Preferably, the bottom outlet of the primary spiral heat recovery device 2 is connected to the lower quench chamber of the gasifier 1. This arrangement allows the entrained water and ash separated by the primary spiral heat recovery device 2 to be returned to the quench chamber of the gasifier 1, which helps maintain the stability of the quench chamber liquid level and reduces ash carryover in subsequent conversion systems.

[0072] like Figure 1 As shown, preferably, the positive pressure flash waste heat power generation unit is a first-stage positive pressure flash unit, comprising a first-stage positive pressure flash evaporator 10, the inlet of the first-stage positive pressure flash evaporator 10 is connected to the gasification black water concentrator 4 and the second-stage spiral heat energy recovery device 7, the flash steam outlet is respectively connected to the first-stage medium heater 16 and the first-stage waste heat generator set 14, the black water outlet is connected to the negative pressure flash evaporator 12, the outlet of the first-stage medium heater 16 and the outlet of the first-stage waste heat generator set 14 are both connected to the flash steam gas-liquid separator 19; correspondingly, the inlet of the heat recovery device 23 in the gasification ash water recycling unit is connected to the flash steam outlet of the lower section of the first-stage positive pressure flash evaporator 10, the feed port of the medium mixer 25 in the organic medium power generation unit is connected to the outlet of the first-stage medium heater 16, and the outlet of the medium circulation pump 29 is connected to the inlet of the first-stage medium heater 16;

[0073] Or the positive pressure flash waste heat power generation unit is a two-stage positive pressure flash unit, comprising a first-stage positive pressure flash evaporator 10 and a second-stage positive pressure flash evaporator 11 connected in sequence, the inlet of the first-stage positive pressure flash evaporator 10 is connected to the gasification black water concentrator 4 and the second-stage spiral heat energy recovery device 7, the flash steam outlet is respectively connected to the first-stage medium heater 16 and the first-stage waste heat generator set 14, the black water outlet is connected to the second-stage positive pressure flash evaporator 11, the outlet of the first-stage medium heater 16 and the outlet of the first-stage waste heat generator set 14 are both connected to the flash steam gas-liquid separator 19, the second-stage positive pressure flash unit 10 is connected to the gasification black water concentrator 4 and the second-stage spiral heat recovery device 7, the flash steam outlet is respectively connected to the first-stage medium heater 16 and the first-stage waste heat generator set 14, the black water outlet is connected to the second-stage positive pressure flash unit ... The outlet of the high-pressure flash evaporator 11 is connected to the secondary medium heater 17 and the negative pressure flash evaporator 12 respectively; correspondingly, the inlet of the heat recovery device 23 in the gasification ash water recycling unit is connected to the lower flash steam outlet of the first-stage positive-pressure flash evaporator 10 and the flash steam outlet of the secondary medium heater 17, the feed port of the medium mixer 25 in the organic medium power generation unit is connected to the outlet of the first-stage medium heater 16 and the outlet of the second-stage medium heater 17, and the outlet of the medium circulation pump 29 is connected to the inlet of the first-stage medium heater 16 and the inlet of the second-stage medium heater 17.

[0074] The positive-pressure flash waste heat power generation unit of the present invention utilizes either a single-stage positive-pressure flash unit or a two-stage positive-pressure flash unit, depending on the temperature of the concentrated black water. Specifically, a single-stage positive-pressure flash unit is used when the concentrated black water is below 235°C, while a two-stage positive-pressure flash unit is used when the concentrated black water is above 235°C. The two-stage flash unit produces more positive-pressure steam, lowers the black water temperature entering the negative-pressure flash waste heat power generation unit, facilitates operation of the negative-pressure flash waste heat power generation unit, reduces the size of the equipment and piping for the negative-pressure flash waste heat power generation unit, and reduces investment.

[0075] Preferably, the first-stage positive-pressure flash evaporator 10 adopts a two-stage flash structure, with the upper flash steam outlet connected to the first-stage medium heater 16, and the lower flash steam outlet connected to the first-stage waste heat generator set 14 and the heat recovery device 23. By adopting a two-stage flash structure, the upper flash evaporator is used to extract non-condensable gases dissolved in the concentrated black water, thereby protecting the first and second waste heat generator sets and improving the waste heat power generation efficiency.

[0076] Preferably, the negative pressure generator 21 is a water ring vacuum pump or a dry screw vacuum pump. Typically, the negative pressure generated by the negative pressure generator 21 ranges from 4 kPa to 38.6 kPa (A), preferably from 5.6 kPa to 25 kPa (A), where A represents absolute pressure. By controlling this negative pressure range, the feed temperature requirements for the gasification ash water recycling unit, equipment investment cost control requirements, and maximum recovery of gasification ash water waste heat can be simultaneously met.

[0077] Preferably, the first-level waste heat generator set 14, the second-level waste heat generator set 15 and the organic medium generator set 26 are composed of a screw expander combined with a generator, or a turbine combined with a generator, wherein the first-level waste heat generator set 14 and the second-level waste heat generator set 15 directly use low-temperature steam to generate electricity, and the organic medium generator set 26 uses circulating medium to generate electricity.

[0078] The method for graded utilization of residual energy from coal gasification of the present invention is described in detail through Examples 2 to 4.

[0079] Example 2

[0080] In the gasifier 1 of this embodiment, coal gasification to prepare crude synthesis gas is carried out by wet entrained flow, the gasification pressure is 6.5 MPa, the gasification temperature is 1350°C, and the feed volume of the gasifier is 60m3. 3 / h.

[0081] This embodiment includes the following steps:

[0082] Step 1: Residual pressure energy recovery: The temperature of the gasifier 1 is 251.08℃, the pressure is 6.51MPa, and the flow rate is 135m 3 / h high-pressure gasified black water and the temperature of the water-washing dust removal tower 3 is 243 ° C, the pressure is 6.27 MPa, and the flow rate is 42m 3 / h high pressure washing black water is sent to the gasification black water concentrator 4 for solid-liquid separation, and the concentrated black water after separation is discharged at 9.5m 3 / h is discharged from the bottom of the gasification black water concentrator 4 and sent to the first-stage positive pressure flash evaporator 10, while the high-pressure gasification gray water with low solid content is discharged at a rate of 166m 3 / h flow overflows from the top of the gasification black water concentrator 4, is filtered and removed by the black water filter 5, and then sent to the residual pressure energy recovery device 6. At the same time, 3 The low-pressure circulating ash water returned from the gasification ash water recycling unit at a flow rate of / h also enters the residual pressure energy recovery device 6. After the high-pressure gasification ash water has been cleaned in the residual pressure energy recovery device 6, the pressure of the low-pressure circulating ash water is reduced to 2.0MPa and sent to the secondary spiral heat energy recovery device 7. The pressurized circulating ash water is pressurized to 7.8MPa by the booster pump 8 and then sent out as high-pressure ash water for direct use.

[0083] Step 2: Spiral waste heat recovery: The temperature of 252.14℃, pressure of 6.47MPa and flow rate of 236KNm3 of the raw material prepared by gasification furnace 1 is 3 / h of high-temperature raw synthesis gas is fed into the primary spiral heat recovery device 2, undergoes countercurrent heat exchange with the boiler feed water fed into the primary spiral heat recovery device 2, and produces 11t / h of low-pressure steam as a by-product. The by-product low-pressure steam is sent to the pipeline network for use. The 22t / h of quenching water and fine ash entrained in the high-temperature raw synthesis gas are separated into gas and liquid during the countercurrent heat exchange process and returned to the quenching chamber of the gasifier 1, thereby reducing the liquid level fluctuation in the quenching chamber and the ash carried by the subsequent conversion system. The high-temperature raw synthesis gas with a temperature of 248°C that has completed the countercurrent heat exchange and gas-liquid separation is sent to the water-washing dust removal tower 3 for water washing and dust removal, and then sent to the subsequent conversion system;

[0084] After the pressure increase in step 1 is completed, the pressure is 2.0MPa, the temperature is 248.5℃, and the flow rate is 166m 3 / h of high-pressure gasified ash water is sent to the secondary spiral heat recovery device 7, and performs countercurrent heat exchange with the boiler feed water sent to the secondary spiral heat recovery device 7 to produce 3t / h of low-pressure steam as a by-product. The by-product low-pressure steam is sent to the pipeline network for use, and the high-pressure gasified ash water with a temperature of 238°C after completing the countercurrent heat exchange is sent to the primary positive pressure flash evaporator 10;

[0085] Step 3, positive pressure flash evaporation waste heat power generation: a two-stage positive pressure flash evaporation unit including a first-stage positive pressure flash evaporator 10 and a second-stage positive pressure flash evaporator 11 is used to perform positive pressure flash evaporation waste heat power generation, and the first-stage positive pressure flash evaporator 10 has an upper and lower two-stage flash evaporation structure: the concentrated black water discharged from the bottom of the gasified black water concentrator 4 in step 1 and sent to the first-stage positive pressure flash evaporator 10 and the high-pressure gasified gray water after the countercurrent heat exchange is completed in step 2 and sent to the first-stage positive pressure flash evaporator 10 for heat energy recovery are flash evaporated to obtain 8.7t / h of first-stage upper flash steam, 13.5t / h of first-stage lower flash steam and first-stage positive pressure flash concentrated black water, the first-stage upper flash steam is sent to the first-stage medium heater 16 to heat the circulating medium with a flow rate of 7t / h, and then sent to the flash steam gas-liquid separator 19 for gas-liquid separation to obtain condensate and non-condensable liquid. Gas, part of the first-stage lower flash steam is sent to the first-stage waste heat generator set 14 to generate electricity, and the generated 1485kW·h of electricity is sent to the power grid, the flash steam that has completed power generation enters the flash steam gas-liquid separator 19 for gas-liquid separation to obtain condensate and non-condensable gas, the non-condensable gas in the flash steam gas-liquid separator 19 is sent to the flare system for treatment, the condensate is sent to the heat recovery device 23, the remaining first-stage lower flash steam is sent to the heat recovery device 23, the first-stage positive pressure flash concentrated black water is sent to the second-stage positive pressure flash evaporator 11 for further flash evaporation to obtain 14t / h of second-stage flash steam and second-stage positive pressure flash concentrated black water, the second-stage flash steam is sent to the second-stage medium heater 17 to heat the circulating medium with a flow rate of 6t / h, and then sent to the heat recovery device 23, and the second-stage positive pressure flash concentrated black water is sent to the negative pressure flash evaporator 12;

[0086] Step 4: Negative pressure flash waste heat power generation: After the secondary positive pressure flash concentrated black water generated in the secondary positive pressure flash evaporator 11 in step 3 is sent to the negative pressure flash evaporator 12, it is flash vaporized under the negative pressure condition of 38.6 kPa (A) provided by the negative pressure generator 21 to obtain 7.7 t / h of flash steam and negative pressure flash concentrated black water. The flash steam is sent to the secondary waste heat generator set 15 for power generation, and the generated 360 kW·h of electricity is sent to the power grid. The flash steam that has completed power generation enters the gas-water separator 20 for gas-liquid separation to obtain non-condensable gas and condensate. The non-condensable gas is discharged through the negative pressure generator 21, and the condensate is sent to the heat recovery device 23 under the action of the condensate pump 22. The negative pressure flash concentrated black water is pressurized by the concentrator feed pump 13 and sent to the flash black water concentrator 30;

[0087] Step 5: Recycling of Gasified Grey Water: The black water pressurized by the concentrator feed pump 13 in step 4 is fed into the negative pressure flash concentrated black water concentrator 30 for liquid-solid separation to obtain clean grey water and bottom concentrated black water. The clean grey water is fed from the top of the flash black water concentrator 30 to the grey water tank 32 and discharged via the grey water pump 33 for recycling. The bottom concentrated black water is fed into the filter 31 for further liquid-solid separation to obtain dehydrated fine slag and filtrate. The fine slag is fed to the slag yard, and the filtrate is fed to the grey water tank 32 for recycling as make-up water.

[0088] At the same time, the condensate obtained by gas-liquid separation in the flash steam gas-liquid separator 19 in step 3, the remaining first-stage lower flash steam, the second-stage flash steam sent in after heating the circulating medium in the second-stage medium heater 17, and the condensed water sent in through the condensate pump 22 in step 4 enter the heat recovery device 23 for degassing and heat exchange, and obtain vent air with a temperature of 109°C and a flow rate of 1.2 t / h and degassed gray water. The vent air is discharged from the top of the heat recovery device 23, and then enters the third-stage medium heater 18 to heat the circulating medium with a flow rate of 0.95 t / h and is then emptied. The degassed gray water is discharged from the bottom of the heat recovery device 23 and recycled under the action of the heat recovery device underflow pump 24;

[0089] Step 6, organic medium power generation: The circulating medium heated in the first-level medium heater 16 in step 3, the circulating medium heated in the second-level medium heater 17, and the circulating medium heated in the third-level medium heater 18 in step 5 are sent to the medium mixer 25 for thorough mixing, and then sent to the organic medium generator set 26 for power generation. The generated 1300 kW·h of electricity is sent to the power grid. The circulating medium that has completed power generation is sent to the medium cooler 27 for cooling, and then sent to the medium collection tank 28. It is then sent again to the first-level medium heater 16, the second-level medium heater 17, and the third-level medium heater 18 for recycling through the medium circulation pump 29.

[0090] In this embodiment, the circulating medium in the first-stage medium heater 16, the second-stage medium heater 17 and the third-stage medium heater 18 is isobutane, or selected from low-boiling-point working fluids such as trifluoroiodomethane, hexafluoropropane, heptafluoropropane and monochlorotrifluoropropylene.

[0091] Example 3

[0092] The difference between this embodiment and embodiment 2 is that the feeding amount of the gasifier is 85m 3 / h;

[0093] The high-pressure gasification ash water with low solid content in step 1 is 220m 3 The flow rate of / h overflows from the top of the gasification black water concentrator 4, is filtered and removed by the black water filter 5, and then sent to the residual pressure energy recovery device 6. The pressurized circulating gray water is then pressurized by the booster pump 8 and sent to the residual pressure generator set 9 to generate electricity. After that, it is sent out as low-pressure gray water for use, and the generated 924kW·h of electricity is sent to the power grid.

[0094] In step 2, the primary spiral heat recovery device 2 produces 19.5 t / h of low-pressure steam as a by-product;

[0095] In step 3, the flow rate of the circulating medium in the first-stage medium heater 16 is 10 t / h, and the flow rate of the circulating medium in the second-stage medium heater 17 is 8 t / h. In step 3, part of the flash steam from the lower stage of the first stage is fed into the first-stage waste heat generator set 14 to generate electricity, and 2100 kW·h of electricity is generated and sent to the power grid.

[0096] The negative pressure condition in step 4 is 5.6 kPa (A); the flash steam in step 4 is sent to the secondary waste heat generator set 15 to generate electricity and generate 600 kW·h of electricity which is sent to the grid;

[0097] In step 5, the flow rate of the circulating medium in the tertiary medium heater 18 is 1.4 t / h;

[0098] In step 6, each circulating medium is fed into the organic medium generator set 26 to generate electricity and 1300 kW·h of electricity is sent to the power grid.

[0099] Example 4

[0100] In the gasifier 1 of this embodiment, coal gasification to prepare crude synthesis gas is carried out by wet entrained flow, the gasification pressure is 4.0 MPa, the gasification temperature is 1350°C, and the feed amount of the gasifier is 33m 3 / h.

[0101] This embodiment includes the following steps:

[0102] Step 1: Residual pressure energy recovery: The high-pressure gasified black water from the gasifier 1 with a temperature of 221°C, a pressure of 4.01 MPa, and a flow rate of 101 m3 / h and the high-pressure gasified black water from the water washing dust removal tower 3 with a temperature of 217°C, a pressure of 3.75 MPa, and a flow rate of 22.6 m3 / h are recycled. 3 / h high pressure washing black water is sent to the gasification black water concentrator 4 for solid-liquid separation, and the concentrated black water after separation is discharged at 6.7m 3 / h is discharged from the bottom of the gasification black water concentrator 4 and sent to the first-stage positive pressure flash evaporator 10, while the high-pressure gasification gray water with low solid content is discharged at a rate of 116m 3 / h flow overflows from the top of the gasification black water concentrator 4, is filtered and removed by the black water filter 5, and then sent to the residual pressure energy recovery device 6. At the same time, 3 The low-pressure circulating ash water returned from the gasification ash water recycling unit at a flow rate of / h also enters the residual pressure energy recovery device 6. After the high-pressure gasification ash water has been cleaned in the residual pressure energy recovery device 6, the pressure of the low-pressure circulating ash water is reduced to 1.5MPa and sent to the secondary spiral heat energy recovery device 7. The pressurized circulating ash water is pressurized to 5.0MPa by the booster pump 8 and then sent out as high-pressure ash water for direct use.

[0103] Step 2: Spiral waste heat recovery: The spiral waste heat from the gasification furnace 1 is prepared by gasification raw materials at a temperature of 226°C, a pressure of 3.98 MPa, and a flow rate of 129 KNm 3 / h of high-temperature crude synthesis gas is fed into the primary spiral heat recovery device 2, undergoes countercurrent heat exchange with the boiler feed water fed into the primary spiral heat recovery device 2, and produces 6.5t / h of low-pressure steam as a by-product. The by-product low-pressure steam is sent to the pipeline network for use. The 18t / h of quenching water and fine ash entrained in the high-temperature crude synthesis gas are separated into gas and liquid during the countercurrent heat exchange process and returned to the quenching chamber of the gasifier 1, thereby reducing the liquid level fluctuation in the quenching chamber and the ash carried by the subsequent conversion system. The high-temperature crude synthesis gas with a temperature of 222°C that has completed the countercurrent heat exchange and gas-liquid separation is sent to the water-washing dust removal tower 3 for water washing and dust removal, and then sent to the subsequent conversion system;

[0104] After the pressure increase in step 1 is completed, the pressure is 2.0 MPa, the temperature is 220℃, and the flow rate is 116m 3 / h of high-pressure gasified ash water is sent to the secondary spiral heat recovery device 7, and performs countercurrent heat exchange with the boiler feed water sent to the secondary spiral heat recovery device 7 to produce 1.2t / h of low-pressure steam as a by-product. The by-product low-pressure steam is sent to the pipeline network for use, and the high-pressure gasified ash water with a temperature of 214°C after completing the countercurrent heat exchange is sent to the primary positive pressure flash evaporator 10;

[0105] Step 3, positive pressure flash evaporation waste heat power generation: a two-stage positive pressure flash evaporation unit including a first-stage positive pressure flash evaporator 10 and a second-stage positive pressure flash evaporator 11 is used for positive pressure flash evaporation waste heat power generation, and the first-stage positive pressure flash evaporator 10 has an upper and lower two-stage flash evaporation structure: the concentrated black water discharged from the bottom of the gasified black water concentrator 4 in step 1 and sent to the first-stage positive pressure flash evaporator 10 and the high-pressure gasified gray water after the countercurrent heat exchange is completed in step 2 and sent to the first-stage positive pressure flash evaporator 10 for heat energy recovery are flash evaporated to obtain 3.2t / h of first-stage upper flash steam, 15.1t / h of first-stage lower flash steam and first-stage positive pressure flash concentrated black water, and the first-stage upper flash steam is sent to the first-stage medium heating The circulating medium with a flow rate of 2.6 t / h is heated in the reactor 16 and then sent to the flash steam gas-liquid separator 19 for gas-liquid separation to obtain condensate and non-condensable gas. Part of the flash steam from the lower stage of the first stage is sent to the first stage waste heat generator set 14 for power generation, and the generated 1660 kW·h of electricity is sent to the power grid. The flash steam that has completed power generation enters the flash steam gas-liquid separator 19 for gas-liquid separation to obtain condensate and non-condensable gas. The non-condensable gas in the flash steam gas-liquid separator 19 is sent to the flare system for treatment, and the condensate is sent to the heat recovery device 23. The remaining flash steam from the lower stage of the first stage is sent to the heat recovery device 23, and the black water concentrated by the positive-pressure flash evaporation of the first stage is sent to the negative-pressure flash evaporator 12;

[0106] Step 4: Negative pressure flash waste heat power generation: After the first-stage positive pressure flash concentrated black water generated in the first-stage positive pressure flash evaporator 10 in step 3 is sent to the negative pressure flash evaporator 12, it is flash vaporized under the negative pressure condition of 25 kPa (A) provided by the negative pressure generator 21 to obtain 8.1 t / h of flash steam and negative pressure flash concentrated black water. The flash steam is sent to the second-stage waste heat generator unit 15 to generate electricity, and the generated 426 kW·h of electricity is sent to the power grid. The flash steam that has completed power generation enters the gas-water separator 20 for gas-liquid separation to obtain non-condensable gas and condensate. The non-condensable gas is discharged through the negative pressure generator 21, and the condensate is sent to the heat recovery device 23 under the action of the condensate pump 22. The negative pressure flash concentrated black water is pressurized by the concentrator feed pump 13 and then sent to the flash black water concentrator 30;

[0107] Step 5: Recycling of Gasified Grey Water: The black water pressurized by the concentrator feed pump 13 in step 4 is fed into the negative pressure flash concentrated black water concentrator 30 for liquid-solid separation to obtain clean grey water and bottom concentrated black water. The clean grey water is fed from the top of the flash black water concentrator 30 to the grey water tank 32 and discharged via the grey water pump 33 for recycling. The bottom concentrated black water is fed into the filter 31 for further liquid-solid separation to obtain dehydrated fine slag and filtrate. The fine slag is fed to the slag yard, and the filtrate is fed to the grey water tank 32 for recycling as make-up water.

[0108] At the same time, the condensate obtained by gas-liquid separation in the flash steam gas-liquid separator 19 in step 3, the remaining flash steam in the lower stage, and the condensed water sent by the condensate pump 22 in step 4 enter the heat recovery device 23 for degassing and heat exchange, and obtain vent air with a temperature of 104°C and a flow rate of 0.9 t / h and degassed gray water. The vent air is discharged from the top of the heat recovery device 23, and then enters the tertiary medium heater 18 to heat the circulating medium with a flow rate of 0.7 t / h and then emptied. The degassed gray water is discharged from the bottom of the heat recovery device 23 and recycled under the action of the heat recovery device underflow pump 24;

[0109] Step 6, organic medium power generation: The circulating medium heated in the first-stage medium heater 16 in step 3 and the circulating medium heated in the third-stage medium heater 18 in step 5 are sent to the medium mixer 25 for thorough mixing, and then sent to the organic medium generator set 26 for power generation. The generated 320 kW·h of electricity is sent to the power grid. The circulating medium that has completed power generation is sent to the medium cooler 27 for cooling, and then sent to the medium collection tank 28. It is then sent back to the first-stage medium heater 16 and the third-stage medium heater 18 for recycling through the medium circulation pump 29.

[0110] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A device for graded utilization of residual energy from coal gasification, characterized in that: It includes a waste pressure energy recovery unit, a spiral waste heat recovery unit, a positive pressure flash waste heat power generation unit, a negative pressure flash waste heat power generation unit, a gasification ash water recycling unit and an organic medium power generation unit; The residual pressure energy recovery and utilization unit comprises a gasification black water concentrator (4), a black water filter (5), a residual pressure energy recovery device (6), and a residual pressure generator set (9) connected in sequence, wherein the inlet of the gasification black water concentrator (4) is connected to the gasification furnace (1) and the water washing dust removal tower (3), the top outlet is connected to the inlet of the black water filter (5), and the bottom outlet is connected to the positive pressure flash evaporation waste heat power generation unit, the outlet of the black water filter (5) is connected to the inlet of the residual pressure energy recovery device (6), the pressure-raising ash water outlet of the residual pressure energy recovery device (6) is connected to the booster pump (8) and the residual pressure generator set (9), and the high-pressure gasification ash water outlet is connected to the spiral waste heat recovery and utilization unit; The spiral waste heat recovery unit comprises a first-stage spiral heat recovery device (2) and a second-stage spiral heat recovery device (7) connected in parallel, wherein the inlet of the first-stage spiral heat recovery device (2) is connected to the gasification furnace (1), and the outlet is connected to the water-washing dust removal tower (3); the inlet of the second-stage spiral heat recovery device (7) is connected to the waste pressure energy recovery device (6), and the outlet is connected to the positive pressure flash waste heat power generation unit; The positive pressure flash waste heat power generation unit comprises a positive pressure flash evaporator, the inlet of the positive pressure flash evaporator is connected to the gasification black water concentrator (4) and the secondary spiral heat energy recovery device (7), the flash steam outlet is respectively connected to the primary medium heater (16) and the primary waste heat generator set (14), the black water outlet is connected to the negative pressure flash evaporator (12), and the outlet of the primary medium heater (16) and the outlet of the primary waste heat generator set (14) are connected to the flash steam gas-liquid separator (19); The negative pressure flash waste heat power generation unit comprises a negative pressure flash evaporator (12), a secondary waste heat generator set (15), a gas-water separator (20), and a condensate pump (22) connected in sequence, wherein the inlet of the negative pressure flash evaporator (12) is connected to the positive pressure flash evaporator, the flash steam outlet is connected to the secondary waste heat generator set (15), the black water outlet is connected to the concentrator feed pump (13), the inlet of the gas-water separator (20) is connected to the outlet of the secondary waste heat generator set (15), the non-condensable gas outlet is connected to the negative pressure generator (21), and the condensate outlet is connected to the condensate pump (22); The gasification grey water recycling unit comprises a flash black water concentrator (30), a filter (31), an grey water tank (32) and a grey water pump (33) connected in sequence, and a heat recovery device (23), wherein the black water inlet of the flash black water concentrator (30) is connected to the concentrator feed pump (13), the clear liquid outlet is connected to the inlet of the grey water tank (32), the concentrated black water outlet is connected to the filter (31), the outlet of the filter (31) is connected to the inlet of the grey water tank (32), the water outlet of the grey water tank (32) is connected to the grey water pump (33), the inlet of the heat recovery device (23) is respectively connected to the outlet of the positive pressure flash evaporator of the positive pressure flash waste heat power generation unit, the water outlet of the flash steam gas-liquid separator (19), and the water outlet of the condensate pump (22), the vent air outlet is connected to the three-stage medium heater (18), and the circulating water outlet is connected to the heat recovery device underflow pump (24); The organic medium power generation unit comprises a medium mixer (25), an organic medium generator set (26), a medium cooler (27), a medium collecting tank (28), and a medium circulation pump (29) which are connected in sequence. The feed port of the medium mixer (25) is connected to the outlet of the first-stage medium heater (16) and the outlet of the third-stage medium heater (18) of the positive pressure flash evaporation waste heat power generation unit, and the outlet is connected to the organic medium generator set (26). The feed port of the medium cooler (27) is connected to the organic medium generator set (26), and the outlet is connected to the medium collecting tank (28). The feed port of the medium circulation pump (29) is connected to the medium collecting tank (28), and the outlet is respectively connected to the first-stage medium heater (16) and the third-stage medium heater (18) of the positive pressure flash evaporation waste heat power generation unit.

2. The device for graded utilization of residual energy from coal gasification according to claim 1, characterized in that: A wear-resistant layer is provided inside the gasified black water concentrator (4).

3. The device for graded utilization of residual energy from coal gasification according to claim 1, characterized in that: The bottom outlet of the first-stage spiral heat energy recovery device (2) is connected to the lower quenching chamber of the gasifier (1).

4. The device for graded utilization of residual energy from coal gasification according to claim 1, characterized in that: The positive pressure flash waste heat power generation unit is a first-stage positive pressure flash unit, comprising a first-stage positive pressure flash evaporator (10), the inlet of the first-stage positive pressure flash evaporator (10) is connected to the gasification black water concentrator (4) and the second-stage spiral heat energy recovery device (7), the flash steam outlet is respectively connected to the first-stage medium heater (16) and the first-stage waste heat power generation unit (14), the black water outlet is connected to the negative pressure flash evaporator (12), the outlet of the first-stage medium heater (16) and the outlet of the first-stage waste heat power generation unit (14) are both connected to the flash steam gas-liquid separator (19); correspondingly, the inlet of the heat recovery device (23) in the gasification ash water recycling unit is connected to the flash steam outlet of the lower section of the first-stage positive pressure flash evaporator (10), the feed port of the medium mixer (25) in the organic medium power generation unit is connected to the outlet of the first-stage medium heater (16), and the outlet of the medium circulation pump (29) is connected to the inlet of the first-stage medium heater (16); Alternatively, the positive pressure flash waste heat power generation unit is a two-stage positive pressure flash unit, comprising a first-stage positive pressure flash evaporator (10) and a second-stage positive pressure flash evaporator (11) connected in sequence, the inlet of the first-stage positive pressure flash evaporator (10) is connected to the gasification black water concentrator (4) and the second-stage spiral heat energy recovery device (7), the flash steam outlet is respectively connected to the first-stage medium heater (16) and the first-stage waste heat power generation unit (14), the black water outlet is connected to the second-stage positive pressure flash evaporator (11), the outlet of the first-stage medium heater (16) and the outlet of the first-stage waste heat power generation unit (14) are both connected to the flash steam gas-liquid separator (19), and the second-stage positive pressure The outlet of the flash evaporator (11) is connected to the secondary medium heater (17) and the negative pressure flash evaporator (12) respectively; correspondingly, the inlet of the heat recovery device (23) in the gasification ash water recycling unit is connected to the flash steam outlet of the lower section of the first-stage positive pressure flash evaporator (10) and the flash steam outlet of the second-stage medium heater (17); the feed port of the medium mixer (25) in the organic medium power generation unit is connected to the outlet of the first-stage medium heater (16) and the outlet of the second-stage medium heater (17); and the outlet of the medium circulation pump (29) is connected to the inlet of the first-stage medium heater (16) and the inlet of the second-stage medium heater (17).

5. The device for graded utilization of residual energy from coal gasification according to claim 4, characterized in that: The first-stage positive pressure flash evaporator (10) adopts an upper and lower two-stage flash evaporation structure, and the upper flash steam outlet is connected to the first-stage medium heater (16), and the lower flash steam outlet is connected to the first-stage waste heat generator set (14) and the heat recovery device (23).

6. The device for graded utilization of residual energy from coal gasification according to claim 1, characterized in that: The negative pressure generator (21) is a water ring vacuum pump or a dry screw vacuum pump.

7. The device for graded utilization of residual energy from coal gasification according to claim 1, characterized in that: The first-stage waste heat generator set (14), the second-stage waste heat generator set (15), and the organic medium generator set (26) are composed of a screw expander combined with a generator, or a turbine combined with a generator.

8. A method for graded utilization of residual energy from coal gasification using the device according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: Step 1, recycling of residual pressure energy: the high-pressure black water from the gasifier (1) and the water-washing dust removal tower (3) is sent to the gasification black water concentrator (4) for solid-liquid separation. The concentrated black water after separation is discharged from the bottom of the gasification black water concentrator (4) and sent to the positive pressure flash evaporator, while the high-pressure gasification ash water with low solid content overflows from the top of the gasification black water concentrator (4) and is filtered and removed by the black water filter (5) and then sent to the residual pressure energy recovery device (6). At the same time, the low-pressure circulating ash water returned by the gasification ash water recycling unit also enters the residual pressure energy recovery device (6). The high-pressure gasification ash water after impurities are removed in the residual pressure energy recovery device (6) is pressurized to increase the pressure of the low-pressure circulating ash water and is sent to the secondary spiral heat energy recovery device (7). The pressurized circulating ash water is either pressurized by the booster pump (8) and sent out as high-pressure ash water for direct use, or sent to the residual pressure generator set (9) to complete power generation and then sent out as low-pressure ash water for use; Step 2, spiral waste heat recovery and utilization: the high-temperature crude synthesis gas prepared from the gasified raw materials from the gasifier (1) is sent to the first-stage spiral heat recovery device (2), and is subjected to countercurrent heat exchange with the boiler feed water sent to the first-stage spiral heat recovery device (2) to produce low-pressure steam as a by-product. The by-product low-pressure steam is sent to the pipeline network for use. The quenching water and fine ash entrained in the high-temperature crude synthesis gas are separated from the gas and liquid during the countercurrent heat exchange process and returned to the quenching chamber of the gasifier (1), thereby reducing the liquid level fluctuation in the quenching chamber and the ash carried by the subsequent conversion system. The high-temperature crude synthesis gas that has completed the countercurrent heat exchange and gas-liquid separation is sent to the water washing dust removal tower (3) for water washing and dust removal, and then sent to the subsequent conversion system. The high-pressure gasified ash water after the pressure increase in step 1 is sent to the secondary spiral heat energy recovery device (7), and is subjected to countercurrent heat exchange with the boiler feed water sent to the secondary spiral heat energy recovery device (7) to produce low-pressure steam as a by-product. The by-product low-pressure steam is sent to the pipeline network for use, and the high-pressure gasified ash water that has completed the countercurrent heat exchange is sent to the positive pressure flash evaporator; Step 3, positive pressure flash evaporation waste heat power generation: the concentrated black water discharged from the bottom of the gasification black water concentrator (4) in step 1 and sent to the positive pressure flash evaporator and the high pressure gasification gray water that has completed countercurrent heat exchange in step 2 and sent to the positive pressure flash evaporator are flash evaporated to obtain flash steam and positive pressure flash evaporation concentrated black water. Part of the flash steam is sent to the first-level medium heater (16) to heat the circulating medium and then sent to the flash steam gas-liquid separator (19) for gas-liquid separation to obtain condensate and non-condensable gas. Part of the flash steam is sent to the first-stage waste heat generator set (14) to generate electricity, and the generated electricity is sent to the power grid. The flash steam that has completed power generation is sent to the flash steam gas-liquid separator (19) for gas-liquid separation to obtain condensate and non-condensable gas. The non-condensable gas in the flash steam gas-liquid separator (19) is sent out for treatment, the condensate is sent to the heat recovery device (23), the remaining flash steam is sent to the heat recovery device (23), and the positive pressure flash evaporation concentrated black water is sent to the negative pressure flash evaporator (12); Step 4, negative pressure flash waste heat power generation: After the positive pressure flash concentrated black water generated in the positive pressure flash evaporator in step 3 is sent to the negative pressure flash evaporator (12), it is flash vaporized under the negative pressure condition provided by the negative pressure generator (21) to obtain flash steam and negative pressure flash concentrated black water. The flash steam is sent to the secondary waste heat generator set (15) for power generation, and the generated electricity is sent to the power grid. The flash steam that has completed power generation enters the gas-water separator (20) for gas-liquid separation to obtain non-condensable gas and condensate. The non-condensable gas is discharged through the negative pressure generator (21), and the condensate is sent to the heat recovery device (23) under the action of the condensate pump (22). The negative pressure flash concentrated black water is pressurized by the concentrator feed pump (13) and sent to the flash black water concentrator (30); Step 5, recycling of gasified grey water: the negative pressure flash concentrated black water pressurized by the concentrator feed pump (13) in step 4 is sent to the flash black water concentrator (30) for liquid-solid separation to obtain clean grey water and bottom concentrated black water. The clean grey water is sent from the top of the flash black water concentrator (30) to the grey water tank (32) and sent out through the grey water pump (33) for recycling. The bottom concentrated black water is sent to the filter (31) for liquid-solid separation again to obtain dehydrated fine slag and filtrate. The fine slag is sent to the slag yard, and the filtrate is sent to the grey water tank (32) for recycling as make-up water. At the same time, the condensate obtained by gas-liquid separation in the flash steam gas-liquid separator (19) in step 3, the remaining flash steam sent to the heat recovery device (23), and the condensed water sent through the condensate pump (22) in step 4 enter the heat recovery device (23) together to obtain vent air and degassed gray water. The vent air is discharged from the top of the heat recovery device (23), and then enters the tertiary medium heater (18) to heat the circulating medium and then emptied. The degassed gray water is discharged from the bottom of the heat recovery device (23) and recycled under the action of the heat recovery device underflow pump (24); Step 6, organic medium power generation: the circulating medium heated in the first-stage medium heater (16) in step 3 and the circulating medium heated in the third-stage medium heater (18) in step 5 are sent to the medium mixer (25) for thorough mixing, and then sent to the organic medium generator set (26) for power generation. The generated electricity is sent to the power grid, and the circulating medium that has completed power generation is sent to the medium cooler (27) for cooling, and then sent to the medium collection tank (28), and then sent again to the first-stage medium heater (16) and the third-stage medium heater (18) of the positive pressure flash waste heat power generation unit through the medium circulation pump (29) for recycling.

9. The method according to claim 8, characterized in that In step three, a first-stage positive pressure flash evaporation unit including a first-stage positive pressure flash evaporator (10) is used to perform positive pressure flash evaporation waste heat power generation, and the first-stage positive pressure flash evaporator (10) has an upper and lower two-stage flash evaporation structure: the concentrated black water discharged from the bottom of the gasified black water concentrator (4) in step one and sent to the first-stage positive pressure flash evaporator (10) and the high-pressure gasified gray water completed in step two with countercurrent heat exchange and sent to the first-stage positive pressure flash evaporator (10) are flash evaporated to obtain first-stage upper flash steam, first-stage lower flash steam and first-stage positive pressure flash concentrated black water, the first-stage upper flash steam is sent to the first-stage medium heater (16) to heat the circulating medium and then sent to the flash steam gas-liquid separator (19) for gas-liquid separation to obtain condensate and non-condensable gas, part of the first-stage lower flash steam is sent to the first-stage waste heat generator set (14) to generate electricity, and the generated electricity is sent to the power grid, the flash steam that has completed power generation enters the flash steam gas-liquid separator (19) for gas-liquid separation to obtain condensate and non-condensable gas, and the flash evaporator The non-condensable gas in the gas-liquid separator (19) is sent out for treatment, and the condensate is sent to the heat recovery device (23), the remaining flash steam of the lower stage is sent to the heat recovery device (23), and the positive pressure flash concentrated black water is sent to the negative pressure flash evaporator (12); correspondingly, in the gasification ash water recycling process described in step five, the condensate obtained by gas-liquid separation in the flash steam gas-liquid separator (19) in step three, the remaining flash steam and the condensate sent in through the condensate pump (22) in step four are sent to the heat recovery device (23) together; in the organic medium power generation process described in step six, the circulating medium heated in the first-stage medium heater (16) in step three and the circulating medium heated in the third-stage medium heater (18) in step five are sent to the medium mixer (25) for full mixing, and are sent to the medium collecting tank (28) after power generation and cooling, and are sent to the first-stage medium heater (16) and the third-stage medium heater (18) again for recycling through the medium circulation pump (29); Alternatively, in step 3, a two-stage positive pressure flash evaporation unit including a first-stage positive pressure flash evaporator (10) and a second-stage positive pressure flash evaporator (11) is used to perform positive pressure flash evaporation waste heat power generation, and the first-stage positive pressure flash evaporator (10) has an upper and lower two-stage flash evaporation structure: the concentrated black water discharged from the bottom of the gasified black water concentrator (4) in step 1 and sent to the first-stage positive pressure flash evaporator (10) and the high-pressure gasified ash completed with countercurrent heat exchange in step 2 and sent to the first-stage positive pressure flash evaporator (10) are flash evaporated to obtain a first-stage upper stage flash steam, a first-stage lower stage flash steam and a first-stage positive pressure flash concentrated black water, and the first-stage upper stage flash steam is sent to the first-stage medium heater ( 16) After the circulating medium is heated in the flash steam gas-liquid separator (19), gas-liquid separation is carried out to obtain condensate and non-condensable gas. Part of the flash steam in the lower section of the first stage is sent to the first stage waste heat generator set (14) to generate electricity, and the generated electricity is sent to the power grid. The flash steam that has completed power generation enters the flash steam gas-liquid separator (19) for gas-liquid separation to obtain condensate and non-condensable gas. The non-condensable gas in the flash steam gas-liquid separator (19) is sent out for treatment, and the condensate is sent to the heat recovery device (23). The remaining flash steam in the lower section of the first stage is sent to the heat recovery device (23). The first stage positive pressure flash concentrated black water is sent to the second stage positive pressure flash Flash evaporation is continued in the evaporator (11) to obtain secondary flash steam and secondary positive pressure flash evaporation concentrated black water, the secondary flash steam is sent to the secondary medium heater (17) to heat the circulating medium and then sent to the heat recovery device (23), and the secondary positive pressure flash evaporation concentrated black water is sent to the negative pressure flash evaporator (12); correspondingly, in the process of recycling the gasified gray water in step five, the condensate obtained by gas-liquid separation in the flash steam gas-liquid separator (19) in step three, the remaining first-stage lower flash steam, the secondary flash steam sent after heating the circulating medium in the secondary medium heater (17), and the condensate sent through the condensate pump (22) in step four are used together. and enters the heat recovery device (23) for degassing and heat exchange; in the organic medium power generation process described in step 6, the circulating medium heated in the first-level medium heater (16) in step 3, the circulating medium heated in the second-level medium heater (17), and the circulating medium heated in the third-level medium heater (18) in step 5 are sent to the medium mixer (25) for thorough mixing, and after power generation and cooling, are sent to the medium collecting tank (28), and are sent again to the first-level medium heater (16), the second-level medium heater (17), and the third-level medium heater (18) through the medium circulation pump (29) for recycling.

10. The method according to claim 8, characterized in that The negative pressure condition in step 3 is 4kPa~38.6kPa.

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