Incineration treatment and energy recovery system for waste alkali liquor of propylene epoxidation device

Abstract

The invention discloses a waste alkali liquor incineration treatment and energy recovery system for a propylene epoxidation device, and belongs to the field of energy conservation and environmental protection. Sodium salt in a molten state formed in the incineration process is fully cooled and dried into a solid state through a cold fluid mixing and membrane wall heat transfer coupling cooling technology, solid alkaline residues and alkaline ash formed in the cooling process are captured and conveyed in a closed mode through a sodium salt dispersing and collecting method, energy recovery of incineration heat release is achieved through a multi-effect heat exchange network, and the energy recovery efficiency is improved. By means of the system and method, up-to-standard emission of smoke generated in the incineration process is achieved.

Description

Technical Field

[0001] The present invention relates to a system for incinerating and treating waste alkali liquor and recovering energy in a propylene epoxidation device, belonging to the field of energy conservation and environmental protection. Background Art

[0002] Propylene oxide is one of the main downstream derivatives of propylene and is an important intermediate for the production of new chemical materials. It is used to produce products such as polyether polyols, propylene glycol, and alcohol ethers, and its end products extend to projects related to people's livelihood, encouraged categories, and rapidly developing categories such as automobiles, furniture, household appliances, high-speed rails, building insulation, and daily chemicals. The co-production of propylene oxide and propylene oxide / styrene (PO / SM) by propylene epoxidation is one of the main process technologies for producing propylene oxide. This process mainly includes steps such as ethylbenzene oxidation, propylene epoxidation, product refining, phenethyl alcohol dehydration, and acetophenone hydrogenation.

[0003] Among them, the propylene epoxidation reaction is a key step. While producing propylene oxide and phenethyl alcohol, there are many side reactions. After the products are refined through processes such as separation, extraction, and alkali washing, a large amount of tar and highly saline alkaline organic waste liquor (hereinafter referred to as waste alkali liquor) will be discharged. The waste alkali liquor contains toxic and harmful substances such as propylene glycol, sodium formate, sodium acetate, sodium benzoate, sodium phenolate, sodium carbonate, and sodium hydroxide. The difficult treatment of waste alkali liquor has become a bottleneck restricting the popularization of the propylene oxide / styrene (PO / SM) co-production process technology and the realization of stable operation.

[0004] Chinese Patent CN118343934A discloses a method and device for treating oxidized waste alkali liquor, which pre-treats the waste alkali liquor through multiple steps such as homogenization adjustment, carbon dioxide removal, precipitation ultrafiltration, and crystallization separation, and then performs biochemical treatment. However, the steam consumption of the vacuum evaporation crystallization system is relatively high, and the treatment efficiency of the biochemical system is relatively low.

[0005] Chinese Patent CN114543102A discloses an integrated boiler for waste alkali liquor incineration and waste heat recovery, including a furnace, a flue, and a steam drum. The furnace, transition flue, and flue inlet are all structures with refractory materials laid on the water-cooled walls. The transition flue is inclined and a slag discharge port is provided at the bottom to keep the high-temperature molten matter generated after the waste alkali liquor is incinerated discharged in a liquid state. However, the extensive use of the water-cooled wall structure causes a high heat load, requires a large amount of fuel consumption, and a large amount of high-temperature molten matter discharged from the slag discharge port contains more impurities after cooling and solidification, and has low resource utilization value.

[0006] Wastewater treatment plants adopting biochemical process technology are difficult to treat the above-mentioned waste alkali liquor. High-temperature thermal oxidation (i.e., incineration) technology is an effective way to remove toxic and harmful substances in the waste alkali liquor. According to relevant data, most hydrocarbons can be completely oxidized at 590-820°C. Generally, an incinerator designed with a combustion temperature of 1100°C and a residence time of more than 2 seconds can achieve a combustion efficiency greater than 99.9% and a destruction and removal efficiency greater than 99.99%.

[0007] There are mainly three difficulties in the incineration treatment of the above-mentioned high-salt alkaline organic waste liquor (hereinafter referred to as waste alkali liquor):

[0008] First, the waste alkali liquor has a large water content and a low calorific value, and a large amount of auxiliary fuel is required for co-combustion. At the same time, sodium elements generate molten sodium salts after high-temperature incineration. Generally, a cooling medium needs to be sprayed to cool the high-temperature flue gas, so that the molten sodium salts are fully cooled and solidified. This process wastes the heat of the high-temperature flue gas, and the low-temperature flue gas after cooling can be used for waste heat recovery, resulting in a low energy recovery efficiency of the incineration device.

[0009] Second, the content of sodium elements in the waste alkali liquor is high, and the ash melting point of the sodium salts generated by high-temperature incineration is low (about 650°C - 850°C). They are in the form of molten droplets in the high-temperature flue gas and are extremely easy to adhere to the inner walls of the incinerator and the flue, and the outer surface of the boiler tube bundle. The dust concentration in the flue gas after cooling is relatively high, and it is extremely easy to block the boiler heat exchange surface and the filter surface of the dust collector, resulting in the blockage and shutdown of the device, and the operation cycle of the incineration device is short.

[0010] Third, the incineration products of the waste alkali liquor, sodium salts, are generally discharged from the incinerator in the forms of molten slag and alkali ash. Among them, the molten slag contains impurities such as part of the refractory lining exfoliation of the incinerator; while the bulk density of the alkali ash is low (about 300 - 500 kg / m 3 ), it has strong water absorption, and once it comes into contact with the ambient air, it is extremely easy to disperse and agglomerate, and its resource utilization value is low. Summary of the Invention

[0011] The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art and provide a system for incineration treatment and energy recovery of waste alkali liquor from a propylene epoxidation device.

[0012] The object of the present invention is achieved by the following technical solutions:

[0013] A system and method for incineration treatment and energy recovery of waste alkali liquor from an epoxidation unit of propylene. The high-salt alkaline organic waste liquor generated by the epoxidation unit of propylene is incinerated by high-temperature thermal oxidation technology. The molten sodium salt formed during the incineration process is fully cooled and dried into a solid state through the coupling cooling process of cold fluid mixing and membrane wall heat transfer. The solid alkali slag and alkali ash formed during the cooling process are captured and tightly transported through the sodium salt dispersion collection method. The energy recovery of the heat released by incineration is realized through a multi-effect heat exchange network. The flue gas generated during the incineration process meets the discharge standards through this system and method.

[0014] The technical principle is as follows: Using high-temperature thermal oxidation technology, that is, using auxiliary fuel and combustion-supporting air combustion to provide a flame, incinerating the waste alkali liquor in the incinerator, fully thermally oxidizing and decomposing the organic matter in the waste alkali liquor, and converting the sodium in the waste alkali liquor into sodium salt; using the reflux flue gas or ambient air as the cold fluid to mix and cool the high-temperature flue gas, and coupling with the membrane wall heat transfer of the subsequent waste heat boiler to cool the high-temperature flue gas, fully cooling and drying the molten sodium salt, and converting it into a solid state for multi-stage capture and tight transportation; using the membrane wall waste heat boiler and heat exchanger for energy recovery; after the flue gas passes through dust removal, using a catalytic denitration reactor to reduce the nitrogen oxides by-produced during the incineration process to nitrogen.

[0015] C m H n O x Na y +O 2 →CO 2 +H 2 O+Na 2 CO 3 (molten state)+NOx+Q

[0016] Na 2 CO 3 (molten state)→Na 2 CO 3 (solid state)-Q

[0017] NOx+NH 3 →N 2 +H 2 O

[0018] A system for incineration treatment and energy recovery of waste alkali liquor from an epoxidation unit of propylene, including an incinerator, a main burner, a waste heat boiler, a dust collector, an induced draft fan, a catalytic denitration reactor, a boiler feed water preheater, a chimney, a combustion-supporting fan, a reflux fan, a reflux flue gas cooler, a cold air duct, a hot air duct, a high-temperature transition flue duct, a low-temperature flue duct, a reflux flue duct, a discharge flue duct, a dust collector suction bypass, an induced draft fan suction bypass, a reflux fan suction bypass, a slag transportation system, an ash transportation system, as well as connecting pipes, valves, pipe fittings, and instruments and control systems for realizing the safe operation of the device.

[0019] As shown Figure 1 In the figure, a main burner is installed at the top of the incinerator. The bottom outlet is connected to the high-temperature transition flue through an expansion joint, and then connected to the waste heat boiler. The waste heat boiler, dust collector, induced draft fan, catalytic denitration reactor, boiler feed water preheater, and chimney are sequentially connected through a low-temperature flue.

[0020] The combustion-supporting fan is connected to the incinerator and the main burner through a cold air duct, an air preheater in the waste heat boiler, and a hot air duct; the recirculation fan is connected to the incinerator through a low-temperature flue, a recirculation flue gas cooler, and a recirculation flue.

[0021] The bottom of the membrane wall cooling cavity of the waste heat boiler is connected to the slag conveying system, and the bottoms of the flue where the economizer of the waste heat boiler is located and the dust collector are connected to the ash conveying system.

[0022] The auxiliary fuel and combustion-supporting air burn in the main burner to form a flame. The waste alkali liquor and combustion-supporting air are incinerated in the incinerator, and the high-temperature flue gas formed by the incineration recovers energy in the waste heat boiler.

[0023] The incinerator is of a vertical top-firing adiabatic type, lined with refractory materials. The main burner, incinerator, high-temperature transition flue, and the inlet of the waste heat boiler are vertically connected from top to bottom and their central axes coincide; the combustion temperature of the incinerator is 950 - 1200 °C, and the flue gas residence time is more than 2 seconds.

[0024] An air box is arranged at the lower part of the incinerator. There are 10 - 20 air holes in the air box that communicate with the furnace of the incinerator. The air holes are tangentially swirlingly distributed. The included angle between the central axis of the air hole and the radial cross-section of the incinerator is in the range of 3 - 10°, and the included angle with the axial vertical cross-section of the incinerator is in the range of 5 - 15°; the recirculation flue gas or ambient air is sprayed into the incinerator through the air holes at a certain angle, fully mixed with the high-temperature flue gas, and forms a swirl during the downward flow process, so that the molten sodium salt formed by the incineration of the waste alkali liquor is fully cooled and dried and converted into a solid state.

[0025] The bottom of the incinerator is connected to the high-temperature transition flue through an expansion joint, and then connected to the membrane wall cooling cavity of the waste heat boiler. The bottom of this cavity is a V-shaped structure with a wider top and a narrower bottom. The included angle between the side wall and the horizontal plane is in the range of 60 - 80°, and a pneumatic or electric vibrating device is arranged outside the wall; rectangular slag discharge ports are formed at the lower edges of the two side walls, so that the alkali slag entrained in the flue gas can smoothly slide to the slag discharge ports.

[0026] The waste heat boiler includes a membrane wall cooling cavity, a superheater, an evaporator, an air preheater, an economizer, and a steam drum. The wall surfaces around and at the bottom of the membrane wall cooling cavity are all of membrane water wall structures. The wall surfaces around and at the top of the flue where the superheater and evaporator are located are also all of membrane water wall structures, and the steam drum is above; the center distance between the heat exchange tubes of the superheater and evaporator of the waste heat boiler is ≥200 mm, and the tube pitch of the air preheater and economizer is ≥150 mm.

[0027] Preferably, a gas shock pulse soot blower or a long telescopic rotary steam soot blower is arranged inside the waste heat boiler; a boat-shaped ash hopper is arranged at the bottom of the flue where the economizer is located, and the included angle between the ash hopper wall plate and the horizontal plane ranges from 60° to 80°.

[0028] The dust collector adopts the form of a bag filter or an electric-bag composite dust collector, and is provided with external thermal insulation; the air bag and pipeline for pulse backwashing are provided with steam tracing or electric tracing, and are externally thermally insulated, and the outer wall temperature ≥ 100 °C.

[0029] A boat-shaped ash hopper is arranged at the bottom of the dust collector, and the included angle between the ash hopper wall plate and the horizontal plane ranges from 60° to 80°. The surface roughness of the inner wall ≤ 0.8 μm, and the surface roughness of the weld ≤ 1.2 μm, so that the caustic ash can slide smoothly to the ash outlet of the ash hopper; the ash hopper is provided with a maintenance hole and a level gauge, and a pneumatic or electric vibrating device is arranged outside the wall plate; the ash hopper is provided with steam tracing or electric tracing, and is externally thermally insulated, and the outer wall temperature ≥ 130 °C.

[0030] The slag conveying system is located at the bottom of the membrane wall cooling cavity of the waste heat boiler, including a caustic slag conveyor and a caustic slag valve. The caustic slag conveyor adopts a water-cooled double-shaft spiral type, and the caustic slag valve adopts an electric double-layer flap valve type; about 5-20% of the sodium salts formed by the incineration of waste alkali liquor form caustic slag, which is cooled, crushed and collected through the slag conveying system.

[0031] The ash conveying system is located at the bottom of the flue where the economizer is located and at the bottom of the dust collector, including an economizer caustic ash conveyor, a dust collector caustic ash conveyor, a caustic ash scraper conveyor and a caustic ash valve; about 80-95% of the sodium salts formed by the incineration of waste alkali liquor form caustic ash, which is collected through the ash conveying system.

[0032] Both the slag conveying system and the ash conveying system adopt a closed design to avoid cold air leakage into them to contact the sodium salts and prevent the sodium salts from caking; the economizer caustic ash conveyor and the dust collector caustic ash conveyor adopt a screw conveyor type and have a forward and reverse function. One end of the screw conveyor is connected to the caustic ash valve at the bottom, and the other end is reserved with a downward ash outlet at the bottom, which can be connected to a ton bag to collect caustic ash; the economizer caustic ash conveyor, the dust collector caustic ash conveyor and the caustic ash scraper conveyor are all provided with steam tracing or electric tracing, and are externally thermally insulated, and the outer wall temperature ≥ 100 °C.

[0033] A roll compactor (optional), adopting a dry roll compaction and vibration granulation method, makes the caustic ash collected by the ash conveying system into white fine particles, with a bulk density ≥ 0.9 g / mL, belonging to heavy soda ash, having the characteristics of solidification, large particles, high density, low hygroscopicity, not easy to cake, not easy to fly ash, good fluidity, etc., meeting the standard requirements of GB / T210-2022 "Sodium Carbonate for Industrial Use".

[0034] A suction bypass for the reflux fan is provided in the inlet flue of the reflux fan, and a pneumatic regulating baffle is configured; a suction bypass for the dust collector is provided in the inlet flue of the dust collector, and a pneumatic regulating baffle is configured; a suction bypass for the induced draft fan is provided in the inlet flue of the induced draft fan, and a pneumatic regulating baffle is configured.

[0035] A method for incineration treatment and energy recovery of waste alkali liquor in a propylene epoxidation unit includes:

[0036] Auxiliary fuel and combustion-supporting air enter the main burner for combustion to form a flame. Waste alkali liquor and combustion-supporting air enter the incinerator for incineration to form high-temperature flue gas at 950 - 1200 °C. The high-temperature flue gas is cooled by mixing with reflux flue gas or ambient air as a cold fluid, and the high-temperature flue gas is cooled to 550 - 700 °C by coupling with the heat transfer of the membrane wall of the subsequent waste heat boiler. Then it enters the waste heat boiler for energy recovery to generate steam. The flue gas temperature drops to 180 - 240 °C, and it passes through a dust collector, a catalytic denitration reactor, and a boiler feed water preheater in sequence for dust removal, denitration, and temperature reduction to 120 - 160 °C, and is discharged into the atmosphere through a chimney.

[0037] The reflux fan transports the low-temperature flue gas at 180 - 240 °C to the reflux flue gas cooler, and after heat exchange with the boiler feed water, the temperature drops to 140 - 180 °C, and then it is introduced into the incinerator to cool and reduce the temperature of the high-temperature flue gas.

[0038] The boiler feed water first exchanges heat with the low-temperature flue gas through the boiler feed water preheater, then exchanges heat with the reflux flue gas through the reflux flue gas cooler, and then enters the economizer of the waste heat boiler to exchange heat with the high-temperature flue gas. The boiler feed water after three times of preheating enters the steam drum, membrane wall, superheater, and evaporator of the waste heat boiler to generate steam, so that the temperature of the discharged flue gas drops to 120 - 160 °C, realizing maximum energy recovery.

[0039] A temperature transmitter is arranged at the lower part of the combustion chamber of the incinerator to measure the flue gas temperature in real time, and the operating temperature of the combustion chamber of the incinerator is regulated by adjusting the flow rate of the auxiliary fuel and the flow rate of the combustion-supporting air, so that the organic matter in the waste alkali liquor is fully thermally oxidized and decomposed.

[0040] A temperature transmitter is arranged in the cooling cavity of the membrane wall of the waste heat boiler to measure the flue gas temperature in real time, and the operating temperature of the cooling cavity of the membrane wall of the waste heat boiler is regulated by adjusting the flow rate of the reflux flue gas or ambient air, so that the molten sodium salt formed by the incineration of the waste alkali liquor is fully cooled and dried.

[0041] A suction bypass for the reflux fan is provided in the inlet flue of the reflux fan, and ambient air is selected to partially or completely replace the reflux flue gas as the cooling medium to improve the operation flexibility of the incineration device.

[0042] An induced draft fan is installed on the low-temperature flue between the dust collector and the catalytic denitration reactor. A temperature transmitter is installed in the inlet flue of the dust collector to measure the flue gas temperature in real time. The flue gas temperature is controlled by adjusting the air volume of the bypass air intake of the dust collector to protect the filter bags of the dust collector.

[0043] A pressure transmitter is installed in the combustion chamber of the incinerator to measure the furnace pressure in real time. The furnace pressure is controlled by adjusting the air volume of the bypass air intake of the induced draft fan or by frequency conversion of the induced draft fan to ensure that the incineration device operates under negative pressure.

[0044] About 5-20% of the sodium salts formed by the incineration of waste alkali liquor form alkali residues, and about 80-95% form alkali ash, which are collected through the slag conveying system and the ash conveying system respectively to improve the purity of sodium carbonate in the alkali ash. The ash conveying system adopts a closed, heat-traced and externally insulated design, and the sodium salts are scattered and collected at a total of 3 positions, namely, the bottom of the membrane wall cooling cavity of the waste heat boiler, the bottom of the flue where the economizer is located, and the bottom of the dust collector, to reduce the caking and blockage of the sodium salts and improve the operation cycle of the device.

[0045] Preferably, the waste alkali liquor incineration treatment and energy recovery system of the propylene epoxidation device of the present invention further includes a roll compactor granulation device. By using the dry roll compaction and vibration granulation methods, the alkali ash collected by the ash conveying system is made into white fine particles, meeting the standard requirements of GB / T 210-2022 "Industrial Sodium Carbonate"; the resource utilization value of the incineration product sodium salts is improved.

[0046] The present invention has the following beneficial effects compared with the prior art:

[0047] (1) The method for treating waste alkali liquor by incineration and recovering energy in the propylene epoxidation device of the present invention incinerates the waste alkali liquor by high-temperature thermal oxidation technology, and thoroughly thermally oxidizes and decomposes the toxic and harmful organic substances in the waste alkali liquor at a temperature of 950-1200 °C.

[0048] (2) The method for treating waste alkali liquor by incineration and recovering energy in the propylene epoxidation device of the present invention couples the mixing of reflux flue gas or ambient air cold fluid with the heat transfer of the membrane wall to cool the high-temperature flue gas to 550-700 °C, so that the molten sodium salts formed by the incineration of the waste alkali liquor are fully cooled and dried, and are transformed into solids, reducing the adhesion and blockage of the heat exchange surface of the waste heat boiler.

[0049] (3) The method for treating waste alkali liquor by incineration and recovering energy in the propylene epoxidation device of the present invention consists of a membrane wall, superheater, evaporator, air preheater, economizer of the waste heat boiler, and a reflux flue gas cooler and a boiler feed water preheater to form a multi-effect heat exchange network, improving the energy recovery efficiency.

[0050] (4) The method for incineration treatment and energy recovery of waste alkali liquor in the propylene epoxidation device according to the present invention separately collects the sodium salt slag and alkali ash formed by incinerating the waste alkali liquor, improves the purity of sodium carbonate in the alkali ash; and uses a roll compactor (optional) to make the alkali ash into industrial sodium carbonate, thereby improving the resource utilization value of sodium salts.

[0051] (5) The method for incineration treatment and energy recovery of waste alkali liquor in the propylene epoxidation device according to the present invention has a closed, heat-traced and externally insulated design for the ash conveying system, and collects sodium salts dispersedly at a total of 3 positions, namely the bottom of the membrane wall cooling cavity of the waste heat boiler, the bottom of the flue where the economizer is located, and the bottom of the dust collector, so as to reduce the caking and blockage of sodium salts and improve the operation cycle of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a schematic diagram of a system for incineration treatment and energy recovery of waste alkali liquor in a propylene epoxidation device according to the present invention.

[0053] Reference numerals: incinerator - 1, main burner - 2, waste heat boiler - 3, dust collector - 4, induced draft fan - 5, catalytic denitration reactor - 6, boiler feed water preheater - 7, chimney - 8, combustion air blower - 9, recirculation fan - 10, recirculation flue gas cooler - 11, cold air duct - 12, hot air duct - 13, high-temperature transition flue - 14, low-temperature flue - 15, recirculation flue - 16, discharge flue - 17, dust collector suction bypass - 18, induced draft fan suction bypass - 19, recirculation fan suction bypass - 20, slag conveying system - 30, ash conveying system - 40, slag conveyor - 31, slag valve - 32, economizer alkali ash conveyor - 42, dust collector alkali ash conveyor - 43, alkali ash scraper conveyor - 44, alkali ash valve - 45, roll compactor - 50. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] In order to make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the drawings.

[0055] A system and method for incineration treatment and energy recovery of waste alkali liquor in a propylene epoxidation device are suitable for incinerating and treating highly saline alkaline organic waste liquor (hereinafter referred to as waste alkali liquor), and are particularly applicable to the propylene oxide industry. For the phenol acetone industry, acrylic acid industry, caprolactam industry, and methanol-to-olefins industry, which also have highly saline alkaline organic waste liquor (hereinafter referred to as waste alkali liquor), the high-temperature thermal oxidation technology, cold fluid mixing and membrane wall heat transfer coupling cooling process, multi-effect energy recovery heat exchange network, sodium salt dispersed collection method, and process equipment layout structure adopted in this invention patent are generally applicable in terms of technical principles.

[0056] A system for incineration treatment and energy recovery of waste alkali liquor in a propylene epoxidation unit, comprising an incinerator 1, a main burner 2, a waste heat boiler 3, a dust collector 4, an induced draft fan 5, a catalytic denitration reactor 6, a boiler feed water preheater 7, a chimney 8, a combustion-supporting fan 9, a reflux fan 10, a reflux flue gas cooler 11, a cold air duct 12, a hot air duct 13, a high-temperature transition flue duct 14, a low-temperature flue duct 15, a reflux flue duct 16, an exhaust flue duct 17, a dust collector air intake bypass 18, an induced draft fan air intake bypass 19, a reflux fan air intake bypass 20, a slag conveying system 30, an ash conveying system 40, as well as connecting pipes, valves, pipe fittings, instruments and control systems for realizing the safe operation of the unit.

[0057] The waste alkali liquor is transported through a pipeline to the combustion chamber of the incinerator 1 for incineration, so as to fully thermally oxidize and decompose the organic matter in the waste alkali liquor and convert the sodium in the waste alkali liquor into sodium salts; the auxiliary fuel burns in the main burner 2 to provide a flame for the incineration of the waste alkali liquor; the combustion-supporting fan 9 provides ambient air as combustion-supporting air; the reflux fan 10 transports the low-temperature flue gas or ambient air to the air box of the incinerator 1 to mix with the high-temperature flue gas to cool it down, and couples with the heat transfer of the membrane wall of the subsequent waste heat boiler 3 to fully cool and dry the molten sodium salts and convert them into solids; the high-temperature flue gas enters the waste heat boiler 3 and sequentially passes through the membrane wall cooling cavity, superheater, evaporator, air preheater, and economizer for heat exchange to generate steam for energy recovery; the low-temperature flue gas then sequentially passes through the dust collector 4, catalytic denitration reactor 6, and boiler feed water preheater 7 for dust removal, denitration, and temperature reduction, and is discharged into the atmosphere through the exhaust flue duct 17 and chimney 8; the sodium salt slag and alkali ash formed by the incineration of the waste alkali liquor are respectively collected by the slag conveying system 30 and ash conveying system 40.

[0058] The main burner 2 is located at the top of the incinerator 1 and is a gas-liquid combined multi-fuel burner, which provides a flame for the incineration of the waste alkali liquor and can use fuel gas or tar alone or in combination as the auxiliary fuel. The ambient air provided by the combustion-supporting fan 9 passes through the cold air duct 12 and hot air duct 13 and enters the main burner 2 to provide the required combustion-supporting air for combustion; the auxiliary fuel is sent to the burner of the main burner 2 through a pipeline, and a flow meter and a regulating valve group are also configured on the auxiliary fuel pipeline to control the load of the main burner 2, and a cut-off valve is configured on each auxiliary fuel pipeline for safety interlock.

[0059] The incinerator 1 is of a vertical top-fired adiabatic type, lined with refractory materials. The main burner 2, incinerator 1, high-temperature transition flue duct 14, and the inlet of the waste heat boiler 3 are vertically connected from top to bottom and their central axes coincide; the combustion temperature of the incinerator 1 is 950 - 1200 °C, the oxygen content is 3 - 10 vol%, and the flue gas residence time is more than 2 seconds.

[0060] The combustion chamber of the incinerator 1 is the space for the combustion of flames and waste alkali liquor. When the temperature in the combustion chamber reaches the feeding temperature, the waste alkali liquor can be transported through a pipeline to the waste alkali liquor atomizing spray gun installed on the incinerator 1 and sprayed into the combustion chamber for incineration. A flow meter, a regulating valve, and a pressure transmitter are configured on the waste alkali liquor pipeline for operation control, and a cut-off valve is configured on the waste alkali liquor pipeline for safety interlock; incineration enables the organic matter in the waste alkali liquor to be fully thermally oxidized and decomposed, and converts the sodium in the waste alkali liquor into sodium salts.

[0061] A wind box is arranged at the lower part of the incinerator 1. There are 10 - 20 air holes communicating with the furnace chamber of the incinerator 1 in the wind box. The air holes are tangentially swirlingly distributed. The included angle between the central axis of the air hole and the radial cross-section of the incinerator is in the range of 3 - 10°, and the included angle with the axial vertical cross-section of the incinerator is in the range of 5 - 15°; the low-temperature flue gas or ambient air extracted from the rear by the reflux fan 10 is introduced into the incinerator wind box and sprayed into the incinerator 1 at a certain angle through the air holes, fully mixed with the high-temperature flue gas, forming a swirl during the downward flow process, and coupling with the heat transfer of the membrane wall of the subsequent waste heat boiler 3 to cool the high-temperature flue gas to 550 - 700 °C, enabling the molten sodium salts formed by the combustion of the waste alkali liquor to be fully cooled and dried, converted into solids, avoiding their adhesion and blockage on the inner walls of the incinerator 1 and the high-temperature transition flue 14, the membrane wall cooling cavity inner wall of the waste heat boiler 3, the heat transfer surface, and the filter surface of the dust collector 4, and improving the operation cycle of the device.

[0062] The waste heat boiler 3 includes a membrane wall cooling cavity, a superheater, an evaporator, an air preheater, a economizer, and a steam drum. The walls around and at the bottom of the membrane wall cooling cavity are all of membrane water wall structure. The walls around and at the top of the flue where the superheater and the evaporator are located are also all of membrane water wall structure. The steam drum is above, used for energy recovery from the incineration flue gas; the center distance between the heat exchange tubes of the superheater and the evaporator of the waste heat boiler 3 is ≥ 200 mm, and the distance between the heat exchange tubes of the air preheater and the economizer is ≥ 150 mm, reducing the accumulation of alkali ash on the heat transfer surface; preferably, a gas shock pulse soot blower or a long telescopic rotary steam soot blower is arranged in the waste heat boiler 3 for purging the alkali ash accumulated on the heat transfer surface and maintaining the heat transfer effect of the heat transfer surface; the flue gas temperature at the outlet of the waste heat boiler 3 is about 180 - 240 °C.

[0063] The reflux fan 10 transports the low-temperature flue gas to the reflux flue gas cooler 11, cools it to 140 - 180 °C after heat exchange with the boiler feed water, and then introduces it into the incinerator 1 wind box to cool the high-temperature flue gas; the boiler feed water first exchanges heat with the low-temperature flue gas through the boiler feed water preheater 7, then exchanges heat with the reflux flue gas through the reflux flue gas cooler 11, and then enters the economizer of the waste heat boiler 3 to exchange heat with the high-temperature flue gas. The boiler feed water after being preheated three times enters the steam drum, membrane wall cooling cavity, superheater, and evaporator of the waste heat boiler 3 to generate steam, reducing the discharge flue gas temperature to 120 - 160 °C, achieving maximum energy recovery.

[0064] The bottom of the membrane wall cooling cavity of the waste heat boiler 3 is a V-shaped structure that is wider at the top and narrower at the bottom. The angle between the side wall and the horizontal plane ranges from 60 to 80°, and a pneumatic or electric vibrating device is provided outside the wall; rectangular slag discharge openings are formed at the lower edges of both side walls, enabling the alkali slag entrained in the flue gas to smoothly slide down to the slag discharge openings; boat-shaped ash hoppers are provided at the bottom of the flue where the economizer of the waste heat boiler 3 is located and at the bottom of the dust collector 4 to receive the alkali ash blown off from the heat exchange surface. The angle between the hopper wall plate and the horizontal plane ranges from 60 to 80° to facilitate the smooth sliding of the alkali ash to the ash discharge opening of the ash hopper; the sodium salts in the flue gas are collected in a dispersed manner at 3 positions, reducing the adhesion, accumulation, and blockage of sodium salts and improving the operation cycle of the device.

[0065] The slag conveying system 30 is located at the bottom of the membrane wall cooling cavity of the waste heat boiler 3. Approximately 5 to 20% of the sodium salts formed by the combustion of the waste alkali liquor form alkali slag, which is cooled, crushed, and collected by the slag conveying system 30. The slag conveying system 30 includes an alkali slag conveyor 31 and an alkali slag valve 32.

[0066] The ash conveying system 40 is located at the bottom of the flue where the economizer of the waste heat boiler 3 is located and at the bottom of the dust collector 4. Approximately 80 to 95% of the sodium salts formed by the combustion of the waste alkali liquor form alkali ash, which is collected by the ash conveying system 40. The collection of alkali slag and alkali ash is distinguished to improve the purity of sodium carbonate in the alkali ash. The ash conveying system 40 includes an economizer alkali ash conveyor 42, a dust collector alkali ash conveyor 43, an alkali ash scraper conveyor 44, and an alkali ash valve 45.

[0067] Both the slag conveying system 30 and the ash conveying system 40 are designed to be airtight to prevent cold air from leaking in and contacting the sodium salts, thereby preventing the sodium salts from caking; the economizer alkali ash conveyor 42 and the dust collector alkali ash conveyor 43 adopt the spiral conveyor type and have the function of forward and reverse rotation. One end of the spiral conveyor is connected to the alkali ash valve 45 at the bottom, and a downward ash outlet is reserved at the other end to be able to connect to a ton bag for collecting alkali ash; the economizer alkali ash conveyor 42, the dust collector alkali ash conveyor 43, and the alkali ash scraper conveyor 44 are all provided with steam tracing or electric tracing and are externally insulated, with the outer wall temperature ≥ 100°C.

[0068] Preferably, the system for incineration treatment and energy recovery of the waste alkali liquor in the propylene epoxidation device of the present invention further includes a roll compactor granulation equipment 50. By using the dry roll compaction and vibration granulation methods, the alkali ash collected by the ash conveying system 40 is made into white fine-grained industrial sodium carbonate with a bulk density ≥ 0.9 g / mL, which belongs to heavy soda ash and has the characteristics of solidification, large particle size, high density, low moisture absorption, not easy to cake, not easy to fly ash, and good fluidity, meeting the standard requirements of GB / T 210-2022 "Industrial Sodium Carbonate".

[0069] The dust collector 4 adopts the form of a bag filter or an electrostatic bag composite dust collector, and is provided with external thermal insulation, and is used to capture the sodium salt powder in the low-temperature flue gas discharged from the waste heat boiler 3; a boat-shaped ash hopper is arranged at the bottom of the dust collector 4, and the included angle between the ash hopper wall panel and the horizontal plane is in the range of 60-80°, the surface roughness of the inner wall is ≤0.8μm, and the surface roughness of the weld is ≤1.2μm, so that the alkali ash can slide smoothly to the ash outlet of the ash hopper; the ash hopper is provided with a maintenance hole and a level gauge, and a pneumatic or electric vibrating device is arranged outside the wall panel; the ash hopper is provided with steam tracing or electric tracing, and is provided with external thermal insulation, and the outer wall temperature ≥130°C, to keep the alkali ash in the ash hopper dry and avoid caking and blockage; the dust concentration of the flue gas at the outlet of the dust collector 4 does not exceed 30mg / Nm 3 , meeting the requirements of pollutant emission limits.

[0070] The catalytic denitration reactor 6 is filled with SCR catalyst, which is used to reduce nitrogen oxides NOx generated by incineration in the flue gas to nitrogen N 2 , and ammonia is used as a reducing agent and enters the catalytic denitration reactor 6 through a spraying device, and participates in the denitration reaction under the action of the catalyst to reduce the nitrogen oxides in the flue gas to below 300mg / Nm 3 , so that the discharged flue gas meets the requirements of pollutant emission limits; the induced draft fan 5 maintains the incineration device in a negative pressure state to prevent the leakage of high-temperature and harmful gases.

[0071] A bypass 20 for the induced draft of the reflux fan is arranged in the inlet flue of the reflux fan 10, and is equipped with a pneumatic regulating baffle; a bypass 18 for the induced draft of the dust collector is arranged in the inlet flue of the dust collector 4, and is equipped with a pneumatic regulating baffle; an induced draft fan 5 is arranged on the low-temperature flue 15 between the dust collector 4 and the catalytic denitration reactor 6, and a bypass 19 for the induced draft of the induced draft fan is arranged in the inlet flue of the induced draft fan 5, and is equipped with a pneumatic regulating baffle; the low-temperature flue gas output by the induced draft fan 5 is divided into two parts, one part is transported to the catalytic denitration reactor 6, and the other part is transported to the reflux fan 10.

[0072] A temperature transmitter is arranged at the lower part of the combustion chamber of the incinerator 1 to measure the flue gas temperature in real time, and the operating temperature of the combustion chamber of the incinerator 1 is regulated by adjusting the flow rate of the auxiliary fuel and the flow rate of the combustion-supporting air, so that the organic matter in the waste alkali liquor is fully thermally oxidized and decomposed.

[0073] A temperature transmitter is arranged in the membrane wall cooling cavity of the waste heat boiler 3 to measure the flue gas temperature in real time, and the operating temperature of the membrane wall cooling cavity of the waste heat boiler 3 is regulated by adjusting the flow rate of the reflux flue gas or the ambient air, so that the molten sodium salt formed by the incineration of the waste alkali liquor is fully cooled and dried.

[0074] A bypass 20 for the induced draft of the reflux fan is arranged in the inlet flue of the reflux fan 10, and ambient air is selected to partially replace or completely replace the reflux flue gas as the cooling medium to improve the operating flexibility of the incineration device.

[0075] A temperature transmitter is installed at the inlet flue of the dust collector 4 to measure the flue gas temperature in real time. The temperature of the flue gas entering the dust collector 4 is controlled by adjusting the air volume of the air suction bypass 18 of the dust collector to protect the filter bags of the dust collector 4.

[0076] A pressure transmitter is installed in the combustion chamber of the incinerator 1 to measure the furnace pressure in real time. The furnace pressure is controlled by adjusting the air volume of the air suction bypass 19 of the induced draft fan or the frequency conversion of the induced draft fan 5 to ensure that the incineration device operates under a negative pressure state.

[0077] Example 1

[0078] The composition and flow rate of the waste alkali liquor generated by a 27 / 600,000 tons / year propylene oxide / styrene (PO / SM) plant are shown in Table 1.

[0079] Table 1

[0080]

[0081]

[0082] Using the system and method for incineration treatment and energy recovery of waste alkali liquor in a propylene epoxidation device of the present invention, the treatment steps are as follows:

[0083] 1) Natural gas is used as fuel to enter the main burner 2 for combustion to form a flame. The ambient air delivered by the combustion air blower 9 is heated by the air preheater in the waste heat boiler 3 and then delivered to the incinerator 1 and the main burner 2 as combustion-supporting air.

[0084] 2) The waste alkali liquor is transported through a pipeline to the waste alkali liquor atomizing spray gun installed on the incinerator 1 for incineration, generating high-temperature flue gas at 950 - 1200 °C.

[0085] 3) The reflux blower (10) transports a part of the low-temperature flue gas at 180 - 240 °C to the reflux flue gas cooler 11 to cool it down to 140 - 180 °C, and then it is introduced into the air box of the incinerator 1 to be mixed with the high-temperature flue gas, and coupled with the heat transfer of the membrane wall of the subsequent waste heat boiler 3 to cool it down to 550 - 700 °C, so that the molten sodium salt is fully cooled and dried to be converted into a solid state.

[0086] 4) The flue gas coming from the incinerator 1 enters the waste heat boiler 3 and successively passes through the membrane wall cooling cavity, superheater, evaporator, air preheater, and economizer for heat exchange. The flue gas temperature drops to 180 - 240 °C, and then successively passes through the dust collector 4, catalytic denitration reactor 6, and boiler feed water preheater 7 for dust removal, denitration, and temperature reduction to 120 - 160 °C, and is discharged into the atmosphere through the chimney 8.

[0087] 5) The boiler feed water is transported through pipelines to the boiler feed water preheater 7 for heat exchange with the low-temperature flue gas, then through the return flue gas cooler 11 for heat exchange with the return flue gas, and then enters the economizer of the waste heat boiler 3 for heat exchange with the high-temperature flue gas. The boiler feed water after three preheats enters the steam drum, membrane wall, superheater, and evaporator of the waste heat boiler 3 to generate steam.

[0088] 6) The induced draft fan 5 maintains the incineration device in a negative pressure state to prevent the leakage of high-temperature and harmful gases.

[0089] 7) The sodium salt slag formed by the incineration of the spent caustic liquor falls to the bottom of the membrane wall cooling cavity of the waste heat boiler 3 and is cooled, crushed, and collected through the slag conveying system 30.

[0090] 8) The sodium salt ash formed by the incineration of the spent caustic liquor is scattered and falls to the bottom of the flue where the economizer of the waste heat boiler 3 is located and the bottom ash hopper of the dust collector 4, and is collected through the ash conveying system 40, and then made into industrial sodium carbonate by the roll pressing and granulation equipment 50.

[0091] The flue gas emission data is shown in Table 2.

[0092] Table 2

[0093] Composition vol% Nitrogen <![CDATA[N 2 > 55.97％ Oxygen <![CDATA[O 2 > 4.23％ Carbon Dioxide <![CDATA[CO 2 > 8.44％ Argon Ar 0.81％ Water <![CDATA[H 2 O]]> 30.55％ Particulate Matter Dust <![CDATA[≤30mg / Nm 3 > Nitrogen Oxides NOx <![CDATA[≤100mg / Nm 3 > Total 100.00％

[0094] The composition analysis results of the slag and ash are shown in Table 3.

[0095] Table 3

[0096] Alkali Residue Alkali Ash Output kg / h 215.24 1937.19 <![CDATA[Sodium carbonate / Na 2 CO 3 > 92.84％ 98.82％ Sodium Hydroxide / NaOH 2.22％ 1.03％ Water Insoluble Matter 4.94％ 0.15％ Total 100.00％ 100.00％

[0097] Example 2

[0098] The composition and flow rate of the spent caustic liquor generated by a 24 / 450,000 tons / year propylene oxide / styrene (PO / SM) plant are shown in Table 4.

[0099] Table 4

[0100]

[0101]

[0102] Using the system and method for incineration treatment and energy recovery of spent caustic liquor in a propylene epoxidation device of the present invention, the treatment steps are as follows:

[0103] 1) Use heavy alcohol tar as fuel to enter the main burner 2 for combustion to form a flame. The ambient air conveyed by the combustion air blower 9 is heated to 300 °C through the air preheater in the waste heat boiler 3 and is conveyed to the incinerator 1 and the main burner 2 as combustion-supporting air.

[0104] 2) The spent caustic liquor is transported through a pipeline to a spent caustic liquor atomizing spray gun installed on the incinerator 1 for incineration, generating high-temperature flue gas at 950 - 1200 °C.

[0105] 3) The reflux blower 10 extracts ambient air as a cooling medium, which is introduced into the air box of the incinerator 1 to be mixed with the high-temperature flue gas, and coupled with the heat transfer of the membrane wall of the subsequent waste heat boiler 3 to cool it down to 550 - 700 °C, enabling the molten sodium salt to be fully cooled and dried into a solid state.

[0106] 4) The flue gas coming from the incinerator 1 enters the waste heat boiler 3 and successively passes through the membrane wall cooling cavity, superheater, evaporator, air preheater, and economizer for heat exchange. The flue gas temperature drops to 180 - 240 °C, and then successively passes through the dust collector 4, catalytic denitration reactor 6, and boiler feed water preheater 7 for dust removal, denitration, and temperature reduction to 120 - 160 °C, and is discharged into the atmosphere through the chimney 8.

[0107] 5) The boiler feed water is transported through a pipeline to the boiler feed water preheater 7 for heat exchange with the low-temperature flue gas, then through the reflux flue gas cooler 11 for heat exchange with the reflux flue gas, and then enters the economizer of the waste heat boiler 3 for heat exchange with the high-temperature flue gas. The boiler feed water after three preheats enters the steam drum, membrane wall, superheater, and evaporator of the waste heat boiler 3 to generate steam.

[0108] 6) The induced draft fan 5 maintains the operation of the incineration device under negative pressure to prevent the leakage of high-temperature and harmful gases.

[0109] 7) The sodium salt caustic residue formed by the incineration of the spent caustic liquor is cooled, crushed, and collected at the bottom of the membrane wall cooling cavity of the waste heat boiler 3 through the slag conveying system 30.

[0110] 8) The sodium salt caustic ash formed by the incineration of the spent caustic liquor is scattered and falls into the bottom of the flue where the economizer of the waste heat boiler 3 is located and the ash hopper at the bottom of the dust collector 4, and is collected and bagged through the ash conveying system 40.

[0111] The flue gas emission data is shown in Table 5.

[0112] Table 5

[0113] Composition vol% Nitrogen <![CDATA[N 2 > 53.53％ Oxygen <![CDATA[O 2 > 3.95％ Carbon Dioxide <![CDATA[CO 2 > 7.70％ Argon Ar 0.62％ Water <![CDATA[H 2 O]]> 34.20％ Particulate Matter Dust <![CDATA[≤30mg / Nm 3 > Nitrogen Oxides NOx <![CDATA[≤100mg / Nm 3 > Total 100.00％

[0114] The composition analysis results of the caustic residue and caustic ash are shown in Table 6.

[0115] Alkali Residue Alkali Ash Output kg / h 63.16 568.46 Composition <![CDATA[Sodium carbonate / Na 2 CO 3 > 91.86％ 96.69％ Sodium Hydroxide / NaOH 0.19％ 0.22％ <![CDATA[Sodium molybdate / Na 2 MoO 4 > 4.10％ 3.06％ Water Insoluble Matter 3.85％ 0.03％ Total 100.00％ 100.00％

[0116] The content not described in detail in the specification of the present invention belongs to the well-known technology in the art.

[0117] Although the present invention has been disclosed above in preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and decorations made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A system for incineration treatment and energy recovery of waste alkali liquor from a propylene epoxidation device, characterized in that: It comprises an incinerator (1), a main burner (2), a waste heat boiler (3), a dust collector (4), an induced draft fan (5), a catalytic denitration reactor (6), a boiler feed water preheater (7), a chimney (8), a combustion-supporting fan (9), a return fan (10), an exhaust flue (17), a slag conveying system (30), and an ash conveying system (40); The waste alkali liquid is transported to an incinerator (1) for incineration, the organic matter in the waste alkali liquid is fully thermally oxidized and decomposed, and the sodium in the waste alkali liquid is converted into sodium salt; the auxiliary fuel is burned in the main burner (2) to provide flame for the incineration of the waste alkali liquid; the combustion-supporting fan (9) provides ambient air as combustion-supporting air; the return fan (10) transports low-temperature flue gas or ambient air to the incinerator (1), mixes it with the high-temperature flue gas to cool it down, and couples with the membrane wall heat transfer of the subsequent waste heat boiler (3) to fully cool and dry the molten sodium salt and convert it into a solid state; After entering the waste heat boiler (3), the high-temperature flue gas passes through the internal membrane wall cooling cavity, superheater, evaporator, air preheater and economizer in sequence for heat exchange, and generates steam for energy recovery; the low-temperature flue gas then passes through the dust collector (4), catalytic denitration reactor (6) and boiler feed water preheater (7) in sequence for dust removal, denitration and cooling, and is discharged into the atmosphere through the exhaust flue (17) and chimney (8); the sodium salt alkali slag and alkali ash formed by the incineration of the waste alkali liquid are collected through the slag conveying system (30) and the ash conveying system (40) respectively.

2. The system for incinerating waste alkali liquor from a propylene epoxidation device and recovering energy according to claim 1, characterized in that: The waste alkali liquor incineration treatment and energy recovery system of the propylene epoxidation device also includes a cold air duct (12) and a hot air duct (13); the main burner (2) is located at the top of the incinerator (1), and the ambient air provided by the combustion-supporting blower (9) is passed through the cold air duct (12) and the hot air duct (13) into the main burner (2) to provide the combustion-supporting air required for combustion; the auxiliary fuel is delivered to the burner of the main burner (2) through a pipeline, and a flow meter and a regulating valve group are also arranged on the auxiliary fuel pipeline to control the load of the main burner (2), and a cut-off valve is arranged on the auxiliary fuel pipeline for safety interlocking.

3. The system for incinerating waste alkali liquor from a propylene epoxidation device and recovering energy according to claim 1, characterized in that: The propylene epoxidation device waste alkali liquor incineration treatment and energy recovery system also includes a high-temperature transition flue (14); the incinerator (1) is a vertical top-burning insulation type, lined with refractory materials, and the main burner (2), the incinerator (1), the high-temperature transition flue (14) and the inlet of the waste heat boiler (3) are vertically connected from top to bottom, and the central axes coincide.

4. The system for incinerating waste alkali liquor from a propylene epoxidation device and recovering energy according to claim 1, characterized in that: The combustion chamber of the incinerator (1) is a space for the combustion of flames and waste alkali liquid. When the temperature in the combustion chamber reaches the feed temperature, the waste liquid is transported through a pipeline to a waste alkali liquid atomizing spray gun installed on the incinerator (1) and sprayed into the combustion chamber for combustion. A flow meter, a regulating valve and a pressure transmitter are arranged on the waste alkali liquid pipeline for operation control. A cut-off valve is arranged on the waste alkali liquid pipeline for safety interlocking. The incineration fully oxidizes and decomposes the organic matter in the waste alkali liquid, and converts the sodium in the waste alkali liquid into sodium salt. A bellows is arranged at the bottom of the incinerator (1), and a wind hole is opened in the bellows, which is communicated with the furnace of the incinerator (1); low-temperature flue gas or ambient air extracted by a return fan (10) is passed into the bellows, sprayed into the incinerator (1) through the wind hole, and fully mixed with the high-temperature flue gas, forming a vortex in the process of flowing downward, and coupled with the membrane wall heat transfer of the waste heat boiler (3) to cool the high-temperature flue gas, so that the molten sodium salt formed by the combustion of the waste alkali liquid is fully cooled, dried, and converted into a solid state.

5. The system for incinerating waste alkali liquor from a propylene epoxidation device and recovering energy according to claim 4, characterized in that: The propylene epoxidation device waste alkali liquor incineration treatment and energy recovery system also includes a reflux flue gas cooler (11), a waste heat boiler (3) including a membrane wall cooling cavity, a superheater, an evaporator, an air preheater, an economizer and a steam drum, the walls around and at the bottom of the membrane wall cooling cavity are all membrane water-cooled wall structures, the walls around and at the top of the flue where the superheater and the evaporator are located are also membrane water-cooled wall structures, and the steam drum is at the top and is used to recover energy from the incineration flue gas; The return fan (10) conveys the low-temperature flue gas to the return flue gas cooler (11), and after heat exchange with the boiler feed water, it is passed into the wind box of the incinerator (1) to cool down the high-temperature flue gas; the boiler feed water first exchanges heat with the low-temperature flue gas through the boiler feed water preheater (7), and then exchanges heat with the return flue gas through the return flue gas cooler (11), and then enters the waste heat boiler (3) economizer to exchange heat with the high-temperature flue gas. After three preheatings, the boiler feed water enters the waste heat boiler (3) steam drum, membrane wall cooling cavity, superheater, and evaporator to generate steam, so that the exhaust flue gas temperature is further reduced, thereby realizing maximum energy recovery; The bottom of the membrane wall cooling cavity of the waste heat boiler (3) is a V-shaped structure that is wide at the top and narrow at the bottom. The angle between the side wall and the horizontal plane is in the range of 60 to 80 degrees, and a pneumatic or electric vibration device is arranged outside the wall; the lower edges of the two side walls form a rectangular slag outlet, so that the alkali slag entrained in the flue gas can smoothly slide to the slag outlet; the flue where the economizer of the waste heat boiler (3) is located and the bottom of the dust collector (4) are both provided with a ship-shaped ash hopper for receiving the alkali ash swept from the heat exchange surface, and the angle between the ash hopper wall plate and the horizontal plane is in the range of 60 to 80 degrees, so that the alkali ash can smoothly slide to the ash outlet of the ash hopper; the sodium salt in the flue gas is dispersed and collected at three positions, so as to reduce the adhesion, accumulation and blockage of the sodium salt and improve the operation cycle of the device.

6. The system for incinerating waste alkali liquor from a propylene epoxidation device and recovering energy according to claim 1, characterized in that: The slag conveying system (30) and the ash conveying system (40) are both sealed in design to prevent cold air from leaking into the system and contacting the sodium salt, thereby preventing the sodium salt from hardening.

7. The system for incinerating waste alkali liquor from a propylene epoxidation device and recovering energy according to claim 1, characterized in that: The waste alkali liquor incineration treatment and energy recovery system of the propylene epoxidation device also includes a roller granulation device (50) which uses a dry roller pressing and vibration granulation method to convert the alkali ash collected by the ash conveying system (40) into industrial sodium carbonate.

8. The system for incinerating waste alkali liquor from a propylene epoxidation device and recovering energy according to claim 1, characterized in that: The dust collector (4) is a bag type dust collector or an electric bag composite dust collector and is provided with external insulation to capture sodium salt powder in the low-temperature flue gas from the waste heat boiler (3); the catalytic denitration reactor (6) is loaded with an SCR catalyst.

9. The system for incinerating waste alkali liquor from a propylene epoxidation device and recovering energy according to claim 1, characterized in that: The propylene epoxidation device waste alkali liquor incineration treatment and energy recovery system also includes a low-temperature flue (15), a return fan air suction bypass (20) is arranged at the return fan (10) inlet flue, and a pneumatic adjustment baffle is provided; a dust collector air suction bypass (18) is arranged at the dust collector (4) inlet flue, and a pneumatic adjustment baffle is provided; an induced draft fan (5) is arranged on the low-temperature flue (15) between the dust collector (4) and the catalytic denitration reactor (6), and an induced draft fan air suction bypass (19) is arranged at the induced draft fan (5) inlet flue, and a pneumatic adjustment baffle is provided; the low-temperature flue gas output by the induced draft fan (5) is divided into two parts, one part is transported to the catalytic denitration reactor (6), and the other part is transported to the return fan (10).

10. A method for incineration treatment of waste alkali liquor from a propylene epoxidation device and energy recovery system according to claim 1, characterized in that: include: Auxiliary fuel and combustion air enter the main burner (2) to burn and form flames, and waste alkali liquid and combustion air enter the incinerator (1) to burn and form high-temperature flue gas at 950-1200°C. The high-temperature flue gas is mixed with the return flue gas or ambient air as a cold fluid to cool the high-temperature flue gas, and coupled with the membrane wall heat transfer of the waste heat boiler (3) to cool the high-temperature flue gas to 550-700°C. The high-temperature flue gas then enters the waste heat boiler (3) for energy recovery to generate steam. The flue gas temperature drops to 180-240°C, and passes through the dust collector (4), the catalytic denitration reactor (6), and the boiler feed water preheater (7) in sequence for dust removal, denitration, and cooling to 120-160°C, and is discharged into the atmosphere through the chimney (8).

Images