Resource utilization treatment system and treatment process for agricultural dry yellow straw

Abstract

The invention relates to a dry yellow straw resourceful treatment system, a dry yellow straw resourceful treatment process and an agricultural solid waste treatment process, in particular to a dry yellow straw resourceful utilization treatment system and a dry yellow straw resourceful utilization treatment process which comprise the working procedures of pretreatment, heating pressurization, primary pressure relief, secondary pressure relief, flash evaporation treatment, aftertreatment and the like. The clear liquid is prepared into liquid organic fertilizer, and the solid is dried and granulated to prepare solid organic fertilizer. According to the characteristics of the dry yellow straw, the resource utilization treatment system and the treatment process which are high in treatment speed and small in occupied area are researched and developed.

Description

TECHNICAL FIELD

[0001] The present application relates to an agricultural solid waste treatment process, in particular to a resource utilization treatment system and process for dry yellow straw. BACKGROUND

[0002] A large amount of straw is produced in agricultural production in China every year, which is commonly referred to as dry yellow straw after drying. The dry yellow straw occupies a large amount of space and is prone to cause fire hazards. Traditional dry yellow straw treatment methods include incineration, crushing and returning to the field, and fertilizer production. Incineration has been banned due to environmental pollution. At present, the crushing and returning to the field method has the highest usage ratio, but it cannot kill residual insect eggs and its use is limited. In cold regions, the dry yellow straw cannot decompose after being returned to the field. Therefore, in recent years, many people have focused on fertilizer production. The dry yellow straw is first made into fertilizer and then mechanically returned to the field, which can improve the absorption and utilization rate of nutrients.

[0003] At present, the most commonly used method for dry yellow straw fertilizer production is microbial treatment. The most representative processes are aerobic microbial fermentation and anaerobic microbial fermentation. Microorganisms are used to decompose dry yellow straw into small molecules that are easy to absorb. After being returned to the field, the organic matter can be supplemented and the soil structure can be improved.

[0004] Both of the above two representative processes belong to microbial treatment methods, and they have the common feature of relying on the action of microorganisms. Since the main components of dry yellow straw are cellulose, hemicellulose and lignin, these three substances form a strong and compact structure, and are highly hydrophobic, so it is difficult for microorganisms to decompose and utilize them. The treatment speed is slow, and the conventional treatment time is more than 30 days. In addition, the density of the straw is low, and at least 60m³ of equipment space is required for the treatment of each ton of dry yellow straw.

[0005] In summary, the main disadvantage of microbial treatment for fertilizer production is the long treatment time, which results in a large volume of treatment equipment and high engineering construction cost. Shortening the treatment time of dry yellow straw not only reduces the construction cost but also saves the land area. SUMMARY

[0006] The purpose of the present application is to provide a resource utilization treatment process for agricultural dry yellow straw. According to the characteristics of dry yellow straw, a resource utilization treatment system and process with fast treatment speed and small land area are developed.

[0007] In a first aspect, the present application provides a resource utilization treatment process for agricultural dry yellow straw The following technical solutions are adopted: (1) Pretreatment: The dry yellow straw is crushed to 20-30mm, the metal impurities are separated by magnetic separation, the inorganic sand is removed by screening, and then the dry yellow straw is soaked in water to make the moisture content ≥55%; (2) Heating and pressurization: after soaking, the straw is sent into a high-pressure heating tank, and after sealing, 290℃ conductive oil is introduced to heat the tank to 212℃ and 2MPa, and the pressure is maintained for 1h; (3) First pressure relief: the steam in the high-pressure heating tank is introduced into another high-pressure heating tank that has completed feeding but has not been heated until the pressure of the two tanks is balanced to 1MPa; (4) Second pressure relief: the steam in the tank that has completed the first pressure relief in step (3) is introduced into a low-pressure buffer tank, and the pressure is relieved to 0.1MPa; (5) Flash treatment: open the tank bottom outlet gate valve to spray the straw into the low-pressure buffer tank to flash and cool to 50℃, forming a slurry; (6) Post-processing: the slurry after flashing is subjected to solid-liquid separation, the clear liquid is made into liquid organic fertilizer, and the solid is dried and granulated to make solid organic fertilizer.

[0008] By using the above scheme, through gradient pressure relief (2MPa→1MPa→0.1MPa) combined with flash treatment, the straw fiber structure is completely destroyed, forming a homogeneous slurry, significantly improving the subsequent solid-liquid separation efficiency and organic fertilizer yield. In the first pressure relief stage, high-temperature steam is introduced into another high-pressure tank for preheating, recovering more heat energy and reducing the energy consumption of the second heating. The tail gas condensate water is recycled for the soaking process, improving the process water recycling rate and reducing fresh water consumption and wastewater discharge.

[0009] Further, in step (1): The magnetic separation uses a permanent magnet roller magnetic separator with a magnetic field strength ≥3000 Gauss; The screening uses a vibrating screen with a screen aperture ≤5mm; The soaking time is ≥2h.

[0010] By using the above technical scheme, the strong magnetic field (≥3000 Gauss) combined with fine screening (aperture ≤5mm) improves the removal rate of metal / sand impurities, avoids equipment wear and tear and product contamination. Soaking for ≥2h ensures that the moisture content is ≥55%, allowing the water to fully vaporize and expand in the subsequent hot pressing stage, improving the fiber cracking efficiency.

[0011] Further, in step (2): Two parallel high-pressure heating tanks are used for alternating operation; In the heating stage, high-pressure steam is sprayed from the tank bottom for material stirring, and the steam pressure is ≥1.5MPa.

[0012] By using the above technical scheme, the double-tank parallel alternating operation eliminates the waiting time for single-tank pressure maintenance, and the system capacity is improved. The tank bottom steam jet stirring (pressure ≥1.5MPa) eliminates material clumping, improves heat transfer efficiency, and avoids local overheating and carbonization.

[0013] Further, in steps (3) and (4): Primary pressure relief time ≤ 10 min, secondary pressure relief time ≥ 30 min; The steam flow rate in the pressure relief process is controlled by an electric regulating valve ≤ 0.5 m / s.

[0014] By adopting the above technical scheme, the primary pressure relief ≤ 10 min avoids fiber rebound caused by sudden pressure drop, and the secondary pressure relief ≥ 30 min ensures stable transition of the slurry and maintains the stability of the molecular weight of the degradation product. The steam flow rate controlled by the electric regulating valve ≤ 0.5 m / s prevents pipeline impact vibration and reduces equipment failure rate.

[0015] Further, in step (5): New air is supplemented to the low-pressure buffer tank during flashing, and the new air flow rate to the straw mass ratio is 10-15 m³ / kg; The average particle size of the straw fiber after flashing is ≤ 0.5 mm.

[0016] By adopting the above technical scheme, the new air supplement (10-15 m³ / kg) realizes rapid cooling (212℃→50℃), while avoiding excessive oxidation and retaining organic matter active ingredients ≥ 90%. The fiber particle size after flashing is ≤ 0.5 mm, which improves the solid-liquid separation speed and increases the release rate of organic fertilizer nutrients.

[0017] Further, in step (6): The solid-liquid separation adopts a horizontal screw centrifuge, and the separation factor is ≥ 3000 g; The liquid organic fertilizer preparation includes adding nitrogen, phosphorus, and potassium nutrient solution and a chelating agent, and the chelation reaction temperature is 60-80℃; The solid organic fertilizer granulation particle size is 2-4 mm.

[0018] By adopting the above technical scheme, high centrifugal force (≥ 3000 g) makes the solid content of the clear liquid ≤ 0.1%, and the solid moisture content ≤ 15%, which guarantees the stability of the fertilizer quality. The chelation reaction at 60-80℃ promotes the complexation of trace elements, and the nutrient utilization rate of the liquid fertilizer is significantly improved. The 2-4 mm granulation particle size reduces the breakage rate during transportation, and the particle compressive strength is ≥ 15 N.

[0019] Further, it also includes tail gas treatment: The flashed steam, odor, and cooling air discharged from the low-pressure buffer tank enter the tail gas condensing device and exchange heat with cooling water to generate condensed water; The non-condensable gas is discharged after being adsorbed by activated carbon; The condensed water is recycled for the straw soaking process in step (1).

[0020] By adopting the above technical scheme, the activated carbon adsorption removes pollutants such as H2S and NH3 in the odor, and the emission index reaches the first level standard of national standard GB14554-93. The recycling of condensed water reduces the consumption of fresh water in the soaking process, and the cost of straw treatment is reduced.

[0021] Further, the tail gas condensing device adopts a plate heat exchanger, the cooling water inlet temperature is ≤25℃, and the condensate water recovery rate is ≥90%.

[0022] By adopting the above technical scheme, the low-temperature cooling (≤25℃) of the plate heat exchanger improves the condensation efficiency, reduces the non-condensable gas treatment load, and the condensate water purity (COD≤50mg / L) meets the recycling requirements.

[0023] In the second aspect, the agricultural dry straw resource utilization processing system provided by the present application adopts the following technical scheme, comprising the following units connected in sequence: A pretreatment unit: The outlet of the pulverizer is connected to the inlet of the magnetic separator; The magnetic separator is provided with a metal impurity outlet connected to a metal recovery bin, and a straw outlet connected to the inlet of a screening machine; The screening machine is provided with an inorganic sand outlet connected to a landfill unit, and a straw outlet connected to the inlet of a soaking bin; The water inlet of the soaking bin is connected to a condensate water recycling pipeline, and the discharge outlet is connected to a feeding device; A hot-pressing treatment unit: The feeding inlets of two parallel high-pressure heating tanks are respectively connected to the feeding device; Each high-pressure heating tank is provided with a steam inlet and outlet at the top and a discharge gate valve and a steam injection port at the bottom; The outer wall of the tank body is wrapped with a heat-conducting oil coil; A pressure relief and flash evaporation unit: A primary pressure relief pipeline: the steam inlet and outlet of No. 1 tank is connected to the steam inlet and outlet of No. 2 tank through a steam pipeline, and a first control valve is arranged on the pipeline; A secondary pressure relief pipeline: the steam inlet and outlet of No. 1 tank is connected to the top inlet of a low-pressure buffer tank through a steam pipeline; The feeding inlet of the low-pressure buffer tank is connected to the discharge gate valve of No. 1 tank, and the top is provided with a tail gas outlet and a fresh air inlet; A post-treatment unit: The inlet of a solid-liquid separator is connected to the discharge outlet of the low-pressure buffer tank; The inlet of a liquid organic fertilizer production device is connected to the liquid outlet of the solid-liquid separator; The inlet of a solid organic fertilizer production device is connected to the solid outlet of the solid-liquid separator; A tail gas treatment unit: The gas inlet of a tail gas condensing device is connected to the tail gas outlet of the low-pressure buffer tank; The gas inlet of a tail gas purification device is connected to the gas outlet of the tail gas condensing device; The inlet of a condensate water collection tank is connected to the condensate water outlet of the tail gas condensing device, and the outlet is connected to the water inlet of the soaking bin through a water pump.

[0024] By adopting the technical scheme, the pulverizer, the magnetic separator and the screening machine are sequentially connected in series in the pretreatment unit, the metal impurities separated by the magnetic separator are directly transported to the metal recovery bin, and the inorganic sand separated by the screening machine is directly introduced into the landfill unit. The design improves the impurity removal rate while avoiding the risk of secondary pollution of the clean straw flow; The discharge port of the soaking bin is synchronously supplied to two parallel high-pressure heating tanks through the feeding equipment, completely solving the production capacity bottleneck problem caused by single-tank feeding, and significantly improving the system throughput. The independent primary and secondary pressure relief pipelines are precisely switched by a special control valve. In the primary pressure relief stage, the high-temperature and high-pressure steam of the first high-pressure heating tank is directly introduced into the second high-pressure heating tank for preheating, and the heat recovery rate is high. In the secondary pressure relief stage, the medium-pressure steam is stably transported to the top inlet of the low-pressure buffer tank to provide an initial pressure environment for subsequent flash evaporation, reducing steam waste; The low-pressure buffer tank simultaneously receives the secondary pressure relief steam and the straw material sprayed from the high-pressure heating tank, uses the steam residual pressure to maintain a micro-positive pressure environment in the tank, and promotes the full puffing and dissociation of the straw fibers, so that the fiber dissociation degree is high. The top of the tank body is integrated with a fresh air supplement inlet and a tail gas discharge outlet, realizing synchronous operation of flash evaporation cooling and tail gas collection, and significantly shortening the processing cycle; The tail gas treatment unit efficiently recovers the flash steam heat through the condenser. The low-temperature condensed water generated is collected in the collection pool and then directed back to the water inlet of the soaking bin by a recycled water pump, forming a process water closed-loop circulation system and reducing fresh water consumption. The low-pressure buffer tank is provided with a built-in cyclone separator, which effectively separates straw debris and gas flow, avoids tail gas pipeline blockage, and reduces annual maintenance frequency; Based on the modular physical connection architecture and the energy-matter double circulation mechanism as the core, the three technical barriers in the field of straw resource utilization are overcome: Energy consumption barrier: Through steam cascade reuse and flash evaporation residual pressure utilization, the high energy consumption of traditional processes is broken; Continuity barrier: Relying on double-tank parallel connection and buffer tank multifunctional integration, zero-interruption production is realized in the whole process; Pollution barrier: By tail gas purification and condensed water closed loop, near-zero emission of pollutants is achieved.

[0025] Preferably, the working pressure of the high-pressure heating tank is ≥2.5 MPa, and the material is 316L stainless steel; The low-pressure buffer tank is provided with a cyclone separator, and the tank body pressure resistance is ≥0.3 MPa.

[0026] By adopting the technical scheme, the corrosion resistance of 316L stainless steel is improved, and the design life of the high-pressure tank (≥2.5 MPa) is increased. The buffer tank has a pressure resistance of ≥0.3 MPa and is provided with a built-in cyclone separator, which avoids the blockage of the tail gas pipeline by straw debris and prolongs the maintenance cycle.

[0027] In summary, this invention employs the above technical solutions to develop a resource utilization and processing system and technology for agricultural dry yellow straw, which simultaneously possesses the following beneficial effects: (1) Resource utilization and processing system and processing technology for agricultural dry yellow straw: A resource utilization processing system with fast processing speed and small land area has been developed for agricultural dry yellow straw. (2) The flash expansion rapid treatment system has the advantages of fast processing speed, good decomposition effect, wide application of raw materials and small footprint compared with traditional microbial treatment processes; compared with traditional treatment processes, the processing time and footprint can be reduced. (3) The resource utilization and processing system and process of agricultural dry yellow straw have the characteristics of strong resistance to load impact and can adapt to the fluctuation of raw material feed quantity and quality; (4) Resource utilization and treatment system and process of agricultural dry yellow straw: the steam released from tank No. 1 is introduced into tank No. 2 for heating of the system itself, which can improve energy utilization and reduce system operating costs. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the resource utilization and treatment system for agricultural dry yellow straw in this application; Detailed Implementation

[0029] The following is in conjunction with the appendix Figure 1 This application will be described in further detail.

[0030] A resource utilization and processing system for dried yellow agricultural straw, referring to Figure 1 It includes the following units connected in sequence: Preprocessing unit: The outlet of the crusher is connected to the inlet of the magnetic separator; The magnetic separator has a metal debris outlet connected to a metal recovery bin, and a straw outlet connected to the inlet of a screening machine; The screening machine is equipped with an inorganic sand outlet connected to the landfill unit and a straw outlet connected to the inlet of the soaking chamber. The inlet of the soaking tank is connected to the condensate recycling pipeline, and the outlet is connected to the feeding equipment; Hot pressing unit: The inlets of the two parallel high-pressure heating tanks are respectively connected to the feeding equipment; Each high-pressure heating tank is equipped with a steam inlet and outlet at the top and a discharge gate valve and a steam injection port at the bottom; The outer wall of the tank is covered with heat transfer oil coils; Pressure relief and flash evaporation unit: Primary pressure relief pipeline: The steam inlet and outlet of tank 1 are connected to the steam inlet and outlet of tank 2 through a steam pipeline, and a first control valve is installed on the pipeline; Secondary pressure relief pipeline: the steam inlet and outlet of the No. 1 tank are connected to the top inlet of the low-pressure buffer tank through a steam pipeline; The feed inlet of the low-pressure buffer tank is connected to the discharge gate valve of the No. 1 tank, and the top is provided with a tail gas outlet and a fresh air inlet; Post-processing unit: The inlet of the solid-liquid separator is connected to the discharge port of the low-pressure buffer tank; The inlet of the liquid organic fertilizer production device is connected to the liquid outlet of the solid-liquid separator; The inlet of the solid organic fertilizer production device is connected to the solid outlet of the solid-liquid separator; Tail gas treatment unit: The gas inlet of the tail gas condensing device is connected to the tail gas outlet of the low-pressure buffer tank; The gas inlet of the tail gas purification device is connected to the gas outlet of the tail gas condensing device; The inlet of the condensate water collection pool is connected to the condensate water outlet of the tail gas condensing device, and the outlet is connected to the water inlet of the soaking bin through a water pump.

[0031] The implementation principle of the embodiment of the present application is that the pulverizer, the magnetic separator, the screening machine and the soaking bin in the pretreatment unit are sequentially connected in series, wherein the metal impurities separated by the magnetic separator are directly transported to the metal recovery bin, and the inorganic sand and soil separated by the screening machine is directly introduced into the landfill unit. This design improves the impurity removal rate while avoiding the risk of secondary pollution of the clean straw flow; the discharge port of the soaking bin is synchronously divided into two parallel high-pressure heating tanks through the feeding equipment, completely solving the production capacity bottleneck problem caused by single-tank feeding, and significantly improving the system throughput. The independent primary pressure relief pipeline and the secondary pressure relief pipeline are precisely switched through a special control valve; in the primary pressure relief stage, the high-temperature and high-pressure steam of the first high-pressure heating tank is directly introduced into the second high-pressure heating tank for preheating, and the heat recovery rate is high; in the secondary pressure relief stage, the medium-pressure steam is smoothly transported to the top inlet of the low-pressure buffer tank to provide an initial pressure environment for subsequent flash evaporation, thereby reducing steam waste; the low-pressure buffer tank simultaneously receives the secondary pressure relief steam and the straw material sprayed from the high-pressure heating tank, uses the steam residual pressure to maintain a micro-positive pressure environment in the tank, and promotes the full puffing and dissociation of the straw fibers, thereby achieving a high fiber dissociation degree; the top of the tank body is integrated with a fresh air supplement inlet and a tail gas discharge outlet, thereby realizing synchronous operation of flash evaporation cooling and tail gas collection, and significantly shortening the processing period; the tail gas treatment unit efficiently recovers the flash evaporation steam heat through the condenser, the low-temperature condensed water generated is introduced into the collection pool, and then is directly returned to the water inlet of the soaking bin through a recycled water pump, thereby forming a process water closed-loop circulation system and reducing fresh water consumption. The low-pressure buffer tank is provided with a built-in cyclone separator, which effectively separates straw debris and gas flow, avoids tail gas pipeline blockage, and reduces annual maintenance frequency.

[0032] The present application also discloses a resource utilization treatment process for dry straw.

[0033] Embodiment 1: Selecting wheat straw as the sample, and the raw material indexes are as follows Component Cellulose Hemicellulose Lignin Crude fat Crude protein Ash Moisture Mass ratio (%) 34.5 22.7 15.0 1.1 2.9 4.9 19.0 System device configuration: Preprocessing unit: Pulverizer: Model FSJ-1000, power 90kW, discharge particle size 20~30mm; Magnetic separator: permanent magnet roller type, magnetic field strength 3500 Gauss, metal impurity removal rate 99.2%; Screening machine: double-layer vibrating screen, upper layer aperture 10mm (remove large particle impurities), lower layer aperture 5mm (separate inorganic sand); Soaking bin: volume 20m³, equipped with liquid level sensor and stirrer, soaking time 2~4 hours.

[0034] Hot pressing treatment unit: High-pressure heating tank: two in parallel, design pressure 2.5MPa, material 316L stainless steel, volume 8m³; Heat conducting oil system: oil temperature 290±5℃, thermal efficiency ≥85%; Steam ejector: injection pressure 1.8MPa, stirring frequency 5 times / minute.

[0035] Pressure relief and flash evaporation unit: Low-pressure buffer tank: pressure resistance 0.35MPa, built-in cyclone separator, effective volume 12m³; Pressure relief pipeline: DN200 stainless steel pipe, equipped with electric regulating valve (flow control accuracy ±2%); Post-treatment unit: Solid-liquid separator: horizontal screw centrifuge LW520, separation factor 3200g; Liquid fertilizer production line: batching tank, chelation reactor (temperature 70±5℃), filling machine; Solid fertilizer production line: rotary dryer (inlet temperature 120℃), double-roll granulator (particle size 3±0.5mm).

[0036] Tail gas treatment unit: Condenser: plate heat exchanger, cooling water inlet temperature 20℃; Purification tower: activated carbon filling layer height 2.5m, empty tower flow rate 0.8m / s.

[0037] Specifically comprising the following steps: (1) Pretreatment process: dry yellow straw is first crushed to 20~30mm by a pulverizer, then the metal impurities in the dry yellow straw are separated by a magnetic separator, then the inorganic sand in the dry yellow straw is separated by a screening machine, and then the dry yellow straw is soaked in a soaking bin for 3 hours to increase the moisture content of the dry yellow straw to ≥55%. Then the dry yellow straw is sent to a high-pressure heating tank.

[0038] (2) Heating and pressure treatment process: After soaking, the wet and dry straw enters the high-pressure heating tank through the feeding equipment. Two high-pressure heating tanks (No. 1 tank and No. 2 tank) are parallel and simultaneously fed. After feeding to the set level, stop feeding, and start the hydraulic sealing device at the inlet to strictly seal the high-pressure heating tank inlet. Then No. 1 tank enters the heating stage, and the heat conduction oil system is started to generate 290℃ high-temperature heat conduction oil, which is input into the outer wall coil of No. 1 tank. The dry straw and moisture in the tank are heated to the boiling point, and the steam generated by gasification gradually increases the pressure in the tank. During the heating process of No. 1 tank, high-pressure steam is injected from the bottom of the tank, and the steam impact force is used to stir the materials in the tank. After heating for 1h, the temperature in the tank rises to 212℃, and the pressure is 2MPa. At this time, stop the heat conduction oil supply, terminate the heating, and enter the pressure maintaining stage, which lasts for 1h.

[0039] (3) First pressure relief treatment process: After the pressure maintaining stage is over, the first pressure relief stage is entered, and the steam exhaust valve at the top of No. 1 tank is slowly opened. The discharged steam is guided into No. 2 tank (No. 2 tank is at normal temperature and pressure at this time) through a pipeline. After 10min of pressure relief, the pressure of No. 1 and No. 2 tanks is balanced, and both stabilize at 1MPa, and the steam stops flowing.

[0040] (4) Second pressure relief treatment process: After the pressure of No. 1 and No. 2 tanks is balanced, the second pressure relief is started, and the steam valve is switched to direct the steam pressure relief from No. 2 tank to the low-pressure buffer tank. After 30min of pressure relief, the pressure of No. 1 high-pressure heating tank is reduced to 0.1MPa, and then the steam valve is closed, and the second pressure relief is completed.

[0041] (5) Discharge and flash evaporation treatment process: After the pressure relief of No. 1 high-pressure heating tank is completed, the discharge is started, and the outlet gate valve at the bottom of No. 1 high-pressure heating tank is slowly opened. The dry straw in the tank is sprayed out and falls into the low-pressure buffer tank under the action of residual pressure, and then flash evaporation occurs due to the sudden drop in pressure, and the water is gasified again to generate flash steam, which is sucked away by the fan, and at the same time, fresh air is supplied to cool the dry straw. After 30min of flash evaporation and cooling, the temperature of the dry straw is reduced from 212℃ to 50℃. After the above-mentioned (3), (4), and (5) stages of treatment, the dry straw changes from the original dense and solid fiber structure to a fine and uniform pulp-like material.

[0042] (6) Post-treatment process: The straw after the flash evaporation and expansion treatment is first treated by a solid-liquid separator to produce clear liquid containing dissolved organic matter and fibrous solid. Then the clear liquid enters the liquid fertilizer production system to produce liquid organic fertilizer through nutrient addition, heating, mixing, and chelation reaction (adding NPK nutrient solution and EDTA chelating agent, and reacting at 70℃ for 45min). The solid enters the solid fertilizer production system to produce solid organic fertilizer through drying, crushing, screening, nutrient addition, and extrusion granulation (drying at 120℃ to a moisture content of 10%~12%, and screening the granules to obtain 3mm particles).

[0043] (7) Tail gas treatment process: The flash steam, odor and cooling air generated by the low-pressure buffer tank are all introduced into the tail gas condensing treatment device, first exchanged with cooling circulating water in the tail gas condensing device to produce condensed water, and the non-condensed gas is introduced into the purification device for purification treatment and then discharged up to the standard. The condensed water is collected in the condensed water pool and returned to the soaking pool in the dry yellow straw pretreatment process as dry yellow straw soaking and humidifying water for reuse.

[0044] The process parameter control details are as follows: Technical effect verification: Fiber dissociation degree: Laser particle size analyzer detects the particle size distribution of the slurry, D50=0.48mm (traditional mechanical crushing D50=2.3mm); Heat energy recovery rate: The first pressure relief steam makes the temperature of No. 2 tank rise to 185℃, saving 63.5% of the secondary heating energy consumption; Water circulation rate: The reuse rate of condensed water is 96.3%, and the water consumption per ton of straw is reduced from 3.8 tons to 0.14 tons.

[0045] The solid and liquid product quality is as follows, reaching the standards of "Organic Fertilizer" (NY / T 525-2021) and "Humic Acid-containing Water-soluble Fertilizer" (NY 1106-2010).

[0046] Solid organic fertilizer product index Liquid organic fertilizer product index Example 2, the application also proposes an improved scheme, a resource utilization treatment process for agricultural dry yellow straw.

[0047] System equipment configuration Pretreatment unit: Pulverizer: Model FSJ-1000, power 90kW, discharge particle size 20~30mm; Binder spraying system: Double-fluid atomizing nozzle, pressure 0.3MPa, coverage area ≥95%; Magnetic separator: Permanent magnet roller type, magnetic field strength 3500 Gauss; Screening machine: Closed double-layer vibrating screen, with negative pressure dust extraction port inside; Soaking bin: Volume 20m³, equipped with liquid level sensor and stirrer. Step 1: Pretreatment Dust suppression by crushing: Dry yellow straw with water content ≤15% is put into the pulverizer and crushed to 25±5mm; simultaneously spray the binder: install the spraying system above the discharge belt at the outlet of the pulverizer to spray 0.8% xanthan gum solution (4L / ton of straw) at 0.4MPa pressure, so that a sticky film layer is formed on the surface of the straw.

[0048] Dust suppression by magnetic separation and screening: The adhesion treated straw is fed into a magnetic separator to separate iron impurities (recovery rate 99.1%); After magnetic separation, the straw is transported to a fully enclosed screening machine, and under negative pressure suction (air speed 1.3 m / s), the sand and soil are separated, and the dust is collected by a bag dust collector (emission concentration ≤8 mg / m³).

[0049] Soaking strengthening: The clean straw is transported to a soaking bin, and 50℃ condensed recycled water is injected to promote water penetration by dissolving the adhesive. After soaking for 3 hours, the moisture content is more than 55%.

[0050] Step 2: Hot pressing treatment The soaked straw is evenly distributed to No. 1 and No. 2 high-pressure heating tanks through a screw feeder; After the No. 1 tank is filled, it is sealed, and 290℃ conductive oil is introduced for heating, while 1.8MPa steam is sprayed from the bottom for stirring; After 60 minutes, the temperature in the tank reaches 212℃, and the pressure is 2.0MPa. Heating is stopped and the pressure is maintained for 60 minutes.

[0051] Step 3: Two-stage pressure relief First pressure relief: slowly open the valve at the top of the No. 1 tank, and 2.0MPa steam is introduced into the No. 2 tank (initial temperature 30℃). After 10 minutes, the pressure of the two tanks is balanced to 1.0MPa; Second pressure relief: switch the valve to direct the steam from the No. 1 tank into a low-pressure buffer tank, and the pressure is reduced to 0.1MPa within 30 minutes.

[0052] Step 4: Flash evaporation discharge Open the bottom gate valve of the No. 1 tank, and the straw slurry is sprayed into the low-pressure buffer tank, causing flash evaporation due to sudden pressure drop; New air is added (flow rate 12m³ / kg of straw) to cool for 30 minutes, and the slurry temperature is reduced to 50℃, with a fiber particle size of 0.48mm.

[0053] Step 5: Post-treatment The slurry is separated by a horizontal screw centrifuge: The solid content of the clear liquid is 0.08%, which is pumped into a liquid fertilizer production line; The solid moisture content is 14.5%, which is transported to a solid fertilizer production line; Liquid fertilizer preparation: add NPK nutrient solution and EDTA chelating agent, and react at 70℃ for 45 minutes; Solid fertilizer preparation: dry at 120℃ to a moisture content of 11%, and sieve to obtain 3mm particles.

[0054] Step 6: Exhaust gas treatment The flash steam (containing H2S 120mg / m³, NH3 85mg / m³) discharged from the low-pressure buffer tank is fed into a condenser; Condensate water (25℃, COD 42mg / L) is recovered to the soaking bin; Non-condensable gas is adsorbed by activated carbon, and H2S≤4mg / m³, NH3≤3mg / m³ (reaching the first level standard of GB14554-93).

[0055] By adopting the above scheme, the binder has synergistic gain on the subsequent process.

[0056] Fiber swelling reinforcement: xanthan gum molecules penetrate into the straw micropores, increasing the water diffusion rate by 35% during hot pressing; Organic matter retention rate: liquid fertilizer organic matter content reaches 291 g / L (control group 265 g / L), reducing nutrient loss due to dust reduction; Equipment maintenance cycle: the wear rate of the cutter of the crusher is reduced by 40% (no hard dust friction).

[0057] In this embodiment 2, the binder selection basis is Harmlessness: xanthan gum is a food-grade polysaccharide (CAS 11138-66-2), and the degradation product is CO2 / H2O, which has no ecological toxicity; Film forming property: a 0.8% solution can form a 20-50μm sticky film on the surface of the straw, effectively bonding dust below 10μm; Compatibility: completely dissolved in the subsequent soaking process, without affecting the hot pressing reaction.

[0058] Synergistic gain of the binder on the subsequent process: Fiber swelling reinforcement: xanthan gum molecules penetrate into the straw micropores, increasing the water diffusion rate by 35% during hot pressing; Organic matter retention rate: liquid fertilizer organic matter content reaches 291 g / L (control group 265 g / L), reducing nutrient loss due to dust reduction; Equipment maintenance cycle: the wear rate of the cutter of the crusher is reduced by 40% (no hard dust friction). Dust suppression effect data Dust suppression verification: The above data detection standards: Dust concentration GB / T 15432-1995 Xanthan gum residue NY / T 798-2015 The embodiments of the specific embodiment are the preferred embodiments of the present application, not limited to the protection scope of the present application, wherein the same parts are indicated by the same reference numerals. Therefore: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A dry yellow straw resource processing technology, characterized in that, The method comprises the following steps: (1) Pretreatment: dry straw is crushed to 20-30 mm, and after magnetic separation to separate metal impurities and screening to remove inorganic sand, the straw is soaked in water to make the water content ≥55%; (2) Heating and pressurizing: the soaked straw is fed into a high-pressure heating tank, and after sealing, 290℃ conductive oil is introduced to heat the tank to 212℃ and 2MPa, and the pressure is maintained for 1h; (3) First pressure relief: the steam in the high-pressure heating tank is introduced into another completed feeding but not heated tank until the pressure of the two tanks is balanced to 1MPa; (4) Second pressure relief: the steam in the tank completed with the first pressure relief in step (3) is introduced into a low-pressure buffer tank, and the pressure is relieved to 0.1MPa; (5) Flash treatment: the tank bottom outlet gate valve is opened, and the straw is sprayed into the low-pressure buffer tank to flash and cool to 50℃ to form a slurry; (6) Post-treatment: the slurry after flash treatment is subjected to solid-liquid separation, the clear liquid is made into liquid organic fertilizer, and the solid is dried and granulated to make solid organic fertilizer.

2. The dry straw resource treatment process according to claim 1, characterized in that, In step (1): The magnetic separation uses a permanent magnet roller magnetic separator, and the magnetic field strength is ≥3000 Gauss; The screening uses a vibrating screen, and the screen aperture is ≤5mm; The soaking time is ≥2h.

3. The dry straw resource treatment process according to claim 1, characterized in that, In step (2): Two parallel high-pressure heating tanks are used for alternate operation; In the heating stage, high-pressure steam is sprayed from the tank bottom to stir the material, and the steam pressure is ≥1.5MPa.

4. The dry straw resource treatment process according to claim 1, characterized in that, In steps (3) and (4): The first pressure relief time is ≤10min, and the second pressure relief time is ≥30min; The steam flow rate is controlled by an electric regulating valve during the pressure relief process, and the steam flow rate is ≤0.5m / s.

5. The dry straw resource treatment process according to claim 1, characterized in that, In step (5): Fresh air is supplemented to the low-pressure buffer tank during flash treatment, and the fresh air flow rate to straw mass ratio is 10-15m³ / kg; The average particle size of the straw fiber after flash treatment is ≤0.5mm.

6. The dry straw resource treatment process according to claim 1, characterized in that, In step (6): The solid-liquid separation uses a horizontal screw centrifuge, and the separation factor is ≥3000g; The liquid organic fertilizer preparation includes adding nitrogen, phosphorus and potassium nutrient liquid and chelating agent, and the chelating reaction temperature is 60-80℃; The solid organic fertilizer granulation particle size is 2-4mm.

7. The dry straw resource treatment process according to claim 1, characterized in that, It also includes tail gas treatment: The flash steam, odor and cooling air discharged from the low-pressure buffer tank enter a tail gas condensing device to exchange heat with cooling water to generate condensed water; The non-condensable gas is discharged after being adsorbed by activated carbon; The condensed water is recycled for the straw soaking process in step (1).

8. The dry straw resource treatment process according to claim 7, characterized in that, The tail gas condensing device uses a plate heat exchanger, the cooling water inlet temperature is ≤25℃, and the condensed water recovery rate is ≥90%.

9. A system for implementing the process for resource utilization of dry straw according to any one of claims 1 to 8, characterized in that, It comprises the following units connected in sequence: Pretreatment unit: The outlet of the crusher is connected to the inlet of the magnetic separator; The magnetic separator is provided with a metal impurity outlet connected to a metal recovery bin, and a straw outlet connected to the inlet of the screening machine; The screening machine is provided with an inorganic sand outlet connected to a landfill unit, and a straw outlet connected to the inlet of the soaking bin; The water inlet of the soaking bin is connected to a condensed water recycling pipeline, and the discharge outlet is connected to a feeding device; Hot-pressing treatment unit: The feeding inlets of two parallel high-pressure heating tanks are respectively connected to the feeding device; Each high-pressure heating tank is provided with a steam inlet and outlet at the top, a discharge gate valve and a steam injection port at the bottom; The tank body is wrapped with a conductive oil coil; Pressure relief and flash unit: First pressure relief pipeline: the steam inlet and outlet of No. 1 tank are connected to the steam inlet and outlet of No. 2 tank through a steam pipeline, and a first control valve is arranged on the pipeline; Secondary pressure relief pipeline: the steam inlet and outlet of the No. 1 tank are connected to the top inlet of the low-pressure buffer tank through a steam pipeline; The feed inlet of the low-pressure buffer tank is connected to the discharge gate valve of the No. 1 tank, and the top is provided with a tail gas outlet and a fresh air inlet; Post-processing unit: The inlet of the solid-liquid separator is connected to the discharge port of the low-pressure buffer tank; The inlet of the liquid organic fertilizer production device is connected to the liquid outlet of the solid-liquid separator; The inlet of the solid organic fertilizer production device is connected to the solid outlet of the solid-liquid separator; Tail gas treatment unit: The gas inlet of the tail gas condensing device is connected to the tail gas outlet of the low-pressure buffer tank; The gas inlet of the tail gas purification device is connected to the gas outlet of the tail gas condensing device; The inlet of the condensate water collection tank is connected to the condensate water outlet of the tail gas condensing device, and the outlet is connected to the water inlet of the soaking bin through a water pump.

10. The system for processing dry straw resources according to claim 9, characterized in that: The working pressure of the high-pressure heating tank is greater than or equal to 2.5 MPa, and the material is 316L stainless steel; A cyclone separator is arranged in the low-pressure buffer tank, and the tank body can withstand a pressure greater than or equal to 0.3 MPa.

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