Method and apparatus for corn steeping and breaking

Abstract

The present application relates to a method and device for corn soaking and crushing, aiming to improve the efficiency and product quality of corn deep processing, wherein a pressurized soaking reactor and a neutral rapid soaking process are used to replace the traditional sulfite countercurrent soaking, and a corn jetting system and a jetting crushing process of the present application are used to achieve efficient crushing of corn with lower energy consumption. The process can achieve 100% germ release and more than 80% fiber release, and does not produce waste water and waste gas, significantly improves the yield of starch, germ and protein, reduces the fiber yield, reduces the equipment investment and land occupation, and promotes the transformation of corn deep processing enterprises to low carbonization and greenization.

Description

Technical Field

[0001] This invention relates to the technical field of corn deep processing, and in particular to methods and equipment for soaking and crushing corn. Background Technology

[0002] Pre-processing corn using revolutionary new processes and equipment for soaking and crushing allows for higher yields of high-value products such as starch, dextrin, sugar, ethanol, amino acids, vitamins, organic acids, or biopharmaceuticals, while also producing higher yields of high-quality byproducts such as germ, protein, and fiber, without generating wastewater or SO2 odor. This has been a long-held aspiration in the field of corn deep processing technology. Traditional wet milling (Doherty process) uses a 0.20-0.25% by weight dilute sulfurous acid solution in 8 or 10 tanks at 48-53℃ for 36-65 hours of reverse soaking to achieve a corn moisture content of over 42% by weight. Then, a first-stage mill with a toothed blade is used to extract the germ via a cyclone separator, followed by a second-stage mill with a cyclone separator. The 0.7-0.9 tons of diluted corn syrup (note: corn syrup is a technical term in wet milling, referring to the residual syrup after soaking corn in sulfurous acid solution; the soaked corn is separated, and the syrup can be sold industrially or sprayed onto fibers as a product) generated during the soaking process needs to be evaporated and concentrated. The SO2 "odor" generated during this process has become a persistent problem threatening the survival of enterprises. Furthermore, the single-stage milling and double-stage milling methods not only consume a lot of energy and have high maintenance costs, but also result in a high germ breakage rate, high starch binding between germ and fiber, low germ yield, and high fiber yield. Scientists and engineers have made unremitting efforts to reduce or eliminate the use of sulfurous acid soaking, thereby decreasing the amount of starch bound to the germ and fiber, increasing the germ yield, and reducing the fiber yield.

[0003] CN102464723A discloses a composite wet corn soaking method for corn starch production. By adding cellulase to reduce the amount of sulfite, the soaking time is reduced from 48 hours to 24 hours, but the waste gas and wastewater problems are not fundamentally solved. The crushing process is still the two-crushing and two-rotating process of the Dor process, which cannot solve the problem of high starch content in the germ.

[0004] CN101372702A discloses a method for shortening the soaking time in corn starch production. This method uses 450-1350 IU / g corn protease and 15-80 IU / g corn cellulase, pressurized to 0.1-0.5 MPa, heated to 60℃, and soaked for 10-20 hours. Then the pressure is released and the reactor is opened. This method uses protease and cellulase instead of sulfite, solving the problems of wastewater and waste gas. However, the use of protease and cellulase increases costs, and the enzyme system converts high-value starch and protein into water-soluble sugars and proteins that are difficult to recover, further increasing the burden on corn steep liquor processing.

[0005] CN109651516 A describes a method that involves soaking Demea corn kernels in 1300-1600 ppm sulfurous acid for 30-36 hours, followed by crushing the corn using a two-crush, two-rotation process to extract the germ. Through refined management, the starch yield is increased by 0.7-1.0 percentage points, and the germ yield by 0.4 percentage points. However, this method still does not eliminate the generation of sulfurous acid in wastewater and waste gas. Furthermore, some starch and protein are converted into soluble proteins and water-soluble sugars, which enter the corn steep liquor, reducing the value of the corn product chain and increasing the burden of processing the corn steep liquor.

[0006] CN104672335A discloses a wet milling process in corn starch production. This method still uses sulfurous acid immersion. By precisely controlling the milling gap between the first and second milling processes, a germ release rate of over 98% is obtained. By increasing the cyclone feed pressure to 0.4-0.5 MPa, the germ yield is further increased to over 98%, while the yield of starch bound to germ and fiber is less than 15%. This method still does not overcome the environmental problems caused by sulfurous acid. Although through refined management, the yield of starch bound to germ and fiber is reduced to an advanced level in the same industry (Doherty process), it is still insufficient.

[0007] CN101607218A discloses a method for separating corn germ, endosperm, and fiber using steam explosion technology: 1. Soaking corn to a water content of 30%. 2. The steam explosion pressure is 1.0-1.5 MPa, and the time is 3-6 minutes. This method uses 1.0-1.5 MPa steam to act on the corn, causing the germ to denature and the endosperm to gelatinize. Specialized equipment needs to be developed for further processing of the denatured germ and gelatinized endosperm.

[0008] CN110200149A discloses a method for producing whole-plant corn silage, characterized by the following steps: S1, fresh whole-plant corn is cut into sections and placed in a steam explosion tank, and steam-exploded for 5 minutes at 0.7-1.5 MPa and 60-80℃ to obtain whole-plant corn slurry; S2, the whole-plant corn slurry is poured into a mixing tank, and an appropriate amount of sugar beet processing residue and stevia extract residue are added. After stirring evenly, 0.33-0.44% formic acid and 0.33-0.44% propionic acid are added by weight of the mixture. After stirring evenly, 1.4%-1.7% lactic acid bacteria silage fermentation agent is added. After mixing evenly, the mixture is transported by belt conveyor to an above-ground kiln for compaction and sealing. After fermentation at 25-35℃ for 40-50 days, the silage can be opened and used. Although the law uses the concept of low-temperature steam explosion, the application deals with whole-plant silage corn, which includes corn, corn stalks, corn leaves, and corn cobs. The purpose is to loosen the fiber structure of the corn stalks, leaves, and cobs, improve the fermentation efficiency of the fibers, and produce silage. This is a different industry and a different product system compared to the process of using corn kernels as raw materials to produce starch (sugar) as the main product through wet milling, while also producing germ (fat), protein, and fiber.

[0009] CN1212377C discloses an improved wet process for producing fuel ethanol. The process involves: purified corn being soaked in a soaking tank at 60-65°C for 4-12 hours; the soaking liquid being the centrifuged clarified liquid from the ethanol production process; the diluted corn slurry after soaking being returned to the ethanol production process to produce DDGS; the soaked corn undergoing two crushing processes and two-stage germ separation to obtain corn flour slurry, which is then saccharified, fermented, distilled, and dehydrated to obtain anhydrous ethanol; and the separated wet germ being washed and dried before being pressed for oil. This method uses acidic centrifuged clarified liquid to soak corn, replacing the traditional sulfur dioxide wet soaking process. The soaking effect is not disclosed; although the germ is separated, the germ yield is low; and high-value-added products such as protein are not separated, resulting in low overall efficiency.

[0010] To reduce investment and meet environmental requirements, the dry corn-to-ethanol process omits the corn soaking stage, directly dry-grinding the corn to control the particle size to 1-3mm, and then proceeding to liquefaction and fermentation. However, this method cannot separate high-value germ and protein, resulting in starch residue as high as 3-5%. It also consumes large amounts of enzymes and yeast, consumes a lot of electricity during dry corn grinding, causes severe equipment wear, and has low economic benefits.

[0011] CN103146768B discloses a method for preparing citric acid. The method is characterized by the following steps: (1) preparing an aqueous solution containing thermoresistant amylase, mixing the aqueous solution containing thermoresistant amylase with starch raw material powder to obtain a mixture, wherein the mixing conditions include a temperature of 70-85℃; (2) spraying the mixture obtained in step (1) once to 90-100℃ and maintaining it; then spraying the product obtained from the first spraying to 120-140℃ and maintaining it; (3) under enzymatic hydrolysis conditions, mixing the product obtained in step (2) with amylase and performing enzymatic hydrolysis to obtain a liquefied liquid containing oligosaccharides; (4) using the liquefied liquid to prepare a fermentation medium, and inoculating Aspergillus niger into the fermentation medium for fermentation under conditions that can generate citric acid, wherein in step (3), the amylase is a thermoresistant amylase, and the enzymatic hydrolysis conditions include an enzymatic hydrolysis temperature of 90-100℃, an enzymatic hydrolysis time of 12-60 min, and the amount of amylase used is 30-40% by weight of the amount of thermoresistant amylase used in the aqueous solution containing thermoresistant amylase prepared in step (1). This method cannot separate high-value germ and protein, and starch residue is as high as 3-5%. It consumes a lot of enzymes, consumes a lot of electricity for dry grinding of corn, causes serious equipment wear and tear, and has low economic benefits.

[0012] Therefore, the corn deep processing sector urgently needs disruptive new technologies and supporting equipment: eliminating the need for sulfurous acid soaking to address environmental concerns; optimizing and simplifying the process flow to reduce installed load, steam consumption, and water consumption, thus transitioning towards low-carbon and green production; increasing the yield of starch (sugar), germ, and protein to genuinely increase enterprise revenue; and promoting intensive production to reduce investment, land use, and labor, facilitating the upgrading and transformation of existing corn deep processing enterprises. Summary of the Invention

[0013] The purpose of this invention is to provide a method and apparatus for soaking and crushing corn. This method utilizes the pressurized soaking reactor and neutral rapid soaking process of this invention to replace the countercurrent sulfurous acid soaking in the traditional wet milling process. It also utilizes the corn spraying system and spray crushing process of this invention to replace the first and second grinding processes in the traditional wet milling process. This results in corn crushing with lower energy consumption, releasing the germ at a 100% release rate and the fiber at a release rate of over 80%, with the weight of starch bound to the released germ and fiber being less than 3.5% by weight, respectively. The soaking and crushing process of this invention does not produce corn steep liquor or discharge wastewater, making the yields of starch (sugar), protein, germ, and fiber closer to the theoretical values, thereby improving the economic benefits for enterprises.

[0014] The first aspect of the present invention relates to a method for soaking and crushing corn, comprising continuously or batch-wise adding corn raw material, water and optional chemical additives into a soaking reactor; soaking and reacting in the soaking reactor at a reaction temperature of 20-100°C and a gauge pressure of 0.1 MPa or higher for 0.5-15 hours to obtain corn with a water content greater than or equal to 35% by weight; maintaining the soaking reactor at the aforementioned gauge pressure or a pressure greater than the aforementioned gauge pressure; and then rapidly crushing the corn with water content continuously or batch-wise through a jet pipe to obtain a slurry.

[0015] In this invention, the moisture content of the corn raw material can be, for example, 9-15% by weight, such as 10-13% by weight.

[0016] In this invention, the moisture content of the water-containing corn is preferably greater than or equal to 38% by weight, more preferably greater than or equal to 40% by weight.

[0017] In one embodiment of the present invention, the corn raw material is first washed with water to remove impurities such as dust from the surface of the corn raw material, and optionally shriveled kernels and corn debris of different sizes, such as corn cobs, corn stalks, stones, etc., as well as possibly gloves, bricks, iron blocks, etc., are separated and removed. Preferably, the water is drained and the drained corn is added to the soaking reactor.

[0018] In one embodiment of the invention, the resulting slurry comprises germ, fiber, starch and endosperm.

[0019] In one embodiment of the present invention, the slurry contains a release germ with a release rate of 100%, a release fiber with a release rate of more than 80%, and a free starch with a release rate of 30-40%.

[0020] In one embodiment of the present invention, the soaking reactor is a batch soaking reactor or a tubular soaking reactor, such as a continuous tubular soaking reactor. For example, the soaking reactor includes one or more pressure vessels or reactors (batch or tower) such as a continuous cooker, tubular reactor, pressure screw conveyor, tower, steam ball, autoclave, decomposition pot, and vulcanizing tank, which can be used individually, in series, or in parallel.

[0021] In one embodiment of the present invention, the soaking reactor is a batch-type soaking reactor, wherein corn raw material is metered and added to the soaking reactor in batches by a screw feeder, and discharged in batches by the jet crushing system of the present invention. The soaking reactor is equipped with a distributor, an external heat exchanger (used to heat the corn and soaking water to the temperature required by the process) and / or an external hot water tank (which provides water for soaking the corn and simultaneously brings the material in the soaking reactor to the temperature required by the process). The soaking reactor is also connected to an external air source or water source (used to pressurize the soaking reactor to the pressure required by the process), and the temperature and pressure of the reactor are precisely controlled by a DCS system.

[0022] In one embodiment of the present invention, the soaking reactor is a continuous tubular reactor, wherein the reactor is metered by a screw feeder and continuously fed with corn raw materials via a rotary valve, and continuously discharged through an external jet crushing system of the present invention via another rotary valve. The soaking reactor is equipped with a distributor, an external heat exchanger (for heating the corn and soaking water to the required process temperature) and / or an external hot water tank (which provides water for soaking the corn while simultaneously bringing the material in the soaking reactor to the required process temperature). The soaking reactor is also externally connected to a gas source or a water source (for pressurizing the soaking reactor to the required process pressure), and the temperature and pressure of the reactor are precisely controlled by a DCS system.

[0023] The water is selected from, for example, drinking water, deionized water, or process circulating water. Preferably, the amount of water added is 30-300% by weight based on the dry weight of corn, more preferably 50-200% by weight, even more preferably 60-150% by weight, and even more preferably 65-120% by weight, for example 65% by weight, 70% by weight, 80% by weight, 90% by weight, and 100% by weight.

[0024] Preferably, in the soaking reactor, the soaking reaction temperature is 40-75°C, more preferably 45-70°C, for example 50°C, 60°C, and 65°C. Preferably, in the soaking reactor, the gauge pressure of the soaking reaction is 0.1-10 MPa, more preferably 0.5-8 MPa, and even more preferably 0.5-6 MPa, for example 1 MPa, 1.2 MPa, 1.5 MPa, 2 MPa, and 6 MPa.

[0025] Preferably, the soaking reaction time is 0.5-14 hours, more preferably 0.5-10 hours, for example 1, 2, 3, 4, 5, 6 and 8 hours.

[0026] After soaking is completed, the soaking reactor is maintained at or above the gauge pressure during the soaking reaction, for example, 0.1-15 MPa, more preferably 0.5-10 MPa, even more preferably 0.5-8 MPa, and even more preferably 1-6 MPa.

[0027] The linear velocity of the water-containing corn rapidly broken by the jet pipe should be sufficient to break the soaked corn to achieve the effect described in this invention. For example, the linear velocity is 50-90 m / s, preferably 55-80 m / s, and more preferably 55-72 m / s.

[0028] In one embodiment, a suitable gas or water, such as air, nitrogen, oxygen and / or water, that does not affect the reaction is introduced into the soaking reactor to increase the pressure of the reactor, while water vapor is not a suitable gas.

[0029] In one embodiment, in addition to corn and water, a chemical additive is added to the soaking reactor. The chemical additive can be an acid, alkali (containing Lewis acids or alkalis), or enzyme, such as citric acid, acetic acid, oxalic acid, sulfuric acid, hydrochloric acid, sodium sulfite, etc. Preferably, the amount of the chemical additive is 0-10% by weight based on the dry weight of the corn, more preferably 0-1.5% by weight, and even more preferably 0-1% by weight, for example, 0% (neutral soaking), 0.5% by weight, and 1% by weight.

[0030] For example, one embodiment of the corn processing method of the present invention includes the following steps:

[0031] (1) Wash the corn raw material with water to remove the dust on the surface of the corn, separate and remove the shriveled kernels and corn impurities of different sizes, and drain the water;

[0032] (2) Weighing step (1) The corn treated and 50-200% by weight of water based on the dry weight of the corn are continuously or in batches added to the soaking reactor. In the soaking reactor, the corn is soaked and reacted at 20-75°C and 0.1-10MPa for 0.5-9 hours. The corn is then continuously or intermittently crushed into the receiving tank by the jet crushing device of the present invention.

[0033] The slurry obtained by the present invention can be further processed by a hydrocyclone to obtain germ, and the underflow slurry of the hydrocyclone can be further processed to obtain fiber and crude starch slurry. Thus, the yield of germ and fiber can be obtained, and the amount of binding starch in germ and fiber can also be measured.

[0034] A second aspect of the invention relates to a system for soaking and crushing corn, particularly a system for implementing the method for soaking and crushing corn according to the present invention, comprising a corn feeder, a soaking reactor, a gas compressor or water pump, a venturi tube, a water tank, and a jet pipe, wherein the gas compressor or water pump, the corn feeder, and the water tank are connected to the soaking reactor, and the venturi tube and the jet pipe are connected in sequence from the outlet of the soaking reactor.

[0035] The corn raw material feeder mentioned above is, for example, a screw feeder, a belt scale, a lifting hopper, a rotary valve, etc.

[0036] The soaking reactor is, for example, a batch soaking reactor or a tubular soaking reactor, such as a continuous tubular soaking reactor. For example, the soaking reactor includes one or more pressure vessels or reactors (batch or tower) such as a continuous cooker, tubular reactor, pressure screw conveyor, tower, steam ball, autoclave, decomposition pot, and vulcanizing tank, which can be used individually, in series, or in parallel.

[0037] A gas compressor or water pump is used to increase the pressure in the soaking reactor and maintain it at a certain pressure level. Depending on the specific reaction conditions, either a gas compressor or a water pump can be used to increase the pressure.

[0038] The function of the venturi tube is to provide a channel for the water pump or gas compressor to deliver the medium into the injection pipe to increase the kinetic energy of the corn during jet crushing, and to draw the corn into the injection pipe through the pressure difference for jet crushing.

[0039] The water supply tank provides the water used for soaking in the soaking reactor. Preferably, the water supply tank is a hot water supply tank to provide the appropriate temperature required for soaking.

[0040] The injection tube is the channel through which the corn is ejected. Preferably, the injection tube is further narrowed in diameter compared to the Venturi tube to increase the linear velocity and kinetic energy of the corn, thereby increasing the corn breakage rate. Therefore, preferably, the diameter of the injection tube is smaller than that of the Venturi tube.

[0041] The soaking reactor of the present invention may be equipped with a bottom valve or a rotary valve to control the discharge of materials.

[0042] The slurry exiting the jet pipe can be injected into a receiving tank, such as an atmospheric pressure receiving tank.

[0043] In one embodiment of the present invention, the soaking and crushing system includes a screw feeder, a pressure soaking tank, a gas compressor (or a water pump), a venturi tube, a hot water tank, a jet pipe, and a receiving tank. Specifically, the screw feeder precisely delivers corn raw materials to the pressure soaking tank. A pump metered and delivered hot water from the hot water tank to the pressure soaking tank, and the temperature of the soaking tank is adjusted to the required process temperature. A gas compressor continuously supplies gas (or a pump continuously supplies water), and the pressure of the soaking tank is adjusted to the required process pressure. After soaking for a certain period (e.g., 0.5-10 hours) to control the corn moisture content to the required process level, the gas compressor (or water pump) adjusts the pressure of the pressure soaking tank to the pressure required for jet crushing. The bottom valve of the pressure soaking tank is opened, and the corn and soaking water, driven by the pressure of the pressure soaking tank, are accelerated through the venturi tube and then accelerated to a certain linear velocity through the jet pipe, and then sprayed into the atmospheric pressure receiving tank to obtain crushed corn and released germ and fiber. Jet crushing can be completed in one step or in multiple steps, provided that the corn crushing rate is 100%, the germ release rate is 100%, and the fiber release rate is above 80%, and the germ damage rate is less than 35%.

[0044] The methods for determining the content of relevant components in this application are as follows:

[0045] (1) Determination of moisture content of corn after soaking: Take the soaked corn and wipe the surface moisture with absorbent paper. Weigh 3-5g of the corn and place it in a METTLERTOLEDO halogen moisture analyzer to quickly determine the moisture content of the corn.

[0046] (2) Determination of germ binding starch

[0047] a. Pretreatment of germ and starch samples: Take about 20g of wet germ sample separated by a germ hydrocyclone and place it in a 3350m sieve; take another stainless steel round basin, put 2000ml of water in the basin, and sieve it in the water with a 3350m sieve to separate the germ, fiber and embryo body. Separate the embryo body connected to the germ and place them separately in petri dishes and dry them in a vacuum oven at 55℃.

[0048] b. Detection of sample: Weigh the dried germ and the peeled starch embryo separately using a 0.01 g balance to obtain W1 and W2 respectively.

[0049] c. Calculation: Germ starch binding rate = W2 / (W1+W2)*100%.

[0050] (3) Determination of fiber-binding starch

[0051] a. Pretreatment of fiber and starch samples: Take about 20g of the initially wet fiber separated by the fiber separation sieve and place it in a 20-mesh sieve; take another stainless steel round basin, put 2000ml of water in the basin, and sieve it in the water with a 20-mesh sieve to separate the fiber from other particles, and obtain the fiber containing the bound starch. Place the fiber on a petri dish and dry it in a vacuum oven at 55℃. Manually peel off the bound starch from the dried fiber to obtain pure fiber and bound starch respectively.

[0052] b. Detection of sample: Weigh the pure fiber and binding starch separately using a 0.01 g balance to obtain W1 and W2 respectively.

[0053] c. Calculation: Fiber-bound starch rate = W2 / (W1+W2)*100%.

[0054] (4) Determination of germ breakage rate

[0055] a. Germ pretreatment: Take the germ separated by the germ hydrocyclone, wash with clean water to remove the carried fibers, and centrifuge to dehydrate.

[0056] b. Testing: Weigh 10g of pretreated embryos and manually sort the whole embryos and damaged embryos.

[0057] c. Calculation: Germ breakage rate = weight of broken germ / 10 * 100%.

[0058] Advantages of this invention: The new method and equipment for soaking and crushing corn eliminate the need for sulfurous acid, thus avoiding the need for a sulfuric acid production system. This reduces equipment investment and land occupation, and solves the problem of SO2 pollution. The soaking time is reduced from 36-48 hours to 0.5-15 hours, saving significant investment in tank construction and land occupation. Based on a processing capacity of 500,000 tons of corn per year, the volume of the soaking tank is 10*450m³. 3 It dropped to 3*150m 3 The investment in soaking equipment is reduced by more than 80% (for example, in one embodiment, the equipment investment was reduced from RMB 46 million to RMB 8 million, saving about 82.6% of the construction investment). The soaking of the present invention does not use sulfurous acid, so no wastewater, odor, or corn steep liquor is generated. It eliminates the need for an acid production system, corn evaporation and concentration, and spraying corn steep liquor onto the fiber, and also saves steam for evaporating corn steep liquor. The jet crushing system of the present invention replaces the first and second mills of the Dorr process. The selection of germ can be completed with a single-stage cyclone and a single-stage washing, saving investment in cyclone and washing systems. The yield of pure germ obtained by the jet crushing system reaches more than about 7.5%, and the fiber yield reaches less than about 7.5%, while the binding starch on germ and fiber is reduced to less than 3.5% by weight. Attached Figure Description

[0059] Appendix Figure 1 A flowchart illustrating one embodiment of the immersion and jet crushing system of the present invention.

[0060] From the appendix Figure 1 As can be seen, the soaking and jet crushing system of the present invention includes a pressure soaking tank, a gas compressor, a venturi tube, a water tank, a jet pipe, and an atmospheric pressure receiving tank. The pressure soaking tank is equipped with a vent valve and a safety valve, and a screw feeder is used to feed the corn raw material. Specifically, the screw feeder precisely delivers the corn raw material to the pressure soaking tank. A pump metered and delivered hot water from the water tank to the pressure soaking tank, and the temperature of the soaking tank is adjusted to the required process temperature. A gas compressor continuously supplies gas, adjusting the pressure of the soaking tank to the required process pressure. After soaking for a certain period and controlling the corn moisture content to meet the process requirements, the gas compressor adjusts the pressure of the pressure soaking tank to the pressure required for jet crushing. The bottom valve of the pressure soaking tank is opened, and the corn and soaking water are accelerated through the venturi tube under the pressure of the pressure soaking tank, and then accelerated to a certain linear velocity through the jet pipe before being sprayed into the atmospheric pressure receiving tank, resulting in crushed corn and released germ and fiber. Jet crushing can be completed in one step or in multiple steps, provided that the corn crushing rate is 100%, the germ release rate is 100%, and the fiber release rate is above 80%, and the germ damage rate is less than 35%. Detailed Implementation

[0061] Example

[0062] The following will be combined with the appendix Figure 1 The technical solutions of the present invention will be further described below with reference to the embodiments. The embodiments of the present invention should not be construed as limiting the present invention.

[0063] Example 1

[0064] Step 1: Remove the shriveled kernels and large and small corn debris from the corn (Northeast corn, with a moisture content of 12.80% by weight), and drain the water;

[0065] Step 2: Weigh and feed 300 kg of corn processed in Step 1 into a 500-liter high-pressure soaking reactor using a screw feeder. Add 190 kg of hot water using a pump, raise the temperature to 60-63℃, and use a compressor to input air to pressurize to 1.5 MPa gauge pressure for soaking and reaction for 3-4 hours. The moisture content of the corn is measured to be 38.6% by weight.

[0066] Step 3: Use the compressor to maintain the pressure of the high-pressure soaking vessel at 1.5MPa, open the bottom valve of the vessel, accelerate the corn and soaking water to 57.7m / s through the Venturi tube and the jet tube, and spray it into the atmospheric pressure receiving tank to break the corn and obtain a slurry containing germ, fiber, free starch and endosperm fragments.

[0067] Step 4: The slurry is fed into a hydrocyclone and the embryo is separated by hydrocyclone separation under an inlet pressure of 0.35-0.75 MPa. The embryo yield is 8.6%.

[0068] Step 5: The underflow slurry from the hydrocyclone is further crushed by a needle mill, washed and separated by a pressure curved screen to obtain crude starch slurry and fiber, with a fiber yield of 6.7%; samples of germ and fiber are taken, and the binding starch content of germ and fiber is measured to be 0.9% by weight and 2.9% by weight, respectively.

[0069] Example 2

[0070] Step 1: Wash the corn (Northeast corn, with a moisture content of 12.8% by weight) with water to remove the dust on the surface of the corn, separate and remove the shriveled kernels and corn impurities of different sizes, and drain the water.

[0071] Step 2: Feed 100 kg / h of corn processed in Step 1 using a screw feeder. Simultaneously, use a metering pump to draw hot water from a hot water tank and pump 70 kg / h of water into the reactor. Continuously add the water into a 500-liter continuous tube reactor through a rotary valve. Maintain the temperature at 60-63℃. Use a compressor to input air and pressurize to approximately 1.5 MPa gauge pressure. Control the pressure and soaking reaction time to approximately 4 hours. Sampling analysis shows that the corn moisture content is 40.2% by weight.

[0072] Step 3: The corn and soaking water are continuously accelerated to 56.3 m / s through a rotary valve, venturi tube, and jet pipe, and continuously sprayed into an atmospheric pressure receiving tank and broken down to obtain a slurry containing germ, fiber, free starch and endosperm fragments.

[0073] Step 4: The slurry is fed into a hydrocyclone and the embryo is separated by hydrocyclone separation under an inlet pressure of 0.35-0.75 MPa. The yield of embryo is 8.3%.

[0074] Step 5: The underflow slurry from the hydrocyclone is further crushed by a needle mill, washed and separated by a pressure curved screen to obtain crude starch slurry and fiber, with a fiber yield of 7.2%; samples of germ and fiber are taken, and the binding starch content of germ and fiber is measured to be 0.8% by weight and 3.2% by weight, respectively.

[0075] Example 3

[0076] Step 1: Wash the corn (Northeast corn, with a moisture content of 12.8% by weight) with water to remove the dust on the surface of the corn, separate and remove the shriveled kernels and corn impurities of different sizes, and drain the water.

[0077] Step 2: Weigh and feed 300 kg of corn processed in Step 1 into a 500-liter high-pressure soaking reactor using a screw feeder. At the same time, add 190 kg of hot water using a pump, raise the temperature to 60-63℃, and continuously supply water and pressurize to 1.0 MPa gauge pressure. Soak and react for 3.5 hours until the corn moisture content reaches 38.2% by weight.

[0078] Step 3: Use a pump to supply water to maintain the pressure of the high-pressure soaking vessel at 1.0 MPa. Open the bottom valve of the vessel and accelerate the corn and soaking water to about 47.3 m / s through the Venturi tube and the jet tube. Spray the corn into the atmospheric pressure receiving tank to break it up and obtain a slurry containing germ, fiber, free starch and endosperm fragments.

[0079] Step 4: The slurry is fed into a hydrocyclone and the embryo is separated by hydrocyclone separation under an inlet pressure of 0.55-0.75 MPa. The embryo yield is 7.9%.

[0080] Step 5: The underflow slurry from the hydrocyclone is further crushed by a needle mill, washed and separated by a pressure curved screen to obtain crude starch slurry and fiber, with a fiber yield of 7.5%; samples of germ and fiber are taken, and the binding starch content of germ and fiber is measured to be 2.7% by weight and 3.4% by weight, respectively.

[0081] Example 4

[0082] Step 1: Wash the corn (Northeast corn, with a moisture content of 13.45% by weight) with water to remove the dust on the surface of the corn, separate and remove the shriveled kernels and corn debris of different sizes, and drain the water.

[0083] Step 2: 100 kg / h of corn processed in Step 1 is continuously fed into a 500-liter continuous tube reactor via a screw feeder. Water is drawn from a hot water tank using a metering pump, and 70 kg / h of water is simultaneously and continuously pumped into the reactor. The temperature is maintained at 60-63℃, and water is supplied by a pump to maintain a pressure of 2.5 MPa gauge pressure. The pressure soaking reaction time is controlled to be about 4 hours. The moisture content of the corn is 40.9% by weight according to the sampling analysis.

[0084] Step 3: The corn and soaking water are continuously accelerated to about 69.8 m / s through a rotary valve, venturi tube, and jet pipe, and continuously sprayed into an atmospheric pressure receiving tank and broken down to obtain a slurry containing germ, fiber, free starch and endosperm fragments.

[0085] Step 4: The slurry is fed into a hydrocyclone and the embryo is separated by hydrocyclone separation under an inlet pressure of 0.35-0.55 MPa. The yield of embryo is 9.7%.

[0086] Step 5: The underflow slurry from the hydrocyclone is further crushed by a needle mill, washed and separated by a pressure curved screen to obtain crude starch slurry and fiber, with a fiber yield of 6.3%; samples of germ and fiber are taken, and the binding starch content of germ and fiber is measured to be 0.2% by weight and 2.1% by weight, respectively.

[0087] Example 5

[0088] Step 1: Wash the corn (Northeast corn, with a moisture content of 10.44% by weight) with water to remove the dust on the surface of the corn, separate and remove the shriveled kernels and corn debris of different sizes, and drain the water.

[0089] Step 2: Weigh and feed 300 kg of corn processed in Step 1 into a 500-liter high-pressure soaking reactor using a screw feeder. Add 190 kg of hot water using a pump, raise the temperature to 60-63℃, and pressurize the water to 2.5 MPa gauge pressure to soak and react for 4 hours until the moisture content reaches 41.9% by weight.

[0090] Step 3: Use a pump to supply water to maintain the pressure of the high-pressure soaking vessel at 2.5 MPa. Open the bottom valve of the vessel and accelerate the corn and soaking water to about 70.1 m / s through the Venturi tube and the jet tube. Spray the corn into the atmospheric pressure receiving tank to break it up and obtain a slurry containing germ, fiber, free starch and endosperm fragments.

[0091] Step 4: The slurry is fed into a hydrocyclone and the embryo is separated by hydrocyclone separation under an inlet pressure of 0.35-0.55 MPa. The embryo yield is 9.9%.

[0092] Step 5: The underflow slurry from the hydrocyclone is further crushed by a needle mill, washed and separated by a pressure curved screen to obtain crude starch slurry and fiber, with a fiber yield of 6.1%; samples of germ and fiber are taken, and the binding starch content of germ and fiber is measured to be 0.1% by weight and 1.3% by weight, respectively.

[0093] Comparative Example 1

[0094] Step 1: Wash the corn (Northeast corn, with a moisture content of 13.8% by weight) with water to remove dust from the surface, separate and remove shriveled kernels and other corn debris, and drain the water.

[0095] Step 2: Weigh 300.0 kg of corn treated in Step 1 and add it to the corn soaking tank. Add 220 kg of water to cover the corn surface by 100-150 mm. Heat to 53℃ and continuously supply sulfurous acid under normal pressure to maintain a sulfurous acid concentration of 2000-3000 ppm. Soak continuously for 50 hours and take samples for analysis. The moisture content of the corn is 42.3% by weight.

[0096] Step 3: The corn in Step 2 is crushed using a toothed mill and the germ is selected by cyclone separation; the underflow is crushed using a second toothed mill and the germ is selected a second time by cyclone separation, with a germ yield of 7.1%.

[0097] Step 4: The underflow slurry of the germ from the secondary selection is further crushed by a needle mill, washed and separated by a pressure curved screen to obtain crude starch slurry and fiber, with a fiber yield of 9.7%; samples of germ and fiber were taken, and the binding starch content of germ and fiber was measured to be 13.7% by weight and 18.9% by weight, respectively.

[0098] Conclusion: Through the comparison of the above examples and Comparative Example 1, it is shown that the pressurized soaking and jet crushing process and equipment provided by the present invention can crush corn germ and fiber products with lower amount of starch adhering to the germ and fiber compared with the traditional wet process, which means that the starch (or sugar) yield is higher; at the same time, the high-value germ yield is higher and the low-value fiber yield is lower, resulting in better economic benefits. Moreover, the present invention does not have the problem of SO2 pollution.

[0099] Any implementation described herein may be freely combined with one or more other implementations described herein. Any technical solutions or technical ideas formed thereby shall be regarded as part of the original disclosure or original record of this invention, and shall not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider such combination to be obviously unreasonable.

Claims

1. A method for soaking and crushing corn, comprising continuously or batch-wise adding corn raw material, water, and optional chemical additives into a soaking reactor; soaking the corn in the soaking reactor for 0.5-15 hours at a reaction temperature of 20-100°C and a gauge pressure of 0.1 MPa or higher to obtain corn with a water content greater than or equal to 35% by weight; maintaining the soaking reactor at the gauge pressure or higher; and then rapidly crushing the corn with water content continuously or batch-wise through a jet pipe to obtain a slurry.

2. The method according to claim 1, wherein, The moisture content of the corn raw material may be, for example, 9-15% by weight, such as 10-13% by weight; and / or The moisture content of the corn is greater than or equal to 38% by weight, preferably greater than or equal to 40% by weight; and / or The resulting slurry contains germ, fiber, starch, and endosperm; and / or The slurry contains a 100% release germ, a release fiber with a release rate of over 80%, and a free starch with a release rate of 30-40%; and / or The water is selected from drinking water, deionized water, or process circulating water, etc. Preferably, the amount of water added is 30-300% by weight based on the dry weight of corn, more preferably 50-200% by weight, even more preferably 60-150% by weight, and even more preferably 65-120% by weight.

3. The method according to claim 1 or 2, wherein, The soaking reactor is a batch soaking reactor or a tubular soaking reactor, such as a continuous tubular soaking reactor; and / or The soaking reactor is a batch-type soaking reactor, in which corn raw materials are metered and added to the soaking reactor in batches via a screw feeder, and discharged in batches via the jet crushing system of this invention. The soaking reactor is equipped with a distributor, an external heat exchanger (used to heat the corn and soaking water to the required process temperature) and / or an external hot water tank (which provides water for soaking the corn while simultaneously raising the material in the soaking reactor to the required process temperature). The soaking reactor is also connected to an external air or water source (used to pressurize the soaking reactor to the required process pressure), and the temperature and pressure of the reactor are precisely controlled by a DCS system; and / or The soaking reactor is a continuous tubular reactor, wherein the reactor is metered by a screw feeder and continuously fed with corn raw materials via a rotary valve, and continuously discharged through an external jet crushing system of the present invention via another rotary valve. The soaking reactor is equipped with a distributor, an external heat exchanger (for heating the corn and soaking water to the required process temperature) and / or an external hot water tank (which provides water for soaking the corn while simultaneously bringing the material in the soaking reactor to the required process temperature). The soaking reactor is also connected to an external air source or water source (for pressurizing the soaking reactor to the required process pressure), and the temperature and pressure of the reactor are precisely controlled by a DCS system.

4. The method according to any one of claims 1-3, wherein, In the soaking reactor, the soaking reaction temperature is 40-75°C, more preferably 45-70°C; and / or In the soaking reactor, the gauge pressure of the soaking reaction is 0.1-10 MPa, more preferably 0.5-8 MPa, and even more preferably 0.5-6 MPa; and / or The soaking reaction time is 0.5-14 hours, more preferably 0.5-10 hours; and / or After soaking, the soaking reactor is maintained at or above the gauge pressure during the soaking reaction, wherein the pressure is 0.1-15 MPa, preferably 0.5-10 MPa, more preferably 0.5-8 MPa, and even more preferably 1-6 MPa; and / or The linear velocity of rapidly crushing the water-containing corn through the jet pipe is 50-90 m / s, preferably 55-80 m / s, and more preferably 55-72 m / s.

5. The method according to any one of claims 1-4, wherein, A suitable gas or water, such as air, nitrogen, oxygen, and / or water, that does not affect the reaction is introduced into the soaking reactor to increase the pressure of the reactor; and / or In addition to corn and water, chemical additives are added to the soaking reactor. These chemical additives can be acids, bases (containing Lewis acids or bases) or enzymes, such as citric acid, acetic acid, oxalic acid, sulfuric acid, hydrochloric acid, sodium sulfite, etc. Preferably, the amount of the chemical additive is 0-10% by weight based on the dry weight of the corn, more preferably 0-1.5% by weight, and even more preferably 0-1% by weight.

6. The method according to any one of claims 1-5, wherein, The slurry is further processed by a hydrocyclone to obtain germ, and the underflow slurry from the hydrocyclone is further processed to obtain fiber and crude starch slurry.

7. A system for soaking and crushing corn, particularly for carrying out the method according to any one of claims 1-6, comprising a corn feeder, a soaking reactor, a gas compressor or water pump, a venturi tube, a water tank, and a jet pipe, wherein the gas compressor or water pump, the corn feeder, and the water tank are connected to the soaking reactor, and the venturi tube and the jet pipe are connected in sequence from the outlet of the soaking reactor.

8. The system according to claim 7, wherein, The corn feeder mentioned above includes a screw feeder, belt scale, lifting hopper, rotary valve, etc.; and / or The soaking reactor is a batch soaking reactor or a tubular soaking reactor, such as a continuous tubular soaking reactor. For example, the soaking reactor includes one or more pressure vessels or reactors (batch or tower) such as a continuous cooker, tubular reactor, pressure screw conveyor, tower, steam ball, autoclave, decomposition pot, and vulcanizing tank. It can be used alone, or in series or in parallel.

9. The system according to claim 8, wherein, The water supply tank is a hot water supply tank; and / or The diameter of the injection tube is smaller than that of the venturi tube; and / or The soaking reactor is equipped with a bottom valve or a rotary valve; and / or The slurry coming out of the jet pipe can be injected into the receiving tank.

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