A rice variable temperature drying method and system suitable for a two-way ventilation dryer

Abstract

This invention relates to a method and system for variable-temperature drying of rice using a two-way ventilation dryer. The method comprises the following steps: (1) establishing multiple regression models with stage drying parameters as influencing factors and stage target drying rate and stage target rice quality as evaluation indicators; (2) inputting the initial drying parameters of different stages into the multiple regression models obtained in step (1) to obtain the real-time drying rate and real-time rice quality; (3) optimizing the rate and quality obtained in step (2) using multiple objective variables to obtain the optimized drying rate and rice quality; (4) comprehensively evaluating the multiple sets of optimized drying rates and rice quality obtained in step (3) to obtain the corresponding specific drying parameters, which are then input into the control cabinet for drying operations. This method solves the problem of incoordination between drying efficiency and quality, and can effectively control the drying rate and the processing quality, appearance quality, edible quality, and nutritional quality of rice.

Description

Technical Field

[0001] This invention pertains to methods for drying grains, and in particular relates to a method and system for drying rice at variable temperature, suitable for a two-way ventilation dryer. Background Technology

[0002] Drying is a crucial step in the post-harvest processing of rice. The issues of drying efficiency and changes in rice quality have always been key focuses of drying process research. Currently, mechanical drying dominates rice drying in my country, primarily employing constant-temperature drying. However, this still presents problems such as unstable rice quality and a mismatch between drying efficiency and quality. While a published document (CN112395753 A) entitled "Drying Method, Apparatus, Equipment, and Storage Medium for Targeted Regulation of Rice Quality" discloses a method for targeted regulation of rice quality, it still relies on constant-temperature drying and does not address the issue of the mismatch between drying efficiency and quality. Existing variable-temperature drying can improve drying efficiency and rice quality, achieving a balance between the two. However, the variable-temperature drying process is complex and unpredictable, with inherent uncertainties and difficulties in determining the temperature transition point. Furthermore, variable-temperature drying only considers changes in a single indicator after drying, such as the rate of cracking, drying rate, and cooked rice taste value. It cannot precisely control changes in rice quality and drying rate at a specific stage of the variable-temperature drying process. In summary, the variable temperature drying process should comprehensively consider both drying rate and rice quality to guide the optimization of drying process parameters. Summary of the Invention

[0003] The present invention aims to overcome the shortcomings of the prior art and provide a method and system for drying rice at variable temperature suitable for a two-way ventilation dryer.

[0004] The present invention provides a method for temperature-controlled drying of rice suitable for a two-way ventilation dryer, comprising the following steps:

[0005] (1) Model establishment: Multiple regression models were established with the stage drying parameters of the rice to be dried as influencing factors, the stage target drying rate and the stage target rice quality as evaluation indicators;

[0006] The drying parameters include: variable temperature drying gradient, hot air apparent velocity, grain discharge roller speed, tempering ratio, and initial moisture content of rice, and the variable temperature drying gradient, hot air apparent velocity, grain discharge roller speed, and initial moisture content of rice are all range values.

[0007] The tempering ratio is determined based on the selected dryer model;

[0008] The variable temperature drying gradient is determined by combining the glass transition theory with a two-way ventilation dryer for the rice to be dried, based on the glass transition curve.

[0009] (2) Model application: Input the initial drying parameters of different stages into multiple regression models obtained in step (1) to obtain the real-time drying rate and real-time rice quality of different drying stages; the initial drying parameters are determined according to the type of dryer, the moisture content of rice harvest and the variable temperature drying process.

[0010] (3) Parameter optimization: Based on the real-time drying rate and real-time rice quality obtained in step (2) at different stages, the drying process parameters are optimized using multiple objective variables to obtain multiple sets of optimized drying rates and rice quality;

[0011] (4) Drying and comprehensive evaluation: The principal component analysis method and membership function method are used to comprehensively evaluate the multiple optimized drying rates and rice quality obtained in step (3), and the corresponding optimal specific drying parameters for different stages are obtained. Then, the optimal specific drying parameters for different stages are input into the control cabinet for drying operation.

[0012] As a further improvement of the present invention, in step (1), after determining the slow tempering ratio of the rice variety and the dryer model used in the experiment, a four-factor, five-level quadratic orthogonal rotational combination experimental scheme is established based on the drying parameters of each stage. The four factors are variable temperature drying gradient, hot air performance wind speed, grain discharge roller speed and initial moisture content of rice. The rice quality evaluation indicators include: crack growth rate, protein content, cooked rice taste value and polished rice appearance color.

[0013] As a further improvement of the present invention, the glass transition curve in step (1) is achieved by the following method: multiple random samples of the same batch of rice are taken to obtain 7 groups of different moisture contents. The rice with different moisture contents is crushed into powder, and the glass transition temperature of the 7 groups of rice is determined by differential scanning calorimetry. The glass transition temperature of the 7 groups of rice and the corresponding moisture contents are fitted to form a glass transition curve.

[0014] As a further improvement of the present invention, the multi-objective variables mentioned in step (3) refer to drying rate, crack growth rate, protein content, rice taste value, and polished rice appearance color. Based on the final drying rate and the final rice quality requirements, the weight of each indicator is assigned, and the specific drying process parameters at different stages are optimized by multi-objective variables.

[0015] As a further improvement of the present invention, step (4) involves using principal component analysis and membership function method to perform factor analysis on the drying rate, crack growth rate, protein content, rice taste value, and polished rice appearance color of rice after optimizing the multi-objective variables. Based on the criterion that the cumulative contribution rate of principal component factors is greater than 80%, each individual evaluation index is standardized. The standardized data and the index coefficients of each principal component comprehensive index obtained through principal component analysis are multiplied accordingly to calculate the comprehensive index score value of different drying processes and the weight of each principal component comprehensive index. Finally, the comprehensive score value of different drying processes is obtained.

[0016] This invention discloses a variable-temperature drying system for rice suitable for a two-way ventilation dryer, comprising the dryer, which is divided into a grain storage section, one or more drying sections, and a grain discharge section from top to bottom. The grain storage section has a grain inlet at the top, and the grain discharge section has a grain outlet at the bottom. The system is characterized in that each drying section consists of an inlet angle tube and an outlet angle tube, arranged in a crisscross pattern. A variable-temperature regulating device is connected to the inlet angle tube, and three or more temperature sensors are arranged side-by-side below the outlet angle tube to detect the rice temperature. Below the temperature sensors, an equal number of wind speed sensors are arranged to detect the wind speed at the grain level. A moisture meter is located on the side of the grain discharge section to detect the moisture content of the rice. The temperature sensors, wind speed sensors, and moisture meter are all connected to a control cabinet. The control cabinet contains a model building and selection module, an index prediction module, a process parameter optimization module, a comprehensive evaluation module, a control module, and a display module, used to guide the optimization of drying process parameters.

[0017] As a further improvement of the present invention, when a continuous dryer is selected, a tempering section is provided below the drying section. A temperature sensor and a wind speed sensor are provided on the tempering section, and a moisture detector is provided at the end of each tempering section and on the side of the grain discharge section.

[0018] As a further improvement of the present invention, when a circulating dryer is selected, the drying sections are connected in sequence, and the grain storage section above the first drying section is the tempering section. Temperature sensors and wind speed sensors are installed on the grain storage section, and a moisture detector is installed on the side of the grain discharge section.

[0019] As a further improvement of the present invention, the outer end of the air inlet angle tube is connected to a temperature regulation device to allow dry air to enter, and the inner end is sealed. The air passes through the grain layer and flows out from the air outlet angle tube of the lower drying section or the upper drying section. The outer end of the air outlet angle tube is open and placed outside the machine body to allow air to flow out, and the inner end is sealed.

[0020] As a further improvement of the present invention, the installation directions of the air inlet angle pipe and the air outlet angle pipe of the adjacent drying section are opposite.

[0021] This invention discloses a method and system for variable-temperature drying of rice suitable for a two-way ventilation dryer. It establishes multiple regression models using the stage drying parameters of the rice to be dried as influencing factors and the stage target drying rate and stage target rice quality as evaluation indicators. Based on these regression models, it optimizes the multi-objective variable drying process parameters. Combined with principal component analysis and membership function method, it comprehensively evaluates the optimized drying rate and rice quality, solving the problem of inconsistency between drying efficiency and quality. This effectively controls the drying rate and the processing quality, appearance quality, edible quality, and nutritional quality of the rice. Attached Figure Description

[0022] Figure 1 This is a flowchart of a rice temperature-controlled drying method applicable to a two-way ventilation dryer according to Embodiment 1 of the present invention;

[0023] Figure 2 This is a flowchart of the variable temperature drying gradient determination method of the present invention;

[0024] Figure 3 This is a flowchart of the bidirectional variable temperature drying method using a continuous bidirectional ventilation dryer in Example 2;

[0025] Figure 4 This is a flowchart of the bidirectional variable temperature drying method using a circulating bidirectional ventilation dryer in Example 3;

[0026] Figure 5 This is the schematic diagram of the PLC controller in Example 4;

[0027] Figure 6 This is a schematic diagram of the continuous bidirectional ventilation dryer used in Embodiment 2 of the present invention;

[0028] Figure 7 This is a schematic diagram of the circulating bidirectional ventilation dryer used in Embodiment 3 of the present invention; Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0030] Example 1

[0031] Figure 1 This is a flowchart of a variable-temperature drying method for rice using a two-way ventilation dryer, provided in Embodiment 1 of the present invention. This embodiment can be used to control the drying rate and rice quality during the variable-temperature drying process. The method can be executed by a variable-temperature drying system, which can be implemented by hardware and software. The steps of the method are as follows:

[0032] Step 100: Using Design Expert software, establish multiple regression models with the stage drying parameters of the rice to be dried as influencing factors and the stage target drying rate and stage target rice quality as evaluation indicators;

[0033] The stage drying parameters are the drying process parameters for each drying stage in the rice drying process. Specific drying parameters include: variable temperature drying gradient, hot air velocity, discharge roller speed, tempering ratio, and initial moisture content of the rice. Evaluation indicators are the measurements of drying rate and rice quality during the rice drying process. Rice quality includes crack growth rate, protein content, cooked rice taste value, and polished rice appearance color. After the drying experiment, regression equations were established for different drying parameters against different evaluation indicators; the tempering ratio is determined based on the selected dryer model.

[0034] Step 110: Input the initial drying parameters of different stages into the multiple regression models obtained in step 100 to obtain the real-time drying rate and real-time rice quality of different drying stages; the initial drying parameters are determined according to the type of dryer, the moisture content of rice harvest, and the variable temperature drying process.

[0035] Step 120: Based on the real-time drying rate and real-time rice quality of different drying sections obtained in Step 110, optimize the drying process parameters using multi-objective variables to obtain multiple sets of optimized drying rates and rice quality.

[0036] Step 130: Use principal component analysis and membership function method to comprehensively evaluate the multiple optimized drying rates and rice quality obtained in step 120, determine the optimal specific drying parameters for each drying stage, and then input the optimal specific drying parameters for different stages into the control cabinet as the drying operation parameters for the same batch of rice.

[0037] Based on the drying rate and rice quality requirements, the weight of each indicator is assigned, and the drying process parameters are optimized using multi-objective variables to obtain multiple sets of optimized drying parameter combinations. Multi-objective variable optimization represents the optimization of drying process parameters for five individual evaluation indicators (drying rate, crack growth rate, protein content, rice taste value, and polished rice appearance color).

[0038] Based on the experimental design and optimized process parameter combinations, principal component analysis and membership function method were used to perform factor analysis on the drying rate, crack growth rate, protein content, cooked rice taste value, and polished rice appearance color of the multi-objective variables after optimization. Based on the criterion that the cumulative contribution rate of principal component factors is greater than 80%, each individual evaluation index was standardized. The standardized data and the index coefficients of each principal component comprehensive index obtained through principal component analysis were multiplied accordingly to calculate the comprehensive index score of different drying processes and the weight of each principal component comprehensive index. According to formula (1), the membership function value μ(x) of the principal component comprehensive index of different drying processes was calculated. i Then, the weights of the principal component comprehensive indices are calculated according to formula (2), and the weights of the principal component comprehensive indices are obtained. Finally, the comprehensive scores of different drying processes are obtained using formula (3).

[0039]

[0040] In the formula: i —1, 2, 3, ..., n;

[0041] μ(x) i —Membership function value of the evaluation index;

[0042] w i —Extracted i The weights of each principal component;

[0043] λ i —Extracted i The contribution rate corresponding to each principal component;

[0044] F—Overall score;

[0045] F i —The score of the i-th principal component.

[0046] like Figure 2 This is a flowchart illustrating the determination of the variable-temperature drying gradient in this application. The variable-temperature drying gradient is determined based on the glass transition temperature of the selected rice variety. Combining glass transition technology with deep-bed drying can specifically include:

[0047] Step 140: Determine the rice variety to be used in the experiment;

[0048] Step 150: Randomly sample the same batch of rice multiple times and obtain 7 groups of different moisture contents (10.1%, 12.5%, 14.3%, 16.2%, 18.3%, 20.4% and 22.2%).

[0049] Step 160: Rice grains with different moisture contents were crushed into powder, and the glass transition temperature of the seven groups of rice grains was determined by differential scanning calorimetry.

[0050] Step 170: A glass transition curve is fitted from the glass transition temperature and rice moisture content data to determine the state of the rice during the drying stage.

[0051] Step 180: Determine the variable temperature drying gradient (heating gradient or cooling gradient) and the time points for temperature changes. The rice temperature is obtained by averaging data collected from temperature sensors at different locations in the drying section. The variable temperature drying gradient can be divided into heating gradient and cooling gradient. To prevent the rice from cracking, the rice must not undergo a glass transition within the variable temperature drying gradient range;

[0052] A temperature gradient represents a gradual increase in the hot air drying temperature, and similarly, a temperature gradient represents a gradual decrease in the hot air temperature. The variable-temperature drying process can be divided into two or three stages, depending on the selected dryer model. To ensure accurate temperature control, the number of temperature stages should not be excessive.

[0053] In the variable-temperature drying process, the temperature range of the drying medium is 30℃~60℃, the apparent wind speed of the rice is 0.2m / s~0.8m / s, the tempering ratio is 1:1, 1:2, 1:3, 1:4, 1:5, and the rotation speed of the discharge roller is 1r / min~5r / min. The variable-temperature drying gradient range is 0℃~15℃.

[0054] The system allows users to input the glass transition temperature (GTH) at different moisture contents into the control cabinet's display screen. The system automatically displays a fitted curve of the moisture content and GTH. The variable-temperature drying heating and cooling gradients show different temperature control schemes, including the magnitude of the temperature gradient and the drying stages. Appropriate drying parameters can be selected based on drying requirements to control both drying efficiency and rice quality.

[0055] Example 2

[0056] This invention provides a method for temperature-varying rice drying using a continuous bidirectional ventilation dryer, such as... Figure 6 As shown, based on the initial drying parameters of the selected dryer as input, the drying rate and quality of rice at different stages are obtained, such as... Figure 3 As shown, the method specifically includes:

[0057] Step 210: Using Design Expert software, multiple regression models are established with the stage drying parameters of the rice to be dried as influencing factors and the stage target drying rate and stage target rice quality as evaluation indicators. These models are then input into the control cabinet 12 of the dryer.

[0058] Step 220: If the selected dryer is a continuous bidirectional ventilation dryer, first determine the number of tempering and drying sections of the continuous bidirectional ventilation dryer, calculate the tempering ratio, and determine the regression model to be applied; according to the selected dryer, input the initial drying parameters into the regression model through the control cabinet 12, and calculate the drying rate and rice quality at different drying stages.

[0059] Most current continuous bidirectional variable temperature dryers have 2-3 drying sections, each with different operating parameters, which aligns with the variable temperature drying range of the method described in this invention. After determining the tempering ratio parameter, the corresponding drying parameters need to be set for each section.

[0060] After the rice passes through the first drying stage, data is collected by a moisture detector 11, a temperature sensor 9, and a wind speed sensor 10. The wind speed data is analyzed to determine if the hot air flow at different locations within the drying stage is uniform, and the wind speed is automatically adjusted accordingly. Based on the collected rice temperature and moisture content data, and combined with the glass transition curve, it is determined whether the rice has reached the required temperature-controlled drying conditions. If the conditions are met, temperature-controlled drying is performed in the next drying stage. If the conditions are not met, the next drying stage maintains the same hot air drying temperature as the previous stage. The steps for the third drying stage are similar to those for the first and second drying stages.

[0061] The drying stage is defined as a combination of the drying section and tempering section of a continuous bidirectional variable temperature dryer. After the first drying stage, data is collected from the moisture meter 11, temperature sensor 9, and wind speed sensor 10. A rice sample is taken at this state, and the drying rate and rice quality (crack growth rate, protein content, cooked rice taste value, and polished rice appearance color) are calculated. A regression model for drying rate and rice quality is established based on the drying parameters at this time. The same regression model is established after the second drying stage. This process allows for the acquisition of regression models for drying rate and rice quality at different drying stages and at the end of the drying process. These models are displayed on the display module 360° within the control cabinet 12, providing predictions of drying rate and rice quality under different drying stage conditions. It also enables targeted control of drying rate and rice quality during the rice processing. The system automatically calculates the drying rate and rice quality at different drying stages by inputting the variable temperature drying gradient, hot air velocity, discharge roller speed, and initial rice moisture content.

[0062] Step 230: After obtaining the drying rate and rice quality at different stages, the parameter optimization module 330 in the control cabinet 12 is used to obtain multiple sets of optimized drying rates and rice quality.

[0063] Step 240: Use the comprehensive evaluation module 340 in the control cabinet 12 to comprehensively evaluate the multiple sets of optimized drying rates and rice quality, determine the optimal specific drying parameters, and then input the drying parameters into the control module 350 in the control cabinet 12 for drying operations.

[0064] Step 250: Based on the drying rate and rice quality obtained by the above method, guidance was provided for optimizing the drying process parameters.

[0065] Among them, based on the drying rate and rice quality obtained from the initial drying parameters according to the selected continuous bidirectional ventilation dryer, the system's process parameter optimization module 330 and comprehensive evaluation module 340 provide guidance on optimizing the drying process parameters, so as to achieve targeted control of the drying rate and quality at different drying stages.

[0066] Example 3

[0067] This invention relates to a method for temperature-controlled drying of rice using a two-way ventilation dryer. When a circulating two-way ventilation dryer is selected as the drying equipment, such as... Figure 7 As shown, based on the initial drying parameters of the selected dryer as input, the drying rate of the dryer and the quality of the rice are obtained, such as... Figure 4 As shown, the method specifically includes:

[0068] Step 260: Using Design Expert software, establish multiple regression models with the stage drying parameters of the rice to be dried as influencing factors and the stage target drying rate and stage target rice quality as evaluation indicators, and input them into the control cabinet 12 of the dryer;

[0069] Step 270: If the selected dryer is a circulating two-way ventilation dryer, the ratio of the tempering section to the drying section of the circulating two-way ventilation dryer should be determined first, and the tempering ratio should be calculated to determine the applied regression model. According to the selected dryer, the initial drying parameters are input into the regression model through the control cabinet 12 to calculate the drying rate and rice quality of different drying cycle stages.

[0070] Step 280: After obtaining the drying rate and rice quality at different drying cycle stages, the parameter optimization module 330 in the control cabinet 12 is used to obtain multiple sets of optimized drying rates and rice quality.

[0071] The rice is circulated multiple times within the circulating two-way ventilation dryer until it reaches a safe storage moisture content, at which point the drying process stops. After the first drying cycle, data is collected by a moisture detector 11, a temperature sensor 9, and a wind speed sensor 10. The wind speed data is analyzed to determine if the hot air velocity at different locations in the drying section is uniform, and the wind speed is automatically adjusted accordingly. Based on the collected rice temperature and moisture content data, combined with the glass transition curve, it is determined whether the rice has reached the variable-temperature drying conditions. If the variable-temperature drying conditions are met, variable-temperature treatment is performed in the next drying cycle. If the variable-temperature drying conditions are not met, the next drying cycle maintains the hot air drying temperature of the previous cycle. The steps for the third drying cycle are similar to those for the first and second drying cycles. After passing through the drying section, the rice in the circulating two-way ventilation dryer is lifted back into the storage section by a conveyor belt for continuous drying until a safe moisture content is reached. The storage section of the circulating two-way ventilation dryer is the tempering section, and the tempering ratio is calculated based on the ratio to the drying section.

[0072] The process of combining the drying section and tempering section of the circulating bidirectional variable temperature dryer constitutes a drying cycle stage. After the rice undergoes the first drying cycle stage, data collected by the moisture meter 11, temperature sensor 9, and wind speed sensor 10 are taken. Rice samples are taken under these conditions, and the drying rate and rice quality (crack growth rate, protein content, cooked rice taste value, and polished rice appearance color) are calculated. A regression model for drying rate and rice quality is established based on the drying parameters at this time. Similarly, a regression model for drying rate and rice quality is established after the rice undergoes the second drying cycle stage. This process allows for the acquisition of regression models for drying rate and rice quality at different cycle stages and the end of the drying process, enabling prediction of drying rate and rice quality under different drying cycle conditions, and also allowing for targeted control of drying rate and rice quality during rice processing. Specifically, the variable temperature drying gradient, hot air velocity, discharge roller speed, and initial rice moisture content are input into the system, which automatically calculates the drying rate and rice quality at different drying cycle stages.

[0073] Step 290: Use the comprehensive evaluation module 340 in the control cabinet 12 to comprehensively evaluate the multiple sets of optimized drying rates and rice quality, determine the optimal specific drying parameters, and then input the drying parameters into the control module 350 in the control cabinet 12 for drying operations.

[0074] Step 300: Provide guidance on optimizing drying process parameters based on the drying rate and rice quality obtained by the above method.

[0075] Among them, based on the drying rate and rice quality obtained from the initial drying parameters of the selected circulating bidirectional ventilation dryer, the system's process parameter optimization module 330 and comprehensive evaluation module 340 provide guidance on optimizing the drying process parameters, thereby achieving targeted control of the drying rate and quality at different drying cycle stages.

[0076] Example 4

[0077] The rice temperature-variable drying method described in Examples 1-3, applicable to a two-way ventilation dryer, is suitable for different dryer models. When a continuous dryer is selected for dryer 1, such as... Figure 6 The dryer 1 is divided into an upper grain storage section 2, a middle section of one or more drying sections 3 and one or more tempering sections 13, and a lower grain discharge section 4 from top to bottom. The grain storage section 2 has a grain inlet at the top and the grain discharge section 4 has a grain discharge outlet 5 at the bottom. Each drying section 3 has a tempering section 13 below it, but the bottommost drying section 3 does not have a tempering section 13 below it.

[0078] Each drying section 3 consists of an inlet angled pipe 6 and an outlet angled pipe 7, which are arranged in a crisscross pattern. The inlet angled pipe 6 is connected to a temperature regulating device 8. Three or more temperature sensors 9 are arranged side by side on the tempering section 13 below the outlet angled pipe 7 to detect the temperature of the rice. Below the temperature sensors 9, there are correspondingly the same number of wind speed sensors 10 to detect the wind speed at the grain layer. At the end of each tempering section 13 and on the side of the grain discharge section 4, there are moisture detectors 11 to detect the moisture content of the rice. The temperature sensors 9, wind speed sensors 10 and moisture detectors 11 are all connected to the control cabinet 12. The control cabinet contains a model building and selection module, an index prediction module, a process parameter optimization module, a comprehensive evaluation module and a display module, which are used to guide the optimization of drying process parameters. The outer end of the air inlet angle tube 6 is connected to a temperature regulating device 8 to allow dry air to enter, while the inner end is sealed. The air passes through the grain layer and flows out from the air outlet angle tube 7 in either the lower or upper drying section. The outer end of the air outlet angle tube 7 is open and placed outside the machine body to allow air to flow out, while the inner end is sealed. The installation directions of the air inlet angle tube 6 and air outlet angle tube 7 in adjacent drying sections are opposite.

[0079] The aforementioned temperature regulation device is used for precise control of temperature changes during the temperature-changing drying process. By automatically adjusting the opening size of the valve, hot and cold air are mixed to achieve the purpose of temperature change.

[0080] This device includes a model building and selection module, an index prediction module, a process parameter optimization module, a comprehensive evaluation module, and a display module inside the control cabinet, such as... Figure 5 As shown, this is used to guide the optimization of the drying process.

[0081] Control cabinet 12 is PLC-controlled and used to receive, collect, and store test data. Different modules are also connected and implemented through the PLC, enabling online data display, parameter adjustment, process optimization, and process evaluation.

[0082] The model building and selection module 310 is used to establish a regression model between drying parameters and different indicators, and to select the corresponding regression equation for different drying parameters.

[0083] The index prediction module 320 is used to predict the values ​​of different evaluation indicators under different drying parameter conditions.

[0084] The process parameter optimization module 330 is used to allocate the weight of each indicator according to the drying rate and rice quality requirements, and to optimize the drying process parameters using multiple objective variables.

[0085] The comprehensive evaluation module 340 uses principal component analysis and membership function method to comprehensively evaluate various optimized evaluation indicators, which is used to guide the selection of drying process parameters;

[0086] The control module 350 is used to control and adjust drying parameters such as drying temperature, hot air velocity, and grain discharge roller speed.

[0087] The display module 360 ​​is used to input drying parameters; set the variable temperature drying gradient; and observe sensor information acquisition data, model establishment and selection results, index prediction results, process optimization results, and comprehensive evaluation results. This module is viewed through the display screen.

[0088] Example 5

[0089] The rice temperature-variable drying method described in Examples 1-3, applicable to a two-way ventilation dryer, is suitable for different dryer models. When a circulating dryer is selected for dryer 1, such as... Figure 7 As shown, each drying section 3 is connected in sequence and there is no tempering section between each drying section 3. The grain storage section 2 above the first drying section 3 is the tempering section. Only the temperature sensor 9 and the wind speed sensor 10 are installed on the grain storage section 2, and only the moisture detector 11 is installed on the side of the grain discharge section 4.

[0090] The other aspects are the same as in Example 4.

Claims

1. A method for temperature-controlled drying of rice suitable for a two-way ventilation dryer, characterized in that... Includes the following steps: (1) Model establishment: Multiple regression models were established with the stage drying parameters of the rice to be dried as influencing factors, the stage target drying rate and the stage target rice quality as evaluation indicators; The stage drying parameters include: variable temperature drying gradient, hot air apparent velocity, grain discharge roller speed, tempering ratio, and initial moisture content of rice. The variable temperature drying gradient, hot air apparent velocity, grain discharge roller speed, and initial moisture content of rice are all range values. The tempering ratio is determined based on the selected dryer model; The variable temperature drying gradient is determined by combining the glass transition theory with a two-way ventilation dryer for the rice to be dried, based on the glass transition curve. The glass transition curves were obtained by the following method: multiple random samplings of the same batch of rice were taken to obtain 7 groups of different moisture contents; rice with different moisture contents were crushed into powder, and the glass transition temperatures of the 7 groups of rice were measured using a differential scanning calorimeter; the glass transition temperatures of the 7 groups of rice and their corresponding moisture contents were fitted into glass transition curves. (2) Model application: Input the initial drying parameters of different stages into multiple regression models obtained in step (1) to obtain the real-time drying rate and real-time rice quality of different drying stages; the initial drying parameters are determined according to the type of dryer, the moisture content of rice harvest and the variable temperature drying process. (3) Parameter optimization: Based on the real-time drying rate and real-time rice quality obtained in step (2) at different stages, the drying process parameters are optimized using multiple objective variables to obtain multiple sets of optimized drying rates and rice quality; (4) Drying and comprehensive evaluation: After optimizing the multi-objective variables using principal component analysis and membership function method, factor analysis was performed on the drying rate, crack growth rate, protein content, rice taste value, and polished rice appearance color of the paddy rice. Based on the criterion that the cumulative contribution rate of the principal component factors is greater than 80%, each individual evaluation index was standardized. The standardized data and the index coefficients of the comprehensive index of each principal component obtained through principal component analysis were multiplied accordingly to calculate the principal component scores and weights of each principal component for different drying processes. Finally, the comprehensive score of different drying processes was obtained, and the optimal specific drying parameters for different stages were obtained. The optimal specific drying parameters for different stages were then input into the control cabinet for drying operations.

2. The method for variable-temperature drying of rice suitable for a two-way ventilation dryer according to claim 1, characterized in that... In step (1), after determining the slow tempering ratio of the rice variety and the dryer model used in the experiment, a four-factor, five-level quadratic orthogonal rotational combination experimental scheme was established based on the drying parameters of each stage. The four factors are variable temperature drying gradient, hot air performance wind speed, grain discharge roller speed and initial moisture content of rice. The evaluation indicators for rice quality include: crack growth rate, protein content, cooked rice taste value, and the appearance and color of polished rice.

3. The method for variable-temperature drying of rice suitable for a two-way ventilation dryer according to claim 1, characterized in that... The multi-objective variables mentioned in step (3) refer to drying rate, crack growth rate, protein content, rice taste value, and polished rice appearance color. Based on the final drying rate and final rice quality requirements, the weight of each indicator is assigned to optimize the specific drying process parameters at different stages using multi-objective variables.

4. A rice temperature-controlled drying system for implementing the rice temperature-controlled drying method applicable to a two-way ventilation dryer as described in any one of claims 1-3, comprising a dryer (1), which is divided from top to bottom into a grain storage section (2), one or more drying sections (3) and a grain discharge section (4), wherein a grain inlet is provided at the top of the grain storage section (2) and a grain discharge outlet (5) is provided at the bottom of the grain discharge section (4); characterized in that Each drying section (3) consists of an inlet angle tube (6) and an outlet angle tube (7), with the inlet angle tube (6) and outlet angle tube (7) arranged in a crisscross pattern. The inlet angle tube (6) is connected to a temperature regulating device (8), and three or more temperature sensors (9) are arranged side by side below the outlet angle tube (7) to detect the temperature of the rice. Below the temperature sensors (9), there are corresponding wind speed sensors (10) of the same number to detect the wind speed of the grain layer. A moisture meter (11) is provided on the side of the grain discharge section (4) to detect the moisture content of the rice. The temperature sensors (9), wind speed sensors (10) and moisture meter (11) are all connected to the control cabinet (12). The control cabinet (12) contains a model establishment and selection module, an index prediction module, a process parameter optimization module, a comprehensive evaluation module, a control module and a display module, which are used to guide the optimization of drying process parameters.

5. A rice temperature-controlled drying system suitable for a two-way ventilation dryer according to claim 4, characterized in that: When the dryer (1) is a continuous dryer, a tempering section (13) is provided below the drying section (3). A temperature sensor (9) and a wind speed sensor (10) are provided on the tempering section (13). A moisture detector (11) is provided at the end of each tempering section (13) and on the side of the grain discharge section (4).

6. A rice temperature-controlled drying system suitable for a two-way ventilation dryer according to claim 4, characterized in that: When the dryer (1) is a circulating dryer, each drying section (3) is connected in sequence. The grain storage section (2) above the first drying section (3) is the tempering section. A temperature sensor (9) and a wind speed sensor (10) are installed on the grain storage section (2), and a moisture detector (11) is installed on the side of the grain discharge section (4).

7. A rice temperature-controlled drying system suitable for a two-way ventilation dryer according to claim 4, characterized in that... Dry air enters through the outer end of the air inlet angle tube (6) and is sealed at the inner end. The air passes through the grain layer and flows out through the air outlet angle tube (7) of the lower or upper drying section. The outer end of the air outlet angle tube (7) is open and placed outside the machine body to allow air to flow out, while the inner end is sealed.

8. A rice temperature-controlled drying system suitable for a two-way ventilation dryer as described in claim 4, characterized in that... The installation directions of the air inlet angle pipe (6) and air outlet angle pipe (7) of adjacent drying sections are opposite.

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