Supplementing process adopting food-grade carbon dioxide as sugar refining clarifying agent

Abstract

The invention discloses a carbonation process adopting food-grade carbon dioxide as a sugar refining clarifying agent. The carbonation process comprises the following steps: storing the food-grade carbon dioxide; vaporizing the liquid carbon dioxide; regulating the pressure of the gaseous carbon dioxide and metering; preparing and adjusting compressed air; primarily mixing gas; storing and heating the mixed gas; secondarily mixing the gas; and carrying out carbonation reaction and automatic control. Food-grade carbon dioxide is adopted as a clarifying agent and is high in purity and few in impurity, secondary pollution of impurities in traditional flue gas to sugar juice is avoided, the sugar juice clarifying effect is improved, the quality of white granulated sugar is guaranteed, accurate control over gas pressure is achieved through a two-stage pressure regulating system, the stability of gas conveying is guaranteed, and the quality of the white granulated sugar is guaranteed. Two-stage mixing is carried out by adopting the static pipeline mixer and the venturi mixer, so that the uniformity of gas mixing is ensured, automatic adjustment of the carbonation process is realized through linkage control of the online pH meter and the mixed gas introduction amount, the pH value of sugar juice is stabilized in an optimal range, the stability and efficiency of carbonation reaction are improved, and the manual operation intensity is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sugar juice clarification in sugar industry, and particularly relates to a saturation process using food-grade carbon dioxide as a sugar clarification agent, which is particularly suitable for sugar production enterprises without lime kiln and boiler. BACKGROUND

[0002] In the sugar industry, saturation process is the core link of sugar juice clarification, which generates calcium carbonate precipitate by the reaction of carbon dioxide and lime milk in sugar juice, and adsorbs impurities in sugar juice, so as to realize sugar juice purification. In the traditional saturation process, carbon dioxide mainly comes from the flue gas generated by calcining lime in the lime kiln or the flue gas of the boiler. This kind of gas is low in cost and easy to obtain, but has problems such as low purity (containing impurities such as sulfur and dust) and unstable composition, which can easily lead to secondary pollution of sugar juice and affect the quality of white granulated sugar.

[0003] The food-grade carbon dioxide can theoretically significantly improve the clarification effect of sugar juice and reduce the subsequent filtration load due to its purity of ≥99.9% and extremely low content of impurities (such as sulfides and particulate matter). However, it is stored in liquid state and needs to be maintained in liquid state at room temperature under high pressure. When used, it needs to go through complex processes such as vaporization, pressure regulation and mixing. Moreover, the sugar industry lacks mature application technology, which leads to its little application in sugar saturation.

[0004] For sugar production enterprises that are restricted by geographical location and cannot build lime kiln and boiler, they are facing the dilemma of shortage of carbon dioxide sources, which seriously threatens the survival of the enterprises and the maintenance of the quality of old brand white granulated sugar. Therefore, it is of great practical significance to develop a process that can effectively use food-grade carbon dioxide as a sugar clarification agent. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art, provide a saturation process using food-grade carbon dioxide as a sugar clarification agent, solve the problem of difficult application of food-grade liquid carbon dioxide in the saturation process of sugar production, realize efficient sugar juice clarification under the condition of no lime kiln and boiler, and further improve the quality of white granulated sugar. The white granulated sugar produced by this process is better than that produced under the condition of lime kiln and boiler.

[0006] To achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0007] In a first aspect, the present application provides a saturation process using food-grade carbon dioxide as a sugar clarification agent, comprising the following steps:

[0008] S1. Storage of food-grade carbon dioxide

[0009] The food-grade liquid carbon dioxide is transported to a carbon dioxide storage tank for storage, and the working pressure of the storage tank is 2.0-2.5 MPa;

[0010] S2. Vaporization of liquid carbon dioxide

[0011] Liquid carbon dioxide is converted into gaseous carbon dioxide by two parallel vaporizers, which vaporize the liquid carbon dioxide completely in a natural warming way;

[0012] S3. Pressure regulation and metering of gaseous carbon dioxide

[0013] The vaporized gaseous carbon dioxide passes through two parallel groups of pressure regulating valves in sequence for pressure and flow control, and the pressure is adjusted to 0.30-0.35 MPa, while the flow of the gaseous carbon dioxide is controlled by a flow meter;

[0014] S4. Preparation and adjustment of air pressure

[0015] The air pressure at 0.7 MPa passes through two parallel groups of pressure regulating valves in sequence for pressure and flow control, and the pressure is adjusted to 0.15-0.2 MPa, while the flow of the air pressure is controlled by a flow meter;

[0016] S5. Primary mixing of gases

[0017] The gaseous carbon dioxide adjusted in step S3 and the air pressure adjusted in step S4 are introduced into a static pipeline mixer and mixed at a volume ratio of 1:4-1:8;

[0018] S6. Storage and heating of mixed gases

[0019] The primary mixed gas enters a gas storage tank for pressure stabilization, and then is heated to 70-80℃ to obtain a first mixed gas;

[0020] S7. Secondary mixing of gases

[0021] Air at 600-1200 m 3 / h is introduced into the first mixed gas by a screw blower and is secondary mixed by a Venturi mixer to obtain a mixed gas meeting the process requirements;

[0022] S8. Saturation reaction and automatic control

[0023] The secondary mixed gas passes through a total regulating valve, and then passes through branch regulating valves to enter a No. 1 saturation tank and a No. 2 saturation tank, respectively. Before the mixed gas enters the saturation tank, the pH value of the saturation juice is monitored by an online pH meter, and a linkage relationship between the online pH meter and the amount of mixed gas introduced is established to realize automatic control of the amount of mixed gas introduced.

[0024] The total volume flow of the carbon dioxide and air pressure mixed gas obtained in step S6 is 600-1200 m 3 / h, it is found that it is very difficult to filter the saturated syrup by using the plate and frame filter press, and after a plurality of sedimentation experiments, it is found that the calcium carbonate particles are fine and the sedimentation speed is fast, so it can be judged that the saturation effect is not very good, in order to solve this problem, a plurality of experiments are repeatedly carried out to verify various factors in the saturation process, and finally it is concluded that the total volume of the saturation gas is insufficient, so that the calcium carbonate gap is not large, and the impurity adsorption capacity has not reached the best state. Therefore, a screw blower is added to blow 600-1200m 3 / h of air into the primary mixed gas, and the air is mixed again by using a Venturi mixer to obtain the mixed gas meeting the process requirements.

[0025] Further, in step S3, the flow rate of the gaseous carbon dioxide is controlled to be 100-250m 3 / h.

[0026] Further, in step S4, the flow rate of the air pressure gas is controlled to be 500-1000m 3 / h.

[0027] Further, in step S7, the total gas volume flow rate after the secondary mixing of the gas is controlled to be 1200-2400m 3 / h.

[0028] Further, in step S8, the logic relationship of the automatic control is that: the pH value of the one-carbon saturated syrup is controlled to be 9.0-9.5, when the online pH meter detects that the pH value of the one-carbon saturated juice is higher than 9.5, the mixed gas inlet amount is automatically increased, and when the online pH meter detects that the pH value of the one-carbon saturated juice is lower than 9.0, the mixed gas inlet amount is automatically reduced; the pH value of the two-carbon saturated syrup is controlled to be 8.0-8.5, when the online pH meter detects that the pH value of the two-carbon saturated juice is higher than 8.5, the mixed gas inlet amount is automatically increased, and when the online pH meter detects that the pH value of the two-carbon saturated juice is lower than 8.0, the mixed gas inlet amount is automatically reduced.

[0029] Further, in step S8, an independent branch regulating valve is arranged at the mixed gas inlet of each saturation tank to realize the independent control of the flow rate of a single tank.

[0030] The optimized process of the application realizes the following effects by improving the gas volume and mixing efficiency:

[0031] (1) The application first systematically solves the application problem of food-grade liquid carbon dioxide in the sugar saturation process, realizes the stable application of food-grade carbon dioxide through vaporization, pressure regulation, multi-stage mixing and other process designs, and provides a feasible solution for sugar-making enterprises without lime kiln and boiler.

[0032] (2) The food-grade carbon dioxide is used as the clarifying agent, which has high purity and less impurities, avoiding the secondary pollution of the traditional flue gas impurities to the sugar juice, improving the clarification effect of the sugar juice, and being conducive to ensuring the quality of white granulated sugar, especially suitable for enterprises that need to maintain the quality of old brands.

[0033] (3) The two-stage pressure regulating system is adopted to realize the accurate control of the gas pressure and ensure the stability of the gas delivery; the static pipeline mixer and the Venturi mixer are adopted for two-stage mixing to ensure the uniformity of the gas mixing.

[0034] (4) The screw blower is arranged to supplement air, solving the problem of the mismatch between the total amount of the mixed gas and the process requirements, ensuring the full performance of the saturation reaction, ensuring that the calcium carbonate particles generated in the saturation process are large and have large voids, the large particle calcium carbonate has a slow descending speed in the settling experiment, the clear juice is clear, and the saturation decolorization rate is increased to 65%.

[0035] (5) The linkage control of the online pH meter and the mixed gas input amount is adopted to realize the automatic adjustment of the saturation process, so that the sugar juice pH value is stabilized in the optimal range, the stability and efficiency of the saturation reaction are improved, and the manual operation intensity is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The special equipment for implementing the process of the present application is shown.

[0037] Wherein: 100 - carbon dioxide tank truck, 101 - carbon dioxide storage tank, 101-1 - carbon dioxide storage tank pressure sensor, 102 - vaporizer, 103 - carbon dioxide pressure regulating valve, 104 - carbon dioxide online pressure and flow meter, 105 - air pressure gas storage tank, 106 - air pressure regulating valve, 107 - air pressure online pressure and flow meter, 108 - static pipeline mixer, 109 - gas storage tank, 1091 - mixed gas pressure sensor, 110 - tube heater, 110-1 mixed gas temperature sensor, 111 - screw blower, 111-1 - fan outlet air temperature sensor, 111-2 - fan outlet pressure sensor, 112 - Venturi mixer, 113 - first mixed gas storage tank, 114 - second mixed gas storage tank, 115 - one carbon gas regulating valve, 115-1 - mixed gas online flow meter, 116 - two carbon gas regulating valve, 116-1 - mixed gas online flow meter, 117 - No. 1 saturation tank, 118 - one carbon online pH meter, 119 - No. 2 saturation tank two carbon, 120 - two carbon online pH meter, 121 - carbon dioxide and air mixing automatic control system, 122 - saturation process automatic control system. DETAILED DESCRIPTION

[0038] The technical solutions of the present application will be further described below in combination with the drawings and specific embodiments.

[0039] If not specifically stated, the instruments or reagents used in the examples are conventional instruments or reagents in the art, which are conventional products available on the market. If not specifically stated, the specific experimental operations involved in the text are understood or known by those skilled in the art according to the common knowledge or conventional technical means mastered by them, and will not be described one by one.

[0040] As shown in Figure 1 A saturation process using food-grade carbon dioxide as a sugar refining agent, comprising the following steps:

[0041] (1) Storage of food-grade carbon dioxide:

[0042] The food-grade liquid carbon dioxide is transported to the factory by a carbon dioxide tank truck 100, and is delivered to a 50m 3 The carbon dioxide storage tank 101 has a working pressure of 2.0-2.5MPa (for example, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5MPa, and most preferably 2.2MPa), and is provided with a carbon dioxide storage tank pressure sensor 101-1.

[0043] (2) Vaporization of liquid carbon dioxide:

[0044] The liquid carbon dioxide in the carbon dioxide storage tank 101 is converted into gaseous carbon dioxide by two parallel vaporizers 102, which use natural warming to completely vaporize the liquid carbon dioxide.

[0045] (3) Pressure regulation and metering of gaseous carbon dioxide:

[0046] The vaporized gaseous carbon dioxide passes through two groups of parallel carbon dioxide pressure regulating valves 103 in turn, which regulate the pressure to 0.30MPa-0.35MPa (for example, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35MPa, and most preferably 0.32MPa), while the instantaneous pressure and flow rate of the gaseous carbon dioxide are displayed by the carbon dioxide online pressure and flow meter 104. The carbon dioxide flow rate is controlled in the range of 100m 3 / h-250m 3 / h (for example, 100, 150, 180, 200, 250m 3 / h, and most preferably 180m 3 / h).

[0047] (4) Preparation and adjustment of air pressure:

[0048] The air pressure gas of 0.7 MPa is introduced from the air pressure gas storage tank 105, and the pressure is adjusted to 0.15-0.20 MPa (for example, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20 MPa, and most preferably 0.18 MPa) through two groups of parallel air pressure regulating valves 106 in turn, while the air pressure gas flow is displayed as 500 m 3 / h-1000 m 3 / h (for example, 500, 600, 700, 800, 900, 1000 m 3 / h, and most preferably 800 m 3 / h) through the air pressure online pressure and flow meter 107.

[0049] (5) Primary mixing of gas:

[0050] The gaseous carbon dioxide adjusted in step 3 and the air pressure gas adjusted in step 4 are introduced into the static pipeline mixer 108, and mixed in a volume ratio of 1:4-1:8 (for example, 1:4, 1:5, 1:6, 1:7, 1:8, and most preferably 1:6).

[0051] (6) Storage and heating of mixed gas:

[0052] The primary mixed gas enters the 3.5 m 3 long gas storage tank 109 for pressure stabilization, and then is heated to 70-80°C (for example, 70°C, 75°C, 80°C, and most preferably 75°C) through the shell-and-tube heater 110 (provided with a mixed gas temperature sensor 110-1).

[0053] (7) Secondary mixing of gas:

[0054] The carbon dioxide and air pressure gas mixed gas obtained in step (6) has a total volume of 600 m 3 / h-1200 m 3 / h (for example, 600, 700, 800, 900, 1000, 1100, 1200 m 3 / h, and most preferably 900 m 3 / h), and it is found after operation that the mud filtration lightness is high, the filtration is difficult, and the production capacity is limited. The dissolved sugar amount of 3 sets of 120 m 2 long plate-and-frame filter presses is only 430 tons / day. Through multiple sedimentation experiments, it is found that the saturated production calcium carbonate particles are small and have a fast sinking speed, resulting in difficult filtration. Therefore, it is repeatedly demonstrated through experiments that the volume of the saturated gas needs to be increased to meet the production requirements, and a screw blower 111 (provided with a blower outlet air temperature sensor 111-1 and a blower outlet pressure sensor 111-2) is added to blow in 600 m 3 / h-1200 m 3 / h (e.g. 600, 700, 800, 900, 1000, 1100, 1200m 3 / h, most preferably 900m 3 / h) of air enters the primary mixed gas, and then passes through the Venturi mixer 112 for secondary mixing to obtain a total volume of 1200m 3 / h-2400m 3 / h (e.g. 1200, 1400, 1600, 1800, 2000, 2200, 2400m 3 / h, most preferably 1800m 3 / h) of mixed gas, which meets the process requirements, the secondary mixed gas enters the first mixed gas storage tank 113 and then enters the second mixed gas storage tank 114. The secondary mixing of gases is controlled by the carbon dioxide and air mixing automatic control system 121.

[0055] (8) Saturation reaction and automatic control:

[0056] The secondary mixed gas enters the filling tanks from the second mixed gas storage tank 114 respectively. The carbon 1 filling enters the No. 1 filling tank 117 through the carbon 1 gas regulating valve 115 (equipped with a mixed gas online flow meter 115-1), and the carbon 2 filling enters the No. 2 filling tank 119 through the carbon 2 gas regulating valve 116 (equipped with a mixed gas online flow meter 116-1).

[0057] Before the mixed gas enters the saturation tank, the pH value of the saturated syrup is monitored by an online one-carbon saturated pH meter 118. The online pH meter 118 is connected to the saturation process automatic control system 122, and the saturation process automatic control system 122 is connected to the one-carbon gas regulating valve 115 to establish an automatic control logic relationship: when the one-carbon online pH meter 118 detects that the one-carbon saturated pH value is higher than the set upper limit of 9.5, the control system 122 controls the one-carbon gas regulating valve 115 to increase the amount of mixed gas introduced; when the pH value is lower than the set lower limit of 9.0, the control system 122 controls the one-carbon gas regulating valve 115 to reduce the amount of mixed gas introduced, so that the pH value of the one-carbon saturated syrup is stabilized within the range of 9.0-9.5.

[0058] Before the mixed gas enters the saturation tank, the pH value of the two-carbon saturation syrup is monitored by an on-line two-carbon saturation pH meter 120, the on-line pH meter 120 is connected with a saturation process automatic control system 122, the saturation process automatic control system 122 is connected with the two-carbon gas regulating valve 116, and an automatic control logic relationship is established: when the two-carbon on-line pH meter 120 detects that the two-carbon saturation pH value is higher than the set upper limit of 8.5, the control system 122 controls the two-carbon gas regulating valve 116 to increase the mixed gas input amount; when the pH value is lower than the set lower limit of 8.0, the control system 122 controls the two-carbon gas regulating valve 116 to reduce the mixed gas input amount, so that the one-carbon saturation syrup pH value is stabilized in the range of 8.0-8.5.

[0059] The saturation process of the present application is shown in Table 1 as follows.

[0060] Table 1. Process parameters of each example

[0061]

[0062] The saturation decolorization rates of Examples 1, 2 and 3 are 57%, 60% and 65% respectively, compared with the traditional process using flue gas,

[0063] The purity of white sugar is increased by 0.1%, 0.13% and 0.2% respectively.

[0064] It can be seen that compared with the traditional process using flue gas, the saturation decolorization rate is increased from 55% of the traditional process to 65% after using the process of the present example, the impurities of white sugar are significantly reduced to close to 0, for example, after the white sugar is dissolved for 20 kg and then filtered by an 8 μm filter, the bottom color is clean without impurities, at the same time, the purity of white sugar is increased by 0.1-0.2%, the product quality is obviously improved, and the process stability is significantly improved, which meets the needs of enterprises to maintain the quality of old brand white sugar.

[0065] The above is only the preferred embodiment of the present application, and does not limit the present application in any form, so any simple modification, equivalent change and modification of the above embodiment according to the technical essence of the present application, which does not deviate from the technical solution of the present application, is still within the scope of the technical solution of the present application.

Claims

1. A saturation process using food-grade carbon dioxide as a sugar clarifier, characterized in that: The following steps are involved: S1. Storage of Food-Grade Carbon Dioxide The food-grade liquid carbon dioxide is transported to a carbon dioxide storage tank for storage. The working pressure of the storage tank is 2.0-2.5MPa; S2. Vaporization of liquid carbon dioxide The liquid carbon dioxide is converted into gaseous carbon dioxide through two parallel vaporizers, and the vaporizers completely vaporize the liquid carbon dioxide by natural heating; S3. Pressure regulation and metering of gaseous carbon dioxide The vaporized gaseous carbon dioxide passes through two sets of parallel pressure regulating valves for pressure and flow control, adjusting the pressure to 0.30MPa-0.35MPa, and the flow rate of the gaseous carbon dioxide is controlled by a flow meter at the same time; S4. Preparation and regulation of compressed air The compressed air with a pressure of 0.7MPa is passed through two sets of parallel pressure regulating valves to control the pressure and flow, and the pressure is adjusted to 0.15MPa-0.2MPa. At the same time, the flow rate of the compressed air is controlled by a flow meter; S5. Primary gas mixing The gaseous carbon dioxide conditioned in step S3 and the compressed air conditioned in step S4 are introduced into a static pipeline mixer and mixed at a volume ratio of 1:4-1:8; S6. Storage and heating of mixed gas The primary mixed gas enters the gas storage tank for pressure stabilization and is then heated to 70-80°C to obtain the primary mixed gas; S7. Gas secondary mixing Use screw blower to blow 600-1200m 3 / h of air enters the primary mixed gas, and then undergoes secondary mixing through a Venturi mixer to obtain a mixed gas that meets the process requirements; S8. Saturation response and automatic control After the secondary mixing, the gas passes through the main regulating valve and then enters the No. 1 saturation tank and the No. 2 saturation tank through the branch regulating valves respectively; before the mixed gas enters the saturation tank, the pH value of the saturated juice is monitored by an online pH meter, and a linkage relationship between the online pH meter and the amount of mixed gas introduced is established to realize automatic control of the amount of mixed gas introduced.

2. The process according to claim 1, characterized in that In step S3, the flow rate of gaseous carbon dioxide is controlled at 100-250m 3 / h.

3. The process according to claim 1, characterized in that In step S4, the flow rate of compressed air is controlled at 500-1000m 3 / h.

4. The process according to claim 1, characterized in that In step S7, the total gas volume flow rate after the secondary mixing of the gas is controlled at 1200-2400m 3 / h.

5. The process according to claim 1, characterized in that In step S8, the logical relationship of the automatic control is: the pH value of the mono-carbon saturated syrup is controlled at 9.0-9.5, and when the online pH meter detects that the pH value of the mono-carbon saturated juice is higher than 9.5, the amount of mixed gas introduced is automatically increased; when the online pH meter detects that the pH value of the mono-carbon saturated juice is lower than 9.0, the amount of mixed gas introduced is automatically reduced; the pH value of the di-carbon saturated syrup is controlled at 8.0-8.5, and when the online pH meter detects that the pH value of the di-carbon saturated juice is higher than 8.5, the amount of mixed gas introduced is automatically increased; when the online pH meter detects that the pH value of the di-carbon saturated juice is lower than 8.0, the amount of mixed gas introduced is automatically reduced.

6. The process according to claim 1, characterized in that In step S8, an independent branch regulating valve is provided at the mixed gas inlet of each filling tank to achieve separate control of the flow rate of a single tank.

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