阅读说明：本技术 一种木糖水解液中和方法及其装置 (Xylose hydrolysate neutralizing method and device ) 是由 罗希韬 黄涛 朱有权 王磊 刘敬涛 李毅 马宗亮 岳志江 于 2019-09-06 设计创作，主要内容包括：一种木糖水解液中和方法及其装置,中和方法包括中和剂配制、调节pH值、保温养晶和卸料步骤,所述木糖水解液中和方法的装置的中和剂配制罐的筒体内安装有中和剂搅拌器,筒体下接中和剂输送泵及输送管路,输送管路末端接中和剂喷嘴,中和剂喷嘴浸入水解液中和罐主体内液面以下,水解液中和罐主体内部设有中和罐搅拌器,中和剂喷嘴位于中和罐搅拌器最顶端桨叶上部,水解液中和罐主体外壁设置控温夹套,温度计和pH计伸入水解液中和罐主体内,水解液中和罐主体底端设有硫酸钙沉淀排放口和中和液出料口。采用本发明能够控温,控制水解液酸碱度,实现木糖水解液的高效混合。(A neutralization method of xylose hydrolysate comprises the steps of neutralizer preparation, pH value adjustment, heat preservation crystal growth and discharging, wherein a neutralizer stirrer is installed in a neutralizer preparation tank of the device of the xylose hydrolysate neutralization method, a neutralizer delivery pump and a delivery pipeline are connected to the lower portion of a cylinder body of a neutralizer preparation tank, the tail end of the delivery pipeline is connected with a neutralizer nozzle, the neutralizer nozzle is immersed below the liquid level in a hydrolysate neutralization tank main body, a neutralization tank stirrer is arranged in the hydrolysate neutralization tank main body, the neutralizer nozzle is located on the upper portion of a top paddle of the neutralizer stirrer, a temperature control jacket is arranged on the outer wall of the hydrolysate neutralization tank main body, a thermometer and a pH meter extend into the hydrolysate neutralization tank main body, and a calcium sulfate precipitation discharge port and a neutralization liquid discharge port are formed in the bottom end of the hydrolysate neutralization tank main body. The invention can control the temperature, control the pH value of the hydrolysate and realize the high-efficiency mixing of the xylose hydrolysate.)

1. A xylose hydrolysate neutralization method is characterized by comprising the following specific operation steps:

(1) Preparing a neutralizing agent: adding calcium bicarbonate and water with specified mass into a neutralizer preparation tank, starting a stirrer, and uniformly mixing for later use;

(2) Adjusting the pH value: after hydrolysis-solid-liquid separation, the xylose hydrolysate enters a hydrolysate neutralization tank from a hydrolysate feeding pipe, the liquid level is controlled to be 10-20cm below the upper edge of the hydrolysate neutralization tank, a neutralizer nozzle is ensured to be completely immersed in the liquid level, a neutralizer stirrer is started, a neutralizer is introduced under the normal temperature condition, the adding speed of the neutralizer is controlled to be 10-300L/min, the temperature of the hydrolysate is not more than 80 ℃, the pH range is accurately controlled to be 3.5-5.0, and the neutralizer is stopped being added after the specified value is reached;

(3) Heat preservation and crystal growth: continuing stirring until no gas is generated, simultaneously opening a temperature control jacket, accurately controlling the temperature of crystal growing at 75-85 ℃, stopping stirring, starting standing for crystal growing for 20-40min, and waiting for the calcium sulfate crystals to be completely precipitated;

(4) Unloading: and discharging the feed liquid through a neutralizing liquid discharge port after the calcium sulfate crystals are completely precipitated, observing the precipitation quantity in the calcium sulfate precipitation device through an ocular lens, closing a precipitation discharge valve under the condition that the precipitation device is fully accumulated, opening the precipitation discharge valve to empty the precipitation device, then closing the precipitation discharge valve, and opening the precipitation discharge valve.

2. The xylose hydrolysate neutralization method according to claim 1, wherein the neutralizing agent is calcium bicarbonate.

3. The xylose hydrolysate neutralization method according to claim 2, wherein the neutralizing agent calcium bicarbonate has a mole fraction concentration of 0.005-0.018.

4. The xylose hydrolysate neutralization method according to claim 2, wherein the neutralizing agent calcium bicarbonate has a mole fraction concentration of 0.0177.

5. A device suitable for the xylose hydrolysate neutralization method of claim 1, which comprises a neutralizer preparation tank, a neutralizer conveying device, a hydrolysate neutralization tank and a precipitate collecting device, and is characterized in that a neutralizer stirrer is arranged in a cylinder body of the neutralizer preparation tank, a neutralizer conveying pump and a conveying pipeline are connected below the cylinder body, the tail end of the conveying pipeline is connected with a neutralizer nozzle, the neutralizer nozzle is immersed below the liquid level in the hydrolysate neutralization tank main body, a neutralization tank stirrer is arranged in the hydrolysate neutralization tank main body, the neutralizer nozzle is positioned on the upper part of a topmost paddle of the neutralizer stirrer, a temperature control jacket is arranged on the outer wall of the hydrolysate neutralization tank main body, a thermometer and a pH meter extend into the hydrolysate neutralization tank main body, a calcium sulfate precipitate discharge port and a neutralized liquid discharge port are arranged at the bottom end of the hydrolysate neutralization tank main body, a precipitate discharge port is provided with a precipitate discharge valve, and the precipitate discharge valve is connected, an ocular lens is arranged above the calcium sulfate precipitation collecting device, and a precipitation discharge port is arranged below the calcium sulfate precipitation collecting device.

6. The apparatus for the xylose hydrolysate neutralization process according to claim 4, wherein the neutralizer transfer pump is selected from the group consisting of high head low flow centrifugal pumps and plunger pumps.

7. The apparatus for the xylose hydrolysate neutralization process according to claim 4, wherein the neutralizer nozzle comprises but is not limited to fan nozzles and spiral nozzles.

8. The apparatus according to claim 4, wherein the neutralization tank agitator comprises but is not limited to a propeller, straight blade, flap blade, frame, ribbon agitator.

9. The apparatus for the neutralization of a xylose hydrolysate according to claim 4, wherein the bottom end of the nozzle of the neutralizer in the neutralization tank is 5-20cm away from the upper edge of the paddle of the stirrer.

10. The apparatus for the neutralization of a xylose hydrolysate of claim 4, wherein the neutralization tank agitator consists of a bottom propeller type and a middle hinged propeller type.

Technical Field

The invention relates to the technical field of xylose production, in particular to a method and a device for neutralizing xylose hydrolysate.

Background

Xylose is a chemical with high added value and is widely applied to the fields of food, medicine and the like, and is mainly used for producing xylitol. Xylose is mainly obtained by hydrolyzing hemicellulose plant raw material containing pentosan by dilute acid, and the catalyst commonly used at present is dilute sulfuric acid with the mass fraction of 0.5-2%. China is a large country for producing and exporting xylose and xylitol. At present, the relatively mature xylose production process comprises the following steps: hydrolysis of dilute acid, neutralization, decolorization, purification, concentration, crystallization and finished product. The principle of the neutralization process is that calcium hydroxide or calcium carbonate and the like are added to neutralize sulfuric acid in the hydrolysate to generate water or carbon dioxide in a non-ionic state, calcium sulfate which is slightly soluble in water is formed at the same time, and most of sulfate radicals and calcium ions are separated out from the hydrolysate in the form of calcium sulfate precipitation. Thus, the ion number in the hydrolysate is greatly reduced, and the pressure of the subsequent ion exchange process is obviously reduced. Sulfate radicals in the hydrolysate leave the system in the form of calcium sulfate solids, but do not enter the sewage system in the form of ions, so that the treatment capacity of anaerobic reaction of the sewage treatment system is effectively increased. However, the neutralization step is difficult to handle because of the harsh operating conditions. If the operation is not proper, the number of sulfate ions in the hydrolysate cannot be reduced, new impurities such as calcium ions can be introduced, or side reaction of xylose in the hydrolysate is caused, so that the yield and the quality of the product are influenced. This is contrary to the set purpose of the process. Many manufacturers have to forego this step without having the knowledge of such techniques. Thereby obviously increasing the working pressure and the economic cost of the ion exchange process, simultaneously, a large amount of sulfate radicals enter the sewage treatment system in the ion exchange process to influence the treatment capacity of the anaerobic fermentation process, increase the sewage treatment cost, and even increase the sewage treatment costCausing the problems that the effluent does not reach the standard and the like. Xylose as a reducing monosaccharide is unstable in an alkaline environment and is easy to isomerize and decompose, and the xylose also has side reaction caused by Maillard reaction with ammonium nitrogen substances, so that the xylose yield is reduced. The use of dilute hydrochloric acid hydrolysis to prepare xylose, followed by neutralization with dilute sodium hydroxide solution, is reported, and chinese patent CN 201610843912.4 discloses a xylose production process, which introduces the use of 0.2-0.2% dilute hydrochloric acid low-temperature hydrolysis, followed by neutralization with sodium hydroxide. At present, the hydrochloric acid corrosion resistance and the abrasion resistance of the xylose hydrolysis reactor are not mature. The hydroxide ion concentration of the dilute sodium hydroxide with the same molar concentration is higher than that of calcium carbonate and calcium bicarbonate by more than 2 orders of magnitude, so that the local alkalinity of hydrolysate in the neutralization process is extremely high, the xylose loss is caused, and the side reaction is aggravated. Therefore, proper neutralizer is selected, optimal process parameters are selected, local overbasing in the reaction process is avoided, and free Ca is reduced to the maximum extent²⁺、SO₄ ^2-the solubility is the key to the xylose hydrolysate neutralization process.

According to the law of conservation of mass, the mass of a neutralizing agent required to be consumed in acid-base neutralization reaction is the same, and compared with calcium hydroxide, calcium carbonate and calcium bicarbonate with the same molar concentration, the calcium bicarbonate has the highest solubility and the lowest alkalinity, the calcium hydroxide and the calcium carbonate belong to insoluble substances and enter hydrolysate in the form of suspension, the mass transfer and heat transfer rate in the reaction process is low, and the alkalinity of a reaction area is extremely high. The normal temperature solubility of the calcium bicarbonate reaches 16g/100g water, so that chemical reaction can be performed in the form of a true solution, and mass transfer and heat transfer resistance can be greatly reduced by matching a reasonable stirring device, and the generation of a local over-high alkalinity area is avoided.

Disclosure of Invention

the invention aims to provide a method and a device for neutralizing xylose hydrolysate, which can control the temperature, control the pH value of the hydrolysate and realize high-efficiency mixing of the xylose hydrolysate.

The invention realizes the aim through the following technical scheme: a method for neutralizing xylose hydrolysate comprises the following specific operation steps:

(1) Preparation of neutralizing agent

Adding calcium bicarbonate and water with specified mass into the neutralizer preparation tank, and starting a stirrer to mix uniformly for later use.

(2) Adjusting the pH value:

After hydrolysis-solid-liquid separation, the xylose hydrolysate enters a hydrolysate neutralization tank through a hydrolysate feeding pipe, the liquid level is controlled to be 10-20cm below the upper edge of the hydrolysate neutralization tank, a neutralizer nozzle 4 is ensured to be completely immersed in the liquid level, a neutralization tank stirrer 6 is started, a neutralizer is introduced under the normal temperature condition, the adding speed of the neutralizer is controlled to be 10-300L/min, the temperature of the hydrolysate is not more than 80 ℃, the pH range is accurately controlled to be pH3.5-5.0, and the neutralizer is stopped to be added after the specified value is reached;

(3) heat preservation and crystal growth: continuing stirring until no gas is generated, simultaneously opening a temperature control jacket, accurately controlling the temperature of crystal growing at 75-85 ℃, stopping stirring, starting standing for crystal growing for 20-40min, and waiting for the calcium sulfate crystals to be completely precipitated;

(4) unloading: after the calcium sulfate crystals are completely precipitated, discharging the feed liquid through a neutralizing liquid discharge port 11, observing the precipitation quantity in the calcium sulfate precipitation device through an ocular lens, closing a precipitation discharge valve under the condition that the precipitation device is fully accumulated, opening the precipitation discharge valve to empty the precipitation device, then closing the precipitation discharge valve and opening the precipitation discharge valve.

The neutralizer is calcium bicarbonate.

The preparation concentration of the neutralizer calcium bicarbonate is 0.005-0.018 (mole fraction), and the most preferable concentration is 0.0177 (mole fraction) and the reduced mass fraction is 14.0%.

A device suitable for a xylose hydrolysate neutralizing method comprises a neutralizer preparation tank, a neutralizer conveying device, a hydrolysate neutralizing tank and a precipitate collecting device. The neutralizing agent preparation tank is characterized in that a neutralizing agent stirrer is installed in a cylinder body of the neutralizing agent preparation tank, a neutralizing agent delivery pump and a delivery pipeline are connected to the lower portion of the cylinder body, the tail end of the delivery pipeline is connected with a neutralizing agent nozzle, the neutralizing agent nozzle is immersed below the liquid level in a hydrolysate neutralization tank main body, a neutralizing tank stirrer is arranged inside the hydrolysate neutralization tank main body, the neutralizing agent nozzle is located at the upper portion of the topmost paddle of the neutralizing tank stirrer, the distance between the two nearest ends is 5-20cm, and the purpose is to achieve mixing of the neutralizing agent in the hydrolysate to the maximum degree and avoid the generation. The outer wall of the hydrolysate neutralization tank main body is provided with a temperature control jacket, a thermometer and a pH meter stretch into the hydrolysate neutralization tank main body, the bottom end of the hydrolysate neutralization tank main body is provided with a calcium sulfate precipitation discharge port and a neutralization solution discharge port, the precipitation discharge port is provided with a precipitation discharge valve, the precipitation discharge valve is connected with a calcium sulfate precipitation collecting device, an eyepiece is arranged above the calcium sulfate precipitation collecting device, and a precipitation discharge port is arranged below the calcium sulfate precipitation collecting device.

The neutralizer preparation tank is used for preparing mixed slurry or solution of the neutralizer and water.

The neutralizer delivery pump employs pumps including, but not limited to, high head low flow centrifugal pumps and plunger pumps.

the neutralizer delivery pump is a high-lift low-flow pump.

The neutralizer nozzle includes, but is not limited to, a fan nozzle and a spiral nozzle.

the neutralizer nozzle is a fan-shaped nozzle.

The neutralization tank agitator includes, but is not limited to, a propeller, straight blade, flap blade, frame, ribbon agitator.

The neutralizing tank stirrer consists of a propeller type at the bottom end and a hinge type at the middle part.

The distance between the bottom end of the neutralizing agent nozzle in the neutralizing tank and the upper edge of the folding blade paddle of the stirrer is 5-20 cm.

And support legs are arranged on the outer side of the lower end of the hydrolysate neutralization tank main body.

The installation position of the device is the position after the hydrolysis process and before the active carbon decoloration process in the whole xylose production process. Namely, the whole process comprises the following steps: hydrolysis, solid-liquid separation, neutralization, activated carbon decoloration, separation, purification, refining, concentration, crystallization, centrifugal separation and xylose pure product.

The invention is only suitable for the xylose production process using sulfuric acid as a catalyst, and is not suitable for hydrochloric acid and the like and Ca²⁺A process for producing an acid catalyst which does not form a precipitate.

The invention has the outstanding advantages that:

1. the feeding amount of the neutralizing agent can be determined by accurately controlling the pH of the material, so that the end point of the neutralization reaction can be controlled.

2. The calcium sulfate dissolving degree in the feed liquid can be minimized by controlling the temperature of the feed liquid, the maximum calcium sulfate precipitation amount is realized, and the load is reduced for the downstream separation and purification process.

3. the rapid dispersion of the neutralizer can be better realized by the design of the nozzle directly immersed in the hydrolysate and the matching of the stirrer, the generation of an alkali passing area is avoided, the occurrence of side reactions is reduced, and the loss of xylose is reduced.

4. the method has the advantages of simple operation, low cost, good mixing effect, strictly controllable process key indexes, accurate temperature control of reaction materials, accurate pH control of reaction end points, ideal mixing effect and high efficiency.

Drawings

FIG. 1 is a schematic diagram of the neutralizer formulation tank of the present invention.

FIG. 2 is a schematic structural view of a neutralization tank and a precipitate collecting device of the xylose hydrolysate neutralizing device according to the present invention.

Labeled as: the device comprises a neutralizer preparation tank barrel 1, a neutralizer stirrer 2, a neutralizer delivery pump 3, a neutralizer nozzle 4, a hydrolysate neutralization tank main body 5, a neutralization tank stirrer 6, a temperature control jacket 7, a thermometer 8, a pH meter 9, a precipitation discharge port 10, a neutralization liquid discharge port 11, a calcium sulfate precipitation collecting device 12, a precipitation discharge valve 13, an eyepiece 14, a precipitation discharge port 15, support legs 16, a hydrolysate feed pipe 17, a hydrolysate feed valve 18, a temperature control jacket heat source inlet 19 and a temperature control jacket heat source outlet 20.

Detailed Description

The technical solution of the present invention is further explained with reference to the drawings and the embodiments.