CN105624022A - Dry-method ozone pretreatment pretreater capable of increasing straw enzymolysis saccharification ratio and method - Google Patents

Abstract

The invention relates to a dry-method ozone pretreatment pretreater capable of increasing the straw enzymolysis saccharification ratio. The dry-method ozone pretreatment pretreater comprises a vertically arranged pretreater body, a feed hopper located on the top of the pretreater body and a discharge port formed in the bottom of the pretreater body; the feed hopper is located in the center of the pretrater top, and a diffuser is arranged under the portion beside the feed hopper in the direction perpendicular to the pretreater body; the diffuser is shaped like a circular conical surface, the vertex of the circular conical surface vertically upwards points to the center of the feed hopper, and rod-like protrusions which are perpendicular to the circular conical surface bus direction are distributed on the circular conical surface in a staggered mode; a plurality of sieve plates perpendicular to the direction of the pretreater body are arranged in the middle of the pretreater body; the sieve plates are each shaped like a mesh, and the rod-like protrusions with different heights are evenly distributed on the sieve plates and are perpendicular to the surfaces of the sieve plates. The dry-method ozone pretreatment pretreater facilitates pretreatment of semi-continuous, automatic and intelligent operation; lignin of straw subjected to ozone treatment is removed, the biodegradation rate is obviously increased, sundry bacteria and pests are killed, the storage property and fermenting property of the product are improved.

Description

A kind of dry method ozone pre-treatment pre-treatment tower and method improving stalk enzymatic saccharification rate

Technical field

The present invention relates to comprehensive utilization of crop straw resources technical field, especially relate to a kind of method of stalk dry method ozone pre-treatment tower and the dry method ozone pretreated straw based on this pre-treatment tower.

Background technology

China's agricultural straw resource enriches, but about has the stalk of 30% not to be utilized effectively. In vast Rural areas, crop straw burning is still the processing mode of main flow, and this not only causes the serious waste of stalk resource, also creates serious atmospheric pollution. Except extensive, the low value-added Land use systems such as traditional straw-returning, straw silage, straw biological refining becomes the straw utilization mode extremely having prospect gradually, is subject in recent years paying close attention to more and more widely.

So-called straw biological refining, is namely made stalk hydrolysis become small-molecule substance by biological method (microorganism, enzyme), then stalk hydrolyzate is converted into by fermentation engineering the technology of product. Biorefinery is the important foundation of biomass resource utilization, but there is bottleneck due to part gordian technique, causes the commercial application of biorefinery technology in straw utilization field to be restricted. Except except the biological treatment means (microbial preparation, zymin, biological respinse condition etc.) needed for biorefinery technology itself, cost is higher, the major technology bottleneck of straw biological refining is mainly that straw biological degradation efficiency is low, and the microtexture of this and stalk has close relationship.

In order to destroy the microtexture barrier of stalk, improve the biological degradation efficiency of stalk, usually before biological degradation, stalk is taked pre-treatment. Preprocessing means can be divided into physics method, chemical method, physico-chemical processes and biological process according to effect principle. Physics method changes the constitutional featuress such as the granular size of stalk, fibre shape by physical action, does not usually produce hazardous and noxious substances, but process effect is also very limited, and energy consumption is higher. Chemical method mainly through chemical substances such as acid, alkali, strong oxidizer, organic solvents to stalk effect, usually physical straw structural modification is not only caused, also it is stalk composition generation chemical transformation, this makes pretreating effect remarkable, but the shortcoming that also existence generates objectionable impurities, reagent remains, reagent cost is high. Physico-chemical processes combines physical action and chemical action in treating processes, often relates to high-temperature and high-pressure conditions, and equipment requirements is higher. Biological process mainly utilizes the microorganism such as soft-rot bacterium, whiterot fungi that stalk is carried out corruption process, process sanitation and hygiene, less energy-consumption, but due to processing efficiency very low and impracticable.

Ozone is as a kind of strong oxidizer, it is possible to the lignin component in efficient exclusively degrading straw, simultaneously that the polysaccharide fraction impact in stalk is less, thus effectively improves straw biological degradation efficiency. But, in current preconditioning technique system (such as patent CN101121175A), the effect of ozone does not obtain enough attention. This is mainly manifested in: 1. ozone is only as a kind of auxiliary treatment condition, and its advantage is not not fully exerted; 2. ozone mechanism carries out under liquid condition, and consumption water, blowdown are serious. Correspondingly, it is only suitable for liquid process (such as patent CN202576407U) for the pretreated equipment of ozone at present, thus lacks and be applicable under solid conditions the pretreated equipment of stalk ozone.

Summary of the invention

For the problems referred to above that prior art exists, the applicant provides a kind of the dry method ozone pre-treatment tower and the method that improve stalk enzymatic saccharification rate. Dry method ozone pre-treatment tower of the present invention is conducive to that pre-treatment is semicontinuous, automatization, intelligent operation; Straw lignin through ozonize is removed, and biological degradation rate significantly improves, miscellaneous bacteria and insect are killed, it is to increase the storge quality of product and leavening property.

The technical scheme of the present invention is as follows:

Improve a dry method ozone pre-treatment tower for stalk enzymatic saccharification rate, comprise the tower body of vertically setting, and be positioned at the hopper at tower body top and be positioned at the discharge port bottom tower body;

Described hopper is positioned at tower top central position, is perpendicular to tower body direction and arranges decollator immediately below described hopper side; Described decollator is cone surface, and hopper center is pointed on the summit of described cone surface straight up, described cone surface is interspersed and is perpendicular to the bar-shaped projection of cone surface generatrix direction;

Some sieve plates being perpendicular to tower body direction are set in the middle part of tower body; Described sieve plate is netted, it is perpendicular to the bar-shaped projection that floor lever of sieve tray is uniformly distributed different heights, the direction that the height of described projection radiates from inside to outside along floor lever of sieve tray mid point reduces gradually so that all protruding apex central points are positioned on same sphere just;

Described discharge port is funnel-form; Evenly arranging inlet mouth around described discharge port on tower body sidewall, described inlet mouth connects taking pipeline and gathers as a total inlet mouth.

The tower body on described hopper side arranges venting port.

The support being used for support tower body is set bottom described tower body.

The cone surface bus of described decollator and vertical direction angular range are 30 �㡫50 ��.

The quantity basis pre-treatment tower actual capacity of described sieve plate is determined, it is ensured that the height of the stalk bed of material on every layer of sieve plate is no more than 50cm;

Netted aperture 20��80 order of described sieve plate, selects according to the particle diameter of stalk particle.

Stalk is first through pulverizing, and powder particle diameter is 80��300 orders; It is adjusted to water ratio not higher than 75%, is added in described pre-treatment tower by hopper, make streams of ozone by inlet mouth flowing from bottom to top in tower body, mix with the stalk after pulverizing, thus reach the effect of pretreated straw;

Described stalk is agricultural crop straw and energy crop.

It is 45%��60% that stalk after pulverizing is adjusted to water ratio.

Neutralizing treatment is carried out by the following method through pretreated stalk particle:

Quantitatively taking pretreated stalk particle sample, add water and be mixed with the mixed solution of 10wt%, 30 DEG C of constant temperature place 30min, measure with pH meter and record pH; With reference to the total acid content of the method mensuration sample of GBT12456-2008, and the mmole number in hydrogen ion contained by every gram of sample;

Then calculate the corresponding calcium hydroxide addition needed according to total acid content, in pretreated straw, add calcium hydroxide according to this addition, and fully stir;

Finally again measure straw powder pH with aforementioned method, it is determined that neutralization; If pretreated straw pH does not reach 5, then add calcium hydroxide.

Described comprise maize straw, wheat stalk, rice straw, broomcorn straw, bagasse, reed, withy millet, awns grass; Stalk is after pulverizing and regulate water content, and stalk material is in the solid porous state of good air permeability.

Cylindrical bump on this pre-treatment tower decollator and sieve plate, its quantity, arrangement mode should be determined according to pre-treatment tower actual design, but to be met above-mentioned design and describe.

The technique effect that the present invention is useful is:

Showing after deliberation, when material is piled up in a reservoir, the bed of material porosity at wall place is relatively big, and the porosity of bed of material inside is less. When gas stream is through the bed of material, the air-flow that the air-flow that the material near wall touches arrives far more than bed of material interior contact. In addition, the excessively thick bed of material due to internal pressure relatively big, porosity reduces, and is also unfavorable for passing through of air-flow. Based on above-mentioned conclusion, this pre-treatment Deethanizer design thinking mainly increases the bed of material and wall face contact area, reduces bed thickness simultaneously as far as possible. Decollator in this pre-treatment tower can make material fall from the position close to wall, on sieve plate formed bed of material edge height, center low, be conducive to uniform stream to pass stockpile. Cylindrical bump on decollator plays the effect of broken material caking in material dropping process, makes the material flowing through decollator be dispersed into powdery. The design of multiple sieve plate, prevents solid accumulation excessively thick, owing to material deadweight causes bottom bed of material permeability to decline. Cylindrical protrusions on sieve plate, considerably increases the bed of material and the contact area in wall face, is conducive to streams of ozone to permeate.

The present invention can the exclusively xylogen in degrading straw, effectively prevent stalk polysaccharide fraction from losing simultaneously, thus significantly improve stalk enzymatic saccharification efficiency. Preprocessing process carries out under the solid conditions of normal temperature and pressure, low for equipment requirements, high-efficiency water-saving, except being applicable to follow-up liquid state fermentation, is also applicable to make the solid state fermentation such as biological fodder, bio-feritlizer field. Ozone pre-treatment can also play sterilization and disinsection effect, is conducive to preventing the living contaminants in pretreated straw fermenting process, it is to increase the storage stability of pretreated straw. In conjunction with the dry method ozone pre-treatment tower of present method, make the dispersion accumulation of material, gas-solid reaction, discharging backfill is disposable completes, it is possible to realize semicontinuous, automatization, intelligent operation. Stalk material is solid state when processing, and water-saving and emission-reducing, eliminates follow-up solid-liquid separation, drying cost. The invention solves agricultural crop straw xylogen, a difficult problem that Mierocrystalline cellulose, hemicellulose are difficult to degraded.

Accompanying drawing explanation

Fig. 1 is the structural representation of pre-treatment tower of the present invention;

In figure: 1-hopper; 2-venting port; The bar-shaped projection of 3-decollator; 4-decollator; The bar-shaped projection of 5-sieve plate; 6-sieve plate; 7-sieve plate rotating shaft; 8-inlet mouth; The total inlet mouth of 9-; 10-discharge port; 11-support;

Fig. 2 is sieve plate top view;

In figure: the bar-shaped projection of 5-sieve plate; 7-sieve plate rotating shaft;

Fig. 3 is sieve plate fish-eye view;

In figure: 7-sieve plate rotating shaft; 14-sieve plate framework; 15-screen cloth;

Fig. 4 is the structural representation of pretreatment unit preferred embodiment of the present invention;

In figure: 12-airway; 13-spout.

Embodiment

Below in conjunction with accompanying drawing, the present invention is specifically described.

As shown in FIG. 1 to 3, this pre-treatment tower main body is tower type container (length-to-diameter ratio >=3). Pre-treatment top of tower center is provided with hopper 1, and hopper 1 side is provided with venting port 2. Being provided with decollator 4 below hopper 1, decollator 4 is in cone surface, and hopper 1 center is pointed at its tip straight up. Decollator 4 cone surface interlocks and is dispersed with the decollator being perpendicular to cone surface generatrix direction bar-shaped protruding 3. The spacing such as pre-treatment tower is inner are provided with some sieve plates 6, and sieve plate 6 is dispersed with the sieve plate being perpendicular to plate face bar-shaped protruding 5, and the height of protruding 5 increases from outside to inside gradually along sieve plate radial direction. Sieve plate 6 can be put cylinder by hydraulic pressure and drive, and is rotated down to vertical state around its rotating shaft 7, in order to downward discharging. Pre-treatment tower bottom is discharge port 10. Above discharge port 10, wall face evenly arranges three inlet mouths 8. When this pre-treatment tower comes into operation, it should access possesses in the pipeline that ozone occurs, import ozone concn is monitored, outlet ozone concn is monitored and tail gas is cleared up, and different according to embodiment, equipment and mode of connection in pipeline can adjust according to actual needs. The pipeline supporting to this pre-treatment tower and equipment thereof, field engineering are the mature technology scheme in the relevant field of ozone application, by this field those of ordinary skill is familiar with, and are easy to obtain.

Hopper 1 in pre-treatment tower, venting port 2, total inlet mouth 9, discharge port 10 can arrange manual valve or pneumavalve. When pre-treatment tower works, the valve of hopper 1 and discharge port 10 should be closed, and prevents ozone from leaking. The valve of venting port 2 and inlet mouth 8 is in order to for subsequent use. Sieve plate 6 can allow its rotating shaft 7 be rotated down 90 ��, in order to the material unloaded on sieve plate 6. The rotary motion of sieve plate 6 is suitable for adopting hydraulic pressure pendulum cylinder to drive. Pre-treatment tower wall can arrange viewing window and set lights near each layer sieve plate 6 place, observes pre-treatment tower inner case to facilitate. Sieve plate 6 is formed primarily of skeleton construction and screen cloth, and skeleton construction and rotating shaft formation are rigidly connected, can with axis of rotation, and skeleton construction upper surface is dispersed with sieve plate as shown in the figure bar-shaped protruding 5. Screen cloth is covered in the frame upper surface of sieve plate 6, and cylindrical bump is then through screen cloth, and screen cloth aperture 20��80 order, selects according to raw material particle size.

Based on above-mentioned pre-treatment tower, the present invention provides a kind of method of dry method ozone pretreated straw. By stalk first through coarse reduction (order number >=10 order), then it is broken to 80 order��300 orders through fine powder. Add a certain amount of clear water to stalk, be adjusted to water ratio not higher than 75%, it is preferable that for making its water ratio reach 45%��60%. Fully stirring straw powder, then at room temperature (25 DEG C) sealing and standing 8h, make moisture enter stalk micropore, stalk particle surface hydration is even.

The straw powder reaching requirement water ratio being added in this dry method ozone pre-treatment tower, add-on is determined according to the volume of powder submergence. Under normal circumstances, stalk material submergence volume should be no more than the 2/3 of pre-treatment tower cumulative volume. Start ozonizer, lead to into streams of ozone to this pre-treatment tower. Leading to the ozone concn into tower body and should be able to reach 30%��70%, airshed should be able to reach 2��8L/min, and concrete Selecting parameter should coordinate the best operating mode of ozonizer. When pre-treatment tower works, the ozone concn of air-flow discharged by monitoring pre-treatment tower, and when it reaches the 1/2 of input ozone concn, the efficiency that material absorbs ozone is very low, and pre-treatment completes, it is necessary to discharging, and recharges.

In the present invention, the stalk through pulverizing is deposited on the sieve plate 6 of pre-treatment tower to form material bed. Streams of ozone is led to into by pre-treatment tower bottom and is upwards moved, and enters material bed through sieve plate 6, reacts with stalk particle. Xylogen in stalk has high cloud density, it is easy to ozone generation cationoid reaction, and be degraded to small-molecule substance. And Mierocrystalline cellulose, hemicellulose in stalk is insensitive to the oxidation of ozone, loses very low. Therefore, ozone pre-treatment can the xylogen in degrading straw in specific manner, retain the natural structure of polysaccharide in stalk simultaneously. Xylogen can greatly improve the degradation efficiency of stalk as anti-degraded barrier the most important in stalk cell wall, the disintegration of its structure. And common acid treatment, alkaline purification, while lignin degrading, also there is hydrolysis and go bad in polysaccharide wherein, and this not only causes the loss of stalk useful component, also easily generates the inhibition being unfavorable for follow-up saccharification, fermentation.

Through the pretreated stalk material of ozone, owing to wherein component is acid after being degraded by ozone oxidation, consequently, it is possible to have influence on the follow-up enzymolysis to stalk or zymotechnique. According to this problem, a kind of method of Pre process stalk acidity when the present invention provides dry method. Can according to the specific requirement of pretreated straw subsequent technique selects whether adopt the method. Concrete grammar is as follows: the first pH of sampling and measuring pretreated straw powder and total acid, by quantitatively taking sample, add water be mixed with 10% mixed solution, 30 DEG C of constant temperature 30min, measure with pH meter and record pH. With reference to the total acid content of the method mensuration sample of GBT12456-2008, and in the mmole number (mmol) of hydrogen ion contained by unit mass (g) sample. Then calculate the corresponding calcium hydroxide addition needed according to total acid content, in pretreated straw, add calcium hydroxide according to this addition, and fully stir. Finally again measure straw powder pH with aforementioned method, it is determined that neutralization. If pretreated straw pH does not reach 5, then add appropriate calcium hydroxide.

Described stalk is various main agricultural crop straw and energy crop, comprises maize straw, wheat stalk, rice straw, broomcorn straw, bagasse, reed, withy millet, awns grass.

Embodiment 1: stalk dry method ozone pre-treatment tower batch operation scheme

By necessarily requirement crushing straw, adjustment straw powder water ratio (specifically can reference example 3,4,5). Pre-treatment tower original state: discharge port 10 is closed, bottom sieve plate 6 is in horizontality, is called " closedown ". Hopper 1 is opened, and middle level sieve plate 6 and upper strata sieve plate 6 are in vertical state, are called " opening ". Feeding in raw material to pre-treatment tower, the bed of material on low layer sieve plate 6 reaches after specifying height, then closes middle level sieve plate 6, continues to be dosed to and specifies height, analogizes with this, completes the reinforced of upper strata sieve plate 6. Reinforced complete, close hopper 1. Lead to the streams of ozone into prescribed concentration and flow, monitor the ozone concn that pre-treatment tower is discharged simultaneously. When the ozone concn that pre-treatment tower is discharged reaches the half of input ozone concn, pre-treatment degree reaches requirement. Stopping leading to into ozone to pre-treatment tower, pre-treatment tower enters discharging state: discharge port 10 is opened, and successively opens bottom, middle level and upper strata sieve plate 6, discharging successively. So far, complete a batch operation circulation.

Embodiment 2: stalk dry method ozone pre-treatment tower semi continuous operation scheme

By necessarily requirement crushing straw, adjustment straw powder water ratio (specifically can reference example 3,4,5). Pre-treatment tower original state and reinforced operation are with embodiment 1. Lead to the streams of ozone into prescribed concentration and flow, monitor the ozone concn that pre-treatment tower is discharged simultaneously. When pre-treatment tower discharge ozone concn is not zero, suspends and lead to into ozone, open discharge port 10 and bottom sieve plate 6, draw off bottom sieve plate 6 material. Close bottom sieve plate 6 and discharge port 10 again, open middle level sieve plate 6 simultaneously, make original position be put in bottom sieve plate 6 in the material of middle level sieve plate 6. Analogize with this, original position is put in middle level sieve plate 6 in the material of upper strata sieve plate 6, opens hopper 1 simultaneously, add new material to upper strata sieve plate 6. Close hopper 1 again, and again lead to the streams of ozone into prescribed concentration and flow, monitor the ozone concn that pre-treatment tower is discharged simultaneously. So far, the flow process that twice beginning in front and back is led to pre-treatment tower between the operation of ozone is a semi continuous operation cycle. This operation scheme can realize lasting operation, and single discharging charging is rapid, ozone utilization rate height, and process is evenly.

Embodiment 3: maize straw dry method ozone pretreating scheme 1

In the program, the operation of pre-treatment tower adopts intermittent type. 20 order sieves are crossed in the first coarse reduction of maize straw, then sieve through fine powder broken mistake 300 order. The water ratio of straw powder is adjusted to 60%. At ozone concn 60mg/L, process when airshed 5L/min. The Lignin degradation rate of final stalk reaches 75%, and cellulase hydrolysis rate reaches 80% (untreated stalk is 10%).

Embodiment 4: maize straw dry method ozone pretreating scheme 2

In the program, the operation of pre-treatment tower adopts semi continuous. 20 order sieves are crossed in the first coarse reduction of maize straw, then sieve through fine powder broken mistake 150 order. The water ratio of straw powder is adjusted to 45%. At ozone concn 60mg/L, process when airshed 5L/min. The Lignin degradation rate of final stalk reaches 66%, and cellulose degradation rate reaches 70% (untreated stalk is 8%).

Embodiment 5: maize straw dry method ozone pretreating scheme 3

In the program, the operation of pre-treatment tower adopts intermittent type. Maize straw can directly be crushed to 80 order sieves, and straw powder water ratio is adjusted to 50%. At ozone concn 70mg/L, process when airshed 8L/min. The Lignin degradation rate of final straw powder reaches 52%, and cellulose degradation rate reaches 60% (untreated stalk is 6%). Pretreating raw material is according in method in patent and acid to pH=5, through milk-acid bacteria and cellulase mixed solid fermentation 10d, the viable count in fermented product reaches 1 �� 10⁹Cfu, by contrast, not pretreated stalk directly carries out above-mentioned fermentation, and viable count only can reach 1 �� 10⁶cfu��

Preferred embodiment:

As shown in Figure 4, sieve plate rotating shaft 7 inside edge can arrange airway 12, and connects pulse of compressed air. Airway 12 the spacing spout 13 such as is provided with towards sieve plate 6 plane side, and the gas in airway 12 is sprayed from spout 13. When sieve plate 6 is horizontality, when the stalk particle on sieve plate 6 is carried out pre-treatment by ozone, high velocity air can make, bottom the stalk bed of material, disturbance occurs, and forms empty sunken passage, facilitates pretreated carrying out. When sieve plate 6 discharging, sieve plate 6 rotates as vertical state, and the material on sieve plate 6 falls under gravity. Thering is provided high pressure air pulse to sieve plate 6, the high velocity air of airway 12 side spout 13 ejection, clashes into sieve plate bar-shaped protruding 5 at sieve plate upper surface and forms eddy current, is conducive to removing material remaining on sieve plate 6, thus the permeability making sieve plate 6 mesh is recovered. When material relatively thin (> 150 order), water ratio higher (> 50%) time, material relatively easily easily sticks on sieve plate 6, and this design is then very necessary.

Claims (10)

1. improve a dry method ozone pre-treatment tower for stalk enzymatic saccharification rate, comprise the tower body of vertically setting, and be positioned at the hopper at tower body top and be positioned at the discharge port bottom tower body; It is characterized in that:

Described hopper is positioned at tower top central position, is perpendicular to tower body direction and arranges decollator immediately below described hopper side; Described decollator is cone surface, and hopper center is pointed on the summit of described cone surface straight up, described cone surface is interspersed and is perpendicular to the bar-shaped projection of cone surface generatrix direction;

Some sieve plates being perpendicular to tower body direction are set in the middle part of tower body; Described sieve plate is netted, it is perpendicular to the bar-shaped projection that floor lever of sieve tray is uniformly distributed different heights, the direction that the height of described projection radiates from inside to outside along floor lever of sieve tray mid point reduces gradually so that all protruding apex central points are positioned on same sphere just;

Described discharge port is funnel-form; Evenly arranging inlet mouth around described discharge port on tower body sidewall, described inlet mouth connects taking pipeline and gathers as a total inlet mouth.

2. pre-treatment tower according to claim 1, it is characterised in that on the tower body on described hopper side, venting port is set.

3. pre-treatment tower according to claim 1, it is characterised in that the support being used for support tower body is set bottom described tower body.

4. pre-treatment tower according to claim 1, it is characterised in that the cone surface bus of described decollator and vertical direction angular range are 30 �㡫50 ��.

5. pre-treatment tower according to claim 1, it is characterised in that the quantity basis pre-treatment tower actual capacity of described sieve plate is determined, it is ensured that the height of the stalk bed of material on every layer of sieve plate is no more than 50cm.

6. pre-treatment tower according to claim 1, it is characterised in that netted aperture 20��80 order of described sieve plate, selects according to the particle diameter of stalk particle.

7. one kind adopts the method for pre-treatment tower pretreated straw according to claim 1, it is characterised in that: stalk is first through pulverizing, and powder particle diameter is 80��300 orders; It is adjusted to water ratio not higher than 75%, is added in described pre-treatment tower by hopper, make streams of ozone by inlet mouth flowing from bottom to top in tower body, mix with the stalk after pulverizing, thus reach the effect of pretreated straw.

8. method according to claim 7, it is characterised in that: described stalk is agricultural crop straw and energy crop.

9. method according to claim 7, it is characterised in that: it is 45%��60% that the stalk after pulverizing is adjusted to water ratio.

10. method according to claim 7, it is characterised in that: carry out neutralizing treatment by the following method through pretreated stalk particle:

Quantitatively taking pretreated stalk particle sample, add water and be mixed with the mixed solution of 10wt%, 30 DEG C of constant temperature place 30min, measure with pH meter and record pH; With reference to the total acid content of the method mensuration sample of GBT12456-2008, and the mmole number in hydrogen ion contained by every gram of sample;

Then calculate the corresponding calcium hydroxide addition needed according to total acid content, in pretreated straw, add calcium hydroxide according to this addition, and fully stir;

Finally again measure straw powder pH with aforementioned method, it is determined that neutralization; If pretreated straw pH does not reach 5, then add calcium hydroxide.