CN1188829A - Digesting and screening technology method for rice and wheat straw pulping - Google Patents

Abstract

A digestion and screening process for pulping with rice or wheat straw include such technological steps as cutting the straw by proper size, removing impurities, immersing in water for softening, digesting at 90-150 deg.C for 2 hr, washing destroying the bind between fibres by means of fluffer, and sieving to obtain paper pulp. Its advantages include reducing alkali consumption from 11.55% to 6.5%, increasing output rate of pulp to 10.3%, shorting digestion time by 52 min, lowering pollution load by 535, and raising productivity.

Description

Digesting and screening technology method for rice and wheat straw pulping

The present invention relates to a kind of digesting and screening technology method for rice and wheat straw pulping, belong to the technical field of paper technology.

Generally in producing the cultural paper process, adopt needlebush sulfate bleached chemical oar, alkali charge (NaOH) total in digestion process is about 22%, straw, wheat straw is compared with needle timber, straw contains lignin 11/71%, wheat straw is 18.12%, and the lignin of needlebush all is about 29%, so the alkali charge of needlebush should be (11.71/29) * 22%=8.9%, if use straw to be raw material, it is soft loose, soup should soak into better than timber, more, so should not be higher than 7% (65% left and right sides whiteness) that just can obtain to bleach with its alkali charge, be used for the production whiteness at the general cultural paper below 70%, in middle-size and small-size paper mill with the alkaline sulfite method, use rice straw cooking paper pulp, total alkali charge straw is more than 11.5%, with wheat straw is about 16%, fiber separation point mainly due to straw pulp of rice and wheat all is higher than needle timber, timber reaches at 86% o'clock and just reaches the fiber separation point deviating from the lignin rate, and will reaching 92% in the lignin rate, the rice wheat just reaches burble point when above, at this moment since in the fibre structure of rice wheat straw the intrinsic lignin concentration of intercellular layer and cell corner all the ratio secondary wall respectively up to 1.45 times with 2.4 times, again owing to three microcells in the eucaryotic cell structure, its lignin removes (referring to subordinate list 1) with same speed simultaneously.

When the plain rate of total dehydration reaches 80%, it is 30% o'clock concentration that intercellular layer lignin concentration only is equivalent to that secondary wall leads in total delignification, and the lignin concentration of cell corner equates with secondary wall concentration in the raw material, unlike wood raw material, the intercellular layer lignin is to remove with the speed of being exceedingly fast than lignin before 50% in total delignification rate, thereby at straw fiber raw material, must delignification lead and reach the high Shi Caineng of pacing and make the wooden concentration of intercellular layer drop to the degree that can make fiber dispersion, this also is the main cause that rice wheat pulp yield can not improve.

Original in addition technical process be chaffcutter → goat's horn dedusting → give soak → boiling → pulp washing → jumping sieve → pulp washing → stock tank storage → CX sieves screening ...

From above-mentioned technological process and production practices, in order to reach the burble point of fiber, have to use high alkali charge, reach lower screening reject rate when sieving by jumping.

When boiling hardness is higher than 11.5 permanganate numbers (KMnO), the screening reject rate is higher than 1%, when hardness is higher than 12KMnO, almost there is half to be sifted out, at this moment can not ordinary production, because reaching before the fiber separation point, the hold its shape degree of attitude of rice wheat straw material is very high, make that (eyelet of sieve approximately is φ 6-8mm) can't pass through when slurry passed through to jump sieve, when screening, remained little, even the screening reject rate is also very high, at this moment can only increases alkali charge and improve boiling temperature (160 ℃) and time (1 hour) by CX, cause that fiber and hemicellulose all have a large amount of losses in the raw material, pulp yield is significantly reduced.

The objective of the invention is to provide a kind of straw ryegrass pulping digesting and screening technology method, it can overcome above-mentioned shortcoming, mainly jumping riddler's preface front, add a slight fiber and discongest equipment, generally not feed, just allow it pass through fluffer, destroy combining between its both fragile and obstinate fiber and the fiber by force, this improvement impels alkali charge significantly to reduce, reduce to below 6.5% by 11.5%, digestion time also reduces 53 minutes, and yield of bleached pulp improves 10.3%, just power consumption and bleachability have raising slightly, but use this technology that use cost is significantly reduced.

The object of the present invention is achieved like this:

A kind of digesting and screening technology method for rice and wheat straw pulping, its digesting and screening technology method for rice and wheat straw pulping is made up of the following step:

1. chaffcutter, goat's horn dedusting

Straw, wheat straw raw material blank are become certain specification, adopt the goat's horn dust collection method then, remove foreign material in the forage;

2., give soak, boiling, pulp washing

Forage after purifying is dipped in the water liquid, approximately 1-2 minute, make forage soft clean, place a container to carry out boiling then, temperature is 90-150 ℃, digestion time is 2 hours, at last slurries is cleaned.

3., discongest, jump sieve, screening

Make above-mentioned slurry by defiberizing machine, destroy obstinate combining between its fiber and the fiber, again through jumping sieve and screening, so just make paper pulp.

Straw wheat pulping and digesting screening technology method is as follows:

Chaffcutter → goat's horn dedusting → give soaks → and boiling → pulp washing → defiberizing machine → jumping sieve → CX sieves screening.

1, chaffcutter, goat's horn dedusting

Straw, wheat straw raw material blank are become certain specification, adopt the goat's horn dust collection method then, remove grass.Foreign material in the material;

2, give soak, boiling, pulp washing

Forage after purifying is dipped in the water liquid, approximately 1-2 minute, make forage soft clean, place a container to carry out boiling then, temperature is 90-150 ℃, digestion time is 2 hours, at last slurries is cleaned.

3, discongest, jump sieve, screening

Make slurry pass through defiberizing machine, it is done the time spent and destroys obstinate combining between fiber and the fiber by force, alkali charge is dropped to below 6.5% by 11.5%, digestion time can reduce 53 minutes, yield of bleached pulp improves 10.3%, owing to increased the equipment of discongesting, improves boiling basicity, using power consumption and bleachability slightly to improve, also is inappreciable (referring to table 2) for resulting cost.

Through jumping sieve and CX screening, just obtain paper pulp again.

As being example with 30,000 tons of annual product bleached pulps, annual economic benefit can reach 1628.7 ten thousand yuan.

Compared with prior art, digesting and screening technology method for rice and wheat straw pulping has following advantage:

1, alkali charge drops to below 6.5% by 11/5%;

2, digestion time reduces 53 minutes;

3, pulp yield increases 10.3%;

4, load decline 5/11.5 * 100 ≈ 43.5% is dyed in boiling, and the expense of polluting processing is also descended.

Embodiment 1, is raw material with the straw wheat straw, cuts into certain size, remove wherein foreign material with the goat's horn dust collection method again, be soaked in the water 2 minutes, make it become soft, be placed in the container boiling 2 hours, temperature reaches 90-150 ℃, in the time slurries are cleaned, through a defiberizing machine, fiber combining is destroyed by force, after jump sieve and screening, so obtain qualified paper pulp, its alkali charge is reduced to 6.5%.

Each film micro area delignification distribution table 1 sample pulp yield (%) of wheat straw fiber eucaryotic cell structure takes off each microcell of this quality rate lignin concentration (g/L) and takes off this quality rate (%)

S ML C S ML C raw material 100 0 0.17 0.41 0.57 00 01 88.2 31.0 0.13 0.33 0.45 30.2 29.2 30.12 63.0 64.1 0.10 0.23 0.33 63.1 65.3 62.33 60.0 72.9 0.07 0.20 0.27 74.3 70.3 71.24 59.9 81.3 0.06 0.13 0.17 80.6 82.2 83.8 is wherein: the S-secondary wall; The ML-intercellular layer; C-cell corner.

Technology 25m rotary spherical digester dress grass amount (over dry behind the division) kg that the old and new's digesting technoloy technology contrast table 2 original technologies are new

0: 30 intensification 0-0.55Mpa of 0: 30 little venting 0.3-0Mpa 0.05 intensification 0.4-0.6Mpa of 1: 30 intensification 0-0.3Mpa of 0: 30 little steam bleeding 0.3-0Mpa 0.05 insulation 0.4Mpa of 3,270 3270 dress alkali number NaOH (100%) 320 180 inferior sodium (100%NaOH meter kh 1: 2.8 1: 2.8 boiling curve idle period of 80 32 liquor ratios (minute), 0: 30 liter of wet 0-0.3mpa of 0: 45 0: 45 intensification 0-0.4Mpa be incubated at 0: 45 0: 15 0: 15 total cooking time of 0: 1 large steam bleeding of 0.55Mpa (minute) 210 157 boiling basicity (Kn value) 9-11 12-14

Claims (1)

1, a kind of digesting and screening technology method for rice and wheat straw pulping is characterized in that digesting and screening technology method for rice and wheat straw pulping is made up of the following step:

1. chaffcutter, goat's horn dedusting

Straw, wheat straw raw material blank are become certain specification, adopt the goat's horn dust collection method then, remove foreign material in the forage;

2., give soak, boiling, pulp washing

Forage after purifying is dipped in the water liquid, approximately 1-2 minute, make forage soft clean, place a container to carry out boiling then, temperature is 90-150 ℃, digestion time is 2 hours, at last slurries is cleaned.

3., discongest, jump sieve, screening

Make above-mentioned slurry by defiberizing machine, destroy obstinate combining between its fiber and the fiber, again through jumping sieve and screening, so just make paper pulp.