CN1980865A

CN1980865A - Procedure for dewatering of suspensions

Info

Publication number: CN1980865A
Application number: CNA2005800185276A
Authority: CN
Inventors: 阿尔内·林达尔
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-05-10
Filing date: 2005-05-08
Publication date: 2007-06-13
Also published as: WO2005108314A1; RU2006142558A; SE0401234D0; SE0401234L; JP2007536084A; SE527884C2

Abstract

This invention relates to a procedure concerning dewatering of suspensions, in particular, suspensions with a relatively low concentration of organic matter or having a dry solid content of less than 15 %. A distinguishing feature of this invention is that dewatering promoting agents are mixed simultaneously with the suspension as thickening occurs. Examples of materials that increases the concentration of organic matter are among others sawdust, synthetic materials that preferably consist of pulverous polyurethane, ground peat or alternatively ground bark. The weight proportion of the additives amounts to at least 5 weight% and preferably to at least 10 weight-% of the total weight of the organic matter. The simultaneous dewatering and mixing is performed with the aid of known dewatering mechanisms. An example of this is the water extracting screw. After the partial dewatering the material is transferred to a press for further dewatering to solid contents above 45 %.

Description

The dewatering of suspended substance

The present invention relates to a kind of suspended substance dewatering, especially have the suspended substance of low relatively organic concentration.Dehydration is used known dewatering unit, and when concentrating generation, suspended substance and those can increase the material of doing solids content to be mixed.

Background technology

From the viewpoint of economy, generally speaking the concentrated removal of machinery liquid is the method cheaper than evaporation concentration expense generally.Concentrate, or can realize by diverse ways the liquid portion dehydration that contains material.Low material concentration just means with solids content, dried solids content compares the liquid that will use separating centrifuge or drum filter to handle large volume usually.Therefore in decant formula separating centrifuge mud from purification of waste water factory concentrated usually, and obtain 20% to 30% solids content.In pulping and paper-making factory normally with the drum filter partial dehydration and obtain 7% to 20% dried solids content.A kind of drum filter of derivation is formed the mariages machine, suspended substance shifts between two annular distributions in this machine, in spissated process, can reach higher relatively dried solids content (＞40%) to paper pulp, yet when the mud from municipal wastewater purification plant is concentrated, be difficult to reach dried solids content above 30%.In order to obtain having used dissimilar pressing machinees than using the higher levels of dried solids concn of above-mentioned dewatering machine.Pressing machine that uses roller and the pressing machine that uses spiral are arranged, rely on press work usually.

The well-known fiber that adds helps except that anhydrating.Therefore in patent US4559143, disclose a kind of method, proved to unite and used macrofiber and polymkeric substance.Well-known in addition centrifugal before the adding liquid polymers be useful, the sludge suspension thing that for example in purification of waste water factory, has diluted.

Recommending to add sawdust and bark among the patent SE9704653-6 comes " damaging by pressure " cell, forms passage and " reinforcement " mud.

Described a kind of particle at Swedish patent 0200217-8 and obtained highly filled method by mechanical dehydration.By this method, the dried content levels in the mud surpasses 50%.Before raw material is sent to above-mentioned dewatering machine, one or more granular additives mix earlier with raw material, wherein the content of trickle raw material is by allowing them pass the pulp strainer (screen cloth) of diameter 2mm or the width of corresponding filter screen limits, and reaches 40 weight % of additive gross weight at least.

The defective of background technology

A defective of many devices is that they significantly compress material, and this can damage the part of material and mechanical means.With equipment is example, and high mechanical pressure can be damaged distribution, press felt and similar parts.The fracture that wearing and tearing that increase and crackle can cause above-mentioned distribution or felt, roll also can be damaged.Increase every kind of operating pressure in addition and all need more energy.In addition, use more that multipotency causes detrimentally affect to physical environment, because often the electric energy that uses produces by combustion of fossil fuels and similar substance, this can cause the discharging of carbon oxides.

In separating centrifuge,, surpass about 25% (once in a while) as the dried fruit solids content and will be difficult to empty raw material after concentrated from the mud of purification of waste water factory.Another defective of separating centrifuge is high investment cost and relative low treatment capacity.Helical pressure provides high relatively dried content levels, but a defective is arranged is exactly to have contained the raw material that will be concentrated in a large number in the water that is extruded for it.This is because pressing machine has and worn the big relatively hole or the wall of sieve aperture.The significant loss of the drum strainer of general type is minimum.In other words be exactly filtered solution be relative clean.Yet being it, an inherent defect of drum strainer can only provide low dried solids content.Even drum strainer has been replenished after the squeezing bucket, can not reach high dried solids content.

Summary of the invention

According to the present invention, need dehydrated suspended substance and a kind of granular solid matter (after this hereinafter being called auxiliary agent) to mix.Described auxiliary agent is made up of polymkeric substance and similar substance, as lower concentration or volumetric concentration much smaller than 1kg/dm ³Urethane.Urethane is that (chemical general formula is RO.CO.NH for the synthetics of urea acid esters ₂).Such ethyl ester is commonly referred to as urethanum, and obtains in this urethanum isolator that can use from utilize as usual refrigerator and refrigerator again.According to the present invention, can add regenerated cellulose (cellulose ethanoate silk, " WETTEX foam ") in addition, sawdust, starch and straw plant are as faint yellow alfa and straw.Even can add peat, the powder of bark and straw plant.According to preference of the present invention, if possible, by before filtering enrichment auxiliary agent molecule in the mode of separation (screening), auxiliary agent must be torn and be milled to relative little particle.The builder granule size of expectation preferably obtains by one-level or what screening.So known screening plant such as reciprocating gird, vibratory screening apparatus or so-called air trap can be used.

The weight ratio of auxiliary agent can change on a large scale at one, yet from the last viewpoint of economy, preferably possible minimum ratio.But in order to obtain effect, need at least 5% weight ratio, more preferably surpass 10% weight ratio.In some instances, concentrate the back and make fragment of brick, particle or bead are useful.At this, the method for using among the patent SE9904313-5 can be used.

The mixing that a basic feature with difference of the present invention is above-mentioned auxiliary agent occurs in a kind of comprehensive step, takes place simultaneously with concentrated.This is meant the concentrating of liquid of the substances content with relative lower concentration, for example mud.Purpose is that solid matter content is between 0.5%～15% along with the thickened solid material concentrates suspended substance.Mixing and spissated comprehensive step can realize by using known device.Therefore can use by turning effort separating liquid and solid belt carcass spiral dewater or centreless spiral dewater.In principle, in its envelope surface opening is arranged around the pipe of spiral, the outside of envelope surface or the inside can cover with plastic coated wire or steel.Another kind of in addition selectable combination is that dewatering unit is connected with central shaft with rotation slurry or pin.

According to prior art embodiments

Contain the fiber of suspension from the mud of paper mill biological treatment, this mud is transported to envelope surface to be had in the spiral dewater of diameter 0.2mm hole.At this, water is forced out by the hole of envelope surface.Cause and enter concentration and in concentration process, become 12.6% from 1.3%.Filtrate by the spiral dewater hole contains not conceivable organic concentration.Therefore contain 3 grams (doing solids content) organic substance in the every premium on currency of filtrate.From spiral dewater, obtain concentrate after mud be transported in the pressing machine of in patent 0004557-2, describing in detail, do solids content by pressing machine compression back and reach 17.6%.

Embodiments of the invention

With the same in the prior art embodiments, being transported to envelope surface from the mud that contains suspended fibers of paper mill biological treatment has in the spiral dewater of diameter 0.2mm hole.Added sawdust from sawmill in the ingress of spiral dewater.Described sawdust is the sawdust that has sieved.The small thing that sieved that has passed through aperture 2mm screen cloth that the sawdust that has sieved has a weight ratio 64%.Sawdust has dried solids content 43%.Obtained in test a kind of surprising mixture completely between sawdust and fiber sludge suspension thing.More surprised is adds sawdust and the concentrated effect that produces.In the sample that the outlet of spiral dewater obtains, do solids content and reached 24%.Within six hours, the weight ratio mean value of sawdust is 41% in any sample that obtains, and about having+and the fluctuation of/-3 weight %.This means that the dried solids content of starting stage in spiral dewater temporarily reaches about 14%.In other words, rely on the dehydration of spiral dewater, do solids content and be increased to 24% from about 14%.Another beneficial effect of noticing is that the filtrate of discharging from spiral dewater is surprising clean.This observation is by analysis has obtained confirmation to filtrate.0.8 gram solid organic matter (being the only dried solids content of 0.8 gram of every liter of liquid) is only arranged in every liter of liquid of filtrate.

The concentrated back mixture of the sawdust of from spiral dewater, discharging, fiber and mud be transported to prior art embodiments in the same pressing machine, although enter the initial solids content high relatively (24%) of doing in the pressing machine, observed big water gaging surprisingly and from pressing machine, flowed out.Filtrate is in fact as clean as the crystal in addition, and the levels of substance of the every premium on currency of filtrate only 0.12 gram has also been confirmed this point.Because good relatively liquid flows out from pressing machine, dried solids content has reached 51.2% high level.

Beneficial effect

Because under help of the present invention, make to obtain high-caliber solids content and become possibility, therefore just have Possible energy savings. The Energy Intensity Reduction of form of ownership has reduced consumption of fossil fuels in addition, thus so that ring It is better that the border becomes. By this important channel, the discharging of oxycarbide can be reduced in other materials for this reason. Dewatered sludge per ton reduces 1m in theory³Water capacity can reduce the discharging 200 kg of carbon oxide (CO₂), can reduce about 3m according to the present invention's dewatered sludge per ton³The water capacity of (ton) that is to say that the present invention causes mud per ton to reduce about 600 kilograms of environmentally harmful CO₂ Only just produce about 200,000 tons every year in Sweden Dewatered sludge, these mud have 100 ten thousand 3m³The water capacity of (ton). If the present invention obtains fully Use, have every year and reduce the potentiality that surpass 100,000 tons of CO2 emissions.

Claims

1. the method for an expel liquid from the mud of the mud that comprises organic material such as purification of waste water factory or paper pulp papermaking factory, the chemical conditioner that it is characterized in that solid granular in concentration process, be added into comprised mechanical part movably for example in the dewatering unit of spiral, pin or lodicule with just right the mixing of liquid material, mixture is transported in another dehydrating step that comprises pressing machine and goes afterwards.

2. the method for claim 1 is characterized in that chemical conditioner comprises sawdust.

3. as claim 1 and 2 described methods, it is characterized in that chemical conditioner comprises synthetic materials, especially pulverous urethane.

4. as claim 1 and 2 described methods, it is characterized in that chemical conditioner comprises the bark that has ground.

5. as claim 1 and 2 described methods, it is characterized in that chemical conditioner comprises the peat that has ground.

6. as the described method of claim 1-6, it is characterized in that chemical conditioner can mix mutually.

7. as the described method of claim 1-7, it is characterized in that the weight ratio of chemical conditioner reaches 10 weight % of dewatered sludge gross weight at least.