Monthly Archives: September 2020

Introduction to Papermaking Wastewater

I. Sources and characteristics of papermaking wastewater

There is a lot of water in the process of paper making. It takes about 300~500 m3, to produce 1 paper. In paper wastewater, it not only contains a large number of raw materials (about 20% of raw materials are lost with wastewater), but also contains a lot of chemicals and other impurities.

For the limited treatment of papermaking wastewater. First of all, we must understand the water quality of papermaking wastewater. There are three kinds of wastewater from alkaline papermaking:

1. cooking wood pulp (or straw pulp) generated waste liquid, also known as black liquid.

2. beating machine and pulping machine discharged wastewater, called beating wastewater.

3. paper machine wastewater, which can be directly used called white water.

The main pollutants contained in these wastewater are as follows:

1. suspended

Includes collapsible and non-collapsible suspensions, mainly fibers and fine fibers (i.e. broken fiber fragments and miscellaneous cells)

2. biodegradable organic compounds

Including low molecular weight hemicellulose, methanol, acetic acid, formic acid, sugar and so on.

3. refractory organic matter

It mainly comes from lignin and macromolecular carbohydrates in fiber raw materials.

4. toxic substances

Black liquor contains rosin acid and unsaturated fatty acids and so on.

5. acid-base poisons

The ph value of alkali pulping wastewater is 9~10, and that of acid pulping wastewater is 1.2~2.0.

6. chroma

The residual lignin in pulping wastewater is highly colored.

II. Recycling of papermaking wastewater

Because papermaking wastewater consists of three kinds of wastewater: black liquid, pulping machine wastewater and papermaking machine wastewater, its recovery and utilization is mainly aimed at these three kinds of wastewater.

  1. black liquor recycling

 (1) Traditional alkali recovery (combustion)

The paper industry uses a large amount of alkali, each production of 1 t pulp needs 200~400 kg caustic soda. About 35% of the black liquor discharged after cooking is inorganic, the main components of which are free NaOH、Na2S、Na2SO4 and other sodium salts combined with organic matter. The purpose of alkali recovery is to convert these sodium salts into NaOH and Na2S recycling to reduce costs and reduce pollution to water bodies.

(2) Wet oxidation

Wet air oxidation refers to the process in which organic matter in wastewater is oxidized and decomposed at high temperature and high pressure, the degree of oxidation depends on the temperature and pressure used. This method is suitable for caustic soda black liquor.

Sewage Treatment in Food & Beverage Industry

In recent years, with the rapid growth of the food industry, the waste water discharged by it greatly pollutes the environment, and loses a lot of energy and water resources, which in turn restricts its own growth. Due to the severe lack of resources in the face of the world at this stage, it is urgent to choose the appropriate waste water disposal punishment to achieve the goal of water saving and energy saving.

The important source of sewage in food industry is the process of food processing, such as punishment, washing, dehydration, filtration, dispersing and refining, deacidification, deodorization and cooking. Sewage contains a large amount of egg white, organic acids and carbohydrates. Due to the existence of many plankton, dissolved organic matter in water grows rapidly, and humus is easy to occur and accompanied by unpleasant gas. At the same time, copper, lead, manganese, chromium and other metal ions other metal ions in these sewage, and bacteria and coliform bacteria often exceed the national discharge scale.

The important pollutants in wastewater are (1) solid substances, such as vegetable leaves, pericarp, minced meat and poultry feathers, etc .;(2) oil, egg white, starch, colloid, etc .;(3) acid, alkali, salt, sugar, etc. dissolved in wastewater :(4) mud sand and other organic matter entrained by qualitative materials ;(5) pathogenic bacteria, etc. Food industry wastewater is characterized by high organic matter and suspended matter content, easy to erosion, the same usually no toxicity. Its harm is to make the water body eutrophication, so as to cause aquatic animals and fish to die, promote the accumulation of organic matter under the water odor, deterioration of water quality pollute the environment.

Since there are many kinds of food, there are many kinds of material springs, the sewage of food industry has the characteristics of suspended matter, high oil content, heavy metal ions, large COD and BOD value, large range of water quality and quantity change, high content of nitrogen and phosphorus compounds, and high water temperature in some environments. Therefore, the punishment of sewage disposal in food industry is usually to accept solid-liquid dispersion skills to remove suspended matter and drifters from sewage to reach the sewage discharge scale.

Solid-liquid dispersion skills we accept Zhejiang Sanlian environmental protection machine equipment deployment Co., Ltd. LW spiral discharge settling machine. It is important to be used in the field of solid and liquid dispersion in all living wastewater, industrial wastewater, chemical, food, pharmaceutical and similar production industries.

The process of wastewater from the food industry is as follows:

The suspension of wastewater in the food industry enters the drum through the feed pipe from the spiral outlet. Under the action of the centrifuge in which the high speed rotation takes place, the solid particles with large specific gravity are deposited on the inner wall of the drum. After dispersing the clear night through the liquid layer adjustment plate opening overflow and flow drum. The relative activity between the spiral body and the drum (that is, the differential speed) is realized by the differential, and its fineness is controlled by the auxiliary motor, thus realizing the continuous dispersion of the centrifuge to the material.

All kinds of waste water biological disposal punishment system is constantly emerging, the above-mentioned food wastewater is to accept the new solid-liquid dispersion skills, with high use rate, simple installation, wide application scope and other advantages, and has been put into practice in foreign countries, to achieve success. We can learn from the disposal and punishment skills of these ancestors, and trust that with the continuous strengthening of people’s awareness of environmental protection, the water environment of our country will certainly change.

Trend of Solid-liquid Separation Production Line from Filter Press to Decanter Centrifuge

Filter press and horizontal screw centrifuge are common solid-liquid separation equipment, the amount of retention is very large, rich sunshine and you solid-liquid separation production line machine from filter press to horizontal screw centrifuge technical advantages:

1. horizontal centrifuge without filter media,

Filter press pressure filtration of filter medium (filter) to separate solid and liquid, need to use high pressure water to avoid filter belt obstruction; horizontal centrifuge high speed rotation to produce Li Xin position to separate solid-liquid centrifugal settlement, It is not suitable for filter medium because of filter screen, which bypasses the common filter clogging problem in filter operation.

2. horizontal screw centrifuge is widely applicable

Filter press can also most of the solid-liquid separation, but the oil, viscosity and other strong adhesion of solid-liquid separation needs pretreatment and incomplete separation; horizontal screw centrifuge separation adaptability, can achieve solid-liquid two-phase separation and solid-liquid three-phase separation, better adaptability to solid-liquid separation.

3.Automation of production line of 3. horizontal screw centrifuge:

Filter press is intermittent operation of manual cutting slag, loading and unloading belong to intermittent operation most or need manual coordination is not conducive to the formation of automatic production line to improve production efficiency; Horizontal centrifuge can realize automatic loading and unloading continuous production automatic loading and unloading can form automatic production line production efficiency.

4. horizontal screw centrifuge parameters adaptive adjustment ability,

In the process of solid-liquid separation and dehydration, the belt filter is adjusted according to the working conditions, and the parameters such as speed, tension, dosage and flushing pressure often depend on the experience of the operator, which requires high operation technology.

5.Low consumption of pre-treatment material for 5. screw centrifuge

Because filter press filter medium (mainly filter net) mesh will not be very small, so filter particle size can not be too small, small particle size should also add a lot of flocculant complex to synthesize large groups to facilitate filtration, which results in the consumption of additional pretreatment materials. In horizontal centrifuge, fine sludge can also be separated from water, so the dosage of flocculant is less, saving material input and reducing production cost;

6. horizontal screw centrifuge production line environment is good:

In addition to the main filter press, the filter press also needs to add medicine and feed conveyor washing pump air compressor and other ancillary equipment, large area, the whole machine is difficult to seal, high pressure cleaning water mist and odor pollution environment, poor production line environment;

7. low maintenance requirements for horizontal centrifuge

The number of easily damaged parts in the fuselage accessories of filter press is many times that of centrifuge. Maintenance is not only labor intensity but also high cost.

It can be seen from the above comparison that the comparison of the same processing conditions with the filter press has great technical advantages, and the solid-liquid separation production line from the filter press to the horizontal screw centrifuge is the development trend.

Analysis of Common Problems of Wastewater Sewage

The solid-liquid separation capacity of horizontal screw centrifuge is strong, high efficiency and high treatment capacity. It has been widely used in sewage treatment in China, which greatly reduces the cost of sewage treatment and creates huge economic value and social environmental protection value. Here are some common operational problems for Decanter centrifuge in sewage treatment, GN discuss with you.

Decanter centrifuge is not easy —— selection is important:

The equipment principle is based on the specific gravity difference of solid and liquid to accelerate the settlement of solid and liquid by applying centrifugal force field to achieve the purpose of separation. Because there may be some differences in the parameters of different fuselage components in the design of Decanter centrifuge, such as slag discharge ability and drum requirement. Since the horizontal screw centrifugation and the use of bias, since it is sewage treatment, in the selection of course, only to buy suitable for the sewage treatment process of centrifugal separator equipment can achieve twice the result with half the effort.

Disstable separation effect —— parameter adjustment are important:

Although the parameter setting habits of each manufacturer are different, in general, in order to better cope with the material change and enhance the general performance of the machine, the commonly used adjustment of the required parameters include the speed adjustment of the drum, the speed difference adjustment of the push differential, and the height of the overflow plate. For different materials, you are too lazy to adjust the parameters to make the machine more suitable. It is really difficult to imagine what kind of teasing performance the engineering mud desliming parameters will have ~ directly to the wastewater treatment of the steel plant

Disparation effect is not good —— pretreatment is important

For the next stage of solid-liquid separation of horizontal screw centrifuge to do a good pretreatment, to achieve the best separation effect;

Decanter centrifuge is easy to damage —— production operation maintenance techniques are important:

Decanter centrifuge is suitable for frequent failures, can not be wronged you, this may be due to poor material applicability, such as material slurry impurities too much, feed too fierce resulting in slag discharge is not smooth, rotary block…

However, most of the feed impurities can be added to the material pretreatment section, the discharge is not smooth can be adjusted according to the material characteristics of the push speed difference, block can always check whether there is a lack of lubricating oil or foreign body stuck in the rotating shaft, These causes of Decanter centrifuge failure can be said to have nothing to do with the operator?

Advantages of Screw Press Sludge Dewatering Machine

I. Widespread application

1. suitable for municipal sewage, food, beverage, chemical, leather, welding materials, paper, printing and dyeing, pharmaceutical and other industries sludge.

2. suitable for dewatering high and low concentration sludge. For low concentration (2000 mg/L~) sludge dewatering, there is no need to build concentration tank, storage tank, reduce construction cost, reduce phosphorus release and anaerobic odor production.

II. Small-scale design

1. Compact design, the dehydrator contains electronic control cabinet, metering tank, flocculation mixing tank and dehydrator body.

2. space is small, easy to repair and replace; small weight, easy to carry.

III. Not easily blocked

1. has the function of self-cleaning. There is no need to clean to prevent clogging, reduce washing water consumption and reduce internal circulation burden.

2. is good at dewatering oily sludge.

 IV. Low speed operation

1. The speed of the screw shaft is about 2~3 rpm, and the power consumption is very low.

2. failure is less, noise vibration is small, operation is safe.

V. Simple operation

1. through the electronic control cabinet, with the bubble medicine machine, mud pump, dosing pump, etc., to achieve 24 hours of continuous unmanned operation.

2. daily maintenance time is short, maintenance operation is simple.

VI. Durable

1. Almost all thebody is made of stainless steel, which can prolong the service life to the maximum extent.

2. replacement parts only spiral shaft and swimming ring, long service period.

 VII. Low investment costs

  1.  Various product specifications, complete series, for different processing scale, can choose the most suitable model, to avoid overuse.
  •  The body is compact in design, integrated in concentration and dewatering, with auxiliary devices such as electronic control cabinet and sludge flocculation mixing tank, which has strong compatibility with supporting equipment and is easy to design.
  •  Small design, easy to adapt to local conditions, can reduce the dehydrator itself space and construction costs.
  •  It has the function of sludge concentration, so it does not need to concentrate and store units to reduce the overall space and construction cost of sewage treatment facilities.
  •  The main body of the dehydrator has the function of self-cleaning, so it is not necessary to use a large amount of water to prevent sludge clogging.
  •  Adopt low speed spiral extrusion technology, low power consumption.
  •  The electronic control cabinet is equipped with automatic control device, from conveying sludge, injecting medicine liquid, concentrating and dewatering, to discharging mud cake, realizing 24 hours automatic continuous unmanned operation and reducing workers’ expenses.