CN105646064A - Engineering method for producing biochar soil from dredging sediment - Google Patents

Abstract

The invention relates to an engineering method for preparing biological carbon soil from dredging bottom mud, and belongs to the field of resource utilization of solid waste. The bio-carbon soil uses dredging bottom mud, poultry manure, and dry straw as raw materials, uniformly mixes them according to a certain mass ratio, adjusts the C/N ratio and water content of the mixture, and adds a certain proportion of nitrogen and water retention agents. Combine mechanical turning and static forced ventilation to carry out strip-stack composting treatment. The composting cycle is about 30 days, and the compost body is kept at 55-65°C for 10-12 days until the compost product is completely decomposed, that is, it is made into biochar. earth. According to actual needs, ecological utilization of biocarbon soil is carried out. The invention realizes the large-scale engineering treatment of dredging bottom mud, poultry manure and crop straw, and provides an ecological solution for non-point source pollution caused by dredging bottom mud and poultry manure, and air problems caused by crop straw burning , Compost products can be used in related ecological engineering construction, so that environmental benefits, economic benefits, and ecological benefits have been organically combined.

Description

An engineering method for preparing biocarbon soil from dredging sediment

technical field

The invention relates to an engineering method for preparing biological carbon soil from dredging bottom mud, and belongs to the field of resource utilization of solid waste.

Background technique

River and lake bottom mud (also known as silt) mainly comes from the sediment carried by surface runoff, terrestrial animal and plant residues, and aquatic animal and plant residues, and pollutants carried by atmospheric dry and wet deposition. It is formed by the precipitation of water bodies under the combined action. Sediment will not only block the river, but also become the "source" of pollutants under certain conditions such as pH, dissolved oxygen, and redox potential. Nutrients, heavy metals, and other substances will be released into the water body, posing a huge threat to water ecological security. .

Ecological dredging is an effective measure to solve the internal pollution of rivers and lakes and dredge waterways. However, if a large amount of sediment from dredging is not properly disposed of, it will bring huge pressure to the ecological environment. Taking a watershed in the upper reaches of Taihu Lake as an example, the average sedimentation depth is 0.9m, and it is planned to dredge the watershed, and the total dredging volume is 2 million cubic meters. The bottom mud from dredging is usually piled up in the mud storage yard as solid waste, which not only occupies a large amount of land, but also easily causes secondary pollution to the environment. The efficient and economical resource utilization of dredged bottom mud has become an ecological The bottleneck restricting the large-scale development of dredging projects. At home and abroad, a large number of patented technologies have been obtained in terms of sediment resource utilization, mainly focusing on the three aspects of sediment manufacturing building materials, water treatment materials, plant substrates and composting, but none of them have achieved large-scale engineering applications.

Regarding the preparation of building materials with bottom mud, Zhang Jian et al. (authorized announcement number: CN103102133B) disclosed a kind of silt-free brick and its preparation method, to dredge silt, fly ash, quicklime, quick gypsum, gelling agent, promote agent and sodium silicate as raw materials, and manufacture burn-free bricks through a steam drying process; The river bottom mud, plant straw, waste glass powder, and binder are mixed in proportion, and the bottom mud bricks are made by pressurized sintering; Zhang Dalei et al. The method for preparing ultra-light and high-strength ceramic aggregates from bank high sand mud is still to obtain building materials through sintering; Zhan Xu et al. (application number: 201210111551.6) disclosed a method for the resource utilization of river silt, mixing silt Other components are fired into clay bricks under certain conditions; Ma Caifeng et al. (Application No.: 201510288573.3) disclose a stoneware tile with river and lake bottom mud as the main raw material and its preparation method. Potassium feldspar is used to prepare stoneware tiles through a certain process; Zhu Jianzhong et al. (application number: 201510242654.X) disclosed a method of using silt to prepare imitation bio-concrete, and the dehydrated silt is made into concrete aggregate through other cementing materials Gao Yufeng et al. (Application No.: 2015102132.X) disclose a non-burning and pressure-free silt brick and a preparation method thereof, using dredged silt, cement, gypsum, slag, fly ash, lime, and early-strength agents as raw materials. Pressure-free and non-burning bricks; Yu Yang et al. (Application No.: 201410555785.9) disclosed a method for preparing a new type of energy-saving sintered wall material using lake silt. The main method is to sinter after adding chemical reagents; Hu Baoan et al. (Application No. : 201410415220.0) discloses a kind of unfired brick and its natural maintenance production method of river and lake dredging mud as the main material, with river and lake dredging mud, cement, sand, fly ash, quicklime, sodium silicate, antifreeze as the main material Preparation of non-fired bricks with a certain process of raw materials; Song Di et al. (application: 201410326354.5) disclosed a method of making bricks without sintering with dredged bottom mud, adding 2,4,6-trisulfide-1 to the bottom mud after dehydration , 3,5-triazine trisodium salt mixed, and then add quicklime, cement, natural zeolite through the mold to manufacture unburned bricks. The common feature of the preparation of building materials from the above sediments is that they need to add exogenous chemical reagents or commercialize other building materials, and most of them need to be combined with pressure sintering to avoid the important principle of economical and energy saving.

Regarding the preparation of materials for water treatment from bottom mud, Song Yonghui et al. (authorized announcement number: CN102093071B) disclosed a method for modifying and manufacturing ceramsite from dredging bottom mud of heavily polluted rivers in cities. Dry lake bottom mud powder and additives Calcium carbonate, sodium silicate and alumina are granulated, and ceramsite is made by sintering; Ren Zhizhong et al. (notification number: CN101747900B) disclose a method for preparing soil conditioner by carbonizing lake bottom mud, and the main technical principle is still The bottom mud is carbonized to make a repair agent; Ning Ping and others (application number: 201410689998.0) disclose a method and application of preparing an adsorbent from the bottom mud of Dianchi Lake, which is prepared by chemical pretreatment and carbonization of the dredging bottom mud. Heavy metal adsorbent; Li Chunhua et al. (Application No.: 201410240993.X) disclose a method of utilizing lake bottom mud and waste additives to prepare water-treated lightweight ceramsite. Dry lake bottom mud powder, steel slag, and straw powder are mixed with a certain Mixing and granulating in a certain ratio, made by sintering; Zhan Heng et al. (Application No.: 201210111554.X) disclosed a method for preparing high-performance water treatment filter material from lake bottom mud, using the bottom mud after lake dredging It is sintered with other added components to make ceramsite under certain pore size and pressure conditions; Pan Jiafen (application number: 201510413073.8) discloses the preparation method of iron-carbon micro-electrolytic ceramsite filler for water treatment. Carbonization at high temperature. In the above cases, the water treatment materials prepared from sediment were not compared with the existing finished materials in terms of performance and economy, avoiding the principle of high efficiency and economy.

Regarding the preparation of plant matrix and compost from bottom mud, Cui Baoshan et al. (authorized announcement number: CN101828512B) disclosed a method of making use of lake bottom mud and coal cinders as cultivation soil, by sieving coal cinders into two particle sizes, Lay them on the culture trays one by one, and finally spread the lake sediment on the upper layer. This patent ignores the negative impact of the sediment on seed germination and plant growth under long-term reducing environmental conditions, and avoids the aeration of the culture substrate, water retention and fertilizer conservation. Efficiency; He Qiang et al. (Application No.: 201410653670.3) disclosed a method for utilizing river silt to control rocky desertification, that is, adding fly ash to the river silt, mixing evenly, making a sphere with a mold, and then putting the pioneer plant Seedling roots are buried in spheres and spread evenly in rocky desertification areas. This method also ignores the seed germination rate of the bottom mud, and does not pretreat the bottom mud; Zhou Lixiang et al. A method for co-composting polluted bottom mud. The invention removes heavy metals in bottom mud by bioleaching, and uses bottom mud, straw, and blue-green algae as raw materials for mixed composting. This patent only considers the heavy metals in the bottom mud, avoids the persistent organic pollutants in the bottom mud, and does not give the specific composting raw material addition ratio, composting process and parameters, and evaluation criteria for the composting end point. The early stage of composting is not conducive to the growth of microorganisms.

Lu Changsong et al. (authorized announcement number: CN102060583B) disclosed a method for making biological carbon soil by static aerobic composting of sludge. By taking fresh municipal sewage treatment plant sludge, backmixing material, and sludge composting conditioner, a certain mass ratio Mix static compost to make bio-carbon soil, and grade and pack the bio-carbon soil according to particle size. However, as early as March 2013, the General Office of the State Council had issued the "Recent Work Arrangements for Soil Environmental Protection and Comprehensive Treatment", which for the first time publicly stated that in agricultural production, the use of sewage containing heavy metals and refractory organic pollutants should be prohibited. As well as sewage treatment plant sludge and dredged bottom sludge that have not been inspected and safely treated, the present invention does not mention heavy metals in sludge, monitoring and evaluation of persistent organic pollutant content. The above patent cases on the preparation of plant substrates and composting from sediment all avoided the analysis of the feasibility of ecological utilization.

Among the above three schemes for resource utilization of dredged sediment, the preparation of building materials and water treatment materials from sediment is difficult to achieve large-scale engineering applications due to high preparation costs and low social acceptance; the preparation of plant substrates from sediment or In the technical case of composting, there is no evaluation of the content of pollutants on the bottom mud as the substrate, and the evaluation of the water retention, fertilizer retention and aeration performance of the substrate in soil science. In view of this, on the basis of fully comparing the existing domestic sediment and sludge agricultural and forestry application standards, the present invention proposes for the first time an engineering method for preparing biocarbon soil from dredging sediment, livestock and poultry manure, and dry crop straw, and finally forms a biocarbon soil with high Added value, low cost, good performance, biocarbon soil that can realize large-scale production of sediment.

Contents of the invention

The purpose of the present invention is to provide an engineering method for preparing bio-carbon soil by dredging bottom mud, so as to solve the problem of bottom mud disposal caused by large-scale ecological dredging.

In order to solve the above object, the present invention adopts the following technical solutions.

(1) Biological carbon soil raw materials:

Dredging bottom mud: the water content is between 75% and 85%, the organic matter content is between 4% and 20%, and the pollutant content is in line with the secondary standard stipulated in the "Soil Environmental Quality Standard GB15618-1995".

Poultry manure: It is dry manure, which is one or a combination of cow manure, pig manure, chicken manure, duck manure, and goose manure.

Straw: One or several dry straws of rice, wheat, rapeseed, and corn, and crushed to a particle size of less than 5mm.

Nitrogen- and water-retaining agent: use one or several kinds of straws such as rice, wheat, rape, corn, etc., and dry distillation at about 600°C under anaerobic or hypoxic conditions. It has the characteristics of large porosity, strong adsorption capacity and high water holding rate.

The mass ratio of the above-mentioned dredging bottom mud, poultry manure, and straw is 1: (0.2-0.5): (0.1-0.3), and the amount of nitrogen and water-retaining agent added is 0.5-1% relative to the mass of the dredging bottom mud. C/N is adjusted to about 30:1, moisture content is 55% to 65%, and the raw materials are evenly mixed with a turner, and the strips are prepared for composting, and then enter the next step.

(2) Composting process:

Bar pile yard: located near the dredging yard, with flat terrain, width: 3-6m, height: 1.0-1.6m, length: 10-60m, and the distance between bar stacks is 10-15m. The anti-seepage measures of the stack yard: the ground is followed by 2 layers of anti-seepage cloth, 5-10cm stones with a particle size of 2cm, and 5-10cm thick clay, and take measures to collect leachate. The leachate is used to adjust composting raw materials and Moisture content during composting. Rainproof measures for strip yards: rain protection is to build unloadable color steel structure greenhouses in strip yards, which have dual functions of sunshade and rainproof.

Temperature: When the length of the stack is less than 10m, select three measuring points, and measure the temperature of the surface, middle and bottom at each point, determine the measurement depth according to the site conditions, and take the average value; when the stacking yard is greater than 10m, each Add a measurement point every 10m, and if it is less than 10m, it is counted as 10m. Each point measures the temperature of the surface, middle, and bottom respectively. The measurement depth is determined according to the site conditions, and the average value is taken. The frequency of temperature measurement is once every 6 hours.

Turning and aeration: The frequency of turning should be appropriately increased or decreased according to the weather conditions on site, but it is generally controlled in the early stage of composting, with mechanical turning every 2 to 5 days. When the temperature of the pile rises above 50°C, the The pile body is forced to ventilate with 0.1~1L.min ^-1 .kg raw material ^-1 , and the pile is turned 1~2 times a day. When the temperature is below 50℃ again, the stack is turned once every 1~2 days.

Decomposition: After 10-15 days of 55-65°C high temperature period, the moisture content of the mixed raw materials drops to below 40% after cooling down to room temperature, and when the germination rate of the seeds of compost products is above 60%, it is considered to be decomposed.

(3) Ecological utilization scheme of biocarbon soil:

After the decomposed compost is lowered to normal temperature, spread the stacks for 3 to 7 days if the weather permits, so as to minimize the moisture content of the compost product. Ecological utilization methods include replacing peat as a plant cultivation substrate, artificial wetlands, ecological floating Islands, plant growth substrates for ecological slope protection, desertification, mine soil amendments, etc., but not limited to these methods.

Compared with traditional technology, the present invention has the following advantages:

1. Compared with the technology of dredging bottom mud to prepare building materials and water treatment materials, the present invention does not add chemical reagents, and the required raw materials, dredged bottom mud, poultry manure, straw, and biomass carbon all come from solid waste, and the manufacturing process is economical Energy saving, high added value of product bio-carbon soil.

2. Compared with the preparation of plant matrix and composting technology from dredged bottom mud, the present invention fully considers the feasibility of agricultural and forestry utilization of dredged bottom mud, evaluates the content of pollutants and composts and decomposes it, and adds not only nitrogen and water retention functions, but also Biomass carbon that promotes the aromatization of humus during composting, speeding up the process of making biochar.

3. The technological process of the present invention is simple, easy to carry out large-scale engineering application, and the invented product has wide application and high social recognition.

Description of drawings

Fig. 1 is overall technical route of the present invention

detailed description

In this project, samples were taken in a watershed in the upper reaches of Taihu Lake in April, July, October, December and March 2015 respectively. There were 10 sampling points each time, and the surface samples and columnar samples were collected respectively (the columnar samples were divided into four layers, Each layer is 10cm), and make parallel samples, 100 samples each time, 5 times a total of 500 samples. The monitoring results show that the bottom mud of the Lianhuadang water system belongs to the type of high organic matter (the mass content of organic matter is more than 6%), and the concentrations of As, Cu, Hg, Cd, Cr, Zn, Pb, and Ni in the bottom mud range from 9.14 to 25.05 and 38.24, respectively. ～98.63, 0.14～0.46, 0.15～0.28, 34.94～110.20, 94.58～185.34, 23.62～110.29, 14.26～36.28mg/kg, the concentration of HCH and DDT in the sediment were 0.07～0.09, 0.06～0.10mg/kg, respectively kg, because the "Soil Environmental Quality Standard GB15618-1995" stipulates that the soil used for agriculture should be stricter than the "Pollutant Control Standards in Agricultural Sludge GB4284-84" and "Sludge Disposal of Urban Sewage Treatment Plants for Landscaping CJ248 CJ248" -2007", so the "Soil Environmental Quality Standard GB15618-1995" was selected as the basis for the resource utilization evaluation of the dredged sediment. The dredged sediment in this watershed meets the standards for soil agriculture and forestry utilization. The bio-carbon soil was prepared from the dredged sediment of the river basin as the main raw material. Specific steps are as follows:

(1) Biological carbon soil raw materials:

The above dredged bottom mud is 100t, the average moisture content is 72%, the average organic matter content is about 6%, and the pollutant content meets the secondary standard stipulated in the "Soil Environmental Quality Standard GB15618-1995"; 25t of dried chicken manure; crushed to granular 11 tons of dry rice straw with a diameter of less than 5mm; Nitrogen and water retention agent: 0.6 tons of biomass carbon produced by dry distillation of rice straw at about 600°C under anaerobic or hypoxic conditions. The average C/N of the mixed raw materials is 30:1, and the average moisture content is 55% to 65%. The raw materials are evenly mixed with a turning and throwing machine, and the strips are prepared for composting, and then enter the next step.

(2) Composting process:

Bar stack yard: located near the dredging yard, with flat terrain, width: 5m, height: 1.5m, length: 10m, and the distance between the bar stacks is 10m, stacked into two piles. The anti-seepage measures of the stack yard: the ground is followed by 2 layers of anti-seepage cloth, 10cm of stones with a particle size of 2cm, and 8cm thick clay, and leachate collection measures are taken. The leachate is used to adjust the composting raw materials and composting process. moisture content. Rainproof measures for strip yards: rain protection is to build unloadable color steel structure greenhouses in strip yards, which have dual functions of sunshade and rainproof.

Temperature: Choose three measurement points, each point measures the temperature of the surface, middle, and bottom respectively, and determine the measurement depth according to the site conditions, and measure at the surface of 0.5 and 1.0 from the ground respectively, and take the average value.

Turning and aeration: The frequency of turning should be appropriately increased or decreased according to the weather conditions on site, but it is generally controlled in the early stage of composting, with mechanical turning every 2 to 5 days. When the temperature of the pile rises above 50°C, the The pile body is forced to ventilate with 0.5L.min ^-1 ·kg raw material ^-1 , and the pile is turned twice a day. When the temperature is below 50°C again, the pile is turned once every 2 days.

Decomposition: the mixed raw materials go through a high temperature period of 55-65°C for 10-15 days, and after cooling down to normal temperature, the moisture content drops below 40%, and the seed germination rate of compost products is above 60%.

The comparison of various soil properties between the obtained original sediment and the biocarbon soil is shown in Table 1. From Table 1, it can be seen that the biocarbon soil has good fertilizer, water, and aeration properties.

Table 1 Comparison of various soil properties between original sediment and biocarbon soil

(3) Ecological utilization scheme of biocarbon soil:

After the decomposed compost is lowered to normal temperature, spread the stacks for 3 to 7 days if the weather permits, so as to minimize the moisture content of the compost product. Ecological utilization methods include replacing peat as a plant cultivation substrate, artificial wetlands, ecological floating Islands, plant growth substrates for ecological slope protection, desertification, mine soil amendments, etc., but not limited to these methods.

Claims (10)

1. a desilting bed mud prepares the engineering method of biological carbon soil, it is characterised in that:

(1) taking desilting bed mud, poultry manure, dry straw as raw material, Homogeneous phase mixing by a certain percentage, the C/N ratio of adjustment batch mixing and water ratio, add a certain proportion of guarantor's nitrogen water-holding agent.

(2) in the way of machinery turning combines with static forced ventilation, carry out bar buttress formula compost treatment, about 30 days compost cycle, make bar buttress temperature maintain 10��15 days at 55��65 DEG C, until composting production becomes thoroughly decomposed completely, namely make biological carbon soil.

According to actual needs, (3) biological carbon soil is carried out eco-utilization.

2. a kind of desilting bed mud according to claim 1 prepares the engineering method of biological carbon soil, it is characterized in that the raw material described in (1), desilting bed mud water ratio is between 75��85%, organic content is between 4��20%, and wherein pollutant load meets the secondary standard of regulation in " soil environment quality standard GB15618-1995 ". Poultry manure is the one or more combination in cow dung, pig excrement, chicken excrement, duck excrement, goose excrement, for argol just. Dry straw is one or more in paddy rice, wheat, rape, corn, and is crushed to below particle diameter 5mm.

3. a kind of desilting bed mud according to claim 1 prepares the engineering method of biological carbon soil, its spy is the raw material desilting bed mud described in (1), poultry manure, stalk example 1 in mass ratio: (0.2��0.5): (0.1��0.3) uses turnover throwing machine Homogeneous phase mixing, initial C/N is adjusted to about 30: 1, and water ratio is 55%��65%.

4. a kind of desilting bed mud according to claim 1 prepares the engineering method of biological carbon soil, it is characterized in that the guarantor's nitrogen water-holding agent described in (1) is biomass carbon, for one or more in paddy rice, wheat, rape, cornstalk biological matter carbon, it adds relative to the mass ratio of bed mud is 1: (0.005��0.01).

5. a kind of desilting bed mud according to claim 1 prepares the engineering method of biological carbon soil, it is characterized in that (2) described bar buttress stockyard is positioned near desilting stockyard, physical features is smooth, width: 3��6m, highly: 1.0��1.6m, length: 10��60m, 10��15m of being separated by between bar buttress.

6. a kind of desilting bed mud according to claim 1 prepares the engineering method of biological carbon soil, it is characterized in that the rainproof measure of antiseepage is carried out in (2) institute bar buttress stockyard, antiseepage is followed successively by 2 layers of antiseepage cloth from ground, 5��10cm particle diameter is the stone of 2cm, the clay of 5��10cm, and carry out leachate collection measure, percolate is for regulating the water ratio in composting material and composting process; Rainproof be bar pile up neatly stockyard construction can the color steel construction booth of unload-type, have sunshade and rainproof double effects concurrently.

7. a kind of desilting bed mud according to claim 1 prepares the engineering method of biological carbon soil, it is characterized in that the mode that the mechanical turning described in (2) combines with static forced ventilation, compost is in earlier stage, mechanical turning in every 2��5 days is once, when heap temperature rises to more than 50 DEG C, to heap body with 0.1��1L min^-1Kg raw material^-1Carry out forced ventilation, and turning every day 1��2 time, when being again in below 50 DEG C, bar is piled up neatly turning in every 1��2 day 1 time, above turning frequency increases in time according to actual ventilation, the weather condition in stockyard or reduces.

8. a kind of desilting bed mud according to claim 1 prepares the engineering method of biological carbon soil, it is characterized in that described in 7, temperature mercurythermometer is measured, its method is, as the long < 10m of stacking, selecting three measurement point, each point surveys surface respectively, middle, the temperature of bottom, determines to measure the degree of depth according to field condition, and averages; As stockyard > 10m, often increase 10m increase a measurement point, less than 10m by 10m, each point surveys surface respectively, middle, the temperature of bottom, determining to measure the degree of depth according to field condition, and average, temperature measuring frequency is every 6 hours 1 time.

9. a kind of desilting bed mud according to claim 1 prepares the engineering method of biological carbon soil, it is characterized in that the standard of becoming thoroughly decomposed described in (2) is that mixing raw material was through 10��15 days 55��65 DEG C of pliotherm periods, and water ratio is down to less than 40% after being down to normal temperature, the rate of emergence of composting production is more than 60%.

10. a kind of desilting bed mud according to claim 1 prepares the engineering method of biological carbon soil, it is characterized in that the eco-utilization described in (3), its step is after normal temperature is down to by the compost become thoroughly decomposed, bar buttress is spread out 3��7 days when weather allows, so that composting production water ratio is down to minimum, eco-utilization mode comprises plant seedling cultivation matrix, the plant growth medium of artificial swamp, ecological floating island, ecological revetment, the modifying agent etc. of desertification, mine soil, but it is not limited to this several mode.