WO2014028996A1

WO2014028996A1 - Process for obtaining a fertilizer from the solid phase of an effluent, and fertilizer

Info

Publication number: WO2014028996A1
Application number: PCT/BR2013/000318
Authority: WO
Inventors: Ivan BERGIER TAVARES DE LIMA; Carlos Alberto SHIMATA; Hernandes DE CAMPOS MONTEIRO; Antonio ARANTES BUENO SOBRINHO; Luis Alberto DE OLIVEIRA RIEGER; José Anibal COMASTRI FILHO; Jair Antonio BORGMANN; José Alberto PINESSO
Original assignee: Empresa Brasileira De Pesquisa Agropecuária - Embrapa; Cooperativa Agropecuária São Gabriel Do Oeste Ltda - Cooasgo; Rieger Irrigação Ltda. - Epp
Priority date: 2012-08-23
Filing date: 2013-08-23
Publication date: 2014-02-27
Also published as: BR102012021219A2; BR102012021219A8; BR102012021219B1

Abstract

The process specifically targets the treatment of pig-rearing waste, consisting in the pre-digestion of the waste, comprising the solid and liquid phases, post-digestion phase separation (e.g. by: screening, floatation, settling, filtration, centrifugation and sedimentation), thermochemical treatment of the sludge (solid phase), optionally with the addition of other nutrients and granulation. Biomass such as algae, abattoir or chiller plant waste, in addition to all types of organic plant material, may be added prior to the step of thermal treatment which is carried out (preferably in a rotary drum) at temperatures of 300 to 1200°C. The fertilizer, the composition of which includes struvite crystals, obtained by means of the process is applied for.

Description

SOLID PHASE FERTILIZER PROCESS

WASTE AND FERTILIZER

The present invention relates to the field of wastewater treatment and the development of an organic fertilizer from the solid phase of fresh or biodigested effluents by pyrolysis. More specifically, the present invention relates to the process of treating swine effluent in which organic matter is removed and biogas is used. The sludge is pyrolised, resulting in a product with agronomic properties, and classified as a fertilizer or soil conditioner. The process of the invention is also applicable to solid phase transformation of organic effluents resulting from industrial, agro-industrial and general urban processes. BACKGROUND OF THE INVENTION

Soil organic matter plays an important role in increasing nutrient retention capacity, structuring and moisture retention in tropical soils, and represents an important compartment for the fixation of atmospheric carbon. However, due to agricultural management, these compounds can be degraded, losing their function as a conditioner of physical and chemical properties, in addition to releasing greenhouse gases. Therefore the stability and reactivity of organic matter are fundamental factors in the choice of an organic fertilizer, both from an agricultural and global climate change point of view.

The pyrolysis solid product is usually produced with the function of reducing the volume and mass of a given raw material at temperatures from 300 to 600 ° C. This thermally altered material degrades much more slowly, creating a large stock of long-term soil carbon, which is about 1500 to 2000 times more stable than unpolyzed organic matter. From the pyrolysis of agricultural residues such as wood, plant residues, animal residues and their By-products, as well as industrial and urban waste, it is possible to synthesize highly stable and highly reactive humic substances that can act as soil conditioners, improving physical and nutritional properties.

Pyrolysis products can be derived from plant, animal and human byproducts and have been shown to have nitrogenous and mineral compounds such as calcium, magnesium, potassium and phosphorus. Harmful substances such as heavy metals are generally present in very small concentrations.

The release of untreated swine effluent into soil, rivers and lakes pose potential risks for disease onset or resurgence, insect proliferation, odor and degradation of natural resources with fish and animal death, plant toxicity, eutrophication. of water resources. Water losses and wastes on the farm increase the volume of effluents produced, aggravating the pollution problem and increasing the costs of storage, treatment, transportation and distribution of waste. The volume of liquid waste depends on management, but generally, Oliveira in his article entitled "Rational use of water in pig farming" (EMBRAPA-CNPSA. Documents, 27, 1993. 188p.) Reports an estimate of waste production in 100 liters per matrix per day in full cycle and 60 liters per matrix per day for piglet production units and 7.0 liters per finished per day. The chemical composition of the waste is also associated with the management system adopted and presents large variations in the concentration of the component elements, depending on the dilution to which they were submitted and the storage system.

Animal waste is usually processed by aerobic (composting) or anaerobic (biodigestion) processes, with the final product (aerobic compost or anaerobic liquid effluent) subsequently distributed in the soil. Although ponds have a reasonable removal of carbonaceous organic material, nitrogen remains in the effluent at very high concentrations and further treatment steps are required. meet the wastewater emission standards set forth in environmental legislation.

Most of the state-of-the-art documents concern the treatment of sewage sludge, which is a waste characterized by having a large amount of organic charge and pathogens in the effluent, having a very strong odor. This material must be treated, resulting in a product with potential fertilizer that can be used in soils. There are several techniques available for sewage sludge treatment: thickening, dehydration and drying, stabilization, conditioning, decontamination, liming, composting, pasteurization, incineration, pyrolysis, gasification, etc. Usually these treatments are performed specialized treatment plants, which generates high cost of storage and transportation.

US6171499 dated 06/01/1997 discloses a method for treating sewage sludge, combining anaerobic digestion and incineration in a few steps: anaerobic digestion with biogas production, mechanical dehydration of digested sludge. , the combustion of natural gas-enriched biogas for the appliance to operate in at least 88% yield, for drying the dehydrated sludge there are two apparatus connected in series, where the first operates with an oil circulation boiler and the second a dryer. fluid bed and cooler, connected to a cyclone. The method according to this invention is applicable to the treatment and transformation of agricultural effluents such as manure into granular and bagged fertilizer.

Some studies on pyrolysis of animal waste are reported. Shinogi et al., In their article entitled "Basic Characteristics of Low-Temperature Carbon Products from Waste Sludge" (Adv. Environ. Res., 2003, 7, 661-665) prepared a 380-manure pyrolysis product by heating to ° C in a limited air atmosphere and reported the properties of the product, which had a low specific surface area of 2.2 m2 g-1, 25.6% ash and 49.2% elemental carbon. The authors described the main use for pyrolysis as a soil conditioner due to the high nitrate, phosphate and potassium ions content. In a second study, entitled "Pyrolysis of Plant, Animal and Human Waste: Physical and Chemical Characterization of the Pyrolytic Products" (Bioresource Technol. 2003, 90, 241-247), Shinogi et al. described the production of pyrolyzed manure through the temperature range 250-800 ° C in closed containers, and at this temperature the specific surface was low (<20 m2 g-1) in this temperature range. The pyrolyzed manure also had a high ash content (up to 60%), a high pH (> 10) and a total carbon content of less than 40%.

Bilitewski in an article entitled "Production and Possible Applications of Activated Carbon from Waste" (Recycling Berlin, 79 Int. Recycling Cong. Thome-Kozimiensky, Ed, Berlin V1, 1979, 714-721), reported a pyrolyzed product from bed. chicken in a fluidized bed reactor. He reported that bird droppings produced a product with a specific surface area of 60.5 m2 g-1, 27.5% elemental carbon and 52.4% ash content.

Patent Application RU2447045 dated 10/26/2010 concerns the transformation of chicken litter by pyrolysis at 500-550 ° C for the purpose of obtaining a high carbon mineral residue and gas phase. . In this case the chicken litter was mixed with waste containing cellulose in the ratio 1: 1 or 1: 0.7 by weight.

Although several methodologies exist for the production of pyrolysis fertilizers from plant, animal and industrial residues, it is necessary to take advantage of the potential represented by the large amount of effluent produced in swine production in order to produce a product with high added value from an alternative source. Thus, a fertilizer product with enhanced and differentiated agronomic and environmental properties can be produced at low cost, producing energy and reducing the effluent's organic load, resulting in nutrient-rich biomass with high stabilized organic matter content.

Thus, one of the advantages of the process lies in a step of thermochemical conversion after digestion, which promotes the utilization of the phase solid (sludge) from swine effluent, highly rich in nutrients essential for plant growth and development, such as nitrogen, phosphorus, potassium, calcium, magnesium and micronutrients, not containing heavy metals, and enhancing the waste by resulting in a new type of slow release nutrient fertilizer. The process can be done on the property of the pig farmer, thus avoiding transportation and storage costs, proving to be technically and economically viable. SUMMARY OF THE INVENTION

The present invention relates to effluent processing to produce useful materials and compositions at an acceptable cost, without producing smelly odors, and with high energy efficiency. In particular, the invention relates to a multi-step process for the production of sludge-based fertilizer from swine wastewater: the biodigested effluent has its solid phase separated and subjected to thermochemical conversion at 600 ° C in a rotary drum. The final product has slow release of nutrients because it contains struvite crystals. Raw materials that have little commercial value are converted into a fertilizer with high added value and differentiated characteristics, having a high content of nitrogen, phosphorus, potassium.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1: Visual characteristics of the fertilizers obtained from biodigested and pyrolyzed swine sludge at 600 ° C (A: 15 rpm for 5 hours; B: 22 rpm for 7 hours; C: 25 rpm for 4 hours; D: 40 rpm for 5 hours).

Figure 2: Hydrogenionic potential (pH) of fertilizers obtained from biodigested and pyrolyzed swine sludge at 600 ° C.

Figure 3: Electrical conductivity of fertilizers obtained from biodigested and pyrolyzed swine sludge at 600 ° C.

Figure 4: Nitrate (NO3-) released in deionized water by fertilizers obtained from biodigested and pyrolyzed swine effluent sludge at 600 ° C. Figure 5: Phosphate (P04-3) released in deionized water by fertilizers obtained from biodigested and pyrolyzed swine sludge at 600 ° C.

Figure 6: Potassium (K +) released in deionized water by fertilizers obtained from biodigested and pyrolyzed swine sludge at 600 ° C.

Figure 7: Scanning electron microscopy image indicating the presence of struvite crystal.

Figure 8: X-ray analysis of the crystal electron microscopy indicating the main elements that make up struvite (P, Mg, O). DETAILED DESCRIPTION OF THE INVENTION

The term "effluent" can be defined as wastewater resulting from industrial, agro-industrial processes, confined animal production systems and domestic sewage that are discharged into the environment. Preferably for the present invention the term "effluent" refers to wastewater from swine confined animal production systems (SPACs).

The effluent, especially from swine SPACs, is subjected to the commonly performed treatment which is prior digestion of the waste, such as digestion, which can be carried out in stabilizing ponds or anaerobic digesters, which digest organic matter under anaerobic conditions (ie in absence of oxygen).

The liquid effluent resulting from biodigestion is subjected to a separation step from the solid phase contained in the effluent, sludge, which may be carried out by one or more separation processes, such as screening, flotation, decantation, filtration, centrifugation, sedimentation. . Remaining liquid effluent after this low solids separation can be reused in the crop as fertigation.

Sludge that has been separated from the liquid part of the effluent is subjected to thermochemical conversion treatment, which may be by combustion, incineration, and more specifically, thermochemical conversion by pyrolysis. The temperature for thermochemical conversion may range from 300-1200 ° C, but is preferably performed at 600 ° C. The conversion drum Thermochemistry is preferably rotary, ranging from 10 to 50 rpm. The residence time varies between 2-10 hours, depending on the waste to be processed and the desired characteristics of the product.

The final product has fertilizing characteristics because it has high levels of essential plant macronutrients such as nitrogen, phosphorus, potassium, calcium, magnesium, and micronutrients such as iron, manganese, zinc and copper. The final product is characterized by slow release nutrients to the soil solution because it contains struvite crystals. Heavy metals, if any, are trapped in the fertilizer matrix. Other types of waste may be added to this solid phase, such as slaughterhouse and refrigerator waste, algal biomass or other terrestrial or aquatic feedstock. Synthetic fertilizers may also be added to balance the chemical formula of the fertilizer produced. The fertilizer can be used in fresh or granulated soil.

The following example is described only to better understand the invention and is not limited to the features set forth in the examples.

EXAMPLE

Pig waste is digested by anaerobic processes (digestion), with the final product being anaerobic liquid effluent. The effluent obtained from the digestion of swine manure passes through an inlet pipe and is pumped into a separation unit consisting of a series of rotary sieves in series, with a 4 mm double-sided cylindrical mesh stainless steel mesh. engines up to 15 hp each, both at low rpm, with horizontal working angle. The pilot system has a 20 hp vacuum hydraulic pump that allows a flow of 40 cubic meters per hour of biodigested effluent in the system, separating approximately 500 kg of sludge per working hour. The yield of the separation process on rotating screens is in the range of 10 to 20% of the separated wet effluent (wet solid phase, or sludge). The liquid phase can be applied as fertigation, and sludge is used for fertilizer production. The separation unit has a scraping blade to distribute the sludge in a movable reservoir, coupled to a conveyor tube with holes in its lower part, so that a greater separation efficiency of the liquid part occurs, with the aim that the Sludge that is transported to the thermochemical conversion drum contains less liquid, increasing process efficiency.

The drum for the thermochemical conversion to the sludge pyrolysis that has been used is rotatable and with adjustable working inclination. The sludge was pyrolyzed using three residence times of 4, 5 and 7 hours and four rotation rates of the thermochemical conversion drum which were 15, 22, 25, 40 rpm under atmospheric pressure and a pyrolysis temperature at around 600 ° C. The drum rotation rate defines the grain size of the product, and can be adjusted up to 50 cycles per minute. The higher the rotation rate, the smaller the final product grain size will be. The working inclination of the thermochemical conversion rotary drum was 10 ° with an internal axis of 50 mm. Thus, just under half of the drum volume, about 400 liters, was filled with sludge, which allowed the processing of about 500 to 600 kg of wet solids per thermochemical conversion step.

The final product is obtained by adjusting the operating time, temperature ramp, final process temperature and rotational rate of the thermochemical conversion drum. The residence time of the material within the drum 6 generally depends on the type of biomass, and may remain for as long as the mass preheat and water evaporate. The flexibility of the system's operation control allows a fine adjustment between rotation rate, temperature rise and end temperature which reduces volatile carbon losses, ie increases the thermochemical conversion rate of volatile carbon and therefore increases the amount of volatile carbon. carbon and yield and quality of the final product. The drum rotation rate should also be adjusted to achieve standardization of product granulation. Table 1 shows the data on the analyzed characteristics of each fertilizer produced at four combinations of pyrolysis drum rotation and residence time tested (A: 15 rpm for 5 hours; B: 22 rpm for 7 hours; C: 25 rpm for 4 hours). hours: D: 40 rpm for 5 hours), and its comparison with air-dried swine sludge without thermochemical treatment (Control).

The drum / charger rotation rate and residence time combinations can be seen in Figure 1, detailing the physical characteristics of each product tested (A: 5 rpm for 5 hours; B: 22 rpm for 7 hours; C: 25 rpm for 4 hours; D: 40 rpm for 5 hours). Table 1 shows the data of the analyzed characteristics of each fertilizer produced in four combinations of pyrolysis drum rotation and residence time, and their comparison with air-dried swine sludge without thermochemical treatment (Control).

Table 1 Characterization of the fertilizers produced, submitted to different rotations and residence times in the pyrolysis rotary drum at 600 ° C (A: 15 rpm for 5 hours; B: 22 rpm for 7 hours; C: 25 rpm for 4 hours;

Control Features * A B C D

Dry Matter (%) 82 89 98 86 91

Total Organic Matter (%) 62 65 62 66 54

Ashes (%) 20 24 36 20 36

Total Organic Carbon (%) 36 38 36 38 32

Nitrogen (%) 4.54 2.26 3.07 3.28 2.97

Phosphorus (g kg-1) 41, 45 17.32 42.55 35.87 34.39

Potassium (g kg-1) 2.61 22.79 8.91 1 1, 35 13.08

Calcium (g kg-1) 29, 17 33.78 78.35 44.89 65.61

Magnesium (g kg-1) 13.30 9.84 24.40 12.36 17.79

Iron (g kg-1) 3.22 16.14 16.28 16.92 24.38

Zinc (g kg -1) 2.181 0.713 2.491 1, 794 1, 605

Manganese (g kg-1) 0.61 1 0.520 1.29 0.99 0.80 Copper (g kg-1) 1.55 0.38 0.99 1.23 1.17 Sodium (g kg-1) 0.56 6.98 2.40 2.73 3.36

* Air-dried sludge without thermochemical treatment.

Drum / charger rotation rate and residence time combinations can be seen in Figure 1, detailing the physical characteristics of each product tested. Figure 2 shows the pH graph and Figure 3 shows the electrical conductivity graph of the fertilizer when released in water. Figures 4, 5, and 6 show respectively the cumulative levels of nitrate, potassium and phosphorus released in water for each of the fertilizers produced (A, B, C and D). The different particle sizes for products A, B, C and D are mainly due to the drum rotation rate, so that smaller grain size is obtained for higher rotation rates (Figure 1). Figures 2 and 3 show respectively the pH and electrical conductivity graphs of 150 ml of solvent water for 1 g of products A, B, C and D. pH values converge to around 8 along of the twenty days analyzed, with no visible differences between each product (Figure 2). On the other hand, the daily evolution of electrical conductivity of product B was different from the others, showing a slow release process of ions, many of which are important fertilizers for plants such as Nitrate (NO3-), Potassium (K +) and Phosphate (PO4). -3).

Figures 4, 5 and 6 show respectively the cumulative levels of nitrate, potassium and phosphate released cumulatively in water over 20 days for each of the fertilizers produced (A, B, C and D). From the joint analysis of figures 1, 3, 4, 5 and 6 it appears that the product B represents a low particle size fertilizer and with slow release properties of nutrient ions to plants. In addition, Figure 7 shows that carbon dioxide release, ie the occurrence of carbon degradation is lower for product B, indicating that the carbon remaining in product B is more stable and less susceptible to physical, chemical and decomposition. / or biological. Therefore, the fertilizer product B obtained by the process described here, with longer residence time and relatively higher rotation rate, brings together unique characteristics of agronomic and environmental application, turning the sludge into a high added value product.

The thermochemical conversion of the resulting material in this example indicated that, unlike biochar derived from plant biomass, the biodigested manure from pyrolyzed swine showed an increase in the amount of oxygen with increasing pyrolysis temperature (Bergier et al., 2013, Low vacuum thermochemical conversion of anaerobically digested swine solids (Chemosphere, v. 92, p.714-720). A more detailed study of the biochar structure and composition obtained from the pyrolysis of pig biodigested manure provides evidence of the presence of struvite crystals. These crystals are formed in biodigester effluent ponds by the chemical reaction between water (H2O), Ammonium (NH4 +), Phosphorus (P) and Magnesium (Mg), most favored at high pH (9.0 to 10.0 ) and for a Mg: P ratio of 1.2: 1 (Nelson et al., 2003, Struvite precipitation in anaerobic swine lagoon liquid: effect of pH and Mg.P ratio and determination of constant rate. Bioresource Technology, v. 89 , pp. 229-236.). The reaction can be described as:

Mg2 + + NH4 + + P043- + 6H2 O- MgNH4. P04. 6H20

From this perspective, increased oxygen in the biochar composition of biodigested swine manure (Bergier et al., 2013. Low vacuum thermochemical conversion of anaerobically digested swine solids. Chemosphere, v. 92, p.714-720) must be associated. largely to the presence of struvite crystals. To confirm this hypothesis, the identification and chemical characterization of these crystals were done by scanning electron microscopy equipped with an elemental X-ray analyzer. Figure 7 shows a scanning electron microscopy image indicating the presence of stranded crystal in the carbonaceous matrix of the manure. pyrolysate. X-ray analysis of these same crystals showed that they are composed of the main elements of struvite, O, Mg and P (Figure 8). So part of the slow release property of The nutrients obtained from the pyrolysis product may be due in large part to the presence of struvite crystals. Maximizing struvite crystallization in biodigester effluent ponds may therefore be important to obtain even more concentrated fertilizers with slow release properties, especially of P and N. Other nutrients are also slowly released, such as potassium, so other processes. and structural conformations of the product are also involved in slow nutrient release.

Claims

1. Process of obtaining fertilizer comprising the steps of:

(i) prior digestion of the waste;

ii) separation of the sludge from the effluent resulting from step i);

iii) thermochemical treatment of sludge;

iv) optionally formulating the mixture with the addition of nutrients;

v) optionally, fertilizer granulation;

characterized by the fact that the residue originates from confined swine production systems.

Fertilizer production process according to claim 1, characterized in that the previous digestion of the residue (step i) takes place by biodigestion.

Fertilizer production process according to claim 1, characterized in that the thermochemical treatment optionally involves the addition of algal biomass, slaughterhouse or refrigerator waste or any other type of organic material of plant origin.

Fertilizer production process according to Claim 1, characterized in that the sewage sludge separation (step ii) comprises at least one separation process selected from: sieving, flotation, decantation, filtration, centrifugation, sedimentation.

Fertilizer production process according to Claim 1, characterized in that the thermochemical treatment (step iii) employs at least one of the following processes: combustion, incineration and pyrolysis.

Fertilizer production process according to claim 1, characterized in that the thermochemical treatment employs temperatures from 300 to 1200 ° C, preferably 600 ° C.

Fertilizer production process according to Claim 6, characterized in that the thermochemical treatment is carried out by rotary drum. Organic fertilizer obtained according to the process described in any one of claims 1 to 7, characterized in that it has struvite crystals in its composition.

Organic fertilizer obtained according to any one of claims 1 to 8, characterized in that it has 1 to 5% total nitrogen, 10 to 50% phosphorus, 5 to 30% potassium, calcium to magnesium ratio of 2 to 10%. : 1 to 4: 1, and 40 to 70% total organic matter.

Organic fertilizer obtained according to the process described in any one of claims 1 to 9, characterized in that it has slow release of nutrients.