TECHNOLOGY AND MECHANIZATION OF APPLYING PEAT SUSPENSION TO SOIL

F. A. MALYSHEV, A. A. BUZUK, I. P. KLENBE

In order to increase soil fertility, the All-Union Scientific Research Institute of Peat (VNIIT) has developed a technology, created, and tested a set of equipment for extracting peat for fertilizer by the hydraulic method. This method of extracting peat for the fundamental improvement of light soils may find broad application in the territory of the Polesye Lowland and other regions where peatlands suitable for peat extraction are widespread, near which there are light soils in need of fundamental enrichment with organic matter.

The technological scheme for extracting peat for agricultural needs by the hydraulic method consists in carrying out a number of sequential operations: washing out the peat deposit, taking in and pumping the hydraulic mass from the washed-out pit, transporting it through a slurry pipeline under pressure to the fields to be fertilized, and distributing the hydraulic mass over the fields (Fig. 1).

The washing out of the peat deposit is carried out by a water jet emerging from the nozzle of hydraulic monitor 2 at a velocity of 35–40 m/sec. Water is supplied to the hydraulic monitors under pressure through flexible hoses 5 from high-pressure pumping station 1. Pumping and transportation of the hydraulic mass from the pit to the agricultural fields is performed by peat-pumping unit 3.

The peat-pumping unit T6NF (Fig. 2) is mounted on a wheeled chassis, is coupled to a DT-55 tractor, and consists of the following main assemblies: the working member—pump 1 of the 6NF type, suction head 2, winch 3 for raising and lowering the suction head, gearbox 4, and frame 5. The capacity of the T6NF machine is 250–300 m³/hour. Its weight in the nonoperating state is 1.68 t, and in the operating state, 1.94 t. The specific ground pressure in the operating state is 0.62 kg/cm².

The high-pressure pumping station NDV-75 is likewise a wheeled unit designed to take water from a reservoir and deliver it through hoses to the hydraulic monitors.

The working member of the NDV-75 pumping station is a 4NDV pump, whose capacity is 150–180 m³/hour and whose maximum head is 100 m of water column. A D-75 engine is installed on the NDV-75 unit. The weight of the unit in the nonoperating state is 1.9 t, and in the operating state, 2.28 t.

The GM-70 hydraulic monitor is a mechanism intended for controlling the water jet when washing out the peat deposit. Changing the direction of the jet in the vertical and horizontal planes is achieved by rotating the barrel in hinged connections—

Fig. 1. Technological scheme for harvesting peat for fertilizer by the hydraulic method:
1—high-pressure pump,
2—hydromonitor,
3—T6NF peat-pumping unit,
4—peat pipeline,
5—slotted cotton-fabric hoses

Fig. 2. T6NF peat-pumping unit in transport position: 1—suction head, 2—6NF pump, 3—winch, 4—reducer, 5—frame

...by means of handles. The weight of the hydraulic monitor in the nonworking state is 120 kg; in the working state, 138 kg. The specific pressure on the ground in the working state is 0.16 kg/cm².

Tests of mechanisms for extracting peat for fertilizer by the hydraulic method were carried out on peat deposits of both lowland and raised-bog type in 1963–1965. In the course of the tests it was found that the set of equipment for the basic fertilization of soils is fully operable and reliable in operation.

The operating moisture content of the peat deposit when peat is extracted by the hydraulic method is 86–89%. The hydraulic mass contains 93–97% water; consequently, to convert 1 m³ of a peat deposit into hydraulic mass, 1.2–2 m³ of water is required.

In our case, with an average output of the hydraulic installation of 1,400 m³ of hydraulic mass per shift, 840 m³ of water is required for washing out the deposit.

The processes of peat formation occur where there are favorable conditions for the accumulation of moisture [1]; therefore, on peat tracts there are in most cases lakes, rivers, and streams that can serve as water sources for washing out the deposit. If the washing out of the deposit is carried out next to a body of water, the water is taken directly from it, without additional costs for supplying water to the high-pressure pump. However, in most cases, owing to technological circumstances, water from the water source must be supplied to the high-pressure pump through canals, and in some cases an additional low-pressure pump must be installed for pumping the water. In cases where the supply of water from the water source to the pump is difficult and requires large material expenditures, it is necessary to make maximum use of thaw waters and water from previously worked-out pits.

At present our institute is working on the question of using groundwater for this purpose. The use of groundwater makes it possible to extract peat by the hydraulic method at peat deposits where there are no open bodies of water and where supplying water to the high-pressure pump presents great difficulties.

The peat deposit is washed out simultaneously by two hydraulic monitors. Water is supplied from the pump to the hydraulic monitors by means of flexible hoses, whose internal diameter is 75 mm and length 25–30 m.

The water jet not only washes out the deposit, but also processes it. When the deposit is washed out, plant fibers, as well as the remains of woody inclusions found in the peat, are comminuted. Processing the peat suspension when it is applied to the soil promotes better interaction of the peat particles with the soil. In addition, during washing out of the deposit the water jet mixes the peat over the entire excavated depth and promotes rapid oxidation of the peat, since together with the water a large quantity of air is drawn in. Mixing peat from the various layers of the deposit is of great importance, for it is known that a deposit consists, over its depth, of several strata that differ in degree of decomposition and botanical composition, and sometimes in ash content and chemical composition.

The content of solid matter in the peat suspension depends on many factors: botanical composition, degree of decomposition, ash content, the stumpiness of the deposit, and the slope and dimensions of the pit being washed out.

The content of solid matter in the peat suspension is an important indicator determining both the shift and the seasonal output of the installation.

The presence of stumps makes it difficult to wash out the peat deposit, causes the peat suspension to flow toward the suction head of the peat-pumping installation, and...

promotes the settling of the peat suspension to the bottom of the pit. In this case, when the peat deposit is washed out, the specific water consumption increases, which helps reduce the amount of solid matter in the hydromass.

It should be noted that lowland peat bogs are treeless or sparsely wooded. By washing out a treeless or sparsely wooded deposit with a degree of decomposition of 35–50%, it is possible to obtain up to 8% solid matter content in the peat suspension. The content of solid matter in the peat suspension also depends on the pressure of the water jet at the outlet of the hydraulic monitor nozzle. As the pressure increases, the peat deposit is subjected to better processing; in addition, this makes it possible to increase the dimensions of the pit being washed out.

The peat suspension is delivered to agricultural fields by means of slurry pipelines. Transporting peat suspension through pipes under pressure is the cheapest of all currently known types of transport.

Many works by both foreign scholars [2, 3] and Soviet scholars [4, 5, 6, 7] have been devoted to the study of liquid motion through pipes and to the development of theoretical principles. The motion of hydromass through pipes differs from the motion of true liquids. When hydromass flows through pipes, the transition from laminar to turbulent motion occurs at a lower value of the Reynolds number [8].

The choice of the slurry-pipeline diameter must necessarily be coordinated with the capacity of the hydraulic installation. The velocity of hydromass motion must be no less than 0.5 m/sec; otherwise, settling of peat particles in the slurry pipeline is inevitable. Settling peat particles in the lower part of the flow remain suspended for some time and create additional resistance, to overcome which additional pressure must be expended.

Using the above-mentioned set of equipment, peat suspension can be transported through metal pipes with a diameter of 350–400 mm over a distance of up to 3 km. If it is necessary to transport the hydromass over a greater distance, an additional booster pump should be installed. It should be noted that pressure losses and the distance over which the peat suspension is transported by the hydraulic installation to agricultural fields depend on the elevation of the fertilized fields above the peat deposit being washed out, the capacity of the peat-pumping installation, and the diameter, material, and quality of manufacture of the pipes.

At present, the All-Union Scientific Research Institute of Peat Industry (VNIIT) is exploring the possibility of switching from metal pipes to flexible hoses made of synthetic materials. In such a slurry pipeline, pressure losses will be lower, and it will be more convenient during installation, dismantling, and transportation.

During prolonged shutdowns, the hydromass must be drained from the slurry pipeline or the pipeline must be flushed with water before stopping, since during the shutdown peat particles settle in the slurry pipeline, as a result of which its effective cross-section is reduced. When work is resumed, the hydromass flows at a higher velocity; in individual sections of the slurry pipeline, laminar flow changes to turbulent flow, which causes significant head losses.

The hydromass is delivered through slurry pipelines to a more elevated point on the field surface, and from there it is directed along furrows to the plots being flooded. For uniform distribution of the hydromass over the spreading fields, plots edged with small embankments are created with a single-share plow. The size of individual plots depends on the slope of the surface: at a slope of up to 0.01 it is 15–25 m², and from 0.01 to 0.02, 10–15 m² [9].

The content of solids in the peat suspension changes only slightly during its transport along the furrows, since, on the one hand, some settling of peat particles is observed, while, on the other hand, the soil absorbs water. Thus, when sandy-loam soil was flooded with hydromass at a surface slope of 0.02, the average solids content at the slurry pipeline was 7.55%; at a distance of 30 m from it, 7.56%; and at 60 m, 7.53%. Uniform application of peat to fields can be ensured by regulating the thickness of the hydromass flooding layer.

On dissected fields, hydromass is supplied under pressure only by means of slurry-pipeline pipes, using tees of the main slurry pipeline, from which pipes are laid along the length of the area being flooded. After flooding is completed, they are moved to the next area.

When the peat begins to turn into a solid mass (at a moisture content of 65–80%), it is advisable to loosen it with disk or tooth harrows and then plow it under to a depth of 25–35 cm. If the peat is not incorporated into the soil in a timely manner, it dries out to a low moisture content, and after this its moisture capacity decreases considerably. In summer, under the conditions of Belorussia, the hydromass dries within 3–7 days to a moisture content of 65–80%.

The hydraulic method of extracting peat for agricultural needs makes it possible to mechanize all operations, beginning with excavation and ending with distribution of the hydromass over the fields. The duration of the peat-extraction season for radical soil improvement by this method is 2.5 times longer than for the extraction of fuel peat, and twice as long as with the milling method.

Accounting for peat can be carried out in two ways: 1) according to worked-out pits and 2) according to the hydromass spread over the fields. The quantity of peat applied to the soil is more correctly accounted for directly in the fields. However, in most cases the flooding fields have an uneven surface, and moreover with a considerable slope in one direction or another. In addition, when the peat dries, it must be incorporated into the soil. This has a substantial effect on timely and correct accounting. Therefore, the main accounting of peat when extracting peat for agricultural needs must be carried out according to the worked-out pits.

Table 1

Calculation of the cost of one ton of peat extracted by the hydraulic method
for radical improvement of light soils

The cost of 1 ton of peat, with a seasonal productivity of the peat-pumping installation of 42 thousand tons of peat recalculated to 60% moisture content, under 30-shift operation, is 60 kopecks (Table 1).

REFERENCES

1. S. N. Tyuremnov. Peat Deposits and Their Exploration. Gosenergoizdat, 1949.

2. L. Schiller. The Motion of Liquids in Pipes. Association of Scientific and Technical Publishing Houses, NKTP Publishing House, 1936.

3. Herriek H. N. Oil and Gas J. No. 11, 1932.

4. F. F. Petrenko. Transactions of VIMT, issue 1, 1938.

5. A. N. Klimentov. On head losses in pipes during the motion of hydromass. Proceedings of the Academy of Sciences of the USSR, Department of Technical Sciences, No. 8, 1939.

6. M. P. Volarovich, N. N. Kulakov, E. P. Semenskii, K. I. Samarina, N. D. Bezzubov. Determination of the velocity profile during the flow of peat pulp through pipes of 570 mm diameter. Journal of Technical Physics, issues 7–8, 1944.

7. N. N. Kulakov, K. I. Samarina. Experimental study of the velocity profile during the motion of peat pulp through pipes. Journal of Technical Physics, vol. 9, 1939.

8. M. P. Volarovich, N. N. Kulakov, K. I. Samarina, E. P. Semenskii, N. D. Bezzubov. Establishment of a calculation formula for the flow of peat hydromass through pipes and determination of the velocity profile in pipes of 755, 570, and 440 mm diameter. Colloid Journal, issues 1–2, 1946.

9. F. A. Malyshev. Hydromechanization of Peat Extraction for Fertilizer. Minsk, 1957.