Agriculture 4. Technologies of storage and processing of agricultural products

 

Assoc. Prof. V.Yu. Ovsyannikov, graduate Ya.I. Kondrateva,

graduate student Yu.S. Kraminova. student T.S. Kirichenko

Voronezh State University of Engineering Technologies, Russia

 

Method of techno - economic analysis of the concentration of

low-temperature systems for liquid media

 

Techno – economic analysis of the plant operations low-concentration liquid media by freezing is performed, as a rule, with the following goals [1, 2]:

a) to compare the concentrating installation of various types;

b) determine the optimum temperature concentration;

c) to determine the optimal speed of the refrigerant or brine.

The criterion for selecting the optimal operation mode of concentrating the installation and comparison of the concentrating units between themselves is part of the annual cost of the refrigeration unit (P), which refers to the crystallizer and is variable. Such operating costs, such as salaries of staff, heating and lighting plant, depreciation and repairs, overheads and other, are not taken into account because they are not in this case constant and do not depend on the mode of operation of concentrating the installation [3, 4].

Write the General equation for the reduced annual costs as follows:

                                   (1)

where Ýð – operating costs; Ê – capital costs; Eí – regulatory efficiency ratio; À – depreciation expense equipment; Ð – the repair costs of the equipment; Ýí and Ýê – the cost of electrical energy for driving the pump, the feed product concentration and compressor refrigeration unit; W – the cost of cooling water in the condenser cooling water refrigeration unit.

Depreciation expense equipment À, ð. consist of the following components

                     (2)

where Êê – the cost of the mold – installation freeze concentration with installation and average transport costs, ð.; Êõà – the cost of the refrigerant or cooling medium charged into the cooling system, ð.; Êèç, Êí, Êê – ñ the price of thermal insulation installation freeze concentration, feed pump and compressor refrigeration unit, R.; τ – the lifetime of the equipment, ð.

The cost of the refrigerant or coolant, filled into the mold, is calculated by the following formula,

,                                                      (3)

where V – the volume of the corresponding part of the evaporator crystallizer – freeze concentration installation, ì3; γ – coefficient the filling volume of the liquid; ρ– the density of the liquid refrigerant or coolant, kg/m3; Sõà – the cost of the refrigerant or coolant, p./kg.

It should be appreciated that the cost of the refrigerant can reach a significant proportion of the total installation cost.

The cost of thermal insulation mold Êèç, ð., must be taken into account only in the calculation of the mold - vymorazhivatelya formula

                                                   (4)

where Fí.î – the total surface of the outer fence of the chiller plant, m2; δèç – the thickness of the insulation, m2; Sèç – the cost of shielding, p./m3.

This should take into account that the thickness of the thermal insulation layer, determined by calculation should exclude condensation of moisture from the air on its outer surface.

The costs of the feed pump Êí, ð. can be calculated from equation

                                                           (5)

where bí – value of the pump drive, referred to 1 kW power it, r./kW; Ní – of the pump power expended on overcoming the hydraulic resistance (Δp) in the crystallizer kW.

When using the intermediate brine component of the pump power required to overcome the hydraulic resistance of the mold may be found by the formula

                                                           (6)

where V – the pump capacity, m3/s; Δp – flow resistance of the mold, Pa; η – efficiency feed pump and the motor.

The cost of the compressor Êê, ð it should also be attributed to the variable part of the above annual costs. To implement the various temperature modes require different sizes of compressors. However, this effect is small and the effect of changes in the depreciation cost of the compressor can be neglected [4-6].

Expenses for the repair of equipment Ð, ð. it can be estimated as a fraction of its value

,             (7)

here p – percentage of the value of a piece of equipment for its repair.

The cost of power consumed in the pump to the initial flow of the medium through the apparatus, can be calculated using the following formula:

                                                                  (8)

where Sý - the cost of electricity p./kW·h.; Ní – power consumed in the pump, kW; τ – number of operating hours per year concentrator installation.

Power consumed by the refrigeration compressor will change when the mode of the concentrating plant. With the constant changes in the useful cooling heat transfer rate it will be linked to a change in the temperature difference between the refrigerant and the medium to be concentrated.

At constant average temperature of the medium entering the concentration, the temperature difference between the refrigerant and be concentrated medium depends on temperature changes of boiling and condensation of the refrigerant, determine the power consumed by the compressor.

Increasing the thermal equivalent of work expended by the pump to move the medium to be concentrated through the working chamber concentrating plant results in increased cooling capacity of the compressor, i.e. to increase the power absorbed by the compressor unit of useful cooling [7].

Operating the annual energy costs for the compressor can be calculated by the formula

,                                        (9)

where Q0 – useful cooling capacity, kW; Ký – specific cooling capacity divided by the power consumed.

Consumption in the cooling water for the condenser W, p. / year in general be expressed by the following equation

,                                                       (10)

here Gω – water flow through the condenser, m3/h; β – the ratio of the amount of fresh water to the circulated (considering evaporation spraying and purging); Sω – , the cost of water, p / m3.

 

 

Literature

 

1. Pap L. Freeze concentration. Translation. with Hungarian, edited by O.G. Komyakova. - M.: Light and Food Industry, 1982. - 97 p.

2. Plotnikov, V.T., Filatkin, V.N. Dividing the chiller plant. M .: Agro-publishing, 1987. - 352 p..

3. Antipov S.T., Ovsyannikov V.Yu., Ryazanov A.N., Yashhenko S.M. Development of the model of analysis and forecast of the fundamental characteristics of the process of cryoconcentration. Storage and processing agricultural. 2001. ¹ 4. pp. 36-38.

4. Ovsyannikov V.Yu. Study of the process of freezing moisture from the extracts of the endocrine and special raw material. Diss. cand. tech. the sciences. Voronezh. State. tech. Acad., 2003. 184 p.

5. Antipov S.T., Ovsyannikov V.Yu., Kondratyev Ya.I. Kinetics of the process of concentration by freezing the cherry juice. Herald of the Voronezh state university of the engineering technologies. 2014, ¹ 4 pp. 44-48.

6. Ovsyannikov V.Yu. Optimal modes freeze plasma concentration. Meat Industry. 2012. ¹ 1. 65-68 p.

7. Antipov S.T., Dobromirov V.E., Ovsyannikov V.Yu. Heat- and mass exchange with the concentration of liquid media by freezing. Voronezh. State. tech. Acad. Voronezh, 2004. 208 p.