Purpose and area of application

The plates are used for replacing steam and oil heating by electric heating. They are installed on hydraulic wood-working presses/laminating machines. Maximal plate size is 5,000x2,000 mm.

Advantages of electric plate-heating system

• A drastic reduction of spendings on energy resources due to decreased power consumption for heating and temperature maintaining (elimination of power losses for heating of intermediate heat carriers, a decreased mass of the plates, high efficiency of electric heaters).
• Explosion-proof design (absence of both steam boilers operating at high pressures and oil tanks heated above the oil flash point).
• Environmental safety of production, elimination of expenses towards ecological damages (absence of boiler plants, steam emissions and oil leakages).
• High reliability and durability, simplicity of service and maintenance (absence of corrosion-liable pipelines and recirculating pumps operating at high temperatures, elimination of channels which periodically become clogged with boiler scale and oil-coking products).
• Independent temperature control for each plate.
• A possibility for abandoning a boiler plant and cutting relevant operation costs. If the boiler plant is used for central heating it can be shut down after the heating season is over.

Typical set for modernizing a two-plate press

Two plates with electric heating devices, terminal-block boxes, thermal converters and compensators for the plates (if necessary), electrical cabinet with equipment and control desk, and connecting cables.
The electrical equipment for heating control is autonomous and requires minimal operation costs.

Technical and economic assessment of the use of electrically heated plates at modernizing wood-working presses

1.1. A modern efficient steam boiler fed by fuel oil is considered as a heat source before modernization. Monthly expenses towards heating during daytime (i.e., without using a reduced tariff on electricity) before and after modernization are 2227 and 141 USD, correspondingly, i.e., they are reduced by the factor of 15.8. For electrically heated plates made from aluminum alloys these expenses decrease by the factor of 2227/98 = 22.7 (see calculations below). The results of calculations are confirmed in long-run operation.

1.2. Electrode-type steam generator DS3423 used as a heat source before modernization (produced by public company "DneproPress", 75 kW power, 60 l capacity, 380 V supply voltage, working temperature of steam is 180 to 200 oC, warm-up time of plates to 130 oC is 1.2 h). Power consumption of the steam generator per month is 176 h * 75 kW = 13200 kW*h. Power consumption of elecrically-heated plates per month is 4704 kW*h (see calculations below). Thus, expenses on energy carriers reduce by the factor of 2.8.

2. Replacement of an oil heater by electrically heated steel plates will be assessed on the example of press MP10-1789-002 with the plate size 2,500x1,300 mm and working temperature 130 oC. The press was manufactured by the SZK company (Minsk, Belarus) in 1997. The oil-heater power is 22.5 kW and actual power consumption for warming-up both the oil heater and the plates to the working temperature is 75 kW. Then energy consumption per month is (75+22.5*8*0.57)*22 = 3913 kW*h (here the shift duration is 8 h and the energy usage rate is 57%). Monthly power consumption of a similar press equipped with electrically heated plates produced by DLC "NOMACON" (10 kW regular power) is (15+10*0.6*8)*22*2 = 2772 kW*h (here actual power consumption for warming-up each plate is 15 kW*h, the shift duration is 8 h and the energy usage rate is 60%). Thus, expenses on energy carriers reduce by the factor of 1.41. The results of calculations are validated in long-run operation.

3. It appears impossible to assess the efficiency of usage of biogenerator-produced gases as a fuel for steam boilers because the data on the cost of catalysts, expenses on around-the-clock service, frequency and costs of preventative maintenance, expenses towards explosion-proof and ecologically-compatible operation of biogenerators are not available.

4. Comparative tests of wood-working presses produced by "RIOM" company ("Horizont" corporation, Minsk, Belarus) equipped with standard tubular electric heaters and those equipped with NOMACON heaters have demonstrated that power consumption of the latter is by the factor of 1.7 lower due to minimal heat losses. This result is confirmed in long-run operation.

Most of the world-class produces of hot presses offer their customers electric heating of the working plates as a main option.

Calculation of cost efficiency of modernization of a steam-heated press

Calculation:

Monthly expenses for fuel oil: 25.6*87=2227 USD

Electricity charges per month (22 days): 0.03*2*1.8*3.3*(8+10)*22 = 0.03*4704 kW*h = 141 USD (0.03*2*1.8*3.3(2.5+10)*22 = 0.03*3267 kW*h = 98 USD)

Monthly savings on energy carriers: 2227-141 = 2086 USD (2227–98=2129 USD)

Pay-back period for modernization costs: 20000/2086/12 = 0.8 year (19000/2129/12 = 0.74 year) ** Next to the steel plates parameters, the characteristic of plates made from aluminum alloys are shown in blue color.

For plates made from aluminum alloys, power consumption on warming-up, the thickness of plates and modernization costs decrease. On their mechanical strength heat-treated aluminum alloys are virtually as good as a steel.

Main parameters of modernized press d4938

** The parameters for electrically heated plates made from aluminum alloys are shown in blue color.