Бурение грунтовых зондов, установка энергетических колодцев

All calculations were based on a typical internationally traded coal of which the properties are given in Table E-l. All flow schemes are based on 100 kg maf coal, and the relevant mass and energy values are all based on this quantity. Taking the mass values per second we get the energy flows in MW.

For drying the coal from 12.5 to 2% moisture 31 MJth are required. As this heat is supposed to be supplied by burning part of the clean fuel gas, this corresponds to an energy penalty of about 19MJe.

For heating the water for the optimal coal-water slurry feed gasifier to 325°С 121 MJth/100 kg maf coal are required.

For a classical Texaco gasifier, the carbon conversion has been set at 95%. In all other cases this has been set at 99%.

The energy required for the production of oxygen was taken as 46 MJe/kmole. If not indicated otherwise, the purity of the oxygen is 95% mole.

For making 300°C process steam for dry-coal feed gasifiers, 3MJth/kg are required.

The heat loss from the gasifiers has been taken as 0.5% of the coal LHV for the coal-water slurry feed gasifiers and as 2% of the coal LHV for the dry coal feed gasifiers. In the latter case it has been assumed that this heat becomes available for making steam.

For all compressors and turbines, an isentropic efficiency of 90% has been assumed. For the adiabatic compression of air to 32 bar, this corresponds to 15.6MJe/kmole air. For wet air compression the energy data were 10.7, and 13.1 MJe/kmole wet air for compression to 32 and 64 bar, respectively. For nitrogen compression the same figures have been taken as for air compression.

For gas quenches a recycle gas compressor is required. The energy consumption is llMJe for 100 kg maf coal intake, except for the two-stage dry-feed gasifier where it is only 7 MJe for 100 kg maf coal intake. The reason for this lower figure is that the gas has to be quenched from 1100 to 900°C instead of from 1500 to 900°C.

In case of the Tophat cycle, corrections have been applied for the approach temperatures in the recuperator. As a standard 25 °С was taken for the temperature difference between the turbine outlet and the humidified air leaving the recuperator. For higher temperature differences the efficiency bonus was one percentage point per 25°C.

For the own energy consumption of the power stations, 2 percentage points were assumed in case no C02 was removed. In case of C02 removal from the fuel gas, this figure was increased to 3 percentage points. For flue gas treating the latter penalty was also used, but it was further increased by an additional penalty of 109 MJe that are required to increase the pressure of C02 from the about 0.1 bar at which it is available in the flue gas to the about 6 bar at which it is present in the fuel gas. This figure corresponds to an additional 3 percentage points penalty in the station efficiency, bringing the total energy consumption for gas treating for this case to 6 percentage points.

It has been further assumed that heat above 250°C can be converted into power with an efficiency of 45% by means of a steam cycle.

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