DK172216B1 - Method of transferring the free heat from a hot, contaminated gas stream to a colder, clean gas stream - Google Patents

Description

in DK 172216 B1

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a method of transferring the free heat from a hot, contaminated raw gas produced by gasification of fuels with oxygen-containing gases to the cold gas to be supplied to the gas turbine in a GUD (gas and steam turbine). -) power plant.

Such a method is known from EP-A-0 185 841.

In the gasification of in particular solid fuels 10, it is a matter of transferring the free-heat, bound to the contaminated raw gas to the cold cleaned gas, which arises from the gasification, when the pure gas must be present at a higher temperature level required for further use. Therefore, it is sought to optimize the overall efficiency to apply as much heat as possible through this waste heat utilization of the raw gas generation on the clean gas for further use in the gas turbine.

To increase the mass flow to the gas turbine 20, the pure gas is mixed with nitrogen. Due to the danger of self-ignition by adding oxygen-containing 0 nitrogen, the pure gas can only be heated to 360 ° C in the heat exchanger. Therefore, a high outlet temperature of the raw gas is followed, while a low outlet temperature is sought to achieve a high thermal efficiency in the waste heat utilization on the raw gas.

In a known embodiment, a so-called "quenchless Konzeption", the crude gas and the purge gas have about the same volume flow and therefore the crude gas / purge heat exchanger at a desired low crude gas outlet temperature becomes an expensive element due to the large heat exchange surface.

The raw gas / purge heat exchanger is usually coupled in front of a waste heat boiler coupled to the carburettor, whose outlet temperature under high waste heat utilization must also be aspirated to be low, thereby also costing it due to its large volume at low outlet temperatures. .

It follows that good utilization of the free heat in the gasification raw gas causes waste heat boiler · 5 and raw gas / pure gas heat exchanger very high construction costs.

The object of the invention is therefore to improve the process of the type described initially in the direction that the construction costs of the same high thermal utilization rate can be substantially reduced.

Since the heat transition conditions are essentially physically predicted, this goal can only be achieved by changing the gradients, ie. the temperature differences between the heat-emitting and the heat-absorbing medium.

The object is fulfilled by the method of claim 1.

In order to solve the said task, it is proposed according to the invention that water be injected into the colder gas stream. This injection can be done in one step.

However, according to a further feature of the invention, the injection of water can also take place in several steps. In any case, of course, it must be ensured that there are no dew point undercuts on the raw gas side.

By means of the injection of water, the gradient in the heat exchanger is increased. Furthermore, the transferred heat flow is increased through the increase of the cooler gas mass flow after the water injection.

At the gasification plant with associated GUD power plant, due to the inventive precaution, the waste heat recovery plant located after the gasification can be reduced.

The convection part located on the radiator part of the waste heat boiler usually becomes very small or may lapse. After the radiation boiler immediately follows the raw gas / purge heat exchanger. Thus, the sum of the installed heating surfaces and thus the construction costs are minimized.

DK 172216 B1 3

It is further advantageous that the outlet temperature of the purge gas can be affected by regulating the amount of water injected, and in this way the effect of a soiling on the raw gas side can be counteracted by the influence on the outlet temperature of the purge gas.

The water or water vapor content in the purge gas, in addition to an increase in heat and mass flow which contributes to the increase in the output of the subsequent gas turbine, has a favorable effect on the NOx emission in the combustion chamber of the gas turbine and thus on the NOx content in the exhaust gas, which is a requirements from an environmental technical point of view. It is also expected that the cleaning temperature, due to the water vapor content, can be raised to above the usual temperature as the self-ignition temperature is shifted upwards.

The invention will now be explained in more detail by way of an embodiment with reference to the schematic drawing, the only figure of which shows an embodiment of the invention.

The raw gas flows in a flow of 108,216

Nm 2 / h Qg ve (3 a temperature of 700 ° C into raw gas / pure 0

the gas heat exchanger at 1 and out at 2 at 300 C. I

countercurrent, the equally large clean gas stream at 3 flows in with approx. 40 ° C in a steam heated preheater, which it leaves 0 25 at 150 C, to run into the first stage of the raw gas / purge heat exchanger at 4. Heated to 0 250 C, the purge gas is removed and cooled at 5 with 7 t / h water to 158 ° C. At 6, 116,922 Nm3 / h of mixed gas / water vapor enters the second stage and is heated to 30 to 250 ° C, extracted and cooled at 7 with 7.5 t / h of water to 170 ° C. At 8, 126,251 NmVh of pure gas and water vapor run into the third stage, which is left with the final temperature 360 ° C.

The crude gas is cooled to 486 ° C in the third stage and in the 2nd stage to 400 ° C. A total of 14.54 Mio. kcal / h as opposed to 7.4 Mio kcal / h in a comparison

Claims (2)

A method of transferring the free heat from a hot, contaminated crude gas resulting from the gasification of fuels with oxygen-containing gases to the cold gas to be supplied to the gas turbine in a GUD power plant using a crude gas / purge gas heat exchanger, characterized in that water is injected into the purge gas stream in one or more steps, whereby the purge gas for water injection is taken out of the heat exchanger and subsequently fed into it again. Process according to claim 1, characterized in that the water injection into the purge gas stream is effected as soon as it has reached a temperature of 250 ° C in the heat exchanger.