Apparatus for conducting a hydrothermal carbonization reaction

Abstract

During hydrothermal carbonization, the carbonization reaction takes place in a reaction tank, at high pressure and high temperature, and with steam feed. Because reactor charging takes place using a batch method, the biomass should be kept on hand in a pulper beforehand, and heated there. Slurry that leaves the reactor, in contrast, subsequently should be cooled in a buffer tank. For this purpose, cooling of the slurry and pre-heating of the biomass are linked. For this purpose, a heat exchanger in the pulper and a further heat exchanger in the buffer tank, which are connected to form a heat circuit, are supposed to be kept on hand. In this way, the slurry to be cooled can give off its heat to the biomass to be heated up, with the effect that significantly less energy leaves the system and has to be supplied to it again at a different location.

Claims

1. An apparatus for conducting a hydrothermal carbonization reaction comprising: (a) a steam generator; (b) a mixing tank; (c) a buffer tank; and (d) a reaction tank connected with the steam generator to receive hot steam and connected with the mixing tank by way of a feed pipe to receive biomass and connected with the buffer tank to drain off a slurry formed in the reaction tank from the hot steam and the biomass; wherein the mixing tank is structured as a pulper and forms a closed heat circuit comprising a first heat exchanger for giving off heat to the biomass contained in the pulper and a second heat exchanger connected with the first heat exchanger and associated with the buffer tank for absorbing the heat from the slurry drained out of the reaction tank into the buffer tank; wherein thermal oil is conducted in the heat circuit as a heat carrier; wherein the at least one of the pulper and the buffer tank is surrounded by at least one heat exchanger coil or wherein at least one heat exchanger coil passes through the pulper or the buffer tank; and wherein at least one third heat exchanger is associated with the heat circuit for withdrawing heat from the heat circuit or for feeding heat into the heat circuit in a targeted manner.

2. The apparatus according to claim 1, wherein the pulper is connected with the reaction tank not only by the feed pipe but also by a gas pipe for charging the pulper with cleaning gas that has been drained from the reaction tank.

3. The apparatus according to claim 1, wherein the pulper is connected with the steam generator to supply hot steam by way of a steam pipe.

4. The apparatus according to claim 3, wherein the pulper has a mixer for mixing the biomass and the hot steam.

5. The apparatus according to claim 4, wherein the mixer comprises at least one of an asymmetrical stirrer and a mixing nozzle arrangement.

6. The apparatus according to claim3, further comprising a centrifugal pump associated with the feed pipe between the pulper and the reaction tank.

7. The apparatus according to claim 5, further comprising a centrifugal pump associated with the feed pipe between the pulper and the reaction tank.

8. The apparatus according to claim 1, wherein the pulper has a funnel-shaped bottom for allowing sand and sludge to settle, wherein an outlet associated with a funnel tip is connected with a sand separator.

9. The apparatus according to claim 1, further comprising a plurality of parallel reaction tanks associated with the pulper.

10. The apparatus according to claim 1, wherein at least one of the pulper and the buffer tank is produced, from a plurality of tank units that communicate with one another.

11. The apparatus according to claim 10, wherein the plurality of tank units are of an identical type.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other objects and features of the invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention.

(2) In the drawings,

(3) FIG. 1 is a schematic representation of the method of functioning of an apparatus according to the invention; and

(4) FIG. 2 is a schematic representation of the heat circuit as well as of the slurry feed.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) FIG. 1, in a schematic representation, shows a reaction tank 1 disposed in the center of the diagram. This tank is connected with a pulper 2 by way of a feed pipe 8, which pulper charges the reaction tank 1 with pre-treated, liquefied biomass. The biomass in the pulper 2 comes from a bunker 6, in which large amounts of biomass are kept on hand. A conveying unit and an impurity separator, particularly a metal separator, which prepares the biomass for the pulper 2, are situated between the bunker 6 and the pulper 2.

(6) The demand for one day's operation of all the reaction tanks 1 connected with the pulper 2, in each instance, is brought into the pulper 2 by way of a feed pipe 8, and kept on hand there, with heated biomass that has been called up being immediately replaced by new, cold biomass from the bunker 6.

(7) Hot steam is blown into the pulper 2 by way of a steam generator 4, which is connected with the pulper 2 by way of a steam pipe 11; the steam heats the biomass contained in the pulper 2, for one thing, and adds water, for another thing, in order to liquefy the biomass to form a slurry.

(8) Using an asymmetrical stirring mechanism, not shown here, the slurry is mixed in the pulper 2, so that uniform heating is guaranteed, and the most homogeneous mixture possible is formed. Sand and sludge from the biomass will settle in the bottom region of the pulper 2. These settled materials can be drained into a sand separator 5.

(9) To save heat energy, the reaction tank 1 will give off what is called purge gas directly into the pulper 2 in the case of excessive pressure, by way of a gas pipe 10, so that the energy that escapes from the reaction tank 1 is retained in the system. The reaction tank is also supplied by the steam generator 4 by way of a steam pipe 12, in order to generate the temperature required in the reaction tank 1, the required water, and the required pressure, and thereby to create the reaction conditions for hydrothermal carbonization.

(10) After the reaction in the reaction tank 1, the slurry, with the carbonized biomass, is drained into the buffer tank 3 by way of a further feed pipe 8; this draining can take place by way of at least partial pressure equalization between reaction tank 1 and buffer tank 3. Because of the pressure gradient between the two tanks 1 and 3, the slurry is drawn into the buffer tank very quickly in this manner, and can subsequently cool off there.

(11) After cooling, the slurry gets to follow-up processing 7 by way of a further feed pipe 8. During the course of further methods, not considered in detail here, process water 20 separated from the slurry can be returned or recirculated to the reaction tank 1, where a further reaction with the organic freights of the process water that are still contained in it can be carried out. Furthermore, in this way the process water is used in the process once again and does not have to be replaced with fresh water.

(12) In total, the result is that the slurry heats up in the pulper 2 and in the reaction tank 1, and is cooled down in the buffer tank 3. The heat of the slurry in the buffer tank 3 can be transferred to the biomass in the pulper 2 by means of heat exchangers in the two tanks 2 and 3, which form a heat circuit 9 between these two tanks 2 and 3, so that less energy can escape from the system. This heat energy transferred to the pulper 2 contributes to less hot steam being required in order to keep the pulper 2 at the required temperature.

(13) FIG. 2 shows a further schematic diagram in which possible heat exchangers 13 and 14 are shown. For one thing, the possibility exists of configuring an outer sheath 15 of the tanks 2, 3 with a double wall. In this way, a hollow chamber 16 forms between the two walls, which chamber can be covered on the outside with an insulation layer 17 in order to prevent heat losses.

(14) A first heat exchanger 13 in the pulper 2 gives off the heat previously absorbed, by way of the inner wall of the double-walled outer sheath 15, and thereby heats the slurry contained in the pulper 2 when it makes contact with the inner wall in question. In addition, the pulper 2 has a heating coil 18 that passes through the pulper 2 and gives off heat to the slurry in the interior of the pulper, as well.

(15) A second heat exchanger 14 in the buffer tank 3 fundamentally works in precisely the opposite way while having the same structure; there the heat carrier that is conducted in the heat circuit 9 absorbs heat from the cooling slurry and transports it to the pulper 2 through the heat circuit 9. Accordingly, the heat transfer coil also functions as a cooling coil 19 here.

(16) What has been described above is therefore an apparatus for conducting a hydrothermal carbonization reaction, which is able to improve the energy balance by means of the use of heat exchangers and the transport of heat through the system, and to structure the method to be more effective by means of already pre-heating and liquefying the biomass in the pulper.

(17) Although at least one embodiment of the present invention has been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.