Method for the use of heat energy from gasification sources in gypsum board production

Abstract

The present invention relates to an improved method for using heat energy in a gypsum board plant. More specifically, the method contemplates taking heat from a gasifier, or other alternative heat source, and using it to dry gypsum boards. In order to control humidity levels, this heat is delivered to one or more board dryers via a heat exchanger.

Claims

1. A method for using a biomass to heat gypsum boards, the method comprising: providing an upstream and a downstream gypsum board dryer, the upstream board drying producing recycled gases having a temperature in excess of an ambient temperature; gasifying the biomass to produce a combustible vapor; burning the combustible vapor to produce a hot gas that is high in humidity; bringing recycled gases from the upstream board dryer into thermodynamic contact with the hot gas to produce a heated recycled gas and a cooled gas; routing the heated recycled gases back into the upstream board dryer; and routing the cooled gas into the downstream board dryer.

2. The method as described in claim 1 wherein the cooled gas is high in humidity.

3. The method as described in claim 1 wherein the step of gasifying the biomass produces a pyrolysis liquor in the vapor phase.

4. The method as described in claim 3 comprising the further step of burning the pyrolysis liquor to produce a hot gas that is high in humidity.

5. The method as described in claim 1 comprising the further step of removing residual carbon and ash from the cooled gas before it is routed into the downstream board dryer.

6. The method as described in claim 1, wherein the bringing the recycled gases from the upstream board dryer into thermodynamic contact with the hot gas is performed using a heat exchanger.

7. The method as described in claim 1, wherein the method includes gasifying paper waste together with the biomass.

8. The method as described in claim 7, the method further comprising separating paper from waste board to provide the paper waste.

9. The method as described in claim 1, wherein the recycled gases from the upstream board dryer are at a temperature between 300-350 F. when being brought into thermodynamic contact with the hot gas.

10. The method as described in claim 1, wherein the heated recycled gas produced by the thermodynamic contacting is at a temperature of approximately 650 F.

11. The method as described in claim 1, wherein the cooled gas produced by the thermodynamic contacting has a temperature of approximately 450 F.

12. The method as described in claim 1, wherein the hot gas has a temperature of about 1800 F. when being brought into thermodynamic contact with the recycled gases from the upstream board dryer.

13. The method as described in claim 1, wherein the cooled gas is high in humidity; wherein the step of gasifying the biomass produces a pyrolysis liquor in the vapor phase; and comprising the further step of removing residual carbon and ash from the cooled gas before it is routed into the downstream board dryer.

14. The method as described in claim 13, wherein the recycled gases from the upstream board dryer are at a temperature between 300-350 F. when being brought into thermodynamic contact with the hot gas.

15. The method as described in claim 13, wherein the method includes gasifying paper waste together with the biomass.

16. The method as described in claim 15, the method further comprising separating paper from waste board to provide the paper waste.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in connection with the accompanying drawings in which:

(2) FIG. 1 is a schematic diagram illustrating the method of the present invention employing gasification sources in the production of gypsum boards.

(3) FIG. 2 is a schematic diagram illustrating an alternative embodiment of the present invention wherein waste heats are employed in the production of gypsum boards.

(4) Similar reference characters refer to similar parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(5) The present invention relates to an improved method for using heat energy in a gypsum board plant. More specifically, the method contemplates taking heat from a gasifier, or other alternative heat source, and using it to dry gypsum boards. In order to control humidity levels, this heat is delivered to one or more board dryers via a heat exchanger. The various components of the present invention, and the manner in which they interrelate, will be described in greater detail hereinafter.

(6) The embodiment of the invention depicted in FIG. 1 is especially suited for biomass, such as yard or tree waste. However, this embodiment can be adapted to use other fuel sources. Whatever the fuel source, it is added to the gasifier 22 and is subsequently converted to CO and H.sub.2 in the gasifier.

(7) Biomass also produces a tremendous amount of pyrolysis liquor which is very high in BTU content. This pyrolysis liquid is in vapor phase in the hot raw gas that exits the gasifier at 24. The hot raw gas is burned in a traditional burner 26 which, in turn, produces very hot gases (i.e. gases with temperatures exceeding 1800 F.). The pyrolysis liquids burn completely in burner 26. The resulting gas also contains the moisture that was contained in the biomass. This is typically 40-50% of the feed stock.

(8) The hot combustion gases and moisture are directed to a heat exchanger 28 where the heat is exchanged with the gases from the first in a series of board dryers (32 and 34). Some gasifiers produce gas with BTU values as low as 100 BTU/CF. Direct combustion of this gas into the gypsum board dryer would produce a volumetric flow problem and change the dynamics of the gypsum board dryer considerably. A heat exchanger is, therefore, necessary.

(9) The recycled gases from the board dryer enters the heat exchanger at a temperature of between 300-350 F. (and preferably 350 F.) and, by way of the heat exchanger, are heated to a temperature of approximately 650 F. The heated gases are then sent back to board dyers 32 and 34 via dampers 38. These heated gases are then used to withdraw moisture from gypsum boards passing through the first in a series of board dyers (32 and 34). Although the preferred embodiment only illustrates two zones, the heated gas can be passed to additional zones in the dryer as needed.

(10) The combustion products and the moisture are cooled in heat exchanger 28 from about 1800 F. to approximately 450 F. This cooled combustion gas (450 F.) with high humidity content is an ideal candidate for introduction into the cooler dryer zones, such as dryer 36. The cooled gases in this step are passed through a baghouse 42 to remove residual carbon or ash which may discolor the board. Typically hot raw gases from these processes contain contaminants. These contaminants could be pyrolysis liquids, carbon particles and sometimes ash. If these contaminants are not completely consumed during combustion they could dirty the resulting board if not otherwise cleaned. Coloration is cause for rejection so it is very important the gas is clean. Alternatively the 450 F. high moisture gas could be used to produce beta plaster by direct injection into a kettle or if pressurized a modified alpha hemi hydrate.

(11) An alternative embodiment of the present invention illustrated in FIG. 2. This embodiment is the same in many respects to FIG. 1, however, it employs waste heat instead of heat from gasification. The waste heat is collected in a boiler 44. This heat is then passed through a heat exchanger 46 whereby it comes into contact with re-circulated gases from a dryer zone. The resulting humid, heated gas is then re-circulated into the dryer zone.

(12) The improvements of the present invention over the traditional method are as follows.

(13) Indirect heating through the use of heat exchanger allows the transfer of the heat without the dilution of the hot gases with combustion by-products or excess air used in combustion. This concept could allow very high temperatures and high humidity's in the hotter zones of the board dryer (1 & 2).

(14) Air leaks into normal board dryers can cause severe energy loses and upset the energy balances. When the energy is delivered to recycle gases/humidified air a controlled amount of air will have to be injected to control the humidity. Air leakage will not cause major problems for the new process. It will, in fact, be necessary and controllable.

(15) The combustion gases once passed through the heat exchanger still contain usable heat. This heat can be cleaned in a bag house and then delivered to the cooler zones of the dryer to finish off its use and to complete the drying of the board.

(16) The combustion gases could also be used in the calciners or gypsum drying processes at the front-end of the board plant. The processes operate at fairly low temperatures. Direct injection of the gases into the calciner would be a very interesting application.

(17) A unique opportunity exists when biomass is the energy feed stock. The unique opportunity entails the use of waste paper from the board plant as part of the feed material. A typical board plant will generate 3-5% waste board per year. The paper content of this waste board is about 5-6% and it can be separated substantially from the core gypsum. For a large scale plant approximately 5,000 tons of paper could be burned per year. The energy produced from gasifying this paper would be about 75,000,000,000 BTU's which is a significant quantity. This paper could be processed through the gasifiers or just burned prior to the gas combustion and added to the gas stream.

(18) The present disclosure includes that contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.