WO2024058749A1

WO2024058749A1 - A plaster firing oven with zero carbon emission

Info

Publication number: WO2024058749A1
Application number: PCT/TR2023/050669
Authority: WO
Inventors: Mehmet Bahattin Daloglu; Timucin Daloglu
Original assignee: Dalsan Yatirim Ve Enerji Anonim Sirketi
Priority date: 2022-09-14
Filing date: 2023-07-10
Publication date: 2024-03-21

Abstract

The present invention relates to an industrial-scale plaster firing oven (1) (furnace) wherein no carbon emission is performed by providing the thermal energy used for receiving the water within raw plaster by means of electricity and by using electric heaters for the thermal energy, in the production of plaster. With the inventive plaster firing oven (1), it is ensured that all of the thermal energy required for the calcination transaction in the process of plaster production is obtained by using electrical energy and thus production is made with zero CO₂ emission during calcination of plaster.

Description

A PLASTER FIRING OVEN WITH ZERO CARBON EMISSION

Technical Field

The present invention relates to an industrial-scale plaster firing oven (furnace) wherein no carbon emission is performed by providing the thermal energy used for receiving the water within raw plaster by means of electricity and by using electric heaters for the thermal energy, in the production of plaster.

Background of the Invention

Particularly, since the early 1990s, there has been an increasing awareness in terms of the global warming problem and accordingly, it was started to make “Global Warming Potential” (GWP) calculations of all emission sources. The amount of energy used during production of construction materials varies substantially based on the types of the said construction materials.

Plaster is a widely used product among construction materials. Particularly, construction materials such as brick, concrete, aerated concrete, briquette and etc. in block form can be used as plaster and also used as the main core material between two cartons in the manufacture of plasterboard.

Production of plaster essentially involves heating natural gypsum (CaSO4.2H20) containing 2 molecules of water such that i molecules of water remain, synthetic gypsum- CaSO4.2H20 may also be released as a by-product as a result of chimney treatment systems which prevents the discharge of sulphur components included in the exhaust gas into the atmosphere following the combustion in electric power generation plants which use high-sulphur fuel oil or coal except natural gypsum. This synthetic gypsum is also frequently used in the plaster or plasterboard sector just like natural gypsum. The heating process of gypsum is usually carried out in suitable ovens at temperature levels of 130-155°C and as a result, fired gypsum is known as calcium sulfate hemihydrate or hemihydrate (HH) in brief. In the sector, this process is called as calcination of plaster as well. Various calcination ovens are used in the industry.

Vertical ovens expressed as “kettle”, particularly preferred in North America, is the most widely used oven. The oven disclosed in the United States patent document no. US 1.746.294 is the most widely used one among of this type of ovens. The oven described in the said document is essentially a large cylindrical structure and the necessary thermal energy is provided from the base upon the base -which is made of heat-resistant steel with specific form- is positioned as suspended on a suitable combustion chamber. The kettle ovens can be basically called as a pot as well. In the United States patent document no. 4.238.238, productivity is increased by adding combustion gases directly into the pot by injecting. Particularly as a result of studies intended for increasing thermal efficiency, all kettle ovens -which are essentially pots with different designs used in North America- are converted into almost entirely internal combustion pots and thereby their thermal efficiency is increased upon being evolved into nonrefractory ovens.

Conventional rotary ovens are frequently used in the industry as well. The use of the typical rotary ovens in the cement sector is also widely seen in the plaster sector. Rotary ovens used in plaster do not contain refractory material inside the oven because transaction is carried out at low temperatures. However, refractor is used inside the combustion chamber which is the heat source. In addition, an indirectly-heated rotary oven is described in the United States patent document no. US 3.871.829. The rotary oven assembly included in this document is received inside the combustion chamber. Another oven is “conical kettle” which is particularly used in United Kingdom countries and identified in the United States patent document no. US 4.629.419. This oven is a structurally inverted cone and the cone is enclosed. Combustion gases are injected into the cone by means of a suitable blower at a high temperature received from the combustion chamber across the structure. Due to the fact that no refractor is used and combustion gases are directly injected into the gypsum, thermal efficiency is greatly enhanced.

Again, another oven that can be said to have a similar structure, is shaped by taking a combustion chamber -which consists of overlapping conical pieces- into a tube and is disclosed in the United States patent document no. US 5.013.237 is non-refractory and it is preferred as an oven which has internal combustion fluidized bed and also high efficiency and quality.

In addition, units with relatively lower thermal efficiency which carry out both grinding and cooking transaction simultaneously within ball or disc mills or hammer mills inside a bearing are used in the sector as well. Thermal energy is provided to this type of cookers with grinding function over a combustion chamber which is coupled to the structure.

In all ovens used in the sector, carbon-based fuels are burned directly or indirectly in the combustion chambers and they are released into the atmosphere after a suitable filtering transaction. In order to obtain one kg of hemihydrate (HH), approximately 0,14 kg of CO2 emission is unfortunately inevitable in a calcination transaction which is carried out by means of thermal energy obtained by using carbon-based fuels.

With approximately 200 million m² of plasterboard and 5 million tons of gypsumbased plaster-like bagged products were produced in Turkey in 2021. The amount of HH within the plasterboard alone is approximately 1.400.000 tons and this is produced with approximately 190.000 tons of CO2 emission. The amount of hemihydrate (HH) used in approximately 5 million tons of gypsum-based mortars produced in the same year is approximately 4 million tons and the amount of CO2 released into the atmosphere was approximately at the level of 560.000 tons.

Likewise, it is estimated that the production of plasterboard in the world was 22 billion m² whereas the production of gypsum -based mortars was 135 million tons in the same year and accordingly, 40 million tons of CO2 emissions was realized. Therefore, today there is need for solutions which enables to avoid all CO2 emissions resulting from gypsum calcination.

On the other hand, it is possible to divide the ovens used in the sector into two groups. The ones performing calcination and both grinding and firing by using relatively higher energy and conventional rotary ovens consume a thermal energy of approximately 950 - 1.250 kJ in order to obtain one kg of HH.

As disclosed in the United States patent documents no. US 4.238.238 and US 4.629.419 and US 5.013.237, these are fluidized-bed or non-refractory ovens. These ovens are usually more efficient ovens with a thermal energy consumption of approximately 770 - 880 kJ in order to obtain one kg of HH.

In relatively more efficient fluidized-bed ovens which bum natural gas or high- calorie liquid fuels, the combustion gases generally enter the oven at a temperature of 800-950 °C. Whereas other type of relatively low-efficiency rotary ovens or units which perform grinding and firing together, the combustion gases are received at a temperature of 600 - 800°C.

With our invention, it will be possible to convert ovens into electric ovens easily and to avoid all CO2 emissions by dismounting combustion chambers using carbon-based fuel and then by connecting sufficient electrical resistance members instead of them in both types of or all gypsum calcination (firing) ovens which enable to reduce the two molecules of water in natural or synthetic gypsum to half molecule of water.

However, since it will be necessary to supply air into ovens at high-temperature in an amount that is quite over the design values due to the fact that the energy carrying capacity (= 1 kJ/kg.K) of air is low, none of the existing furnaces can be converted into an electrically heated air system. In order to supply the equivalent energy provided by the combustion air -that is used during the combustion of natural gas or liquid carbon based fuels- to the furnace at the temperature of the furnace design, it is necessary to use approximately 4-5 times air. Conversion into electric heating is not possible in furnaces which are not designed for air circulation in this amount.

In Table 1, one sample is listed from both types of oven groups

Table 1. Operating values of exemplary plaster firing ovens

In the event that the rotary oven included in the Table 1 is built to operate directly with the air heated by electrical resistance, the amount of air to be supplied to the rotary oven is approximately 67.600 kg per hour (= 85.000 Nm h) when the current gas inlet temperature at 700°C. Likewise, in the event that the fluidized- bed oven included in the Table 1 is built to operate directly with the air heated by electrical resistance, the amount of air to be supplied to the oven is approximately 23.000 kg per hour (= 28.700 Nm³/h) when the current gas inlet temperature at 900°C. The increased air circulation for both types of ovens is too high for both oven sections and dust filter capacities of oven and they cannot be operated. As a result, although existing ovens can be converted into electric heating, they can only operate if their capacity is reduced to approximately 14 of their nominal capacity. Therefore, today there is need for plaster firing oven solutions whereby all CO2 emission is avoided and also which will operate only with the superheated air heated only by electrical energy.

Summary of the Invention

An object of the present invention is to realize a plaster firing oven which enables to obtain all of the thermal energy required for the calcination transaction in the process of plaster production by using electrical energy and thus to make production with zero CO2 emission during calcination of plaster.

Another object of the present invention is to realize a plaster firing oven all of which can be converted into ovens heated by electrical energy and which utilizes water with high energy carrying property in order to increase the energy carried by the heating air that is required for firing.

Another object of the present invention is to realize a plaster firing oven whereby the total amount of air to be used for the firing transaction is reduced by injecting water into the volume wherein electrical resistors are included.

Detailed Description of the Invention “A Plaster Firing Oven with Zero Carbon Emission” realized to fulfil the objectives of the present invention is shown in the figures attached, in which:

Figure 1 is a schematic view of the inventive electric plaster firing oven unit.

Figure 2 is a schematic view of a plaster firing oven -which is operated with an available solid, liquid or gaseous fuel- such that it is converted into the inventive electric plaster firing oven.

The components illustrated in the figures are individually numbered, where the numbers refer to the following:

1. Oven

2. Oven body

3. Heating column

4. Resistance member

5. Air bellows

6. Spray member

7. Pump

8. Combustion chamber

The inventive plaster firing oven (1) which enables to obtain the thermal energy required for the calcination transaction in the process of plaster production by using electrical energy, thus to make production with zero CO2 emission during calcination of plaster and to make production at nominal capacities upon the energy carried by the heating air is increased comprises: at least one oven body (2) wherein the firing transaction is carried out; at least one heating column (3) wherein at least one resistance member (4), that will be used for the heating transaction and that is electrically operated, is included; at least one air bellows (5) which enables to generate the heating air to be used for the firing transaction in the oven body (2), by providing the air to be heated inside the heating column (3); and at least one spray member (6) which enables to spray water to the heating column (3) by means of a pump (7) in order to increase the energy that is carried by the heating air generated upon the air -that is provided by the air bellows (5)- is heated by means of resistance members (4) in the heating column (3). (Figure 1)

In the inventive plaster firing oven (1), the oven body (2) is a firing chamber wherein the calcination transaction is carried out by using the heating air generated in the heating column (3). The heating column (3) wherein the heating air is generated is connected to the oven body (2). In another preferred embodiment of the invention, at least one combustion chamber wherein no gas, liquid or solid-fuelled assemblies are included is located between the oven body

(2) and the heating column (3). (Figure 2) Upon the combustion assemblies located in the combustion chamber (8) existing in a plaster firing oven -which is operated with the available solid, liquid and gaseous fuel- are dismounted, the firing transaction can be continued by using the air heated by means of the electrical resistance members (4). Thereby, the combustion chamber (8) enables the heating air generated in the heating column (3) to access the oven body (2) by aiding the said air passage.

In the inventive plaster firing oven (1), the heating column (3) is a vertical pipe wherein a plurality of resistance members (4) are included. The heating column

(3) can have different geometries and also dimensions that can accommodate the desired number of resistance members (4) in thereof. Therefore, the fact that the heating column (3) has different shapes such as square or is positioned horizontally will not prevent the thermal energy generated by the resistance members (4) from being transferred to the air supplied from the air bellows (5).

In the inventive plaster firing oven (1), the resistance members (4) is located inside the heating column (3) depending on the amount of air desired to be heated. A plurality of resistance members (4) are located inside the heating column (3) and the air supplied from the air bellows (5) is heated by means of electrically- operated resistance members.

In a preferred embodiment of the invention, the resistance member (4) with heating characteristic is a tubular (tube-type) resistor. In another preferred embodiment, the resistance member (4) can be a serpentine, spiral or micaceous heating resistor. The wire of the resistance member (4) can be any of metallic alloys (Nickel-chromium, iron-chromium, aluminum, tungsten, molybdenum and tantalum) or ceramic compositions or ceramic metals (molybdenum disilicide, lanthanum chromite) or carbon/graphite members. The electrical energy required for the resistance element (4) can be supplied over a solar panel or mains electricity or from both sources together. The resistance member (4) can be directly fed from the direct current energy generated by means of solar panel and/or it can also be fed by converting the alternating current supply at any voltage level into direct current by means of a suitable rectifier.

In a preferred embodiment of the invention, the air bellows (5) transmit the air - which will be heated by means of the resistance members (4)- to the heating column (3). Thereby, it is ensured that the heating air is generated by heating the air by means of resistance members (4).

In the inventive plaster firing oven (1), the spray member (6) is located inside the heating column (3) and sprays water to the air being heated to increase the heat carrying capacity of the heating air that is generated in the heating column (3). In a preferred embodiment, the spray member (6) is a nozzle that is resistant to high temperature and can pulverise water. The spray members (6) sprays water to the heating column (3) by pulverising it via the pump (7) and ensures that it mixes with the heating air.

The inventive plaster firing oven (1) can be a rotary or fluidized-bed oven which is operated with an available solid, liquid or gaseous fuel (Figure 2) and it can also be an electrical plaster firing oven wherein a plaster firing transaction that is rebuilt/built is carried out without including the combustion chamber (8) (Figure 1). When it is desired to convert a rotary or fluidized-bed oven -which is operated with an available solid, liquid or gaseous fuel- included in the Figure 2 into an electrically-operated plaster firing oven (1); the combustion assemblies located in the combustion chamber (8) are dismounted and then the heating column (3), the resistance member (4), the air bellows (5), the spray member (6) and the pump (7) are integrated into the existing oven operating with an available solid, liquid or gaseous fuel. Thereby, it is possible to switch into the electric working principle enabling zero carbon emissions of ovens which are included in the market; operate with solid, liquid or gaseous fuel and performs carbon emission. On the other hand, as stated in the Figure 1, the status of the electrically-operated plaster firing oven (1) can be formed over again as a new oven wherein the combustion chamber (8) is not included. Thereby, the existing solid, liquid or gas-fuelled plaster firing ovens (1) which are converted into electrical operation and the electrically-operated plaster firing ovens (1) which are re-built are industrial-scale ovens whereby it is ensured to obtain all of the thermal energy required for the calcination transaction in the process of plaster production by using electrical energy in the oven body (2) and thus to make production with zero CO2 emission during calcination of plaster. In the inventive plaster firing oven (1), water is sprayed to the air -that is heated by the air bellows (5) in the heating column (3)- by means of the spray members (6) and the pump (7) by pulverising the said water in order to increase the heat carrying capacity of the air. The heating air, which is mixed with the pulverized water and has increased intensity and energy, is provided to the oven body (2) directly from the heating column (3) or over the combustion chamber (8) with dismounted assemblies and it is ensured that the calcination transaction medium desired inside the oven body (2) is created.

For example, it is possible to operate with a capacity of 22 tons.HH/hour by injecting approximately 6.900 kg of water into air of 6.400 Nm3/hour (=8.100 kg/hour) and feeding a moist superheated steam-air mixture into the oven body (2) at a temperature of 900°C in order to convert a fluidized-bed oven -which is included in the Figure 1 and currently available- into an electric oven. Temperature of the superheated steam-air mixture to be fed into the plaster firing oven (1) will change the amount of water to be provided to the system. The temperature can vary between 500-1000°C and it is also preferred to be between 780-900°C.

It is possible to develop a wide variety of embodiments of the inventive plaster firing oven (1) with zero carbon emission; the invention cannot be limited to examples disclosed herein and it is essentially according to claims.

Claims

1. A plaster firing oven (1) which enables to obtain the thermal energy required for the calcination transaction in the process of plaster production by using electrical energy, thus to make production with zero CO2 emission during calcination of plaster and to make production at nominal capacities upon the energy carried by the heating air is increased; comprising at least one oven body (2) wherein the firing transaction is carried out; characterized by at least one heating column (3) wherein at least one resistance member (4), that will be used for the heating transaction and that is electrically operated, is included; at least one air bellows (5) which enables to generate the heating air to be used for the firing transaction in the oven body (2), by providing the air to be heated inside the heating column (3); and at least one spray member (6) which enables to spray water to the heating column (3) by means of a pump (7) in order to increase the energy that is carried by the heating air generated upon the air -that is provided by the air bellows (5)- is heated by means of resistance members (4) in the heating column (3).

2. A plaster firing oven (1) according to Claim 1; characterized by the oven body (2) which is a firing chamber wherein the calcination transaction is carried out by using the heating air generated in the heating column (3).

3. A plaster firing oven (1) according to Claim 1 or 2; characterized by at least one combustion chamber (8) which is included between the oven body (2) and the heating column (3) and wherein no gas, liquid or solid-fuelled assemblies are included.

4. A plaster firing oven (1) according to Claim 3; characterized by the combustion chamber (8) which enables the heating air generated in the heating column (3) to access the oven body (2) by aiding the said air passage.

5. A plaster firing oven (1) according to any of the preceding claims; characterized by the heating column (3) which is a vertical pipe wherein a plurality of resistance members (4) are included.

6. A plaster firing oven (1) according to any of the preceding claims; characterized by the heating column (3) which can have different geometries and also dimensions that may accommodate the desired number of resistance members (4) in thereof.

7. A plaster firing oven (1) according to any of the preceding claims; characterized by the spray member (6) which is located inside the heating column (3) and sprays water to the air being heated to increase the heat carrying capacity of the heating air that is generated in the heating column (3).

8. A plaster firing oven (1) according to any of the preceding claims; characterized by the spray member (6) which is a nozzle that is resistant to high temperature and can pulverise water.

9. A plaster firing oven (1) according to any of the preceding claims; characterized by the spray members (6) which sprays water to the heating column (3) by pulverising it via the pump (7) and ensures that it mixes with the heating air.

10. A plaster firing oven (1) according to any of the preceding claims; characterized by the resistance member (4) with heating characteristic which is a tubular (tube-type) resistor.

11. A plaster firing oven (1) according to any of the preceding claims; characterized by the resistance member (4) which can be a serpentine, spiral or micaceous heating resistor.

12. A plaster firing oven (1) according to any of the preceding claims; characterized by the resistance member (4) wire of which can be any of metallic alloys (Nickel-chromium, iron-chromium, aluminum, tungsten, molybdenum and tantalum) or ceramic compositions or ceramic metals (molybdenum disilicide, lanthanum chromite) or carbon/graphite members.

13. A plaster firing oven (1) according to any of the preceding claims; characterized by the resistance member (4) wherein the electrical energy required can be supplied over a solar panel or mains electricity or from both sources together.

14. A plaster firing oven (1) according to any of the preceding claims; characterized by the resistance member (4) which can be directly fed from the direct current energy generated by means of solar panel and/or it can also be fed by converting the alternating current supply at any voltage level into direct current by means of a suitable rectifier.