JPH0229112B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a smokeless solid fuel using a carbonaceous material, particularly a solid material of coal and/or coke particles and a bitumen binder, a smokeless solid fuel produced as described above, and a furnace for use in this method. Pertains to. Air pollution from various fuels is becoming an increasingly important issue in several countries, for example the UK's Clean Air Act sets out requirements regarding the smoke-emitting nature of fuels for home heating. There is. a solid of carbonaceous particles and a bitumen binder;
For example, "raw charcoal briquettes" burn with smoke depending on the nature and amount of volatiles. These solids are therefore usually treated by some kind of heat treatment, for example by carbonization, if appropriate after a previous oxidation treatment. The smokeless rendering of small solids of carbonaceous material by oxidation is known from French Patent No. 1047584 and its supplementary patents No. 63415, No. 66133 and No. 67980. The method includes two heating stages at different temperatures followed by a cooling stage. In this method, the reaction rate is primarily controlled by the oxygen content and/or temperature of the process gas, and therefore complex gas regulation measures are required. Furthermore, it is not described to what extent the carbonaceous material is rendered smokeless. In the present invention, the problem of adjusting the reaction rate is
For a given solid, the reaction rate is influenced by 3.
This is accomplished by adjusting several variables: rate, temperature, and oxygen content of the process gas. If a given temperature and oxygen content are maintained, the gas velocity, which is easily regulated by an electric fan, dominates the reaction rate. Furthermore, it has been found that carrying out three or more oxidation steps in a particular order results in a high degree of process flexibility. In addition to the considerable reduction in tar content, the mechanical strength of the solids is considerably improved, for example in terms of compressive strength, abrasion resistance and drop resistance. According to the invention, a smokeless solid fuel is produced from a solid of carbonaceous material, in particular coal and/or coke particles, and a bitumen binder. The solids are subjected to an oxidative heat treatment consisting of at least three stages using hot gases, and then the agglomerates are cooled. The first stage is a heating drying stage, the second stage is an oxidation stage, and the third stage is a final oxidation stage. Smokeless means a tar content that meets the requirements set out for domestic heating in the UK Safe Air Act.
Means less than 1.4% by weight. Next, the method of the present invention will be explained in more detail. For example, the solids of coal and/or coke particles and bituminous binder may be in the form of briquettes, extracts, pellets, etc., such as the solids described in British Patent No. 1,498,494 and French Patent No. 7,538,325. It is also possible to use pulverized coal, coking coal, pulverized anthracite, or any coal fines, pure or mixed with other substances, carbonaceous products or wastes. The binder may be any conventional bitumen material, such as coal tar pitch, petroleum bitumen or pitch, ethylene decomposition residue pitch, and the like. A preferred binder is a petroleum bitumen, such as a high vacuum bitumen or a decomposed bitumen, especially a hard bitumen with a penetration of eg 1-15 dmm and a softening point of 80-95°C. It is also possible to use semi-blown or fully blown precipitates which may contain fluxing oils, in particular propane bitumen. In the first stage of heat treatment, the solid material is heated to, for example, 250°C. The solids lose no residual water and an exothermic reaction, oxidation of the binder, begins. The temperature of the gas just before it collides with the solid is approximately 250-350℃
Preferably the temperature is adjusted to 250-300°C. However, it is also possible to use lower or higher temperatures, provided that the loss of residual water and the initiation of an exothermic reaction occur, and at the same time spontaneous combustion of the solids does not occur. The purpose of the first stage gas flow is primarily to provide the required amount of heat. In the second stage, the temperature of the solid increases due to an exothermic reaction and becomes higher than the gas inlet temperature. In order to prevent ignition of the solids, it is necessary to adjust the conditions, for example by reducing the gas inlet temperature or preferably by water spraying. The purpose of the gas flow is to remove the heat generated inside the solid. Therefore, the gas outlet temperature is higher than the gas inlet temperature. Usually, the gas inlet temperature is the first
The temperature is set at 5-50°C below the stage, preferably 20°C below, but the reaction rate is increased by increasing the gas velocity, reducing the oxygen content and/or adding water while maintaining the temperature as described above. It is also possible to make adjustments. For each oxygen concentration of the gas, there is an equilibrium gas velocity at which the heat generated by the exothermic reaction is removed by the gas. If the gas velocity is lower than the equilibrium velocity, the exothermic reaction will not be regulated and the solids will begin to burn. On the other hand, if the gas velocity is too high, the center of the solids will not be hot enough and the solids will not be sufficiently de-smoked in a given time. Furthermore, injection of water and/or air is also possible, and in some cases preferred, to reduce the reaction rate.
In the case of water, evaporation of the water first lowers the temperature, and then the steam generated by the evaporation lowers the partial oxygen concentration. Therefore, a reduction in the reaction rate occurs in two ways. The purpose of the third stage heat treatment is to remove fumes from the remaining unreacted parts of the solids. As the second stage exothermic reaction progresses, the rate decreases as the concentration of unreacted material decreases. Presumably, the outer layer of the solid has already reacted with oxygen, but the reaction in the center of the solid is not yet complete since oxygen diffusion takes some time. In order to quickly complete the reaction, the gas inlet temperature is increased again, for example to the same value as in the first stage. In principle it is possible to use any other temperature, but the same precautions need to be taken with this temperature as in the second stage. It is sometimes necessary to add a fourth, fifth, etc. heat treatment step to remove or convert the final remnants of potential fumes. For the reasons described in the third stage above, the temperature of the final stage is almost always the second from the last.
The second stage will be higher temperature. The total processing time is typically less than 2 hours, usually about 80 minutes, and consists of, for example, four stages of 20 minutes each. A suitable layer thickness of the solid material is 10-50 cm. Preferably, the gas velocity and oxygen content of the hot gas are such that the core temperature of the solid is at any stage.
Temperatures are adjusted such that the temperature does not exceed 420° and at the same time does not exceed 200°C in the second stage or any subsequent stage. The oxidative heat treatment can therefore be carried out in a moving grate furnace using air and/or fumes as vehicles for heat exchange with the solids. After the second stage, the exothermic reaction must be controlled by a minimum gas velocity through the bed to prevent ignition of the solids. The gas velocity leaving a 40 cm thick layer of 30 g oval briquettes is e.g. 1.6 for an oxygen content of 17-18% by volume.
m/s. Oxygen contents greater than 10% by volume are preferred. It is clear that the fumes generated during heat treatment can be burned, condensed or recycled to avoid environmental pollution. A final cooling step is required for safe handling, storage and use of the solids. In this way the exothermic reaction is stopped and the ignition of the hot solids is prevented. It is appropriate to cool the solid with air and/or water. Air cooling requires time and space. Spraying with water is also possible, but clearly the quickest and least space-consuming method is immersion in an aquarium. Water temperature and soaking time can be varied to adjust the final temperature and moisture content of the solids. If the solid is further cooled in air, some of the moisture absorbed during soaking will evaporate. Typical, non-limiting values are a hot solid temperature of 350°C, a temperature of 110°C after 7 minutes of water cooling, and a water bath temperature of 80-85°C. The heat treatment implementation equipment may be obtained from any known kettle or furnace operating batchwise or continuously. For example, circulating furnaces, moving grate furnaces, tunnel furnaces, etc. can be used. A mobile grate furnace is preferred. The furnace is
at least three regions, preferably in a rest position, which are regulated separately by burners or water nozzles or the like;
Preferably three separate compartments are included. It is also possible to use a fluidized bed type furnace. When hot gas passes through a horizontal layer of solids from below to above, it is observed that the solids in the upper layer reach a maximum temperature due to heat generation in the lower layer. Of course, this is the opposite of the first stage. In the first stage the gas will provide heat and initially the temperature of the upper layer will be lower. The resulting solid may be particularly suitable for domestic use. Examples Examples (Comparative Examples) Pulverized dry anthracite is fed to a heating mixer,
Heated to 80°C and then at 220°C 5.5% by weight of H80/90 bitumen binder (softening point 80-90°C, penetration 6-15 dmm measured by ASTM-D5) was added to the coal. After stirring for 10 minutes at 80°C, the mixture was compressed. 46 kg of small briquettes (approximately 9 cm ³ , 11.2 g, water content 4.3% by weight) were obtained. 2 without atmospheric conditioning, i.e. in the air.
Smoke removal was carried out in the regional experimental reactor. The charcoal briquettes were placed in a metal basket (70 x 70 x 15 cm). The layer thickness was 14 cm. These were heat-treated at 250°C for 20 minutes in region 1 and at 230°C (gas inflow temperature) for 40 minutes in region 2. At the end of the treatment the upper layer reached 315°C. After forced cooling in air, the briquettes were analyzed. Weight 10.8g, water content 0, residual tar content 1.6
weight%. This fuel therefore did not meet the requirements of the UK Safe Air Act referred to above. Example 250℃ for 20 minutes, 230℃ for 20 minutes and 285℃ for 20 minutes
The experiment of the example was repeated using a heat treatment consisting of three steps of minutes. At the end of the process, the upper layer is
It reached 360℃. The residual tar content was 1.2% by weight. The temperature increase at the end of the heat treatment in the example apparently worked to remove 25% more tar in the same amount of time. EXAMPLES The method of the invention was carried out under the conditions shown in the table below. The mechanical properties of raw briquettes and heat-treated briquettes were measured. Rapid cooling was performed by immersion in water.

【table】

【table】

[Table] Thus, the briquettes after the oxidative heat treatment of the present invention are substantially smokeless and exhibit improved mechanical properties.

Claims (1)

[Claims] 1. Using a solid material of coal and/or coke particles and a bitumen binder as a raw material, the solid material is subjected to at least three stages of oxidation heat treatment using a high-temperature oxygen-containing gas, and then the solid material is The first stage lowers the inlet temperature of the hot gas to 250°C.
The second stage is an oxidation stage in which the inflow temperature of the high-temperature gas is lowered to within 50 °C of the first stage, and the third stage is the heating and drying stage in which the inflow temperature of the high-temperature gas is lowered to the second stage. The final oxidation stage is a final oxidation stage in which the temperature is higher than the inlet temperature of A method for producing smokeless solid fuel, characterized by adjusting the temperature so that the temperature does not drop below 200°C during the step. 2. The method according to claim 1, wherein the number of stages is four, and the inflow temperature of the high-temperature gas in the fourth stage is higher than the inflow temperature in the third stage. 3. The method according to claim 1 or 2, characterized in that the hot gas passes through a layer of solid material with a thickness of 10 to 50 cm. 4. A method according to any one of claims 1 to 3, characterized in that the oxygen content of the gas is greater than 10% by volume. 5 Claims 1 to 4 characterized in that the solid material is cooled by water and/or air.
The method described in any of the paragraphs. 6. The method according to any one of claims 1 to 5, characterized in that the bitumen binder is petroleum bitumen with a penetration of 1 to 15 dmm and a softening point of 80 to 95°C. 7. The method according to any one of claims 1 to 6, characterized in that the bitumen binder is a high vacuum bitumen or a degraded bitumen.