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Detailed explanation of sludge modified carbonizationresource utilization technology

2021-05-28 11:22:03

Comparison of carbonization technology:

According to China's national conditions, our team thought about two issues a few years ago:

First, why choose carbonization technology as our R & D direction? Second, how to solve the energy needed for carbonization? That is, how to solve its cost problem on the road of carbonization? We have been solving these two problems over the years.

Carbonization, as everyone here knows, mainly refers to a reaction process in which sludge is heated under the condition of isolating air. The traditional carbonization is nothing more than drying and carbonization, and finally a resource utilization.

The reason why we chose carbonization is that as a design institute, we compared various processes and technologies at home and abroad a few years ago. We believe that carbonization has more advantages than other process routes. For example, it occupies a small area and the reduction is obvious. It is obvious for the solidification of heavy metals. The final carbonized particles have no peculiar smell, and there are relatively more ways of recycling.

Why hasn't carbonization been promoted particularly well in China these years? The reason is that an important bottleneck restricting the promotion of carbonization in China is that the relative cost of carbonization technology imported from abroad is relatively high. Based on the above reasons, we are thinking, how to solve the problem of energy and cost? Therefore, in recent years, we have developed sludge carbonization technology, and we call it sludge modified carbonization technology. Sludge modified carbonization technology is actually a new treatment technology combining modification technology and carbonization technology. It's my first time to appear at such a conference today. Next, I'd like to introduce some important aspects of our technology with you.

I will explain this technology to you in a popular way. I use a modifier to convert the organic matter such as protein and sugar in the sludge into oil and gas. This oil and gas is transformed into oil and gas in the process of carbonization. The oil and gas is exported from the carbonization furnace and burned in the combustion chamber, which provides a main energy source for the carbonization furnace. When the organic matter content is more than 50%, the whole sludge modified carbonization system can achieve energy self-sufficiency. Of course, if the organic matter content is less than 50%, we need to add external auxiliary energy in the whole system to solve the whole energy balance.

technological process:

This is the process flow chart of sludge modified carbonization. The double solid line part is the direction of sludge flow, the dotted line part is the direction of steam flue gas, and the wave line is in the direction of water.

In the whole system, at present, we include such parts: mixing section, primary drying section, greasing section, secondary drying section, carbon chemical section, as well as dust removal and cooling section and flue gas synthesis section at the back end. As you can see, after the sludge enters from the front, it finally enters the carbonization section. The carbonized particles in the carbonization section finally return to the primary drying section, and the carbonized particles finally come out of the drying furnace. This is different from other carbonization processes. Next, let me introduce one by one.

The purpose of mixing section is to add a modifier in this place for mixing. The original mud in this place has a buffer function, and the amount of modifier is very small, one thousandth. The modifier is added in the mixing section to keep its moisture content unchanged, with a moisture content of 80%.

Next, the sludge enters the primary drying section. The primary drying furnace in the primary drying section actually has no external energy. Where does its energy come from? Its energy is mainly the heat source from the carbonization furnace in the rear carbonization section. The first part of energy is that there is some thermal circulating water in the carbonization furnace, and the primary drying furnace uses the waste heat of the thermal circulating water of the carbonization furnace. In the second part, the high-temperature carbonized particles from the carbonization section are called carbonization heat carrier. The temperature of this part of heat carrier just out of the furnace is 500 ℃, and this part of heat also returns to the drying furnace for waste heat recovery. The third part is the carbonization section. After the final oil and gas combustion, the flue gas is high-temperature flue gas at about 500 ℃. We also return to the primary drying furnace for waste heat recovery. In these three parts of energy, we return all the energy that can be used by the carbonization furnace to the previous drying furnace for waste heat recovery. Among them, the flue gas is subject to direct heat exchange, the carbonized particles are subject to indirect heat exchange, and the hot circulating water is also subject to indirect heat exchange. At this time, the water content of sludge will be reduced from 80% to about 60% - 65%.

The sludge from the primary drying furnace enters the greasing section, which requires us to provide a thermal environment from the primary drying furnace. Just now, it was said that the flue gas directly exchanged by the primary drying furnace comes from carbonization. After the exchange, the temperature of the exchanged flue gas is about less than 100 ℃, and this flue gas enters my greasing section to provide a good thermal environment for the greasing section. In the greasing section, the sugar and protein in the organic matter of sludge are transformed into oil. It takes a time period. The most important function of this time period is to realize such a function in this place.

At present, we rarely see the thermal process in many reactants. The sludge and modifier react to release heat and evaporate water to reduce the water content. The water content in the greasing section can be reduced from 60% - 65% to 30% - 35%. Later, I will introduce several other functions of the greasing section.

The sludge in the greasing section enters the secondary drying section, which is equivalent to an insurance section. This section is optional. For some with good organic matter content or good moisture content of the sludge in front, the secondary drying section is not required in the process of normal operation. This part is to use external energy to further guarantee the whole system. When my sludge enters the carbonization section, its moisture content must be less than 35%. The change of water content varies according to the mud quality. As I said just now, if the water content and organic matter conditions of the whole system are good, there is no need for secondary drying system if this place meets the requirements.

The secondary dried mud enters the carbon chemical industry section. The current carbonization furnace is a little different from the traditional carbonization furnace. It should realize several functions: first, ensure that the carbonization process must be an oxygen free and oxygen deficient environment. The second is that the oil and gas from the carbonization process should be used as the heat source of a carbonization furnace in the furnace. Third, the water vapor in the carbonization furnace should be led out in advance to avoid consuming the heat source required for back-end carbonization. In the fourth carbon chemical section, the high-temperature flue gas, carbonization heat carrier and thermal circulating water shall be led to the front primary drying furnace for waste heat recovery. After our carbonization furnace, the moisture content is reduced from 30% - 35% to 0% - 5%. Generally speaking, the moisture content of carbonized particles is basically equal to 0, which is between the moisture in the air at ordinary times. Therefore, after a large number of tests, the moisture content of carbonized particles is basically below 5%.

This part is the direction of the whole sludge flow. In the dust removal and cooling section, this part is equivalent to generating flue gas, odor and water vapor, which is dedusted by the dust collector and then cooled by the separation tower. Finally, all flue gas is introduced into the flue gas synthesis section produced by us. This equipment is called flue gas synthesis tunnel for treatment, and the last one is discharged up to the standard. In this flue gas synthesis section, this is our latest technology, in which sulfur dioxide and nitrogen oxides are reacted and converted into fertilizer. After half a year's operation, the fertilizer has actually been generated, and the removal efficiency of sulfur dioxide and nitrogen oxides has reached more than 95%.

This is a process flow of our current application in China Construction Northeast Institute.

We think that carbonization should do two particularly important things. First, we should get through the process flow. If the process flow is not connected, the whole system can not achieve heat balance no matter how good the equipment is. The second is to solve the second problem I just mentioned after realizing heat balance. The solution of energy balance should be solved from the sludge itself. The third is that the equipment itself should make use of the energy that the system can use as much as possible.

Briefly introduce the two key points in our process flow chart

The first fatty process. We started this part of the work three or four years ago. At the beginning of modification, it was modified to make oil. Later, we will talk about the carbonization furnace. At the beginning, the oil made by the carbonization furnace wanted to sell oil. At that time, the price of oil was very high. Later, it was found that the oil was made. As a result, it was found that the back-end process of oil was particularly complex, including the classification of oil. Finally, it would be better for us to directly use the oil in the carbonization furnace for energy. The greasing section has four very important functions, which are obtained through our experiments for many years.

1. Oil production from fat conversion has just been introduced.

2. The process of fat conversion is an exothermic reaction, which can continuously release heat through its own reaction, which plays a great role in evaporating water and reducing water content.

3. Reduction of heavy metals. The whole reaction process of reducing heavy metals is in the patent, which is not introduced here. I'll say a few words later.

4. In the process of fat conversion, we know that the sludge in the fat conversion section is very smelly. There are some relevant materials in the modifier, which can make the fat conversion process play a role of sulfur and nitrogen fixation, and the role of sulfur and nitrogen fixation is a role of deodorization. The taste in the whole modification room is not so big.

The second is the carbonization section. You can imagine that there are four things in the carbonization furnace: sludge, steam, oil and gas, volatile part, and flue gas after combustion. It is a very important process for these four things to realize subsection classification in one furnace. We have to solve it in the research of carbonization furnace in recent years, not only to ensure that the sludge is carbonized in the absence of oxygen, but also to ensure that these four things should realize subsection classification carbonization in one furnace.

These are some of our patented technologies. As I said just now, we began to study the modifier a few years ago, slowly solve the problem of heavy metals in the modifier, and finally slowly start to build a carbonization furnace and drying furnace. For connecting the whole process chain and connecting the process chain through continuous productive experiments, we finally applied for the sludge modified carbonization treatment system. We named it sludge modified carbonization process.

Process layout:

This is the three-dimensional plan we made in the sewage treatment plants in the two cities. Because the site is relatively limited, they are all large sewage treatment plants and the original sludge storage yard. In that case, we made a layout. Inside, you will find that the whole modification section is placed on the second floor. Of course, we advocate that if the site area is sufficient, it should be placed on one floor as far as possible to solve the whole carbonization process. Whether on the first floor or on the second floor, the whole floor area is very small. Taking the scale of 100 tons as an example, the whole sludge treatment workshop covers an area of 3500-4000 square meters.

Take a brief look at the process plan. This is our current mixing section. The front is the raw mud bin, mixer and the back buffer bin. According to different sizes, the buffer bin and raw mud bin are different. The number of sets of carbonization equipment to be equipped according to the scale also needs to be considered in the design.

This is the drying and carbonization section. We basically put it together. We can see that the mixed raw mud enters the primary drying furnace for drying. The dried sludge enters the modification room for modification, and the modified sludge enters the secondary drying furnace. Just now, it was said that the secondary drying furnace can be used or not. This is a guaranteed furnace. The secondary dried sludge enters the carbonization furnace, the flue gas of the carbonization furnace is used for primary dry waste heat, and the carbonized particles of the carbonization furnace are used for primary dry waste heat recovery.