JPS5933802B2 - How to use reaction heat - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method of utilizing reaction heat.

More specifically, this is a reaction in which heat removal by evaporation of a heating medium is used to cool an exothermic reaction system, the generated vapor is compressed and heated and used to heat an endothermic glue boiler, and the condensed heating medium is circulated for cooling. It concerns how heat is used.

In an exothermic reaction, heat is released as the reaction progresses, and there are three methods for disposing of this reaction heat.

(k) Adiabatic reaction operation (2) Isothermal reaction operation In the case of an adiabatic reaction operation, the reaction heat is not removed to the outside of the system, so the temperature of the reaction system increases as the reaction progresses.

This method is applicable only to systems in which there is no risk of reaction runaway even when the reaction temperature increases.

Isothermal reaction operation is applied to systems where the desired product yield or quality cannot be obtained unless the reaction proceeds at a predetermined temperature, or where there is a risk that the reaction will run out of control. removed.

Conventionally, as a method for removing reaction heat, it has often been used to preheat raw materials in gas-phase reactions or gas-synthetic reactions, and this method has also been applied in liquid-phase reactions.
The most commonly used method, as shown in FIG. 1, is to provide a cooling coil or jacket b in the reactor a, and to remove the reaction heat by flowing a refrigerant through the cooling coil or jacket b.

In the case of a seed reactor, as shown in Figure 2, a condenser C is attached to the reactor a, and the reaction liquid is evaporated by the reaction heat, and then condensed by the condenser C and refluxed. A reflux cooling method that keeps the reaction temperature constant is also often used.

However, in any case, since the heat of reaction is removed by taking it outside, the heat of reaction is ultimately carried out of the yarn by cooling water and discarded.

On the other hand, in an endothermic reaction, heat must be supplied from the outside in order for the reaction to proceed.

In addition to endothermic reactions, distillation tower boilers are also a type of endothermic system in a broad sense.

Steam is often used as a heat source for these.

Combining an exothermic system and an endothermic system is considered to be extremely advantageous in terms of energy saving, and in particular, using an exothermic reaction as a heat source further increases the effect.

Based on this viewpoint, the present inventor conducted various studies on how to utilize reaction heat, and found that in a butadiene purification and polymerization system, the polymerization heat of butadiene is removed by evaporation of a heating medium, and the resulting vapor is compressed and The temperature is raised and used as a heating source for the purification system of butadiene monomer, and the condensed heat medium is depressurized and
It has been found that when cooled and recirculated to cool the reaction system, the amount of heat required for the butadiene purification system is greatly reduced compared to the conventional method, and based on this knowledge, the present invention was achieved.

That is, the present invention utilizes heat removal by evaporation of a heat medium to cool an exothermic reaction system, compresses and raises the temperature of the generated steam and uses it to heat a reboiler, and further depressurizes and cools the condensed heat medium and circulates it. It relates to the method of utilizing the heat of reaction used.

The present invention is applicable to a combination of an exothermic system and an endothermic system, and is particularly applicable to a combination of a butadiene polymerization system and a butadiene purification system, an ethylene/propylene copolymerization system (which may contain a third monomer), and a combination of these monomers. It is advantageously applied to combinations of an exothermic reaction polymerization system and a seven-mer purification system, such as a combination of an isoprene polymerization system and an isoprene purification system.

At this time, it is of course possible to use heat removal by evaporation of a heat medium to condense the monomer evaporated in the purification system, and add a circulation path that compresses and heats the evaporated heat medium and uses it to heat the reboiler. Even in such a heat medium cooling/heating circulation cycle, a single compressor can heat and cool multiple heat exchangers.

Furthermore, depending on the type of heating medium, if two types of heating medium are used and the circulation cycle is performed in two stages, the heat of polymerization reaction can be used for purification of the solvent, recovery and purification of monomer from the strip liquid. If the circulation path of the heat medium is shortened in this way, it will be more advantageous in terms of thermal efficiency.

The heat medium used in the present invention is not particularly limited, and those having a large heat capacity, thermally stable, and non-corrosive, such as ammonia, freon, hydrocarbons, alcohols, ethers, and ketones, are used. It is selected in consideration of the fluid temperature, operating pressure, critical temperature and critical pressure of the heat medium.

There are also no particular restrictions on the formation of the compressor.

Any of the usual reciprocating type, centrifugal type, axial flow type, rotary type, and screw set can be used.

Furthermore, there are many other embodiments of the combination of the exothermic system and the endothermic system to which the present invention is applied.

Although the exothermic system may be the above-mentioned polymerization system, the corresponding endothermic system may be, for example, a reboiler for purifying a solvent used in polymerization, a steam generator reboiler for steam stripping, or a multipurpose steam generator reboiler.

There is no need to specifically limit the endothermic system, and it is sufficient to select the optimum application for the entire system of the exothermic system and the endothermic system, and perform an optimal design.

FIG. 3 shows a schematic diagram of a conventional polybutadiene production process.

As seen in the figure, the heat taken away by the cooling water in the purification tower and polymerization reactor is not recovered but is wasted.

The case where the method of the present invention is applied to the above process is illustrated in FIGS. 4 and 5.

FIG. 4 shows a case where the present invention is applied to the polymerization reactor a of the cooling coil (or jacket) type shown in FIG.

In the figure, d is a compressor, e is a reboiler, f is a pressure reducing valve, and g is a condenser.

Ammonia is used as a heat medium, and ammonia is supplied in liquid form to the cooling coil (or jacket) b, and the heat of reaction is removed by its heat of evaporation.

The evaporated ammonia is compressed and heated in the compressor d, and is led to the butadiene purification tower boiler e, where it is condensed while supporting the heat.

This is then passed through a pressure reducing valve f to reduce the pressure, cool it, and recycle it to the cooling coil (or jacket) b.

The amount of heat generated by the polymerization reaction in this polymerization apparatus is 1
,000,0OOkcal/hr.

Additionally, the amount of heat required for the butadiene purification system was approximately the same.

In this example, the flow rate of circulating ammonia is 5,000 kg.
/hr, and the absorption and discharge conditions of compressor d were as follows.

The compressor d used is a reciprocating type.

Suction pressure/temperature 3kg/d-to℃ Discharge pressure/temperature 25// 58//The energy required to drive the compressor under these operating conditions is 200,000
It was kcal/hr.

That is, only about 115 liters of energy is required compared to the conventional method.

FIG. 5 shows a case where the present invention is applied to the polymerization reactor a of the reflux cooling type shown in FIG.

In the figure, d, e, f, and g indicate the same parts as in FIG. 4.

l-butane was used as a heat medium.

The monomer or solvent vapor generated from the polymerization reactor a is condensed by removing heat by evaporating i-butane in a condenser C, and the evaporated i-butane is compressed and heated in a compressor d and sent to a butadiene purification tower. The mixture was then circulated in the same manner as in Figure 4.

The flow rate of circulating i-butane was 14,000 kg/hr, and the absorption and discharge conditions of the compressor were as follows.

Suction pressure temperature: 1.1 kg/cytt-10°C Discharge humidity temperature: 8.6 // 60°C The energy required to drive the compressor under these operating conditions is 300,000 kc
al/hr.

FIG. 6 is a modification of FIG. 5, and in the reflux cooling system, for reflux cooling, the vapor of the reactant generated in reactor a is compressed in compressor d, and then a multi-purpose steam generator reboiler e is used. A stage is shown in the case where steam is generated here and the condensed steam is led to reactor a.

[Brief explanation of drawings]

Figure 1 is a diagram showing a conventional coil (jacket) cooling system, Figure 2 is a diagram showing a conventional reflux cooling system, Figure 3 is a schematic diagram of the butadiene production process, and Figure 4 is a diagram showing a coil (jacket) cooling system of the present invention. 5 and 6 are diagrams showing the reflux cooling-heating circulation system of the present invention. a... Polymerization reactor, b...-coil (or jacket), c... condenser, d...
...Compressor, e...Reboiler, f...
...Pressure reducing valve, g...Condenser.

Claims (1)

[Claims] 1. It is characterized by using heat removal by evaporation of the heat medium to cool the exothermic reaction system, compressing and heating the generated vapor and using it to heat the reboiler, and further cooling the condensed heat medium and circulating it. How to use the heat of reaction.