RU1790982C - Method for controlling adsorption apparatuses operating in parallel - Google Patents

Abstract

Usage: can be used in the automation of industrial and sanitary installations for technological and ventilation emissions, mainly by adsorption methods. SUMMARY OF THE INVENTION: the total flow rate of the steam-air mixture being cleaned is continuously measured, its values are compared with the average allowable total flow rate, the difference between these flow rates is determined and the number of adsorption apparatuses operating is changed depending on the sign and the value of the obtained flow difference. Moreover, when the consumption of the mixture being cleaned is reduced, the devices with the least saturated adsorbent layer are turned off and put into reserve, and when they increase, they are sequentially removed from the reserve and the devices with the most saturated adsorbent layer are turned on. 2 silt

Description

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The invention relates to the protection of the environment, in particular the air basin, can be used in the automation of industrial and sanitary installations for technological and ventilation emissions, mainly by adsorption methods.

A known method of controlling parallel-running devices, according to which by measuring the temperature front of sorption in each of the adsorbers, determining the speed of its movement, calculating the average value of this parameter for the entire group of adsorbers and then correcting the flow rate of the vapor-air mixture (PVA) entering each device according to the deviation of the rate of movement of the temperature front of the sorption of the corresponding adsorber from its average value, the optimal distribution is indeed ensured s PVA cleaned by adsorption apparatus that, in the end, WHO-giving. the ability to significantly increase the economic efficiency of the adsorption treatment system as a whole.

However, the known method also has drawbacks, the main of which is that effective practical application of this method is possible only in the case of a fairly stable total consumption of PVA (load) entering the cleaning system, or if it deviates from the nominal no more than the value equal to the maximum load of one device, i.e. in the modes / phi of which the speed П В С in adsorbers is close to the speed accepted during the design of the installation. For example, during the operation of 10. paralleled apparatuses, the maximum load of one adsorber will be equal to 10% of the total PVA consumption (when operating 5 apparatuses, 20%, etc.). At the same time, the analysis of the modes of adsorption treatment plants in real XI

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Under the current production conditions, it shows that almost constantly there are sharp fluctuations in the load (up to 50-70%) during one shift. The frequency and amplitude of these vibrations is determined by the operating mode of the blowers supplying the PVA for cleaning, and depends on the operating mode of the main equipment, which is a source of harmful emissions into the atmosphere.

The noted circumstance testifies to that. that, with a strictly fixed number of adsorbers operating in parallel and a variable amount of cleaned PVA equipment, they are operated, as a rule, under conditions of high underload, which leads to an increase in current costs, in particular, to a large overspending of steam when the adsorbers are in desorption mode. The known method of controlling this task cannot be solved, and since it is exceptional, relevant, there is a need to develop an additional control loop, the task of which is to ensure at each moment of time the optimal (or close to it) number of devices connected in parallel .

An object of the invention is to increase the cost-effectiveness of purification under conditions of a variable amount of PVA to be purified.

Achieving this goal is ensured by the fact that they additionally measure the value of the total PVA flow to the cleaning, compare it with the average allowable flow, determine the difference between these flow rates and, depending on the sign of the difference, change the amount of work - adsorbers, moreover, with a decrease in the flow rate, the PVAs are sequentially turned off and the devices with the least saturated adsorbent layer are put into reserve, and when the flow rate is increased, they are sequentially introduced from the reserve and turn on the devices with the most saturated adsorbent layer.

Thus, the optimum number of adsorbers in operation is determined by the amount of PVA supplied for purification. The graph of this dependence is shown in fig. 1. At the same time, it is not indifferent for the rational operation of the adsorbers which of the working apparatuses is to be put into the reserve as a priority and which of those in the reserve should be included in the work. The withdrawal to the reserve of the apparatus with the least saturated adsorbent layer (in the first approximation - having worked the least time or processed the least amount of PVA) is explained by the fact that the adsorber, which is close to saturation, does not make sense to keep in reserve, it is advisable to saturate it and withdraw it to desorption. With this in mind, it is advisable, first of all, to turn on the device that was last put into reserve, i.e. adsorber with the most (of the reserve) saturated adsorbent layer. For these reasons, the adsorber put into reserve after desorption should be included in the work of the last of the devices in reserve.

The foregoing indicates that any of the adsorption apparatuses operating in parallel can, in principle, be in one of five technological states: adsorption, desorption line (if any), desorption, reserve after adsorption, reserve after desorption.

A block diagram of a device explaining the operation of the proposed control method is shown in Fig. 2. It consists of flowmeters 1, 2, 3, which measure the amount of PVA entering each individual adsorber; flow controllers 4, 5, 6; actuators 7, 8, 9; temperature meters 10,11,12; functional devices 13, 14, 15 that determine the speed of movement of the sorption front in the apparatus; a computing unit 16 calculating an average speed of movement of the sorption front; a flow meter 17 measuring the total amount of PVA for purification; block 18 forming control actions; a unit 19 for selecting a minimum signal; a block 20 controlling the switching of the adsorbers and the storage device 21.

The essence of the operation of the control method is as follows.

The signals from the flow sensors 1,2 3, in accordance with the known method of controlling a group of simultaneously operating adsorbers, are supplied to the corresponding controllers 4, 5, b, acting on the actuators 7, 8, 9. Since the speed of working out the adsorbent layer in the apparatuses is different, for the optimal distribution of PVA among adsorbers, the speed of the sorption temperature front in each of the apparatuses is determined using signals from temperature sensors 10,11,12 in functional devices 13, 14, 15. The output signals of these devices are sent to computing unit 16, where both the average velocity of the temperature of the sorption front for the entire group of adsorbers operating in parallel and the deviations from this average value of the velocities of the heat front in individual devices are calculated. The output signals of block 16, proportional to the values of these deviations, correct the settings of the flow controllers 4, 5, 6.

Simultaneously with the operation of this known control loop, a signal proportional to the total amount of PVA being cleaned from the flow meter 17 is continuously supplied to the control action generating unit 18, where, in accordance with the graph shown in Fig. 1, the interval according to the PVA flow rate is first determined working adsorber:

AX Xi-Xi-i (1) and the average nominal load on the system:

A (X2 + X3) / 2 (2) Then, this value A is compared with the value of the current consumption of PVA Xg, and based on the obtained difference and the flow interval A X, the adsorber switching condition is formed:

1Xg -A | (D X / 2) (3) If condition (3) is satisfied and the value (Xg - A) has a negative sign (which indicates a decrease in the total consumption of PVA), the input of the switching control unit 20 signal about the need to turn off one adsorber with the least saturated adsorbent layer. After that, the value of A automatically changes to the value of A X and takes a new value: A A-AX (A) If condition (3) is also fulfilled, but the value (Xg - A) has a positive sign (i.e., if the flow rate PVA increases) to the input of block 20, a signal is received about the need to withdraw from the reserve and turn on one adsorber with the most saturated adsorbent layer. After that, the value of A also automatically changes by the value of DC and assumes a new value

A A + AX (5) If, upon further monitoring of the current value of the flow rate Xg, condition (3) is again fulfilled, then, depending on the sign of the quantity (Xg - A), either one more adsorber with the most (or least) saturated adsorbent layer. By

the claim of a particular apparatus to be put into operation from the reserve or output to the reserve is carried out in block 19 on the basis of signals received from temperature meters 10, 11, 12 through function 5

10 15

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25 30 35 40 45

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channel blocks 13, 14, 15. In this block, signals proportional to the current level of the sorption front are compared with each other and the input (adsorber code) that has a signal corresponding to the minimum (maximum) level of the sorption front is determined. The corresponding code is assigned to the output of this block, which is the input of block 20.

When a signal is sent to this unit about an excess of the number of working devices, a signal is sent from its output to turn it off and put one of the adsorbers in reserve. Deactivation is carried out using the regulators 4, 5, 6 and their actuators 7, 8, 9. When a signal is sent about the lack of the number of working devices, the signal to retry from the reserve and turn on one of the devices passes in the same sequence through the same elements control, as in the previous case. Along with the closing or opening of the control valves, the same signal is applied to the function blocks 13, 14, 15 to block or unblock their outputs. Information about switching a particular device also enters the storage device 21, which operates on the principle of the first to enter, the last to exit. This makes it possible to write into it and send back to block 20 information about the adsorber codes in the sequence of increasing the level of the sorption front.

Using the proposed control method makes it possible to reduce the steam consumption for desorption by 5% and reduce the adsorbent costs by 3% due to the reduction of the apparatus operating time in the desorption mode and the more economical use of the adsorbent. The economic effect for the installation of purification of ventilation emissions with a capacity of 2880 thousand m3 / day is 35924.4 rubles.

Claims (1)

The claims A method of controlling simultaneously operating adsorption apparatuses by adjusting the flow rate of the vapor-air mixture into each of them, measuring the temperature front of sorption in each of the adsorbers, determining the speed of its movement, calculating the average value of this parameter for the entire group of devices, and correcting the flow rate of the vapor-air mixture entering each of them , by the deviation of the rate of movement of the temperature front of the sorption of the corresponding adsorber from its average value, including the fact that, with In order to increase economic efficiency under conditions of a variable amount of steam-air mixture, the total flow rate of the steam-air mixture to be cleaned is additionally measured, compared with the average permissible total flow rate, the difference between these flow rates is determined and depending on the sign of the difference obtained and in proportion to its value, the number of working adsorbers is changed, while with a decrease in the total flow rate of the steam-air mixture, the devices with the least us are switched off and put into reserve a saturated adsorbent layer, with an increase in the total flow rate, they are sequentially removed from the reserve and apparatuses with the most saturated adsorbent layer are turned on.