Technological process method for producing pipe pile by using waste heat of cement

Abstract

The invention relates to the technical field of cement kiln waste heat utilization, aims at solving the problems that in the prior art, economic benefits are poor, the manufacturing cost is high, diversified production cannot be achieved, the cement waste heat utilization rate is low, the production cost is high, the industry is not energy-saving and environment-friendly, and the process arrangement flexibility is poor, and provides a technological process method for producing pipe piles through cement waste heat. Comprising a kiln tail SP boiler system, a kiln head AQC boiler system, a grate cooler and a waste heat-containing power generation pipe pile production system which are connected with one another, superheated steam generated by the kiln tail SP boiler system and the grate cooler enters the kiln head AQC boiler system and generates high-temperature saturated steam, the high-temperature saturated steam formed by mixing in the kiln head AQC boiler system is guided into the waste heat-containing power generation pipe pile production system, and low-temperature saturated steam is guided into the kiln tail SP boiler system for recycling. The device has the beneficial effects of high economic benefit, low manufacturing cost, convenience in diversified production, high cement waste heat utilization rate, low production cost, convenience in energy conservation and environmental protection and high process arrangement flexibility.

Description

Technical Field

[0001] The invention relates to the technical field of cement kiln waste heat utilization, and in particular to a process method for producing pipe piles by utilizing cement waste heat. Background Art

[0002] As a typical high-energy consumption and high-emission key industry, cement has always attracted much attention. At present, the main technical breakthrough directions of energy conservation and emission reduction in waste heat power generation system in cement industry include: 1. Mainly for energy efficiency improvement of existing processes and equipment transformation and upgrading; 2. Mainly for raw material substitution for emission problems in calcination process; 3. Mainly for fuel substitution for coal emission problems in calcination process; and 4. Carbon capture, utilization and storage (CCUS) for terminal disposal. According to the current situation of cement industry, technological development and market preparation, the periods when these four technical breakthrough directions play the main role are different. In the near future, energy conservation and emission reduction of waste heat technology of cement kiln are expected to be upgraded and transformed from existing processes and equipment.

[0003] The waste heat of cement kilns mainly comes from the flue gas at the tail of the kiln and the grate cooler for cooling clinker. With the improvement of energy utilization technology, cement companies are gradually adopting a new type of high-efficiency, low-pressure loss six-stage preheating and predecomposition system. Despite this, the outlet temperature of the preheater is still around 280°C. At the same time, the grate cooler has developed to the fourth generation, and the recovery efficiency, cooling efficiency, and operation efficiency of the grate cooler have been greatly improved. In the future, there is little room for improving the parameters of the grate cooler and the replacement cost will increase. At present, the waste heat of cement kilns is mainly used for power generation, and the economic benefits of using heat energy only for power generation are not high. The diversified utilization of waste heat from cement kilns will become a future trend. The cost of waste heat power generation system is high, 5,000 to 7,000 yuan per kilowatt; the comprehensive investment payback period is long, about 5 to 8 years; and professional technology and equipment are required. If you want to recover the cost in a short time and improve the utilization efficiency of waste heat power generation, you need to seek diversified thermal energy production. At present, the utilization rate of cement waste heat is low, the production cost is high, the industry cannot be energy-saving and environmentally friendly, and the process layout flexibility is poor. Summary of the invention

[0004] The present invention aims to provide a process flow method for producing pipe piles using cement waste heat, so as to solve the problems in the prior art of low economic benefits, high cost of waste heat power generation system, inability to achieve diversified production, low utilization rate of cement waste heat, high cost of pipe pile production, inability of a single industry to save energy and protect the environment, and poor flexibility of process layout.

[0005] The embodiment of the present invention is achieved as follows:

[0006] The embodiment of the present invention provides a process method for producing pipe piles using cement waste heat, which includes a kiln tail SP boiler system and a kiln head AQC boiler system;

[0007] The above-mentioned kiln tail SP boiler system is connected to the above-mentioned kiln head AQC boiler system, and the bottom end of the above-mentioned kiln head AQC boiler system is also connected to a grate cooler and a waste heat power generation pipe pile production system;

[0008] The superheated steam generated by the SP boiler system at the end of the kiln enters the AQC boiler system at the head of the kiln, and the flue gas at the tail of the grate cooler enters the AQC boiler system at the head of the kiln. The superheated steam of the SP boiler system at the end of the kiln and the superheated steam generated by the grate cooler are mixed in the AQC boiler system at the head of the kiln to form high-temperature saturated steam and low-temperature saturated steam. The high-temperature saturated steam is introduced into the waste heat power generation pipe pile production system, and the low-temperature saturated steam is introduced into the SP boiler system at the end of the kiln for repeated use.

[0009] The present embodiment discloses a process flow method for producing pipe piles using cement waste heat. Since the waste heat power generation pipe pile production system is set up next to the waste heat power generation system of the cement plant, the excess heat of the cement plant can be used not only for power generation but also for producing pipe piles, and the economic benefits of production will be greatly increased. As a result, the process flow method for producing pipe piles using cement waste heat has the beneficial effects of high economic benefits, low cost of the waste heat power generation system, easy to achieve diversified production, high cement waste heat utilization rate, low production cost, easy to save energy and protect the environment, and high flexibility in process layout.

[0010] Optionally: the above-mentioned waste heat power generation pipe pile production system has a curing room, and a steam conduit is provided between the above-mentioned curing room and the above-mentioned kiln head AQC boiler system, and the two ends of the above-mentioned steam conduit are respectively connected to the above-mentioned curing room and the above-mentioned kiln head AQC boiler system.

[0011] Such arrangement makes it easy to introduce the high-temperature saturated steam in the kiln head AQC boiler system into the curing chamber through the steam conduit, thereby facilitating the curing of the pipe piles in the curing chamber and realizing the production of the pipe piles.

[0012] Optionally: the internal temperature of the above-mentioned curing room is 40°C to 80°C, and the internal humidity of the above-mentioned curing room is 80% to 100%.

[0013] With such settings, the humidity and temperature can effectively maintain the pipe piles and is conducive to the production of qualified pipe piles.

[0014] Optionally, a cold air valve is provided at one end of the curing room close to the kiln head AQC boiler system, and the cold air valve is connected to the steam conduit along the radial direction of the steam conduit.

[0015] With such arrangement, the cold air valve can perform secondary regulation on the oxygen and humidity inside the curing room, and can ensure that there is enough oxygen in the curing room for people to breathe.

[0016] Optionally: a pressure relief valve is provided on one side of the cold air valve close to the kiln head AQC boiler system, and the pressure relief valve is fixedly connected to the steam conduit.

[0017] With such arrangement, the pressure relief valve can release pressure, thereby facilitating the emergency release of high-temperature and high-pressure saturated steam inside the steam conduit, thereby ensuring the safety of the pressure relief personnel in an emergency.

[0018] Optionally, a temperature and pressure reducing device is provided at one end of the pressure relief valve close to the kiln head AQC boiler system, and the temperature and pressure reducing device is fixedly connected to the steam conduit.

[0019] With such arrangement, the unstable saturated steam is controlled through the above-mentioned temperature reducer and pressure reducer to stabilize the steam temperature at 40°C to 80°C and the humidity at 80% to 100%, which is beneficial to control the humidity and temperature inside the above-mentioned curing room.

[0020] Optionally, a first stop valve is provided at one end of the above-mentioned temperature and pressure reducing device close to the above-mentioned kiln head AQC boiler system, and the above-mentioned first stop valve is fixedly connected to the above-mentioned steam conduit.

[0021] With such arrangement, the first stop valve can control the saturated steam to enter the above-mentioned temperature reducing and pressure reducing device, so that the first stop valve can control the flow direction of the saturated steam.

[0022] Optionally, one end of the first stop valve close to the kiln head AQC boiler system is radially connected to an emergency vent pipe, and a second stop valve is provided on the emergency vent pipe.

[0023] With such arrangement, the second stop valve is in a closed state under normal circumstances. In case of an emergency in production, the first stop valve is quickly closed and the second stop valve on the emergency vent pipe is opened to ensure safe production.

[0024] Optionally: the above-mentioned kiln tail SP boiler system comprises a preheater, an SP boiler, a kiln tail drum, a high-temperature fan and a first blowdown expansion tank;

[0025] A dusty flue gas pipe is connected between the top of the preheater and the SP boiler, a dusty flue gas branch pipe is connected in the radial direction of the dusty flue gas pipe, a first electric shutter valve is installed on the dusty flue gas branch pipe, and the high-temperature fan is connected to one end of the dusty flue gas branch pipe away from the dusty flue gas pipe;

[0026] The SP boiler has a first U-shaped tube, a second U-shaped tube and a third U-shaped tube inside, the inlet of the first U-shaped tube is connected to a first water inlet pipe, the outlet of the first U-shaped tube is connected to a first water outlet pipe, and the first water outlet pipe is connected to the kiln tail drum;

[0027] The inlet of the second U-shaped tube is connected to a second water inlet pipe, which is connected to the kiln tail drum; the outlet of the second U-shaped tube is connected to a saturated steam outlet pipe, which is connected to the kiln tail drum;

[0028] The inlet of the third U-shaped tube is connected to a saturated steam introduction pipe, which is connected to the kiln tail drum. The outlet of the third U-shaped tube is connected to a superheated steam pipe, which is provided with a first electric gate valve at the kiln tail, a muffler at the kiln tail and a second electric gate valve at the kiln tail.

[0029] A dusty flue gas branch pipe is connected between the bottom of the SP boiler and the dusty flue gas branch pipe, and a second electric shutter valve is installed on the dusty flue gas branch pipe;

[0030] A first sewage pipe is connected between the kiln tail drum and the first sewage expansion container, and a kiln tail electric regulating valve is installed on the first sewage pipe;

[0031] A first chain conveyor is provided at the bottom end of the SP boiler, and two groups of first ash guide pipes are connected between the SP boiler and the first chain conveyor. The two groups of first ash guide pipes are provided with a first manual gate valve, a first rotary feeder and a first flexible connection in sequence, and a first kiln ash bin is provided at the discharge end of the first chain conveyor.

[0032] With such arrangement, the above-mentioned SP boiler system at the kiln tail discharges dusty high-temperature gas through the outlet at the top of the above-mentioned preheater and enters the above-mentioned SP boiler through the above-mentioned dusty flue gas pipe. The dusty high-temperature gas exchanges heat with water in the above-mentioned SP boiler to generate superheated steam. The superheated steam enters the above-mentioned AQC boiler system at the kiln head through the above-mentioned superheated steam pipe, and then flows into the above-mentioned waste heat power generation pipe pile production system through the above-mentioned kiln head AQC boiler system. The dust in the dusty high-temperature gas enters the above-mentioned first chain conveyor through the above-mentioned first manual gate valve on the above-mentioned first ash guide pipe, the above-mentioned first rotary feeder and the above-mentioned first flexible connection. The above-mentioned first chain conveyor transports the kiln ash to the above-mentioned first kiln ash bin and other places for treatment.

[0033] Optionally: the kiln head AQC boiler system has an AQC boiler, and the two sides of the AQC boiler are respectively provided with a second blowdown expansion tank, a third blowdown expansion tank, a low-pressure drum and a high-pressure drum;

[0034] The AQC boiler has a common economizer, a low-pressure section evaporator, a low-pressure section superheater, a high-pressure section economizer, a high-pressure section evaporator, a high-pressure section low-temperature superheater and a high-pressure section high-temperature superheater inside;

[0035] The inlet of the public economizer is connected to a feed water pump, the outlet of the public economizer is connected to a second water outlet pipe, and the second water outlet pipe is connected to the first water inlet pipe;

[0036] The inlet and outlet of the low-pressure section evaporator are both connected to the low-pressure drum, a third water inlet pipe is connected between the low-pressure drum and the first water inlet pipe, and a first electric regulating valve at the kiln head is connected in parallel to the third water inlet pipe;

[0037] The low-pressure section superheater is connected to the low-pressure drum, and the inlet of the high-pressure section economizer is connected to the first water inlet pipe. The first water inlet pipe is provided with an electric water inlet stop valve and a second electric regulating valve in parallel with the kiln head;

[0038] The outlet of the high-pressure section economizer is connected to the high-pressure drum, the inlet and outlet of the high-pressure section evaporator are both connected to the high-pressure drum, one end of the high-pressure section low-temperature superheater is connected to the high-pressure drum, the other end of the high-pressure section low-temperature superheater and one end of the high-pressure section high-temperature superheater are both connected to the superheated steam pipe, the other end of the high-pressure section high-temperature superheater is connected to an air guide pipe, the air guide pipe is connected to the steam conduit, and the air guide pipe is provided with an emergency air release valve, a first electric gate valve at the kiln head, a second electric gate valve at the kiln head and a steam turbine room;

[0039] The outlet of the second blowdown expansion tank and the outlet of the third blowdown expansion tank are both connected to the first blowdown system, the inlet of the second blowdown expansion tank is connected to the low-pressure boiler drum, a third electric stop valve is connected between the inlet of the second blowdown expansion tank and the low-pressure boiler drum, the inlet of the third blowdown expansion tank is connected to the high-pressure boiler drum, and a fourth electric stop valve is connected between the inlet of the third blowdown expansion tank and the high-pressure boiler drum;

[0040] The bottom of the AQC boiler is connected to the grate cooler, a second chain conveyor is provided at the bottom of the AQC boiler, a second ash guide pipe is connected between the AQC boiler and the second chain conveyor, a second manual gate valve, a second rotary feeder and a second flexible connection are provided on the second ash guide pipe in sequence, and a second kiln ash bin is provided at the discharge end of the second chain conveyor.

[0041] With such arrangement, the dusty high-temperature gas with a tail temperature of 240°C to 400°C in the grate cooler arranged at the lower part of the kiln head AQC boiler system enters the AQC boiler, and the dusty high-temperature gas exchanges heat with water in the AQC boiler to generate high-temperature saturated steam, and the high-temperature saturated steam enters the air guide pipe and is discharged into the steam turbine room or the steam conduit through the emergency air release valve, the first electric gate valve at the kiln head and the second electric gate valve at the kiln head, thereby facilitating the discharge of the high-temperature saturated steam into the waste heat power generation pipe pile production system, wherein the superheated steam from the SP boiler system at the kiln tail enters the AQC boiler system at the kiln head, the low-temperature saturated steam mixed by the AQC boiler system at the kiln head enters the SP boiler again through the first water inlet pipe for repeated use, and the high-temperature saturated steam mixed by the AQC boiler system at the kiln head enters the curing room through the first stop valve, the temperature and pressure reducer and the pressure relief valve to achieve the curing of the pipe piles.

[0042] Based on the above description, the process flow method for producing pipe piles using cement waste heat disclosed in the present invention has the beneficial effects of high economic benefits, low cost of waste heat power generation system, easy to realize diversified production, high utilization rate of cement waste heat, low production cost, energy saving and environmental protection, and high flexibility of process layout. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 This is a process flow chart of a method for producing pipe piles using waste heat of cement in accordance with an embodiment of the present invention, which includes a process flow chart of power generation using waste heat;

[0045] Figure 2 It is a process flow chart of the waste heat power generation pipe pile production system in an embodiment of the present invention;

[0046] Figure 3 It is a process flow chart of the SP boiler system at the kiln tail in an embodiment of the present invention;

[0047] Figure 4 It is a process flow chart of the kiln head AQC boiler system in an embodiment of the present invention;

[0048] Figure 5 This is a process flow chart of power generation without waste heat in the second embodiment of the present invention.

[0049] Icons: 1-SP boiler system at the end of the kiln, 2-AQC boiler system at the head of the kiln, 3-grate cooler, 4-waste heat power generation pipe pile production system, 5-curing room, 6-steam duct, 7-cold air valve, 8-pressure relief valve, 9-temperature and pressure reducer, 10-first stop valve, 11-emergency vent pipe, 12-second stop valve, 13-preheater, 14-SP boiler, 15-kiln drum, 16-high temperature fan, 17-first sewage expansion tank, 18-dust-containing flue gas pipe, 19-dust-containing flue gas branch pipe, 20-first electric shutter valve, 21-first U-shaped pipe, 22-second U-shaped pipe, 23-third U-shaped pipe, 24-first water inlet pipe, 25-first water outlet pipe, 26-second water inlet pipe, 27-export saturated steam pipe, 28-introduction saturated steam pipe, 29-superheated steam pipe, 30-kiln tail first electric gate valve, 31-kiln tail silencer, 32-kiln tail second electric gate valve, 33-dust flue gas branch pipe, 34-second electric shutter valve, 35-first sewage pipe, 36-first chain conveyor, 37-first ash guide pipe, 38-first manual gate valve, 39-first rotary feeder, 40-first soft connection, 41-first kiln ash bin, 42-AQC boiler, 43-second sewage expansion tank, 44-third sewage expansion tank, 45-low-pressure drum, 46-high-pressure drum, 47-public economizer, 4 8-low-pressure section evaporator, 49-low-pressure section superheater, 50-high-pressure section economizer, 51-high-pressure section evaporator, 52-high-pressure section low-temperature superheater, 53-high-pressure section high-temperature superheater, 54-feedwater pump, 55-second water outlet pipe, 56-third water inlet pipe, 57-first electric regulating valve at kiln head, 58-electric water inlet stop valve, 59-second electric regulating valve at kiln head, 60-air guide pipe, 61-emergency air release valve, 62-first electric gate valve at kiln head, 63-second electric gate valve at kiln head, 64-steam turbine room, 65-first sewage system, 66-third electric stop valve, 67-fourth electric stop valve, 68-second chain conveyor, 69-second ash guide Pipe, 70-second manual gate valve, 71-second rotary discharger, 72-second soft connection, 73-second kiln ash bin, 74-first electric gate valve, 75-third soft connection, 76-first dust collector, 77-steam generator, 78-high temperature boiler, 79-fourth sewage expansion tank, 80-switch valve, 81-second sewage system, 82-second electric gate valve, 83-fourth soft connection, 84-second dust collector, 85-air cooling valve, 86-third chain conveyor, 87-third ash guide pipe, 88-third manual gate valve, 89-third rotary discharger, 90-fifth soft connection, 91-third kiln ash bin, 92-kiln tail electric regulating valve. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0051] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Embodiment 1

[0053] See also Figure 1 , Figure 2 , Figure 3 and Figure 4 In the case of waste heat power generation, this embodiment proposes a process method for producing pipe piles using waste heat of cement, including a kiln tail SP boiler system 1 and a kiln head AQC boiler system 2;

[0054] The kiln tail SP boiler system 1 is connected to the kiln head AQC boiler system 2, and the bottom of the kiln head AQC boiler system 2 is also connected to a grate cooler 3 and a waste heat power generation pipe pile production system 4;

[0055] The superheated steam generated by the SP boiler system 1 at the end of the kiln enters the AQC boiler system 2 at the head of the kiln, and the flue gas at the tail of the grate cooler 3 enters the AQC boiler system 2 at the head of the kiln. The superheated steam of the SP boiler system 1 at the end of the kiln and the superheated steam generated by the grate cooler 3 are mixed in the AQC boiler system 2 at the head of the kiln to form high-temperature saturated steam and low-temperature saturated steam. The high-temperature saturated steam is introduced into the waste heat power generation pipe pile production system 4, and the low-temperature saturated steam is introduced into the SP boiler system 1 at the end of the kiln for repeated use.

[0056] The present embodiment discloses a process flow method for producing pipe piles using cement waste heat. Since a pipe pile production system 4 containing waste heat power generation is set up next to the waste heat power generation system of the cement plant, the excess heat of the cement plant can be used not only for power generation but also for producing pipe piles, and the economic benefits of production will be greatly increased. As a result, the process flow method for producing pipe piles using cement waste heat has the beneficial effects of high economic benefits, low cost of waste heat power generation system, convenience for diversified production, high utilization rate of cement waste heat, low production cost, convenience for energy conservation and environmental protection, and high flexibility in process layout.

[0057] See also Figure 1 , Figure 2 , Figure 3 and Figure 4 The waste heat power generation pipe pile production system 4 has a curing room 5, and a steam conduit 6 is arranged between the curing room 5 and the kiln head AQC boiler system 2. The two ends of the steam conduit 6 are respectively connected to the curing room 5 and the kiln head AQC boiler system 2, so that it is convenient to introduce the high-temperature saturated steam in the kiln head AQC boiler system 2 into the curing room 5 through the steam conduit 6, and then it is convenient to cure the pipe piles inside the curing room 5, so as to realize the production of pipe piles.

[0058] The internal temperature of the curing room 5 is 40° C. to 80° C., and the internal humidity of the curing room 5 is 80% to 100%. Such humidity and temperature can effectively cure the pipe piles and are conducive to the production of qualified pipe piles.

[0059] A cold air valve 7 is provided at one end of the curing room 5 close to the kiln head AQC boiler system 2. The cold air valve 7 is connected to the steam duct 6 along the radial direction of the steam duct 6. The cold air valve 7 can perform secondary regulation on the oxygen and humidity inside the curing room 5, and can ensure that there is enough oxygen in the curing room 5 for people to breathe.

[0060] A pressure relief valve 8 is provided on the side of the cold air valve 7 close to the kiln head AQC boiler system 2. The pressure relief valve 8 is fixedly connected to the steam conduit 6. The pressure relief valve 8 can relieve pressure to facilitate the emergency discharge of high-temperature and high-pressure saturated steam inside the steam conduit 6, thereby ensuring the safety of the pressure relief personnel in an emergency.

[0061] A temperature and pressure reducing device 9 is provided at one end of the pressure relief valve 8 close to the kiln head AQC boiler system 2. The temperature and pressure reducing device 9 is fixedly connected to the steam conduit 6. The unstable saturated steam is controlled by the temperature and pressure reducing device 9 to stabilize the steam temperature at 40°C to 80°C and the humidity at 80% to 100%, which is beneficial to control the humidity and temperature inside the curing room 5.

[0062] A first stop valve 10 is provided at one end of the temperature and pressure reducing device 9 close to the kiln head AQC boiler system 2. The first stop valve 10 is fixedly connected to the steam conduit 6. The first stop valve 10 can control the saturated steam entering the temperature and pressure reducing device 9, so that the first stop valve 10 can control the flow direction of the saturated steam.

[0063] An end of the first stop valve 10 close to the kiln head AQC boiler system 2 is radially connected to an emergency vent pipe 11, and a second stop valve 12 is provided on the emergency vent pipe 11. The second stop valve 12 is in a closed state under normal circumstances. In case of an emergency in production, the first stop valve 10 is quickly closed and the second stop valve 12 on the emergency vent pipe 11 is opened to ensure safe production.

[0064] See also Figure 1 , Figure 2 , Figure 3 and Figure 4The kiln tail SP boiler system 1 comprises a preheater 13, an SP boiler 14, a kiln tail drum 15, a high temperature fan 16 and a first blowdown expansion tank 17;

[0065] A dusty flue gas pipe 18 is connected between the top of the preheater 13 and the SP boiler 14, a dusty flue gas branch pipe 19 is connected radially to the dusty flue gas pipe 18, a first electric shutter valve 20 is installed on the dusty flue gas branch pipe 19, and a high-temperature fan 16 is connected to one end of the dusty flue gas branch pipe 19 away from the dusty flue gas pipe 18;

[0066] The SP boiler 14 has a first U-shaped tube 21, a second U-shaped tube 22 and a third U-shaped tube 23 inside. The inlet of the first U-shaped tube 21 is connected to a first water inlet pipe 24, and the outlet of the first U-shaped tube 21 is connected to a first water outlet pipe 25. The first water outlet pipe 25 is connected to the kiln tail drum 15.

[0067] The inlet of the second U-shaped tube 22 is connected to a second water inlet pipe 26, which is connected to the kiln tail drum 15; the outlet of the second U-shaped tube 22 is connected to a saturated steam outlet pipe 27, which is connected to the kiln tail drum 15;

[0068] The inlet of the third U-shaped tube 23 is connected to a saturated steam introduction pipe 28, which is connected to the kiln tail drum 15. The outlet of the third U-shaped tube 23 is connected to a superheated steam pipe 29, on which a first kiln tail electric gate valve 30, a kiln tail muffler 31 and a second kiln tail electric gate valve 32 are provided.

[0069] A dusty flue gas branch pipe 33 is connected between the bottom of the SP boiler 14 and the dusty flue gas branch pipe 19, and a second electric shutter valve 34 is installed on the dusty flue gas branch pipe 33;

[0070] A first sewage pipe 35 is connected between the kiln tail drum 15 and the first sewage expansion container 17, and a kiln tail electric regulating valve 92 is installed on the first sewage pipe 35;

[0071] The bottom end of the SP boiler 14 is provided with a first chain conveyor 36, and two groups of first ash guide pipes 37 are connected between the SP boiler 14 and the first chain conveyor 36. The two groups of first ash guide pipes 37 are provided with a first manual gate valve 38, a first rotary feeder 39 and a first flexible connection 40 in sequence. The discharge end of the first chain conveyor 36 is provided with a first kiln ash bin 41. The SP boiler system 1 at the kiln tail discharges dusty high-temperature gas through the top outlet of the preheater 13 and enters the SP boiler 14 through the dusty flue gas pipe 18. The dusty high-temperature gas The body exchanges heat with water in the SP boiler 14 to generate superheated steam, and the superheated steam enters the kiln head AQC boiler system 2 through the superheated steam pipe 29, and then flows into the waste heat power generation pipe pile production system 4 through the kiln head AQC boiler system 2. The dust in the dusty high-temperature gas enters the first chain conveyor 36 through the first manual gate valve 38, the first rotary feeder 39 and the first flexible connection 40 on the first ash guide pipe 37. The first chain conveyor 36 transports the kiln ash to the first kiln ash bin 41 and other places for treatment.

[0072] See also Figure 1 , Figure 2 , Figure 3 and Figure 4 The kiln head AQC boiler system 2 has an AQC boiler 42, and the two sides of the AQC boiler 42 are respectively provided with a second blowdown expansion tank 43, a third blowdown expansion tank 44, a low-pressure drum 45 and a high-pressure drum 46;

[0073] The AQC boiler 42 has a common economizer 47, a low-pressure section evaporator 48, a low-pressure section superheater 49, a high-pressure section economizer 50, a high-pressure section evaporator 51, a high-pressure section low-temperature superheater 52, and a high-pressure section high-temperature superheater 53 inside;

[0074] The inlet of the common economizer 47 is connected to a feed water pump 54, and the outlet of the common economizer 47 is connected to a second water outlet pipe 55, and the second water outlet pipe 55 is connected to the first water inlet pipe 24;

[0075] The inlet and outlet of the low-pressure section evaporator 48 are both connected to the low-pressure drum 45. A third water inlet pipe 56 is connected between the low-pressure drum 45 and the first water inlet pipe 24. The third water inlet pipe 56 is connected in parallel with a kiln head first electric regulating valve 57.

[0076] The low-pressure section superheater 49 is connected to the low-pressure boiler drum 45, and the inlet of the high-pressure section economizer 50 is connected to the first water inlet pipe 24, on which the first water inlet pipe 24 is provided with an electric water inlet stop valve 58 and a second electric regulating valve 59 in parallel at the kiln head;

[0077] The outlet of the high-pressure section economizer 50 is connected to the high-pressure drum 46, the inlet and outlet of the high-pressure section evaporator 51 are both connected to the high-pressure drum 46, one end of the high-pressure section low-temperature superheater 52 is connected to the high-pressure drum 46, the other end of the high-pressure section low-temperature superheater 52 and one end of the high-pressure section high-temperature superheater 53 are both connected to the superheated steam pipe 29, the other end of the high-pressure section high-temperature superheater 53 is connected to the air guide pipe 60, the air guide pipe 60 is connected to the steam conduit 6, and the air guide pipe 60 is provided with an emergency air release valve 61, a first electric gate valve 62 at the kiln head, a second electric gate valve 63 at the kiln head and a steam turbine room 64;

[0078] The outlet of the second blowdown expansion tank 43 and the outlet of the third blowdown expansion tank 44 are both connected to the first blowdown system 65, the inlet of the second blowdown expansion tank 43 is connected to the low-pressure drum 45, a third electric stop valve 66 is connected between the inlet of the second blowdown expansion tank 43 and the low-pressure drum 45, the inlet of the third blowdown expansion tank 44 is connected to the high-pressure drum 46, a fourth electric stop valve 67 is connected between the inlet of the third blowdown expansion tank 44 and the high-pressure drum 46;

[0079] The bottom of the AQC boiler 42 is connected to the grate cooler 3. A second chain conveyor 68 is provided at the bottom of the AQC boiler 42. A second ash guide pipe 69 is connected between the AQC boiler 42 and the second chain conveyor 68. A second manual gate valve 70, a second rotary feeder 71 and a second flexible connection 72 are provided on the second ash guide pipe 69 in sequence. A second kiln ash bin 73 is provided at the discharge end of the second chain conveyor 68. The dusty high-temperature gas with a tail temperature of 240°C to 400°C in the grate cooler 3 provided at the lower part of the kiln head AQC boiler system 2 enters the AQC boiler 42. The dusty high-temperature gas is heat-exchanged with water in the AQC boiler 42 to generate high-temperature saturated steam. The high-temperature saturated steam enters the AQC boiler 42. The steam enters the air guide pipe 60 and is discharged into the turbine room 64 or the steam conduit 6 through the emergency air release valve 61, the first electric gate valve 62 at the kiln head and the second electric gate valve 63 at the kiln head, so as to facilitate the high-temperature saturated steam to be discharged into the waste heat power generation pipe pile production system 4, wherein the superheated steam from the SP boiler system 1 at the kiln tail enters the AQC boiler system 2 at the kiln head, and the low-temperature saturated steam mixed by the AQC boiler system 2 at the kiln head enters the SP boiler 14 again through the first water inlet pipe 24 for reuse, and the high-temperature saturated steam mixed by the AQC boiler system 2 at the kiln head enters the curing room 5 through the first stop valve 10, the temperature and pressure reducer 9 and the pressure relief valve 8 to realize the curing of the pipe piles.

[0080] See also Figure 1 , Figure 2 , Figure 3 and Figure 4In this embodiment, the pipe pile is a silicate product made of cement, sand and crushed stone through batching, pouring, steaming and other process processes. The autoclave curing chamber 5 in its production process requires steam and temperature. The waste heat power generation system of the cement plant generally includes a kiln tail SP boiler system 1 and a kiln head AQC boiler system 2. The high-temperature exhaust gas at the outlet of the preheater 13 of the kiln tail SP boiler system 1 enters the SP boiler 14 to exchange heat with the first U-shaped tube 21, the second U-shaped tube 22 and the third U-shaped tube 23, and generates superheated steam for waste heat power generation. The dusty high-temperature gas at the outlet of the preheater 13 exchanges heat with water in the SP boiler 14 to generate superheated steam. The exhaust gas after heat exchange goes from the bottom of the SP boiler 14 through the second electric shutter valve 34 on the dusty flue gas branch pipe 33 to the high-temperature fan 16, and finally reaches the exhaust gas treatment workshop for treatment.

[0081] See also Figure 1 , Figure 2 , Figure 3 and Figure 4 In this embodiment, the water of the SP boiler 14 comes from the common economizer 47 of the AQC boiler 42. The water inlet is regulated by the first electric regulating valve 57 and the second electric regulating valve 59 at the kiln head. The water passes through the SP boiler 14, and the water is heated to generate steam and then enters the SP boiler 14 for circulation. The superheated steam generated by the SP boiler 14 enters the superheated steam pipe 29 and enters the kiln head AQC boiler system 2 through the first electric gate valve 30 and the second electric gate valve 32 at the kiln tail on the superheated steam pipe 29. In case of emergency, the water can be discharged from the outlet of the SP boiler 14. Emergency air release is carried out through the kiln tail silencer 31, and the steam is discharged into the atmosphere through the first electric gate valve 30 and the kiln tail silencer 31 at the kiln tail. The circulating waste water generated in the kiln tail drum 15 is discharged into the first sewage expansion tank 17 through the kiln tail electric regulating valve 92 on the first sewage pipe 35 until it is processed in the sewage treatment system of the cement plant. The dust in the high-temperature gas in the SP boiler 14 enters the first chain conveyor 36 through the first manual gate valve 38, the first rotary feeder 39 and the first soft connection 40. The first chain conveyor 36 transports the kiln ash to the first kiln ash bin 41 for processing.

[0082] See also Figure 1 , Figure 2 , Figure 3 and Figure 4 In this embodiment, the flue gas with a tail temperature of 240°C to 400°C in the grate cooler 3 enters the AQC boiler 42, and the dust-containing high-temperature gas exchanges heat with water in the AQC boiler 42 to produce high-temperature saturated steam. The exhaust gas after heat exchange passes from the top of the AQC boiler 42 through the first electric gate valve 74 and the third flexible connection 75 to the first dust collector 76 for exhaust gas treatment.

[0083] See also Figure 1 , Figure 2 , Figure 3 and Figure 4 In this embodiment, the water of the AQC boiler 42 comes from the feed water pump 54 of the cement plant, and the water intake is controlled by a regulating valve. The water flows in three ways: one way goes to the SP boiler 14; one way goes to the low-pressure drum 45; and one way goes to the high-pressure drum 46. The water is heated by the AQC boiler 42, the low-pressure drum and the high-pressure drum to generate steam, and the generated steam enters the AQC boiler 42 again for circulation. The high-temperature saturated steam of the AQC boiler 42 enters the turbine room 64 through the first electric gate valve 62 at the kiln head of the air guide pipe 60 or enters the steam conduit 6 in the waste heat power generation pipe pile production system 4 through the second electric gate valve 63 at the kiln head of the air guide pipe 60.

[0084] See also Figure 1 , Figure 2 , Figure 3 and Figure 4 In this embodiment, the supersaturated steam from the AQC boiler 42 uses the first stop valve 10 to control the steam flow direction. Under normal circumstances, the second stop valve 12 on the emergency vent pipe 11 is closed, and the steam enters the pipe pile production process through the first stop valve 10. In case of an emergency in production, the first stop valve 10 is quickly closed and the second stop valve 12 on the emergency vent pipe 11 is opened to ensure safe production.

[0085] See also Figure 1 , Figure 2 , Figure 3 and Figure 4 In this embodiment, the unstable saturated steam is controlled by the temperature reducer 9 so that the stable temperature of the steam is between 40°C and 80°C and the humidity is between 80% and 100%. In order to ensure that there is enough oxygen in the curing room 5 for people to breathe, a cold air valve 7 is provided to perform secondary regulation of the oxygen intake and the temperature in the curing room 5. The function of the pressure relief valve 8 is to ensure safe artificial pressure relief in an emergency.

[0086] Embodiment 2

[0087] See also Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 , combined with the first embodiment, in the absence of waste heat power generation, one end of the waste heat power generation pipe pile production system 4 is provided with a steam generator 77, a high temperature boiler 78, and a fourth sewage expansion container 79;

[0088] The high-temperature gas at the outlet of the preheater 13 and the flue gas with a tail temperature of 240°C to 400°C in the grate cooler 3 enter the steam generator 77 together. The water inside the high-temperature boiler 78 circulates inside the steam generator 77 and returns to the high-temperature boiler 78. In this way, the water entering the steam generator 77 from the high-temperature boiler 78 is water, and what comes out of the steam generator 77 and returns to the high-temperature boiler 78 is saturated steam. The saturated steam in the high-temperature boiler 78 passes through the steam generator 77 and is introduced into the steam conduit 6 in the waste heat power generation pipe pile production system 4.

[0089] The high-temperature boiler 78 is connected to the fourth sewage expansion tank 79 by a pipeline, and a switch valve 80 is provided on the pipeline. The outlet of the fourth sewage expansion tank 79 is connected to the second sewage system 81. When the water in the high-temperature boiler 78 circulates many times and needs to be replaced, the switch valve 80 is opened, and the waste water in the high-temperature boiler 78 flows into the fourth sewage expansion tank 79, and then discharged to the second sewage system 81 through the fourth sewage expansion tank 79 for treatment.

[0090] The exhaust gas after heat exchange inside the steam generator 77 is sent from the top of the steam generator 77 through the second electric gate valve 82 and the fourth flexible connection 83 to the second dust collector 84 for exhaust gas treatment.

[0091] See also Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 In this embodiment, an air cooling valve 85 for blowing air is provided on the pipeline from the grate cooler 3 to the steam generator 77 to prevent dusty flue gas with excessively high temperature from entering the steam generator 77 .

[0092] See also Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 In this embodiment, a third chain conveyor 86 is provided at the bottom of the steam generator 77, a third ash guide pipe 87 is connected between the steam generator 77 and the third chain conveyor 86, a third manual gate valve 88, a third rotary discharger 89 and a fifth flexible connection 90 are provided on the third ash guide pipe 87 in sequence, a third ash bin 91 is provided at the discharge end of the third chain conveyor 86, the ash generated in the steam generator 77 enters the third chain conveyor 86 through the third manual gate valve 88, the third rotary discharger 89 and the fifth flexible connection 90, and the third chain conveyor 86 transports the ash to the third ash bin 91 for processing.

[0093] The beneficial effects of embodiment 1 and embodiment 2 in this technical solution are as follows:

[0094] 1. Diversified economic benefits of cement plants. Compared with using excess heat from cement plants to generate electricity and produce pipe pile products, the economic benefits of producing pipe pile products will be greatly increased.

[0095] 2. Reduce production costs. The raw materials in pipe pile production are mainly cement and lime, and the auxiliary materials are sand, fly ash and silicon-containing tailings, etc. Using cement waste heat to generate steam can not only solve the temperature and steam problems required for equipment and maintenance in the production process of pipe piles, but also some raw materials and cement in cement plants are also raw materials for pipe piles. Joint production in cement plants can reduce raw material transportation costs, fuel costs for steam combustion, boiler costs and operation and maintenance costs, etc.

[0096] 3. Industrial integration for energy conservation and environmental protection. Formulate an integrated production plan for cement and pipe pile products industry to promote industrial resource sharing and complementary capabilities, form positive feedback, and achieve the goal of reducing overall costs by improving production efficiency, thereby enhancing the company's market competitiveness. At the same time, the integrated industry shares sewage and waste gas treatment systems to achieve the goal of energy conservation and environmental protection. For example, the waste gas from the pipe pile production process can share the waste gas treatment system of the cement production line.

[0097] 4. The flexibility of process layout is improved. In order to improve the efficiency of waste heat power generation, waste heat power generation needs to be built at a location close to the heat source. Now, new layout plans can be provided for the waste heat utilization of cement plants to improve the flexibility of process layout.

[0098] 5. Multi-stage utilization of waste heat from cement kiln. The waste heat from cement kiln comes from the outlet of preheater 13 and grate cooler 3. The waste gas from grate cooler 3 has a wind temperature of 0°C to 1200°C, and the waste gas is sent to the kiln and decomposition furnace (not shown in the figure) through secondary and tertiary air ducts respectively; the waste gas has a wind temperature of 400°C to 800°C, and enters the waste heat power generation system (not shown in the figure); the waste gas has a wind temperature of 300°C to 500°C, and can enter the coal mill (not shown in the figure), the raw material drying system (not shown in the figure), and the steam generator 77; the waste gas has a wind temperature of 200°C to 400°C, and can enter the steam generator 77 for producing pipe piles. The outlet waste gas of preheater 13 has a wind temperature of 260°C to 350°C, and can directly enter the waste heat power generation system (not shown in the figure), the steam generator 77, and the curing room 5.

[0099] 6. Cement plant reconstruction: For cement plants with a daily production capacity of less than 5,000 tons and no waste heat power generation system, the technical solution of Example 2 can fully utilize energy while improving economic benefits.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A process method for producing pipe piles using cement waste heat, characterized in that: It includes the SP boiler system at the end of the kiln (1) and the AQC boiler system at the head of the kiln (2); The kiln tail SP boiler system (1) and the kiln head AQC boiler system (2) are connected to each other, and the bottom end of the kiln head AQC boiler system (2) is also connected to a grate cooler (3) and a waste heat power generation pipe pile production system (4) respectively; The superheated steam generated by the SP boiler system (1) at the kiln tail enters the AQC boiler system (2) at the kiln head, and the flue gas at the tail of the grate cooler (3) enters the AQC boiler system (2) at the kiln head. The superheated steam of the SP boiler system (1) at the kiln tail and the superheated steam generated by the grate cooler (3) are mixed in the AQC boiler system (2) at the kiln head to form high-temperature saturated steam and low-temperature saturated steam. The high-temperature saturated steam is introduced into the waste heat-containing power generation pipe pile production system (4), and the low-temperature saturated steam is introduced into the SP boiler system (1) at the kiln tail for repeated use.

2. The process method for producing pipe piles using cement waste heat according to claim 1 is characterized in that: The waste heat power generation pipe pile production system (4) comprises a curing room (5), a steam conduit (6) is arranged between the curing room (5) and the kiln head AQC boiler system (2), and two ends of the steam conduit (6) are respectively connected to the curing room (5) and the kiln head AQC boiler system (2).

3. The process method for producing pipe piles using cement waste heat according to claim 2 is characterized in that: The internal temperature of the curing room (5) is 40°C to 80°C, and the internal humidity of the curing room (5) is 80% to 100%.

4. The process method for producing pipe piles using cement waste heat according to claim 2 is characterized in that: A cold air valve (7) is provided at one end of the curing room (5) close to the kiln head AQC boiler system (2), and the cold air valve (7) is connected to the steam conduit (6) along the radial direction of the steam conduit (6).

5. The process method for producing pipe piles using cement waste heat according to claim 4 is characterized in that: A pressure relief valve (8) is provided on one side of the cold air valve (7) close to the kiln head AQC boiler system (2), and the pressure relief valve (8) is fixedly connected to the steam conduit (6).

6. The process method for producing pipe piles using cement waste heat according to claim 5 is characterized in that: A temperature and pressure reducing device (9) is provided at one end of the pressure relief valve (8) close to the kiln head AQC boiler system (2), and the temperature and pressure reducing device (9) is fixedly connected to the steam conduit (6).

7. The process method for producing pipe piles using cement waste heat according to claim 6 is characterized in that: A first stop valve (10) is provided at one end of the temperature and pressure reducing device (9) close to the kiln head AQC boiler system (2), and the first stop valve (10) is fixedly connected to the steam conduit (6).

8. The process method for producing pipe piles using cement waste heat according to claim 7 is characterized in that: An end of the first stop valve (10) close to the kiln head AQC boiler system (2) is radially connected to an emergency vent pipe (11), and a second stop valve (12) is provided on the emergency vent pipe (11).

9. The process method for producing pipe piles using cement waste heat according to claim 2 is characterized in that: The kiln tail SP boiler system (1) comprises a preheater (13), an SP boiler (14), a kiln tail drum (15), a high temperature fan (16) and a first blowdown expansion tank (17); A dusty flue gas pipe (18) is connected between the top end of the preheater (13) and the SP boiler (14); a dusty flue gas branch pipe (19) is connected in the radial direction of the dusty flue gas pipe (18); a first electric shutter valve (20) is installed on the dusty flue gas branch pipe (19); and the high-temperature fan (16) is connected to an end of the dusty flue gas branch pipe (19) away from the dusty flue gas pipe (18); The SP boiler (14) has a first U-shaped tube (21), a second U-shaped tube (22) and a third U-shaped tube (23) inside, the inlet of the first U-shaped tube (21) is connected to a first water inlet pipe (24), the outlet of the first U-shaped tube (21) is connected to a first water outlet pipe (25), and the first water outlet pipe (25) is connected to the kiln tail drum (15); The inlet of the second U-shaped tube (22) is connected to a second water inlet pipe (26), the second water inlet pipe (26) is connected to the kiln tail drum (15), the outlet of the second U-shaped tube (22) is connected to a saturated steam outlet pipe (27), the saturated steam outlet pipe (27) is connected to the kiln tail drum (15); The inlet of the third U-shaped tube (23) is connected to a saturated steam introduction pipe (28), the saturated steam introduction pipe (28) is connected to the kiln tail drum (15), the outlet of the third U-shaped tube (23) is connected to a superheated steam pipe (29), and the superheated steam pipe (29) is provided with a first kiln tail electric gate valve (30), a kiln tail silencer (31) and a second kiln tail electric gate valve (32); A dusty flue gas branch pipe (33) is connected between the bottom of the SP boiler (14) and the dusty flue gas branch pipe (19), and a second electric shutter valve (34) is installed on the dusty flue gas branch pipe (33); A first sewage pipe (35) is connected between the kiln tail drum (15) and the first sewage expansion container (17), and a kiln tail electric regulating valve (92) is installed on the first sewage pipe (35); A first chain conveyor (36) is provided at the bottom end of the SP boiler (14), two groups of first ash guide pipes (37) are connected between the SP boiler (14) and the first chain conveyor (36), the two groups of the first ash guide pipes (37) are provided with a first manual gate valve (38), a first rotary discharger (39) and a first flexible connection (40) in sequence, and a first kiln ash bin (41) is provided at the discharge end of the first chain conveyor (36).

10. The process method for producing pipe piles using cement waste heat according to claim 9, characterized in that: The kiln head AQC boiler system (2) comprises an AQC boiler (42), and two sides of the AQC boiler (42) are respectively provided with a second blowdown expansion tank (43), a third blowdown expansion tank (44), a low-pressure boiler drum (45) and a high-pressure boiler drum (46); The AQC boiler (42) has a common economizer (47), a low-pressure section evaporator (48), a low-pressure section superheater (49), a high-pressure section economizer (50), a high-pressure section evaporator (51), a high-pressure section low-temperature superheater (52) and a high-pressure section high-temperature superheater (53) inside; The inlet of the common economizer (47) is connected to a feed water pump (54), the outlet of the common economizer (47) is connected to a second water outlet pipe (55), and the second water outlet pipe (55) is connected to the first water inlet pipe (24); The inlet and outlet of the low-pressure section evaporator (48) are both connected to the low-pressure drum (45); a third water inlet pipe (56) is connected between the low-pressure drum (45) and the first water inlet pipe (24); and a first electric regulating valve (57) at the kiln head is connected in parallel to the third water inlet pipe (56); The low-pressure section superheater (49) is connected to the low-pressure drum (45), and the inlet of the high-pressure section economizer (50) is connected to the first water inlet pipe (24). The first water inlet pipe (24) is provided with an electric water inlet stop valve (58) and a second electric regulating valve (59) at the kiln head in parallel; The outlet of the high-pressure section economizer (50) is connected to the high-pressure drum (46), the inlet and outlet of the high-pressure section evaporator (51) are both connected to the high-pressure drum (46), one end of the high-pressure section low-temperature superheater (52) is connected to the high-pressure drum (46), the other end of the high-pressure section low-temperature superheater (52) and one end of the high-pressure section high-temperature superheater (53) are both connected to the superheated steam pipe (29), the other end of the high-pressure section high-temperature superheater (53) is connected to an air guide pipe (60), the air guide pipe (60) is connected to the steam conduit (6), and the air guide pipe (60) is provided with an emergency air release valve (61), a first electric gate valve (62) at the kiln head, a second electric gate valve (63) at the kiln head, and a steam turbine room (64); The outlet of the second blowdown expansion tank (43) and the outlet of the third blowdown expansion tank (44) are both connected to a first blowdown system (65); the inlet of the second blowdown expansion tank (43) is connected to the low-pressure boiler drum (45); a third electric stop valve (66) is connected between the inlet of the second blowdown expansion tank (43) and the low-pressure boiler drum (45); the inlet of the third blowdown expansion tank (44) is connected to the high-pressure boiler drum (46); a fourth electric stop valve (67) is connected between the inlet of the third blowdown expansion tank (44) and the high-pressure boiler drum (46); The bottom of the AQC boiler (42) is connected to the grate cooler (3), a second chain conveyor (68) is provided at the bottom of the AQC boiler (42), a second ash guide pipe (69) is connected between the AQC boiler (42) and the second chain conveyor (68), a second manual gate valve (70), a second rotary discharger (71) and a second flexible connection (72) are provided in sequence on the second ash guide pipe (69), and a second kiln ash bin (73) is provided at the discharge end of the second chain conveyor (68).

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