A malt drying internal circulation waste heat recovery system

Abstract

A malt drying internal circulation waste heat recovery system, comprising fresh air external circulation, waste heat recovery internal circulation, parallel waste heat recovery unit, heating system, drying device, PLC system five parts, fresh air external circulation and waste heat recovery internal circulation switch through PLC system control, need to complete more than once fresh air external circulation, can be switched to waste heat recovery internal circulation mode, so as to realize closed cycle, especially in winter, can greatly reduce the waste caused by outdoor air temperature rise, and reduce the steam consumption.

Description

Technical Field

[0001] This invention belongs to the field of waste heat recovery in food processing, and relates to a malt drying internal circulation waste heat recovery system. Background Technology

[0002] Malt is the main raw material for beer production. Barley malt requires multiple processing steps. After germination, barley malt typically has a moisture content of 42%-48%. Through drying, the moisture content needs to be reduced to around 4% for storage. The drying process of malt varies depending on the specific needs of beer production. During the drying process, the malt undergoes different temperature stages. At high temperatures, the sugars in the malt undergo caramelization, producing different colors and flavors. Currently, malt drying often uses high-temperature steam to heat the air and then uses this hot air to dry the malt. However, the dried gas has both high temperature and high humidity, and the air volume is extremely large. This high-humidity air is usually processed through heat exchange equipment to recover sensible heat and some latent heat. The exhaust temperature is higher than the outdoor air temperature. Especially in malt processing plants in northern regions, the fresh air temperature is low in winter, requiring a large amount of heat to heat the fresh air. This open-loop system consumes a lot of heat and results in significant energy waste. Summary of the Invention

[0003] This invention designs an internal circulation waste heat recovery system for malt drying. It utilizes an absorption heat pump and a two-stage heating process to recover waste heat from the low-temperature, high-humidity air emitted during the malt production process. Simultaneously, it condenses to reduce humidity and reintroduces the recovered heat into the dehumidified air. Especially in winter, this system can significantly reduce waste caused by outdoor air heating and also reduce steam consumption.

[0004] This invention is implemented as follows: a malt drying internal circulation waste heat recovery system comprises five parts: a fresh air external circulation system, a waste heat recovery internal circulation system, a heating system, a drying device, and a PLC system. The fresh air external circulation and waste heat recovery internal circulation are switched via the PLC system. At least one fresh air external circulation cycle is required before switching to the waste heat recovery internal circulation mode. The waste heat recovery internal circulation includes an air side and a water circulation side. The air side includes a drying device moisture outlet connected to the No. 1 moisture inlet of an air-water heat exchanger via a duct, enabling air-water heat exchange. Air volume regulating valve group 1 is set to open at the moisture inlet and outlet of heat exchanger No. 1, and air volume regulating valve 3 is set to close. A water collection tank is set to collect the moisture condensate after dehumidification at the moisture outlet of heat exchanger No. 1. The moisture outlet of heat exchanger No. 1 is connected to fan No. 2 through a pipe and is started. Fan No. 2 is connected to air inlet of heat exchanger No. 2 through an air duct. Air volume regulating valve group 2 is set to open at the air outlet and air inlet of heat exchanger No. 2. The outlet of heat exchanger No. 2 is connected to a drying device through an air duct, and air volume regulating valve 2 is set to close.

[0005] The heating system includes two modes: fresh air external circulation and waste heat recovery internal circulation. The fresh air external circulation is the normal process flow for malt drying. Before starting the waste heat recovery internal circulation mode, at least one fresh air external circulation needs to be completed. The waste heat recovery internal circulation mode needs to be started after at least one fresh air external circulation is completed. The steam pump installed at the steam boiler's steam supply port is started, valve group 1 is closed, and the steam inlets of absorption heat pump 1 and absorption heat pump 2 are connected through steam pipes. The steam outlets of absorption heat pump 1 and absorption heat pump 2 are connected to the steam boiler through steam pipes.

[0006] On the water circulation side, circulation pump 1 is installed at the cooling water outlet of absorption heat pump 1 and connected to the cooling water inlet of gas-water heat exchanger 1 via a pipeline. The cooling water outlet of gas-water heat exchanger 1 is connected to the cooling water inlet of absorption heat pump 1. Circulation pump 2 is installed at the cooling water outlet of absorption heat pump 2 and connected to the low-temperature waste heat inlet of absorption heat pump 1 via a pipeline. The low-temperature waste heat outlet of absorption heat pump 1 is connected to the cooling water inlet of absorption heat pump 2. The high-temperature water outlet of absorption heat pump 2 is connected to the high-temperature water inlet of gas-water heat exchanger 2 via a pipeline. The high-temperature water outlet of gas-water heat exchanger 2 is connected to circulation pump 3 and then connected to the high-temperature water inlet of absorption heat pump 2 via a pipeline.

[0007] The PLC system is used to switch between fresh air external circulation and waste heat recovery internal circulation. When the fresh air external circulation is running, air volume regulating valve 1, air volume regulating valve 2, air volume regulating valve 3 and valve group 1 are open, and air volume regulating valve group 1, air volume regulating valve group 2, valve group 2 and valve group 3 are closed.

[0008] Before the system switches states, the waste heat recovery internal circulation completes one fresh air external circulation operation. The air volume regulating valve 1, air volume regulating valve 2, air volume regulating valve 3 and valve group 1 are closed, while the air volume regulating valve group 1, air volume regulating valve group 2, valve group 2 and valve group 3 are open.

[0009] The beneficial effects of this invention are:

[0010] 1. The low-temperature heat of the dried humid air is recovered through a two-stage absorption heat pump, and the moisture in the humid air is condensed.

[0011] 2. The heat source for the absorption heat pump is steam from the steam boiler. After switching to internal circulation, the absorption heat pump can be driven to achieve the drying requirements. Attached Figure Description

[0012] Figure 1 This is a system diagram of the present invention.

[0013] As shown: 1. Steam boiler, 2. Steam-gas heat exchanger, 3. Gas-gas heat exchanger, 4. Drying device, 5. Gas-water heat exchanger No. 1, 6. Water collection tank, 7. Absorption heat pump No. 1, 8. Absorption heat pump No. 2, 9. Gas-water heat exchanger No. 2, 10-1. Air volume regulating valve 1, 10-2. Air volume regulating valve 2, 10-3. Air volume regulating valve 3, 10-4. Air volume regulating valve group 1, 10-5. Air volume regulating valve group 2, 11-1. Fan No. 1, 11-2. Fan No. 2, 12-1. Valve group 1, 12-2. Valve group 2, 12-3. Valve group 3, 13. Steam pump, 14-1. Circulation pump 1, 14-2. Circulation pump 2, 14-3. Circulation pump 3, 15. Exhaust vent, 16. PLC. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] I. Fresh Air External Circulation Mode

[0016] When the steam pump (13) is installed at the steam supply port of the steam boiler (1) and starts, it is connected to the steam inlet of the steam heat exchanger (2) through a steam pipe. The steam outlet of the steam heat exchanger (2) is connected to the steam boiler through a steam pipe. When the steam outlet and steam inlet of the steam heat exchanger (2) are connected to the steam inlet, the valve group 1 (12-1) is in the open state during external circulation, and the valve group 2 (12-2) and valve group 3 (12-3) are in the closed state.

[0017] Fan 1 (11-1) is set to start before air volume regulating valve 1 (10-1). Air volume regulating valve 1 (10-1) is open. Air volume regulating valve 1 (10-1) is connected to the fresh air inlet of gas heat exchanger (3) through air duct. The fresh air outlet of gas heat exchanger (3) is connected to the fresh air inlet of steam heat exchanger (2) through air duct. Air volume regulating valve 2 (10-2) is installed at the fresh air outlet of steam heat exchanger (2) and is in the open state. Air volume regulating valve 2 (10-2) is connected to the fresh air inlet of drying device (4) through air duct. The moisture outlet of drying device (4) is connected to the moisture inlet of gas heat exchanger (3) through air duct. Air volume regulating valve (10-3) is set at the front end of the moisture inlet and is in the open state. Air volume regulating valve group 1 (10-4) is closed. Exhaust port (15) is set at the moisture outlet of gas heat exchanger (3).

[0018] II. Waste Heat Recovery Internal Circulation

[0019] When the steam pump (13) is installed at the steam supply port of the steam boiler (1) and is started, the valve group 1 (12-1) is closed. The steam inlet of the absorption heat pump 1 (7) and the absorption heat pump 1 (8) are connected through the steam pipe. The steam outlet of the absorption heat pump 1 (7) and the absorption heat pump 1 (8) are connected to the steam boiler through the steam pipe.

[0020] After completing one or more fresh air external circulations, the moisture outlet of the drying device (4) is connected to the moisture inlet of the air-water heat exchanger No. 1 (5) through a duct. The moisture inlet and moisture outlet of the air-water heat exchanger No. 1 (5) are equipped with a flow rate regulating valve group 1 (10-4) in the open state and a flow rate regulating valve (10-3) in the closed state. The moisture outlet of the air-water heat exchanger No. 1 (5) is equipped with a water collection tank (6) for recovering the moisture condensate after dehumidification. The moisture outlet of the air-water heat exchanger No. 1 (5) is connected to the fan No. 2 (11-2) through a pipe and is started. The fan No. 2 (11-2) is connected to the air inlet of the air-water heat exchanger No. 2 (9) through a duct. The air outlet and air inlet of the air-water heat exchanger No. 2 (9) are equipped with a flow rate regulating valve group 2 (10-5) in the open state. The outlet of the air-water heat exchanger No. 2 (9) is connected to the drying device (4) through a duct and the flow rate regulating valve 2 (10-2) is closed.

[0021] When the steam pump (13) is installed at the steam supply port of the steam boiler (1) and is started, the valve group 1 (12-1) is closed. The steam inlet of the absorption heat pump 1 (7) and the absorption heat pump 1 (8) are connected through the steam pipe. The steam outlet of the absorption heat pump 1 (7) and the absorption heat pump 1 (8) are connected to the steam boiler through the steam pipe.

[0022] The cooling water outlet of absorption heat pump 1 (7) is connected to the cooling water inlet of gas-water heat exchanger 1 (5) via a pipe. The cooling water outlet of gas-water heat exchanger 1 (5) is connected to the cooling water inlet of absorption heat pump 1 (7). The cooling water outlet of absorption heat pump 2 (8) is connected to the low-temperature waste heat inlet of absorption heat pump 1 (7) via a pipe. The low-temperature waste heat outlet of absorption heat pump 1 (7) is connected to the cooling water inlet of absorption heat pump 2 (8). The high-temperature water outlet of absorption heat pump 2 (8) is connected to the high-temperature water inlet of gas-water heat exchanger 2 (9) via a pipe. The high-temperature water outlet of gas-water heat exchanger 2 (9) is connected to the circulating pump 3 (14-3) and then connected to the high-temperature water inlet of absorption heat pump 2 (8) via a pipe.

[0023] When the fresh air external circulation system is running, the PLC (16) controls the air volume regulating valve 1 (10-1), air volume regulating valve 2 (10-2), air volume regulating valve 3 (10-3), and valve group 1 (12-1) to be open, and the air volume regulating valve group 1 (10-4), air volume regulating valve group 2 (10-5), valve group 2 (12-2), and valve group 3 (12-3) to be closed.

[0024] Before switching states, the PLC (16) needs to complete one fresh air external circulation system operation, control the air volume regulating valve 1 (10-1), air volume regulating valve 2 (10-2), air volume regulating valve 3 (10-3), and valve group 1 (12-1) to be closed, and the air volume regulating valve group 1 (10-4), air volume regulating valve group 2 (10-5), valve group 2 (12-2), and valve group 3 (12-3) to be open.

[0025] This invention is not limited to this embodiment. Any equivalent concept or modification within the technical scope disclosed in this invention shall be included within the protection scope of this invention.

Claims

1. A malt drying internal circulation waste heat recovery system, characterized in that: The system consists of five parts: fresh air external circulation, waste heat recovery internal circulation, heating system, drying device, and PLC system. The fresh air external circulation and waste heat recovery internal circulation are switched by the PLC system. The waste heat recovery internal circulation can only be switched after the fresh air external circulation has been completed more than once. The waste heat recovery internal circulation includes an air side and a water circulation side. The air side includes the drying device (4) and the moisture outlet is connected to the moisture inlet of the air-water heat exchanger No. 1 (5) through the air duct. The moisture inlet and moisture outlet of the air-water heat exchanger No. 1 (5) are equipped with air volume regulating valve group 1 (10-4) in the open state. The air volume regulating valve 3 (10-3) When the state is closed, the moisture outlet of the gas-water heat exchanger No. 1 (5) is equipped with a water collection tank (6) for recovering the moisture condensate after dehumidification. The moisture outlet of the gas-water heat exchanger No. 1 (5) is connected to the fan No. 2 (11-2) through a pipe and is started. The fan No. 2 (11-2) is connected to the air inlet of the gas-water heat exchanger No. 2 (9) through a duct. The air outlet and air inlet of the gas-water heat exchanger No. 2 (9) are equipped with a flow regulating valve group 2 (10-5) when it is opened. The outlet of the gas-water heat exchanger No. 2 (9) is connected to the drying device (4) through a duct. The flow regulating valve 2 (10-2) is closed.

2. The malt drying internal circulation waste heat recovery system according to claim 1, characterized in that: The heating system includes two modes: fresh air external circulation and waste heat recovery internal circulation. The fresh air external circulation is the normal process flow of malt drying. Before starting the waste heat recovery internal circulation mode, it is necessary to complete the fresh air external circulation once. The waste heat recovery internal circulation mode needs to be started after completing the fresh air external circulation once. The steam boiler (1) is started with the steam pump (13) installed at the steam supply port, and the valve group 1 (12-1) is closed. The steam inlet of absorption heat pump 1 (7) and absorption heat pump 2 (8) is connected through the steam pipe. The steam outlet of absorption heat pump 1 (7) and absorption heat pump 2 (8) is connected to the steam boiler through the steam pipe.

3. The malt drying internal circulation waste heat recovery system according to claim 1, characterized in that: On the water circulation side, the cooling water outlet of absorption heat pump 1 (7) is connected to the cooling water inlet of gas-water heat exchanger 1 (5) via a pipe. The cooling water outlet of gas-water heat exchanger 1 (5) is connected to the cooling water inlet of absorption heat pump 1 (7). The cooling water outlet of absorption heat pump 2 (8) is connected to the low-temperature waste heat inlet of absorption heat pump 1 (7) via a pipe. The low-temperature waste heat outlet of absorption heat pump 1 (7) is connected to the cooling water inlet of absorption heat pump 2 (8). The high-temperature water outlet of absorption heat pump 2 (8) is connected to the high-temperature water inlet of gas-water heat exchanger 2 (9) via a pipe. The high-temperature water outlet of gas-water heat exchanger 2 (9) is connected to the cooling water inlet of circulation pump 3 (14-3) via a pipe. The high-temperature water inlet of absorption heat pump 2 (8) is connected to the high-temperature water inlet of absorption heat pump 2 (8) via a pipe.

4. The malt drying internal circulation waste heat recovery system according to claim 1, characterized in that: The PLC system is used to switch between fresh air external circulation and waste heat recovery internal circulation. When the fresh air external circulation is running, the air volume regulating valve 1 (10-1), air volume regulating valve 2 (10-2), air volume regulating valve 3 (10-3), and valve group 1 (12-1) are open, while the air volume regulating valve group 1 (10-4), air volume regulating valve group 2 (10-5), valve group 2 (12-2), and valve group 3 (12-3) are closed.

5. The malt drying internal circulation waste heat recovery system according to claim 1, characterized in that: Before the system switches states, the waste heat recovery internal circulation completes one fresh air external circulation operation. The air volume regulating valve 1 (10-1), air volume regulating valve 2 (10-2), air volume regulating valve 3 (10-3), and valve group 1 (12-1) are closed, while the air volume regulating valve group 1 (10-4), air volume regulating valve group 2 (10-5), valve group 2 (12-2), and valve group 3 (12-3) are open.

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